Design And Development Of Interface Monitoring System For Broadband Trunking Interconnection

The wireless trunking communication system is an important part of urban rail transit communication system.It provides means of communication between fixed users such as control center dispatchers,depot dispatchers,station staff,and mobile users such as train drivers,disaster prevention personnel,maintainer and public security officers.Now the narrowband digital trunking system commonly used in the urban rail transit industry can not meet the needs of the development of the industry,and the system is evolving to Broadband Trunking Communication(B-TrunC)system based on LTE-M.Due to the important responsibilities of the broadband trunking system for train dispatching and train operation safety,and the serious consequences that broadband trunking communication failure may cause,the monitoring and assessment for broadband trunking network status and communication process is of great significance.At present,the broadband trunking specification of the urban rail transit industry has just been formulated,and there is no corresponding monitoring devices to complete the relevant work yet.Therefore,an urban rail transit broadband trunking interface monitoring system based on LTE-M designed in this thesis,and a mapping scheme from the user plane to the control plane is designed to achieve fault diagnosis of the LTE-M communication network.The main research contents and achievements of this thesis include:(1)The network architecture,network element function and signaling format of broadband trunking system in urban rail transit based on LTE-M and B-TrunC are introduced in the thesis.The new requirements of urban rail transit industry development for trunking system are analyzed as well.(2)Through the research on relevant protocols and the analysis of massive LTE-M packets,the implementation scheme of fault diagnosis is proposed,and combined with the application requirements of broadband trunking in urban rail transit,the function demands of the interface monitoring system are proposed,and the architecture of the whole system is designed accordingly,and the development of functional modules is completed.The messages from the interface DA,DU D2,and S1-T are decoded.(3)Through detailed analysis and elaborate design of the user plane data and control plane signaling,the correlations between terminal identities and their encryption keys are established,the one-to-one and one-to-many mappings of the user plane data with control plane signaling are performed through Internet Protocol(IP)address,Tunnel Endpoint Identifier(TEID)and other identifiers.Each user data can find corresponding LTE-M and broadband trunking signaling,and according to the security encryption mechanism ofLTE-M system,the NAS decryption and decoding in the case of multiple terminals can be realized,which helps to quickly and accurately locate communication signaling failure.(4)The test software is designed and developed to test decoding functions for messages from interface DA,DU,D2 and S1-T in the laboratory environment.The test environment is built using the LTE-M communication equipment to test the functions of the user plane and control plane association module and the NAS decryption module.The test results show that the system is functional and stable,and the design goal of signaling monitoring and fault diagnosis is realized.