DVB-T

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DVB-T is an abbreviation for "Digital Video Broadcasting — Terrestrial"; it is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 [1] and first broadcast in the UK in 1998. [1] This system transmits compressed digital audio, digital video and other data in an MPEG transport stream, using coded orthogonal frequency-division multiplexing (COFDM or OFDM) modulation. It is also the format widely used worldwide (including North America) for Electronic News Gathering for transmission of video and audio from a mobile newsgathering vehicle to a central receive point.

Digital Video Broadcasting open standard for digital television broadcasting

Digital Video Broadcasting (DVB) is a set of international open standards for digital television. DVB standards are maintained by the DVB Project, an international industry consortium, and are published by a Joint Technical Committee (JTC) of the European Telecommunications Standards Institute (ETSI), European Committee for Electrotechnical Standardization (CENELEC) and European Broadcasting Union (EBU).

Digital terrestrial television is a technology for broadcast television in which land-based (terrestrial) television stations broadcast television content by radio waves to televisions in consumers' residences in a digital format. DTTV is a major technological advance over the previous analog television, and has largely replaced analog which had been in common use since the middle of the 20th century. Test broadcasts began in 1998 with the changeover to DTTV beginning in 2006 and is now complete in many countries. The advantages of digital terrestrial television are similar to those obtained by digitising platforms such as cable TV, satellite, and telecommunications: more efficient use of limited radio spectrum bandwidth, provision of more television channels than analog, better quality images, and potentially lower operating costs for broadcasters.

United Kingdom Country in Europe

The United Kingdom, officially the United Kingdom of Great Britain and Northern Ireland but more commonly known as the UK or Britain, is a sovereign country lying off the north-western coast of the European mainland. The United Kingdom includes the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands. Northern Ireland is the only part of the United Kingdom that shares a land border with another sovereign state‍—‌the Republic of Ireland. Apart from this land border, the United Kingdom is surrounded by the Atlantic Ocean, with the North Sea to the east, the English Channel to the south and the Celtic Sea to the south-west, giving it the 12th-longest coastline in the world. The Irish Sea lies between Great Britain and Ireland. With an area of 242,500 square kilometres (93,600 sq mi), the United Kingdom is the 78th-largest sovereign state in the world. It is also the 22nd-most populous country, with an estimated 66.0 million inhabitants in 2017.

Contents

Basics

Rather than carrying one data carrier on a single radio frequency (RF) channel, COFDM works by splitting the digital data stream into a large number of slower digital streams, each of which digitally modulates a set of closely spaced adjacent sub-carrier frequencies. In the case of DVB-T, there are two choices for the number of carriers known as 2K-mode or 8K-mode. These are actually 1,705 or 6,817 sub-carriers that are approximately 4 kHz or 1 kHz apart.

Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around twenty thousand times per second to around three hundred billion times per second. This is roughly between the upper limit of audio frequencies and the lower limit of infrared frequencies; these are the frequencies at which energy from an oscillating current can radiate off a conductor into space as radio waves. Different sources specify different upper and lower bounds for the frequency range.

DVB-T offers three different modulation schemes (QPSK, 16QAM, 64QAM).

DVB-T has been adopted or proposed for digital television broadcasting by many countries (see map), using mainly VHF 7 MHz and UHF 8 MHz channels whereas Taiwan, Colombia, Panama and Trinidad and Tobago use 6 MHz channels. Examples include the UK's Freeview.

Freeview (UK) digital terrestrial television platform in the United Kingdom

Freeview is the United Kingdom's digital terrestrial television platform. It is operated by DTV Services Ltd, a joint venture between the BBC, ITV, Channel 4, Sky and transmitter operator Arqiva. It was launched in 2002, taking over the licence from ITV Digital which collapsed that year. The service provides consumer access via an aerial to the six DTT multiplexes covering the United Kingdom. In April 2014 it had some 60 DVB-T TV channels, 26 digital radio channels, 10 HD channels, six text services, 11 streamed channels, and one interactive channel. A number of new HD channels launched in 2014, from a new group of multiplexes awarded to Arqiva. The new HD channels were launched in selected areas on 10 December 2013 with a further roll-out during 2014.

