• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.108-125
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• 2015

We propose a new time-division half-duplex estimate-and-forward (EF) relaying strategy suitable for a relay with mobility. We reconfigure EF relaying to guarantee a strong relay-destination link which is required to achieve a high rate using EF relaying. Based on the reconfigured model, we optimize the relaying strategy to attain a high rate irrespective of the relay position with preserving the total transmit bandwidth and energy. The proposed relaying strategy achieves high communication reliability for any relay position, which differs from conventional EF and decode-and-forward (DF) relaying schemes.

• 대한기계학회논문집A
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• 제32권5호
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• pp.430-436
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• 2008

This paper proposes a way to predict electrical lifetime of a relay using Accelerated Life Testings (ALTs). The relay of interest mounting on printed circuit boards is usually under an inrush current stress. The inrush current is generated and accelerated through controlling a lamp switching device in the ALT. We find that the dominant failure mechanism under high levels of inrush current would be contact welding in the contact surface of the relay and the contact welding process is accelerated according to increase in inrush current. The electrical lifetime model based on Inverse Power Law in term of inrush current is proposed, and parameters characterizing relay's lifetime distribution are statistically estimated using ALTA 6 PRO software.

• Journal of Electrical Engineering and Technology
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• 제5권3호
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• pp.407-414
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• 2010

This paper proposes a probability measure for the evaluation of relay performance from two aspects, namely, correct trip and no-unwanted trip. They are developed based on the relationship between relay settings and relay measurements, which follow a Gaussian probability model. The proposed method based on strict mathematical derivation is applied to protection capability evaluation of distance relays under various settings. Considering the specific attributes of each protection zone, the optimal settings are also determined accordingly. The protection capability could demonstrate clearly the relay performance under various settings and the optimal settings could provide good references for engineering applications.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.997-999
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• 1997

This Paper presents a relay modeling technique to deal with the relay transient characteristics. Existing relay models are based on steady-state concepts. The ninth-order state space mathematical model of the Mho distance relay has been constructed. Computer modeling of a typical distance relay is done within the Transient Analysis of Control System(TACS) subsection of the ElectroMagnetic Transient Program(EMTP).

• 융합신호처리학회논문지
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• 제7권2호
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• pp.45-52
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• 2006

이동 Ad-hoc 네트워크(Mobile Ad-hoc Network)는 자기 조직화, 기반망에 독립적인 네트워크의 특성상 많은 응용 분야를 가지고 있다. 본 논문에서는 mRelay(Multi-hop Relay) 시스템이라고 명명한 MANET을 위한 멀티미디어 응용 서비스 모델을 제안한다. mRelay 시스템은 무선 멀티미디어 통신 기능을 가진 무인 이동체를 mRelay 단말로 사용하여 멀티흡 통신 기반의 인터넷 연동이 가능한 멀티미디어 서비스를 제공한다. 멀티흡 라우팅 프로토콜인 AODV가 수정되어 mRelay 단말에 적용되었고, mRelay 시스템이 실내에서의 다양한 시나리오 상황에서 기반망 도움 없이 이동 Ad-hoc 네트워크를 구성하고 유지하며, 안정적인 멀티흡 멀티미디어 서비스가 가능함을 보였다. mRelay 시스템은 다양한 이동 Ad-hoc 네트워크의 응용 서비스에 활용될 수 있을 것이다.

• Journal of Communications and Networks
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• 제17권1호
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• pp.47-57
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• 2015

With the ever growing demand of data applications, the joint macro-relay networks are emerging as a promising heterogeneous deployment to provide coverage extension and throughput enhancement. However, the current cellular networks are usually designed to be performance-oriented without enough considerations on the traffic variation, causing substantial energy waste. In this paper, we consider a joint macro-relay network with densely deployed relay stations (RSs), where the traffic load varies in both time and spatial domains. An energy-efficient scheme is proposed to dynamically adjust the RS working modes (active or sleeping) according to the traffic variations, which is called traffic-aware relay sleep control (TRSC). To evaluate the performance of TRSC,we establish an analytical model using stochastic geometry theory and derive explicit expressions of coverage probability, mean achievable rate and network energy efficiency (NEE). Simulation results demonstrate that the derived analytic results are reasonable and the proposed TRSC can significantly improve the NEE when the network traffic varies dynamically.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권11호
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• pp.5455-5475
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• 2016

