Development and Performance Analysis of Non-data Aided MMSE Receiver for DS-CDMA Systems

Abstract

In this paper, a non-data aided minimum mean square error (MMSE) receiver with enhanced multiple access interference (MAI) suppression is proposed for direct-sequence code-division multiple-access (DS-CDMA) systems over a multipath fading channel. The design of the proposed receiver is via the following procedure: First, an adaptive correlator is constructed based on the linearly constrained minimum variance (LCMV) criterion to collect each multipath signal and suppress MAI blindly. A maximum ratio combiner is then utilized to coherently combine the correlator outputs. With a set of judicious chosen weight vectors, effective diversity combining can successfully suppress MAI and the desired signals can be effectively retained. Finally, further performance improvement against the finite data sample effect is achieved using a decision-aided scheme in which the channel response is obtained by the decision data and incorporated with the MMSE method to compute the refined weight vector. Performance analysis based on the output signal-to-interference-plus-noise ratio (SINR) is done to examine the efficacy of the proposed non-data aided MMSE receiver, which can offer the similar results as those of the MMSE receiver with the channel estimation correctly obtained beforehand. Computer simulation results then confirm correctness of the analysis results and demonstrate that the proposed blind receiver can successfully resist MAI as well as the finite data sample effect, and significantly outperform than the conventional blind receivers.