Converged Satellite And Terrestrial LTE Networks Based On SDN With Performance Simulation

Satellite communications have advantages of huge coverage,less geographical condition limitation,wide bandwidth,high flexibility,and insensitivity to communication distance.It is widely used in civilian and military communications.These advantages are even more prominent when major disaster events occur.Terrestrial LTE network has been widely used commercially.The integration of land mobile communication system and satellite communication system,enabling mobile communications network to realize truly seamless coverage,has been the focus both the academic and industry fields.The construction of traditional satellite network has the high cost and poor flexibility.Software Defined Networking(SDN)technology separates the control function from the forwarding function,so the network switching equipment can be transformed into a simple forwarding component.To improve the flexibility and expansibility of a satellite network,we apply SDN technology to it,making the full usage of network component and the network architecture simpler and clearer.Supported by the National High-Tech Development Project(863 project),the test and simulation of next generation converged satellite and terrestrial broadband communication networks,this dissertation has applied the SDN technology to the satellite network,and performed a more comprehensive simulation on the converged satellite and terrestrial LTE networks based on SDN by using NS-3.Firstly,this dissertation describes the architecture of the converged satellite and terrestrial networks and the protocol stack of the LTE system,reviews the SDN and its key technologies,and briefly introduces NS-3 network simulation tools to be used.Secondly,this dissertation integrates the idea separating data plane from control plane in SDN to satellite networks,and proposes the architecture of the converged satellite and terrestrial LTE networks based on SDN.Then we build the simulation model of the proposed network architecture by using the NS-3 network simulation software,and evaluate the network performance of that converged network with different simulation scenarios.The main contributions of this dissertation are as follows:(1)In view of the disadvantages of traditional satellite networks,such as high construction cost,low equipment utilization and the inconvenience of operation and maintenance in the later period,we apply the SDN technology to the satellite network on the basis of both domestic and foreign research results,improving its flexibility and scalability.We proposed the converged satellite and terrestrial LTE networks architecture based on SDN and designed its protocol stack,and described the communication process of data flows between users in detail.(2)Since the existing NS-3 system lacks the part of a satellite,a simplified satellite link model is designed.For the SDN part,we implemented an external OFSID(OpenFlow Software Implementation Distribution)library associated with internal OpenFlow module.The main work is on the implementation of the simulation platform for the converged network architecture based on NS-3 system in C++.We set the satellite network topology and satellite link parameters in simulation scenario,and evaluate the performance of the converged network architecture.(3)Through the theoretical calculation and analysis,we concluded the advantages listed below for the converged satellite and terrestrial network architecture based on SDN:a)the decrease of the configuration update cycle could make the satellite network configure optimal network parameters rapidly according to the needs of traffic and network status,which makes the network have better real-time and flexibility;b)the new architecture can simplify the design of satellite and decrease the number of ground stations,which reduces the cost of design and implementation of a satellite system.Finally,we summarize the whole dissertation and point out some issues to be addressed in the future.