What is DVB-T2?
DVB-T2 is the world’s most advanced digital terrestrial transmission system offering higher efficiency, robustness and
flexibility. It introduces the latest modulation and coding techniques to enable highly efficient use of valuable terrestrial
spectrum for the delivery of audio, video and data services to fixed, portable and mobile devices. These new techniques
give DVB-T2 a 50% increase in efficiency over any other DTT system in the world. DVB-T2 is not designed to replace
DVB-T in the short to medium term; rather the two standards will coexist in for many years.
The most widely adopted and deployed standard for Digital Terrestrial Television (DTT) is DVB-T, published in March
1997. Services are on air in more than 40 countries with many more set to launch in the coming years. A mature and wellestablished
standard, it benefits from economies of scale that lead to very low receiver prices and is flexible enough to enable a wide range of business models. (See separate DVB-T Fact Sheet.) Nonetheless, the approach of ASO (Analogue Switch-Off) in Europe and other developed DTT markets generated an impetus to update the standard, as had already
been achieved with DVB-S2 for satellite broadcasting. There will be many competing demands for the spectrum that
will be released at ASO. With DVB-T2 the DVB Project offers broadcasters a means of using that spectrum in the most efficient ways possible using state-of-the-art technology.
As with all DVB standards, the final specification is based on a carefully considered set of Commercial Requirements.
Key requirements included an increase in capacity and improved robustness. The new standard was also required to be able to reuse currently existing receive antennas and downlinks.
The DVB-T2 specification was approved by the DVB Steering Board and published as a DVB BlueBook in the Summer of 2008. Work on the validation and verification of the new standard has continued within DVB and successful interoperability
plug fests have been held in Turin in March 2009 and in Berlin in June 2010. The formal DVB-T2 specification was
published by ETSI (European Telecommunications Standards Institute) in September 2009 (EN 302 755).
How does it work?
As with its predecessor, DVB-T2 uses OFDM (orthogonal frequency division multiplex) modulation, with a large number of
sub-carriers delivering a robust signal. Also in common with DVB-T, the new specification offers a range of different modes
making it a very flexible standard. In the realm of error correction, DVB-T2 uses the same coding that was selected for DVB-S2 and DVB-C2. LDPC (Low Density Parity Check) coding combined with BCH (Bose-Chaudhuri-Hocquengham)
coding offers excellent performance in the presence of high noise levels and interference, resulting in a very robust signal. Several options are available in areas such as the number of carriers, guard interval sizes and pilot signals, so that the overheads can be minimised for any target transmission channel. A new technique, called Rotated Constellations, provides significant additional robustness in difficult channels. Also, a Multi-PLP (Physical Layer Pipes) mechanism is provided to separately adjust the robustness of each delivered service within a channel to meet the required reception conditions (e.g. in-door antenna/roof-top antenna). This flexible mechanism also allows transmissions to be tailored such that a receiver can save power by decoding only a single service rather than the whole multiplex of services.
How does it work (cont’d)
DVB-T2 also specifies a transmitter diversity method, known as Alamouti coding, which improves coverage in small-scale single-frequency networks. Finally, DVB-T2 has defined a way that the standard can be compatibly enhanced in the future
through the use of Future Extension Frames. Compared to DVB-T, DVB-T2 can offer a much higher data rate or a much more robust signal. For example, in the UK a DVB-T channel typically has a data rate of 24 Mbit/s, whereas a DVB-T2 channel can carry 36 Mbit/s, while keeping the robustness equal
Next Steps for DVB-T2
Italy has seen a recent launch of DVB-T2 for pay-TV services. Early 2011, Sweden and Finland will start their DVB-T2
HD services, which will eventually be nationwide. Advanced trials are currently also taking place in Austria, Denmark, the
Czech Republic and Germany. With the positive results of the UK launch, more and more other countries are considering
the launching of services using DVB-T2 in the near future. Outside Europe, the first countries that are considering DVBT2
are Australia and Singapore. With its market proven technology and falling prices, DVB-T2 is even being considered
by green-field areas (without pre-existing digital TV networks) such as developing countries.