Joint downlink power allocation, beamforming weights and base assignment

The paper considers the transmitter optimization problem for a multi-base, multi-user downlink channel with multiple antennas at each base station. We consider joint optimization of three parameters: transmitted powers, beamforming weights and base stations (BS) assignment. We solve the downlink optimization problem by transforming it to a dual uplink problem. The uplink optimization problem is simpler to solve, and it is used to estimate the beamforming vectors and user-to-base assignments of the downlink problem. The proposed algorithm not only minimizes the transmitted power, but also is able to achieve feasible solutions for SIR requirements that are not feasible using traditional methods. In addition, in contrast to previous analysis, we consider a system that utilizes soft handoff mechanism. We show that soft handoff, while very useful for transmission continuity, cannot reduce the sum of the base stations powers.