• Journal of Astronomy and Space Sciences
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• v.24 no.4
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• pp.417-430
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• 2007

The selection of ground stations is one of the essential process of IGS (International GNSS Service) products. High quality GPS data should be collected from the globally distributed ground stations. In this study, we investigated an effect of ground station network selection on GPS satellite ephemeris. The GPS satellite ephemeris obtained from the twelve ground station networks were analyzed to investigate the effect of selection of ground stations. For data quality check, the observations, the number of cycle slips, and multipath of pseudoranges for L1 and L2 were considered. The ideal network defined by Taylor-Karman structure and SOD (Second Order Design) were used to obtain the optimal ground station network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.125-133
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• 2007

In this paper, the frequency sharing issue between cellular time division duplex-orthogonal frequency division multiple access (TDD-OFDMA) Systems and terrestrial Fixed Systems has been studied. The conventional advanced minimum coupling loss (A-MCL) includes only the formulation to calculate the interference from one interfering system. Therefore, A-MCL must be modified to assess the aggregated interference from base stations(BS) and mobile stations(MS). By applying the modified model, the coexistence analysis are done according to the average number of MS per sector, BS-to-BS distance, and the main beam direction of the terrestrial fixed system. In the case of 20 MS per sector, the BS-to-BS distance and the minimum distance between a terrestrial fixed system and BS are 5.8 km and 2.5 km, respectively. It is about 25dB that the difference between maximum and minimum interference signal power which varies with the main beam direction of the terrestrial fixed system. Moreover, for 40% of the main beam direction of the terrestrial fixed system, interference signal power is less than the maximum permissible interference.

• International Area Studies Review
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• v.13 no.1
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• pp.391-416
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• 2009

The purpose of this paper is to provide an ideal agreement proposal for the satisfactory settlement of FTA origin criteria negotiations, which will be the most severe issue in both inter-governmental FTA negotiations to begin in the near future. Towards this end, we, the authors, based on our nine FTA related agreements already concluded with other countries, researched the concrete origin criteria in the previous origin agreements, analyzed the characteristics of these agreements, and derived the ideal origin rule. As a result, we came to the conclusion that in consideration of Korea and China's FTA's substantial transformation test, it's better to choose any one criterion from the following. Criterion 1: CTH (Change of Heading) and Criterion 2: Value Added Criteria by 40% within region. In addition, we also did that in calculating the ratio of value added, the calculation method and price criteria should be more simple and standardized. It led to the conclusion that the objective deduction method should be used mainly and that CIF or FOB should be used as the price criterion.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11C
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• pp.702-711
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• 2011

In this paper, we derived a closed-form equation of a Best Linear Unbiased Estimator (BLUE) and its Crammer-Rao Lower Bound (CRLB) for the estimation of the position of the emitter based on the Time Difference of Arrival (TDOA) teclmique. The BLUE and CRLB were derived for the case of estimating 2 dimensional position of the emitter with 3 base stations or sensors, and for this purpose, we nsed an approximated equation of the TDOA hyperbola equation obtained from the first order Taylor-series after setting the reference points of the position. The derived equation can be used for any kind of noises which are uncorrelated in each other in the TOA measurement noises and for a white Gaussian noise also.

• Journal of Cadastre & Land InformatiX
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• v.46 no.2
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• pp.313-323
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• 2016

Recently, "Cadastral Confirmation Surveying" has been established to promote efficiently and systematically its work. To do so, it is necessary that cadastral control point should be set up and transverse grid coordinates should be determined for high accuracy and boundary restoration based on the cadastral control point. This study expects the potentially institutional problem of detail surveying and the limitation of Network-Real Time Kinematic, introduced to measure the cadastral control point first in the issued regulation, and thus presents the improvement and the management of the block boundary of larger parcel as solutions. This can be applied promptly, when the location difference of ground and border, registered in cadastral record for quake and others, occurs. Thus, the public confidence of cadastral record may become higher and relevant social costs get reduced by the advanced prevention effect of boundary dispute, which represents much to the management of cadastral institution. Provided cadastral confirmation surveying is implemented with the management of the block boundary of larger parcel, proposed in this study.

