What is a dab receiver? Russian authorities have returned to the idea of ​​digital radio

Stages of development of DAB

European firms founded the Eureka-147 consortium in 1987 with the aim of developing a fundamentally new system digital radio DAB broadcasts. The participants in this project are about 50 companies and organizations from the UK, Germany, France, Holland, Italy, Sweden, Switzerland, Norway, Finland, Japan, Canada, the USA and several other countries. In 1995, IRPA im. A.S.Popova.
In 1992, L- and S-bands were allocated to DAB based on a worldwide agreement. The first receivers, mainly for measurement purposes, were built in 1988. Since 1990, a number of members of the Eureka 147 project have taken part in the JESSI project, which developed the first integrated circuit for commercial DAB receivers. The first consumer DAB receiver was presented at an exhibition in 1995 in Berlin. The miniaturization of receivers continues; currently, their serial production is carried out by Grundig, Philips, etc. Several tens of thousands of receivers are already in use in European countries.

Great Britain
In 1994, the UK government decided to allocate the 217.5-230 MHz frequency range for terrestrial DAB. This band can accommodate seven multi-program DAB signals (called “DAB blocks” or “ensems”), each occupying approximately 1.55 MHz of bandwidth. This provides guard frequency intervals between DAB signals of approximately 200 kHz wide. To facilitate the identification of ensembles, each of them is assigned a short identifier (11B, 11C, 11D, 12A, 12B, 12C, 12D). Ensemble 12B from September 1995 uses the BBC to broadcast five national programs received throughout the UK. Ensembles 11C, 11D, 12A, 12D are reserved for Independent National Radio (INR) Services.
Already at the first stage, an area covering the territory of London and its suburbs, which is home to more than 10 million people, was served. By now, more than half of the country's population can take part in the program.

Germany
In 1995, at a conference in Wiesbaden, it was decided on the possibility of using frequencies in VHF bands II (87 - 108 MHz), III (174 - 240 MHz), and in the L-band (1452 - 1467.5 MHz) for terrestrial DAB. In the same year, experimental DAB broadcasting of seven sound programs and service information from 13 radio stations at frequencies of 12 TV channels. Additional local programs broadcast in L-band. In North Rhine-Westphalia by 1996, five transmitters operating at frequencies of TV channel 12 were installed; additional local stations began broadcasting in Cologne and Düsseldorf. At the beginning of 1996, 2,000 receivers were distributed among listeners; by the end of the same year, the population already had 15,000 thousand DAB receivers with varying levels of service. Since 1997, regular DAB broadcasts began in Bavaria.
Today, more than 60% of the country's territory is provided with broadcasting in this standard. It is expected that by 2004 the DAB signal will be available throughout Germany. The complete transition from analogue to digital broadcasting should be completed between 2010 and 2015. For broadcasting, a network of transmitters will be used operating in TV channel 12 (223-230 MHz, one DAB block for each land) and in the L-band (1452-1467.5 MHz), where 100 DAB blocks are given to regional programs. With this distribution, a minimum of twelve high-quality stereo audio programs and a number of supplementary information channels can be received anywhere in Germany using a DAB receiver with a simple whip antenna.

Russia
Work on the creation of a digital radio broadcasting system began in Russia at the beginning of 1980 at the VNIIRPA named after. A.S. Popov, which culminated in the creation domestic system DVR, prototypes of transmitting and receiving equipment and the organization of experimental broadcasting in Novgorod in 1993. However, since in 1995 the Eureka-147/DAB system, which differs significantly from the domestic one, was standardized as a pan-European system, then, starting from 1993, all work was focused on the implementation of this system in Russia. Unfortunately, what follows is mainly not facts, but intentions.
For experimental broadcasting in St. Petersburg, the Ministry of Communications decided to allocate a frequency band in the range 92 - 100 MHz. Experienced work were successfully carried out, however, for the implementation of the specified CRW system on a scale Russian Federation these efforts are not enough. There is still no unified federal program for introducing digital standard on television and radio-electronic media.
To solve the broadcasting problem, it is necessary to solve many organizational problems, first of all, the allocation of a separate frequency range. European experience has shown that using the 88-108 MHz range in conjunction with existing FM stations is inappropriate. At the end of 1999, the board of the Ministry of Communications of the Russian Federation outlined a three-stage strategy for the transition to digital radio broadcasting, designed for 10-15 years:

2001-2002 Experimental broadcasting in Moscow and St. Petersburg of 6 state stations: “Radio Rossii”, “Mayak”, “Mayak-FM”, “Yunost”, “Orpheus” and one local one. It is possible to transmit paging or multimedia information.

2002-2003 Expansion of experimental broadcasting to Moscow and Leningrad region, the appearance of 6 commercial stations.

2003-2010 Full coverage of the territory of the Russian Federation, in the future - a reduction in the number of analogue VHF stations.

The range of 176-230 MHz was recommended for development. However, a strategy is not a program and no real steps have yet been taken to implement this concept. Russian bureaucracy is stronger than progress. Specific frequencies in the recommended range can be allocated only after a lengthy analysis of the electromagnetic situation, which must be carried out by the Radio Research Institute. And after the allocation of frequencies by the Committee of the Ministry of Communications, they still have to win a competition for its use in the MPTR (Ministry of Press and Television and Radio Broadcasting). After this, the only thing left is to find funds to implement the project. You can’t count on government funding, much less public funds. Recently, some Western companies - manufacturers of DAB equipment - became interested in the state of the Russian project. Wanting to enter the Russian market, they are ready to finance the deployment of an experimental broadcast zone. This is probably the most realistic scenario successful development events.
On May 14, 2002, experimental transmissions of stereophonic sound broadcasting programs “Radio Russia”, “Mayak” and “Yunost” began in digital format via the communications and broadcasting satellite “Express-6A” (location point 80 degrees east) to the territory of Russia from Kaliningrad to Vladivostok. However, this is not yet a regular broadcast.

