Research And Implementation Of Data Service In MCPTT Terminal

MCPTT(Mission Critical Push To Talk)is a new generation broadband digital trunking protocol proposed by the 3GPP(3rd Generation Partnership Project)standards organization in 2016.It is an application layer service running on LTE(Long Term Evolution)network.The data service of MCPTT system is the core service of broadband trunking communication system,which mainly includes services such as login,affiliate,short message,long message,short message in offline mode,picture,file and large multimedia data.At present,MCPTT system is in the early stages,so there are few completed solutions for the data service of the MCPTT system at home and abroad.Therefore,the research and implementation of MCPTT terminal data service is of great significance.Based on an overview of the current status of data service research on digital trunking systems at home and abroad,the data service functions of MCPTT terminal is researched and implemented.The main contributions are listed as follows:1.Based on the composition of MCPTT system,the functions of the MCPTT terminal data service are described,and the performance of the MCPTT terminal data service is analyzed;2.The interface between the MCPTT data terminal and the SIP application server,the interface between the MCPTT data terminal and the HTTP server,and the interface between the MCPTT data terminal and the MSRP server are defined.A terminal software architecture that separates interface,function,and data is proposed,which improves the flexibility and scalability of the MCPTT data terminal software,and the signaling process of MCPTT terminal data service is designed.3.Based on the MCPTT terminal data breakpoint retransmission mechanism,a solution for large-scale multimedia data fragment transmission is proposed,based on the parameters such as data size and channel quality,on the basis of ensuring the success rate of data transmission,parallel adaptive file breakpoints retransmission algorithm is proposed to select appropriate data fragmentation and retransmission times to reduce data transmission time.Based on the terminal device discovery technology,a layered architecture design solution for device discovery is proposed to make the device discovery module of MCPTT data terminal portable and adaptable to various network environments.4.Based on the Android operating system,the development environment for MCPTT terminal data service functions is deployed.Using the Java programming language,various sub-modules such as data service processing module,signaling encapsulation and parsing module,signaling receiving and sending module,HTTPS module,and device discovery module are developed,and the services of MCPTT terminal such as login,affiliate,short message,long message,short message in offline mode,picture,file and large multimedia data are realized;5.A test system for data service function of MCPTT system is built to test the functions such as login,affiliation,short message,long message,off-line mode short message,picture,file and large multimedia data service.The performance such as session establishment delay,data transmission success rate and terminal mobile phone power consumption are tested.The test results show that the developed MCPTT terminal data service can meet the design requirements.