Analysis of intersymbol interference in fading channels



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Tropospheric propagation paths are becoming very attractive in both military and commercial use due to their high data rate capability. This type of propagation has the characteristic of a frequency-selective fading channel. It is of interest in this dissertation to study how this selectivity affects the digital error probabilities, since the data rate capability of radio channels is limited by the symbol distortion and intersymbol interference. Two procedures for the evaluation of the probability of error for binary receivers in the presence of intersymbol interference in random channels are studied. The first one is observed to be useful when the channel is slowly varying as compared with the signal transmission rate. The second procedure is showed to have an advantage over the slowly-varying method in that the selectivity of the medium can be easily incorporated. For the slowly-varying channel, a unified analysis of the effects of fading and intersymbol interference due to filtering is presented for both the Rayleigh and the Rician fading channel. The matched filter operation is replaced by a Butter-Worth filter at the front end of the receiver. It is observed that when no diversity is used (L=l), the main degradation of the performance curves is due to fading, but when this degradation is totally or partially eliminated (perhaps using diversity) the effects of bandlimiting become an important factor for the -2 design. [...]