Digital multimedia broadcasting

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KBS1 DMB on a Samsung phone in South Korea

Digital Multimedia Broadcasting ( DMB ) [ ˈdɪdʒɪtəl ˌmʌltiˈmiːdiə ˈbɹɔːdˌkɑːstɪŋ ] is a digital transmission system. With DMB, mobile devices, e.g. B. cell phones , via satellite (S-DMB) or terrestrial transmission (T-DMB) with data. T-DMB is based on the DAB radio standard , which has been expanded to include audiovisual content.

DMB as a transmission technology was developed by Robert Bosch GmbH and the Heinrich Hertz Institute , but later mainly adapted by Asian mobile phone providers and marketed as a commercial product. In Europe, DMB has hardly been used commercially, but has been tested in some projects.

technology

Technically speaking, T-DMB extends DAB to include audiovisual content. H.264 is used for video, BSAC or AAC + for audio and the Binary Format for Scenes (BIFS) for limited locally interactive content . An additional error correction ensures high transmission security in mobile use. Depending on the error protection, a net data rate of up to 1.5 Mbit / s (typically 1 Mbit / s) is possible, which is sufficient for the transmission of three to four TV programs plus audio programs and data services in a DAB ensemble.

The specification of DAB / DMB includes various modes for use in the range from 30 MHz to 3 GHz.

DMB extends DAB, whereby DMB inherits the full functionality of DAB. A mixed operation of conventional DAB services and formats with new DMB video services is therefore also possible. Each recipient can see which services are involved and can decide whether to use them or whether to ignore them. For example, you can create an ensemble with three DAB audio programs (MPEG-1 audio layer 2 encoding) and a DMB-specific video service (MPEG transport stream with H.264 video and AAC + / BSAC audio) and additional data services such as For example, MOT-BWS and IP -based transmission of multimedia services in enhanced packet mode , which are already specified in the DAB standard.

IP-based services can also be broadcast via DAB ensembles. Since DMB inherits the full DAB functionality, a DMB ensemble (more precisely a DAB ensemble or DAB / DMB mixed ensemble) is also able to transmit IP-based transmission of multimedia services in enhanced packet mode . One example is BT-Lifetime in England. BT-Lifetime is based - like DAB and DMB - on the European and worldwide standard EUREKA 147 for the transmission of digital radio, video and multimedia content. For the decoding, however, additional decoder software is required that also supports the Internet protocol. Conversely, BT Lifetime receivers are also not DMB-capable today without an additional software upgrade; In some cases, retrofitting will not be possible either. However, DAB Audio Services can be received and decoded. In the Digital Extended Broadcasting project , on the other hand, a standardized interface for DAB, DVB-H and UMTS / MBMS is to be specified through an IP-based solution for DAB . Should this interface be introduced, it could only be supported by new devices. However, new and old devices can still receive the previous programs, so that a smooth transition would be guaranteed. However, DxB was rejected in WorldDAB and an introduction is therefore not to be expected immediately. Efforts to harmonize and combine different standards (e.g. on the basis of universal receivers) are still ongoing. According to its own information, the Japanese electronics manufacturer Sharp has developed the first dual receiver that can receive DVB-H and DMB signals. Production is expected to start in July 2007.

Another type of time slicing is possible with the aim of reducing the power consumption of the receivers via appropriate signaling parameters and is provided in the basic standard of DAB. To avoid conceptual confusion, the term micro time slicing was recently created. This is based on short bursts of a few milliseconds in length, with the switch-on time essentially depending on the data rate of the service. So far, however, this feature has not yet been used at DMB because the energy efficiency of the DMB process has so far been considered sufficient.

The DAB coverage in Germany is around 80%, whereby the existing offer has been accepted by around 200,000–300,000 (as of 10/2006) users. As an extension of DAB, DMB could increase customer acceptance and thus justify the investments made in DAB. A use in the car would be conceivable, since traffic data ( TMC , TPEG-ML) are already being transmitted via DAB . DMB receivers can usually also decode DAB. DAB will continue to be an audio-only service and today's DAB receivers can still be used.

commitment

Central Europe

Frequency allocations for DMB in Germany have been made in band III and in the L band from 2006 . Until recently, the maximum transmission power was limited to 1 kW for band III and 4 kW for the L band; in southern Germany, the transmission power was increased on a trial basis to 10 kW in band III and 6 kW in the L band. In contrast to Korea, where the VHF frequency range is used, the L-band should primarily be used here. However, the MI FRIENDS project of the Bavarian State Media Authority is also running in Volume III, as this is also suitable.

