Multi-Cell Beamforming under Per-Cell Power Constraints

In this paper, we consider the problem of joint adaptive beamforming from multiple Access Points (APs), equipped with array antennas, to multiple single-antenna User Equipments (UEs). We derive an iterative algorithm for Multi-Cell Beam-Forming (MCBF) under per-cell power constraints and the constraint that a UE may receive data transmission from a single AP. The scheme is suitable for coordinated beamforming downlink transmission in a Coordinated Multi-Point (CoMP) cellular network. Simulation results indicate that as compared to uncoordinated transmission by means of a Grid of Beams (GoB) based Space Division Multiple Access (SDMA) scheme, MCBF offers much higher throughput for cell-edge UEs. For a single cluster of nine sectorized cells with four-element antenna arrays in an urban macro-cellular environment, MCBF obtains a 13 fold increase in 5 percentile user throughput at 2 bits/s/Hz/sector cell throughput as compared to GoB-SDMA.