Jammer Excision in Spread Spectrum Communications via Discrete Evolutionary Transform

In this paper, we propose time-frequency jammer excision techniques for direct sequence spread spectrum communications. One method is based on the estimation of the instantaneous frequency (IF) of each of the chirp jammer components using a combination of the discrete evolutionary and the Hough transforms. The second method is based in Wiener masking, and reduces the interference in a mean-square fashion. In the first method, the jammer is synthesized and subtracted from the baseband received signal, while in the second method a mean-square estimate of the message is obtained. The IF-based method applies equally well to multi-component chirp jammers with constant or time-varying amplitudes, and instantaneous frequencies not necessarily parametrically modeled. A statistical analysis of this method is developed based on the signal to interference and noise ratio. We will show that the Wiener masking method is a general method requiring the spectrum of the spreading function. The two methods are illustrated by simulations.