| With the rapid development of computer technology, network transmission technology and Digital signal processing technology, various IP based packet switch network real-time multimedia applications are widely in use. As a typical IP application, VoIP (Voice over IP) has been a hotspot of technology research now. It also accords with the evolution trend of "networks merging" (including telephone network, data network and cable TV network). VoIP is an IP telephone based technology which provides various value-added services. It can fully and efficiently take advantage of global network resources and provide more multimedia services than traditional technologies do. As a critical part of VoIP system, VoIP gateways are widely used to supply cheap VoIP accessing services and value-added services based on it. The thesis firstly clarifies the principles of SIP and RTP/RTCP protocol based on thorough analysis and research. It presents a design model and implementation of VoIP Gateway under embedded Linux environment, and then it illustrates the implementation of SIP and RTP/RTCP protocol stack in detail. The software architecture is modularized and leveled with different modules communicating through uniform interfaces and different layers keeping loose coupling. These make the structure more clear and the codes more portable and extensible, which can be easily applied to similar telecommunication systems. This solution has already been adopted and implemented in the VoIP Gateway based on embedded Linux platform. According to the function validation test, this system meets the requirements of VoIP gateway well in multi-services uniform access heterogeneous networks. In the end, the thesis makes expectations of future work, it gives the objective and method of improvement, and these would make the gateway more advanced. |
PDF Full Text Request