DVB-T is an abbreviation for "Digital Video Broadcasting — Terrestrial". This system transmits compressed digital audio, digital video and other data in an MPEG transport stream, using coded orthogonal frequency-division multiplexing modulation, it is the format used worldwide for Electronic News Gathering for transmission of video and audio from a mobile newsgathering vehicle to a central receive point. Rather than carrying one data carrier on a single radio frequency 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 spaced adjacent sub-carrier frequencies. In the case of DVB-T, there are two choices for the number of carriers known as 8K-mode; these are 1,705 or 6,817 sub-carriers that are 4 kHz or 1 kHz apart. DVB-T offers three different modulation schemes. DVB-T has been adopted or proposed for digital television broadcasting by many countries, using VHF 7 MHz and UHF 8 MHz channels whereas Taiwan, Colombia and Trinidad and Tobago use 6 MHz channels.
Examples include the UK's Freeview. 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 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, the ETSI E-Book and the Nordic countries and Ireland NorDig. DVB-T has been further developed into newer standards such as DVB-H, a commercial failure and is no longer in operation, DVB-T2, finalised in August 2011. 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, it allows the receiver to cope with strong multipath situations.
Within a geographical area, DVB-T allows single-frequency network 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 time-aligned, 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 SFN capability; the longer the guard interval the larger is the potential SFN area without creating intersymbol interference. It is possible to operate SFNs which do not fulfill the guard interval condition if the self-interference is properly planned and monitored. With reference to the figure, a short description of the signal processing blocks follows. Source coding and MPEG-2 multiplexing: Compressed video, compressed audio, data streams are multiplexed into MPEG program streams. One or more MPEG-PS's are joined together into an MPEG transport stream. 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.
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; 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. MUX adaptation and energy dispersal: The MPEG-TS is identified as a sequence of data packets, of fixed length. 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 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, denoted in STBs menus as FEC. There are five valid coding rates: 1/2, 2/3, 3/4, 5/6, 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. 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 const
DVB-T2 is an abbreviation for "Digital Video Broadcasting — Second Generation Terrestrial". DVB has been standardized by ETSI; this system transmits compressed digital audio and other data in "physical layer pipes", using OFDM modulation with concatenated channel coding and interleaving. The higher offered bit rate, with respect to its predecessor DVB-T, makes it a system suited for carrying HDTV signals on the terrestrial TV channel; as of 2014, it was implemented in broadcasts in the United Kingdom, Finland, Sweden, Thailand Flanders, Ukraine, Denmark and some other countries. In March 2006 DVB decided to study options for an upgraded DVB-T standard. In June 2006, a formal study group named TM-T2 was established by the DVB Group to develop an advanced modulation scheme that could be adopted by a second generation digital terrestrial television standard, to be named DVB-T2. According to the commercial requirements and call for technologies issued in April 2007, the first phase of DVB-T2 would be devoted to provide optimum reception for stationary and portable receivers using existing aerials, whereas a second and third phase would study methods to deliver higher payloads and the mobile reception issue.
The novel system should provide a minimum 30% increase in payload, under similar channel conditions used for DVB-T. The BBC, ITV, Channel 4 and Channel 5 agreed with the regulator Ofcom to convert one UK multiplex to DVB-T2 to increase capacity for HDTV via DTT, they expected the first TV region to use the new standard would be Granada in November 2009. It was expected that over time there would be enough DVB-T2 receivers sold to switch all DTT transmissions to DVB-T2, H.264. Ofcom published its final decision on 3 April 2008, for HDTV using DVB-T2 and H.264: BBC HD would have one HD slot after digital switchover at Granada. ITV and C4 had, as expected, applied to Ofcom for the 2 additional HD slots available from 2009 to 2012. Ofcom indicated that it found an unused channel covering 3.7 million households in London, which could be used to broadcast the DVB-T2 HD multiplex from 2010, i.e. before DSO in London. Ofcom indicated that they would look for more unused UHF channels in other parts of the UK, that can be used for the DVB-T2 HD multiplex from 2010 until DSO.
