Throughput maximization in UAV-enabled mobile relaying with multiple source nodes.

This paper investigates throughput maximization problem in an unmanned aerial vehicle (UAV) enabled decode-and- forward (DF) relaying system with multiple source nodes (SNs), a rotary-wing UAV is dispatched to assist information transmission from SNs to one destination node (DN) when the direct links are severely blocked. Our goal in this paper is to maximize the throughput of the mobile relaying system by jointly optimizing the time scheduling, transmit power as well as UAV trajectory. In the formulated problem, the UAV flight needs to meet several mobility constraints, such as maximum speed, flight altitude, and initial/final location. To coincide with practice, we consider an energy-constrained rotary-wing UAV, namely the propulsion-related power consumption of the UAV is subjected to a power budget. Moreover, a fair uplink information transmission scheme from the SNs to the relay mounted on the UAV over a finite time horizon is also designed. The formulated problem is a non-convex problem. To obtain the solution, the original problem is decomposed into three subproblems, and successive convex approximation (SCA) technique is applied to appropriately deal with the non-convexity. Then, an iterative algorithm that alternately optimizes these subproblems is proposed. Finally, our proposed design is demonstrated by numerical results, which shows that higher gains can be achieved by our design compared with benchmarks.