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