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

Paper approved by R. Kohno, the Editor for Spread Spectrum Theory and Applications of the IEEE Communications Society. Manuscript received October 8, 2004; revised October 11, 2005. This paper was presented in part at the IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, Lisbon, Portugal, September 2002.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.This work was supported in part by the Korea Science and Engineering Foundation (KOSEF) through the National Research Lab. (NRL) Program funded by the Ministry of Science and Technology (No. M10300000316-06J0000-31610)