Combined pre- and post-equalization for uplink time division duplex MC-CDMA in fading channels

Equalization at the receiver of multi-carrier code-division multiple-access (MC-CDMA) systems is a well known and well investigated topic in multi-carrier communications. Moreover, pre-equalization techniques for uplink time division duplex (TDD) MC-CDMA systems have been introduced and investigated recently. In this paper, combined pre- and post-equalization for uplink TDD/MC-CDMA systems in fading channels is proposed. Especially, it is shown that by choosing the corresponding pre- and post-equalization techniques in a preferred way considerable performance improvements are achieved compared to pre- or post-equalization alone. For combined equalization the design criterion for pre-equalization at the transmitter is optimal power assignment with respect to the fading channel rather than Suppression of multiple-access interference, whereas multiple-access interference cancellation followed by maximum ratio combining of the almost interference free received signal is the main task at the receiver. As a result, new single-user bounds for MC-CDMA systems transmitting over fading channels and, thus, considerable performance improvements are achieved by applying this novel concept of combined equalization.