Research On Key Routing Technologies Of Large-scale Low Earth Orbit Broadband Satellite Network

The large-scale network of low earth orbit(LEO)broadband satellites uses a large number of members to relax the strict requirement for single ones.Relying on inter-satellite link networking,the satellite network could break through the geographical location limitations and achieve global uninterrupted signal coverage,providing large-bandwidth,low-latency,seamlessly connected and compatible services to all users around the world.The large-scale LEO broadband satellite network is compatible with the terrestrial communication network system and is an important part of the space-ground integrated networks,and has immediately become the research focus in various countries around the world.As a key technology of network communication,routing affects the efficiency of information transmission and the quality of network services.In a large-scale LEO broadband satellite network with hundreds or thousands of nodes,the constant high-speed movement of satellites causes frequent changes in the topology.At the same time,the limited resources on satellites make it impossible for large-capacity storage and large-scale real-time calculations.These problems add great trouble in routing design of large-scale LEO broadband satellite networks.In this regard,this thesis has carried out research on the routing design of large-scale single-layer LEO polar orbit broadband satellite network,including multipath unicast routing unicast routing,dynamic unicast routing and multicast routing.The main research content and contributions of this thesis are as follows:1.A unicast routing algorithm based on Node Disjoint-based Multipath(NDM)is proposed.In view of the complexity and diversity of the spatial environment,traditional static routing can no longer cope with the problems of increased delay,packet loss even unreachable data caused by uneven traffic distribution,network congestion,and node failure.For this reason,this paper has carried out the research on unrelated multipath static unicast routing algorithm.This algorithm uses the regularity of the satellite network to analyze the periodic changes of the source node and the destination node across the polar regions during the network operation,and designs up to three completely unrelated paths to avoid the delay caused by rerouting planning and improve system robustness.Specifically,we combine the comprehensive advantages of alternative multipath and parallel multipath to set the priority of three paths: the path with the shortest propagation distance is used as the main path,and the remaining two are used as backup paths.In this way,the main path can perform efficient and fast data transmission without congestion;when the main path is lightly congested,the system adaptively starts a backup path together with the main path for parallel transmission;when the main path is heavily congested,the main path is interrupted and the remaining two are enabled so that data integrity and reliability could be guaranteed.The simulation results show that compared with the Discrete-Time Dynamic Virtual Topology Routing(DT-DVTR)algorithm,Explicit Load Balancing(ELB)routing algorithm,the NDM algorithm achieves higher throughput,lower transmission delay and packet loss rate when faced with different degrees of network congestion.This advantage is even more obvious in the case of extreme congestion.As a conclusion,our proposed algorithm effectively improves the transmission efficiency,adaptive adjustment capability and fault tolerance of large-scale single-layer LEO polar orbit broadband satellite networks.2.A Minimal Dynamic Cost(MDC) unicast routing algorithm is proposed.This research aims to solve the large resource occupation caused by dynamic unicast routing in the large-scale LEO broadband satellite network routing calculation and update,and the high delay caused by channel congestion or node failure.The algorithm first converts the propagation delay,queuing delay,and processing delay consumed by the data from the satellite source to the destination node into path cost,waiting cost and processing cost,and then takes the path with the lowest total cost as the main path so that fastest network communication can be ensured.In order to avoid the occurrence of data packet loss as much as possible,the algorithm uses the M/M/1/k model to set packet loss expectations,thereby calculating the maximum threshold of a single satellite data buffer queue,and excluding paths that exceed the threshold to ensure path's reliability.Before path detection,the algorithm determines the relative position of the source node and the destination node,and sets the minimum hop flooding area,which shortens the data flooding time and saves limited network resources.The simulation results show that,with Beijing as the source node,in the short-range communication with Hong Kong and Taiwan,as well as in the long-distance communication with Berlin and Washington,the MDC algorithm has achieved better performance than terrestrial data communication in terms of delay.When compared with the Dynamic Source Routing(DSR)protocol algorithm,Location-Assisted On-demand Routing(LAOR),the MDC algorithm has achieved lower delay and packet loss rate in the state of no congestion or different levels of congestion,which meets the needs of users for low delay and data complete requirements to maximize the efficient transmission of data and higher-quality network services.3.A Cluster-based Multicast Routing(CMR) algorithm is proposed.Aiming at the problems of high cost of multicast trees,poor link sharing of routing algorithms,and longdistance multicast paths caused by the time-varying topology of large-scale LEO broadband satellite networks,the Cluster-based Multicast Routing(CMR)algorithm is proposed.The algorithm transforms the satellite network into a relatively stable Manhattan model,dividing the network into two clusters through discussion of group members,and then selects a cluster head for each cluster.As the root node of the multicast tree,the cluster head can share the pressure of the multicast source node.During the construction of the multicast tree,four priority levels are set,so that the number of shared nodes can be increased,unnecessary paths being reduced,sharing rate of the multicast tree being increased.Simulation results show that compared with CCST algorithm,FIM algorithm,and MRA algorithm,the CMR algorithm takes into account the total number of multicast tree hops and the number of transit nodes,thereby achieving lower multicast tree generation overhead and avoiding single point of failure congestion.This algorithm greatly improves broadband utilization and transmission efficiency,improves multicast fluency and network stability,and realizes real-time transmission of data from multicast sources to member nodes worldwide.