Autonomous Airborne Transportation: Field Trials in Urban Water Landscapes

Unmanned aerial vehicles (UAVs) operating on unlicensed spectra have short operational range. To perform complex beyond visual line-of-sight UAV operations, licensed-spectrum cellular systems can be leveraged for intelligent transportation applications, including parcel delivery via UAVs. This work investigates the long-term evolution (LTE) network-enabled UAV performance at different altitudes under real propagation conditions over a water body in an urban area. In this work, connectivity characterization relies on real data from commercial cellular networks. The performance metrics in this investigation include reference signal received power (RSRP), reference signal received quality, and signal-to-interference-and-noise ratio (SINR). This research discusses the impact of UAV altitude, location of base stations (BSs), and cellular radio frequency on UAV connectivity. Our preliminary data show that handover to higher frequency bands limits the RSRP at UAV terminals, although higher frequency bands have increased bandwidth for better data throughput. The RSRP and SINR are poor when the serving BSs are comparatively distant and obstructed by nearby BSs, respectively. This work also compares the over-the-water propagation environment to other published propagation environments to identify cellular coverage challenges over water surfaces.