The Research Of Multi-media Communication System Based On N-ISDN Access

In recent years, with the increasing need of digital communication services, the problem of access to internet is the bottle-neck restricting the development of digital services, which is a new issue to be resolved. On the other hand the net based on Copper-wire is widely used, potential and developmental. The research in the paper is about H. 320 Multi-media Communication Protocol based on Copper-wire N-ISDN access.Firstly, the paper compares V.90, Modem, XDSL, ISDN in their characters, difficulties, management and costs. Finally, we choose to construct the H.320 Multi-media communication system based on N-ISDN.Secondly, in the theoretical part of the paper, the basic theory of H. 320 Multi-media communication is introduced, such as the compression of Video and Audio data, H. 320 Stack Protocol and especially introduced the theory, relative protocol and the technique of access to the net of N-ISDN. In the application part of the paper, the design of Hardware and Software is introduced in detail, emphasizing on the application of key technique, software work.The design combines the advantages of hardware' s high-speed and software's low resources: 1)MC145572 is chosen to access the netproviding 128kbit/s, 2B+D full dual channels; 2) Because of B channel' slarge amount of user data and its high demands of real-time performance, the GSC hardware channel of Intel 80C152 used as CUP of the system is used to wrap/unwrap B channel' s SDLC, ensuring the system real-time working. And software method can resolve D channel's work for its less data communication; 3)CPU 80C152 is synchronized with MC145572 by a simple synchronous circuit, avoiding the complex FPGA interface circuit; 4) Data transmission use DMA, which reduces the delay of data transmission and CPU occupying; 5) 8bit software look-up table method can achieve 16bit CRC quickly, which reduces the resource of both hardware and software. Using these techniques can ensure the system working fast and stably. The Multi-media communication system studied in the paper is applied to safe production monitor and management system in Pengzhou, Sichuan province, which is also can be used in Video phone, long-distance education, traffic management, no man monitor system etc. In a word, the research can be widely used in Copper-wire net access systems.