Doppler Spread and Coherence Time.pptx

Doppler spread and coherence time

1. Doppler Spread and Coherence Time

2. Doppler spread is a measure of the spectral broadening caused by the time or R ange of frequencies over which the received Doppler spectrum is essentially non-zero . Doppler Power Spectrum gives the statistical power distribution of the channel v/s frequency. Doppler Spread

3. The Doppler power spectrum is the Fourier transform of At(∆t ) is given by Doppler Power Spectrum

4. When a pure sinusoidal tone of frequency fc is transmitted, the received signal spectrum, called the Doppler spectrum. The spectrum components in the range fc – fd to fc + fd, where fd is the Doppler shift. Unlike the power delay profile, the Doppler power spectrum is non-zero strictly for ∆ f€ (-f D , f D ).

5. f D is maximum Doppler spread or Doppler spread. The Doppler spread f D is given by As long as the communication bandwidth B << fc, the Doppler power spectrum can be treated as approximately constant.

6. Coherence time Tc is used to characterize the time varying nature of the frequency depressiveness of the channel in the time domain. Values for the Doppler spread and the associated channel coherence time for LTE at Pedestrian, Vehicular, and Maximum Speeds are given in Table below for two possible LTE frequency bands. Coherence Time (TC)

7. Coherence Time (TC)

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