An Energy-efficient Aerial Backhaul System with Reconfigurable Intelligent Surface

TL;DR

This paper introduces a novel aerial RIS-based wireless architecture mounted on high-altitude platforms to enhance backhaul connectivity for UAV base stations, significantly improving energy efficiency in urban scenarios.

Contribution

It proposes a new aerial RIS system with optimized placement and phase control, addressing urban backhaul challenges and demonstrating high computational efficiency.

Findings

Achieves higher energy efficiency than benchmark schemes.

Effectively overcomes urban obstacles for backhaul links.

Provides a computationally efficient optimization algorithm.

Abstract

In this paper, we propose a novel wireless architecture, mounted on a high-altitude aerial platform, which is enabled by reconfigurable intelligent surface (RIS). By installing RIS on the aerial platform, rich line-of-sight and full-area coverage can be achieved, thereby, overcoming the limitations of the conventional terrestrial RIS. We consider a scenario where a sudden increase in traffic in an urban area triggers authorities to rapidly deploy unmanned-aerial vehicle base stations (UAV-BSs) to serve the ground users. In this scenario, since the direct backhaul link from the ground source can be blocked due to several obstacles from the urban area, we propose reflecting the backhaul signal using aerial-RIS so that it successfully reaches the UAV-BSs. We jointly optimize the placement and array-partition strategies of aerial-RIS and the phases of RIS elements, which leads to an increase in energy-efficiency of every UAV-BS. We show that the complexity of our algorithm can be bounded by the quadratic order, thus implying high computational efficiency. We verify the performance of the proposed algorithm via extensive numerical evaluations and show that our method achieves an outstanding performance in terms of energy-efficiency compared to benchmark schemes.