• 방송공학회논문지
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• 제4권2호
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• pp.164-175
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• 1999

본 논문에서는 QPSK 디지틀 전송 기술을 사용하는 위성방송 전송 시스템에 대한 위성 채널 특성과 전송 신호 특성에 대한 영향을 분석하여 전송 시스템의 설계 기준점을 결정할 수 있도록 하였다. 전송 채널 특성에 의한 열화도는 약 2.0dB, 전송 신호 스펙트럼 특성에 의한 열화는 0.4dB, 그리고 수신기 특성에 대해 약 0.2dB의 열화 특성을 갖는 위성 및 전송 시스템에 대한 가용 설계 파라미터 값들을 제안하였다. 열화 특성을 만족하는 설계 파라미터 값들은 ${\pm}\;0.5dB$ 이내의 진폭 응답 특성 그리고 0.1nsec/MHz, $0.2sec/MHz^2$ 이내의 전파 지연 특성을 나타내었다. 또한, 최대 서비스 가용도를 갖는 위성 전송 시스템의 TWTA 동작은 0dB OBO가 적당하며, 위상 잡음 영향을 최소화하기 위해서는 0.707 damping 계수 및 40kHz 대역폭을 갖는 PLL 회로가 최적의 동작 특성을 나타내었다. 본 논문의 시스템 성능 분석 및 설계 파라미터 값들은 위성을 통한 고속 데이터 전송 시스템에 대한 설계 기준점으로 활용될 수 있다.

• Journal of Positioning, Navigation, and Timing
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• 제5권4호
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• pp.181-191
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• 2016

A Satellite Based Augmentation System (SBAS) provides differential correction and integrity information through geostationary satellite to users in order to reduce Global Navigation Satellite System (GNSS)-related errors such as ionospheric delay and tropospheric delay, and satellite orbit and clock errors and calculate a protection level of the calculated location. A SBAS is a system, which has been set as an international standard by the International Civilian Aviation Organization (ICAO) to be utilized for safe operation of aircrafts. Currently, the Wide Area Augmentation System (WAAS) in the USA, the European Geostationary Navigation Overlay Service (EGNOS) in Europe, MTSAT Satellite Augmentation System (MSAS) in Japan, and GPS-Aided Geo Augmented Navigation (GAGAN) are operated. The System for Differential Correction and Monitoring (SDCM) in Russia is now under construction and testing. All SBASs that are currently under operation including the WAAS in the USA provide correction and integrity information about the Global Positioning System (GPS) whereas the SDCM in Russia that started SBAS-related test services in Russia in recent years provides correction and integrity information about not only the GPS but also the GLONASS. Currently, LUCH-5A(PRN 140), LUCH-5B(PRN 125), and LUCH-5V(PRN 141) are assigned and used as geostationary satellites for the SDCM. Among them, PRN 140 satellite is now broadcasting SBAS test messages for SDCM test services. In particular, since messages broadcast by PRN 140 satellite are received in Korea as well, performance analysis on GPS/GLONASS Multi-Constellation SBAS using the SDCM can be possible. The present paper generated correction and integrity information about GPS and GLONASS using SDCM messages broadcast by the PRN 140 satellite, and performed analysis on GPS/GLONASS Multi-Constellation SBAS performance and APV-I availability by applying GPS and GLONASS observation data received from multiple reference stations, which were operated in the National Geographic Information Institute (NGII) for performance analysis on GPS/GLONASS Multi-Constellation SBAS according to user locations inside South Korea utilizing the above-calculated information.

• 한국항행학회논문지
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• 제20권5호
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• pp.425-432
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• 2016

사용자 위치 추정 시 위성 궤도는 GPS에서 송신하는 방송궤도력을 주로 이용하는데, 이를 이용할 경우 수 미터의 오차를 유발하기 때문에 높은 정확도가 필요한 분야에서는 사용할 수 없다. 오차를 유발하는 요소 중 위성 궤도와 시계에 의한 오차는 IGS에서 제공하는 RTS (real-time service)로 보정할 수 있다. 본 논문에서는 3개월간 방송궤도력과 RTS 보정정보의 궤도 및 시계 정확도를 분석하였다. IGS final을 기준으로 단일 위성과 전체 위성의 3개월간 궤도 및 시계 오차 분석을 수행하였으며, 사용자의 위치와 위성의 종류에 따른 오차 변화도 분석하였다. 그림자 조건, 태양활동, 지자기활동과 오차들과의 상관관계도 분석하였다. 보정정보에 지연시간을 적용하고 이를 다항식으로 모델링한 후 외삽하여 실제 RTS 보정정보와 궤도 및 시계정확도를 비교하였다. 방송궤도력과 RTS 보정정보가 적용된 방송궤도력으로 데이터로 PPP를 수행하고 1일 위치 추정성능을 분석하였다. 그 결과 RTS 적용 시 3D 궤도오차와 시계 오차는 방송궤도력의 1/20, 1/3 수준이었으며, 위치해의 3D 오차는 방송궤도력의 1/5 수준으로 나타났다.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1999년도 학술대회
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• pp.81-84
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• 1999

The paper describes MPEG-2 encoder system developed by ETRI. The encoder system consists of video encoder, audio encoder and program multiplexer. The system can be used as an SDTV encoder as well as a sub-picture encoding module of an HDTV encoder. In order to reduce the hardware size and increase the system reliability, most parts of the MPEG-2 encoding algorithm are implemented with ASIC chips except the rate control part. The developed system is compliant with MPEG-2 and ATSC.

