Real-time Performance Study Of Communication System For Train Control System Under Moving Block Conditions

Moving Automatic System is the most advanced occlusion system in rail transportation field,which can effectively shorten the train tracking interval time and reduce the comprehensive maintenance cost of signal system equipment,and has been widely used in urban rail transportation.The Moving Automatic System relies on the wireless communication subsystem of the train control system for real-time,large-capacity bi-directional information transmission between the train and the ground,so the change pattern of the real-time performance of the communication system for train control system will directly affect the transmission delay of the train control service data,and then affect the train tracking efficiency.In this paper,we use Hierarchical Timed Colored Petri Net(HTCPN)to establish a train tracking operation model based on communication,and conduct dynamic simulation on the transmission process of train control data between on-board equipment and ground equipment and train tracking operation scenarios.Based on the simulation results,we analyze the change of real-time performance of the communication system for train control System and the train tracking characteristics under the mobile occlusion condition.The research content of this paper is divided into two parts.The first part is to establish train control communication system models based on railway digital mobile communication system(GSM-R)and railway broadband mobile communication system(LTE-R)respectively according to the composition of train control communication system and train control data transmission process.The mobile terminal model,base station model and wireless block center model describe the train ground communication process,The train control data is detected and retransmitted according to the error retransmission mechanism,which ensures the reliability of train control data transmission and the authenticity of simulation.The wireless channel model comprehensively considers the factors such as shadow fading,path loss,small-scale fading,link interruption and handoff,and can truly simulate the transmission environment of train control data in the air interface.The wireless channel model is simulated with CPN Tools to study the variation laws of radio wave loss characteristics,signal-to-noise ratio,channel capacity,bit error rate,base station boundary rate,coverage field strength and minimum reception level.Then,the real-time performance of the train control communication system is analyzed,and the effects of train position,fading channel,handoff,train control data length and error retransmission mechanism on the end-to-end transmission delay of GSM-R and LTE-R train control data are studied.The distribution law of train control data transmission delay during train operation is analyzed,and the real-time performance of GSM-R and LTE-R is compared.It is found that LTE-R has better real-time performance,At the same time,it is more vulnerable to the influence of channel quality.The second part puts forward the formal description of the train tracking model according to the principle of moving block train tracking operation,and establishes the on-board control model combined with the line conditions and train braking performance.The train tracking operation scene is simulated,and the tracking operation characteristics under the control of GSM-R and LTE-R systems are studied by comparative method.The simulation results show that the asynchronous and concurrent mechanism of HTCPN is suitable for the modeling and Simulation of multi train tracking operation under real-time communication,and verify that LTE-R train control mode can adjust the train operation state more efficiently and flexibly.At the same time,it shows that improving the real-time performance of communication system for train control system can improve the efficiency of train tracking,and the research results can provide reference for the design and application of the next generation train control system.