Coordinated beamforming for wireless multicast cell with nonregenerative multi-antenna relay

This paper considers the wireless multicast cell, in which two source nodes with multiple antennas communicate with two destinations over a common medium simultaneously assisted by a multi-antenna relay node. Assume that the sources and relay have individual power constraints. The purpose of this work is to develop an optimal algorithm to compute the source beamforming vectors and the relay beamforming matrix to maximize the system sum-rate, subject to the power constraints in the sources and relay. The problem is nonconvex and apparently has no simple solution. In this paper, We first develop the beamforming vectors at the sources, and then explore the linear beamforming matrix for the nonregenerative relay, Finally, we present a coordinated optimal algorithm to jointly optimize the vectors and matrix, which performance is compared with the conventional methods. Simulations demonstrate that our algorithm outperforms the conventional methods.