Joint trajectory and power optimization for UAV-relay-assisted Internet of Things in emergency

Abstract

In emergency situations, existing Internet of Things (IoT) infrastructure is vulnerable to natural disasters and unable to provide reliable services to users in disaster areas. Due to flexible maneuverability and fast deployment, unmanned aerial vehicle (UAV) plays an important role in the IoT deployment in emergency since it can be fast deployed as aerial relay to significantly enhance the communication capacity in disaster areas by designing efficient UAV trajectory. In this paper, a UAV relay communication model for multi-user data transmission is designed. When the communication between the user area and base station (BS) is interrupted, BS first sends information to the UAV, and then the UAV acts as a relay to forward the information to the users. According to the model, a joint UAV trajectory and power allocation scheme is proposed. The goal is to maximize the downlink achievable sum rate of all users by jointly optimizing UAV trajectory and BS/UAV power subject to the UAV mobility and information causality constraints. In view of the non-convexity of the formulated problem, an efficient iterative algorithm is proposed which optimizes the UAV trajectory and the BS/UAV transmit power alternately to obtain the approximately optimal solution to the original problem. Simulation results show that the proposed iterative algorithm can not only optimize the UAV trajectory, but also effectively improve the downlink achievable sum rate compared with the benchmark schemes.