Robust Air-to-Air Channel Model for Swarms of Drones in Search and Rescue Missions

Abstract

Drones have greatly enhanced search and rescue missions. They help improve the response time of the rescue team. They can cover vast challenging terrains quickly. Drones used in rescue missions are expensive. Because of the challenging terrains, if any drone crashes, it cannot be retrieved. This paper presents two contributions. The first contribution is a cruising scheme for a swarm of drones heading to a dangerous area to rescue victims. The proposed scheme guarantees the safety of the drones during the mission. It guarantees that no drone is lost; whenever a drone's controller fails, another drone will guide it home. Basically, each pair of drones should monitor the control system of one another. In case no watchdog signal is sent, an error is perceived and the operational drone begins to control the malfunctioning one (the drone with a failed controller). Every drone sends all its sensor data to the other drone every 1msec. When a fault occurs, the operational drone sends back the control signals to the malfunctioning one to control its actuators. A robust air-to-air communication channel between pairs of drones, is needed in order to realize the proposed navigation scheme and to achieve a safe cruise and a successful mission to every single drone in the whole swarm. Therefore, the second contribution is a channel model for the air-to-air links between pairs of drones. It is assumed that drones' transceivers use the 802.11n protocol. Simulations are conducted to test the proposed channel model in two scenarios. The first one is fault- free and the other one is when one of the controllers in a pair of drones, fails. The separating distance between every two drones in each pair and their relative velocity with respect to one another, differ in both scenarios. The proposed channel is robust as it achieves approximately zero BER in both scenarios.