Misplaced Pages

Digital Audio Broadcasting

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.

This is an old revision of this page, as edited by 81.158.38.101 (talk) at 02:48, 12 February 2007 (→Criticisms). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Revision as of 02:48, 12 February 2007 by 81.158.38.101 (talk) (→Criticisms)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)

Digital Audio Broadcasting (DAB), also known as Eureka 147, is a technology for broadcasting of audio using digital radio transmission. DAB uses multiplexing and compression to combine multiple audio streams onto a single broadcast frequency called a DAB ensemble. Other digital audio broadcasting systems are listed in the article on digital radio.

The original objectives of converting to digital transmission were to enable higher fidelity, more stations and more resistance to noise, co-channel interference and multipath than in analogue FM radio. However, in the UK, Denmark, Norway and Switzerland, which are the leading countries with regard to implementing DAB, 99% of stereo stations on DAB use a bit rate below 192 kbps MP2, which means that they sound worse than FM for stationary reception of music. With mobile reception, FM can suffer from fading caused by multipath, and can sound worse than DAB.

In November 2006, WorldDMB announced that the DAB system was in the process of being upgraded, and it will adopt the AAC+ audio codec to improve the efficiency of the system and stronger error correction coding to improve the robustness of transmissions. This means there are effectively now two different versions of the DAB system: the older one, developed in the late 1980s, and an upgraded version, which has been named "DAB+" . Existing DAB receivers are incompatible with the new DAB standard, but receivers that will support the new DAB standard will become available in spring 2007.

History

DAB (or Eureka-147) was developed as a research project in the late 1980s for the European Union (Eureka project number EU147). This research project was started in 1987 by a consortium that had been formed a year earlier. The MP2 (MPEG-1 layer-2) audio coding technique was created as part of the EU147 project. DAB was the first standard based on orthogonal frequency division multiplexing (OFDM) modulation technique, which has become one the most popular transmission schemes for modern wideband digital communication systems.

In 1990, audio codec, modulation and error-correction coding schemes were selected and the first trial broadcasts were made, and in 1993, public demonstrations were done in the United Kingdom. In 1993, the protocol specification was finalized, and in 1994 it was adopted by the ITU-R standardization body. In 1995, the protocol specification was adopted by the European community and in 1997 it was adopted by ETSI. Pilot broadcasts were launched in several countries in 1995.

The UK was the first country to receive a wide range of radio stations via DAB. Commercial DAB receivers began to be sold in 1999 and over 50 commercial and BBC services were available in London by 2001. The UK has to date been the most successful market for DAB and is being projected to be in 40% of homes by 2009.. By 2006, 500 million people worldwide 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 world wide. The standard was coordinated by the European DAB forum, formed in 1995 and reconstituted to the World DAB Forum in 1997, which represents more than 30 countries. In 2006, World DMB Forum took over the coordination.

DAB and FM/AM compared

Traditionally radio programs were broadcast on different frequencies via FM and AM, and the radio had to be tuned into each frequency. This used up a comparatively large amount of spectrum for a relatively small number of stations, limiting listening choice. DAB is a digital radio broadcasting system that through the application of multiplexing and compression combines multiple audio streams onto a single broadcast frequency called a DAB ensemble.

Within an overall target bit rate for the DAB ensemble, individual stations can be allocated different bit rates. The number of channels within a DAB ensemble can be increased by lowering average bit rates, but at the expense of the quality of streams. Error correction under the DAB standard makes the signal more robust but reduces the total bit rate available for streams.

Utilization of frequency spectrum and transmitter sites

DAB gives substantially higher spectral efficiency, measured in programmes per MHz and per transmitter site, than analogue communication. However, since there are no plans yet to cease analogue FM transmissions, and most radio channels are transmitted both over FM and digitally, this advantage is not exploited to a high degree.

FM transmissons require 0.3 MHz per program. Since the frequency re-use factor is approximately 15, only one out of 15 transmitters can use the same channel frequency without problems with co-channel interference. This results in 1 / 15 / (0.3 MHz) = 0.22 programmes/transmitter site and MHz. DAB with 192kbps codec requires 1.536 MHz * 192kbps / 1136 kbps = 0.26 MHz per channel. The frequency re-use factor for local programmes and multi-frequency broadcasting networks (MFS) is typically 4, resulting in 1 / 4 / (0.26 MHz) = 0.96 programmes per transmitter site and MHz. This is 4.3 times as efficient. For single frequency networks (SFN), for example of national programmes, the channel re-use factor is 1, resulting in 1/1/0.25 MHz = 3.85. 3.85. 17.3 times as efficient as FM.

