Joint Communication-Motion Planning for UAV Relaying in Urban Areas

Abstract

In this paper, we consider a challenging surveillance scenario where there could exist line-of-sight (LOS) propagations and non-line-of-sight (NLOS) propagations in air-to-ground (ATG) channel and air-to-air (ATA) channel due to obstacles in urban areas, and a ground mobile robot is deployed to survey this area and transmit collected data to a remote base station via an unmanned aerial vehicle (UAV) relay. In this scenario, we aim to plan the optimal transmit power and trajectory of the UAV relay to minimize energy consumption while maintaining the communication quality. Existing works typically rely on the free-space path loss model and the statistical channel model, thus neglect the positions and shapes of obstacles and may fail in practical NLOS scenarios. In this paper, we first exploit the end-to-end packet error rate (PER)-based communication model, which captures the LOS propagation and NLOS propagation. Then, taken the information of obstacles in environment into consideration, we propose an UAV relay-assisted joint communication-motion planning (UAV-JCMP) method for minimizing the total energy consumption in urban areas. By decomposing the concave problem into two subproblems and dividing its domain into several convex subdomains according to LOS conditions, we further get the optimal solution. At last, numerical results demonstrate that substantial energy-efficient improvements can be achieved over methods that only optimize communication energy consumption and methods using statistical channel model. We further discuss the robustness of UAV-JCMP method towards terrain measurement error.