Asymptotic bit error probabilities of some closed-loop transmit diversity schemes

Transmit diversity techniques have received a lot of attention recently, and open–loop and closed–loop downlink transmit diversity modes for two transmit antennas have been included into 3GPP WCDMA Release 5. System capacity can be increased from that of open–loop modes if the transmitter can be provided additional side information of the downlink channel. In a frequency division duplex (FDD) system this requires a separate feedback channel. Quantization of the feedback messages in closed–loop transmit diversity schemes reduces the performance of the system. However, this effect has not been usually taken into account in the analysis. In this paper we analyze the effect of quantization and deduce an analytic formula for the asymptotic bit error probability of the closed–loop transmit diversity schemes defined in 3GPP WCDMA specification.