Interference Analysis and Reduction for Wireless Systems

Throughout time, people have and will continue to use communications at an ever-increasing pace in an interference environment [1]. In addition to the widespread use of satellite systems during the decades of the 1970s and the 1980s, we are now living through the mobile revolution. A large percentage of the communications needs can be carried out satisfactorily, even in a bad interference situation, and people are willing to show moderation. For example, hearing a distant cochannel repeater when your local repeater is not active, while annoying, is not ‘‘unacceptable interference.’’ Hearing adjacent channel splatter while carrying on a conversation on simplex or your local repeater, while affecting the quality of the conversation, is not truly unacceptable interference. If it makes communication completely impossible, then it should be considered interference, although it still may not necessarily be harmful or willful. Take note at this point that many of the noise sources to be defined here do not affect FM/PM type radio operation except to cause desensing of the radio, possibly masking the desired signal. This is the reason we strive to define and derive the qualitative measures by which we can design modern wireless system in an ever-increasing interference background. Up to this point, we have examined and analyzed distortion mainly in the form of fading that is caused to information signals by the wireless channel for the types of wireless systems currently being used. In this and the following chapters, we shall analyze and study interference and include