Adaptive modulation for multiuser orthogonal random beamforming systems

Abstract

In this paper, we present and analyze a rate-adaptive multiuser orthogonal random beamforming (ORBF) system. The goal is to maximize the average spectral efficiency (ASE) while satisfying a target bit error ratio (BER) constraint. We first derive the cumulative distribution function of the post-scheduling signal-to-interference-plus-noise ratio (SINR) with a new approach. The average BER and the ASE are derived as closed-form expressions. Finally, we obtain the optimal switching SINR thresholds maximizing the ASE under average BER constraint. Simulation results show performance improvement in terms of ASE.