Performance of DS/SSMA Communications in Impulsive Channels - Part I: Linear Correlation Receivers

The performance of digital linear correlation receivers is studied in a multiuser environment. There are assumed to be two types of sources interfering with data transmission: multiple-access interference, and additive channel noise which is attributed to impulsive noise sources in the environment. The contribution of multiple-access interference is examined by considering
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asynchronous users transmitting simultaneously over a linear channel using the binary PSK direct-sequence spreadspectrum multiple-access (DS/SSMA) technique. Alternatively, the effects of the non-Gaussian impulsive channel in such a system are studied by modeling the samples of noise after front-end filtering. Errorprobability performance under these conditions is compared to that for additive white Gaussian noise (AWGN) channels. Due to computational complexity, exact analysis is limited here to systems utilizing short spreading sequences. Computationally simple methods are proposed for approximating the average error probability when the length of the signature sequences is large. Furthermore, some asymptotic results are obtained for the case of infinitely long sequences. In all cases, performance variation is examined as the shape of the noise density varies with SNR held constant. The results of this analysis indicate that the presence of impulsive noise can cause significant performance degradation over that predicted from an AWGN model, even when the total noise power does not increase.