• 한국위성정보통신학회논문지
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• 제8권4호
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• pp.58-63
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• 2013

무선통신 시스템 간의 주파수 간섭은 시스템의 성능을 감소시키거나 운용을 제한할 수 있으므로 신규 시스템의 도입 이전에 기존 시스템들과의 주파수 양립성 평가가 반드시 수행되어야 한다. 본 논문에서는 1.6 GHz 대역 무선항행위성업무 시스템의 인접대역에서 신규 이동통신업무 시스템을 운용하기 위한 양립성 평가 알고리즘을 제시하였으며, 동일 지역 내에서 운용되는 이동통신업무시스템과 무선항행위성업무 시스템 상호 간의 최소결합손실 (Minimum Coupling Loss; MCL) 분석 결과로부터 두 시스템 간의 주파수 공유를 위한 조건을 도출하였다.

• Journal of information and communication convergence engineering
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• 제7권3호
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• pp.404-411
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• 2009

In this paper, in order to increase system capacity and reduce the transmitting power of the user's equipment, we propose an efficient power estimation consisting of a modified open-loop power control (OLPC) and closed-loop power control (CLPC) schemes for mobile/satellite communications systems. The OLPC works well if the forward and reverse links are perfectly correlated and the CLPC is sensitive to round-trip delay (RTD). Therefore, it is not effective in mobile/satellite system. In order to solve the above problem, we added monitoring equipment to both the OLPC and CLPC to use information about transmitting power that has not yet been received by the receiver over the satellite/ATC channel. Moreover, we adapted an efficient pilot diversity of both OLPC and CLPC in order to get a better signal to interference plus noise ratio (SIR) estimation of the received signal.

• Journal of Communications and Networks
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• 제13권5호
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• pp.494-498
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• 2011

Satellite digital multimedia broadcasting (S-DMB) systems use gap fillers (GFs) to provide wireless multimedia services to non-line-of-sight locations. GFs act as repeaters, and S-DMB systems require GF networks in order to guarantee mobile reception. Each GF covers a cell or sector. In order to provide contiguous coverage of an area comprising two or more cells or sectors, multiple GFs are needed. However, when multiple GFs are situated close to each other, interference is likely to occur. As a result, in this study, we have investigated system-level environments for planning the design of interference-free GF networks in S-DMB systems. Our investigations revealed that S-DMB services are unavailable because of quality deterioration caused by interference when the delay attributable to a GF and the satellite signals exceeds ${\pm}$256 chips and the distance between the GF and its reception terminal is greater than 4.6 km. On the basis of this analysis, we conducted a field test that confirmed that the above-mentioned time delay can be controlled in such a way as to ensure high quality S-DMB services.

• 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.

• 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.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.59-62
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• 1998

Satellite communication systems will play an important role in establishing high-speed information communication network ddue to the characteristics of flexibility of bandwidth, mobile communication, wide coverage, multipoint and broadcasting. Also satellite systems have the capability to supply terrestrial B-ISDN with flexible links for accessing networks as well as trunking networks. Therefore, satellites must provide compatibility to earth-based B-ISDN signalling interface, services and network capability. This paper proposed interworking model between terrestrial B-ISDN and satellite B-ISDN signalling protocol and illustrated basic call-process procedure of satellite B-ISDN signalling protocol supporting point-to-point and point-to-multipoint connection.

• 제어로봇시스템학회논문지
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• 제17권12호
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• pp.1240-1247
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• 2011

The localization of mobile robot in environment is a major concern in mobile robot navigation. So, many kinds of localization techniques have been researched for several years. Among them, the positioning system using ultrasound has received attention. Most of these ultrasonic positioning systems to synchronize the transmitters and receivers are used for RF (Radio Frequencies). However, due to the use of RF, the interference problems can not be avoided and the performance of radio frequencies directly affects the positioning performance. So we proposed the ultrasonic positioning system without synchronizing RF. The proposed system is based on existing USAT (Ultrasonic Satellite System) adopted infrastructure transmitting type, and consists of transmitter and receiver synchronizing modules instead of the radio frequency transmitters and receiver. The ultrasonic transmitters and receivers are synchronized individually by the transmitter and receiver synchronizing modules. In order to calculate the bias between the transmitter and receiver synchronizing modules, new positioning algorithm similar to GPS was proposed. The positioning performance of the improved USAT without synchronizing RF and the validity of the proposed positioning algorithm are verified and evaluated by experiments.

• 한국위성정보통신학회논문지
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• 제11권1호
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• pp.12-15
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• 2016

최근 핀테크 열풍과 더불어 모바일 결제 시장에서 글로벌 IT 기업들의 경쟁이 치열해지고 있다. 본 논문에서는 모바일 결제 기술을 소개하고 그 특징 및 동향을 분석한다. 근거리 통신을 사용한 오프라인 기반의 모바일 결제 기술의 방식 별 특징 및 장단점 등을 서술하고, 이 분야의 글로벌 선두 기업인 애플, 삼성, 구글이 출시한 모바일 결제 서비스 사례를 통하여 그 특징들을 비교 분석한다. 급속한 성장이 예상되는 모바일 결제 시장에서 더욱 안정된 서비스를 제공을 위해서는 다양한 근거리 통신 및 보안기술에 대한 연구가 필요하다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2003년도 하계학술대회
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• pp.20-22
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• 2003

본 논문에서는 Photonic Bandgap(PBG)를 공진 특성을 이용하여 마이크로파 발진기의 위상잡음을 줄이기 위한 기술을 제시한다. 마이크로스트립 라인으로 구현한 공진기는 낮은 Q(Quality factor)를 가진다. PBG를 적용했을 때 공진기의 Q값을 높여줌으로써 발진기의 위상잡음 특성이 향상됨을 보이고자 한다.

• 한국위성정보통신학회논문지
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• 제12권1호
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• pp.43-48
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• 2017

Recently, demands on civilian UAV (Unmanned Aerial Vehicle) has been increasing and appropriate communication system is required for the UAV. In this paper, the performance of the UAV communication system using commercial wireless mobile network is discussed. The main service area of the wireless mobile network is ground level however the flying range of the UAV is normally in high altitude. Because of this mismatch of service area the performance of the UAV communication system is degraded in high altitude. To compensate performance degradation of the UAV communications system in high altitude, adaptive array antenna is introduced which is able to overcome altitude limitation of the UAV communication system.