The above capacity improvement may not always be achieved at the L-band frequencies, since these are more sensitive to obstacles than the FM band frequencies, and may cause "shadow fading" for hilly terrain and for indoor communication. The number of transmitter sites or the transmission power required for full coverage of a country may be rather high at these frequencies, to avoid that the system becomes noise limited rather than limited by co-channel interference.

Benefits of DAB

Current AM and FM terrestrial broadcast technology is well established, widely-used, compatible, and relatively inexpensive to manufacture. Even though digital audio technologies are less established, less standardized, and relatively expensive, DAB offers a number of benefits over analog AM and FM systems, in terms of ease of user access, more stations per area, and reception quality.

DAB radios make it easier for listeners to choose programs, because DAB systems automatically tune to all the available stations and provide list of all stations. DAB can carry "radiotext" (in DAB terminology, Dynamic Label Segment, or DLS) from the station giving real-time information such as song titles, music type and news or traffic updates. Advance programme guides can also be transmitted. A similar feature also exists on FM in the form of the RDS. (However, not all FM receivers allow radio stations to be stored by name.) Some DAB radios offer a pause facility on live broadcasts, caching the broadcast stream on local flash memory, although this function is limited.

DAB is more bandwidth efficient than analog for national radio stations due to the use of SFNs, enabling more stations to be placed into a smaller section of the spectrum, although it is only marginally more efficient than FM for local radio stations. In certain areas — particularly rural areas — the introduction of DAB gives radio listeners a greater choice of radio stations. For instance, in South Norway, radio listeners overnight experienced an increase in available stations from 6 to 21 when DAB was introduced in November 2006.

DAB transmits several channels per multiplex, meaning ownership and maintenance can be outsorced and provided by one organisation instead of each radio station, lowering the maintenance cost over time. Mono talk radio, news and weather channels and other non-music programs need significantly less bandwidth than a typical music radio station, which allows DAB to carry these programs at lower bit rates, leaving more bandwidth to be used for other programs.

The DAB standard reduces multipath fading and signal noise, which afflict existing analogue systems. DAB stations often provide better sound in car stereos in dense urban areas where FM radios suffer from multipath interference. In an equally covered area , DAB will generally produce less hiss and crackle than FM. Also, as DAB transmits digital audio, there is no hiss with a weak signal, unlike with FM. However, DAB is not immune to reception problems; in DAB fringe areas, listeners may only be able to get a "bubbling mud" sound.

Criticisms of DAB

Criticism of Sound Quality

In the UK, Denmark, Norway and Switzerland, which are among the leading countries with regard to implementing DAB, 99% of stereo stations on DAB use a bit rate below 192 kbps MP2, which is the bit rate at which the MP2 audio codec begins to dip into the 'Annoying' audio quality band in blind listening tests . This means that all these stations broadcast with a sound quality that is lower than FM sound quality. In order to increase the choice of stations in each multiplex, broadcasters have utilised lower bit rates. However DAB uses the MP2 audio codec, which is meant to be used at bit rate levels of 192 kbit/s or higher to provide good audio quality.

The following paragraph about bit rate levels to be used on DAB was written by an engineer in the BBC Research & Development department and highlights why bit rates as low as 128 kbit/s should not be used on DAB:

A value of 256 kbit/s has been judged to provide a high quality stereo broadcast signal . However, a small reduction, to 224 kbit/s is often adequate, and in some cases it may be possible to accept a further reduction to 192 kbit/s, especially if redundancy in the stereo signal is exploited by a process of 'joint stereo' encoding (i.e. some sounds appearing at the centre of the stereo image need not be sent twice). At 192 kbit/s, it is relatively easy to hear imperfections in critical audio material.

— 

On 6 July 2006 the BBC reduced the bitrate transmission of Radio 3 from 192 kbit/s to 160 kbit/s. The resulting degradation of audio quality prompted a number of complaints to the Corporation. The BBC later announced that following this testing of new equipment, it would resume the previous practice of transmitting Radio 3 at 192 kbit/s whenever there were no other demands on bandwidth.

Reception quality and coverage

The reception quality on DAB is often very poor even for people that live well within the coverage area. The reason for this is that the old version of DAB uses weak error correction coding so that when there are a lot of errors with the received data not enough of the errors can be corrected and a "bubbling mud" sound occurs. This situation will be improved upon in the new DAB standard that uses stronger error correction coding and as signal powers are increased.

