DVB

Digital Video Broadcasting, the group, with over 200 members in 25 countries, which developed the preferred scheme for digital broadcasting in Europe. Initially the DVB Group put together a portfolio of broadcast standards; the major ones including a satellite system, DVB-S, and now the more efficient DVB-S2, a matching cable system, DVB-C (and now DVB-C2), and a digital terrestrial system, DVB-T (and now DVB-T2). DVB-H is a newer broadcast standard designed for terrestrial operation with hand-held devices, typically mobile TVs, phones and tablets where power must be conserved.

DVB-S (1995) is the original DVB forward error coding and modulation standard for satellite television. DVB-S is used for both broadcast network feeds and for direct broadcast satellite services.

DVB-S2 (2003) is used for all new European digital satellite multiplexes, and satellite receivers will be equipped to decode both DVB-S and DVB-S2. Currently its main use is to distribute HDTV. DVB-S2 is based on DVB-S adding two key features: allowing changing encoding parameters in realtime (VCM, Variable Coding and Modulation) and ACM (Adaptive Coding and Modulation) to optimize the transmission parameters for various users for a claimed net performance gain of 30 percent (ie, more data transmitted for more channels).

DVB-T is a transmission scheme for digital terrestrial television (DTT). Its specification was approved by ETSI in February 1997 and DVB-T services started in the UK in autumn 1998.
As with the other DVB standards, MPEG-2 sound and vision coding are used. It uses Coded Orthogonal Frequency Division Multiplexing (COFDM) modulation. It enables effective operation in very strong multipath environments (that cause picture ‘ghosting’ in analog TV reception), meaning in can operate an overlapping network of transmitting stations using the same frequency. In the areas of overlap, the weaker received signals are rejected. Where transmitters carry the same programming the overlapping signals provide more reliable reception, known as a single-frequency network (SFN).

DVB-T2 (2009). The DVB TM-T2 technical group worked on a more advanced DTT standard focusing on modulation, channel encryption and signal layout. The resulting DVB-T2 offers a 50 percent increase in payload capacity under similar reception circumstances. Its error correction coding, shared with DVB-S2 and DVB-C2, involves LDPC (Low Density Parity Check) coding combined with BCH (Bose-Chaudhuri-Hocquengham) coding, offering a very robust signal. Along with other changes it is more flexible, supporting SD, HD, UHD, mobile TV, radio, or any combination thereof.

DVB-C (1994) for digital transmission via cable transmits an MPEG-2 or MPEG-4 family digital audio/digital video stream, using a QAM modulation with channel coding.

DVB-C2 (2010) almost doubles the payload so relieving the many cable networks that were running at near capacity.

The DVB digital TV standards are used around the world with notable exceptions being ATSC in the USA and Canada, ISDB in Japan, DMB-T/H (Digital Multimedia Broadcast-Terrestrial/ Handheld) in China, and T-DMB in South Korea.

There are several additional DVB transmission standards that can be found on the website. These include DVB-RCS2 that provides an air interface specification for low-cost two-way satellite broadband VSAT (very small aperture terminal) systems to provide dynamic, demand-assigned transmission capacity for a wide range of users. It provides a broadband Internet connection with no need of local terrestrial infrastructure. Data speeds of several tens of Mb/s down to terminals, and up to 10 Mb/s or more can be achieved.

DVB-CPCM DVB Content Protection and Copy Management is a digital rights management standard which is under development. This is intended as a practical rights management system primarily for European digital television; but other countries may adopt it.

CPCM allows adding information to digital content, such as TV programs, that shows how content may be used by other CPCM-enabled devices. Content providers can store flags with the content to indicate how it may be used. All CPCM-enabled devices should obey these flags, allowing or denying its movement, copying to other CPCM devices, controlling use on other equipment, and observing time limits.

The full technical specification of DVB-CPCM is available for free downloading at the DVB website.

Website: www.dvb.org

See also: COFDM, IP, IP over DVB