Based On The Performance Of The Hfc Network, The Docsis Mac Protocol Simulation And Its Applications

With the application of optical fibers in broadband backbone networks, the traditional access networks have become the bottleneck for the development of the communication networks. Compared to XDSL, DAN and WITL access techniques, HFC networks are competitive candidates of broadband access networks because of its rich frequency resource, extensive coverage area and smooth transmission from HFC to pute fiber.The DOCSIS protocol has been the primary standard that transmits transparent bi-directional IP traffic over HFC network. Firstly the paper thoroughly studys the DOCSIS protocol. Then based on what we have got, by utilizing OPNET, we validate the influence of the piggyback, fragmentation and concatenation on the system performance, then the influence of the different Truncated Binary Exponential Back-off windows setting on the system performance is compared. Finally on condition that the system load and the number of CM are fixed, the relations among the MAP size, the number of contention slots, priority settings and access delay of the upstream channel are discussed, and the good performance parameters are gained. The article also provides the important reference value for the complicated system simulation in the future.As the increment service of the cable television, the VOD service has been fully developmented. But how to combine the DOCSIS protocol with the VOD service and to realize I-VOD are the focus points in the near future. By Utilizing the DOCSIS protocol as a return method and taking the priority level of the clients into account, the paper introduces a realization method of I-VOD that is dynamic allocation between admission contention slots and interactive contention slots of contention slots on HFC uplink, which not only reduces the cost of exploitation of the VOD system platform but also brings the development of the broadband IP service and the VOD service together.