Research On UAV Relay Deployment For Emergency Communication

In an emergency scenario,it is difficult for the destroyed ground infrastructure to provide reliable services to users in the disaster area.In the case of isolation between the disaster area and the ground base station,Unmanned Aerial Vehicle(UAV)can be used as an air relay to establish a communication bridge between the disaster area and the outside world,tracking and serving by virtue of its controllability and flexible deployment.By combining multi-carrier technology with UAV relay,sub-channels can be flexibly allocated to different users and the performance of the system can be improved.Therefore,this article focuses on the deployment of UAV relays in emergency scenarios,and studies the UAV relay deployment problems for different service ranges and different service scenarios.The problem includes semi-dynamic UAV relay deployment design and dynamic non-relay deployment.For these two designs,the trajectory optimization and resource allocation schemes of the UAV relay are proposed,and the theoretical derivation and simulation analysis of the proposed schemes are carried out.Firstly,the relevant technologies and theories of UAV relay deployment are introduced.Aiming at the research background of this article,the basics of UAV communication are introduced,and the basic principles of channel model,information transmission and trajectory optimization are introduced respectively,and the basic model and solution process of continuous convex approximation are analyzed.For UAV relay technology,the relevant theories of hovering UAVs and mobile UAVs are analyzed,and the basic model of UAV relay deployment is brought out by analyzing their basic models.Aiming at the problem of communication network resource allocation,user scheduling,multi-carrier transmission technology and power allocation algorithm are demonstrated.Secondly,considering serving multiple stationary users,a data relay transmission system under semi-dynamic UAV relay deployment is proposed,and a joint base station and UAV power and trajectory optimization scheme is designed for this system.In this scheme,when the communication between the multi-user area and the base station is interrupted,the base station first sends information to the drone,and then the drone acts as a relay to forward the information to the user.Under the constraints of UAV mobility,base station and UAV power budget,and information transmission causality,by jointly optimizing the base station and UAV power and UAV trajectory in each time slot,the system downlink can be maximized.And compare the system performance under the three optimized trajectories.Aiming at the above optimization problem,a two-step iterative algorithm is proposed.Compared with the benchmark scheme,the joint optimization scheme proposed in this thesis can significantly improve the achievable downlink rate of all users.Finally,considering serving multiple mobile users,a user tracking and data relay transmission system under semi-dynamic drone relay deployment is proposed,and a joint trajectory optimization and resource allocation scheme is designed for this system.This scheme considers mobile users in emergency scenarios,and combines multi-carrier technology with user scheduling to realize user tracking and data relay transmission.Under the constraints of UAV mobility,sub-carrier power and information transmission causality,by optimizing the UAV’s flight trajectory,sub-carrier power and user scheduling,the average reach and rate of the system downlink is maximized.Aiming at the above optimization problem,a three-step iterative algorithm is proposed.Compared with the benchmark scheme,the proposed scheme can adaptively adjust the resource allocation and UAV trajectory according to the channel conditions.Different from semi-dynamic drone relay deployment,this solution focuses on considering mobile users and improving user fairness.By using drone maneuverability to design flight trajectories,it maximizes the reachability of each user.And on this basis,the reach and speed can be improved.