• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.05a
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• pp.213-214
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• 2019

eLoran 지상파 전파항법시스템은 위성항법시스템 전파교란에 대비한 백업시스템으로 인정 받고 있다. 따라서 해양분야에서는 위성항법시스템을 이용한 측위와 항법분야에서 전파교란이 발생하는 경우에 대비한 eLoran 활용이 주요 관심사였다. 그러나 위성항법시스템은 측위와 항법분야 이외에 시각동기분야에서도 중요한 역할을 하고 있다. 대표적인 예가 AIS의 시각동기이다. 본 논문에서는 eLoran 지상파 전파항법시스템이 시각동기분야에서 어떻게 활용될 수 있는지를 살펴본다. 이를 위해 eLoran 시각동기 성능에 대해 분석하고, 활용 가능 응용분야에 대해 알아본다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.12
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• pp.1310-1317
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• 2012

The Global Navigation Satellite System (GNSS) like US Global Positioning System (GPS) and EU Galileo are based on providing precise time and frequency synchronized ranging signals. Because of the exploitation of very precise timing signals these GNSS are used to provide both navigation and time distribution services. Moreover, because the positioning accuracy will improve as more satellites become available, we should expect that a combination of Galileo and GPS will provide better performance than those of both systems separately. However, Galileo will not use the same time reference as GPS and thus, a time difference arises - the GPS-Galileo Time Offset (GGTO). The navigation solution calculated by receivers using signals from both navigation systems will consequently contain a supplementary error if the GGTO is not accounted for. In this paper, we compared GPS Time (GPST) with Galileo Sytem Time (GST) and analyzed the effects of GGTO on positioning accuracy by simulation test. And then we also analyzed the characteristics of two representative GGTO correction methods such as the navigation message based method at system level and the estimation method at user level and propose the conceptual design of the novel correction method being capable of preventing previous method's problems.

• Journal of the Korea Society of Computer and Information
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• v.14 no.2
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• pp.111-118
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• 2009

Against Anomaly of GPS, there are several projects of independent satellite navigation systems like Galileo of Europe and QZSS of Japan and modernization of terrestrial navigation system like Loran. In domestic, the need of independent navigation system was proposed and DGPS signal was nominated as the possible substitute. The DGPS signal uses medium frequency, which travels through the surface and cause the additional delay rather than the speed of light according to Conductivities and elevations of the irregular terrain. The similar approach is Locan-C. Loran-C has been widely used as the maritime location system. Loran-C uses the ASF estimation method and provides more precise positioning. However there was rarely research on this area in Korea Therefore, we introduce the legacy guaranteed model of additional delay(ASF) and present the results of implementation. With the comparison of the original Monteath results and BALOR results respectively, we guarantee that the implementation is absolutely perfect. For further works, we're going to apply the ASF estimation model to Korean DGPS system with the Korean terrain data.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.74-75
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• 2013

Pseudolite is a contraction of the term "pseudo-satellite," used to refer to something that is not a satellite which performs a function commonly in the domain of satellites. Pseudolite are most often small transceivers that are used to create a local, ground-based GPS alternative. This paper proposes a clock synchronization scheme for pseudolite.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.6
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• pp.1312-1317
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• 2013

Pseudolite is a contraction of the term "pseudo-satellite", used to refer to something that is not a satellite which performs a function commonly in the domain of satellites. Pseudolite are most often small transceivers that are used to create a local, ground-based GPS alternative. Pseudo-range measurement of pseudolite has around 300m range error, when time synchronization error of $1{\mu}sec$ occurs. Therefore the time synchronization methods play an important part in navigation augmentation using pseudolite. This paper proposes three clock synchronization methods that are installation method of pseudolite station, method using KRISS-UTC and method using PRN code phase difference for pseudolite. The simulation platform structure is presented for evaluating proposed clock synchronization performance.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.815-821
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• 2021

This study addresses on the design of performance monitoring system for the time synchronization service of the enhanced long-range navigation (eLoran) system, which has a representative ground-wave radio broadcast system capable of providing positioning, navigation, timing and data (PNT&D) services. The limitations of time-synchronized systems due to the signal vulnerabilities of the global navigation satellite system (GNSS) are explained, and the performance monitoring system for the eLoran timing service as a backup to the GNSS is proposed. The time synchronization service using eLoran system as well as system configurations and the user requirements in the differential Loran (dLoran) system are described to monitor the time synchronization performance. The results of the designed system are presented for long-term operation in the eLoran testbed environment. As the results of time performance monitoring, we were able to verify the time synchronization precision within 43.71 ns without corrections, 22.52 ns with corrections. Based on these results, the eLoran system can be utilized as a precise time synchronization source for GPS timing backup.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.40-41
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• 2016

