Digital terrestrial television

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Digital Terrestrial Television (DTTV or DTT) is an implementation of digital technology to provide a greater number of channels and/or better quality of picture and sound using aerial broadcasts to a conventional antenna (or aerial) instead of a satellite dish or cable connection. The technology used is ATSC in North America, ISDB-T in Japan, DVB-T in Europe and Australia,and DMB-T/H in China (including Hong Kong); the rest of the world remaining mostly undecided. ISDB-T is very similar to DVB-T and can share front-end receiver and demodulator components.

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DTTV is transmitted on radio frequencies through the airwaves that are similar to standard analog 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. 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.

New developments in compression have resulted in the MPEG-4/AVC standard which will enable two high definition services to be coded into a 24 Mbit/s European terrestrial transmission channel.

The DVB-T standard is not used for terrestrial digital television in North America. Instead, the ATSC standard calls for 8VSB modulation, which has similar characteristics to the vestigial sideband modulation used for analogue television. This provides considerably more immunity to interference, but is not immune - as DVB-T is - to multipath distortion and also does not provide for single-frequency network operation (which is in any case not relevant in the United States).

Both systems use the MPEG-2 transport stream and video codec; they differ significantly in how related services (such as multichannel audio, captions, and program guides) are encoded.

DTTV is received via a digital set-top box, or integrated receiving device, that decodes the signal received via a standard aerial antenna. However, due to frequency planning issues, an aerial with a different group (usually a wideband) may be required if the DTTV multiplexes lie outside the bandwidth of the originally installed aerial. This is quite common in the UK, see external links.

Main article: List of digital television deployments by country

The United Kingdom (1998), Sweden (1999) and Spain (2000) were the first to launch DTT with platforms heavily reliant on pay television. All platforms experienced many starter problems, in particular the British and Spanish platforms which failed financially. Nevertheless, Boxer, the Swedish pay platform which started in 2004, proved to be very successful.

DTT in the United Kingdom was launched in November 1998 as a primarily subscription service branded as ONdigital, a joint venture between Granada Television and Carlton Communications, with only a few channels being available free to air. ONdigital soon ran into financial difficulties with subscriber numbers below expectations, and in order to attempt to reverse their fortunes, it was decided that the ITV and ONdigital brands should align, and the service was rebranded ITV Digital in 2001. Despite an expensive advertising campaign, ITV Digital struggled to attract sufficient new subscribers and in 2002 closed the service. After commercial failure of the Pay TV proposition it was relaunched as the free-to-air Freeview platform in 2002. Top Up TV, a lite pay DTT service, became available in 2004. Of all countries, British DTT has currently the highest penetration rate. UK covers Northern Ireland DTT.

In the Republic of Ireland IT's TV was the sole applicant for a digital terrestrial television license under the provisions of the Irish Broadcasting Act 2001. It proposed a triple play deployment with Broadband, TV and Digital Radio services. However following financial difficulties with other DTT deployments, most particularly in the neighbouring UK and in Spain and Portugal, Its TV failed to get its license conditions varied or to get a time extension and its license was eventually withdrawn for non performance. Under subsequent legislation in May 2007, RTÉ and the separate broadcasting and spectrum regulators are mandated to invite applications during 2008 under the Broadcasting (Amendment) Act 2007 and the reglators are rumoured to be inviting licence applications in January in then and June 2008 respectively. RTÉ Networks is required to broadcast in digital under the new Act and will receive an automatic license through the RTÉ Authority and will upgrade part of its network over a 2 year period. No upgrades to relays (small transmitters) have been announced. These may not be upgraded until the next decade.

In Spain most multiplexes closed after the failure of Quiero TV, the country's original pay DTT platform. DTT was relaunched on 30 November 2005, with approximately 30 free-to-air national and autonomous region TV and radio services.

In Sweden, DTT was launched in 1999 solely as a paid service. Today (2007) there are 38 channels in 5 MUXs. 11 of those are free-to-air channels from a number of different networks. Switch-off of the analogue TV service started in September 2005 and finished on 15 October 2007.

Finland launched DTT in 2001, and terminated analogue transmissions nationwide as the third country in the world on 1 September 2007. Finland has successfully launched a mixture of pay and free-to-air DTT services.

Germany launched a free-to-air platform region-by-region, starting in Berlin in November 2002. The analogue broadcasts are planned to cease soon after digital transmissions are started. Berlin became completely digital on 4 August 2003.

France's TNT (Télévision Numérique Terrestre) offers 18 free and 11 pay channels. A 70% DTT penetration rate is expected by March 2007. Free-to-view satellite services offering the same DTT offer are also expected to be readied by the end of 2006.

Luxembourg launched DTT services in April 2006. The national service launched in June 2006. On 1 September 2006, Luxembourg became the first European country to transition completely to DTT.

