MIMO Capon Receiver for Space-Time Coded CDMA systems

Recently, the space-time coded code division multiple access (ST-coded CDMA) has been widely investigated for the great demand on capacities and transmission rates in the future wireless communication systems. The Alamouti's space-time block code scheme is examined here where two linearly constrained minimum variance (LCMV) filters are designed in the receiver. In this paper, the two weight vectors of the LCMV filters are shown to be related each other. Then only half of the computational complexity is required to detect the space-time coded symbols. Furthermore the LCMV filters are very sensitive to finite samples and signature vector errors. We propose both the forward-backward averaging technique and the eigenspace technique to enhance the system performance. Moreover, we present a subspace-based channel estimator which utilizes the space-time coding property to improve the performance of channel estimator. Computer simulations are given to demonstrate the effectiveness of the channel estimation and receiver design for the ST-coded CDMA systems.