Digital Audio Broadcasting - Big Picture

Digital Audio Broadcasting (DAB) is a digital radio standard for broadcasting digital audio radio services in many countries around the world but not in North America where HD Radio is the standard for digital radio.

The DAB standard was initiated as a European research project in the 1980s.`{`1`}` The Norwegian Broadcasting Corporation (NRK) launched the first DAB channel in the world on 1 June 1995 (NRK Klassisk),`{`2`}` and the BBC and Swedish Radio (SR) launched their first DAB digital radio broadcasts in 27 September 1995. DAB receivers have been available in many countries since the end of the 1990s.

DAB is generally more efficient in its use of spectrum than analogue FM radio,`{`3`}` and thus can offer more radio services for the same given bandwidth. The sound quality can be noticeably inferior if the bit-rate allocated to each audio program is not sufficient. DAB is more robust with regard to noise and multipath fading for mobile listening,`{`4`}` although DAB reception quality degrades rapidly when the signal strength falls below a critical threshold, whereas FM reception quality degrades slowly with the decreasing signal, providing effective coverage over a larger area.

The original version of DAB used the MP2 audio codec. An upgraded version of the system was released in February 2007, called DAB+, which uses the modified discrete cosine transform (MDCT) based HE-AAC v2 (AAC+) audio codec. DAB is not forward compatible with DAB+, which means that DAB-only receivers are not able to receive DAB+ broadcasts.`{`5`}` However, broadcasters can mix DAB and DAB+ programs inside the same transmission and so make a progressive transition to DAB+. DAB+ is approximately twice as efficient as DAB, and more robust.

In spectrum management, the bands that are allocated for public DAB services, are abbreviated with T-DAB, As of 2018, 41 countries are running DAB services.`{`6`}` The majority of these services are using DAB+, with only Ireland, UK, New Zealand, Romania and Brunei still using a significant number of DAB services. See Countries using DAB/DMB. In many countries, it is expected that existing FM services will switch over to DAB+. Norway is the first country to implement a national FM radio analog switchoff, in 2017, however that only applied to national broadcasters, not local ones.

From: https://en.wikipedia.org/wiki/Digital_Audio_Broadcasting#DAB+

The term ``DAB`` most commonly refers both to a specific DAB standard using the MP2 audio codec, but can sometimes refer to a whole family of DAB-related standards, such as DAB+, DMB and DAB-IP.

WorldDAB, the organisation in charge of the DAB standards, announced DAB+, a major upgrade to the DAB standard in 2006, when the HE-AAC v2 audio codec`{`11`}` (also known as eAAC+) was adopted. AAC+ uses a modified discrete cosine transform (MDCT) algorithm.`{`7`}``{`8`}` The new standard, which is called DAB+, has also adopted the MPEG Surround audio format and stronger error correction coding in the form of Reed-Solomon coding. DAB+ has been standardised as European Telecommunications Standards Institute (ETSI) TS 102 563.

As DAB is not forward compatible with DAB+, older DAB receivers cannot receive DAB+ broadcasts. However, DAB receivers that will be able to receive the new DAB+ standard via a firmware upgrade went on sale in July 2007. If a receiver is DAB+ compatible, there will be a sign on the product packaging.

DAB+ broadcasts have launched in several countries like Australia, Czech Republic, Denmark, Germany, Hong Kong (now terminated), Italy, Malta, Norway, Poland, Switzerland, Belgium (October 2017),`{`12`}` the United Kingdom and the Netherlands. Malta was the first country to launch DAB+ in Europe. Several other countries are also expected to launch DAB+ broadcasts over the next few years, such as Austria, Hungary, Thailand, Vietnam and Indonesia. South Africa began a DAB+ technical pilot in November 2014 on channel 13F in Band 3. If DAB+ stations launch in established DAB countries, they can transmit alongside existing DAB stations that use the older MPEG-1 Audio Layer II audio format, and most existing DAB stations are expected to continue broadcasting until the vast majority of receivers support DAB+.`{`13`}`

Ofcom in the UK published a consultation for a new national multiplex containing a mix of DAB and DAB+ services, with the intention of moving all services to DAB+ in the long term.`{`14`}` In February 2016, the new national network Sound Digital launched with three DAB+ stations.`{`15`}`

From: https://en.wikipedia.org/wiki/Digital_Audio_Broadcasting#DAB+_2