A receiver feasibility study for the spread spectrum high capacity mobile radio system

Considerable theoretical work has been done on the applications of spread spectrum techniques to high capacity cellular mobile radio systems. [1], [2], [3], [4]. This theoretical work assumes a receiver structure that is mathematically convenient and does not address the problem of implementing such a receiver. The study reported on here examines a number of possible configurations and modifications of the mathematical model with respect to the feasibility of their physical implementation with advanced and state-of-the-art components. The critical component in a spread spectrum receiver employing time-frequency coded signals is a tapped delay line with a maximum delay that is twice the duration of the signal waveform. For current signal designs the maximum delay is about 600 microseconds. Both surface acoustic wave (SAW) devices and charge coupled devices (CCD) are considered as possible realizations of this component. The current design limitations of both SAW devices and CCD's, as applied to the proposed application, are discussed. In addition, the extent to which the limitations of future devices will have to be improved in order to meet the requirements of a fully developed spread spectrum system is presented.