Digital Radio Mondiale
Encyclopedia
Digital Radio Mondiale is a set of digital audio broadcasting
technologies designed to work over the bands currently used for AM broadcasting
, particularly shortwave
. DRM can fit more channels than AM, at higher quality, into a given amount of bandwidth, using various MPEG-4
codec
s.
Digital Radio Mondiale is also the name of the international non-profit consortium
designing and implementing the platform. Radio France Internationale
, TéléDiffusion de France, BBC World Service
, Deutsche Welle
, Voice of America
, Telefunken
(now Transradio
) and Thomcast (now Technicolor SA) took part at the formation of the DRM consortium.
The principle of DRM is that bandwidth is the limited element, and computer processing power is cheap; modern CPU
-intensive audio compression techniques enable more efficient use of available bandwidth, at the expense of processing resources.
-comparable sound quality, but on frequencies below 30 MHz (long wave, medium wave and short wave), which allow for very-long-distance signal propagation. VHF is also under consideration, under the name "DRM+". DRM has been designed especially to use portions of older AM transmitter
facilities such as antennas, avoiding major new investment. DRM is robust against the fading and interference which often plague conventional broadcasting on these frequency ranges.
The encoding and decoding can be performed with digital signal processing
, so that a cheap embedded
computer with a conventional transmitter and receiver can perform the rather complex encoding and decoding.
As a digital medium, DRM can transmit other data besides the audio channels (datacasting
) — as well as RDS-type metadata
or program-associated data
as Digital Audio Broadcasting
(DAB) does. Unlike most other DAB systems, DRM uses in-band on-channel
(IBOC) technology and can operate in a hybrid mode called Single Channel Simulcast
, simulcast
ing both analog signal
and digital signal
.
, and the ITU
has approved its use in most of the world. Approval for ITU region 2
(North and South America and the Pacific) is pending amendments to existing international agreements. The inaugural broadcast took place on June 16, 2003, in Geneva
, Switzerland
, at the ITU's annual World Radio Conference.
Current broadcasters include All India Radio
, BBC World Service
, Deutschlandradio
, biteXpress, HCJB
, Radio Canada International
, Deutsche Welle
, Radio Netherlands Worldwide, RTÉ Radio
(RTÉ), Radio Exterior de España
, RAI
, Kuwait Radio, Radio New Zealand International
, Vatican Radio
, Voice of Russia
and Radio Romania International
.
Until now DRM receivers have typically used a personal computer
. A few manufacturers are presently selling stand alone DRM receivers (Himalaya Electronics, Technisat
, Morphy Richards
, Starwaves, UniWave, Sarapulsky Radiozavod), which are mostly based upon the no longer available Radioscape RS500 module. The UniWave set is based upon the NewStar Electronics WR608 module. New modules are expected from NewStar Electronics (WR998), from Analog Devices, and others. Kenwood
and Fraunhofer
presented a prototype standalone receiver chip in September 2006.
Morphy Richards
is mass producing DRM receivers, which are being promoted by the broadcaster Deutsche Welle. The receivers cost under £169.99 in the UK (as of October 2008). At the time of writing, Morphy Richards are only distributing these sets around Germany, Austria and the UK, but Europe-wide distribution is expected shortly, with grey market
importers using German sourced radios to distribute across Europe. UniWave has created a receiver called the Di-Wave 100, capable of receiving MOT Slideshow, pictures, and text (Journaline) streams. Support of low bitrate videos (Diveemo) is expected in an upcoming version of this receiver. It is not currently offered for sale.
The British Broadcasting Corporation BBC
has trialed the technology by broadcasting BBC Radio Devon
in the Plymouth area. The trial lasted for year (April 2007 - April 2008). Digital Radio Mondiale is being considered by Ofcom
for introduction in Britain
in 2012 on the present AM medium wave band.
RTE has also run single and multiple programme overnight tests during a similar period on the 252KHz LW transmitter in Trim, Co.Meath, Ireland which was upgraded to support DRM after Atlantic 252 closed.
n spectrum regulator, the Australian Communications and Media Authority
, announced that it had "placed an embargo on frequency bands potentially suitable for use by broadcasting services using Digital Radio Mondiale until spectrum planning can be completed" "those bands being "5950–6200, 7100–7300, 9500–9900, 11650–12050, 13600–13800, 15100–15600, 17550–17900, 21450–21850 and 25670–26100 kHz.
The United States
Federal Communications Commission
states in Part 73, section 758 that: "For digitally modulated emissions, the Digital Radio Mondiale (DRM) standard shall be employed." Part 73, section 758 is for HF
broadcasting only.
