Research And Implementation Of Switching Function In MCPTT System

MCPTT(Mission Critical Push to Talk)protocol is a new generation broadband trunking communication protocol based on LTE proposed by 3GPP in 2016.MCPTT system is a professional command and dispatch system based on MCPTT protocol,which is mainly used in government communication,public security,transportation communication,military communication and other departments.The switching function of MCPTT system is the core function of broadband trunking communication system,which mainly includes functions such as login,affiliate,single call,group call,priority call,alert,pre-established session and geographical report.At present,MCPTT system is in the early stages,so there are few completed solutions of MCPTT system at home and abroad.Therefore,the research and implementation of MCPTT system switching function is of great significance.Based on an overview of the research status of digital trunking system switching functions at home and abroad,the switching function of MCPTT system is researched and implemented.The main contributions are listed as follows:1.Based on the composition of MCPTT system,the switching function of MCPTT system is analyzed and the factors affecting the usability of switching function in MCPTT system under high concurrency are given.2.A centralized and quasi distributed MCPTT system architecture is proposed.The software architecture of MCPTT participating server and controling server are designed.Besides,the signaling flows of MCPTT system switching function are designed.The interfaces between MCPTT participating server and media forwarding server,MCPTT controling server and MCPTT controling server,MCPTT participating server and MCPTT terminals are defined.3.A mechanism for database read and write based on mysql and redis is designed.And a hot switch mechanism based on zookeeper which improves the availability of switching function is proposed.MCPTT controling server registers a node in zookeeper which can be monitored by participating server.When an event occurs on the node,the MCPTT participating server can switch to the backup MCPTT controling server.4.Based on linux operating system,the system network elements such as MCPTT participating server,MCPTT controling server and media forwarding server are developed by using C and C++programming languages.The functions of MCPTT system such as login,affiliate,single call,group call,priority call,alert,pre-establish session,geographical location report,single call and group call based on quasi distributed MCPTT system are implemented.5.A test system for switching function of MCPTT system is built to test the functions such as login,affiliation,single call,group call,priority call,alert,pre-established session,geographical location report based on centralized architecture and cross-system call functions based on quasi distributed architecture.The test results show that the developed MCPTT system switching function can meet the design requirements.