Joint power control and beamforming for capacity improvement in wireless networks with antenna arrays

The interference reduction capability of antenna arrays and the power control algorithms have been considered separately as means to increase the capacity in wireless communication networks. The minimum variance beamformer maximizes the carrier to interference ratio (CIR) when it is employed in the receiver of a wireless link. In a system with omnidirectional antennas, power control algorithms are used to maximize the CIR as well. We consider a system with power control capabilities which uses antenna arrays at the receivers. An iterative algorithm is proposed to jointly update the transmission powers and the beamformer weights so that it converge to the jointly optimal beamforming and transmission power vector. The algorithm is distributed and uses only local interference measurements. In an uplink transmission scenario it is shown how base assignment can be incorporated in addition to beamforming and power control such that a globally optimum solution is obtained. The network capacity increase and the saving in mobile power achieved by beamforming are evaluated through a numerical study