• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.4 s.107
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• pp.358-367
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• 2006

In this paper, a mathematical formulation of protection ratio and its calculation method are suggested for a radio relay system with diversity techniques. The analysis of protection ratio and its physical meaning have been performed for the space or frequency diversity system, and in particular protection ratios are reviewed in terms of the parameters of diversity improvement factor, which comprises antenna gain, separation distance between antennas, frequency and its difference between carriers, and distance. As one of simulated results, the co-channel protection ratio of 60 dB is obtained for the space diversity system regarding 6.2 GHz, 60 km, 64-QAM, and 25 m between antennas, which gives 15 dB less than the co-channel protection ratio of the non-space diversity system. In addition, the co-channel protection ratio for the frequency diversity system gives 64 dB in case of frequency offset of 0.5 GHz under the same conditions as the space diversity system, which brings about 11 dB less than the co-channel protection ratio of non-frequency diversity system. In consequency, it is interesting to note that the space diversity system is less sensitive to interference in comparison to the frequency diversity system and provides better quality of service for a given interference.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.11
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• pp.7-13
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• 2010

For swiftness and economic feasibility of parcel delivery, optimal location of mail exchanging centers considering not only section delivery distance but also some weights like the number of delivery vehicles are necessary. In this paper, a mechanism with section delivery distance and vehicle number for locating of mail distribution centers which connect some mail centers of major cities in Republic Korea by applying GOSST theory is proposed. This mechanism for locating mail exchange centers can make the total delivery distance of postal matters less than not only present method which assigns Daejun as mail exchange center, but also Steiner tree method which does not consider weights like number of delivery vehicles. The mechanism is good for protecting the environment as well as rapid and economic delivery. In experiment, the proposed mechanism could curtail total delivery distance by 2.52 percentages compared with Steiner tree method and by 6.66 percentages compared with present method. The mechanism may be used in electric power transmission routing, distribution line topology design, power relay station locating where various voltages and other weights should be considered.

• The KIPS Transactions:PartC
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• v.19C no.1
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• pp.9-18
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• 2012

In 2010, Pedro et al. proposed RFID distance bounding protocol based on WSBC cryptographic puzzle. This paper points out that Pedro et al.'s protocol not only is vulnerable to tag privacy invasion attack and location tracking attack because an attacker can easily obtain the secret key(ID) of a legal tag from the intercepted messages between the reader and the tag, but also requires heavy computation by performing symmetric key operations of the resource limited passive tag and many communication rounds between the reader and the tag. Moreover, to resolve the security weakness and the computation/communication efficiency problems, this paper also present a new RFID distance bounding protocol based on WSBC cryptographic puzzle that can provide strong security and high efficiency. As a result, the proposed protocol not only provides computational and communicational efficiency because it requires secure one-way hash function for the passive tag and it reduces communication rounds, but also provides strong security because both tag and reader use secure one-way hash function to protect their exchanging messages.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.40-42
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• 2015

Our D2D (Device-to-Device) advertisement dissemination algorithm based on the convergence of a D2D communication and a social commerce service is able to efficiently deliver advertisement messages of small business owners. We here assume high user-density areas as target-areas, and these target areas can form several target-groups based on geographical proximity. Also, the isolated target-areas which are not included in the target-groups may have the opportunities for forming a new target-group in consideration of the maximum distance with AP. In this paper, we evaluate performances with respect to the total number of successfully received users and the average number of relay users in accordance with variation in the maximum distance for isolated target-areas.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.10
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• pp.602-609
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• 2003

This paper describes the fault location calculation using neuro-fuzzy systems in combined transmission lines with underground power cables. Neuro-fuzzy systems used in this paper are composed of two parts for fault section and fault location. First, neuro-fuzzy system discriminates the fault section between overhead and underground with normalized detail coefficient obtained by wavelet transform. Normalized detail coefficients of voltage and current in half cycle information are used for the inputs of neuro-fuzzy system. As the result of neuro-fuzzy system for fault section, impedance of selected fault section is calculated and it is used as the inputs of the neuro-fuzzy systems for fault location. Neuro-fuzzy systems for fault location also consist of two parts. One calculates the fault location of overhead, and the other does for underground. Fault section is completely classified and neuro-fuzzy system for fault location calculates the distance from the relaying point. Neuro-fuzzy systems proposed in this paper shows the excellent results of fault section and fault location.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.6
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• pp.1011-1016
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• 2020

