• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.135-141
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• 2013

Subway in Korea, most of a metropolitan public transport use only worth ten million people a day floating population of wireless communication can be considered HOT SOPT. These three operators' 2G/3G/4G / Wi-Fi / T-DMB frequency and the number of services to co-exist, and the subway train passengers and subway party for operation and management of the communication network is also the co-subway passenger safety and for this service for the effects of mutual interference of whether the verification was necessary. This research and testing different frequency / communication interference between services and testing to determine whether, through the subway authorities and mobile operators in each frequency-specific interaction check and there is no interference to the safety and quality of subway passengers communication services that can be verified as the data was found. The verification methods in the metro area, not just from one region to determine whether the interference with a common verification methods can be applied.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1154-1160
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• 2010

In this paper, a novel printed meander monopole antenna is proposed for wireless USB dongle applications. Dual-wideband resonance is obtained by utilizing a printed meander monopole radiator. The proposed antenna was fabricated on a thin FR-4 substrate with a thickness of 1 mm and a dielectric constant of 4.6. The antenna is fed by a $50{\Omega}$ coaxial cable. This novel USB dongle antenna measures only $10{\times}50mm^2$. The measured results demonstrates that the antenna supports WiBro, Bluetooth/ISM, WLAN, S-DMB, and WiMAX service bands.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11C
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• pp.1049-1058
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• 2009

After the efficiency of H.264 video compression has been announced, it replaced MPEG-2 standard in several applications. So transcoding methods of MPEG-2 to H.264 have been studying because there are variety devices and contents followed by MPEG-2. Although H.264 supported various service such as IPTV, DMB, digital broadcasting etc, but users using MPEG-2 devices cannot accessible to them. This paper propose H.264 to MPEG-2 transcoding for users of MPEG-2 devices without displacement H.264. The proposed method predicted a motion vector for MPEG-2 encoder after it extracted from motion vectors of variable blocks in H.264 to improve processing time. Also it predicted a optimal motion vector using modified boundary matching algorithm after grasped a special character for boundary and background of object. The experimental results from proposed method show a considerable reduction in processing time, as much as 65% averagely, with a small objective quality reduction in PSNR.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.9
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• pp.1015-1022
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• 2007

In this paper, we proposed a wideband design of planar inverted-F antenna(PIFA) using two-layer, patches and modified ground structure. The antenna consists of two layer patches with common feed and modified ground plane to control resonance frequency and antenna input impedance. The measured bandwidth is 1,492 MHz(BW: 67.7 %, 1,457${\sim}2,949$ MHz) for VSWR<2, and 1,170 MHz(BW: 21 %, 4,970${\sim}$6,140 MHz) for VSWR<2.5. It covers service bands of DCS1800, DCS1900, UMTS(WCDMA), WiBro, WLAN(IEEE 802.11b), satellite DMB. WLAN(IEEE 802.11a) in Korea and radiation patterns shows constant figure with frequency change.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5C
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• pp.454-463
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• 2010

After the efficiency of H.264 video compression has been announced, it replaced MPEG-2 standard in several applications. So transcoding methods of MPEG-2 to H.264 have been studying because there are variety devices and contents followed by MPEG-2. Although H.264 supported various service such as IPTV, DMB, digital broadcasting etc, but users using MPEG-2 devices cannot accessible to them. This paper propose H.264 to MPEG-2 transcoding for users of MPEG-2 devices without displacement H.264. The proposed method predicted a motion vector for MPEG-2 encoder after it extracted from motion vectors of variable blocks in H.264 to improve processing time. Also it predicted a optimal motion vector using modified boundary matching algorithm after grasped a special character for boundary and background of object. The experimental results from proposed method show a considerable reduction in processing time, as much as 68% averagely, with a small objective quality reduction in PSNR.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.6
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• pp.1104-1114
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• 2007

Digital video compression technique has played an important role that enables efficient transmission and storage of multimedia data where bandwidth and storage space are limited. The new video coding standard, H.264/AVC, developed by Joint Video Team(JVT) significantly outperforms previous standards in compression performance. Especially, variable length code(VLC) plays a crucial pun in video and image compression applications. H.264/AVC standard adopted Context-based Adaptive Variable Length Coding(CAVLC) as the entropy coding method. CAVLC of H.264/AVC requires a large number of the memory accesses. This is a serious problem for applications such as DMB and video phone service because of the considerable amount of power that is consumed in accessing the memory. In order to overcome this problem in this paper, we propose a variable length technique that implements memory-free coeff_token, level, and run_before decoding based on arithmetic operations and using only 70% of the required memory at total_zero variable length decoding.