On 31 August 2009, DRM+ has become an official broadcasting standard with the publication of the technical specification by the European Telecommunications Standards Institute
; this is effectively a new release of the whole DRM spec with the additional mode permitting operation above 30 MHz up to 174 MHz.
Wider bandwidth channels are used, which allows radio stations to use higher bit rates, thus providing higher audio quality. A 100 kHz DRM+ channel has sufficient capacity to carry one low-definition 0.7 megabit/s wide mobile TV channel: it would be feasible to distribute mobile TV
over DRM+ rather than DMB
or DVB-H
.
DRM Plus is now successfully tested in Band III, and this gives the DRM system the widest frequency usage; it can be used in band I, II and III. It is possible that DRM+ can co exist with DAB in band III.
can broadcast 20 kbit/s using channels 10 kHz wide and up to 60 kbit/s using 20 kHz channels.) Useful bitrate depends also on other parameters, such as:
DRM offers the possibility to use different audio coding system (source coding) depending on the bitrate:
All codec
s can optionally be combined with spectral band replication
.
Broadcasters have some freedom of choice depending on the material they send. The most commonly used mode is HE-AAC
(also called AAC+) that offers an acceptable audio quality somewhat comparable to FM broadcast
.
The choice of transmission parameters depends on signal robustness wanted and propagation conditions. Transmission signal is affected by noise, interference, multipath wave propagation and Doppler effect
.
It is possible to choose among several error coding schemes and several modulation patterns: 64-QAM, 16-QAM and 4-QAM. OFDM modulation has some parameters that must be adjusted depending on propagation conditions. This is the carrier spacing which will determine the robustness against Doppler effect (which cause frequencies offsets, spread: Doppler spread) and OFDM guard interval which determine robustness against multipath propagation (which cause delay offsets, spread: delay spread). The DRM consortium has determined four different profiles corresponding to typical propagation conditions:
The trade-off between these profiles stands between robustness, resistance in regards to propagation conditions and useful bit rates for the service.
This table presents some values depending on these profiles. The more the carrier spacing is the more the system is resistant to Doppler effect (Doppler spread). The more the guard interval is the more the system is resistant to long multipath propagation (delay spread).
The resulting low-bit rate
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
.
There is also a lower bandwidth two-way communication version of DRM as a replacement for SSB communications on HF - note that it is NOT compatible with the official DRM specification. It may be possible in some future time for the 4.5 kHz bandwidth DRM version used by the Amateur Radio community to be merged with the existing DRM specification.
The Dream software
will receive the commercial versions and also limited transmission mode using the FAAC AAC encoder.
This table shows an example of useful bitrates depending on protection classes
The lower the protection class the higher the level of error correction.
Digital radio
Digital radio has several meanings:1. Today the most common meaning is digital radio broadcasting technologies, such as the digital audio broadcasting system, also known as Eureka 147. In these systems, the analog audio signal is digitized into zeros and ones, compressed using formats such as...
technologies designed to work over the bands currently used for AM broadcasting
AM broadcasting
AM broadcasting is the process of radio broadcasting using amplitude modulation. AM was the first method of impressing sound on a radio signal and is still widely used today. Commercial and public AM broadcasting is carried out in the medium wave band world wide, and on long wave and short wave...
, particularly shortwave
Shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
. DRM can fit more channels than AM, at higher quality, into a given amount of bandwidth, using various MPEG-4
MPEG-4
MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
s.
Digital Radio Mondiale is also the name of the international non-profit consortium
Consortium
A consortium is an association of two or more individuals, companies, organizations or governments with the objective of participating in a common activity or pooling their resources for achieving a common goal....
designing and implementing the platform. Radio France Internationale
Radio France Internationale
Radio France Internationale was created in 1975 as part of Radio France by the Government of France, and replaced the Poste Colonial , Paris Mondial , Radio Paris , RTF Radio Paris and ORTF Radio Paris...
, TéléDiffusion de France, BBC World Service
BBC World Service
The BBC World Service is the world's largest international broadcaster, broadcasting in 27 languages to many parts of the world via analogue and digital shortwave, internet streaming and podcasting, satellite, FM and MW relays...
, Deutsche Welle
Deutsche Welle
Deutsche Welle or DW, is Germany's international broadcaster. The service is aimed at the overseas market. It broadcasts news and information on shortwave, Internet and satellite radio on 98.7 DZFE in 30 languages . It has a satellite television service , that is available in four languages, and...
, Voice of America
Voice of America
Voice of America is the official external broadcast institution of the United States federal government. It is one of five civilian U.S. international broadcasters working under the umbrella of the Broadcasting Board of Governors . VOA provides a wide range of programming for broadcast on radio...
