Analysis of UAV Communications in Cell-Free Massive MIMO systems

TL;DR

This paper investigates UAV communications using cell-free massive MIMO systems, deriving spectral efficiency bounds and comparing performance with traditional networks, highlighting advantages of cell-free architectures.

Contribution

It introduces spectral efficiency bounds for UAV and ground user communications in cell-free massive MIMO with Ricean channels and compares different power and user scheduling strategies.

Findings

Cell-free massive MIMO outperforms traditional multi-cell MIMO.

User-centric association improves system fairness.

Power allocation strategies enhance spectral efficiency.

Abstract

We study support for unmanned aerial vehicle (UAV) communications through a cell-free massive MIMO architecture, wherein a large number of access points (APs) is deployed in place of large co-located massive MIMO arrays. We consider also a variation of the pure cell-free architecture by applying a user-centric association approach, where each user is served only from a subset of APs in the network. Under the general assumption that the propagation channel between the mobile stations, either UAVs or ground users (GUEs), and the APs follows a Ricean distribution, we derive closed-form spectral efficiency lower bounds for uplink and downlink with linear minimum mean square error channel estimation. We consider several power allocation and user scheduling strategies for such a system, and, among these, also minimum-rate maximizing power allocation strategies to improve the system fairness. Our numerical results reveal that cell-free massive MIMO architecture and its low-complexity user-centric alternative may provide better performance than a traditional multi-cell massive MIMO network deployment.