Research For Multimedia Multicasting Mechanism On Partial-multicast Network

As multimedia and network technologies grow rapidly, multimedia applications have become very popular. However, there are still many unsolved problems in transmission of multimedia with high quality, which still persecute researchers and users. In order to solve QoS problems in multipoint multimedia communications, multicast became the most popular means of transmission. There are various routing algorithms for multicasting. These algorithms often perform well for certain purposes, while not for the others. Therefore, it is necessary to adopt different algorithms according to various multimedia application features for best overall performance. What's more, they can only be used within a multicast area called Multicast Island, but can not reach the place where there are no linked multicast routers. Unfortunately, Internet is such a partial-multicast network which can not provide multicasting totally. Thus new mechanisms are in need in order to implement multicast in such partial-multicast networks.Under the support from Innovation Foundation of China National Ministry of Science and Technology for the project (No. 00C26224210641) - "Cooperation Distance Learning Groupware", Key Science and Technology Item Foundation of China National Education Ministry for the project (No. 2000175) - "Key Technologies in Modern Distance Learning: Interactive Real-time Education Software Tools" and National High Technology Research and Development Program of China (No. 2002AA119010) – "Demonstration System of Digital Audio/Video Codec, Transmission, Testing and Application", through the design and development of several multimedia systems, the problems in multimedia multicasting have been studied in this thesis, and a novel flexible multicasting framework for distributed multimedia applications on partial-multicast networks (FMPN) is presented.After reviewing the basic knowledge of multimedia transmission technology, especially multicasting technology, this thesis described FMPN, which adopts most matched multicasting algorithms for different applications and data types by data classification. FMPN utilize non-multicasting routers to transfer multicast packets, thus expand the multicast network as needed. On the other hand, by providing different virtual channels on the same physical network, FMPN lays the basis for algorithms adoption, and provides independent channels for sub-streams generated by layered encoder. In order to have better analysis to application and media, this thesis classifies multicasting data into three hierarchical levels: application type, data type and data layer. Adopting different algorithms for different application types and data types, algorithm selection in Adaptive multicasting makes a compromise, gains the feasibility and has best overall performance.In the last chapter, this thesis gives a summary of several multimedia systems in network application the author has taken part in during the study research work while pursuing master degree. These systems are all based on multimedia multicasting technologies, and cover a broad range from LAN e-learning to distance communication, and from video conference to monitoring through network. They have provided a platform for the author's experimentations on his idea. Two of them have adopted such idea in practice, and achieve the performances as expected.