MMSE-Optimal Sequential Processing for Cell-Free Massive MIMO With Radio Stripes

TL;DR

This paper introduces an optimal sequential processing algorithm for uplink cell-free massive MIMO with radio stripes, significantly reducing fronthaul signaling while maintaining high spectral efficiency and low MSE.

Contribution

It develops a novel uplink sequential processing algorithm for cell-free mMIMO with radio stripes, proven to be optimal in spectral efficiency and MSE, and analyzes its fronthaul requirements.

Findings

Algorithm achieves optimal spectral efficiency and MSE.

Significantly reduces fronthaul signaling compared to sub-optimal methods.

Maintains high communication performance with reduced signaling overhead.

Abstract

Cell-free massive multiple-input-multiple-output (mMIMO) is an emerging technology for beyond 5G with its promising features such as higher spectral efficiency and superior spatial diversity as compared to conventional multiple-input-multiple-output (MIMO) technology. The main working principle of cell-free mMIMO is that many distributed access points (APs) cooperate simultaneously to serve all the users within the network without creating cell boundaries. This paper considers the uplink of a cell-free mMIMO system utilizing the radio stripe network architecture with a sequential fronthaul between the APs. A novel uplink sequential processing algorithm is developed which is proved to be optimal in both the maximum spectral efficiency (SE) and the minimum mean square error (MSE) sense. A detailed quantitative analysis of the fronthaul requirement or signaling of the proposed algorithm and its comparison with competing sub-optimal algorithms is provided. Key conclusions and implications are summarized in the form of corollaries. Based on the analytical and numerical simulation results, we conclude that the proposed scheme can greatly reduce the fronthaul signaling, without compromising the communication performance.