Rethinking Mutual Coupling in Movable Antenna MIMO Systems

TL;DR

This paper models movable antenna MIMO systems considering mutual coupling effects, proposing optimization algorithms to enhance capacity, and demonstrating significant capacity gains through simulations.

Contribution

It introduces a circuit-theoretic model for MA-enabled MIMO systems with mutual coupling, and develops novel algorithms for optimizing antenna positions to maximize capacity.

Findings

Mutual coupling effects can be exploited to improve MIMO capacity.

The proposed algorithms effectively optimize antenna positions considering mutual coupling.

Simulation results show significant capacity improvements using the proposed methods.

Abstract

Movable antenna (MA) systems have emerged as a promising technology for future wireless communication systems. The movement of antennas gives rise to mutual coupling (MC) effects, which have been previously ignored and can be exploited to enhance the capacity of multiple-input multiple-output (MIMO) systems. To this end, we first model an MA-enabled point-to-point MIMO communication system with MC effects using a circuit-theoretic framework. The capacity maximization problem is then formulated as a non-concave optimization problem and solved via a block coordinate ascent (BCA)-based algorithm. The subproblem of optimizing MA positions is challenging due to the presence of the analytically intractable MC matrices. To overcome this difficulty, we develop a trust region method (TRM)-based algorithm to optimize MA positions, wherein Sylvester equations are employed to compute the derivatives of the inverse square roots of the MC matrices. Simulation results show significant capacity gains from leveraging MC effects, primarily due to customizable MC matrices and superdirectivity.