위성전파항법시스템은 이용의 편리성으로 인해 다양한 분야에서 측위, 항법 및 시각동기 정보를 획득하기 위한 목적으로 널리 활용되고 있다. 그러나 위성전파항법시스템은 낮은 신호전력특성 때문에 전파간섭에 매우 취약하다. 전파간섭으로 인한 위성전파항법시스템의 가용성 저하 사례가 빈번해짐에 따라 백업 시스템에 대한 필요성과 국제적 공조를 통한 백업 시스템 마련에 대한 기술 협력의 공감대가 높아지고 있다. R-Mode는 현재 해상에서 활용되고 있는 전파신호를 이용하여 거리측정을 하는 방법으로써 신규 전파항법 인프라 구축에 따른 큰 투자 없이 적은 비용으로 위성전파항법시스템의 백업 시스템을 구현한다는 장점을 갖는다. 본 논문에서는 R-Mode의 기술 현황과 국제 표준화 동향에 대해 살펴본다. 그리고 R-Mode를 국내에 적용하기 위해 고려해야 할 사항들을 설명한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.6
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• pp.910-915
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• 2018

The precise time, which is an essential element of the Global Navigation Satellite System (GNSS), such as US GPS, GLONASS in Russia, Galileo in Europe, and Beidou in China, is an important foundation for various economic activities around the world. Communication systems, power grids, IoT, Cloud computing and financial networks operate based on the precise time not only for the operating principles, but also for the synchronization and operational efficiency between tasks. In this paper, we introduce the Atomium software for the first time in South Korea. Atomium was developed by ORB in Belgium to calculate the clock error(clock solution) with GNSS signal observation data based on PPP method. The observation data is provided by Korea Research Institute of Standards and Science(KRISS). The results of MJD57106 with Atomium software are presented.

• Electronics and Telecommunications Trends
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• v.36 no.4
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• pp.61-71
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• 2021

Navigation satellite systems (GPS, GLONASS etc.) provide three main services, i.e., positioning for location based services, navigation for multi-modal transportation services, and timing for communication and critical infrastructure services. They were started as military systems but were extended to civil service. Navigation satellite navigation system began with GPS in the USA and GLONASS in Russia at nearly the same time. Indian NavIC and Chines BDS announced their FOCs in 2016 and 2020, respectively and European Galileo and Japanese QZSS are catching up others. In these days, Navigation Satellite System, Positioning, Navigation, and Timing services are part of our daily life very closely. They are required for autonomous driving car, Unmanned vehicles like UAV, UGV, and UMV, 5G/6G telecommunications, world financial system, power system, survey, agriculture, and so on. The services among navigation satellite systems are very competitive and also cooperative one another. This article describes the status of these systems and evolution in the technical and service senses, which may be helpful for planning korea positioning system(KPS).

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.05a
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• pp.3-4
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• 2018

과거 3-4년 전까지 위성전파항법시스템의 백업 시스템으로 유일하게 논의되고 있었던 현실적 대안은 eLoran이었다. eLoran은 기존에 활용성이 낮아져 서비스가 점차 중단되고 있는 로란-C 시설을 개선하여 보다 높은 PNT 성능을 제공하도록 고안되었다. 기존에 로란-C 시설이 있는 국가나 지역에서는 위성전파항법시스템의 백업 시스템으로 eLoran을 효과적으로 확보할 수 있는 것이다. 그러나 기존 로란-C 시설을 이미 철거하였거나, 로란-C 시설을 가지고 있지 않았던 국가 입장에서는 eLoran을 확보하기 위해 로란-C 시설을 보유한 국가보다 더 많은 시설구축 비용이 필요하게 된다. 반면에 R-Mode는 현재 해상에서 활용되고 있는 전파신호를 이용하므로 신규 전파항법 인프라 구축에 따른 큰 투자 없이 적은 비용으로 위성전파항법시스템의 백업 시스템을 구현할 수 있다는 장점을 갖는다. 대한민국은 세계에서 유일하게 국가안보적 측면에서 GPS 전파간섭의 위협을 받고 있는 국가이다. 대한민국이 직면한 GPS 전파간섭은 해외에서 보고되고 있는 좁은 지역에서의 개인적 소규모 전파간섭과는 차원이 다르다. 특히 지난 2016년 3월 말, 우리나라는 약 엿새간 수도권과 강원지역 등이 동시에 GPS 전파간섭의 영향권 안에 든 바 있다. 이때 GPS 전파간섭은 과거에 발생한 GPS 전파간섭보다 더 넓은 지역에 영향을 주었고, 어선과 같은 소규모 선박의 조업까지 방해하는 피해를 안겼다. 본 논문은 대한민국이 하루 속히 해결해야 할 현안으로 인식되고 있는 위성전파항법시스템의 백업 시스템으로 중파 비컨 R-Mode를 적용할 필요가 있는지 논하고자 한다.