Space-time MMSE multiuser detection in multipath channels with RS coding

The performance of minimum mean squared error (MMSE) multiuser detection (MUD) using array processing and Reed-Solomon (RS) coding is analyzed for binary, direct sequence code division multiple-access (DS-CDMA) systems used over multipath channels. Wang and Poor (1999) discussed the performance of the space-time MMSE MUD in multipath channels with no FEC coding. In this paper we investigate the performance of a base station receiver that combines space diversity, multipath diversity MUD, and RS channel decoding. The improvement in the bit-error rate (BER) using channel coding is evident in our simulation results. It is shown that employing RS codes with space-time MMSE-MUD improves the system performance significantly compared to both the uncoded space-time MMSE-MUD and the coded space-time RAKE receiver. We also present the Gaussian approximation for MMSE-MUD used in multipath channels. This Gaussian approximation gives accurate results when compared to our simulation results. Based on the validity of this approximation, we define upper bounds for the coded system BER. These upper bounds, which are shown to be tight, can be a helpful tool in predicting the system performance with different system parameters