Abstract

This chapter considers an entirely different setup: There is no LOS path (some object blocks it), but many reflected paths. We will first show that these multipath channels behave randomly and, thus, can be modeled statistically. This is known as a fading channel since the current SNR depends on the current random realization of the channel. We will then extend the statistical model to MIMO channels and obtain what is known as independent and identically distributed (i.i.d.) Rayleigh fading. Depending on how quickly the channels vary over time, we will consider different ways of extending the capacity concept to handle fading channels. The benefit of using multiple antennas to combat fading variations will be demonstrated and the spatial fading correlation created by the propagation environment’s geometry will be studied.