Distributed beamforming for multiuser peer-to-peer and multi-group multicasting relay networks

We generalize the concept of multiuser peer-to-peer (MUP2P) relay networks to that of a multi-group multicasting (MGM) relay network where each source may broadcast its message to a group of multiple users. State-of-the-art beamforming methods, which have been proposed for MUP2P relay networks, are shown to be straightforwardly extendable to such MGM networks. These methods aim to minimize the total transmitted relay power subject to receiver quality-of-service (QoS) constraints using convex approximations of the underlying non-convex problem. Due to the increase in number of receivers, these approximations may become inaccurate in the MGM case leading to severe performance degradation and problem infeasibility. To avoid this drawback, we propose an iterative method where the aforementioned convex approximations are successively improved. Our technique overcomes the difficulties emerging in the MGM and MUP2P relay networks for large numbers of users and outperforms the state-of-the-art methods developed for MUP2P relay networks.