Multi-Hop THz-Backhaul for Enhanced Urban Air Mobility Communications

Urban Air Mobility (UAM) represents an innovative mobility solution designed to alleviate the traffic congestion associated with conventional two-dimensional transportation, which has already saturated both urban and underground spaces. The development of unmanned aerial vehicles (UAVs) and electric vertical takeoff and landing (eVTOL) aircraft is a key enabler for this new, sustainable mode of transporting goods and passengers. To ensure safe operation - especially as these vehicles advance toward autonomous capabilities - and to maintain connectivity for passengers, UAM requires high data-rate, reliable, and low-latency communications. Within the 6G framework, several architectural solutions have been proposed, incorporating components such as terrestrial stations, satellites, and UAVs. In this paper, we propose a two-tier architecture: an aerial tier that leverages multi-hop THz communications among UAM vehicles as backhaul links, and a terrestrial tier comprising conventional cellular base stations (BSs) along with a number of enhanced base stations (eBSs) equipped with high-elevation antenna systems to provide aerial coverage for UAM vehicles (UVs). We will show that our approach ensures reliable UAM connectivity even in high-density urban airspaces, striking an optimal balance between the required number of eBSs and the airborne THz backhauling.