The DVB-T2 draft standard was ratified by the DVB Steering Board on 26 June 2008, published on the DVB homepage as DVB-T2 standard BlueBook. It was handed over to the European Telecommunications Standards Institute by DVB. ORG on 20 June 2008; the ETSI process resulted in the DVB-T2 standard being adopted on 9 September 2009. The ETSI process had several phases. Since the DVB-T2 physical layer specification was complete, there would be no further technical enhancements, receiver VLSI chip design started with confidence in stability of specification. A draft PSI/SI specification document was agreed with the DVB-TM-GBS group. Prototype receivers were shown in September IBC 2008 and more recent version at the IBC 2009 in Amsterdam. A number of other manufacturers demonstrated DVB-T2 at IBC 2009 including Albis Technologies, DekTec, Enensys Technologies, Pace, Rohde & Schwarz, Thomson Broadcast and TeamCast; as of 2012, Appear TV produce DVB-T2 receivers, DVB-T2 modulators and DVB-T2 gateways. Other manufacturers planning DVB-T2 equipment launches include Alitronika, CellMetric, Digital TV Labs, Humax, NXP Semiconductors, ProTelevision Technologies, Screen Service, SIDSA, Sony, ST Microelectronics and T-VIPS.
The first test from a real TV transmitter was performed by the BBC Research & Innovation in the last weeks of June 2008 using channel 53 from the Guildford transmitter, southwest of London: BBC had developed and built the modulator/demodulator prototype in parallel with the DVB-T2 standard being drafted. Other companies like ENKOM or IfN develop software based decoding. NORDIG published a DVB-T2 receiver specification and performance requirement on 1 July 2009. In March 2009 the Digital TV Group, the industry association for digital TV in the UK, published the technical specification for high definition services on digital terrestrial television using the new DVB-T2 standard; the DTG's test house: DTG Testing are testing Freeview HD products against this specification. Many tests broadcast transmission using this standard are being in process in France, with local Gap filler near Rennes CCETT. DVB-T2 was tested in October 2010, in Geneva region, with Mont Salève's repeater, in UHF band on Channel 36.
A mobile van was testing BER, quality reception, with special PCs used as spectrum analysers, constellation testers. The van was moving in Canton Geneva, France. However, none were demonstrated in TELECOM 2011 at Palexpo; the following characteristics have
Digital terrestrial television
Digital terrestrial television is a technology for broadcast television in which land-based 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, has replaced analog, 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, telecommunications: more efficient use of limited radio spectrum bandwidth, provision of more television channels than analog, better quality images, lower operating costs for broadcasters. Different countries have adopted different digital broadcasting standards; the amount of data that can be transmitted is directly affected by channel capacity and the modulation method of the transmission. North America uses the ATSC standard with 8VSB modulation, which has similar characteristics to the vestigial sideband modulation used for analog television.
This provides more immunity to interference, but is not immune to multipath distortion and does not provide for single-frequency network operation. The modulation method in DVB-T is COFDM with either 16-state Quadrature Amplitude Modulation. In general, 64QAM is capable of transmitting a greater bit rate, but is more susceptible to interference. 16 and 64QAM constellations can be combined in a single multiplex, providing a controllable degradation for more important program streams. This is called hierarchical modulation. DVB-T are designed to work in single frequency networks. Developments in video compression have resulted in improvements on the original H.262 MPEG 2 codec, surpassed by H.264/MPEG-4 AVC and more H.265 HEVC. H.264 enables three high-definition television services to be coded into a 24 Mbit/s DVB-T European terrestrial transmission channel. DVB-T2 increases this channel capacity to 40 Mbit/s, allowing more services. DTTV is received either via a digital set-top box, TV gateway or more now an integrated tuner included with television sets, that decodes the signal received via a standard television antenna.