If the signal reception becomes marginal the audio will first start to burble or cut out rapidly and if the signal continues to degrade the audio will cut out more often. As well, long distance reception is much harder for hobbyist radio enthusiasts, because each frequency/multiplex is used more often. As DAB is either at the early stages of deployment, DAB coverage is poor in nearly all countries in comparison to the high population coverage provided by FM.

Criticisms

Transmission on DAB is far more expensive than on FM , and measures taken by broadcasters to limit their costs have resulted in some DAB ensembles having to carry too many channels, forcing bit rates to be reduced to levels that deliver sound quality inferior to traditional FM (Digital audio broadcasting#Criticisms of DAB in the UK). As well, DAB programming is not provided for traffic announcements. Although DAB could offer traffic announcements, there are no traffic announcement services available via DAB, so RDS FM remains the only way to receive localised traffic announcements when listening to the radio or CDs when driving.

Concerns have been raised about the hardware, chipsets, and environmental issues. In 2006 tests finally begun using the much improved HE-AAC codec for DAB. However, the new DAB standard is not backwards compatible, leaving early DAB adopters with incompatible hardware (similar to what happened with HD Radio and others). DAB chipsets, as with other digital radio schemes, have never been very power efficient. Revised DAB+ AAC+ chipsets are projected by manufacturers to be up to seven times more power efficient, increasing battery life for portable radios by a factor of three. . Environmentalists have warned that a national migration to the DAB standard will render all FM receivers obsolete and will result in large amounts of electronics waste.

Technology

Bands and modes

Eureka 147 DAB uses a wide-bandwidth broadcast technology and typically spectra have been allocated for it in Band III (174–240 MHz) and L band (1452–1492 MHz), although the scheme allows for operation almost anywhere above 30 MHz. The US military has reserved L-Band in the USA only, blocking its use for other purposes in America, and the United States has reached an agreement with Canada that the latter will restrict L-Band DAB to terrestrial broadcast to avoid interference.

DAB has a number of country specific transmission modes (I, II, III and IV). For worldwide operation a receiver must support all 4 modes: Mode I for Band III, Earth; Mode II for L-Band, Earth and satellite; Mode III for frequencies below 3 GHz, Earth and satellite; and Mode IV for L-Band, Earth and satellite.

Services and ensembles

Various different services are embedded into one ensemble (which is also typically called a multiplex). These services can include primary services, such as main radio stations; secondary services, such as additional sports commentary services; and data services. Different data services include Electronic Programme Guide (EPG); Collections of HTML pages and digital images (Known as 'Broadcast Web Sites'); Slideshows, which may be synchronised with audio broadcasts; Videos; Java Platform Applications; IP tunneling; and other raw data.

Bitrates and transmission

An ensemble has a maximum bitrate that can be carried, but this depends on which error protection level is used. However, all DAB multiplexes can carry a total of 864 "capacity units". The number of capacity units, or CU, that a certain bit rate level requires depends on the amount of error correction added to the transmission.

The stronger the error protection (which requires higher levels of redundant information to be added) the more robust the transmission will be, but this reduces the overall bit rate that can be transmitted. In the UK, most services transmit using 'protection level three', being an FEC of 0.5 which equates to a maximum bit rate per multiplex of 1152 kbit/s. Immunity to fading and inter-symbol interference (caused by multipath propagation) is achieved without equalization by means of the OFDM and DQPSK modulation techniques.

Single frequency networks

Main article: Single-frequency_network

OFDM also features Single frequency network (SFN) communication, meaning that a network of transmitters over a whole a country or a region sends the same radio programmes over the same frequency channel without interference problems. A major advantage of DAB over FM is the provision of single frequency networks (SFNs). Provided the transmitters are synchronised, the multiplex licence holder may operate several in a relatively small geographic area at the same multiplex frequency without any destructive interference occurring at the receiver. SFNs allow substantial service areas to be built up steadily and efficiently as the network develops, funding allows and frequency spectra becomes available.

