Joint Energy and Trajectory Optimization for UAV-Enabled Relaying Network With Multi-Pair Users

This article investigates an unmanned aerial vehicle (UAV)-enabled wireless communication network with multiple pairs of source-destination ground users (GUs), where the rotary-wing UAV acts as an aerial mobile relay to transfer information from the source GUs to corresponding destination GUs when the direct terrestrial communication is blocked. On the premise of satisfying the communication requirements of all GUs, we intend to minimize the total energy consumption of supporting the propulsion and communication by jointly optimizing communication time, UAV transmit power allocation and UAV trajectory. To tackle the formulated non-convex problem, we first transform the original problem into a more tractable form with a finite number of optimization variables using the path discretization approach. Then, we decompose the joint optimization problem into three subproblems to find a near optimal solution. Finally, these subproblems can be efficiently solved via the proposed iterative algorithm based on block coordinate descent and successive convex approximation (SCA) techniques. As the initial UAV trajectory has significant influence on the final results, we put forward a novel trajectory initialization scheme by combining the classic Pickup-and-Delivery Problem with fly-hover-communication protocol. Numerical results demonstrate that our proposed design contributes to significant performance enhancement compared with other two benchmarks.