DRM SYSTEM

The DRM standard has been developed for medium and short wave bands. The developers decided to turn to these bands because they provide unprecedented opportunities for long-distance broadcasting at significantly lower costs for its organization, and the technical quality of broadcasting no longer meets modern requirements.
The DRM (Digital Radio Mondiale) organization was founded in March 1998. It is a non-profit international consortium that includes more than 60 participants from Europe, Asia and America, including the Russian channel "Voice of Russia". The new standard, called “system A,” is based on a modified prototype of the Skywave-2000 system, developed by the French company Thomcast. In the fall of 2000, the International Telecommunication Union recommended its members to use it, after which the name “DRM system” stuck.
The format is characterized by flexible transmission parameters, allowing it to be used in all bands below 30 MHz. At the same time it can be used for the VHF band. The first DRM systems will broadcast in the standard radio channel bandwidth of 9/10 kHz. Subsequently, wider streams can be generated, increasing the quality of signal transmission. To implement the new system, existing AM transmitters can be upgraded, which will remove a number of transition problems.

The main advantages are as follows:


Improve reception and sound quality

Can be used in all ranges

Combined data and audio transmission possible

There is a choice of modes to optimize throughput/quality and reception reliability/stability

Very high spectrum efficiency: 3 to 4 bit/Hz/s;

The system is open to future improvements, new compression methods and encoding processes. For RF broadcast channels below 30 MHz, a bandwidth of 9 or 10 kHz is currently used.

DRM system can be used:


within the nominal bandwidth, in accordance with this layout;

within channels with a bandwidth of multiples of 4.5 kHz (half 9 kHz) or 5 kHz (half 10 kHz), in order to be able to co-broadcast with an analogue AM signal or to provide higher transmission capacity if this is allowed in the future.

Brief description of the DRM standard

Unlike the DAB standard, which uses MPEG II, DRM uses a more modern version of MPEG-4 compression. It includes an adaptive AAC (Advanced Audio Coding) signal compression engine in mono and stereo options, as well as CELP (Code-exited Linear Prediction) for high-quality coding of speech and noise-like signals. In MPEG-4, long-term prediction is carried out not in the time plane, but in the spectral plane. The encoder makes a prediction and then encodes either the difference between the actual and predicted signal, or the input signal itself if its value can be encoded more compactly than the difference. In addition, the encoder supports several new mechanisms related to the stream's ability to adapt to changes in channel parameters. Any of the options can be supplemented with the SBR (Spectral Band Replicatoin) technique, designed to improve the quality of high-frequency transmission. When transmitting at frequencies below 30 MHz, all formats except stereo use the 9/10 MHz band. The use of SBR technology requires a wider bandwidth.
In addition to audio signals, data can be transmitted in a digital stream. The multiplexed audio and data stream form the Main Service Channel (MSC). Up to 4 streams are transmitted to the MSC, each of which carries either audio or data. The MSC channel information is divided into logical frames of 400 ms each. In addition to the MSC, two additional channels are formed. The main and service channels are multiplexed in a certain way, resulting in the formation of transport superframes with a duration of 1200 ms.
The first additional channel, Fast Access Channel - FAC (high-speed access channel), carries data on the parameters of the radio frequency signal and information that allows you to highlight individual services. Signal parameters include stream identifier, occupied bandwidth, modulation type, coding type, interleaving depth index, number of transmitted services. These parameters are transmitted in every FAC frame. Parameters that characterize services include an indication of the type of service (audio/data), a conditional access flag, a language indicator, and some others. They are transmitted sequentially - in one frame, parameters related to one service.
The second additional channel, Service Description Channel - SDC (Service Description Channel), contains information related to conditional access, program guide, copyright information, supporting information for some applications, and links to alternative frequencies on which the same channel is transmitted. SDC information is placed at the beginning of each superframe and begins with references to alternative frequencies. This allows you to automatically select the channel that is currently best received.
DRM, like DAB, uses the COFDM modulation system. This system is very effective for transmitting signals over a radio channel with multipath propagation of radio waves and selective signal fading, characteristic of short waves. A guard interval is used to compensate for multipath interference. It should not exceed 20% of the total symbol duration so as not to reduce the channel capacity. The number of carriers placed in the channel's frequency band is limited by the Doppler frequency shift of the signal that occurs in mobile reception mode. Taking these factors into account, approximately 200 carriers are used in the 9/10 kHz band. Their exact number, as well as the duration of the symbol and the guard interval, depends on the nature of the propagation of radio waves (surface or spatial), the expected transmission range and the required reliability.
The channels included in the MSC are divided into 2 parts, differing in the importance of information for correct decoding. They are subject to separate noise-resistant coding, characterized by varying degrees of noise immunity. As noise-resistant coding, data interleaving and convolutional coding with code rates from 0.5 to 0.8 are used. Data interleaving in COFDM systems is implemented in both time and frequency, which allows signal restoration at a high level of selective fading in the radio channel. In addition, to combat this phenomenon, pilot signals are introduced into the stream, allowing the receiver to estimate the degree of attenuation of the signals at each carrier frequency. The level of protection imposed also depends on the range and expected distance of the signal. In particular, when transmitting on short waves, the interleaving depth is 2.4 s, and on long and medium waves - 0.8 s. In addition, shorter wavelengths use convolutional coding with lower code rates and introduce more pilot signals.

