Research On Software-defined Low-earth Orbit Satellite Network Networking Protocol With Separating Transmission And Control

Low-earth orbit satellites will become important parts of future low-earth orbit satellite mobile communication systems due to their advantages in terms of low orbital altitude,low equipment cost,and easy networking.However,the topology of low-earth orbit satellite network changes frequently.Satellites and inter-satellite links in the network are prone to failure,which brings severe challenges to the design of routing algorithms.At the same time,the centralized low-earth orbit satellite network architecture can no longer meet the real-time control requirements of satellite networks.Under the satellite network architecture based on the idea of software-defined network(SDN),satellite and inter-satellite link failure will also affect the transmission of signaling information.Once a satellite or link failure occurs in the existing software-defined satellite network,signaling information will be sent according to the path that has been planned by ground SDN controller,causing ground SDN controller unable to send and receive signaling information.Therefore,this thesis designs a software-defined low-earth orbit satellite network architecture with separating transmission and control,which decouples the satellite plane into a control plane and a user plane.On the one hand,as a controller,the satellite monitors satellite or link failure of the network,updates the topology in time,and calculates the transmission route of signaling information based on a limited number of basic network topologies of low-earth-orbit satellite network.On the other hand,as a switch,the satellite transfer the service initiated by user terminals according to a certain routing strategy and land these service through the feeder link.The ground SDN controller only computes user plane routes.Under the designed architecture,the satellite can quickly update the topology,and calculate the transmission link of signaling information,which solves the problem of unstable control plane routing caused by ground SDN controller’s inability to receive and send signaling information.On the premise of deep analysis of the topological characteristics of the low-earth orbit satellite network,and aiming at the problem that satellites and inter-satellite links are prone to failure,this thesis proposes a dynamic and static combined routing algorithm for the control plane.The proposed algorithm makes full use of the periodicity of the low-earth orbit satellite network to divide the satellite operation cycle into several time periods by using four time intervals to form several topology switching time points,thereby extracting a limited number of basic network topologies.Then,after the basic network topologies being added,the satellites update the basic network topologies according to link information update mechanism so that triggers the routing update.When a satellite or link failure occurs,the satellite can recalculate the forwarding path for signaling information,which improves the network’s ability to cope with failures.Additionally,when dividing the network topology,the snapshot sequence routing algorithm only divides the satellite operation cycle at equal intervals,therefore,the divided topology is different from the actual network topology.Whereas,the dynamic and static combined routing algorithm fully considers the influence of satellites entering and exiting the polar circle on the topology,whose divided topology can better match the real network topology.Finally,the algorithm is simulated by OPNET in this thesis.Compared with the existing snapshot sequence routing algorithm,the simulation results show that the dynamic and static combined routing algorithm can quickly deal with satellites and inter-satellite links failures.The dynamic and static combined routing algorithm can obtain lower packet loss rate and higher throughput.Aiming at the problem that the segment routing algorithm of the user plane of the traditional software-defined satellite network architecture fails to provide differentiated services for service with different priorities,a table-driven combined label forwarding routing algorithm is proposed in this thesis,which adopts different forwarding methods for service with different priorities.It can not only meet the service requirements of the best efforts of ordinary service,thereby ordinary service can be sent in time and quickly.It can also meet the service requirements of path planning of high-priority service,so that ground SDN controller can plan resources and path for high-priority service.The table-driven combined label forwarding routing algorithm is simulated through OPNET.Compared with the segment routing algorithm of the traditional software-defined satellite network architecture on the user plane,the proposed routing algorithm can provide differentiated services for service with different priorities.Simulation results show that the performance of proposed algorithm is better than traditional algorithm in terms of delay and routing cost.