Cognitive Radio Pune University MCQs
Cognitive Radio Pune University MCQs
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “Architecture Evolution”.
1. ______ has many single- purpose radios in one structure.
a) SPEAKeasy – 2
b) Modular multifunctional information transfer system
c) Integrated communications, navigation, and identification architecture
d) Cluster HMS
Answer: c
Explanation: ICNIA design consists of many single-purpose radios in one structure. However the modern Software Defined Radio behaves as a general purpose device generating different waveforms at different frequencies using the same radio tuner and processors.
2. Which was the first Software Defined Radio that included a programmable voice coder?
a) SPEAKeasy – 1
b) SPEAKeasy – 2
c) ICNIA
d) Cluster HMS
Answer: b
Explanation: SPEAKeasy – 2 was an appropriately sized radio with features such as programmable voice coder, DSP resources to support different waveforms.
3. When was SDR forum found?
a) 1992
b) 1994
c) 1996
d) 1995
Answer: c
Explanation: The SDR forum was found in 1996 by Wayne Bonser of Air Force Rome Lab to develop industry standards for SDR hardware and software.
4. Which protocol is used to control Digital Modular Radio over Ethernet?
a) OSPF
b) SNMP
c) IPX
d) TELNET
Answer: b
Explanation: A Digital Modular Radio has four channels with full duplex communication. It is controlled over an Ethernet interface which uses Simple Network Management Protocol .
5. Which of the following does not extend from military application to commercial application?
a) Carrier Sense Multiple Access
b) Frequency Hopping
c) Direct Sequence Spread Spectrum
d) Emitter Location
Answer: a
Explanation: Frequency hopping, direct sequence spread spectrum, demand-assigned multiple access, variable data rates are some techniques which have extend from military application to commercial application.
6. Military applications need __________ in addition to mobile subscriber sets.
a) fixed infrastructure
b) mobile infrastructure
c) partitioned infrastructure
d) parted infrastructure
Answer: b
Explanation: Commercial applications are supported by fixed infrastructure such as cell phone towers and base stations. However such facilities are not available for military application. Thus, a mobile infrastructure is required.
7. Which of the following is not a standard body that involves in inter networking?
a) ETSI
b) ITU
c) IEEE
d) VSO
Answer: d
Explanation: ITU, ISO, ETSI, ARIB, IEEE, TIA, and ANSI are the standard bodies overlooking inter networking. VSO is a standard body that monitors bus/backplane hardware.
8. Which of the following is not a key parameter of information services in military application?
a) Quantity
b) Suitability
c) Multi-tenancy
d) Timeliness
Answer: c
Explanation: Quantity, quality, timeliness , and suitability are the key parameters of information services in military application.
9. Quantity is measured in terms of ________
a) BER
b) link availability
c) peak data rate
d) band
Answer: c
Explanation: Quantity is measured in terms of two factors. One is the number of different communication mode present in the software radio. The other is the peak and average data rates available to the subscribers.
10. Which of the following is not directed by Air Interface Standards?
a) Channel modulation
b) Interconnects
c) Frequency allocation
d) Access protocols
Answer: b
Explanation: Channel modulation, frequency allocation and access protocols are few air interface standards. They affect interoperability over the air.
11. What does cost effectiveness mean in terms of military requirements?
a) Backward compatibility
b) Cheap replacement of existing radios
c) Futuristic design
d) Fast replacement of existing radios
Answer: a
Explanation: Cost effectiveness means the new design must be able to communicate with previous versions of radios. The design must be compatible with radios which are meeting the end of their lifetime.
12. Which of the following is not an advanced requirement in terms of Software Defined Radio?
a) Adaptive networks
b) Adaptive diversity
c) Multiband
d) Innovation signaling
Answer: c
Explanation: Adaptive networks, adaptive diversity, transparent bridging, channel modeling, innovation signaling are some advanced functional needs of SDR. These techniques can elevate the quality of voice, data and wireless services.
13. Timeliness is the period between production of information and its availability to the subscriber.
a) True
b) False
Answer: a
Explanation: Timeliness is one of key parameters of military applications. Timeliness is the period between production of information and its availability to the subscriber. Process and queuing delays increase the duration of this period.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “Antenna Tradeoffs – 1”.
1. The parameters of the antenna considered for RF access are ______
a) RF band and bandwidth
b) RF band and resonant frequency
c) noise constraints and bandwidth
d) directivity and RF band
Answer: a
Explanation: The parameters of the antenna considered for RF access are RF band and bandwidth. Antenna architecture determines the number and bandwidth of RF channels. This imposes constraint on number and bandwidth of ADCs.
2. How is bandwidth expressed in a Software Defined Radio?
a) Ratio of highest RF to lowest RF
b) Ratio of median RF to lowest RF
c) Ratio of lowest RF to highest RF
d) Ratio of lowest RF to median RF
Answer: c
Explanation: Bandwidth can be expressed as a percentage of carrier frequency. An alternate method is to take the ratio of lowest RF to highest RF over which the parameters such as VSWR are operable.
3. What type of antenna is the Yagi antenna?
a) Surface-wave
b) Resonant
c) Traveling wave
d) Aperture
Answer: a
Explanation:The Yagi antenna is a surface-wave antenna operating at 1 – 6 GHz range. It is used as radar feed and array. The setup of a Yagi antenna consists of a driven element, a reflector, and one or more directors.
4. What is the operating range of a pyramidal horn antenna?
a) 1 – 6 GHz
b) 1 – 5 GHz
c) 300 MHz – 70 GHz
d) 100 MHz – 35 GHz
Answer: c
Explanation: The pyramidal horn antenna is an aperture type antenna operating in the range 300MHz – 70GHz. It is used in radar communication.
5. The increase in the bandwidth of the antenna causes the thermal noise power to ______
a) decrease linearly
b) increase linearly
c) increase exponentially
d) decrease exponentially
Answer: b
Explanation: Wider bandwidth results in increase of noise which reduces the value of SNR, affecting the performance negatively. Filtering of antenna channels according to subscriber signals can give better performance.
6. Which method is used to estimate time-difference of arrival and angle of arrival?
a) Optical interferometry
b) Interferometric dynamic measurement
c) Frequency scanning interferometry
d) Phase interferometry
Answer: d
Explanation: Time-difference of arrival and angle of arrival are determined by phase interferometry. These parameters play an important role in network-based emitter location techniques.
7. Both TDOA and CDMA continuously compute ______
a) time difference of arrival
b) time of arrival
c) angle of arrival
d) time delay of arrival
Answer: b
Explanation: Time Difference of Arrival and Code Division Multiple Access continuously compute time of arrival in order to recover the direct sequence and spread spectrum waveform.
8. Antenna separation effectively controls _________
a) directivity
b) external noise
c) self-generated interference
d) external interference
Answer: c
Explanation: Antennas in same enclosure or when closely spaced often lead to interference. This can be mitigated by antenna separation. The benefit of separation can be estimated by link-based spreadsheet.
9. Which of the following gives permissible levels of exposure to radiation in terms of whole body average SAR as per US FCC?
a) 0.02
b) 0.04
c) 0.06
d) 0.08
Answer: d
Explanation:The radiation from antenna might have a harmful impact on the human body. The US FCC imposes a limit of 0.08 for whole body average SAR and 1.6 for spatial peak SAR.
10. Human body interaction causes distortions in antenna pattern and health risk in human beings.
a) True
b) False
Answer: a
Explanation: Human body interaction causes distortions in antenna pattern and health risk in human beings. Handheld device generally tilt the wire antenna away from the user for minimal absorption and better radiation efficiency.
11. Which of the following is not a concern for antenna tradeoff?
a) RF access
b) Calibration
c) Phase noise
d) RF MEMS
Answer: d
Explanation: RF access, antenna calibration, phase noise are some parameters which influence antenna tradeoffs. The antenna establishes the available RF band and is responsible for the directional properties of the system.
12. SPEAK easy aimed to developed a full band antenna that operated over the range ______
a) 2 MHz to 2000 MHz
b) 2 Hz to 2 MHz
c) 20 Hz to 2 MHz
d) 20 MHz to 2000 MHz
Answer: a
Explanation: The RF range of 2 MHz to 2000 MHz was aimed to be achieved by SPEAKeasy. This falls in the range of 1000:1, it spans over 3 decades.
13. What was the frequency range achieved by SPEAKeasy – 1?
a) 20 – 300 MHz
b) 5 – 300 MHz
c) 30 – 3000 MHz
d) 30 – 400 MHz
Answer: d
Explanation: SPEAK easy split the operating range into three bands: a) 2 – 30 MHz; b) 30 – 400 MHz; and c) 400 – 2000 MHz. Band b was achieved by SPEAK easy – 1 and band a, b was achieved by SPEAKeasy – 2.
14. Which of the following are frequency independent antennas?
a) Dielectric rod and Yagi
b) Log-periodic and Equiangular Spiral
c) Half-wave dipole and Half-wave slot
d) Axial mode helix and Pyramidal horn
Answer: b
Explanation: Log-periodic and Equiangular spiral antennas are frequency independent antennas. Log – periodic antenna operates over the range 10 MHz – 12 GHz. Equiangular spiral operates over the range 100 MHz – 35 GHz.
15. Lower gain antenna reduces link margin and decreases the outage probability proportionally.
a) True
b) False
Answer: b
Explanation: Lower gain antenna reduces link margin and increases the outage probability proportionally. These antennas become optimal when aggregate cost and quality of information services across the combination of bands and modes is considered.
This set of Software Defined Radio online test focuses on “Antenna Tradeoffs – 2”.
1. Which of the following option cannot be employed to overcome fading?
a) Reduced channel symbol rates
b) Diversity transmission and reception
c) Decreased bandwidth
d) Structured data
Answer: c
Explanation: Increased instantaneous bandwidth for multipath resolution and equalization can mitigate the effect of fading. The reduction of channel symbol rate can reduce intersymbol interference. Diversity transmission and reception, and structuring of data provide resilience against fading.
2. Which of the following can reduce the probability of non-recoverable fade depth?
a) Diversity
b) FEC
c) Interleaving
d) FEC and Interleaving
Answer: a
Explanation: Diversity transmission and reception can reduce the probability of non-recoverable fade depth. It tends to choose the signal with maximum strength, improving the error floor. FEC and interleaving are useful for compensating the erasure caused by fading.
3. Doppler spread is given by _______
a) carrier frequency times the ratio of maximum velocity of a transmitter divided by propagation velocity
b) carrier frequency times the ratio of minimum velocity of a transmitter divided by propagation velocity
c) carrier frequency times the ratio of propagation velocity divided by maximum velocity of a transmitter
d) carrier frequency times the ratio of propagation velocity divided by minimum velocity of a transmitter
Answer: a
Explanation: Doppler spread is given by carrier frequency times the ratio of maximum velocity of a transmitter divided by propagation velocity. Doppler spread is observed in the study of spatial coherence.
4. The rule of thumb for antenna diversity states that for an antenna separation of 10 wavelengths or more, there is a considerable probability for the diversity signal to be substantially decorrelated from the primary signal.
a) True
b) False
Answer: a
Explanation: Doppler spread introduces decorrelation as a function of antenna separation.The rule of thumb for antenna diversity states that for an antenna separation of 10 wavelengths or more, there is a considerable probability for the diversity signal to be substantially decorrelated from the primary signal.
5. Cellular systems employ ____ sectorization.
a) two way
b) four way
c) eight way
d) three way
Answer: d
Explanation: The three way sectors are functionally distinct. Each sector is assigned with separate RF channels to satisfy high subscriber densities.
6. _____ offers fade resistance for slow-moving mobiles.
a) FEC
b) Diversity
c) Frequency hopping
d) Interleaving
Answer: c
Explanation: Frequency hopping can provide fade resistance for slow-moving mobiles. GSM’s frequency hopping plan improves SNR by averaging deep fades.
7. Which stage carries out diversity combining?
a) RF access stage
b) IF stage
c) Bit stream processing stage
d) Development
Answer: b
Explanation: Diversity combining is performed in the IF stage. Diversity antennas require parallel RF/IF converters and ADC channels.
8. ______ combiner picks the diversity channel with maximum received signal strength.
a) Baseband diversity
b) Carrier diversity
c) Digital diversity
d) Analog diversity
Answer: d
Explanation: Analog diversity combiner selects the diversity channel with maximum signal strength whereas digital diversity combiner uses time delay and addition of signal to yield signal of better strength and coherence.
9. The increase in demand for DSP resources due to the introduction of diversity can be controlled by _______
a) dynamically-pooled DSP resources
b) increasing DSP resources
c) fixing the number of users
d) combining diversity with frequency hopping
Answer: a
Explanation: All subscribers do not require diversity simultaneously. Dynamically pooled DSP resources can be used to enhance channels with low carrier to interference ratio.
10. The physical location of the antennas may cause _____
a) site interference
b) co-site interference
c) diversity interference
d) diversity combining interference
Answer: b
Explanation: The impact of physical location of the antennas on self-generated EMI is called as co-site interference.It occurs when two or more closely located RF systems affect each other negatively.
11. Military applications resort to channelized architectures due to _____
a) excess of bandwidth
b) lack of bandwidth
c) excessive programmability
d) excess of bandwidth and programmability
Answer: d
Explanation: Military application resort to channelized architectures due to excess of bandwidth and programmability. The channelized architectures have dedicated antenna and RF conversion subsystem for each subbandof resonant antenna.
12. Which of the following is not influenced by antenna characteristics?
a) Gain
b) Number of ADC’s
c) Number of DAC’s
d) Diversity
Answer: d
Explanation: Gain, number of antenna channels required to support multiband multimode operation, number of ADC’s and number of DAC’s are parameters influenced by antenna characteristics.
13. Which of the following is not observed due to co-site interference?
a) Eddy currents
b) Near field effects
c) Multicarrier active intermodulation
d) Multicarrier passive intermodulation
Answer: d
Explanation: Co-site interference may result in multimode, multiband antenna interaction, eddy currents, near field effects, electrical isolation and multicarrier active intermodulation.
14. Which of the following is not a challenge posed by antenna?
a) Multiband antenna
b) RF MEMS
c) Co-site interference
d) Programmability
Answer: b
Explanation: RF MEMS can improve the performance of the antenna by introducing re-configurability. Multiband antenna, co-site interference, and programmability are challenges posed by antenna.
15. Cost of production electronics is an exponential function of parts count, number of antennas, and related RF/IF paths.
a) True
b) False
Answer: b
Explanation: Cost of production electronics is a linear function of parts count, number of antennas and related RF/IF paths.Antenna and RF system accounts for nearly 60% of the total cost of a radio node.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “”.
1. Which of the following is not present in the conversion stages of super heterodyne receiver?
a) Local oscillator
b) Additional filter
c) Step attenuator
d) Amplifier
Answer: c
Explanation: Each conversion stage of super heterodyne receiver has one LO, additional filters and amplifiers. Step attenuator is present after the pre-selector filters. It confines the total power at the input of first conversion stage within its linear range.
2. Which of the following is used in base station applications?
a) Super heterodyne receiver
b) Direct conversion receiver
c) Digital-RF receiver
d) Homodyne receiver
Answer: a
Explanation: Super heterodyne receiver is used in base station applications. Direct conversion receiver is used in handsets. Digital-RF receiver performs demodulation at RF.
3. Direct conversion receiver is a heterodyne receiver.
a) True
b) False
Answer: b
Explanation: The direct conversion receiver is a homodyne receiver which may use non-zero baseband center frequency.
4. Which of the following is a challenge for direct conversion receiver?
a) GaAs circuitry
b) CMOS circuitry
c) LO leakage and DC bias
d) Difference between CMOS and GaAs circuitry
Answer: c
Explanation: LO leakage and DC bias are a challenge for wide band digital signal processing using direct conversion receiver.
5. In which technique RF is amplified until it is hard-limited into a square wave?
a) Super heterodyne receiver
b) One-bit direct conversion digital receiver
c) Two-bit direct conversion digital receiver
d) Phase crossing counter receiver
Answer: b
Explanation: One-bit direct conversion digital receiver amplifies RF until it is hard limited into a square wave. An advantage of this architecture is that the channel states are stored in lookup tables.
6. When ____ of N zero crossings count becomes small, a signal is considered to be present.
a) mean
b) correlation
c) standard deviation
d) variance
Answer: d
Explanation: When zero crossings are simply counted, a small variance of N zero crossings indicate a signal to be present. A disadvantage of this technique is the presence of high speed logic and lack of equalization.
7. Which of the following is not used to control interference at RF?
a) Programmable digital notch filters
b) Active cancellation
c) Frequency separation
d) Antenna separation
Answer: a
Explanation: Physical antenna separation, frequency separation, programmable analog notch filters and active cancellation are the steps used to control interference at RF.
8. The ______ of out-of-band signal with bandpass characteristic of the receiver gives the interference in the receiver owing to out-of-band energy at the transmitter.
a) correlation
b) correlation and convolution
c) integral
d) convolution
Answer: d
Explanation: The convolution of out-of-band signal with bandpass characteristic of the receiver gives the interference in the receiver owing to out-of-band energy at the transmitter.This type of interference can affect the roll-offs. Frequency separation is employed to suppress this type of interference.
9. ____ separates uplink and downlink.
a) Frequency Division Duplexing
b) Time Division Duplexing
c) Frequency Division Multiplexing
d) Time Division Multiplexing
Answer: a
Explanation: Frequency Division Duplexing separates uplink and downlink to minimize interference. SDR operating on TDD can create dynamic FDD nets by a protocol that dynamically defines uplink, downlink and frequency separation.
10. A _____filter establishes maximum and minimum possible level for processing.
a) adaptive
b) flooring
c) roofing
d) content
Answer: c
Explanation: A roofing filter establishes the maximum and minimum linearly possible level for processing. It is also referred to as co-site filter.
11. Which of the following is a characteristic to be possessed by a roofing filter?
a) Low insertion loss
b) Fixed bandwidth
c) High insertion loss and fixed bandwidth
d) High insertion loss
Answer: a
Explanation: A roofing filter must have low insertion loss, programmable bandwidth and programmable center frequency for effective interference suppression.
12. Active cancellation is the process of introducing transmitted signal in the _____ for subtraction from the input signal.
a) transmitter
b) low pass filter
c) equalizer
d) receiver
Answer: d
Explanation: Active cancellation is the processing of introducing transmitted signal in the receiver for subtraction from the input signal. It is a part of interference suppression process.
13. In active radar blanking, communication between RF stage and rest of the communication system is ___ while the control line is ____
a) on, inactive
b) off, inactive
c) off, active
d) on, absent
Answer: b
Explanation: In active blanking, communication between RF stage and rest of the communication system is off while the control line is inactive. This is an example for active cancellation.
14. The required active cancellation is equal to ____ between the maximum non distorting input signal and the radiation level at the antenna.
a) half the difference
b) the difference
c) twice the difference
d) the correlation
Answer: b
Explanation: The amount of active cancellation to be provided is equal to the difference between the maximum non distorting input signal and the radiation level at the antenna. It is also given by the ratio of peak energy at the output of the receiver antenna terminal to the maximum linear energy.
15. The number and characteristics of roofing filter are determined by modulation of the subscriber signal.
a) True
b) False
Answer: a
Explanation: The modulation of the subscriber signal and bandwidth of the passband interference determine number and characteristics of roofing filter. The use of roofing filter establishes a noise floor and prevents dropped calls.
This set of Software Defined Radio Interview Questions and Answers focuses on “RF and IF Processing Tradeoffs – 2”.
1. RF integrated circuits generally comprise of _____
a) resonators and resistors
b) resistors
c) diodes
d) resonators and capacitors
Answer: d
Explanation: RF integrated circuits consist of off-chip resonators, inductors, and capacitors. Each device increases the production cost which is linear function of number of components.
2. RF MEMS gives _______ alternative to electronic switching circuits.
a) an electromechanical
b) a mechanical
c) an electro-dynamic
d) an interconnected
Answer: a
Explanation: RF MEMS gives an electromechanical alternative to electronic switching circuit. RF MEMS can aid in the reduction of size, weight and power.
3. Which of these is not a technique used to induce sharp resonance in resonators?
a) Rigidity
b) Bulk
c) Acoustic
d) Piezoelectric
Answer: a
Explanation: Resonator achieves sharp resonance by using bulk, acoustic and piezoelectric effects. By adapting the mentioned effects, quality factor in the range of 10,000 can be achieved.
4. In resonators with nanoscale I-beams, which factor does not affect the mechanical frequencies of I-beams?
a) Size
b) Density
c) Stiffness
d) Distance between beam and bottom of the cavity
Answer: b
Explanation: In resonators with nanoscale I-beams suspended over the cavity, the mechanical frequencies of I-beam are determined by size and stiffness of I-beam, and the distance between the beam and bottom of the cavity.
5. The industry standard figure of merit for an RF switch is ______
a) R0C1
b) R1C0
c) C0R1
d) C1R0
Answer: b
Explanation: The industry standard figure of merit for an RF switch is R1C0. It is given by the product of ON-resistance and OFF-capacitance. It is measured in femtoseconds.
6. RF MEMS allows selection of ____ and ____, increasing the degree of freedom in design process.
a) digital circuit and reverse engineering
b) analog circuit and reverse engineering
c) digital circuit and reengineering
d) analog circuit and reengineering
Answer: b
Explanation: RF MEMS allows the selection of switches from a collection of analog circuit and components. This is the direct implementation of MEMS in the design. Reengineering and selection of analog circuits are according to the programmability requirements of software defined radio.
7. Superconducting analog filters can reduce noise and interference introduced by wide bandwidth of SDR architecture.
a) True
b) False
Answer: a
Explanation: Superconducting analog filters can reduce noise and interference introduced by wide bandwidth of SDR architecture. The combined use of superconducting filter and regular anti-aliasing filter can offer better spectral purity.
8. Superconductors use ____ to maintain working temperature near _____
a) heat sinks, 70K
b) open cooling system, 80K
c) forced air, 75K
d) closed cooling system, 70K
Answer: d
Explanation: Superconductor analog filters make use of closed cooling system, and thermo-electric coolers to maintain working temperature near 70K.
9.RF amplifiers tend to be ____ amplifiers.
a) class A
b) class B
c) class C
d) class AB
Answer: c
Explanation: RF amplifiers operate in saturated mode . It non-linearly distorts the waveform. Class A, class B, and class AB are linear amplifiers. The output signals are linearly related to input signals.
10.Which of the following modulation type is incompatible with class C operation?
a) Frequency modulation
b) BPSK
c) QPSK
d) QAM
Answer: d
Explanation: Class C operation is incompatible with amplitude sensitive modulation type such as QAM. However it does not face any complication with amplitude insensitive modulation type such as FM.
11. Electronically Programmable Analog Components are also called as ____
a) FPGA
b) FPAA
c) Gate Array ASIC
d) Cell based ASIC
Answer: c
Explanation: Electronically Programmable Analog Components are also called as Field Programmable Analog Array . FPAAs combine conventional analog circuit such as filter, amplifier with programmable interconnect.
12. Which of the following is not a challenge to RF/IF conversion stage in military application?
a) Low phase noise
b) Tunable pre-selector
c) Single RF/IF up-down conversion
d) Fast tuning synthesizers
Answer: c
Explanation: Tunable pre-selector is required for co-site rejection. Low phase noise and fast tuning synthesizers are required for JTIDS and EPLRS. Single RF/IF up-down conversion is a commercial application challenge.
13. ____ fixes the input power dynamic range such that there are no sinusoidal RF conversion artifacts in the output.
a) Noise Figure
b) Two tone intermodulation product
c) Harmonics
d) SFDR
Answer: d
Explanation: Spurious Free Dynamic Range fixes the input power dynamic range such that there are sinusoidal RF artifacts in the output. The artifacts tend to mask weak signal.
14. The Nyquist criterion states that the sampling frequency of a band limited analog waveform must be at least ______ component to properly reconstruct the signal.
a) half the maximum frequency
b) twice the maximum frequency
c) half the minimum frequency
d) twice the minimum frequency
Answer: b
Explanation: The Nyquist criterion states that the sampling frequency of a band limited analog waveform must be at least twice the maximum frequency component to properly reconstruct the signal. Aliasing can be overcome by meeting Nyquist criterion and using filters.
15. The useful dynamic range applicable for antenna, RF/IF conversion, and ADC’s is given by the ratio of smallest processable signal to the smallest detectable signal.
a) True
b) False
Answer: b
Explanation: The useful dynamic range is given by the ratio of largest processable signal to the smallest detectable signal. It is applicable for antenna, RF/IF conversion, and ADC’s. Dynamic range is one of the controlling parameters in the design of software defined radio.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “ADC Tradeoffs – 1”.
1. Which of the following is the first step in establishing acceptable aliasing power?
a) Establish the relation between CIR and BER
b) Fix BER threshold
c) Convert BER threshold to CIR threshold
d) Apply the instantaneous dynamic range requirement of ADC
Answer: b
Explanation: The first step in establishing acceptable aliasing power is to fix the BER threshold based on QOS requirements of the waveform. The second step is to establish a relationship between CIR and BER. Then the BER threshold is converted to CIR threshold. The fourth and the final step is to apply the instantaneous dynamic range requirement of ADC.
2. Noise must be less than _____ of the ADC.
a) half of the LSB
b) LSB
c) half of the MSB
d) MSB
Answer: a
Explanation: The effect of aliasing, spurious response in IF/RF processing and other noise must be less than half of the least significant bit of the ADC. If this condition is satisfied, then all the bits of ADC give only the useful signal power.
3. To avoid aliasing, the wideband ADC is ____ by anti-aliasing filters to suitably alter the _____ waveform.
a) succeeded, digital
b) preceded, digital
c) succeeded, analog
d) preceded, analog
Answer: d
Explanation: Aliasing prevents faithful restoration of the signal. To avoid aliasing, the wideband ADC is preceded by anti-aliasing filters to suitably alter the analog waveform. The filters must have satisfactory stop-band attenuation.
4. The shape factor of an anti-aliasing filter is given by the ratio of the frequency at ___ dB attenuation point to the frequency at ___ dB point.
a) 80, 3
b) 3, 80
c) -80, -3
d) -3, -80
Answer: c
Explanation: Anti -aliasing filters require large shape factor for suppression of signals closer to the upper band-edge of ADC passband. The shape factor of an anti-aliasing filter is given by the ratio of the frequency at -80 dB attenuation point to the frequency at -3 dB point.
5. Which among the following filters has the slowest roll-off?
a) Cauer
b) Chebychev
c) Butterworth
d) Bessel
Answer: d
Explanation: Bessel function has the slowest roll-off factor among the four filters. The approximate value of shape factor is 6. It is a monotonic filter.
6. Which of the following expressions give the relation between power and quantization step size ?
a) p=q 2 /2R
b) p=q/2R
c) p=q 2 /R
d) p=q 2 *2R
Answer: a
Explanation: p=q 2 /2R is the relation between power and quantization step size. R is the input resistance.
7. Which of the following expressions give the SNR at the output of ADC?
a) SNR=6.02*B+1.76+10log(f s /2f max )
b) SNR=6.02*B+1.76+10log(2f max /fs)
c) SNR=12.04*B+1.76+10log(2f max /fs)
d) SNR=6.02*B+1.76
Answer: a
Explanation: SNR=6.02*B+1.76+10log(f s /2f max ) is the expression for SNR at the output of ADC. B is the number of bits. f s is the sampling frequency. f max is the maximum frequency component of the signal.
8. In non-monotonic filters, attenuation increases with frequency.
a) True
b) False
Answer: b
Explanation: In monotonic filters, attenuation increases with frequency. Non-monotonic filter has less attenuation. It allows energy beyond the passband and exhibits phase distortion.
9. Which of the following is untrue about Sigma-Delta ADC?
a) f s >2f max
b) Zero crossing detector consists of a sample and hold circuit
c) Aperture jitter is minimized due to integration
d) The integrating filter is preceded by a zero crossing detector
Answer: b
Explanation: Sigma-Delta ADC does not require a sample and hold circuit. The zero-crossing detector can be implemented by threshold logic.
10. Quadrature sampling uses ____ to ____ the bandwidth available for a particular sampling rate.
a) integration, quadruple
b) complex numbers, quadruple
c) complex numbers, double
d) integration, double
Answer: c
Explanation: Quadrature sampling uses complex numbers to double the bandwidth available for a particular sampling rate. It is a polyphase filter. Real signals are combined with cosine and sine reference signal generated by a local oscillator.
11. ____, ____ and ____ must be properly matched for effective representation of input signal in quadrature sampling.
a) Modulators, signal paths, correlator
b) Signal paths, modulators, zero crossing detector
c) Low pass filters, zero crossing detector, correlator
d) Low pass filters, modulators, signal paths
Answer: d
Explanation: Low pass filters, modulators,and signal paths must be properly matched for effective representation of input signal in quadrature sampling. Amplitude mismatch, inconsistent time duration in filters may lead to degradation of complex signal.
12. Which of the following is not a characteristic of IC implementation of quadrature sampling ADC?
a) Thermal difference is less than lumped components
b) Matching of passive component on IC substrate is easy
c) Matching of passive component on IC substrate is difficult
d) Thermal difference among filters is not large
Answer: c
Explanation: The integrated circuit implementation of quadrature sampling ADC is effective because of short signal paths, easy matching of passive components on IC substrate and low thermal difference among filters.
13. In Nyquist sampling, the ____ frequency is ______to the duration of the observation interval.
a) maximum recoverable, proportional
b) minimum resolvable, inversely proportional
c) maximum recoverable, inversely proportional
d) minimum resolvable, proportional
Answer: b
Explanation: In Nyquist sampling, the maximum recoverable frequency is given by the expression f s /2. The minimum resolvable frequency is inversely proportional to the duration of the observation interval. The observation interval is given by the number of time domain points.
14. Which of the following is not a characteristic of DAC?
a) Linearity
b) Level conversion
c) Grounding
d) Sample and hold circuit
Answer: d
Explanation: DAC does not use sample and hold circuit. However it does make use of setup and hold circuit which is similar to sample and hold circuit. Linearity, level conversion, grounding, and isolation of digital from analog waveform are characteristics of a DAC.
15. The principle behind Sigma-Delta ADC is oversampling.
a) True
b) False
Answer: a
Explanation: It can be observed from the expression SNR=6.02*B+1.76+10log\
\), as the sampling frequency increases, SNR increases. This is the principle behind Sigma-Delta ADC. The amount of oversampling is given by the ratio of sampling frequency to Nyquist frequency.
This set of Basic Software Defined Radio Questions and Answers focuses on “ADC Tradeoffs – 2”.
1. Which of the following is not a part of traditional RF subsystems?
a) Filter
b) Low noise amplifier
c) Multiplexer
d) Frequency translation
Answer: c
Explanation: The traditional RF subsystems comprise of preamplifier, low noise amplifier, filters, RF distribution, frequency translation, and filtering stages that convert RF signals to IF signals. Multiplexer is used in digital RF systems.
2. Limited dynamic range in digital RF system can be improved by _____
a) digital filter
b) digital amplifier
c) digital equalizer
d) digital suppressor
Answer: a
Explanation: RF ADC has a high sampling rate and it oversamples the bandwidth of the signal. The oversampling gain increases the dynamic range with the help of digital integrating filters.
3. ____ and ____ are the parameters that define software defined radio applications.
a) Linearity, SNR
b) Dynamic range, SNR
c) Linearity, Dynamic range
d) Bandwidth, SNR
Answer: c
Explanation: Linearity and Dynamic range are the parameters that define software defined radio applications. SNR is measured to determine the dynamic range. The SNR and DNR value is computed from the antenna to end user.
4. Which of the following influences the spurious free dynamic range?
a) Second-order intercept
b) Second-order intermodulation product
c) Third-order intercept
d) Third-order intermodulation product
Answer: d
Explanation: The point at which the output noise level is tangential to the power of the third-order intermodulation product of ADC determines the spurious free dynamic range of ADC.
5. The point of intersection of the fundamental signal with the power of third-order intermodulation product is called as _____
a) input-referenced third-order intercept point
b) output-referenced third-order intercept point
c) input-referenced third-order intermodulation point
d) output-reference third-order intermodulation point
Answer: a
Explanation: The increase in the third-order intermodulation product eventually results in the intersection of fundamental signal with the power of third-order intermodulation product. This is referred as input-reference third-order intercept point . The output power of the fundamental signal saturates before IP3.
6. Signal to noise ratio is the preferred metric when ____
a) desired signal bandwidth is less than Nyquist bandwidth
b) desired signal bandwidth is approximately equal to Nyquist bandwidth
c) desired signal bandwidth is greater than Nyquist bandwidth
d) bandpass sampling is used
Answer: b
Explanation: Signal to noise ratio is the preferred metric for ADC performance when the desired signal bandwidth is approximately equal to Nyquist bandwidth. Radar matched filter is an example for this condition. The matched filter optimally operates with the square shape of the radar pulses.
7. Which of the following is the preferred metric when the desired signal bandwidth is less than Nyquist bandwidth?
a) Noise Power Ratio
b) Spurious Free Dynamic Range
c) Full Power Analog Input Bandwidth
d) Half Power Analog Input Bandwidth
Answer: b
Explanation: Spurious Free Dynamic Range is the preferred metric when the desired signal bandwidth is less than Nyquist bandwidth. First generation cellular base station is an example for this condition. The AMPS signal is much smaller in bandwidth when compared to the spectrum allocation accessed by a cell site ADC.
8. The ratio of ______ the notch filter to the ____ the notch filter gives the Noise Power Ratio.
a) maximum spectral density inside, spectral density outside
b) spectral density inside , maximum spectral density outside
c) spectral density outside, maximum spectral density inside
d) maximum spectral density outside, spectral density inside
Answer: c
Explanation: The ratio of spectral density outside the notch filter to the maximum spectral density inside the notch filter gives the Noise Power Ratio. Noise Power Ratio is the preferred metric when the number of narrow band channels in the signal spectrum is high. It is measured by flooding the Nyquist bandwidth with white noise.
9. If W a is the receiver bandwidth and NF is the noise figure, the noise power of a noise limited receiver is given by the expression ____
a) P m =-184dBm+10log(W a )+NF
b) P m =-174dBm+10log(W a )+NF
c) P m =-174dBm+10log+W a
d) P m =-184dBm+10log+W a
Answer: b
Explanation: If W a is the receiver bandwidth and NF is the noise figure, the noise power of a noise limited receiver is given by the expression P m =-174dBm+10log(W a )+NF. The noise power of the noise limited receiver must be matched to power of the least significant bit of ADC.
10. Which of the following applications takes only SFDR as its performance metric?
a) Spread spectrum access
b) Wideband digital receiver
c) Cellular Phone
d) Spectrum analysis
Answer: b
Explanation: Spurious Free Dynamic Range is used in wideband digital receiver to quantify the reliability of detection of weak signals in the presence of strong in-band interference.
11. Which of the following metrics is considered for spread spectrum method?
a) SNR
b) SNR, SFDR
c) SNR, SFDR, NPR
d) SNR, NPR
Answer: c
Explanation: Spread spectrum uses SNR, SFDR and NPR for performance analysis. SNR is affected by small signals in an environment of strong interference. SFDR is degraded due to spatial filtering. NPR is affected by inter-channel cross talk.
12. Which of the following conditions does not affect SNR?
a) Small signals in an environment of strong interference
b) Wide band channelized receiver
c) High fidelity instrumentation
d) High dynamic range
Answer: d
Explanation: SNR is affected by small signals in an environment of strong interference in spread spectrum technique. Wide band channelized receiver affect SNR in Mobile Cellular applications. In spectrum analysis, SNR is influenced by high-fidelity instrumentation
13. The sampling rate of promising SDR technology ranges between _____
a) 1 MHz – 100 MHz
b) 10 MHz – 100 MHz
c) 1 MHz – 1 GHz
d) 1 MHz – 10 GHz
Answer: b
Explanation: The sampling rate of promising SDR technology ranges between 10 MHz – 100 MHz. The resolution falls in the range of 30 dB– 60 dB. Frequency division multiplexing uses few MHz IF-bandwidth. PCM, cellular band allocation, 3G, and air navigation signals use hundreds of MHz.
14. The NPR for an SDR can be determined by matching the radio noise floor to the ADC input noise level.
a) True
b) False
Answer: b
Explanation: The SNR and DNR can be determined by matching the radio noise floor to the ADC input noise level. This imposes the design rule that the total noise power should be less than half of the least significant bit of ADC. The ratio of spectral density outside the notch filter to the maximum spectral density inside the notch filter gives the Noise Power Ratio.
15. The point at which the output noise power of the fundamental signal shifts away from the ideal output power by 1-dB is called 1-dB expansion point.
a) True
b) False
Answer: b
Explanation: The increase in the third-order intermodulation product eventually results in the intersection of the fundamental signal with the power of third-order intermodulation product. This is referred as IP3. The output power of the fundamental signal saturates before IP3.The point at which the output noise power of the fundamental signal shifts away from the ideal output power by 1-dB is called 1-dB compression point.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “Digital Architecture Tradeoffs – 1”.
1. ____ is obtained by the product of number of parallel hardware elements and clock speed.
a) MIPS
b) MOPS
c) MFLOPS
d) KPI
Answer: b
Explanation: Millions of operation per second is obtained by the product of number of parallel hardware elements and clock speed. An operation is a logical transformation of data carried out by portion of hardware in one clock cycle.
2. A combination of a band and mode is called ______
a) matched pair
b) matched set
c) type
d) personality
Answer: d
Explanation: Each combination of band and mode is a multiple personality. A personality combines RF band, channel set, air interface waveform, protocol, and related functions.
3. Which of the following is not a hardware module?
a) Memory
b) DSP
c) Workstation
d) RF
Answer: d
Explanation: The development of a SDR involves accurate analysis of functional and statistical structure of hardware and software. The key step in system analysis is the identification of processing resources and characterization of processing capacity of digital hardware. Memory, DSP and workstation are few examples of digital hardware.
4. ____ is a technique where multiple instructions are overlapped during execution.
a) Pipelining
b) Caching
c) Instruction fetching
d) Mapping
Answer: a
Explanation: Pipelining is a technique where multiple instructions are overlapped during execution. Pipeline consists of many stages that vary from processor to processor. Pipelining increases the overall throughput of instruction execution.
5. ____ serves as a system control processor.
a) ADC
b) Bus host
c) DSP
d) Memory
Answer: b
Explanation: Bus host serves as a system control processor. Analog to Digital Converter is responsible for the conversion of an analog signal into a digital signal suitable for further processing. Digital Signal Processor supports real time channel processing.
6. Which of the following is not a type of digital-interconnect?
a) DSP
b) Dedicated interconnect
c) Wideband bus
d) Shared memory
Answer: a
Explanation: Dedicated interconnect, wideband bus and shared memory are different types of available digital-interconnect. In dedicated interconnect, the vendor of a board provides a suitable interconnect. Shared memory reserves a block of memory for communication. The performance of shared memory can be enhanced by operating with programmable Direct Memory Access or equivalent hardware.
7. Interconnect efficiency is a function of ____ being transferred.
a) number of data blocks
b) size of data blocks
c) type of data blocks
d) accuracy of data blocks
Answer: b
Explanation: Interconnect efficiency is a function of size of data blocks being transferred. Most buses exhibit low throughput for smaller block size. In addition to block size, features such as Direct Memory Access overhead, handshaking mechanism affect the overall throughput.
8. MFLOPS stands for Millions of Fixed Point Operation per Second.
a) True
b) False
Answer: b
Explanation: MFLOPSstands for Millions of Floating Point Operation per Second. An operation is a logical transformation of data carried out by portion of hardware in one clock cycle. MIPS, MOPS, MFLOPS are differentiated by their logical scope.
9. Architecture of local and global memory among processors can contribute to algorithm performance.
a) True
b) False
Answer: a
Explanation: Architecture of local and global memory among processors can contribute to algorithm performance. Balancing high speed data flow and bandwidth reduction leads to clustering of memory and processing capacity.
10. Which of the following is the first step in FEC decoding?
a) Input bitstream synchronization
b) Descramble
c) Decode
d) Symbol puncturing
Answer: a
Explanation: The first step in FEC decoding is input bitstream synchronization. It is followed by reversing the effect of symbol puncturing and estimation of transmitted bits. Then the resulting signal is decoded and descrambled.
11. FEC operations are ____
a) byte-serial
b) byte-parallel
c) bit-serial
d) bit-parallel
Answer: c
Explanation: Forward error control operations are bit-serial. It involves bit-level manipulations. They are usually carried out in registers of length 11, 13 etc. Additional bit-masking is required to implement FEC functions.
12. _____ interleave two systematic concatenated codes.
a)Turbo codes
b) Soft codes
c) Convolution codes
d) Trellis codes
Answer: a
Explanation: Turbo codes interleave two systematic concatenated codes. It improves error protection. Turbo codes exhibit high performance with low complexity encoding and decoding algorithms.
13. Which of the following ASIC is preferred in IF stage?
a) FEC ASICs
b) Digital filtering ASICs
c) Transceiver ASICs
d) INFOSEC ASICs
Answer: b
Explanation: Digital filtering ASICs are preferred in IF stage as they perform IF-baseband frequency translation and filtering. FEC ASICs are used for encapsulation in modem entity.
14. The access of architecture level functions from component level building blocks may be called _____
a) Universal plug and play
b) Tunneling
c) Ethernet
d) Point-to-point protocol
Answer: b
Explanation: The integration of Application Specific Integrated Circuits in SDR necessitates a means for passing control and data information. The access of architecture level functions from component level building blocks may be called tunneling. It requires the refinement of layered virtual machine architecture.
15. Which of the following options is not an aspect of tunneling facility?
a) Definition of interface points
b) Identification of constraints
c) Identification of processing capability
d) Resolving conflicts
Answer: c
Explanation: The functions of the tunneling facility include the definition of interface points, use of tunneled components, identification of constraints, and resolution of conflicts. The interfaces to the application objects are described to the radio infrastructure by using Tunnel function.
This set of Software Defined Radio Questions and Answers for Freshers focuses on “Digital Architecture Tradeoffs – 2”.
1. FPGA’s are designed specifically for fast implementation of ____
a) state machines
b) state flow
c) state machines and state flow
d) state machines and sequential logic
Answer: d
Explanation: A Field Programmable Gate Array is a configurable logic circuit. It consists of programmable logic blocks that can be connected in different formations. The layout is specifically designed for fast implementation of state machines and sequential logic.
2.State machines consist of ____ that represents the number of states.
a) a memory
b) states
c) clock
d) control signal
Answer: a
Explanation: State machines consist of a memory that represents the number of states. It detects input andgenerates output as a function of state transition.
3. A state transition maps the relation between ____and ____ to compute the _____
a) present state, input, output
b) present output, input, feedback
c) input, feedback, output
d) present state, output, feedback
Answer: a
Explanation: A state transition maps the relation between present state and input to compute the output. The output map chooses an appropriate output to be created during state transition.
4. Which of the following exhibits low efficiency when implemented using FPGA?
a) FFT algorithm
b) Database algorithm
c) Convolution algorithm
d) FEC algorithm
Answer: b
Explanation: Field Programmable Gate Array is suitable for algorithms having limited data scope such as Fast Fourier Transform and digital filtering. However degradation of performance occurs when -FPGA is used for algorithms operating on bulk data such as database algorithms.
5. Which of the following is not a layer in the soft radio model proposed by Srikanteswara?
a) Application layer
b) Configuration layer
c) Processing layer
d) Tunneling layer
Answer: d
Explanation: Srikanteswara envisioned a soft radio model with four layers. The processing layer comprises of reconfigurable hardware. The configuration layer translates packet header into configuration commands. The soft radio layer passes the processed data and errors to application layer. The application layer controls architecture parameters.
6. CORBA IDL is suitable for translating application layer request into a soft radio interface layer request.
a) True
b) False
Answer: a
Explanation: Common Broker Request Architecture was developed by Object Management Group. It facilitates communication between devices regardless of underlying hardware and different programming languages being used.
7. Early DSP devices contained ____ extension and ____ extension.
a) addressing, pipelining
b) instruction, data format
c) addressing, data format
d) instruction, pipeling
Answer: b
Explanation: Early DSP devices contained instruction extension and data format extension. These extensions increase the throughput by saving instruction cycles.
8. Which of the following addressing modes contain operand in the instruction?
a) Direct
b) Indirect
c) Register
d) Immediate
Answer: d
Explanation: Instruction set extension includes direct, indirect, register, and immediate addressing modes. Immediate addressing mode contains the operand in the instruction. The other addressing modes contain some form of address as a part of instruction.
9. ____ enables context switching.
a) Push/Pop of register stack
b) ALU
c) Bus
d) Memory
Answer: a
Explanation: An example of instruction set extension is rapid context switching. It is implemented using push/pop of register stack hardware. Hardware semaphore can be used for error-free sharing of resources.
10. Which of the following is not a data format extension?
a) Boolean
b) Floating
c) Fix
d) Double
Answer: a
Explanation: Fix, floating point and double are few types of data format extension used for representation of numbers. Boolean is a data type.
11. Clipper Chip Key – Escrow involves using ____ for security.
a) one way key
b) two way key
c) four way key
d) eight way key
Answer: b
Explanation: The Clipper Chip Key users are bound to provide their cryptography keys in escrow to the government. Two government agencies hold a portion of the key. The information is decrypted for investigation by the governmentonly upon the agreement of two government agencies.
12. ____ algorithm was used by Clipper Chip Key – Escrow cryptography technique for transmission of information.
a) Baton
b) Havequick
c) Saville
d) Skipjack
Answer: d
Explanation: Skipjack algorithm was used by Clipper Chip Key – Escrow cryptography technique for transmission of information. It uses the Diffie-Hellman key exchange algorithm for distribution of cryptographic session keys.
13. Which of the following is not a programmable INFOSEC module?
a) KY series
b) KG84
c) CYPRIS
d) VME
Answer: a
Explanation: KY series in involved in analog voice encryption. KG84 introduced externally invoked modes for authentication and streaming. CYPRIS and VME are advanced INFOSEC modules.
14. Programmable DSP are suitable for front-end filtering.
a) True
b) False
Answer: b
Explanation: DSP consumes lot of power and is suitable for channel modem and baseband signal processing tasks. ASIC is more power efficient and appropriate for front-end filtering.
15. Which of the following is not a DSP core?
a) Motorola DSP56300
b) TI TMS320/C54x
c) Motorola 56300
d) STEL-2000
Answer: d
Explanation: DSP cores are processors produced to be a part of DSP ASIC device. Motorola DSP56300 is a 24 – bit processor. TI TMS320/C54x and Motorola 56300 have 16 – bit processors.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “Software Architecture Tradeoffs – 1”.
1. _____ is assembling a cohesive set of data and functions to define an object.
a) Message passing
b) Encapsulation
c) Polymorphism
d) Inheritance
Answer: b
Explanation: The first step in the development of object oriented models is the identification of object classes. This is accomplished by encapsulation. Encapsulation is assembling a cohesive set of data and functions to define an object.
