Research On And Implement Of Embedded VoIP Terminal Based On SIP Potocol

With the simple and flexible advantages, SIP protocol has been gradually taking the place of the original H.323 protocol and becomes the core protocol in VoIP, thus, the research on VoIP terminals based on SIP becomes a hot issue. However, most recent research is put on soft terminals, and embedded terminals also have the complexity problems on the signaling control and common use, so this thesis designs and implements a kind of embedded terminal that simplifies the signaling control for the common use of the sip terminal.The terminal this thesis research on can make users from different locations communicate with others in voice over IP. It uses sip signal technology to set up the voice session and complete the signal control, with the SDP and RTP transport technology, the terminal achieves the real-time voice communication from end to end.This thesis outlines the development trend and key technology about VoIP, and the research emphasis is put on the sip signaling, real time transport and media negotiation.On the base of research, the whole design structure of the terminal for common use is introduced, which mainly uses the posix system to enhance the applicability of the terminal. Subsequently, the realization thought and framework of the application layers is described in detail, and this part includes user agent and media session module, in the user agent module, a kind of UA structure based on the transaction state machine is designed to solve the complexity problem on the signaling control, in the part of media session, the interface and work flow about voice processing is mainly introduced. Through tests, the terminal can make a good control for sip signal and also has a high compatibility.