Compared to FM where service areas operating at the same carrier frequency cannot overlap, a typical DAB network will comprise several relatively low powered closely spaced transmitters operating at the same multiplex frequency. This saves frequency spectrum, reduces the complexity and cost of the transmitter hardware and avoids the need for frequent re-tuning of mobile receivers as they move about within the network. It also means that each transmitter has a smaller audience, thus mitigating the service loss should a transmitter fail. Because of this synchronisation, receivers which are located in places where the service areas of two or more transmitters overlap will interpret one of the signals as a slightly delayed version of the other, effectively an apparent deliberate multipath interference. The actual delays will depend on the radio path geometry and any extra delays that may be added artificially when the network is commissioned. Within the receiver then a relatively simple form of delay filtering may be applied to extract the desired data.

'DAB version 2'

WorldDMB, the organisation in charge of the DAB standards, announced in a press release in November 2006 , that DAB would be adopting the HE-AAC audio codec, which is also known as AAC+. Also being adopted are the MPEG Surround format, and stronger error correction coding called Reed-Solomon coding. The new standard has been named DAB+.

Receivers that support the new DAB standard will be released in the UK in Spring 2007, and Ofcom has said that services using the old MPEG-1 Audio Layer II audio format used on the old DAB system can be switched off once the vast majority of receivers can support the new HE-AAC audio format. The new HE-AAC audio format is around 3 - 4 times as efficient as the old MPEG-1 Audio Layer II audio format, so this will allow 3 - 4 times as many stations to transmit as is currently possible, or the audio quality can be increased, or a combination of both these things can occur.

DAB and DAB2 can't be used for mobile TV because they don't include any video codecs. DAB related standards Digital Multimedia Broadcasting (DMB) and DAB-IP are suitable for mobile radio and TV both because they have MPEG 4 AVC and WMV9 respectively as video codecs. However a DMB video subchannel can easily be added to any DAB transmission -- as DMB was designed from the outset to be carried on a DAB subchannel. DMB broadcasts in Korea carry conventional MPEG 1 Layer II DAB audio services alongside their DMB video services.

Regional implementations of DAB

Australia

Australia has been testing DAB broadcasting systems since 1999, and larger parts of greater Sydney and Melbourne have DAB coverage. In October 2005, Helen Coonan, the Australian Minister for Communications, Information Technology and the Arts, announced Australia's plans for adopting a Eureka 147 DAB system, but with the proviso that the Australian radio industry should investigate the use of newer audio compression technology that would allow more services to be broadcast in the available spectrum (e.g., the spectruem which has been reserved in Band III and L-Band . Australia will probably settle with the AAC+ codec provided with upgraded DAB standard. The Australian Government has set a launch date for digital radio in the country with 1 January 2009 being the set date.

Austria

In Austria so far there is just a test operation of DAB. The national broadcasting company ORF tests Digital Audio Broadcasting in the capital Vienna and in the province Tirol.

Belgium

DAB was launched in Belgium in 1997. The transmitter network is rather dense, resulting in an excellent mobile coverage. The ensembles include audio services (four new "DAB only" programmes and simulcasts from FM), programme related data (program type, announcements and dynamic label) and data services. The receiver situation is improving the last year. Tuners, kitchen radios and handheld devices are on the market and sales are growing fast as a result of a marketing campaign. Investments in new DAB services and more networks are expected, especially for the commercial and regional networks. An upgrade of the transmitter network for excellent indoor coverage is planned.

Canada

Promotion of digital radio is mostly taking place by the Canadian Association of Broadcasters, which represents private broadcasters in Canada, though an organization called Digital Radio Rollout, Inc. Currently, CBC operates DAB stations in Ottawa, Toronto, Vancouver, Montreal, and Windsor, Ontario. All these markets also contain commercial stations that operate secondary DAB frequencies. All together, according to the 2005 edition of WRTH, 11 million potential listeners will be covered by this service. There are stations in Halifax, Nova Scotia that are currently field-testing DAB and a DAB-only station is schduled to operate soon. Altogether, DAB has been well-received in Canada and coverage, whilst still using the L-band, is excellent. Compared to CHUM's subscription digital radio service using the L-band, the stations currently operating in DAB right now are free-to-air.

