A Space-time Graph Based Interruptions-tolerant Routing Algorithm In Satellite Disruption-tolerant Network

Satellite network using a space platform as a carrier,such as a synchronous satellite or a medium or low orbit satellite,a stratospheric balloon,and a manned or unmanned aerial vehicle,is a network system that acquires,transmits and processes spatial information in real time.As an important national infrastructure,satellite network can support high-dynamic and broadband real-time transmission of Earth observation while supporting major applications such as ocean navigation,emergency rescue,navigation and positioning,air transportation,and space monitoring and control with ultra-long-range,large-delay reliable transmission of null detection.Therefore,the expansion of human science,culture and production activities into space,ocean,and even deep space is a hot research topic on a global scale.Since the 21 st century,with the development of science and technology,satellite networks have global coverage capabilities,and have been able to support audio,image and video communication services becoming an important part of the new generation of global mobile communication systems.It is precisely its important role that requires its high reliability.There are multiple nodes in the satellite network,and the inter-satellite link is used to provide a communication path,which can implement route lookup and packet information forwarding.However,the time-varying characteristics of the satellite network topology:(1)The inter-satellite link and the link of the satellite link change with time,resulting in frequent network cutting and lack of end-to-end path.The TCP/IP protocol in the traditional static network cannot complete the data transmission in the satellite network environment;(2)The space environment of the nodes in the satellite network is complex,and the high-speed motion causes the link conditions to change with time.When the unpredictable interruption occurs in the network,it cannot be quickly repaired.Therefore,the routing strategy for preventing unpredictable interruption in the satellite network is studied important.(3)In the satellite network,due to the imbalance of load on some nodes or equipment failure,the inter-satellite link failure will occur frequently.Especially in military situations,the satellite network is vulnerable to military strikes and unpredictable interruption.Therefore,it is very important tostudy the data re-planning after the unpredictable interruption of the satellite network.For the first problem,this paper adopts the Disruption-Tolerant Networking(DTN)network model,and the data transmission protocol follows the BP/LTP protocol in the DTN network.For the second and third problems,the Space-Time graph model is used to characterize the time-varying network topology,and the data transmission strategy for preventing and dealing with unpredictable interrupts is designed on the model.The main contributions of the paper are as follows:This paper uses the space-time graph model to model the satellite network topology,and it analyzes the current status and routing strategy of the satellite network.We classify the disruption problems in satellite networks,determine the transmission problems caused by unpredictable interrupts,and establish an unpredictable interruption probability model.Based on the characteristics of unpredictable interruption in the network,the modeling method of space-time graph is established;On this basis,a specific space-time graph construction algorithm is proposed.For the unpredictable interruption problem in satellite networks,in order to design a routing strategy to prevent unpredictable interruption,the interruption probability is combined with the transmission energy cost with the data transmission of the DTN network.The transfer process defines a mathematical model of the space-time graph edge weight;An algorithm for preventing unpredictable interrupt routing based on space-time graph model is proposed.When the delay requirement is met,when an unpredictable interruption occurs in the network,the data transmission task is completed with the minimum energy cost and the maximum success probability.In the satellite DTN network,the specific impact on the data transmission in the network after the occurrence of unpredictable interruption is analyzed.The routing problems concerned before and after the unpredictable interruption are presented in the form of mathematical model.A space-time graph based unpredictable interruptions-resilient routing algorithm in satellite Disruption-Tolerant networksl is proposed.After an interruption,a set of routes with minimum energy cost is found on the updated space-time graph model,and the time delay requirement is met.When an unpredictable interruption occurs in the satellite network,the problem of data transmission provides a practicalsolution.After an unpredictable interruption in the satellite network,normal data transmission is guaranteed and its energy cost is minimized.A space-time graph based unpredictable interruptions-resilient routing algorithm can effectively solve the unpredictable interruption problem in satellite networks compared with other traditional routing algorithms.