These devices now include digital video recorder functionality. However, due to frequency planning issues, an aerial capable of receiving a different channel group may be required if the DTTV multiplexes lie outside the reception capabilities of the installed aerial; this is quite common in the UK. Indoor aerials are more to be affected by these issues and need replacing. Main articles: List of digital television deployments by country, Digital television transition Afghanistan launched digital transmissions in Kabul using DVB-T2/MPEG-4 on Sunday, 31 August 2014. Test transmissions had commenced on 4 UHF channels at the start of June 2014. Transmitters were provided by GatesAir. Bangladesh had its first DTT service DVB-T2 / MPEG-4 on April 2016 launched by the GS Group; the service is called RealVU. It is done with partnership with Beximco. GS Group acts as a supplier and integrator of its in-house hardware and software solutions for the operator's functioning in accordance with the modern standards of digital television.
RealVu provides more than 100 TV channels in HD quality. The digital TV set-top boxes developed by GS Group offer such functions as PVR and time-shift, along with an EPG. India adopted DVB-T system for digital television in July 1999; the first DVB-T transmission was started on 26 January 2003 in the four major metropolitan cities by Doordarshan. The terrestrial transmission is available in both digital and analog formats. 4 high power DVB-T transmitters were set up in the top 4 cities, which were upgraded to DVB-T2 + MPEG4 and DVB-H standards. An additional 190 high power, 400 low power DVB-T2 transmitters have been approved for Tier I, II and III cities of the country by 2017; the Indian telecom regulator, TRAI, had recommended the I&B to allow private broadcast companies to use the DTT technology, in 2005. So far, the Indian I&B ministry only permits private broadcast companies to use satellite, cable and IPTV based systems; the government's broadcasting organisation Doordarshan had started the free TV service over DVB - T2 to the mobile phone users from February 25 onwards and extended to cover 16 cities including the four metros from April 5, 2016.
Israel started digital transmissions in MPEG-4 on Sunday, August 2, 2009, anal
Television, sometimes shortened to tele or telly, is a telecommunication medium used for transmitting moving images in monochrome, or in color, in two or three dimensions and sound. The term can refer to a television set, a television program, or the medium of television transmission. Television is a mass medium for advertising and news. Television became available in crude experimental forms in the late 1920s, but it would still be several years before the new technology would be marketed to consumers. After World War II, an improved form of black-and-white TV broadcasting became popular in the United States and Britain, television sets became commonplace in homes and institutions. During the 1950s, television was the primary medium for influencing public opinion. In the mid-1960s, color broadcasting was introduced in most other developed countries; the availability of multiple types of archival storage media such as Betamax, VHS tape, local disks, DVDs, flash drives, high-definition Blu-ray Discs, cloud digital video recorders has enabled viewers to watch pre-recorded material—such as movies—at home on their own time schedule.
For many reasons the convenience of remote retrieval, the storage of television and video programming now occurs on the cloud. At the end of the first decade of the 2000s, digital television transmissions increased in popularity. Another development was the move from standard-definition television to high-definition television, which provides a resolution, higher. HDTV may be transmitted in various formats: 1080p, 720p. Since 2010, with the invention of smart television, Internet television has increased the availability of television programs and movies via the Internet through streaming video services such as Netflix, Amazon Video, iPlayer and Hulu. In 2013, 79 % of the world's households owned; the replacement of early bulky, high-voltage cathode ray tube screen displays with compact, energy-efficient, flat-panel alternative technologies such as LCDs, OLED displays, plasma displays was a hardware revolution that began with computer monitors in the late 1990s. Most TV sets sold in the 2000s were flat-panel LEDs.
