Representation of nonstationary narrowband random processes and their application and effectiveness as jamming signals in spread spectrum communication systems

Abstract

A representation of nonstationary narrowband random processes in terms of nonstationary quadrature components is proposed in a form analogous to that used to represent wide sense stationary narrowband random processes. The represen­tation is then applied to a specific case in which the nonstationary narrowband random process is generated by the product of white noise and a deterministic periodic signal and then is processed by a narrowband filter. This representation is used in the modeling of a bi-level pulsed noise jammer which is assumed to be present in a communication channel. The effect of such a jammer on a direct sequence, binary phase shift keyed (DS-BPSK) spread spectrum communication receiver is evaluated and characterized in terms of the error rate performance of the receiver. Families of performance curves are plotted to demonstrate the effect of various parameters, namely signal-to-noise ratio, jammer power to signal power ratio, and processing gain, on the error rate of the complete spread spectrum receiver. The analysis carried out differentiates between two cases, namely fast jammers and slow jammers. However, the analytical tools developed make it possible to consider either one of the two cases without resorting to quasi-stationary arguments as has been done in the past.