Distributed beamforming based on sum rate maximization in multi-user systems

In this paper, the problem of distributed beamforming is considered for relay networks, in which a base station transmits to multiple single antenna destinations with the help of a set of cooperating relay nodes. The beamforming weights are obtained through maximizing the sum rate subject to two different types of power constraints, namely the total relay power constraint and individual relay power constraints. The proposed scheme iteratively searches the optimal relay weights by deriving the partial derivatives of the sum-rate and applying the gradient search algorithm. Simulation results show that the proposed iterative scheme with provable convergence achieves a near optimal sum rate with a few iterations.