The DVB-T Standard is published as EN 300 744, Framing structure, channel coding and modulation for digital terrestrial television. This is available from the ETSI website, as is ETSI TS 101 154, Specification for the use of Video and Audio Coding in Broadcasting Applications based on the MPEG-2 Transport Stream, which gives details of the DVB use of source coding methods for MPEG-2 and, more recently, H.264/MPEG-4 AVC as well as audio encoding systems. Many countries that have adopted DVB-T have published standards for their implementation. These include the D-book in the UK, the Italian DGTVi, [2] the ETSI E-Book and the Nordic countries and Ireland NorDig.

ETSI nonprofit european standards organization

The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization in the telecommunications industry in Europe, headquartered in Sophia-Antipolis, France, with worldwide projection. ETSI produces globally-applicable standards for Information and Communications Technologies (ICT), including fixed, mobile, radio, converged, broadcast and internet technologies.

MPEG-2 standard for the generic coding of moving pictures

MPEG-2 is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods, which permit storage and transmission of movies using currently available storage media and transmission bandwidth. While MPEG-2 is not as efficient as newer standards such as H.264/AVC and H.265/HEVC, backwards compatibility with existing hardware and software means it is still widely used, for example in over-the-air digital television broadcasting and in the DVD-Video standard.

H.264 or MPEG-4 Part 10, Advanced Video Coding is a block-oriented motion-compensation-based video compression standard. As of 2014, it is one of the most commonly used formats for the recording, compression, and distribution of video content. It supports resolutions up to 8192×4320, including 8K UHD.

DVB-T has been further developed into newer standards such as DVB-H (Handheld), which was a commercial failure and is no longer in operation, and DVB-T2, which was initially finalised in August 2011.

DVB-H is one of three prevalent mobile TV formats. It is a technical specification for bringing broadcast services to mobile handsets. DVB-H was formally adopted as ETSI standard EN 302 304 in November 2004. The DVB-H specification can be downloaded from the official DVB-H website. From March 2008, DVB-H is officially endorsed by the European Union as the "preferred technology for terrestrial mobile broadcasting". The major competitors of this technology are Qualcomm's MediaFLO system, the 3G cellular system based MBMS mobile-TV standard, and the ATSC-M/H format in the U.S. DVB-SH now and DVB-NGH in the future are possible enhancements to DVB-H, providing improved spectral efficiency and better modulation flexibility. DVB-H has been a commercial failure, and the service is no longer on-air. Finland was the last country to switch-off its signals in March 2012.

DVB-T2 is an abbreviation for "Digital Video Broadcasting — Second Generation Terrestrial"; it is the extension of the television standard DVB-T, issued by the consortium DVB, devised for the broadcast transmission of digital terrestrial television. DVB has been standardized by ETSI.

DVB-T as a digital transmission delivers data in a series of discrete blocks at the symbol rate. DVB-T is a COFDM transmission technique which includes the use of a Guard Interval. It allows the receiver to cope with strong multipath situations. Within a geographical area, DVB-T also allows single-frequency network (SFN) operation, where two or more transmitters carrying the same data operate on the same frequency. In such cases the signals from each transmitter in the SFN needs to be accurately time-aligned, which is done by sync information in the stream and timing at each transmitter referenced to GPS.

The length of the Guard Interval can be chosen. It is a trade-off between data rate and SFN capability. The longer the guard interval the larger is the potential SFN area without creating intersymbol interference (ISI). It is possible to operate SFNs which do not fulfill the guard interval condition if the self-interference is properly planned and monitored.

Technical description of a DVB-T transmitter

Scheme of a DVB-T transmission system Dvbt tx scheme.svg
Scheme of a DVB-T transmission system

With reference to the figure, a short description of the signal processing blocks follows.

