Cell-free Massive MIMO with Short Packets

TL;DR

This paper extends the finite-blocklength framework to cell-free Massive MIMO, analyzing packet error probabilities in URLLC, and demonstrates the superiority of MMSE processing and the efficiency of cell-free architectures over small-cell and cellular networks.

Contribution

It adapts the finite-blocklength analysis to cell-free Massive MIMO with imperfect CSI and linear processing, providing new insights into reliability and antenna requirements.

Findings

MMSE processing is essential for high reliability in URLLC.

Cell-free Massive MIMO outperforms small-cell and cellular networks in antenna efficiency.

Larger antenna arrays are needed for comparable performance in small-cell and cellular networks.

Abstract

In this paper, we adapt to cell-free Massive MIMO (multiple-input multiple-output) the finite-blocklength framework introduced by \"Ostman et al. (2020) for the characterization of the packet error probability achievable with Massive MIMO, in the ultra-reliable low-latency communications (URLLC) regime. The framework considered in this paper encompasses a cell-free architecture with imperfect channel-state information, and arbitrary linear signal processing performed at a central-processing unit connected to the access points via fronthaul links. By means of numerical simulations, we show that, to achieve the high reliability requirements in URLLC, MMSE signal processing must be used. Comparisons are also made with both small-cell and Massive MIMO cellular networks. Both require a much larger number of antennas to achieve comparable performance to cell-free Massive MIMO.