• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.85-86
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• 2013

AT-DMB의 향상계층은 DQPSK 신호에 BPSK 또는 QPSK 신호를 더하여 변조하는 계층변조 방식을 사용하였기 때문에 수신기에서 채널 왜곡을 보상해야 신호의 복조가 가능하다. 다중 경로가 많은 지역에서는 주파수 선택적 페이딩이 발생하기 때문에 페이딩을 정확하게 추정하지 못하면 AT-DMB 향상계층 수신 성능이 저하되게 된다. 채널왜곡 추정을 위하여 AT-DMB 수신기에서는 채널추정 값을 스무딩하는 대역제한 필터를 사용한다. AT-DMB의 향상 계층 성능은 이 스무딩 필터의 대역폭에 따라 결정이 되며 적절한 필터 대역을 채널의 지연에 따라 설정해야 한다. 특히 SFN 환경에서는 수신 전력이 큰 둘 이상의 서로 다른 지연시간을 가지면서 수신이 되기 때문에 고정 대역폭 스무딩 필터를 사용한 채널왜곡 추정은 성능의 저하를 가져올 수 있다. 본 논문에서는 채널 지연 값을 추정하고 필터의 대역폭을 가변적으로 결정하는 방법에 대하여 설명하고 실험 결과를 보여준다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.1020-1030
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• 2006

As the Terrestrial DMB(T-DMB) has been launched, service providers are focusing on finding a business model as well as preparing the variety of data services. So, the need for development of the CAS(Conditional Access system) is urgently required and its domestic standardization is also in progress. This Paper proposes design and implementation methods of an Ensemble Re-multiplexer and receiver platform for its verification that can be used for the CAS system in T-DMB. And, with transmitting ensemble stream scrambled by the proposed Ensemble Re-multiplexer, we verified their performance by do-scrambling and decoding according to scramble mode at the receiver platform.

• Journal of Broadcast Engineering
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• v.16 no.1
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• pp.23-32
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• 2011

Design and Implementation of Clipcast Service via Terrestrial DMB This paper outlines the system design and the implementation process of clipcast service that can send clips of video, mp3, text, images, etc. to terrestrial DMB terminals. To provide clipcast service in terrestrial DMB, a separate data channel needs to be allocated and this requires changes in the existing bandwidth allocation. Clipcast contents can be sent after midnight at around 3 to 4 AM, when terrestrial DMB viewship is low. If the video service bit rate is lowered to 352 Kbps and the TPEG service band is fully used, then 320 Kbps bit rate can be allocated to clipcast. To enable clipcast service, the terminals' DMB program must be executed, and this can be done through SMS and EPG. Clipcast service applies MOT protocol to transmit multimedia objects, and transmits twice in carousel format for stable transmission of files. Therefore, 72Mbyte data can be transmitted in one hour, which corresponds to about 20 minutes of full motion video service at 500Kbps data rate. When running the clip transmitted through terrestrial DMB data channel, information regarding the length of each clip is received through communication with the CMS(Content Management Server), then error-free files are displayed. The clips can be provided to the users as preview contents of the complete VOD contents. In order to use the complete content, the user needs to access the URL allocated for that specific content and download the content by completing a billing process. This paper suggests the design and implementation of terrestrial DMB system to provide clipcast service, which enables file download services as provided in MediaFLO, DVB-H, and the other mobile broadcasting systems. Unlike the other mobile broadcasting systems, the proposed system applies more reliable SMS method to activate the DMB terminals for highly stable clipcast service. This allows hybrid, i.e, both SMS and EPG activations of terminals for clipcast services.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1513-1526
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• 2009

The SVC (Scalable Video Coding) scheme can be effectively used for reducing the redundancy and for improving the coding efficiency but, it requires very high computational complexities. In order to accelerate the successful standardization and commercialization of the Advanced Terrestrial-DMB service, it is necessary to overcome this problem. For this aim, in this paper, we propose an efficient aggregated encoder control algorithm, which shows better performances than the conventional control scheme. Computer simulation result shows that the proposed scheme performs about up to 0.3dB better than those of the conventional scheme. Additionally, based on this control scheme, we propose a fast mode decision method by constraining the redundant coding modes based on the statistical properties of the quantization parameter in the spatial scalable encoder. Through computer simulations, it is shown that the proposed control schemes reduce the heavy computational burden up to 12% compared to the conventional scheme, while keeping the objective visual qualify very high.