Major manufacturers announced the discontinuation of CRT, DLP, fluorescent-backlit LCDs by the mid-2010s. In the near future, LEDs are expected to be replaced by OLEDs. Major manufacturers have announced that they will produce smart TVs in the mid-2010s. Smart TVs with integrated Internet and Web 2.0 functions became the dominant form of television by the late 2010s. Television signals were distributed only as terrestrial television using high-powered radio-frequency transmitters to broadcast the signal to individual television receivers. Alternatively television signals are distributed by coaxial cable or optical fiber, satellite systems and, since the 2000s via the Internet; until the early 2000s, these were transmitted as analog signals, but a transition to digital television is expected to be completed worldwide by the late 2010s. A standard television set is composed of multiple internal electronic circuits, including a tuner for receiving and decoding broadcast signals. A visual display device which lacks a tuner is called a video monitor rather than a television.
The word television comes from Ancient Greek τῆλε, meaning'far', Latin visio, meaning'sight'. The first documented usage of the term dates back to 1900, when the Russian scientist Constantin Perskyi used it in a paper that he presented in French at the 1st International Congress of Electricity, which ran from 18 to 25 August 1900 during the International World Fair in Paris; the Anglicised version of the term is first attested in 1907, when it was still "...a theoretical system to transmit moving images over telegraph or telephone wires". It was "...formed in English or borrowed from French télévision." In the 19th century and early 20th century, other "...proposals for the name of a then-hypothetical technology for sending pictures over distance were telephote and televista." The abbreviation "TV" is from 1948. The use of the term to mean "a television set" dates from 1941; the use of the term to mean "television as a medium" dates from 1927. The slang term "telly" is more common in the UK; the slang term "the tube" or the "boob tube" derives from the bulky cathode ray tube used on most TVs until the advent of flat-screen TVs.
Another slang term for the TV is "idiot box". In the 1940s and throughout the 1950s, during the early rapid growth of television programming and television-set ownership in the United States, another slang term became used in that period and continues to be used today to distinguish productions created for broadcast on television from films developed for presentation in movie theaters; the "small screen", as both a compound adjective and noun, became specific references to television, while the "big screen" was used to identify productions made for theatrical release. Facsimile transmission systems for still photographs pioneered methods of mechanical scanning of images in the early 19th century. Alexander Bain introduced the facsimile machine between 1843 and 1846. Frederick Bakewell demonstrated a working laboratory version in 1851. Willoughby Smith discovered the photoconductivity of the element selenium in 1873; as a 23-year-old German university student, Paul Julius Gottlieb Nipkow proposed and patented the Nipkow disk in 1884.
This was a spinning disk with a spiral pattern of holes in it, so each hole scanned a line of the image. Although he never built a working model
Cable television is a system of delivering television programming to consumers via radio frequency signals transmitted through coaxial cables, or in more recent systems, light pulses through fiber-optic cables. This contrasts with broadcast television, in which the television signal is transmitted over the air by radio waves and received by a television antenna attached to the television. FM radio programming, high-speed Internet, telephone services, similar non-television services may be provided through these cables. Analog television was standard in the 20th century, but since the 2000s, cable systems have been upgraded to digital cable operation. A "cable channel" is a television network available via cable television; when available through satellite television, including direct broadcast satellite providers such as DirecTV, Dish Network and Sky, as well as via IPTV providers such as Verizon FIOS and AT&T U-verse is referred to as a "satellite channel". Alternative terms include "non-broadcast channel" or "programming service", the latter being used in legal contexts.
Examples of cable/satellite channels/cable networks available in many countries are HBO, Cinemax, MTV, Cartoon Network, AXN, E!, FX, Discovery Channel, Canal+, Fox Sports, Disney Channel, Nickelodeon, CNN International, ESPN. The abbreviation CATV is used for cable television, it stood for Community Access Television or Community Antenna Television, from cable television's origins in 1948. In areas where over-the-air TV reception was limited by distance from transmitters or mountainous terrain, large "community antennas" were constructed, cable was run from them to individual homes; the origins of cable broadcasting for radio are older as radio programming was distributed by cable in some European cities as far back as 1924. To receive cable television at a given location, cable distribution lines must be available on the local utility poles or underground utility lines. Coaxial cable brings the signal to the customer's building through a service drop, an overhead or underground cable. If the subscriber's building does not have a cable service drop, the cable company will install one.
