On the performance of FDDW CDMA closed-loop transmit diversity modes in Nakagami and Rician fading channels

Transmit diversity techniques provide attractive solutions for increasing downlink capacity in 3G systems within low-mobility 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 studied. 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 requires a separate feedback channel. 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. Furthermore., we provide analytical results for the resulting SNR gains of WCDMA closed-loop transmit diversity modes in the case of single-path Nakagami-m, and Rician fading channels.