• Journal of Korean Society of Transportation
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• v.24 no.3 s.89
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• pp.103-112
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• 2006

For recent innovation of If technology and the beginning of Digital Multimedia Broadcasting (DMB) service, it has been dramatically increased to setup TV system in a car for watching TV and receiving traffic Information. Watching TV while driving would distract a driver s cognitive and visual attention as eating food, operating the radio, using a cell phone. However, there is paucity of empirical researches and it is uncertain how watching TV in driving impacts on the driver's cognition in the concrete. Therefore, we surveyed domestic drivers on the attitude watching TV while driving as well as conducted experiments through a driving simulator. Especially, we recruited two groups of participants to explore the effects of watching TV on driving behavior. The result proved that the participants who watched TV while their driving had relatively narrower the attention span than the Participants who did not watch TV. Also, those who watched TV drove with less stability and more urgent operations of the brake and accelerator than those who did not watched TV Finally, we discussed limitations and implications of the study.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.4 s.95
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• pp.366-372
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• 2005

This paper presents analysis of a slot array antenna having a low side lobe level and high front-to-back ratio for a repeater system of a satellite DMB(Digital Multimedia Broadcasting) service. Antennas for this repeater system require a high gain and enough isolation to reduce interferences between signals in system. Therefore, it is necessary to suppress a side lobe level and to increase front-to-back ratio. Unlike a structure 134 by lossy microstrip lines, in this work a single cavity-backed slot antenna array using a single waveguide feed is proposed to obtain the reliability for high power handling and high radiation efficiency. The side lobe level and front-to-back ratio are enhanced with tapered array technique and an optimized vertical reflector. The measured side lobe levels in H- and E-plane are under $-33.24\;\cal{dB}$ and $-35.78\;\cal{dB}$, respectively. The front-to-back ratio over $37.84\;\cal{dB}$, and the peak gain of over $17\;\cal{dBi}$ are measured.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2007.02a
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• pp.169-172
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• 2007

최근 DMB 서비스와 같이 저 전력 무선 환경에서 유료 콘텐츠 서비스가 활발히 이루어지고 있다. 이러한 콘텐츠 서비스를 정당한 서비스 수신자에게 제공하기 위해서는 서비스 제공자와 수신자 사이에 안전한 키 교환이 필요하다. 본 논문에서는 모바일 콘텐츠 서비스를 위한 효율적 인 ID-기반의 그룹 키 교환, 즉 다수의 서비스 수신자들(클라이언트)과 서비스 제공자(서버) 사이의 인증된 동적 그룹 키 교환 프로토콜을 제안한다 제안한 프로토콜은 클라이언트의 계산량이 낮아 저 전력 모바일 환경에 적합하며, 또한 가입과 탈퇴 발생 시에도 효율적으로 키 교환을 수행할 수 있다. 제안한 그룹 키 교환 프로토콜은 랜덤 오라클 모델에서 그 안전성을 제공한다.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.235-241
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• 2006

The demand of 3D terrain mapping techniques is increasing in many application fields such as CNS(Car Navigation System), web service system, DMB(Digital Multimedia Broadcasting) systems and etc To construct a 3D terrain map, it is a pre-requite step that register data collected from different surveying sources. This Paper Present the methodology to register airborne photo, LIDAR data, and digital map, which are major data sources to create a 3D terrain mao. For this purpose, we developed the generally applicable algorithm that uses linear features to register airborne photos and digital maps to LIDAR data. The algorithm explicitly formulates step-by-step methodologies to establish observation equations for transformation. The results clearly demonstrate the proposed algorithm is appropriate to register these data sources.