Studying Of The Protocol Implementation For Cable Modem

Following the broadband service of audio and video to be provided, the recent method of narrowband access does not adapt to the requirement of the real-time service. So increasing the access speed will be emphasis to build information superhighways. This thesis included the studying of implementing DOCSIS specification in view of Protocol Engineering. At first, author researched into the electric characteristic of physical layer of the protocol and how to process the MPEG packet in its transmission convergence sublayer, and protracted the SDLIGR of Cable Mode initialization. Then the paper designed for Cable Modem frame by using a kind of top grade special CPU and an ASIC, when analyzing the hardware architecture, and finally formed the entire hardware system by integrating FLASH, DRAM, EPROM, and E2PROM memories, Ethernet, RS232 interfaces, and high frequency circuit. Basing on those, author probed into software design in Cable Modem. The author used pSOSytem, a embedded real-time operating system, as a software base, to combine the software modules and interface drivers, in form of plug-in, and OS, and then the system software does not assume the hardware. The system was divided into modules and the thesis described their function and implement according to multi-process programming and module independency. The thesis also exemplified the DOCSIS applications module implement and designed for tasks included by the module, using the thought of message driving and inter-process communication by message queue. When designing for the control software, author resolved the data exchange between two layers by using buffer technique which implements the efficient "zero-copy"method by passing buffer pointer, discussed the infection, derived from illogicality allocation algorithmic, and the way. In the course of studying, author put forward the method which controls CPE number by software, the processing method which shares the codes by using upstream bandwidth parameters to restrict downstream bandwidth, and the method which avoids changing FLASH codes by chance. The product has used these methods and is running normally. In the end, author brought forward some blue point to advance Cable Modem design, for example, advancing DOCSIS appendix D, the more accurate divide of software functions and so on.