Sequential detection for multiuser MIMO CDMA systems with single spreading code per user

We consider multiuser MIMO CDMA systems where each user has multiple transmit antennas and different transmit antennas of the same user use the same spreading code. Because transmit antennas of the same user use the same spreading code, inter antenna interference would degrade the system performance. We propose a novel decision-window-based data detection (sequential detection) method to mitigate the inter antenna interference. We also modify the existing single-user single-antenna channel estimation algorithm for multiuser multiantenna systems. The simulation results show that, under the same channel estimation algorithm, the proposed sequential detection scheme with decision window of two symbols significantly outperforms the non-sequential one which is a special case of the proposed one when the decision window is of one symbol. It also outperforms the existing SIC-VBLAST, decorrelator-VBLAST, and MMSE-VBLAST schemes.