• Journal of IKEEE
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• v.15 no.3
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• pp.218-226
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• 2011

In this paper, the leaky electric field intensity of outdoor CATV facilities on CDMA mobile service band defined in technical regulation related with CATV is investigated if appropriate or not. From experimental and theoretical analysis results, Maximum allowable power level of CATV leakage should be -110dBm/1.23MHz. Also, the CATV leakage intensity thresholds, which may not nearly give an impact on the uplink performance of CDMA mobile base station for outdoor background noise of -100~-80dBm/1.23MHz to be measured in outdoor environment, couldn't conform to the current CATV technical regulation. Therefore, the leakage intensity in the current CATV technical regulation is rated as a too much low level in view of an overly worst case.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2285-2291
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• 2015

At present, available positioning satellites are not only the GPS, but also GLONASS, GALILEO, QZSS, BeiDou. However, the differential GPS, the augmentation service for increase the positioning accuracy, is follow the RTCM version 2.3 standard. So, it can service the correction information about only GPS. For solve this problem, RTCM is making the new version of RTCM message standard that can service the correction information for all of available GNSS. In South Korea, the software DGNSS RSIM system was installed at almost the whole DGNSS reference station. In this reason, that can cope with the new RTCM version 2.4 quickly. However, the DGNSS Reference Station based RSIM 1.3 can not make the GNSS's PRC simultaneously and can not support RTCM version 2.4. Thus, in this paper, the version of RTCM 2.4 is analyzed and the RTCM version 2.4 message generating module's architecture for software DGNSS reference station is designed.

• Journal of Navigation and Port Research
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• v.37 no.5
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• pp.463-469
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• 2013

This paper focuses on GPS positioning accuracy variations according to locations of obstacles which surround GPS station. We derived precise coordinates of a GPS station which has a good visibility. Its observation data was rewritten by assuming signal blocking due to obstacle in the elevation angle of $10^{\circ}$ to $70^{\circ}$. We processed daily and hourly data for 10 days. In the results using daily data, RMSE was at 10mm level. And RMSE increased to 100mm levels in case of hourly data. As the elevation angle of obstacle increased, the horizontal and vertical RMSE increased, while the height estimates decreased. These results showed the higher the elevation angle of the obstacle increased the loss of large amounts of data by blocking satellite signals direction. In terms of the direction, when the blocking thing was located in the east or west, the coordinate has larger error in the east-west direction. And if signal was blocked at the south direction, the difference between the east-west error and the south-north position error was reduced.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.10
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• pp.912-920
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• 2012

In this paper, we derived a closed-form equation of a Best Linear Unbiased Estimator (BLUE) estimator for the 3 dimensional estimation of the position of the emitter based on the Time Difference of Arrival (TDOA) technique. The BLUE derived for the case of estimating 3 dimensional position of the emitter with 4 base stations or sensors, and for this purpose, we used an approximated equation of the TDOA hyperbola equation obtained from the first order Taylor-series after setting the reference points of the position. The derived equation can be used for any kind of noises which are uncorrelated in each other in the TOA measurement noises and for a white Gaussian noise also.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.5
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• pp.919-939
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• 2021

As a next-generation communication technology, 5G networks are capable of handling large amounts of traffic based on higher speeds, shorter communication delays, and higher connectivity compared to 4G networks. In this 5G network environment, base stations are installed all over the city at high density due to their characteristics, and are connected to user terminals to provide services. Therefore, if the base station is damaged by a malicious attacker, it is expected to cause great damage to users and society as a whole. So the need for secure communication equipment such as 5G base stations has emerged. Therefore, in this paper, we propose the security functional requirements derived using threat modeling, a systematic methodology for 5G base stations, and the security assurance requirements at the level that can cope with the backdoor issues. The security requirements proposed in this paper can be used for base station design and development to construct a secure network environment as a security evaluation standard for 5G base stations.