Research And Implementation Of IP Phone Based On SIP

With the rapid development of internet and digital communication technology, internet has more and more influence on people's life, meanwhile stimulates the fast development of all kinds of applied technology. Herein IP communication technology is a typical example.VoIP (so called IP telephone) communication controlling system mainly can be described as H.323 for ITU-T and SIP for IETF. SIP is the controlling protocol in the applied level and run in the IP network to process multimedia communication. Comparing with H.323, SIP protocol has the advantages, such as simple and flexible structure, easy to extend and suitable for internet connect, etc. It is adaptive to popularize and apply in large-scale. Based on the research of VoIP technology this thesis brings forward the project of VoIP terminal for SIP, moreover design and implement the IP telephone terminal based on SIP.Firstly this thesis researches the related technology of VoIP based on discussing the current status and development trend of IP telephone, and then analysis the system structure of SIP protocol and the open protocol stack OSIP. Secondly, this thesis brings out the system project as a whole. It is designed by module project and based on the requirement of IP telephone terminal. There is four modules for the system, main controlling module, SIP module, internet transfer module and media transact module for audio & video module. The design for SIP module is based on OSIP protocol stack, implements SIP function through the design of UA frame above protocol stack. Internet transfer module adopts UDP transfer mode to implement the transfer of SIP message and multimedia data. Media transact module adopts G.729A and H.263 as the compress projects of audio and video. The thesis researchs the principle and structure of SIP server, and also designs a SIP server with register and proxy function.The thesis tests and analysises for the system after design on the IP telephone terminal. The result shows the SIP telephone termial runs stably, and achieves the requirements for all functions in the design. Finally, this article sums up the main points of research and raises the future work.