Digital Video Broadcasting

Color TV was introduced for the mass market during 1960. The resolution of most of the TVs today is 625 lines for PAL and 525 lines for NTSC. So the performance of TV video that is displayed is not impressed.

There have been many attempts to change to digital TV with high resolution, high sound and additional features. This lead to the concept of digital video broadcasting (DVB) that was introduced during 1993 by European launching group.

Digital video broadcasting is satellite transmission, or cable technology or terrestrial transmission. There are different standards to measure the level of quality such as:

1. Standard Definition TV (SDTV)

2. Enhanced Definition TV (EDTV) and

3. High Definition TV (HDTV)

DVB was a flexible container (MPEG 2) for transmitting the data.

The different data i.e. carried by MPEG 2 are:

1. Network Information Table (NIT)

2. Service Description Table (SDT)

3. Event Information Table (EIT) and

4. Time and Date Table (TDT)

NIT contains the different services provided by a provider and some additional information for integrated receiver, decoder (set top box) etc.

The SDT contains the names and parameter for each service. The ETT contains status information about the current transmission. The TDT contains update information for set top boxes.

DVB Data Broadcasting Profiles

The MPEG 2 container can carry different types of data using some of the following profiles.

1. Data pipe: It provides a simple asynchronous end-to-end delivery of data.

2. Data streaming: Provides streaming oriented, asynchronous or synchronous end-to-end delivery of data.

3. Multi-protocol encapsulation: A number of data network protocols can be implemented on top of MPEG 2 layer.

4. Data carousels: Allows periodic transmission of data.

5. Object carousels: Allows periodic transmission of objects that are platform independent.

DVB for High Speed Internet Access

Digital video broadcasting can be used for high bandwidth, asymmetric internet access.

An information provider (video store) offers its data to potential customers, with the help of a service provider. Service provider in turn transmits this information to a satellite provider. If a customer wants to download information from a particular site, the information provider of that site transmits that information to a satellite provider via a service provider. In case fixed network, we can use leased lines for this purpose.

The satellite provider multiplexes this stream with other digital TV channels and transmits it to the customer via a satellite and satellite receiver.

The customer can now receive the requested information with the help of a DVB adapter. This information is usually encrypted to enhance only payees get this facility. As it transmits data streams along with other programs no additional link in between is necessary. However the data rates can decrease when more number of users tries to access simultaneously.