Co-Located vs Distributed vs Semi-Distributed MIMO: Measurement-Based Evaluation

TL;DR

This paper compares different MIMO antenna topologies in indoor environments, demonstrating that semi-distributed multi-antenna APs can reduce the number of APs while maintaining similar spectral efficiency to fully-distributed single-antenna APs.

Contribution

It provides a measurement-based evaluation of co-located, distributed, and semi-distributed MIMO systems, highlighting the efficiency of semi-distributed multi-antenna APs.

Findings

Semi-distributed multi-antenna APs can reduce the number of APs needed.

Semi-distributed APs achieve comparable spectral efficiency to fully-distributed single-antenna APs.

Analysis includes both conjugate beamforming and zero-forcing precoding methods.

Abstract

With the growing interest in cell-free massive multiple-input multiple-output (MIMO) systems, the benefits of single-antenna access points (APs) versus multi-antenna APs must be analyzed in order to optimize deployment. In this paper, we compare various antenna system topologies based on achievable downlink spectral efficiency, using both measured and synthetic channel data in an indoor environment. We assume multi-user scenarios, analyzing both conjugate beamforming (or maximum-ratio transmission (MRT)) and zero-forcing (ZF) precoding methods. The results show that the semi-distributed multi-antenna APs can reduce the number of APs, and still achieve the comparable achievable rates as the fully-distributed single-antenna APs with the same total number of antennas.