by December 5, 2002 0 comments

Late 1940s Pennsylvania, US. Though television is becoming a staple diet all over, residents in the mountains of Pennsylvania aren’t able to enjoy it because of poor signal quality. Because of the frequencies allotted to television, the signals can only be received in “line of sight” from the transmitting antenna, so television transmitters in the cities can’t transmit their signals to these mountainous regions.

Enter John Walson, an appliance storeowner, whose TV sales are suffering. Walson puts an antenna on top of a nearby mountain, and signals received are transported to his store over twin-lead antenna wire. He also works to improve picture quality by using co-axial cables and signal amplifiers. Soon, other towns in these mountainous regions follow suit heralding the birth of cable TV, also known as CATV (Community Antenna Television).

Cut to 2002. Cable TV is big news, big technology and big money–umpteen channels, pay-per-view options, interactive television, Internet over cable and cable telephony. Though many of these haven’t reached India yet, the technology’s very much here and growing. Join us as we go through what’s available now and what’s coming.

The earliest cable systems consisted of antennas in strategic places connected with long cables to TV sets in different homes. Cable providers inserted amplifiers at regular intervals because the signal became weaker as it traveled through the long cable. This led to more distortion and noise the further away you were from the antenna, because of the many amplifiers in between.
Today, satellites and Earth stations are an important part of the cable TV setup. Briefly, this is how it works. Transmitting antennas, or uplinks, send programming signals to satellites, which are relayed back to Earth. 

These satellites are in a geo-stationary orbit 22,300 miles above the Earth, revolving in synchronization with the Earth’s rotation. Transponders in the satellite (acronym for transmitter and responder) receive and transmit these signals to ‘dishes’ or Earth stations back on the planet.

You’d have seen many of these dish antennas or TVRO (Television Receive Only) antennas at your local cablewallah’s setup. The cablewallah has many of these to receive programming signals from the multitude of programming services available–Indian and foreign. You can also set up your own TVRO to receive programs directly from the satellite.

The headend is the brain of the cable TV system. It receives signals from various sources like satellites, television antennas, and locally produced programs. It then amplifies, processes, and transmits these signals through a cable network to your home. Its components include antennas, preamplifiers, frequency converters, demodulators, modulators, processors, and scrambling and descrambling equipment.

The cable network comprises coaxial cable and fiber optic cable (called HFC for hybrid fiber-coaxial) that your cablewallah uses to deliver your favorite programs to you. The network could a purely coaxial-based network too. 

The first segment of the network, called the trunk line system, connects the eadend to the first bridging amplifiers or fiber optic nodes. Trunk lines can also include power supplies and other electronic components. The next segment, the feeder system, then carries the signal to your neighborhood. Up till this point, the network could be either fiber-optic or coaxial-based. The last segment, the drop line, is coaxial cable that connects your TV to the feeder system.

Bandwidth available to cable systems have increased from 200 MHz–33 channels, up to 550 MHz and even 1 GHz today. With the advent of digital signals, this bandwidth can pack whopping 1,000 channels. The number of channels in analog is much lesser, as each channel on analog takes about 6 MHz.

The last decade or so has seen various applications of the cable system that go beyond just receiving a variety of TV programs.

Enhancements to the TV experience came from set-top boxes and interactive television that work with cable, satellite or terrestrial broadcasts. 

Set-top boxes let you do a variety of things from video on demand to shopping through your TV to Internet surfing and checking mail. Some of them come with built-in hard disks and powerful processors. You can record TV programs on them for later viewing, get high-speed Internet access, play games, and even store e-mail. If you have an analog TV, but the program is broadcast in digital, you can see it in digital signal through a set-top box.

Interactive Television or iTV, gives you interactive content on TV. These include links to limited websites, chatting or e-mailing through the TV, answering questions in real-time on a quiz program, localized information about weather or sports, home banking, Electronic Program Guides, distance learning, interactive magazines and music selection, or the ability to switch camera angles, say during a sports event. Basically, it lets you use your TV as part of a network, much like your PC on the Internet, rather than just a standalone, passive device. There was a time, when the possibility of the PC and TV converging into a single device made headlines all over. However, the idea didn’t take off due to various reasons–iTV technology couldn’t match the PC when it came to browsing or mail checking, TV is seen largely as a ‘lean-back’ medium, while the PC is a ‘lean-into’ medium–at the end of the day, why would a
consumer pay more to get a service that gives you less than an existing service?

There are figures now saying that subscribers to iTV services in the US, at around 16 to 18 million, are around the same number as subscribers to satellite TV services. However, iTV is currently a lie-low area, and few players are increasing their current bouquet of services or investing in this

Communicate through cable 
The major success of the cable system has been extending itself to high-speed Internet access through cable modems and providing telephony through cable.

Cable modems: As the name suggests, these modems work with the same coaxial or fiber-optic cable that brings TV to your home. The cable provider has a CMTS (Cable Modem Termination system) that takes the traffic coming in from customers on a single channel and routes it to an ISP to give you Internet connection. Cable modems give you decent bandwidth and an always-on connection, which incidentally, could also pose a security risk.

They’ve been around for a while now, and are slated to grow. Various researchers have come up with good growth forecasts for cable modems. 

Computer Economics expects the subscriber base of cable modems to grow from 5.7 million installed systems in 2000 to 27.6 million systems in 2005. DataQuest forecasts the subscriber base to grow up to 14 million by 2004, while Allied Business Intelligence forecasts that data over cable subscriber penetration will increase from 3.3 million in 1999 to 58.6 million in 2005.

Cable telephony: Much like the recently much-talked-about VoIP (Voice over IP) that gives you voice over the Internet, cable telephony gives you voice over your cable TV network. 

Providing a two-way network with global access over what is traditionally a one-way, high-capacity, geographically restricted network is the biggest challenge for the cable system. 

There are also technical problems like noise on the line from signal ingress–whether broadcast TV, or amateur and citizen band radio; impulse noise–from things like a loose amplifier or corroded connector; and common-path distortion. Moreover, noise is more of a problem on lower bandwidths, which is where telephone signals are carried. 

Common path distortions happen at the junction of dissimilar materials. This means that the cable industry has to combine fiber, coaxial, and copper wire for telephony very carefully.

Again, according to Allied Business Intelligence, cable telephony has a bright future. From 2.93 million in 2001 (in the US), subscribers are expected to grow to 5.2 million by the end of this year. According to them, this success is because of cost savings for cable companies and the convenience of delivering television, high-speed Internet, and telephone services over the same line. 

Another research agency, Probe Research, has also predicted that voice-over-cable lines will
grow strongly in the next three years, particularly in the AsiaPacific region. 

What lies ahead?
Convergence still seems to be the mantra for cable. After broadband Internet and telephony through cable, the current buzz about a wirelessly networked home may find a comfortable partner in cable modems. Conexant Systems, which makes semiconductors for cable or DSL modems, has announced that it’s adding Wi-Fi chips to these semiconductors. What this means is that manufacturers can build devices that not only connect to an external network over cable, but also create their own wireless network.

Are we looking at a ubiquitous cable line for all our connectivity, wired or wireless?

Next month, we take you through the cablewallah’s setup in your area, and how all those movies, songs, and ads get to your screen.

Pragya Madan

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