The standard cable used in the U. S. is RG-6, which has a 75 ohm impedance, connects with a type F connector. The cable company's portion of the wiring ends at a distribution box on the building exterior, built-in cable wiring in the walls distributes the signal to jacks in different rooms to which televisions are connected. Multiple cables to different rooms are split off the incoming cable with a small device called a splitter. There are two standards for cable television. All cable companies in the United States have switched to or are in the course of switching to digital cable television since it was first introduced in the late 1990s. Most cable companies require a set-top box or a slot on one's TV set for conditional access module cards to view their cable channels on newer televisions with digital cable QAM tuners, because most digital cable channels are now encrypted, or "scrambled", to reduce cable service theft. A cable from the jack in the wall is attached to the input of the box, an output cable from the box is attached to the television the RF-IN or composite input on older TVs.
Since the set-top box only decodes the single channel, being watched, each television in the house requires a separate box. Some unencrypted channels traditional over-the-air broadcast networks, can be displayed without a receiver box; the cable company will provide set top boxes based on the level of service a customer purchases, from basic set top boxes with a standard definition picture connected through the standard coaxial connection on the TV, to high-definition wireless DVR receivers connected via HDMI or component. Older analog television sets are "cable ready" and can receive the old analog cable without a set-top box. To receive digital cable channels on an analog television set unencrypted ones, requires a different type of box, a digital television adapter supplied by the cable company. A new distribution method that takes advantage of the low cost high quality DVB distribution to residential areas, uses TV gateways to convert the DVB-C, DVB-C2 stream to IP for distribution of TV over IP network in the home.
In the most common system, multiple television channels are distributed to subscriber residences through a coaxial cable, which comes from a trunkline supported on utility poles originating at the cable company's local distribution facility, called the "headend". Many channels can be transmitted through one coaxial cable by a technique called frequency division multiplexing. At the headend, each television channel is translated to a different frequency. By giving each channel a different frequency "slot" on the cable, the separate television signals do not interfere with each other. At an outdoor cable box on the subscriber's residence the company's service drop cable is connected to cables distributing the signal to different rooms in the building. At each television, the subscriber's television or a set-top box provided by the cable company translates the desired channel back to its original frequency, it is displayed onscreen. Due to widespread cable theft in earlier analog systems, the signals are encrypted on m
DVB-SH is a physical layer standard for delivering IP based media content and data to handheld terminals such as mobile phones or PDAs, based on a hybrid satellite/terrestrial downlink and for example a GPRS uplink. The DVB Project published the DVB-SH standard in February 2007; the DVB-SH system was designed for frequencies below 3 GHz, supporting UHF band, L S-band. It improves the existing DVB-H physical layer standard. Like its sister specification, it is based on DVB IP Datacast delivery, electronic service guides and service purchase and protection standards. DVB-SH specifies two operational modes: SH-A: specifies the use of COFDM modulation on both satellite and terrestrial links with the possibility of running both links in SFN mode. SH-B: uses COFDM on the terrestrial link; the DVB-SH incorporates a number of enhancements when compared to DVB-H: More alternative coding rates are available The omission of the 64QAM modulation scheme The inclusion of support for 1.7 MHz bandwidth and 1k FFT FEC using Turbo coding Improved time interleaving Support for antenna diversity in terminalsRecently, results from BMCO forum shows a radio improvement of at least 5.5 dB on signal requirements between DVB-H and DVB-SH in the UHF frequencies.
