Time-frequency representation of a signal through non-stationary multipath fading channel

Spectral analysis is only applicable to stationary signals and most of the real signals in many practical applications are non-stationary. Time-frequency methods are applied to analyze non-stationary signals and this paper presents different time-frequency methods to analyze a modulated random signal through a multi-path fading channel with emphasis on time-varying power spectra. Short-time Fourier transform (STFT) divides the full time interval signal into a number of small intervals and is not useful for analyzing signal to determine frequency contents of a time varying voltage spectra. Wigner-Ville distribution (WVD) is the most popular time-frequency energy distributions to develop time-frequency plane for estimation and detection of non-stationary process. The objective of this paper is to analyze time-frequency relationship of a non-stationary amplitude varying fading channel. In this paper, STFT and WVD are applied to the time varying non-stationary multipath fading channel to analyze time-frequency contents. The result shows that WVD provides better time-frequency relationship than that obtained by Fourier transform, and the analysis procedure will be used in future to analyze time-frequency relationship of amplitude varying non-stationary channel using Wavelet transform.