This set of Cognitive Radio Questions and Answers for Aptitude test focuses on “Next Generation Wireless Network – Spectrum Sharing – 2”.
1. What is the basic unit of channel allocation?
a) P frame
b) Q frame
c) R frame
d) S frame
Explanation: A Q frame is the basic unit of channel allocation. When a Q frame is allocated by a base-station, the base-station can use its control and data channels for coordination and data communication between the users.
2. What is the full form of DQSDR?
a) Dynamic Quality of Service Distributed Reservation scheme
b) Distributed Quality of Service Dynamic Reservation scheme
c) Dynamic Quality of Service Distributed Resource scheme
d) Distributed Quality of Service Dynamic Resource scheme
Explanation: In Distributed Quality of Service Dynamic Reservation scheme, a base-station competes with an interfering base-station to allocate a spectrum band that satisfies the quality of service requirements of the user application.
3. What is the use of a common control channel?
a) Transmission coordination
b) Spectrum allocation
c) Spectrum analysis
d) Time of arrival synchronization
Explanation: The common control channel is used to exchange spectrum information among xG users and also support transmission coordination. The common control channel is mainly classified as an in-band channel or as an out-of-band channel.
4. Which among the following is a common control channel used by a radio to gain access to a system?
a) Paging Channel
b) Random Access Channel
c) Access Grant Control Channel
d) Cell Broadcast Channel
Explanation: Common control channel transfers control information from a radio to a base-station. Random access channel is required to gain access to a system. It is invoked when the radio starts a call or replies to a page.
5. Which among the following may be employed to select a common control channel in cooperative intra-network spectrum sharing?
c) K-nearest neighbour
Explanation: In a local group, each node shares several channels with its neighbours. Each group may employ a clustering algorithm to select a common channel for communication. Distributed sensing and spectrum sharing is also carried out in the common channel.
6. What is a local bargaining group?
a) Local bargaining group is a set of users with a threshold limit guaranteed to provide minimum spectrum allocation to each user
b) Local bargaining group is a set of users with a threshold limit that determines one particular user to operate the spectrum band
c) Local bargaining group is a set of users with a threshold limit on the number of transmissions permissible over a certain period
d) Local bargaining group is a set of users that compete for access of the spectrum band
Explanation: Local bargaining scheme is a cooperative intra-network sharing technique. It improves spectrum utilization and ensures fairness in the allocation of spectrum. It involves creating a local bargaining group with a threshold limit that ensures minimum allocation of spectrum to each user of the group.
7. Which among the following is not a function of the dynamic spectrum access protocol?
a) Collision avoidance
b) Resolve spectrum access contention
c) Transparency for primary user
d) Efficient dynamic spectrum allocation
Explanation: The primary user does not interact or coordinate with the secondary user. Therefore the secondary user must be made transparent for the primary user. DSAP should avoid collision between primary users and secondary users by introducing power constraints. The spectrum should be allocated such that average network throughput is increased.
8. How is dynamic spectrum access protocol advantageous for cooperative spectrum sharing?
a) Central entity is used to lease the spectrum
b) Sophisticated spectrum sharing algorithms are used to allocate the spectrum
c) Distributed communication
d) Reduced communication overhead
Explanation: The dynamic spectrum access protocol (DSAP) is a centralized protocol where a central entity is used for leasing spectrum to users in a limited geographical area. DSAP consists of clients, DSAP server, and relay for relaying information between the server and the clients that are not in the direct range of the server.
9. What type of scheme is non-cooperative intra-network spectrum sharing?
a) Spectrum centric
b) Application centric
c) Device centric
d) Access centric
Explanation: Non-cooperative intra-network spectrum sharing allocates channels depending on observed interference patterns and neighbours. The device is modified so that it can choose the channels for communication. This method exhibits poor performance when compared to cooperative schemes but the communication overhead is reduced.
10. Which among the following is applied to resolve contention between users in non-cooperative intra-network spectrum sharing?
a) Random access techniques
b) Multiple access techniques
c) Spread spectrum techniques
d) Multiplexing techniques
Explanation: Non-cooperative intra-network spectrum sharing is a rule based spectrum access approach. When more than one closely located nodes access the same channel, random access techniques are used to resolve contention. The rules help to reduce communication overhead.
11. The selection of a common control channel is difficult in centralized networks.
Explanation: The selection of a common control channel is difficult in distributed cognitive wireless networks due to the time varying spectrum environment and lack of a central controlling entity. It is overcome by choosing a licensed or an unlicensed channel as the dedicated common control channel.
12. Which among the following methods is associated with dynamic open spectrum channel protocol?
a) Centralized inter-network spectrum sharing
b) Distributed inter-network spectrum sharing
c) Cooperative intra-network spectrum sharing
d) Non-cooperative intra-network spectrum sharing
Explanation: Dynamic open spectrum channel protocol aids the cooperative intra-network spectrum sharing. A busy tone is exchanged between the transmitter and the receiver in the selected busy tone channel during communication on the data channel.
13. What term should replace the labels ‘A’ and ‘B’?
a) Spectrum management, Spectrum sensing
b) Spectrum access, Spectrum allocation
c) Spectrum management, Spectrum access
d) Spectrum access, Spectrum sensing
Explanation: Spectrum sensing and spectrum access are the two major functions of the spectrum sharing process. Spectrum sensing is responsible for locating unused spectrum bands. Spectrum access is responsible for choosing the best available spectrum that meets the quality of service requirements and policies from all available spectrum.
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