Radio Propagation and Adaptive Antennas for Wireless Communication Networks, 2nd Edition

CHAPTER EIGHTPrediction of Signal Distribution in Space, Time, and Frequency Domains in Radio Channels for Adaptive Antenna Applications

Multipath phenomena limit performance of wireless communication systems by introducing fast fading due to frequency spread in narrowband systems and by causing intersymbol interference in wideband systems due to time delay (TD) spread. Finally, a strong multiplicative noise occurs in all kinds of wireless links becoming a great problem in land communications [1–30]. As was mentioned in Chapters 1 and 5, to mitigate the effects of multiplicative noise and the noise due to interference between users in multiple access communication, the directional, sectorial, and adaptive antennas (array or multibeam) are used in one or both ends of the channel, which was defined in Chapter 7 as a multiple-input-multiple-output (MIMO) channel. Using the adaptive antenna together with the corresponding processing algorithms operating in the space, time, and frequency domains (see details in Chapter 7) allows the channel to radiate the desired energy in the desired direction or to cancel the undesirable energy from the undesirable direction (see Fig. 7.21, Chapter 7). The same method is used to minimize effect of multipath fading.

However, the operational ability of all kinds of antennas, and mostly of adaptive antennas, strongly depends on the degree of accuracy to predict propagation characteristics of the actual channel. These types of propagation models, which ...