Performance of Coded Uplink MC-CDMA with Combined Pre- and Post-Equalization in Fading Channels

Abstract

In this paper, the novel concept of combined equalization is investigated for coded uplink MC-CDMA. For combined-equalization it is presumed that channel state information (CSI) is available at the transmitter (Tx) as well as at the receiver (Rx). As a result, combined-equalization achieves considerable performance improvements over preor post-equalization applied alone if the corresponding preand post-equalization techniques within combined-equalization are chosen in a preferred way. For combined-equalization the design criterion at Tx is optimal power assignment with respect to CSI rather than avoidance of multiple-access interference (MAI), whereas MAI cancellation followed by maximum ratio combining (MRC) of the almost interference free signal is the main task at Rx. Thus, combined-equalization offers two degrees of freedom - at Tx and Rx - in order to resolve the two contrary design goals of optimal power allocation with respect to the fading channel and MAI supression/avoidance. As a result, improved single-user bounds for MC-CDMA systems transmitting over fading channels are achieved in the case of combined-equalization. Simulation results show that these improved single-user bounds can be approached very closely even for fully-loaded systems if the combined pre- and postequalization techniques are chosen accordingly.