Source coding and MPEG-2 multiplexing (MUX)
Compressed video, compressed audio, and data streams are multiplexed into MPEG program streams (MPEG-PS's). One or more MPEG-PS's are joined together into an MPEG transport stream (MPEG-TS); this is the basic digital stream which is being transmitted and received by TV sets or home Set Top Boxes (STB). Allowed bitrates for the transported data depend on a number of coding and modulation parameters: it can range from about 5 to about 32 Mbit/s (see the bottom figure for a complete listing).
Splitter
Two different MPEG-TSs can be transmitted at the same time, using a technique called Hierarchical Transmission. It may be used to transmit, for example a standard definition SDTV signal and a high definition HDTV signal on the same carrier. Generally, the SDTV signal is more robust than the HDTV one. At the receiver, depending on the quality of the received signal, the STB may be able to decode the HDTV stream or, if signal strength lacks, it can switch to the SDTV one (in this way, all receivers that are in proximity of the transmission site can lock the HDTV signal, whereas all the other ones, even the farthest, may still be able to receive and decode an SDTV signal).
MUX adaptation and energy dispersal
The MPEG-TS is identified as a sequence of data packets, of fixed length (188 bytes). With a technique called energy dispersal, the byte sequence is decorrelated.
External encoder
A first level of error correction is applied to the transmitted data, using a non-binary block code, a Reed-Solomon RS (204, 188) code, allowing the correction of up to a maximum of 8 wrong bytes for each 188-byte packet.
External interleaver
Convolutional interleaving is used to rearrange the transmitted data sequence, in such a way that it becomes more rugged to long sequences of errors.
Internal encoder
A second level of error correction is given by a punctured convolutional code, which is often denoted in STBs menus as FEC (Forward error correction). There are five valid coding rates: 1/2, 2/3, 3/4, 5/6, and 7/8.
Internal interleaver
Data sequence is rearranged again, aiming to reduce the influence of burst errors. This time, a block interleaving technique is adopted, with a pseudo-random assignment scheme (this is really done by two separate interleaving processes, one operating on bits and another one operating on groups of bits).
Mapper
The digital bit sequence is mapped into a base band modulated sequence of complex symbols. There are three valid modulation schemes: QPSK, 16-QAM, 64-QAM.
Frame adaptation
the complex symbols are grouped in blocks of constant length (1512, 3024, or 6048 symbols per block). A frame is generated, 68 blocks long, and a superframe is built by 4 frames.
Pilot and TPS signals
In order to simplify the reception of the signal being transmitted on the terrestrial radio channel, additional signals are inserted in each block. Pilot signals are used during the synchronization and equalization phase, while TPS signals (Transmission Parameters Signalling) send the parameters of the transmitted signal and to unequivocally identify the transmission cell. The receiver must be able to synchronize, equalize, and decode the signal to gain access to the information held by the TPS pilots. Thus, the receiver must know this information beforehand, and the TPS data is only used in special cases, such as changes in the parameters, resynchronizations, etc.
Spectrum of a DVB-T signal in 8k mode (note the flat-top characteristics) Dvbt spectrum.jpg
Spectrum of a DVB-T signal in 8k mode (note the flat-top characteristics)
OFDM Modulation
The sequence of blocks is modulated according to the OFDM technique, using 1705 or 6817 carriers (2k or 8k mode, respectively). Increasing the number of carriers does not modify the payload bit rate, which remains constant.
Guard interval insertion
to decrease receiver complexity, every OFDM block is extended, copying in front of it its own end (cyclic prefix). The width of such guard interval can be 1/32, 1/16, 1/8, or 1/4 that of the original block length. Cyclic prefix is required to operate single frequency networks, where there may exist an ineliminable interference coming from several sites transmitting the same program on the same carrier frequency.
DAC and front-end
The digital signal is transformed into an analogue signal, with a digital-to-analog converter (DAC), and then modulated to radio frequency (VHF, UHF) by the RF front end. The occupied bandwidth is designed to accommodate each single DVB-T signal into 5, 6, 7, or 8 MHz wide channels. The base band sample rate provided at the DAC input depends on the channel bandwidth: it is samples/s, where is the channel bandwidth expressed in Hz.
Available bit rates (Mbit/s) for a DVB-T system in 8 MHz channels
ModulationCoding rate Guard interval
1/41/81/161/32
QPSK 1/24.9765.5295.8556.032
2/36.6357.3737.8068.043
3/47.4658.2948.7829.048
5/68.2949.2169.75810.053
7/88.7099.67610.24610.556
16-QAM 1/29.95311.05911.70912.064
2/313.27114.74515.61216.086
3/414.92916.58817.56418.096
5/616.58818.43119.51620.107
7/817.41819.35320.49121.112
64-QAM 1/214.92916.58817.56418.096
2/319.90622.11823.41924.128
3/422.39424.88226.34627.144
5/624.88227.64729.27330.160
7/826.12629.02930.73731.668

Technical description of the receiver

The receiving STB adopts techniques which are dual to those ones used in the transmission.