2. _____ facilitates interconnection across physical boundaries of various devices.
a) Polymorphism
b) Message passing
c) Filtering
d) Modulation
Answer: b
Explanation: Message passing permits conceptual integration of software components. It also facilitates interconnection across physical boundaries of various devices used for development such as FPGA.
3. Syntax and semantics of messages are compiled in a ______
a) data dictionary
b) data directory
c) method dictionary
d) method directory
Answer: a
Explanation: Syntax and semantics of messages are compiled in a data dictionary. The proper format and meaning of messages are necessary for successful integration of software and hardware.
4. ____ enables the definition of reusable classes.
a) Polymorphism
b) Inheritance
c) Object
d) Overloading
Answer: b
Explanation: Property inheritance allows the definition of reusable classes of software objects. This allows the synthesis of task-specific objects. FIR is an example for a generic software object and mark filter is an example for task-specific software object.
5. _____ is the ability of a software object to exhibit different behavioursin accordance to the current context.
a) Polymorphism
b) Inheritance
c) Object
d) Class
Answer: a
Explanation: Polymorphism is the ability of a software object to exhibit different behaviours in accordance to the current context. Polymorphism adds a degree of independence to underlying data structure. It also eliminates duplicate code.
6. Abstract external objects are called ____ in UML terminology.
a) actions
b) actors
c) actuators
d) actuation
Answer: b
Explanation: The UML is a general purpose, modeling language intended to provide a standard way for defining the design of a system. Abstract external objects are called actors in UML terminology. Actors have properties and behavior that shape the system design.
7. ____ is an isochronous stream.
a) Control flow
b) Data flow
c) Signal flow
d) Control flow and data flow
Answer: c
Explanation: Signal flow is an isochronous stream. Data flow contains near-real-time data packets. Control flow shifts control of processor towards software objects. The context diagram identifies all signal flows, data flows, and control flows with external entities.
8. _____ must invoke an appropriate response from the software.
a) Object
b) Call
c) Event
d) Prompt
Answer: c
Explanation: External event is a stimulus that invokes an appropriate response from the system. Each event might invoke more than one system response. A comprehensive collection of events is called an event-response list.
9. Techniques such as positive acknowledgement and timeouts must be employed to prevent ____ of critical event.
a) delay
b) continuous selection
c) retransmission
d) suspension
Answer: d
Explanation: Interference generates false messages and masks legitimate messages. The permanent suspension of a falsely masked message can be prevented by techniques such as positive acknowledgement and timeout.
10. A trace of the path created by stimulus-response event pair is called ____
a) procedure
b) sequence
c) tracer
d) thread
Answer: d
Explanation: Each event might invoke more than one system response. A comprehensive collection of events is called an event-response list. A trace of the path created by stimulus-response event pair is called thread. For example, if caller and respondent are objects, then a trace would contain the caller, handset, MTSO, PTSN, and the respondent.
11. In UML terminology, the process of tracing is called ____
a) context diagram
b) context flow
c) use-case analysis
d) event flow
Answer: c
Explanation: A trace of the path created by stimulus-response event pair is called thread. In UML terminology, the tracing of the interactions among external actors and the encapsulated system is called use case analysis.
12. _____ thread must be completed within a short window.
a) Isochronous
b) Near-real-time data packets
c) Non-critical
d) Use-case analysis
Answer: a
Explanation: Signal flow is an isochronous stream. Isochronous thread must be completed within a short window. Isochronous threads tend to be classes with timing constraints especially in multiple inheritance object oriented environment.
13. Enterprise architectures should promote ____ paths among object representations.
a) evolution
b) progression
c) continuity
d) migration
Answer: d
Explanation: Enterprise architecture promotes standard classes and facilitates reusable objects. Enterprise architectures should promote migration paths among object representations. Enterprise architecture is open for alternatives to prevent inappropriate suppression of software definition approach.
14. Setup and control is a message useful for object interfaces.
a) True
b) False
Answer: a
Explanation: The proper format and meaning of messages are necessary for successful integration of software and hardware. Setup and control, state and state transition, information stream with specific timing constraint, timing and frequency standard information are examples of useful messages for object interfaces.
15. The degree of “reach” required is determined by the number of the software components.
a) True
b) False
Answer: b
Explanation: The degree of “reach” required is determined by the scope of the software components. If an object is locally defined, then team level agreement on data and behavior is sufficient. If it were to extend among multiple teams, agreement on a large scale is required.
This set of Software Defined Radio Interview Questions and Answers for Experienced people focuses on “Software Architecture Tradeoffs – 2”.
1. The channel object obtains system resources for the _____
a) channel
b) mode
c) band
d) waveform
Answer: d
Explanation: The channel object may be organized as a set of software objects that carry out the assigned sub-system level functions of RF control, modem processing, INFOSEC, and internetworking. The channel object obtains system resources for the waveform.
2. ____ are the functional objects that implement the personalities of channel objects.
a) Agents
b) Ghost objects
c) Modem objects
d) Modem events
Answer: a
Explanation: Agents are the functional objects that implement the personalities of channel objects. It may be organized around the top-level system functions of RF control, modem processing, etc. It may also serve as hosts for buses, manage IO processes, etc.
3. System control handles ____
a) message processing
b) protocol stacks
c) boot-up
d) internetworking
Answer: c
Explanation: Message processing, managing protocol stacks and internetworking are examples of back-end objects. System control handles system boot-up, initial time of day, current hop, etc.
4. Which of the following is not a stage of a state machine?
a) Waiting for instantiation
b) Waiting for timer
c) Fetching the waveform
d) Waiting for response
Answer: b
Explanation: A state machine is any device that stores a status for a given time. The status may change according to the input. Waiting for instantiation, fetching the waveform, and waiting for response are the three stages of a state machine. Conditions for switching from one state to another are a part of the state machine.
5. _____ can be in exactly one of a countable number of states at any given time.
a) Push-down automata
b) Agent state machine
c) Finite state machine
d) Infinite state machine
Answer: c
Explanation: A state machine is any device that stores a status for a given time. It consists of a finite set of distinct states, a set of inputs, a set of outputs, a next state map and an output map. Finite state machine can be in exactly one of a finite number of states at any given time.
6. How can a finite state machine be converted into a push down automata?
a) By including a push-down stack
b) By including a push-down stack with Push function
c) By including a push-down stack with Pop function
d) By including a push-down stack with Push and Pop function
Answer: c
Explanation: A finite state machine be converted into a push down automata by including a push-down stack with Push and Pop function. Push-down automata supports unlimited number of states. The availability of stack space and time taken to reach certain states are challenges for push-down automata.
7. ____ is responsible for availability of resources on the logical path over which the channel is defined.
a) Finite state machine
b) Push-down automata
c) Agent state machine
d) Channel control state machine
Answer: d
Explanation: At the top level, each channel object, mode or personality has a top-level channel-setup state machine. Channel control state machine is responsible for availability of resources on the logical path over which the channel is defined. It is generally referred to as infrastructure state machine.
8. In the software factory, _____ protocol profiles are defined so that combinations of services and applications can work together.
a) independent
b) aggregate
c) mutually consistent
d) fixed
Answer: c
Explanation: Communication services are a part of software radio architecture. They carry out applications such as internet access and radio-specific applications. Mutually consistent protocol profiles are defined so that combinations of services and applications can work together.
9. A sequence of calls links____ layer with radio application layer.
a) service
b) radio infrastructure
c) hardware
d) application
Answer: a
Explanation: A sequence of calls behaves as interface between service layer and radio application layers. It sets up radio applications. It creates link for information services. It is used for bridging in military applications.
10. The software tradeoffs at ____ level of the architecture involve the user.
a) communication services
b) radio application
c) radio infrastructure
d) hardware
Answer: a
Explanation: Seamless access to facilities of other layers, enhanced capability, enhanced interoperability, easy access to off-the-shelf software products and protocols are few tradeoffs seen in the communication services level of the architecture.
11. _____ translates laptop level display information to a level suitable for handheld device.
a) Transmission Control Protocol
b) Graphic User Interface
c) Simple Network Management Protocol
d) Wireless Access Protocol
Answer: d
Explanation: Wireless Access Protocol is a technical standard for accessing information over a mobile wireless network. It is interoperable with different network technologies such as CDMA and GSM. It translates laptop level display information to a level suitable for handheld device.
12. Which of the following is not a facility offered by infrastructure layer?
a) Synchronization
b) High speed interconnect
c) Resource management
d) Position generation
Answer: b
Explanation: Infrastructure layer manages the resources of the distributed multiprocessor environment. It simplifies interfaces and entities for efficient deployment. Synchronization, resource management, position generation, and signal path packages are some services facilitated by infrastructure layer.
13. Radio application layer constructs physical and virtual radio channels.
a) True
b) False
Answer: a
Explanation: Radio application layer binds distributed objects together into waveforms. It constructs physical and virtual radio channels from paths provided by infrastructure layer. The interface between radio application layer and infrastructure layer is defined by CORBA IDL.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “Performance Management Tradeoffs”.
1. Which of the following expression can be used to compute processing demand provided if , P s , P bs , P bb and P mo stands for IF, source, bitstream, baseband, and management overhead processing demand respectively?
a) P=P if +P s +P bs +P bb +P mo
b) P=P bb +N*(P if +P mo )+P s +P bs
c) P=P if +N*(P s +P bs +P bb )+P mo
d) P=P if +(P bs *P bs *P bb )+P mo
Answer: c
Explanation: P=P if +N*(P s +P bs +P bb )+P mo is the expression used to compute processing demand. Processing demand depends on a first-order approximation on the signal bandwidths. It is also influenced by the intricacy of the operations in the IF, baseband, bitstream, and source segments.
2. Resource utilization is the ratio of average _____ to average _____
a) offered demand, effective capacity
b) offered demand, offered capacity
c) effective demand, effective capacity
d) effective demand, offered capacity
Answer: a
Explanation: Resource utilization relates processing demand to processing capacity. It is given by the ratio of average offered demand to average effective capacity. It can be estimated for buses, CPUs, storage devices, I/O devices, and DSP chips.
3. Effective utilization is observed when utilization value is kept _____
a) greater than 0.5
b) less than 0.5
c) between 0.5 – 0.75
d) between 0.65 – 0.75
Answer: b
Explanation: Good performance is observed when utilization is less than 0.5. There is 50% available capacity. The unprecedented performance degradation generally causes utilization to fall in the range between 0.5 – 0.75. When utilization is greater than 0.75, the system is regarded as unstable.
4. _____ characterizes data flow path.
a) Data path model
b) Queuing model
c) Operational model
d) Critical resource model
Answer: d
Explanation: The first step in performance management process is the identification of critical resources. Critical resource model characterizes data flow path, control flow path and each of the significant processing source.
5. Which of the following is the second step in performance management technique?
a) Comparison of critical resource model
b) Creation of queuing models
c) Categorization of critical resource model
d) Creation of performance management spreadsheet
Answer: d
Explanation: The performance management spreadsheet systematizes the description of processing demand. If processing capacity is estimated early in the development cycle, facility utilization can be automatically estimated.
6. _____ are software configuration items that are encapsulated as objects.
a) Pseudo objects
b) Load objects
c) Rounded objects
d) Quantified objects
Answer: d
Explanation: Quantified objects are software configuration items that are encapsulated as objects. It is accessed via message passing, consumes particular data and program memory, and consumes specified processing resources.
7. Which of the following is not a step involved in the estimation of MIPS change induced by re-hosting scenarios?
a) Translation of instruction mix to the new processor
b) Determination of instruction mix of the library object
c) Deposition of instruction mix to the new processor
d) Determination of demand per processor to manage resource utilization
Answer: c
Explanation: The change induced in MIPS due to re-hosting scenarios is computed by determining the instruction mix of the library object, translating the instruction mix to the new processor, and determining demand per processor to manage resource utilization. It is important to determine this parameter to compute the number of new processors required for large scale application.
8. Which of the following is not described about an object in a performance management spreadsheet?
a) Thread
b) Instruction set
c) Processor
d) Trigger event
Answer: b
Explanation: The performance management spreadsheet identifies the particular thread managed by an object, processor on which it runs, event that triggers the thread, and the stimulus rate of those events. The spreadsheet also sums the total demand produced by a processor.
9. The _____ is the sum of the time delays experienced in each processor that supports the thread.
a) overall delay
b) aggregate delay
c) response time
d) aggregate time
Answer: c
Explanation: The response time is the sum of the time delays experienced in each processor that supports the thread. The resource management spreadsheet computes these sums for all threads defined in the system. The traces of the thread over the network are used to verify the accuracy of the calculation.
10. The number of instructions per invocation is called _____
a) object complexity
b) thread complexity
c) instruction complexity
d) instruction set complexity
Answer: b
Explanation: The number of instructions per invocation is called the execution complexity, thread complexity, sub thread complexity, or just the complexity. The product of processor MIPS and processor fraction divided by invocation rate yields equivalent instructions per invocation.
11. The total software demand is given by __________
a) Thread activation rate +
b) + Sub thread load factor
c) Thread activation rate* Complexity * Sub thread load factor
d) Thread activation rate + Complexity + Sub thread load factor
Answer: c
Explanation: The total software demand is given by the product of thread activation rate, complexity, and sub thread load factor. The load factor reflects the number of times a sub thread is invoked for an incoming stimulus. The number of instructions per invocation is called the complexity.
12. Which of the following is not a software requirement required by CDMA?
a) Symbol integration
b) Blind equalization
c) Tracker
d) Viterbi decoder
Answer: a
Explanation: Carrier tracking is achieved by tracker. Viterbi decoder is a maximum likelihood majority decoder. Blind equalization is implemented by weighted tapped delay line filter. These functionalities are accomplished using software. Although symbol integration is required by CDMA, it is implemented using ASIC.
13. _____ is the intersection of a thread with a processor.
a) Link
b) Sub thread
c) Wire
d) Process
Answer: b
Explanation: A thread is a complete path from event trigger to response. A sub thread is the intersection of a thread on a processor. It may consist of a single object invocation, or multiple objects may be invoked.
14. Determining the overall performance is a step carried out to establish specification.
a) True
b) False
Answer: a
Explanation: Determining the average performance, selecting a variance ratio, and using incomplete Gamma function are the steps involved in establishing specification.
15. The performance management process consists of two steps.
a) True
b) False
Answer: b
Explanation: Identification of critical resources, creation of performance management spreadsheet, analysis of queuing implications, and analysis of variance are the four steps in the performance management process.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “Smart Antenna ”.
1. Smart antenna integrates the contributions of _____ antenna elements.
a) band distributed
b) band centralized
c) spatially distributed
d) spatially centralized
Answer: c
Explanation: Smart antenna integrates the contributions of spatially centralized antenna elements. Frequency reuse and co-channel suppression characteristics of smart antenna provide wireless communication systems with large capacity and high quality links.
2. If a multibeam array has ____, it may not be feasible to assign a complete frequency-reuse plan to each beam.
a) a single beam
b) two beams
c) less than five beams
d) more than ten beams
Answer: d
Explanation: If a multibeam array has more than ten beams, it may not be feasible to assign a complete frequency-reuse plan to each beam. This is due to the interference with adjoining sectorized antennas.
3. Interference with adjoining sectorized antennas can be avoided by _____
a) frequency nulling
b) spatial nulling
c) spatial beam-forming
d) frequency beam-forming
Answer: b
Explanation: The interference with adjoining sectorized antenna can be avoided by the introduction of spatial nulls in the direction of nonsubscriber signal components. In high traffic intensity areas, nulls track subscribers that are on the same frequency and cancel their path movements.
4. Spatial nulling subsystem replaces three element sectors of conventional base station with ____ disposed antenna elements.
a) four spherically
b) eight spherically
c) four circularly
d) eight circularly
Answer: d
Explanation: Spatial nulling subsystem replaces three element sectors of conventional base station with eight circularly disposed antenna elements. The signal is then preamplified and converted to digital form using eight wideband ADCs.
5. In the context of smart antenna, SAT stands for _____
a) Scholastic Assessment Test
b) Site Acceptance Test
c) Saturation
d) Supervisory Audio Tones
Answer: d
Explanation: The out-of-band Supervisory Audio Tones generated by the basestation is relayed in the mobile. The base station can therefore differentiate its subscribers from cochannel interference based on SAT.
6. _____ process determines delay azimuth parameters.
a) Stationary
b) Auto correlation
c) Cross correlation
d) Convolution
Answer: c
Explanation: Cross correlation process determines delay azimuth parameters needed for the final beam forming-equalization stage. The resulting signal exhibits enhanced carrier to interference ratio.
7. Which of the following statements is false regarding the spatial distribution of a wavefront?
a) Multipath components are collinear with direct path
b) Multipath components have less signal strength than direct path
c) Multipath components are present
d) Multipath components exhibit time delay
Answer: a
Explanation: Multipath components exhibit delay with respect to main components. They are not collinear with direct path. They have less signal strength than direct path. When interference is present, it tends to mix with multipath components.
8. In space-time adaptive processing, _____ and equalization parameters are calculated _____
a) diversity, jointly
b) diversity, independently
c) beamforming, jointly
d) beamforming, independently
Answer: c
Explanation: Space-time adaptive processing involves two-dimensional filtering technique using a phased array antenna with multiple spatial channels. In space-time adaptive processing, beamforming and equalization parameters are calculated jointly.
9. In ____, the interference has difference placement on the long-code.
a) GSM
b) AMPS
c) CDMA
d) FDMA
Answer: c
Explanation: Cellular systems employ different techniques to differentiate subscriber signal from co-channel interference. In the case of CDMA, the interference has a different placement on the long-code. In the case of GSM, the burst has different header bits.
10. ____ is a method used for calculating beamforming weights.
a) Sample matrix inversion
b) Indirect matrix inversion
c) Convolution
d) Correlation
Answer: a
Explanation: Sample matrix inversion or direct matrix inversion is a method used for calculating beamforming weights based on a known training sequence of length L. Adaptive algorithms iterate the weights in accordance to the received training sequence. A final estimate is obtained at the end of the training sequence.
11. ____ technique exploits lack of coherence between desired signal and interference.
a) Multibeam arrays
b) Adaptive spatial nulling
c) Beamforming
d) Space-time adaptive processing
Answer: d
Explanation: Space-time adaptive processing technique exploits lack of coherence between desired signal and interference. It separated the signals in parameter space. It can be employed to reduce collinear interference.
12. In_____, the highest-power signal is demodulated to estimate its bitstream.
a) maximum likelihood
b) sequential interference cancellation
c) least mean square
d) recursive least square
Answer: b
Explanation: In sequential interference cancellation, the highest-power signal is demodulated to estimate its bitstream. By employing this technique, co-channel interference from strongest interferer can be reduced substantially.
13. Decoded Channel Bits Interface is defined between ____ functional block and ____ functional block.
a) antenna, RF/IF
b) RF/IF, modem
c) modem, INFOSEC
d) INFOSEC, bitstream
Answer: c
Explanation: The process of digital to analog conversion, filtering add noise to signals. To mitigate this condition, an interface is introduced between the smart antenna and the core base station. Decoded Channel Bits Interface is defined betweenmodem functional block and INFOSEC functional block.
14. Multibeam antenna technology is more complex than null-forming.
a) True
b) False
Answer: b
Explanation: Null forming is more complex than mutlibeam antenna technology. Multibeam antenna is used to enhance SNR. Null-forming is used to suppress interference in high density traffic.
15. Maximum likelihood techniques formulate the likelihood ratio for a sequence of channel symbols.
a) True
b) False
Answer: a
Explanation: Maximum likelihood techniques formulate the likelihood ratio for a sequence of channel symbols. The maximum likelihood ratio determines signal parameter estimate.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “Software Component Characteristics”.
1. Which of the following is not present in the source segment of a mobile unit?
a) Narrowband ADCs
b) Source encoder
c) Source decoder
d) Interface to the PSTN
Answer: d
Explanation: Source segment of mobile unit differs from basestation. The mobile unit source segment comprises of source encoder, source decoder, narrowband ADCs, and narrowband DACs. The bases tation consists of interface to the public switched telephone network for access to remote source coding.
2. ____ is the process of non-linear compression and expansion of analog electronic signal.
a) Quantization
b) Companding
c) Pulse code modulation
d) Modulation
Answer: b
Explanation: Companding is the process of non-linear compression and expansion of analog electronic signal. The dynamic range of the signal is compressed at the transmitter and is expanded to the normal range at the receiver. It helps in the preservation of information content.
3. CELP stands for ____
a) Codebook Evolved Linear Processing
b) Codebook Excited Linear Prediction
c) Cross-correlation Excited Linear Prediction
d) Cross-correlation Evolved Linear Processing
Answer: b
Explanation: Codebook Excited Linear Prediction is a linear speech coding algorithm. It uses an adaptive and a fixed codebook as the input of the linear prediction model.
4. ____ software supports system control and user-interface functions.
a) Voice processing
b) Mode processing
c) Message processing
d) Network processing
Answer: c
Explanation: Message processing software supports system control and user-interface functions. It sets up the direction of the channel, its associated crypto algorithm, AGC loop bandwidth, and transmission and reception parameters.
5. User interface software allows the ____ of ____ between a core system processor and an external head.
a) direction, signal
b) distribution, channel control
c) distribution, signal
d) direction, channel control
Answer: b
Explanation: User interface software determines and controls status externally. User interface software allows the distribution of channel control between a core system processor and an external head. The core system processor implements user interface functions. The external head may request status and provide control parameters.
6. The ____ function is used to connect two front end channels.
a) joining
b) assembling
c) bridging
d) cooperative
Answer: c
Explanation: The front end channels typically operate in different modes and bands. The bridging function is used to connect two front end channels. For example a standard radio can be bridged with frequency hopped radio using bridging function.
7. ____ messages hold setup information for digitally vocoded voice.
a) Bitstream
b) INFOSEC
c) Modem
d) Internetworking
Answer: d
Explanation: Internetworking messages hold setup information for digitally vocoded voice, along with the type of vocoder, and the associated data rate. Internetworking also uses ACK, NACK, buffer management, and message forwarding functions.
8. Which of the following is not an SDR function associated with presentation layer?
a) Radio network configuration
b) Encryption
c) Virtual terminals
d) Object request broker
Answer: a
Explanation: Encryption, virtual terminals, object request broker for interconnecting applications are the SDR functions associated with presentation layer. The presentation layer provides translation and mappings with control code translations.
9. Which of the following is not a responsibility of the data link layer?
a) Framing
b) Integration
c) Addressing
d) Error control
Answer: b
Explanation: The data link layer is responsible for framing, physical addressing and error control. It also retransmits packet if necessary. The SDR functions include creation of point to point interface and adaptive quality management.
10. Bitstream processing performs _____
a) data encryption
b) transmission termination
c) connection tests
d) frame alignment
Answer: d
Explanation: Data encryption, transmission termination, and frame alignment are functions carried out by INFOSEC processing software. Frame alignment, bit stuffing and bit interleaving are functions of bitstream processing software.
This set of Software Defined Radio Architecture Questions and Answers for Aptitude test focuses on “Essential Function of Software Radio”.
1. Which of the following is not a part of the channel encoder/decoder section in the functional model of software defined radio?
a) RF/Channel access
b) Source coding
c) IF processing
d) Modem
Answer: b
Explanation: The channel encoder/decoder section comprises of RF/Channel access, IF processing, and modem. RF/Channel access includes antenna and RF conversion. IF processing stage includes filtering, and frequency translation. Modem is responsible for waveform definition.
2. ____ may include digital beam forming.
a) Modem
b) ADCs
c) Channel access
d) IF processing
Answer: d
Explanation: IF processing may include filtering, frequency translation, digital beam forming, joint space time equalization, integration of space diversity and frequency diversity.
3. ____ connects sources that are physically remote from the radio node.
a) INFOSEC
b) RF/Channel access
c) Network support
d) Communication services
Answer: c
Explanation: The sources, which are physically remote from the radio node, are connected via Synchronous Digital Hierarchy, Local Area Network or other networks to the radio node by service and network support.
4. Joint control may grow towards autonomous selection of ____ and ____
a) band, mode
b) band, personality
c) mode, personality
d) personality, protocol
Answer: a
Explanation: Joint control may grow towards autonomous selection of band, mode, and data format. Joint control guarantees system stability, error recovery, and isochronous streaming of voice and video.
5. _____ is essential to ensure that the required resources do not exceed the available resources of a radio platform.
a) Joint control
b) Host processor
c) Host controller
d) Evolution support
Answer: d
Explanation: Evolution support is essential to ensure that the required resources do not exceed the available resources of a radio platform. It monitors the definition and download process of waveform personalities. It also verifies whether a personality is safe for activation.
6. ____ ensures data integrity.
a) INFOSEC
b) TRANSEC
c) Network support
d) Source coding
Answer: a
Explanation: Information security operations such as authentication and stream enciphering ensure data integrity. Further, authentication reduces fraud and stream enciphering assures privacy.
7. ____ device allows inclusion of new hardware components without external physical intervention.
a) Configurable
b) Plug and Play
c) DSP
d) ASIC
Answer: b
Explanation: Plug and Play device facilitate the inclusion of hardware components without physical configuration or external user intervention. A challenge posed by plug and play modules is the definition of interface points.
8. Which of the following is not characteristic of a plug and play module?
a) Compatibility
b) Configurability
c) Controllability
d) Predictability
Answer: b
Explanation: The plug and play module must be compatible with radio environment. It must be controllable under defined module and have predictive usage of resources.
9. ____ must preserve radio service-defining properties of the system.
a) Module control
b) Module composition
c) Joint control
d) Joint composition
Answer: b
Explanation: Module composition must preserve radio service-defining properties of the system. It prevents erroneous results from being generated on control commands. It also ensures proper consumption of computational resources.
10. Digital translation of a baseband signal into an IF is an example for ____
a) continuous-time point operation
b) continuous-frequency point operation
c) discrete-time point operation
d) discrete-frequency point operation
Answer: c
Explanation: Digital translation of a baseband signal into an IF is an example for Discrete-time point operation. Discrete-time point operation involves the multiplication of discrete time-domain baseband waveform by a discrete reference carrier to give sampled in-phase IF waveform.
11. Which among the following is not a property of offline software support?
a) System analysis
b) Air interface modes
c) Re-hosting of hardware
d) Signal processing
Answer: b
Explanation: System analysis, re-hosting existing software on new hardware, and advanced signal processing are properties of offline software support. It is achieved by prototyping and linking with channel processing streams. It also allows debugging of algorithms.
12. How are the bits at the output of INFOSEC stage referred?
a) Black bits
b) Shielded bits
c) White bits
d) Clear bits
Answer: d
Explanation: The bits at the output of INFOSEC are referred to as clear bits. These are then operated on to give network or source bits. Network bits comply with network protocols and the source bits are passed to source decoder.
13. _____ stream characterizes radio surrounding usage in terms of time, frequency, and space.
a) Online adaption
b) Offline adaption
c) Environment management
d) Real-time channel processing
Answer: c
Explanation: Environment management stream characterizes radio surrounding usage in terms of time, frequency, and space. It also includes channel identification and estimation of channel interference levels.
14. Digital-access bandwidth is approximately double of the sampling rate of the ADC in the isochronous subscriber signal-processing path.
a) True
b) False
Answer: b
Explanation: Digital-access bandwidth is approximately half of the sampling rate of the ADC in the isochronous subscriber signal-processing path. Digital access bandwidth and degree of flexibility are two important parameters of a software defined radio.
15. The introduction of plug and play modules in software defined radio involves partitioning of functions and components
a) True
b) False
Answer: a
Explanation: A partition should ensure clear matching of functions to components. The physical interfaces among components must correspond to logical interfaces among functions.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “Hardware Architecture – 1”.
1. Which among the following is not a part of RF front-end section in receive mode?
a) Antenna-matching unit
b) Low-noise amplifier
c) Power amplifier
d) ADC
Answer: c
Explanation: The RF front-end section in receive mode consists of antenna-matching unit, low noise amplifiers, filters, local oscillators, and analog to digital converters. The power amplifier is a part of RF front-end section in transmit mode.
2. The circuits of transmit mode in RF front end _____ RF signal.
a) suppresses
b) synthesizes
c) boosts
d) modulates
Answer: b
Explanation: The circuits of transmit mode in RF front end synthesizes RF signal. The generated signal must not introduce disturbance at any other frequencies and affect other users of the spectrum.
3. ____ time aligns a signal and fits it into the information bandwidth.
a) AGC
b) Channel equalizer
c) Modem
d) Tracking loop
Answer: c
Explanation: The modem generates the signal to be transmitted and processes the signal received in case of a full duplex radio. It also time aligns, de-spreads a signal and fits it into the information bandwidth.
4. The number of times an electronic signal changes its state is measured by ____
a) word rate
b) signal rate
c) bit rate
d) baud rate
Answer: d
Explanation: Baud rate gives the rate at which information is sent in a communication channel. The number of times an electronic signal changes state is measured by baud rate.
5. The modem may include ____ to correct channel multipath artifacts.
a) equalizer
b) frequency offset
c) AGC
d) interference suppressor
Answer: a
Explanation: The modem may include equalizer to correct channel multipath artifacts and for filtering and delay distortions. Equalization is carried out after the modem time aligns a signal according to baud time.
6. ____ can be used to correct encoded symbols received in error.
a) Fine filter
b) Structured redundancy
c) Tracking loop
d) De-spreading
Answer: b
Explanation: If the waveform were to include error detection and correction technique such as FEC coding, structured redundancy would be introduced in the coding process. The structured redundancy is exploited to detect and correct encoded sequences that were received in error.
7. The modem groups the bits to be transmitted into ____
a) packet
b) symbol
c) frame
d) segment
Answer: a
Explanation: The procedure performed for transmission at the modem is the inverse of the procedure performed for reception. The modem groups the bits to be transmitted into packet, and then structured redundancy is introduced for error correction at the receiver.
8. A ____ is used to represent a symbol.
a) scale
b) number
c) figure
d) waveform shape
Answer: d
Explanation: Each symbol is represented by a waveform. The modem synthesizes the waveform and filters it to fit within the desired bandwidth.
9. ____ depends on the amount of redundancy in a data stream.
a) Encryption
b) Data compression
c) Encoding
d) Grouping of data
Answer: b
Explanation: Data coding has different types of redundancies within a message or between messages. Data compression ranges from 10% to 50% depending on the amount of redundancy present in original information data stream.
10. The modem must control ____ to produce the desired carrier frequency.
a) filter
b) low noise amplifier
c) power amplifier
d) antenna-matching unit
Answer: c
Explanation: The modem controls external RF elements, including transmit and receive mode, carrier frequency and smart antenna. The modem controls power amplifier and local oscillators to produce the desire carrier frequency.
11. Speech application typically runs on ____ processor.
a) DSP
b) GPP
c) FPGA
d) ASIC
Answer: a
Explanation: The application processer usually runs voice coder, video coder, data coder, and web browser functions. Speech and video applications run on DSP processor. Text and web browsing run on GPP processor.
12. Which of the following is not a characteristic of cryptographic security?
a) Confidentiality
b) Authentication
c) Authorization
d) Latency
Answer: d
Explanation: The cryptographic security function must encrypt any information to be transmitted. Confidentiality, data integrity, authentication, source authentication, authorization and non-repudiation are the characteristics of cryptographic security as defined by US National Institute of Science and Technology .
13. ____ is used to identify the creator of information.
a) Integrity authentication
b) Source authentication
c) Integrity authorization
d) Source authorization
Answer: b
Explanation: Integrity authentication verifies the reliability of data. Source authentication is used to identify the creator of information. Digital signature and key agreement techniques are examples of authentication services.
14. Encryption is a generalized process.
a) True
b) False
Answer: b
Explanation: Each application has a distinctive encryption process, and encryption cannot be generalized. The Digital Encryption Standard and Advanced Encryption Standard from US National Institute of Technology monitor the standard for cryptographic process.
15. The modem controls the antenna matching unit to maximize voltage standing wave ratio.
a) True
b) False
Answer: b
Explanation: Antenna matching unit is a part of RF front end section in transmit mode and in receive mode. In transmit mode, the modem controls the antenna matching unit to minimize voltage standing wave ratio.
This set of Software Defined Radio Architecture MCQs focuses on “Hardware Architecture – 2”.
1. ____ is used to optimize voltage standing wave ratio.
a) Antenna-matching unit
b) Radiating element
c) Antenna tuner
d) Power amplifier
Answer: c
Explanation: Antennas, operating over a wide frequency range, use antenna tuner to optimize the voltage standing wave ratio. It also results in improvement of radiation efficiency.
2. In ____ antenna, the interface boundary between radio and antenna is blurred.
a) multiple input multiple output
b) single input single output
c) single input multiple output
d) multiple input single output
Answer: a
Explanation: Wide bandwidth, large number of parallel receivers, and modem signal processing blur the interface boundary between radio and antenna in multiple input multiple output antennas.
3. Full duplex means _____
a) only transmission
b) only reception
c) transmission and reception but not at the same time
d) transmission and reception
Answer: d
Explanation: Full duplex means transmission and reception will be carried out simultaneously. Filtering may be done to prevent interference between high power transmission signal and low power received signal.
4. ____ filters can be used to aid full duplex communication.
a) Surface wave acoustic
b) Surface acoustic wave
c) Skin wave acoustic
d) Skin acoustic wave
Answer: b
Explanation: Full duplex means transmission and reception will be carried out simultaneously. Bulk acoustic wave filters, Surface acoustic wave filters, Yttrium-Iron-Garnet circulators are complex structures used to aid full duplex communication.
5. The dynamic range of signals during reception may be maximized by ____
a) frequency conversion
b) automatic gain control
c) frequency conversion and filtering
d) filtering
Answer: b
Explanation: The dynamic range of signals that can be processed at the receiver may be maximized by automatic gain control. Frequency conversion and filtering are done to minimize interference within the operating range of the radio.
6. The error corrected bits are ____ to complete the communication process.
a) grouped
b) re-transmitted
c) parsed
d) discarded
Answer: c
Explanation: The error corrected bits are parsed to identify the header, address, message, traffic, etc. The expected service is delivered to the user after being processed by various protocol layers.
7. The ____ are converted to ____ by ____ detector/demodulator combination.
a) bits, symbols, bit
b) symbols, bits, symbol
c) bits, symbols, symbol
d) symbols, bits, bit
Answer: b
Explanation: The symbols, obtained from down conversion process, are converted to bits by symbol detector/demodulation combination. Matched filter is an example for a detector.
8. Which among the following options have forward error correction integrated into the demodulation process?
a) Trellis code modulation
b) Soft decoding
c) Trellis code modulation and soft decoding
d) Block codes
Answer: a
Explanation: Forward error correction is carried out to reduce the number of bits received in error. It can be integrated into demodulation process such as in Trellis code modulation. It can be closely associated with demodulation process such as in soft decoding of convolution codes.
9. Which of the following is not included under MAC processing?
a) Framing
b) Frame synchronization
c) Error detection
d) IP addressing
Answer: d
Explanation: Media Access Control processing includes framing information, frame synchronization, error detection, MAC addressing, link management, and payload encapsulation. The output of this stage is in the form of bits.
10. Network processing layer is designed with ____ connectivity support.
a) point-to-point
b) hop-to-hop
c) end-to-end
d) hop-to-point
Answer: c
Explanation: The network processing layer is preceded by medium access control. The input to network processing layer is in the form of bits. The network processing layer is designed with end-to-end connectivity support and its output is transferred to the application layer.
11. The external RF components must be provided with ____ for effective control of parameters such as tuning frequency.
a) control unit
b) physical wires
c) digital interfaces
d) transceiver
Answer: c
Explanation: The external RF components must be provided with digital interfaces for effective control of tuning frequency, transmit/receive mode, VSWR, transmit power level sensing and gain control.
12. Which among the following is not considered for detection of abnormal behaviour in power amplifier?
a) Temperature
b) Transmitted power level
c) Received power level
d) VSWR
Answer: c
Explanation: Power amplifier is a part of RF front end section in transmit mode. It must be informed of transmit/receive mode to start and stop transmission. Transmitted power level, VSWR, and temperature are monitored for detection of abnormal behavour in power amplifier.
13. Web browsing requires ____ for effective operation.
a) low latency
b) data cache
c) buffer
d) fast computation
Answer: b
Explanation: Web browsing needs to store information of webpages which are frequently accessed to avoid transmission of redundant information. Large data cache is required to store the specified information. It is typically implemented using local hard disk.
14. Ad hoc network introduces jitter in packet delivery.
a) True
b) False
Answer: a
Explanation: In ad-hoc networking, the reception and re-transmission of signal at each node introduces an overall non-uniform delay. Thus ad hoc network introduces jitter in packet delivery and is compensated by using jitter buffer.
15. Each time the transceiver changes frequency, the antenna tuner will need to be informed of the new frequency.
a) True
b) False
Answer: a
Explanation: Each time the transceiver changes frequency, the antenna tuner will need to be informed of the new frequency. The antenna tunermay sense VSWR and adjust the tuning elements to minimize VSWR.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “Software Architecture – 1”.
1. GNU radio supports distributed computing.
a) True
b) False
Answer: b
Explanation: GNU radio does not support distributed computing. The implementations are limited to a single processor and therefore do not support high bandwidth protocols.
2. GNU radio uses ____ for baseband processing.
a) DSP
b) GPP
c) FPGA
d) ASIC
Answer: b
Explanation: GNU radio uses general purpose processor for baseband processing. This confines the signal processing capabilities to one particular processor. It is one of limitations of using GNU radio.
3. Procedural programming involves ____
a) encapsulation
b) abstraction
c) aspects
d) modularity
Answer: d
Explanation: Procedural programming is based on the concept of procedure call. The hardware requirement of procedural programming consists of stack register and instruction for calling subroutines.
4. ____ extends data type of linear programming to description of characteristics and behaviour.
a) Declarative programming
b) Object oriented programming
c) Non-structured
d) Array oriented
Answer: b
Explanation: Object oriented programming extends data type of linear programming to describe objects. Objects are described by their characteristics and behaviour. Member variables define characteristics and functions define behaviour.
5. ____ belong to a class and exist as a single copy.
a) Member variables
b) Instance variables
c) Class variables
d) Variables
Answer: c
Explanation: Class variables belong to a class and exist as a single copy. Instance variables belong to individual objects. Instance variables exists as many copies. Each copy is paired with a separate object. Member variables include class variables and instance variables.
6. The property of providing selective information is called ____
a) abstraction
b) encapsulation
c) inheritance
d) polymorphism
Answer: a
Explanation: Abstraction allows only selective and applicable information to be made available while other information may be hidden. Abstraction reduces complexity between layers of implementation as only relevant information will be available to each layer. Encapsulation, inheritance and polymorphism are other properties of object oriented programming.
7. A class may be considered as an implementation of the concept ____
a) overriding
b) encapsulation
c) overloading
d) polymorphism
Answer: b
Explanation: Encapsulation is the concept of fusing data and functions together as a single unit. Functions for accessing data are an example for encapsulation.
8. In component based programming, a component may have ____
a) only one subunit
b) only one class
c) one or more subunits
d) one or more classes
Answer: d
Explanation: Component based programming is an extension of object oriented programming. A component is the basic unit of component based programming and may have one or more classes. It is defined by functionality and interfaces.
9. ____ service selects and de-selects component instances.
a) Package
b) Distribution
c) Compatibility
d) Institution
Answer: b
Explanation: Distribution service may select and de-select component instance depending on the request made by client of component service. It also manages the component instances assigned for execution on remote host processors.
10. Components are ____
a) substitutable
b) rigid
c) non-changeable
d) only early-binded
Answer: a
Explanation: A significant aspect of component based programming is that components are substitutable. A component may be replaced by another component or an updated version during design time or run time provided the new component meets the set requirements. Substitutability supports late binding.
11. In aspect oriented programming, the functions that appear at many points in an application are called ____
a) sliced functions
b) multi-cutting functions
c) split-cutting concerns
d) cross-cutting concerns
Answer: d
Explanation: Aspect oriented programming allows for the establishment of relationship between classes. Aspect is the key unit of modularity in aspect oriented programming. The program logic is divided into smaller parts called concern.
12. The dominant design philosophy in software defined radio design is ____
a) linear programming
b) object oriented programming
c) component based programming
d) aspect oriented programming
Answer: c
Explanation: Component based programming is an extension of object oriented programming. Component based programming is preferred for SDR design as the functional blocks of radio system can be easily represented using separate components.
13. Which among the following is the advantage of using design pattern?
a) Modularity
b) Ease of implementation
c) Non-structured
d) Common terminology
Answer: d
Explanation: Design patterns are programming methodologies. Code reuse and common terminology are the major advantages of using design pattern. The use of common terminology creates better understanding among team members.
14. GNU radio is a ____ based architecture.
a) Java
b) C#
c) Python
d) C
Answer: c
Explanation: GNU radio is a Python based architecture. It is designed to run on computers with Linux operating system. It can be used as external RF hardware to develop software radios and has several signal processing components.
15. Aspect oriented programming requires the creation of new language constructs unlike component based programming.
a) True
b) False
Answer: a
Explanation: Aspect oriented programming requires the creation of new language constructs that associate an aspect to a particular class. Component based programming is a coding style. It does not have strict definitions in mainstream languages.
This set of Software Defined Radio Architecture Question Paper focuses on “Software Architecture – 2”.
1. Software communication architecture runs on _______ and _______ hardware.
a) heterogeneous, centralized
b) homogeneous, centralized
c) heterogeneous, distributed
d) homogeneous, distributed
Answer: c
Explanation: Software communication architecture is a complex architecture that provides support for secure signal processing applications that run on heterogeneous and distributed hardware. It was developed under Joint Tactical Radio System program.
2. Which of the following is not a facility provided by software communication architecture?
a) Installation of waveform
b) Management of waveform
c) Management of thread
d) Interaction with external services
Answer: c
Explanation: Software communication architecture is a component based management architecture. The infrastructure provides the facility to create, install, manage, and de-install waveforms for a component. It provides control of hardware and supports communication with external services via interfaces.
3. CORBA is used to ____
a) install waveform
b) maintain consistent interfaces
c) control hardware
d) manage hardware
Answer: b
Explanation: Common Object Request Broker Architecture is used to maintain consistent interfaces. Remote procedure calls can be made as if the data resides on local memory even if the data actually resides on a remote computer.
4. Different pieces of software communication architecture is linked to the operating system through ____
a) Common Object Request Broker Architecture and Interface Definition Language
b) Aspect Oriented Programming and Interface Definition Language
c) Common Object Request Broker Architecture and Aspect Oriented Programming
d) Component Based Programming and Aspect Oriented Programming
Answer: a
Explanation: Interface Definition Language is the language used by CORBA to describe component interfaces. The operating system performs system calls and is located at the core of software communication architecture.
5. The software communication architecture is partitioned into ____ parts.
a) two
b) three
c) four
d) five
Answer: c
Explanation: The software communication architecture is partitioned into four parts namely the framework, the profiles, the API, and the waveforms. The framework is further partitioned into three parts namely base components, framework control, and services.
6. ____ class has only two member methods namely start and stop.
a) Property Set
b) Lifecycle
c) Resource
d) Port Supplier
Answer: c
Explanation: Resource class has only two member methods namely start and stop and one attribute namely the identifier. It inherits from Property Set class, Lifecycle class, Port Supplier class, and Testable Object class to offer functionalities such as initialization of a component into the framework.
7. The Property Set class facilitates other classes to ____ the resource class values.
a) copy
b) inherit
c) delete
d) query
Answer: d
Explanation: The Property Set class facilitates other class to configure and query the resource class values by providing a set of interfaces. During run time, querying can be performed by query interface and reconfiguration can be performed by configure interface.
8. ____ class can release the component from the framework.
a) PortSupplier
b) PropertySet
c) Resource
d) Lifecycle
Answer: d
Explanation: Lifecycle class provides Resource class with the ability to initialize and release a component from the framework using initialize and releaseObject interfaces. Initialization sets the component to a known state.
9. The interface releaseObject ____ a component ____ CORBA.
a) installs, to
b) manages, in
c) relocates, in
d) unbinds, from
Answer: d
Explanation: The interface releaseObject is an interface associated with Lifecycle class. It unbinds a component from CORBA. It carries out the work required to delete an object.
10. Which of the following is not a method of the ResourceFactory class?
a) createResource
b) releaseResource
c) shutdown
d) freezeResource
Answer: d
Explanation: ResourceFactory class is used when a Resource has to be explicitly created. The createResource interface creates an instance of the desired Resource, the releaseResource calls the releaseObject interface, and shutdown terminates the ResourceFactory.
11. ____ class is the entry point of any component.
a) Port
b) Resource
c) Resource Factory
d) Port Supplier
Answer: a
Explanation: Port class is the entry point of any component. The explicitly defined methods of Port class are connectPort and disconnectPort. The actual connection based implementations are guided by a waveform’s application specific interface.
12. The interface getPort belongs to Port class.
a) True
b) False
Answer: b
Explanation: Port Supplier class returns a particular port from a set of ports defined for a component. The interface getPort belongs to Port Supplier class. It returns the port specified in the method argument.
13. The software communication architecture supports multiple processors in the core.
a) True
b) False
Answer: a
Explanation: The location independence offered by CORBA allows multiple processors to be present in the core. Legacy software, non-CORBA processing hardware, security, management software, and an integrated file system are other parts of the structure of SCA.
14. Which of the following is not a goal set by Joint Tactical Radio System while publishing SCA?
a) Increased flexibility
b) Increased interoperability
c) Reuse of design modules
d) Reduction of operation cost
Answer: c
Explanation: Increased flexibility and interoperability, reduction of supportability and operation cost and easy technology insertion are some of the goals of Joint Tactical Radio System. Reuse of design modules is an optimization technique adapted to achieve the goal of JTRS.
15. The components of a system can be described by using ____
a) XML
b) BPMN
c) UML
d) HTML
Answer: a
Explanation: Extensible Markup Language is a text-based language that uses tags to define items, their attributes, and values. It is used for structuring information being exchanged. Unified Modeling Language and Business Process Model and Notation focus on modeling.
This set of Software Defined Radio Architecture Questions and Answers for Campus interviews focuses on “Computational Processing Resources”.
1. PowerPC is an example for ____
a) General Purpose Processor
b) Digital Signal Processor
c) Application Specific Integrated Circuit
d) Field Programmable Gate Array
Answer: a
Explanation: PowerPC is a general purpose processor. It is generally programmed using standard C or C++. It provides different types of addressing modes, floating point and integration computation, large memory, and on and off chip cache memory.
2. ____ usage of resources within a module is a constraint imposed by software defined radio.
a) Unbounded
b) Bounded
c) Exhaustive
d) Extensive
Answer: b
Explanation: Software defined radio has two constraints to consider during execution namely bounded usage of resources within a module or acceptable usage of computational resources and timing constraints.
3. ____ is a function in which the function definition includes the function itself.
a) User defined function
b) Pre-defined function
c) Main function
d) Recursive function
Answer: d
Explanation: Recursive function is a function in which the function definition includes the function itself. A recursive function must also consist of a base case which does not involve calling the function itself and a set of rules that reduce towards the base case.
