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

CHAPTER SEVENAdaptive Antennas for Wireless Networks

As was mentioned in previous chapters, the main problem in mobile or stationary wireless communications, satellite and aircraft (megacell), outdoor (macrocell and microcell), and indoor (picocell), is the additional noise factor (to the white or additive noise). This noise has two aspects to it: (1) the multiplicative noise caused by multipath propagation fading, delay spread (DS), and Doppler spread (see definitions in Chapter 1) and (2) the co-channel interference noise caused by interactions of information sent by different users located in the area of service and involved in the multiple access communication occurred in real time during servicing. Both of these physical phenomena degrade the grade of service (GOS), the quality of service (QOS), the capacity of the information data stream and, finally, the efficiency of wireless communication networks.

Several methods have been developed during the last two to three decades to eliminate these kinds of noise factors. These methods are based on filtering [1–5], signal processing [6–12], and the so-called adaptive or smart antenna systems [13–22]. The term “smart antenna” reflects the antenna's ability to adapt to the communication channel environment in which it operates. Because both terms, “adaptive antennas” and “smart antennas,” are interchangeable, from now on we will use the term adaptive antennas since it is based on analog and digital beam-forming technology [23–29]. ...