PROSPECTS FOR DIGITAL BROADCASTING

It must be recognized that digital broadcasting is superior in quality and capabilities to analogue. However, qualitative superiority does not always translate into quantitative superiority, as happened with the DAB standard. Therefore, digital broadcasting will not completely replace analogue broadcasting very soon, and it is too early to talk about the disappearance of traditional radio. It was expected that in almost all developed countries of Europe since 1997-98. Regular DAB broadcasting will begin, and by the year 2000, coverage of 80% of the European population will be completed. However, the actual rate of coverage is noticeably lower than forecasts. Manufacturers are in no hurry to increase the production of appropriate receivers because they are not confident in the sales market. And the market is not ready to accept new receivers, since most listeners are satisfied with the quality analogue broadcasting on VHF and does not yet see the possibilities of the new format. There is also real competition from record companies interested in listening to recordings rather than radios in cars - sales revenues significantly exceed the royalties of radio stations.
The original mistake was that DAB was seen only as a technical standard. However, the history of technology clearly demonstrates that only technical advantages are not yet a decisive argument for the mass consumer when choosing a product; there must still be some other advantages. Guessing what will be in demand by the market is an impossible task. Suffice it to recall such recording formats as DAT, DCC or minidisc, which have not supplanted the compact cassette and are retreating under the onslaught of solid-state memory.
When developing DAB, the possibility of transmitting additional information was included initially, but the broadcasting concept was initially preserved: the same principle of constructing programs, the same annoying advertising. Today's broadcast programs are primarily aimed at the faceless average listener and appeal to a national audience. With this approach, it is impossible to take into account the regional characteristics of the audience, local interests and traditions, etc. The DAB standard is designed for local and regional broadcasting and fully meets the interests of commercial radio, but in general the change in strategy is quite slow. To interest the consumer, and thereby stimulate the manufacturer, the BBC was the first to create new program For digital format, other broadcasters followed suit.
DAB radio is planned to be used not only for broadcasting traditional radio programs (free and encrypted), but also for transmitting business information. It will be displayed on the DAB receiver display or on the computer monitor in the form of teletext. This possibility exists thanks to the use of the MOT (Multimedia Object Transfer) protocol, designed to bring heterogeneous data to a standard teletext format. In addition, it is planned to use DAB services to transmit encrypted information intended for a narrow circle of subscribers. This service can be used by banks, insurance offices and other organizations to distribute information between branches.
Another service that is expected to be developed within the framework of national DAB projects is the provision of information on road conditions. This is especially true given that DAB radio is heavily geared towards mobile reception. In addition to providing wide range related information, digital broadcasting implies the possibility of organizing on-demand programs and other interactive services. In mobile receivers, GSM networks are supposed to be used as a return channel.

The future position of DAB in the market may be negatively affected by the widespread adoption of DVB satellite television broadcast receivers, which are clearly favored by both industry and radio stations. The commissioning of digital multiplex radio dRadio ensured the broadcast of up to 40 uncoded radio programs in MPEG-2 format via the HotBird-5 satellite in one single DVB channel. The salvation of DAB so far is that only stationary receivers have been developed for DVB, designed for operation in one of three modes: DVB-S (receiving a signal from a satellite), DVB-C (via cable) and DVB-T (terrestrial). However, new direct systems satellite broadcasting allow you to receive programs in a moving car.
At the end of 2001, two national networks of satellite direct digital radio broadcasting began regular operation in America - Sirius Satellite Radio and XM Satellite Radio. Dozens of new high-quality radio programs immediately appeared on the air. Experts note not only a fundamentally different business model of satellite broadcasting, which can exist even without traditional radio advertising, with the money of subscribers, but also the expected revolutionary changes in programming and in the choice of the content of listened programs, which will become available to radio listeners themselves. This entire range of pleasures costs the listener $9.95 a month. Companies are confident that, as with cable television, audiences will want to pay for something that directly serves their interests and does not contain advertising they hate. Sirius Satellite Radio and XM Satellite Radio are full of optimism, and the cost of the receivers is already comparable to the cost of existing car radios. Given that about 24 million car receivers are sold annually in the US, by 2007 it is predicted that 15 percent of all cars will be equipped with satellite broadcast reception equipment.
Three satellites Sirius Satellite Radio cover the entire territory of the United States with a digital signal. Reception is carried out on an antenna measuring 20-30 cm. In addition to satellites, the company has deployed a network of 100 ground-based repeater transmitters. 100 channels are broadcast from satellites in MPEG-2 format.
XM Satellite Radio Holdings Inc. offers radio listeners 71 music channels, their repertoire covers the masses musical styles from classical music to rock. In addition, radio listeners are offered news channels, for which content is provided by CNBC, CNN Headline News, USA Today and C-SPAN, as well as several other agencies. Sports and entertainment programs, talk shows and programs for children are broadcast via satellites. In the space segment of the digital satellite broadcasting system, two communication satellites code-named Rock and Roll are operating. The signal is received from satellites directly to radio receivers, and in urban areas with multi-storey buildings, terrestrial repeaters will additionally be used to broadcast the signal.

