The performance of any communication system depends on the characteristics of the transmission medium and can often be improved by using techniques which successfully exploit these characteristics, for example by using an optimum modulation method. The important characteristics for the communications engineer are the frequency and time responses of the channel, and the magnitude and nature of the noise. The channel responses have been discussed in earlier chapters; we now deal with the problem of noise. There are two basic reasons for a study of noise. Firstly there is a need to understand the nature of the noise in order. | The Mobile Radio Propagation Channel. Second Edition. J. D. Parsons Copyright 2000 John Wiley Sons Ltd Print ISBN 0-471-98857-X Online ISBN 0-470-84152-4 Chapter 9 Man-made Noise and Interference INTRODUCTION The performance of any communication system depends on the characteristics of the transmission medium and can often be improved by using techniques which successfully exploit these characteristics for example by using an optimum modulation method. The important characteristics for the communications engineer are the frequency and time responses of the channel and the magnitude and nature of the noise. The channel responses have been discussed in earlier chapters we now deal with the problem of noise. There are two basic reasons for a study of noise. Firstly there is a need to understand the nature of the noise in order to devise methods by which it can be characterised. Knowledge of the sources of noise may also lead to methods by which it can be suppressed. Secondly there is a vital need to be able to predict the performance of communication systems that have to operate in noisy environments. A mobile radio system is beset with noise from various sources each having different characteristics. Firstly there is receiver noise which is Gaussian in nature and arises from the receiving system itself. Receiver noise is usually expressed in terms of nkT B where n is the factor by which the total receiver noise exceeds ambient noise. Atmospheric noise may also be present but it decreases rapidly with frequency and is generally negligible in the VHF range. Galactic noise is also insignificant in the VHF band as it is well below the background noise. By far the most important source of noise in mobile communication is the noise radiated by electrical equipment of various kinds. This noise commonly termed man made noise is impulsive in nature and therefore has characteristics quite different from Gaussian noise. It can be detected at frequencies up to 7 GHz 1 and .
