Research On Link Self Updating Mechanism Based On Leo Satellite Network

In the multi-layer satellite network model of the integration of heaven and earth,low earth orbit(LEO)has become one of the most effective ways of global real-time communication because of its low communication delay,short earth cycle,wide global coverage,large communication capacity and low launch cost.The applied routing strategy and routing algorithm are the key technologies to ensure the transmission stability of various communication services in satellite networks.In recent years,with the development of global communication,the demand for service load is becoming larger and larger,the computing power of space nodes is insufficient,and the resources of LEO satellites are becoming increasingly tense.How to ensure the stability of satellite networking and improve communication efficiency in the complex and changeable LEO satellite network environment is a key problem to be solved urgently.Aiming at the above problems,this paper mainly completes the following work:(1)In the LEO satellite networking scenario,a slot routing mechanism combined with dynamic delay and a short delay priority path(SDP)routing calculation strategy are proposed.Firstly,in OMNeT++network simulation software,the link delay of Leo inter satellite link at each time is calculated according to the simplified general perturbations(SGP4).The dynamic topology is discretized into static topology sequence,and the link connection state and delay attribute are updated after each topology switching.In order to consider the influence of inter satellite link delay change on Routing in the process of path selection,a SDP static route update strategy is proposed.The dynamic delay is taken as the routing weight,and the short delay priority path is calculated in advance,which is updated and marked into the satellite.During link switching,the flooding mechanism under dynamic routing is replaced by replacing the routing table.The simulation results show that the SDP update strategy is significantly improved compared with the time slot static routing scheme,and the average link transmission delay is reduced by 29.2%.(2)Considering the impact of delay change on service end-to-end transmission delay in the same time slice,and dealing with link emergencies in space network,a distributed delay update for short delay priority(DDU-SDP)is proposed.Firstly,based on the influence of dynamic delay,the time slot division rules are designed to improve the update accuracy of link state.Secondly,the link state update mechanism combined with breadth first search tree(bfst)is introduced to pre calculate the link state broadcast table,and calculate the feasible path set according to the topology planning results and store it in the satellite nodes.For the whole satellite network,link state changes can be divided into two types:internal changes caused by time slot switching and link failure.When the expected time slot switching occurs,DDU-SDP updates the link connection state and delay value of the whole network according to the pre calculated link state broadcast table,and each node updates the broadcast state table and feasible path set as the routing strategy of the current time slot.When a sudden link failure occurs,flood change information and update the feasible path set.Compared with SDP slot routing,it ensures the quality of service of the whole network.Through the simulation of multi-channel traffic in Walker Constellation,when using DDU-SDP strategy,the average delay of services in the network is reduced by 20.6%compared with SDP and 43.6%compared with time slot topology.(3)The joint simulation platform is designed through OMNeT++and STK.In the project,the network scenario module,inter satellite link module and satellite node module of Leo networking are designed.The visibility data in satellite network is processed by MATLAB and imported into OMNeT++,and the data interaction between STK and OMNeT++is completed.The function of relevant routing update mechanism is realized.The whole simulation system provides a stable guarantee for the above strategy verification.Through the research of this paper,time slot routing and distributed dynamic routing are used to update the routing,which solves the routing optimization decision-making problem in the case of high dynamic delay in LEO satellite networks.It lays a foundation for the engineering application of link state self-renewal in space network.