OVERVIEW

Digital and analog signal transmission are disturbed by the presence of undesired waves. These waves can be generated by the thermal motion of electrons in the front-end receiver of a microwave amplifier, by adjacent radio transmitters, or by any other means including deliberate jamming. By analogy with the familiar term used in acoustics, these disturbing waveforms are considered as noise, or inter ference. Noise is most certainly one of the system parameters over which the designer has only partial control and is usually hard to describe in exact mathematical terms. It is a nuisance factor in error-free system operation, but if a positive approach to the noise problem is taken then we can consider it as a providential gift to the telecommunications engineering profession. Without noise our professional life would be dull: There would be no challenging problems of long distance transmission; any data rate could be achieved in a noiseless channel. Through continuous combat with various noise problems, new and more efficient signal processing, coding, and modulation techniques have been discovered.

The receiver of a digital microwave system has at its input the desired radio signal, front-end noise, and undesired adjacent or co-channel interference waves. This composite signal is random in nature. In order to evaluate the quality of this radio system, probabilistic solutions have to be sought. The final performance of a digital radio system, in addition to the conventional specifications of transmitter power, radiated spectrum, and receiver noise figure, is specified...