Coordinated trajectory planning for efficient communication relay using multiple UAVs

•A nonlinear model predictive control based communication relay strategy is proposed.•The motions of ground mobile nodes and relay UAVs are predicted for optimization.•Deploying UAVs can improve the network connectivity in a mobile ad hoc network.•The improvement rate becomes less significant as the number of UAVs increases.•The improvement becomes significant when mobile nodes have a low transmission power.

This paper investigates the use of small UAVs as communication relay nodes for expanding communication links and improving communication quality for a fleet of naval vessels. This paper firstly deals with the UAV deployment for stationary communication nodes, and then, proposes a decentralised nonlinear model predictive trajectory planning strategy for a dynamic environment. By exploiting motion estimates of vessels and states of UAVs, the trajectory planning algorithm finds a control input sequence optimising network connectivity over a certain time horizon. Numerical simulations are performed for both stationary and manoeuvring vessels to verify the feasibility and benefit of the proposed approach.