Analysis on the impact of multi-element transmit antenna system on multiuser diversity [mobile wireless systems]

In this paper, the performance of a multiuser diversity system paired with a multi-element transmit antenna system is analyzed under the assumption of independent Rayleigh fading. A measure of system level performance is an achievable spectral efficiency as a function of the number of users and antennas. Spectral efficiency is obtained from the instantaneous signal-to-noise ratio (SNR) distribution combined by both transmit diversity at each link and multiuser diversity at system level when the base station transmitter adapts to channel variations using a constant power variable rate strategy. Numerical results show that closed-loop antenna techniques provide an additional gain with multiuser diversity systems due to array gain, even though space diversity gain reduces multiuser diversity gain. On the other hand, the space-time block coding (STBC) that provides full order space diversity gain only has a destructive impact on multiuser diversity.