| In recent years,with the breakthroughs in high-throughput satellite technology and small satellite constellation technology,the Space-air-ground Integrated Network(SAGIN)which combines satellite networks,air network platforms,and ground-based networks have been affected by more and more scholars in academia and industry are paying attention.The air-space-ground integrated network has significant advantages:satellite network coverage is wide,air network flexibility is strong,and ground network resources are abundant.SAGIN can combine network advantages at different levels and play a major role in various fields such as ground monitoring and mapping,navigation guidance,and military operations.In response to the above-mentioned problems,this thesis takes the combination of Software Defined Network(SDN)and the SAGIN architecture as the starting point,then takes the optimization of the earth-satellite global network performance as the research goal.The thesis starts from the SDN-oriented SAGINcommunication architecture.Controller deployment,dynamic priority ant colony routing algorithm and other aspects have been researched in detail,aiming to provide scientific theory and technical support for key issues such as air-space-ground integrated network communication architecture design,network integration,and routing planning.The main work of this thesis include:The core modules and system composition of the air-space-ground integrated network and SDN architecture are researched,and the characteristics of the centralized control of SDN technology,the separation of data and forwarding planes,and the opening of the underlying network configuration programming interface are applied to the SAGIN.Detailed analysis and design of a layered communication framework of SDN-oriented SAGIN and analysis of core modules and functions such as SDN satellite switches and SDN satellite gateways.The thesis has given strong proof of the feasibility and practicability of the application of SDN architecture in SAGIN.Mathematical modeling is performed on the ground-satellite SDN control link,and the LEO satellite constellation configuration is designed and optimized with the goal of minimizing network maintenance delay.The deployment of the SDN controller in the air-space-ground integrated network is researched.The satellite coverage and handover factor is the research points.On the basis of ensuring the quality of the ground-satellite communication link,an SDN Controller deployment algorithm based on the ground-satellite coverage value is designed.Compared with the traditional deployment of the controller based on the static node topology on the ground,the dynamic controller deployment algorithm can ensure the minimum handover numbers of the ground-satellite link during the satellite operation cycle and significantly improve the "blank coverage" problem.The thesis researches the problem of satisfying the routing planning of network services with different priorities for terrestrial users in the LEO/MEO distributed SDN network.The thesis proposes a dynamic priority ant colony routing algorithm based on the quality of service.The algorithm is based on a distributed SDN network Qo S constraint model.Firstly,the satellite network model topology is dynamically discretized using the concept of satellite timing diagrams.Secondly,indicators such as satellite delay,remaining bandwidth,and link utilization are defined,and the network cost function is customized.Adjusting the ant colony pathfinding parameters reasonably guarantees the balance between the different indicators of the SDN world-ground integrated network,and meets the diverse Qo S requirements of users.The simulation results show that the algorithm effectively combines the advantages of SDN to overcome the shortcomings of the integrated network,and guarantees Qo S requirements of different priority services.Compared with the OSPF protocol and the RIP protocol,the end-to-end delay is decreased by 15.3% and 16.7% respectively. |
PDF Full Text Request