Comprehensive Analysis and Evaluation of Single/Multi-User Joint Transmit-Receive Diversity

The spatial diversity has long been recognized as a powerful technique to mitigate the multipath fading effect and to improve the signal transmission quality (and hence the capacity of wireless systems). Joint transmit-receive diversity (JTRD), which utilizes transmit diversity and receive diversity jointly at both transmitter and receiver, is expected to further enhance the capacity of wireless systems. This paper provides a comprehensive analysis and evaluation of single/multi-user JTRD. Firstly assuming single-user transmission, the principle of JTRD is presented. The relationship between suboptimal JTRD and optimal JTRD is given. Optimal JTRD is shown to be equivalent to maximum eigenmode transmission. A recursive solution method is developed for determining optimal JTRD weight vectors. Received signal-to-noise ratio (SNR) analysis of optimal/suboptimal JTRD is also presented to show that the fading correlation is not always a negative factor in a strongly asymmetric MIMO channel. Then, an incorporation of JTRD into multi-user MIMO communications is presented. Zero-forcing-based precoder is designed to remove multi-user interference. Expressions for the received SNR of uplink and downlink transmissions are presented. Two types of multi-user JTRD are shown to be equivalent to hybrid beamforming and full digital beamforming. Also in this paper, user and sum capacities achievable by single/multi-user JTRD in Rayleigh faded MIMO channels are evaluated using Monte-Carlo numerical computation method to confirm the theoretical findings.