The Research On Data Broadcasting And Terminal Receiving Algorithm Of Interactive TV

The recent evolution of network technology imprompts mergence of Internet, telecommunication network and digital TV network. Cable TV network subordinate to the digital TV network is playing a signficant role due to its possession of the largest number of terminal users and the widest application. With development of service mergence, one-directional service cannot meet users' demands. Services on Cable TV network are undergoing a transition from traditional programs to coexsitence of multiple services including bidirectional audio/video on demand and interactive data services. Cable TV network of new generation has a great unsymmetry exists between bandwidths for uplink and downlink, since it is a network designed originally in the mode of broadcast transmission. Such unsymmetry is embodied in two aspects, one is the difference between the bandwidths for uplink and downlink, and the other is the difference between common and individual characteristics of information requirement. Accordinly, in designing new data service support and implementation, further studies should be conducted with consideration to the inherent features of cable network on the basis of Internet and telecommunication network technology.Studies in this dissertation are primarily based on the project of "Development of Experimental System and Terminal for Application of Cable Bidirectional Service in Hainan Province". Major studies focus on key issues and techniques for data services in a bidirectional cable TV network, including one-directional data broadcasting and its terminal reception algorithm, interactive data services and its scheduling strategy, and design and application of metadata.Data are distributed in a carousel manner in data broadcast services, and thus users are required to receive their desired data as quickly as possible. To address such requirement, this dissertation proposes a memeory replacement algorithm for a data broadcast terminal LRU-G. Based on data broadcast system of a browser, the algorithm constructs a directional graph model for tree-type file system at a front end and broastcasts its transition matrix to the terminal. Meanwhile, a memory replacement algorithm LRU-G based on directional graph is provided for the terminal. Compared with algorithms LRU and LIX, LRU-G can effectively improve hit ratio, reduce waiting time and enhance user experience.For a massive high-speed data broadcast service, the most-concerned issue is how to receive all desired data in one cycle. This dissertation provides a strategy for handling massive high-speed data by a terminal, including mechanisms of cache, multi-thread and transmission resuming. With such strategy, the terminal can increase download speed while reducing package lost ratio. The advantages of this software strategy have been proved in our comparison experiments.Research on the new interactive data service over DOCSIS bi-directional cable TV network should incorporate the feature of the cable TV network. This dissertation proposes a compound P2P topology structure which distributs P2P content index via data broadcast as well as a broadcast-as-demand algorithm PRLS under such topology structure. The structure of data broadcaster plus P2P central server can utilize free channels to reponse to user requests andthus increase bandwidth utilization ratio. The broadcast-as-demand algorithm PRLS enables broadcast based on resource hotness and different lengths so as to shorten users' average waiting time.During promotion of bi-directional data services, one of the critical issues is studying metadata system and defining new service specifications. In this dissertation, a metadata mergence model under MPEG-21 unified framework is designed, and interactive data services can be triggered via digital TV program content. Such design is novel and has been practiced in Hainan Province.Currently, the deployment of a demonstrative bidirectional cable network is going on in Hainan Province, to which some of the research work and results in this dissertation have been applied.