The Research On Service Models For Streaming Media In Heterogeneous Networks

With the ripid development of multimedia technology, network technology and computer technology, video-on-demand, network broadcast, video conferencing, video telephony and other multimedia applications have become part of everyday life. After years of development, small or medium scale video service system is becoming more mature. However, there are some great challenges on the way towards the large or ultra-large scale video service system, including challenges to the existing existing video server architecture, service strategy, storage and transmission technique, caused by the expansion of system size, the heterogeneous network, the user needs upgrading. Current research of the ultra-large scale video service system are focused on scalable video server architecture and efficient bandwidth sharing strategy, which are two major means of expanding the video service systems. Service models for streaming media in heterogeneous networks presented in this dissertation are developed to solve the two problems, which has an important theoretical value and practical significance.The work in this dissertation is based on "China High Performance Broadband Information Network (named 3TNet)" project, "Hainan IPTV demonstration network building" and "Hainan bidirection HFC experimental network" projects. This dissertation discusses service models for streaming media in heterogeneous networks, including service structure, service model, and bandwidth multiplexing. The main research contents and contributions are summarized as follows:The capacity of a single server is quite limited, clustered servers are needed to provide large scale streaming media services. Based on transmission characteristics and the hierarchical caching architecture of 3Tnet, the dissertation proposed and implemented a VOD service scheme to support remote storage video VCR function. It makes full use of the high bandwidth and distributed storage policy of 3TNet, decreases the demand of the storage capacity of streaming media server. The result of business management proves that the proposed scheme can greatly reduce the load on the center server and provide null startup latency for clients.In unicast VOD systems, the server has to reserve a dedicated video channel for each user for the entire duration of the video session. Consequently, the required server and network bandwidth resources increase linearly with the number of concurrent users to support. Multicast is an effective solution. Based on the project of CATV, the dissertation analyzed the characteristics of HFC network, and designed a streaming media service platform for the network. Based on the broadcast characteristics of HFC, the dissertation proposes a novel delivery scheme, named as piecewise patching (PP). The piecewise patching scheme provides the video data for the users in a piecewise mode instead of a whole patching stream which includes all missing data. Simulation results show that the scheme improves the performance of Time-shift TV service significantly in terms of total server bandwidth requirement.For the Internet, multicast can be used widely because of the limiting technical condition. At present, the storage, computing power of client has been greatly improved. Clients as streaming media service node become a reality; application layer multicast is a new way to solve expansion of services. The dissertation proposed a new transmission scheme applied on the Time-shifted TV. On the basis of Patching, P2P was introduced to reduce the bandwidth of the Video Server and the bone network. The scheme can significantly reduce the pressure of the Video Server. Based on the scheme, the dissertation designed a new Service Architecture named by Time-shifted TV on demand based on grid (GridTVOD). In GridTVOD, media servers and service nodes composed a streaming media service grid, which was designed on the base of Globus MDS. The GridTVOD used a peer-to-peer approach to cooperatively stream video using patching techniques, in which each peer can serve as both a client and a mini-video server.