Opportunistic Beamforming with Single Beamforming Matrix for Virtual Antenna Arrays

Opportunistic beamforming is a promising technique for downlink channels in cellular systems. When opportunistic beamforming is to support multiple users at a time, beams should be formed to avoid interference and this requires the feedback of channel state information (CSI) from users to a base station (BS). With limited feedback, to minimize the impact of interference, the best beamforming matrix can be selected from a set of multiple beamforming matrices. Thus, when a different set of users are to be supported by a scheduler, a new beamforming matrix has to be selected, which may require excessive complexity. To avoid this problem, in this paper, we propose an opportunistic beamforming approach with single beamforming matrix. In addition, we show that the proposed approach suits for a virtual antenna array where multiple BS units form a transmit antenna array.