The main advantage of direct satellite broadcasting over existing VHF radio stations is globality. However, the costs of creating such a system are quite high. In countries and regions with low population density or located at a considerable distance from the equator, satellite radio may be inefficient and unpopular for purely economic reasons. And in a number of cases, terrestrial digital broadcasting has more prospects in the foreseeable future, in contrast to the United States, if only due to orders of magnitude lower costs for their implementation. This is where DRM comes into the picture.
The development of digital broadcasting in "long-range" ranges is especially important for Russia, given its vast territory and average population density of 9 people per square kilometer. IN small towns, where more than half of the country's population lives, commercial VHF-FM broadcasting is often unprofitable. Therefore, excellent prospects are open for almost forgotten bands below 30 MHz in Russia.
However, there are other problems. When introducing digital radio broadcasting in the AM bands, it is necessary to ensure that the reception capabilities of more than 2 billion existing analogue radio receivers are maintained. This can be achieved by simultaneous transmission a half-rate digital broadcast signal and a compatible single-sideband analog broadcast signal. In this case, owners of conventional radio receivers will receive an analog program, and a digital one will be heard as weak high-frequency noise. The radio frequency spectrum of the emitted compatible signal does not exceed the 9 kHz allocated today by the ITU for one radio channel. In clean digital mode transmission spectrum transmitted signal can occupy the same standard 9 kHz or, in the case of extended mode, 12 kHz, while achieving increased sound quality and the transmission of additional multimedia information.
The digital technology behind future DAB receivers will also make it possible to receive DRM signals. For radio stations, the transition to digital broadcasting in the short, medium and long wave bands means a significant (by about three-quarters) reduction in broadcast costs while maintaining the same coverage radius. At the same time, transmitting stations can continue to use the existing infrastructure.

Hello Geektimes.

Digital radio broadcasting is gradually being introduced into various countries. In Europe and Australia this is the DAB/DAB+ standard, in the USA HD Radio, in China CDR (China Digital Radio). Among the advantages for the user - more clear sound due to the digital stream, additional services (for example, the name of the song and the name of the artist on the receiver screen), and, in the case of DAB, larger number stations compared to FM. Receivers that support digital radio are already relatively inexpensive, starting at around $40.

Russia has not yet officially joined either standard, but if it does, it will most likely be DAB. Its test operation has already been carried out in Moscow, and receivers on the European market are geographically more accessible to the Russian Federation than American ones. New European cars (of which, again, there are more than American ones) are often already equipped with a DAB receiver. Well, for now, for test purposes, anyone can run DAB at home, if they have an SDR transceiver.

(Image Source/Getty)

Details under the cut (be careful, there are a lot of long and boring configs).

How it works

Unfortunately, different standards are incompatible with each other.

European DAB is an MP2 or AAC stream transmitted using ODFM in channels with frequencies from 174 to 239 MHz. A maximum of more than 30 channels are possible, the width of each is about 1.5 MHz; several stations can be transmitted simultaneously in a channel. According to Wikipedia, using DAB using a bitrate of 192kbps is 3 times more efficient in terms of number of stations than regular FM.

The spectrum of one DAB channel on an SDR screen looks like this:

For comparison, this is what FM stations look like at the same scale:

In American HD Radio we took a different path - digital channels were added “to the side” to the already existing FM stations. This made it possible not to allocate new frequencies and maintain compatibility with old receivers. The downside is that in large cities the FM airwaves are already busy. On the other hand, even maximum number 50 stations for FM is quite good; listeners most likely don’t need more.

The HD Radio spectrum looks like this (screenshot from YouTube):

Chinese CDR I decided to copy the American approach, unfortunately, my zero knowledge of Chinese is not enough to find more detailed information on it.

As for receivers, their price on Amazon ranges from $30 for the simplest models, to >100$ for more advanced ones with a touchscreen, Wifi or color screen.

But “the Chukchi is not a reader,” so we will launch a test radio in DAB/DAB+ format ourselves. Unfortunately, it won’t be possible to launch HD Radio, the format is closed, and there are no available encoders for it.

Launch DAB/DAB+

The process is actually not complicated, but it is very painstaking in terms of creating the necessary configs. For the test, we will need Linux and an SDR with transfer capability, such as HackRF or USRP.

1. Compiling the project

Linux is needed to compile the encoder. I was using Ubunty, finished image for VirtualBox was downloaded from http://www.osboxes.org/ubuntu/.

Compiling ODR-AudioEnc
First you need to compile the DAB/DAB+ audio encoder, you can find it at github.com/Opendigitalradio/ODR-AudioEnc.

Git clone https://github.com/Opendigitalradio/ODR-DabMux.git cd ODR-DabMux/ ./bootstrap.sh ./configure make sudo make install
Compiling ODR-DabMod
This is a modulator that actually sends data to the transmitter. The assembly principle is the same, the command for downloading is:

Git clone https://github.com/Opendigitalradio/ODR-DabMod.git
If any libraries are missing during the build, they need to be installed using apt-get.

Now all the parts of the project have been collected, and with all this we will try to take off.

2. Configuration

Unfortunately, USRP did not work in a virtual machine, and it was too lazy to install a full-fledged Linux on a disk. Therefore, I did not consider the streaming mode - the multiplex was assembled from pre-prepared mp3 files, and the resulting IQ file was launched under Windows. Yes, in general, streaming broadcasting is not necessary for the home, there was no task to make a “pirate station”.

Data preparation
There will be 2 channels in our multiplex, for which I downloaded 2 mp3 files from youtube and named them (who would have guessed) sound01.mp3 and sound02.mp3 respectively.

Convert files to WAV with a bitrate of 48000:
ffmpeg -i sound01.mp3 -ar 48000 sound01.wav
ffmpeg -i sound02.mp3 -ar 48000 sound02.wav

Let's convert them to DAB format:
odr-audioenc --dab -b 128 -i sound01.wav -o prog1.mp2
odr-audioenc --dab -b 128 -i sound02.wav -o prog2.mp2

The output should be 2 files prog1.mp2 and prog2.mp2.

