Noise reduction in communication channels

THE DEVELOPMENT of communication theory has led to the introduction of concepts such as integration, correlation, matched filtering, “comb” filtering, probability of detection, etc. Much confusion centers about their significance because of functional equivalence and because of inadequately defined purposes in their use. Thus, it may be overlooked that integration and correlation are equivalent operations, or that matched filtering or comb filtering are techniques of integration. The purpose in using these concepts can be understood properly only within frameworks of suitable criteria of performance. For example, it is frequently assumed that the end object of a filtering technique is to improve the signal-to-noise ratio, whereas it is actually a means to an end. This end is to increase the information rate over a communication channel or to increase the probability of detection of a search radar, etc.