基于时间触发机制的以太网在CBTC系统应用中的研究
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摘要
基于通信的列车控制(Communications-Based Train Control,CBTC)系统在我国城市轨道交通的发展中占据着越来越重要的地位。国内CBTC系统的应用研究还处于起步阶段,进行相关的理论研究是非常有必要的。
CBTC的数据通信系统(Data Communicate System,DCS)不仅包含有线局域网通信,而且包含车地之间的无线局域网(Wireless LAN,WLAN)通信。列车在WLAN中经常发生的越区切换等问题会增加信息的延迟时间。在通信量增加的情况下,基于以太网的事件触发机制的DCS会带来通信的不确定性。相比之下,时间触发(Time-triggered,TT)机制能够增加系统通信的确定性,提高系统的实时性。松散时间触发(Loosely time-triggered,LTT)机制是TT的一种弱化形式,适用于带有WLAN的实时分布式控制系统。本文主要针对CBTC系统通信的不确定性问题,设计了一个时间触发层协议,并对其进行了验证。
首先,根据标准的TCP/IP四层协议模型,论文确立了时间触发层协议在标准的TCP/IP四层协议模型中的位置。同时,结合CBTC系统的车地通信的特点,分析并给出了时间触发层协议所要实现的功能需求。
其次,论文对LTT机制进行了深入的研究。从研究LTT机制的原理出发,以车地通信中车载控制器(Vehicle On Board Controller,VOBC)与区域控制中心(Zone Controller,ZC)之间的通信为研究对象,设计了CBTC系统的时间触发层协议,给出了时间触发层协议的实现流程。根据VOBC与ZC之间通信的特点,选用了主从式的架构,设计了可以进行时间窗动态分配的调度表。在此基础上,论文进一步从定性的角度分析了时间触发层协议的性能。
然后,论文按照从上至下的分层思想建立了车地通信、时间触发层协议以及无线信道的赋时层次有色Petri网(Hierarchical Timed Colored Petri Net,HTCPN)模型。为了记录消息的延迟时间,方便于系统性能的分析,利用建模工具的赋时特性,在消息中加入了时间戳。
最后,论文利用时间触发层协议建立了车地通信的多车模型。分别对ET机制和LTT机制下的车地通信模型进行了仿真。仿真结果表明,在通信列车数量增加的情况下,相比ET机制,LTT机制能够增加系统通信的确定性,提高系统通信的实时性。
Communication-based train control system (CBTC) in China's urban rail transit development process, is occupying an increasingly important position. There are many issues to be overcome and to improve CBTC system for the study area.
Data communications system of CBTC (Data Communicate System, DCS) includes not only wired LAN communications, and includes the vehicle-ground communications with the wireless LAN communication. Trains in the wireless local area network are often making a handover and confront with sudden drop of channel quality issues, which will increase the delay time. In addition, DCS is structured on the products of commercial off-the-shelf, the traditional event-triggered mechanism Ethernet when traffic communication increased will bring uncertainty. In contrast, time-triggered (Time-triggered, TT) mechanism can bring about more certain communication and improve the systems real-time property. Loosely time-triggered (Loosely time-triggered, LTT) mechanism is a weakened form of TT, suited for wireless local area network with real-time distributed control system. For safety-related control systems, to the extent possible, to reduce the uncertainty brought about by the impact of the communication. In this paper, how to solve the CBTC system for the uncertainty of communication problems, primarily the following research work:
First of all, the paper made reference to seven OSI protocol model and the standard TCP / IP protocol four-level model, analysis and the established the location of the time-triggered protocol to study in standard TCP / IP protocol model in this paper. At the same time, this paper combined with the CBTC system the characteristics of vehicle-ground communications, made a analysis and gave the functional requirements the time-triggered protocol in order to achieve.
Secondly, this paper has a research on the mechanism of LTT in-depth. From a detailed study of the LTT mechanism's principle, this paper focuses on vehicle-ground communications by Vehicle On Board Controller (VOBC) and Zone Controller (ZC) and designs the CBTC system time-triggered layer protocol, gives the realization of the process of time-triggered layer protocol. In accordance with the characteristics of communication between VOBC and ZC and using the master-slave architecture, it designed the scheduling table with which the time window can be dynamically assigned to. On this basis, the paper researched and analyzed of the performance of time-triggered protocol further from the perspective of qualitative.