Creation of a multiplex

First we need to create a file describing the configuration of our “radio station”. Let me remind you that in one DAB channel there can be many stations, each with its own parameters.

Create a file “config.mux” with the following text:

General ( dabmode 1 nbframes 2000 ; Set to true to enable logging to syslog syslog false ; Enable timestamp definition necessary for SFN ; This also enables time encoding using the MNSC. tist false ) remotecontrol ( telnetport 0 ) ensemble ( id 0x4fff ecc 0xec ; Extended Country Code local-time-offset auto international-table 1 label "mmbtools" shortlabel "mmbtools" ) services ( srv-p1 ( label "Station1" ) srv-p2 ( label "Station2" ) ) subchannels ( sub-p1 ( type audio inputfile "prog1.mp2" bitrate 128 id 10 protection 4 ) sub-p2 ( type audio inputfile "prog2.mp2" bitrate 128 id 11 protection 4 ) ) components ( comp-p1 ( service srv-p1 subchannel sub-p1 ) comp- p2 ( service srv-p2 subchannel sub-p2 ) ) outputs ( output1 "file://output.eti?type=raw" )
The config describes the channels that will be in the multiplex and their data sources. The nbframes parameter specifies how many frames to create, 2000 frames corresponds to approximately one minute of playback.

When the file is saved, create a multiplex:

Odr-dabmux config.mux
The output should be a file output.eti, in my case its size was 12MB.

Broadcast

There are two possibilities here. On "real" Linux, odr-dabmod can directly transfer data to the transceiver, but it did not work under VM. Therefore, as an output parameter, I specified a raw file that will contain data compatible with Gnu Radio.

Create the config.ini file:

transport = file source = output.eti loop=0 digital_gain=0.9 rate=2048000 output = file format = complexf_normalised ;format = s8 filename = output.iq
The key point here is the output format and its type. For USRP I use the complexf_normalised format; for HackRF, in theory, 8-bit s8 is suitable.

Save the config and start the conversion:

Odr-dabmod config1.ini
All! The output should be config.iq, in my case about 700MB in size per minute of recording (IQ float format). We copy it to the “main” computer, and Linux can be closed.

3. Testing

As I said earlier, I don’t have a DAB receiver, the Chukchi are not a reader, I don’t listen to the radio at all :) For testing, I used an RTL-SDR “whistle” and a free program

With digital television everything is more or less clear. How does the “digitalization” of radio broadcasting happen? The main and leading standard in the broadcasting industry today is Digital Audio Broadcasting (DAB) technology, developed in the late 1980s as part of the Eureka 147 project.

During development this standard persecuted simple goals: improving the quality of radio broadcasts, improving noise immunity, introducing interactivity and new services into radio. It is important to note that the start of work on the DAB standard dates back to 1981, when employees of the Institut für Rundfunktechnik (IRT) worked on this project. Since 1987 the work was transferred to the European research project group (Eureka 147).

The standardization of DAB technology is carried out by the World DAB Forum, which represents more than thirty countries around the world. It is interesting that the World DAB Forum does not include the USA, since this country was chosen own system digital radio – HD Radio (IBOC).

Many people do not understand the point of switching to digital radio; they are also satisfied with those radio stations that today broadcast in the AM and FM bands. But maybe we should face the truth? It's the 21st century, AM technology was introduced to the world in the 1920s, FM in the 1940s. It turns out that today we receive radio signals using a system developed seventy years ago. So DAB technology offers the oldest broadcast technology a move into the digital age.

Previously, DAB broadcasting used the MP2 audio stream encoding system (MPEG-1 layer-2). It was developed in the late 1980s and refined in the early 1990s. The new DAB specification, DAB-2 (DAB+), will use audio compression methods such as MPEG 2 Advanced Audio Coding AAC, MPEG 4 Error Resilient BSAC (Bit Slice Arithmetic Coding), MPEG 4 AAC+ SBR and likely WindowsMedia audio codecs.

That is, the audio quality, say, 128 kbit/s, achieved using new audio codecs and the ability to record the signal in the AAC format will sound better than an audio stream with the same bitrate, but compressed using the MPEG 2 layer 2 method and the ability to record in MP3 format. Roughly speaking, today the quality of the audio stream when listening to DAB radio corresponds to the quality of the average MP3 file (from 128 to 256 kbps).

We receive a DAB signal

More than 475 million people around the world today have access to more than 800 different DAB broadcasts, services and services. There are currently over 200 different DAB receivers available on the market for consumers and their number continues to grow.

It is worth noting that DAB receivers can be completely confused with radio receivers, which are positioned as “digital”, but, in fact, are analogue with some additional digital features. For example, the “automatic digital tuner” parameter does not mean that the receiver will receive a digital signal.

Today there are several types of DAB receivers. First of all, these are car devices that, in addition to the AM and FM bands, also support digital radio. Many manufacturers offer DAB tuners that are compatible with car radios that were released several years ago. Other manufacturers produce completely ready-made DAB solutions, which involve a complete replacement of the car's audio system. The main companies producing car DAB receivers: Alpine, Blaupunkt, Clarion, Goodmans, Grundig, JVC, Kenwood, Ministry of Sound, Pioneer, REVO Digital, Siemens VDO.

In second place are DAB receivers, which are intended for use as part of a home personal computer. When you install such a receiver in a PC, you get the opportunity to listen to digital radio broadcasts on your computer without any additional network or Internet connections. You can also record broadcasts in mp3 format directly to your hard drive. Similar devices are produced by: Modular Technology, Mtech, PersTel, Terratek.

