MMSE pre-filtering techniques for TDD MC-CDMA downlink transmissions

We discuss signal pre-filtering in the downlink of a multi-carrier code-division-multiple-access (MC-CDMA) network operating in a time-division-duplex (TDD) mode. The base station (BS) is equipped with multiple antennas and channel state information (CSI) is available at the transmit side due to the channel reciprocity between uplink and downlink transmissions. The pre-filtering coefficients are designed so as to minimize the sum of mean square errors at all mobile terminals (MTs). The resulting scheme mitigates the detrimental effects of multiple access interference (MAI) and multipath propagation, thereby allowing the use of simple and power efficient single-user detection (SUD) techniques at the MTs. Simulation results are given to highlight the effectiveness of the proposed method with respect to other existing pre-filtering schemes.