The only commercial DMB offer in Germany was Watcha from MFD Mobiles Fernsehen Deutschland . According to a press release by the ALM, Mobiles Fernsehen Deutschland GmbH (MFG) is returning its licenses for DMB mobile phone television. In a letter to the state media authorities, the company announced that it would stop broadcasting the ProSiebenSat.1 Mobile and MTV Mobile programs. In its report, the ALM sums up “Unfortunately, the DMB format was not able to establish itself with the customers. The expectations have not been met ”.

Samsung , LG and Perstel exhibited around 18 different DMB receiver models at IFA 2005 in 2005 . Since all state media authorities had advertised and licensed DMB licenses, the legal basis for mobile television in the DMB standard was laid for coverage of around 80 percent of the population.

Watcha had a technical reach of more than 13 million people; ARD, ZDF, N24 , ProSiebenSat.1 Mobile and MTV Music were broadcast . In addition, bigFM broadcast a radio program that was highlighted with rapidly changing still images. The customer could choose between two mobile phones that are required as end devices for receiving mobile TV: Samsung SGH-P900 (only supports L band) and LG V9000. These can also receive the free DAB radio programs, as DMB terminals are downward compatible.

There is also the “D2” MP3 player from Cowon with DMB reception and the “IRIVER B20” multimedia receiver with a 2.4-inch TFT display and a housing that is barely larger, weight approx. 75 g . A VHF FM tuner, a DAB and a DMB receiver (Digital Multimedia Broadcasting) are built in, as well as an internal memory for audio and video files, which can be accessed via the USB2 interface (which is also a battery charger) .

From 2006 to 2010, the DMB test program “WDR-Mobil-TV” ran in Cologne with WDR television live in MPEG4 QVGA 320 × 240 pixels, 30 fps recoded at 384 kbit / s. It was broadcast on VHF channel 12 from the Kölnturm am Mediapark with 10 kW in a DMB / DXB multiplex (1/4 of a terrestrial TV channel), also in the same format Das Erste (ARD TV program 1: 1 adopted). Since 2011, only " EinsLive " have been running , where a freeze frame loop with regularly changing content is played for the current radio program (e.g. music titles, news and current temperatures), "WDR-Mobil-TV" (WDR2) with current news Texts and still images as well as "WDR-DMB test" with cartoons (KiRaKa) or changing still images as a 60 min. Video loop from 2007. Reception result in portable and mobile operation: in contrast to DAB reception (same VHF channel) is included DMB at the same critical points (ground floor in the house, narrow city streets) less sound interference and hardly any dropouts.

The MI FRIENDS project of the Bavarian State Center for New Media in Munich was one of the most comprehensive model projects with which the operation of fee-financed mobile broadcasting (audio and video services) should be tested . Italy, Austria, Liechtenstein and Switzerland are also participating in the BLM project through the MI FRIENDS sub-projects Lake Constance and South Tyrol / Transalp .

In the first test region of Munich, a total of 12 DMB and 19 DAB programs with DMB receivers could be used with MI FRIENDS during the 2006 soccer world championship through broadcasts in the 1.5 MHz wide frequency blocks LC and LG (UHF), 11C, 11D , 12A and 12D (VHF). Were broadcasted u. a. the ARD program, the ZDF and the BFS .

Also as part of the MI FRIENDS project, four channels were broadcast following the soccer World Cup in Regensburg . These were Rmobil (a television program with a strong local reference for mobile use), Rmix (a national program), Rockantenne2go (a radio program with picture support) and GongFM (also a radio program with picture support). The aim here was to test additional services, personalized content and interactivity.

Two further test areas were the Lake Constance region (a non-realized sub-project), in which the use in leisure time behavior was to be tested, and South Tyrol , which was selected as a test region with tourist use and for testing in topographical problem areas.

All projects have now been completed and evaluated. The results of the accompanying research were published as part of the series of publications by the Bavarian State Center for New Media. When selecting the test regions, the focus was on obtaining evaluation results that should be transferable to almost all European regions. The BLM concludes that the question of refinancing infrastructure and program costs has not yet been resolved for regular operations and writes literally: “Last but not least, the fact that a clear majority of the users surveyed is not ready to use mobile radio is of decisive importance to pay additional fees. "

South Korea

In South Korea, the commercial S-DMB service (S = satellite) went into operation in the third quarter of 2005; this service is chargeable. According to the MIC (Ministry for Information and Communication), T-DMB had around 1.3 million users on April 1, 2007.

