Pre-filtering technique for MAI cancellation in MC-CDMA systems

[[abstract]]Multicarrier code division multiple access (MC-CDMA), is a promising multiplexing technique for future communication systems. In this study, we employ the well-known Walsh-Hadamard spreading codes for synchronous downlink transmission of MC-CDMA systems. The spreading codes allow that the frequency diversity to be efficiently exploited. However, multipath propagation may cause orthogonality among users is distorted, and this distortion produces multiple access interference (MAI). To eliminate this effect, we propose a pre-filtering-based MC-CDMA system which uses a pre-filtering technique at the transmitter and an equal gain combining (EGC) scheme at the receivers, respectively. Our proposed pre-filtering technique transforms the transmitted signals so that the MAI can be eliminated, and the EGC scheme weights the signals received from all subcarriers so that channel distortions can be compensated. Furthermore, the proposed technique can calculate the transmitted power over all subcarriers to satisfy the required quality of service of each user and archive MAI-free. In this paper, performance in terms of bit error rate is analyzed; in comparison with the EGC, orthogonal restoring combining, and maximal ratio combining schemes at receiver, respectively. Copyright (c) 2011 John Wiley & Sons, Ltd.[[note]]SC