Optimal Multiuser Zero Forcing With Per-Antenna Power Constraints for Network MIMO Coordination
The authors consider a multicell Multiple-Input Multiple-Output (MIMO) coordinated downlink transmission, also known as network MIMO, under per-antenna power constraints. They investigate a simple multiuser Zero-Forcing (ZF) linear precoding technique known as Block Diagonalization (BD) for network MIMO. The optimal form of BD with per-antenna power constraints is proposed. It involves a novel approach of optimizing the precoding matrices over the entire null space of other users' transmissions. An iterative gradient descent method is derived by solving the dual of the throughput maximization problem, which finds the optimal precoding matrices globally and efficiently.