Design And Implementation Of Train-ground Wireless Communication Monitoring System For Communication Based Train Control (CBTC) System

CBTC(Communication Based Train Control)system uses the way of train-ground wireless communication to complete the two-way real-time information exchange between the train and the wayside control equipment.At present,the WLAN technology based on 802.11 protocols is mainly used in the train-ground wireless communication of CBTC.The train-ground wireless communication generally adopts the public free 2.4GHz band,which will undoubtedly increase the security risk of the system communication.In recent years,there have been a number of cases that the civilian communication equipment interferes with the normal operation of train.According to the comprehensive survey of relative studies,there are few studies on the train-ground wireless communication monitoring.However,it is urgent to monitor the wireless communication of CBTC.Main contributions of this paper are as follow:(1)Researching the centroid localization algorithm and the loss model of wireless signal propagation and proposing an improved algorithm based on RSSI.It is also verified that the proposed algorithm can significantly reduce the positioning error in the aspects of the number of beacons,the number of unknown nodes and the communication radius.(2)The principle and security of CBTC train-ground wireless communication is studied;analyzing the design requirements;putting forward the overall framework of train-ground wireless communication monitoring system for CBTC;designing and implementing the functional modules of the monitoring system.(3)We also have tested the performance of the system and verified the correctness of each module.The monitoring system can effectively capture the network packets;can effectively analyze the data packets,as well as get the source of IP address,destination IP address,protocol type and other information;can effectively monitor the devices connected to the network,and get the information of SSID,MAC address,signal strength and other information;the improved positioning algorithm is realized by the positioning module,and the localization function of the illegal device is realized successfully.The train-ground wireless communication monitoring system for CBTC has realized the monitoring function,and it also has realized the localization function of the illegal device which connected to the train-ground wireless network.The system operation is simple,which has a certain value in engineering applications.