DVB-T

DVB-T is an abbreviation for Digital Video Broadcasting — Terrestrial. It means transmitting digital signal (multiplex) and using radio frequency spectrum much more efficiently. Digital broadcasting has many advantages over the old, analog broadcasting that is still in use today.

Terrestrial broadcasting means transmission of TV channels via transmitters which are usually put on high transmitting sites. Until recently there was only analog broadcasting which means one transmitter operating on some frequency and transmitting only one TV channel. Digital video broadcasting (DVB-T) means broadcasting a package of TV channels called multiplex. This kind of broadcasting has many advantages: efficient usage of radio frequency spectrum, better sound and picture quality, possibility of additional services, possibility of high-definition picture (HDTV) and wide screen picture format to mention just the most important properties.

Because of these advantages we will switch to digital broadcasting (DVB-T). This applies to the whole Europe and later to other countries. There are many standards for digital video broadcasting, DVB-T is one of the widely adopted. It will be used in Europe, Russia, Australia, India and many other countries (see picture below). Each country has its own date for analog switch-off. In Europe most countries will switch off analog Tv transmitters by the year 2012.

Radio frequency spectrum is a natural and limited resource. Usually we are not aware of this fact. Broadcasting (radio and television) is just one of the services which uses this spectrum. One part of radio frequency spectrum is allocated for television services and is divided into channels. Each channel has central frequency and bandwidth (e.g. in UHF frequency band channel bandwidth is 8 MHz). Broadcasting of television picture over radio waves was developed decades ago. Because of physical laws which define propagation of radio waves, transmitters are installed on high sites to have large coverage area. Radio waves, of course, know nothing about country borders. Therefore countries need to reach agreement on frequency usage in order to avoid interference. First major agreement in this regard was reached in 1961 in Stockholm, Sweden, where a conference was held. This conference defined frequency plan which defined technical parameters for every television transmitter allowed to operate. The implication of this agreement was that only a limited part of radio frequency spectrum allocated to television services was assigned to each country. This agreement (also called Stockholm 1961agreement or ST61 for short) also defines precise procedures to be taken before each transmitter is put into operation.

Needs for radio frequency spectrum allocated to television services have increased significantly. Every country has come to the point where adding new TV services was not possible because all radio frequency channels (assigned to each country) have already been used. Because of advances in digital technology, efficient compression of audio and video signals and digital broadcasting has become feasible. This altogether has brought to the conclusion that one radio frequency channel can be used to transmit more than one TV program (as is the case of analog broadcasting). Digital video broadcasting (DVB-T) means broadcasting a multiplex, a package of various services. Because of this new technology and a need to redefine radio frequency spectrum allocated to television a conference was held in Geneva, Switzerland in 2006. On this conference countries have agreed on new assignments of radio frequency channels taking into account that broadcasting will be digital (Europe is using DVB-T standard for terrestrial digital video broadcasting). The conference (its agreement is called Geneva 2006 agreement or GE06 for short) decided also that analog television broadcasting should cease by 2015 (each country can decide to switch off analog television transmitters earlier).

DVB-T modulation

DVB-T Standard

Single frequency networks (SFN)