The improvements to signal requirements translates to better in-building penetration, better in-car coverage and extension of outdoor coverage. DVB-SH chipsets are being developed now by DiBcom and NXP Semiconductors, are expected to be available in beginning of 2008. Initial specifications show that the chipsets supports both UHF and S-Band and are compatible with DVB-H. DiBcom has announced a DVB-SH chip with availability in 2008 Q3. Dibcom DVB-SH 2008 Q3; the chip "has dual RF tuners supporting VHF, UHF, L-Band and S-Band frequencies". French Agence de l'innovation industrielle is now financing this effort through TVMSL, a project led by Alcatel-Lucent that plans to develop a DVB-SH standard suitable for hybrid satellite and terrestrial transmission. Other partners involved in TVMSL are Sagem Wireless, Alenia, RFS, Philips, DiBcom, TeamCast, UDcast, CNRS, INRIA, CEA-LETI. ICO, one of the biggest satellite operators in the United States, in 2007 announced a nationwide deployment of an hybrid satellite/terrestrial network in DVB-SH with Alcatel-Lucent and Expway.
ICO G1 satellite carrying DVB-SH technology on board was launched on April 14, 2008. It is the world's first DVB-SH satellite in orbit. Eutelsat W2A satellite carrying a Solaris Mobile DVB-SH S band payload was launched on 3 April 2009, it will cover Western Europe. S-band payload was scheduled to enter into service in May 2009 but this not occurred due to an anomaly being investigated. On 1 July 2009, Solaris Mobile filed the insurance claim; the technical findings indicate that the company should be able to offer some, but not all of the services it was planning to offer. Inmarsat's S band satellite programme, called EuropaSat, will deliver mobile multimedia broadcast, mobile two-way broadband telecommunications and next-generation MSS services across all member states of the European Union and as far east as Moscow and Ankara by means of a hybrid satellite/terrestrial network, it will be built by Thales Alenia Space and launched in early 2011 launched by ILS. DVB-H/SH trials are now underway in many cities and countries: Ireland,United Kingdom,Malaysia, Singapore,Helsinki, Cambridge, Paris, Madrid, Sydney,South Africa, Taiwan,The Hague, Bern, New Zealand,Philippines, Budapest, Erlangen,Sri Lanka and India.
DVB-SH in S-band is seen as an alternative in Europe. Recent field trials and studies showed better performance in radio than DVB-H standard that would lead to much cheaper costs for network deployments. In France again, SFR and Alcatel-Lucent teamed up to deploy a DVB-SH trial; the results confirmed the theorical assumptions on the superiority of the DVB-SH to DVB-H, being the natural evolution of this legacy one. In Italy, 3 Italia, RAI and Alcatel-Lucent joined forces for the first DVB-SH trial in Italy. In United States, Dish Network and Alcatel-Lucent joined forces for the first DVB-SH trial in US. Electronic program guide E-VSB ATSC standard Handheld projector IP over DVB DVB over IP MediaFLO Mobile DTV Alliance industry association Mobile TV a term for the entire category Multimedia Broadcast Multicast Service OFDM system comparison table Spectral efficiency comparison table WiMAX DVB-SH standardization history, performance evaluation, research papers on DVB-SH system, DVB-SH trials and other scientific contributions DVB Project DVB-H.org DVB-SH: Mobile digital TV in S-Band Alcatel April 2008 April 2008 in Italian Echostar Mobile Eutelsat ICO AT&T CruiseCast
Digital Video Broadcasting - Satellite - Second Generation is a digital television broadcast standard, designed as a successor for the popular DVB-S system. It was developed in 2003 by the DVB Project, an international industry consortium, ratified by ETSI in March 2005; the standard is based on, 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. DVB-S2 is envisaged for broadcast services including standard and HDTV, interactive services including Internet access, data content distribution; the development of DVB-S2 coincided with the introduction of HDTV and H.264 video codecs. Two new key features that were added compared to the DVB-S standard are: A powerful coding scheme based on a modern LDPC code. For low encoding complexity, the LDPC codes chosen have a special structure known as Irregular Repeat-Accumulate codes. VCM and ACM modes, which allow optimizing bandwidth utilization by dynamically changing transmission parameters.