The EU recommended in December 2005 that its Member States cease all analogue television transmissions by the year 2012. Some EU member states decided to complete the transition as early as 2007 (e.g. Finland), nevertheless two member states (unspecified in the announcement) have expressed concerns that they would not be able to switch due to technical limitations.

In the United States by no later than February 17, 2009, all U.S. television broadcasts will be exclusively digital, by order of the Federal Communications Commission, with legislation setting this deadline signed into law in early 2006.[1] Furthermore, starting March 1, 2007, new television sets that receive signals over-the-air, including pocket sized portable televisions, must include digital or HDTV tuners for digital broadcasts.[2] Currently, most U.S. broadcasters are beaming their signals in both analog and digital formats; a few are digital-only. Citing the bandwidth efficiency of digital TV, after the analog switch-off the FCC will auction off channels 52–59 (the lower half of the 700 MHz band) for other communications traffic[3], completing the reallocation of broadcast channels 52–69 that began in the late 1990s. The analog switch-off ruling, which so far has met little opposition from consumers or manufacturers, would render all non-digital televisions dark and obsolete within 2 years. The FCC has determined that an external tuning device can simply be added to non-digital televisions to lengthen their useful lifespan. (However, as of March 2007, external tuning devices are not widely available, are relatively expensive, and require bulky AC power supplies.) Currently, even the earliest televisions continue to work with present broadcast standards. This mandate was designed to help provide a painless transition to the new standards.

In Venezuela, tests are being performed with full deployment to start 2008-2009. DTT will coexist with analog standard television for some time, until full deployment of the system on a nationwide level is accomplished.

The broadcasting of digital terrestrial transmissions has led to many countries planning to phase out existing analogue broadcasts. This table shows the launches of DTT and the closing down of analogue television in several countries.

  • Official launch: The official launch date of digital terrestrial television in the country, not the start for trial broadcasts.
  • Start of closedown: The date for the first major closedown of analogue transmitters.
  • End of closedown: The date when analogue television is definitely closed down.
  • System: Transmission system, e. g. DVB-T, ATSC or ISDB-T.
  • Interactive: System used for interactive services, such as MHP and MHEG-5.
  • Compression: Video compression standard used. Most systems use MPEG-2, but the more efficient H.264/MPEG-4 AVC has become increasingly popular among networks launching later on. Some countries use both MPEG-2 and H.264, for example the UK which uses MPEG-2 for standard content but MPEG-4 for some HD broadcasts.
Country
 Official launch
 Start of
closedown
 End of
closedown
 System
 Interactive
 Compression
 References
Albania 2005-08 DVB-T [citation needed]
Andorra 2007-09-25 DVB-T MHP [4]
Australia 2001-01-01 The new government has also extended the starting date of digital-only transmission in metropolitan markets for a year from December 2008[5] 2013-12-31 DVB-T MPEG-2 [citation needed]
Austria 2006-10-26 2007-03-05[6] DVB-T MHP [citation needed]
Belgium 2002/2003 2008-12-31 (Flemish Community) 2011 (Francophone Community) DVB-T No MPEG-2 [citation needed]
Brazil 2007-12-03 — 2016-06-29 SBTVD H.264/MPEG-4 AVC [citation needed]
Canada 2011-08-31 ATSC MPEG-2 [7]
China 2007-2008 DMB-T/H [citation needed]
Croatia 2007 2010 DVB-T [citation needed]
Czech Republic 2004 2007-08 2010-10 DVB-T MHP MPEG-2 [citation needed]
Denmark 2006-03-31 2009-11-01 DVB-T MHP MPEG-2, H.264 [citation needed]
Estonia 2006-12-15 2012-02 (planned) DVB-T H.264 [8]
Faroe Islands 2002-12 2002-12 DVB-T [citation needed]
Finland 2001-08-27 2007-09-01[9] 2007-09-01 DVB-T MHP (abandoned) MPEG-2 [10]
France 2005-03-31 2008-03 2011-11-30 DVB-T MPEG-2, H.264 [citation needed]
Germany 2002-11 2003-08 2008 (planned) DVB-T MPEG-2 [citation needed]
Hong Kong 2007 2012 DMB-T/H MHEG-5 (TVB) MEPG-2, H.264 [11][12]
Ireland 1999 and 2006-2008 Trial, 2008 launch planned 2012 early likely due to NI 2012 late likely due to NI/& EC goal DVB-T RCT abandoned MPEG-4 likelyH.264
Italy 2004-01-01 2010-01-01 DVB-T MHP [citation needed]
Japan 2003-12-01 2011-07-24 (planned) ISDB-T [citation needed]
Luxembourg 2006-04 2006-09-01 2008/2009 DVB-T [citation needed]
Malaysia 2006-09 (trials) 2015 DVB-T H.264 [citation needed]
Mexico 2004-07-05[13] 2022-01-01 ATSC [14]
Morocco 2007-06-01 DVB-T [citation needed]
Netherlands 2003 2006-12-11 DVB-T [citation needed]
New Zealand 2008-07 75% or 2012 1 year after start DVB-T MHEG-5 H.264/MPEG-4 AVC [15][16]
Norway 2007-09 [17] 2008-03 2009-12 DVB-T H.264/MPEG-4 AVC [citation needed]
Philippines 2006-10 (trials)/ 2007 2010 (planned) 2015 (planned) DVB-T (testing) [citation needed]
Romania 2005-12-01 2012-12-31 (planned) DVB-T [citation needed]
Russia 2012 2017 DVB-T
Slovenia 2007-09 2010 2010 DVB-T H.264/MPEG-4 AVC [citation needed]
South Africa 2006-03 2008-11-01 2011-11-01 DVB-T H.264/MPEG-4 AVC [citation needed]
South Korea 2001 2012-12-31 2012-12-31 ATSC [citation needed]
Spain 2000-05 2008[18] 2010-04-03 DVB-T MHP [citation needed]
Sweden 1999-04-01[19] 2005-09-19 2007-10-15 DVB-T MHP MPEG-2/H.264[20] [citation needed]
Switzerland 2001 2002-03 2009-10 DVB-T [citation needed]
Taiwan 2006-07 2008 2010 DVB-T [citation needed]
Turkey 2006-02 (trial services) DVB-T [citation needed]
United Kingdom 1998-11-15 2007 (Whitehaven) 2012 DVB-T MHEG-5 MPEG-2, H.264 [21]
United States 2009-02-17 ATSC MPEG-2 [citation needed]
v • d • e
Wireless Video and Data Distribution Methods

