Digital Radio Mondiale (DRM) is an international non-profit consortium committed to designing an open platform for digital radio broadcasting around the world, especially on shortwave.
The main advantage of such digital broadcasting is that it yields sound quality comparable to FM, but over short wave distances. As a digital medium, DRM can also transmit other digital data besides digitized music, including text, pictures and computer programs. DRM has been designed expecially to use older transmitters designed for audio AM, so major new investments are not required for early transmissions. The encoding and decoding can be performed with digital signal processing, so that small computers added to a conventional transmitter and receiver can perform the rather complex encoding and decoding.
The organisation has recently received approval for the AM standard from the IEC, and the ITU has approved its use in most of the world. (Approval for the Americas is pending amendments to other existing international agreements.) Its inaugural broadcast was held in 2003, on June 16th in Geneva, Switzerland, at the ITU's annual World Radio Conference.
Unlike the PAC compression algorithm currently used by iBiquity's IBOC system in the U.S, DRM's system uses MPEG-4 to code the audio. The resulting low-bitrate digital information is modulated using COFDM, similar to iBiquity's signal. Both systems can run in hybrid mode, with both analogue and digital, or in all-digital mode. iBiquity has been tested only on mediumwave AM with 10kHz channel spacing, however DRM has also been tested successfully on shortwave and longwave, and with 9kHz channel spacing as well.
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External links
DRM in generel
DRM radio techniques
DRM radio techniques digital decoding
DRM's COFDM
Index