Digital Audio Broadcasting (DAB) is a digital radio technology used in several countries for broadcasting radio stations. Particularly used in Europe, the DAB standard was initiated as a European research project and was launched by BBC in 1995. Since then, DAB receivers have been made available in many countries.
Digital Radio Mondiale (DRM) is a group of digital audio broadcasting technologies that were designed to work over shortwave bands used for AM broadcasting. DRM is the only open standard digital system for different bands below 30 MHz that uses existing frequencies and bandwidth across the globe. However, the DRM consortium plans to extend the system to bands up to 120 MHz.
AM and FM radio stations use iBiquity’s in-band on-channel (IBOC) digital radio technology to transmit audio and data through a digital signal in conjunction with their analog signals. HD Radio is the trademark for this technology.
HD Radio was selected as the digital audio broadcasting method for the US by the Federal Communications Commission (FCC) in 2002. Officially known as NRSC-5 (NRSC-5B), it is the only digital system to be approved by the FCC for digital AM/FM broadcasts in the US.
In-band on-channel (IBOC) transmits digital radio and analog radio broadcast signals simultaneously on the same frequency. The method uses additional subcarriers or sidebands to piggyback the digital information on a normal AM or FM analog signal. This eliminates any complicated extra frequency allocation issues.
IBOC allows for multiple program channels though this involves making additional bandwidth available in the modulation baseband. This involves removal of stereo on FM.