Research On UAV Deployment Algorithms In Cellular D2D Communication Systems

Unmanned aerial vehicle(UAV)are unmanned aircrafts operated by radio remote control equipments and self-contained program control devices.Benefited from the advantages of small size,low cost and strong mobility,UAV are widely used in the applications including express service,security and explosion-proof,disaster relief and video recording,etc.In recent years,the application of UAV in wireless communication systems has attracted explosive attention.Through flexible and efficient deployment,UAV can work as base station(BS)or relay equipments so as to provide user with network access and data forwarding services,and the user service experience and whole network performance can be improved significantly.In UAV communication systems,how to design an efficient UAV deployment algorithm by considering the available network resources,user service requirements and UAV characteristics is an important issue to be solved.In this thesis,the UAV deployment algorithm is studied.The main contents of this thesis are summarized as follows:First of all,the research background,UAV communication network structure,deployment issues and physical layer security issues of UAV communication are described,and the UAV deployment algorithms are classified and summarized.Secondly,for the communication scenario with one BS,multiple UAVs,multiple requesting users(RU)and serving users(SU),a joint UAV deployment and content placement algorithm is proposed by considering the content fetching delay,energy consumption and the deployment cost of UAV.By defining system cost as the weighted sum of the content fetching delay,energy consumption and the deployment cost of UAV,the joint UAV deployment and content placement problem is formulated as a system cost minimization problem.Since the formulated problem is a complicated non-convex integer programming problem,we first consider an initial UAV deployment and content caching strategy,and transform the original problem into a RU association problem.To deal with this one-to-many mapping problem,virtual BS and UAV nodes are introduced and Kuhn-Munkres(K-M)algorithm are adopted to determine the RU association strategy.Then,the obtained RU association strategy is adjusted by examining the cache capacity constraints of BS and UAV.In order to further reduce system cost,redundant UAV are removed via a proposed cost difference-oriented greedy method.Finally,the optimal location of remaining UAV is determined by applying extensive search algorithm.Thirdly,addressing the data transmission problem of jammer-assisted UAV security communication system,we assume that the source needs to transmit data to the destination directly in device to device(D2D)transmission mode,or forwards its data to the destination through the deployed UAV relay based on UAV relay forwarding mode,and then a joint optimization algorithm of the transmission power of the source,UAV and jammer,as well as UAV and jammer deployment is proposed.By defining the security energy efficiency of D2 D transmission mode and UAV relay forwarding mode as the ratio of security rate to power,the transmission power and the UAV and jammer deployment joint optimization problem is formulated as a security energy efficiency maximization problem under the constraints of maximum transmission power and user minimum transmission rate.Then,the optimization problems of D2 D transmission mode and UAV relay transmission mode are solved respectively.As the optimization problems of the two modes are non-convex and nonlinear,the original optimization problems of the two modes are decomposed into UAV and jammer deployment sub-problem and transmission power optimization sub-problem.By applying the extensive search algorithm and the successive convex approximation(SCA)technology,the joint source,UAV and jammer transmit power optimization,as well as UAV and jammer deployment strategy are obtained.Finally,the main research work of this thesis is summarized,and the research directions that can be further expanded are analyzed.