Other features include enhanced modulation schemes up to 32APSK, additional code rates, the introduction of a generic transport mechanism for IP packet data including MPEG-4 audio–video streams, while supporting backward compatibility with existing MPEG-2 TS based transmission. DVB-S2 achieves better performance than its predecessors – allowing for an increase of available bitrate over the same satellite transponder bandwidth; the measured DVB-S2 performance gain over DVB-S is around 30% at the same satellite transponder bandwidth and emitted signal power. When the contribution of improvements in video compression is added, an HDTV service can now be delivered in the same bandwidth that supported an early DVB-S based MPEG-2 SDTV service only a decade before. In March 2014, DVB-S2X specification has been published by DVB Project as an optional extension adding further improvements. Direct input of one or more MPEG-2 Transport Streams. MPEG-TS is supported using a compatibility mode; the native stream format for DVB-S2 is called Generic Stream, can be used to efficiently carry IP-based data, including MPEG-4 AVC/H.264 services.
Backward compatibility to DVB-S, intended for end users, DVB-DSNG, used for backhauls and electronic news gathering. Variable coding and modulation to optimize bandwidth utilization based on the priority of the input data. Adaptive coding and modulation to allow flexibly adapting transmission parameters to the reception conditions of terminals, e.g. switching to a lower code rate during fading. Four modulation modes: QPSK and 8PSK are proposed for broadcast applications, can be used in non-linear transponders driven near to saturation. 16APSK and 32APSK are used for professional, semi-linear applications, but can be used for broadcasting though they require a higher level of available C/N and an adoption of advanced pre-distortion methods in the uplink station in order to minimize the effect of transponder nonlinearity. Improved rolloff: α = 0.20 and α = 0.25 in addition to the roll-off of DVB-S α = 0.35. Improved coding: a modern large LDPC code is concatenated with an outer BCH code to achieve quasi-error-free reception conditions on an AWGN channel.
The outer code is introduced to avoid error floors at low bit-error rates. A single forward error correction or FEC frame may have 16,200 bits. If VCM or ACM is used, the broadcast can be a combination of short frames. Several code rates for flexible configuration of transmission parameters: 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6, 6/7, 8/9, 9/10. Code rates 1/4, 1/3, 2/5 have been introduced for exceptionally poor reception conditions in combination with QPSK modulation. Encoding values 9/10 behave poorly under marginal link conditions. However, with targeted spot Ku or Ka band downlinks these code rates may be recommended to prevent out-of-region viewing for copyright or cultural reasons. Optional input stream synchronization to provide a constant end-to-end delay. Depending on code rate and modulation, the system can operate at a C/N between −2.4 dB and 16 dB with a quasi-error free goal of a 10−7 TS packet error rate. Distance to the Shannon limit ranges from 0.7 dB to 1.2 dB. Modes and features of DVB-S2 in comparison to DVB-S: Envisaged scenarios for DVB-S2 by the standard document are: Broadcasting television services in SDTV or HDTV.
Optionally, this transmission may be backwards compatible with DVB-S, but does not benefit from the 30% extra bandwidth. Interactive services including Internet access. Data generated by the user may be sent by mobile wireless, or satellite uplink. Professional applications, where data must be multiplexed in real time and broadcast in the VHF/UHF band; these transmissions are not intended for the average viewer. Large-scale data content distribution; these include point-to-point and multicast services, as well as transmission to head-ends for distribution over other media. The conversion process from DVB-S to DVB-S2 is being accelerated, due to the rapid increase of HDTV and introduction of 3D-HDTV; the main factor slowing down this process is the need to replace or upgrade set-top boxes, or acquire TVs with DVB-S2 integrated tuners, which makes the transition slower for established operators. Cu