PERFORMANCE ANALYSIS OF AN OVERLAID SPREAD SPECTRUM COMMUNICATION SYSTEM FOR MOBILE RADIO APPLICATIONS
Abstract
There has been growing interest over the past decade in utilizing spread spectrum techniques for civilian applications, particularly for systems operating in interference limited environments. This is a result of the ability of spread spectrum systems to resist unintentional interference (e.g., cochannel interference) as well as hostile jamming signals. Most proposed civilian applications of spread spectrum techniques have assumed that any such fielded system would occupy exclusively the frequency allocation over which it operated (with the possible exception of other spread spectrum users operating in a Code Division Multiple Access mode). An interesting related application is that in which the spread spectrum system operates collocated, both spectrally and geographically, with a more conventional narrowband system. The term "overlay" has been used to describe this configuration. The possibility of employing spread spectrum techniques in civilian mobile radio applications has received considerable attention in the past few years. In this research we examine an extension of this to overlaid systems. In particular we consider the feasibility of collocated operation of a DPSK frequency hopped spread spectrum system with a conventional narrowband FM system, both of which are deployed in a cellular configuration. In any such joint usage of the radio spectrum there exists a considerable potential for intersystem interference. When the application considered is cellular radio systems there are several forms that this intersystem interference can take. We examine each of these in detail to determine the amount of degradation each system would experience due to the presence of its spectral coinhabitant. Results are presented that depict the PBE and SDR which the spread spectrum and narrowband FM system could achieve, respectively, for various levels of system loading. It is found that, with the proper choice of system parameters, it would be possible for both systems to achieve acceptable levels of performance, for both upstream and downstream transmission, even when each system is moderately loaded.
Degree
Ph.D.
Subject Area
Electrical engineering
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