by January 2, 2003 0 comments



In Centre, Andheri (E), Mumbai. The cable head-end for IMC’s (IndusInd Media and Communications) InCableNet network is located here. Also located here is sister company, In2Cable’s NOC (Network Operations Center), which controls cable Internet access to Mumbai, and to the rest of India.

Let’s look at the cable TV setup first. IMC, like most other MSOs (Multi-Service Operators), uses an HFC (hybrid fiber-cable) network. Signals from their head-end to the subscriber’s locality are carried via fiber optic. Within that locality, 
signals are carried to each home via cable.


The
cable modem. The wire on top connects to your PC’s Ethernet card.
The one below to the TV and the last to the power connector

Cable head-end
Within the cable head-end, signals from the satellite dish are fed into a Foxcom, a device that then feeds the IF signal to power dividers. From the power divider, the signal goes into receivers–one for each TV channel that is beamed to your home. From here, the signal goes to a modulator, which converts the signal to various RFs for the various channels. 

All these frequencies are combined into a single signal by a combiner and sent to a post-amplifier, which as the name suggests, amplifies the signal. From here, the signal is sent to a transmitter, which converts the RF signal to optical for transmission via fiber-optic cable. 

From the transmitter, the signal goes to a distribution amplifier, and then via fiber to various ‘nodes’. These nodes also have distribution amplifiers with receivers and transmitters that amplify the signal so it can travel for further distances without much loss of quality. The signal then reaches your TV via cable.

There is a limit to the number of amplifiers that can be used in series when transmitting these signals. On an average, with an analog signal, you can have up to 40 amplifiers in a
se    ries. InCableNet states that they use not more than 10-15 amplifiers in a series.

Service network
In2Cable’s cable Internet services also utilize the same network.

To get your home connected to their cable network, you first need to ensure whether they provide services in your city. In2Cable has a Category A ISP license to operate all over India. Currently, they are present in 11 cities–Delhi, Mumbai, Bangalore, Hyderabad, Agra, Ahmedabad, Baroda, Belgaum, Indore, Nagpur and
Nasik.

On your end, you need an Ethernet card and a cable modem. Initially, In2Cable provided cable modems as part of the package, but not anymore.

You see the MDB (master database), LDB (local database) and the DNS server. The Internet connections to Mumbai and the rest of India are controlled from here

You can, however, ask their franchisees to help you get one. The franchisee, most likely your local cablewallah, is responsible for installing these pieces of hardware for you and ensuring two-way connectivity–from the service provider to you and from you to the service provider. This is important since data will travel upstream and downstream on your Internet 
connection.

Any troubleshooting with this physical connectivity is also the franchisee’s responsibility. However, if there is a problem in the logical connectivity, for instance, in spite of all hardware and connections being in order, you’re still not able to connect to the service provider’s site–In2Cable steps in for troubleshooting.

The bandwidth provided ranges from 64 kbps to 1 Mbps depending on user requirements. A complete list of packages and tariffs for individuals, SOHOs, cyber cafés, and so on is available at www.in2cable.com
/acc_rates.htm.

Cable Internet setup
From the service provider’s premises, the data signal is sent via the same network as cable TV. A CMTS (Cable Modem Termination System) connects to the combiner to feed in the data signal. The combiner combines this signal with the other RF signals and sends these to the post amplifier and from there to the transmitter.

The same fiber optic and cable that bring you the TV signal now also bring the data signal along. 

At your premises, a splitter splits the signal and sends it to the tuner in your TV and to your cable modem, which is connected to your TV and to the Ethernet card in your PC. The tuner and the cable modem recognize the signal as RF and data respectively and thus you can watch television and use an always-on Internet connection simultaneously.

The CMTS is also connected to a switch, to which are connected an authentication server, a DNS server, a cache engine, and so on. This is what gives you your IP address and sends your requests via a router and gateway to the Internet.

Incidentally, you can choose to have a static IP or a dynamic IP address–the former will cost you more.

For the return path, your data signal travels to the nodes and via receivers and amplifiers in these nodes to a receiver at the head-end. From there, it travels to the CMTS and through that to the mail server or the Internet.

In the case of In2Cable, their cable Internet networks in other cities are also monitored and controlled via the Mumbai NOC. 
So, apart from a local database, they also have a master database and other equipment for Internet connections to other parts
of  the country.

Internet gray market
ISPs are one way of getting an Internet connection. There are also other ‘gray’ ways of doing so. For instance, when wiring up buildings for cable TV access, your local cablewallah also pulls Ethernet cables between buildings–making a LAN in your apartment complex. He then buys bandwidth for ‘private’ usage and supplies you with an Internet connection. 
Similarly, cyber cafés that buy bandwidth for five or seven PCs can sometimes extend it to their entire building by making a similar LAN.
Not only are these ways illegal, they also provide you with no guarantee of quality of service, and neither can you look at your Internet provided for assistance in case of cyber crimes. 
In the case of registered ISPs, your data–including your IP address, access times, and in the case of cable Internet, the address of your Ethernet card–is recorded at their end. So, in case of complaints of their services being used for nefarious purposes, there is hope of redressal as these ISPs are also bound by law to help in such investigations.

Local channels
Ever seen a Windows start-up screen on your local TV channel and wondered what it’s doing there? Ever considered how those ads scroll across the bottom of the screen as you tune into the
latest movie?

There are various ways in which the PC and TV interact to bring you the local cable TV channel’s transmission.
First, those scrolling ads are made on the PC using specialized software. These software define the size of the ad and the area available to the ad creator to exhibit his
creativity. 

To put these ads into a movie, an overlay box connected to the CPU receives a video in signal from a VCR and gives a video 
out signal, with the ads, to the modulator.

Another way in which a CPU could be used is to capture the entire day’s programs–movies with ad breaks, songs, and so on–on to the CPU’s hard disk and then connect this to the modulator. Various software let you get the movie on to your hard disk, define intervals in which commercial breaks can be inserted, and once you insert those commercials, you’re ready to roll
the movie. 

The other way to broadcast the movie, of course, is manually. Here, the movie is played on a VCD or VCR and the signal is sent to the modulator. Remember those ‘Insert CD 2’ messages you sometimes see on TV? That’s because each CD can pack only 650 MB of data, which is insufficient for a movie. So, someone has to change the CD once one CD has played through.

Pragya Madan

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