Practical Multiuser Beamforming in WCDMA

In this paper, we present a multiuser beamforming technique that has been developed to overcome spreading code limitation problem in high speed downlink packet access (HSDPA), which is a packet enhancement to the third generation wideband code division multiple access (WCDMA) mobile communication system. The new technique is based on closed loop transmit diversity scheme included already in 3GPP WCDMA Release ´99 specification, and the key idea is to transmit simultaneously to those users that have requested orthogonal beam weights. First, link simulations are performed to study inter-user interference effect, because the transmission occurs simultaneously to multiple users. Furthermore, system simulations are done with all HSDPA features in macro cell environment. The standardized closed loop scheme is the baseline reference and per antenna rate control (PARC) scheme provides comparison against open loop multiple-input multiple-output (MIMO) scheme. The simulation results demonstrate significant cell throughput gain compared to reference simulations in one and three sector case.