Design And Implementation Of LTE-M Interface And Network Performance Monitoring System

With the rapid development of urban rail transit,LTE-M,which based on the fourthgeneration mobile communication technology,is gradually replacing WLAN and becoming the first choice of CBTC train-wayside wireless communication system technology in China.LTE-M system,which transmits the safety related services and other services of the train control system,is an important part of the CBTC system.During the construction and operation of the LTE-M system,it is of great significance to monitor its working status and regularly evaluate the performance of the communication network for the smooth opening and safe operation of urban rail transit.Referring to the specific requirements of the LTE-M series standards of China Urban Rail Transit Association for LTE-M system performance,the LTE-M interface and network performance monitoring system is designed and implemented in this thesis.The system can monitor the CBTC data and LTE-M signaling of the LTE-M system,and evaluate the performance of the LTE-M communication network through the monitoring data.The main contents and contributions of this thesis include:(1)The network architecture,network element functions,interface functions and integrated services of the LTE-M system are introduced in detail.The purpose and necessity of interface monitoring and the reason for choosing SGi and S1 as the monitoring interface are analyzed as well.(2)In this thesis,the characteristics of LTE-M system as well as system requirements of real-time monitoring,fault analysis and communication network performance evaluation of LTE-M system during maintenance and operation are simultaneously considered to describe design requirements of the interface monitoring system.According to the modular design concept,the complex interface monitoring system is decomposed into data acquisition module,real-time monitoring module,offline analysis module,network evaluation module and support module.The following functions of the LTE-M interface and network performance monitoring system are realized:1)The functions of data collection,filtering and storage are realized by efficiently collecting and analyzing the data of SGi interface and S1 interface.2)The real-time monitoring of CBTC business is realized by counting the transmission interval of adjacent data packets,while the function of CBTC offline analysis is realized by the time stamp and data content of the same data stored at both the ground and the vehicle.3)The fault locating of the LTE-M system is realized by acquiring the physical cell identifier of the metro from the TAU and establishing a mapping between the location of metro and time.4)The function of signaling analysis and multi signaling synthesis of the same terminal are realized by analyzing the characteristics of the same communication signaling process.5)The function of one-to-many association between data and signaling is realized by establishing the association between CBTC information and signaling through TEID and combining with the multi-signaling synthesis function of the same terminal.6)The function of effectiveness evaluation of LTE-M system communication network is realized by fuzzy comprehensive evaluation method.(3)The functions and reliability of the system are validated in the laboratory and Daxing International Airport Line.The test results indicate that all modules of the interface monitoring system work right and stablly and the design goal of the system is achieved.At present,this system has been actually applied to the Daxing International Airport Line,which has played an important role in the smooth opening and safe operation of the line.