Superbat Blog

REVIEW:

DAB is (Digital Audio Broadcasting) shorthand for digital audio broadcasting DAB is following the AM, FM broadcasting traditional analog broadcast the third generation;

European Eureka-147,

US IBOC (In-Band On-Channel)

France DRM (Digital Radio Mondiale),

China Eureka-147,

frequency:

UK: Band III (174 - 230.0 MHz),

Germany: Band III (174 - 230.0 MHz) and L Band (1452 - 1492MHz),

Canada: L Band (1452 - 1492MHz)

Satellite digital audio broadcasting DAB-S three forms:

1) The European Eureka-147 system, use the 1452 - 1492MHz (L Band), currently only supports terrestrial digital audio broadcasting DAB-T use did not launch a satellite;

2) US WorldSpace (WorldSpace) satellite digital audio radio service (SDARS, Satelite Digital Audio Radio Service) system, using 1467 - 1492MHz (L Band)

3) US Sirius XM's Satellite Digital Audio Radio Service (SDARS) systems, use 2320 - 2345MHz (S Band)

I. Overview:

DAB is (Digital Audio Broadcasting) shorthand for digital audio broadcasting DAB is following the AM, FM broadcasting traditional analog third-generation broadcasting.

Compared to traditional analog broadcasts, DAB broadcast can provide higher quality, lower transmission power can be realized, covering a wider area. DAB with anti-noise, interference, resistance to decay, zero signal distortion for high speed mobile reception and so on. Within a certain range from multipath interference, suitable for use in a highly mobile environment, such as a car.

Second, characteristics

DAB and traditional broadcasting (FM, AM) The biggest difference is that DAB can receive multimedia messages, including text, data, images, video, and even real-time information updates.

Because digital features, DAB can transmit any text or even an image signal, enabling the DAB radio and TV are connected, in order to restore the digital signal in the video image.

In this sense, DAB longer a purely broadcasting system only transmits audio signals, already belongs to Digital Multimedia Broadcasting DMB.

Digital Audio Broadcasting

Analog audio broadcasting

Transferring content

Voice, text, pictures, video clips and other multimedia content

sound

Mobility

Signal and sound quality

Without the interference of multipath propagation, ensure quality

The sound quality is affected by terrain noise, other signal interference

Channel load

Through better compression techniques, a channel can simultaneously transmit multiple sets of near CD-quality program

A channel can only send a standard quality audio program

Spectrum

Can SFN

It requires the use of complex frequency network

DAB's original intention was to change traditional broadcast technology to improve the sound quality of the broadcast and provide high-speed mobile reception performance.

DAB has become Britain and other Western European countries digital audio broadcasting standard, most taxis are equipped with DAB receiver.

The current DAB system can be divided into the world, the European Eureka-147, US IBOC (In-Band On-Channel) and the French DRM (Digital Radio Mondiale), as well as Japan and some other countries develop their own DAB system, using our current pilot Eureka-147 system.

DAB digital radio is an association made up of 12 members - the famous EUREKA-147 being developed, the original name of the system is a digital audio broadcasting (DAB), and has been used as a criterion for distinguishing real DAB radio and other audio broadcasting . In 1994, Eureka-147 is an international standard adopted today, most of the world is not to achieve this standard is being tested to this standard. The only objection to embrace high-definition broadcasting and satellite digital broadcasting of the United States and select a new broadcast format transfer method Japan.

Third, the application scenarios

DAB main advantage is mobile, portable and multimedia broadcasting receiving apparatus can be divided into vehicle type, household type, portable type and a computer to receive cards.

If you listen to audio programs, by household, automotive, handheld digital broadcast radio, or a MP3 digital broadcast receiving function and the like.

If neither listen to audio programs, and video programs, and enjoy data services, you can have a DAB mobile multimedia broadcast receiving function mobile phones, car receivers, GPS navigation systems, personal multimedia player (PMP), MP4, Pocket PC ( PDA), a variety of end digital cameras, laptop computers and other reception.

Using DAB technology as navigator can receive a broadcast, like, understand real-time traffic information, weather conditions, and so open an elevated ramp. With respect to the previously used Traffic Message Channel TMC Navigator, the wider area covered DAB technology, listen to the signal and sound quality is also superior.

By digital television, Internet, mobile phones and other new methods on playing slowly DAB digital audio broadcasting development in most countries, the development process basically stuck in the 1990s plan.

Fourth, the working frequency

When selecting DAB frequency is usually work to be considered, as frequency increases, the allowable distance between the transmitting station to be reduced, so that the number of transmitters needed to increase the relationship between the square.

Conventional DAB receiver for the L-band and band III. Britain can only receive on Band III DAB signal, using Band III and L Band DAB digital radio in Germany, and Canada use only L Band.

(1) Band I (47 - 68MHz), seldom used

In the band, since the effect of ultra-distance (E horizon) make the application received limited. In addition, in the band, especially the so-called "that noise", such as subway interference for DAB, it is not the ideal working band.

