Transmitter-Based Processing for Down-Link DS/CDMA Systems with Multiple Transmit Antennas

Abstract

In cellular wireless communication systems, there have been various receiver-based techniques for performance improvement. However, it may be desirable to use transmitterbased techniques to improve the down-link capacity, since the implementation complexity is less critical at a base station (BS) than at a mobile station (MS). This paper presents a transmitterbased processing for the down-link direct-sequence code-division multiple-access (DS/CDMA) systems with multiple transmit antennas. We propose a combined pre-rake/pre-decorrelating approach. This approach combines the advantage of pre-rake scheme, to achieve diversity gain and average received signal-tonoise ratio (SNR) gain, with that of pre-decorrelating scheme, to suppress multiple access interference (MAI) and multipath interference (MPI). Furthermore, to make the total transmit power the same as that without pre-rake/pre-decorrelating processing, two power normalization methods are presented. Simulation results show that the proposed schemes significantly outperform the conventional transmitter-based techniques. The effects of the number of users and the block size on the bit error rate (BER) performance are also investigated.