On 16 June 2005 the CRTC approved two subscription satellite digital services, which are partnerred with the Sirius (Sirius Canada Inc.) and XM services (Canadian Satellite Radio Inc.) in the United States, and a third subscription service to be provided by the CHUM radio group using terrestrial transmitters that will only cover mainly urban areas in the south. This system intends to use a derivative of the DAB system for transmission. Among the services planned to be offered on the channels includes urban music, rock, oldies, dance, Motown, francophone, classical, opera, Christian, Aboriginal, and radio theatre. With CTVglobemedia's purchase of CHUM, however, there is currently no indication regarding how this will affect the service (to see a list of channels used in the Canadian implementation of DAB, see this footnote )

On 15 December 2006, the CRTC, on reviewing the status of DAB in Canada and finding that it was not progressing well, changed its previous policies and will now allow testing of digital systems being tried in the United States, including in-band and out-of-band FM systems. The Eureka 147 system will still be used, but transitional licences will become permanent licences at renewal. Eureka 147 will also be viewed as complementary, and broadcasters will be able to add one Eureka 147 station for each AM or FM station that they now operate.

China

China decided to use DAB and T-DMB for broadcasting radio and televisions. China placed early in 2006 an order of 500 000 receivers. They already broadcast some programs at Beijing and Guangdong.

Czech Republic

There is currently no DAB coverage in the Czech Republic. However the infrastructure is in place to provide coverage to 20% of the population around Prague. In April 2006 the Czech Parliament adopted a version of the media law focused on digital broadcasting. Public Czech Radio has applied for permission to broadcast DAB. The new digital radio stations CRo 4 - Radio WAVE, Radio Cesko, Radio Leonardo and Radio D-dur are provided by Czech radio. These programs are currently transmitting via DVB-T and the Internet. The three current radio stations from Plzen applied for new DAB frequencies in L-band. The Czech Council for Radio and TV broadcasting announced that the DAB licence procedure will start on autumn 2006.

Denmark

In Denmark an extensive rollout of DAB has been made by Danmarks Radio. The goal is that the entire country should be covered in 2007. More info can be obtained from http://www.dabradio.dk/ including a current coverage map. 700,000 Danes (13%) had access to a DAB radio in 2006 and DAB radio is increasing in popularity.

Finland

Finland switched off their DAB transmitters in 2005. Finland is now investigating providing digital radio via other digital broadcasting systems, such as DVB-H.

France

In a public consultation on digital radio, the four largest French radio broadcasters objected to using the current DAB system; new stakeholders were in favour of keeping compatibility with the UK version. The French communications regulator CSA decided to launch a technical forum about the right choice for digital radio. Some broadcasters asked the regulator to strictly adopt the digital radio system in order to preserve transborder roaming (car radio) and some suggested to design technical variants of the European standard. Implementation of Band III has been strongly suggested by most contributors. The five largest French radio broadcasters are currently participating in a trial of the DVB-H and T-DMB digital broadcasting system in Paris.

Only one VHF T-DAB assignment is implemented. In France T-DAB is implemented in L-band. The percentage of households that can already, or are expected in the near future to receive the quoted number of VHF multiplexes is not significant. However, for the future digital Plan, France has decided to implement T-DAB in Band III. CSA has authorised for 6 months an experiment over Paris for T-DMB on channel 11B. The experiment is established by TF1, Europe 1, Europe 2 and VDL, and for duration of six months, beginning on 15 October 2005. It is authorised to broadcast a set of programs of radio or television having been already the object of agreements with the Council.

Germany

After some years of test operation, regular T-DAB service was launched in April 1999. Licences have been granted to 8 different network operators. They use the T-DAB frequency blocks of the WI95 Plan. The cumulative area of all allotment areas corresponds to seamless coverage of Germany. All network operators are obliged to implement the networks within a time frame of 5 to 8 years in order to provide coverage of more than 80% of the total population.

About 85% of the German households are located within the service area of T-DAB transmitter networks. However, the market penetration of receiver equipment is still low. In order to improve the situation, several activities are underway. The platform of the "Initiative for Digital Broadcasting" chaired by the Federal Ministry of Economics and Labour investigates T-DAB issues and aspects of improving the market development.

An "Initiative for Marketing Digital Radio" has been founded by the German network operators and is an open forum for equipment manufacturers, program providers, network operators and marketing experts. An associated "Initiative for Marketing Digital Radio" plays its role as marketing enterprise and is equipped with a budget which is adequate to organize and perform PR- and marketing activities on a larger scale.

Indonesia

Indonesia will begin DAB trial transmission on August 2006. There will be four DAB radio stations: Prambors, Ramako, Sonora and I-Radio. On the trial period, DAB radios will use 10 D FHV frequency.

