• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.3-4
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• 2008

We propose an efficient uplink bandwidth request-allocation algorithm for variable-rate real-time service in IEEE 802.11 broadband wireless access networks. By introducing a notion of target delay under the framework of dual feedback, the proposed algorithm can assure the desired level of QoS while minimizing wastage of bandwidth allocation.

• ETRI Journal
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• 제28권1호
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• pp.67-76
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• 2006

This study aims to identify the factors that influence adoption intentions towards portable Internet service, based on the individual characteristics that assist in creating markets and developing strategies. Two types of factors are defined: individual characteristics including demographics, existing services usages, prior knowledge, adoption attitudes, and service evaluations; and adoption intentions including the willingness to subscribe, subscription term, willingness to pay, usage type, and preferred terminal. The results indicate that the importance of demographic variables depends on adoption intentions, and that users of mobile Internet service and wireless LAN are probably targets for portable Internet service. Furthermore, the results demonstrate the need for an enhanced perception of the usefulness and ease of use of service, as well as an intensive marketing activity for potential users and a bearable innovation to stimulate the market for portable Internet service.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 2003년도 춘계공동학술대회
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• pp.744-748
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• 2003

Developing an interactive satellite multi­media system, such as a digital video broadcasting (DVB) return channel via satellite (RCS) system, is gaining popularity over the world To accommodate the increasing traffic demand we are motivated to investigate an alternative for improving return channel utilization We develop an efficient method for optimal packet scheduling in an interactive satellite multimedia system using hybrid CDMA/TDMA channels. We formulate the timeslot-code assignment problem as a binary integer programming (BIP) problem, where the throughput maximization is the objective, and decompose this BIP problem into two sub-problems for the purpose of solution efficiency. With this decomposition, we promote the computational efficiency in finding the optimal solution of the original BIP problem Since 2001, ETRI has been involved in a development project where we have successfully completed an initial system integration test on broadband mobile Internet access via Ku-band channels using the proposed resource allocation algorithm.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2006년도 하계학술대회
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• pp.43-46
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• 2006

IEEE 802.16 WirelessMAN aiming to broadband wireless access (BWA) is evolving to 4G mobile communication system through the standardization of IEEE 802.16e supporting mobility on existing fixed WirelessMAN system. It is necessary for hand-over to provide seamless data service while MS (Mobile Station) moves to another BS (Base Station). Because the performance of handover affects packet loss or delay of any communications, it must consider low latency handover mechanism in packet based network. In this paper, we describes handover scheme of IEEE 802.16e with the cell edge interference problem and shows the way to solve the problem in frequency reuse one deployment. Our scheme reduces the handover latency and packet loss probability.

• 정보통신설비학회논문지
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• 제8권4호
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• pp.201-206
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• 2009

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference (ISI) or Multiple Access Interference (MAI) to degrade the performance of W-CDMA (Code Division Multiple Access) system. Constant Modulus Algorithm (CMA) which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. Consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.

• Journal of Communications and Networks
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• 제4권4호
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• pp.292-301
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• 2002

Wireless LAN technology is complementary to 3G systems and could be used to provide high bandwidth hotspot coverage, for example in railway stations and offices, in order to provide the high bandwidth video and broadband services such as those emerging on DSL fixed access. The IST Projects BRAIN and MIND have investigated a number of key technical enablers for such a system beyond 3G. These include scenarios and business models, design of an all-IP access network, consideration of ad hoc network extensions, enhancing Wireless LAN efficiency and compatibility with IP and, finally, terminal middleware and signalling for rapid adaptations to network QoS changes.

• 한국위성정보통신학회논문지
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• 제2권1호
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• pp.7-13
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• 2007

새롭고 효과적인 도플러 효과 보상 기법은 성상도 추정에 기반하며, 이론적 분석과 시뮬레이션 결과에서 알 수 있듯이 영점 성상도를 이용한 변형된 변조방식을 사용해 평균 파워를 감소시킬 수 있다. 제안된 기법은 위성 송수신기에서 고속으로 이동하는 단말로 보내는 파워를 줄여줌으로써 위성 OFDM 에서 매우 효과적으로 신호를 전달할 수 있다.

• ETRI Journal
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• 제32권3호
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• pp.475-478
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• 2010

A multiband meandered monopole antenna is proposed for digital video broadcasting handheld (DVB-H), global positioning system, personal communications service, wireless broadband (Wibro), and wireless local area network (WLAN) applications. The proposed antenna consists of a meandered line, a shorted length strip line, and a conductor strip between a meandered line and a microstrip feed line. By tuning a short strip and a conductor, a multiband impedance matching is achieved. The proposed antenna has an omnidirectional radiation and yields an antenna gain of greater than -3 dBi in the DVB-H band and 4.5 dBi in the Wibro and WLAN bands. Details of the proposed antenna design and experimental results are presented.

• 한국통신학회논문지
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• 제29권10A호
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• pp.1167-1176
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• 2004

본 논문에서는 위성 하향 링크에서 강우 감쇄와 음영 페이딩에 대한 적응형 전송을 위한 MC-CDMA(multicarrier CDMA) 방식을 제시하고, Ka 대역 이동위성채널에서 페이딩, 강우 감쇄, 재전송 방식에 따른 적응형 MC-CDMA 하향링크의 성능을 비교 분석하였다. 제시된 하향 링크는 광대역 MC-CDMA 전송을 통해 수십 Mbit/s 처리율과 채널 환경에 따라 약 1 bit/s/Hz에서 4.7 bit/s/Hz의 주파수 효율을 제공할 수 있다.

• 전자통신동향분석
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• 제23권6호
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• pp.112-123
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• 2008

기존 이동통신 환경은 통신사업자 중심의 서비스 제공에서 이용자의 적극적인 참여와 소통의 모바일 2.0 시대로 패러다임이 전환되고 있다. 모바일 2.0은 단지 기술적 진화만을 의미하지 않으며 이동통신 전반 에코시스템에서 이용자의 역할과 비즈니스 모델의 변화를 가져올 것으로 전망되고 있다. 이러한 의미를 지니는 모바일 2.0에 대한 국내외 담론이 크게 개진되고 있지만 모바일 2.0 촉진을 위한 에코시스템 핵심 성공요인을 체계적으로 분석하고 와이브로와 HSDPA를 중심으로 모바일 브로드밴드의 수용특성을 파악한 연구는 거의 없는 실정이다. 이에 본 논문에서는 모바일 2.0의 특징과 에코시스템을 살펴보고 에코시스템을 구성하는 참여자의 역할과 모바일 2.0의 핵심 성공 요인을 파악하고자 한다. 또한 시장조사 결과를 바탕으로 와이브로와 HSDPA의 국내 모바일 브로드밴드 수용자의 특성을 분석하고자 한다. 이를 종합하여 모바일 2.0을 촉진시키기 위한 시장활성화 방향을 제언하고자 한다.