Wireless: Modeling Random Fading Channels

Groves of trees rustling in the wind scramble received power from one second to the next in a point-to-point microwave link. Or a cellular handset drops a call after moving just a few centimeters from an operable location. Or the tap-delay line filter of a linear equalizer becomes unstable, incapable of canceling the intersymbol interference experienced by a wireless receiver. While the causes and effects of each channel-related problem are varied, the channel analysis is nearly identical for each case - if rigorous stochastic channel modeling is employed.

The goal of this chapter is to develop the terminology, definitions, and basic concepts of modeling a random wireless channel that can be a function of time, frequency, and receiver position in space. While the task of joint characterization may seem daunting, only a few basic concepts are required. In fact, this chapter applies the concept of duality to show that understanding random fading in one dependency leads immediately to understanding in others.

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