Ireland

Ireland's public service broadcaster and owner of the sole national transmission network, RTÉ, launched its DAB service to the East and North-East on November 30, 2006, using Channel 12C. It initially began with six stations (four live), consisting initially of the RTÉ radio stations. Today FM was added a week later. All stations are using bit rates of 112 and 128kbit/s (there is one station at 64kbit mono but it is not yet on-air). Nearly a year previously, on December 20, 2005, RTÉ announced that DAB trials would begin along the east coast on January 1, 2006.

By January 5, two transmitters, Clermont Carn and Three Rock Mountain, were transmitting a single multiplex on channel 12C, carrying 6 channels - RTÉ Radio 1, RTÉ 2fm, RTÉ Lyric FM, Raidió na Gaeltachta, Today FM and the World Radio Network, all at 192 kbit/s. In May, this was reduced to just RTÉ Radio 1 and RTÉ 2FM at 160 kbit/s. These test DAB transmissions ceased on July 13 and DAB remained off-air until the public commencement that November.

DAB development was limited by the lack of Band III frequencies until the GE06 Conference earlier this year. Prior to GE06 (formerly known as RRC-06), the Republic of Ireland had only two channels allocated to DAB: 12C to RTÉ for the entire country and 12A allocated to commercial broadcasting. However, roll-out using the lower channels made available after the conference will most likely be limited until the RTÉ television broadcasts in Band III are moved to UHF. Local radio franchise areas have been allocated an L band DAB channel, as well as any counties which do not match radio franchises. L band capable receivers are relatively rare in Europe, although are the standard in Canada and other countries.

Malta

T-DAB spectrum licenses have been awarded in March 2006. In August 2005, the Malta Communications Authority (MCA) together with the Ministry for Competitiveness and Communications published Malta's policy and implementation strategy on T-DAB. It is expected that the 3 T-DAB band III frequency blocks allotted to Malta under the WI-95 allotment plan be made available to those interested to provide T-DAB services in Malta.

The Netherlands

In March 2005, following criticism from politicians from all parties, the Dutch Minister of Economic Affairs Laurens Jan Brinkhorst announced that The Netherlands has postponed plans to continue rolling out DAB, and will instead evaluate newer technologies. The new which will be assessed include the new version of DAB DRM+ and DVB-H, and are more efficient than the current version of DAB, so it is likely that The Netherlands will end up using an upgraded version of DAB based on the AAC+ codec.

Dutch public radio has been transmitting in block 12C since 2004. Nine radio channels are available, including a non-stop Top 2000 channel and a continuous repetition of the last news bulletin. Territorial coverage of the Netherlands is currently limited, but 70% of the population is covered.

New Zealand

New Zealand is trailing DAB since November 2006 in Wellington and west Auckland but wants to use new DAB+ standard once testing is finished

Norway

Twenty stations are available on DAB, including all of NRKs broadcast channels and commercial P4 as well as their DAB-only transmisson P4 Bandit, and private broadcaster Moox Radio with a music channel. An audio book channel, Bokradioen, was taken off air because of royalty issues. NRK has several nice DAB channels, some which are exclusive to DAB and some which are available via the FM net in larger cities. National commercial broadcaster Kanal 24 as well as newcomer Radio2Digital recently received their DAB licences. As the DAB network is expanded, some local radio stations are licenced to broadcast via DAB.

The first test transmissions were started in the middle of the 1990s. NRK Alltid klassisk started broadcasting in June 1995 and was the world's first all-digital around-the-clock radio, with non-stop classical music. NRK Alltid nyheter (news radio) started broadcasting in 1997, at a time when there were only about 25 DAB receivers in Norway. DAB radio in Norway is divided into a national multiplex on channel 12D, and several regional multiplexes. The regional multiplexes broadcast versions of NRK P1 with regional programming and several other NRK channels which do not fit on the national band.

As of December 2006 about 70% of the population is potentially covered by DAB, but FM is by far the most common method of radio distribution. In Norway the DAB market was very small until the close of 2004, with few available receivers and little demand. Since Christmas 2004, the market has been growing; more than 100,000 units were sold in total through 2005 and 2006. As of January 2007, DAB is experiencing a slow but steady increase in popularity. Today, many less urbanised areas can receive about 20 DAB channels.

On the 26th of November 2006, the Norwegian government decided to let DAB coverage expand to 80% of the population, with two multiplexes available in all areas in May 2007. Norway aims at reaching full national DAB coverage before 2014. The Norwegian Minister of Culture stated that NRK’s FM-transmissions were to be switched of, but did not provide a specific date, only suggesting that this could happen some time after 2014. .

