Abstract
A new multiple access communication system with orthogonal multicarrier (OM) transmission via Direct Sequence Spreading Spectrum (DS/SS) which can transmit data at high speed in wireless environmenthas attracted in recent years. The combination of the orthogonal frequency division multicarrier and Direct Sequence Code Division multiple access (OFDM--CDMA) provides an efficient and flexible way to access and distribute multiple multiplexed data source, and the OFDM--CDMA scheme proves to be robust in combating multipath and fading of transmission channels. In this paper, a new adaptive equalizer scheme for the receiver of OFDM--CDMA system is proposed to reduce the multiple access interference (MAI) arisen from multipath propagation and cross-correlation between the code sequences. The proposed adaptive equalizer consists of a cascade of an adaptive prefilter and an adaptive postfilter to take a balance between the compensation of channel effect and the MAI cancellation to avoid noise enhancement at the same time. We also propose new adaptive algorithm for blind channel estimation. Finally, the performance of the proposed method is analyzed and the asymptotic convergence property is also discussed. From several simulation results, we find that the proposed adaptive equalizer algorithm performs better than the other equalizers.