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.

翻译：无蜂窝大规模多输入多输出（CF-mMIMO）是一种相较于传统MIMO覆盖范围和频谱效率更优的下一代无线接入技术。鉴于未来许多应用将使用非授权频段，网络可能遭遇甚至受限于系统外（OoS）干扰。与来自其他服务用户的系统内干扰不同，系统外干扰的导频信号未知或不存在，这使得估计OoS干扰信道变得困难。本文针对采用带状（菊花链）拓扑的上行CF-mMIMO系统，提出了一种新颖的序贯算法用于抑制OoS干扰。所提方法在性能上与完全集中式干扰抑制合并算法相当，但显著降低了对前传链路负载的需求。