MMSE Optimization with Per-Base-Station Power Constraints for Network MIMO Systems

Cooperative transmission with multiple base stations is a way to overcome the interference limitation of conventional cellular system. We investigate the problem of linear transceiver design for such a network Multiple-Input-Multiple- Output (MIMO) system with per-base-station power constraints. Four design goals are considered: minimizing the total sum-MSE subject to per-base-station power constraints; minimizing the total transmit power subject to a total sum-MSE target and per-base-station power constraints; minimizing the maximum weighted user-MSE subject to per-base-station power constraints; minimizing the total transmit power subject to a set of user-MSE targets and per-base-station power constraints. For these problems, we derive globally optimal transmitters by reformulating the problems as convex Second Order Cone Programs (SOCPs). We also propose iterative algorithms for joint transmitter/receiver optimization. The joint transceiver optimization exploits that for the optimal transmitter, the receivers can be updated as linear MMSE filters. We prove that the proposed algorithms converge to local optima due to the non-convexity of the problems.