Research And Implementation Of Distributed MCPTT System

MCPTT(Mission Critical Push to Talk)standard is a new generation broadband trunking communication standard based on LTE proposed by 3GPP.MCPTT system is a professional command and control system based on MCPTT standard,which has the function of register,group affiliation,private call and group call,and is mainly used in government,public security,and other departments.At present,many communication companies and research institutions at home and abroad has realized the centralized MCPTT system,but its user capacity and reliability is unable to meet the need of users.Distributed system architecture can improve the user capacity and reliability of a system,therefore,the research and implementation of distributed MCPTT system is of great significance.Based on an overview of the research status of broadband digital trunking system and distributed system at home and abroad,the distributed MCPTT system is researched and implemented.The main contributions are listed as follows:1.Based on the composition and functions of MCPTT system,performances such as the user capacity and fault tolerance are analysed,and the mechanism of service registration and discovery,load balancing,service routing in distributed system and the technology of Zookeeper distributed coordination component,Redis server cluster,My SQL server cluster is researched.2.A distributed MCPTT system architecture is proposed,system components are horizontally expanded,which can improve the user capacity and reliability of the system.The service registration and discovery mechanism and service routing mechanism in the process of calling is designed,which can cooridinate the communication of different system components with the help of Zookeeper coordinate component and Redis database.3.A load balancing program for the participating MCPTT server based on the least connection algorithm and a load balancing program for the controlling MCPTT server based on the round-robin algorithm are designed,and a load balancing algorithm for media server is proposed,which calculate the real-time load of the media server by linear regression prediction model and assign the task to the media server with the lowest real-time load,and can improve the user capability of the system.An automatic fault discovery mechanism and an availability check mechanism are designed,which can improve the reliability of the system.4.Based on Linux operating system,the identity management server,the participating MCPTT server,the controlling MCPTT server and the media server's software are developed by using C and C++ programming languages.The functions such as register,group affiliation,private call and group call are implemented.In addition,the load balancing,the automatic fault discovery and the availability check of the system are guaranteed,which improved the user capacity and reliability of the system.5.A test environment for the distributed MCPTT system is built to test the functions such as register,group affiliation,private call and group call,and the performances such as the user capacity and the fault tolerance.The test results show that the developed distributed MCPTT system can meet the design requirements.