Mobile-assisted scheduling for downlink multi-beam phase-sweep transmit diversity (PSTD) with partial feedback

In this paper. we consider a wireless access network with K mobile devices and an access point with n(T) transmit antennas. We shall propose a novel mobile-assisted scheduling algorithm for the Multi-beam Phase-Sweep Transmit Diversity (MB-PSTD) systems. We consider the downlink system performance with respect to maximal-throughput and proportional-fair utility functions. We show that the MB-PSTD scheme could significantly enhance the downlink system performance compared to the conventional PSTD schemes by fully utilizing the n(T) degrees of freedom in the system. With the mobile-assisted scheduling algorithm. the feedback requirement is substantially reduced. The beam-sweeping facilitates the multi-user selection diversity between slow mobility users while the multi-beam fully utilize the intrinsic system degree of freedom. As we increase n(T), the MB-PSTD system performance is gradually limited by the multi-beam interference because it more and more difficult to find a set of users perfectly aligned with the n(T) orthogonal beams. Yet, the multi-beam, interference could be reduced by increasing the number of active users (K) in the system. Asymptotically at large n(T) and K, we show that the system capacity scales linearly instead of logarithmically with respect to the transmitted power