4. Which among the following is not an example of primitive recursive function?
a) Sequential logic
b) Traversal filter
c) Recursive filter
d) Ackermann function
Answer: d
Explanation: A primitive recursive function is one in which the upper bound or the number of iterations to be performed is known. Most computable functions studied in number theory are primitive recursive. These include addition, subtraction, multiplication, etc. Sequential logic, traversal filter, recursive filter, bit manipulation, and data packing are common primitive recursive functions.
5. _______ function is a subset of ________ function.
a) Total recursive, primitive recursive
b) Partial recursive, total recursive
c) Primitive recursive, total recursive
d) ÎĽ-recursive, partial recursive
Answer: c
Explanation: Primitive recursive function is a subset of total recursive function. Total recursive function is a subset of partial recursive function. Partial recursive functions are otherwise called ÎĽ-recursive function.
6. If Z is a function of Y, and Y is a function of X then Z is a function of X. Which among the following options is the concept that supports the given statement?
a) Composition
b) Recursion
c) Primitive recursion
d) Aggregation
vAnswer: a
Explanation: Composition is the point wise application of one function to the result of another to produce a third function. A set is closed under composition of functions.
7. Which among the following is the only conditional branching structure suitable for primitive recursion?
a) For loop
b) While loop
c) Do while loop
d) Go-to statement
Answer: a
Explanation: A primitive recursive function is one in which the upper bound or the number of iterations to be performed is known. Consider for a loop from i = 1 to N, N is fixed before entry into the loop and cannot be change within the loop. The for loop is the only structure that satisfies primitive recursive function.
8. A computable function must have a ____ that computes the function.
a) infinite procedure
b) finite dataset
c) finite procedure
d) infinite dataset
Answer: c
Explanation: A computable function must have afinite procedure or algorithm that computes the function. The function must be computable with the available information and instruction and must not require special insights or computational models.
9. Consider a function x to y. Partial function does not require every element of x to be mapped to some element of y.
a) True
b) False
Answer: a
Explanation: Partial function does not require every element of x to be mapped to some element of y. An example for partial function is the mapping of natural logarithm function to real numbers.
10. Digital signal processors have ____ functions to support high speed signal processing.
a) subtraction and accumulation
b) division and subtraction
c) addition and subtraction
d) multiplication and accumulation
Answer: d
Explanation: The DSP internal architecture is optimized to perform multiplication and accumulation quickly. This is done with the help of one or more multiplier and one or more accumulators. The memory structure is designed to fetch operands and instructions in parallel.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “Interface Technologies”.
1. Architecture is a design, development, and delivery ____
a) control block
b) node
c) framework
d) component
Answer: c
Explanation: Architecture is a framework in which a set of functions may be defined and developed through a set of components according to specified design rules. The three main units of representation are components, functions, and design rules.
2. Point set topology is a ____ with a family of ___ that have topological properties.
a) set, subsets
b) point, subpoints
c) point, subsets
d) set, subpoints
Answer: a
Explanation: A process may not have a vector space that maps control state to a software process. Such a process has a point set topology. The subset includes process over which the software operations are valid.
3. The family of subset is closed under ____
a) equality
b) equivalency
c) union
d) order
Answer: c
Explanation: The topological space includes a set X and a family of subsets. The subsets include the set X itself as well as an empty set. The family of subset is closed under union and finite intersection.
4. Given a set of four elements, the power set consists of ____ elements.
a) four
b) eight
c) twelve
d) sixteen
Answer: d
Explanation: Given a set with X number of elements, the power set consists of 2 X number of elements. The given statement includes four singletons, six doubletons, four triplets, the set itself and an empty set.
5. Discrete topology includes only ____ in the topological space.
a) empty set
b) empty set and power set
c) power set
d) original set
Answer: c
Explanation: Discrete topology includes only power set in the topological space. On the other hand a topology containing only the empty set and the original set X is referred as power set.
6. The number of possible subsets of a power set originating from a set with X number of element is given by the expression ____
a) 2 X
b) 2 X-1
c) 2 2 x-1
d) 2 2 x-2
Answer: d
Explanation: The number of possible subsets of a power set originating from a set with X number of element is given by the expression 2 2 x-2 . This expressed is referred as double exponential. It is not possible for all candidate topologies to be closed under union and finite intersection. It is necessary to define finite interface topologies more compactly.
7. Given a set of interfaces, the empty set is a valid interface only if ____
a) all pins condition exists
b) only one pin at a time condition exists
c) no pins condition exists
d) power set condition exists
Answer: c
Explanation: The empty set is included in the topology when the interface works even when no input is provided. For example, a system enters into safe mode or reset mode when it is unplugged.
8. The ordered set of points in the topological space sharing some type of relationship are called ____
a) simplex
b) simplicial complex
c) complex
d) s connected
Answer: a
Explanation: The ordered set of points in the topological space that is said to be adjacent by sharing some type of relationship is called simplex. Lower dimensionality simplexes induce higher dimensionality simplex. A simplex may be embedded in Euclidean space.
9. ____ describes the behaviour of a system in terms of relationship with external factors.
a) Logical view
b) Component view
c) Use case view
d) Deployment view
Answer: c
Explanation: The logical view defines object, classes, and interfaces. The component view is responsible for partitioning functionality. Use case view describes the behaviour of a system in terms of relationship with external factors. The deployment view defines the relationship of components with physical entities.
10. In incidental cohesion, functions share little relationship with each other.
a) True
b) False
Answer: a
Explanation: Cohesion is the relationship among elements within a module. In incidental cohesion, functions share little relationship with each other. It is the loosest form of coupling. Functional cohesion is the tightest form of coupling.
This set of Software Defined Radio Multiple Choice Questions & Answers focuses on “Radio Resource Analysis”.
1. In conventional cellular radio, the mobile traffic generates ____ streams based on ____ traffic.
a) revenue, data
b) data, voice
c) voice, data
d) data, revenue
Answer: a
Explanation: The mobile traffic supported at a fixed level of quality is seen as a resource. In a multiband, multimode software defined radio, the traffic takes up particular band and mode. The mobile traffic generates revenue streams based on data and voice traffic.
2. Which among the following is not considered as a basic limitation of radio platform?
a) Processing capacity
b) RF coverage
c) Digital access bandwidth
d) Type of service
Answer: d
Explanation: A radio platform has standard limits defined for RF coverage, digital access bandwidth, and processing capacity. All bands and modes with satisfactory link quality available at region of interest and meeting the set limits are considered as useful radio resource.
3. Which among the following is a standard telephony metric?
a) Service provider
b) Mobile brand
c) Line of sight
d) Call duration
Answer: d
Explanation: As mobile traffic is treated as a resource, it is necessary to measure the mobile traffic being serviced. Arrival rate, call duration, and class of traffic such as voice or fax are metrics employed to measure the mobile traffic.
4. Network operator can identify problematic areas by monitoring the progress of ____
a) channel state machine
b) node state machine
c) channel transition system
d) node transition system
Answer: a
Explanation: Network operator can identify problem areas by monitoring the progress of channel state machine. For example, when the number of handoff failures increases in a cell site, it indicates the need for a gap filter or improved handoff techniques.
5. ODMA stands for ____
a) Orthogonal Driven Multiple Access
b) Opportunity Driven Multiple Access
c) Orthogonal Direct Multiple Access
d) Opportunity Direct Multiple Access
Answer: b
Explanation: Opportunity Driven Multiple Access is used to improve the capacity and coverage area towards the boundaries of the cell. Mobile stations outside the coverage area can communicate with the base station via multi-hop transmission.
6. Peer networks provide ____ spectrum.
a) temporally limited
b) temporally unlimited
c) spatially limited
d) spatially unlimited
Answer: c
Explanation: Peer networks provide spatially limited spectrum. The nodes communicate within a spatial region defined by radio horizon. The hierarchical networks provided spatially unlimited spectrum owing to the base station infrastructure.
7. Which among the following is not used to characterize air interface mode?
a) Frequency band
b) RF Access
c) Modulation type
d) Bandwidth
Answer: b
Explanation: Efficiency of spatial use is estimated by link budget. The efficiency of spectrum usage can be computed from frequency band, modulation type, and bandwidth of air interface mode. Noise figure and range variations are also included in the computation of link budget.
8. Transmitter determines ____ and ____
a) radiated power, duration of transmission
b) faded power, duration of transmission
c) radiated power, antenna gain
d) faded power, antenna gain
Answer: c
Explanation: Transmitter determines radiated power and antenna gain. Receiver determines receiver antenna gain and receiver sensitivity. These parameters determine the quality of received signal as per link budget equation.
9. ____ were formalized in Asynchronous Transfer Mode networks.
a) Quality of service metrics
b) Quality of service contracts
c) Grade of service metrics
d) Grade of service contracts
Answer: b
Explanation: Quality of service contracts were formalized in asynchronous transfer mode networks. The ATM access protocols determine the quality of end to end connections to be offered by a network. These networks add bit errors and delay packets to accomplish their service.
10. Antenna patterns affect the spectrum available to the users.
a) True
b) False
Answer: a
Explanation: The spectrum available to users in a particular coverage area depends on the allocated spectrum, antenna patterns, propagation environment, and the radio network architecture. Peer networks employ spatially limited spectrum and hierarchical network employ spatially unlimited spectrum.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Radio Flexibility”.
1. SINCGARS is a family of ____ radios.
a) high frequency
b) very high frequency
c) ultra-high frequency
d) super high frequency
Answer: b
Explanation: Single-Channel Ground and Airborne Radio System consists of a family of radios that operate in the very high frequency band. They use frequency modulation. The radio is meant for command and control signals of voice and tactical data.
2. Demand Assign Multiple Access is ____ function.
a) a technical
b) an administrative
c) a multiplexing
d) a literal
Answer: b
Explanation: Demand Assign Multiple Access is related to channel and resource allocation. It can be classified based on switching technique or control schemes. It is employed in AN/WSC – 3.
3. In ____, the data signal is multiplied with a chip code data stream.
a) Frequency Hopping Spread Spectrum
b) Time Division Multiple Access
c) Direct Sequence Spread Spectrum
d) Frequency Division Multiple Access
Answer: c
Explanation: The direct sequence spread spectrum is used to spread the transmitted signal over a bandwidth wider than the information bandwidth. It offers secure communication with reduce interference.
4. Which among the following techniques use direct sequence spread spectrum?
a) Code Division Multiple Access
b) Frequency Division Multiple Access
c) Time Division Multiple Access
d) Orthogonal Frequency Division Multiple Access
Answer: a
Explanation: Code Division Multiple Access is a channel access method. It allows a user to occupy the allocated bandwidth for an entire period. This is accomplished by spread spectrum technology where each user is provided with a spreading code for transmission.
5. Position Location Reporting System offers an accuracy of ____
a) 15-m
b) 13-m
c) 10-m
d) 20-m
Answer: a
Explanation: Position Location Reporting System provides positioning, location, and reporting information for tactical commanders. It is an ultra-high frequency transceiver radio used for geo-location with 15-m accuracy.
6. The ____ helps to achieve over-the-horizon transmission in position location reporting system.
a) sub-master station
b) subordinate station
c) connecting station
d) master station
Answer: d
Explanation: Position Location Reporting System consists of a computer controlled master station with cryptographic security. It assists the network in using the user units as relay for over-the-horizon transmission.
7. Which among the following is not supported by AN/ARC-164 HaveQuickΙΙ?
a) Air-to-air communication
b) Ground-to-ground communication
c) Air-to-ground communication
d) Ground-to-air communication
Answer: b
Explanation: AN/ARC-164 HaveQuickΙΙ is a direct line of sight system operating in the ultra high frequency band. It uses amplitude modulated waveforms. It operates as a single channel or a frequency hopping radio.
8. Which of the following is a parameter used for co-ordination between aircraft and ground radio in HaveQuick?
a) Song of the day
b) Number of the day
c) Word of the day
d) Date of the day
Answer: c
Explanation: HaveQuick is initialized with the parameters word of the day, time of the day, and a net number. It is given as input to pseudo random number generator to control frequency. Word of the day is a transmission security variable.
9. AN/ARC-220 uses software realized ____
a) FPGA
b) ASIC
c) GPP
d) DSP
Answer: d
Explanation: AN/ARC-220 is a high frequency radio operating in the range 2 – 29.999 MHz. It uses software realized DSP and is software capable. It offers secure voice and data communication.
10. VanuAnywave is an example for software defined radio.
a) True
b) False
Answer: a
Explanation: VanuAnywave is a software defined system that uses off the shelf hardware and proprietary software. It provides software implementation of base transceiver station, base station controller, and transcoder and rate adaption unit modules of the base station subsystem.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Aware Radios – 1”.
1. The network does not have a ____ to pose questions about the radio.
a) standard categorization
b) standard classification
c) standard language
d) standard definition
Answer: c
Explanation: The inability to gain knowledge by asking questions due to the lack of a standard language and the inability to understand radio structure due to the lack of computationally accessible description are the primary factors for the overall lack of awareness in a radio.
2. The model of equalizer should contain ____ knowledge about equalizers.
a) non-automatic
b) codified
c) automatic
d) non-codified
Answer: b
Explanation: The model of equalizer should contain codified knowledge about equalizers. Equalizer is included as a part of the modem software. The radio may be made aware that an equalizer’s time domain taps reflect the channel impulse response.
3. Which among the following is a function of radio model?
a) DSP
b) RF conversion
c) Coding
d) User interface
Answer: c
Explanation: A radio model should contain representation of it functions and components. Transmission, reception, and coding are examples of functions of radio. Antenna, RF conversion, and DSP are examples of components of radio.
4. The CR prototype introduces ____ frames into the model based ____ architecture.
a) Radio Knowledge Representation Language, coding
b) Radio Knowledge Reasoning Language, reasoning
c) Radio Knowledge Reasoning Language, coding
d) Radio Knowledge Representation Language, reasoning
Answer: d
Explanation: The CR prototype introducesRadio Knowledge Representation Language frames into the model based reasoning architecture. The CR prototype improves the original framework of cognitive radio. This is achieved by introducing machine learning, natural language processing, and radio architecture.
5. Baseband processor hosts ____ software.
a) encoding
b) decryption
c) protocol
d) encryption
Answer: c
Explanation: The internal structure radio model should aid system level interactions with the network. A detailed report on internal capabilities and the ability to download new capabilities when required must be made possible by the radio model. For example, the baseband processor contains protocol and control software.
6. Which among the following is considered as second level capability in radio cognition?
a) Pre-programmed
b) Goal-driven
c) Radio aware
d) Context aware
Answer: d
Explanation: Context awareness is responsible for obtaining the context of external communication with minimal user involvement. Natural language, societal roles, and discourse are a part of model scope.
7. A conventional programmed digital radio or a software radio is represented by level ____ capability.
a) one
b) two
c) six
d) zero
Answer: d
Explanation: The level zero capability represents a radio with no model based reasoning capability. It is called as pre-programmed radio model and does not have a model scope.
8. SINCGARS ____ combines with SINCGARS radios and elevates operational ability in the Tactical Internet environment.
a) Advanced System Innovation Policy
b) Advanced System Improvement Program
c)Advanced System Innovation Program
d) Advanced System Improvement Policy
Answer: b
Explanation: SINCGARS ASIP radios are software programmable. They provide improved data capability. They also offer better FEC for low-speed data modes, a GPS interface, and an Internet controller. They reduce size and weight.
9. ____ is forward and backward ____ with theintegrated broadcast service.
a) Joint Transport Terminal, compatible
b) Joint Tactical Terminal, compatible
c) Joint Transport Terminal, convertible
d) Joint Tactical Terminal, convertible
Answer: b
Explanation: Joint Tactical Terminal is a high performance software radio.Joint Tactical Terminal is forward and backward compatible with the integrated broadcast service. The changes in format and protocol can be adapted by JTT by using a software download.
10. Which among the following is a prototype for mobile ad-hoc network?
a) Near Term Digital Radio
b) Single-Channel Ground and Airborne Radio System
c) Position Location Reporting System
d) Multifunction Information Distribution System
Answer: a
Explanation: Near Term Digital Radio is a mobile packet data radio. It has self-organizing and self-healing network capability. Near Term Digital Radio consists of two parts namely clustering and routing.
11. Mobile ad-hoc network is a ____ type of ____ network.
a) decentralized, wired
b) decentralized, wireless
c) centralized, wired
d) centralized, wireless
Answer: b
Explanation: Mobile ad-hoc network is a decentralized type of wireless network. Routing is accomplished by nodes forwarding data to other nodes. This is carried out on the basis of connectivity and specific routing algorithm.
12. Enhanced Position Location Reporting System used ____ communication network.
a) OFDMA
b) FDMA
c) CDMA
d) TDMA
Answer: d
Explanation: Enhanced Position Location Reporting System operates in the ultra-high frequency band. It uses frequency hopping, spread spectrum waveform. The two main functions of EPLRS is data distribution and position location and reporting.
13. Which among the following is used by routers of Near Term Digital Radio?
a) Open Shortest Path First
b) Routing Information Protocol
c) Radio Routing Information Protocol
d) Radio Open Shortest Path First
Answer: d
Explanation: Clustering labels a network into cluster heads and cluster members. Radio Open Shortest Path First is used by routers of Near Term Digital Radio. ROSPF adjacencies are introduced and eliminated in accordance to mobile ad-hoc network information provided by NTDR routers.
14. Radios that perceive all or part of their surrounding are considered adaptive systems.
a) True
b) False
Answer: b
Explanation: Radios that perceive all or part of their surrounding are considered aware systems. For examples, a voice radio capable of sensing audio frequencies. Awareness extends from simple protocol decisions to controlling network for maintaining the state of awareness.
15. Interference may be estimated by sensing RF spectrum.
a) True
b) False
Answer: a
Explanation: An aware radio uses various sensors to gather information on the environment. An RF spectrum may be sensed to gain information on interference, channel and signals.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Aware Radios – 2”.
1. Cognition capability level one may be achieved by ____ technology.
a) rule based expert systems
b) radio based expert systems
c) radio built experimental systems
d) rule built expert systems
Answer: a
Explanation: Cognition capability level one involves goal driven reasoning. It may be achieved by rule based expert systems technology. Rule based systems serve as a means to store, interpret and utilize information.
2. Goals maybe defined in ____ context by introducing ____ awareness.
a) temporal, IF
b) temporal, environment
c) spatial, environment
d) spatial, IF
Answer: c
Explanation: Environmental sensing extends goal driven reasoning to goals defined in spatial context. Location, position, and timing are some examples of functions that require environmental sensors. RF bands and modes are also sensed.
3. ____ involves processing input and output data.
a) Pre-programming
b) Context awareness
c) Radio awareness
d) Goal driven reasoning
Answer: b
Explanation: Context awareness involves understanding the characteristics of communication. The input and output data is analyzed to gain insight on factors that influence the nature of computing and communication services to be used.
4. Computer based planning is ____ level capability.
a) one
b) two
c) four
d) five
Answer: c
Explanation: The architecture of planning includes evaluating a situation to fix a goal. The goal drives candidate plans which are examined for pros and cons. The examination leads to action and implementationwhich brings about a change in the situation.
5. A network changing air interface may be tackled by applying ____ structure to situations.
a) model
b) logical
c) protocol
d) flow
Answer: b
Explanation: Network changing air interface or a user making change arbitrarily may be tackled by applying logical planning structure to situations. However the elements of planning must have fair level of relaxation on the completeness and consistency of planning process.
6. Negotiation capability requires the ______
a) evaluation of goals for plans
b) partition of environment
c) organization of goals for plans
d) management of conflicting plans
Answer: d
Explanation: Negotiation capability requires the management of conflicting plans and conduction of negotiations. It is a cognition level five capability. The expected level of competency includes ontology such as KQML and formalized knowledge.
7. The cognition level six to eight require _______
a) planning
b) negotiating
c) pre-programming
d) machine learning
Answer: d
Explanation: The cognition level six to eight require machine learning. It involves incorporatingfluency, adapting established plans and protocols. Learning in cognitive radios allows autonomous understanding of radio environment.
8. Which among the following is not a mobile ad hoc network waveform?
a) Multi user objective system
b) Soldier radio waveform
c)Wideband networking waveform
d) Bowman very high frequency waveform
Answer: d
Explanation: JTRS Network Enterprise Domain is responsible for the creation, sustainment, and improvement of interoperable software and network legacy waveforms. Bowman VHF is a legacy waveform.
9. Digital modular radio is an example for _________
a) software programmable radio
b) software capable radio
c) software defined radio
d) software dependent radio
Answer: c
Explanation: Digital modular radio is a software defined radio designed for communication in war zone. It is compatible with previous communication systems and tactical systems such as HF, DAMA, HaveQuick, and SINGCARS. It also includes software defined cryptographic functions.
10. Digital Modular Radio offers coverage of ____
a) 2 KHz to 2 MHz
b) 2 MHz to 2 GHz
c) 2 KHz to 5 MHz
d) 2 MHz to 5 GHz
Answer: b
Explanation: Digital modular consists of four programmable RF channels with coverage of 2 MHz to 2 GHz with duplex communication. It does not require any change in hardware to modify the waveform being used.
11. Small Unit Operations – Situational Awareness System was developed by ____
a) Defense Advanced Research Projects Agency
b) Defense Advanced Research Program Agency
c) Defense Awareness Research Projects Agency
d) Defense Awareness Research Program Agency
Answer: a
Explanation: Small Unit Operations – Situational Awareness System was developed by Defense Advanced Research Projects Agency to take advantage of the combined operation of advanced communication, navigation, and situational awareness.
12. Small Unit Operations – Situational Awareness System uses ____ ranging for navigation.
a) ELF
b) ULF
c) RF
d) EHF
Answer: c
Explanation: Small Unit Operations – Situational Awareness System uses RF ranging and other sensors for navigation with high accuracy. It is particularly useful for military communication in rough terrain. It also provides support for mission planning and training.
13. ____ is characterized by software communication architecture compliance.
a) Near term Digital Radio
b) HaveQuick
c) Joint Tactical Radio System
d) Joint Tactical Terminal
Answer: c
Explanation: Joint Tactical Radio System aims to increase the flexibility and interoperability of globally deployed systems. The operations such as waveform modification are to be accomplished through easy technology and capability upgrades.
14. Propagation model is a system level model.
a) True
b) False
Answer: a
Explanation: The internal structure model of a radio should provide vast amount of information the characteristics of a network. Propagation models, Quality of service models, and queuing models are some system level models used to characterize a cognitive network.
Answer: a
Explanation: Certain user interactions employ negotiation dialogs such as additional costs for roaming. Negotiation dialogs requires natural language analysis, generational capability, and causality analysis.
Sanfoundry Global Education & Learning Series – Cognitive Radio.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Adaptive Radio”.
1. Which among the following is an operating parameter which cannot be adapted?
a) Frequency
b) Instantaneous bandwidth
c) Modulation schemes
d) Environment
Answer: d
Explanation: An adaptive radio oversees its own performance and is open for modification of operating parameters. Frequency, instantaneous bandwidth, modulation schemes, error correction coding, equalizers, data rate, and transmission power are few examples of operating parameters that can be adapted.
2. ____ spread spectrum is ____ when ___ is programmed.
a) Frequency hopped, adaptive, hop
b) Frequency hopped, not adaptive, hop
c) Direct sequence, not adaptive, sequence
d) Direct sequence, adaptive, hop
Answer: b
Explanation: Frequency hopped spread spectrum is not adaptive when hop is programmed. However when the hop pattern is modified to mitigate collision, the frequency hopping radio can be considered as adaptive.
3. A radio that supports ____ channel bandwidths is ____
a) joint, adaptive
b) joint, not adaptive
c) multiple, not adaptive
d) multiple, adaptive
Answer: c
Explanation: A radio that changes instantaneous bandwidth and system timing as per the network load may be considered as adaptive. However a radio that simply supports multiple channel bandwidths is not adaptive.
4. An adaptive radio changes its intermediate frequency characteristics in accordance to ____
a) encryption method
b) enciphering method
c) network load
d) channel characteristics
Answer: d
Explanation: An adaptive radio is changes the operating parameters in accordance to sensor input for effective communication. Thus an adaptive radio changes its intermediate frequency characteristics in accordance to channel characteristics.
5. Which among the following exhibit some amount of adaptive quality?
a) Digital European Cordless Telephone
b) Racal 25
c) Digital Modular Radio
d) Position Location Reporting System
Answer: a
Explanation: Digital European Cordless Telephone finds the noise floor and interference of all available channels. The carrier frequencies are then selected based on the information obtained from sensing such that there is reduction in the amount of interference.
6. TVWS stands for ____
a) Telephone Variable White Space
b) Telephone Variable White Space
c) Television Wide Space
d) Television White Space
Answer: d
Explanation: Television White Space refers to the unused space found between channels actively used in UHF and VHF spectrum. The major regulatory agencies such as FCC of the US, Ofcom of the UK, and the ECC of CEPT in Europe are developing rules for unlicensed use of TV Whitespace.
7. The ECC studied the operational requirements of cognitive radio in the range ____
a) 460 – 560 MHz
b) 470 – 650 MHz
c) 470 – 790 MHz
d) 460 – 690 MHz
Answer: c
Explanation: The Electronics Communication Committee studied the technical and operational requirements of cognitive radio in white space of the ultra-high frequency band in the range 470-790 MHz. It acts as a foundation for regulatory activities in ECC.
8. Which among the following is not a challenge imposed by decision making in cognitive radio?
a) Centralization
b) Distribution
c) Algorithms
d) Wrong choices
Answer: d
Explanation: The first challenge for decision making is where and how the decision should be taken. The second challenge is whether the implementation must be centralized or distributed. The third challenge is the selection of decision algorithm.
9. The concrete ____ of learning process is a challenge imposed by learning in cognitive radio.
a) definition
b) classification
c) categorization
d) manipulation
Answer: a
Explanation: The concrete definition of learning process, its objectives and contributions, is a challenge imposed by learning in cognitive radio. The learning mechanisms employed may be supervised or unsupervised.
10. In dynamic security implementation, there is an increase in the number of potential interaction that can lead to a violation.
a) True
b) False
Answer: a
Explanation: In dynamic security implementation, there is an increase in the number of potential interaction that can lead to a violation. This leads to a decrease in time and special scales of these interactions. These conditions amplify the challenges.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Cognitive Radio”.
1. ____ are used to interact with the environment.
a) Sensors
b) Actuators
c) Structure models
d) Memory
Answer: b
Explanation: A cognitive radio consists of sensors to collect information on the environment, actuators to interact with the environment, and a model of the environment with observed events stored in memory.
2. Cognitive radio requires ____ to lower the impact in case of malfunction.
a) diodes
b) regulators
c) PID controllers
d) bridges
Answer: b
Explanation: Cognitive radio requiresregulators to lower the impact in case of malfunction. The most popular regulator used to constraint a cognitive radio is a regulatory policy engine that has machine-readable and interpretable policies.
3. The ____ property allows elimination of a policy upon producing undesirable results.
a) evaluate
b) examine
c) try out
d) permanent
Answer: c
Explanation: Machine readable policy controlled radio allows a policy to be implemented on few radios to assess the impact of the policy. If the results are undesirable, then policy can simply be eliminated. This enables quick decision making.
4. _________ regulations can be made in policy driven approach.
a) Material variant
b) Size variant
c) Temperature variant
d) Spatially variant
Answer: d
Explanation: Policy driven approach allows temporal and spatially variant regulation. For example, a radio can automatically adapt to varying jurisdictions imposed by different countries by modifying or uploading a policy.
5. Which among the following allows quality of service measurement?
a) Software capable radio
b) Software programmable radio
c) Software defined radio
d) Aware radio
Answer: d
Explanation: An aware radio provides quality of service measurement and channel state information in addition to the services provided by software defined radio. However it cannot modify the radio parameters according to sensor input.
6. Which among the following is a quality not available in a software capable radio?
a) Frequency hopping
b) Networking capability
c) Link establishment
d) Programmable cryptography
Answer: b
Explanation: Frequency hopping, link establishment, and programmable cryptography are the features available in software capable radio. Each higher level radio possesses these basic capabilities with additional qualities. Networking capability and multi-waveform interoperability are additional features exhibited by software programmable radio.
7. Cognitive radio includes ____
a) heterogeneous infrastructure
b) asymmetrical infrastructure
c) equivalence infrastructure
d) symmetrical infrastructure
Answer: a
Explanation: Heterogeneous network have heterogeneous radio framework management. It is possible to allocate frequency bands to different radio access technologies. Thus combination of different technologies can be achieved by heterogeneous network.
8. Bands are allocated to radio access technology ____ in such a way that ____ is ____
a) dynamically, capacity, minimized
b) statically, interference, minimized
c) dynamically, capacity, maximized
d) statically, interference, maximized
Answer: c
Explanation: Bands can be allocated to radio access technology dynamically in such a way the capacity is maximized and interference is minimized. The network operator may employ different radio access technology in accordance to time, frequency, and location. It can be used to acquire or exchange spectrum user rights.
9. Which among the following is not listed under cognitive capability?
a) Knowledge on operational environment
b) Adjustment of operational parameters
c) Knowledge on geographical environment
d) Establishment of policies
Answer: b
Explanation: A cognitive radio has cognition, reconfiguration, and learning capability. The automatic and dynamic adjustment of operation parameters based on obtained knowledge to achieve set objective falls under reconfiguration capability.
10. Adaptive radio can experiment new settings.
a) True
b) False
Answer: b
Explanation: An adaptive radio can monitor itself and modify parameters according to sensor input. However learning from results of operations and experimenting with new data and policies is possible only in a cognitive radio.
11. Cognitive pilot channel is used ____
a) to obtain knowledge
b) for geo-location
c) for database access
d) for spectrum sensing
Answer: a
Explanation: Cognitive pilot channel, geo-location, database access, and spectrum sensing are means to gain knowledge. The automatic and dynamic adjustment of operation parameters is done based on obtained knowledge.
12. Heterogeneous cognitive radio is a ____ centric approach.
a) security
b) RF band
c) network
d) environment
Answer: c
Explanation: Heterogeneous cognitive radio has a network centric approach where one or more operators operate several radio access networks using the same or different radio access technologies. Frequency bands allocated to these radio access networks are fixed.
13. In ____, radio access technologies use the same frequency band.
a) network centric approach
b) spectrum sharing
c) spectrum sensing
d) RF band centric approach
Answer: b
Explanation: Spectrum sharing cognitive radio permits same or different radio access technologies to use same frequency band by using unoccupied sub-bands in an intelligent and coordinated way.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “”.
1. Global Positioning System uses ____ to determine geo-location of receiver.
a) time of arrival
b) time difference of arrival
c) time of arrival and angle of arrival
d) time difference of arrival and angle of arrival
Answer: b
Explanation: Global Positioning System is a satellite based radio navigation system. It offers a resolution of 100m and requires unobstructed line of sight from satellites. It uses time difference of arrival to determine geo-location of receiver.
2. GPS receivers include a signal that is ____ filtered when it reaches a radio from a satellite.
a) Gaussian
b) Blackman
c) Kalman
d) Sobel
Answer: c
Explanation: Kalman filter uses observed values and provides accurate estimates of unknown variables using joint probability distribution over the variables for each time frame. GPS receivers include a one pulse per second signal that is Kalman filtered.
3. Kalman filter estimates ____
a) time of arrival
b) time difference of arrival
c) propagation delay
d) location
Answer: c
Explanation: Kalman filter provides high resolution estimation of propagation delay from each satellite irrespective of their position. Kalman filter uses input from ground monitoring stations, space weather information, etc. The GPS receivers can estimate time with approximately 340 nanoseconds of jitter.
4. GPS requires at least ___ satellites in view of the receiver.
a) three
b) two
c) five
d) four
Answer: d
Explanation: GPS receiver monitors several satellites to precisely compute the location and clock deviation. It requires at least four satellites to be present in its field of view. Three position coordinates and clock deviation from satellite time are the unknown entities to be computed.
5. ____ aids in the exploitation of unused channels.
a) Spectrum awareness
b) Self awareness
c) Radio resource awareness
d) Location awareness
Answer: a
Explanation: A radio that is aware of spectrum occupancy can use this information to exploit open channels on a non-interference basis. This is the first step in efficient usage of available spectrum. It is done in such a way that primary user of the spectrum is unaffected.
6. ____ proposes the presence of secondary users for improved spectral efficiency.
a) Cognitive radio
b) Software defined radio
c) Software capable radio
d) Programmable digital radio
Answer: a
Explanation: Cognitive radio technologies support the presence of lower priority secondary users. This involves sensing the environment to find unused available spaces in the licensed spectrum for communication. It aims at effective usage of frequency, time and energy.
7. ____ gives available and unavailable spectrum frequency.
a) Unlicensed user pattern
b) Spectrum use pattern
c) Licensed space pattern
d) Licensed user pattern
Answer: b
Explanation: Spectrum use pattern gives the frequencies which are unavailable and unavailable in the band of interest at a particular time and location. It is also known as radio environment, or electromagnetic environment.
8. The secondary user intentionally senses surrounding environment in ____
a) policy approach
b) database approach
c) active awareness
d) passive awareness
Answer: c
Explanation: In active awareness, the secondary user actively senses surrounding environment and performs transmission based on the obtained information. In passive awareness, the radio environment information is obtained outside the secondary communication system.
9. ____ involve the measurement of distinctive features to label and describe individuals.
a) Electrical signals
b) Biometrics
c) Biostatistics
d) Physical signals
Answer: b
Explanation: Biometrics involves the measurement of distinctive features to label and describe individuals. These features are either physiological or behavioural. Different aspects of human physiology, chemistry, and behaviour can be used for biometric authentication.
10. Which among the following is not a behavioural biometric identifier?
a) Voice recognition
b) Gait
c) Fingerprint
d) Typing rhythm
Answer: c
Explanation: Behavioural biometrics is a subclass of biometrics involving the measurement of unique, distinctive and measurable pattern in individuals. Software is required for analysis. It is cost effective means to improve security.
11. Which among the following is not a characteristic of biometric?
a) Measurability
b) Shape
c) Universality
d) Permanence
Answer: b
Explanation: Universality indicates every individual should possess the trait. Permanence indicates the selected trait must remain invariant for longer period of time. Measurability indicates the means to obtain the biometric.
12. During ____, the biometric of an individual is captured and stored.
a) sampling
b) enrollment
c) admission
d) learning
Answer: b
Explanation: The first time an individual uses a biometric system is called as enrollment. During enrollment, the biometric of an individual is captured and stored. At any time, the biometric information is detected and compared with the information stored at the time of enrollment.
13. The first step in verification mode is to ____ users.
a) perform one to one comparison of
b) perform one to may comparison among
c) run recognition of
d) generate reference model for
Answer: d
Explanation: Verification mode involves three steps. The first step is to generate reference models for users. Then samples are matched with reference model to generate a threshold for recognition. The third step involves testing.
14. Triangulation may be used for geo-location.
a) True
b) False
Answer: a
Explanation: Triangulation is the process of determining the location of an unknown point by forming triangles to it from known points. In the absence of GPS, triangulation may be used for geo-location based on cooperative and non-cooperative sensing.
15. Spectrum awareness prevents hidden node problem.
a) True
b) False
Answer: b
Explanation: Spectrum awareness is affected by hidden node problem. A receiver might experience interference but may be incapable of informing the cognitive radio. A cooperative approach may be used to mitigate the problem but it is not a complete solution.
This set of Cognitive Radio Questions and Answers for Freshers focuses on “Available Technologies for Cognitive Radio – 2”.
1. Which among the following does not have significant use for time of day information?
a) Policy monitoring
b) Global positioning system
c) Geo-location
d) Frequency division multiplexing
Answer: d
Explanation: Time awareness is essential for a radio to learn and behave. Time of the day information is used in time division multiplexing and for gating policies in and out. It is used to compensate propagation delay from satellites to GPS receiver such that there is only 340 ns jitter.
2. ____ in a radio system can be used to keep track of time of the day.
a) Local oscillator
b) Source
c) Filter
d) Amplifier
Answer: a
Explanation: Local oscillator is used as master timing control circuit in receivers of RF applications. It may also be used with mixer to change the frequency of a signal. Accuracy may be increased and jitter may be decreased by using complex circuitry.
3. Atomic clocks have a stability of ____
a) 10 -5
b) 10 -8
c) 10 -10
d) 10 -11
Answer: d
Explanation: Atomic clocks have a stability of 10 -11 . However they consume high power and are large in size. Local oscillators have a stability of 10 -6 . Local oscillators drift over time and may result in inaccuracy of about 90 ns.
4. A radio which enters into vibration mode autonomously is ____
a) environment aware
b) self aware
c) spatially aware
d) spectrum aware
Answer: c
Explanation: A radio must be capable of supporting communication over wireless link, also must be capable of turning off communication under certain situations. This type of awareness is termed as spatial or situational awareness. For example, a radio that enters into vibration mode upon entering a movie theater autonomously.
5. The ____ encourages that license holders in exclusive management policy bands be allowed to sublease their spectrum.
a) Spectrum Policy Testing Facility
b) Strategic Policy Testing Facility
c) Spectrum Policy Task Force
d) Strategic Policy Task Force
Answer: c
Explanation: The Spectrum Policy Task Force operates under Federal Communication Commission. Its primary goal is to evaluate policies and promote effective use of spectrum. It is also responsible for using the spectrum in such a way the public benefit is improved.
6. Which among the following is not a recommendation of Spectrum Policy Task Force?
a) Radio spectrum interference tolerance
b) Quantity spectrum use
c) Regulatory models for licensed and unlicensed users
d) Single regulatory model
Answer: d
Explanation: The Spectrum Policy Task Force does not encourage a single regulatory model applicable for all spectrums. It recommends a regulatory model that provides a balanced spectrum model. It includes the allocation of spectrum based on market oriented model.
7. ____ are spectrum bands that exist between channels to minimize interference.
a) White noise
b) White space
c) Empty noise
d) Empty space
Answer: b
Explanation: Spectrum Policy Task Force supports the use of white spaces between spectrums. Unlike analog signal, multiple digital signals can be packed into the spectrum bands, increasing transmission. Thus, white space can be utilized significantly.
8. A policy must be verified by ____ for certification.
a) policy scalability engine
b) policy performance engine
c) policy interpretation engine
d) policy examination engine
Answer: c
Explanation: A policy may be written by regulatory agencies or by a third party which is later approved by regulatory agencies. A policy is a legal operating requirement and therefore must be verified by policy examination engine for certification.
9. Cognitive radio requires ____ to interpret multiple rules and policies simultaneously.
a) interpretation capability
b) intuitive capability
c) interference capability
d) inference capability
Answer: d
Explanation: A variety of policies exists to accommodate and regulate various modes and environment. It is not possible to code every possibility in a radio and it becomes necessary for the radio to understand the policy. Cognitive radio must infer from policies provided they are defined using well known language framework.
10. ____ routing involves broadcasting ____ for routing.
a) Proactive, search packets
b) Reactive, search packets
c) Proactive, routing table
d) Reactive, routing table
Answer: b
Explanation: Reactive routing involves broadcasting search packets which returns one or more paths to the destination node and returns that path to the source node. Proactive routing does involve the maintenance of a routing table to forward a node in the direction likely to reach the destination, however this table is not broadcasted.
11. Continuous spectrum granting beacon is a spectrum sensing technique.
a) True
b) False
Answer: b
Explanation: Continuous spectrum granting beacon is a technique employed during subleasing. It supports shut-down-on-command feature, and is carried out within a bounded response time. Time based granting of spectrum, and RTS-CTS inhibit send are other techniques used for subleasing.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Location Awareness – 1”.
1. ______ gives the coordinates of a point in space to represent an object.
a) Surrounding
b) Image
c) Location
d) Position
Answer: d
Explanation: Position gives the coordinates of a point in space to represent the location of an object. Location is the physical place occupied by an object. Environment is related to the volume usedat the location.
2. Sensing process mainly consists of ____
a) actuators and networks
b) sensors and data-processing methods
c) sensors and actuators
d) actuators and data-processing methods
Answer: b
Explanation: Similar to the location and environment awareness features appearing in nature, location and environment awareness engines consist of three stages namely sensing, awareness, and adaption. Sensing is the first step and is accomplished by sensors and data processing methods.
3. ____are used to convert acquired signals from the environment into ____ signals suitable for cognitive radio.
a) Sensors, physical
b) Sensors, electrical
c) Actuators, electrical
d) Actuators, physical
Answer: b
Explanation: Sensors are used to convert acquired signals from the environment intoelectrical signals suitable for cognitive radio. It is critical to learn and interact with the environment. The acquired signals may be electromagnetic, optic or sound.
4. Radio sensing is a technique that utilizes ____
a) hearing sensors
b) electromagnetic sensors
c) image sensors
d) acoustic sensors
Answer: b
Explanation: Radio sensing is a sensing technique that utilizes electromagnetic sensors. Radio vision is a sensing technique that employs image sensors. Radio hearing is a sensing technique that utilizes acoustic sensors.
5. Which among the following is not an example for electromagnetic sensors?
a) Antenna
b) CCD sensors
c) RF sensors
d) Anisotropic magneto resistance sensors
Answer: b
Explanation: Electromagnetic sensors are used to convert electromagnetic signals into electrical signals. Antenna is the most commonly used radio sensing sensor. Location information is obtained from received signal statistics such as time of arrival in antenna based wireless positioning system.
6. Which among the following is type of image sensor described by its structure?
a) Colour
b) Monochromatic
c) Global
d) Charge Coupled Device
Answer: d
Explanation: An image sensor detects light waves and converts into signals of small bursts of current that convey information to form an image. The image sensors are classified as Complementary Metal Oxide Semiconductor or Charge Coupled Device based on structure and colour or monochromatic based on chroma type.
7. Image sensors contain ____ made of light sensitive elements.
a) film
b) frames
c) photons
d) pixels
Answer: d
Explanation: Image sensors contain pixels made of light sensitive elements, micro lenses, and micro electrical components. The sensor also has wire bonds, cover glass, contact pads and interconnecting paths.
8. The function of cover glass is to ____
a) prevent entry of light
b) protect the sensor
c) transfer signals
d) protect contact pads
Answer: b
Explanation: The cover glass is the top most layer providing protection to the sensor and wires while allowing light to reach light sensitive area. The wires transfer signals to the contact pads which is the bottom layer. The package is used to protect contact pads.
9. Which among the following is not an action carried out in image formation?
a) Analog to digital conversion
b) Digital to analog conversion
c) Conversion of photon into electron
d) Conversion of signal charge to electrical signal
Answer: b
Explanation: The first step in image formation is the conversion of photons into electrons. The charges are then collected and transferred. The charge is then converted into an electrical signal such as voltage which is then converted into a digital signal using an analog to digital converter.
10. ____ can convert a scene into text or voice.
a) Cognitive sensing system
b) Adaptive sensing system
c) Cognitive vision system
d) Adaptive vision system
Answer: c
Explanation: Computer vision aims to provide human like vision and perception to computers. Cognitive radios with cognitive vision systems can covert a scene into a text, voice or an image based on the application. These systems are limited by size and cost.
11. Which among the following is a scarce resource in terms of cognitive vision systems?
a) Bus
b) Memory
c) Processing hardware
d) Network
Answer: b
Explanation: Large amount of information has to be stored for learning and articulation of knowledge. It is important to consider memory as a scarce resource and methods must be developed to use it efficiently. Selection of information of interest and data mining are some techniques to use memory efficiently.
12. Which among the following is not a concern for cognition vision system?
a) RF environment
b) Characteristics of visual sensory sub-process
c) High level representational framework
d) Low level visual sensory sub-process
Answer: a
Explanation: The construction of cognition vision system involves the selection of appropriate high level representation framework, basic visual sensory sub-process, characteristics of visual sensory sub-process catering to the requirement of desired cognition system, negotiator of control process, and properties of control process.
13. Radio hearing sensors use sound propagation for ____
a) converting electromagnetic signal into electrical signals
b) positioning
c) imaging
d) navigation
Answer: d
Explanation: Radio hearing sensors convert acoustic signals into electrical signals. Sound propagation is used for navigation, detection, and communication. For example, acoustic location estimation maybe used for cognitive location aware systems.
14. Image sensors are typically passive.
a) True
b) False
Answer: a
Explanation: Image sensors are utilized in a passive manner since they only receive signals. Radio hearing and radio sensors are active sensors since they exhibit both transmission and reception characteristic in wireless systems. Image sensors require direct exposure to the environment whereas radio sensors might operate inside a bag.
Answer: a
Explanation: Sensing is accomplished by sensors and data processing algorithm. Radio sensing, radio vision, and radio hearing have different data processing procedures associated with them. Antenna based positioning systems utilize different algorithm from acoustic based location systems.
Sanfoundry Global Education & Learning Series – Cognitive Radio.
This set of Cognitive Radio Interview Questions and Answers for freshers focuses on “Location Awareness – 2”.
1. Which among the following is not feature of location awareness core?
a) Mobility management
b) Topographical information
c) Seamless positioning
d) Security
Answer: b
Explanation: Location sensing is followed by location awareness. Location awareness means to be aware of the location. The results of location awareness are transferred to cognition engine. Seamless positioning and interoperability, security and privacy, statistical learning and tracking, and mobility management are features of location awareness core.
2. European SPACE project uses ____
a) radio hearing method
b) environment imaging method
c) waveform based method
d) environment sensing based method
Answer: c
Explanation: Seamless positioning may be achieved by waveform based method. This approach requires knowledge on all type of existing and future waveforms of current and future systems. European SPACE project is an example of this method and offers centimeter level positioning accuracy.
3. In European SPACE project, the ____ approach helps to support future waveforms.
a) vendor libraries
b) plug and play
c) programming
d) pre-defined libraries
Answer: b
Explanation: The SPACE prototype consists of sensors, algorithms, and existing waveforms. The most appropriate positioning mechanism is selected based on user requirement and environment. The prototype has plug and play property which enables easy integration of future waveforms and positioning techniques.
4. RSS based location estimation algorithm is an example of ____
a) traffic based method
b) waveform based method
c) environment sensing based method
d) source based method
Answer: c
Explanation: Environment sensing based method may be used for seamless positioning. It monitors channel parameters and changes the algorithm accordingly. In RSS location based algorithm, location of device and path loss coefficient of channel environment are used to maintain accuracy.
5. Environment based method has ____ waveform based method.
a) higher complexity than
b) lower complexity than
c) equal complexity as
d) equal time duration as
Answer: b
Explanation: Seamless positioning involves maintenance of position accuracy regardless of changes in channel environment. Waveform based approach and environment sensing based approach are the two techniques employed to achieve seamless positioning. Waveform based approach requires large database of all existing and future waveform and hence is more complex than environment sensing based method.
6. In ____, interoperability is achieved by using ____ waveform.
a) cognitive-cognitive radio, same
b) cognitive-legacy radio, different
c) cognitive-cognitive radio, different
d) legacy-legacy radio, different
Answer: a
Explanation: There are two arrangements namely cognitive-cognitive radio and cognitive-legacy radio. Communication maybe carried out if both cognitive radios use the same waveform. Otherwise a waveform is chosen by both radios prior to communication.