  1. ^ Section 3002 of the Deficit Reduction Act of 2005, Pub. L. No. 109-171, 120 Stat. 4 (February 8, 2006), amending the Communications Act of 1934, section 309(j)(14), codified at 47 U.S.C. § 309(j)(14).
  2. ^ FCC rule requires all new TVs to be digital. The Boston Globe (2007-02-26). Retrieved on 2007-04-24.
  3. ^ FCC: Wireless Services: Lower 700 MHz. Federal Communications Commission (2004-10-28). Retrieved on 2007-05-09.
  4. ^ , <http://www.tdt.ad/>
  5. ^ Complete digital TV switch over by 2013, Sydney Morning Herald, 2007-12-18, <http://news.smh.com.au/complete-digital-tv-switch-over-by-2013/20071218-1hun.html>. Retrieved on 2007-12-21
  6. ^ DVB-T: Zeitplan, DVB-T.at, <http://www.dvb-t.at/wann-wie-umstellen/zeitplan.html>. Retrieved on 2007-07-03
  7. ^ Broadcasting Public Notice CRTC 2007-53 - Determinations regarding certain aspects of the regulatory framework for over-the-air television, Canadian Radio and Television Commission, May 17, 2007, <http://www.crtc.gc.ca/archive/ENG/Notices/2007/pb2007-53.htm>
  8. ^ Launch of DTT services in Estonia, DigiTAG Web Letter, December 15, 2006, <http://www.digitag.org/WebLetters/2006/External-Dec2006.html>
  9. ^ Digi-tv esillä ympäri maata. Finnish Ministry of Communications. Retrieved on 2007-08-15.
  10. ^ Finland will switch over to all-digital television, Finnish Ministry of Transport and Communications, 2007-08-31, <http://www.digitv.fi/sivu.asp?path=9;1239;9758>
  11. ^ OFTA(2007-06-04), Hong Kong Technical Standard for Digital Terrestrial Television Broadcasting, Hong Kong
  12. ^ (Chinese) 望月. "獨家專訪TVB 折解數碼廣播七大疑團 (Exclusive interview with TVB on digital broadcasting)", e-zone AVzone, 6/9/2007, pp. 4-5. 
  13. ^ http://www.cft.gob.mx/cofetel/radio_tv/periodo_tran_tdt.shtml
  14. ^ , <http://www.cft.gob.mx/cofetel/radio_tv/periodo_tran_tdt.shtml>
  15. ^ , <http://tvnz.co.nz/view/page/1382967>
  16. ^ , <http://www.beehive.govt.nz/ViewDocument.aspx?DocumentID=31480>
  17. ^ RiksTV - Når kommer det?, RiksTV.no, <http://rikstv.no/Nar-kommer-det/>. Retrieved on 2007-07-04
  18. ^ Local channels
  19. ^ Nya tillstånd för digitala TV-sändningar, Swedish Radio and TV Authority, January 20, 2001, <http://www.rtvv.se/se/Press/Nyheter/000120/>
  20. ^ As of June 2007, H.264 is only used for HDTV in the Mälaren Valley region.
  21. ^ What is Digital Switchover?. DAS TV (2007-07-01). Retrieved on 2007-08-13.

Retrieved from "http://en.wikipedia.org/wiki/Digital_terrestrial_television"
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