Transmitter-based processing for the down-link DS/CDMA systems with multiple transmit antennas

There have been various receiver-based techniques for performance improvement of wireless communications systems. However, receiver-based techniques have a restricted application in the down-link because they increase computational complexity of the mobile station (MS). In this paper, a transmitter-based processing scheme for the down-link direct-sequence code division multiple access (DS/CDMA) systems with multiple transmit antennas is proposed. The proposed scheme uses a pre-RAKE method to exploit diversity gain and pre-decorrelating method to suppress multiple access interference (MAI) and multiple path interference (MPI). To make the total transmit power the same as that without pre-decorrelating processing, we present three power normalization methods and compare the performance of those with one another.