Joint Precoding and Fronthaul Compression for Cell-Free MIMO Downlink With Radio Stripes

TL;DR

This paper introduces a novel joint precoding and fronthaul compression scheme for cell-free MIMO downlink using radio stripes, demonstrating significant performance improvements through advanced Wyner-Ziv compression techniques.

Contribution

It is the first to design downlink data transmission with joint precoding and fronthaul compression in radio stripe topologies, leveraging Wyner-Ziv compression for enhanced performance.

Findings

WZ compression outperforms standard methods in sum-rate.

Radio stripe topology reduces fronthaul cabling complexity.

Proposed scheme achieves notable sum-rate gains.

Abstract

A sequential fronthaul network, referred to as radio stripes, is a promising fronthaul topology of cell-free MIMO systems. In this setup, a single cable suffices to connect access points (APs) to a central processor (CP). Thus, radio stripes are more effective than conventional star fronthaul topology which requires dedicated cables for each of APs. Most of works on radio stripes focused on the uplink communication or downlink energy transfer. This work tackles the design of the downlink data transmission for the first time. The CP sends compressed information of linearly precoded signals to the APs on fronthaul. Due to the serial transfer on radio stripes, each AP has an access to all the compressed blocks which pass through it. Thus, an advanced compression technique, called Wyner-Ziv (WZ) compression, can be applied in which each AP decompresses all the received blocks to exploit them for the reconstruction of its desired precoded signal as side information. The problem of maximizing the sum-rate is tackled under the standard point-to-point (P2P) and WZ compression strategies. Numerical results validate the performance gains of the proposed scheme.