MULTI-CELL BEAMFORMING FOR INTERFERENCE MITIGATION

Abstract

Beamforming for multi-user MIMO has emerged as an atiractive way to increase spectral efficiency of cellular wireless communication. The optimization of beamforming vector can be carried out for single cell processing, coordinated beainforming and multi-cell processing, considered in this report. Intra cell and inter cell interference exist at each user which degrade the performance of the system and users are not able to use spectnlm effectively. Numbers of optimal techniques have been presented in the literature for interference mitigation. In this report interference mitigation is performed at transmitter only. The total power optimization problem is considered for beamforming vector calculation. The precoding vector computation in single cell processing using convex optimization toolbox 'SeDuMi l.IR" has been 14 investigated. With the assumption that BSs are connected by the high capacity backhaul links, joint beamforming vector optimization problem is formulated for 2 cell system. The iterative algorithm based on the uplink downlink duality principle has been studied. The large scale analysis for SCP, CBf and MCP is formulated for the limit that users per cell and number of antennas at BS tend to infinity. The perfornmnce of the large scale approximation given for SCP, CBf and MCP has been investigated and results of large system approximation for CBf is compared with the solution of iterative algorithm presented for CBf. The coordinated beamforming optimization problem is converted into standard fonnat of SOCP and solution is obtained using convex optimization toolbox "SeDuMi 1 .1 R". Results obtained are analyzed and compared with the results of iterative algorithm given for CBf.