• 한국군사과학기술학회지
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• 제15권1호
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• pp.46-56
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• 2012

Traitor Tracing schemes are broadcast encryption systems where at least one of the traitors who were implicated in the construction of a pirate decoder can be traced. This traceability is required in various contents delivery system like satellite broadcast, DMB, pay-TV, DVD and so on. In this paper, we propose a public key traitor tracing scheme with key-update method. If the system manager can update a secret key which is stored in an authorized decode, it makes a pirate decoder useless by updating a secret key A pirate decoder which cannot update a secret key does not decrypt contents in next session or during tracing a traitor, this scheme has merits which will make a pirate decoder useless, therefore this scheme raises the security to a higher level.

• 방송과미디어
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• 제14권1호
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• pp.73-80
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• 2009

• 한국항해항만학회지
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• 제34권7호
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• pp.511-516
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• 2010

GPS anomaly has increased according to the degradation of satellite performance, and many GPS users could be exposed to any kinds of error-included signals without any previous notice when unscheduled error occurred. RSIM (Reference Station Integrity Monitors) is a typical monitoring method to broadcast PRC (Pseudo Range Correction) for users. However, there were some cases that the receiver detected the anomalous satellite's signal even though it was unhealthy set, consequently it occurred a large range error. Then it is important to monitor the integrity of GPS signal and it is needed to devise the correction method of pseudorange by eliminating error-occurred PRN for notification to GPS users when it is monitored that the anomaly occurred. This paper proposes the basic concept of how to correct the pseudorange. The paper also shows the analysis results of PRN10 GPS anomaly occurred on day 39 in 2007 with corrected results by eliminating anomaly satellite (PRN10). The proposed correction method shows decreased pseudorange error range compared to the case when the anomaly satellite were used.

• ETRI Journal
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• 제29권3호
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• pp.329-335
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• 2007

This paper considers a timeslot assignment problem in an interactive satellite multimedia (ISM) system with digital video broadcast-return channel via satellite (DVB-RCS). The timeslot assignment problem is formulated as a binary integer programming to maximize the overall weighted throughput and is shown to be NP-hard. Thus, three real-time heuristic algorithms including ratio-based, packet-size (PS)-based, and transmission gain (TG)-based are derived, and some computational experiments are made. Considering the results, the ratio-based heuristic algorithm is demonstrated to be the most effective and efficient. We propose adapting the ratio-based heuristic algorithm to the timeslot assignment problem to greatly improve the ISM system utilization.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1996년도 학술대회
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• pp.27-31
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• 1996

In this paper, The SSPA(Solid State Power Amplifier) is 100 watts amplifier which is used with C-Band Satellite communication Up-Link frequency, 5.875 ∼6.425 GHz. SSPA requires more output power than is available from a single GaAs FET with result it is necessary to combine the output of many device. To achieve a high power, it is important to make a good N-way power divider which has a small different phase, good combining efficiency and high power handling capability. The reliability of Power GaAs FET decrease with increasing junction temperature, power amplifier in general dissipate amount of power. It is important to provide them with a heatsink and a temperature compensation circuit to dispose of the unwanted heat. To compensate temperature, Using PIN diode attenuator, it is enable to get a precision gain control. The output power of the SSPA is more than 100 watt with which the TWTA (Traveling-Wave Tube Amplifier) can be replaced. Each stage was measured by the Network analyzer PH8510C, Power meter Booton 42BD, The gain is more than 53 dB, flatness is less than 1.5 dB.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.638-643
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• 2002

MODIS (MODerate-resolution Imaging Spectroradiometer) onboard the first Earth Observing System (EOS) satellite, Terra, was launched successfully at the end of 1999. The direct broadcast MODIS data has been received and utilized in Korea Meteorological Administration (KMA) since february 2001. This study introduces utilizations of this data, especially for the derivation of sea surface temperature (SST). To produce the MODIS SST operationally, we used a simple cloud mask algorithm and MCSST algorithm. By using a simple cloud mask algorithm and by assumption of NOAA daily SST as a true SST, a new set of MCSST coefficients was derived. And we tried to analyze the current NASA's PFSST and new MCSST algorithms by using the collocated buoy observation data. Although the number of collocated data was limited, both algorithms are highly correlated with the buoy SST, but somewhat bigger bias and RMS difference than we expected. And PFSST uniformly underestimated the SST. Through more analyzing the archived and future-received data, we plan to derive better MCSST coefficients and apply to MODIS data of Aqua that is the second EOS satellite. To use the MODIS standard cloud mask algorithm to get better SST coefficients is going to be prepared.