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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 on 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, 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.

Portable DAB/DAB+ and FM receiver, circa 2016. This unit requires two "AA" size batteries. (Headphones not shown).

As DAB requires digital signal processing techniques to convert from the received digitally encoded signal to the analogue audio content, the complexity of the electronic circuitry required to do this is higher. This translates into needing more power to effect this conversion than compared to an analogue FM to audio conversion, meaning that portable receiving equipment will have a much shorter battery life, and require higher power (and hence more bulk). This means that they use more energy than analogue Band II VHF receivers. However, thanks to increased integration (radio-on-chip), DAB receiver power usage has been reduced dramatically, making portable receivers far more usable.

FM radio switch-off

Norway

Band II VHF receivers. However, thanks to increased integration (radio-on-chip), DAB receiver power usage has been reduced dramatically, making portable receivers far more usable.

FM radio switch-off

Norway

Norway was the first country to announce a complete switch-off of national FM radio stations. The switch-off started on 11 January 2017 and ended on 13 December 2017.[24][25] The 2017 switch-off did not affect some local and regional radio stations. They can continue to transmit on FM until 2027.

The timetable for the closure of FM signals in 2017 was as follows:[26]