Digital Radio Mondiale
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Digital Radio Mondiale (DRM) is an international non-profit consortium committed to designing an implementing an open-source platform for digital radio broadcasting around the world, especially on shortwave. Unlike most other DAB systems, DRM uses IBOC technology and can operate in a hybrid mode called Single Channel Simulcast, simulcasting both analogue and digital. Unlike fellow IBOC system HD Radio, it also requires no royalties for patents, and works far better on AM.
The main advantage of such digital broadcasting is that it yields sound quality comparable to FM, but over shortwave distances. As a digital medium, DRM can also transmit other digital data besides digitized music, including text, pictures, and computer programs (datacasting) — as well as RDS-type metadata or program-associated data like DAB does. DRM has been designed especially 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 (ITU region 2) is pending amendments to other existing international agreements. The inaugural broadcast took place on June 16, 2003, in Geneva, Switzerland, at the ITU's annual World Radio Conference.
DRM's system uses the MPEG-4 based standard aacPlus to code the music and CELP or HVXC for speech programs. All codecs can optionally be combined with SBR. The resulting low-bitrate digital information is modulated using COFDM. It can run in simulcast mode by switching between DRM and AM, and it is also prepared for linking to other alternatives (e.g. DAB or FM services). DRM has been tested successfully on shortwave, mediumwave (with 9 as well as 10 kHz channel spacing) and longwave.
External links
DRM in general
- Digital Radio Mondiale (DRM) - official homepage (http://www.drm.org/)
- hard-core-dx: Latest news on DRM (http://www.hard-core-dx.com/index.php?topic=drm)
- (pdf) DRM - progress on the receiver front (http://www.ebu.ch/trev_293-jackson.pdf)
- A Listeners' Guide to Digital AM (DRM) (http://www.rnw.nl/realradio/html/drm.html)
- DRM - Digital Radio Mondiale - Digital AM radio below 30MHz (http://www.aoruk.com/drm.htm)
- Kortbølge stationsdatabase kan downloades efter registrering (tager nogle dage): The World Top Shortwave Broadcasting Database (http://www.ilgradio.com/ilgradio.htm): "This ILGRadio Database is now in use by more than 23 000 listeners, living in 139 countries all over the world!"
DRM radio stations
- biteXpress, a German experimental radio station broadcasting in DRM. (http://www.bitexpress.de/) (Available also as live stream.)
- Passion Radio, a radio station based in Sussex, UK trialling a DRM Broadcast. (http://www.passionradio.co.uk/) (Available also as live stream.)
DRM radio techniques
- Welcome to the DRM Software Radio website (http://www.drmrx.org/)
- DRM Receiver Modifications (http://www.drmrx.org/receiver_mods.html)
- "bird-nest" DRM receiver (http://www.drmrx.org/mods/Simple_fixed_channel_DRM-v2.pdf)
- Dream - an open-source software DRM Receiver (http://drm.sourceforge.net)
DRM's COFDM
- Explaining some of the magic of COFDM, J H Stott (BBC) (http://www.bbc.co.uk/rd/pubs/papers/paper_15/paper_15.html): "COFDM is particularly well matched to these applications, since it is very tolerant of the effects of multipath."
- Coded Orthogonal Frequency Division Multiplexing (COFDM) (http://www.digitalradiotech.co.uk/cofdm.htm)
- All About OFDM from SSS Online and Pegasus Technologies (http://www.sss-mag.com/ofdm.html)
- OFDM, VOFDM, COFDM, Orthogonal Frequency Division Multiplexing: tutorials (http://www.palowireless.com/ofdm/tutorials.asp)
- OFDM, VOFDM, COFDM, Orthogonal Frequency Division Multiplexing: resources (http://www.palowireless.com/ofdm/resources.asp)
- COFDM/8-VSB Controversy Archive & Links (http://www.digitaltelevision.com/cofdm/)
Index
- dmoz: Digital Broadcasting (http://dmoz.org/Science/Technology/Television/Digital_Broadcasting/)da:Digital Radio Mondiale
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