I. Cable Modem and HFC Cable Modem and HFC are a method for realizing user broadband data access using cable TV networks. This solution is independent transmission of cable-making signals, and the coaxial cable is used by the coaxial cable after optical interface. Co-pass transmission, the system terminal CM completes the upper and downlink signal processing of the data signal. HFC is the earliest and entered the market in broadband access technology, with broadband and relative economic characteristics. HFC can provide 60 road analog broadcasting and television in a 500-house optical node cover area, at least 2 channels per household, speed up to 10Mbit / s, with a single network to provide a variety of types of simulation and digital services . The advantage is that the cable modulator does not rely on ATM technology, but directly adopts IP technology. At the same time, its disadvantage is also very obvious, and its network structure is tree, so when the user increases, the return noise accumulation in the low frequency end varies, and the essence of the tree structure is a bus shared, so when used When the number of users of the CM is increased, the bandwidth allocated to the user is narrowed within the unit time, which causes the network integral performance when the user is online, especially when performing VOD, video conference, etc., the network overall performance is lowered.
Compared with the Ethernet mode, Cable Modem and HFC have more advantages. First of all, it does not have to re-wiring, only for the original line, calculated according to each spot 500 user, approximately 400 route transformation cost per user Yuan or so. The transmission distance can reach more than 1,000 meters. At the same time, it has great advantages in equipment management, billing, security, bandwidth management. It is only possible to compare with Ethernet technology on the selectability and maturity of the current product.
