| PSTN (Public Switched Telephone Network) is a type of circuit switched network. The call process on PSTN is based on signal system, which creates call process by creating circuit channel,provide goog voice but depends on high cost. The quick develop of VoIP technology brought significant contributions to the convinence and speed for communication.Therefore,voice communication based on Next Generation Network will replace the circuit switch network. However, both the package switched network and the traditional circuit switched network will exist for a long time due to the cost and some technical problems. Therefore ,the gateway is needed to convert the signals between the IP network and PSTN. This thesis is focused on how to design a low cost gateway.The SIP/PSTN gateway discussed in the thesis is based on Sesssion Initiation Protocol forwarded by IETF. It was designed to allow that the PSTN telephone subscriber calls the user in IP network and the user in IP network calls the PSTN telephone subscriber as well. This gateway consists of the translation software and the hardware interface that connects with both networks.In this thesis, firstly, we introduce the relative technology of the SIP gateway and basic principles of the SIP protocol;secondly we discuss the requirements for setting up the translation gateway between the IP network and PSTN network; afterwards, We designed the whole layered system structure including hardware and software,then implemented them with OOD.Our experiments showed that the low cost SIP/PSTN gateway design is feasible. It will be an excellent communication solution in small and middle-size enterprises after further improvement is made.Furthermore, the hardware of the gateway is outside PC while the software depends on PC.In the future, it could be replanted to embedded operating system and chipset,which could improved to embedded gateway (both single way or multiple way).This kind of device is not occurred in board yet.It is believed to be an advanced product. |
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