, Telefunken
Telefunken
Telefunken is a German radio and television apparatus company, founded in Berlin in 1903, as a joint venture of Siemens & Halske and the Allgemeine Elektricitäts-Gesellschaft...
(now Transradio
Transradio
Transradio is a German radio communication systems producer, specialised in research, development and design of AM, VHF/FM and DRM broadcasting systems....
) and Thomcast (now Technicolor SA) took part at the formation of the DRM consortium.
The principle of DRM is that bandwidth is the limited element, and computer processing power is cheap; modern CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
-intensive audio compression techniques enable more efficient use of available bandwidth, at the expense of processing resources.
Features
DRM can deliver FMFrequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
-comparable sound quality, but on frequencies below 30 MHz (long wave, medium wave and short wave), which allow for very-long-distance signal propagation. VHF is also under consideration, under the name "DRM+". DRM has been designed especially to use portions of older AM transmitter
Transmitter
In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating...
facilities such as antennas, avoiding major new investment. DRM is robust against the fading and interference which often plague conventional broadcasting on these frequency ranges.
The encoding and decoding can be performed with digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
, so that a cheap embedded
Embedded system
An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...
computer with a conventional transmitter and receiver can perform the rather complex encoding and decoding.
As a digital medium, DRM can transmit other data besides the audio channels (datacasting
Datacasting
Datacasting is the broadcasting of data over a wide area via radio waves. It most often refers to supplemental information sent by television stations along with digital television, but may also be applied to digital signals on analog TV or radio...
) — as well as RDS-type metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
or program-associated data
Program-associated data
Program Associated Data or Program Service Data is a concept related to broadcasting which consists of a number of different fields or streams which are displayed on many HD Radio & satellite radio receivers in order to describe the program being transmitted, including different information such...
as Digital Audio Broadcasting
Digital audio broadcasting
Digital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....
(DAB) does. Unlike most other DAB systems, DRM uses in-band on-channel
In-band on-channel
In-band on-channel is a hybrid method of transmitting digital radio and analog radio broadcast signals simultaneously on the same frequency....
(IBOC) technology and can operate in a hybrid mode called Single Channel Simulcast
Single Channel Simulcast
Single/Multi Channel Simulcast is the simultaneous transmission of an amplitude modulated and Digital Radio Mondiale in the same or a neighbouring channel ....
, simulcast
Simulcast
Simulcast, shorthand for "simultaneous broadcast", refers to programs or events broadcast across more than one medium, or more than one service on the same medium, at the same time. For example, Absolute Radio is simulcast on both AM and on satellite radio, and the BBC's Prom concerts are often...
ing both analog signal
Analog signal
An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...
and digital signal
Digital signal
A digital signal is a physical signal that is a representation of a sequence of discrete values , for example of an arbitrary bit stream, or of a digitized analog signal...
.
Status
The LW/MW/SW standard has been approved by the IECInternational Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
, and the ITU
International Telecommunication Union
The International Telecommunication Union is the specialized agency of the United Nations which is responsible for information and communication technologies...
has approved its use in most of the world. Approval for ITU region 2
ITU region
The International Telecommunication Union , in its International Radio Regulations, divides the world into three ITU regions for the purposes of managing the global radio spectrum...
(North and South America and the Pacific) is pending amendments to existing international agreements. The inaugural broadcast took place on June 16, 2003, in Geneva
Geneva
Geneva In the national languages of Switzerland the city is known as Genf , Ginevra and Genevra is the second-most-populous city in Switzerland and is the most populous city of Romandie, the French-speaking part of Switzerland...
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
, at the ITU's annual World Radio Conference.
Current broadcasters include All India Radio
All India Radio
All India Radio , officially known since 1956 as Akashvani , is the radio broadcaster of India and a division of Prasar Bharati. Established in 1936, it is the sister service of Prasar Bharati's Doordarshan, the national television broadcaster. All India Radio is one of the largest radio networks...
, BBC World Service
BBC World Service
The BBC World Service is the world's largest international broadcaster, broadcasting in 27 languages to many parts of the world via analogue and digital shortwave, internet streaming and podcasting, satellite, FM and MW relays...
, Deutschlandradio
Deutschlandradio
Deutschlandradio is a national German public broadcasting radio broadcaster. It operates four national networks, Deutschlandfunk, Deutschlandradio Kultur, Dokumente und Debatten and DRadio Wissen....