7. Which among the following is done to establish communication?
a) Legacy radio reconfigures for communication
b) Cognitive radio uses different waveform for communication
c) Cognitive radio adapts legacy radio waveform
d) Legacy radio adapts cognitive radio waveform
Answer: c
Explanation: Communication between cognitive and legacy radio may be achieved only if the former uses the waveform supported by legacy radio. Legacy radio does not have re-configurability features.
8. Tracking the position of cognitive radio without ____
a) authorization violates user privacy
b) authorization is an adversarial attack
c) authentication violates user privacy
d) authentication is an adversarial attack
Answer: a
Explanation: Security and privacy are major points of concern in a cognitive radio. The two main threats are tracking the position of cognitive radio without authorization and adversarial attack. The former is a threat to user privacy and the latter can lead to malfunction of several location based application.
9. Geopriv is a working group under the ____
a) International Engineering Task Force
b) International Education Task Force
c) Internet Engineering Task Force
d) Internet Education Task Force
Answer: c
Explanation: Geopriv is working group under IETF mainly involved in wired networks. It examines the authorization, privacy, security, and integrity required for a particular transfer of information.
10. Which among the following is not a location based service?
a) Package tracking
b) Road side assistance
c) Patient tracking
d) Handover
Answer: d
Explanation: Location awareness applications are mainly classified into location based services, location assisted transceiver optimization, location assisted network optimization, and location assisted environment identification. Package tracking, road side assistance, and patient tracking are location based services. Handover falls under location assisted network optimization.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Environment Awareness – 1”.
1. Which among the following is not feature of environment awareness core?
a) Propagation channel characteristics
b) Topographical information
c) Meteorological information
d) Security
Answer: d
Explanation: Environment awareness engine consists of environment sensing, environment awareness core, and environment adaption. The type of information required, means to acquire the information, and utilization of collected information are concerns of environment awareness engine.
2. ____ is the practice describing the arrangement of a particular place.
a) Topology
b) Topography
c) Digital elevation model
d) Time mapping
Answer: b
Explanation: Topography describes the shapes and features of land surface. It provides accurate and detailed description of a place, city, town, or any tract of land. It includes vegetation and human made structures.
3. Which among the following is not an example of topographical application?
a) Geoscience
b) Topographic maps
c) Nano-topography
d) Networking
Answer: d
Explanation: One of the main applications of topography is topographic maps. There are applications being developed where a captured image is used as input to gather information on the location and environment. This is feature of interest for location and environmental awareness in cognitive radio.
4. ____ is the science of quantitative land surface analysis.
a) Geology
b) Geography
c) Geoscience
d) Geomorphometry
Answer: d
Explanation: Geomorphometry involves describing the terrain, the three dimensional quality of the surface, and the identification of landmarks. It uses mathematical, statistical, and image processing techniques to describe the land surface.
5. Propagation characteristics provide _________
a) characteristics of atmosphere
b) characteristics of weather
c) characteristics of signal progression
d) characteristics of traffic
Answer: c
Explanation: Propagation characteristics provide information on signal progression through a medium or channel environment. It studies the effect of channel on a signal.
6. ________ provides information on path loss behaviour.
a) Very large scale statistics
b) Large scale statistics
c) Small scale statistics
d) Very small scale statistics
Answer: b
Explanation: Large scale statistics provides information on path loss behaviour of channel environment. Small scale statistics provides information on variations caused in the received signal in time and frequency due to short displacements.
7. Which among the following is a step in defining propagation characteristics in environment awareness engine using cognitive radio?
a) Terrain mapping
b) Temperature monitory
c) Object tracking
d) Channel environment adaption
Answer: d
Explanation: The first step in defining propagation characteristics using cognitive radio is environment recognition and classification. It is followed by obtaining the parameters necessary for statistical propagation model. The final step is channel environment adaption.
8. The traditional means for obtaining propagation channel characteristics is called ____
a) statistical signal modeling
b) statistical channel modeling
c) propagation channel modeling
d) statistical modeling
Answer: c
Explanation: Propagation channel modeling involves performing extensive measurements and data processing to define propagation channel characteristics. Delay spread, Doppler spread, and angular speed are few channel characteristics.
9. Objects are ____ in the context of environment awareness.
a) land forms
b) landmarks
c) human made entities
d) natural entities
Answer: c
Explanation: Objects are human made entities present in the target environment permanently or temporarily in the context of environment awareness. Vehicles, appliances, packages are few examples of objects. However structures such as buildings are not considered as objects.
10. Bat echolocation is employed in ____
a) cognitive radar
b) cognitive triangulation
c) cognitive phase shift method
d) cognitive taping
Answer: a
Explanation: Bat echolocation is employed in cognitive radar and cognitive sonar. An important feature of environment awareness is object detection, identification, and tracking. These features have direct effect on the environment. Cognitive radar and cognitive sonar may accomplish these specified requirements.
11. Meteorological information focuses on ____ of the target region.
a) channel
b) structure
c) weather
d) relief
Answer: c
Explanation: Meteorological information focuses on weather of the target region and its effect on signal propagation. Weather conditions such as snow, rain, temperature, humidity, and pressure have an effect on signal propagation and are measured using sensors.
12. Which among the following can be used as a metric for studying the effect of rain on signal propagation?
a) Symbol rate
b) Bit rate
c) Carrier to interference ratio
d) Delay spread
vAnswer: c
Explanation: Meteorological information is studied to adapt the radio in accordance to the weather condition. Rain might induce carrier to interference ratio degradation, carrier to interference ratio improvement, or it might result in any change.
13. LOS – NLOS identification is a ____ application.
a) location based service
b) location assisted network optimisation
c) location assisted transceiver optimization
d) location assisted environment identification
Answer: d
Explanation: The ability to distinguish among different propagation environment as a function of line-of-sight is desirable at user terminal. LOS transmission characteristics differ from that of NLOS. LOS – NLOS identification is a location assisted environment identification application.
14. Indoor positioning systems require higher accuracy than outdoor positioning systems.
a) True
b) False
Answer: a
Explanation: Indoor positioning systems require higher accuracy than outdoor positioning systems. For example, asset management in industrial areas requires an accuracy of 0.05 – 30 m. Most autonomous location aware applications require high accuracy.
15. Adaptive beam forming is a location based service.
a) True
b) False
Answer: b
Explanation: Adaptive beam forming, interference avoidance, and link adaption are location based transceiver optimization applications. Package tracking and child finder are examples of location based service.
This set of Cognitive Radio Interview Questions and Answers for Experienced people focuses on “Environment Awareness – 2”.
1. In ____ approach, the distance between two cognitive radios is found by estimating ____ information.
a) cooperative location awareness, triangulation
b) cooperative location awareness, ranging
c) composite location awareness, triangulation
d) composite location awareness, time of flight
Answer: b
Explanation: In cooperative location awareness approach, a cognitive radio transmits a signal through channel environment. Another radio obtains ranging information from the received signal.
2. In cooperative location awareness, the transmitter and the receiver are ____
a) nottime reliant
b) not duplex
c) not co-located
d) not active
Answer: c
Explanation: In cooperative location awareness, individual radios are used for transmission and reception. The transmitter and the receiver are not co-located. It is accomplished by cognitive positioning system.
3. ____ is the first step in cognitive ranging protocol.
a) Ranging parameter set up
b) Angle of arrival set up
c) Line of sight determination
d) Meteorological determination
Answer: a
Explanation: Cognitive ranging protocol has three steps namely ranging parameter set up, two-way time of arrival ranging, and time stamp report. The ranging parameter set up stage is otherwise known as a loop stage.
4. What is the minimum number of radios required for cooperative location awareness?
a) One
b) Two
c) Three
d) Four
Answer: b
Explanation: In cooperative location awareness, at least two radios are required for operation. Before ranging, the two radios bargain or offer feedback to each other during the ranging parameter setup stage. The next step is to carry out two way ranging.
5. In ____ approach, transmitter and receiver are co-located.
a) active self-location awareness
b) passive self-location awareness
c) active cooperative location awareness
d) passive cooperative location awareness
Answer: a
Explanation: Self location awareness may be active or passive. In active self-location awareness, transmitter and receiver are used. The transmitter and receiver are co-located. Cognitive radar is an example of this approach.
6. ____ may be used in passive self-location awareness approach.
a) Cognitive sonar
b) Image sensor
c) Infrared sensor
d) Hall sensor
Answer: b
Explanation: Passive self-location awareness approach involves observing the environment and capturing desired signals without transmitting signals into the environment. Human vision is an example of the approach in nature.
7. The closed loop feedback exists ____
a) between transmitter and environment
b) between receiver and environment
c) between transmitter and receiver
d) among transmitter, environment, and receiver
Answer: d
Explanation: The implementation of closed loop feedback is simplified by co-located transmitter and receiver in self-location awareness. Thus achieving feedback loop is simpler in self-location awareness than in cooperative location awareness.
8. Self-location awareness offers ____
a)only absolute ranging
b)only relative ranging
c)only non-relative ranging
d)only absolute ranging and non-relative ranging
Answer: b
Explanation: Self-location awareness provides only relative ranging information. Cooperative location awareness provides absolute and relative ranging and positioning information because they are not co-located.
9. Bat echolocation systems employ ____ modulation.
a) amplitude
b) frequency
c) phase
d) amplitude shift keying
Answer: b
Explanation: Bat echolocation system is an example of range accuracy adaption systems. It uses frequency modulation during emission to identify the target in its path.
10. Bat echolocation system _____ on moving close to the target.
a) increases transmitted signal duration
b) increases transmitted signal bandwidth
c) decreases transmitted signal duration
d) decreases transmitted signal bandwidth
Answer: c
Explanation: Bat echolocation systemadjusts emitted sound duration, bandwidth, and repetition rate during the process of target identification. It decreases transmitted signal duration on moving close to the target.
11. Which among the following is a parameter for Cramer-Rao lower bound?
a) Decision theory
b) Bayesian statistics
c) Wald test
d) Fisher information
Answer: d
Explanation: Cramer Rao lower bound states the variance of any unbiased estimator is at least as high as the inverse of Fisher information. It may be employed as an optimization criterion in bat echolocation systems.
12. Cognitive ranging protocol may be used as a handshaking mechanism.
a) True
b) False
Answer: a
Explanation: Cognitive ranging protocol has three steps namely ranging parameter set up, two-way time of arrival ranging, and time stamp report. Each stage involves transfer of information and acknowledgement between the radio devices. It is carried out after transmission parameters are determined.
13. Maximum likelihood estimator at the receiver uses only NLOS signals.
a) True
b) False
Answer: b
Explanation: Cramer Roa lower bound at the receiver is achieved by using maximum a posteriori and maximum likelihood estimator. Maximum a posteriori uses LOS and NLOS signals to achieve CRLB while maximum likelihood uses only LOS signals.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Environment Awareness – 3”.
1. ____ affects range accuracy adaption.
a) Resonance frequency
b) Bit rate
c) Symbol rate
d) Bandwidth
Answer: d
Explanation: The amount of bandwidth available affects range accuracy adaption based on the optimisation technique utilised to choose parameter values. Resolution of bandwidth is another parameter that affects range accuracy adaption.
2. Two way ranging can resolve ____
a) amplitude difference
b) frequency difference
c) phase difference
d) amplitude and phase difference
Answer: c
Explanation: Synchronisation of oscillators of two transmitters may not be possible. In such a case, the measurement of path from the transmitter to receiver and from receiver to transmitter may be used to compensate for phase difference.
3. Time of arrival data from two base stations may provide ____ of a location.
a) position circle
b) point
c) peak circle
d) peak point
Answer: a
Explanation: Time of arrival is the time taken by a radio signal to cover the distance from a transmitter to a remote receiver. Time of arrival data from two substations offers the position circle of a location. Additional data from a third substation provides precise single point location.
4. Which among of the following may be employed to synchronise base station to local reference station?
a) Two signals of different frequency
b) Two signals of different phase
c) Four signals of different frequency
d) Four signals of different phase
Answer: a
Explanation: Synchronisation between base station and local reference station may be achieved by using accurate synchronous clocks, employing two signals of different frequency, or through measurement to or triggering from a common reference point.
5. Propagation loss is more in ____
a) lower carrier frequencies
b) higher carrier frequencies
c) lower bandwidth
d) higher bandwidth
Answer: b
Explanation:At higher carrier frequencies, higher propagation loss, and lower range and penetration are observed. The influence of weather and attenuation is more at higher carrier frequencies when compared to lower carrier frequencies.
6. Which among the following parameter of transceiver does not affect range accuracy?
a) Bandwidth
b) Resolution of bandwidth
c) Transmission power level
d) Receiver power level
Answer: d
Explanation: The support exhibited by transceiver towards arbitrary bandwidth and resolution, and arbitrary transmission level can affect the performance of range accuracy adaption. These factors may be controlled by software defined radio capability of cognitive radio.
7. Which among on the following transceiver parameter may be used to improve range accuracy adaption?
a) Randomizing transmit power level
b) Decreasing the length of observation symbols
c) Increasing the length of observation symbols
d) Randomizing carrier frequencies
Answer: c
Explanation: The length of observation symbols is a transceiver parameter that affects range accuracy. Range accuracy improves by increasing the length of the observation symbols. However this introduces difficulties such as large overhead.
8. ____ exhibits the effect of channel distortion.
a) Equalization tap coefficient
b) Filter tap coefficient
c) Channel tap coefficient
d) Signal tap coefficient
Answer: c
Explanation: The channel tap coefficient is an environmental parameter that affects range accuracy. Channel tap coefficient exhibits the effect of channel distortion on a propagating signal. It is used in the final result computation of range accuracy at the receiver end.
9. Which among the following is an environmental parameter that affects ran accuracy?
a) Phase dependent coefficient of attenuation
b) Frequency dependent coefficient of attenuation
c) Phase dependent coefficient of channel
d) Frequency dependent coefficient of channel
Answer: d
Explanation: Frequency dependent coefficient of channel, path loss coefficient, and LOS/NLOS condition are some of the environmental parameters that affect range accuracy. The amount of influence shown by the frequency dependent coefficient of channel depend on the frequency dependent feature of the radio.
10. Multiuser interference is an example of external interference.
a) True
b) False
Answer: a
Explanation: Interference sources are of two types namely internal interference and external interference. Multiuser interference is an example of external interference. Inter-symbol interference is an example of internal interference.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Techniques – Optimisation of Radio Resources – 1”.
1. The ____ function provides the share of ____ to the parameter to be optimised.
a) subjective, a particular variable
b) subjective, each variable
c) objective, each variable
d) objective, a particular variable
Answer: c
Explanation: The objective function provides the share of each variable to the parameter to be optimised.The objective function is given by the product of objective coefficient and decision variable. The physical layer is described in terms of objective functions for radio resource optimisation.
2. Objective space is described using ____ set of ____ functions.
a) one dimensional, objective
b) multi-dimensional, objective
c) one dimensional, exponential
d) multi-dimensional, exponential
Answer: b
Explanation: Objective space comprises of total possible solutions to a problem. It is defined over multidimensional set of objective functions. Radio resources that define radio behaviour form the cognitive radio objective space.
3. Which among the following is a potential goal for resource allocation optimisation?
a) Resources are used only to satisfy needs
b) Resources are kept in waiting
c) Resources are permanently allocated for each task
d) Resources are allocated with a permanent priority schedule
Answer: a
Explanation: The utilization of resources by each node is monitored with a global perspective of optimising radio resources. It should be done without compromising the quality of service available to the user and avoid over usage of resources.
4. Multi objective optimisation involves ____ over more than one criterion.
a) integrating
b) deriving equations
c) encapsulating
d) decision making
Answer: d
Explanation: Multi objective optimisation involves decision making over more than one criterion. It deals with mathematical optimisation problems where optimisation of many objective functions has to be carried out simultaneously.
5. Which among the following is not an alternative expression for Pareto optimal?
a) Dominated
b) Pareto efficient
c) Non inferior
d) Non dominated
Answer: a
Explanation: The optimisation of all objectives simultaneously is not possible as improvement of one objective might negatively affect another objective. A Pareto optimal solution is one where none of the objective functions may be improved without degrading another objective value.
6. A set of Pareto optimal solutions is referred to as ____
a) Pareto square
b) Pareto box
c) Pareto circle
d) Pareto boundary
Answer: d
Explanation: A set of Pareto optimal solutions is referred to asPareto boundary or Pareto frontier. The Pareto front of a multi-objective optimisation is bounded by nadir objective vector and ideal objective vector.
7. Which among the following have direct dependency relationship?
a) BER and bandwidth
b) BER and SINR
c) SINR and bandwidth
d) Bandwidth and power
Answer: a
Explanation: Direct dependency involves the one to one relationship between two parameters. Indirect dependency involves creating links between parameters based on objective dependency. Bit error rate directly depends on bandwidth and is indirectly related to signal to noise ratio.
8. Bit error rate depends on ____
a) source
b) route
c) channel
d) receiver
Answer: c
Explanation: Bit error rate is defined by the amount of bits received in error from the total number of bits received. Bit error rate primarily depends of channel type and modulation technique.
9. Which among the following is a monitor parameter of BER?
a) Noise power
b) Transmission power
c) Path loss
d) Bandwidth
Answer: b
Explanation: A monitor parameter is one which can be set by the cognitive radio. Meters are factors that can be measured and used for analysis but cannot be controlled. Transmission power is a monitor parameter. Noise and path loss are meters.
10. Bit error rate calculation depends on ____ at the receiver.
a) correlator
b) signal to noise ratio
c) analog to digital converter
d) error detection codes
Answer: b
Explanation: Cognitive radio sets the transmitted power. The transmitted power, the path loss, and the noise floor can be used to compute received power and noise power. SNR is an important factor in this calculation.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Techniques – Optimisation of Radio Resources – 2”.
1. Which among the following is an objective not dependent on bandwidth?
a) Bit error rate
b) Interference power
c) Throughput
d) Power
Answer: d
Explanation: Bandwidth measures the capacity of spectrum used by the radio. It influences a number of objects such as bit error rate, interference power, throughput, and spectral efficiency. Modulation type, symbol rate, and pulse shape filter are control monitors.
2. ____ is used to reduce inter-symbol interference.
a) Root raised cosine filter
b) Sinc filter
c) Root raised sinc filter
d) Cosine filter
Answer: a
Explanation: The raised cosine filter is an implementation of Nyquist low pass filter. It is used for pulse shaping and to minimise inter-symbol interference. It derives its name from the frequency spectrum which resembles a cosine function.
3. ____ filter is required to form ____ filter.
a) Two raised cosine filter, one sinc filter
b) Two raised sinc filter, one raised cosine filter
c) Two root raised cosine filter, one raised cosine filter
d) Two raised cosine filter, one root raised cosine filter
Answer: c
Explanation: Two root raised cosine filter is required to form one raised cosine filter. It may be used to reduce inter-symbol interference. It involves installing one root raised cosine filter at the transmitter and the other filter at the receiver.
4. Spectral efficiency may be expressed in terms of ____
a) Hertz
b) bits per second
c) Hertz per bit per second
d) bits per Hertz per second.
Answer: c
Explanation: Spectral efficiency describes the amount of information transferred in a channel. It may be used to determine quality of service. Spectral efficiency may be expressed in terms of Hertz per bit per second.
5. The minimisation of bandwidth causes ____
a) low symbol rate
b) high symbol rate
c) high power
d) low power
Answer: a
Explanation: The minimisation of bandwidth causes low symbol rate and utilization of algorithm such GMSK. The maximisation of bandwidth causes high symbol rate and higher modulation method.
6. Which among the following is an expression for spectral efficiency?
a) η=\(\frac{R_sk}{B}\). where R s is the symbol rate, B is the bandwidth, K is the number of bits per symbol
b) η=R sB where R s is the symbol rate, B is the bandwidth, K is the number of bits per symbol
c) η=\(\frac{Bk}{R_s}\)where R s is the symbol rate, B is the bandwidth, K is the number of bits per symbol
d) η=BK where B is the bandwidth
Answer: a
Explanation: Spectral efficiency is given by the product of number of bits per symbol and symbol rate divided by bandwidth. It helps in achieving balance between symbol rate and modulation type.
7. The modification of a signal due to extraneous power exhibited by a signal from a nearby channel is called ____
a) co-channel interference
b) adjacent channel interference
c) inter-symbol interference
d) inter-carrier interference
Answer: b
Explanation: The modification of a signal due to extraneous power exhibited by a signal from a nearby channel is called adjacent channel interference. It may be due to inadequate filtering, improper tuning or poor frequency control. It may be classified as adjacent channel leakage ratio and adjacent channel selectivity.
8. The aim of interference objective is ____
a) to determine compatibility of waveform and frequency
b) to determine compatibility of waveform and radio environment
c) to compare channels
d) to compare signals
Answer: d
Explanation: The interference objective depends on bandwidth. It is measured at various frequencies and is defined by interference map. The interference map is used to determine the overlap present between signals trying to operate on the same spectrum.
9. Signal to interference plus noise ratio gives ____
a) lower bound on channel capacity
b) upper bound on channel capacity
c) upper bound on receiver capacity
d) lower bound on channel capacity
Answer: b
Explanation: Signal to interference plus noise ratio gives upper bound on channel capacity in wireless communication system. It takes into account factors such as noise, interference, path loss, and bandwidth. It is a parameter that defines the quality of wireless connection.
10. Signal to interference plus noise ratio is defined as ____
a) ratio of noise power to interference power
b) ratio of signal power to sum of noise and interference power
c) ratio of sum of noise and interference power to signal power
d) ratio of interference to noise power
Answer: b
Explanation: Signal to interference plus noise ratio is defined as ratio of signal power to sum of noise and interference power. If the noise power were to be zero, the expression reduces to signal to interference ratio. If the interference were to be zero, the expression reduces to signal to noise ratio.
11. ____ is a measure of good information received.
a) Latency
b) Data rate
c) Bit rate
d) Throughput
Answer: d
Explanation: Data rate is a measure of rate at which data arrives regardless of transmission errors. Throughput is the measure good information available at the receiver.
12. Which among the following is an objective that influences throughput?
a) Bit error rate
b) Bandwidth
c) Spectral efficiency
d) Signal to interference ratio
Answer: a
Explanation: Bit error rate is an objective for that influences throughput. Modulation type, symbol rate, and number of bits per packet are the monitor parameters. Throughput does not have any meters that influence the result.
13. Which among the following is a simple expression of throughput objective?
a) R th =kR s where R s is symbol rate
b) R th =kR b where R b is bit rate
c) R th =R s R b where R s is symbol rate and R b is bit rate
d) R th =R s /R b where R s is symbol rate and R b is bit rate
Answer: a
Explanation: The simple expression of throughput objective is given by R th =kR s . The complexities involved in the measurement of throughput are due to restricted retransmissions and no coding. As a result, a single bit error leads to packet error. By taking this into account, the expression of throughput is given by R th =R b (1-P e ) l .
14. Gaussian minimum shift keying is based on frequency shift keying.
a) True
b) False
Answer: a
Explanation: Gaussian minimum shift keying involves Gaussian filtering the modulating signal and passing it through frequency modulator. The second method uses quadrature modulator otherwise known as I-Q modulator.
15. Minimum shift keying experiences phase discontinuities.
a) True
b) False
Answer: b
Explanation: Minimum shift keying does not experience phase discontinuities because frequency changes occur at the carrier zero crossing points. This is expressed by setting the modulation index to 0.5.
This set of Cognitive Radio Questions and Answers for Experienced people focuses on “Techniques – Optimisation of Radio Resources – 3”.
1. In multiobjective analysis, ____ function is used for selection.
a) subjective
b) single valued
c) utility
d) set
Answer: c
Explanation: In multi objective analysis, single utility function involves combining several objectives into a single number. Ranks are assigned to solutions. The solution that maximizes utility function is selected.
2. The significance of weighted sum utility function approach is that the ____ can be determined.
a) optima at extreme edges
b) optima at centre
c) concavity at extreme edges
d) concavity at centre
Answer: a
Explanation: The weighted sum approach involves computing the sum of product of objective function and the weight assigned to them. The significance of weighted sum utility function approach is that the optima at extreme edges can be determined.
3. Cobb Douglas function is otherwise called ____
a) linear function
b) weighted sum function
c) logarithmic function
d) linear logarithmic function
Answer: d
Explanation: Cobb Douglas function is otherwise called linear logarithmic function. It is an advanced version of weighted sum approach. The result is shaped by the logarithmic function. The logarithmic function adds convexity to the optimisation curve.
4. ____ defines the amount of change constituted by the substitution of one parameter by another parameter.
a) Rigidity
b) Elasticity
c) Replaceable
d) Replicable
Answer: b
Explanation: Elasticity defines the amount of change constituted by the substitution of one parameter by another parameter. A value of 1 indicates perfect substitution. Constant elasticity by substitution does not require independent input value and is suitable for multi objective analysis.
5. Utility function is an example of ____
a) no preference method
b) a post priori method
c) interactive method
d) a priori method
Answer: d
Explanation: A priori method requires setting up of certain amount of desired traits before optingthe solution process. When no desired traits are specified in multi objective optimisation, it is regarded as no-preference method.
6. ____ builds a matrix with ____ assigned to columns and ____ assigned to rows.
a) Multiple single objective Pareto sampling, elasticity, weights
b) Repeated single objective, elasticity, weights
c) Multiple single objective Pareto sampling, objectives, ranks
d) Repeated single objective, objectives, ranks
Answer: c
Explanation: Multiple single objective Pareto sampling calculates all objectives for each member of the population. A matrix is built with columns representing the objectives, and the rows represent individual rank for each objective.
7. In ____ approach, the ____ members are saved after each process or test.
a) multiple single objective Pareto sampling, dominant
b) repeated single objective, dominant
c) multiple single objective Pareto sampling, recessive
d) repeated single objective, recessive
Answer: b
Explanation: Repeated single objective involves operating on the same set of members multiple times using single, different objective each time. The dominant members from each test are recorded for final analysis of Pareto set.
8. Which among the following is a monitor parameter for power consumption?
a) Throughput
b) Modulation type
c) SINR
d) Interference
Answer: b
Explanation: Modulation type and symbol rate are monitor parameters for power consumption. Each waveform utilizes certain amount of power based on the processes used at the transmitter and the receiver for proper operation.
9. Effective isotropic radiated power is given by ____
a) product of input power to the antenna and gain of the antenna
b) sum of input power to the antenna and gain of the antenna
c) difference of input power to the antenna and gain of the antenna
d) ratio of product of input power to the antenna and gain of the antenna
Answer: a
Explanation: Effective isotropic radiated power measures the combination of the power emitted by the transmitter and the capability of the antenna to wield that power in a particular direction. It is given by the product of product of input power to the antenna and gain of the antenna.
10. Non coherent receivers require more power than coherent receivers.
a) True
b) False
Answer: b
Explanation: Non coherent receivers require less power than coherent receivers. This is because coherent receivers involve frequency and phase correction in their reception process. Since additional processes are carried out, more power is consumed. Similarly, higher symbol rate requires more processing speed, and consequently more power.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Artificial Intelligence – 1”.
1. Bayesian networks uses ____
a) directed cyclic graph
b) directed acyclic graph
c) undirected cyclic graph
d) undirected acyclic graph
Answer: b
Explanation: A Bayesian network is a probabilistic graphical model where a group of variables and their conditional dependencies are represented using directed acyclic graph. Directed acyclic graph is a directed graph and does not have directed cycles.
2. Bayesian network can match ____ with ____
a) an incident, probable cause
b) a definite cause, probable consequence
c) a incident, similar incident
d) a cause, similar cause
Answer: a
Explanation: A Bayesian network examines an event and determines the probability of a known cause activating that event. For example, a Bayesian network can be used to examine the symptoms of a person and match it with a probable disease.
3. Bayesian network that models speech signals are called ____
a) signal Bayesian network
b) sequential Bayesian network
c) series Bayesian network
d) dynamic Bayesian network
Answer: d
Explanation: Bayesian network that replicate sequence of variables such as speech signals are called as dynamic Bayesian network. It has been applied in robotics, bioinformatics, and digital forensics. It is a generalisation of Hidden Markov Model and Kalman filter.
4. Which among the following is not represented by node in Bayesian network?
a) Latent variables
b) Observable variables
c) Hypotheses
d) Conditions
Answer: d
Explanation: The nodes in a Bayesian network represent latent variables, observable variables, unknown parameters, and hypotheses. The conditions are represented using edges. The nodes which are not connected by edges are conditionally independent.
5. The process of computing the ____ of variables when provided with supporting conditions is called ____
a) prior distribution, probabilistic inference
b) posterior distribution, probabilistic inference
c) prior distribution, probabilistic query
d) posterior distribution, probabilistic query
Answer: b
Explanation: The process of computing the posterior distribution of variables when provided with supporting conditions is called probabilistic inference. It is probability of one or more variable taking a particular set of values.
6. Expert system is a computer system capable of resolving _____ problems.
a) recognition
b) decision making
c) transfer
d) storage
Answer: b
Explanation: An expert system is a computer system that performs decision making based on facts and heuristic approach. It can solve difficult issues occurring within a specific domain.
7. Which among the following is used expert systems?
a) If-then rules
b) Arithmetic rules
c) Logical rules
d) Procedure rules
Answer: a
Explanation: Expert systems are enriched with information and use reasoning to solve complex decision making problems. The process is depicted with a set of if-then conditions instead of conventional procedural code.
8. What are the two major units of expert systems?
a) Knowledge base and performance engine
b) Performance engine and inference engine
c) Radio base and performance engine
d) Knowledge base and inference engine
Answer: d
Explanation: Knowledge base is a large storage of facts and rules obtained from experts of a domain. Inference engine uses the knowledge to deduce new solutions and resolve the query presented by the user.
9. Which among the following is considered as disadvantage of expert system?
a) Fast prototyping
b) Development process
c) Maintenance
d) Knowledge acquisition
Answer: d
Explanation: The process of gathering information for knowledge base is difficult as it required input from highly experienced and valued domain experts. Several tools are being developed to automate the process of collecting relevant information, designing, and maintenance of rules.
10. DENDRAL is an example for expert system.
a) True
b) False
Answer: a
Explanation: DENDRAL is a successful implementation of expert system in organic chemistry. It was developed in 1965. It is applied in chemical analysis to predict molecular structure.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Techniques – Artificial Intelligence – 2”.
1. Which among the following is the basic component of artificial neural networks?
a) Motors
b) Neurons
c) Nephrons
d) Nuclei
Answer: b
Explanation: Artificial neural networks are constructed using nodes which imitate the functionality of biological neurons. The network is a collection of algorithms that vaguely meets the performance of human brain in recognition of patterns.
2. What type of connection is present between nodes in neural networks?
a) Sampled
b) Not weighted
c) Weighted
d) Non-existent
Answer: c
Explanation:The connection between neurons or nodes is weighted. If the number associated with the weight is positive, then it is an excitatory condition. If the number associated with the weight is negative, then it is an inhibitory condition.
3. What type of approach do artificial neurons employ for computation?
a) Comparative
b) Connectionistic
c) Conservative
d) Condensed
Answer: b
Explanation: The distributed signal activity being carried out at once through connections may be represented using numbers. The connection is improved based on collected information over time and this process is referred to as learning.
4. What function calculates the value to be given as input to a neuron based on the output obtained by the last processed neuron?
a) Correlation
b) Direction
c) Propagation
d) Signalling
Answer: c
Explanation: The propagation function is responsible for determining the input to a neuron in accordance to the output obtained from the previously processed neurons and their connections labelled as weighted sum. A bias term may be included to the outcome of the propagation function.
5. What is the terminology used to describe the connection where a set of neuron in one layer is connected to one neuron in the next layer?
a) Fully connected
b) Partially connected
c) Splitting
d) Pooling
Answer: d
Explanation: The various types of connections used to join neurons present in adjacent layers contribute to the organisation of the neural network. When every neuron is connected to every neuron in the next layer, it is called as fully connected. When a set of neurons is connection to one neuron in the next layer, it is called as pooling.
6. Which among the following maybe used for modulation detection in neural networks?
a) Phase based probability
b) Time based probability
c) Time based statistics
d) Phase based statistics
Answer: c
Explanation: Artificial neural networks may be used for signal classification and modulation detection in cognitive radio. The popular techniques employed for modulation classification is called as time based statistics and frequency analysis. The neurons and complex algorithms make it possible to build and process data in interesting ways.
7. In ____ time, Markov chain is called as ____
a) continuous, Markov process
b) discrete, Markov process
c) continuous, Bayesian process
d) discrete, Bayesian process
Answer: a
Explanation: A Markov chain is a stochastic model. It represents a progression of events in which the probability of each event depends on the state achieved by the past event.
8. What does the term “hidden” refer to in hidden Markov model technique?
a) Parameters of input
b) Sate sequence
c) Parameters of model
d) Fixed standards of model
Answer: b
Explanation: In a hidden Markov model, the state is not directly available to the observer. The output, dependant on the state, is available. The parameters of the model are not hidden, and the model is referred to as hidden Markov model even when the parameters are explicitly available.
9. Which among the following is not commonly determined by using hidden Markov model?
a) Channel transition probabilities
b) Decision making in cellular network
c) Channel quality
d) Signal classification
Answer: d
Explanation: Hidden Markov models use past data to predict future actions. It may be used to describe channel quality. It determines whether the process should move to the next or remain in the present state. The current channel statistics may be modelled and use for decision making in cellular network.
10. A hidden Markov model can be considered a generalisation of mixture model.
a) True
b) False
Answer: a
Explanation: A mixture model is used to represent the presence of a sub-category within an overall category. In hidden Markov model, the hidden variables are related based on Markov process and are not independent of each other. The hidden variables control the mixture component to be selected for each observation.
This set of Cognitive Radio Quiz focuses on “Techniques – Artificial Intelligence – 3”.
1. Which among the following gives the definition of fuzzy logic?
a) Fuzzy logic follows Boolean logic where zero stands for true and one stands for false
b) Fuzzy logic follows Boolean logic where zero stands for false and one stands for true
c) Fuzzy logic allows the assignment of any real number from zero to one to variables
d) Fuzzy logic allows the assignment of any whole number from zero to one to variables
Answer: c
Explanation: Fuzzy logic allows the assignment of any real number from zero to one to variables. It is a multi-valued logic. It implements the condition of partial truth. The truth value may fall anywhere between completely false to completely true.
2. Which among the following is a false statement about Fuzzy logic?
a) Fuzzy logic may use imprecise information
b) Fuzzy logic uses only accurate information
c) Fuzzy logic may represent vague information
d) Fuzzy logic may use non-numerical information
Answer: b
Explanation: Fuzzy logic is based on the observation that decision making sometimes involves making use of inaccurate and imprecise information. The fuzzy logic models are generally vague but are capable of identifying, representing, and modifying unclear information and data.
3. Which among the following is the correct sequence of events that occur in application of fuzzy logic?
a) Fuzzify the input, execute the applicable rules, and de-fuzzify the output
b) Execute the applicable rules, fuzzify the input, and de-fuzzify the output
c) Fuzzify the input, de-fuzzify the output, and execute the applicable rules
d) Execute the applicable rules, fuzzify the input, and fuzzify the output
Answer: a
Explanation: The implementation of fuzzy logic generally involves three steps namely fuzzify the input into fuzzy membership functions, execute every rule in the defined rule base to generate the fuzzy output, de-fuzzify the output to get distinct output values.
4. What is the term used to refer to variables that take non-numerical as input?
a) String variables
b) Character variables
c) Linguistic variables
d) Morphological variables
Answer: c
Explanation: Linguistic variables are assigned non-numerical values to aid the representation of facts and rules. For example, a linguistic variable may take “hot” and “cold” as input. In order to take advantage of the scale offered by fuzzy logic, additional words such as “rather” or “somewhat” may be used.
5. Which among the following uses past solutions to solve current problems?
a) Artificial neural networks
b) Fuzzy logic
c) Knowledge based systems
d) Case based reasoning
Answer: d
Explanation: Case based reasoning is the process of developing solutions to current problems based on solutions that have already been applied under similar conditions. The process initially involves the comparison of functional and operational characteristics for resemblance. If the similarity is limited, then reasoning is applied for modification of solution to suit the current problem.
6. Which among the following is an algorithm useful for case based reasoning?
a) Viterbi algorithm
b) K- nearest neighbours algorithm
c) Forward algorithm
d) Backward algorithm
Answer: b
Explanation: K-nearest neighbours algorithm uses k number of training examples that have input characteristics similar to that of current condition under interest to fix target value for the current condition. This may be accomplished by using mode, average, or some other interpolation technique.
7. What is the process of identifying a parameter value from a training set that could result in the minimisation of error called?
a) K-nearest neighbours algorithm
b) Leave one out cross validation algorithm
c) Bayesian algorithm
d) Markov theorem
Answer: b
Explanation: The level of importance exhibited towards a parameter can be varied by adjusting the weights associated with each parameter. The degree of importance may be increased by increasing the value on scale. Leave one out cross validation algorithm is employed to learn the weights from the instances defined in the training set.
8. Case based reasoning is a cyclic process.
a) True
b) False
Answer: a
Explanation: Case based reasoning begins with the identification of a case that best suits the case under investigation. The case is then modified to suit the current situation. The modified case is evaluated based on performance. Finally, the new case is added to the case base according to the performance level.
9. Which among the following is used for quality determination in evolutionary algorithm?
a) Subjective function
b) Fitness function
c) Loss function
d) Utility function
Answer: b
Explanation: Fitness solution determines the degree of closeness exhibited by the designed solution to the specified expectations as a single figure of merit. Evolutionary algorithm determines optimal solutions by eliminating sub-optimal solutions based on the figure of merit assigned by fitness solutions.
Answer: a
Explanation: Genetic algorithm employs recombination and mutation to solve a problem. The solution is presented in the form of string of numbers. It is popularly applied for optimisation problems.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Architecture – Cognitive Radio Functions”.
1. Which among the following function is achieved by using acoustic sensor?
a) Effector function
b) User interface function
c) Cognition function
d) Software defined function
Answer: b
Explanation: The user interface functions use various devices such as haptic sensors, acoustic sensors, and video sensing functions. The haptic sensors get input from buttons, the acoustic sensors parses through recorded voice to interpret the input, and visual perception is employed to use videos as input.
2. What service is offered by system applications?
a) Interaction services
b) Information services
c) Intra-system communication
d)Media dependent services
Answer: b
Explanation: System application offers information services of value to the user. It is responsible for providing the applications such as phone book, text messaging, networking, and gaming, etc. It is also responsible for hiding information that is not primarily important for a user such as the technology being used for communication.
3. Which among the following is not carried out by local effector function?
a) Speech synthesis
b) Text analysis
c) Multimedia display
d) Geo-location
Answer: d
Explanation: Speech synthesis, text analysis, multimedia display, and graphics fall under the category of local effector functions. It involves finding user information on information states, identifying plans, and determining the probability of potential communication through parsing and interpretation.
4. Which among the following gives the full form of RXML?
a) RicXon Macro Language
b) RicXon Micro Language
c) RoXen Macro Language
d) RoXen Micro Language
Answer: c
Explanation: RoXen Macro Language is a server scripting language with syntax similar to that of HTML. The functions which impart external communication and internal reasoning in a self-aware radio are implemented using RXML.
5. Which among the following statements is true about the RXML statements given?
<Cognitive radio platform/>
<Functional-Components>
<Func1/><Func2/><Func3/><Func4/><Func5/><Func6/>
</Functional-Components>
</Self>
a) The hardware and software platform is dependent of the functional components of the cognitive radio
b) The functional components of the cognitive radio are dependent on the hardware and software platform
c) The hardware and software platform are independent of each other
d) The hardware and software platform is independent of the functional components of the cognitive radio
Answer: d
Explanation: The organisation of the statements defines a cognitive radio with six functional components. The enclosure of the functional components within <Functional-Components> and </Functional-Components> indicate that the hardware and software platform is independent of the functional components of the cognitive radio.
6. Which among the following describes the functions of cognitive radio?
a) Define personalities
b) Monitor knowledge
c) Define antenna direction using pre-stored tables
d) Support plug and play
Answer: b
Explanation: The cognition functions of a cognitive radio include monitoring and constructing knowledge, particularly of repeated actions and characteristics exhibited by user, surroundings, and radio. This helps information services to match the preferences of the user.
7. What degree of capability is achieved by the installation of a GPS receiver in a radio?
a) Aware
b) Adaptive
c) Cognitive
d) Programmable
Answer: a
Explanation: An aware device can obtain useful information. A device with GPS receiver is capable of sensing its location. However, a device becomes adaptive only when it uses the information for an application such as a map.
8. How can a radio be trained to accept commands from one owner entity?
a) Perception functions
b) Sensory functions
c) Awareness functions
d) Adaptive functions
Answer: a
Explanation: Perception functions can sense and trace known, unknown, and background information at all time. It is considered as a sub-category of cognition functions. The ability to accept commands from a particular entity and ignore all other entities is provided by perception functions.
9. Which among the following categories include an accelerometer?
a) Global effectors
b) Environmental sensors
c) Local effectors
d) User interface sensors
Answer: b
Explanation: Environmental sensors measure various characteristics in the surrounding domain. This includes temperature, vibration, power, exposure to light, position of sun, velocity, etc. It enables perception.
10. Adaption may be pre-programmed.
a) True
b) False
Answer: a
Explanation: Awareness enables adaption. Adaption is ability to direct a change according to input obtained from sensing. Adaption may be achieved without introducing learning through pre-programming. However, it is not possible to program all possible changes hence the next level of capability cognition is required.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Architecture – Cognitive Radio Components”.
1. What method may introduce a trade-off between time and space in cognitive radio structure?
a) Introduction of fully programmed solutions
b) Introduction of partial solutions
c) Introduction of real time solutions
d) Introduction of large memory
Answer: b
Explanation: The introduction of partial solutions help in solving complex problems because a subset of problems relating to the complex problem will be solved first. The number of calculations may not be completely reduced but there is slight development in the overall computational burden.
2. What is the full form of NP complexity?
a) Non-deterministic polynomial time
b) Non-linear polynomial time
c) Non-probabilistic polynomial time
d) Non-trainable polynomial time
Answer: a
Explanation: The non-deterministic polynomial time is a complexity class in the computational complexity theory. It is used to differentiate decision problems. NP is a collection of decision problems. When a decision results in action, it must have proof that can be confirmed in polynomial time by a deterministic Turing machine.
3. Which among the following is a characteristic that need not be compulsorily present to overcome self-referential inconsistency in cognitive radio?
a) Definition of process as a priori tightly bounded time epochs
b) Step counting function
c) Susceptible to Gödel-Turing condition
d) Pre-defined actions that uses O resources
Answer: c
Explanation: In order to computationally support real time transmission and reception, a process must be defined in priori tightly bounded time epochs. A pre-defined action that uses O resources is defined in advance and a reliable step counting function must be present. This will help in avoiding unpredictable usage of resources and unpredictable self-referential loops.
4. Why is the RXML statement <Self/> added in cognitive radio?
a) To add cognitive architecture to cognitive radio
b) To define functions
c) To define interfaces
d) To eliminate components
Answer: a
Explanation: The cognitive radio must evaluate, monitor, and access all resources including affirming downloads. The statement <Self/> is a self-referential component. It is used to add the aware, adaptive, and cognitive radio architecture to aware, adaptive and cognitive radio.
5. What capability demand was boosted upon introduction of machine learning in cognitive radio?
a) RF sensing
b) Haptic sensing
c) Knowledge acquisition
d) Resource acquisition
Answer: c
Explanation: Availability of knowledge of a certain degree is essential in cognitive radio to extract user knowledge pertaining to information services. The repeated occurrences of similar activity are considered as learning opportunities. This is exploited by machine learning for incremental knowledge acquisition.
6. Which among the following methods enable identification of learning opportunities in machine learning in cognitive radio?
a) Gamma distribution
b) Joint probability statistics
c) Variance
d) Uniform distribution
Answer: b
Explanation: Machine learning uses joint probability statistics for exploiting learning opportunities that arise due to repeated occurrence of similar situation. High quality use cases help to locate classes of user and knowledge that fine tune the set of services being provided.
7. Which ontologies must work together for seamless user interaction experience?
a) <User/> and <Self/>
b) <User/> and <RF/>
c) <Self/> and <User/>
d) <Self/> and <Func/>
Answer: b
Explanation: The best user interaction experience is built when the radio can understand vague commands from the owner. This requires continuous development of user ontology. It also requires the matching of user ontology with RF domain actions.
8. What does grounding mean in terms of ontology comprehension in cognitive radio architecture?
a) Association of language used by user with that of cognitive radio
b) Association of language used by cognitive radio with that of user
c) Association of network used by user with that of cognitive radio
d) Association of network used by cognitive radio with that of user
Answer: b
Explanation: Grounding initially beings with installation of a speech recognition subsystem that identifies common phrases used by the owner while referring to particular services. It is accomplished by text and speech recognition. It also involves asking “yes or no” questions either verbally or on display.
9. Which among the following is added to AACR architecture to construct dialogs?
a) NL acoustic facility
b) NL visual facility
c) Synonyms
d) Distributive inference hierarchy
Answer: c
Explanation: The RF concepts are presented to non-technical users by carefully constructing dialogs between <RF/> and <User/>. The introduction of synonyms in AACR architecture coordinates cognition–NL–synthesis interface. For example, the term antenna is associated with wireless-remote speaker.
10. <User/> learns jargon to express connectivity opportunities to cognitive radio.
a) True
b) False
Answer: b
Explanation: <RF/> learns jargon to express connectivity opportunities to cognitive radio in <User/> terms. The NL visual facility is employed for improving user jargon one instance at a time.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Architecture – Design Rules”.
1. Which among the following support video-acoustic combination of interfaces in cognitive radio?
a) Full-media correlation interfaces
b) Full-media difference interfaces
c) Cross-media correlation interfaces
d) Cross-media difference interfaces
Answer: c
Explanation: The functional components operate together for effective operation of cognitive radio. The functional component “User SP” combines with itself for reducing operations provoked by irrelevant triggering actions. For example, video-acoustic combination help in eliminating voice commands when the person is not talking on video.
2. Which among the following is accomplished by the combination of cognition and effector functions?
a) Control of user
b) Control of cognition components
c) Establish efferent path for control of effectors
d) Establish efferent path for cognition components
Answer: c
Explanation: The combination of cognition and effector functions is used to establish the efferent path for the control of effectors. The information services deliver the relevant data to effectors. The cognition function then arranges the data, develops a path, and oversees the flow of information.
3. Which among the following methods may be used to estimate interference in cognitive radio?
a) Model the radio
b) Model the user behaviour
c) Model the channel
d) Model the propagation of signal
Answer: d
Explanation:The cognition function replicate the propagation of radio signal with good quality to determine the level of interference expected towards other users of the spectrum. It may also be used to verify whether the interference level is within the specified limits imposed by the protocols pertaining to the location.
4. What may be determined by modelling the domain of applications in cognitive radio?
a) Determine parameters that support the application
b) Determine the number of applications that run simultaneously
c) Determine application that use same resources
d) Determine the priority of applications
Answer: a
Explanation: The cognition functions model the domain of application to find out the parameters that offer the additional support needed for effectively running an application. Quality of service, data rate, and probability of link closure are examples of such parameters that influence wireless communication.
