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
d) Frequency division multiplexing
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
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 ____
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
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
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
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
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
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
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
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.
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.
Sanfoundry Global Education & Learning Series – Software Defined Radio.
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