Toward Ubiquitous and Flexible Coverage of UAV-IRS-Assisted NOMA Networks

This paper studies methods to achieve a high and flexible coverage performance of a large-scale cellular network. The network shall enable unmanned aerial vehicles (UAVs) for non-orthogonal multiple access (NOMA) transmission enhancement so as to simultaneously serve two users. The considered scenario consists of a network with a tier of base stations and UAVs. Each UAV is mounted with an intelligent reflecting surface (IRS) in order to serve as an aerial IRS reflecting signals between a base station and a user in the network. All the UAVs in the network are deployed based on a newly proposed three-dimensional (3D) point process leading to a tractable yet accurate analysis of the association statistics, which is otherwise difficult to analyze due to the mobility of UAVs. In light of this, we also analyze the downlink coverage of UAV-IRS-assisted NOMA transmission for two users and derive the corresponding coverage probabilities. Our coverage analyses shed light on the optimal allocations of transmit power between NOMA users and UAVs to accomplish the goal of ubiquitous and flexible NOMA transmission. We also conduct numerical simulations to validate our coverage analysis results while demonstrating the improved coverage performance achieved by aerial IRSs.