This system transmits compressed digital audio, video, and other data in "physical layer pipes" (PLPs), using OFDM modulation with concatenated channel coding and interleaving. The higher offered bit rate, with respect to its predecessor DVB-T, makes it a suited system for carrying HDTV signals on the terrestrial TV channel (though many broadcasters still use plain DVB-T for this purpose).
It is currently broadcasting in the United Kingdom (Freeview HD, four channels, plus an extra multiplex in Northern Ireland carrying 3 SD channels), Italy (Europa 7 HD, twelve channels), Finland (21 channels, 5 in HD), Sweden (five channels), Serbia (10 SD and HD version of the public broadcaster’s channel RTS), Ukraine (32 SD and HD channels in four nationwide multiplexes), Denmark and some other countries.
Preliminary investigationIn March 2006 DVB decided to study options for an upgraded DVB-T standard. In June 2006, a formal study group named TM-T2 (Technical Module on Next Generation DVB-T) 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 (fixed) and portable receivers (i.e., units which can be nomadic, but not fully mobile) using existing aerials, whereas a second and third phase would study methods to deliver higher payloads (with new aerials) and the mobile reception issue. The novel system should provide a minimum 30% increase in payload, under similar channel conditions already used for DVB-T.
The BBC, ITV, Channel 4 and Channel 5 agreed with the regulator Ofcom to convert one UK multiplex (B, or PSB3) 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 (with existing switched over regions being changed at the same time). It was expected that over time there would be enough DVB-T2 receivers sold to switch all DTT transmissions to DVB-T2, and H.264.
Ofcom published its final decision on April 3, 2008, for HDTV using DVB-T2 and H.264: BBC HD would have one HD slot after digital switchover (DSO) 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 specification
The DVB-T2 draft standard was ratified by the DVB Steering Board on June 26, 2008, and published on the DVB homepage as DVB-T2 standard BlueBook,. It was handed over to the European Telecommunications Standards Institute (ETSI) by DVB.ORG on June 20, 2008. The ETSI process resulted in the DVB-T2 standard being adopted on September 9, 2009. The ETSI process had several phases, but the only changes were text clarifications. Since the DVB-T2 physical layer specification was complete, and there would be no further technical enhancements, receiver VLSI chip design started with confidence in stability of specification. A draft PSI/SI (program and system information) specification document was also agreed with the DVB-TM-GBS group.
TestsPrototype 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, Arqiva, DekTec, Enensys Technologies, Harris, Pace, Rohde & Schwarz, Tandberg, Thomson Broadcast and TeamCast. Other manufacturers planning DVB-T2 equipment launches include Alitronika, CellMetric, Cisco, Digital TV Labs, Humax, NXP Semiconductors, Panasonic, 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 (processor) based decoding.
NORDIG published a DVB-T2 receiver specification and performance requirement on the July 1, 2009. In March 2009 the Digital TV Group (DTG), the industry association for digital TV in the UK, published the technical specification for high definition services on digital terrestrial television (Freeview) 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, strength,and quality reception, with special PCs used as spectrum analysers, constellation testers. The van was moving in Canton Geneva (Switzerland), and France (Annemasse,Pays de Gex). However, there was none demonstrated in TELECOM 2011 at Palexpo.
The following characteristics have been devised for the T2 standard:
- COFDM modulation with QPSK, 16-QAM, 64-QAM, or 256-QAM constellations.
- OFDM modes are 1k, 2k, 4k, 8k, 16k, and 32k. The symbol length for 32k mode is about 4 ms.
- Guard intervals are 1/128, 1/32, 1/16, 19/256, 1/8, 19/128, and 1/4. (For 32k mode, the maximum is 1/8.)
- FEC is concatenated LDPC and BCH codes (as in DVB-S2 and DVB-C2), with rates 1/2, 3/5, 2/3, 3/4, 4/5, and 5/6.
- There are fewer pilots, in 8 different pilot-patterns, and equalization can be based also on the RAI CD3 system.
- In the 32k mode, a larger part of the standard 8 MHz channel can be used, adding about 2% extra capacity.
- DVB-T2 is specified for 1.7, 5, 6, 7, 8, and 10 MHz channel bandwidth.
- MISO (Multiple-Input Single-Output) may be used (Alamouti scheme), but MIMO will not be used. Diversity receivers can be used (as they are with DVB-T).
- Multiple PLP to enable service specific robustness.
- Bundling of more channels into a SuperMUX (called TFS) is not in the standard, but may be added later.