Fading Models From Spherically Invariant Processes

We advocate the use of the exceedingly general class of spherically invariant random processes to model fading in wireless communications. These processes encompass most of the models in practical use. After summarizing their main properties: 1) we prove that they are differential-entropy maximizers; 2) we describe a mathematical technique, based on Mellin transforms, useful to evaluate the performance of digital communication over a channel affected by spherically invariant fading; 3) We show how sharp upper and lower bounds to system performance can be derived when only a limited knowledge of the fading process statistics is available; and 4) we derive the spherically invariant fading distributions yielding the best and worst performance for a given signal-to-noise ratio.