A low-complexity two-stage receiver for space–time block-coded CDMA MIMO systems

A low-complexity two-stage receiver for the space–time block-coded (STBC) code-division multiple-access (CDMA) multiple-input multiple-output (MIMO) system is proposed in this paper. The STBC CDMA MIMO system has been extensively studied for the great demand for capacity and transmission rate in future wireless communication systems. The blind Capon multiuser receivers implemented by linearly constrained minimum variance (LCMV) filters are designed to achieve this goal. However, the LCMV filter suffers from the heavy computational load and slow convergence speed. The proposed two-stage receiver contains partially adaptive linear filters in parallel followed by a channel estimator and symbol detector. Two transformation schemes are designed for the partially adaptive linear filters. The uniqueness and exactness of channel estimation are analyzed when the noise power approaches zero. To alleviate the finite sample effects, the forward–backward averaging technique is introduced to enhance system performance. Based on the weighting analysis, we also present a simplified two-stage receiver. The computational complexities of the compared receivers are calculated. Computer simulations demonstrate that the proposed two-stage receiver has better performance than the Capon receiver with much lower computational load.