Optimum discrete distributed beamforming for single group multicasting relay networks with relay selection

In this paper, broadcast beamforming with relay selection is considered in wireless relay networks where there is no direct link between the source and the receivers. A source node transmits common information to many users employing multiple relays which use amplify-and-forward relay protocol. The channel state information is assumed to be available at a single relay to compute the relay weights and distribute them. Discrete relay weights are used due to several advantages including decreased overhead for the feedback channel. Multiple relay selection is employed in order to decrease network complexity and improve bandwidth efficiency. Nonlinear joint optimization problem is converted to a liner form and optimum solution is found by using mixed integer linear programming.