Description And Implementation Of SDL-Based Communication Protocol For Onboard-Trackside Equipment In CTCS-3

China Train Control System level3is based on GSM-R, offering the safely reliable data transmission channel between the on-board and trackside equipment to achieve the two-way communication between each other. In order to ensure the security and reliability of data transmission, the correctness and reasonableness of CTCS-3communication protocols which is used to against a variety of security risks between on-board and trackside equipment is particularly important.In the paper, according to security-related data transmission requirements, the protocol system architecture and the safely transfer standard of communication protocol for onboard-trackside equipment in CTCS-3system were described in detail. Then formal description language SDL and its support tool Telelogic TAU were chosen to describe communication protocol for onboard-trackside in CTCS-3system, and established its SDL model. Based on the model, the message sequence diagram and error reporting were generated by the co-simulation and verification, which can verify the accuracy of SDL model. Finally, SDL model were converted into C code automatically, the application program of CTCS-3communication protocol can be obtained to running on CTCS-3certification testing and evaluation platform successfully.The standard description language SDL was introduced in the paper. Based on the idea of protocol engineering, the communication protocol for onboard-trackside equipment in CTCS-3system were describe using formal description techniques, which not only eliminate language ambiguity in protocol description, but also reduce development errors, shorten development cycles in the process of realizing communication protocol software..