Angle Feedback for NOMA Transmission in mmWave Drone Networks

TL;DR

This paper explores the use of angle-based limited feedback for NOMA transmission in mmWave UAV networks, demonstrating its advantages over distance feedback in wide user regions through analytical and simulation results.

Contribution

It introduces a novel user angle feedback scheme for NOMA in UAV networks and analyzes its performance compared to traditional feedback methods.

Findings

Angle feedback outperforms distance feedback in wide user regions.

Analytical outage sum rate results closely match simulations.

Proper feedback scheme selection depends on deployment geometry.

Abstract

In this paper, we consider an unmanned aerial vehicle (UAV) based wireless network using non-orthogonal multiple access (NOMA) transmission in millimeter-wave frequencies to deliver broadband data in a spectrally efficient fashion at hotspot scenarios. The necessity for the NOMA transmitter to gather information on user channel quality becomes a major drawback in practical deployments. We therefore consider various limited feedback schemes for NOMA transmission, to relieve the complexity of tracking and feeding back the full channel state information (CSI) of the users. In particular, through beamforming we allow NOMA to exploit the space domain, and hence the user angle emerges as a promising (yet novel) limited feedback scheme. We show that as the user region for NOMA transmission gets wider, the users become more distinctive at the transmitter side with respect to their angles, making user angle feedback a better alternative than distance feedback in such scenarios. We rigorously derive and analyze the outage sum rate performance for NOMA transmission considering various user ordering strategies involving full CSI, angle, and distance feedback schemes. Our analytical results for NOMA outage sum rates using those feedback schemes match closely with simulations, and provide useful insights on properly choosing a limited feedback scheme for different deployment geometries and operating configurations.