Then, this paper established Hierarchical timed colored Petri net (HTCPN) model for the vehicle-ground link communication, time-triggered layer protocol, as well as the wireless channel from top to bottom. In order to record the delay time for system performance analysis, we insert in the message a time stamp using the timed characteristic of modeling tools.
Finally, we use the time-triggered layer protocol model to establish vehicle-ground communications with multi-vehicle model. The thesis, respectively, does a simulation about the multi-vehicle communication model with the time-triggered layer protocol model or not. The simulation results show that when the trains involved in the communication are increasing, compared to ET mechanism, LTT mechanism could make a more established system of communication and improve the system's communications real-time property.
CBTC的数据通信系统(Data Communicate System,DCS)不仅包含有线局域网通信,而且包含车地之间的无线局域网(Wireless LAN,WLAN)通信。列车在WLAN中经常发生的越区切换等问题会增加信息的延迟时间。在通信量增加的情况下,基于以太网的事件触发机制的DCS会带来通信的不确定性。相比之下,时间触发(Time-triggered,TT)机制能够增加系统通信的确定性,提高系统的实时性。松散时间触发(Loosely time-triggered,LTT)机制是TT的一种弱化形式,适用于带有WLAN的实时分布式控制系统。本文主要针对CBTC系统通信的不确定性问题,设计了一个时间触发层协议,并对其进行了验证。
首先,根据标准的TCP/IP四层协议模型,论文确立了时间触发层协议在标准的TCP/IP四层协议模型中的位置。同时,结合CBTC系统的车地通信的特点,分析并给出了时间触发层协议所要实现的功能需求。
其次,论文对LTT机制进行了深入的研究。从研究LTT机制的原理出发,以车地通信中车载控制器(Vehicle On Board Controller,VOBC)与区域控制中心(Zone Controller,ZC)之间的通信为研究对象,设计了CBTC系统的时间触发层协议,给出了时间触发层协议的实现流程。根据VOBC与ZC之间通信的特点,选用了主从式的架构,设计了可以进行时间窗动态分配的调度表。在此基础上,论文进一步从定性的角度分析了时间触发层协议的性能。
然后,论文按照从上至下的分层思想建立了车地通信、时间触发层协议以及无线信道的赋时层次有色Petri网(Hierarchical Timed Colored Petri Net,HTCPN)模型。为了记录消息的延迟时间,方便于系统性能的分析,利用建模工具的赋时特性,在消息中加入了时间戳。
最后,论文利用时间触发层协议建立了车地通信的多车模型。分别对ET机制和LTT机制下的车地通信模型进行了仿真。仿真结果表明,在通信列车数量增加的情况下,相比ET机制,LTT机制能够增加系统通信的确定性,提高系统通信的实时性。
Communication-based train control system (CBTC) in China's urban rail transit development process, is occupying an increasingly important position. There are many issues to be overcome and to improve CBTC system for the study area.
Data communications system of CBTC (Data Communicate System, DCS) includes not only wired LAN communications, and includes the vehicle-ground communications with the wireless LAN communication. Trains in the wireless local area network are often making a handover and confront with sudden drop of channel quality issues, which will increase the delay time. In addition, DCS is structured on the products of commercial off-the-shelf, the traditional event-triggered mechanism Ethernet when traffic communication increased will bring uncertainty. In contrast, time-triggered (Time-triggered, TT) mechanism can bring about more certain communication and improve the systems real-time property. Loosely time-triggered (Loosely time-triggered, LTT) mechanism is a weakened form of TT, suited for wireless local area network with real-time distributed control system. For safety-related control systems, to the extent possible, to reduce the uncertainty brought about by the impact of the communication. In this paper, how to solve the CBTC system for the uncertainty of communication problems, primarily the following research work:
First of all, the paper made reference to seven OSI protocol model and the standard TCP / IP protocol four-level model, analysis and the established the location of the time-triggered protocol to study in standard TCP / IP protocol model in this paper. At the same time, this paper combined with the CBTC system the characteristics of vehicle-ground communications, made a analysis and gave the functional requirements the time-triggered protocol in order to achieve.
