The Application Research Of OTN Switching Technology In The Railway Optical Transmission Network

Combined with the expansion of railway communication networks and continuous enrichment of service types,the traffic load carried by the networks has also rapidly increased.The status of railway communication networks is directly related to the safety of trains,so ensuring the safe operation of networks is of vital importance.The rapid increase of traffic load will cause network bandwidth shortage,which results in the blocking of some services.It further affects regular network running and threatens the security and reliability of railway communication.Considering the classification and bandwidth allocation of railway communication networks,WDM(Wavelength Division Multiplexing)equipment will meet more significant bandwidth pressure.Therefore,the efficient usage of WDM network bandwidth and equipment upgrade have become important research directions of railway optical networks.OTN Switching derived by OTN(Optical Transport Network)technology implements traffic grooming of different services through ODU(Optical Channel Data Unit)cross-connect and multiplexes various low-rate services to transmit on a single wavelength.It can effectively reduce network blocking probability and improve transmission quality.This paper focuses on OTN Switching technology and its performance in railway communication networks,as well as KSP(K Shortest Paths)and RWA(Routing and Wavelength Assignment)algorithms to complete network resources allocation and performance evaluation.Themain research contents include:(1)This paper concentrates on OTN Switching.The characteristics and advantages of OTN Switching are analyzed.Three main architectures of OTN Switching combining with WDM are investigated in detail.Then,the function and effect of OTN Switching are demonstrated by an example.(2)This paper proposes a Link Level based K Shortest Paths algorithm(LL-KSP).Considering the hierarchy of railway communication networks and the link level,this algorithm divides link's level according to its bandwidth.It assigns services to a high-level link preferentially,for effectively utilizing high-quality transmission resources and improving the network transmission quality.(3)This paper proposes a Multi-dimensional Performance Indicators-Routing and Wavelength Assignment(MDPI-RWA)algorithm.RWA algorithm is an important resource allocation algorithm in optical networks,which can assign routing and wavelength resources for services and derive relevant network performance parameters.In order to evaluate network performance,besides traditional network Mean Blocking Probability(MBP),this algorithm replenishes the Mean Bandwidth Blocking Ratio(MBBR)of services and the Jain's fairness index(JFI).MBBR can measure services'running status and JFI is to judge link load balancing state in the network.The algorithm more comprehensively measures the network running status from the perspectives of services and load distribution.(4)This paper compares the OTN Switching scenario with traditional WDM scenario.The simulation algorithm adopts a topology in a part of railway convergence layer network as the background and presents the MBP and JFI values in two scenarios.The results show that OTN Switching can obviously reduce network blocking probability and balance load distribution in the network through traffic grooming.Secondly,this paper considers the relationship between MBP and the number of nodes equipped with OTN Switching,which provides a reference for future network upgrading.In two different topologies,as the number of OTN Switching nodes increases,the MBP value decreases,and the network performance improves.Meanwhile,the number of OTN Switching nodes has a threshold value.Once it is exceeded,the network performance is not enhanced dramatically.The threshold value is related to the network state such as its topology.