Some New Results on Stochastic Beamforming Schemes

Abstract

In this paper, we provide some recent results on stochastic beamforming (SBF), which has been proposed to approximately approach the channel capacity for the multi-input single-output (MISO) downlink channels. We respectively consider close-loop and open-loop systems, as well as the scenario with partial channel state information received at the transmitter. We combine SBF with the orthogonal space-time block code (OSTBC), the quasi-orthogonal space-time block code (QOSTBC) and antenna subset selection (ASS) schemes to improve multicast rate in different scenario settings. In particular, in the close-loop scenario, QOSTBC ensures a virtual full rate high-rank SBF transmission. Despite of the inter-symbol interference at the receiver, QOSTBC harvests antenna gain and therefore improves the SBF multicast rate. In the open-loop scenario, we show that SBF and OSTBC can provide better multicast rate compared with the classic space-time coding scheme and the classical transmit beamforming scheme. When partial channel state information is known at the transmitter, we propose to adopt the SBF-ASS scheme, which employs a proper antenna subset to perform better SBF transmission. Our simulation results validate the superiority of different SBF schemes. Hence, by combining with OSTBC, QOSTBC and ASS schemes, SBF becomes more flexible to meet performance requirements in different scenario settings.