Next come home stationary DAB Hi-Fi tuners, which are available in two versions: both built into an existing audio system at home, and individual devices. There are options on the market that only support DAB, but if you wish, you can also find combined devices (DAB/FM/AM). The first such tuner was released in September 1998. by Arcam. The leading manufacturers of such equipment today are: Acoustic Solutions, Arcam, ARION, BUSH, Cambridge Audio, Cymbol, ELANsat, Eltax, Genus Digital, Goodmans, Grundig, Hitachi, i.Tech Dynamic, Intempo, Kiiro, Maycom, Ministry of Sound, Morthy Richards, Panasonic, PersTel, PURE Digital, Restek, Roberts, Sangean, Sony, TAG McLaren, TEAC, Terratec.

And the last type of DAB receivers is portable. Those that we take with us on the road or listen to on the way to work. Commercial portable DAB devices have only recently emerged but are already available on the market. Today, the main problem with launching such receivers into mass production was their power consumption, which has now been reduced to the level of a conventional CD player. Work to further reduce energy consumption is currently underway. Leading companies in this area are: ARION, BUSH, Grundig, Maycom, Ministry of Sound, Perstel, Philips, Pure Digital. Roberts.

Judging by the number of companies offering various solutions for DAB technology, we can confidently say that DAB has a future, the market is developing, and users’ interest in the new radio concept is gradually growing. In addition, DAB technology brings something new to the concept of radio services. Various additional services and interactive services transform the broadcast format itself. Among similar services you can note:

• radio broadcasting as such (primary service);
• Additional Information;
• transferring information (for example, downloading a song currently playing on the radio to a DAB receiver);
• electronic program guide (EPG);
• slideshows synchronized with audio broadcast;
• video;
• Java applications.

Most countries in the world that were thinking about switching from analogue to digital radio broadcasting preferred the DAB standard. Real DAB services are already available in most of Europe, Canada, Taiwan and South Korea. Test launches are taking place in China, South Africa and Turkey. Interest in technology is growing in Russia, South and Latin America, the Middle East and Southeast Asia. The United States has developed and preferred its own digital radio broadcasting standard - HD Radio.

In Russia today there is not a single T-DAB transmitter. However, issues related to the issuance of licenses for broadcasting in the DAB format are already being actively discussed. The main problem due to which the implementation of this standard in Russia is being postponed indefinitely is the mandatory replacement of existing radios, receivers and tuners with new, digital ones.

Until a fairly cheap and high-quality product of this kind appears on the market, we can only dream of the spread of DAB radio in our country. After all, the majority of Russians today are quite satisfied with the quality of FM radio stations.

Well, what kind of digital radio did they come up with? We already have numbers in the receiver instead of a scale and the names of the stations are displayed! Do we need it? Will it reach Russia by air or via their Internet? There is no answer here in a few words. Let's try three.

Here's what interested parties say about this - Digital Radio Development Bureau (DRDB):

“This is not satellite radio, and not Internet radio. No, it's not that. In fact, this is a new way of radio broadcasting through a network of terrestrial transmitters.

It gives you more freedom of choice, best quality sounds and a lot of additional information. In general, almost like a regular radio, only better.”

Such are the optimistic messages. How much better? And what additional information is offered to us?

To begin with, we note that we are talking about DAB radio (Digital Audio Broadcasting), since no one forbids calling both satellite and Internet radio digital - there is no monopoly on the adjective.

For lovers of antiquity: Evoke-2 with FM range (photo from pure-digital.com).

Therefore, if we literally translate the phrase DAB digital radio, scattered in abundance throughout the pages of DRDB, we get - “digital radio of the digital audio broadcasting type.” It’s a complete tautology and nonsense, but that’s how it is in a world where an enemy lawyer is waiting for you around every corner.

The DAB standard has been developed since the late 1980s by a consortium of 12 companies called EUREKA-147. In 1994, it was proclaimed as a global one, minus the dissenting opinion of the USA and Japan.

The Americans, however, rely on satellite and HD radio (High Definition), and the Japanese entangle themselves in cable radio networks (just like we do with the ever-memorable three-program loudspeakers, only without the Japanese numbers).

Of all the other countries, DAB radio is doing best in Sweden, Germany and the UK. Of course, the British are conservative people and prefer the centuries-old (one with a small tail) terrestrial radio broadcast.

In fact, each country is free to choose its own frequency range, within the limits imposed by the standard. The British, so, liked 217.5 - 230 MHz. Well, let them tell themselves, the neighbors still can’t hear it, because there is complete down-to-earthness.

A tempting offer from the Ministry of Sound (photo from ministryofsound.com).

Let's say, a UHF device (Band III) for the English market will still work in Germany, although some stations broadcast there in the L band, but in Canada, where there is already one continuous L DAB broadcast, it will have to rest. Unfortunately, dual-band receivers are not yet produced.

How does DAB broadcasting work? First of all, radio stations are not broadcast individually, but as part of a block called a multiplex.

The same package may contain information of a different nature - text and graphic, which is especially convenient for mobile users: all kinds of motorists, tourists, and traveling salesmen.

A strange thing - digital radio for digital computer(photo from modulartech.com).

More precisely, at the end of the twentieth century they counted on such unsurpassed amenities. And now all self-respecting citizens already have multimedia mobile phone organizers with universal access to wireless Internet, so such capabilities of the radio standard will most likely remain a pleasant and unhelpful addition.

Let's go back to multiplexes. All component signals of the packet, using the COFDM (Coded Orthogonal Frequency Division Multiplexing) system, which performs time-frequency sampling of the analog stream and its digitization, are mixed in a special way and modulate a certain number of carrier radio waves, the number of which depends on the information richness of the broadcast (according to the carrier standard, there can be from 192 to 1536).