Countries and territories using DVB-T or DVB-T2

Digital terrestrial television systems worldwide. Countries using DVB-T or DVB-T2 are shown in blue. Digital broadcast standards.svg
Digital terrestrial television systems worldwide. Countries using DVB-T or DVB-T2 are shown in blue.

Americas

Europe

Oceania

Asia

Africa

See also

Notes

  1. 1 2 "What is DVB-T" . Retrieved 2009-07-19.
  2. "DGTVi - Per la Televisione Digitale Terrestre".
  3. DVB.org, Official information taken from the DVB website
  4. "About - DVB" . Retrieved 26 June 2016.
  5. El Espectador , Colombia adopta el estándar europeo para la tv digital terrestre, 28 August 2008
  6. Evaluamos , TV Digital no ha llegado a toda Colombia y la CNTV ya piensa en modificar la norma, July 2011
  7. "News - DVB" . Retrieved 26 June 2016.
  8. "KTV Ltd" . Retrieved 26 June 2016.
  9. "Plan for the introduction of terrestrial digital television broadcasting(DVB-T) in the Republic of Bulgaria" (in Bulgarian). Ministry of Transportation, Information Technology and Communications. Retrieved 2012-12-17.
  10. "Digital Television". NURTS (TV tower operator). Retrieved 2012-12-17.
  11. "Digital Ísland" (in Icelandic). fjarskiptahandbokin.is. Retrieved 2009-10-27.
  12. "Russia adopts DVB-T2".
  13. "ETV: trial DVB-T2 network" (in Serbian). Archived from the original on 16 April 2012. Retrieved 22 March 2012.
  14. "100,000 likes – Oqaab reaches over 1 Mio TV Households". 31 March 2015. Retrieved 26 June 2016.
  15. 1 2 3 4 5 6 7 8 "Samart eyes Middle East market for digital TV-enabled smartphone" . Retrieved 26 June 2016.
  16. http://www.abu.org.my/Latest_News-@-Digital_TV_services_to_be_introduced_in_Bangladesh_by_2014__.aspx
  17. "PERSYARATAN TEKNIS ALAT DAN PERANGKAT PENERIMA TELEVISI SIARAN DIGITAL BERBASIS STANDAR DIGITAL VIDEO BROADCASTING TERRESTRIAL – SECOND GENERATION" (PDF). Kominfo. Retrieved 1 April 2017.
  18. Standar Penyiaran Televisi Digital
  19. Hawkes, Rebecca (26 February 2014). "Kuwait TV opts for Harris DVB-T2 technology". www.rapidtvnews.com/. Retrieved 2014-04-11.
  20. "Kyrgyztelecom launches DVB-T2 & DVB-S2".
  21. "Qatar Goes DVB-T2". https://www.dvb.org . 11 December 2013.External link in |website= (help)
  22. "Tajikistan Confirms DVB-T2 Adoption".
  23. Mochiko, Thabiso (26 November 2010). "BusinessDay - State U-turn on Nyanda's digital-TV signal plan". BusinessDay.co.za. BDFM Publishers. Archived from the original on 30 November 2010. Retrieved 26 November 2010.
  24. "DVB-T2 chosen as digital TV standard" . Retrieved 2011-01-03.

Related Research Articles

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Digital audio broadcasting digital radio standard

Digital audio broadcasting (DAB) is a digital radio standard for broadcasting digital audio radio services, used in many countries around the world, though not North America.

8VSB is the modulation method used for broadcast in the ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the DVB-T standard uses COFDM.

A satellite modem or satmodem is a modem used to establish data transfers using a communications satellite as a relay. A satellite modem's main function is to transform an input bitstream to a radio signal and vice versa.

