Digital Terrestrial Television (
DTTV or
DTT) is the technological evolution and advance from analogue terrestrial television, which broadcasts land based (terrestrial) signals. The purpose of digital terrestrial television, similar to digital versus analogue in other platforms such as cable, satellite, telecoms, is characterised reduced use of spectrum and more capacity than analogue, better-quality picture, and lower operating costs for broadcast and transmission after the initial upgrade costs. A terrestrial implementation of
digital television technology uses aerial broadcasts to a conventional
antenna (or aerial) instead of a
satellite dish or
cable connection.
Competing variants of digital terrestrial television technology are used around the world. Advanced Television Standards Committee ATSC is the one used in North America and South Korea, an evolution from the analogue National Television Standards Committee standard NTSC. ISDB-T is used in Japan, with a variation of it used in Brazil, Argentina, Peru, Chile[1] and most recently Venezuela, while DVB-T is the most prevalent, covering Europe, Australia, New Zealand, Colombia, Uruguay and some countries of Africa.DMB-T/H is China's own standard (including Hong Kong, though Hong Kong's private operators use DVB-T); the rest of the world remains mostly undecided, many evaluating multiple standards. ISDB-T is very similar to DVB-T and can share front-end receiver and demodulator components. The United States of America has switched from Analogue to Digital terrestrial television, while Europe is hoping to have completed its switchover mostly by 2012.
DTTV is transmitted on radio frequencies through the airwaves that are similar to standard analogue television, with the primary difference being the use of multiplex transmitters to allow reception of multiple channels on a single frequency range (such as a UHF or VHF channel).
The amount of data that can be transmitted (and therefore the number of channels) is directly affected by the modulation method of the channel.[2] The modulation method in DVB-T is COFDM with either 64 or 16 state Quadrature Amplitude Modulation (QAM). In general a 64QAM channel is capable of transmitting a greater bitrate, but is more susceptible to interference. 16 and 64QAM constellations can be combined in a single multiplex, providing a controllable degradation for more important programme streams. This is called hierarchical modulation.ref
