Research On CTCS-3 Board-Ground Communication Protocol Conformance Testing Based On TTCN-3

CTCS level 3 is one of the important components of Chinese Train Control System (CTCS),which uses wireless communication systems(GSM-R) to achieve a two-way continuous information transmission between the train and the ground.It is a train control system based on wireless communication.In this system,board-ground communication protocol is not only the guarantee of reliable data communication between the train and ground,but also the foundation of the whole system's safety.In reference to Euroradio safety protocol which is defined in ERTMS standards, CTCS-3 board-ground communication protocol is designed with domestic reality.To make sure that the train and the ground devives can communicate with each other correctly,we must perform test on the protocol.The protocol testing is an important branch of protocol engineering,and it is a prerequisite for the normal work of the protocol realization.Protocol conformance testing is the foundation of various types of testing work.Thus the conformance testing of board-ground communication protocol of CTCS level 3 is very important.In this paper,with board-ground communication protocol of CTCS level 3 standards and specifications,a conformance testing method is in-depth studied.For conformance testing,its process is divided into three phases:test generation,test implementation and test execution.Test generation is the generation of test sequences.In this phase,we analyse the communication protocol,establish FSM(Finite State Machine) model and then generate test sequences.Test implementation is based on TTCN-3(the Testing and Test Control Notation version 3),and use TTworkbench to build test system.Finally we run through the test system and give an analysis of test results.This paper firstly introduces the related theory and technology in detail,including protocol conformance testing theory,test sequence generation based on FSM,the development,characteristics,advantages,application direction of standardized test language TTCN-3 and test software TTworkbench support for TTCN-3 language. Secondly,CTCS-3 board-ground communication protocol model was established using formal modeling method based on FSM according to the characteristic of CBTC communication protocol.Thirdly,conformance test sequences of CTCS-3 board-ground communication protocol are genetated based in FSM and a mature UIO(Unique Input Output) algorithm.Then common comformance abstract test methods are analysis in detail and the whole test system is designed including test system configuration,the internal structure of the design,test case description,the design and implementation of codecs and protocol adapter.At last a comformance test on CTCS-3 board-ground communication protocol is performed using the built test system,and a test verdict and a analysis of test result is given.