Currently, we are faced with the transition to digital broadcasting. But what does it actually mean? Digital technology is already in the production of radio and television twenty years ago. Now is the time for its implementation at the transmitter, one of the last links in the direction of listeners and viewers who depend on terrestrial reception.Digital television is a broad term. We must distinguish between the digital output (production program) and the actual broadcast - to send signals to our rooftop antennas.You can make the TV with the latest digital technology, and send it to analog or to produce in old-fashioned analog and transfer it to digital. So be careful when you talk about digital television.
If you do not know what the difference between analog and digital signals, take a look at this simple example. You can tell the size of a TV screen in two different ways. If you show the size of your hands, it is an analog value. The screen size is represented with the distance between the left and right hands. This distance can be arbitrarily small and the value (in this case, the distance between the hands or the size of the screen) can be any value from zero (both hands), and the maximum duration of your hands.
To report the screen size in the digital you would measure it with a meter tape or ruler, noting the number at the end of the screen and rounding that number to some appropriate number of decimal places. That number now is digital (numeric) screen size. What you did in fact analog-digital conversion. Now you have a number representing the size of the screen. Since you have a round number is not the exact value of screen size, but the value that is sufficient for most purposes. To measure the exact value will require an infinite number of decimal places that it is impossible to achieve, and we usually do not require that the exact number.
Why are we switching to digital television broadcasting? The main reason is the more efficient use of radio spectrum. In the analog world for each channel (program) took a single frequency (RF channels). The capacity of this channel is 6 MHz (USA) and 8 MHz (Europe). Number of radio spectrum available for television broadcasting is limited.Therefore, there are a number of channels (frequencies) that can be used for television broadcasting. We can reuse these frequencies, if we can ensure that the transmitters send at the same frequency are far enough away to avoid interference. Many countries have used all the frequencies assigned to them and further enhance the television stations with terrestrial broadcasting can not. New technology must be developed. And it was. Audio and video signals are digital and can be effectively compressed with different compression methods. Digital broadcasting can use one frequency channel to transmit packets of compressed television, radio and data services is called a multiplex.
Different digital standards were developed. ATSC is used in North America, DMB-T is used in China, ISDB-T is used in Japan, while Europe, Australia and many other countries have decided to use DVB-T. Each of these standards transmits digital data stream. This transport stream contains compressed audio and video. There are two popular codecs or compression algorithms (standards) used for compression: MPEG-2 and the new, higher level MPEG-4. All of these standards are incompatible, and you need a digital receiver (Set-Top-Box), which is compatible with the transmission and compression standards used in your country.
With the growing popularity of satellite broadcast technology, there were numerous companies providing a full range of satellite services in terms of TDM / TDMA solutions, internet via satellite, multi-media via satellite, teleport services, television broadcasting, including DTH and broadcast solutions. In order to provide these services to some of the most interesting antennas operating in the Ku, ESC, DBS & C Group are used. In connection with an emergency in satellite technology, now you can link the remote province on the main switching network through the implementation of paragraph Multipoint solutions, point-to-point solutions, broadcast and multicast applications, depending on your budget.
This helps in increasing the coverage and subscribers in a short time and less operating cost.Various solution providers offer broadcast on demand and optimal quality of satellite networks for television and radio broadcasting. To provide unparalleled solutions to teleport to a well-integrated and flexible platform for radio and TV transmission all over, broadcasting and telecommunications companies to use the Hi-Tech technology and optimized satellite communication systems.
With constantly evolving satellite technology, you can take from one end to teleport solutions for multimedia broadcasting, content distribution, IP-communications and other telecommunications and satellite communications requirements, wherever you are using multiple remote sites. You have to C-band and Ku-band transponders that can support the Telecommunications Trunking, VSAT, satellite news gathering (SNG), analog TV, digital DTH, and high-definition television.
They are suitable for full or accidental use, and the possibility of transponder leasing and available.There many companies that will provide you with full support for the deployment of technology to teleport right from design, planning, program management, installation, integration, commissioning and implementation of the teleport rooms 24 / 7 support for service and network management. Different types of transmission of satellite communication and broadcasting solutions available on the market are outlined below:
- Radio and TV solutions through fixed and mobile ground station solutions for radio and television requirements.
- Fixed Earth Solutions for uplinking the major television and radio channels
- Mobile earth stations for digital TV signals and digital data services
- Television receive only (TVRO) through fixed and mobile TVRO systems and services
- Digital audio broadcast services (DAB) to promote the radio stations to broadcast digital radio programs and data in satellite receivers
When we talk about digital broadcasting, we often talk about a better quality picture and sound, HDTV, MPEG compression and more choice. However, most people do not know about the technology that lies at the heart of digital broadcasting and the added benefits of digital technology, not the best picture and sound quality.
The roots of the transition to digital television broadcasts are in a more efficient use of radio spectrum. In the analog world of television, we radio-frequency channels (frequencies), where each frequency transmits a single channel (program) and to avoid interference as the frequency can be used only once away. Digital technology allows the use of advanced compression algorithms to compress audio and video signals, so that we can use one frequency channel to transmit more than one service (usually three to ten or more channels), and we can build a network of transmitters operating on the same frequency significantly lower than the number of frequencies (channels) needed to cover the territory.
There are several standards for digital television broadcasting. For terrestrial television countries, the use of systems such as DVB-T, T-DMB, ATSC and DVB-T. DVB-T, perhaps the most widely used - it is used in Europe, Russia, Australia, India and many other countries. All of these systems based on COFDM - Coded Orthogonal Frequency Division Multiplexing. This modulation scheme with many thousands of closely spaced bears, each of which digital information.
Frequency plans for DVB-T based on the selections - an area where all the transmitters transmit on the same frequency. How can we pass on the same frequency without interference? Well, there are obstacles, but to some extent it is constructive. It helps to demodulate the signal. The fact is that at any point of signals from different transmitters arrive at different times. But because the signal is digital signal is received. Character length - digital data with which each carrier is modulated - it's more than the difference in arrival times from different transmitters. In addition, each symbol duration with guard interval. During the guard interval same characters with different arrival times can be obtained without any interference between the characters. This is a basic principle of a single frequency network (SFN).
Of course, the maximum distance between transmitters operating at the same frequency depends on the length of guard interval. With proper planning SFNs distance of 70 km can be achieved. This means that all transmitters in the area working on the same frequency and broadcast the same content. This is a huge advantage over analog television, where we have a lot of frequencies to cover the same area.
