Research On Real-Time Performance Of Train Communication Network Based On Ethernet

Train communication network is the core of rail vehicle network control system,which is responsible for the reliability and safety of train operation.Traditional train communication network will not be able to meet the requirements of massive data that high real-time transmission in the future.With the advantages of high speed and high bandwidth,Ethernet will become the main development object of train communication network.At the same time,the introduction of Ethernet technology will bring reliability and real-time problems.The real-time performance of train Ethernet communication is studied from three perspectives of topology optimization,switch scheduling and terminal equipment access in this paper.Aiming at the network performance of train communication network is affected by the topology,and a bipartite graph assignment algorithm based on the weight of the communication traffic between devices is proposed.Firstly,according to the actual communication situation between devices in the network,the train switched Ethernet model is established to calculate the communication traffic weight between devices.Through the bipartite graph assignment algorithm to achieve matching devices to switches,and build a new topology.Verifying the reliability of the optimized topology by the network timeliness reliability model,and the network performance of the topology is analyzed by simulation.The results show that the optimized topology can greatly improve the network performance which network delay,link utilization and throughput compared with the unoptimized topology.Aiming at the problem of large queuing delay in switches,a priority-based comprehensive hierarchical scheduling algorithm is proposed.Firstly,according to the data type and real-time requirement of train communication network,the static scheduling which assigns data types to different priorities is presented,and the final priority of data frames in the same data type is determined by dynamic scheduling.Then different priority queues are assigned different time slices by time allocation scheduling.The network calculus theory is used to calculate the maximum end-to-end delay of fixed priority scheduling algorithm and comprehensive hierarchical scheduling algorithm,and the advantages of the two scheduling algorithms are compared by simulation.The results show that the new scheduling algorithm has great advantages to improve the real-time performance in network.Aiming at the media contention between devices,a bandwidth allocation strategy based on time division multiplexing is proposed.Firstly,the time division multiplexing mechanism is used to allocate the network bandwidth by the data type.Then a communication scheduling model based on temporal constraints is established to schedule the time slots of real-time periodic data,and the temporal constraint strategy is used to obtain multiple static tasks table,which making sure each device to receive the static scheduling table at the initial stage of the system.Each device sends data in the specified time slot according to the static schedule to avoid the collision of network data frames,and at the same time reserve more bandwidth for the transmission of real-time aperiodic data,ensuring the real-time and reliability of the train communication network.