Poland

"Polskie Radio S.A.", the Polish public sound broadcaster, had to stop broadcast its 4 audio services in Band II DAB Block (105,008 MHz), which covered 8% of the Polish population, due to the lack of electromagnetic compatibility with the existing VHF FM services. In October 2001 the test transmission was resumed in Warsaw on the DAB Block 10B. It is foreseen that this transmission will form the first part of the SFN covering Central Poland.

In January 2004 Poland's Office of Telecommunications and Post Regulation (URTiP) has presented a new concept of a frequency planning in Band III. This idea is based on full exploitation of the spectrum by digital sound and television broadcasting after analogue switch off and changing channel spacing from 8 to 7 MHz. This allows to accommodate three national T-DAB layers and one national DVB-T multiplex at the same time.

The official governmental document concerning the digital radio is still being prepared. Unlike in the case of DTT it will not be a possible strategy but rather an analysis of implementation of the system available: T-DAB/DMB or DVB-T/DVB-H. One of the document's recommendations is to plan digital radio networks as flexible as possible in order to be able to implement a chosen system. Polskie Radio (the public broadcaster) intends to locate its own audio services within the DVB-T multiplex.

Romania

As of summer 2005, in Bucharest there is a single emitter that broadcasts five radio stations multiplexed on channel 12A (223,936 MHz - Band III). The five digital radio stations (three public service and two commercial) are: Radio România Actualitati, Radio România Muzical, Antena Bucurestilor, Radio Romantic and ProFM.

Russian Federation

There are no T-DAB transmitters working at present time, but two licences for commercial T-DAB broadcasting services supposed to be granted now, because of existing interest and demands.

Singapore

In Singapore, MediaCorp's SmartRadio was launched on 19 November 1999. Using the Eureka 147 DAB system, SmartRadio provides six digital-only stations and eight simulcast FM services, along with images and text to supplement the audio. Singapore was the first country to reach full DAB coverage .

Sweden

Swedish radio is currently offering 7 channels DAB-transmissions and cover 35-40% of the population. On 14 December 2005 the Swedish Culture minister, Leif Pagrotsky, announced that the Swedish government was freezing investment in DAB, citing that DAB was very expensive to transmit and that cheaper digital radio systems should be investigated, and digital radio should also be transmitted via the Internet and via the digital terrestrial TV system. The government decision has been criticised by Swedish broadcasters.

On the 21st December 2006, the Swedish Government renewed Swedish Radio's license to transmit DAB broadcasts in Sweden. The license also allows Swedish Radio to test technologies as DAB version 2 and DMB . DAB transmissions continue with coverage of Stockholm and other cities.

Switzerland

The extension map shows the order in which the various regions will be added to the DAB network. In 2005, the North-Eastern parts of Switzerland and the main traffic artery in the Ticino will be fitted out for DAB reception. The year after, Central Switzerland will be added to the DAB reception area and by the end of 2007, the whole German speaking population should be within reach of one of the DAB stations.

The tunnels along the main traffic arteries should be covered by DAB by the end of 2007. The remaining regions will be fitted out for DAB reception during the years 2007 to 2010. By 2010, DAB will be available in all of Switzerland.

United Kingdom

In the United Kingdom, the rollout of digital radio is proceeding. It currently operates the world's biggest digital radio network, with 103 transmitters. Experimental transmissions by the BBC started in 1990 with permanent transmissions covering London in September 1995. In September 1997 the BBC announced its national DAB rollout plans and soon reached 65% coverage. In 2006 the majority of national broadcasters all broadcast on DAB (as well as traditional AM/FM). As well as being available on DAB, many radio stations are also available via Freeview, digital satellite, cable and the Internet, although these are mostly immobile reception methods.

The public service broadcaster, the BBC, has been promoting its DAB Digital Radio stations since September 1995 and at present (2006) covers about 88% of the population, including the major motorway network. Progress beyond this figure seems to be slow, leaving some 9,000,000 of the UK population who still do not know when they will be able to receive DAB. The switch from analogue TV to digital TV (DSO) is imminent, possibly relegating DAB to a lower order of priority. FM will not be switched off when analogue TV is switched off, however, which is a growing misconception.

