H.323-based Voip System And Key Technologies To Achieve

At the end of twenty century Internet made surprised success and became another worldwide communication network after PSTN. With these years' development, IP technology has become one of the key technologies in future network and IP based packet switch has been the mainstream. Now information network based on the multimedia communication has become the focus all over the world. IP phone is one of the multimedia services under this background and has access great success and widely application, also it is a cheering omen of the emergency of the next generation network. In this paper a study of several important problems related with VoIP( Voice over IP) is conducted.In the first chapter the VoIP background and the existing techniques are introduced briefly.In chapter Ⅱ, we analyze the protocol and units of H.323 system and present two schemes, which focus on enterprises' applications.In chapter Ⅲ, DTMF signal's generation and detection is discussed and implemented by TI C54X assemble.In chapter Ⅳ, the echo cancellation technique in IP gateway is studied. After that, we discuss the implement of echo canceller based on DSP.