A decentralized downlink beamforming algorithm for multicell processing

In this paper, we tackle the problem of intercell-interference in the absence of cooperation amongst base stations (BSs). The problem originates from the simultaneous transmissions of several BSs to their local users within their corresponding cells using the same frequency band. We propose a decentralized downlink beamforming scheme in cellular interference channels so that individual BSs can independently design their own beamforming vectors based on the locally attainable second order statistical channel state information at each BS. In this scheme, while each BS minimizes a combination of its total transmit power and the resulting total interference on the other vulnerable users of the adjacent cells, it assures that certain targeted signal-to-interference-plus-noise ratio (SINR) levels are achieved at its local users. Using the reciprocity of wireless network and the uplink-downlink duality, we develop a fast-converging iterative algorithm for downlink transmissions by distributed BSs. Finally, we derive a feasibility condition for the existence of a unique solution to the proposed optimization problem. This condition can be used to develop a scheduling algorithm for choosing a set of feasible users within each cell. Simulation results confirm the effectiveness of the proposed decentralized algorithm in closely following the performance curve of its centralized counterpart.