Cellular land-mobile radio: Why spread spectrum?

It is widely recognized that the electromagnetic spectrum is a beleaguered resource, and nowhere is this more evident than in the land-mobile radio service. The existing allocations of spectrum have long been oversubscribed in many major cities, and huge backlogs of potential users with no allocations have built up in many areas. Cellular land-mobile radio systems are widely recognized to provide a potential solution to this problem, and cellular systems using conventional analog modulation techniques have been proposed [l], [2]. This article discusses the authors' belief that spreadspectrum can substantially improve the spectral efficiency of a cellular land-mobile radio system, as well as making it more versatile and better adapted to the environment. It should be emphasized, however, that the theoretical work on which this belief is based is in a very preliminary stage and that much more study and simulation, as well as a field trial, are required before the validity of the claims made here can be established. Indeed, much of the work described here is controversial and, hence, a major function of this paper is to present these views to a wider audience and thereby encourage further discussion of them.