The Design And Implementation Of Digital Transmission System For Semi-Automatic Block Control Information

There are large amounts of semi-automatic block sections under jurisdiction of HarbinRailway Bureau. And most of the outside interval line used overhead line, so many problemsrose in overtime service, high failure rate, maintenance difficultly, and affect traffic safety etc.Based on the comprehensive analysis and comparison of block information transmissiontechnique between the railway stations at home and abroad, the paper proposes the opticalcommunication technology substitution of the original overhead line, and research ontransmission equipments for transmitting control information between stations.The principle of the safe information transmission between stations is very simple. Thelocal information condition which is collected by the transmission equipment of thesource-station, Through optical channel transmission to the aim-station, and then theaim-station deals with the information and outputs the condition of correlate information.Secure information transfer between stations fall within the scope of functional safety,Information collection and driving is easily implemented, and guarantee the consistencyinformation that is passed is even more important. Therefore, this paper focus on the softwareand hardware of the transmission equipment reliability issues on the research and designwork.In terms of hardware design, in terms of hardware design, in order to ensure thatinformation transmission, processing and response time (including executive communicationinterface protocol), the development platforms were compared in this paper.And a SOC,which could run independently, C8051F060was chosen as a development platform. Comparing with the traditional8051MCU, there are some comprehensive promotion in theperformance, such as rich on-chip resources, flexible configuration and processing ability ofhigh speed instruction, which provide a strong guarantee for improving the transmissionspeed of the control information. In addition, some necessary techniques were taken forreliability, availability, maintainability and security of the system. In terms of reliability, thecomponents at or above the industrial grade were chosen, the data acquirement circuit, drivecircuit and communication circuit adopt the mature circuit which has been used for manyyears; In terms of availability, hot-standby redundancy structure was adopted. the host and thestandby parallel output, common drive relays, duplex channel was used between stations. Interms of maintainability, the transmission device which combined a set of boards supports hotplug-in, self-diagnostic and maintenance; In terms of security, dual-CPU hardware structurewas desgined. The dynamic pulse was used as the source of acquiring and output. The2oo2(two out of two) code was used in the output logic, Driving execution units adopted the"safety and" circuit.In terms of software design, because the information transmission channels betweendevices is special fibre channel or2M channel, which belongs to the safety communicationfield of the closed transmission system.Therefore, this paper used the security defensetechnology, such as the time stamp technology, timeout check, source identifier SIDrecognition technology, the feedback of information when receive an error message, a32-bitCRC cyclic redundancy check code and32-bit detection system of double checkingmeasures.Which effectively overcome six risks of security threats,such as data framesrepetition,data frame deletion, data frame insertion, data frame corruption, data frame errorand data frame delay when data is received,all of those ensured the functional security ofcontrol information. The safety protocol, accordance with "railway signal safetycommunication protocol-I (RSSP-I)" of the railway signal safety communication protocolspecification [2010]267, was introduced in the data communication layer, and which gave theinter-communication ability to the equipment.