Trajectory Optimization and Retrieving Monitory System for UAV-assisted Offshore Maritime Communications

With more human activities operated at the seas within miles to the coast, off-shore maritime communications has been attracted researchers’ attention. Different from territorial wireless communications, unmanned aerial vehicles (UAVs) are usually employed as relays in maritime communications to compromise the shortage of base stations and to avoid the high cost of using satellites. Thus, how to maximize the period of UAVs’ services to achieve high data rate with a safe retrieving strategy become an interesting challenge. In this paper, we propose a trajectory optimization and retrieving monitory strategy for UAV-assisted communications in a wireless maritime network containing vessels, offshore base stations, satellites and UAVs. Both UAV and satellite are used as relays to serve the users on board. In our proposed design, a retrieving threshold is set and monitored at the UAVs in order to maximize the UAVs’ service period before returning to the station with enough battery power, and the total throughput of users is derived mathematically as the UAVs’ trajectory design criteria, and a simplified convex optimization method is developed to resolve the problem. A simple convex optimization algorithm is utilized to jointly optimize the service period of the UAVs, the energy state of the UAVs and the total throughput. Compared with other algorithms, we consider the monitoring of energy. The algorithm can maximize the service time of UAV while improving network throughput and optimizing UAV trajectory. The simulation results express that our proposed strategy is capable to improve the data rate of maritime users effectively.Maritime communications, Satellite-UAV net- works, trajectory optimization, convex optimization