Adaptive correlator receiver performance in direct sequence spread spectrum communication

The authors analyze the bit error rate (BER) performance of the adaptive correlator in a complex channel with both multipath and narrowband interference. They extend previous work by presenting analytical BER expressions and results for narrowband (filtered noise) interference. The adaptive correlator is shown to be capable of removing relatively wideband interference in the transmission bandwidth. This is due to the fact that the correlator becomes a finite impulse response (FIR) filter with a deep notch in the interfering band. As the length of the spreading code increases, the FIR filter length will also increase, thus increasing the correlator´s ability to remove interference. The error propagation of the least-mean-square (LMS) adaptive algorithm is shown, and is seen to be significant at high bit error rates when a large convergence factor is used