Optimal Multiuser Zero-Forcing with Per-Antenna Power Constraints for Network MIMO Coordination

TL;DR

This paper develops an optimal block diagonalization method for network MIMO systems with per-antenna power constraints, enhancing throughput through a novel gradient descent approach and demonstrating significant coordination benefits.

Contribution

It introduces a globally optimal precoding design for multiuser zero-forcing in network MIMO with per-antenna constraints, using a new null space optimization and iterative gradient method.

Findings

Achieves higher throughput compared to non-optimized schemes.

Demonstrates the effectiveness of the proposed optimal BD in network MIMO.

Validates the approach through comprehensive simulations.

Abstract

We consider a multi-cell multiple-input multiple-output (MIMO) coordinated downlink transmission, also known as network MIMO, under per-antenna power constraints. We 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. The comprehensive simulations illustrate several network MIMO coordination advantages when the optimal BD scheme is used. Its achievable throughput is compared with the capacity region obtained through the recently established duality concept under per-antenna power constraints.