# Cognitive Radio Questions and Answers – Techniques – Optimisation of Radio Resources – 2

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This set of Cognitive Radio Multiple Choice Questions & Answers (MCQs) 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
View Answer

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.
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2. ____ is used to reduce inter-symbol interference.
a) Root raised cosine filter
b) Sinc filter
c) Root raised sinc filter
d) Cosine filter
View Answer

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
View Answer

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.
View Answer

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
View Answer

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.
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6. Which among the following is an expression for spectral efficiency?
a) η=$$\frac{R_sk}{B}$$. where Rs is the symbol rate, B is the bandwidth, K is the number of bits per symbol
b) η=RsB where Rs is the symbol rate, B is the bandwidth, K is the number of bits per symbol
c) η=$$\frac{Bk}{R_s}$$where Rs is the symbol rate, B is the bandwidth, K is the number of bits per symbol
d) η=BK where B is the bandwidth
View Answer

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
View Answer

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
View Answer

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
View Answer

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.
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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
View Answer

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
View Answer

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
View Answer

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) Rth=kRs where Rs is symbol rate
b) Rth=kRb where Rb is bit rate
c) Rth=RsRb where Rs is symbol rate and Rb is bit rate
d) Rth=Rs/Rb where Rs is symbol rate and Rb is bit rate
View Answer

Answer: a
Explanation: The simple expression of throughput objective is given by Rth=kRs . 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 Rth=Rb(1-Pe)l.
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14. Gaussian minimum shift keying is based on frequency shift keying.
a) True
b) False
View Answer

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
View Answer

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.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn