Large system analysis of base station cooperation on the downlink

This paper considers maximizing the network-wide minimum supported rate in the downlink of a two-cell system with symmetric channel statistics, where each base station (BS) is endowed with multiple antennas. This is done for different levels of cell cooperation. At one extreme, we consider single cell processing where the BS is oblivious to interference created at the other cell. At the other, we consider full cooperative macroscopic beamforming. In between, we consider coordinated beamforming, which takes account of intercell interference, without full cooperation. Lagrangian duality and large system analysis, where the numbers of antennas at the BS N and of users in each cell K both grow large, with cell loading K/N tending to a finite constant β, are combined to obtain concise expressions for asymptotically optimal beamformers and limiting SINRs, thereby simplifying beamformer design and comparison of the schemes.