Digital radio is the technology in which sound is processed and transmitted as a stream of binary digits. In case of AM/FM broadcast, the radio quality suffers from interference caused by signals bouncing off walls, buildings, hills, and other structures, while digital radio system offers improved sound quality at low bit rates by using the latest digital compression technologies. At the transmitting site, the signal is compressed using MPEG algorithms, and modulated using coded orthogonal frequency division multiplexing (COFDM).
Digital radio system allows efficient use of allocated frequency as multiple radio channels can be broadcast on a single frequency. Value-added services such as electronic program guide, emergency warning feature (EWF), updates on news and weather, and more, can easily be provided simultaneously along with the program.
Digital radios are also easier to tune – instead of fiddling with a dial to find the strongest frequency for a station, listeners choose a station by name from a menu, with the digital radio automatically locking on to the appropriate frequency. Some digital radios come with on-board storage, allowing listener to pause and rewind live radio.
In the present analogue broadcast systems, the world-wide standardisation on just two systems (FM and AM) is available, which enables listeners to use one radio to receive programs at any location. But in the development of digital systems, similar standardization could not be achieved, and countries around the world have chosen different standards through rigorous trials and examining the suitability of the digital radio technology to meet regional and application-oriented needs. Accordingly, the listener needs to purchase a radio receiver supporting specific digital radio standard being adopted in the country/region.
DAB+ is one of the most-widely adopted digital-radio standard worldwide, on-air in more than 40 countries. During 1980s, DAB was introduced as a research project in Europe, and was gradually adopted by different standardization bodies, such as ITU and ETSI. The first country to broadcast a range of radio station through DAB was United Kingdom. It is based on the MPEG-1 Audio Layer II audio coding format. In February 2007, DAB+ standard was introduced as an upgraded version of DAB.
The DAB+ standard adopted the HE-AAC version 2 audio codec, which is three times more efficient audio-compression technique than MP2. This enhanced the received audio quality with the increase in number of available stations. DAB+ is not backwards compatible with DAB so older radios cannot receive DAB+ stations. DAB+ uses a wide-bandwidth broadcast technology and typically spectra have been allocated for it in Band III (174–240 MHz) and L band (1.452–1.492 GHz).
In Europe, DAB+ is firmly established as the core future platform for radio. Outside Europe, the key areas of development are currently in Australia, South-East Asia, Korea, China, the Middle East, and South Africa.
DAB+ broadcasts have launched in several countries like Australia, Czech Republic, Denmark, Germany, Italy, Malta, Norway, Poland, Switzerland, Belgium, the United Kingdom, and the Netherlands. In December 2017, Norway became the first country to completely switch off national FM services, and adopted DAB+ digital radio standard; however local radio channels are still operating in FM mode.
WorldDAB has announced that its most recent market report shows more than 75 million consumer and automotive DAB/DAB+ receivers sold in Europe and Asia-Pacific at the end of 4Q2018. Higher the frequency the smaller is the range of coverage. DAB+ operates in VHF Band III (174–240 MHz), and L band while the FM broadcast in VHF Band II (87.5–108 MHz). Hence, smaller the coverage, the greater number of transmitters needed for coverage. No country has so far set a date for a complete switch-off of FM. Norway is still the only country closing down FM for national networks. Cost of replacing radio devices with digital radio receivers might be a concern for developing nations. Therefore, FM is likely to remain as part of a hybrid future and will operate alongside DAB+ and the internet. It is very much essential to study the pros and cons before adopting any digital radio technology.