5. When does a cognitive radio give up control of application?
a) High traffic load
b) Long period without input from user
c) On receiving pre-emptive command from user
d) Bad weather conditions
Answer: c
Explanation: The cognition function transfers the control of applications, interfaces, and radio resources on receiving pre-emptive command from the network or from the user. The control may be transferred to a network or a primary user depending on defined protocols.
6. Which among the following tasks may be assigned software defined radio forum manager?
a) Assessment of propagation link
b) Assessment of input from user
c) Administration of computational resources
d) Administration of propagating signals
Answer: c
Explanation: The cognition functions supervise the computational resources available in a platform. Certain SDR functions such software defined radio forum manager may be assigned the task of management of resources. The appropriate constraints of a resource must be considered before allocation.
7. What type of characteristic should be possessed by the topological model of the worldcreated by the cognitive radio?
a) Explicit and ambiguous
b) Explicit and axiomatic
c) Implicit and ambiguous
d) Implicit and axiomatic
Answer: b
Explanation: The cognition functions define an explicit topological model of the world including the users, the radio environment, the connecting networks, and the internal structure of the radio. Time, space, frequency, and propagation of signal are clearly defined and the model is therefore axiomatic.
8. Which among the following combination is responsible for the cognition cycle?
a) Environment – cognition
b) Effectors – SDR
c) SDR – SDR
d) Cognition – cognition
Answer: d
Explanation: The cognition-cognition combination helps in the following operations namely orienting, planning, decision-making, and creating actions which form the cognition cycle. The user may control the elements of the radio through cognition sub system.
9. Which among the following functions control the environmental sensors?
a) Cognition function
b) Local effector function
c) User SP function
d) Perception function
Answer: a
Explanation: The cognition functions control the environmental sensor. Data is sent from the cognition function to switch on/off the environmental sensors, constructing internal paths from the sensors and enabling control parameters.
10. The allocation of computational resources must be in agreement with the requirements of user communication.
a) True
b) False
Answer: a
Explanation: The cognition functions sets up and administers the radio resources which includes hardware resources, software personalities, and function. The allocation of computational resources to applications, interfaces, and functions must be in agreement with the requirements of user communication.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “ Architecture – Cognition Subsystem”.
1. Which among the following is not a part of the cognition subsystem?
a) Inference hierarchy
b) Cognition cycle
c) Organisation
d) Channel state
Answer: d
Explanation: The information services exhibit cognitive behaviour by using a set of design rules, functions, and components defined by the cognitive radio architecture that allow continuous growth through easy updates. The section of the cognitive architecture responsible for cognitive behaviour consists of inference hierarchy, cognition cycle, and temporal organisation.
2. How does the cognition cycle operate?
a) Active
b) Reactive
c) Passive
d) Activated
Answer: b
Explanation:The cognition cycle carries out its functions in a reactive sequence. Stimuli from the outside world are accepted by the sensors. The information is passed to the cognition cycle to generate a response.
3. Which among the following modes support real-time interaction?
a) Waking
b) Sleeping
c) Prayer
d) Prolong
Answer: a
Explanation: The waking behaviour supports real time interaction with user and obtains real time input from the environment. It is also referred to as awake-state. However it does not imply a fixed state but a collection of behaviours.
4. What type of control is exhibited by awake-state of cognition subsystem?
a) Temporally different
b) Isochronous
c) Asynchronous
d) Serial
Answer: b
Explanation: The awake-state or waking behaviour controls the cognitive radio resources isochronously. It maps the stored environmental interactions to the present input-response case being operated. Machine learning converts these interactions and cases into knowledge.
5. Which among the following modes should be invoked when a considerable period of disuse is expected?
a) Off
b) Prayer
c) Sleeping
d) On
Answer: c
Explanation: When long periods of disuse are predicted, the cognitive radio should enter into sleeping behaviour by itself. The cognitive radio is trained to identify situations that require sleeping behaviour. It may seek permission before entering sleep mode.
6. What type of operations is performed in sleeping behaviour?
a) No operation
b) Non incremental machine learning
c) Incremental machine learning
d) Current knowledge generation
Answer: b
Explanation: During sleeping behaviour, the radio processes the experience accumulated during the waking behaviour. This is accomplished by using non-incremental machine learning algorithms. It will map the present case integrated knowledge to overall integrated knowledge.
7. What is the responsibility of prayer behaviour?
a) Invoke sleeping behaviour
b) Invoke waking behaviour
c) Resolve conflicts
d) Erase present input-response behaviour
Answer: c
Explanation: When the user chooses to disregard the decision taken by the cognitive radio, it is added to a list of conflicts. These conflicts may be resolved using overall knowledge developed during sleeping behaviour. Otherwise it is added to a list of unresolved conflicts which is resolved during praying behaviour.
8. What language is used by prayer behaviour to work with the home network while resolving a conflict?
a) Web Ontology Language
b) Radio Knowledge Representation Language
c) RoXen Macro Language
d) Knowledge Query and Manipulation Language
Answer: d
Explanation: Prayer behaviour resolves conflict with the help of home network. The conflict is presented to the network using Knowledge Query and Manipulation Language. If the conflict is resolved, it is integrated into overall knowledge.
9. The entrance of a stimulus invokes a new cognition cycle.
a) True
b) False
Answer: a
Explanation: The entrance of a stimulus invokes a new cognition cycle during the waking behaviour. It is also invoked by the completion of cognition cycle which was already in process. The stimulus is obtained by monitoring the information signals such as voices, images, radio signals, etc.
10. Match the numbered blocks with the correct word to complete the cognition cycle.
a) 2 – Orient, 3 – Observe, 4 – Decide, 5- Act, 6 – Plan
b) 2 – Observe, 3 – Orient, 4 – Decide, 5- Act, 6 – Plan
c) 2 – Orient, 3 – Observe, 4 – Decide, 5- Plan, 6 – Act
d) 2 – Observe, 3 – Orient, 4 – Plan, 5- Decide, 6 – Act
Answer: d
Explanation: The major states or phases of the cognition cycle are observe, orient, plan, decide, and act respectively. The flow of control moves from observation to action. Certain situations demand for parallel operation of all states.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “ Architecture – Observe and Orient Phase of Cognition Cycle ”.
1. What is the function of the observe phase?
a) Sense and perceive
b) Sense and respond
c) Perceive and respond
d) Sense and forget
Answer: a
Explanation: The observe phase interacts with the environment by analysing the input information stream. It may accept multiple inputs from different directions and in different format.
2. What is binding?
a) Naming each path
b) Associating a path for each type of input
c) Developing subsets from multiple inputs
d) Naming each input
Answer: c
Explanation: Binding is the process of grouping input from several directions into a single input or into a group of subsets. It helps to assign a priority level for each input such that the time-sensitive operations are completed first for effective performancce.
3. What is the significance of binding?
a) Less usage of resources
b) Faster implementation
c) Easier to process
d) Easier to compare with prior experience
Answer: d
Explanation: The newly formed bindings are compared with prior experience to identify a close match. The binding is then grouped with the prior experience. This is done to detect patterns that could help in prediction, modelling, and decision making.
4. Which among the following is a requirement of observe phase?
a) Large memory
b) Large bus
c) Precise clock
d) Accurate timer
Answer: a
Explanation: The cognitive radio requires large reserve of memory for storing all experiences. This means that every audio, video, email, and radio signals for over a year must be available for access in memory. Thus architecture capable of retaining information and rapidly correlating current stimulus with available information is required.
5. What is the function of the orient phase?
a) Determine the resources required for a process
b) Determine the weight of a binding
c) Determine the number of bindings that could be processed
d) Determine the duration of a process
Answer: b
Explanation: The orient phase determines the significance or weight of a binding which is formed by associating a stimulus with prior experience. The operations are performed on internal data structures which behave as short term memory.
6. What invokes the change from short term memory to long term memory?
a) Instruction from user
b) Internal structure
c) Environment
d) Prior experience
Answer: c
Explanation: The environment provides the redundancy required to trigger a transfer from short term memory to long term memory. The sleep cycle moderates the transfer and also analyses the contents of short term memory since the last sleep cycle.
7. Which among the following is an expression for matching current stimulus to stored experience?
a) Stimulus tracker
b) Stimulus recognition
c) Experience recognition
d) Experience tracker
Answer: b
Explanation: In addition to binding, stimulus recognition refers to the matching of current stimulus to stored experience. It is carried out when there is an exact match between the stimulus and prior experience. However it does not mean that the reaction is always apt for the condition being worked.
8. Which among the following may be a viable criterion for binding?
a) Number of unmatched features
b) Number of words
c) Number of letter
d) Number of symbols
Answer: a
Explanation: Binding involves matching the current stimulus to a prior experience based on the degree of closeness. The number of unmatched features is an example for a criterion that may be used for binding. If the number of unmatched features is less than the threshold, the binding information is forwarded to the planning stage of cognition cycle.
9. What is instance based learning?
a) It is a family of algorithms that generates new problem instances
b) It is a family of algorithms that compares new problem instances with instances available in training
c) It is a family of algorithms that compares new problem instances with each other to determine the degree of similarity
d) It is a family of algorithms that compares new problem instances with each other to determine the degree of dissimilarity
Answer: b
Explanation: Instance based learning is a family of algorithms that compares new problem instances with instances available in training. Instance based learning builds hypotheses directly from training instances. The significance of instance based learning is that hypotheses complexity increases with increase in data.
10. Observe phase involves cognition components.
a) True
b) False
Answer: b
Explanation: Observe phase involves user sensory perception and environment sensor components. The orient phase uses cognition components of the aware, adaptive, and cognitive radio architecture.
11. Match the numbered paths with the correct word to complete the cognition cycle.
a) 1 – Normal, 2 – Immediate, 3 – Urgent
b) 1 – Normal, 2 – Urgent, 3 – Immediate
c) 1 – Immediate, 2 – Urgent, 3 – Normal
d) 1 – Immediate, 2 – Normal, 3 – Important
Answer: c
Explanation: The orient phase may omit the planning stage when immediate or urgent action is required. For example, a power failure directly invokes the act stage to save data.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Architecture – Plan and Decide Phase of Cognition Cycle”.
1. Which among the following stages has to be selected after the orient stage when detailed analysis has to be carried out to determine the course of action?
a) Observe
b) Plan
c) Decide
d) Act
Answer: b
Explanation: In planning stage, the information collected and organised during the observe phase and the orient phase are used to generate an action plan. By choosing planning stage, the process is carried out in a deliberated and calculated manner.
2. What among the following is not characteristic of a causal model?
a) Causal models make predictions about the behaviour of the system
b) Causal models assign truth value
c) Causal models do not include the effect of intervention
d) Causal models determine probabilistic dependence of variables
Answer: c
Explanation: Causal models are mathematical models that describe the causal relationship present within a system or a group. The causal relationships are extracted using statistical data. In research-quality and industrial-level cognitive radio, planning tools include causal models.
3. Which among the following techniques are used for reasoning?
a) Plan calculus
b) Plan sequence
c) Plan series
d) Plan theory
Answer: a
Explanation: Plan calculus applies reasoning over time, user identity, space, and context. It offers information such as when and where. It also provides the context, and reports internal requests. The context may involve location, action, state of existence, etc.
4. Which among the following function is used in the plan phase?
a) User sensory perception
b) Cognition function
c) Local effectors
d) System application
Answer: c
Explanation: The set of actions selected by the plan phase are performed by local effector functions. Each action is mapped as a request by plan calculus. Plan calculus generates and compares plans and finds conflicts.
5. Which among the following is the building block of causal tool?
a) Graph theory
b) Probability
c) Logic
d) Variables
Answer: d
Explanation: Variables are the building blocks of causal models. The values may represent the likelihood of occurrence of an event, a characteristic of an individual, the population of a system, or any quantitative value. Language, logic, probability, and graphs are tools used for developing causal models.
6. What is the function of decide phase?
a) Generation of alternatives
b) Evaluation of alternatives
c) Establishment of priority
d) Selection among alternatives
Answer: d
Explanation: The decide phase selects from a number of options generated by the planning phase. It is responsible for allocating computational and radio resources to support software in accordance to the activated plan.
7. Which among the following holds true for autonomous decision?
a) Correlation between present condition and reference condition is high
b) Correlation between present condition and reference condition is low
c) Covariance between present condition and reference condition is positive
d) Covariance between present condition and reference condition is negative
Answer: a
Explanation: Autonomous decisions are taken when the correlation between present and reference condition is high. It is preferred when the radio has been operated previously in the same spatial-temporal context. Knowledge representation depends on the radio procedure components.
8. What kind of decision relies on external confirmation?
a) Tactical decision
b) Independent decision
c) Predictable decision
d) Tentative decision
Answer: d
Explanation: Tentative decisions are consulted with the user for confirmation before execution. This leads to better user experience in the future. In certain situations, the selected option is executed and the user interaction is recorded to resolve conflict.
9. The decision phase controls the timing of alerts in a radio.
a) True
b) False
Answer: a
Explanation: Other than selecting a particular option from a set of plans, the decision phase chooses the timing to alert a user. It might alert immediately or put off the interruption according to the circumstances of the user .
10. Which among the following options should replace the block labelled ‘A’?
a) New state
b) Act state
c) Evaluate state
d) Manipulate state
Answer: a
Explanation: New states are established when new models are introduced in addition to the existing internal structure. It influences observe phase and learn phase. New states are constantly included by integrating knowledge into RXML knowledge structures.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Architecture – Act and Learning Phase of Cognition Cycle”.
1. What function belongs to external oriented actions in act phase?
a) Parse images and videos
b) Compose messages for interaction with environment
c) Parse incoming RF signals
d) Parse texts
Answer: b
Explanation: The function of the act phase is to engage in contact with outside world by composing messages for interaction with the local environment. The message may also have to be transferred to another cognitive radio or to a cognitive node.
2. Which among the following may be used to represent information that is continuously changing?
a) Knowledge Manipulation Language
b) Web Ontology Language
c) RoXen Macro Language
d) Radio eXtensibleMarkup Language
Answer: b
Explanation: Web Ontology Language is a family of knowledge representation languages for developing ontologies. Ontologies are similar in structure to class hierarchies in object-oriented programming. Ontologies are suitable for information that changes continuously such as the data found on the Internet.
3. What forms the constituents of ontology in Web Ontology Language?
a) Individuals and groups
b) Individuals and property assertions
c) Groups and property assertions
d) Characteristics and property assertions
Answer: b
Explanation: Ontology in Web Ontology Language is composed of individuals and property assertions that associate the individuals to each other. The ontology is controlled by axioms that assign constraints on individuals and their relationship.
4. What does the term “performatives” refer to Knowledge based Query and Manipulation Language?
a) Operations performed on supporting devices
b) Operations performed on radio knowledge
c) Operations performed on radio hardware
d) Operations restricted to radio self
Answer: b
Explanation: Knowledge based Query and Manipulation language supports communication among software agents and knowledge based systems. The KQML message format and protocol allows a radio to perform operations and utilize the knowledge available in another radio.
5. What is the purpose of knowledge based system?
a) To explicitly describe knowledge
b) To accumulate large database
c) To recycle data
d) To develop languages
Answer: a
Explanation: Knowledge based system is a computer program that provides solution to complex problems by using knowledge and reasoning. It is important that the knowledge is described explicitly. This assists easy application of reasoning to new knowledge.
6. Which statement is used to encapsulate the introduction of a new model into the existing models?
a) <iCRplatform/>
b) <Self/>
c) <Self>
d) <iCRplatform>
Answer: b
Explanation: The act phase introduces new models to internal structures and updates existing model. The addition of new specify-explore-refine model is encapsulated by the statement <Self/>. Knowledge acquisition in act phase generates data structures.
7. Which among the following factors affect knowledge representation?
a) Radio resources
b) Plan phase information
c) Actuators
d) Orient phase information
Answer: a
Explanation: The act stage activates operations with pre-fixed amount of resources and time. The knowledge representation depends on the radio resources, and radio knowledge being applied to the parameters contributing to the process.
8. Which among the following is not a guided principle relating to self-monitoring behaviour of cognitive radio?
a) Unrestricted while loops cannot be used
b) Only bounded iterations are permitted
c) Unrestricted first order predicate calculus is permitted
d) Unrestricted for loops cannot be used
Answer: c
Explanation: Self-monitoring behaviour is required in a cognitive radio to ensure bounded usage of resources within bounded time. First order predicate calculus is avoided as it is not possible to determine the period of completion. Bounded iterations whose completion time is independent of the calculation of iteration control of the loop.
9. Learning is a function of perception.
a) True
b) False
Answer: a
Explanation: Learning is a function of perception, observation, decision, and action. Learning also occurs by the introduction of new specific-explore-refine models to existing structure. Learning involves the comparison of prior and current states.
10. Which among the following options should replace the block labelled ‘A’?
a) Future state
b) Present state
c) Prior state
d) Clear state
Answer: c
Explanation: Prior state exists between decide phase and observe phase. The prior state works with current state to determine the effectiveness of a communication mode. It is also used to associate RF mode in accordance to the specific-explore-refine model.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Architecture – Inference Hierarchy – 1”.
1. Which among the following is an outcome of inference hierarchy?
a) Organisation of data structures
b) Control of internal flow of information
c) Control of external flow of information
d) Dissemination of knowledge
Answer: a
Explanation: The inference hierarchy organises the information from observation to action phase in the corresponding data structures. It aids in including machine learning with real-time performance during the wake epoch.
2. Which among the following occupies the bottom most position in inference hierarchy?
a) Primitive stimuli
b) Atomic symbols
c) Primitive symbols
d) Atomic stimuli
Answer: d
Explanation: Atomic stimuli refer to the external signals available from the outside world in unprocessed form. It includes the RF, image, location, and acoustic information that enter from the outside environment.
3. What is the atomic symbol equivalent of an image?
a) Small group of blocks
b) Small group of phoneme
c) Small group of pixels
d) Small group of points
Answer: c
Explanation: Atomic symbols succeedatomic stimuli. It is the most fundamental symbolic units of a domain. Phonemes are considered as the most primitive form of speech. Pixels are considered most primitive form of an image.
4. Which among the following is obtained by collection of atomic symbols?
a) Aggregated sequence
b) Atomic sequence
c) Primitive sequence
d) Primary sequence
Answer: c
Explanation: Primitive sequence is formed by assembling similar atomic symbols in a coherent manner. Primitive sequences generally have spatial or temporal likeliness which is visible and can be identified from a heap of information.
5. Which is the primitive sequence equivalent of text?
a) Sentence
b) Paragraph
c) Word
d) Character
Answer: c
Explanation: Primitive sequence is formed by assembling similar atomic symbols in a coherent manner. Words that compose a text, tokens that form speech in a speech composer, and objects that form an image are examples of primitive sequence in their respective domains.
6. What is the capability of a basic sequence?
a) Communicate message with meaning
b) Construct a word
c) Identify useful information from data
d) Collect data
Answer: a
Explanation: Basic sequence can deliver messages with meaning. These messages are defined using the ontology made available by primitive sequence. For example, a phrase is constructed using words .
7. What is the visual information equivalent of a basic sequence?
a) Blob
b) Object
c) Image
d) Video clip
Answer: d
Explanation: Primitive sequence is succeeded by basic sequence. Context can be drawn from the information offered by a basic sequence. Phrases composed of words and video clip composed of images are examples of basic sequences.
8. Which among the following is concerned with syntax and semantics of information?
a) Sequence cluster
b) Basic sequence
c) Primitive sequence
d) Atomic symbols
Answer: a
Explanation: Sequence clusters are developed on the basis of shared properties. Knowledge discovery and data mining and the semantic web provide various means for defining or determining sequence clusters from basic and primitive sequence.
9. What is degree of association required for context cluster?
a) Space-Time association
b) Time-Frequency
c) Frequency-Time association
d) Space-Time-Frequency association
Answer: d
Explanation: Context cluster is developed by space-time-frequency association on a multidimensional level. It is accomplished by using unsupervised machined learning using statistical or non-linear methods.
10. Which among the following is a non-linear machine learning techniques?
a) Linear regression
b) Logistic regression
c) Discriminant analysis
d) Support vector machines
Answer: d
Explanation: Support vector machine is a supervised machine learning algorithm. It consists of learning algorithms that study data related to classification and regression analysis. It is typically used for creating context clusters in inference hierarchy.
11. The identification of “baseball” from words such as “hit”, “pitch”, and “run” is possible only by the functionality level of context cluster.
a) True
b) False
Answer: b
Explanation: Sequence cluster is capable of determining themes from basic sequences that share similar characteristics. The capability of context cluster is to comprehend a discussion on baseball and draw conclusions based on the actions of the user.
12. What is the minimum requirement for taxonomy on radio knowledge?
a) Speed
b) Approximate models
c) Abstraction
d) Polymorphism
Answer: c
Explanation: Abstraction includes the construction of formal and informal models of meta- knowledge ranging from concepts to structured mathematical models of space, time, and frequency. Taxonomy requires a hierarchical model capturing the physical world as well as the internal structure radio.
13. Which among the following may be used for processing speech channels?
a) Symbol processing
b) Natural Language processing
c) Speech synthesiser
d) Text synthesiser
Answer: b
Explanation: Speech channels may be processed by using natural language processing facilities that have significant a priori models of language and discourse. Natural language processing is generally embedded in the inference hierarchy of cognitive radio.
14. XTAG caters to the requirement of cognitive radio.
a) True
b) False
Answer: b
Explanation: Cognitive radio should initiate transmission when it receives a command “transmit” with an attached message. However XTAG abilities only allow differentiating a verb from a noun but it cannot comprehend the meaning of a command and initiate action.
15. Which among the following option should replace the block labelled “B”?
a) Observe phase
b) Natural language processing functions
c) Mappings
d) Orient phase
Answer: b
Explanation: Sensory information, characters, words, and phrases are a part of the hierarchical structure of observe phase. They are mapped to the natural language processing function which uses information from a priori natural language knowledge. Natural language processing is required to integrate speech, and textual exchanges in cognitive radio.
This set of Cognitive Radio MCQs focuses on “Architecture – Inference Hierarchy – 2”.
1. Which among the following is achieved by applying horizontal cognition component s in inference hierarchy?
a) Radio skills are embedded
b) Context cluster is developed
c) Hierarchy is demolished
d) Hierarchy is established
Answer: a
Explanation: Radio skills are embedded by the introduction horizontal cognition components in inference hierarchy. When radio knowledge is static, radio skills are generated by the intervention of algorithms and inference engines.
2. What is the function of horizontal cognition components with radio skills?
a) Monitor user behaviour
b) Send request to user
c) Control radio personalities
d) Train internal behaviour
Answer: c
Explanation: The horizontal cognition components control radio personalities. It is carried out during the observe phase and the orient phase of the wake cycle. The radio skills are included in active data structures during the process of training or sleeping.
3. Which among the following is avoided in horizontal specify-explore-refine models?
a) Resource dependencies
b) Control dependencies
c) Data dependencies
d) Logical dependencies
Answer: d
Explanation: The specify-explore-refine models are continually compared to their associated phase in the hierarchical structure. This enables the model to respond on time and to take immediate action. This is primarily due to the lack of logical dependencies among components.
4. What is the function of a sensory pre-processing system?
a) Conversion of atomic stimuli into primitive sequence
b) Conversion of atomic stimuli into atomic symbols
c) Conversion of atomics symbols into atomic stimuli
d) Conversion of primitive sequence into atomic stimuli
Answer: b
Explanation: The conversion of atomic stimuli into atomic symbols by using a sensory pre-processing subsystem. Advanced signal and video processing tools are required to isolate atomic symbols in industrial cognitive radio.
5. When does the extraction of primitive sequence from higher aggregates is carried out?
a) Wake cycle
b) Prayer cycle
c) Sleep cycle
d) Live cycle
Answer: c
Explanation: The formation of atomic symbols can take place by two procedures. The atomic stimuli may combine to form atomic symbol. The atomic symbols may also be formed by learning from higher aggregates. The first type occurs during wake cycle while the second is carried out during sleep cycle.
6. Which phase is responsible for fast retrieval of data?
a) Act
b) Plan
c) Decide
d) Observe
Answer: d
Explanation: Observe phase accumulates all sensor data. The data is parsed and allotted to various processing nodes for fast parallel retrieval. Observe phase occupies large amount of storage to support memory based learning techniques.
7. Which among the following specifies the correct sequence of steps followed to obtain primitive sequence in speech?
a) Isolate the basic sequence, analyse the basic sequence, analyse the primitive sequence
b) Isolate the basic sequence, isolate the primitive sequence, analyse the basic sequence
c) Analyse the basic sequence, isolate the basic sequence, analyse the primitive sequence
d) Isolate the basic sequence, analyse the primitive sequence, analyse the basic sequence
Answer: a
Explanation: In speech, the sensor obtains input that correlate with the definition of basic sequence. In order to obtain the primitive sequence, the basic sequence is isolated from background noise. The basic sequence is analysed to identify potential boundaries of primitive sequence. The primitive sequence is then extracted and statistically analysed.
8. Which among the following is used to save radio skill set knowledge?
a) RaXon Macro Language
b) Web Ontology Language
c) Knowledge Query and Manipulation Language
d) Radio Knowledge Representation Language
Answer: d
Explanation: The radio skills obtained by horizontal cognition components associated with each phase are saved in radio knowledge representation language frame. The skill sets are also developed by information from a priori knowledge which is available in the form of RKRL frames.
9. Which among the following is not a class of knowledge required for constructing inference hierarchies?
a) Informal model
b) Axiomatic model
c) Ontology model
d) Behavioural model
Answer: d
Explanation: A cognitive radio requires significant amount of knowledge to be embedded in inference hierarchies. This includes internal and external knowledge. Internal knowledge is required to reason with itself and external knowledge is required to reason with outside environment. Informal model, axiomatic model, and ontology model are few classes of knowledge that are employed to structure the inference hierarchy.
10. A white space may act as a boundary to derive primitive sequence.
a) True
b) False
Answer: a
Explanation: When aggregated data is available, primitive sequence may be derived by selecting an atomic symbol as a boundary. In a text based system, a white space is regarded as a boundary for generating primitive sequence. For example, white spaces are employed to separate words in text.
11. What application is supported by IBM research tool XTAG?
a) Data analysis
b) Natural Language Processing
c) Machine learning
d) Artificial Intelligence
Answer: b
Explanation: An XTAG system is a grammar development tool based on Tree Adjoining Grammar . It consists of a parser, an X-window grammar development interface, and a morphological analyser. Other tools include SNeps , AGFL, and PC KIMMO which may be employed for natural language processing.
12. How does the cognitive radio access the a priori models?
a) Chat box
b) Handshake mechanism
c) Requests
d) Mappings
Answer: d
Explanation: The cognitive radio access the a priori models using mappings that exist between the word, phrase, dialog, and scene levels of the observation phase hierarchy and the encapsulated speech components.
13. Choose the appropriate labels to complete the diagram.
a) Control, training, model update
b) Training, control, model update
c) Model update, control, training
d) Model update, training, control
Answer: a
Explanation: The diagram depicts the steps involved in the application and improvement of radio skills. The radio skills developed from static and active knowledge available in observe phase is used to control radio personalities. The radio skill model is also continually updated by using information from act phase.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Architecture Maps – 1”.
1. What is an architecture map?
a) Architecture map describes the internal structure of cognitive radio
b) Architecture map describes the sequence of events that occur between stimulus and response
c) Architecture map describes the flow of inference from observation to act phase
d) Architecture map represents cognition functions implemented using cognition components
Answer: d
Explanation: Architecture map represents cognition functions implemented using cognition components. It consists of data structures, processes, and flows which are represented using topological maps over abstract domains.
2. Why should a cognitive radio be capable of differentiating “User” and “Things” entities?
a) To properly filter the signals
b) To offer different levels of priority
c) To amplify the signals
d) To re-direct the signals
Answer: b
Explanation: The architecture model builds an environment consisting of world, cognitive radio, and a world model within the cognitive radio. The world is composed of entities such as user, home network, people, things, networks, etc. The cognitive radio must be capable differentiating these entities to respond in accordance to pre-determined priority levels.
3. What is a known sequence?
a) The known sequence refers to the currently recorded stimulus from the outside world
b) The known sequence refers to the immediate past stimulus from the outside world
c) The known sequence refers to a series of stimuli from the outside world
d) The known sequence refers to integrated knowledge of the cognitive radio
Answer: d
Explanation: The known sequence corresponds to context cluster sequence of the inference hierarchy. The known sequence refers to the integrated knowledge present in the cognitive behaviour model of cognitive radio.
4. What are the constituents of a known sequence?
a) Radio Knowledge Representation Language frames
b) Knowledge Query and Manipulation Language frames
c) Radio eXtensible Markup Language frames
d) Web Ontology Language frames
Answer: a
Explanation: Known sequence describes the integrated knowledge of cognitive radio. The known sequence is developed by embedding Radio Knowledge Representation Language frames in the cognitive radio. It is also possible to develop known sequence through independent machine learning.
5. Which among the following is the definition of novel sequence?
a) Novel sequence is a record of types of response generated by cognitive radio
b) Novel sequence is a record of types of stimulus encountered by cognitive radio
c) Novel sequence describes the current stimulus-response of cognitive radio
d) Novel sequence is the integration of current stimulus-response and known sequence
Answer: c
Explanation: Novel sequence corresponds to the content cluster level of inference hierarchy. It describes the current stimulus-response unit of cognitive behaviour model. The highest level of sequence unit “Scenes” is composed of known sequence and novel sequence.
6. Which among the following is a data structure included in the architecture map in addition to the general structure of cognition cycle?
a) Decide
b) Dialog state
c) Act
d) Plan
Answer: b
Explanation: The cognitive radio section of the architecture map is composed of sequences of inference hierarchy, world model composed of bindings between a-priori data structures and the current scene, and phases of cognition. Dialog states, action requests, plans, and action are additional data structures added to support the phases of cognition cycle.
7. Which among the following is not a part context section of a RKRL frame?
a) Uniform Resource Locator
b) Time
c) Location of frame
d) Stimulus
Answer: d
Explanation: The cognition functions and phases are represented using data structures. The data structures are mapped to RKRL frames which are made up of handle, model, body, resources, and context. The handle may correspond to a set or a stimulus. The body may correspond to a subset or a response. The context may correspond to a URL, source, time or location.
8. Which among the following is used to represent processing components?
a) Flowchart
b) Scatter diagram
c) Topological map
d) Histogram
Answer: c
Explanation: The processing components are represented using topological maps in cognitive radio. Input, transformation, reasoning, and projection are few examples of the processing components used in cognitive radio.
9. Which among the following is the map that bridges the world unit with the cognitive radio unit in architecture map?
a) Input
b) Reasoning
c) Planning
d) Acting
Answer: a
Explanation: The input map connects the world unit to the sensory data segment of the cognitive radio in architecture map. It is made up of components that convert external input to the format of internal sensory data.
10. Which among the following is the correct definition of nearest sequence?
a) Nearest sequence is the known sequence that closely matches the novel sequence
b) Nearest sequence is the novel sequence that closely matches the known sequence
c) Nearest sequence refers to two similar known sequences
d) Nearest sequence refers to two similar novel sequences
Answer: a
Explanation: Nearest sequence corresponds to the context cluster sequence of inference hierarchy. Nearest sequence is the known sequence that closely matches the novel sequence. Nearest sequence, known sequence, and novel sequence belong to the “Scene” variable which holds the upper most position among the sequence formation maps of architecture map.
11. Waking behaviour prevents unmanageable accumulation of data.
a) True
b) False
Answer: b
Explanation: Sleeping/dreaming behaviour prevents unmanageable accumulation of data. Sleeping/dreaming behaviour develop specify-explore-refine model using the information collected during waking behaviour. This helps in embedding real-time experience in the next waking behaviour.
12. Which among the following phases do the components B1, B2 belong?
a) Act
b) Decide
c) Plan
d) Orient
Answer: d
Explanation: The component B1 and B2 belong to the orient phase of cognition cycle. B1 evaluates word and phrase bindings to form dialog states. B2 is responsible for creating action requests based on binding and dialog state.
This set of Cognitive Radio Objective Questions & Answers focuses on “Architecture Maps – 2”.
1. Which among the following is the component that determines nearest sequence?
a) Observe
b) Orient
c) Reason
d) Project
Answer: c
Explanation: Nearest sequence refers to the known sequence that closely matches the novel sequence. The reasoning component is responsible for identifying the best match between known sequence and novel sequence. The projection component binds the known sequence, the novel sequence, and the nearest sequence to scene variable.
2. Which among the following components map the output of act phase to various sections of architecture map?
a) Effect
b) Input
c) Decide
d) Transform
Answer: a
Explanation: The act phase is responsible for activating tasks and allocating the necessary resources for completing the task within the specified time. The effector components may change the radio’s internal state and displays, synthesize speech, and transmit information on wireless networks.
3. Which among the following variables consider user communication context?
a) Words
b) Phrase
c) Dialog
d) Scene
Answer: d
Explanation: Scene bindings consider user communication context. This information is used in the generation of plans whichdeal with the context of a situation. The plans are created by the assessment of action requests during the plan phase.
4. Which among the following is the definition of the term domain in the context of architecture map?
a) Domain is the set of subsets of internal data structures over which the map is defined
b) Domain is the set of subsets onto which the map exhibits its output
c) Domain is the set of subsets of variables
d) Domain is the set of subsets of bindings
Answer: a
Explanation: Domain is the set of subsets of internal data structures over which the map is defined. Range is the set of subsets onto which the map exhibits its output. Each topological map consists of a domain and a range.
5. What is the advantage of expressing API components as maps?
a) Easy maintenance
b) Easy accessibility
c) Limited usage of resources
d) Limited constraints
Answer: d
Explanation: API defined as a map lists the methods and the procedure applicable for subsets s1 of a domain that map onto subsets s2 of a range. This enables easy establishment of API while avoiding the constraints the limit the application of API in cognitive radio.
6. Which among the following is a method of keeping track of multiple stimuli-response bindings in an industrial strength cognitive radio?
a) Hypothesis management
b) Recycle management
c) Component management
d) Behaviour management
Answer: a
Explanation: Hypothesis management maintains a record of more than one possible binding of stimuli to a response, scene, state, etc. One approach is to store only the N-best hypothesis. Another approach is to set a threshold on probability and only bindings that meet the threshold are stored for future use.
7. Which among the following has to be carried out for reverse flow of knowledge?
a) Training interfaces
b) Hypothesis management
c) Linear flow of signals
d) Data management
Answer: a
Explanation: The interfaces have to be trained to ensure flow of knowledge can occur from inference hierarchy to the perception systems. This aids in maintaining and altering the internal structure of radio. For example, the vision subsystem and the audio subsystem exchange knowledge to take decision when there is a mismatch in one domain in a two way identification system.
8. Which among the following situationsrequire special training?
a) Recognition of user indoor
b) Recognition of user outdoors on a sunny day
c) Recognition of user’s outdoors during a snowstorm
d) Recognition of user indoor during a snowstorm
Answer: c
Explanation: Visual recognition of user’s outdoors during a snowstorm requires additional processing than indoors as several matching cues might be hidden. This might limit the level of accessibility offered to the user as threshold condition will not be met due to reduced number of matches. Thus special training such as reverse flow of knowledge is required.
9. Which among the following is not an example of noise?
a) Pre-processing algorithm bias
b) Truncation of low energy signal
c) Binding mismatch
d) Conversion error
Answer: c
Explanation: In communication theory, noise refers to anything that hinders proper communication. It occurs in voice signals, images, videos, location estimates, etc. It is a critical aspect in industrial strength cognitive radio.
10. Which among the following is a collection of subsets of a set that is closed under complement and closed under countable union?
a) Sigma algebra
b) Algebra
c) Delta algebra
d) Whole set
Answer: a
Explanation: Sigma algebra on a set is a collection of subsets of a set that is closed under complement and closed under countable union. It is also known as measurable space. It is employed in hypothesis management to combine the amount of belief attached to each event as a function of the values allotted to the probability of each event.
11. The transformation component converts atomic stimuli/symbols to primitive sequence.
a) True
b) False
Answer: a
Explanation: The transformation component consists of units such as speech recogniser, low level software radio interface components which convert atomic stimuli/symbols into primitive sequence. Similarly components from immediate lower level sequence combine to form higher level sequences.
12. Which among the following phases do the components A1, A2, A3 belong?
a) Observe
b) Orient
c) Act
d) Decide
Answer: a
Explanation: The components A1, A2, and A3 belong to observe phase of the cognition cycle. A1 is called as input map which connect the world unit to sensory data. A2 is a transformation component that converts atomic stimuli into primitive sequence. A3 is projection component that binds sequence to bindings.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Building CRA on SDR Architecture – 1”.
1. Which among the following is not a component of hardware defined radio?
a) Demodulator
b) Antenna
c) Filters
d) Analog to digital converter
Answer: d
Explanation: A typical hardware defined radio used as a frequency modulated/ amplitude modulated broadcast receiver consists of radio hardware such as antenna, filters, and demodulators. The primary function is the conversion of radio signals into audio signals.
2. Which among the following is an important characteristic of software radio?
a) Digital demodulation and analog filtering
b) Analog demodulation and digital filtering
c) Analog demodulation and filtering
d) Digital demodulation and filtering
Answer: d
Explanation: The progression from hardware defined radio to software radio is marked by the introduction of the analog-to-digital converter and digital-to-analog converter in radio. An ideal software radio performs operations such as modulation, demodulation, frequency translation, and filtering digitally.
3. Which among the following represents the scale of spectrum band likely to be accessed by software defined radio?
a) 800 MHz – 900 MHz
b) 800 MHz – 850 MHz
c) 30 MHz – 2.5 GHz
d) 30 MHz – 250 MHz
Answer: c
Explanation: The software defined radio desirably operates over a large range of frequencies that cover various bands of the spectrum. The radio should be capable of supporting various applications such as TV bands, air traffic control bands, industrial medical and scientific bands, etc. For example, 30 MHz – 2.5 GHz has a bandwidth of 2.47 GHz which is most suitable for the spectrum requirements of cognitive radio.
4. What is term used to refer to a handset with multiple single band RF chips?
a) Pocket radio
b) Multi-set radio
c) Slice radio
d) Fixed radio
Answer: c
Explanation: The nature of RF devices such as antennas and filters normally support narrowband RF synthesis and intermediate frequency conversion. Wideband operation drives up cost and power consumption. One approach involves the installation of multiple single band RF chips in a handset. This handset is called as a slice radio or a Velcro radio.
5. Which among the following terms define the design space used to describe the development of software defined radio?
a) Digital access bandwidth and programmability
b) Digital access bandwidth and feasibility
c) Programmability and feasibility
d) Analog access bandwidth and feasibility
Answer: a
Explanation: The software defined radio design space consists of a series of practical levels that represent the growth from hardware defined devices to ideal software defined radio. The design space is a plot between digital access bandwidth and programmability. The development of devices is due to increased availability and capability of resources.
6. Which among the following is considered as the most power-efficient device?
a) ASIC
b) FPGA
c) DSP
d) GPP
Answer: c
Explanation: Digital signal processors are simple to program, cost-effective, and power-efficient when compared to other devices such as ASIC and FGPA. However small memory and complicated instruction set architecture can increase the re-programmability cost of a digital signal processor.
7. How are the general purpose processors classified?
a) Based on memory
b) Based on bus
c) Based on interface
d) Based on instruction set
Answer: d
Explanation: Complex Instruction Set Computer processor consists of a single instruction to carry out loading, evaluation, and storing operation. Reduced Instruction Set computer processor consists of a series of instructions to carry out loading, evaluation, and storing operation. The general purpose processors are commonly classified based on the instruction set.
8. Which among the following is not an API of the software communication architecture put forth by the SDR forum?
a) Physical
b) MAC
c) Security
d) Transport
Answer: d
Explanation: An application programming interface is a computing interface that connects to a software component or a system. Components may access the API as per the terms presented by the API itself. In software communication architecture, API determines access to the physical layer, to the logical link layer, to the medium access control layer, to the security features, and to the input/output components.
9. Where does black processing occur in software communication architecture?
a) Black processing occurs between antenna and RF channel
b) Black processing occurs between antenna and RF conversion
c) Black processing occurs between RF conversion and INFOSEC module
d) Black processing occurs between antenna and INFOSEC module
Answer: d
Explanation: Military radios assign the term ‘red’ for secret information. The term ‘black’ is used to refer to protected or encrypted information during transmission. Black processing generally takes place between the antenna and INFOSEC module, particularly the decryption process.
10. Which among the following is given as input to the system control unit?
a) Human-machine interface
b) Global framework
c) Fault management
d) Configuration management
Answer: a
Explanation: System control resembles a framework. It contains a set of basic functions that are arranged in the form of a computational architecture in accordance with the norms of CORBA. It accepts input from the human-machine interface unit and overlooks the management of virtual channels, networks, security, etc.
11. Which among the following correspond to the point plotted in the graph?
a) COTS Handset
b) Programmable radio
c) Software defined radio
d) Virtual radio
Answer: c
Explanation: The graph depicts the design space of software defined radio. The plotted point corresponds to an ideal software defined radio. An ideal software radio is one in which every physical layer function is software defined. The radio must be flexible, multifunction, programmable, and easy to upgrade.
12. Constraint programming consists of variables, constraints, and domains.
a) True
b) False
Answer: a
Explanation: In constraint programming, a problem is described as a mathematical equation. For example, ‘a’, ‘b’, ‘c’ are three whole numbers and the sum of ‘a’ and ‘b’ must be equal to ‘c’. Here ‘a’, ‘b’, and ‘c’ are the variables. The whole number corresponds to a domain. The sum of ‘a’ and ‘b’ must be equal to ‘c’ corresponds to a constraint.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Building CRA on SDR Architecture – 2”.
1. Which among the following is a challenge in security management?
a) Authentication
b) Validation
c) Encryption and decryption
d) Balancing convenience and security
Answer: d
Explanation: Security management is controlled by the system control unit. It is responsible for protecting the user data using various safety measures such as encryption. Security management must carefully balance convenience and security. This can be a timing consuming process.
2. Which among the following is not a common feature between virtual channel management and network management?
a) Identification of resources
b) Verification of availability of resources
c) Matching resources with requirements of application
d) Applicable for radio resources
Answer: d
Explanation: Direct virtual channel management is responsible for identifying and verifying radio resources. It finds channels to transmit information, determines channels to listen for information, determines the channels that can be used simultaneously, etc. The network management performs the same operation on digital paths, not on radio resources.
3. What is used by the cognitive radio to justify the usage of resources?
a) Computational model
b) Component cycle
c) Function cycle
d) Cognition model
Answer: a
Explanation: A computational model is used by the cognitive radio to keep track and to justify the usage of internal resources. The computational model consists of analog and digital parameters of performance. It also establishes the relationship between parameters on the basis of measurement and control.
4. Which among the following is used to represent interdependencies in cognitive radio?
a) Representation language
b) Constraint language
c) Ontology language
d) Modelling language
Answer: b
Explanation: The cognitive radio learns from the data structures of various phases of the cognition cycle and inference hierarchy to determine relationships among the information that would benefit the user. Constraint languages may be used to express the interdependencies found in the information. For example, constraint language may be used to express the number of channels supported by the radio hardware during failure mode.
5. Which among the following caused the shift of complexity management from networks to cognitive radio?
a) Introduction of multiple bands in radio
b) Introduction of multiple modes in radio
c) Introduction of multiple bands and multiple modes in radio
d) Elimination of multiple bands in radio
Answer: c
Explanation: The transition from software defined radio to cognitive radio is due to the availability of resources and technology that allow the incorporation of awareness, adaptability, and cognition skills in the radio. For example, cellular networks manage the wireless protocols for the user but the emergence of cognitive radio with the capability of supporting multiple bands and modes shift the responsibility of protocol management towards the radio itself.
6. What is parallel virtual machine?
a) Parallel virtual machine is a centralised computing system developed by joining a set of serial computers
b) Parallel virtual machine is a distributed computing system developed by joining a set of parallel computers
c) Parallel virtual machine is a centralised computing system developed by joining a set of parallel computers
d) Parallel virtual machine is a distributed computing system developed by joining a set of serial computers
Answer: b
Explanation: A parallel virtual machine is a distributed computing system developed by joining a set of parallel computers into a single virtual machine. Complex computational problems may be solved more efficiently by utilizing collective power and memory of many computers. It may be used for resource allocation in cognitive radio.
7. Which among the following may be inferred by analysing temporal properties of simultaneous processes?
a) Time difference of transmission
b) Timeout in fault tolerant systems
c) Time of arrival in receiver
d) Time difference of arrival in receiver
Answer: b
Explanation: The examination of temporal properties of simultaneous processes may determine timeout in fault tolerant systems, duration control in real time systems, etc. It may be regarded as a logic-based approach for reasoning about time. It may be employed for planning activities in cognitive radio.
8. Which among the following programming styles approach a problem as a series of constraints imposed on a possible solution?
a) Linear programming
b) Constraint programming
c) Object oriented programming
d) Aspect oriented programming
Answer: b
Explanation: Constraint programming approaches a problem as a series of constraints imposed on a possible solution. Constraint based scheduling is a method that uses constraint programming to solve scheduling problems. It may be used as a planning tool in cognitive radio.
9. Which among the following is a characteristic observed in constraint programming?
a) No changes can made on definition of the system
b) Only independent variables are applied
c) Strict norms to compute a value
d) Definition of relationship between variables and constraints
Answer: d
Explanation: Constraint programming is applied to a group of problems thatpermit the conversion of a problem into variables. It should be possible to define the problem as a mathematical equation. A final model is constructed based on the relationship between the variables and the constraints. The model is used to compute the value of variables.
10. What is the T250 model of Mitsubishi?
a) Single-mode handset
b) Dual-mode handset
c) Three-mode handset
d) Four-mode handset
Answer: c
Explanation: The T250 model of Mitsubishi is a three-mode handset. It operates in Time Division Multiple Access mode on 850 or 1900 MHz, Advanced Mobile Phone System mode on 850 MHz, and in Cellular Digital Packet Data mode on 1900 MHz. It is a primitive example of multiband, multimode wireless device.
11. Parallel virtual machine is implemented using homogeneous computers.
a) True
b) False
Answer: b
Explanation: Parallel virtual machine is implemented using a set of heterogeneous computers that work as a combined and flexible computational resource. Message-passing, task and resource management, and fault notification is accomplished by using a run time environment and library. Parallel virtual machine supports unicasting, multicasting, and broadcasting.
12. Which among the following correspond to the point plotted in the graph?
a) COTS Handset
b) Digital cell site
c) Software defined radio
d) Cognitive radio
Answer: b
Explanation: The graph depicts the design space of software defined radio. The plotted point corresponds to the digital cell sites. These devices are typically constructed using Application Specific Integrated Circuits . The devices depend greatly on digital filter ASICs for frequency translation and filtering. They access the spectrum at IF frequency.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “The xG Network Architecture – 1”.
