Non-Orthogonal Multiple Access for mmWave Drone Networks with Limited Feedback

TL;DR

This paper explores the use of NOMA with limited feedback in mmWave UAV networks, proposing beam scanning and analyzing optimal UAV altitude to enhance sum rates and outage performance.

Contribution

It introduces a NOMA framework with distance-based user ordering and beam scanning for UAV-BS in mmWave networks, optimizing altitude for maximum sum rates.

Findings

NOMA with distance feedback outperforms orthogonal access in sum rates.

Beam scanning improves coverage and sum rate performance.

Optimal UAV altitude maximizes achievable sum rates.

Abstract

Unmanned aerial vehicle (UAV) base stations (BSs) can be a promising solution to provide connectivity and quality of service (QoS) guarantees during temporary events and after disasters. In this paper, we consider a scenario where UAV-BSs are serving large number of mobile users in a hot spot area (e.g., in a stadium). We introduce non-orthogonal multiple access (NOMA) transmission at UAV-BSs to serve more users simultaneously considering user distances as the available feedback for user ordering during NOMA formulation. With millimeter-wave (mmWave) transmission and multi-antenna techniques, we assume UAV-BS generates directional beams and multiple users are served simultaneously within the same beam. However, due to the limitations of physical vertical beamwidth of the UAV-BS beam, it may not be possible to cover the entire user region at UAV altitudes of practical relevance. During such situations, a beam scanning approach is proposed to maximize the achievable sum rates. We develop a comprehensive framework over which outage probabilities and respective sum rates are derived rigorously and we investigate the optimal operational altitude of UAV-BS to maximize the sum rates using our analytical framework. Our analysis shows that NOMA with distance feedback can provide better outage sum rates compared to orthogonal multiple access.