Then all this wealth, through transceiver devices, enters the user receiver, is decoded by the audio processor and, finally, begins to delight the ear of the listener, who does not care about all sorts of cofdm and multiplex.

Unobtrusive high-tech (photo from pure-digital.com).

What does the consumer get from new technology? - here it is, the main question.

To begin with, the notorious CD-quality sound is achieved - digital after all.

Well, that's not the main thing, even if useful property: the acoustics of a portable or kitchen radio are still not so great, but where else do we listen to the radio? Although music lovers and car enthusiasts and wearers of good headphones can feel the difference compared to regular FM transmission.

What is more important is the use of hidden radio air reserves. Both for listeners and radio journalists, along with advertisers. In developed countries, there is nowhere for the apple to fall in the FM range: everything has long been divided and redistributed.

And with a DAB receiver, most Brits can listen to fifty new stations - twice as many as on analogue radio. And this is just the beginning.

Now about the interference that inevitably accompanies radio transmissions: there is none. Either you hear everything perfectly, or you hear nothing at all. In the city, as we know, radio interference does not make itself too noticeable due to the proximity of the transmitters, but in uninhabited rough terrain all these snake hisses, crackles and interruptions in sound unfold in full force.

With headphones you will understand what DAB is (photo from pure-digital.com).

And, by the way, DAB broadcasting is ensured by lower transmitter power. Electricity, you know, is saved, and the coverage is greater. Surprisingly, only 65% ​​of UK residents can receive the BBC in one form or another, while commercial DAB broadcasts can already be received by 85%.

It's also nice that the receiver quickly scans the entire range, and then it remains to choose among the names of the available stations, completely forgetting about the inconvenient frequency numbers.

Well, on topic different pictures and signatures, for which 20% of the channel capacity is left, we have already spoken. But these 192 Kb / s should not be neglected either: if not the Internet, but for free and something useful can be drawn among advertising.

This is how things stand today. What does the average English consumer say?

Until recently, he was silent: the prices for receivers started from 400 pounds (about $630). The breakthrough was made by a small company Imagination Technologies, which until then had nothing to do with the radio market, although there are more than 20 manufacturers of DAB equipment.

She decided to put on this sluggish technological site, developed a perfect microprocessor and programs in a year and a half, after which she threw the Evoke-1 receiver (translated as “call”, but you can sound like “eva like”) on the market cheaper than the magical 100 pounds ( about $157).

7 Radio was most valued in the old days (photo from bbc.co.uk)

And then everything stirred. Since last Christmas, 135,000 receivers have already been sold (for the entire period until 2002, only 50,000 were purchased by the British), the company cannot cope with orders, experts predict millions of copies, and that by 2010 the usual FM radio may die out altogether for the needs of DUB.

And in the reception room of Imagination Technologies, along with others, Sharp, Intel and Hitachi were noticed - give them a license. And a dozen different models are already ready. But let's get back to our homeland.

As you can see, we were never able to give a clear answer to the last two questions identified in the preamble of the article. They preferred a figure of silence and transferred these questions to the category of rhetorical.

Do we need it? We’re not prophets, we don’t know for sure, which means we’re not sure, and besides, we haven’t tried it. Shall we wait in Russia?

News about the development of radio broadcasting in the DAB+ (Digital Audio Broadcasting) format in Europe causes a little envy. The most “advanced” in this regard were Switzerland, Great Britain and Norway. The latter promises to completely turn off analogue FM broadcasting in a few months, replacing it with digital one. And even our closest neighbors, the Latvians, decided to begin year-long testing of the new format before allocating funds for further work. To be fair, it should be noted that Estonia and Lithuania, after conducting a similar study, decided to postpone the transition to digital broadcasting for now.

The average person has a lot of questions: what kind of DAB+ format is this, why implement it, and what will it bring to the average listener? Probably, we will also have to buy new receivers: what is known about them and what about Russian developments, or are we importing them from abroad again? How much will the devices cost?

First steps

Let's start with the background. The transfer of radio broadcasting to digital was initially included in the federal target program “Development of television and radio broadcasting in the Russian Federation for 2009-2015”, approved in September 2009.

The main goal of the proposed transition was a dramatic improvement in the quality of reception compared to traditional analogue radio broadcasting in the short wave range.

The Federal Target Program focused on the development of radio broadcasting in the DRM (Digital Radio Mondiale) format. In short, this is a set of technologies using MPEG-IV codecs, which make it possible to provide digital broadcasting with higher quality in the traditional ranges for analogue broadcasts.

All in one

It is worth mentioning a purely Russian development - the RAVIS system, presented in 2005.

RAVIS allows you to broadcast multimedia services: video, text (information about road conditions, etc.), static images, etc.

This abbreviation stands for “Russian Real-time AudioVisual Information System” (abroad it sounds a little differently: RAVIS, Real-time AudioVisual Information System). It is intended for broadcasting in the ranges 66 – 74 and 87.5 – 108 MHz (what is commonly referred to as the VHF and FM bands). The technology was developed by Viktor Dvorkovich and his son Alexander, specialists in digital video information systems. They later organized the Sad-Kom company.

The main advantage of RAVIS is the ability to transmit from 10 to 15 programs with CD-quality stereo sound in one standard radio channel in the specified ranges. It is no secret that in large cities there is already a problem of frequency distribution for new broadcasters (the ranges are not unlimited) and this solution would resolve the situation.

And here we move on to one of our first questions: what, in addition to what was promised? High Quality audio content, can this system “boast” compared to conventional broadcasting?