(2) Band II (87.5 - 108MHz), digital terrestrial broadcasting

The band is allocated to the use of terrestrial sound broadcasting, FM broadcasting is now occupied. Obviously, DAB eventually be transmitted in the band. The band is not only assigned to sound broadcasting, and because it is close to 100MHz, for terrestrial digital sound broadcasting is particularly desirable.

(3) Band III (174 - 230.0 MHz) initial trial network

The band equally well suited for digital terrestrial sound broadcasting, particularly in the field test conducted DAB or implementation of the initial phase, for example, 233 - 230MHz 12 TV channels.

(4) Band IV / V (470 - 790MHz), a cellular network synchronization

In the UHF band, more than 80% for television coverage. If the synchronization network is small hive synchronization network, and the maximum driving speed is limited, then, UHF band for DAB, it is entirely possible applications.

(5) L-band (1452 - 1492MHz), local coverage and small synchronous network

European Broadcasting Union (EBU) have pointed out that, with the work to cover the ground in the 1.5GHz range DAB digital synchronization network, although technically possible, but compared with the VHF (such as TV channel 12 band, the number of stations to transmit 16 times larger , its operating costs are significantly higher, according to rough estimates, about four times when operating in the VHF band. in addition, car receivers, the system requires two antennas, one for the VHF band, one for 1.5GHz.L band mostly for local coverage and small synchronous network.

Frequency from 1228MHz to 1575MHz frequency is called L band DAB digital radio frequency, also applied to the broadcast service via satellite.

(6) S-band (2300 - 2600MHz), compared with the current configuration of your Pleiades

In order to achieve the same coverage and L-band, S-band to work on the satellite transponder, the need for more power. At the same time, due to the higher masking, in the "shadow" region requires additional padding transmitter. In addition, due to the Doppler effect, making them less effective at filling transmitters operating in the same frequency. In general, digital sound broadcasting in the S-band work is an expensive option, and provides only very limited technical possibilities.

V. signal source covering

DAB signals can be transmitted in different ways to cover the user receiver, ground grids, satellites, local radio and electrical (optical) cable network.

1. Ground SFN synchronization network coverage.

The so-called single frequency network, a synchronous network refers to all base stations have transmitters operate at the same frequency as the center block, a modulation signal is also accurate synchronization, all transmitters really achieve consistency. In this case, the edge of the coverage area for each transmitter, a plurality of signal transmitters are complemented each other, thereby increasing transmission reliability.

When the distance between the transmitter and the network layout to meet certain conditions, each transmitter can achieve power and mutual assistance, and therefore synchronous network transmitter power does not need a lot, usually <1KW.

Construction of single-frequency synchronous network through terrestrial transmitters network to achieve coverage for the population, urban and densely covered with smaller countries and regions such as Europe and Japan.

And FM radio fundamental area that the DAB SFN SFN synchronization can run at the same center frequency, bandwidth 1.536MHz frequency blocks a large area of multiple programs covering. Single frequency network synchronization technology, in the same spectral width, compared with the traditional broadcasts generally can be transmitted more than three times the program, or at the same number of transfer programs, the desired spectral width of only traditional broadcasting 1 / 3, the larger the area of synchronous network coverage, spectrum use DAB system more economical.

2. The satellite coverage.

Satellite digital audio broadcasting DAB-S is different from the digital TV broadcast, audio broadcast of each program bandwidth is much smaller than television, satellite digital audio broadcasting use of L-band, enabling high-speed mobile reception state.

Advantages satellite digital audio broadcasting DAB-S having the relatively large coverage area; broadcast infrastructure and operating costs are much lower than the terrestrial digital audio broadcasting DAB-T, can save considerable numerous terrestrial base station transmitter synchronization network construction and maintenance cost; can achieve global broadcast coverage.

DAB-S is suitable for a vast, complex terrain of countries and regions, strictly speaking, not to get involved in Europe, the United States has come to the world.

* DAB-S at present there are three main forms:

1) The European Eureka-147 system, use the 1452 - 1492MHz (L Band), currently only supports terrestrial digital audio broadcasting DAB-T use did not launch a satellite;

2) US WorldSpace (WorldSpace) satellite digital audio radio service (SDARS, Satelite Digital Audio Radio Service) system, using 1467 - 1492MHz (L Band);

WorldSpace's SDARS by three geostationary satellites Star of Africa AfriStar, AsiaStar Asia Star, Star AmeriStar Americas offer SDARS, we plan to achieve global coverage.

WorldSpace CD era in the company's development, due to the high price of the receiver, the satellite signal blind spots, slow satellite launch by the Internet, MP3, mobile phones and other impact player, WorldSpace company was bankrupt in 2008 and the termination of audio broadcasting services.

3) US Sirius XM's Satellite Digital Audio Radio Service (SDARS) systems, use 2320 - 2345MHz (S Band).

Via satellite and terrestrial repeaters (Ground Reapter) network, mainly for domestic users.

XM Radio and Sirius by the BBC in the 1990s started operations SDARS, not good for operating in 2007 merged into Sirius XM Radio.

3. The local radio coverage.

Use a DAB transmitter covering local city.

4. Cable, light coverage.

DAB signal is transmitted to the user receiver via cable or fiber optic cable network.