• Journal of Navigation and Port Research
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• v.36 no.6
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• pp.437-442
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• 2012

As of 2012, for service-area-widening and commercialization of DGPS service, the Ministry of Land, Transport and Maritime Affairs has completed a DGPS service via Terrestrial Digital Multimedia Broadcasting and doing experimental broadcasting. In this study, kinematic positioning tests were conducted based on DGPS service via T-DMB using low-cost GPS equipments in a dynamic environment. Standalone GPS, single-reference NDGPS via NTRIP, and virtual-reference DGPS via T-DMB surveys were conducted at the same time. And horizontal positioning errors were computed by comparing them with the result of high-precision positioning. As a result, when the DMB transmission interval was 3 seconds, horizontal positioning errors of standalone GPS, NTRIP-DGPS, and DMB-DGPS were 2.3m, 1.0m, and 0.7m, respectively. When the interval was 1 second, horizontal positioning errors were 2.0m, 1.2m, and 0.8m, respectively. Thus horizontal positioning accuracies improved with the DMB-DGPS compared to the traditional single-reference NDGPS.

• Journal of Broadcast Engineering
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• v.13 no.6
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• pp.817-827
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• 2008

The terrestrial-digital multimedia broadcasting(T-DMB) is now provided for the public service and the number of receivers reaches 15 million at the present of August 2008. The service of T-DMB itself has been succeeded in the presence. It is however remained as a supplementary role of stationed TV. It is necessary to find an additional business model as a new media to acquire surplus escaping from the deficit of the present T-DMB service. In the present paper, data service of T-DMB is proposed as candidate of such solution. Especially, TTI(Traffic and Travel Information) service is proposed as a killer application using TPEG(Transport Protocol Experts Group). At present, TPEG has not been so popular in the sense of various user satisfaction. Thus the variety of service including bi-directional service using DMB2.0 as in the sphere of Web2.0 is necessary for the service providers. In the paper, the restriction of TPEG-POI(Point of Interest) application service using the conventional mobile communication infrastructure is indicated. To overcome such restriction, TPEG-UCM(User Created Message) application service model using individual bi-directional media which is initiated and interacting by the users is proposed. In the experiment, the application program shows the usability of the proposed method so that the implementation results show its operability.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2006.11a
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• pp.161-164
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• 2006

이 논문에서는 AT-DMB (advanced terrestrial digital multimedia broadcasting) 시스템에서 채널정보를 이용하여 Viterbi 복호기의 성능을 향상시키는 방법을 제시하고 그 성능을 살펴보았다. 채널정보는 부반송파를 16-QAM 계층변조한 수신신호로부터 자력적으로 추정한다. 모의실험을 통해 채널정보를 이용한 Viterbi 복호기가 채널정보를 이용하지 않는 복호기에 비해 약 1 dB의 성능향상을 나타냄을 알 수 있었다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.5
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• pp.128-137
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• 2009

This research aimed at providing the direction for future improvement of broadcast subtitle design by identifying the user perception on broadcast subtitles of Terrestrial DMB. First, we contemplated on the existing research about broadcast subtitles. As a result, we found out that broadcast subtitle plays an essential role when watching a program and that the minimization of letters, clear fonts and color arrangement, rearrangement of components were identified as main factors that increase readability. However, the terrestrial DMB user evaluation on image quality, composition, color and brightness was not that positive. In addition, the evaluation on the readability of broadcast subtitle, information transmission, subtitle composition, letter font, number and size of letter was more negative. Developing a subtitle design which considers user convenience and suits terrestrial DMB screens in aspects of broadcast subtitle form and composition, limit of information, clearness and size of the letter is required.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.392-394
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• 2019

Tunnels and subterranean roads, which are representative evacuation facilities for national or regional disasters, have radio relay broadcasting facilities for legal reasons and convenience reasons. However, this system is limited to radio broadcasting and it is impossible to effectively communicate disaster or emergency situations that occur locally due to broadcasting of national broadcasting without DMB broadcasting. In order to improve this, we construct a remote disaster broadcasting system at each regional disaster station and implement a system to transmit it to each tunnel using internet or LTE network. The system in the tunnel transmits the emergency broadcasting signal through the existing relay equipment through the modulator which decodes the SMS, the media file, the real time broadcasting or the image received by the digital signal and converts it into FM and DMB frequency. The method proposed and implemented in this study can be used to provide efficient information and remote field control in case of emergency in tunnel and underground roadway.

• Journal of Korea Multimedia Society
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• v.12 no.5
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• pp.664-676
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• 2009

As data broadcasting has become available, diverse contents can now be provided through digital TV, IPTV and DMB; yet it is true in the current situation that killer contents are insufficient that can satisfy users. On the contrary, in case of the web, with the advent of web 2.0 aiming at user-centered services, the contents market has grown greatly. The ideas and technologies of Web 2.0, if gratified into data broadcasting, are expected to make a contribution to the vitalization of contents. This paper proposes a method of using RSS, as a concrete example of applying web 2.0 to data broadcasting. Accordingly, we have developed a system for producing data services for the ground wave DMB data broadcasting, by using RSS at the stage of authoring news and the like, for which provision of the latest information is important. And for IPTV, we have developed a data broadcasting application so that users can select the RSS they want, as well as a creation system for using RSS at the authoring stage. It is anticipated that the application of RSS by means of the system will simplify the authoring process, making easy the provision of the latest information through the web, and thereby making possible the provision of diverse services to users.