1. Which among the following statements is true about the wireless network without xG architecture?
a) Existing wireless networks exhibit homogeneity in the spectrum policies and heterogeneity in the communication technologies
b) Existing wireless networks exhibit heterogeneity in the spectrum policies and homogeneity in the communication technologies
c) Existing wireless networks exhibit homogeneity in the spectrum policies and the communication technologies
d)Existing wireless networks exhibit heterogeneity in the spectrum policies and the communication technologies
Answer: d
Explanation: The currently available wireless networks express heterogeneity in both spectrum policies and communication technologies. For the effective incorporation of communication protocols, a clearly defined xG architecture model is required.
2. Which among the following statement is true about the primary network?
a) Primary network handles requests from xG users
b) Primary network uses the spectrum band periodically
c) Primary network has a dedicated spectrum band
d) Primary network competes for access to a spectrum band
Answer: c
Explanation: The currently available fixed infrastructure wireless network represents a primary network. It possesses the rights of a dedicated spectrum band. Cellular networks and TV broadcast networks are examples of the primary network.
3. Which among the following statement is false about the primary user?
a) Primary users are also known as licensed users
b) Primary users have exclusive right to use a spectrum band
c) Primary users are a part of the primary network
d) Primary users compete with the secondary users to access the spectrum band
Answer: d
Explanation: Primary users have exclusive rights to use a spectrum band. The primary base-station is responsible for monitoring and controlling the users accessing the spectrum band. Primary users have higher priority when compared to secondary users.
4. What are the units of the primary network?
a) Primary node and primary base-station
b) Primary user and primary base-station
c) Primary user and secondary user
d) Primary user and primary node
Answer: b
Explanation: Primary users are licensed users of the spectrum. Primary base-station refers to the fixed infrastructure network component with a spectrum license. The primary base-station contains legacy protocols and xG protocols for supporting communication through xG networks.
5. Which among the following is not a term used to refer to the xG network?
a) Cognitive radio network
b) Intelligent spectrum access network
c) Dynamic spectrum access network
d) Unlicensed network
Answer: b
Explanation: The xG network is also known as the secondary network, unlicensed network, cognitive radio network and dynamic spectrum access network. The xG does not have an exclusive right to use any spectrum band. xG networks aim to make use of temporarily unused spectrum bands.
6. What are the types of structures used to develop xG networks?
a) Infrastructure and ad hoc networks
b) Only infrastructure network
c) Only ad hoc networks
d) Centralised and distributed infrastructure network
Answer: a
Explanation: xG networks are made up of both infrastructure networks as well as ad hoc networks. xG users exist in a mixed spectrum environment and possess additional features to transmit on the licensed band. The path between the sender and the receiver depends on the type of network.
7. Which among the following connection is established by xG base-station?
a) Single hop for xG users
b) Multi-hop for xG users
c) Single hop for primary users
d) Multi-hop for primary users
Answer: a
Explanation: xG base-station is capable of providing single hop connection for xG users accessing the licensed portion of the spectrum. It is similar to a primary base-station with fixed network infrastructure network components however it has additional xG capabilities.
8. Which among the following statements is false about spectrum broker?
a) Spectrum broker is also known as scheduling server
b) Spectrum broker is connected to multiple networks
c) Spectrum broker bridges primary network and xG network
d) Spectrum broker is a central network entity
Answer: c
Explanation: Spectrum broker is responsible for sharing the spectrum resources among the different users of the xG network. It also works as an information manager supporting the combined operation of several xG networks. A spectrum broker is connected to each network in an area for coordinated operation.
9. What does the term spectrum heterogeneity mean in the context of xG architecture?
a) Licensed band and unlicensed band
b) UHF band and VHF band
c) Radio band and visible light band
d) Radio band and infrared band
Answer: a
Explanation: xG architecture exists in a mixed spectrum environment with licensed and unlicensed bands. Wideband access technology allows xG users to operate on both bands. xG users can communicate by using a base-station or by opting for a multi-hop connection.
10. Which among the following does not come under network heterogeneity?
a) xG network access
b) xG ad hoc access
c) Primary network access
d) xG spectrum access
Answer: d
Explanation: xG network access refers to the communication established via xG base-station on licensed and unlicensed spectrum band. xG ad hoc access refers to communication among xG users using an ad hoc connection on licensed and unlicensed spectrum band. Primary network access refers to the communication carried out using primary base-station on licensed spectrum band.
11. The primary user must contain legacy protocols and xG protocols for xG communication.
a) True
b) False
Answer: b
Explanation: Primary users do not undergo any modification to support xG base-stations and xG users. The operation of the primary user should not be hindered by unlicensed users. Similarly the xG users operating on the licensed band should not affect other primary users.
12. Which type of connection is depicted in the following diagram?
a) Centralised connection
b) Ad hoc connection
c) Fixed infrastructure connection
d) Single hop connection
Answer: b
Explanation: The connection depicted in the diagram is an xG ad hoc access connection. xG users may communicate among themselves using an ad hoc connection on licensed and unlicensed spectrum band. Ad hoc connection is typically a multihop connection. This type of connection is also known as xG connection without infrastructure.
This set of Cognitive Radio Question Bank focuses on “The xG Network Architecture – 2”.
1. What is the function of the xG network in the licensed band?
a) Exploit unused spectrum holes
b) Route xG users
c) Route primary users
d) Manage information for primary users
Answer: a
Explanation: The xG users on the xG network exploit the unused spectrum holes that are available for a limited time in the licensed spectrum band. This may be carried out by applying various cognitive communication techniques.
2. Which among the following is an additional function carried out xG users in the licensed band?
a) Route primary users
b) Detection of the presence of primary users
c) Detection of the presence of secondary users
d) Route secondary users
Answer: b
Explanation: An xG user should ensure that the primary user is not affected by the operations of the xG users. The primary user does not have the capability to detect the presence of the primary user and request for termination of the connection. Hence the xG user listens for the arrival of the primary user.
3. Which among the following affects the channel capacity of spectrum holes?
a) Interference at nearby primary users
b) Interference at nearby xG users
c) Distance between the xG user and primary base-station
d) Distance between the xG user and xG base-station
Answer: a
Explanation: The amount of primary users prone to interference caused by xG users in unused spectrum holes of licensed spectrum band determines the channel capacity of spectrum holes. Interference avoidance with primary users is an important criterion in the design of xG architecture.
4. What is the terminology used to refer to the transfer of users from one spectrum to another spectrum?
a) Spectrum routing
b) Mobile routing
c) Mobile handoff
d) Spectrum handoff
Answer: d
Explanation: If a primary user returns to a spectrum band currently being used by an xG user, the xG user should remove itself from the spectrum and continue operating in a different spectrum band immediately. This is referred to as spectrum handoff.
5. Which among the following relies on efficient allocation of spectrum?
a) Effective multiplexing
b) Effective modulation
c) Capacity of open spectrum access
d) Diversity
Answer: c
Explanation: Factors such as the capacity of open spectrum access and quality of service rely on the ability of a radio to efficiently allocate radio spectrum. xG network architecture aims for effective use of unlicensed spectrum band which have multiple heterogeneous networks.
6. Which among the following is true about xG users in an unlicensed spectrum band?
a) xG user has equal rights to access the spectrum
b) xG user vacate the spectrum band upon arrival of the primary user
c) xG user vacate the spectrum band upon arrival of another xG user
d) xG users compete for the position of primary user
Answer: a
Explanation: In the unlicensed spectrum band, each user has the same right to access the spectrum bands. The xG users present in one particular area may use the same portion of the spectrum band for communication.
7. Which among the following is required for effective use of spectrum in an unlicensed spectrum band?
a) Spectrum sharing algorithms
b) Scheduling algorithms
c) Planning algorithms
d) Decision-making algorithms
Answer: a
Explanation: xG users compete to access the unlicensed spectrum band since every user has an equal right to access the spectrum. Intelligent spectrum sharing algorithms ensure effective spectrum usage and good quality of service. If many xG networks are present, impartial sharing on a network level is required.
8. Which among the following may not be achieved by using xG networks for military applications?
a) Select intermediate frequency bandwidth
b) Improve security
c) Select compatible modulation scheme
d) Reduce interference
Answer: d
Explanation: xG networks allow the selection of intermediate frequency bandwidth, and compatible modulation and coding techniques. It is capable of adapting to the changing radio environment of a battlefield. xG networks also carry out secure spectrum handoff.
9. Which among the following is a requirement of emergency networks?
a) Quality of service
b) Determine of charges for usage
c) Minimum latency
d) Parsing incoming information
Answer: c
Explanation: Emergency networks require minimum latency, and a large radio spectrum to accommodate a high volume of traffic including voice, video, and data. Since xG networks do not rely entirely on fixed infrastructure for communication and are capable of utilizing unused spectrum bands, they are used for reliable communication under emergency conditions.
10. Which among the following is a requirement of a cognitive mesh network?
a) Large spectrum
b) Quality of service
c) Security
d) Effective modulation scheme
Answer: a
Explanation: Cognitive mesh networks require high capacity to support applications that require high throughput. xG networks are capable of accessing large portions of the spectrum and can support the demand generally present in dense urban areas. Cognitive mesh networks are used for providing broadband connectivity.
11. Which among the following is not true about Mobile Virtual Network Operator?
a) MVNO owns wireless infrastructure
b) MVNO purchases infrastructure at retail price
c) MVNO is a form of leased network
d) MVNO might operate with mobile virtual network enabler
Answer: d
Explanation: Mobile Virtual Network Operator does not own wireless network infrastructure. It purchases network services from a mobile network operator. In this method, the primary network provides opportunistic access to licensed spectrum. This is an example of leased network implementation in xG architecture.
12. xG networks allow usage of spectrum band without a fixed infrastructure.
a) True
b) False
Answer: a
Explanation: xG networks allow usage of spectrum band without a fixed infrastructure by maintaining communication priority and response time. It is also capable of adding a temporary or permanent spectrum to infrastructure links that are used for relaying traffic.
13. What type of network is depicted in the following diagram?
a) xG ad hoc access
b) xG network access
c) Primary network access
d) Secondary network access
Answer: b
Explanation: The diagram depicts xG network access connection. xG network access refers to the communication established via xG base-station on the licensed and unlicensed spectrum band. xG base station is a fixed infrastructure network component that provides single hop connection to xG users.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Spectrum Sensing – 1”.
1. Which among the following is the function of out-of-band sensing?
a) Detect primary base-station
b) Detect spectrum holes
c) Detect primary user
d) Detect xG users
Answer: b
Explanation: A cognitive radio should be aware of its surrounding radio environment. Spectrum sensing allows a radio to find the unused spectrum in the radio environment. In out-of-band sensing, cognitive radio users focus on the identification of spectrum holes over a wide frequency range to transmit their information.
2. What is the purpose of in-band sensing?
a) Interference avoidance
b) Sharing spectrum information
c) Sharing spectrum resources
d) Spectrum handoff
Answer: a
Explanation: Spectrum sensing identifies unused spectrum holes that are available for transmission for cognitive radio users. During transmission, the cognitive radio users continue to monitor the spectrum band. They also sense other users of the primary network in order to avoid interference. Spectrum sensing carried out during transmission is called in-band sensing.
3. Why is cooperation required in spectrum sensing?
a) Elimination of base-station
b) Elimination of xG users
c) Interference avoidance
d) Improvement of sensing accuracy
Answer: d
Explanation: The cognitive radio user monitors and studies the local radio environment to identify the current spectrum availability. The information gathered by each user is shared between its neighbours. This practice is known as cooperation in sensing and it improves the sensing accuracy.
4. Which among the following is the most practical method to identify spectrum holes?
a) Detect primary user transmission
b) Detect primary user receiving information
c) Detect secondary user transmission
d) Detect secondary user receiving information
Answer: a
Explanation: The detection of primary users receiving information within the communication range of xG users is considered as the most efficient means for determining spectrum holes. However this is not always feasible as it is laborious to measure the channel between a transmitter and a primary receiver. Hence sensing is predominantly carried out by detecting the transmission operation of primary users.
5. Which among the following is not a transmission detection technique?
a) Matched filter detection
b) Energy detection
c) Cyclostationary detection
d) Interference based detection
Answer: d
Explanation: Transmission detection is based on the identification of weak signals sent by the primary transmitter obtained by the local observations of the xG users. Transmitter detection is also known as non-cooperative method. Interference based detection and cooperation detection are other spectrum sensing techniques.
6. What is the terminology used to represent the absence of a licensed user in the spectrum?
a) Grounded hypothesis
b) Fixed hypothesis
c) Null hypothesis
d) Zero hypothesis
Answer: c
Explanation: The following equation represents the basic hypothesis model for transmitter detection,
s = n [U1]
s = a*i + n [U2]
where s is the signal available at the xG user, i is the signal transmitted by the primary user, n is the AWGN, and a is the amplitude gain of the channel.
U1 is the null hypothesis which indicates the absence of signals from the licensed users in the spectrum band. U2 is termed alternate hypothesis which indicates the presence of signals from the licensed users in the spectrum band.
7. Which among the following techniques requires prior knowledge of the primary signal?
a) Matched filter detection
b) Energy detection
c) Cooperation detection
d) Cyclostationary detection
Answer: a
Explanation: The matched filter detection method requires prior knowledge of the signal to be transmitted by the primary user such as the pulse shape, the packet format, and the order and modulation type. If the information is available, then the matched filter is the most compatible detection method. Matched filter can maximize the signal to noise ratio.
8. What is the advantage of using matched filter detection?
a) Rapid increase in processing gain
b) Simultaneous detection
c) High accuracy
d) Low power consumption
Answer: a
Explanation: Matched filter detection achieves high processing gain rapidly due to coherency. However when accurate information is not available about the signal transmitted by the primary user, then the matched filter detection method exhibits poor performance.
9. Which among the following is not an operational unit in energy detection?
a) Integrator
b) Squaring unit
c) Correlator
d) Threshold device
Answer: c
Explanation: Energy detection consists of three operational units namely squaring device, integrator, and threshold device. The received signal energy is measured by squaring and integrating the received signal over an interval T. The output of the integrator is then evaluated by the threshold device to determine the existence of the primary user in the licensed spectrum.
10. Which among the following are factors of significance in the energy detection technique?
a) Probability of detection and probability of exception
b) Probability of detection and probability of false alarm
c) Probability of detection and probability of useful information
d) Probability of false alarm and probability of useful information
Answer: b
Explanation: Probability of detection and probability of false alarm are factors of significance in energy detection technique. They depend on the signal to noise ratio, time-bandwidth product, complete and incomplete gamma functions, and generalized Marcum Q-function.
11. Sensing control is implemented in the physical layer of the OSI model.
a) True
b) False
Answer: b
Explanation: Sensing control is essential to adapt sensing operation in accordance with the dynamic radio environment. It operates in the physical and data-link layer of the OSI model. It coordinates the sensing operations among xG users in a distributed manner. It helps to avoid false alarms in cooperative sensing.
12. What is the detection technique employed in the following diagram?
a) Matching filter detection
b) Cooperation detection
c) Energy detection
d) Cyclostationary detection
Answer: d
Explanation: In cyclostationary detection, modulated signals are coupled with sine wave carriers or pulse trains to incorporate periodicity. By exploiting the periodicity, noise energy is differentiated from modulated signal energy. Hence it yields better noise performance than other transmitter detection techniques.
This set of Cognitive Radio Questions and Answers for Entrance exams focuses on “Next Generation Wireless Network – Spectrum Sensing – 2”.
1. Which among the following is achieved by coupling a modulated signal with a sine wave carrier?
a) Causality
b) Periodicity
c) Linearity
d) Stability
Answer: b
Explanation: Modulated signals are coupled with sine wave carriers, hopping sequences, or cyclic prefixes to attain periodicity. The signals are regarded as cyclostationary due to periodic mean and autocorrelation.
2. Which among the following is not an advantage of using cyclostationary feature detection?
a) Better performance than energy detection
b) Does not require prior knowledge of the signal transmitted by the primary user
c) Robust noise performance
d) Rapid attainment of high processing gain
Answer: d
Explanation: The primary advantage of using cyclostationary feature detection is its ability to differentiate noise signals from modulated signals. This is due to incorporated redundancy in modulated signals. However cyclostationary feature detection is computationally intensive and demands long observation time.
3. What is the purpose of out-of-band sensing?
a) Fast switching
b) Fast routing
c) Fast discovery
d) Fast handoff
Answer: c
Explanation: Out-of-band sensing computes the time duration required by a cognitive radio user to detect a completely available spectrum band for transmission. Sensing order and stopping rule are factors that overlook out-of-band sensing.
4. Which among the following is a factor of concern for in-band sensing?
a) Identification of stop period for the search process
b) Identification of the start period for the search process
c) Selection of spectrum for evaluation
d) Selection of duration for transmission
Answer: d
Explanation: In-band sensing is mainly concerned with interference avoidance. Sensing time and transmission time are the major factors computed by in-band sensing. The duration and the frequency at which sensing should be carried out to achieve satisfying sensing accuracy is determined by in-band sensing.
5. Which among the following are problems of transmitter detection?
a) Secondary user uncertainty and xG base station uncertainty
b) xG base station uncertainty and primary base station uncertainty
c) Receiver uncertainty and shadowing uncertainty
d) Transmitter uncertainty and receiver uncertainty
Answer: d
Explanation: When the xG user communication range does not include the transmitter, interference is unavoidable as receiver information is unavailable. This is known as receiver uncertainty. In certain situations, the xG user has a good line of sight with the receiver but is unaware, this is known as shadowing uncertainty.
6. What is the terminology used when xG base-station is involved in gathering sensing information?
a) Cumulative
b) Centralized
c) Distributed
d) Aggregated
Answer: b
Explanation: Cooperation detection can be carried out with a centralized structure or with a distributed structure. Centralized cooperation detection involves the collection of sensing information by the xG base station to determine spectrum holes. Distributed cooperation detection detects spectrum holes by using information exchanged by xG users.
7. Which among the following is an interference of interest in xG architecture?
a) Expected interference at primary user
b) Expected interference at xG user
c) Expected interference at channel
d) Expected interference at spectrum broker
Answer: a
Explanation: The expected amount of interference on the primary user due to an xG user is the interference of interest in xG architecture. Interference at the primary transmitter can be controlled through the radiated power, the out-of-band emissions, and the location at the transmitters.
8. Which among the following is not a disadvantage of cooperation detection?
a) Overhead traffic
b) Receiver uncertainty
c) Shadowing uncertainty
d) Additional storage
Answer: c
Explanation: The main drawback of cooperation detection is the increased strain on networks with limited resources as the number of operations and overhead traffic is increased. When the xG user communication range does not include the transmitter, interference is unavoidable as receiver information is unavailable. Receiver uncertainty is not solved by cooperation detection.
9. What is an interference temperature model?
a) Interference temperature model is constructed by using the cumulative RF energy from multiple transmissions
b) Interference temperature model is constructed by using the RF energy from a single transmission
c) Interference temperature model is constructed by using the sampling RF energy from periodic transmissions
d) Interference temperature model is constructed by using the sampling IF energy from periodic transmissions
Answer: a
Explanation: An interference temperature model is constructed by using the cumulative RF energy from multiple transmissions. A threshold limit is set on the aggregate level. The xG users are permitted to use the spectrum band provided their transmission levels are within the threshold limit.
10. Which among the following is not a disadvantage of the interference detection method?
a) Requirement of modulation of unlicensed signal
b) Requirement of the activity level of licensed and unlicensed users
c) Management of interference at the receiver
d) Disregard for the effect of multiple xG users
Answer: c
Explanation: The interference detection method requires information such as type of unlicensed signal modulation, power control, and the activity level of licensed and unlicensed users. It does not consider the effect of multiple xG users. It requires the location of nearby primary users.
11. Spectrum decisions are affected by the co-location of data transmission and sensing function.
a) True
b) False
Answer: a
Explanation: Spectrum decisions are affected by the co-location of data transmission and sensing function. This problem is overcome by developing a separate sensor network for cooperative spectrum sensing while an operational network is constructed for data transmission.
12. Which among the following condition is represented in the following diagram?
a) Transmitter uncertainty
b) Shadowing uncertainty
c) Receiver uncertainty
d) Access point uncertainty
Answer: b
Explanation: Shadowing uncertainty is the situation when the xG user cannot sense the receiver when there is a clear line of sight between the receiver and xG user. It also cannot sense the transmitter since the line of sight between the transmitter and the xG user is hindered by the receiver.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Spectrum Management – 1”.
1. Which among the following is not considered for associating a cognitive radio user to an unused spectrum band?
a) Time-varying radio environment
b) Bandwidth
c) QoS requirement
d) Application policies
Answer: d
Explanation: The various characteristics of the unused spectrum bands determined during spectrum sensing depend on the time-varying radio environment, operating frequency, bandwidth, and quality of service requirements of the cognitive radio user. Spectrum management is required to correctly associate a user to a compatible spectrum band among all available spectrum bands in xG networks.
2. What among the following is not a function of spectrum management?
a) Sensing
b) Decision
c) Mobility
d) Repair
Answer: d
Explanation: The major functions of spectrum management are spectrum sensing, spectrum analysis, and spectrum decision-making. Spectrum sharing and spectrum mobility are also included in the management framework. Every function operates over all layers of the OSI model except sensing which is implemented only in the physical layer.
3. Which among the following functions prevent collision?
a) Spectrum analysis
b) Spectrum decision
c) Spectrum mobility
d) Spectrum sharing
Answer: d
Explanation: In the unlicensed portion of the spectrum, cognitive radio users have equal access to the spectrum and attempt to access the spectrum simultaneously. Spectrum sharing coordinates the network access such that collision is avoided in overlapping portions of the spectrum.
4. What is the function of spectrum mobility?
a) Detect spectrum holes
b) Gather information about available spectrum bands
c) Vacate spectrum band
d) Monitor spectrum band
Answer: c
Explanation: The cognitive radio users only have temporary access to the unused spectrum in the licensed band. If the primary user demands access, the spectrum mobility function of the spectrum management framework intervenes and transfers the cognitive radio user to another vacant position.
5. What is the function of the spectrum analysis unit?
a) Detect spectrum holes
b) Prevent collision between multiple users
c) Match spectrum bands with user requirements
d) Listen for the arrival of the primary user
Answer: c
Explanation: Spectrum analysis defines the characteristics of the spectrum bands and verifies whether the characteristics meet the user requirements. Interference level, channel error rate, link-layer delay, holding time, and path loss are few of defining parameters of a spectrum band.
6. Which parameter can be used to compute the permissible power of xG users?
a) Distance between the primary transmitter and xG user
b) Amount of interference at the primary receiver
c) Amount of interference at xG user
d) Distance between the primary receiver and xG user
Answer: b
Explanation: Channel capacity can be estimated by determining the permissible power of an xG user. The permissible power is computed by determining the amount of interference at the primary receiver. The amount of interference sometimes depends on the number of users in the spectrum.
7. Which among the following statements is false about the outcome of increasing transmission power?
a) Transmission range at higher frequencies is maintained
b) Path loss is increased
c) Interference is increased
d) Transmission range at lower frequencies is maintained
Answer: b
Explanation: Path loss is proportional to the operating frequency. Hence, transmission range gradually reduces with an increase in frequency when the transmission power is not modified. If transmission power is increased, the path loss is decreased with an increase in the amount of interference.
8. Which among the following factors affect the error rate?
a) Encoding techniques
b) Modulation scheme
c) Channel capacity
d) Access techniques
Answer: b
Explanation: Wireless link errors are parameters of importance in characterizing the spectrum band. The modulation scheme and the amount of interference in the spectrum band influence the error rate. Wrongful sensing decisions are also a contributing factor to the high error rate.
9. What is the primary cause of the link-layer delay?
a) Selection of appropriate protocol
b) Selection of routing path
c) Packet generation
d) Frame generation
Answer: a
Explanation: Each spectrum band is assigned a different protocol with respect to the interference level, path loss, and wireless link errors of the band. The link-layer packet transmission delay differs with different protocols.
10. What is holding time?
a) The duration required to identify a spectrum hole
b) The duration available after the arrival of the primary user to vacate the spectrum band
c) The duration over which the xG user can use the licensed spectrum band
d) The duration over which the xG user can use the unlicensed spectrum band
Answer: c
Explanation: Holding time refers to the period over which the xG user can occupy the licensed spectrum band before the arrival of the primary user. High holding time ensures high quality. Statistical handoff patterns are used to construct xG networks with longer holding time.
11. Which among the following is a challenge for spectrum management?
a) Asynchronous sensing
b) Multiple spectrum band operation
c) Availability of non-contiguous spectrum bands
d) Reconfiguration
Answer: d
Explanation: Transmission parameters of a radio should be reconfigurable for effective operation in certain spectrum bands. For example, if the signal to noise cannot be modified, then the bit error rate can be altered to maintain the channel capacity by employing adaptive modulation techniques.
12. Which among the following terms should replace the labels ‘A’ and ‘B’ in the diagram?
a) A – Link layer delay, B – Scheduling Information
b) A – Link layer establishment, B – Spectrum broker
c) A – Scheduling information, B – Link layer delay
d) A – Spectrum broker, B – Link layer establishment
Answer: a
Explanation: Link-layer delay is one of the defining parameters of quality of service. Various link layer protocols suitable for different path loss, wireless link error, and interference are available. Link layer packet transmission delay changes with respect to the selected protocol. Scheduling information ensure fair sharing of spectrum resources in the unlicensed spectrum band.
This set of Cognitive Radio Questions and Answers for Campus interviews focuses on “Next Generation Wireless Network – Spectrum Management – 2”.
1. Which among the following is the expression for channel capacity as per Shannon-Hartley theorem?
B is bandwidth, N is the average noise power, and S is the average received signal power.
a) C=B+log 2
\)
b) C=B+log 2
\)
c) C=B log 2
\)
d) C=B log 2
\)
Answer: d
Explanation: Shannon Hartley theorem states the maximum rate of transmission over a channel of specified bandwidth containing noise. The calculated channel capacity creates an upper bound for maximum error-free information transmission.
C=B log 2
\)
Here B is bandwidth, N is the average noise power, and S is the average received signal power.
2. Which among the following an expression for spectrum capacity in OFDM based xG networks?
α refers to a set of unused spectrum units, G is the channel power gain at frequency f, S 0 is the signal power per unit frequency and N_0is the noise power per unit frequency.
a) C=∫ α \(\frac{1}{2}\)log 2
\)
b) C=∫ α \(\frac{1}{2}\)log 2
\)
c) C=∫ α B log 2
\)
d) C=∫ α B log 2
\)
Answer: a
Explanation: Orthogonal Frequency Division Multiplexing is a digital modulation scheme. The data stream is divided into several closely spaced subcarrier signals at different frequencies. The spectrum capacity of OFDM xG networks is given by the expression,
C=∫ α \(\frac{1}{2}\)log 2
\)
Here α refers to a set of unused spectrum units, G is the channel power gain at frequency f, S 0 is the signal power per unit frequency, and N 0 is the noise power per unit frequency.
3. Which among the following is not selected in accordance with the user requirement?
a) Interference
b) Data rate
c) Tolerable error rate
d) Transmission mode
Answer: a
Explanation: Following the characterization of the spectrum, the spectrum band for transmission is selected by weighing the spectrum characteristics and the quality of service requirements. Spectrum manager fixes the data rate, tolerable error rate, transmission mode, the bandwidth of transmission, and the delay bound according to the user requirements.
4. Which among the following is not a challenge for spectrum management?
a) Interference avoidance
b) Quality of service awareness
c) Seamless communication
d) Interference temperature measurement
Answer: d
Explanation: xG users should not cause interference to primary user communication. The handoff to a different spectrum band upon arrival of the primary user should be seamless. The dynamic spectrum environment and quality of service requirements should be analyzed and managed for effective communication.
5. Which among the following is a challenge for spectrum decision models?
a) Combining multiple characterization parameters
b) Supporting OFDM networks
c) Supporting multiple spectrum bands
d) Maintaining a decision model for each characterization parameter
Answer: a
Explanation: Spectrum decision models can be built for various characterization parameters such as signal to noise, date rate, error rate, and other parameters that affect the quality of service. However a decision model combining several spectrum parameters is not available. Spectrum decision models support OFDM networks that have multiple spectrum bands operating simultaneously for transmission.
6. Which among the following is not a requirement for multiple spectrum band transmission by xG user?
a) Spectrum holes
b) Compatibility with internal policies
c) Contiguous spectrum band
d) Compatibility with quality of service
Answer: c
Explanation: xG users can transmit packets on multiple spectrum bands provided the available spectrum meets the quality of service requirements and the spectrum policies required for communication. However it does not require the multiple spectrum bands to be contiguous. This exhibits a vast improvement in communication quality during the spectrum handoff.
7. Which among the following is not an advantage of avoiding contiguous spectrum bands for transmission?
a) Low delay
b) Low power consumption
c) Low interference
d) Mitigation of quality of service degradation
Answer: d
Explanation: The primary advantage of using a contiguous spectrum band is the mitigation of the quality of service degradation. This is because when a user has to vacate a spectrum band on the arrival of the primary user, the other bands continue to transmit maintaining communication. Low power is consumed in each band and less interference with the primary user is achieved.
8. Which among the following replaces the static sine pulses of OFDM to improve flexibility?
a) Wavelet bases
b) Triangular pulses
c) Impulse bases
d) Ramp pulses
Answer: a
Explanation: In multi-carrier wavelet packet modulation, wavelet bases replace the static sine/cosine pulses of OFDM. This technique provides higher sideband suppression. It also reduces inter-channel interference and inter-symbol interference.
9. Which among the following is not a disadvantage of using OFDM?
a) Complex computation is necessary
b) Sensitive to frequency offset
c) High peak to average power ratio
d) Low data rate
Answer: a
Explanation: OFDM requires only the computation of fast Fourier transform and inverse fast Fourier transform of the signal to be transmitted. However it requires the subcarriers to remain orthogonal and exhibits a large peak to average power ratio due to the presence of complex sinusoids in time domain OFDM signals.
10. What is the full form of CE-OFDM?
a) Closed Envelope Orthogonal Frequency Division Multiplexing
b) Constant Envelope Orthogonal Frequency Division Multiplexing
c) Constant Evolute Orthogonal Frequency Division Multiplexing
d) Closed Evolute Orthogonal Frequency Division Multiplexing
Answer: b
Explanation: In Constant Envelope Orthogonal Frequency Division Multiplexing, the complex modulated signals are positioned in a complex conjugated arrangement to obtain a real value inverse fast Fourier transform output. Also, phase modulation is applied in the real value time domain. This technique reduces the high peak to average power ratio of OFDM.
11. Spectrum decision over heterogeneous spectrum band with different characteristics is a challenge in spectrum management.
a) True
b) False
Answer: a
Explanation: xG users operate in licensed and unlicensed spectrum bands. In licensed spectrum bands, the operations of the primary users are collected during spectrum analysis and the decision taken should not affect the primary user transmission. Likewise, intelligent spectrum sharing algorithms should be selected for xG users operating on the licensed bands which have equal rights for spectrum access.
12. Which among the following terms should replace the labels ‘A’, ‘B’, and ‘C’ in the diagram?
a) A – Sensing information, B – Spectrum sensing, C – Reconfiguration
b) A – Sensing information, B – Reconfiguration, C – Spectrum sensing
c) A – Spectrum sensing, B – Reconfiguration, C – Sensing information
d) A – Reconfiguration, B – Spectrum sensing, C – Sensing information
Answer: a
Explanation: Spectrum sensing examines the available spectrum bands, gathers information about the spectrum band, and detects spectrum holes. It is implemented in the physical layer. In-band sensing is carried out to sense the arrival of primary users and transfer the information to the spectrum mobility function unit. Reconfiguration is necessary to alter the transmission parameters in accordance with the dynamic radio environment.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Spectrum Mobility – 1”.
1. What is spectrum mobility?
a) Spectrum mobility involves seamless channel switchover
b) Spectrum mobility involves sharing spectrum information among secondary users
c) Spectrum mobility involves managing spectrum sensing and spectrum sharing
d) Spectrum mobility involves sharing spectrum information between secondary users and xG base station
Answer: a
Explanation: Spectrum mobility involves performing seamless channel switchover while maintaining the performance of current secondary user communication. Spectrum mobility is required when degradation of the current channel condition is observed or when the primary user arrives in the licensed band.
2. Which among the following statements is false?
a) Arrival of primary user triggers handoff
b) Primary user communication is of high priority
c) Secondary user can occupy licensed spectrum band until completion of communication
d) Secondary user moving in a band should not interrupt primary user communication
Answer: c
Explanation: In the licensed band, primary user communication holds a higher priority than the secondary user. The primary user can initiate handoff by appearing in the licensed spectrum band. It can also initiate handoff when secondary user transmission coverage overlaps with that of a primary user in the same band.
3. What are the units of spectrum mobility?
a) Spectrum sensing and spectrum sharing
b) Spectrum handoff and spectrum management
c) Connection management and spectrum management
d) Spectrum handoff and connection management
Answer: d
Explanation: Spectrum handoff is the process of transferring current data communication from one channel to another channel. Connection management adjusts the protocols associated with each layer of the OSI model to sustain the quality of service requirements of secondary user communication.
4. Which among the following is a concern of a primary user?
a) Link maintenance probability
b) Number of handoff
c) Handoff latency
d) Effective data rate
Answer: c
Explanation: Spectrum handoff is the process of transferring current data communication from one channel to another channel. The delay caused by spectrum handoff is termed as handoff latency. High handoff latency at the secondary user increases the amount of interference at the primary user.
5. Which among the following is an essential feature of spectrum mobility in FTP communication?
a) Storage of packets
b) Authentication
c) Encryption
d) Data recovery
Answer: a
Explanation: Connection management in spectrum mobility enforces protocols with respect to the application for maintaining communication. FTP requires protocols to store packets that are transmitted during handoff. But real-time applications do not require storage of packets as the information is obsolete for the corresponding application.
6. Which among the following is the basic unit of spectrum pool?
a) Contiguous licensed spectrum band
b) Non-contiguous licensed spectrum band
c) Contiguous unlicensed spectrum band
d) Contiguous licensed spectrum band
Answer: a
Explanation: The spectrum pool comprises of a collection of contiguous licensed spectrum bands. Each spectrum band contains several channels. A spectrum band is considered as a preliminary bandwidth unit for operating any wireless access technology.
7. What is link maintenance probability?
a) Link maintenance probability is the measure of duration of transmission before handoff
b) Link maintenance probability is the measure of sustenance of transmission during handoff
c) Link maintenance probability is the measure of duration to find back-up channels
d) Link maintenance probability is the measure of the strength of link during transmission
Answer: b
Explanation: Link maintenance probability is the measure of sustenance of the communication of secondary user, when the secondary user vacates a channel. Link maintenance probability increases with the number of handoffs. Link maintenance probability is one of the performance measuring parameters of spectrum mobility.
8. Which among the following is integrated in IEEE 802.22 Wireless Regional Area Network?
a) Route decision model
b) Back up channel list
c) Interference floor
d) Spectrum decision model
Answer: b
Explanation: The most preferred approach for mitigating performance degradation, due to poor channel characteristics, is building a backup channel list. The potential target channels are added to a list. The list is maintained by sharing information between users in the area. It is integrated in the IEEE 802.22 Wireless Regional Area Network.
9. What is the terminology used for a handoff between spectrum bands without changing the current base station?
a) Intra-cell/Intra-pool handoff
b) Inter-cell/Intra-pool handoff
c) Inter-cell/inter-pool handoff
d) Intra-cell/inter-pool handoff
Answer: a
Explanation: When an xG user switches from one spectrum band to another in the same spectrum pool without selecting an alternate base station, it is termed as intra-cell/intra-pool handoff. A cell is a unit of coverage area. Spectrum pool is a set of contiguous licensed spectrum bands.
10. What is intra-cell/inter-pool handoff?
a) Same spectrum pool and same base-station
b) Same spectrum pool and different base-station
c) Different spectrum pool and different base-station
d) Different spectrum pool and same base-station
Answer: d
Explanation: When an xG user switches from one spectrum pool to another spectrum pool within a single cell coverage area, it is termed as intra-cell/inter-pool handoff. The is no transfer from serving base-station to the neighbour base-station. A Cell is a unit of coverage area. Spectrum pool is a set of contiguous licensed spectrum bands.
11. Prediction of availability of channels can mitigate sensing delay.
a) True
b) False
Answer: a
Explanation: Target channel selection relies on channel capacity, availability of channel during handoff, and availability of channel in the future. Prediction of channel availability reduces sensing delay since partial sensing is performed instead of conventional sensing. Accuracy is improved due to the integration of historical spectrum statistics.
12. Which among the following method is represented in the following diagram?
a) Non-handoff
b) Proactive handoff
c) Reactive handoff
d) Hybrid handoff
Answer: d
Explanation: Hybrid handoff is a combination of proactive handoff and reactive handoff. As shown in the diagram, the backup channel list is created in advance of handoff. In proactive handoff, handoff is performed before the triggering event. But hybrid handoff follows reactive handoff meaning that handoff is performed only after the triggering event.
This set of Cognitive Radio Questions & Answers for Exams focuses on “Next Generation Wireless Network – Spectrum Mobility – 2”.
1. What is a non-handoff?
a) xG user selects a channel from the unlicensed band
b) xG user selects a channel in the licensed spectrum band
c) xG user removes another user in the unlicensed band
d) xG user eliminates a primary user in the unlicensed band
Answer: b
Explanation: Spectrum handoff is the process of changing the spectrum band and modifying the communication parameters to suit the selected spectrum band. In the non-handoff method, the xG users select an unused spectrum in the licensed band which is temporarily unoccupied by the primary user. The disadvantage of this method is the high waiting latency.
2. What is reactive handoff?
a) xG user performs sensing and sensing is performed before the triggering event
b) xG user performs sensing and sensing is performed after triggering event
c) Primary user performs sensing and sensing is performed before the triggering event
d) Primary user performs sensing and sensing is performed after triggering event
Answer: b
Explanation: In the reactive handoff, the xG user begins to sense for available spectrum bands for handoff only after the triggering event. The advantage of this method is that the best available spectrum band is selected. However this method exhibits longer handoff latency.
3. Which among the following is a disadvantage of proactive handoff?
a) High latency
b) Increased number of handoffs
c) Prior planning
d) Unused saved channels
Answer: d
Explanation: In the proactive handoff, the xG user continues to sense during transmission, and the handoff is carried out prior to the triggering event. Low handoff latency is observed and multiple handoffs are reduced. The disadvantage of this method is the lack of usage of back up channels and degradation of performance due to poor sensing.
4. Which among the following is a challenge for spectrum mobility in the time domain?
a) QoS maintenance
b) Cooperative sensing
c) Interference temperature measurement
d) Reconfiguration
Answer: a
Explanation: xG networks change constantly in the wireless spectrum in accordance with the available spectrum band. The available spectrum bands tend to vary with time. Thus QoS maintenance becomes difficult. The radio should alter its position to meet the QoS requirements.
5. Which among the following should be adapted in spectrum mobility management?
a) Single-layer approach
b) Double layer approach
c) Cross-layer approach
d) Alternate layer approach
Answer: c
Explanation: Spectrum handoff depends on the spectrum environment as well as the application requirements. By choosing a cross-layer approach, the operational overhead among the functionalities is reduced. This increases the switching time.
6. Which among the following method is suitable for delay-sensitive application?
a) Reactive handoff
b) Proactive handoff
c) Non-handoff
d) High handoff
Answer: b
Explanation: In the proactive handoff, the xG user continues to sense during transmission, and the handoff is carried out prior to the triggering event. In reactive handoff, the xG user begins to sense for other bands only after the triggering event. Proactive handoff is suitable for delay-sensitive application.
7. Which among the following is influenced by spectrum switching time?
a) Transmit time
b) Access time
c) Recovery time
d) Sensing time
Answer: c
Explanation: Spectrum switching time depends on hardware as well as the algorithms used for spectrum sensing, spectrum decision, link layer, and routing. The spectrum switching time caused by spectrum mobility increases the recovery time.
8. Why is inter-cell handoff required?
a) To support spectrum mobility in time domain
b) To support spectrum mobility in frequency domain
c) To support spectrum mobility in the phase domain
d) To support spectrum mobility in space domain
Answer: d
Explanation: When xG users move from one cell to another, the available spectrum bands change. This demands the development of inter-cell handoff. It also demands continuous allocation of spectrum.
9. Which among the following is not a challenge of connection management?
a) Estimation of accurate latency
b) Reduction of delay
c) Reduction of loss
d) Maintenance of multiple handoffs
Answer: d
Explanation: Connection management initially selects the best available spectrum band using algorithms that analyze the channel characteristics and the application requirements. Further challenges for connection management are the estimation of accurate latency, and reduction of delay and loss during spectrum handoff.
10. Which among the following is responsible for recovering the routing table in case of route break?
a) xG user
b) xG base-station
c) Primary base-station
d) Spectrum broker
Answer: a
Explanation: Route breaking is likely to occur during spectrum handoff. The xG user has to recover the routing table in case of a route break. One approach is to build a new routing table for handoff and the other method is to create a routing table for the redundant channel before beginning data transmission.
11. Hybrid handoff is a combination of proactive handoff and reactive handoff.
a) True
b) False
Answer: a
Explanation: Hybrid handoff is a combination of proactive handoff and reactive handoff. An alternate channel is proactively sensed before or during transmission. However handoff is performed only after the triggering event.
12. Which among the following should replace the labels ‘A’ and ‘B’?
a) Spectrum management and connection management
b) Spectrum mobility and connection management
c) Connection management and spectrum handoff
d) Spectrum mobility and spectrum handoff
Answer: c
Explanation: Spectrum handoff is the process of transferring current data communication from one channel to another channel. Spectrum handoff is implemented in the physical layer. Connection management ensures that the xG user maintains the quality of service and prevents quality degradation at the time of spectrum switching by modifying the protocols associated with each layer in the OSI model.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Spectrum Sharing – 1”
1. Which among the following is not used as an attribute for classifying spectrum sharing?
a) Architecture
b) Spectrum allocation behaviour
c) Spectrum access technique
d) Spectrum sensing behaviour
Answer: d
Explanation: Based on the architecture, the spectrum sharing techniques are categorized as centralized and decentralized. Based on spectrum allocation behaviour, the techniques are categorized as cooperative and non-cooperative. Based on the spectrum access technique, the methods are categorized as overlay and underlay.
2. Which among the following statement is false about cooperative sensing?
a) Cooperative spectrum sharing is alternately known as collaborative spectrum sharing
b) Cooperative spectrum sharing studies the effect of communication of one node on other nodes
c) Cooperative spectrum sharing withholds the interference information
d) Cooperative spectrum sharing minimizes collision caused by users accessing the same portion of the spectrum
Answer: c
Explanation: Cooperative spectrum sharing studies the effect of communication of one node on other nodes. It also involves distributing the interference measurements among the users in the network. This information is utilized by spectrum allocation algorithms which provide spectrum access to users.
3. Which among the following is true non-cooperative spectrum sharing?
a) Non-cooperative spectrum sharing optimizes spectrum sharing algorithms
b) Non-cooperative spectrum sharing reduces effective spectrum utilization
c) Non-cooperative spectrum sharing distributes interference measurements to other users in the network
d) Non-cooperative spectrum sharing works only with spectrum broker
Answer: b
Explanation: Non-cooperative spectrum sharing only considers the communication of the one particular node. Due to the lack of information about other users, it exhibits reduced spectrum utilization. However due to minimal communication requirements, it is suitable for certain resource-constrained practical applications.
4. What is the parameter used to differentiate the overlay and underlay spectrum sharing technique?
a) Delay in unlicensed spectrum
b) Delay in licensed spectrum
c) Degree of interference exhibited towards primary user
d) Degree of interference exhibited towards secondary user
Answer: c
Explanation: The overlay and underlay spectrum sharing techniques are classified based on the amount of interference directed towards the primary users while operating in the licensed spectrum band. Overlay exhibits zero interference while the underlay technique exhibits considerable interference which is regarded as noise by primary users.
5. Which among the following method is employed in underlay spectrum sharing?
a) Time division multiple access
b) Spread spectrum techniques
c) Frequency division multiple access
d) Time division duplexing
Answer: b
Explanation: Underlay spectrum sharing technique employs spread spectrum techniques while transmitting in the licensed portion of the spectrum band. Spread spectrum involves stretching a signal over a bandwidth which is wider than its original bandwidth. Therefore bandwidth utilization and interference towards the primary user is increased.
6. Which among the following is true about centralized spectrum sharing?
a) Centralized spectrum sharing does not rely on fixed infrastructure units
b) Centralized spectrum sharing holds each node responsible for spectrum allocation
c) Centralized spectrum sharing reduces the overhead of communication
d) Centralized spectrum sharing has a controlling entity for spectrum allocation and spectrum access
Answer: d
Explanation: Centralised spectrum sharing consists of a central entity for performing spectrum allocation and spectrum access. Each node in the network forwards information on the spectrum and the interference to the central entity. The central entity builds the spectrum allocation map using the collected information.
7. Which among the following has to be carried out after the spectrum is allocated for communication?
a) Listen for the arrival of the primary user
b) Handshake mechanism between transmitter and receiver
c) Estimate the duration of communication
d) Forward interference information to spectrum broker
Answer: b
Explanation: The selected portion of the spectrum must be informed to the receiver of data. This is accomplished by invoking a transmitter-receiver handshake protocol that is used for effective communication in xG networks.
8. Which among the following is not a step in spectrum sharing?
a) Spectrum sensing
b) Spectrum mobility
c) Spectrum access
d) Spectrum management
Answer: d
Explanation: Spectrum sharing process is integrated with spectrum sensing, spectrum allocation, spectrum access, handshake mechanism, and spectrum mobility. Thus the selection of best available spectrum, prevention of collision due to the overlapping portion of the spectrum, and seamless connection for communication regardless of the location of the user involves spectrum sharing.
9. Which among the following layer operation is similar to that of spectrum sharing?
a) Physical
b) Data-link
c) Network
d) Transport
Answer: b
Explanation: The data link layer particularly the MAC portion is responsible for collision avoidance. Likewise, spectrum sharing is responsible for avoiding collision between licensed and unlicensed users of the licensed spectrum band as well as for avoiding collision among xG users in the unlicensed band.
10. Which among the following is a constraint observed in hardware constrained MAC protocol for cognitive radio networks?
a) Hidden terminal problem
b) Synchronization among xG users
c) Synchronization between xG user and primary user
d) Shadowing uncertainty
Answer: a
Explanation: Sensing in a limited geographic area with a fixed bandwidth limit on secondary users is a challenge for hardware constrained MAC protocol. Thus hidden terminal problem is observed in the hardware constrained MAC protocol. The demand for synchronization among xG users is a problem of concern for cognitive MAC protocol.
11. Transmitter-receiver handshake does not involve any central entity such as the primary base-station.
a) True
b) False
Answer: b
Explanation: The transmitter-receiver handshake conveys the selected spectrum for communication to the receiver. This protocol is not limited between a transmitter and a receiver and may also include external entities such as a primary base-station especially in methods such as cooperative spectrum sharing.
