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Dialup UK Article - Internal Functions Of Cable Modem
Cable Modems one of the newest technologies that have been
introduced in the world of Internet. Cable data networks integrate
the elements necessary to advance beyond dial up modem technology.
Cable modems make optimum use of the unutilized bandwidth
of the cable TV service. They provide such measures as privacy,
security, data networking, Internet access, and best quality
service features. The term generally refers to a modem that
operates over the ordinary cable TV network cables. Cable
modem technology offers high-speed access to the Internet
and World Wide Web services.
Actually, the term "Cable Modem" can be ambiguous
as a Cable Modem works more like a Local Area Network (LAN)
interface than as a modem. Your cable Modem needs to be connected
to the TV outlet for your cable TV. On other end, the cable
TV operator connects a Cable Modem Termination System (CMTS)
at their end. The network architecture enables a user cable
modem to connect to a CMTS that in turn connects to a regional
data center for access to Internet services. Thus, through
a system of network connections, a cable data network is capable
of connecting users to other users anywhere in the global
network. Let us now see working of the various parts of the
cable modem.
One of the most important devices is a tuner. The tuner connects
to the outlet of the CATV. The tuner receives a digital signal
from the modulator and then passes this on to the demodulator.
The modulator in cable modems is used to convert digital information
into a series of analog signals. They contain a QAM, like
demodulators. However, instead of having an A/D converter,
modulators have a D/A converter. This converts the information
from digital form to analog form. On other hand, demodulator
usually contains a device called quadrature amplitude modulation
(QAM). QAM takes these analog signals and encodes information
in them by varying their amplitudes and their phases. This
signal goes through the A/D converter to be converted into
digital form, in a series of 0s and 1s. The demodulator consists
of an error correction unit that checks for errors, as well
as a MPEG frame synchronizer that makes sure groups of data
stay together and in order. The modulator, like the demodulator,
contains an error correction module to check for errors. Both
modulator and demodulator perform two most important function
of the cable modem. One, the usual data conversion and transmission
and other is to preserve the integrity f the data while transmitting
the data.
Another important part is called the MAC or The Media Access
Control mechanism. This part is positioned between the upstream
and downstream paths. MAC act as an interface between hardware
and software portions of the networks. Usually, MAC need the
help of the cable modem's central processing unit to carry
out all of their responsibilities. This leads us to the microprocessor
of a cable modem that usually help MAC perform some of its
function apart from processing tasks.
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