, biteXpress, HCJB
HCJB
HCJB, "The Voice of the Andes", was the first radio station with daily programming in the South American country of Ecuador and the first Christian missionary radio station in the world. The station was founded in 1931 by Clarence W. Jones, Reuben Larson, and D. Stuart Clark.- History :Radio...
, Radio Canada International
Radio Canada International
Radio Canada International is the international broadcasting service of the Canadian Broadcasting Corporation . Until 1970, it was known as the CBC International Service and was sometimes referred to as the "Voice of Canada" in its early years.- The early years :The idea for creating an...
, Deutsche Welle
Deutsche Welle
Deutsche Welle or DW, is Germany's international broadcaster. The service is aimed at the overseas market. It broadcasts news and information on shortwave, Internet and satellite radio on 98.7 DZFE in 30 languages . It has a satellite television service , that is available in four languages, and...
, Radio Netherlands Worldwide, RTÉ Radio
RTÉ Radio
RTÉ Radio is a department of Irish national broadcaster Raidió Teilifís Éireann. RTÉ Radio broadcasts four analogue channels and five digital channels....
(RTÉ), Radio Exterior de España
Radio Exterior de España
Radio Exterior de España is a Spanish international radio station operated by Radio Nacional de España. The station is primarily intended for Spaniards living abroad. It broadcasts 24-hours a day on short-wave radio, satellite and the Internet. Transmissions are in Spanish, French, Arabic, Ladino,...
, RAI
RAI
RAI — Radiotelevisione italiana S.p.A. known until 1954 as Radio Audizioni Italiane, is the Italian state owned public service broadcaster controlled by the Ministry of Economic Development. Rai is the biggest television company in Italy...
, Kuwait Radio, Radio New Zealand International
Radio New Zealand International
Radio New Zealand International , a division of Radio New Zealand, is the official international broadcasting station of New Zealand. It broadcasts a variety of news, current affairs and sports programmes in English and news in seven Pacific languages...
, Vatican Radio
Vatican Radio
Vatican Radio is the official broadcasting service of the Vatican.Set up in 1931 by Guglielmo Marconi, today its programs are offered in 47 languages, and are sent out on short wave , medium wave, FM, satellite and the Internet. The Jesuit Order has been charged with the management of Vatican...
, Voice of Russia
Voice of Russia
Voice of Russia is the Russian government's international radio broadcasting service owned by the All-Russia State Television and Radio Company. Its predecessor Radio Moscow was the official international broadcasting station of the Union of Soviet Socialist Republics.-Early years:Radio Moscow...
and Radio Romania International
Radio Romania International
Radio România Internaţional is a Romanian radio station owned by the Romanian public radio broadcaster Societatea Română de Radiodifuziune that broadcasts abroad.According to the Romanian law nr...
.
Until now DRM receivers have typically used a personal computer
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
. A few manufacturers are presently selling stand alone DRM receivers (Himalaya Electronics, Technisat
TechniSat
TechniSat is a German manufacturer and market leader of direct broadcast satellite receivers as well. They also produce televisions, car navigation and entertainment systems...
, Morphy Richards
Morphy Richards
Morphy Richards is a business located in the Swinton Meadows Industrial Estate, Swinton, near Mexborough, South Yorkshire.-Product range:It specialises in the manufacture of toasters, hairdryers, bread makers, kettles and sandwich toasters and other appliances. In its early stage it also made...
, Starwaves, UniWave, Sarapulsky Radiozavod), which are mostly based upon the no longer available Radioscape RS500 module. The UniWave set is based upon the NewStar Electronics WR608 module. New modules are expected from NewStar Electronics (WR998), from Analog Devices, and others. Kenwood
Kenwood Electronics
is a Japanese manufacturer of amateur radio as well as Hi-Fidelity and portable audio equipment.-History:The company first started in 1946 as the Kasuga Radio Co. Ltd. In Komagane City, Nagano Prefecture, Japan. In 1960 the firm was renamed "Trio Corporation"...
and Fraunhofer
Fraunhofer Society
The Fraunhofer Society is a German research organization with 60 institutes spread throughout Germany, each focusing on different fields of applied science . It employs around 18,000, mainly scientists and engineers, with an annual research budget of about €1.65 billion...
presented a prototype standalone receiver chip in September 2006.