12. Which among the following terms should replace the label ‘A’?
a) Centralised intra-network spectrum sharing
b) Centralised inter-network spectrum sharing
c) Distributed inter-network spectrum sharing
d) Distributed intra-network spectrum sharing
Answer: b
Explanation: xG networks are generally overlapped to maximize the opportunistic usage of a licensed spectrum band. An example of a centralized inter-network approach is the common spectrum coordination channel protocol designed to support the combined existence of IEEE 802.11b and IEEE 802.16a.
This set of Cognitive Radio Questions and Answers for Aptitude test focuses on “Next Generation Wireless Network – Spectrum Sharing – 2”.
1. What is the basic unit of channel allocation?
a) P frame
b) Q frame
c) R frame
d) S frame
Answer: b
Explanation: A Q frame is the basic unit of channel allocation. When a Q frame is allocated by a base-station, the base-station can use its control and data channels for coordination and data communication between the users.
2. What is the full form of DQSDR?
a) Dynamic Quality of Service Distributed Reservation scheme
b) Distributed Quality of Service Dynamic Reservation scheme
c) Dynamic Quality of Service Distributed Resource scheme
d) Distributed Quality of Service Dynamic Resource scheme
Answer: b
Explanation: In Distributed Quality of Service Dynamic Reservation scheme, a base-station competes with an interfering base-station to allocate a spectrum band that satisfies the quality of service requirements of the user application.
3. What is the use of a common control channel?
a) Transmission coordination
b) Spectrum allocation
c) Spectrum analysis
d) Time of arrival synchronization
Answer: a
Explanation: The common control channel is used to exchange spectrum information among xG users and also support transmission coordination. The common control channel is mainly classified as an in-band channel or as an out-of-band channel.
4. Which among the following is a common control channel used by a radio to gain access to a system?
a) Paging Channel
b) Random Access Channel
c) Access Grant Control Channel
d) Cell Broadcast Channel
Answer: b
Explanation: Common control channel transfers control information from a radio to a base-station. Random access channel is required to gain access to a system. It is invoked when the radio starts a call or replies to a page.
5. Which among the following may be employed to select a common control channel in cooperative intra-network spectrum sharing?
a) Regression
b) Munging
c) K-nearest neighbour
d) Clustering
Answer: d
Explanation: In a local group, each node shares several channels with its neighbours. Each group may employ a clustering algorithm to select a common channel for communication. Distributed sensing and spectrum sharing is also carried out in the common channel.
6. What is a local bargaining group?
a) Local bargaining group is a set of users with a threshold limit guaranteed to provide minimum spectrum allocation to each user
b) Local bargaining group is a set of users with a threshold limit that determines one particular user to operate the spectrum band
c) Local bargaining group is a set of users with a threshold limit on the number of transmissions permissible over a certain period
d) Local bargaining group is a set of users that compete for access of the spectrum band
Answer: a
Explanation: Local bargaining scheme is a cooperative intra-network sharing technique. It improves spectrum utilization and ensures fairness in the allocation of spectrum. It involves creating a local bargaining group with a threshold limit that ensures minimum allocation of spectrum to each user of the group.
7. Which among the following is not a function of the dynamic spectrum access protocol?
a) Collision avoidance
b) Resolve spectrum access contention
c) Transparency for primary user
d) Efficient dynamic spectrum allocation
Answer: b
Explanation: The primary user does not interact or coordinate with the secondary user. Therefore the secondary user must be made transparent for the primary user. DSAP should avoid collision between primary users and secondary users by introducing power constraints. The spectrum should be allocated such that average network throughput is increased.
8. How is dynamic spectrum access protocol advantageous for cooperative spectrum sharing?
a) Central entity is used to lease the spectrum
b) Sophisticated spectrum sharing algorithms are used to allocate the spectrum
c) Distributed communication
d) Reduced communication overhead
Answer: a
Explanation: The dynamic spectrum access protocol is a centralized protocol where a central entity is used for leasing spectrum to users in a limited geographical area. DSAP consists of clients, DSAP server, and relay for relaying information between the server and the clients that are not in the direct range of the server.
9. What type of scheme is non-cooperative intra-network spectrum sharing?
a) Spectrum centric
b) Application centric
c) Device centric
d) Access centric
Answer: c
Explanation: Non-cooperative intra-network spectrum sharing allocates channels depending on observed interference patterns and neighbours. The device is modified so that it can choose the channels for communication. This method exhibits poor performance when compared to cooperative schemes but the communication overhead is reduced.
10. Which among the following is applied to resolve contention between users in non-cooperative intra-network spectrum sharing?
a) Random access techniques
b) Multiple access techniques
c) Spread spectrum techniques
d) Multiplexing techniques
Answer: a
Explanation: Non-cooperative intra-network spectrum sharing is a rule based spectrum access approach. When more than one closely located nodes access the same channel, random access techniques are used to resolve contention. The rules help to reduce communication overhead.
11. The selection of a common control channel is difficult in centralized networks.
a) True
b) False
Answer: b
Explanation: The selection of a common control channel is difficult in distributed cognitive wireless networks due to the time varying spectrum environment and lack of a central controlling entity. It is overcome by choosing a licensed or an unlicensed channel as the dedicated common control channel.
12. Which among the following methods is associated with dynamic open spectrum channel protocol?
a) Centralized inter-network spectrum sharing
b) Distributed inter-network spectrum sharing
c) Cooperative intra-network spectrum sharing
d) Non-cooperative intra-network spectrum sharing
Answer: c
Explanation: Dynamic open spectrum channel protocol aids the cooperative intra-network spectrum sharing. A busy tone is exchanged between the transmitter and the receiver in the selected busy tone channel during communication on the data channel.
13. What term should replace the labels ‘A’ and ‘B’?
Answer: d
Explanation: Spectrum sensing and spectrum access are the two major functions of the spectrum sharing process. Spectrum sensing is responsible for locating unused spectrum bands. Spectrum access is responsible for choosing the best available spectrum that meets the quality of service requirements and policies from all available spectrum.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Upper Layers Issue – 1”.
1. Which among the following is not an upper layer issue?
a) Channel sensing
b) Routing
c) Security
d) Congestion control
Answer: a
Explanation: Upper layer issues are the challenges in the application layer, the transport layer, and the network layer in the implementation of cognitive radio networks. Route selection and maintenance is a challenge of the network layer. Prevention of intrusion is a challenge of the transport layer.
2. Which among the following is a not route metric?
a) Power efficiency
b) Interference
c) Cost
d) Data size
Answer: d
Explanation: Route metrics are parameters whose values are evaluated to assign a cost to a link in the path between the source and the destination. Routing algorithms rely on route metrics to select the optimum path for forwarding the packets.
3. Which among the following is an issue for routing in cognitive radio networks?
a) Spectrum sensing
b) Power allocation
c) Spectrum knowledge
d) Spectrum characterization
Answer: c
Explanation: The routing layer requires information about the spectrum for determining the path of communication. The consolidation of information obtained by sensing and by characterization operations of the physical layer is a challenge as it is difficult to decide which information should be stored. The user requires local as well as global knowledge of the spectrum.
4. What is the term used to define the additional data that has to be transferred other than the message during communication?
a) Encoded bits
b) Payload
c) Support bits
d) Overhead
Answer: d
Explanation: Overhead refers to the additional transmissions that exceed the allowable number of transmissions resulting in a decrease of efficiency and throughput of the entire network. For example, in cooperative sensing, before transmission of information, the sensing information collected by a user has to be forwarded to other secondary users in the network.
5. Which among the following is false about the routing issue link failure?
a) Interference is a route metric used to represent link failure
b) Link capacity is a route metric used to represent link failure
c) Link failure is caused by the displacement of an intermediary node
d) Link failure is caused by the arrival of the primary user
Answer: b
Explanation: Link failure arises due to the arrival of a primary user or due to the lack of replacement of a displaced intermediary node. Link failure, depending on the triggering event, may be recovered by employing an extra power signal.
6. Which among the following is not a route metric of the routing issue mobility handling?
a) Delay
b) Interference
c) Throughput
d) Link stability
Answer: c
Explanation: Mobility handling is required when a secondary user moves from one place to another due to the arrival of a primary user or due to variation in the spectrum environment. It is also required when an intermediary node leaves the path of communication. Mobility handling is responsible for finding an alternate node and re-establishing communication.
7. Which among the following issues consider cost as a route metric?
a) Spectrum knowledge
b) Overhead
c) Link failure
d) Best path selection
Answer: d
Explanation: Best path selection considers the following route metrics namely delay, power efficiency, interference, throughput, and cost. The path that closely meets the quality of service requirements of the application is chosen as the best path. The cognitive radio network calculates several paths considering the possibility of the arrival of a primary user, the robustness of a path, etc.
8. Why common channel control is required for routing?
a) Transmission coordination
b) Time of arrival synchronization
c) Broadcasting
d) Spectrum analysis
Answer: c
Explanation: The existing routing protocols for functionalities such as neighbour discovery, route discovery, and route establishment need to broadcast messages either globally or locally. The lack of a common control channel makes it difficult to send broadcast messages in xG networks.
9. Which among the following issues require channel-based models for analysis?
a) Common control channel
b) Spectrum knowledge
c) Queue management
d) Intermittent connectivity
Answer: d
Explanation: Intermittent connectivity is caused due to the time-changing nature of the spectrum and loss of channel due to the arrival of the primary user. It is also due to the fact that when the user chooses a channel for communication, the node cannot be reached through other channels. Thus channel-based models are required for developing time-based solutions.
10. Why is queue management required?
a) Form a queue of xG users which require access for a particular channel in the licensed band
b) Handle multiple interfaces
c) Form a queue of xG users which require access for a particular channel in the unlicensed band
d) Form a queue of xG users to forward information to spectrum broker
Answer: b
Explanation: An xG terminal uses multiple interfaces to interact with multiple nodes. Queue management is responsible for finding an interface best suited for the traffic in the spectrum environment. Queues are generated after evaluating each interface with each traffic type.
11. What is the best path from N1 to N3 in dynamic source routing?
a) N1 – N4 – N2 – N3
b) N1 – N4 – N5 – N4 – N1 – N2 – N3
c) N1 – N4 – N5 – N3
d) N1 – N2 – N3
Answer: d
Explanation: Dynamic source routing initiates by broadcasting a packet to nodes N2 and N4. N2 broadcasts request packets to N3 and N5. N3 identifies itself as the target. N5 forwards the packets to N4 and N3. The nodes which received the request packet for a second time discard the request packets. N3 identifies two routes N1-N2-N3 and N1-N4-N5-N3. N3 returns the path N1-N2-N3 in reverse order since it is the shorter route.
12. Which among the following is not a network layer attack?
a) Network endo parasite attack
b) Jamming attack
c) Channel ecto parasite attack
d) Low cost ripple effect attack
Answer: b
Explanation: Network endo parasite attack increases the amount of interference. Channel ecto parasite attack switches its interference to a channel occupied by a high priority user. Low cost ripple effect attack shares false channel assignment information.
13. Cross layer approach is the combination of route selection and spectrum management.
a) True
b) False
Answer: a
Explanation: Cross layer approach jointly considers route and spectrum selection in xG networks. Typically, route selection is carried out centrally with a global view of the network. On constructing a route, each hop is associated with a time slot and a channel.
This set of Cognitive Radio online test focuses on “Next Generation Wireless Network – Upper Layer Issue – 2”.
1. Which among the following does not cause performance degradation on TCP level?
a) Link error
b) Packet loss
c) Admission control
d) Access delay
Answer: d
Explanation: Transmission Control Protocol is a connection oriented, reliable, end to end protocol of the transport layer. TCP generally exhibits performance degradation in wireless networks due to a high packet loss rate. Cognitive radio introduces new challenges such as interruption due to loss of availability of a channel.
2. Which among the following influences packet loss probability?
a) Operation frequency
b) Interference level
c) Available bandwidth
d) Medium Access Control protocol
Answer: d
Explanation: Packet loss probability is computed to predict wireless link error. It relies on the access technology, operating frequency, interference level, and available bandwidth. Wireless channel access delay relies on operation frequency, interference level, and medium access control protocol.
3. Which among the following factors influence round trip time?
a) Access technology
b) Power efficiency
c) Cost
d) Frequency of operation
Answer: d
Explanation: Round trip time depends on the frequency of operation. An increased number of link layer retransmissions is required to send a packet across the wireless channel when a high packet error rate is observed at a particular frequency band.
4. What is spectrum handoff latency?
a) Spectrum handoff latency is the time taken to switch to a new frequency during handoff
b) Spectrum handoff latency is the period over which an xG user can use licensed band before handoff
c) Spectrum handoff latency is the time taken to estimate the path between a current licensed band and a new licensed band
d) Spectrum handoff latency is the time taken to send handoff information to the spectrum broker
Answer: a
Explanation: Depending on the available spectrum, the operational frequency of the radio changes with time. When the radio changes its frequency of operation, the time taken for the new frequency to become operational is called spectrum handoff.
5. Which among the following increases with an increase in spectrum handoff latency?
a) Overhead
b) Time of arrival
c) Round trip time
d) Link layer delay
Answer: c
Explanation: High spectrum handoff latency leads to increased round trip time. This in turn leads to retransmission time out. Existing protocols deduce the cause as packet loss and invoke the congestion avoidance mechanism resulting in the decrease of throughput. Cognitive radio network requires transport protocols that support spectrum mobility.
6. Which among the following is the first step in multipath routing?
a) Selection of a spectrum band for transmission
b) Identification of multi-paths
c) Evaluation of route metrics
d) Selection of route metrics
Answer: a
Explanation: In multipath routing, the multiple paths are discovered first. The routes are evaluated on route metrics such as delay and link stability, and then the node selects a route for transmission. One approach is to employ dynamic source routing for route discovery. Multipath routing suits the dynamic nature of cognitive networks and exhibits increased efficiency.
7. Which among the following is true about tree based routing?
a) Tree based routing is a distributed routing scheme controlled by a multiple network entities
b) Tree based routing is a distributed routing scheme controlled by a single network entity
c) Tree based routing is a centralized routing scheme controlled by a single network entity
d) Tree based routing is a centralized routing scheme controlled by a multiple network entities
Answer: c
Explanation: Tree based routing is a centralized network scheme controlled by a single network entity. xG users register at the centralized entity. One approach is to construct a route based on end to end throughput at the centralized entity using the minimum spanning tree algorithm.
8. Which unit is responsible for initiating local coordination?
a) Primary user
b) Secondary user
c) Central entity
d) Intermediary node
Answer: d
Explanation: Local coordination routing is a combination of routing and spectrum assignment protocol, and local coordination scheme. The routing and spectrum assignment protocol generates multiple paths and assigns a cost for each hop in the path. The intermediary nodes initiate local coordination and find alternate paths to tackle link failure.
9. Which among the following occurs when intermediary nodes choose identical frequency bands?
a) Link failure
b) Increased cost
c) Increased power
d) Increased delay
Answer: d
Explanation: In the location coordination scheme, multihop paths are created, where intermediary nodes might select an identical frequency band. It results in increased switching delay. This can be avoided by introducing a scheduling mechanism such as polling.
10. Which among the following statements is false about spectrum aware routing?
a) Spectrum aware routing does not require local spectrum knowledge
b) Spectrum aware routing requires cooperation sensing
c) Spectrum aware routing performs poorly during link failure
d) Spectrum aware routing does not generate large overhead
Answer: a
Explanation: Spectrum aware routing operates with global knowledge as well as with local knowledge. Each user is aware of another user when global knowledge is available. Otherwise each user constructs spectrum routes using spectrum availability information obtained locally by distributed protocol.
11. Which layer is associated with based utility attack?
a) Physical layer
b) Data link layer
c) Network layer
d) Transport layer
Answer: b
Explanation: Based utility attack involves the modification of characteristics of function parameters to obtain more bandwidth. It increases the amount of delay in the network. It is observed in the data link layer.
12. A key depletion attack is a malicious attack on the network layer.
a) True
b) False
Answer: b
Explanation: The key depletion attack is a malicious attack on the transport layer. It is employed to destruct the underlying cipher system. It leads to the degradation of the efficiency of communication.
13. What type of mechanism is exhibited in the following diagram?
a) Slow start
b) Three way handshake mechanism
c) Fast retransmission
d) Selective retransmission
Answer: a
Explanation: The slow start mechanism involves starting the communication with a minimum number of packets. On receiving an acknowledgment, the amount of packets is doubled. This is continued until the number the packets reach the receiver’s buffer limit or until congestion is detected.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Cross Layer Design – 1”.
1. Which among the following is a disadvantage of the signaling pipe?
a) Lack of instant signaling
b) Separate headers for non-adjacent layers
c) Unreliable delivery of information
d) Generation of interface between non-adjacent layers
Answer: a
Explanation: Interlayer signaling allows signaling information to pass from layer to layer along with packet flow. The processing path in the protocol stack may pass from top to bottom or from bottom to top. This is not suitable for cross-layer implementation since it requires instant signaling.
2. What is the full form of CLASS approach?
a) Cross-Layer Skipping Shortcuts
b) Cross-Layer Super Shortcuts
c) Cross-layer Support Shortcuts
d) Cross-Layer Signalling Shortcuts
Answer: d
Explanation: Direct Interlayer Communication provides shortcuts between layers that are performed out of the band. Cross-Layer Signalling Shortcuts support the exchange of messages between non-adjacent layers eliminating the need for processing at each layer.
3. Which among the following is false about the CLASS approach?
a) Eliminates insertion of signaling information
b) Supports only unidirectional communication
c) Reduce overhead
d) Eliminate interception of packet at non-destination layer
Answer: b
Explanation: CLASS eliminates interception of packet at non-destination layer, reduces processing overhead, eliminates insertion of signaling information, and supports bidirectional communication. Signaling message typically includes the Internet Control Message Protocol.
4. Which among the following is implemented parallel to the protocol stack?
a) Interlayer signaling pipe
b) Direct inter layer communication
c) Central cross-layer plane
d) Cross talk
Answer: c
Explanation: The Central cross-layer plane is the most popularly used implementation of cross-layer design concept. It can be implemented as a shared database. Otherwise, each protocol layer creates separate interfaces for its internal protocol parameters and functions.
5. Which among the following is not a disadvantage ICMP protocol for direct inter layer communication?
a) IP headers are included
b) High protocol processing overhead
c) Limited to request-respond action
d) Loss of message packet cannot be identified
Answer: d
Explanation: ICMP protocol has a large protocol header and protocol processing overhead. It is limited to request-response actions. However, cross-layer design demands for asynchronous communication. This can be overcome by creating a call back function with a procedure suited to the needs of the layers under consideration.
6. Which among the following is not a cross-layer design challenge associated with the lower layer of the protocol stack?
a) Topology configuration
b) Interference mitigation
c) Cooperative sensing
d) Energy consumption
Answer: a
Explanation: Spectrum sensing is capable of detecting interference only at the transmitters. Interference measurements should be shared to identify the amount of interference at other users and receivers. This is carried out by cooperative sensing. However cooperative sensing generates large communication overhead that leads to reduced performance in terms of channel capacity and energy consumption.
7. Which among the following may be employed to reduce performance degradation on a route with interference towards primary users?
a) Multiple spectrum brokers
b) Spatially distributed amplifiers
c) Multi-spectrum interfaces
d) Spatially distributed base-stations
Answer: c
Explanation: If a route between two xG users causes interference to surrounding primary users, it might affect the end-to-end latency or might cause packet loss along the route. This could be overcome by using multiple spectrum interfaces at intermediary nodes which introduces multiple hops in a route.
8. Which among the following is true about the explicit congestion network?
a) Explicit congestion notification is an extension of the data link layer and network layer
b) Explicit congestion notification is an extension of transport and network layer
c) Explicit congestion notification is an extension of transport and data link layer
d) Explicit congestion notification is an extension of the physical and data link layer
Answer: b
Explanation: Explicit congestion notification informs about network congestion to end devices without dropping packets. It is possible only when the end devices and the underlying infrastructure support ECN. The procedure involves marking a bit in the IP header to indicate upcoming congestion.
9. Which among the following is not a challenge for spectrum sensing?
a) Continuous sensing of spectrum
b) Energy consumption
c) Switching between sensing and transmission
d) Limit sensing when a single radio is deployed
Answer: d
Explanation: Radio cannot sense the entire available spectrum continuously. An upper limit is established on energy consumption for a period of time. Thus accurate spectrum knowledge is unavailable at all times. Cross-layer interaction is required for switching between transmissions and sensing operations during in-band sensing operation.
10. Which among the following accounts for the additional routing costs generated for cross-layer information processing?
a) Security
b) Processing efficiency
c) Latency
d) Delay
Answer: b
Explanation: Processing efficiency accounts for the additional routing costs applicable for cross-layer information processing. It especially affects the high speed links where only the time to live field of a packet is decreased to ensure fast processing of packets.
11. Re-routing with cross-layer design is more efficient due to the availability of sensing information.
a) True
b) False
Answer: a
Explanation: The sensing information from the physical layer helps the intermediary nodes to construct better routes. The triggering event for a packet loss can be rightly identified as link failure or node failure with sensing information.
12. Which among the following options should replace the labels ‘A’, ‘B’, and ‘C’?
a) Cross layer controller, Interface to network, Interface to node
b) Cross layer controller, Interface to node, Interface to network
c) Interface to node, Cross layer controller, Interface to network
d) Interface to network, Cross layer controller, Interface to node
Answer: c
Explanation: Cross layer implementation on node level is desired to alter the threshold on individual wireless connections, to dynamically limit resources available at the MAC layer, and to improve the error performance of encoding schemes. Cross-layer implementation on the network level is desired to improve the quality of service and effective usage of resources.
This set of Cognitive Radio online quiz focuses on “Next Generation Wireless Network – Cross Layer Design – 2”.
1. What is cross-layer design?
a) Cross-layer design allows non adjacent layers to exchange information which are traditionally relevant to a layer itself
b) Cross-layer design allows only adjacent layers to exchange information with each other
c) Cross-layer design provides control of lower layer functions to the upper layer functions
d) Cross-layer design provides control of upper layer functions to the lower layer functions
Answer: a
Explanation: Cross-layer design allows non-adjacent layers to exchange information which is traditionally relevant to a layer itself. By adapting cross-layer design, a global view of the radio framework and the surrounding environment can be obtained. It helps to eliminate problems that arise due to a lack of resource information at the time of transmission.
2. Which among the following statements is false about cross-layer design?
a) High quality of service can be provided by exchanging information among all layers of the protocol stack
b) Diverse waveforms are employed for power and modulation process
c) Cross-layer design helps to eliminate channel variations caused by blurring
d) Cross-layer design makes channel connections unpredictable
Answer: d
Explanation: Cross-layer design creates diverse waveforms to establish predictable connections under the existing channel conditions and medium access control parameters. High quality of service can be provided by exchanging information among all layers of the protocol stack. Cross-layer design also helps to achieve higher throughput.
3. Which among the following cannot be achieved by creating a mutual database?
a) Administration of capacity
b) Recovery of data
c) Rapid access to data by every layer
d) Limited resource usage
Answer: d
Explanation: The construction of a mutual database is one of the design methodologies employed in the implementation of the cross-layer design. A mutual database is built by combining information obtained from all layers of the protocol stack. It helps to administrate resource allocation as well as help in the recovery of data particular to each layer.
4. Which among the following is not a design methodology in the implementation of cross-layer design?
a) Exchange of information among several layers during run time
b) Storage of information in different storage structures
c) Construction of mutual database with easy access for each layer in the protocol stack
d) Construction of channel models to estimate the propagation of a signal in the channel environment
Answer: d
Explanation: Cross-layer design requires the characteristic parameters of each layer to be made available to other layers of the protocol stack during run time. In order to achieve this, different degree of abstraction is required. This requires the development of new data structures such as constructing squares for storing information.
5. Which among the following is a building unit of cross-layer hub?
a) Cross-layer intra hub module
b) Cross-layer interface
c) Cross-layer scheduler
d) Cross-layer director
Answer: a
Explanation: Cross design involves the sharing of information among different layers of the protocol stack. For example, spectrum occupancy information gathered in the physical layer must be accurately transferred to the MAC layer through a proper interface. The units required to implement the cross-layer design are interfaces, controllers, schedulers, and inter hubs.
6. Which among the following is not an expected result of cross-layer design?
a) High end to end throughput
b) Reduced network capacity
c) Reduced interference
d) Reduced power consumption
Answer: b
Explanation: Cross-layer design involves the exchange of information over various interfaces to achieve a better quality of service than possible by following the traditional layered approach. The exchange of information can be between physical and data link layer, data link and transport layer, network and transport layer, etc. Cross-layer design aims to achieve a high end to end throughput, increase the network capacity, optimize network utilization, reduce interference and power consumption.
7. Which among the following is not an advantage of employing cross-layer design implementation?
a) High accuracy of computation results required in algorithms
b) Elimination of wasteful calculations
c) High quality of service
d) Better performance during spectrum handoff
Answer: d
Explanation: Cross-layer design improves the accuracy and the productivity of algorithms by extending the amount of information at hand. Cross-layer design helps to adjust in accordance with the varying resource availability. It eliminates computations that are performed due to a lack of communication between the layers of the protocol stack.
8. Which layer performs adaptive modulation and coding?
a) Network layer
b) Transport layer
c) Physical layer
d) Data link layer
Answer: c
Explanation: Adaptive modulation and coding is the process of adjusting signal parameters such as the modulation type, coding technique, and protocol parameters to the characteristics of the channel selected for transmission. The adaptive modulation system requires channel state information at the transmitter.
9. Which among the following is not a function of the MAC layer in cognitive radio?
a) Manage accessibility of assets
b) Change client configuration
c) Change density of design
d) Choose multiple access techniques
Answer: d
Explanation: MAC layer in cognitive radio should manage the level of accessibility provided for resources of the radio. MAC layer should be aware of channel occupancy and surrounding spectrum environment to quickly handle changes in the environment and to mitigate loss produced due to mobility. MAC layer should have the capability to change design configuration.
10. Which among the following combination of layers can be used to improve blockage control?
a) Physical-Datalink
b) Datalink – network
c) Physical-Transport layer
d) Datalink- Transport layer
Answer: c
Explanation: The transport layer can correctly classify the reason for blockage provided the signal transmission information collected in the physical layer is made available via cross-layer design. For example, it can be used to detect the cause for packet loss.
11. What type of optimisation technique is represented in the following diagram?
a) Fuzzy Logic
b) Hidden Markov Model
c) Case Based Reasoning
d) Evolutionary Algorithm
Answer: a
Explanation: Fuzzy Logic is a many valued logic in which the value assigned to variable ranges between completely true to completely false. It is applied for frequently changing parameters or inaccurate parameters. It utilizes concepts such as enrolment capacities, semantic factors, and a central base.
Answer: a
Explanation: Cross-layer communication between data link and network layer can minimize the wastage of resources caused by packet loss. One approach involves allocating the resources for link-layer needs based on hop count in the network layer module. For higher hop count, the power is divided among the packets, and the best available channel is selected for transmission.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Communication Policies – 1”.
1. Which among the following are the recommendations proposed in the Spectrum Policy Initiative created in 2003?
a) Spectrum Sharing Innovation Test bed and Spectrum Sensing Tools
b) Spectrum Sharing Innovation Test bed and Spectrum Management Tools
c) Cross-layer Innovation Test bed and Spectrum Sensing Tools
d) Cross-layer Innovation Test bed and Spectrum Management Tools
Answer: b
Explanation: Spectrum Sharing Innovation Testbed and Spectrum Management Tools are the recommendations proposed in the Spectrum Policy Initiative created in 2003. Most of the recommendations pertained to the modification of the spectrum management infrastructure. The initiative states that technological advances can be exploited to overcome spectrum scarcity by spectrum sharing.
2. What is the purpose of Spectrum Sharing Innovation Test Bed?
a) Spectrum Sharing Innovation Test Bed sets aside a portion of the spectrum for testing
b) Spectrum Sharing Innovation TestBed determines terrain suitable for testing
c) Spectrum Sharing Innovation TestBed creates environment models for testing
d) Spectrum Sharing Innovation TestBed constructs conditioned chambers for testing
Answer: a
Explanation: Spectrum Sharing Innovation TestBed sets aside a portion of the spectrum for testing and evaluating the developing spectrum sharing methods. The Spectrum Policy Initiative predicted a likely surge in spectrum usage and developing spectrum sharing methods have to be tested accordingly.
3. What is the full form of CSIS organization?
a) Center for Skills and Intermediary Studies
b) Center for Skills and International Studies
c) Center for Strategic and International Studies
d) Center for Strategic and Intermediary Studies
Answer: c
Explanation: The Center for Strategic and International Studies is a private, bipartisan public policy research organization that offers inferences and solutions to current and upcoming problems. The center carries out strategic analyses of political, economic, and security issues with a focus on issues concerning international relations, trade, and technology.
4. Which among the following is a problem addressed by CSIS?
a) Shortage of short range plans
b) Lack of common spectrum testing techniques
c) Challenges in negotiating international spectrum agreements
d) Construction of flexible spectrum management infrastructure
Answer: c
Explanation: CSIS addressed four problems namely shortage of long range plans, lack of means to solve conflicts among spectrum management organizations, challenges in negotiating international spectrum agreements, and security and economic issues which might grow due to lack of technological development.
5. What are the recommendations proposed by CSIS for the improvement of spectrum management?
a) Establish fixed norms for proposing spectrum management algorithms
b) Establish research consortium to support the government and private sectors
c) Establish fixed regulations for spectrum sharing
d) Establish fixed regulations for spectrum sensing
Answer: b
Explanation: The research consortium sets goals for spectrum innovation research. It is responsible for solving technical conflicts that tend to arise with the change in technology. CSIS also recommended the formation of an organization comprising of the White House, National Security Council, National Economic Council, and spectrum advisory board.
6. Which among the following is the official US regulatory body for the RF spectrum?
a) International Organisation for Standardisation
b) Institute of Electrical and Electronics Engineers
c) American National Standards Institute
d) Federal Communication Commission
Answer: d
Explanation: Federal Communication Commission overlooks the communication carried out over radio, television, wire, satellite, and cable. The FCC consists of jurisdiction over the areas of broadband access, fair competition, radio frequency use, and public safety.
7. Which among the following is not addressed by the study conducted by Toffler associates in 2001?
a) Spectrum management
b) Technological impact of cognitive radio
c) Long term strategies for spectrum sharing
d) Methods of spectrum reallocation
Answer: b
Explanation: Toffler associates proposed a set of recommendations for spectrum policy. The study conducted by the Toffler associates focused on spectrum management, spectrum reallocation techniques, and long term spectrum sharing strategies. The group suggested the development of a framework capable of handling the changing techniques of spectrum access, spectrum sharing, and spectrum mobility.
8. Which among the following instigated a review of spectrum policy at FCC?
a) Establishment of Spectrum Policy Task Force
b) Establishment of research consortium
c) Collaboration with Federal Aviation Administration
d) Collaboration with the American National Standards Institute
Answer: a
Explanation: FCC stated that establishing the Spectrum Policy Task Force led to a thorough review of the spectrum policy of the FCC. The Spectrum Policy Task Force identified that a cognitive radio demanded changes in the spectrum policy. It also required different approaches to implement the spectrum policy.
9. Which among the following factors hinders effective spectrum usage according to the SPTF?
a) Lack of spectrum access
b) Lack of antenna technology
c) Lack of physical components of radios
d) Lack of high capacity processors
Answer: a
Explanation: Spectrum Policy Task Force identified the lack of capacity is due to the current regulations applied on spectrum access. SPTF supported multiple dimensional access of the spectrum. The FCC relies on SPTF to create spectrum policies and spectrum management techniques that could lead to better overall usage of the available spectrum.
10. Which among the following areas will not have an impact on cognitive radio?
a) Maximize the flexibility of spectrum usage
b) Promote spectrum access in rural areas
c) Apply a qualitative approach to interference management
d) Allow easement for spectrum overlays and underlays
Answer: c
Explanation: The recommendations proposed by SPTF maximize spectrum usage by allowing unlicensed users and promotes opportunistic spectrum access through secondary market policies. The SPTF promotes spectrum access in rural areas by altering the power levels, leasing, and geographical licensing.
11. The calculation of relative values of consumer services compared with scientific investigation and Earth exploration is a challenge imposed on policymakers by the mobile transmitter, mobile receiver configuration.
a) True
b) False
Answer: b
Explanation: The calculation of relative values of consumer services compared with scientific investigation and Earth exploration is a challenge imposed on policymakers by the mobile transmitter, fixed receiver configuration. This information helps in assigning the usefulness of creating a mechanism to access an unused spectrum in a location.
12. Which among the following is false about the defence science board?
a) Defence Science Board comprises of technology and business experts
b) Defence Science Board is a Federal Advisory Committee for the US Department of Defence
c) Defence Science Board researches for the FCC
d) Defence Science Board is identified that using spectrum multiple dimension can reduce spectrum scarcity
Answer: c
Explanation: Defence Science Board is an advisory committee composed of technology and business experts, which conducts research pertaining to the US department of defence. It identified that by utilizing the spectrum in multiple dimensions such as time, frequency, and modulation, spectrum scarcity can be reduced. It promoted real-time sharing of spectrum.
This set of Basic Cognitive Radio Questions and Answers focuses on “Next Generation Wireless Network – Communication Policies – 2”.
1. Which among the following do not belong to the fixed transmitter, mobile receiver configuration?
a) Broadcasting
b) Radio position determination
c) Radio astronomy
d) Standard time signal services
Answer: c
Explanation: Broadcasting primarily includes consumer communication applications such as AM, FM, etc. Radio positioning includes services such as GPS and radio navigation. The long-wave standard time signal produced by The National Institute of Standards and Technology which continuously broadcasts time and frequency signals at 60 kHz is an example of standard time signal services.
2. Which among the following is a policy challenge for the fixed transmitter, mobile receiver configuration?
a) Determining transmission parameters to avoid interference
b) Determining reception parameters to avoid interference
c) Determining the distance of propagation to avoid interference
d) Determining coverage area to avoid interference
Answer: a
Explanation: The major policy challenge for the fixed transmitter, mobile receiver configuration is the determination of transmission parameter levels which do not cause interference and are economically feasible. For example, determining the number of stations required for broadcasting in a region.
3. Which among the following would result in increased out-of-band rejection at receivers while broadcasting?
a) Periodic transmissions
b) Increased transmission power
c) Frequency reuse
d) Close band spacing between stations
Answer: d
Explanation: The close band spacing between stations is a potential method for increasing the station density. However it causes increased out-of-band rejection at the receivers. Reduction of transmission and increased frequency reuse are other approaches for increasing station density. However these methods result in reduced coverage.
4. Which among the following is true about passive sensing configuration?
a) Transmitter location is unknown
b) Receiver location is unknown
c) Base station location is unknown
d) Operational area is unknown
Answer: d
Explanation: Mobile transmitter, fixed receiver configuration includes active and passive meteorological and Earth exploration system. In passive sensing configuration, the operational area is unknown. In the active sensing configuration, the transmitter location is unknown.
5. What device characteristic is necessary for the mobile transmitter, fixed receiver configuration?
a) Sensitive transmitter
b) Sensitive receiver
c) Sensitive analog to digital converter
d) Sensitive digital to analog converter
Answer: b
Explanation: Mobile transmitter, fixed receiver configuration employs sensitive receivers. Sensitive receivers require the adjacent channel systems to have small out-of-band emission. This is achieved by using guard bands.
6. Which among the following configurations include radio astronomy services?
a) Fixed transmitter, mobile receiver
b) Mobile transmitter, mobile receiver
c) Fixed transmitter, fixed receiver
d) Mobile transmitter, fixed receiver
Answer: c
Explanation: Fixed transmitter, fixed receiver configuration includes point-to-point, point-to-multipoint, and radio astronomy services. Both endpoints are in fixed locations. The communication path may be one way between the transmitter and receiver or it may be two way between two transceivers.
7. Which among the following is a policy challenge for radio astronomy systems?
a) Determination reception parameters to avoid interference
b) Determination of the location of the fixed receiver
c) Determination of transmission power
d) Determination of operation frequency
Answer: b
Explanation: Radio astronomy studies the celestial phenomena by measuring the radio waves characteristics emitted by the physical processes occurring in space. The location of the fixed receiver is a policy challenge as the receiver has to be located at a spot with minimum interference from commercial systems.
8. Which among the following configuration include the private land mobile radio?
a) Fixed transmitter, mobile receiver
b) Mobile transmitter, mobile receiver
c) Fixed transmitter, fixed receiver
d) Mobile transmitter, fixed receiver
Answer: b
Explanation: Mobile transmitter, mobile receiver configuration includes a variety of mobile services. The private land mobile radio services allow governments, commercial organizations, and non-profit organizations to use mobile and fixed communication systems to guarantee safety, increase productivity and efficiency.
9. Which among the following is necessary to ensure operation free of interference?
a) Maximum data rate
b) Maximum coverage area
c) Minimum distance of operation
d) Minimum transmission power
Answer: c
Explanation: The mobile transmitter, mobile receiver configuration presents an environment with different power levels and unknown geometries between the receivers and transmitters. It is difficult to provide operation free of interference without fixing the minimum separation distance. In other words, all interference computations are performed assuming minimum separation distance.
10. Which among the following is a policy challenge of the mobile transmitter, fixed receiver configuration?
a) Conflict between the required amount of frequency by the radio system and frequency used
b) Determination of transmission power
c) Conflict between transmitter and receiver on encoding scheme
d) Determination of the location of the transmitter
Answer: a
Explanation: The policy challenge of the mobile transmitter, fixed receiver configuration is that the frequency usage is extremely small but it demands a large amount of frequency. The operational frequencies also tend to be particular to the physical characteristics of the chemicals that are to be sensed.
11. Center of Strategic and International Studies proposed a shift from the reactive spectrum management model to a proactive spectrum policy.
a) True
b) False
Answer: b
Explanation: Federal Communication Commission proposed a shift from the reactive spectrum management model to a proactive spectrum policy. FCC aims to put forth a spectrum policy that will improve the public benefits obtained from spectrum usage.
12. Which among the following institutions were involved in identifying the changes in Spectrum regulation?
a) Government Accountability Office
b) Defence Science Board
c) Toffler associates
d) Federal Communication Commission
Answer: d
Explanation: Many institutions of research and regulation conducted studies to analyze the need for spectrum and to identify the changes that need to be made to existing regulations and policies of the RF spectrum. Government Accountability Office, Defence Science Board, and Toffler associates were involved in analyzing the need for spectrum. Federal Communication Commission and the Center of Strategic and International studies were involved in identifying the modification of regulations.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Spectrum Awareness – 1”.
1. Which among the following is not an objective of cognitive radio?
a) Adapt to the available spectrum
b) Minimize radio presence in the spectrum environment
c) Maximize radio presence for the networks
d) Exploit spectrum holes
Answer: d
Explanation: The objectives of the cognitive radio are to minimize the radio presence in a network while gathering data about the spectrum from the spectrum environment and to adapt to the available spectrum determined from the gathered data. The dynamic characteristics of the cognitive radio rely on its ability to sense the propagation conditions.
2. Which among the following is a definition of spectrum efficiency?
a) Number of bits per Hertz of bandwidth
b) Number of bauds per Hertz of bandwidth
c) Number of Hertz per bit of symbol sequence
d) Number of Hertz per bit of symbol sequence
Answer: a
Explanation: Modulation designers describe spectrum efficiency in terms of the number of bits per Hertz of bandwidth. It is used as a metric for measuring the performance of modulation techniques.
3. Which among the following outcome occur on increasing the energy per bit exponentially as per Shannon limit?
a) Radiated spectral energy increases at the second power of the spectral information density
b) Radiated spectral energy increases at the third power of the spectral information density
c) Spectral information density increases at the third power of the radiated spectral energy
d) Spectral information density increases at the second power of the radiated spectral energy
Answer: b
Explanation: Shannon limit specifies the maximum rate at which communication can be carried out without error in a channel with a given bandwidth. Shannon limit supports a claim that spectrum efficiency of infinite bits per Hertz can be achieved by increasing energy per bit exponentially. This results in the increase of radiated spectral energy at the third power of spectral information density.
4. Which among the following is a traditional method employed for effective use of spectrum?
a) Minimization of nodes per second
b) Maximization of nodes per second
c) Maximization of bits per Hz
d) Minimization of bits per Hz
Answer: c
Explanation: Spectrum efficiency metrics of traditional digital communication is simple as it involves measuring only the number of bits per Hz. When the number of bits per Hz is maximized, a minimal amount of spectrum is occupied. However defining spectrum metrics for cognitive radio is difficult as it includes the area of propagation in addition to the amount of spectrum.
5. Which among the following is an appropriate unit for spectrum usage in cognitive radio?
a) Bits per unit area
b) Noise per unit area
c) Noise temperature per unit area
d) Symbols per unit area
Answer: a
Explanation: Spectrum usage in the cognitive radio includes the area of propagation along with the amount of spectrum used. Hence the number of bits per unit area is an appropriate unit for spectrum usage in cognitive radio. This necessitates the inclusion of propagation in the Shannon limit.
6. Which among the following is a not consequence of increasing modulation depth?
a) Increase energy need
b) Increase spectral efficiency
c) Reduce effective spectrum usage of other users of the spectrum
d) Reduced noise floor
Answer: d
Explanation: Modulation depth provides the degree of difference between a modulated signal and an unmodulated signal. The increase of modulation depth is a poor solution for effective spectrum usage as it increases the energy needs of the operation. It affects the operation of other spectrum users as it results in the increase of noise floor or it precludes the operation at quickly increasing radii from the transmitter.
7. Which among the following phenomenon considers the operation of other users of the spectrum?
a) Spectrum efficiency
b) Spectrum reuse
c) Channel capacity
d) Signal energy
Answer: d
Explanation: Spectrum reuse is a critical phenomenon that includes the optimal operation of other users of the spectrum through spectrum sharing. It involves reporting the information of spectrum usage to spectrum broker and distributing spectrum usage information to other nodes.
8. Which among the following is a common factor between peer to peer cognitive radio and a digital radio?
a) Automation
b) Inbuilt rules
c) Time cycle
d) Local operation
Answer: b
Explanation: Peer to peer cognitive radio rely on spectrum usage information from local neighbours but is mostly controlled by a set of comprehensive rules which are provided by the manufacturer. This reduces the amount of overhead in communication but leads to reduced efficiency. Decisions are taken by combining local spectrum awareness and inbuilt rules.
9. Which among the following is not a prerequisite for cooperative sensing?
a) Non-corrupt neighbouring radios
b) Knowledge of spectrum environment
c) Knowledge of limits of transmission parameters
d) Central entity
Answer: d
Explanation: Cooperative spectrum sharing involves sharing spectrum usage and noise information to other nodes of the spectrum. This mode considers the operation of other spectrum users thus raising the overall spectrum efficiency of the network. It requires non-corrupt neighbouring radios, knowledge of spectrum environment, understanding of limits imposed on transmission parameters, and transparent sharing of spectrum information by transmitters.
10. Which among the following institution introduced interference temperature as a metric for interference?
a) Federal Communication Commission
b) American National Standards Institute
c) International Standards Organization
d) British Standards Institute
Answer: a
Explanation: Federal Communication Commission introduced interference temperature as a metric for modeling interference at the primary user produced by the secondary user. It is a measure of RF power generated by undesired transmitters and noise sources that are present in the receiver system per unit of bandwidth.
11. Diffracted propagation undergoes attenuation at the rate of the third power of distance.
a) True
b) False
Answer: a
Explanation: Cognitive radio shifts communication from direct propagation to diffracted propagation. Diffracted propagation undergoes attenuation at the rate of the fourth power of distance. It hinders the ability of the radio to sense, calculate interference, and evaluate the outcome of communication.
12. Which among the following is false about multiple input, multiple output scheme?
a) MIMO generates multiple orthogonalized channel
b) Channel awareness is used to design link
c) Coverts multiple path into multiple channels
d) Eliminates multiple path
Answer: d
Explanation: Multiple input, multiple output is a technique that introduces multiple antennas at the transmitter and the receiver generating several paths for transmission. MIMO introduces channel awareness on an architectural level and is employed in the generation of links and topology. It utilizes multipath and converts multiple paths into multiple channels.
This set of Advanced Cognitive Radio Questions and Answers focuses on “Next Generation Wireless Network – Spectrum Awareness – 2”.
1. Which among the following is an advantage of using Fast Fourier Transform for spectrum sensing?
a) Analysis of computation complexity in the FFT window
b) Analysis of phase in the FFT window
c) Analysis of period enclosed in the FFT window
d) Analysis of frequencies enclosed in the FFT window
Answer: d
Explanation: Fast Fourier transform is used for performing spectrum sensing by using a wideband analog to digital converter and extensive digital signal processor. This method proves advantageous as it enables the analysis of frequencies enclosed in the FFT window.
2. Which among the following is not a limitation of employing FFT?
a) Wideband ADC is required
b) Restriction on bandwidth
c) Increased energy demand
d) High delay
Answer: d
Explanation: FFT operation demands wideband ADC and extensive digital signal processing. The ADC imposes restrictions on the instantaneous bandwidth. The energy usage is increased due to the high amount of digital signal processing.
3. Which among the following parameters do not exhibit better performance in the spectrum analyzer when compared to the FFT technique?
a) Complexity
b) Bandwidth
c) Short signal detection
d) Power
Answer: c
Explanation: Spectrum analyzers are employed for spectrum sensing by tuning to a band with the scan frequency adjusted to dwell at a frequency bin for a desired period. The spectrum analyzer exhibits reduced complexity and power requirements when receiver components are shared. It also scans over large ranges of signals.
4. Which among the following is accomplished by sampling sub-Nyquist in wideband FFT spectrum sensing?
a) Reduction of complexity
b) Improved signal detection
c) Reduced power consumption
d) Shorter time delay
Answer: d
Explanation: Time delay and interleaving time can be controlled by sampling sub-Nyquist and by using appropriate filters in wideband FFT spectrum sensing. The short delay simplifies compatibility with MAC layer timing.
5. Which among the following layers have a similar impact due to interference caused by primary user transmission?
a) Physical layer and MAC layer
b) MAC layer and network layer
c) Network layer and Transport layer
d) Transport layer and Physical layer
Answer: c
Explanation: The effect of primary user transmission on the MAC layer and network layer is complete and irreversible blockage of a packet. It can be mitigated by retransmitting acknowledgments in the MAC layer. It can be mitigated in the network layer by selecting protocol with effective packet restoration mechanisms.
6. Which among the following is the impact of primary user interference in the physical layer?
a) High bit error rate
b) High delay
c) High collision
d) High energy demand
Answer: a
Explanation: The effect of primary user interference in the physical layer is a high bit error rate. It can be mitigated by adjusting the coding dynamically. It also can be resolved by allowing higher layers to tackle interference for a period of time.
7. Which among the layers fail to route a packet due to primary user interference?
a) Physical layer
b) Data link layer
c) Network layer
d) Transport layer
Answer: d
Explanation: The effect of primary user interference in the transport layer is the failure to route a packet. It can be mitigated by identifying missing packets using the sequence number and requesting of the retransmission of the packets.