One that can also broadcast multimedia services: video, text (information about road conditions, etc.), static images, etc. According to the idea, all these “benefits” can be received directly in a moving car, using standard whip antennas in urban environments with dense buildings, a multi-beam signal in the absence of direct visibility of the transmitter antenna, as well as in areas with difficult terrain, in mountainous areas and in dense forests . Of course, the initial resolution for a television mobile television “picture” is small: only 640x480 pixels, but it was assumed that it would be increased to the standard 720x576 pixels. For broadcasters, this solution promises, first of all, a reduction in the power consumption of transmitting devices.

From August 2009 to April 2010, additional improvements and field tests of the RAVIS system model were carried out in Moscow and Sochi. As a result, the national standard was approved - GOST R 54309 - 2011 “RAVIS Real-Time Audiovisual Information System”.

Later, the “Space and Telecommunications” working group of the Russian Presidential Commission for Modernization and Technological Development recognized the project as promising, but economically poorly developed and recommended it for improvements at the Skolkovo Foundation.

On October 16, 2015, at a meeting of the State Commission on Radio Frequencies of the Russian Federation, a decision was made “On the organization of experimental zones of the RAVIS digital broadcasting system.”

This is what it prescribed:

"1. Allocate the radio frequency bands 65.8-74 ​​MHz and 87.5-108 MHz to the Non-Profit Partnership for the Support of Regional Television "Association of Regional Television Companies" and the Moscow Institute of Physics and Technology (MIPT) for carrying out experimental, experimental and design work on radio broadcasting of the RAVIS system in Kazan , Krasnodar, Izhevsk and Kaliningrad...

2. The results of experimental, experimental and design work must be presented by the Non-profit partnership for the support of regional television "Association of Regional Television Companies" to the SCRF no later than the fourth quarter of 2018."

Well, a little about the receiver of this format. Here the results are even more modest than in the case of DRM broadcasting: only approximate cost future models - about 100 - 120 dollars.

Development ways

So, at the moment there are three main directions along which it was planned to develop digital radio broadcasting in our country.

The prospects for DRM in Russia are disappointing. After 2012, events in the bands intended for broadcasts in this format developed very quickly and not for the better. The main state Russian broadcasters: Radio Russia and Mayak left the long and medium wave bands in 2014 - 2015. Radio Russia also left short waves.

In 2013, the European Broadcasting Union (EBU) recognized the DAB+ standard as the most promising.

As Deputy Director General of the All-Russian State Television and Radio Broadcasting Company Sergey Arkhipov stated, the reduction in broadcasting in these bands is due to a decrease in state funding for the All-Russian State Television and Radio Broadcasting Company in 2014.

To be fair, it should be noted that some foreign “radio giants” have also cooled off towards the DRM broadcast format - first of all, Deutsche Welle, which has been at the forefront of research in this area for a long time. This is due to the general trend of curtailing short-wave and medium-wave broadcasts. Currently, the most active “players” here are Romania and India. About radio receivers of this standard ( Russian production) was already mentioned at the beginning of the material, and since then nothing new has appeared on the market at the moment.

Moreover, in 2013, the European Broadcasting Union (EBU) recognized the DAB+ standard as the most promising. It “is distinguished by its stability, high spectrum efficiency and cost-effectiveness,” according to SCRF materials. DAB+ uses newer codecs and allows up to 16 stations to be broadcast in stereo on one frequency. He, like the mentioned RAVIS, can diversify the services for the owner of the receiver through text messages, announcements, etc.

The DAB+ standard is designed for broadcasting in the so-called third radio frequency range - from 174 to 230 MHz. Now in Russia this range is occupied analogue television, but after turning it off it should be freed (the question is when?).

Receivers with DAB+ are relatively inexpensive, they are produced by several foreign companies (our receivers are not on the market yet).

What's next?

DAB/DAB+ digital radio coverage map in 2014. Blue marked "interested"

As for Russian radio broadcasting in the DAB+ standard, here too the situation is at the experimental testing stage. Test broadcast RTRS was carried out from the Ostankino TV tower, programs from the Mayak radio station were used for broadcasts. In November 2014, at the XVIII International Congress of the National Association of Television and Radio Broadcasting (NAT), during the International Exhibition of Professional Equipment NATEXPO, a demonstration of radio signal transmission in the DAB+ digital standard was held for the first time in Russia at the RTRS stand.

DAB+ radio is currently broadcast in more than 40 countries, including Norway, Switzerland, the UK, Germany and Denmark.

For this purpose, the stand was equipped with several radio receivers of various models, which received the signal from a transmitter specially installed on the Ostankino TV tower.

The following is information from the protocol of the State Commission on Radio Frequencies under the Ministry of Telecom and Mass Communications of Russia dated June 30, 2015 “On the results of work in the experimental zone of experimental digital audio broadcasting of the DAB+ standard in the radio frequency band 174-230 MHz”:

“Instruct the Federal Agency for Press and mass communications(FSUE RTRS) to continue research within the framework of the research work "Development of recommendations for the implementation of the digital broadcasting standard DAB+ in the Russian Federation" regarding the issues of ensuring electromagnetic compatibility with radio electronic equipment of various radio services in the range 174-230 MHz and submit in the IV quarter of 2015 in State Commission on Radio Frequencies draft decision of the SCRF on the use of the radio frequency band 174-230 MHz for the creation of digital radio broadcasting networks of the DAB+ standard on the territory of the Russian Federation.”

As we see from this long excerpt, SCRF only took note of the report and instructed RTRS to continue work in terms of ensuring electromagnetic compatibility with radio-electronic equipment of various radio services. So there's still more to come.

DAB+ radio is currently broadcast in more than 40 countries, including Norway, Switzerland, the UK, Germany and Denmark.