The Design And Implementation Of VoIP System Based On SIP

In recent years,some virtual operator licenses has been issued by the ministry of industry and information technology,which has led the private capital into the telecom market and given the further development to the domestic market of VoIP network phone.Compared with the traditional phone,VoIP network phone has advantages of low cost,low bandwidth,and supply of various multimedia services,which makes the VoIP network phone become a hot spot in the field of embedded field and network communication field.Embedded VoIP client voice terminal is the combination of embedded technology and network communication technology.Voice transmission over the network can be realized by the terminal which can make full use of existing computer network to conduct the voice data business based on embedded technology.Embedded VoIP client voice terminal provides the hardware foundation for VoIP network phone.It must need the support of signaling protocol whether traditional phone or VoIP network phone.The most influential signaling protocol standards are H.323 protocol proposed by ITU-T and SIP protocol proposed by IETF currently.The SIP protocol references the design idea of Internet standards and protocols,which are conciseness,open,compatible and easy to extend,it has been applied to various fields,so the prospect of SIP protocol is more optimistic than H.323 protocol.Firstly,this paper introduces the communication principle and related technology of VoIP network phone.Then the overall design of VoIP system is put forward according to the requirements presented by the enterprise.Overall design consists of two parts:1)the design of VoIP client voice terminal;2)the design of VoIP server.The hardware of VoIP client voice terminal mainly consists of three modules,which are main processing module,voice processing module and network communication module.The software of VoIP client voice terminal mainly realizes the communication function of network module,the voice acquisition and playback function of voice module and the data processing function of main processor.The design of VoIP server adopts three-tier architecture based on the C/S system architecture,the function modules of the server mainly including terminal management,communication management,log information,session monitoring and recording playback and so on.The paper emphases on some issues such as real-time communication,full duplex communication and network communication mechanisms and so on.Finally,the whole system carries on terminal module functional test and system scenario test with the existing network environment of the laboratory,including the interactive audio intercom test,which mainly carries on the related tests on overall system reliability and stability,clarity of voice quality,then make an analysis and summary of the test results.The test results show that the system works stably with clear voice.The interaction of SIP signaling between server and terminal works normally.The server can establish connections for terminals,and realize session monitoring and recording playback and so on.The desired requirements are achieved.