Efficient UAV Deployment for Vehicular Communications in Highway Scenarios: Hovering or Flying?

Unmanned aerial vehicles (UAVs) have emerged as pivotal mobile base stations (UAV-BSs) for vehicular communications, particularly in regions without terrestrial infrastructure. This paper deploys multiple UAV-BSs to cover a highway segment devoid of existing infrastructure. We introduce and compare two UAV-BS deployment strategies: hovering and flying, taking into account their distinct specifications. We assume full-duplex (FD) UAV-BSs facilitate both uplink (UL) and downlink (DL) communication for half-duplex (HD) vehicular users. These systems grapple with self-interference from FD UAV-BSs, interference among HD vehicular users, and inter-carrier interference (ICI) resulting from the Doppler effect induced by mobility, ultimately affecting the quality of service (QoS) for vehicular users. To address this challenge, we propose a resource allocation scheme for both systems, optimizing power allocation and frequency assignment to maximize system data rate while ensuring QoS in both UL and DL. Through theoretical analysis, we compare the computational complexity of the resource allocation scheme between the two systems. Our simulation results show the advantages of the flying UAV-BSs system, particularly in terms of a higher system data rate, an increased probability of feasibility, a reduced number of required UAV-BSs, a lower vehicular user outage ratio, and the potential for lower computational complexity in resource allocation.