Research On Video-conferencing-oriented P2P Streaming Overlay Structure

The traditional video conferencing is implemented by means of either special cable line or deployment of a lot of proxy servers, which results in both high cost and poor scalability. The problem mentioned above is solved by adoption of P2P streaming technology with low cost and high scalability. It can meet the real-time demand etc, by constructing proper overlay structure and employing appropriate data scheduling.Firstly, traditional P2P streaming overlay structures are studied, namely tree-based and Mesh-based structure. The working mechanism and node management are studied. The performance of the two structures is compared.A hybrid structure is discussed further. The node organization, structure optimization scheme and data delivery method are analyzed respectively, both the advantages and the disadvantages of it is pointed out. Based on the previous study, a novel hybrid structure is proposed: Main Tree Skirt Mesh Hybrid Structure (MTSMHS). MTSMHS combines the best features of tree-based and Mesh-based structures and results in shorter delay, better dynamics accommodating ability and lower overhead, so it meets the video conferencing application demands.The main work in this paper is as follows: (1) Based on the analysis of video conferencing features, MTSMHS design is proposed, depicting major modules of the system and of the node in detail. (2) The main tree initialization method and node management schemes are proposed, the former is done using the will-stay-time information, the latter deals with node join, graceful leave and accidental leave. (3) Four structure optimization schemes are proposed: Firstly, backup parents scheme improves the resilience against churn in main tree; Secondly, approach of nodes'roles transformation between tree and Mesh, enhances the capability of main tree; Thirdly, high bandwidth node preemption scheme decreases the height of main tree; Fourthly, node deployment optimization scheme based on IP resolution technique makes use of the node landmark information achieving shorter delay; (4) An efficient data scheduling strategy is proposed, namely macro zone-division scheduling together with micro scheduling based on combination of node-ID and IP. It avoids duplicate packets and achieves better transmission efficiency by implementing a hybrid pull and push mechanism. Through the simulation experiments, MTSMHS shows a good real-time and low control overhead performance.At last, based on MTSMHS a video conferencing system module is designed; both the management of nodes and the system maintenance coding modules are finished. In conclusion, P2P streaming technology used in the conferencing application can solve some problems in the system to a certain extent, having some theoretical and application value.