【作者】 杨明；

【导师】 陈祥献；

【作者基本信息】 浙江大学 ， 电子信息技术及仪器， 2012， 硕士

【摘要】 安全、可靠是列车控制系统永恒的主题。在基于通信的列车控制系统(Communication Based Train Control, CBTC)中,及时、可靠的数据通信是保证列车安全运行的前提和基础。而CBTC系统中与安全的数据通信关系最为直接的是安全通信协议。本文为CBTC系统中安全相关的数据传输设计了一个功能相对完善的安全通信协议,并采用了基于OPNET Modeler的仿真测试方法对协议性能进行了初步的检验。在安全通信协议的设计过程中,本文首先分析了CBTC系统在安全相关数据传输方面的需求,随后在充分理解欧洲标准EN50159对构建安全数据通信应采取的安全措施提出的要求的基础上,详细阐述了协议中采用的安全措施与协议进行数据传输的过程。为在OPNET Modeler中完成协议的仿真测试,本文通过修改OPNET Modeler中无线模块代码实现了移动节点在无线接入点间的切换,并建立了安全通信协议状态机模型。在构建仿真测试网络模型时,本文参照了沈阳地铁1号线的网络拓扑结构,并在应用层模拟了二乘二取二安全计算机的连接特点。最后,本文通过仿真分析了发包间隔与报文长度对平均时延的影响。报文平均时延受发包间隔的影响并不显著,表明协议中采用的安全措施并未带来过重的系统开销。尽管平均时延会随着数据包长度的增长而增加,但时延增长幅度仍可满足CBTC的系统应用需求。在已有的研究中,鲜有提及OPNET Modeler的故障注入功能,本文在协议的测试过程中引入了链路故障,并创建了丢包、延时仿真场景,对协议的故障导向安全功能及健壮性进行了验证。仿真测试结果表明协议具备良好的实时性和一定的抵御错误的能力,可以应用于CBTC系统中。更多还原

【Abstract】 Safety and reliability are the permanent theme of the train control system. In CBTC system, the punctual and reliable data communication is the precondition and foundation of the safe train operation. It’s the safety-critical communication protocol that has the most direct relationship with the safe data transmission. This paper designs a safety-critical communication protocol with relatively perfect functions for the safety-critical data transmission in CBTC and studies the elementary characteristics of the protocol using OPNET Modeler.In the protocol design process, the demands on the safety-critical data transmission given by CBTC system is analyzed first. Then, with a full understanding of the requirements to safety measures that are addressed in EN50159and supposed to be applied in the safety-critical data communication, the safety-measures and the data transmission process of the protocol are specified.In order to carry out the protocol simulation in OPNET Modeler, the switch between different wireless access points for mobile stations is realized through adding codes to the wireless module of OPNET Modeler and the protocol logic is translated to the finite state machine model. For the network modeling, the network topology of Shenyang subway1is taken into account and the connection features of the dual-duplex safe computer are simulated in the application layer.Finally, the effects on the average delay that the packet sending interval and the packet size have are studied through the analysis of the simulation results. The average delay has little relationship with the packet sending interval, which indicates the safety measures of the protocol won’t result in overloaded system consumption. Though the average delay would increase with the growth of packet size, the growth range is still within the CBTC application requirements. While in the past researches, the fault-injection function of OPNET Modeler has been seldom focused on. To verify the fail-safe function and the robustness of the protocol, a link failure is introduced and a packet loss scenario as well as a delay scenario are created. The simulation results show that the protocol well satisfies the real-time response requirements and has a certain fault-defense capability. So it can be applied in CBTC system.更多还原