Applied Research Of Network Coding In Application Layer Multicast System

Along with the unceasing expansion of Internet, the original broadcast becomes more and more expensive. Therefore the multicast technology is presented which limit the broadcasting range. And according to the different levels of multicast, there are IP multicast and the application layer multicast (ALM).IP multicast is in the network level, and needs router support in the network foundation structure. IP multicast can avoid the data packet redundant transmission on the physical link, thus it can save the network bandwidth. But because of the scale, reliability, congestion control and so on, IP multicast has not obtained the widespread deployment in Internet.Compared with the IP multicast, the nodes in ALM are usually the end system. So those nodes can carry out more complex operations. At the same time, these nodes may also constitute overlay network along with the system request. These characteristics of ALM enable it to carry on the fusion with the network coding technique well.The concept of network coding put forward a brand-new research direction in the network transmission. In traditional network transmission, the node can only store and forward the information and it cannot achieve the maximum throughput of the network. While the network coding is proposed to encode the received information makes more information clues be hold with the similar capacity. So that it not can only improves the network throughput to the upper limit of maximum flow-minimum cut theorem, but can plays the positive role on network toughness and security. These features of network coding make it more suitable for multicast.At present, the study of network coding has two directions. (1) Basic math theoretical research. It mainly includes studying the structure of network coding with set theory and matrix theory, studying the relationship between network coding and topology with graph theory and information theory, solving various parameters of network coding, proving theoretically the other uses feasibility of network coding, and so on. (2) Application of network coding under specific circumstances. It mainly includes the applications of network coding in wireless networks, ALM, P2P file distribution and streaming media delivery network.Now, the most applied research of network coding in ALM is still in theory. And the research of practical application is still rare. Although network coding based ALM shows a great advantage in theory, but this kind of superiority not yet reflects in the practical application. Therefore, in real system if the network coding can achieve the theoretical effects and how to use it are worth further study.This dissertation takes the research work of the National Natural Science Foundation project "Research on High Quality Application Layer Multicast with Network Coding" (60672051) as a foundation. The subject is how utilize the network coding technique in actual network environment. It designs and realizes the linear network code in the specific ALM system, mainly to the media data partition strategy, encoding/decoding mechanism, and buffer mechanism, and discusses how to expand the network coding to the popular multicast system. Through the combination of theoretical and experimental methods, it analyzes the network coding system performance on the actual multicast system.In Self-Similar Structured Multicast (S3M), it designs deterministic linear coding and random linear coding strategy, and through the simulation experiment analyzes the influence of network coding on the S3M performance. On this basis, for the characteristics of hybrid mesh multicast model (HM-ALM), it designs the deterministic network coding algorithm. Through the experiments on encoding /decoding algorithm and the system experiments, it analyzes the algorithm characteristics and the performance on HM-ALM.In addition, this dissertation also chooses BitTorrent as the experiment carrier on which the network coding used. With the simulation of BitTorrent, simplifying its part mechanisms and operations, the random network encoding algorithm is realized.Studies show that network coding overhead of encoding/decoding algorithm is not large, it able to adapt to multicast system characteristics of the end systems' heterogeneity. Therefore, the network coding has usability in ALM. Network coding is also influential to the ALM system performance. With the ration package redundancy, it reduces the system transmission delay, enhances the system robustness, and maintains the system performance steadiness when the system presents the fluctuation.The innovation of this dissertation are:(1) Proposes a network coding mechanism based on the ALM network topology, and analyzes its impact on the multicast performance; (2) Introduces the random factor in the deterministic linear coding, that is advantageous in the coding scheme expansion; (3) Carries on the network coding function to the popular multicast system, studies the promotion of network coding to its system performance.The following research work include:the combination of deterministic linear coding and random linear coding under particular circumstances; the network coding and source coding joint solution in streaming media applications; and the network coding actual applied research under the situation with multi-source multi-sink, and so on.