Wiener Feedback Filtering for Suppression of Residual ISI and Correlated Noise in MC-CDMA

Abstract

Multi-carrier CDMA takes advantage of frequency diversity by spreading each user symbol across multiple sub-carriers to improve the transmission performance. However, the performance of linear detection schemes is affected by the residual inter-symbol interference (ISI) and the correlated noise present in decision variables. In order to improve the performance, a decision feedback equalization (DFE) scheme is proposed in this paper. In the feedback stage, an optimal Wiener filter is designed to predict and suppress the residual ISI and the correlated noise caused by the channel equalization and code despreading in the feedforward stage. Simulations show that the proposed DFE scheme significantly outperforms the conventional linear minimum mean-square error (MMSE) receiver. By this scheme, a noise penalty between MC-CDMA and ideally coded OFDM is largely reduced.