The Research Powerhouse Behind DMB
The Research Powerhouse Behind DMB
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  • 승인 2005.02.01 12:01
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Ahn Chieteuk, vice president and head of the Digital Broadcasting Research Division of ETRI
Electronics and Telecommunications Research Institute With more than 75 percent of Koreans using mobile phones and 60 percent of them having access to the Internet, it is hoped that Digital Multimedia Broadcasting (DMB) services will invigorate the Korean IT industry. To further examine this issue, the Korea IT Times held the following interview with Ahn Chieteuk, vice president and head of the Digital Broadcasting Research Division of ETRI, to hear from him about the background and features of DMB soon to go into full commercial operation. What was the background behind the national development of DMB technologies It has been quite some time this concept was first thought of, dating as far back as 1998 when the nation was in the throes of an economic crisis. Under such circumstances, we received a request from the government to embark on a project that would drastically improve national economic capability. From that time onward, I think the seed was sown. As you may know, mobile broadcasting, like FM radio, has been available for some time. Satellite broadcasting is used in Europe and the US to provide such services as music, news and weather. However, not many people thought of watching television on the move. In fact, it's already possible to enjoy mobile TV broadcasting if one wishes to listen to the audio track via the radio. However, nobody ever paid much attention to this possibility. Anyhow, one must be the world's best in order for one's concepts to make progress and earn their keep. However, it becomes very difficult to "reap a harvest after one has just sown the seed" as we say in Korean. So, one has to borrow the ideas and capabilities of others. That's why we thought of grafting video technologies, and specifically MPEG-4, a data compression standard, to Digital Audio Broadcasting (DAB), which is widely adopted in Europe and where mobile video broadcasting had not developed into an industry. That's how we began developing DMB technologies in earnest. There had been a prolonged national controversy over which technology was suitable for the transmission of ground wave digital TV broadcasting. Did this controversy hamper the development of DMB technologies in any way For nearly three years prior to April 2004, there had been a pitted controversy between the government and the union of media workers over the issue. As a result, a host of suggestions were made including that of adopting mobile broadcasting service based on the Advanced Television Systems Committee (ATSC) terrestrial transmission standard of the U.S. However, even though the ATSC transmission standard is not technologically impossible, it would require a considerable period of time to implement and no one could tell for sure whether its adoption could be viable industrially. However, a host of evidence indicating that the adoption of DMB could be technologically feasible began to emerge from late 2001 onward, especially with its successful trial run in downtown Seoul in 2003. Ironically, this disagreement over the issue, spanning over 10 years, had the effect of revitalizing the development of DMB technologies. What are the advantages of adopting DMB technologies in comparison to other broadcasting systems such as DVB DVB was not developed for mobile broadcasting. The official DVB Internet Web site clearly states this and that DVB was developed for high-quality video broadcasting for stationary TV viewing. It goes further by not recommending DVB for mobile broadcasting. Moreover, the cost of putting the infrastructure in place for DVB-T, for example, is relatively expensive. Anyhow, the important point I would like to make is that whatever digital video broadcasting system one adopts, be it DMB, DVB or ATSC, one has to have as many "gap fillers" as possible in order for mobile users to have good reception of digital video broadcasts. Such being the case, DMB is relatively advantageous when viewed in terms of establishing gap fillers. This is because while terrestrial DMB involves 200 mega hertz, other broadcasting systems use higher frequencies. Satellite DMB, for instance, uses 2.6 GHz while DVB-H, a UHF Band standard, uses 600 mega hertz. Cellular phones operate on frequencies of more than 800 mega hertz. In any case, the strength of a wave is required to be above a certain level in order to make broadcasting for mobile users possible. When a wave passes through concrete walls, for instance, it loses about one-third of its power and cannot reach such places as the rear of a building or subways. Due to the characteristics of radio waves, the maximum distances they can reach become shorter with higher frequencies when the same power is applied. That's why terrestrial DMB has the lowest frequency. With its low frequency, the maximum distance it can reach grows longer with higher diffraction rates. Accordingly, one needs to install fewer gap fillers with terrestrial DMB than with any other system. What is the difference between satellite and terrestrial DMB The general public commonly believes that they can receive satellite DMB directly. They are right in this supposition, but it is almost impossible to receive in downtown areas. Why this is so is because the broadcasting satellite revolves in its geostationary orbit above the equator, thereby resulting in its transmission waves toward Korea in Northeast Asia being slanted. Because of this, one cannot receive satellite transmissions in places like the interiors of buildings or underground areas including subways. Even in expressways in rural areas, too, it becomes quite difficult, as there are such obstacles as road signs, tunnels and even trees, to provide broadcasting services by means of direct transmissions from satellites. Then, what sets it apart from terrestrial DMB Technically, the only difference is the frequency. Then there is no other choice but install as many gap fillers as possible. The life span of DMB phone batteries is regarded as an emerging problem that must be tackled. What effort is being made to address this issue Ever since Samsung SDI first launched 1000mAH products in the second quarter of last year, the company has converted its main capacity of its 5mm thick square-shaped battery from 900mAH to 1000mAH. Having launched its 1050mAH-capacity 5mm battery at the end of last year, the company plans to seize market leadership by continuously making larger capacity batteries for use with cellular phones. LG Chemical, too, last year launched a range of 5mm square-shaped lithium ion batteries of the 1000 mAH class for use with cellular phones. Since then, 1000mAH class products accounted for more than 35% of the company's total battery sales. Recently, the company introduced batteries with capacities of 2000mAH to the market by improving the capacities of the 10mm thick 1850mAH class batteries it had developed last year. Despite such efforts by battery manufacturers, it is somewhat difficult to operate DMB phones with batteries of 1000mAH capacities with ease. In fact, the operating time of DMB phones currently on the market is about two hours and it gets even shorter when these are used to access DMB together with the telephone service. Thus, further technological innovation is required to increase the duration of DMB phone operability in addition to making them light and compact. Other than watching TV, what multimedia functions can be used with DMB phones By using data channels, it is possible to use telematics to access information on travel, transportation, locations and other related information. Two-way data services such as M-Commerce are possible by linking DMB with broadcast contents through mobile networks. By combining DMB with portable digital players, one can save broadcast contents to a hard drive for further viewing. What projects is ETRI currently engaged in to further develop DMB technologies Until now, we have introduced DMB technologies simply to provide TV broadcasting for mobile users. However, the future of one-way DMB technologies is out of our hands and we're currently working on next-generation technologies such as data broadcasting, interactive broadcasting and the technologies that we call third dimensional 'information creative broadcasting'.

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