Research On Several Crucial Aspects Of Multimedia Conferencing In NGN Environment

Next Generation Network (NGN) is the direction of development of the telecommunication network. The emergence and development of NGN provides solid supports in the infrastructure level for the maturity and evolution of multimedia interactivity technology.It is relatively long time for the emergence of multimedia conferencing. The enterprise level application of it is very mature. In this thesis, according to our research work within a long period, we analyzed the form of multimedia conferencing with mathematical tools, and we bring forward the ACPMP functional model. And we demonstrated, induced and summarized eight principles for design of high performance and high simultaneity multimedia conferencing system in NGN environment. Based on theoretical analysis, we defined "System Acquaintance ratio", which is used to evaluate the user relation composition and the application orientation of the whole system.We analyzed several main standard families related to multimedia conferencing in this thesis. We concluded that the trend is for SIP, which is loose coupled, multi-application supported, and highly scalable. To meet the requirements of providing large scale multimedia conferencing service in the NGN environment, we defined GMIP, which can be carried by SIP, based on the eight principles. We defined the entities, provided the reference model for signaling and media interactivity, and regulated the PDLJ definition based on XML Schema, and provided the definition and generation method for those PDUs. Afterward we described how we implemented the GMIP stack for the real deployment.In this thesis, we concentratively discussed the high performance media mixing or combination algorithm. For audio mixing, we designed two new input-weighted algorithms, namely ASW and AEW, and then bring out the optimized audio mixing model for them. We also developed algebra sum segmented weighted algorithm, and after the analysis for the parameters, we proposed two algorithms for practical applications. With in the field of video combination, we give out the general model for video combination and transcoding, and then we developed two DCT domain resampling algorithms and the corresponding motion vector composition algorithms, then we proposed the generalized video combination and transcoding process. As for NAT traversal, we analyzed and studied many solutions, such as MIDCOM, STUN, TURN and ICE. We proposed that all the SIP/GMIP Signalling must be proxied or relayed by server-side entities, and media stream should do the NAT traversal work. We design an optimized NAT traversal solution for media stream combined with the signaling process. Then we compared our solution to other solutions, and made it a part of the whole architecture of GMIP.We do reverse engineering work to some famous multimedia communication system in real operation, and summarized the advantages and disadvantages of them. Using the results of the conferencing form, protocol, media processing and transportation, taking the aim which is to providing the large scale multimedia conferencing service, we bring out the models, methodology and architecture of GMI system, and we provided some samples for the implementation of GMI system. In the end, we compared GMI system to some successfully operated multimediacommunication systems, so as to find out the advantages of GMI system, and to see the shortcomings in the mean time.