EmbeddedIP-PBX Voice Gateway Based On SIP Research & Design

There are two protocols applied extensively in IP telephone and multimedia communication at present:SIP and H.323. SIP borrows the dynamic Internet mode to put up network. It has many characteristics such as simple, flexible ,scalable, distributedly controlled, and good adaptability to the Internet and so on .While H.323 protocol is unable to support users'mobility ,more mature but complex than SEP,but its expansibility is worse. Because the future network is a packet switched network ,and it tends to use the concise and effective protocols.SEP draws many reaserchers' attention by virtual of outstanding advantages .so it is applied more and more in IP phone and multimedia communication. But SIP isn't perfect , the problems existing in practical application can't be avoided yet such as vedio meeting.By analyzing the background of SIP and embedded EP-PBX voice gateway at home and abroad presently,this project chose to research and design embedded IP-PBX voice gateway based on SIP.While improving quality of the voice, this paper studied several key techniques deeply such as optimizing voice coding compressed algorithm, designing the intellectual jitter buffer ,packet loss concealment techniqu-e,and analyzing their applications.The thesis studied the security RTP/RTCP and worked as the middleware of RTP/RTCP and UDP/TCP. What's more,. aiming to achieve the differrent visit levels.this project brought forward to setting the DMZ area to place the common sevices such as Web ,ftp and so on.On the basis of the above research ,this thesis put forward the design and partial implemention of the modules of the voice gateway.The voice gateway designed in this project is scalable easily.especially in the software part.During the plan and implemention of the software, advanced techniques and standard coding not only improved the quality of the software but also enchanced the performance of the whole system ,for instance security and hight voice quality in bad network envirment.The disadvantages of the voice gateway lay two aspects: its compatibility with H.323 protocol ,its limited functions.