An Air-to-Ground Relay Communication Planning Method for UAVs Swarm Applications

For civil applications of Unmanned Aerial Vehicles (UAVs) for search, and emergency, data transmission between UAVs and Ground Control Stations (GCS) is always suffered from long distance, undulating terrains or other interferences. Thus, relaying is a critical enhancing technology in wireless communications for better service quality. In this paper, a planning method for fixed-wing relay UAV (RU) serving to sequential tasks of UAV swarm is proposed. Firstly, considering characteristics of signal propagation, antenna, environment and UAV, the UAV-to-GCS and UAV-to-UAV communication models are designed. And the limits of communication are investigated, which are crucial issues to provide a guarantee for swarm mission. Meanwhile, based on the analysis of relay UAVs requirements during the spatial distribution of tasks, a mixed integer nonlinear programming problem (MINLP) is constructed to solve the approximate number of relay nodes and access locations. Then aiming for the minimum number of relay UAVs, a continuous time-sharing relay UAVs reward model is constructed, and the consensus-based bundle algorithm (CBBA) is adopted to obtain the maximum rewards, including the number of relay nodes, mission sequences and route planning. Finally, the numerical simulation for a typical scenario is conducted to show the performance of the proposed approach.