• 한국전자파학회논문지
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• 제22권1호
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• pp.24-29
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• 2011

네트워크 부호화를 이용한 양 방향 중계 기법은 기존의 단 방향 중계 프로토콜보다 송신 시간을 줄임으로써 전송량을 높일 수 있는 장점을 가지며, 부호화 협력 프로토콜은 물리층에서 이루어지는 부호화를 적용한 알고리즘으로 프로토콜의 신뢰성을 높일 수 있는 장점을 가진다. 본 논문에서는 이러한 두 프로토콜의 장점을 결합한 양 방향 중계 네트워크에서의 부호화 협력 프로토콜을 제안하였다. 제안하는 프로토콜이 기존의 양 방향 증폭후 재전송 프로토콜보다 우수한 신뢰성과 전송량을 가지며, 기존의 양 방향 하이브리드 복호 후 재전송 프로토콜과 동일한 전송량을 가지면서 보다 우수한 신뢰성을 가짐을 시뮬레이션 결과를 통해 증명한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.2936-2951
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• 2016

An emerging satellite technology, Operationally Responsive Space (ORS) is expected to provide a fast and flexible solution for emergency response, such as target tracking, dense earth observation, communicate relaying and so on. To realize large distance transmission, we propose the use of available relay satellites as relay nodes. Accordingly, we apply software defined network (SDN) technology to ORS networks. We additionally propose a satellite network architecture refered to as the SDN-based ORS-Satellite (Sat) networking scheme (SDOS). To overcome the issures of node failures and dynamic topology changes of satellite networks, we combine centralized and distributed routing mechanisms and propose a fast recovery routing algorithm (FRA) for SDOS. In this routing method, we use centralized routing as the base mode.The distributed opportunistic routing starts when node failures or congestion occur. The performance of the proposed routing method was validated through extensive computer simulations.The results demonstrate that the method is effective in terms of resoving low end-to-end delay, jitter and packet drops.

• Journal of Communications and Networks
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• 제11권2호
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• pp.196-206
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• 2009

Over the last five years, relaying or multihop techniques have been intensively researched as means for potentially improving link performance of wireless networks. However, the data rates of relays are often limited because they cannot transmit and receive on the same frequency simultaneously. This limitation has come to the attention of researchers, and recently a number of relay techniques have been proposed specifically to improve the data efficiency of relaying protocols. This paper surveys transmission protocols that employ first single relays, then multiple relays and finally multiple antenna relays. A common feature of these techniques is that novel signal processing techniques are required in the relay network to support increased data rates. This paper presents results and discussion that highlight the advantages of these approaches.

• 한국콘텐츠학회논문지
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• 제5권4호
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• pp.219-226
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• 2005

최근 스포츠에 대한 관심이 고조되고 주 5일 근무제가 도입되면서 레저 및 웰빙에 대한 욕구가 증대되고 있다. 본 논문에서는 이러한 사회적 여건 변화에 따라 언제, 어디서나 자유롭게 스포츠 중계 서비스를 받을 수 있도록 무선 네트워크를 이용하는 PDA용 야구 중계 시스템을 설계하고 구현하였다. 본 논문에서 구현한 야구 중계 시스템은 PDA 클라이언트와 중계 보고자, 중계 서버의 세 부분으로 구성되어 있다. 사용자는 PDA를 이용하여 야구 중계 외에도 야구와 관련된 다양한 정보를 검색하고 조회할 수 있다.

• 조명전기설비학회논문지
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• 제29권6호
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• pp.58-62
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• 2015

When an emergency generator is running, it supplies the power for critical loads. Generator protection requires the consideration of many abnormal conditions that may occur with generators include overvoltages and ground faults. Modern day power systems create harmonics within the electrical network that can have an impact upon the associated protective system. This paper focuses on the analysing of the cause and development of a solution for the malfunction of induction disc type overcurrent ground relay by generation of harmonics during emergency generator operation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.260-279
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• 2015

In this paper, we investigate physical layer security for multiple decode-and-forward (DF) relaying underlay cognitive radio networks (CRNs) with fixed transmit power at the secondary network against passive eavesdropping attacks. We propose a simple relay selection scheme to improve wireless transmission security based on the instantaneous channel information of all legitimate users and the statistical information about the eavesdropper channels. The closed-form expressions of the probability of non-zero secrecy capacity and the secrecy outage probability (SOP) are derived over independent and non-identically distributed Rayleigh fading environments. Furthermore, we conduct the asymptotic analysis to evaluate the secrecy diversity order performance and prove that full diversity is achieved by using the proposed relay selection. Finally, numerical results are presented to verify the theoretical analysis and depict that primary interference constrain has a significant impact on the secure performance and a proper transmit power for the second transmitters is preferred to be energy-efficient and improve the secure performance.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 추계학술대회
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• pp.812-814
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• 2015

In this Paper, we proposed optimization of system performance, power splitting protocols applied to relay in the cooperative communication undergo co-channel interference. When relay adjust power distribution factors undergo co-channel interference, it is possible to optimize and maximize the channel capacity of the receiver. Because of energy haversting, interfence transfer to new power source. If we found optimal power levels, to solve inability in system, and to increase the efficiency of the network.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.949-951
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• 1998

Because of the zero sequence mutual coupling of parallel lines, the distance calculation performed by a distance relay is incorrect. To achieve correct operation, the relay has to use not only the measured quantities of faulty line, but also the zero sequence current of healthy line. But the zero sequence current of the healthy line cannot be always measured. Therefore, we propose the neural network method to estimate the zero sequence current and the criterion to determine whether faulty line or not.

• ETRI Journal
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• 제39권5호
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• pp.729-736
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• 2017

This work investigates secure cluster-aided multi-hop randomize-and-forward networks. We present a hop-by-hop multi-hop transmission scheme with relay selection, which evaluates for each cluster the relays that can securely receive the message. We propose an analytical model to derive the secure connectivity probability (SCP) of the hop-by-hop transmission scheme. For comparison, we also analyze SCPs of traditional end-to-end transmission schemes with two relay-selection policies. We perform simulations, and our analytical results verify that the proposed hop-by-hop scheme is superior to end-to-end schemes, especially with a large number of hops or high eavesdropper channel quality. Numerical results also show that the proposed hop-by-hop scheme achieves near-optimal performance in terms of the SCP.

• 한국통신학회논문지
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• 제40권2호
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• pp.369-371
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• 2015

본 논문은 신호대잡음비(signal-to-noise ratio:SNR) 기반의 선택적 전달 기법에서의 아웃티지 성능을 분석한다. 전달 단말은 수신된 신호대잡음비의 값이 정해진 값보다 크면 수신된 신호를 재전송하고 정해진 값보다 작으면 수신된 신호를 재전송하지 않는다. 제안된 시스템에 대해서 정확한 아웃티지 확률을 구한다.