Digital radio

Digital radio is the use of digital technology to transmit or receive across the radio spectrum. Digital transmission by radio waves includes digital broadcasting, and especially digital audio radio services. This should not be confused with Internet radio which also is digital but not transmitted by radio waves in the radio spectrum.

In digital broadcasting systems, the analog audio signal is digitized, compressed using an audio coding format such as AAC+ (MDCT) or MP2, and transmitted using a digital modulation scheme. The aim is to increase the number of radio programs in a given spectrum, to improve the audio quality, to eliminate fading problems in mobile environments, to allow additional datacasting services, and to decrease the transmission power or the number of transmitters required to cover a region. However, analog radio (AM and FM) is still more popular and listening to radio over IP (Internet Protocol) is growing in popularity.

In 2012, four digital wireless radio systems are recognized by the International Telecommunication Union: the two European systems Digital Audio Broadcasting (DAB) and Digital Radio Mondiale (DRM), the Japanese ISDB-T and the in-band on-channel technique used in the US and Arab world and branded as HD Radio. - 5G Broadcast is a joint digital terrestrial broadcasting platform for radio and television under development in the UHF band being tested in 20 countries (2025) for more than five years.

An older definition, still used in communication engineering literature, is wireless digital transmission technologies, i.e. microwave and radio frequency communication standards where analog information signals as well as digital data are carried by a digital signal, by means of a digital modulation method. This definition includes broadcasting systems such as digital TV and digital radio broadcasting, but also two-way digital radio standards such as the second generation (2G) cell-phones and later, short-range communication such as digital cordless phones, wireless computer networks, digital micro-wave radio links, deep space communication systems such as communications to and from the two Voyager space probes, etc.

Digital audio radio service standards may provide terrestrial or satellite radio service. Digital radio broadcasting systems are typically designed for handheld mobile devices, like mobile-TV systems and unlike other digital TV systems which typically require a fixed directional antenna. Some digital radio systems provide in-band on-channel (IBOC) solutions that may coexist with or simulcast with analog AM or FM transmissions, while others are designed for designated radio frequency bands. The latter allows one wideband radio signal to carry a multiplex of several radio-channels of various bitrates as well as data services and other forms of media. Some digital broadcasting systems allow single-frequency network (SFN), where all terrestrial transmitters in a region sending the same multiplex of radio programs may use the same frequency channel without self-interference problems, further improving the system spectral efficiency.

While digital broadcasting offers many potential benefits, its introduction has been hindered by a lack of global agreement on standards and many disadvantages. The DAB Eureka 147 standard for digital radio is coordinated by the World DMB Forum. This standard of digital radio technology was defined in the late 1980s, and is now being introduced in some European countries. Commercial DAB receivers began to be sold in 1998 and, by 2006, 500 million people were in the coverage area of DAB broadcasts, although by this time sales had only taken off in the UK and Denmark. In 2006 there are approximately 1,000 DAB stations in operation. There have been criticisms of the Eureka 147 standard and so a new 'DAB+' standard has been introduced.

The DRM standard has been used for several years to broadcast digitally on frequencies below 30 MHz (shortwave, mediumwave and longwave). Also there is now the extended standard DRM+, which is designed for VHF bands. Tests of DRM+ has been made in countries such as in Brazil, Germany, France, India, Sri Lanka, the UK, Slovakia, Italy (incl. the Vatican), as well as Sweden.

The two pan-European associations for community radio Community Media Forum Europe (CMFE) and AMARC Europe have stated to the European Commission that FM radio should be retained for local radio. In case of a future digital transition DRM+ would be the choice.