Simulation Research Of Train Communication Network Based On OPNET

As the direction of modern train follows in the course of high speed, automatization and comfort, more and more control information and management information come into being. Furthermore, this information badly needs to be mutual transmitted and switched among computers in rolling stock. At the same time, the field bus technology and embedded computer control technology develop quickly, which makes contributions to the safety, fast, reliable and accurate of information transmission in railway vehicles. In order to create a standardized train-vehicle equipment standard for data communication, TCN, the international standard for train communication network IEC61375-1 has been developed by the twenty-second working group (WG22) Joint International Union of Railways (UIC) of International Electrotechnical Commission (IEC) Technical Committee of the Ninth (TC9). Field bus technology is being applied to the field of rail vehicle communication network in recent years for its openness, security, real-time and cost advantages. Therefore, some standards based on LonWorks,CAN bus and field bus technology WorldFIP were added into the vehicle-level bus network standard IEC61375-3 which IEC have been formulated since August 2006.Consequently, a wider range of field bus technology are used in train communication network.This paper, firstly gives a general introduction to the development and application status of the main train communication control networks home and abroad, and focus mainly on train traffic control network based on field bus technology. It then introduces briefly the OPNET simulation software in the simulation mechanism and modeling methods. Through the analysis of the train communication network architecture, the general bus-based TCN vehicle-level bus model is designed, and the rationality of the model is verified by contrasting the several different actual models of the train communication network topology.Followed above, this paper gives more details to LonWorks bus and its relevant technical characteristics. As well as analyzes the LonTalk communication protocol and its media access control methods to MAC layer (P persist CSMA predictable), the author makes some modifications in bus process and node according to the existing Ethernet node model. After a design of LonTalk node model, a LonWorks-based vehicle-level bus has been set up. Through the simulation results, the author concludes that LonWorks bus can be used as vehicle-level bus because of its better performances in bus utilization and collision rate when comparing with Ethernet.In addition, the author introduces the CAN working principles and the communication protocol (CAN 2.0), and then focuses more on its media access control methods to MAC layer—CSMA/CD with priority level (lossless bit-by-bit arbitration). The process and node model are designed in OPNET modeler, on the basis of which, the vehicle class train communication network model is built. Through the analyses of simulation results and the studies in node number,message service,priority and error rate, it shows that CAN bus is reliable and stable and it can be used as vehicle-level bus or equipment bus in the train communication control networks.