Cognitive Radio Multiple Choice Questions & Answers (MCQs) 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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
Clarification: 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.