Research On Multiple Access And Routing Methods In Spatial Information Network

With the development of space communication technologies,the types of network services are increasingly diverse,and the network environment is becoming more and more complex.Spatial information network is an important development direction of space communication networks.Space-based satellite network,as an important part of spatial information network,has brought new challenges to satellite multiple access methods and satellite network routing methods due to the complexity of network structure and the high dynamic of network topology.This paper studies the space-based access network's multiple access protocol and the space-based backbone network's routing protocol of spatial information network.In the research of multiple access protocol for the space-based access network,this paper focuses on the problems of limited satellite channel resources and frequent switching of satellite-ground link,caused by LEO satellites' high-speed motion.To solve this problem,it proposes a multiple access protocol that adapts to LEO access scenarios.In this way,satellite access efficiency is improved.Based on this,firstly this paper studies the existing satellite multiple access protocol,then proposes an improved protocol CFDAMA-LS on the basis of combined free demand assignment multiple access(CFDAMA)protocol.In the CFDAMA-LS protocol,for the LEO access scenario,the access switching control part is added,and the access switching control strategy is introduced,which enables efficient switching of the satellite-ground link.For packet accumulation under high bursty traffic,the slot application algorithm based on source prediction is adopted in the slot application stage,thus packet accumulation is reduced.In time-slot allocation stage,a weighted timeslot allocation algorithm based on priority ranking is adopted to reduce the average access delay and ensure the fairness of user access.In the research of multi-layer satellite network routing protocol for the space-based backbone network,this paper hopes to design a dual-layer satellite network routing protocol that adapts to the background project's constellation structure.The inter-satellite routing delay is reduced,at the same time,packet loss due to routing failure is reduced.In this paper,the schemes and design ideas of classical multi-layer satellite routing protocols are firstly analyzed.It is found that these protocols have problems such as over-ideal design,poor resilience,and complex implementation mechanisms.Based on the satellite grouping and routing protocol(SGRP),this paper proposes a dual-layer satellite network routing protocol based on dynamic group partition and hierarchical routing mechanism.This protocol abandons the group partitioning mechanism based on the snapshot cycle,instead it adopts a dynamic group partitioning mechanism based on the inter-satellite link state.Each LEO satellite selects an appropriate group manager according to its own manager selection strategy and the state of the cross-layer inter-satellite link,which ensures the connectivity of cross-layer inter-satellite links and has strong resistance to destruction.This protocol adopts the subsection routingmechanism.The medium earth orbit(MEO)layer and the LEO layer independently exchange routing information,and no routing information interaction occurs between layers.Thus the process of network topology aggregation and route centralized distribution is avoided.At the same time,different routing and forwarding strategies are selected according to different communication distances,which effectively reduces delays in inter-satellite routing.the MEO layer-assisted routing mechanism is adopted when the routing information of the LEO layer is invalid,which effectively reduces packet loss due to real-time loss of routing information.Finally,in the network simulation software OPNET Modeler,the two improved protocols are modeled respectively,and a corresponding simulation platform is designed and implemented.On this basis,corresponding simulation scenarios are set up to verify the performance of two protocols.Simulation results show that the CFDAMA-LS protocol can adapt to the LEO access scenario,and has better performance in terms of slot allocation scheduling and access fairness than the CFDAMA-PB protocol.The performance of double-satellite network routing protocols based on dynamic group partitioning and hierarchical routing mechanisms is also superior to the classic SGRP protocol in terms of packet loss rate and transmission delay.In the same simulation environment,the global average end-to-end delay and packet loss rate of the SGRP protocol are 160 ms and 0.15% respectively.While,the simulation results of the routing protocol proposed in this paper are 126 ms and 0.03%.