8. Which among the following is the impact of having poor spur free dynamic range?
a) Difficulty in short signal detection
b) Overloading
c) Additive noise
d) High complexity
Answer: c
Explanation: Spur free dynamic range is the maximum range over which self-generated signals are absent. Poor SFDR results in spur which resembles tonal signals and give the appearance of an occupied signal. This results in the addition of noise to the received signals.
9. Which among the following results in low sensitivity?
a) Poor collision mitigation mechanism
b) Poor signal processing
c) Poor noise figure
d) Poor linear noise amplifier performance
Answer: c
Explanation: Noise figure quantifies the amount of self-generated noise at the receiver. It lower sensitivity and makes it difficult to find other users of the spectrum. Decreased sensitivity causes a reduction in the amount of power allowed for transmission.
10. Under good propagation conditions, increasing the transmission energy is a poor technique to increase spectrum efficiency.
a) True
b) False
Answer: a
Explanation: Effective spectrum usage considers both the amount of spectrum used and the area of propagation. Under good propagation conditions, increasing the transmission energy is a poor technique to increase spectrum efficiency. By increasing the efficiency of a single radio, the spectrum cannot provide proper communication conditions for other users of the spectrum.
11. Which among the following statements holds true about the give graph?
a) The energy required per bit increases exponentially with exponential increase in bits per Hertz
b) The energy required per bit increases linearly with exponential increase in bits per Hertz
c) The energy required per bit increases linearly with linear increase in bits per Hertz
d) The energy required per bit increases exponentially with linear increase in bits per Hertz
Answer: d
Explanation: The graph shows that the energy required per bit increases linearly with exponential increase in bits per Hertz. The cost of energy varying from one to two bits per Hertz is equal to the variation from six to sever bits per Hertz. Bits per Hertz can be a valid measure for spectrum efficiency provided perfectly stable channel and power are available.
Answer: a
Explanation: The removal of uncertainty can reduce the required amount of power at the cognitive transmitter with the certainty of non-interference to the victim receiver. Although multipath scenarios cannot be eliminated, installing multiple sensors to observe the same transmission can reduce the amount of assumption about interference.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Position Awareness – 1”.
1. Which among the following statements is false about a very high frequency omnidirectional range ?
a) VOR is a radio navigation system for aircrafts
b) The frequency range of VOR is 108.00 to 117.95 MHz
c) VOR is intolerant of diffraction
d) VOR signals show more accuracy than nondirectional radio beacon
Answer: c
Explanation: Very high frequency omnidirectional range is a radio navigation system incorporated in aircrafts to stay on route with the help of radio signals transmitted by a network of ground radio beacons. A prominent feature of VOR is that the bearing from the station to the aircraft is unaffected by wind and orientation of the aircraft.
2. Which among the following is used to determine the position of an aircraft using very high frequency omnidirectional range ?
a) Round trip time of a radial from a single VOR station
b) Intersection of radials from a single VOR station in different directions
c) Intersection of radials from a single VOR station with a delay between the signals
d) Intersection of radials from two different VOR stations
Answer: d
Explanation: Line of position in very high frequency omnidirectional range is called the radial. The line of position consists of a highly directional signal sent by the VOR ground station using a phased antenna array and a reference signal in phase with the directional antenna. The intersection of radials from two different VOR stations is used to determine the position of an aircraft.
3. What is the accuracy range offered by very high frequency omnidirectional range?
a) 50 m
b) 60 m
c) 80 m
d) 90 m
Answer: d
Explanation: Very high frequency omnidirectional range is a short-range radio navigation system. The signals are kept in the line of sight between the transmitter and receiver. It offers an accuracy of 90 m.
4. Which among the following techniques is employed in long range navigation ?
a) Round trip time of a radio pulse
b) Time difference between two radio pulses
c) Phase difference between two continuous signals
d) Phase difference between the transmitter and the receiver
Answer: b
Explanation: Long range navigation is a hyperbolic radio navigation system operating at low frequencies. The hyperbolic navigation system in LORAN uses the time difference between radio pulses to locate the object of interest. An electronic clock was employed to generate trigger signals that maintain a fixed delay such as 1 ms between the transmitters.
5. What is the parameter which differentiates LORAN – B from LORAN – A?
a) Method of extraction of timing
b) Number of receivers
c) Number of transmitters
d) Determination of station location
Answer: a
Explanation: LORAN – B employed phase comparison variation and hence used a different method of timing extraction compared to LORAN A. The disadvantage of LORAN B is that its pulse length was about 40 microseconds and the technique exhibited phase distortion.
6. Which among the following techniques were employed for the identification of pairs in LORAN stations?
a) Modulation technique
b) Encoding scheme
c) Phase comparison between signals
d) Pulse repetition frequency
Answer: d
Explanation: LORAN stations are composed of a master station and two slave stations. Each pair typically broadcasted over the following frequencies of 1.75, 1.8, 1.85, or 1.9 MHz. However, the location of stations is such that it allowed a particular station to pick up signals from at least three stations. Thus to detect to pairs of signals, pulse repetition frequency comparison is employed.
7. Which among the following is essential for geo-location using IP address?
a) Database of registration lifetime of IP packets
b) Database of IP addresses
c) Database of routing path
d) Database of port address
Answer: b
Explanation: Geo-location software translates an IP address into a geo-location and provides the name of a country, city, or zip code. The software exploits the IP address of the sender included in the IP packet. There are a number of geo-location databases that offer different levels of accuracy.
8. Which among the following are sources for constructing an IP database?
a) Network routing information
b) Data mining
c) Regional Internet registry
d) Data scrubbing
Answer: d
Explanation: The primary source of the IP address database is the regional internet registries that assign the IP addresses to organizations within their service area. Network routing information extracted at the endpoint of an IP address, data mining, and data provided by Internet Service Providers are useful for constructing the IP database.
9. Which among the following is an application of geo-location software?
a) Regional licensing
b) Firewall
c) Address translation
d) Diagnostic tools
Answer: a
Explanation: Internet services such are live streaming sporting events, or online streaming of television shows and music might be permitted to broadcast only over certain licensed territories. Geolocation is applied to avoid license violations. Fraud detection, Geomarketing, and gaming are other regions of interest.
10. Very High Frequency Omnidirectional Range begins with transmission of frequency modulated signal.
a) True
b) False
Answer: b
Explanation: Very High Frequency Omnidirectional Range begins with transmission of amplitude modulated signal with a constant frequency. The transmitted signal passes through a set of antenna in a circle introducing frequency modulated Doppler onto the received signal. The relative phase angle between amplitude modulated signal and frequency modulated signal is employed to find the location of the source.
This set of Cognitive Radio Problems focuses on “Next Generation Wireless Network – Position Awareness – 2”.
1. Which among the following is not an outcome of destination location addressing?
a) Reduced interference
b) Reduced power consumption
c) Reduced handovers
d) Reduced dropped calls
Answer: c
Explanation: Destination location addressing propagates via only known nodes in a path to reach the destination. This prevents signal propagation from running off course and optimizes power consumption. It also results in the reduction of interference and dropped calls by combining the knowledge of geolocation, velocity vector, and planned path.
2. Which among the following is not a common feature between the time of arrival and time difference of arrival?
a) Straight-line of sight
b) High resolution system clock
c) Propagation at speed of light
d) Shape of curve
Answer: d
Explanation: Time of arrival and time difference of arrival are two time-based approaches. Both approaches require a high-resolution system clock with signals that propagate at the speed of light. It requires a straight line of sight path as the signal delay directly relates to the line of sight distance.
3. Which among the following is not a step in time of arrival and time difference of arrival process?
a) Analysis of signal propagation
b) Track error bound
c) Conversion to equation
d) Analysis of channel path
Answer: d
Explanation: The signal propagation is analyzed by multiple receivers or by multiple antennas. This results in the conversion of the time delay to the phase difference, time difference, or frequency shift which is then converted to equations of range, or other parameters.
4. Which among the following is an essential for the time of arrival approach?
a) Time tag and phase tag the transmitted signal
b) Phase tag the transmitted signal
c) Time tag and frequency tag the transmitted signal
d) Time tag the transmitted signal
Answer: d
Explanation: The time of arrival approach relies on time tagging the transmitted signal and computing the time of arrival of the signal at the receiver. When many receivers with known locations obtain the same signal, the multiple iso-range spheres intersect providing the location of the transmitter. Likewise, when transmitters provide knowledge of their location in the time-tagged transmitted signal, a receiver can compute its location.
5. What curve is obtained by plotting the time difference of arrival?
a) Parabola
b) Sphere
c) Hyperbola
d) Ellipse
Answer: c
Explanation: The time difference of arrival approach involves computing the time difference between the reception of a signal at one location and the reception of the same signal at a different location. The plot of time difference of arrival produces a hyperboloid surface with its foci at the two receivers.
6. How many surfaces are required to geolocate a transmitter on a two-dimensional plane using time difference of arrival approach?
a) Two
b) Three
c) Four
d) Five
Answer: b
Explanation: When a number of receivers at known locations receive the same sign, the obtained hyperboloids intersect at the location of the transmitter. The number of surfaces required to geolocate a transmitter in 2 D plane is three and the number of surfaces required to geolocate a transmitter in 3 D plane is four.
7. What type of signal is employed by LORAN?
a) Intermittent
b) Continous
c) Burst
d) Buffer
Answer: c
Explanation: LORAN system sends a known burst signal with fixed periodicity from multiple transmitters. The receivers construct time difference of arrival hyperboloid curve to determine the location of the transmitter. LORAN provides published charts corresponding to hyperboloid curves, to find the intersection of two-time difference pairs.
8. Which among the following is the first step in the determination of position using time difference of arrival?
a) Time tag the transmitted signal
b) Solving for the position of source transmitter
c) Determining the time difference of arrival curve
d) Conversion to a common coordinate system
Answer: a
Explanation: The hyperboloid curve of time difference of arrival approach is drawn by considering the speed of propagation and difference between the arrival times of the same signal at two receivers. To expand the curve to include three receivers, the results are converted to a common coordinate system. Finally, the curve equations are solved to identify the position of the source.
9. Which among the following computations might be employed as a technique for determining the time difference of arrival?
a) Cross-correlation
b) Probability density function
c) Cumulative density function
d) Standard deviation
Answer: a
Explanation: Time can be estimated using correlation in a wideband transmission environment. In time difference of arrival approach, the received signals are digitized in their corresponding stations and are transferred to a common processing location for calculating cross correlation. The peak of the cross correlation provides the time difference of arrival.
10. The angle of arrival approach requires antenna array at the receivers.
a) True
b) False
Answer: a
Explanation: In the angle of arrival approach, multiple receivers combine to compute the angle of arrival. The technique requires an antenna array at the receivers. The bearing to the signal and the known location of multiple receivers provide the location of the transmitter.
11. Which among the given conditions is represented in the following diagram?
a) Hyperbola one receiver and source in the same plane and the second receiver in another plane
b) Hyperbola with two receivers and source in the same plane
c) Hyperbola with two receivers in the same plane and source in another plane
d) Hyperbola with each receiver in one plane and a source in another plane
Answer: c
Explanation: The time difference of arrival approach involves computing the time difference between the reception of a signal at one location and the reception of the same signal at a different location. The hyperboloid curve of time difference of arrival approach is drawn by considering the speed of propagation and difference between the arrival times of the same signal at two receivers. When the receivers and the source are present in the same plane, the hyperbola appears V-shaped with an axis of symmetry through the two receivers.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Cognition Policy Engine – 1”.
1. Which among the following is an important assumption while operating with the Policy Core Information Model?
a) No storage is necessary
b) Cooperative storage
c) Centralized storage
d) Distributed storage
Answer: c
Explanation: Policy Core Information Model utilizes a centralized database. The policy enforcement point sends a request for a policy decision to the policy decision point. The policy decision point obtains information from the centralized database to take policy decisions.
2. Which among the following is the first step in the operation of a cognition policy engine?
a) The cognitive engine transfers data to the policy engine
b) The policy engine requests data from cognitive radio
c) The policy engine obtains the set of policies to be downloaded
d) The policy engine determines the information of interest
Answer: c
Explanation: The first step in the operation of the cognition engine is to collect the set of policies to be downloaded for the operation of the radio. The policy next determines the information to be monitored on the radio platform. Then the cognitive radio grants the policy engine with the requested situational data. This results in the processing of appropriate policy rules.
3. The policy requests and decisions exchange between the policy decision point and policy enforcement point may be over common open policy service.
a) True
b) False
Answer: a
Explanation: The common open policy service belongs to the internet protocol suite. It offers a client/server model for providing policy control over the quality of service signaling protocols. The policy requests and decisions exchange between the policy decision point and policy enforcement point may be over common open policy service.
4. Which among the following statements is true about the spectrum policy management?
a) Eliminate cooperative sensing
b) Eliminates network administrators
c) Resolve conflicts in policy rules
d) Maintain homogeneity with legacy radios
Answer: c
Explanation: The spectrum policy management solves the conflicts in policy rule by identifying inconsistencies. It depends on the network administrators to determine the applicable spectrum policy for the spectrum environment, spectrum sharing mechanism, and other issues that arise due to cross layer design.
5. Which among the following is not a function of spectrum policy management?
a) Monitor spectrum utilization
b) Detect RF interference
c) Control run-time configuration of cognitive radio
d) Authorization of updates in cognitive radio
Answer: d
Explanation: Spectrum policy management analyses spectrum utilization and detects RF interference. The configuration of the cognitive radio during run time is controlled by spectrum policy management to meet the selected spectrum policies. However, it requires authorization to perform changes to the radio.
6. Which among the following preceded the DARPA NeXt Generation radio communication program?
a) FFC Policy-Based Survivable communication program
b) DARPA Policy-Based Survivable communication program
c) FCC Frequency Agile Radio
d) DARPA Frequency Agile Radio
Answer: b
Explanation: DARPA Policy-Based Survivable communication program preceded the development of DARPA NeXt Generation radio communication program. It provided high survivability in the military environment and better performance gain could be achieved by downloading dynamic mission policies to supervise the radio networks automatically.
7. Which among the following is not a goal of the DARPA NeXt Generation radio communication program?
a) Dynamically redistribute allocated spectrum
b) Sense spectrum automatically
c) Expand communication bandwidth
d) Select operating mode
Answer: c
Explanation: The DARPA NeXt Generation radio communication program aims to develop a radio with technology that can dynamically redistribute the available spectrum in radio networks, thereby making the best use of available communication bandwidth. The spectrum should be sensed automatically. The selected operating mode should maximize the survivability of communication networks and reduce the amount of interference to other users of the spectrum.
8. Which among the following languages initially influenced the KAoS policy language?
a) DARPA Agent Markup Language and Knowledge Query and Markup Language
b) DARPA Agent Markup Language and eXtensibleMarkup Language
c) DARPA Agent Markup Language and RoXenMarkup Language
d) eXtensible Markup Language and RoXenMarkup Language
Answer: b
Explanation: KAoS policy language expresses and applies policies in the software agent context. It was initially based on DARPA Agent Markup Language and eXtensibleMarkup Language. But due to poor descriptive logic of DAML, KAoS shifted towards the Web Ontology Language to represent knowledge about domains and rule-based policies.
9. Which among the following is not a primary rule of role based access control?
a) Role definition
b) Role assignment
c) Role authorization
d) Permission authorization
Answer: a
Explanation: Role based access control is a mechanism that provides access depending on roles and the corresponding privileges and does not rely on policies. It can implement mandatory access control as well as discretionary access control. The following are the primary rules namely role assignment, role authorization, and permission authorization.
10. Which among the following protocol is employed management information base?
a) Telecommunications Network
b) Simple Network Management Protocol
c) Network File System
d) File Transfer Protocol
Answer: b
Explanation: The management information base is a device-specific database that uses the Simple Network Management Protocol for remotely managing a network resource on the basis of IP communications. The MIB should provide a standard interface for monitoring and configuring a device to gain the support of IP capable devices.
This set of Cognitive Radio written test Questions & Answers focuses on “Next Generation Wireless Network – Cognition Policy Engine – 2”.
1. Which among the following functions is not supported by the Ponder policy management framework?
a) Administration of domain hierarchies
b) Positive authorization
c) Negative authorization
d) Memory optimization
Answer: d
Explanation: The ponder policy management framework consists of a policy language with a set of tools and source code available freely on the internet. The tools can administrate domain hierarchies, allow positive and negative authorization policies, delegate policies, and support event-triggered condition-action rules.
2. Which among the following policies is associated with event-triggered condition-action rules?
a) Obligation policies
b) Authorization policies
c) Assignment policies
d) Acknowledgment policies
Answer: a
Explanation: The Ponder language is regarded as a declarative, object-oriented language that can define obligation and authorization policies. Obligation policies are event-triggered condition-action rules that can be used to describe adaptable management actions. Authorization policies are used to define the set of resources available for each user access.
3. Which among the following is a unique feature of Ponder language?
a) Analysis
b) Authorization
c) Priority assignment
d) Memory optimization
Answer: c
Explanation: Policy language allows assignment of priorities and preference. Priority assignment aids in the resolution of conflicts as the sequence of execution is clearly defined. It allows the prioritization of rules to reflect local management priorities. For example, a rule can ensure that efficiency is given more importance than reliability.
4. Which among the following plays the role of a policy decision point in KAoS?
a) Priority manager
b) Spectrum broker
c) Domain manager
d) Resource administrator
Answer: c
Explanation: KAoS is a semantic web language and is used to enforce policies in terms of software context. The domain manager operates as the policy decision point and interprets policies to control the behaviour of the network. It administers policies ranging over all domains.
5. Which among the following can be observed as a result of hierarchical policy management?
a) Extension of policy decision point beyond linear order of priorities
b) Introduction of rigidity between groups
c) Higher degree of abstraction
d) Easy access between management units
Answer: a
Explanation: Hierarchical policy management and domain groupings introduce additional flexibility by allowing a policy decision point to extend beyond the linear ordering of priorities. In the inheritance hierarchy, policies created from the local domain have higher priority in the device.
6. Which among the following is the function of meta-policies?
a) Resource allocation
b) Administration of layer-specific application hierarchies
c) Administration of domain hierarchies
d) Handle non-linear priorities
Answer: d
Explanation: Metapolicies can aid policy decision point in handling nonlinear priorities, solving conflicts, and ambiguities between overlapping rules. Metapolicies constrain the interpretation of groups of policies. For example, language can permit the addition of domain-specific information without modification.
7. Which among the following is the expansion PCIM framework?
a) Priority Core Infrastructure Model
b) Policy Core Infrastructure Model
c) Policy Core Information Model
d) Priority Core Information Model
Answer: c
Explanation: Policy Core Information Model initiated the process of standardizing policy management terminology. It represents network management policies. The framework can support vendor-specific implementations.
8. Which among the following is not a primary goal of network access part of the cognitive policy engine?
a) Promote manual control of networks
b) Develop machine-readable policies
c) Security
d) Network application performance
Answer: a
Explanation: Network policy management involves the creation of policy enabled devices that are capable of enforcing policies. The administrators use policy languages to represent network objectives. Policy servers configure the device to accomplish the objectives. Security, optimization of the performance of network applications, automating the control of networks, and the development of machine-readable policies are the primary objectives.
9. In common open policy service, the provisional models store all policies at the policy decision point.
a) True
b) False
Answer: b
Explanation: Common open policy service has two models namely the outsourcing model and the provisional model. In the outsourcing model, the policy decision point holds all policies. In the provisional model, only the policies requested by the policy enforcement point are downloaded.
10. Which among the following options should replace the labels ‘A’, ‘B’, and ‘C’?
a) Status monitor, Policy engine, Policy database
b) Policy database, Policy engine, Status monitor
c) Status monitor, Policy database, Policy engine
d) Policy engine, Policy database, Status monitor
Answer: b
Explanation: The policy engine interprets and enforces spectrum policies. Additionally, it overlooks platform events to provoke alteration in the radio function. The interface between the policy engine and radio platform represents the controlling and monitoring functions of the radio.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Network Cognitive Techniques”.
1. Which among the following is not a challenge identified by Situation-Aware Protocols in Edge Network Technologies developed by DARPA?
a) Knowledge representation
b) Learning
c) Composition
d) Observation
Answer: d
Explanation: Situation-Aware Protocols in Edge Network Technologies was developed to determine the effectiveness of cognitive approaches to adaptive composition and the adaption of protocol structures. Knowledge representation, learning, selection, and composition are the challenges identified by SAPIENT.
2. Which among the following is not a characteristic of transactional applications?
a) Large delay
b) Timing variability
c) Small transmitted packets
d) Variably sized received packets
Answer: a
Explanation: Transactional applications exhibit small packet sizes, variable sizes in received packets, and variability in timing. On the other hand, a constant packet size with inter arrival delay is typically observed in media applications.
3. Which among the following processes are combined to select protocol elements?
a) Network information and media access control information
b) Network information and application information
c) Protocol element knowledge and application information
d) Protocol element knowledge and network information
Answer: c
Explanation: Protocol element knowledge is responsible for adapting to network conditions. Protocol element knowledge and application knowledge are combined to select and define protocol elements.
4. Which among the following is a network parameter that should be considered while framing a new policy?
a) Latency
b) Topology
c) Flow rate
d) Bit error rate
Answer: a
Explanation: Network parameters namely packet ordering, packet checksums, packet loss, congestion, link capacity, link failure, latency, and strength of a signal on the link are essential to validate a new protocol. High end sensors can be employed to calculate hysteresis and damping algorithms to mitigate noise that provokes unwanted response.
5. Which among the following is an objective of sensing the network conditions?
a) Automatic sensing of repeaters in the route
b) Automatic detection of quality of service requirements
c) Creation of a database of application requirement
d) Measurement of parameters that maintain present working state
Answer: d
Explanation: Network conditions are sensed to detect the values of parameters that are essential to maintain the present working state and also for pursuing new states. A system generally initiates with TCP/IP configuration, and modifications are applied to improve the performance. When a protocol composition is incompatible, network sensing is responsible for identifying the source of the defect as well as for selecting an appropriate protocol.
6. Which among the following is achieved by introducing virtual infrastructure beneath the transport layer?
a) Inheritance
b) Interoperability
c) Encapsulation
d) Polymorphism
Answer: b
Explanation: The interoperability IP infrastructure is built based on modular programming and data abstraction. The operational challenges of a layer are confined within that layer. The data is transferred by using packets or is included as additional information in the procedural call between layers.
7. Which among the following is an objective of interoperable virtual IP infrastructure?
a) Flow control
b) Error control
c) Congestion control
d) End to end connectivity
Answer: d
Explanation: The interoperable virtual IP infrastructure can combine a number of incompatible subnetworks into a virtual network. This enables the assumption that the properties of the network correspond to the end to end protocols. The internetwork is constructed over several subnetworks, and routes to provide end to end connectivity.
8. Which among the following may result in the failure of link-layer checksum?
a) Negative acknowledgment
b) Error burst
c) Route failure
d) Packet loss
Answer: b
Explanation: The failure of link layer checksum determined by the device driver for a line card used to connect the host to the network indicates error bursts on a link. Likewise, a high delay in communication among a group of hosts indicates congestion.
9. Which among the following is not a parameter of influence while constructing adaption schemes for a network?
a) Compatibility of composition with objective
b) Knowledge of inherent assumptions
c) Knowledge of database evaluation
d) Knowledge of external conditions
Answer: a
Explanation: The structural adaption scheme requires knowledge of external conditions that influence the protocol elements. It also requires knowledge of inherent assumptions relevant to certain protocol elements that affect its sustainability. It requires the mapping of composition with the objective to achieve the desired quality of service.
10. What are terms that should replace the label ‘A’ and ‘B’?
a) Predefined protocols, Rule based protocols
b) Static algorithms, Situation aware protocols
c) Situation aware protocols, Static algorithms
d) Rule based protocols, Predefined protocols
Answer: b
Explanation: Under good network conditions, good throughput with low latency can be achieved with minimal protocol support. However with deteriorating channel conditions, advanced protocol mechanisms capable of adapting to the changing channel conditions required. These protocols have compensatory mechanisms extending towards applications that are not satisfied by traditional architectures.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – User Cognitive Techniques – 1”.
1. Which among the following is an application of speech recognition?
a) Stress characterization
b) Network support
c) Access control
d) Decoding
Answer: c
Explanation: Speech recognition supports access control by providing user authentication. Voice comparison can be used to establish the identity of a person. It can also be employed to identify communicating parties and personalization of devices.
2. Which among the following is the process of providing voice samples to generate a template in speech recognition?
a) Authentication
b) Verification
c) Identification
d) Enrollment
Answer: d
Explanation: Voice samples are obtained from users to generate a model or a template. The verification phase involves the comparison of a signal taken from the application with that of a template for matching. The result of verification may be positive or negative identification.
3. Which among the following parameters influence errors that occur in speaker recognition?
a) Amplitude dependency
b) Pitch dependency
c) Text dependency
d) Rate of speech dependency
Answer: c
Explanation: Speaker recognition consists of two errors namely false recognition and recognition failure . The systems are characterized by whether the speech is dependent on text involving phrase prompts or independent of text such as a conversational speech.
4. Which among the following categories include a badge for authentication?
a) Traits
b) Knowledge
c) Token
d) Behaviour
Answer: c
Explanation: The major categories of user authentication are knowledge, traits, token, and behaviour. PINs and passwords are associated with knowledge. Keys and badges are associated with tokens. Behaviour involves usage patterns. Features such as voice and fingerprint are used to sense behaviour. An implementation including four categories offers strong protection.
5. Which among the following is false about behaviour based authentication?
a) Behaviour authentication supports continuous mode operation
b) Behaviour authentication includes recognizing patterns
c) Behaviour authentication includes biometric detection
d) Behaviour includes network interaction
Answer: c
Explanation: Behaviour based user authentication involves recognizing actions, interests, tendencies, and patterns. Behaviour based user authentication exhibits minimal intrusion to user activity, and is transparent. It supports continuous mode operation and requires a limited amount of resources.
6. Which among the following is not a disadvantage of adapting specialized hardware for processing?
a) Update management
b) Functionality modification
c) High bandwidth requirement
d) Security
Answer: d
Explanation: Biometric based user authentication obtains input information through an input device such as a microphone, camera, etc. The information is processed by using software, or specialized hardware. Specialized hardware increases the complexity of introducing updates and modifying functionalities on the fly. Software processing offers lower security than specialized hardware.
7. Which among the following is a traditional method for language identification?
a) Phrase translation
b) Word translation
c) Letter translation
d) Phonetic translation
Answer: d
Explanation: Phonetic transcription is a traditional method for language identification. Phones are the subunits of basic sounds of speech. The relation between the occurrences of phones in different language is analyzed to develop a statistical model for each language for identification.
8. How to obtain cepstrum coefficients?
a) Cepstrum coefficients are obtained by taking Fourier transform of the spectrum
b) Cepstrum coefficients are obtained by taking Fourier transform of decibel spectrum
c) Cepstrum coefficients are obtained by taking Laplace transform of decibel spectrum
d) Cepstrum coefficients are obtained by taking Laplace transform of the spectrum
Answer: b
Explanation: Cepstrum coefficients are features employed in speech signal processing. It is obtained from the spectrum of a speech signal. Cepstrum coefficients are obtained by taking the Laplace transform of the decibel spectrum. Shifted delta cepstrum coefficients measure the changes in the speech spectrum over multiple frames of spectrum to model language characteristics.
9. Which among the following is not a region of interest associated with text to speech conversion?
a) Transcript generation
b) Pronunciation of named entities
c) Quality of voice synthesis
d) Conveyance of expression
Answer: a
Explanation: Text to speech conversion voices textual information. The source of the information could be text based communication or display readouts. The regions of interest are associating news with particular voice and tone, producing human sounding voice, pronunciation of named entities, quality of voice synthesis, and conveyance of expression.
10. Speaker stress characterization enables cognitive radio to assess the success of a decision on the basis of verbal cues.
a) True
b) False
Answer: a
Explanation: Speaker characterization is the process of finding the emotional state of a user through speech processing. Knowledge of stress state helps to improve situational awareness, identify irritation, determine stress level, and assess the success of a decision on the basis of verbal cues.
This set of Cognitive Radio Question Paper focuses on “Next Generation Wireless Network – User Cognitive Techniques – 2”.
1. Which among the following is the maximum limit on one way delay for normal conversation?
a) 450
b) 500
c) 400
d) 300
Answer: d
Explanation: The allowable one way delay for normal conversation is less than 300 millisecond seconds. Speech coding provides intelligible and quality speech, stress detection, language independence, error free transmission, and tone communication.
2. Which among the following is not a requirement of services that are explicitly invoked?
a) Replicate user interface
b) Modeling user intent
c) Common means to describe user state
d) Automatic detection of input modality
Answer: d
Explanation: Services can be provided by automatic detection or by explicit request. Cognitive radio employs hybrid request handling techniques with respect to the applications. The service requires interfaces to represent the user state, predict the outcome of a task, and to duplicate the human interface.
3. Which among the following statements is false about background suppression?
a) Enhance the effectiveness of text to speech conversion
b) Enhance the effectiveness of a speed coder
c) Extract useful background noise
d) Enhance communication in the presence of noise
Answer: a
Explanation: Background noise suppression enhances the effectiveness of communication and speech coders. It is used to extract information that can be utilized to introduce situational awareness. It also employed to increase voice quality and the cognition level of coded speech.
4. Which among the following is the first step in auditory scene analysis?
a) Pitch scale detection
b) Filtering
c) Grouping
d) Segmentation
Answer: d
Explanation: Auditory scene analysis consists of two steps namely segmentation and grouping. Initially, the auditory scene is subdivided into time-frequency zones or segments that exhibit coherent structure. Then the segments tracing back to the same source in auditory streams are grouped.
5. What are the two mechanisms applied in auditory scene analysis?
a) Controlled mechanism and off-controlled mechanism
b) Master mechanism and slave mechanism
c) Serial mechanism and intermittent mechanism
d) Simultaneous mechanism and sequential mechanism
Answer: d
Explanation: Simultaneous mechanism permits the arrangement of segments on the basis of frequencies. The sequential mechanism locates the segments with similar properties in time.
6. Which among the following operation employs heuristic rules in computational auditory scene analysis?
a) Re-synthesis
b) Source extraction
c) Segmentation
d) Grouping
Answer: b
Explanation: Computation auditory scene analysis applies heuristic grouping rules developed using psychological observations to separate a source from a single channel of audio. It separates the sound into music, voice, noise, etc.
7. Which among the following provides the procedure of active suppression?
a) Filter with cut off frequencies
b) Emission of sound to cancel noise
c) Emission of sound to shape noise
d) Extraction of noise sample
Answer: b
Explanation: Active noise suppression mitigates the noise experienced by a user by producing a sound to compensate for the undesired noise field. It can reduce the damage inflicted by exposure to high noise levels and reduce the Lombard effect.
8. Which among the following learning methods does not involve explicit planning?
a) Channel based
b) Network based
c) Reactive
d) Adaptive
Answer: c
Explanation: Reactive reasoning and learning does not involve explicit planning. The cognitive system can be programmed to respond to user voice commands and common device configurations. The adaptive cognitive radio stores user preferences, incorporates speech recognition models, and user intent models to learn from past experiences.
9. Which among the following is a disadvantage of network based reasoning?
a) False recognition
b) Protocol standardization
c) High memory requirements
d) Exhaustive resource utilization
Answer: b
Explanation: Cognitive radio can utilize a large network of services to complete user requests. Network based reasoning can collect information localized to a location such as finding restaurants, detecting traffic, detecting weather, etc. It introduces flexibility in the radio and reduces the amount of resources used. However, it exhibits poor latency and requires protocol standardization.
10. Mixed excitation linear prediction coding standard is employed for speaker stress characterization.
a) True
b) False
Answer: b
Explanation: Mixed excitation linear prediction coding standard was developed for speech compression. It supports bit rates of 600 bits/s, 1200 bits/s, and 2400 bits/s. It can be employed for background noise suppression by integrating with spectral subtraction.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Radio Environment Map – 1”.
1. What is a radio environment map?
a) Radio environment map represents a collection of access points in the immediate vicinity
b) Radio environment map provides insight on radio environment over multiple domains such as regulation and frequency emission
c) Radio environment map represents cognitive radios in the immediate vicinity
d) Radio environment map represents cognitive radios participating in cooperative sensing
Answer: b
Explanation: Radio environment map provides an abstraction of real time radio environment. It defines the radio environment of cognitive radio using multiple characteristic features such as geographical conditions, regulation, policy, capability of radio equipment, and radiofrequency emissions.
2. Which among the following statements is false about the radio environment map?
a) Radio environment map does not require complex circuitry in the user device
b) Radio environment map records radio frequency emissions
c) Radio environment map is a spatiotemporal database
d) Available resource map is extended from a radio environment map
Answer: d
Explanation: Radio environment map is a spatiotemporal database capable of supporting cognitive functionalities such as planning, learning, and reasoning of the user equipment. The radio environment map is an extension of the available resource map which includes all radio activities in the unlicensed wide area network in real time.
3. Which among the following incorporates knowledge to support cognition functionality?
a) External administration support
b) Internal administration support
c) External network support
d) Internal network support
Answer: c
Explanation: External networks are other networks in an area with knowledge to promote cognition functionality. For example, a sensor network created to gather information on cognitive radio networks. Internal network offer communication services and cognition functionality.
4. Which among the following is an advantage of spectrum sensing with radio environment map?
a) High sensitivity
b) Low transmission power
c) Reduction in observation time
d) High dynamic range
Answer: c
Explanation: The radio environment map holds both present and past radio environment information. Spectrum sensing with prior knowledge is more effective than continuous scanning of the entire radio spectrum. Consequently, the observation time, cost, and energy consumption of radio can be reduced.
5. Which among the following is achieved by combing learning with data mining in the radio environment map?
a) Observation intelligence
b) Learning
c) Network intelligence
d) Resource intelligence
Answer: c
Explanation: The incorporation of information obtained from reasoning, learning, and data mining in the radio environment map provides network intelligence. Network nodes obtain cognitive capabilities through network intelligence irrespective of the cognition capability of subscriber radios. Cognition capability can be provided to the legacy networks by combining them with the radio environment map.
6. Which among the following units communicates with radio environment map in legacy radios?
a) Local control and access manager
b) Local bus manager
c) Specialized processor
d) Network radio resource manager
Answer: d
Explanation: The radio environment map aids legacy radios or hardware reconfigurable radios by providing smart network operation by introducing cognitive strategies to the network radio resource manager. While in cognitive radios, it aids in situational awareness and adaptations.
7. Which among the following statements is false about a radio operating with the radio environment map?
a) Aware of application layer operations
b) Aware of physical layer operations
c) Awareness of performance metrics
d) Incompatibility with underlying radio access technology
Answer: d
Explanation: Radio environment map enables a radio to be aware of performance metrics such as data rate, spectral efficiency, etc. A radio with a radio environment map is comprehensive of each layer of protocol stack under different and varying radio environments. Radio environment map is compatible with underlying radio access technology regardless of the cognition capability of user radio.
8. Which among the following statements is false about the incorporation radio environment map in communication systems?
a) Radio environment map supports adaption regardless of available resources
b) Radio environment map allows network access on the basis of performance metrics
c) Radio environment map supports collaborative information processing
d) Radio environment map supports various network architectures
Answer: a
Explanation: Effective adaption of radio environment map is limited by radio scenarios such as available services, user policy, radio equipment capability, and available spectrum. Radio environment map supports various network architectures, collaborative information processing, and network access on the basis of performance metrics.
9. Which among the following technologies is employed to predict performance metrics?
a) Network based ontology
b) Very large scale integrated circuits
c) Radio propagation simulation tools
d) Geographical information system
Answer: c
Explanation: Radio propagation simulation tools are used to predict important parameters such as path loss, signal to noise ratio, and geographical environment information. Location specific radio propagation techniques with 3 D terrain maps offer accurate predictions that can provide better system planning and management.
10. Which among the following is a function of policy service?
a) Policy decision
b) Policy life cycle management
c) New policy request
d) Policy enforcement
Answer: b
Explanation: Police service is involved in the maintenance of policies that were downloaded and included in the radio frame by a policy authority. It performs policy life cycle management operations such as parsing the policy language, monitoring operation status, and eliminating outdated policies.
11. The cyclic coordinate method of optimization depends on the properties of objective functions.
a) True
b) False
Answer: a
Explanation: Cognitive radios apply optimization techniques to handle complex parameters. Classical optimization techniques depend on the properties of the objective function. They are analytically more traceable when compared to heuristic optimization techniques. The cyclic coordinate method and the steepest descent method are examples of optimization algorithms.
This set of Cognitive Radio Assessment Questions and Answers focuses on “Next Generation Wireless Network – Radio Environment Map – 2”.
1. Which among the following phenomenon require site specific propagation prediction?
a) Location awareness
b) Geographical awareness
c) RF environment
d) Position awareness
Answer: b
Explanation: Geographical awareness provides information on terrain and geographical information pertaining to radio propagation and channel properties. Terrain recognition, site specific propagation prediction, and exploitation of geographical information database are the techniques applied to gain geographical awareness.
2. Which among the following is a common problem incorporated by a channel on cognitive radios?
a) Switching delay
b) Transmitter uncertainty
c) Doppler shift
d) Receiver uncertainty
Answer: c
Explanation: The major degradation introduced by channels on cognitive radio is shadowing, fading, and Doppler shift. Predictive models constructed using short term and long term observations with radio environment map increase awareness of channels. This helps in developing better plans to tackle the effect of channel degradation.
3. Which among the following is an approach that can be applied to overcome the effect of channel fading?
a) Discarding particular channel from use
b) Transmission and reception during fixed time slots
c) Selection of appropriate waveform
d) Compromising quality of service
Answer: c
Explanation: Radio environment map provides the cognitive radio with channel characteristics with respect to the location and the direction of a mobile user. The characteristics of the channel help construct channel links and develop predictive models. With the help of predictive models, a waveform suitable to the channel characteristics can be constructed to adapt to the channel.
4. Which among the following problems could be overcome by spreading gain?
a) Delay due to fading
b) Delay due to multipath
c) Call drop due to multipath
d) Call drop due to fading
Answer: c
Explanation: Cognitive radio with radio environment map can predict call drop resulting due to multipath or shadowing. It can be prevented by switching on the backup power amplifier, increasing the number of RAKE fingers, spreading gain, changing power control policy, or by opting intersystem handoff.
5. Which among the following is termed as a local radio environment map?
a) Wide area network level
b) Hop to hop level
c) User equipment terminal
d) Local area network level
Answer: c
Explanation: The radio environment map installed on a user’s terminal equipment is called a local radio environment map. Each map is unique to its user device. The local radio environment map enables the cognitive radio to store current status and past experiences.
6. Which among the following statements is false about the radio environment map on a network level?
a) Radio environment map is compatible with hybrid node technology
b) Radio environment map introduces network intelligence
c) Radio environment map merges into the core of cognitive radio architecture
d) Radio environment map is dependent on network topology
Answer: d
Explanation: Radio environment map installation on a network level requires analyses of different structures and services in accordance with the requirements of various applications. Radio environment map introduces network intelligence and merges into the core of cognitive radio architecture. It is independent of network topology and can operate in hybrid node technology.
7. Which among the following statements is false about the introduction of a cognitive radio in a wireless regional area network?
a) Availability of spectrum access information to the secondary user
b) Availability of spectrum access information to the primary user
c) Knowledge of antenna height
d) Usage pattern of wireless regional area network
Answer: b
Explanation: The wireless regional area network comprises base stations, repeaters, and consumer premise equipment. It provides fixed wireless access services in rural areas. The inclusion of a radio environment map provides knowledge of location, antenna height, transmission power, and opportunistic spectrum access. It provides knowledge distribution and usage patterns of secondary users.
8. Which among the following require radio transceiver database?
a) RF environment awareness
b) Location awareness
c) Power consumption awareness
d) Energy consumption awareness
Answer: a
Explanation: RF awareness means to be aware of spectrum utilization, spectrum users, topology, interference, and other RF characteristics. Radio transceiver database, cooperative sharing, sensor networks, and field measurement are the methods applied to gain RF environment awareness.
9. Which among the following techniques require geographic information database?
a) Policy awareness
b) Regulation awareness
c) Mobility and trajectory awareness
d) Background environment awareness
Answer: c
Explanation: Mobility and trajectory awareness computes the speed and direction of a cognitive radio. Speed and trajectory is estimated by analyzing the change of location of the radio over a period of time and by utilizing the resources of a geographic information database.
10. Which among the following options should replace the labels ‘A’ and ‘B’ in the model implementation of radio environment map?
a) Learning, Local/Global radio environment map, Awareness, Decision
b) Learning, Awareness, Local/Global radio environment map, Decision
c) Awareness, Learning, Decision, Local/Global radio environment map
d) Awareness, Local/Global radio environment map, learning, decision
Answer: c
Explanation: The Radio Environment Map obtains information from sensor input of radio and the knowledge provided by network support. Awareness is obtained through observed information and REM. Learning helps the radio to adapt with the help of past experiences, decisions, observations, and plans. After a decision is taken, the REM is updated.
This set of Cognitive Radio Multiple Choice Questions & Answers focuses on “Next Generation Wireless Network – Knowledge Representation”.
1. Which among the following processes is required to extend radio adaption beyond predefined knowledge?
a) Sorting
b) Knowledge acquisition
c) Reasoning
d) Learning
Answer: d
Explanation: The reasoning engine is responsible for applying the gathered knowledge in accordance with the current state of the system. However, the reactions will be limited to previously defined knowledge even under new situations. Learning provides the ability to study input, identify patterns, and modify the operation of the radio system as per the demands of the situations.
2. Which among the following processes under learning action initiates a change in the action selection policy?
a) Observation of state of the radio system
b) Decision making in reasoning engine
c) Analyses of the outcome of the decision selected by the reasoning engine
d) Modification of knowledge base
Answer: d
Explanation: The modification of the knowledge base step is generally the final step in a single learning cycle. The knowledge base is modified in accordance with the outcome of the actions implemented by the reasoning engine. The existing information in the knowledge base is altered, or the action selection policy is changed. Otherwise, new knowledge entries are included in the database.
3. What is called declarative knowledge?
a) Declarative knowledge represents a range of values applicable for assigning a variable
b) Declarative knowledge represents assumed statements
c) Declarative knowledge asserts and reasons over descriptive factual knowledge
d) Declarative knowledge represents predicted knowledge
Answer: c
Explanation: Declarative knowledge involves asserting and reasoning over descriptive factual knowledge about an object. Declarative knowledge describes the semantic relationships between objects.
4. Which among the following is concerned with the effect on a knowledge system?
a) Behaviour knowledge
b) Declarative knowledge
c) Narrative knowledge
d) Status and system knowledge
Answer: a
Explanation: Behavioural knowledge involves actions and their effect on the knowledge system. Both internal and external effectors altering the system and the environment are included. An event begins with a set of assertions and terminates with a varying set of assertions.
5. Which among the following is a benefit of symbolic knowledge representation?
a) No encryption is required
b) Fast translation
c) Less memory storage
d) Easy human comprehension
Answer: d
Explanation: Symbolic knowledge representation typically involves graphical or natural language notations. It is easy for humans to understand. It offers a simplistic means for conveying underlying information for human understanding and interpretation.
6. Which among the following is not used for symbolic knowledge representation?
a) Interface
b) Objects
c) Semantic nets
d) Frames
Answer: a
Explanation: In symbolic representation and reasoning systems, storage is performed using extensible data structures to capture facts, descriptions, and properties related to a concept. Semantic nets, rules, frames, and objects are some of the structures employed to represent knowledge.
7. Which among the following is employed for associating new concepts in the learning process for ontology based systems?
a) Dissimilarities between two consequent entries
b) Similarities between two consequent entries
c) Similarities to existing entries in memory
d) Dissimilarities to existing entries in memory
Answer: c
Explanation: Learning in ontology based system involves integrating new knowledge with existing collection of entries in memory. A classifier is used to assess the degree of similarity between a new entry and the existing entries. The classifier accomplishes this by analyzing the properties and values of a new entry.
8. What does an arc in a decision tree represent?
a) An action
b) A decision
c) Set of all possible choices
d) Set of all possible plans
Answer: c
Explanation: A decision tree is a directed graph with a hierarchical set of nodes and arcs. A node represents a choice or a decision. An arc from one decision node to another decision node represents all possible choices associated with that node.
9. What is the parameter of analysis in reinforcement learning?
a) Number of requests during wake cycle
b) Number of processes to achieve final outcome
c) Degree of failure
d) Degree of success
Answer: d
Explanation: Reinforcement based learning assigns a weightage to an action on the basis of the degree of success of its outcome. When situations requiring similar action arise, the weightage associated with an action is analyzed for compatibility. The degree of success is computed by measuring the closeness of the obtained outcome with the expected outcome.
10. Which among the following statements provides the difference between reinforcement-based learning and temporal difference technique?
a) State represented by a directed graph
b) Assignment of weightage to an action on the basis of the degree of success
c) Computation of degree of success
d) Priori model of the sequence of possible states
Answer: d
Explanation: The temporal difference algorithm does not a priori model of the sequence of possible states as the temporal difference algorithm constructs the state representation during execution. The states are composed as a value function and are stored on a neural network.
11. Which among the following is not a challenge of employing reasoning and learning stage in the cognitive radio?
a) Computational requirement
b) Quality of Service
c) Edge conditions
d) Predictable behaviour
Answer: b
Explanation: Cognitive radio should provide a large amount of computational resources to achieve the results of each operation. Edge conditions refer to the devices which are positioned in a location without regular service and hence cannot benefit from learning techniques. Predictable behaviour refers to the ability to estimate the outcome of each step of the operation but not the final outcome.
12. Which among the following is not a challenge for case based reasoning implementation?
a) Memory
b) Fixed ontology and knowledge representation
c) Pattern matching
d) Accuracy of reasoning
Answer: b
Explanation: Case based reasoning requires a large case database. It requires a large amount of computational resources for pattern matching and to modify the solution of a close match to satisfy the current problem. Case based reasoning can be implemented in any system provided it has large memory and processing power regardless of ontology and knowledge representation.
13. Which among the following options should replace the label ‘A’, ‘B’, and ‘C’ in rule based system?
a) Memory, Inference Engine, Knowledge Base
b) Memory, Knowledge Base, Inference Engine
c) Knowledge Base, Memory, Inference Engine
d) Inference Engine, Memory, Knowledge Base
Answer: c
Explanation: The knowledge base of the rule based system is composed of rules specified in the form of “if-then” clauses. The memory unit consists of the current state of the system. The inference engine is responsible for pattern matching.
14. Temporal reasoning allows a system to reason about its operational characteristics at discrete points in time.
a) True
b) False
Answer: b
Explanation: Temporal reasoning allows a system to reason about its operational characteristics during an interval of time. For example, spectrum sensing over a period can help identify intervals of spectrum underutilization within that period of time.
