• 산업경영시스템학회지
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• 제39권3호
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• pp.1-9
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• 2016

NSS (Navigation satellite system) provides the information for determining the position, velocity and time of users in real time using satellite-networking, and is classified into GNSS (Global NSS) and RNSS (Regional NSS). Although GNSS services for global users, the exactitude of provided information is dissatisfied with the degree required in modern systems such as unmanned system, autonomous navigation system for aircraft, ship and others, air-traffic control system. Especially, due to concern about the monopoly status of the countries operating it, some other countries have already considered establishing RNSS. The RNSS services for users within a specific area, however, it not only gives more precise information than those from GNSS, but also can be operated independently from the NSS of other countries. Thus, for Korean RNSS, this paper suggests the methodology to design the satellite constellation considering the regional features of Korean Peninsula. It intends to determine the orbits and the arrangement of navigation satellites for minimizing PDOP (Position dilution of precision). PGA (Parallel Genetic Algorithm) geared to solve this nonlinear optimization problem is proposed and STK (System tool kit) software is used for simulating their space flight. The PGA is composed of several GAs and iterates the process that they search the solution for a problem during the pre-specified generations, and then mutually exchange the superior solutions investigated by each GA. Numerical experiments were performed with increasing from four to seven satellites for Korean RNSS. When the RNSS was established by seven satellites, the time ratio that PDOP was measured to less than 5 (i.e. better than 'Good' level on the meaning of the PDOP value) was found to 94.3% and PDOP was always kept at 10 or less (i.e. better than 'Moderate' level).

• Journal of Positioning, Navigation, and Timing
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• 제13권2호
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• pp.117-129
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• 2024

In this paper, we survey recent trends of International Global Navigation Satellite System (GNSS) organizations such as the International Committee on GNSS (ICG), International Civil Aviation Organization (ICAO), International Maritime Organization (IMO), and International Telecommunication Union (ITU), and investigate their impact on the maritime and aviation sectors. Each international organization promotes international cooperation, improvement of service quality, assurance of security, compliance with international regulations, and technological innovation and development. ICG develops a variety of satellite navigation enhancement systems. ICAO establishes international aviation regulations and standards to enhance aviation safety and security. IMO establishes international shipping conventions and rules to protect and regulate the shipping environment. Lastly, ITU establishes international communication regulations and standards. Investigation of such international organizations plays an important role in increasing the efficiency and reliability of GNSS systems. Each international organization promotes international cooperation, improvement of service quality, assurance of security, compliance with international regulations, and technological innovation and development. In the future, interoperability and compatibility with new satellite navigation systems and other GNSS and satellite navigation enhancement systems must be secured, so and thus investigation of international organizations must be conducted first.

• Journal of Positioning, Navigation, and Timing
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• 제13권1호
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• pp.35-44
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• 2024

This investigation primarily focuses on the generational characteristics of satellites utilized in the existing Global Navigation Satellite System (GNSS) and Regional Navigation Satellite System (RNSS), with a central emphasis on comparing the operational status of the latest generation satellites. Variations among satellite generations in physical attributes, energy consumption, and timekeeping are observed, enabling an exploration of the developmental trends over successive generations. Through a comparative analysis of the latest generation satellites, particularly in terms of performance, this study aims to furnish essential insights into the satellites employed within each system. Consequently, it will contribute to a foundational understanding of the past, present, and future GNSS satellites.

• 전기전자학회논문지
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• 제24권2호
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• pp.461-467
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• 2020

오늘날 민간에서 사용 중인 측위 시스템의 대부분은 위성의 신호를 수신하여 현재 위치를 계산하는 글로벌 위성항법 시스템(GNSS; Global Navigation Satellite System)을 기반으로 한다. 미국이 GPS (Global Positioning System)를 통하여 입증한 GNSS의 효용성은 다양한 국가에서 위성항법 시스템을 구축하고 고도화 하도록 이끌었다. 그중 중국은 앞선 IT 기술력과 자금력을 바탕으로 자체 GNSS인 베이더우 위성항법 시스템(BDS; BeiDou Navigation Satellite System)의 급진적인 개발을 성공시켰다. 중국이 빠르게 전 세계로 BDS의 서비스 영역을 확대하고 있는 것을 고려할 때 우리나라에서도 BDS에 대한 체계적인 연구가 요구된다. 따라서 본 논문에서는 BDS의 공개 신호인 B1C에 대한 전반적인 정보를 제공하여 B1C 신호 체계 설계 및 BDS B1C 수신기 설계에 활용될 수 있도록 한다.

