MPOE based prefiltering and MRT beamforming with matched filter receiver for DS-CDMA systems

Abstract

In order to reduce the complexity of the mobile receiver, we develop two prefilter models using a linear FIR prefilter for minimizing the probability of error in multi-user transmission scenario. We consider downlink transmission. In the first system model, we have a single common prefilter for all users at the base station transmitter and in the second system model, we consider an individual prefilter for each and every user. We assume complete knowledge of the channel at the base station. In order to fully utilize the knowledge available at the transmitter, the filter weights are computed, conditioned on the transmitted bit vector sequence. This also makes the computation of the prefilter coefficients linear in the number of users as opposed to the exponential complexity otherwise. Coefficients of FIR prefilter are computed by minimizing the conditional probability of error and the mean square error. To further improve the performance of the proposed models, we consider Maximum Ratio Transmission (MRT) beamforming at the base station for both the models. Simulation results illustrate the performance of the proposed system models.