Spatial-Multiplexing Phase-Sweep Transmit Diversity (SM-PSTD) for Multiantenna Base Stations With Mobile-Assisted Scheduling and Incremental Rate Feedback

摘要

Phase-sweep transmit diversity (PSTD) has been widely studied in 3G1X and Universal Mobile Telecommunications Systems (UMTS) for its performance gain and simplicity. However, conventional PSTD systems are designed based on a single-sweeping beam, and only one user is selected for transmission at any time. Therefore, it fails to fully exploit the available spatial degree of freedom. In this study, a novel spatial-multiplexing phase-sweep transmit diversity (SM-PSTD) scheme with partial feedback mobile-assisted scheduling is being proposed. The downlink performance (system capacity and proportional fairness) of a multiantenna base station has been its focus. The spatial-channel sweeping facilitates the multiuser selection diversity between users, while the spatial multiplexing significantly enhances the system capacity. As the number of transmit antennas n{sub}T is increased, the SM-PSTD system performance is gradually limited by the multiuser interference because it is more and more difficult to find a set of users perfectly orthogonal within the n{sub}T spatial channels. Yet, the multiuser interference could be reduced by increasing the number of active users K in the system. Asymptotically, at large n{sub}T and K, it shows that the system capacity scales linearly instead of logarithmically with respect to the transmitted power.