Morphy Richards
Morphy Richards
Morphy Richards is a business located in the Swinton Meadows Industrial Estate, Swinton, near Mexborough, South Yorkshire.-Product range:It specialises in the manufacture of toasters, hairdryers, bread makers, kettles and sandwich toasters and other appliances. In its early stage it also made...
is mass producing DRM receivers, which are being promoted by the broadcaster Deutsche Welle. The receivers cost under £169.99 in the UK (as of October 2008). At the time of writing, Morphy Richards are only distributing these sets around Germany, Austria and the UK, but Europe-wide distribution is expected shortly, with grey market
Grey market
A grey market or gray market also known as parallel market is the trade of a commodity through distribution channels which, while legal, are unofficial, unauthorized, or unintended by the original manufacturer...
importers using German sourced radios to distribute across Europe. UniWave has created a receiver called the Di-Wave 100, capable of receiving MOT Slideshow, pictures, and text (Journaline) streams. Support of low bitrate videos (Diveemo) is expected in an upcoming version of this receiver. It is not currently offered for sale.
The British Broadcasting Corporation BBC
BBC
The British Broadcasting Corporation is a British public service broadcaster. Its headquarters is at Broadcasting House in the City of Westminster, London. It is the largest broadcaster in the world, with about 23,000 staff...
has trialed the technology by broadcasting BBC Radio Devon
BBC Radio Devon
BBC Radio Devon is the BBC Local Radio service for the English county of Devon. It began transmissions on 17 January 1983, replacing a previous breakfast show for Devon and Cornwall broadcast on the local frequencies of Radio 4....
in the Plymouth area. The trial lasted for year (April 2007 - April 2008). Digital Radio Mondiale is being considered by Ofcom
Ofcom
Ofcom is the government-approved regulatory authority for the broadcasting and telecommunications industries in the United Kingdom. Ofcom was initially established by the Office of Communications Act 2002. It received its full authority from the Communications Act 2003...
for introduction in Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
in 2012 on the present AM medium wave band.
RTE has also run single and multiple programme overnight tests during a similar period on the 252KHz LW transmitter in Trim, Co.Meath, Ireland which was upgraded to support DRM after Atlantic 252 closed.
International regulation
On 28 September 2006, the AustraliaAustralia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
n spectrum regulator, the Australian Communications and Media Authority
Australian Communications and Media Authority
The Australian Communications and Media Authority is an Australian government statutory authority within the Department of Broadband, Communications and the Digital Economy portfolio...
, announced that it had "placed an embargo on frequency bands potentially suitable for use by broadcasting services using Digital Radio Mondiale until spectrum planning can be completed" "those bands being "5950–6200, 7100–7300, 9500–9900, 11650–12050, 13600–13800, 15100–15600, 17550–17900, 21450–21850 and 25670–26100 kHz.
The United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
states in Part 73, section 758 that: "For digitally modulated emissions, the Digital Radio Mondiale (DRM) standard shall be employed." Part 73, section 758 is for HF
High frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...
broadcasting only.
DRM Plus
While the initial version of DRM covers the broadcasting bands below 30 MHz, the DRM consortium voted in March 2005 to begin the process of extending the system to the VHF bands up to 108 MHz. DRM Plus (DRM+) will be the name of this technology.On 31 August 2009, DRM+ has become an official broadcasting standard with the publication of the technical specification by the European Telecommunications Standards Institute
European Telecommunications Standards Institute
The European Telecommunications Standards Institute is an independent, non-profit, standardization organization in the telecommunications industry in Europe, with worldwide projection...
; this is effectively a new release of the whole DRM spec with the additional mode permitting operation above 30 MHz up to 174 MHz.
Wider bandwidth channels are used, which allows radio stations to use higher bit rates, thus providing higher audio quality. A 100 kHz DRM+ channel has sufficient capacity to carry one low-definition 0.7 megabit/s wide mobile TV channel: it would be feasible to distribute mobile TV
Mobile TV
Mobile television usually means television watched on a small handheld device. It may be a pay TV service broadcast on mobile phone networks or received free-to-air via terrestrial television stations from either regular broadcast or a special mobile TV transmission format...
over DRM+ rather than DMB
Digital Multimedia Broadcasting
Digital Multimedia Broadcasting is a digital radio transmission technology developed in South Korea as part of the national IT project for sending multimedia such as TV, radio and datacasting to mobile devices such as mobile phones...
or DVB-H
DVB-H
DVB-H is one of three prevalent mobile TV formats. It is a technical specification for bringing broadcast services to mobile handsets. DVB-H was formally adopted as ETSI standard EN 302 304 in November 2004. The DVB-H specification can be downloaded from the official DVB-H website...
.
DRM Plus is now successfully tested in Band III, and this gives the DRM system the widest frequency usage; it can be used in band I, II and III. It is possible that DRM+ can co exist with DAB in band III.
