COMPUTER NETWORKS AND COMMUNICATIONS
WIRELESS COMMUNICATION TECHNOLOGIES
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Mean excess delay & Excess delay spread
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Coherence time &Doppler spread
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RMS delay spread & Coherence time
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None of the above
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Detailed explanation-1: -10. Which of the following describes time varying nature of the channel in a small scale region? Explanation: Delay spread and coherence bandwidth describes the time dispersive nature of the channel in a local area.
Detailed explanation-2: -Doppler Spread and Coherence time are parameters which describe the time varying nature of the channel in a small-scale region.
Detailed explanation-3: -The coherence bandwidth is proportional to the inverse of the RMS delay spread, or roughly to the reciprocal of the maximum excess delay [4, p. 960]. Narrow band signals, then, are susceptible to flat fading.
Detailed explanation-4: -The coherence time is the time over which the channel-gain-values correlation coefficient drops below a predefined threshold. The coherence time is typically used to quantify the pace of appreciable channel changes and is important, for example, for determining handoff and resource allocation time constraints.
Detailed explanation-5: -Coherence bandwidth is a statistical measurement of the range of frequencies over which the channel can be considered “flat", or in other words the approximate maximum bandwidth or frequency interval over which two frequencies of a signal are likely to experience comparable or correlated amplitude fading.