DVB-C stands for "Digital Video Broadcasting - Cable" and it is the DVB European consortium standard for the broadcast transmission of digital television over cable. This system transmits an MPEG-2 or MPEG-4 family digital audio/digital video stream, using a QAM modulation with channel coding. The standard was first published by the ETSI in 1994, and subsequently became the most widely used transmission system for digital cable television in Europe, Asia and South America. It is deployed worldwide in systems ranging from the larger cable television networks (CATV) down to smaller satellite master antenna TV (SMATV) systems.

Advanced Television Systems Committee (ATSC) standards are a set of standards for digital television transmission over terrestrial, cable, and satellite networks. It is largely a replacement for the analog NTSC standard, and like that standard, used mostly in the United States, Mexico and Canada. Other former users of NTSC, like Japan, have not used ATSC during their digital television transition because they adopted their own system called ISDB.

Digital Radio Mondiale Digital radio broadcasting standard

Digital Radio Mondiale is a set of digital audio broadcasting technologies designed to work over the bands currently used for analogue radio broadcasting including AM broadcasting, particularly shortwave, and FM broadcasting. DRM is more spectrally efficient than AM and FM, allowing more stations, at higher quality, into a given amount of bandwidth, using various MPEG-4 audio coding formats.

Digital radio is the use of digital technology to transmit or receive across the radio spectrum. Digital transmission by radio waves includes digital broadcasting, and especially digital audio radio services.

DVB-S2

Digital Video Broadcasting - Satellite - Second Generation (DVB-S2) is a digital television broadcast standard that has been designed as a successor for the popular DVB-S system. It was developed in 2003 by the DVB Project, an international industry consortium, and ratified by ETSI in March 2005. The standard is based on, and improves upon DVB-S and the electronic news-gathering system, used by mobile units for sending sounds and images from remote locations worldwide back to their home television stations.

Single-frequency network

A single-frequency network or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel.

Digital terrestrial television in the United Kingdom encompasses over 100 television, radio and interactive services broadcast via the United Kingdom's terrestrial television network and receivable with a standard television set. The majority of digital terrestrial television (DTT) services, including the five former analogue channels, are broadcast free-to-air, and a further selection of encrypted pay TV services are also available.

1080p set of HDTV high-definition video

1080p is a set of HDTV high-definition video modes characterized by 1,920 pixels displayed across the screen horizontally and 1,080 pixels down the screen vertically; the p stands for progressive scan, i.e. non-interlaced. The term usually assumes a widescreen aspect ratio of 16:9, implying a resolution of 2.1 megapixels. It is often marketed as full HD, to contrast 1080p with 720p resolution screens.

Digital television adapter

A digital television adapter (DTA), commonly known as a converter box, is a television tuner that receives a digital television (DTV) transmission, and converts the digital signal into an analog signal that can be received and displayed on an analog television set. The input digital signal may be over-the-air terrestrial television signals received by a television antenna, or signals from a digital cable system. It normally does not refer to satellite TV, which has always required a set-top box either to operate the big satellite dish, or to be the integrated receiver/decoder (IRD) in the case of direct-broadcast satellites (DBS).

A Web-to-TV installation provides a way to show web television or other over-the-top content from the Internet, to a television set. Various technologies to do this include Home theater PCs, digital media receivers, and Smart TVs.

Digital multimedia broadcasting

Digital multimedia broadcasting (DMB) is a digital radio transmission technology developed in South Korea as part of the national IT project for sending multimedia such as TV, radio and datacasting to mobile devices such as mobile phones, laptops and GPS navigation systems. This technology, sometimes known as mobile TV, should not be confused with Digital Audio Broadcasting which was developed as a research project for the European Union. DMB was developed in South Korea as the next generation digital technology to replace FM radio, but the technological foundations were laid by Prof. Dr. Gert Siegle and Dr. Hamed Amor at Robert Bosch GmbH in Germany. The world's first official mobile TV service started in South Korea in May 2005, although trials were available much earlier. It can operate via satellite (S-DMB) or terrestrial (T-DMB) transmission. DMB has also some similarities with the main competing mobile TV standard, DVB-H.

References