Research On Failure Recovery Mechanism Of High-Speed Railway Optical Transport Network

The Optical Transport Network(OTN)of high-speed railway is an important part of the ground infrastructure of high-speed railway.It provides services for the operation of train dispatching,train running control,the emergency treatment of failure and so on.Once there is failure in OTN,the normal operation of entire railway network will be affected seriously.Therefore,it is necessary to conduct an in-depth study on the failure recovery mechanism of OTN.This paper mainly studies the recovery mechanism of multi-failure.According to the distributed location of failed links,there are two kinds of failure scenarios:one is a large-scale and centralized failure caused by natural disasters or other factors,the other is decentralized multi-link failure caused by the aging of fiber-optic equipment,human factors or other factors.These links are usually under the same management domain.Based on the above content,the main work of this paper is as follows:(1)A recovery scheme of multi-failure about the Improved Ant Colony Optimization Algorithm Based on Two-Dimensional Space(IACO-2D)algorithm is proposed.This scheme mainly has an intensive study on Routing and Wavelength Assignment(RWA)algorithm based on the first failure scenario.In this scheme,the problem of wavelength assignment is solved by First Fit(FF)algorithm.And the problem of routing is solved by IACO-2D algorithm.In IACO-2D algorithm,the theory of Maklink's graph is used to construct a two-dimensional planning space.By improving the transition probability of the traditional Ant Colony Optimization(ACO)algorithm,the network can select a low-occupancy link with higher probability when routing.The simulation assumes two fault scenarios.Compared with the ACO algorithm,IACO-2D algorithm improves the ratios of resource utilization by 25.46%,23.18%respectively.And the ratios of blocking are made decrease by 16.46%and 15.16%respectively.(2)An Improved Fast Recovery Based on Multicast Tree(IFR-MT)algorithm is proposed.IFR-MT algorithm mainly has an intensive study on the recovery scheme of established path based on signalling for the second failure scenario.The failure recovery is accomplished by constructing an optical multicast tree model for OTN and combining the distributed recovery mechanism to establish an inter-tree Label Switching Path(LSP)for the end nodes of the failed links.IFR-MT algorithm and Multiple Sub-backup Path Reprovisioning(MSPR)algorithm are compared from a theoretical perspective and a simulation environment.Theoretically,the application of recovery time and recovery rate model analysis proves that the performance of IFR-MT algorithm is better than MSPR algorithm.Results of simulation prove the feasibility of the algorithm in the actual railway network topology.Compared with MSPR algorithm,IFR-MT algorithm has a higher rate of recovery by 20.7%and 28.7%respectively in the ring-2 and ring-3;And IFR-MT has a lower time of recovery by an average of about 40.2ms and 31.9ms respectively.