On space-time block coding in downlink of multiuser CDMA systems

In this paper, we introduce a new transmission scheme for downlink of multiple antenna code division multiple access (CDMA) systems. In the proposed scheme, the Alamouti´s space-time block coding (STBC) method is extended to multiuser systems. Moreover, to mitigate multiple access interference in the conventional receivers, the linear transmit preceding technique is used in the transmitter. We show that using STBC codes in conjunction with transmit preceding in CDMA systems can significantly increase the capacity of these systems. In this method, the mobile terminals are simple and they do not need any information about other users´ spreading sequences. Our computer simulations show that the proposed method has the same performance as the methods based on the combination of receive diversity and multiuser detection in the uplink of CDMA systems