Orthogonal Beamforming for SDMA Downlink with Limited Feedback
The Proc. of IEEE Intl. Conf. on Acoustics, Speech and Signal Proc., Honolulu, HI, Apr. 2007
On a multi-antenna downlink channel, separation of multiple users by transmit beamforming enables simultaneous transmission from the base station to the users, resulting in high sum throughput. This paper proposes and analyzes a practical algorithm for joint orthogonal beamforming and scheduling, which is enabled by feedback of quantized channel state information. In this approach, the base station generates multiple sets of orthogonal beamforming vectors and associates each vector with a specific user. Subsequently, the base station selects one set of beamforming vectors and the associated users for downlink transmission such that the throughput is maximized. Unlike an exhaustive approach, the proposed algorithm has computational complexity that increases only linearly with the number of users since it does not require an exhaustive search over all possible subsets of users.