Rapid change in network topology in high-speed VANET(: Vehicular Ad Hoc Network) is an important task for routing protocol design. Selecting the next hop relay node that affects the performance of the routing protocol is a difficult process. The disadvantages of AODV(: Ad Hoc On-Demand Distance Vector) related to VANET are end-to-end delay and packet loss. This paper proposes the AAODV (Advanced AODV) technique to reduce the number of RREQ (: Route Request) and RREP (: Route Reply) messages by modifying the AODV routing protocol and adding direction parameters and 2-step filtering. It can be seen that the proposed AAODV reduces packet loss and minimizes the effect of direction parameters, thereby increasing packet delivery rate and reducing end-to-end delay.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.202-205
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• 1990

In this paper the development of new technique based on the travelling-wave information contained in the post fault voltage and current signals has been presented. To develop fault location methods which can cope with close-up fault and zero-inception angle problems, magnitude of the backward wave has been used. The technique developed can be incorporated in a generalized algorithm for application as a high speed distance scheme. In this way some of the problems and limitations associated with travelling wave schemes are avoided. Verification of the relay operating principles is presented through digital computer numerical simulation using an electromagnetic transient program(EMTP) in conjunction with simulation of the proposed algorithms.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.12
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• pp.74-79
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• 2012

Currently, separated buses were increased to limit a fault currents in power transmission system. However, separated buses caused bad influences such as a decrease of reliability and stability. Superconducting fault current limiter (SFCL) was proposed to limit a fault current lately and that has many merits beside any other solutions. Therefore, we proposed the install of Superconducting fault current limiter (SFCL) in power transmission system with separated bus. And our proposal was verified by reliability of power system.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.157-158
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• 2008

전 세계적으로 광역정전에 대한 많은 연구가 진행되고 있다. 본 논문에서는 I-PIU를 통해 동기화된 데이터를 취득 이용하여 실시간 계통 감시는 물론 광역정전 방지에 대한 방향을 마련하는데 목적을 두고 있다. 또한 민감도(Sensitivity Factor)와 취약도(Vulnerability Index)를 이용한 예측 알고리즘의 적용으로 실시간 계통의 상황감시는 물론 계통의 위험을 미리 알리는 거리계전기 모니터링 시스템을 설계하였다. 이는 운영자로 하여금 계통의 위험 요소를 적절한 조치를 취해 제거함으로써 치명적인 정전 사고 방지와 효율적 관리는 물론 앞으로의 광역정전 방지를 위한 역할을 기대할 수 있다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.61-62
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• 2008

기존에는 보호 계전기가 어떠한 상황이 되어 동작을 하게 되면 그 당시의 기록을 직접 인터페이스 하여 계전기 동작원인에 대해 분석을 하였다. 하지만 최근 변전소 자동화시스템이 도입되어 세계적으로 변전소 자동화 시스템이 구축되어 가고 있다. 이에 따라 업체들 또한 변전소 자동화 국제 표준 프로토콜인 IEC 61850규격에 맞추어 장비들을 개발함으로서 변전소 자동화가 진전되고 있다. 본 연구에서는 변전소 자동화용 IED들이 이벤트가 발생했을 때 IED들이 제대로 동작하였는가에 대한 평가를 하는 진단 모듈을 IEC 61850 기반으로 개발하여 변전소 자동화용으로 개발된 보호 계전 IED들에 대한 진단을 IEC 61850에서 정의하고 있는 서비스들을 이용하여 기존방식 보다 편리하고 좀 더 정확하게 보호 계전 IED들을 진단 및 검증하는 방법을 제안한다.