Research On Optimization Algorithm Of Constellation Design And Shortest Path In Time-varing Satellite Networks

In order to meet the needs of users to communicate anytime and anywhere,as well as the requirements of system performance to support multi-services,satellite communications has become the focus of current research for the features of the global seamless coverage and the large-scale multi-service traffic.The high-speed mobility of nodes and the dynamic change of the topological structure in satellite communication networks pose some problems and challenges to the constellation design and shortest path optimization.This thesis focuses on the study of constellation design and shortest path optimization technology in the time-varying satellite network.The detailed research works are as follows:Firstly,a brief overview of the development and some key technologies in satellite communications are presented,and the constellation design and path optimization theory are described detailedly.After that,the analysis and summary of the existing methods and algorithms are shown based on the research of the dynamic topology control strategy in time-varying satellite networks.Secondly,the existing constellation structures of the time-varying satellite networks are analyzed in the perspective of constellation design optimization,and an optimal design scheme of double-layer hybrid satellite network for Chinese latitude range is proposed with the consideration of the worst case observation point theory and the street of coverage theory.In order to solve the problems of poor survivability and long processing delay for single-layer satellite networks,and the problems of the complex management and high link redundancy for triple-layer satellite networks,the networking analysis and constellation design for MEO and LEO satellites have been presented by using Walker constellation and polar orbit constellation respectively.In addition,aiming at the problem that the traditional satellite coverage performance index cannot be used to evaluate the satellite constellations with different configurations generally,a unified evaluation model of satellite constellations is proposed based on Analytic Hierarchy Process(AHP).The coverage performances of simulation results are comprehensive analyzed to verify the performances of the scheme for the seamless and continuous multi coverage in China.Finally,dynamic topology structures of the time-varying satellite networks are analyzed in the perspective of shortest path optimization.Aiming at the problem that Dijkstra shortest path algorithm cannot always ensure the optimal path in time-varying satellite topological networks,an optimized shortest path algorithm has been proposed based on CP(CP-Dijkstra)by considering the determinacy of satellite node movement and the periodicity dynamic change of satellite network topology structrue.Before transmitting message,each satellite node checks whether the CP is updated or not to chooses different methods to deal with the message,until the message is successfully forwarded to the destination node.With this scheme,a series of paths where the message has gone through is named the shortest path.Simulation results show that the proposed CP-Dijkstra algorithm has the better network performances than the traditional DVTR algorithm in the time-varying satellite networks.