Research On Overlay Multicast Routing Technology For Group-Multimedia Applications

With the development of distributed multimedia applications and broadband technology, Multimedia group communication applications, such as multi-point video conference, major news and events live, Internet-on-demand TV, network video monitoring and so on, continue to emerge. Multicast technology has been widely used in the group communication applications. To meet the requirements of these applications, researchers have conducted IP Multicast technology for nearly two decades of research. However, due to existence of IP Multicast scalability issues, it leads that the technology can not be takes a lot of time for the technology to be large-scale configured in the Internet. In recent years, application layer-based overlay network multicast service technology has been more and more attention. Without underlying equipment upgrades and extension, multicast services can be configured as needed. However, due to capacity limitations of end system, the current overlay network multicast routing technology for large-scale multimedia group communication applications, still faces three major challenges:1) Insufficient capacity of end system leads to a longer overall distribution delay of problems; 2) Dynamics of end system leads to a longer overall distribution delay of problems; 3) Local disaster leads to quality decline in the distribution.The dissertation’s work is supported by Scientific and Technological Project of Wuhan City, "Vehical Multimedia Communication System"(No.20033001005-5-1) and Scientific and Technological Project of Hubei Province, "FTTH Access Technology Stream" (No.2006AA101A03). To solve the problem of longer delay distribution In the process of multicast tree construction, the problem of low proportion of latency optimization with dynamic changes of network conditions, and the problem of local disaster leading to quality decline in the distribution, overlay network multicast routing technology and application technology of multimedia content distribution system have been in-depth studied.The major contributions of this dissertation are as follows:(1)Degree-Constrained Optimized Minimum delay spanning tree algorithm. Overlay Multicast spanning tree algorithms have larger latency issues under the condition of degree-constrained. The existing node selection model calculates only the length of delay as a judgment basis for the order of node joining tree, without considering the node’s relay capacity constraints. In this case, a node with shorter delay but poor degree may be chosen firstly, resulting in larger overall delay. This dissertation studies degree-constraints’influences on the multicast delay, and claims Degree-Constrained Optimized Minimum delay spanning tree algorithm(DCMD-D). Compared with the DCMD-H algorithm, DCMD-D algorithm is more accurate in the calculation of judgment metric weights. Experiments show that the proposed algorithm could achieve2%-6% lower latency. The result applied to real-time group-multimedia system construction can reduce user waiting time.(2) Residual Degree Unrelated Optimized sub-tree rearrangement algorithm. Overlay multicast tree rearrangement algorithms have the problem of lower optimization proportion under the sparse environments with rare remaining degree. The existing rearrangement activation model set remaining degree as a necessary condition, so that only a residual degree of nodes can be rearranged, resulting in lower optimization proportion. This dissertation proposes sub-tree rearrangement algorithm, not considering whether there are residual degree nodes. Compared with Ye algorithm, the proposed algorithm can be applied to optimize free nodes with no residual degree, and improves the ratio of delay optimization. Experiments show that when the tree remaining less than 15% degree available, the proposed algorithm can achieve 5%-10% higher delay optimization ratio. The result applied to real-time group-multimedia system maintenance, can provide sustainable long service quality.(3) Overlay multicast tree Forward reconstruction algorithm with no correlation. Overlay multicast tree reconstruction algorithms have not efficient disaster recovery issues under the high probability of nodes’ failure. The existing backup selection model cannot exclude "loop backup" between the node and its backup node. The sub-tree are left in exceptional circumstances for "loop-backup" accursed, resulting in splitting down the success rate of recovery. This dissertation presents a "loop-backup" detection mechanism that limits the sub-tree left event occurs. Compared to Jinhan algorithm, the proposed algorithm can improve the success rate of tree recovery. Experiments show that when the tree failure probability is higher than 10%, he proposed algorithm can achieve 4.5%-7.5% higher success rate of tree recovery, while only 1%-3% increases in the recovery delay. This is significant for the improvement of real-time group-multimedia system’s fault tolerance and self-recovery capability.(4) multi-service overlay system model for multimedia content distribution. At present, most traditional distribution systems adopt special distribution services framework, often only for the characteristics of multimedia applications with a single provision, and cannot provide service guarantee for group-multimedia communication. To solve this problem, this dissertation designed to work on a tiered service multimedia group-communication system architecture. Compared with traditional single system, the system can simultaneously achieve pictures, video and real-time streaming and other types of distribution services. It leaves out repeat system development and saves the system maintenance overhead. Meanwhile, incorporating this overlay multicast theoretical results, this dissertation designs distinct service-quality assurance mechanism for group multimedia services to improve performance and stability.In summary, this dissertation results from the application-layer overlay network to explore the perspective of the quality(QoS) of efficient and reliable multicast distribution control strategy for large-scale multimedia group-communication system design, and provide innovative science guiding ideology. It is of an important theoretical significance for research and development of automotive multimedia communication systems, IPTV useful products. Finally, this dissertation shows the prospects for future research.