Audio source coding
Useful bitrates for DRM range from 6.1 kbit/s (Mode D) to 34.8 kbit/s (Mode A) for a 10 kHz bandwidth (+/- 5 kHz around the central frequency). It is possible to achieve bit rates up to 72 kbit/s (Mode A) by using a standard 20 kHz (+/-10 kHz) wide channel. (For comparison, pure digital HD RadioHD Radio
HD Radio, which originally stood for "Hybrid Digital", is the trademark for iBiquity's in-band on-channel digital radio technology used by AM and FM radio stations to transmit audio and data via a digital signal in conjunction with their analog signals...
can broadcast 20 kbit/s using channels 10 kHz wide and up to 60 kbit/s using 20 kHz channels.) Useful bitrate depends also on other parameters, such as:
- desired robustness to errors (error codingForward error correctionIn telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels....
) - power needed (modulationModulationIn electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...
scheme) - robustness in regard to propagation conditions (multipath propagation, doppler effectDoppler effectThe Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...
), etc.
DRM offers the possibility to use different audio coding system (source coding) depending on the bitrate:
- MPEG-4MPEG-4MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
HE-AACHE-AACHigh-Efficiency Advanced Audio Coding is a lossy data compression scheme for digital audio defined as a MPEG-4 Audio profile in ISO/IEC 14496-3. It is an extension of Low Complexity AAC optimized for low-bitrate applications such as streaming audio...
(High Efficiency - Advanced Audio CodingAdvanced Audio CodingAdvanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....
). AAC is a perceptual coder suited for voice and music and the High Efficiency is an optional extension for reconstruction of high frequencies (SBR: spectral bandwidth replication) and stereo image (PS: Parametric Stereo). 24 kHz or 12 kHz sampling frequencies can be used for core AAC (no SBR) which correspond respectively to 48 kHz and 24 kHz when using SBR oversampling. - MPEG-4MPEG-4MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
CELP which is a parametric coder suited for voice only (vocoder) but that is robust to errors and needs a small bit rate. - MPEG-4MPEG-4MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
HVXC which is also a parametric coder for speech programs that uses an even smaller bitrate than CELP.
All codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
s can optionally be combined with spectral band replication
Spectral band replication
Spectral band replication is a technology to enhance audio or speech codecs, especially at low bit rates and is based on harmonic redundancy in the frequency domain....
.
Broadcasters have some freedom of choice depending on the material they send. The most commonly used mode is HE-AAC
HE-AAC
High-Efficiency Advanced Audio Coding is a lossy data compression scheme for digital audio defined as a MPEG-4 Audio profile in ISO/IEC 14496-3. It is an extension of Low Complexity AAC optimized for low-bitrate applications such as streaming audio...
(also called AAC+) that offers an acceptable audio quality somewhat comparable to FM broadcast
FM broadcasting
FM broadcasting is a broadcasting technology pioneered by Edwin Howard Armstrong which uses frequency modulation to provide high-fidelity sound over broadcast radio. The term "FM band" describes the "frequency band in which FM is used for broadcasting"...
.
Bandwidth
DRM broadcasting can be done using a choice of different bandwidths:- 4.5 kHz. Gives the ability for the broadcaster to do a simulcastSimulcastSimulcast, shorthand for "simultaneous broadcast", refers to programs or events broadcast across more than one medium, or more than one service on the same medium, at the same time. For example, Absolute Radio is simulcast on both AM and on satellite radio, and the BBC's Prom concerts are often...
and use the lower-sideband area of a full 9 kHz channel for single sideband AMAmplitude modulationAmplitude modulation is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. AM works by varying the strength of the transmitted signal in relation to the information being sent...
(designated H3E by the ITUItuItu is an old and historic municipality in the state of São Paulo in Brazil. The population in 2009 was 157,384 and the area is 641.68 km². The elevation is 583 m. This place name comes from the Tupi language, meaning big waterfall. Itu is linked with the highway numbered the SP-75 and are flowed...
), with a 4.5 kHz DRM signal occupying the area traditionally taken by the upper-sideband. However the resulting bit rate and audio quality is not great. This would only apply to the region–1 (European) medium wave and long wave bands, or to the region–3 (Asian/Oceanian) medium wave band. - 5 kHz. Gives the ability for the broadcaster to do a simulcastSimulcastSimulcast, shorthand for "simultaneous broadcast", refers to programs or events broadcast across more than one medium, or more than one service on the same medium, at the same time. For example, Absolute Radio is simulcast on both AM and on satellite radio, and the BBC's Prom concerts are often...
and use the lower-sideband area of a full 10 kHz channel for H3E single sideband AM, with a 5 kHz DRM signal occupying the area traditionally taken by the upper-sideband. However the resulting bit rate and audio quality is marginal (7.1—16.7 kbit/s for 5 kHz). This regime would apply to the AM band in region–2 and to the short wave bands the world over. - 9 kHz. Occupies all the standard bandwidth of a region–1 long wave or medium wave broadcast channel so that the existing frequency plan can be reused. Also used for the region–3 medium wave band.
