Cable Modems
What is a Cable Modem?
"Cable Modem" is a modem that operates over the regular TV
cables network. A subscriber is able to use the cable modem to receive data to his
personal computer, while simultaneously receive cable television service.
What is a CATV Network?
A CATV (CAble TV) network is basically designed and used for distribution of
cable TV.
In the last 10 years, the cables companies use the same infrastructure also for
Internet communication.
Signals in CATV network can flow in both directions. Data from the subscriber
(upstream) is carried over the lower frequencies, and data to the subscriber
(downstream) is carried over the higher frequencies.
Most of the cables networks are Hybrid Fiber-Coax networks. The signals run in optical fiber from the cables central office to sites (called CMTS) located near the subscriber. From this sites the signals run in coaxial cables to the subscriber home.
Cables networks enable data speed that ranges from 0.5 to 50 Mbps. The distance can be up to 100 miles.
The Cable Modem Termination System (CMTS - this is the cables company's site near the subscribers) can communicate with all the subscribers connected to it, whereas each of the subscribers can talk only with the CMTS. If one subscriber wants to send data to other subscriber, it will have to go through the CMTS.
Normally, up to 2000 subscribers will be connected to one CMTS. The media of a certain CMTS is shared between all subscribers connected to it.
Cable Modems
What is a cable modem?