Joint network optimization and beamforming for Coordinated Multi-Point Transmission using mixed integer programming

Coordinated Multi-Point Transmission (CoMP) has been proposed for 4G standards, like WiMAX and LTE-Advanced, as an effective mean to control intercell interference and to increase spectral efficiency in single frequency reuse networks. In practical systems, the remarkable benefits of CoMP operation over conventional single basestation transmission need to be traded against a significant overhead in network complexity and associated operational costs. In order to retain the benefits of CoMP at reasonable costs, we consider the problem of joint basestation selection and multicell beamforming (JBSB). We address this problem via a mixed integer second order cone programming (MI-SOCP) approach. We propose a novel MI-SOCP formulation of the JBSB problem and a reformulation with tighter continuous relaxations. Based on this formulation, we propose fast algorithms to find almost optimal feasible solutions. We show via simulations that the proposed algorithms outperform existing solutions in terms of both complexity and total transmitted power at a guaranteed signal-to-interference-plus-noise-ratio (SINR) level at each mobile station (MS).