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
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
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
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?
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
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
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
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
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.
d) amplitude shift keying
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
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
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.
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.
Explanation: Cramer Roa lower bound (CRLB) 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.
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