Virtual Cell Beamforming in Cooperative Networks.

We study the coordinated transmission problem in cooperative cellular networks where a cluster of base stations forms a <bold>virtual cell</bold> to serve a mobile station (MS). The performance of such an MS-centric virtual cell network is dictated by the beamformer that enables to suppress interference; however, designing a beamformer is highly challenging due to the coupled nature of interference and desired signals under arbitrarily formed virtual cells. We develop a new formulation of the beamforming problem for sum-rate maximization in virtual cell networks and analyze the structure of its optimal solutions. Based on this analysis, we develop a beamforming algorithm that can balance between desired signal maximization and interference minimization, so as to maximize the sum-rate. We show through extensive simulations that our <bold>balanced beamforming</bold> algorithm mitigates edge user effect and outperforms existing algorithms in various scenarios where virtual cells are allowed to overlap. [ABSTRACT FROM PUBLISHER]