Research On Cooperative Transmission Mechanism In Uav-based Backscatter Communication Network

The number of terminals accessing the network is increasing explosively with the fast development of wireless communication technology.Wireless devices such as sensors are limited by the size of their batteries and have limited power.The traditional way of replacing batteries imposes high maintenance costs on equipment deployed on a large scale.Some researchers have proposed a backscattering communication network,which uses radio frequency(RF)signals to communicate,avoiding the use of high-power components and significantly reducing the power consumption of the circuit.At the same time,there are several challenges in backscatter communication,such as short communication distance and low data rate.In recent years,UAV-based assisted wireless communication has attracted wide attention.Due to its flexible deployment,high probabilistic line-of-sight link with ground users and controllable mobility,UAV can realize aerial base station or mobile relay function.UAVs also have great potential applications in backscatter communication networks,both as data collectors and RF signal sources.The combination of UAV and backscatter communication network,with controllable distance between receiver and node,can not only serve more devices,but also improve the efficiency and reliability of the network.However,due to the limited energy of UAV,how to design the cooperation mechanism between UAV and nodes to improve the efficiency of collecting node information is the key problem to be solved in UAV-assisted backscatter communication network.Focusing on this problem,this thesis carries out research.Based on typical scenarios,two kinds of cooperation mechanisms are proposed to meet the requirements of the total amount of data transmitted by nodes and the data rate of transmission.In this thesis,a single UAV trajectory optimization and resource allocation algorithm for energy efficiency optimization is proposed in order to solve the problem that different data acquisition methods of UAV affect the link state and communication quality tradeoff between UAV and node during the process of backscattering data transmission from node to UAV.On the premise of ensuring the total amount of data required to be transmitted by nodes,the energy efficiency of UAV-assisted backscatter communication network is optimized by clustering target regions and jointly optimizing the trajectory of UAVs,the hover time of each region and the ratio between the collected energy and transmission time of nodes in each region.In this thesis,the fractional programming algorithm is utilized to solve the problem iteratively.Compared with the existing two benchmark schemes,the proposed algorithm improves the energy efficiency of the system with simulation results.In this thesis,a collaborative resource allocation mechanism of multi-UAV backscatter communication network for throughput improvement is proposed to solve the problem that communication quality of edge nodes is limited due to the doubly near-far effects.Due to the doubly near-far effect,distant nodes may not obtain sufficient energy,which limits their data rate.In this thesis,the target region is divided into two concentric circular regions,and the cooperation mechanism of two UAVs is designed to collect the data of all nodes.Among them,the data of the inner circular node is collected by the hovering of the major UAV,while the outer circular node is collected by the flight of the auxiliary UAV.The throughput of UAV-assisted backscatter communication network is optimized by jointly optimizing spectrum,time resource allocation,flight trajectory of the auxiliary UAV,and hover height of the major UAV.For the non-convex objective function,this thesis adopts the algorithm based on block coordinate descent to solve iteratively.Compared with the benchmark hover scheme,the proposed scheme improves the system throughput with simulation results.