Joint transmitter-receiver adaptive forward-link DS-CDMA system

Abstract

A joint transmitter-receiver adaptive DS-CDMA system over a slow flat fading forward-link channel is considered. A set of spreading sequences is designed to support all users with a uniform target SIR. This set of sequences reduces to the optimum solution of the transmitter optimization problem of choosing a set of sequences to meet the SIR target with a minimum total transmission power when the channel reduces to an AWGN channel. The MMSE receiver is employed for signal reception and receiver weights of each user are adapted independently and simultaneously without information from other users. Estimates of the MSE at each receiver are sent back to the base-station. An adaptive algorithm is designed to estimate channel parameters using the feedback information and update the spreading sequences at the base-station. The algorithm gives a set of sequences which satisfies the target SIR and has total transmission power close to the theoretical total power after a moderate number of iterations. Simulation results show that performance improvement can be achieved with the proposed joint adaptation scheme.