Research On UAV Deployment And Resource Allocation For Multi-Hop UAV Relay System

Benefitting from the strong mobility,low costs and quick deployment,unmanned aerial vehicle(UAV)is enabled to play an important role in wireless communications.Different from the traditional ground communication link that will be blocked by buildings commonly,the airto-ground(AtG)link reduces the path loss of wireless signals through the advantage of the AtG line-of-sight(LoS)transmission.Therefore,UAV as an aerial wireless access point can bring higher performance improvement for the wireless relay system.However,for the long-distance communication scenario,if there is only a single UAV relay to assist communication between the ground base station(GBS)and the user,such a dual-hop UAV relay system cannot support reliable long-distance connectivity for its limited backhaul capacity,which makes it necessary to take advantage of multi-UAV collaboration to establish multi-hop UAV relay system for remote data transmission.However,only limited existing studies focus on the multi-hop UAV relay system,and there are the following problems:1)Insufficient consideration on the transmission capacity analysis of the multi-hop UAV relay system;2)UAVs are mostly static deployment for the multi-hop UAV relay system in the multi-user scenario,and the flexibility of UAV is not fully utilized to improve the user communication quality.To tackle the above problems,this thesis aims to impro ve the capability of the multi-hop UAV relay system and studies the system in the single-user and the multiuser scenarios respectively.1)Considering the single-user scenario,this thesis studied the optimal deployment of multi-hop UAV relay under different resource allocation schemes with the goal of end-to-end throughput maximization.Moreover,we analyzed the relationship between the user-GBS transmission distance,the number of UAV relays and the user-GBS communication performance.The conclusion is of instructive significance to the deployment of multihop UAVs in practical scenarios.2)In the view of the problem that multi-hop UAVs are mostly static deployment in existing studies,which can hardly meet the actual demand of the users.Therefore,in order to maximize the user transmission,this thesis proposed a joint optimization scheme of the association between GBS,UAV and user,UAV flight trajectory and communication resources in the further consideration of the multi-user scenario.Finally,the simulation result verifies that the proposed scheme can effectively improve the user communication rate.