- 10 kHz. Occupies all the standard bandwidth of a region–2 AM or worldwide short wave broadcast channel (giving 14.8—34.8 kbit/s) so the existing frequency plan can be reused.
- 18 kHz. Occupies an adjacent pair of region–1 long wave or medium wave channels or an adjacent pair of region–3 medium wave channels according to the existing frequency plan. This offers the possibility of offering better audio quality.
- 20 kHz. Occupies an adjacent pair of region–2 AM or worldwide short wave channels according to the existing frequency plan. This offers the possibility of offering better audio quality (giving 30.6—72 kbit/s).
- 100 kHz for DRM+. This bandwidth can be used in band I, II and III and DRM+ can transmit four different programs in this bandwidth.
Modulation
The modulation used for DRM is COFDM (Coded Orthogonal Frequency Division Multiplexing), where every carrier is modulated with QAM (Quadrature Amplitude Modulation) with a selectable error coding.The choice of transmission parameters depends on signal robustness wanted and propagation conditions. Transmission signal is affected by noise, interference, multipath wave propagation and Doppler effect
Doppler effect
The Doppler effect , named after Austrian physicist Christian Doppler who proposed it in 1842 in Prague, is the change in frequency of a wave for an observer moving relative to the source of the wave. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from...
.
It is possible to choose among several error coding schemes and several modulation patterns: 64-QAM, 16-QAM and 4-QAM. OFDM modulation has some parameters that must be adjusted depending on propagation conditions. This is the carrier spacing which will determine the robustness against Doppler effect (which cause frequencies offsets, spread: Doppler spread) and OFDM guard interval which determine robustness against multipath propagation (which cause delay offsets, spread: delay spread). The DRM consortium has determined four different profiles corresponding to typical propagation conditions:
- A: Gaussian channel with very little multipath propagation and Doppler effect. This profile is suited for local or regional broadcasting.
- B: multipath propagation channel. This mode is suited for medium range transmission. It is nowadays frequently used.
- C: similar to mode B, but with better robustness to Doppler (more carrier spacing). This mode is suited for long distance transmission.
- D: similar to mode B, but with a resistance to large delay spread and Doppler spread. This case exists with adverse propagation conditions on very long distance transmissions. The useful bit rate for this profile is decreased.
The trade-off between these profiles stands between robustness, resistance in regards to propagation conditions and useful bit rates for the service.
This table presents some values depending on these profiles. The more the carrier spacing is the more the system is resistant to Doppler effect (Doppler spread). The more the guard interval is the more the system is resistant to long multipath propagation (delay spread).
The resulting low-bit rate
Bit rate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
digital information is modulated
Modulation
In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted...
using COFDM. It can run in simulcast
Simulcast
Simulcast, shorthand for "simultaneous broadcast", refers to programs or events broadcast across more than one medium, or more than one service on the same medium, at the same time. For example, Absolute Radio is simulcast on both AM and on satellite radio, and the BBC's Prom concerts are often...
mode by switching between DRM and AM, and it is also prepared for linking to other alternatives (e.g. DAB
Digital audio broadcasting
Digital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....
or FM services).
DRM has been tested successfully on shortwave
Shortwave
Shortwave radio refers to the upper MF and all of the HF portion of the radio spectrum, between 1,800–30,000 kHz. Shortwave radio received its name because the wavelengths in this band are shorter than 200 m which marked the original upper limit of the medium frequency band first used...
, mediumwave
Mediumwave
Medium wave is the part of the medium frequency radio band used mainly for AM radio broadcasting. For Europe the MW band ranges from 526.5 kHz to 1606.5 kHz...
(with 9 as well as 10 kHz channel spacing
Channel spacing
Channel spacing is a term used in radio frequency planning. It describes the frequency difference between adjacent allocations in a frequency plan. Channels for mediumwave radio stations, for example are allocated in internationally-agreed steps of 9 or 10 kHz: 10 kHz in ITU Region 2 and 9 kHz...
) and longwave
Longwave
In radio, longwave refers to parts of radio spectrum with relatively long wavelengths. The term is a historic one dating from the early 20th century, when the radio spectrum was considered to consist of long, medium and short wavelengths...
