Distributed Signal Processing for Out-of-System Interference Suppression in Cell-Free Massive MIMO

TL;DR

This paper introduces a distributed algorithm for suppressing out-of-system interference in cell-free massive MIMO, achieving near-centralized performance with reduced fronthaul load, enhancing future wireless network robustness.

Contribution

A novel sequential distributed algorithm for OoS interference suppression in CF-mMIMO with stripe topology, reducing fronthaul load while maintaining high performance.

Findings

Performance comparable to centralized methods

Significantly reduced fronthaul load

Effective in uplink interference suppression

Abstract

Cell-free massive multiple-input-multiple-output (CF-mMIMO) is a next-generation wireless access technology that offers superior coverage and spectral efficiency compared to conventional MIMO. With many future applications in unlicensed spectrum bands, networks will likely experience and may even be limited by out-of-system (OoS) interference. The OoS interference differs from the in-system interference from other serving users in that for OoS interference, the associated pilot signals are unknown or non-existent, which makes estimation of the OoS interferer channel difficult. In this paper, we propose a novel sequential algorithm for the suppression of OoS interference for uplink CF-mMIMO with a stripe (daisy-chain) topology. The proposed method has comparable performance to that of a fully centralized interference rejection combining algorithm but has substantially less fronthaul load requirements.