Effects of of weighted despreading sequence on CDMA performance

Abstract

This paper addresses the effects of a weighted despreading sequence on the performance of a coherent receiver in a DS-CDMA system. The chip weighting waveforms used in the receiver are designed for the purpose of multiple access interference rejection by emphasizing the transitions of the received signal of interest. Since the resulting weighted despreading sequence is determined only by one parameter, this leads to easy tuning of the weighted despreading sequence in practice to achieve the best performance. The criterion of tuning the parameter is to maximize the derived signal to interference plus noise ratio of the decision variable based on the relative strength between white noise and multiple access interference. As a result, according to the proposed approach, we can reject the multiple access interference without knowing the co-user's spreading codes, timing, and phase since maximizing the signal to interference plus noise ratio in Gaussian noise minimizes the probability of error of the receiver.