• Journal of electromagnetic engineering and science
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• 제14권3호
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• pp.299-305
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• 2014

A wideband circularly polarized (CP) antenna with a single feed is proposed for use in global navigation satellite systems. Its primary radiation elements are composed of two orthogonal bowtie dipoles, which are equipped with double-printed vacant-quarter rings to allow direct matching of the antenna to a single $50-{\Omega}$ coaxial line and to produce CP radiation. The crossed bowtie dipole is appropriately incorporated with a planar metallic reflector to produce the desired unidirectional radiation pattern as well as to achieve a wideband characteristic in terms of impedance matching and axial ratio (AR) bandwidths. The designed antenna was fabricated and measured. The prototype antenna with an overall 1.2-GHz frequency size of $0.48{\lambda}_o{\times}0.48{\lambda}_o{\times}0.25{\lambda}_o$ produced a measured ${\mid}S_{11}{\mid}$<-10 dB bandwidth of 1.05-1.79 GHz and a measured 3-dB AR bandwidth of 1.12-1.64 GHz. It also showed right-hand CP radiation with a small gain variation (${\pm}0.3dB$) and high radiation efficiency (>93%) over the operational bandwidth.

• 한국항공운항학회지
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• 제14권1호
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• pp.55-62
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• 2006

Ionospheric signal delay is a critical factor for precision differential GNSS(Global Navigation Satellite Systems) applications such as GBAS(Ground-Based Augmentation System) and SBAS (Satellite-Based Augmentation System). Most concern is the impact of the ionospheric storm caused by the interaction between Solar and geomagnetic activities. After brief description of the ionosphere and ionospheric storm, ionospheric models for SBAS are discussed. History of recent ionospheric storms is reviewed and their impact on GNSS is discussed. In order to support Korean GNSS augmentation system development, a preliminary study on the regional ionosphere performed. A software tool for computing regional ionospheric maps is being developed, and initial results during a recent storm period is analyzed.

• 한국항공운항학회지
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• 제15권1호
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• pp.11-17
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• 2007

One of the key elements for developing GNSS (Global Navigation Satellite Systems) is the comprehensive analysis of GNSS satellite orbit including the capabilities to generate precision navigation message. The orbit characteristics of Japan's own GNSS system, called QZSS (Quasi Zenith Satellite System) is analyzed and its navigation message, which includes orbit elements and correction terms, is investigated. QZSS-type orbit simulations were performed using a precision orbit integrator in order to analyze the effect of perturbation forces, e.g. gravity, Moon, Sun, etc., on the orbit variation. A preliminary algorithm for creating orbit element corrections was developed and its accuracy is evaluated with the simulation data.

• 한국항공운항학회지
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• 제21권1호
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• pp.8-14
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• 2013

As GNSS(Global Navigation Satellite System) is used in various filed, many countries establish GNSS system independently. But GNSS system has the limitation of accuracy and stability in stand-alone mode, because this system has error elements which are ionospheric delay, tropospheric delay, orbit ephemeris error, satellite clock error, and etc. For overcome of accuracy limitation, the DGPS(Differential GPS) and RTK(Real-Time Kinematic) systems are proposed. These systems perform relative positioning using the reference and user receivers. ETRI(Electronics and Telecommunications Research Institute) is developing precision navigation system in point of extension of GNSS usage. The precision navigation system is for providing the precision navigation solution to common users. If this technology is developed, GNSS system can be used in the fields which require precision positioning and control. In this paper, we introduce the precision navigation system and perform design and algorithm verification.

• 항공우주시스템공학회지
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• 제4권1호
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• pp.19-22
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• 2010

The accuracy and integrity of global navigation satellite systems (GNSS) can be improved by using GNSS augmentation systems. Large ionospheric spatial gradient, during ionosphere storm, is a major threat for using GNSS augmentation systems by increasing the spatial decorrelation between a reference system and users. Ionosphere decorrelation behavior can be analyzed by using dual frequency GPS data. GNSS receivers have their own biases, called inter-frequency bias (IFB) between dual(P1 and P2) frequencies and they must be accurately estimated before computing ionosphere delays. GPS network data in Korea is used to compute each receiver's IFB, and their estimation accuracy and variability are analyzed. IFB estimation methodology to apply for ionosphere gradient analysis is discussed.

• Journal of Positioning, Navigation, and Timing
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• 제13권3호
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• pp.215-220
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• 2024

In urban areas, signals can be blocked and reflected by buildings, reducing the reliability of global navigation satellite systems (GNSS). To address this, the zonotope shadow matching (ZSM) algorithm has been proposed to estimate the set-valued receiver position by calculating the GNSS shadow based on the zonotope. However, the existing study only analyzed the performance of ZSM in dense urban areas where GNSS shadows occur frequently, and the performance analysis in various urban environments was insufficient. Therefore, in this paper, we analyzed the performance of the ZSM algorithm in four urban environments with different characteristics. The results showed that the receiver position estimation performance of ZSM was relatively poor in environments where buildings were not densely populated, and the performance of ZSM was shown to be effective in urban environments with narrow roads and tall buildings.