The Analysis And Verification Of Safety Function Module In CTCS-3Wireless Interface

To meet demands of passenger dedicated line and the high-speed railway construction, the development of high-speed railway is flourishing, Chinese Train Control System Level3(CTCS-3) arises at this historic moment. At the same time, in order to ensure the safety operation of train, safety communications has become particularly important.According to EN50159, CTCS-3which is based on the GSM for Railway (GSM-R) radio communication mechanism belongs to category3transfer system, and protection level requirements of this kind of system for repetition, deletion, insertion, re-sequencing, corruption, delay and masquerade are strong protection degree. However Euroradio SFM does not supply any protective measures for repetition, deletion, re-sequencing and delay. Thus it is learned that:risk vulnerabilities exist in Euroradio. For analyzing the risk protection capability of Euroradio SFM, this paper shows a detailed discussion.Firstly, from the perspective of analyzing the probability of data loss in data transmission of CTCS-3, the paper uses TimeNet4.0to establish simple data communication model, channel fault recovery model, the end-to-end data transmission delay model which are based on Deterministic and Stochastic Petri Net (DSPN). Under three different combinations of network coverages and the number of receiving terminals, the paper makes a combination simulation for these models to simulate and achieves the following conclusions:under any conditions of different network coverages and the number of receiving terminals, CTCS-3can meets data frame transfer delay indicators of QoS, at the same time, thus the correctness of modeling approach and thoughts can be verified.Secondly, the paper establishes data transmission expansion model of CTCS-3, and under different combinations of network coverage and the number of receiving terminals simulates this model and the fault recovery model, and finds that:under the extreme condition of only data loss causing dangerous output of train control system, the simulation results can not meet data transmission security requirements in SIL4of the relevant specifications for CTCS-3. In order to ensure that the CTCS-3meets the safety requirements, appropriate protective measures for time-dependent transmission risks must be added to SFM. Finally, studying from serial number, time stamp and EC of RSSP-II SFM, and combing with communication mechanism characteristics of CTCS-3, the paper analyzes applicability of these protective measures in CTCS-3, and makes a conclusion that serial number and time stamp is fully applicable, while EC protection mechanism is conflict with retransmission mechanism of CTCS-3so that EC is not applicable. Designing clock offset update process for CTCS-3with the method of double timestamp, and then paper adds the design results and serial number to Euroradio SFM to provide strong protection measures for time-related risks. As a result, a communication protocol which meets requirements of category3transmission system in EN50159is realized.The research results of the paper provide research foundation for consummate safety communication protocols of Euroradio, provide a theoretical basis for the other existing research results in the field of safety communication protocols, and make up a shortcoming of safety communication protocol changing with no reasons in those articles.