Joint Transmit Power and Trajectory Optimization for Two-Way Multihop UAV Relaying Networks

Unmanned aerial vehicle (UAV) has been more and more widely used in military and civilian, with its unique advantages of flexibility, convenience, and wide coverage. As flying stations, UAVs can quickly set up relay communication links for different missions, to enhance the receiving signal power, increase the system capacity, and expand the communication coverage. In this article, we investigate a two-way multihop UAV relaying network, where there are two ground users as sources and multiple UAVs as relays to help the two ground sources exchange information. For the purpose of enhancing the efficiency of the investigated UAV-assisted relaying, we come up with a productive two-way multihop UAV relaying pattern, which can achieve a data rate of $({1}/{2})$ data packets per time slot with the decode-and-forward protocol. Then, we further formulate a joint transmit power and trajectory optimization problem for the UAVs in this two-way multihop relaying scenario. The formulated problem is nonconvex which makes it difficult to solve directly; hence, we propose an iterative algorithm to obtain an approximate optimal solution based on block coordinate descent and successive convex optimization techniques. Numerical results demonstrate that our proposed two-way multihop UAV relaying network achieves significant throughput gains compared with other benchmark schemes.