Transmit diversity combining for wideband DS/CDMA in wireless communication systems

Wideband code-division multiple-access (CDMA) will be utilized in the third generation or 3G wireless communication systems because of its high frequency utilization efficiency and suitability for handling multimedia and multi-rate services. In this paper, we present a system with a simplified receiver structure for DS/CDMA wireless communication handsets, in which improved performance is demonstrated when compared to a conventional DS/CDMA system with a RAKE receiver at the mobile station. The proposed system is obtained by finding the optimal solution to a general multiple-input single-output (MISO) DS/CDMA smart antenna system. It is shown that this solution reduces to a pre-RAKE with space transmit diversity system under the assumption that a simplified receiver structure is invoked. Numerical results show that significant system performance and capacity improvements are possible. They also reveal that the proposed system is not too sensitive to channel estimation errors.