Coordinated multi-cell transmission for distributed antenna systems with partial CSIT

In this letter, a multi-cell distributed antenna system (DAS) with multiple users served via linear beamforming in each cell is considered. We focus on joint beamformer optimization (JBO) with the target of system weighted sum capacity maximization based on only partial channel state information at the transmitter (CSIT), which includes instantaneous intra-cell and large-scale inter-cell CSIT. After the formulation of a non-convex JBO problem, an algorithm is proposed to find the globally optimal beamformers based on monotonic optimization and the bisection method. Simulation results are provided to show the superiority of the proposed algorithm and the noticeable performance gain of the JBO based on partial CSIT. The proposed algorithm can be used as a benchmark for low-complexity JBO scheme design for practical applications.