Leakage Subspace Precoding and Scheduling for Physical Layer Security in Multi-User XL-MIMO Systems

TL;DR

This paper explores how spherical-wavefront propagation in multi-user XL-MIMO systems enhances physical-layer security, proposing a leakage subspace precoding method that outperforms traditional strategies in securing communications against eavesdroppers.

Contribution

It introduces a leakage subspace precoding and scheduling approach leveraging spherical-wavefront effects for improved physical-layer security in XL-MIMO systems.

Findings

Spherical-wavefront propagation improves immunity against eavesdroppers.

Leakage subspace precoding outperforms zero-forcing in secrecy sum-rate.

Method is effective under various eavesdropper collusion scenarios.

Abstract

We investigate the achievable secrecy sum-rate in a multi-user XL-MIMO system, on which user distances to the base station become comparable to the antenna array dimensions. We show that the consideration of spherical-wavefront propagation inherent to these set-ups is beneficial for physical-layer security, as it provides immunity against eavesdroppers located in similar angular directions that would otherwise prevent secure communication under classical planar-wavefront propagation. A leakage subspace precoding strategy is also proposed for joint secure precoding and user scheduling, which allows to improve the secrecy sum-rate compared to conventional zero-forcing based strategies, under different eavesdropper collusion strategies.