Measurement-Based Characterization of LOS and NLOS Drone-to-Ground Channels

The last few years have seen a rapid growth in unmanned aerial vehicle (UAV) based innovations and technologies, particularly for smaller drones. The rapid response to natural disasters, high data rate access in public safety situations, and the robustness of long-haul communication relays are highly dependent on airborne communication networks. A more precise channel characterization of air-to-ground links is imperative to establish these drone-based communication networks. However, there have been very limited efforts to understand the unique propagation channels encountered in drone-based communications, especially for wideband beamforming systems. In this paper, we perform a measurement-driven study to characterize air-to-ground wireless channels between UAV platforms and terrestrial users in practical Line of Sight (LOS) and Non Line of Sight (NLOS) scenarios across a wide range of carrier frequencies, including cellular (900 MHz and 1800 MHz), and WiFi (5 GHz) frequency bands. Furthermore, we investigate the feasibility of drone-based beamforming using IEEE 802.11-like signaling. We find that the drone-to-ground path loss differences are frequency dependent and closely related to drone altitude. The drone-based beamforming system can improve throughput significantly over IEEE 802.11 SISO schemes with select carrier frequencies in both LOS and NLOS scenarios up to 73.6% and 120.1%, respectively. Since our study spans many critical frequency bands, these results serve as a fundamental step towards understanding drone-to-ground communications and impact of beamforming-based applications in future aerial networks.