Phase-sweep transmit diversity (PSTD) for shared data channels: a critical analysis

In this paper we propose a promising multiantenna scheme specifically suitable for hybrid Code & Time Division Multiplex (CTDM) high speed shared channels commonly employed in 3GPP and 3GPP2 standards (HSDPA/1xEVDO(HDR)/1xEVDV). The scheme is called Phase Sweep Transmit Diversity (PSTD) and was originally proposed for power controlled dedicated voice channels. PSTD is shown to provide the benefits of beamforming without the requirement channel or weight information feedback from the receiver to the transmitter. We evaluate the benefits of PSTD for two antenna configurations: (a) the so-called BF-2V configuration that encompasses two closely-spaced (λ/2) vertically polarized antenna columns and (b) the so-called DIV-2V antenna configurations, in which case the two antenna columns are widely-spaced (1020 λ). When compared to Selection Transmit Diversity (STD) and the baseline case of a single antenna transmission, PSTD offers significant gains for low-tier mobility users. In addition, the closely spaced antenna configuration produces consistently higher sector throughput as compared to the widely spaced configuration.