9.1 INTRODUCTION

The field of public telecommunications has experienced an unprecedented growth, expansion, and development during the last several years on both the theoretical and applied fronts. In this area of communications, microwave radio, from its introduction in the late 1940s to the present, has become one of the primary media for transmitting information from point to point and from a point into a given area. The advent of satellite communication technology in 1962 and consequent sharing of bands between satellite and radio relay coupled with the explosive growth of microwave radio routes at these frequencies has led to increased sharing of frequency spectrum and to generation of increased mutual interference. This added interference is playing a dominant role in limiting the capacity, efficiency, reliability, and cost of communication systems. In addition, the advances in low-noise receiver technology have made the ubiquitous thermal noise, which used to limit the performance of earlier communication systems, of secondary importance in system design and engineering.

With the expected increase in congestion of frequency spectrum, use of satellites, various frequency reuse techniques, and migration to use of higher bands, the role played by interference is likely to increase in the future. Interference is a ubiquitous property of the environment in which various communication systems coexist either in the same or adjacent frequency bands and is also caused by nonideal mechanisms utilized in the process of communications.

Until now, the system designer almost...