Live and let live: Flying UAVs without affecting terrestrial UEs

Abstract

High-speed cellular connectivity for drones (UAVs) is a key requirement for infrastructure monitoring and live broadcasting applications, among others. Different from ground mobile phones (UEs), however, UAVs benefit from unique line-of-sight conditions to multiple base stations (BSs), which may result in degraded performances for UEs in the surroundings. We experimentally evaluate this effect on a controlled LTE testbed, measuring up to 21.75 Mbps uplink throughput reduction for ground UEs in presence of UAVs. To mitigate this effect, we propose a new approach designed to reduce interference to adjacent BSs through a combination of steerable directional transmitters and optimized flight control. We design a control mechanism to jointly optimize the trajectory of the drone and the directional orientation of the uplink transmission. Based on an empirical characterization of aerial signal propagation in 3D, the proposed control algorithms solve optimal trajectory problems on a directed graph representation of the aerial space. Our evaluation shows average interference reduction at neighboring BSs of 5.87 dB and average improvement of the drone signal-to-noise ratio of 9.23 dB compared to traditional channel-unaware flight control solutions employing omni-directional transmitters.