This set of Cognitive Radio Assessment Questions and Answers focuses on “Next Generation Wireless Network – Radio Environment Map – 2”.
1. Which among the following phenomenon require site specific propagation prediction?
a) Location awareness
b) Geographical awareness
c) RF environment
d) Position awareness
Explanation: Geographical awareness provides information on terrain and geographical information pertaining to radio propagation and channel properties. Terrain recognition, site specific propagation prediction, and exploitation of geographical information database are the techniques applied to gain geographical awareness.
2. Which among the following is a common problem incorporated by a channel on cognitive radios?
a) Switching delay
b) Transmitter uncertainty
c) Doppler shift
d) Receiver uncertainty
Explanation: The major degradation introduced by channels on cognitive radio is shadowing, fading, and Doppler shift. Predictive models constructed using short term and long term observations with radio environment map increase awareness of channels. This helps in developing better plans to tackle the effect of channel degradation.
3. Which among the following is an approach that can be applied to overcome the effect of channel fading?
a) Discarding particular channel from use
b) Transmission and reception during fixed time slots
c) Selection of appropriate waveform
d) Compromising quality of service
Explanation: Radio environment map provides the cognitive radio with channel characteristics with respect to the location and the direction of a mobile user. The characteristics of the channel help construct channel links and develop predictive models. With the help of predictive models, a waveform suitable to the channel characteristics can be constructed to adapt to the channel.
4. Which among the following problems could be overcome by spreading gain?
a) Delay due to fading
b) Delay due to multipath
c) Call drop due to multipath
d) Call drop due to fading
Explanation: Cognitive radio with radio environment map can predict call drop resulting due to multipath or shadowing. It can be prevented by switching on the backup power amplifier, increasing the number of RAKE fingers, spreading gain, changing power control policy, or by opting intersystem handoff.
5. Which among the following is termed as a local radio environment map?
a) Wide area network level
b) Hop to hop level
c) User equipment terminal
d) Local area network level
Explanation: The radio environment map installed on a user’s terminal equipment is called a local radio environment map. Each map is unique to its user device. The local radio environment map enables the cognitive radio to store current status and past experiences.
6. Which among the following statements is false about the radio environment map on a network level?
a) Radio environment map is compatible with hybrid node technology
b) Radio environment map introduces network intelligence
c) Radio environment map merges into the core of cognitive radio architecture
d) Radio environment map is dependent on network topology
Explanation: Radio environment map installation on a network level requires analyses of different structures and services in accordance with the requirements of various applications. Radio environment map introduces network intelligence and merges into the core of cognitive radio architecture. It is independent of network topology and can operate in hybrid node technology.
7. Which among the following statements is false about the introduction of a cognitive radio in a wireless regional area network?
a) Availability of spectrum access information to the secondary user
b) Availability of spectrum access information to the primary user
c) Knowledge of antenna height
d) Usage pattern of wireless regional area network
Explanation: The wireless regional area network comprises base stations, repeaters, and consumer premise equipment. It provides fixed wireless access services in rural areas. The inclusion of a radio environment map provides knowledge of location, antenna height, transmission power, and opportunistic spectrum access. It provides knowledge distribution and usage patterns of secondary users.
8. Which among the following require radio transceiver database?
a) RF environment awareness
b) Location awareness
c) Power consumption awareness
d) Energy consumption awareness
Explanation: RF awareness means to be aware of spectrum utilization, spectrum users, topology, interference, and other RF characteristics. Radio transceiver database, cooperative sharing, sensor networks, and field measurement are the methods applied to gain RF environment awareness.
9. Which among the following techniques require geographic information database?
a) Policy awareness
b) Regulation awareness
c) Mobility and trajectory awareness
d) Background environment awareness
Explanation: Mobility and trajectory awareness computes the speed and direction of a cognitive radio. Speed and trajectory is estimated by analyzing the change of location of the radio over a period of time and by utilizing the resources of a geographic information database.
10. Which among the following options should replace the labels ‘A’ and ‘B’ in the model implementation of radio environment map?
a) Learning, Local/Global radio environment map, Awareness, Decision
b) Learning, Awareness, Local/Global radio environment map, Decision
c) Awareness, Learning, Decision, Local/Global radio environment map
d) Awareness, Local/Global radio environment map, learning, decision
Explanation: The Radio Environment Map (REM) obtains information from sensor input of radio and the knowledge provided by network support. Awareness is obtained through observed information and REM. Learning helps the radio to adapt with the help of past experiences, decisions, observations, and plans. After a decision is taken, the REM is updated.
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