Study On The Survivability Of Optical Transport Network Of High-speed Railway

The optical transport network of high-speed railway is the nerve center of ground infrastructures,providing accurate and timely information for train status,remote failure diagnosis,train dispatching,command of control and emergency operation of trains.It is the basis and prerequisite for ensuring the safety operation of high-speed railway.In the event of a transmission interruption,it will not only degrade the control system to a lower rank,but also even result in suspension which will seriously affect the normal operation of the high-speed railway.Therefore,ensuring the safe operation of high-speed railway optical transport network is of great significance.This thesis mainly studies the survivability of optical transport network of high-speed railway.Through certain protection and recovery technology to improve network survivability,considering the reliability and effectiveness,we further improve the algorithms on the basis of previous studies,to make them more flexible,which can meet the needs of the actual network.The existing LCD-SPP algorithm allows two services to share protection resources under certain link correlation,so the utilization ratio of resources is increased compared with the traditional SPP algorithm.But the threshold is determined in a random way,which makes it difficult to use in a practical network;The existing MBR algorithm cannot protect the service when the working path and backup path fail simultaneously,so the reliability is poor.To solve these problems,the following research is done:1.Adding threshold on the basis of LCD-SPP algorithm,an algorithm of Link Correlation Degree with Failure Probability-Shared Path Protection(LCDFP-SPP)is proposed in this thesis.The average failure probability of the link in the network is obtained through the failure probability of the optical fiber.Using the average failure probability of the link and the user's requirement for the reliability of network which is the maximum network failure rate that the user can bear,the link correlation threshold is derived.Protection resources can be shared if the link correlation less than or equal to the threshold,otherwise the separation of backup paths must be guaranteed.The simulation results show that the LCDFP-SPP has greatly improved the resource utilization ratio compared with the SPP,and its blocking ratio is obviously reduced,and the network failure ratio is also satisfied with the user's requirement.2.An algorithm of Multiple Sub-backup Path Reprovisioning(MSPR)for multiple failures is proposed in this thesis.For each service connection request,a working path,a protection path and several sub-backup paths are assigned to it first.When the failure occurs simultaneously in the working path and the backup path,the sub-backup path can be combined with partial working path into a new working path and then complete the switching of service.Then the network assigns new backup path and sub-backup paths to the request to prevent the next failure.The simulation results show that the MSPR improves restoration ratio of connection and the whole network survivability compared with MBR and SPP,and its resource utilization rate decreases only slightly.Therefore,MSPR is more suitable for complex networks with the high demand of survivability,which conforms to the future trend of optical transport network of high-speed railway.