ABSTRACT
When the mechanisms that cause fading in communication channels were first modeled in the 1950s and 1960s, the principles developed were primarily applied to over-the-horizon communications covering a wide range of frequency bands. In the analysis of communication system performance, the classical additive-white-Gaussian-noise channel, with statistically independent Gaussian noise samples corrupting data samples free of intersymbol interference, is the usual starting point for developing basic performance results. An important source of performance degradation is thermal noise generated in the receiver. Large-scale fading can be considered to be a spatial average over the small-scale fluctuations of the signal. A simple way to model the fading phenomenon was introduced by Bello in 1963; he proposed the notion of wide-sense stationary uncorrelated scattering. The model treats signals arriving at a receive antenna with different delays as uncorrelated. A completely analogous characterization of signal dispersion can be specified in the frequency domain.
