• 한국통신학회논문지
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• 제37권7C호
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• pp.592-600
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• 2012

본 논문에서는 이동형 중계기 시스템에서 네트워크 진입절차를 거치지 않는 분산적 주파수 분할기법을 제시하였다. 이를 위해 각기 중계기들의 주파수 분할의 기준 신호, Frequency Indicator(FI) 신호와 이를 전송하기 위한 Energy Detection(ED) 구간을 정의 하였다. 또한 중계기간 통신을 원활하게 하기 위하여 중계기 자신에게 연결된 단말을 이용하여 인접한 곳에 위치한 중계기들에게 ED구간에 FI신호를 전송하는 기법을 정의하였다. 그리고 이를 바탕으로 여러 토폴로지 환경에서의 시뮬레이션을 진행하여 셀 수율에서 향상이 있음을 확인하였다.

• 대한전기학회논문지:전력기술부문A
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• 제52권8호
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• pp.437-443
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• 2003

In this paper an expert system is developed to decide the resetting area of protective devices in power transmission systems. A configuration change in power transmission networks from a substation extension such as new line or bus addition need resetting of protective devices around the point of configuration changes. To find the resetting area in complex power system is very difficult, especially when the distance protective relays are considered to be reset. The proposed expert system, in this paper to find the resetting area has many rules based on the changes of fault currents and apparent factors from the power system alteration. It solves the problem to find relay resetting area using the network information in the database and the rule-base. The case study shows a result of the problem to find relay resetting area in KEPCO system when there is any configuration change.

• Journal of Communications and Networks
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• 제18권4호
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• pp.629-638
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• 2016

In this paper, we investigate an energy-efficient resource allocation problem in a two-way relay (TWR) network consisting of multiple user pairs and an amplify-and-forward (AF) relay. As the users and relay have individual energy efficiencies (EE), we formulate a multi-objective optimization problem (MOOP). A single-objective optimization problem (SOOP) of the MOOP is introduced using a weighted-sum method, which achieves a single Pareto optimal point of the MOOP. To derive the algorithm for the SOOP, we propose a more tractable equivalent problem using the Karush-Kuhn-Tucker conditions of the SOOP, which guarantees convergence at the local optimal points. The proposed equivalent problem can be efficiently solved by the proposed iterative algorithm. Numerical results demonstrate the effectiveness of the proposed algorithm in achieving the optimal EE in multi-user AF TWR networks.

• Journal of Electrical Engineering and Technology
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• 제7권2호
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• pp.151-156
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• 2012

The current study presents a zero-one integer programming approach to determine the minimum break point set for the coordination of directional relays. First, the network is reduced if there are any parallel lines or three-end nodes. Second, all the directed loops are enumerated to reduce the iteration. Finally, the problem is formulated as a set-covering problem, and the break point set is determined using the zero-one integer programming technique. Arbitrary starting relay locations and the arbitrary consideration of relay sequence to set and coordinate relays result in navigating the loops many times and futile attempts to achieve system-wide relay coordination. These algorithms are compared with the existing methods, and the results are presented. The problem is formulated as a setcovering problem solved by the zero-one integer programming approach using LINGO 12, an optimization modeling software.

• 한국인터넷방송통신학회논문지
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• 제16권1호
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• pp.121-127
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• 2016

위성통신은 상공에 있는 인공위성을 통신의 중계기로 이용한 통신 방법으로 통신 범위가 광범위하고 고속 데이터를 전송할 수 있어 차세대 통신으로 각광받고 있다. 하지만 지상과 위성 간의 거리가 멀어 전파 지연 시간이 매우 길고 패킷이 손상된다는 단점이 있다. 따라서 본 연구에서는 패킷 손상을 보완하기 위하여 Link Relay H-ARQ 방식을 적용하였다. 또한, 지연 시간을 보완하는 새로운 방식인 Modified Link Relay H-ARQ 방식을 제안한다. 위성통신의 채널 구현을 위해 Markov 채널을 적용하여 성능을 분석해 본 결과, Link Relay H-ARQ 방식을 적용한 경우 BER과 PER 성능이 향상되고, Modified Link Relay H-ARQ 방식을 적용한 경우 Throughput 성능이 향상됨을 확인하였다.

• 한국통신학회논문지
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• 제36권12B호
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• pp.1647-1658
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• 2011

본 논문에서는 3GPP LTE-Advanced에서 지원하고 있는 Relay Node의 FDD 모드에서 무선 백홀 링크 성능 향상을 위한 방안을 제안한다. 백홀 링크에서 Carrier Aggregation을 적용하기 위한 고려 사항을 살펴보고 이를 위한 RRC (Radio Resource Control) 메시지와 Relay startup 절차를 제안한다. 또한 Type 1 Relay에서 백홀과 엑세스 링크사이의 full-duplexing 가능한 reference signal를 설계하여 자원 활용을 극대화 할 수 있는 방안을 제시한다. 마지막으로 본 논문에서는 LTE Release 10 Relay의 백홀 자원 할당 방법내에서 주기적으로 전송되는 상향 제어 정보 및 무선 채널 정보의 효율적인 전송 방법을 제안한다. 이후의 3GPP RAN(Radio Access Network) 표준화는 LTE-Advanced 요소 기술들을 개선시키는 방향으로 진행될 것으로 예상되기 때문에 본 논문에서 제안된 기술들에 대한 표준 채택 논의가 활발히 진행될 것으로 기대된다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권3호
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• pp.956-970
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• 2015

In this paper, we study the design of network coding for the generalized transmit scheme in multiple input multiple output Y channel, where K users wish to exchange specified and shared information with each other within two slots. Signal space alignment at each user and the relay is carefully constructed to ensure that the signals from the same user pair are grouped together. The cross-pair interference can be canceled during both multiple accessing channel phase and broadcasting channel phase. The proposed signal processing scheme achieves the degrees of freedom of ${\eta}(K)=K^2$ with fewer user antennas.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권3호
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• pp.258-272
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• 2010

The low-rate (LR) UWB is a promising technology for the ubiquitous sensor network (USN) due to its extremely low power consumption and simple transceiver implementation. However the limited communication range is a bottleneck for its widespread use. This paper deals with a new frame structure of class 4 active RFID multi-hop relay system based on ISO/IEC 18000-7 standard integrating with IEEE 802.15.4a LR-UWB PHY layer specification, which sets up a connection to USN. As a result of the vital importance of the coverage and throughput in the application of USN, further we analyze the performance of the proposed system considered both impulse radio UWB (IR-UWB) and chirp spread spectrum (CSS). Our simulation results show that the coverage and throughput are remarkably increased.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.196-198
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• 2002

This paper represents a new approach for the protective relay of power transmission lines using a Artificial Neural Network(ANN). A different fault on transmission lines need to be detected, classified and located accurately and cleared as fast as possible. However, The protection range of the distance relay is always designed on the basis of fixed settings, and unfortunately these approach do not have the ability to adapt dynamically to the system operating condition. ANN is suitable for the adaptive relaying and the detection of complex faults. The backpropagation algorithm based multi-layer perceptron is utilized for the learning process. It allows to make control to various protection functions. As expected, the simulation result demonstrate that this approach is useful and satisfactory.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.233-235
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• 2001

This paper deals with frequency control of demand users that have power plants by under-frequency relay. The demand users supply electrical power to a part of their loads by their power plants and to other rest of their loads by utility. While electrical power supply is stopped by faults of utility network, the system of demand users network is separated from total power system and their system frequency goes below normal limits. In this paper, this situation and the effect of under-frequency relay application are simulated by EMTDC.