Using Unmanned Aerial Vehicle chain to improve link capacity of two mobile nodes

The link capacity of ground mobile nodes varies dramatically and is often under the required quality level due to limited communication range and signal blocking of terrain. To improve the link capacity of ground mobile nodes, Unmanned Aerial Vehicles (UAVs) have emerged as relay platforms. By establishing a communication relay chain between ground mobile nodes, UAVs can provide required communication quality for ground nodes. Since ground nodes are continuously moving, UAVs also need to control their motion to maintain the relay chain. However, existing work have not considered the mobility of ground nodes or not set the link capacity as optimization objects. In this paper, we study the optimization problem of motion control of UAVs to maximize the link capacity of two ground mobile nodes. We propose an artificial potential field (APF) based solution. In APF-based solution, communication object is formulated as attractive force and collision avoidance of UAVs are formulated as repulsive force. UAVs change their speed and heading angle under the joint force. Simulation results demonstrate that the proposed APF-based solution has better performance than gradient estimate method under different scenarios. We also analyze the impact of motion constrains of UAVs and show that the performance of APF-based solution can be improve when loosing some of the motion constraints.