Multiple Access in Aerial Networks: From Orthogonal and Non-Orthogonal to Rate-Splitting

TL;DR

This paper surveys multiple access techniques for aerial networks, highlighting the potential of rate-splitting multiple access (RSMA) to outperform traditional methods like SDMA and NOMA in aerial communication scenarios.

Contribution

It provides a comprehensive review of multiple access methods for aerial networks and models the weighted sum-rate performance of RSMA in a two-user downlink system.

Findings

RSMA can achieve better spectral efficiency than SDMA and NOMA.

The paper models and analyzes the weighted sum-rate performance of RSMA in aerial systems.

Open issues and future research directions are discussed.

Abstract

Recently, interest on the utilization of unmanned aerial vehicles (UAVs) has aroused. Specifically, UAVs can be used in cellular networks as aerial users for delivery, surveillance, rescue search, or as an aerial base station (aBS) for communication with ground users in remote uncovered areas or in dense environments requiring prompt high capacity. Aiming to satisfy the high requirements of wireless aerial networks, several multiple access techniques have been investigated. In particular, space-division multiple access(SDMA) and power-domain non-orthogonal multiple access (NOMA) present promising multiplexing gains for aerial downlink and uplink. Nevertheless, these gains are limited as they depend on the conditions of the environment. Hence, a generalized scheme has been recently proposed, called rate-splitting multiple access (RSMA), which is capable of achieving better spectral efficiency gains compared to SDMA and NOMA. In this paper, we present a comprehensive survey of key multiple access technologies adopted for aerial networks, where aBSs are deployed to serve ground users. Since there have been only sporadic results reported on the use of RSMA in aerial systems, we aim to extend the discussion on this topic by modelling and analyzing the weighted sum-rate performance of a two-user downlink network served by an RSMA-based aBS. Finally, related open issues and future research directions are exposed.