Design And Realization Of TCN Gateway Based On Ethernet And MVB

Multifunction Vehicle Bus (MVB) and Wire Train Bus (WTB) of TCN are widely used among Chinese train network. Traditional TCN bus has certain advantages in certainty and real-time capability during communication. As Chinese railway modernization, communication between on-board devices are more frequent, multimedia services are more plentiful, which enhances requirements on communication speed. Speed of traditional TCN bus is relatively low, speed of MVB is1.5MBit/s and for WTB it is1MBit/s. The low speed of TCN bus can not meet the requirement of increasing communication traffic. Other problems as inflexible networking, hard to communicate with ground and expensive hardware boards, these problems greatly limit the development of Chinese train network.As the most widely used local area network, Ethernet has many advantages such as fast communication speed, flexible networking forms, low installation costs and so on. However, the CSMA/CD medium access mechanism used in traditional Ethernet introduces uncertainty and real-time problems in the communication process, which is the biggest obstacle for using Ethernet in TCN. After analyzing the flaws in real-time capability of traditional Ethernet, an improved Ethernet protocol is proposed in this paper by designing a real-time scheduling layer over the MAC layer of Ethernet data link layer and using the master-slave scheduling mode based on priority. A real-time solution is proposed which can absolutely solve the real-time problem for using Ethernet in WTB.Using this improved Ethernet as train bus combined with the MVB bus as vehicle bus, an Ethernet/MVB gateway is designed. By building a communication platform, functional test is used for each module of the gateway. Then is the overall test, such as accurateness of data transmission, the frame reply time, the delay analysis for cross-gateway data and so on. The test result indicates that reply delay of network data frame is significantly decreased by using the Ethernet based real-time solution in train bus. Real-time capability is greatly improved. This solution absolutely solves the real-time problem for using Ethernet in WTB.