Define the terms – delay spread, Doppler shift coherence bandwidth.

Define the terms – delay spread, Doppler shift coherence bandwidth.

Ans. The small – scale fading is less predictable and more potentially destructive than large –scale fading, most of the discussion is based on small-scale fading. Delay spread and Doppler effect are the two main effects observed on the signal due to small- scale fading and leads to the concept of coherence bandwidth. Contribution of large-scale fading is also unavoidable in the resultant signal.

  • Delay spread – In the mobile radio environment, as a result of the multipath reflection phenomenon, the signal transmitted from a cell site and arriving at a mobile unit will be from different paths and since each paths has a different path length, the time of arrival for each path is different. For an impulse transmitted at the cell site, by the time this impulse is received at the mobile unit it is no longer an impulse but rather a pulse with a spread width that we call the delay spread. The measured data denote that the mean delay spreads are different in different kinds of environment.

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