Research And Implementation Of Multi-mode Media Gateway In Digital Trunking Communication System

Digital trunking system is a professional wireless communication system,which has the characteristics of short call setup time,group call support and high channel utilization.It is widely used in public safety and transportation fields.In digital trunking system,the media gateway is used for the call service processing,including voice data forwarding and communication channel allocation.Multi-mode media gateway supports multi-mode voice data forwarding,voice codec conversion and multi-mode call channel assignment function.It not only supports the voice call service of narrowband digital trunking,but also supports the application of trunking system in the broadband network scenario.Therefore,the development of multi-mode media gateway is of great significance to the research of broadband digital trunking.Based on the review of the research in domestic and foreign digital trunking communication system media gateways,the multi-mode media gateway is studied and implemented.The main works of this paper are listed as follows:1.The architecture of digital trunking communication system is analyzed.The call service processing,channel assignment,data forwarding and encoding format conversion of multi-mode media gateway are described in details.The signaling processing of multi-mode media gateway is designed.Data forwarding method,which is based on UDP punching technology,is proposed to solve the voice distribution issues in complex network scenario;2.The architecture of multi-mode media gateway is proposed.The interface and signaling of related sub-modules of multi-mode media gateway are defined.The working processes of control sub-module,service sub-module and NAT traversal sub-module of multi-mode media gateway are designed.The conversion method is illustrated for voice codec in media gateway;3.Based on the Linux operation system,the main program,control sub-module,service sub-module and NAT traversal sub-module of multi-mode media gateway are developed by using C language.Single call,group call and voice encode format conversion are realized;4.Duplex single-mode single call,duplex multi-mode single call,simplex single-mode single call,simplex multi-mode single call,single-mode group call and multi-mode group call are tested.The test results demonstrate that multi-mode media gateway realizes the establishment and removal of call services,and the allocation and recovery of channel and port.It is also realized call service data reception and forwarding,and voice encoding format conversion to meet the design requirements.