On the Decomposition Method for Distributed Downlink Beamforming in Multi-Cell Systems

In this paper, we consider the minimum power downlink beamforming problem for a multi-cell system using the decomposition method. Since this problem has coupled constrained, it may not be easy to solve. However, the dual problem can be decomposed and allows to derive a distributed iterative beamforming algorithm for a time-division duplexing (TDD) based multi-cell system. The resulting algorithm does not require any backhaul transmissions between base stations (BSs) through iterations. As a result, it can be seen that the iterative algorithm for distributed beamforming consists of per- cell beamforming and closed-loop power control from users to BSs in a multi-cell system.