In 2006, around 50 different types of DMB receivers were available on the market in Korea. The prices were between 80 and 800 € and were divided into the following three main segments:

  • Low price (USB receiver, etc.) US $ 80–120
  • Mid price (cell phones) US $ 200–500
  • High price (pure DMB receiver with screen multimedia player and navigation) US $ 200–800

DMB receivers with integrated navigation, MS multimedia player and picture-in-picture function based on WIN CE 5.0 were already available on the market from US $ 550. The German company Blaupunkt already offered its navigation system Lucca 5.2 with DMB in Korea in 2007 .

From June 2006 further licenses for commercial (advertising-financed) operation were issued. 7 video, 13 audio and 8 data channels are currently available.

In February 2008 the free, terrestrial T-DMB offer with 6 channels had around 10 million customers, the satellite-based competing system with 19 paid channels had around 1.3 million customers. According to their own statements, the operator of the satellite offer needs 2.5-3 million customers in order to be profitable. The terrestrial DMB offer is also used by 1.17% of the owners of a corresponding device according to a random sample from August 1st. Receivers are mainly found in cell phones (48.8%), but also in multifunctional displays in cars (37.8%), media players (9.4%) and USB dongles (3.8%).

By the end of 2009, the number of T-DMB users had already risen to 20 million.

People's Republic of China

The People's Republic of China has ordered 500,000 T-DMB receivers from Samsung. 300,000 of them for the province of Guangdong (approx. 80 million inhabitants) and 200,000 for Beijing . In the People's Republic of China, T-DMB is the first choice of the Chinese regulatory authority SARFT, along with other solutions .

Planned rollout:

  • Beijing / Tianjin : DAB / DMB field trials (two audio and one video service) since 2005
  • Guangdong: various DAB / DMB field trials since 2005, two multiplexes with four audio and two video services on the air
  • Shanghai : the Oriental Pearl Group has started the Mobile TV project. Field trials with DAB-IP (see also BT Lifetime under Technology) since 2005. DMB field trials are planned for 2006.

rating

DAB is intended for a bandwidth of around 1.5 MHz, over which, depending on the error protection, around 0.8 Mbit / s of user data can be transmitted. This is sufficient for about three TV programs with 300 kbit / s each plus audio programs and data services per ensemble, with an ensemble occupying only a quarter of the television channel and correspondingly more programs are possible by combining several ensembles, e.g. B. in Munich: 12 DMB and 19 DAB programs and additional telematics and data services.

DAB / DMB was primarily developed for mobile reception and uses a method for power-efficient decoding in which only the relevant carriers are selectively received and decoded. The power consumption of DMB receivers is around 150 mW without time slicing. Time slicing is also provided for with DAB / DMB, but has not yet been used in practice due to its low power consumption.

By using the modulation method OFDM and the simple coding ( QPSK ) relatively large are single-frequency networks (Single Frequency Networks, SFN) possible, as opposed to multi-frequency networks (multi-frequency networks, MFN) allow the same frequency in neighboring cells.

The specification of DAB / DMB includes the use of 30 MHz to 3 GHz with various modes. Frequency assignments for DAB have been made in Germany in band III and in the L-band.

DAB / DMB is designed for mobility (in the vehicle, even at high speed). Reception tests by DMB in S-Bahn show that undisturbed reception is possible here too. Due to the limited transmission power in Germany (1 kW in band III and 4 kW in the L band), it is currently only available to a limited extent inside buildings.

Individual evidence

  1. DLM press release 07/2008: DMB test project in Germany ended. ( Memento of the original from April 30, 2008 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. In: alm.de  @1@ 2Template: Webachiv / IABot / www.alm.de
  2. Sub-projects DMB project. ( Memento of the original from January 17, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: mi-friends.org  @1@ 2Template: Webachiv / IABot / www.mi-friends.org
  3. subprojects. ( Memento of the original from January 17, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: Mi-friends.org  @1@ 2Template: Webachiv / IABot / www.mi-friends.org
  4. DMB pilot project MI FRIENDS. In: blm.de
  5. Will DTT emerge as mobile TV victor? In: telecoms.com , July 30, 2008 (English)
  6. Mobile television in South Korea: hardly any interest, wrong target group. In: Areamobile.de , August 11, 2008
  7. Amitabh Kumar: Implementing Mobile TV: ATSC Mobile DTV, MediaFLO, DVB-H / SH, DMB, WiMAX, 3G Systems, and Rich Media Applications . Focal Press Media Technology Professional Series Focal Press, 2010, ISBN 978-0-240-81287-8 ( excerpt from Google book search).

Web links