Cognitive Radio Questions and Answers – Next Generation Wireless Network – Cross Layer Design – 2

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This set of Cognitive Radio online quiz focuses on “Next Generation Wireless Network – Cross Layer Design – 2”.

1. What is cross-layer design?
a) Cross-layer design allows non adjacent layers to exchange information which are traditionally relevant to a layer itself
b) Cross-layer design allows only adjacent layers to exchange information with each other
c) Cross-layer design provides control of lower layer functions to the upper layer functions
d) Cross-layer design provides control of upper layer functions to the lower layer functions
View Answer

Answer: a
Explanation: Cross-layer design allows non-adjacent layers to exchange information which is traditionally relevant to a layer itself. By adapting cross-layer design, a global view of the radio framework and the surrounding environment can be obtained. It helps to eliminate problems that arise due to a lack of resource information at the time of transmission.
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2. Which among the following statements is false about cross-layer design?
a) High quality of service can be provided by exchanging information among all layers of the protocol stack
b) Diverse waveforms are employed for power and modulation process
c) Cross-layer design helps to eliminate channel variations caused by blurring
d) Cross-layer design makes channel connections unpredictable
View Answer

Answer: d
Explanation: Cross-layer design creates diverse waveforms to establish predictable connections under the existing channel conditions and medium access control parameters. High quality of service can be provided by exchanging information among all layers of the protocol stack. Cross-layer design also helps to achieve higher throughput.

3. Which among the following cannot be achieved by creating a mutual database?
a) Administration of capacity
b) Recovery of data
c) Rapid access to data by every layer
d) Limited resource usage
View Answer

Answer: d
Explanation: The construction of a mutual database is one of the design methodologies employed in the implementation of the cross-layer design. A mutual database is built by combining information obtained from all layers of the protocol stack. It helps to administrate resource allocation as well as help in the recovery of data particular to each layer.
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4. Which among the following is not a design methodology in the implementation of cross-layer design?
a) Exchange of information among several layers during run time
b) Storage of information in different storage structures
c) Construction of mutual database with easy access for each layer in the protocol stack
d) Construction of channel models to estimate the propagation of a signal in the channel environment
View Answer

Answer: d
Explanation: Cross-layer design requires the characteristic parameters of each layer to be made available to other layers of the protocol stack during run time. In order to achieve this, different degree of abstraction is required. This requires the development of new data structures such as constructing squares for storing information.

5. Which among the following is a building unit of cross-layer hub?
a) Cross-layer intra hub module
b) Cross-layer interface
c) Cross-layer scheduler
d) Cross-layer director
View Answer

Answer: a
Explanation: Cross design involves the sharing of information among different layers of the protocol stack. For example, spectrum occupancy information gathered in the physical layer must be accurately transferred to the MAC layer through a proper interface. The units required to implement the cross-layer design are interfaces, controllers, schedulers, and inter hubs.
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6. Which among the following is not an expected result of cross-layer design?
a) High end to end throughput
b) Reduced network capacity
c) Reduced interference
d) Reduced power consumption
View Answer

Answer: b
Explanation: Cross-layer design involves the exchange of information over various interfaces to achieve a better quality of service than possible by following the traditional layered approach. The exchange of information can be between physical and data link layer, data link and transport layer, network and transport layer, etc. Cross-layer design aims to achieve a high end to end throughput, increase the network capacity, optimize network utilization, reduce interference and power consumption.

7. Which among the following is not an advantage of employing cross-layer design implementation?
a) High accuracy of computation results required in algorithms
b) Elimination of wasteful calculations
c) High quality of service
d) Better performance during spectrum handoff
View Answer

Answer: d
Explanation: Cross-layer design improves the accuracy and the productivity of algorithms by extending the amount of information at hand. Cross-layer design helps to adjust in accordance with the varying resource availability. It eliminates computations that are performed due to a lack of communication between the layers of the protocol stack.
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8. Which layer performs adaptive modulation and coding?
a) Network layer
b) Transport layer
c) Physical layer
d) Data link layer
View Answer

Answer: c
Explanation: Adaptive modulation and coding is the process of adjusting signal parameters such as the modulation type, coding technique, and protocol parameters to the characteristics of the channel selected for transmission. The adaptive modulation system requires channel state information at the transmitter.

9. Which among the following is not a function of the MAC layer in cognitive radio?
a) Manage accessibility of assets
b) Change client configuration
c) Change density of design
d) Choose multiple access techniques
View Answer

Answer: d
Explanation: MAC layer in cognitive radio should manage the level of accessibility provided for resources of the radio. MAC layer should be aware of channel occupancy and surrounding spectrum environment to quickly handle changes in the environment and to mitigate loss produced due to mobility. MAC layer should have the capability to change design configuration.
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10. Which among the following combination of layers can be used to improve blockage control?
a) Physical-Datalink
b) Datalink – network
c) Physical-Transport layer
d) Datalink- Transport layer
View Answer

Answer: c
Explanation: The transport layer can correctly classify the reason for blockage provided the signal transmission information collected in the physical layer is made available via cross-layer design. For example, it can be used to detect the cause for packet loss.

11. What type of optimisation technique is represented in the following diagram?
Find the type of optimisation technique from the given diagram
a) Fuzzy Logic
b) Hidden Markov Model
c) Case Based Reasoning
d) Evolutionary Algorithm
View Answer

Answer: a
Explanation: Fuzzy Logic is a many valued logic in which the value assigned to variable ranges between completely true to completely false. It is applied for frequently changing parameters or inaccurate parameters. It utilizes concepts such as enrolment capacities, semantic factors, and a central base.

12. Cross-layer communication between data link and network layer can minimize the wastage of resources caused by packet loss.
a) True
b) False
View Answer

Answer: a
Explanation: Cross-layer communication between data link and network layer can minimize the wastage of resources caused by packet loss. One approach involves allocating the resources for link-layer needs based on hop count in the network layer module. For higher hop count, the power is divided among the packets, and the best available channel is selected for transmission.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter