Investigation of the Performance of Different Adaptive Space-Time Transmit Diversity Schemes

No Thumbnail Available



Journal Title

Journal ISSN

Volume Title


Addis Ababa University


Transmit diversity techniques provide attractive solutions for increasing downlink capacity in 3G systems. Open-loop and closed-loop transmit diversity modes with two transmit antennas have already been included into 3G Partner Project WCDMA (wideband code division multiplexing access), and schemes exploiting a large 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 work, a scheme which combines a closed-loop and open-loop transmit diversity (adaptive space-time transmit diversity) is investigated and the signal-to-noise ratio (SNR) to bit error rate (BER) performance of this adaptive space-time transmit diversity schemes are evaluated on a flat Rayleigh fading channel. The performance results obtained from the simulations show that adaptive space-time transmit diversity schemes have better error rate performance than the space-time transmit diversity. Finally, this work has shown that adaptive power allocation scheme in conjunction with the Alamouti scheme has an improved error rate than the open loop transmit diversity (Alamouti scheme) and also adaptive space time modulation has an improved error rate performance than the Alamouti scheme. Moreover, this thesis showed the tradeoff between schemes combining both adaptive rate and power with different percentages and increasing the power at the same time reducing the data rate has an improved error rate performance than reducing the power at the same time increasing the data rate of the system