Semidefinite relaxation based beamforming in clustered cooperative multicell MISO systems

In this paper, we propose a novel coordinated downlink beamforming strategy based on the semidefinite relaxation (SDR) approach for a clustered multicell cellular system. As base station (BS) cooperation can provide significant performance improvement for the system capacity and interference suppression, we divide the whole network into a number of clusters. In each cluster, several BSs share the common user data and cooperatively design their signaling strategies. In this system, maximizing the sum-rate requires solving a global nonconvex optimization problem. We apply the semidefinite programming (SDP) relaxation to convert the original problem into distributed convex SDP which can be solved efficiently and optimally with convex optimization techniques. Numerical results show that the proposed beamforming algorithm provides a remarkable sum-rate enhancement and outperforms some existing schemes.