DTH-SATELLITE TV

DTH (Direct to Home)

DTH stands for Direct-to-Home. It is a wireless system for delivering television programming directly to a viewer's house.

Components of a Satellite TV System/ DTH System

There are five major components involved in a direct to home (DTH) or direct broadcasting (DBS) satellite system: the programming source, the broadcast center, the satellite, the satellite dish and the receiver.

·         Programming sources are simply the channels that provide programming for broadcast. The provider doesn't create original programming itself; it pays other companies (HBO, for example, or ESPN) for the right to broadcast their content via satellite. In this way, the provider is kind of like a broker between you and the actual programming sources. (Cable TV companies work on the same principle.)

·         The broadcast center is the central hub of the system. At the broadcast center, the TV provider receives signals from various programming sources and beams a broadcast signal to satellites in geosynchronous orbit.

·         The satellites receive the signals from the broadcast station and rebroadcast them to Earth.

·         The viewer's dish picks up the signal from the satellite (or multiple satellites in the same part of the sky) and passes it on to the receiver in the viewer's house.

·         The receiver processes the signal and passes it on to a standard TV.

Satellite TV Signal

Satellite signals have a very long path to follow before they appear on TV screen. Because satellite signals contain such high-quality digital data, it would be impossible to transmit them without compression. Compression simply means that unnecessary or repetitive information is removed from the signal before it is transmitted. The signal is reconstructed after transmission.

Standards of Compression

Satellite TV uses a special type of video file compression standardized by the Moving Picture Experts Group (MPEG). With MPEG compression, the provider is able to transmit significantly more channels. There are currently five of these MPEG standards, each serving a different purpose. DirecTV and DISH Network, the two major satellite TV providers in the United States, once used MPEG-2, which is still used to store movies on DVDs and for digital cable television (DTV). With MPEG-2, the TV provider can reduce the 270-Mbps stream to about 5 or 10 Mbps (depending on the type of programming).

Encryption and Transmission 

After the video is compressed, the provider encrypts it to keep people from accessing it for free. Encryption scrambles the digital data in such a way that it can only be decrypted (converted back into usable data) if the receiver has the correct decryption algorithm and security keys.

Once the signal is compressed and encrypted, the broadcast center beams it directly to one of its satellites. The satellite picks up the signal with an onboard dish, amplifies the signal and uses another dish to beam the signal back to Earth, where viewers can pick it up.

India’s DTH Provider- Tata Sky

It uses MPEG-2 digital compression technology and transmits using INSAT 4A at 83.0 E. It is a Joint Venture between the TATA Group, that owns 80% and STAR Group that owns a 20% stake. It was launched in 2006 and offers close to 173 channels including some interactive channels