What Is A Cable Modem?
Introduction ][ What Is A Cable Modem?
][ How Does It Work? ][ Advantages And Disadvantages ][ Transmission Of Data ][ What Is MAC? ][ What Standards Exist? ][ Bibliography/Links ][ Copyright Notice ][ From The Author ][ Assignment QuestionsA cable modem is basically a modem that operates on cable TV lines instead of on telephone lines, like the traditional analog modems. They operate exactly the same except for their reliance on different types of cables.
In it's own right it shouldn't really be called a modem, because it works more as a Local Area Network (LAN) interface. While this is only a technical point, it still has to be mentioned.
Setting up a cable modem needs more than just plugging it in and watching it go to work. You have to make sure that your cable TV will provide cable modem access, and also that they are set up to handle it. The cable TV provider, (also known as the Head-End), can have many cable modems attached to it, and it is set up as a 'tree' structure.
Differences Between Cable Modems, Ethernet, And Analog Modems.
There are three main types of cable modems: The internal cable modem, the external cable modem, and the interactive set-top box. The internal and external cable modems use the cable independently, and the interactive set-top box uses the cable along with the TV. Using this method you can either have the internet on your TV or on your PC. A diagram of how to set up your TV to work with a cable modem is shown on the How Does It Work? page.
Types Of Cable Modems.
There are five different parts to a cable modem. These are the Tuner, the Demodulator, the Burst Modulator, the MAC, and the Interface.
The tuner provides both upstream and downstream signals, and it is connected directly to the head-end. If you have a poor quality tuner then it is possible that it won't be able to correctly receive the digital signals.
The demodulator is what converts the digital signals into data that you can see, and is only used in the receive direction. Many cable modems have a combined modulator and burst demodulator, but a seperate demodulator is the better way to go.
The burst modulator only operates in the transmit direction, and it feeds the tuner. It also operates the digital/analog converter on the selected frequency.
MAC is an abbreviation for Media Access Control, and it sits between the receive and transmit paths. This can be built into the hardware of the cable modem or it can be somewhere in between the hardware and the software.
The interface is how your cable modem is connected to your computer, whether it be ethernet, USB, PCI bus, etc. All of the data that goes through the MAC has to pass through the interface for it to be accessible.
The Insides Of A Cable Modem.
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