In this article, we model the distributed relay assignment network as a many-to-one matching market with peer effects. We discuss two scenarios for throughput optimization of relay networks: the scenario of aggregate throughput optimization and the scenario of fairness performance optimization. For the first scenario, we propose a Mutual Benefit-based Deferred Acceptance (MBDA) algorithm to increase the aggregate network throughput. For the second scenario, instead of using the alternative matching scheme, a non-substitution matching algorithm (NSA) is designed to solve the fairness problem. The NSA improves the fairness performance. We prove that both two algorithms converge to a globally stable matching, and discuss the practical implementation. Simulation results show that the performance of MBDA algorithm outperforms existing schemes and is almost the same with the optimal solution in terms of aggregate throughput. Meanwhile, the proposed NSA improves fairness as the scale of the relay network expands.

• 조명전기설비학회논문지
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• 제28권1호
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• pp.69-78
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• 2014

In this paper, characteristics of wireless power transfer (WPT) systems using magnetically coupled resonance scheme with relay coils are investigated and modeled. Especially, asymmetric frequency splitting characteristics in over-coupled region of WPT with relays are measured and accurately modeled. Transmitter, receiver, and relay coils are modeled with R, L, C equivalent circuits. Using these circuit models and mutual inductances between coils, a WPT system is described with a linear matrix equation. For under-coupled region, a matrix is simplified considering only mutual inductances between adjacent coils. An analytical transfer characteristic of WPT system vs. distance is extracted using an inverse matrix that is acquired by Gauss elimination method for the simplified matrix. For over-coupled region, a matrix considering mutual inductances between non-adjacent coils is used to predict a frequency splitting characteristics accurately. A 6.3MHz WPT system with relay coils is implemented and measured. An accuracy of the model is investigated by comparing the output of the model with the measured results.

• 전기전자학회논문지
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• 제13권4호
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• pp.75-81
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• 2009

차세대 셀룰러 시스템은 중계기를 이용한 다중 홉 전송을 사용함으로써 신호의 전달 거리가 감소하고 이를 통한 전송률을 증대시킨다. 그러나 다중 홉 전송을 이용한 전달 거리 감소는 외부 셀 입장에서 간섭량의 증가를 의미하기 때문에 중계기의 위치는 셀룰러 시스템 성능에 영향을 줄 수 있다. 본 논문에서는 중계기의 전송 전력과 위치에 따른 간섭량의 변화를 고려하여 최대의 전송률을 내기 위한 중계기 위치를 결정한다. 중계기 위치 결정을 위한 조건은 수학적인 모델로 분석되었고 모의실험 결과를 통해서 그 성능을 검증하였다. 본 논문의 분석에 따르면 하나의 셀의 평균 오수신 확률을 최소화 시킬 수 있는 중계기 설치 지점과 중계기 전송 전력이 존재하며, 주파수 재사용에 따른 셀들 간 간섭이 심각하지 않은 상황에서 중계기는 평균 오수신 확률을 감소시켜줌으로써 셀 용량 증대에 기여하였다. 반면 셀간 간섭이 심각한 경우 중계기의 사용은 오히려 해당 셀의 오수신 확률을 증가시키므로 지양해야 한다는 결론에 도달하였다.

• 한국통신학회논문지
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• 제36권9A호
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• pp.758-766
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• 2011

무선 협력 통신 기술은 유선 기간망과 연결 없이 설치 가능한 중계국(Relay Station)을 이용하여 추가적으로 기지국을 설치하지 않아도 커버리지 확장, 음영지역의 해소, 링크 전송률을 향상시킬 수 있다. 중계국은 중요한 이동 통신자원 중 하나로 등장하면서 많은 연구들이 최적의 중계국 선택 방안, 중계국 분배 알고리즘과 같은 주제에 초점을 맞추어 진행하여 왔다. 그러나 특정한 환경에 배치한 중계국 수와 획득할 수 있는 링크 전송률 이득사이 관계를 정확히 분석하는 수학적 모델에 대한 제안은 없었다. 본 논문에서는 Voronoi tessellation에 의한 중계국 기반 클러스터 기법을 제안한다. 또한 Voronoi tessellation에 기반하여 배치한 중계국 수와 사용자가 획득할 수 있는 링크 전송률 이득 사이 관계에 대한 수학적 분석 모텔을 추출한다. 본 논문에서 제안된 수학적 분석 모델의 정확성은 Erceg 경로 손실 모델에 기반한 시뮬레이션에 의해 검증되었다.