Secondly, this paper has a research on the mechanism of LTT in-depth. From a detailed study of the LTT mechanism's principle, this paper focuses on vehicle-ground communications by Vehicle On Board Controller (VOBC) and Zone Controller (ZC) and designs the CBTC system time-triggered layer protocol, gives the realization of the process of time-triggered layer protocol. In accordance with the characteristics of communication between VOBC and ZC and using the master-slave architecture, it designed the scheduling table with which the time window can be dynamically assigned to. On this basis, the paper researched and analyzed of the performance of time-triggered protocol further from the perspective of qualitative.
Then, this paper established Hierarchical timed colored Petri net (HTCPN) model for the vehicle-ground link communication, time-triggered layer protocol, as well as the wireless channel from top to bottom. In order to record the delay time for system performance analysis, we insert in the message a time stamp using the timed characteristic of modeling tools.
Finally, we use the time-triggered layer protocol model to establish vehicle-ground communications with multi-vehicle model. The thesis, respectively, does a simulation about the multi-vehicle communication model with the time-triggered layer protocol model or not. The simulation results show that when the trains involved in the communication are increasing, compared to ET mechanism, LTT mechanism could make a more established system of communication and improve the system's communications real-time property.
引文
[1]郜春海.基于通信的轨道交通列车运行控制系统[J].现代城市轨道交通.2007,2:7-10
[2]IEEE Std 1474.1-1999.Institute of Electrical and Electronics Engineers,Inc.,“IEEE Standard for Communications-Based Train Control(CBTC) Performance and Functional Requirements”.New York.1999.5-8
[3]舒安洁,李开成.CBTC系统信息安全传输的研究[J].微计算机信息.2006.22(3).44-46
[4]杨仕平,桑楠,熊光泽.基于Ethernet技术的安全关键实时网络[J].软件学报.2005,第16卷,第1期.
[5]A.Benveniste,P.Caspi,P.L.Guernic,H.Marchand,J.-P.Talpin,and S.Tripakis.A protocol for loosely time-triggered architectures.In EMSOFT,pages 252-265,2002.
[6]A.Benveniste,P.Caspi,M.DiNatale,C.Pinello,A.Sangiovanni.LooselyTime-Triggered Architectures based on Communication-by-Sampling.Systemes communicants.Projet S4.
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[11]范昊,吴哲辉,曾庆田.一种兼顾协议正确性验证和性能评估的Petri网方法.计算机科学.2005.32(12).48-52
[12]王晶,樊晓桠.一种基于Petri网通信协议的分析和验证.计算机应用.2005.25(1).165-167
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[15]吴东勇,张勇.用有色Petri网建立基于通信的列车控制系统的层次模型[J].交通运输系统工程与信息,2005.17(10):2388-2391.
[16]徐田华,唐涛.基于有色Petri网的ETCS通信系统与列车间隔分析[J].系统仿真学报.2007,第19卷,第21期。
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[20]David Bradbury,Simulation of a Time Triggered Protocol[D].University of Sydney,Australia.
[21]Stavros Tripakis,Claudio Pinello,Albert Benveniste.Implementing Synchronous Models on Loosely Time Triggered Architectures.IEEE Computer Society.2008.
[22]Chiheb Kossentini and Paul Caspi.Approximation,Sampling and Voting in Hybrid Computing Systems.Verimag Research Report.2006.1.
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[27]Jan Romberg and Andreas Beuer.Loose Synchronization of Event-Triggered Networks for Distribution of Synchronous Programs.EMSOFT'04,Semptember 27-29,2004,Pisa,Italy.
[28]Coloured Petri Nets.http://www.daimi.au.dk/CPnets
[29]HOLZMANNG.Design And Validation of Computer Protocols.Pearson Education POD Facsimile edition.1990.45-53
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[2]IEEE Std 1474.1-1999.Institute of Electrical and Electronics Engineers,Inc.,“IEEE Standard for Communications-Based Train Control(CBTC) Performance and Functional Requirements”.New York.1999.5-8
[3]舒安洁,李开成.CBTC系统信息安全传输的研究[J].微计算机信息.2006.22(3).44-46
[4]杨仕平,桑楠,熊光泽.基于Ethernet技术的安全关键实时网络[J].软件学报.2005,第16卷,第1期.
[5]A.Benveniste,P.Caspi,P.L.Guernic,H.Marchand,J.-P.Talpin,and S.Tripakis.A protocol for loosely time-triggered architectures.In EMSOFT,pages 252-265,2002.
