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

In this paper, the novel concept of combinedequalization 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 preand postequalization techniques are chosen accordingly.