UK broadcasters and Ofcom have used lower bit rates to vastly increase the choice & variety of radio stations available to the public from each multiplex, leading to criticisms of reduced audio fidelity (see the Criticism of DAB in the UK section below). By August 2005, the BBC national DAB multiplex contained a number of different services, including Radios 1-5, and digital-only services such as Radio Five Live Sports Extra, 6 Music, 1Xtra and BBC7, as well as an EPG.

The Digital One national commercial multiplex began broadcasts on 15 November 1999 with 69% coverage and since then its DAB network has always been more extensive than the BBC's. It contains eight audio stations, an EPG and an experimental video service for mobile phones which was launched in October 2006. Digital One also developed along with Frontier Silicon a low cost silicon chip used in the majority of receivers and is directly responsible for DAB receiver prices falling below £100 in 2002, and as little as £30 in 2006. As a result of this, DAB portable radios are now outselling their analogue counterparts at the highstreet chain Currys.Digital (formerly Dixons).

In addition to the national services, by the end of 2004 there were 48 local and regional radio multiplexes, providing over 250 commercial and 34 BBC stations. For example, in London there are already more than 51 different digital stations available. Further regional and local multiplexes are being planned by Ofcom, the UK regulator. The UK has by far the largest number of DAB stations broadcasting in the world, the highest numbers of listeners to these services, and the lowest average audio quality in the world.

Critics of DAB in the UK argue that DAB stereo stations in the UK have poorer sound quality than FM, and point out that a large and growing number of DAB music stations are transmitting in mono. Also, 90 UK local radio stations are either unable to transmit on DAB because there is no space for them on a local DAB multiplex or because they are unable to pay the high transmission costs of DAB that the multiplex operators (that are mostly owned by the large commercial radio groups) are being charged by transmission companies and having to pass on. Ofcom announced in 2005 that it regarded DRM (Digital Radio Mondiale) as an option for the local stations unable to secure carriage or unable to pay the high transmission costs of DAB.

See also

References

  1. http://www.digitalradiotech.co.uk/dab/worldwide_dab.htm
  2. http://www.david.robinson.org/commsbill/#1_2_3
  4. http://www.worlddmb.org/benefits.php
  5. http://www.digitalradiotech.co.uk/dab/worldwide_dab.htm
  6. http://www.telos-systems.com/techtalk/00222.pdf (page 17) - the curve for MP2 is labelled 'LII'
  7. http://www.david.robinson.org/commsbill/#1_2_3
  8. http://www.for3.org/second/BBC_R3_news.html#poorDAB
  9. http://www.for3.org/second/campaign_update.html#dab_rethink
  10. http://www.digitalradiotech.co.uk/articles/All-DAB-receivers-will-be-obsolete-in-a-few-years-time.php
  11. http://www.worlddab.org/upload/uploaddocs/WorldDMBPress%20Release_November.pdf
  12. http://www.worlddab.org/upload/uploaddocs/WorldDMBPress%20Release_November.pdf
  13. Minister Helen Coonan's speech to the Australian radio industry 14 October 2005
  14. http://www.digitaleradio.be/dab/home/home.html
  15. Channels used in the Canadian implementation of DAB (L-Band)include 1452.816 MHz 1454.560 MHz1456.304 MHz1458.048 MHz1459.792 MHz 1461.536 MHz 1463.280 MHz1465.024 MHz 1466.768 MHz 1468.512 MHz 1470.256 MHz 1472.000 MHz 1473.744 MHz 1475.488 MHz 1477.232 MHz 1478.976 MHz 1480.720 MHz 1482.464 MHz 1484.208 MHz 1485.952 MHz 1487.696 MHz 1489.440 MHz 1491.184 MHz
  16. http://tdab.cz/
  17. http://politiken.dk/erhverv/article168837.ece
  18. http://www.digitalradio.de/
  19. http://www.rte.ie/radio/dab.html
  20. 50 000 DAB-radioer solgt
  21. http://www.propaganda-as.no/hovedseksjon/media/dab-salget+tok+av+i+fjor/art365341.html%7C DAB-salget tok av i fjor
  22. http://www.tu.no/data/article64433.ece%7CSikrer DAB
  23. http://www.investromania.ro/news/news.php?aid=2606
  24. http://www.smartradio.sg/aboutsr.htm
  25. http://www.sr.se/cgi-bin/p2/program/artikel.asp?nyheter=1&ProgramID=1012&artikel=1107289
  26. http://www.nyteknik.se/art/48499
  27. http://www.dab-digitalradio.ch/
  • Stott, J. H.; The How and Why of COFDM, BBC Research Development

External links

Category: