Transmit Diversity Weight Generation for Wireless Fdd Systems with Feedback

Transmit diversity techniques provide attractive solutions for increasing downlink capacity in 3G systems within lowmobility environments. Open-loop and closed-loop transmit diversity modes with two transmit antennas have already been included into 3GPP WCDMA Release 4, and schemes exploiting a larger number of transmit antennas are being developed. System capacity can be increased from that of open–loop modes if the transmitter is equipped with additional side information of the downlink channel. In a frequency division duplex (FDD) system this means that the receiver has to provide the information through some feedback mechanism. In this paper we give two feedback signal designs and an algorithm to design corresponding transmit weights utilizing linear functions of order statistics of the underlying random process. This provides a simple tool to design closed– loop transmit diversity systems depending on the feedback capacity of the system and propagation environment.