Optimal Interference Management In Multi-Antenna, Multi-Cell Systems

Intercell interference is a major limiting factor in wireless multi-cell networks. Recently, it has been shown that significant performance gains can be achieved by cooperation between base stations. Different degrees of cooperation are possible: From full cooperation, where multiple base stations form a virtual antenna array, to weak cooperation, where base stations take into consideration the interference caused to users in neighboring cells. In this work, weak cooperation in the form of interference management is investigated. The base stations are equipped with multiple antennas, while the mobile terminals only have a single antenna. Due to the spatial degrees of freedom, a base station can serve multiple users in the same slot. Each base station performs beamforming, user group selection, and scheduling, while the terminals treat interference as noise. The corresponding resource allocation problem is cast as a utility maximization problem, which includes common performance objectives such as sum-throughput, max-min fairness, and proportional fairness. Due to interference, the resulting utility maximization problem is a nonconvex optimization problem. Still, after a suitable reformulation, the problem can be solved to global optimality using the framework of monotonic optimization. In other words, we provide a framework for computing the jointly optimal beamforming, user selection, and scheduling strategy for each base station, under an arbitrary utility objective.