[6]A.Benveniste,P.Caspi,M.DiNatale,C.Pinello,A.Sangiovanni.LooselyTime-Triggered Architectures based on Communication-by-Sampling.Systemes communicants.Projet S4.
[7]杨霓霏,段武.铁路信号系统安全相关通信标准与安全协议研究[J].中国铁路.2008,6.
[8]K.Jensen,“A brief introduction to Colored Petri Nets”.Workshop on the Applicability of Formal Models,2 June 1998,Aarhus,Denmark.
[9]闫石,唐涛.基于有色Petri网的ETCS2级形式化建模[D].北京,北京交通大学,2006:31
[10]李斌,辛海红,胡铭曾.一种高效的用户级通信协议的研究与实现[J].计算机工程.2006.32(1).148-50.
[11]范昊,吴哲辉,曾庆田.一种兼顾协议正确性验证和性能评估的Petri网方法.计算机科学.2005.32(12).48-52
[12]王晶,樊晓桠.一种基于Petri网通信协议的分析和验证.计算机应用.2005.25(1).165-167
[13]CPN帮助文件.
[14]曹大海,王建民.基于着色Petri网的图形化工作建模工具的设计与实现[D].北京:清华大学,2005.13-16.
[15]吴东勇,张勇.用有色Petri网建立基于通信的列车控制系统的层次模型[J].交通运输系统工程与信息,2005.17(10):2388-2391.
[16]徐田华,唐涛.基于有色Petri网的ETCS通信系统与列车间隔分析[J].系统仿真学报.2007,第19卷,第21期。
[17]Armin Z,G(u|¨)nter H.A train control system case study in model-based real time system design [C]// International parallel and distributed processing symposium(IPDPS).France:IEEE,2003:118-126.
[18]Buchholz P,Kemper P.Hierarchical Reachability Graph Generation for Petri Nets[J].Formal Methods in System Design,2002,21(3):281-315.
[19]Hermann Kopetz,Astrit Ademaj.The Time-Triggered Ethernet(TTE) Design.Vienna University of Technology,Real-Time Systems Group.Treitlstr.3/182-1,A- 1040 Vienna,Austria.
[20]David Bradbury,Simulation of a Time Triggered Protocol[D].University of Sydney,Australia.
[21]Stavros Tripakis,Claudio Pinello,Albert Benveniste.Implementing Synchronous Models on Loosely Time Triggered Architectures.IEEE Computer Society.2008.
[22]Chiheb Kossentini and Paul Caspi.Approximation,Sampling and Voting in Hybrid Computing Systems.Verimag Research Report.2006.1.
[23]Albert Benveniste,Nenoit Caillaud,Paul Caspi.Communication by Sampling in Time-Sensitive Distributed Systems.EMSOFT'06,October 22-25,2006,Seoul,Korea.
[24]Klaus Steinhammer,Petr Grillinger.A Time-Triggered Ethernet(TTE) Switch.Vienna University of Technology,Real-Time Systems Group.Treitlstr.3/182-1,A-1040 Vienna,Austria.
[25]Astrit Ademaj and Hermann Kopetz.Time-Triggered Ethernet and IEEE 1588 Clock Synchronization.Vienna University of Technology,Real-Time Systems Group.Vienna,Austria.
[26]Petr Grillinger,Astrit Ademaj,Klaus Steinhammer,Hermann Kopetz.Software Implementation of a Time-Triggered Ethernet Controller.Vienna University of Technology,Real-Time Systems Group.Treitlstr.3/182-1,A-1040 Vienna,Austria.
[27]Jan Romberg and Andreas Beuer.Loose Synchronization of Event-Triggered Networks for Distribution of Synchronous Programs.EMSOFT'04,Semptember 27-29,2004,Pisa,Italy.
[28]Coloured Petri Nets.http://www.daimi.au.dk/CPnets
[29]HOLZMANNG.Design And Validation of Computer Protocols.Pearson Education POD Facsimile edition.1990.45-53
[30]Yuan Cao,Ru Niu,TianHua Xu,Tao Tang.Wireless Test Platform of Communication Based Train Control(CBTC) System in Urban Mass Transit.IEEE download.
[31]陈锋华,刘伶,陈松.基于通信的列车控制(CBTC)系统[J].铁路通信信号工程.2005,01
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