by January 4, 2000 0 comments

Imagine accessing the Internet at
10 megabits per second. That is 300 times faster than your 33.6 kbps modem! What about
getting speeds even three times faster than that? And that too at less than Rs 1,500 a
month? Drooling already? Wait. We are not there yet. And when we reach there, it is more
likely that it will be through your neighborhood cable network than through your telephone
line.

Cable TV? Yes, the same cable that brings Star TV and BBC to your
drawing room, will bring the Internet to your PC.

But why not the telephone line? It is working fine, isn’t it?
Forget it. Your telephone line just can’t handle the huge amount of data that will
have to be pumped down your PC so that you can watch movies off the Net without first
having to spend days downloading it. Hence the switch to cable.

A cable modem connects to a PC using the same coaxial cable that brings
all those channels to your idiot box. Cable modems give you high-speed data access using a
hybrid fiber or coaxial cable (HFC) network. The modem that you currently use is meant for
point-to-point communications. That is, it connects to a similar modem at the other end
and gives users at either end the ability to communicate to each other. Cable modems on
the other hand work from a single transmitting point to several receiving points. Also,
with cable modems you’re always connected. No more the hassles of dialing for half an
hour or more, only to end up with a dud connection to VSNL! Cable modems are more complex
than ordinary analog ones and they have features normally found in network hardware like
bridges, routers, and Ethernet hubs.

A cable modem network offers high
speed downloads and high bandwidth applications like video on demand

A cable modem transmits digital data down your coaxial cable line in much the
same way as it currently transmits television signals. When data is sent to you (as when
you download a file or mail) digital data is modulated and placed on a 6 MHz television
carrier signal. Two popular technologies used to do this are QPSK (up to 10 Mbps) and
QAM64 (up to 36 Mbps). This signal can be put in 6 MHz channels alongside TV signals
without destroying or distorting your favorite cable channels. Sending data back from your
PC using cable is trickier. To make coaxial cable suitable to receive and send
data, a spectrum of frequencies will have to be dedicated to carry data from the user to
the Internet. Sending data requires a frequency spectrum between 5 and 40 MHz. In addition
to this, today’s one-way amplifiers used for boosting cable signals along the network
will have to be replaced by two-way amplifiers that will be smart enough to pick out input
and output signals and amplify the correct frequency range for each. Finally, the cable
company should have an IP Router that will take care of accurate reception of all signals
from outside and of routing signals to the Internet. You can connect cable to a PC using Ethernet 10BaseT. A
variation on this is the hybrid cable modem. This gadget uses the cable for getting those
huge videos to your PC but when you send data back, it uses an ordinary modem.

Cable modems:

  • Free up phone lines

  • You’re always connected

  • Are cheaper

Unlike ISDN, cable modems are comparatively easy to install. If and
when this technology takes off we’ll see a whole range of applications like distance
learning, Net broadcasts of live events (these already exist but they’ll be full
screen), security services and perhaps karaoke over the Internet. Till then, drool at the
thought of what’s ahead!

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