DAB

Digital Broadcasting Today
The world of digital broadcasting is not static - it demands flexibility and adaptability to meet the demands of the ever more rapid digital development, spectrum efficiency, new applications and device features. WorldDMB is at the forefront of these changes with its ever growing family of standards based on DAB (Digital Audio Broadcasting).

WorldDMB's three most well-known standards are the original digital radio standard DAB, the recently developed additional radio standard DAB+ and the multimedia/video standard DMB. Over 500 million people around the world can now receive over 1000 different DAB/DAB+/DMB services. Commercial DAB receivers have been on the market since summer 1998. There are now over 1000 different DAB receivers commercially available. There are also over 190 different DMB receivers in the market, which of course can also receive DAB services. DAB+ receivers have also recently entered the market and with the quick take up of the standard throughout the world the number is expected to increase in the next year.

DAB, DAB+ and DMB
When the original DAB (Digital Audio Broadcasting) was first developed in the late 1980s, it was based on MPEG Audio Layer II coding, which was then state of the art and is still a commonly used coding technology in radio nowadays.

Since then, MPEG Audio Layer III, better known as MP3 has conquered the market of digital music players and radio streams. Even though still the most successful technology on the market, MP3 has already been overtaken in efficiency and performance by MPEG-4 (AAC). This development called for an additional audio coding system in DAB which would allow for more efficiency at lower bitrates - hence the birth of DAB+.

Another important innovation was the addition of video/multimedia capabilities to Digital Audio Broadcasting, allowing DAB to become a digital mobile television platform DMB (Digital Multimedia Broadcasting) as well as a multimedia digital radio platform.

Both for DMB and DAB+ the technical basis remains to be DAB. In other words, the physical layer is still the same, just new applications, new transport protocols and a second error control coding layer was added. All three technologies can therefore be used alongside each other on one multiplex and basically use the same infrastructure, so there is a whole range of possible multiplex scenarios.

Benefits of DAB, DAB+ and DMB
Easy programme selection
Rather than searching wavebands as present, users can select all available stations or preferred formats from a simple text menu.
Perfect reception
DAB eliminates interference and the problem of multipath while in a car. It "blankets" wide geographical areas with an even, uninterrupted signal. Once full services are up and running, a driver will be able to cross an entire country staying tuned to the same station with no signal fade, without altering frequency.
One receiver does it all!
DAB is quite unique in that both music and data services can be received using the same receivers. Furthermore DMB receivers also can receive these music and data services as well as video and graphics.
Programme-associated data
DAB/DAB+/DMB broadcasts can display text information in far greater details than the RDS system, such as programme background facts, a menu of future broadcasts and complementary advertising information. Broadcasters can also display picture radio and other interactive services. Receivers that are attached to a small screen, can display visual information as diverse as weather maps, CD information, traffic and safety information, stock updates and mobile TV.
Information services
Services from sources other than the broadcasting station are included within the same channel for the user to access at will. These include news headlines, detailed weather information or even the latest stock prices.
Targeted music or data services
Because digital technology allows a massive amount of different information, specific information user groups can be targeted with great accuracy because each receiver can be addressable.
Wide choice of receivers
It is possible to access DAB/DMB services on a wide range of receiving equipment including fixed, mobile and portable radio receivers with displays or screens including personal computers and some mobile phones. Other types of receivers also include: USB, digital cameras, PDAs, MP3 players, pocket TVs, in car radios and TV screens and many more.
DAB: A system designed for terrestrial mobile reception
DAB services are available on terrestrial networks, and the same receiver can be used to provide radio programmes and/or data services for national, regional, local and international coverage. The DAB system requirers a low field strength, which allows the technology to much more mobile than other standards.
Lower transmission costs for broadcasters
DAB/DAB+/DMB allows broadcasters to provide a wide range of material simultaneously on the same frequency. This not only makes room for a vastly increased number of programmes to increase user choice, but also has important broadcast cost-cutting implications.

tomado de: http://www.worlddab.org/technology