Cooperative MIMO-beamforming for multiuser relay networks

In this paper, we develop a beamforming algorithm for multiuser MIMO-relaying wireless systems. We consider a relaying scenario with multiple sources transmitting to one or more destination nodes through several relay terminals. Each relay is equipped with multiple antennas. We jointly design the beamforming matrices of the cooperating relays by minimizing both the noise received at each destination node and the interference caused by the sources not targeting this node. We impose additional constraints that preserve the received signal from each source at its targeted destination node. The relay beamforming problem is shown to be a convex optimization problem and is formulated as a second-order cone program that can be efficiently solved using interior point methods. Numerical simulations are presented showing the superior performance of our beamforming technique compared to previously proposed zero forcing relay beamforming.