Optimum phase-only discrete broadcast beamforming with antenna and user selection in interference limited cognitive radio networks

Phase-only beamforming presents certain advantages in radar and communication systems. In cognitive radio, antenna and user selection are the two tools for increasing the quality of service (QoS) for the users. In this paper, discrete single group multicast transmit phase-only beamformer design is presented with antenna subset and user selection. The problem is converted into linear form and solved efficiently by using mixed integer linear programming to find the optimum subset of antennas and secondary users together with optimum beamformer phase coefficients. It is shown that significant power saving is possible compared to fixed antenna systems.