Intersymbol interference and the Rayleigh fading channel



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Presented herein is an analysis of the effects of intersymbol interference on the performance of digital communication systems operating over channels corrupted by Rayleigh fading and additive Gaussian noise. The results are applicable to systems employing coherent detection schemes. For mean signal-to-noise ratios of 15 dB or less, and for typical pulse shapes with reasonably well-synchronized sampling, intersymbol interference is shown to contribute no significant amount to the average probability of biterror over the Rayleigh fading channel. As the mean signal- to-noise ratio is Increased to higher levels, the Incremental bit-error probability caused by Intersymbol interference is seen to be limited to some fractional part of the total biterror probability. Under normal circumstances, this limiting fraction is itself not large, being less than 0.2 for most examples considered in this study. Such results contrast sharply with those obtained in the absence of fading, in which case the bit-error probability at signal-to-noise ratios in excess of 15 dB is almost entirely due to intersymbol interference. Of particular Interest is the numerical integration technique used to calculate the bit-error probabilities for both types of channel. This is a very simple, straightforward approach and appears to be superior in some respects to the more sophisticated schemes currently under discussion In the literature.