.
| Mode | OFDM Carrier spacing (Hz) | Number of carriers | Symbol length (ms) | Guard interval length (ms) | Nb symbols per frame | |||
|---|---|---|---|---|---|---|---|---|
| 9 kHz | 10 kHz | 18 kHz | 20 kHz | |||||
| A | 41.66 | 204 | 228 | 412 | 460 | 26.66 | 2.66 | 15 |
| B | 46.88 | 182 | 206 | 366 | 410 | 26.66 | 5.33 | 15 |
| C | 68.18 | - | 138 | - | 280 | 20.00 | 5.33 | 20 |
| D | 107.14 | - | 88 | - | 178 | 16.66 | 7.33 | 24 |
There is also a lower bandwidth two-way communication version of DRM as a replacement for SSB communications on HF - note that it is NOT compatible with the official DRM specification. It may be possible in some future time for the 4.5 kHz bandwidth DRM version used by the Amateur Radio community to be merged with the existing DRM specification.
The Dream software
Dream DRM Receiver
Dream is a popular GPL licensed open source software implementation of a Digital Radio Mondiale receiver that runs on FreeBSD, Linux, Apple Mac OS X and Microsoft Windows....
will receive the commercial versions and also limited transmission mode using the FAAC AAC encoder.
Error coding
Error coding can be chosen to be more or less robust.This table shows an example of useful bitrates depending on protection classes
- OFDM propagation profiles (A or B)
- carrier modulation (16QAM or 64QAM)
- and channel bandwidth (9 or 10 kHz)
| Protection class | A (9 kHz) | B (9 kHz) | B (10 kHz) | C (10 kHz) | D (10 kHz) | |||
|---|---|---|---|---|---|---|---|---|
| 64-QAM | 16-QAM | 16-QAM | 64-QAM | 16-QAM | 64-QAM | 16-QAM | 64-QAM | |
| 0 | 19.6 | 7.6 | 8.7 | 17.4 | 6.8 | 13.7 | 4.5 | 9.1 |
| 1 | 23.5 | 10.2 | 11.6 | 20.9 | 9.1 | 16.4 | 6.0 | 10.9 |
| 2 | 27.8 | - | - | 24.7 | - | 19.4 | - | 12.9 |
| 3 | 30.8 | - | - | 27.4 | - | 21.5 | - | 14.3 |
The lower the protection class the higher the level of error correction.
See also
- AMSSAmplitude modulation signalling systemThe amplitude modulation signalling system is a digital system for adding low bit rate information to an analogue amplitude modulated broadcast signal in the same manner as the Radio Data System for frequency modulated broadcast signals.This system has been standardized in March 2006 by ETSI as...
AM signalling system - Digital Audio BroadcastingDigital audio broadcastingDigital Audio Broadcasting is a digital radio technology for broadcasting radio stations, used in several countries, particularly in Europe. As of 2006, approximately 1,000 stations worldwide broadcast in the DAB format....
(DAB) - Digital Multimedia BroadcastingDigital Multimedia BroadcastingDigital Multimedia Broadcasting is a digital radio transmission technology developed in South Korea as part of the national IT project for sending multimedia such as TV, radio and datacasting to mobile devices such as mobile phones...
(DMB) - Digital Radio Oceane (DRO)
- DVB-HDVB-HDVB-H is one of three prevalent mobile TV formats. It is a technical specification for bringing broadcast services to mobile handsets. DVB-H was formally adopted as ETSI standard EN 302 304 in November 2004. The DVB-H specification can be downloaded from the official DVB-H website...
(Digital Video Broadcasting - Handhelds) - DVB-TDVB-TDVB-T is an abbreviation for Digital Video Broadcasting — Terrestrial; it is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first published in 1997 and first broadcast in the UK in 1998...
(Digital Video Broadcasting - Terrestrial) - ETSI Satellite Digital RadioETSI Satellite Digital RadioETSI Satellite Digital Radio describes a standard of satellite digital radio. It is an activity of the european standardisation organisation ETSI....
(SDR) - HD RadioHD RadioHD Radio, which originally stood for "Hybrid Digital", is the trademark for iBiquity's in-band on-channel digital radio technology used by AM and FM radio stations to transmit audio and data via a digital signal in conjunction with their analog signals...
, American system for digital radio - ISDB-Tsb, Japanese system for digital radio.
External links
- Digital Radio Mondiale (DRM) - official homepage
- How to receive DRM on the long-, medium- and shortwave bands
- Diorama DRM receiver. An open source DRM receiver written by the Institute of Telecommunications of the University Kaiserslautern (Germany))
- WinDRM DRM software for amateur radioAmateur radioAmateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
users. - Dream - an open-source software DRM Receiver