| Convergent Multimedia Conferencing was proposed by 3 GPP R8. It was defined as a multimedia application including message, audio, video and data. Some advantage function, such as conference policy, floor control, sidebar, also should be supported in the conferencing. In the 3 GPP technical document, a SIP-based conferencing framework defined in IETF RFC 4353 was recommended to design and realize the convergent multimedia conferencing system. Within this framework, a conference control server was defined to realize the function of conference logic, signaling process and conference instances maintaining. A media server was defined to provide the media mix and other media function. Through the media control progress between conference control server and media server, the media server was controlled by the conference control server to provide media service according to the conference logic. Design of the media control protocol architecture and message flows to make media control more effective is now the focus study of Convergent Multimedia Conferencing Framework.H.248 was recommended to control media server in 3GPP technical document. H.248/MEGACO was developed by ITU-T and IETF jointly, and was widely used in Softswitch systems. In the Softswitch system, H.248 was used to control media gateway to provided indicated media function. Due to the complex message mechanism and protocol extension mechanism, H.248 was not suitable for the media control in SIP-based system. Mediactrl working group was founded by IETF to develop a protocol for SIP-based system. The protocol was named as Media server Control Protocol (MCP). SIP and SDP offer/answer mode was used in the negotiation of the MCP media control channel. With its simple and clean message architecture, flexible protocol extensive mechanism, MCP can match the requirements of media control procudure in systems based on SIP.Based on analysis and comparsion between H.248 and MCP protocal, an MCP-based convergent multinedia conferencing system was developed with the previously developed H.248-based system. The development work includs several parts. An MCP protocal stack was designed and realized at first. Second, new media control logic and procedure was designed. Thrid, related media control logic of conference control server and main control logic of media server were redesigned. At last, a media stream optimization solution was also considered. Then, a test plan was designed to test the upgraded system and optimization solution. And the test result shows the system and solution work effectively, and the quality of media stream was improved significantly.In this thesis, the principle and mechanism of H.248 and MCP are analized and compared. Then, the design and realization of a convergent multimedia conferencing system based on MCP are described, including the design of media control flows, the design and realization of MCP protocol stack, upgrading proposal of conference control server and media server. A media optimization solution is also considered in this thesis. At last, test plan are designed to test the solution and related system's function, and part of the test case results are given. |
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