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The DVB Project
The DVB project was set up in 1993 and came from a market led perception that digital broadcasting to the home needed technical standards of transmission to avoid the anarchy of proprietry boxes which has developed in analogue satellite transmission. However, the DVB is not itself a standards making body; it provides a forum for suppliers to agree specifications which are then passed to existing standards making bodies (ETSI, ISO) for ratification. DVB is market led, so that so called 'commercial modules' pass requirements to 'technical modules' and not the other way around.
An early decision was not to 'reinvent the wheel.' So MPEG2 was readily adopted. But the use of MPEG2 alone will not make services interoperable; modulation, multiplexing, service information and conditional access, all needed defining. It was felt fundamental that all methods of distribution should be considered. Initially, the group considered itself to be European, but the interest in adopting its specifications has meant that the work has become truly international and "European" has been dropped from the title.
The first achievement in December 1993 was a specification for digital satellite broadcasting using QPSK modulation. This was closely followed by specification for digital cable transmission using 64QAM in January 1994. Further specifications for service information, a common scrambling system, a code of conduct for Conditional access suppliers have followed. The group recognised that interactive data services were predicted to grow to over $40billion p.a. by the millenium and this need has been reflected in all the specifications.
In terms of digital terrestrial broadcasting, the DVB opted to support OFDM, rather than single carrier, because of the very dense relay population in Europe. Also it was felt that high definition was not the strong driver that it had been in the USA. However, the scheme does allow for a future upgrade to include HDTV. The group considered the number of carriers in the OFDM transmission and opted to make this a user specified parameter, allowing for an early implementation at 2,000 carriers, with the possibility to increase to 8,000 when technology and commercial considerations allowed. The requirement for flexibility in frequency planning and the possibility to trade data-rate against coverage, was built in by requiring different forms of modulation (QPSK, 16QAM and 64QAM) and different code rates to be implemented in the receiver. The DVB spec was agreed in December 1995 and achieved ETSI approval in April 1996.
Although, initially, terrestrial transmission was primarily led by the UK, other European countries have shown considerable interest and a European-wide interest group, DIGITAG, was established at the 1996 IBC Conference to develop and harmonise digital terrestrial television internationally.