RESTORE: Low-Energy Drone-Assisted NLoS-FSO Emergency Communications

Drones are becoming an alternative for the rapid but temporary deployment of data-communication infrastructure in disaster-struck areas. A drone may be equipped with communications equipment to provide network connectivity for stranded users and first responders. This equipment is generally radio-frequency based. However, the drone service time is greatly limited by the power consumed for propulsion and communications, and exacerbated by the restricted battery capacity. Rather than improving rate-allocation strategies and flight paths, we dramatically reduce the consumed power by 100-fold or more with the adoption of non-direct line-of-sight free-space optical communications (NLOS-FSOC). NLOS-FSOC uses diffuse reflectors to make the optical signal detectable to stations with line-of-sight to the diffuse reflector and not necessarily with the transmitter. We also propose a heuristic scheme, called RESTORE, to determine the drone's optimal flying altitude that provides the largest coverage. We analyze the proposed system by evaluating its performance and compare it to leading drone-assisted emergency communications and show that the proposed approach not only dramatically reduces energy consumption but also provides 130% more aggregated data rates and serves more than 100% of users than existing communications systems.