Low-complexity partitioned-spreading CDMA system with multistage MMSE reception

In this paper, we propose a low-complexity multistage filter for the partitioned-spreading CDMA (PS-CDMA). The proposed method embodies a MMSE filter that operates on the soft output of interference cancellation. Extrinsic information on the partitioned symbol is exchanged between the MMSE filter and the partitioned-spreading APP detector to improve the system performance. It is shown via variance evolution the signal-to-noise ratio of this novel technique achieves that of the single-user channel even for heavily loaded systems. It also outperforms IDMA by a fraction of dB to a few dBs, for a variety of system loads. The complexity of the proposed system is much lower that of its counterparts for conventional CDMA, which makes it a viable alternative for future 3G or beyond 3G systems