• 한국전자파학회논문지
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• 제21권10호
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• pp.1128-1135
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• 2010

릴레이 기반 셀룰러 시스템은 사용자의 요구를 충족시키는 서비스를 제공하기 위해 도입되었다. 릴레이 중계기를 사용하는 주된 요인은 서비스 영역 확장 및 요구 서비스를 만족시킬 수 있는 시스템 처리율 증가이다. 본 논문에서는 직교 주파수 분할 다중 접속(OFDMA: Orthogonal Frequency Division Multiple Access) 기술이 적용된 고정 릴레이(fixed relay) 기반 셀룰러 시스템에서 공평성을 고려한 효율적인 부반송파 할당 방안을 제시한다. 릴레이 중계기에 적합한 효율적인 자원 할당 방법을 통해서 사용자의 QoS를 보장할 수 있도록 하며, outage 확률 및 사용자 당 평균 데이터 처리율(throughput)의 관점에서 기존의 비례 공정 알고리즘(proportional fairness algorithm)과의 성능 비교를 통해 제시된 알고리즘의 유용성을 관찰한다.

• 전기학회논문지
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• 제57권2호
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• pp.172-178
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• 2008

If the fault occurs on the underground power cable systems, the fault current on the sheath has an influence on all sections of cable because it's returned through earth at the directly grounded point and operation point of SVL(Sheath Voltage Limiter) on each insulated joint box. Therefore, the earth resistance and the operation of SVL have an effect on the zero-sequence current, and then the impedance between relaying point and fault point is increased. That causes the overreach of distance relay. For these reasons, the distance relay algorithm for protecting an underground power cable systems hasn't been developed till now. In this paper, new distance relay algorithm is developed for protecting a underground power cable system using fuzzy inference system which is the one of ACI(Advanced Computational Intelligence) techniques. This algorithm is verified by EMTP simulation of real power cable system, and proves to effectively advance the errors

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권9호
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• pp.1513-1527
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• 2011

This paper investigates the capacity rate problems for a joint decode-and-forward (JDF) based two-way relaying with network coding. We first characterize the achievable rate region for a conventional three-node network scenario along with the calculation of the corresponding maximal sum-rate. Then, for the goal of maximizing the system sum-rate, opportunistic relay selection is examined for multi-relay networks. As a result, a novel strategy for the implementation of relay selection is proposed, which depends on the instantaneous channel state and allows a single best relay to help the two-way information exchange. The JDF scheme and the scheme using relay selection are analyzed in terms of outage probability, after which the corresponding exact expressions are developed over Rayleigh fading channels. For the purpose of comparison, outage probabilities of the amplify-and-forward (AF) scheme and those of the scheme using relay selection are also derived. Finally, simulation experiments are done and performance comparisons are conducted. The results verify that the proposed strategy is an appropriate method for the implementation of relay selection and can achieve significant performance gains in terms of outage probability regardless of the symmetry or asymmetry of the channels. Compared with the AF scheme and the scheme using relay selection, the conventional JDF scheme and that using relay selection perform well at low signal-to-noise ratios (SNRs).

• 한국통신학회논문지
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• 제34권11A호
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• pp.844-851
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• 2009

핸드오버는 multi-hop relay 시스템에서 이동성을 제공하기 위해 필요하다. 핸드오버의 주요 목적은 MS가 한 BS의 air-interface에서 다른 BS의 air-interface로 이동할 때 연속 연결을 제공하는 것이다. 특히 이종기계간의 핸드오버는 차세대 네트워크에 필수적이다. Mobile WiMAX MMR system에서의 수직 핸드오버 기술은 기술자들이 Mobile WiMAX system을 overlaid cell환경으로 가져오는데 매우 유용하다. 이 기술은 Micro cell(Frequency 1,FA1) and Macro cell(Frequency 2,FA2)사이에 놓인 Ubiquitous 환경에서 시스템 성능향상을 위해 MRS를 다른 시스템으로 핸드오버 하는 기술에 적용될 것이다. 이 논문에서 FA1과 FA2 주파수를 사용하여 제안된 조건들에 따라 MRS들이 수직 핸드오버를 수행했다. 그리고 중심에 있는 Macro cell과 그것을 싸고 있는 6개의 Macro cell들의 BS나 섹터로부터 받은 간섭 및 성능을 분석한다.

• 한국통신학회논문지
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• 제33권8A호
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• pp.829-837
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• 2008

멀티미디어 데이터의 전송영역 확장을 위한 기술로 고정 릴레이 기반 셀룰러 시스템에 대한 관심이 지속적으로 증가하고 있다. 고정 릴레이 기반 셀룰러 시스템에서 릴레이를 추가함으로 생기는 셀 간 또는 섹터 간 간섭은 기지국과 단말기 또는 릴레이와 단말이 사이의 높은 링크성능을 보장하지 못하여 성능저하를 가져올 수 있기 때문에 간섭을 회피하기 위한 자원할당은 매우 중요하다. 본 논문에서는 리피터 중계기를 이용한 셀룰러 시스템과 릴레이를 이용한 셀룰러 시스템의 성능을 비교하여 릴레이 중계기를 이용할 때 셀 커버리지 확장을 비교하고자 한다. 비교를 위해 셀룰러 시스템에 고정 릴레이를 설치할 때 셀 간과 섹터 간 간섭을 피하기 위하여 리피터 중계기를 사용하는 경우의 자원할당과는 다른 자원 할당 방법을 제안한다. 제안된 기법은 인접한 기지국들과 릴레이들에게 서로 다른 주파수 자원을 할당하여 간섭을 줄임으로서 높은 데이터 전송영역의 확장이 가능하며, 기지국들과 릴레이들이 동시에 동작할 때 각 섹터에서 전체 주파수 대역을 사용함으로서 주파수 효율성을 높일 수 있다.

• Journal of electromagnetic engineering and science
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• 제13권3호
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• pp.173-177
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• 2013

This paper presents a new method for analyzing the maximum efficiency of a wireless power transfer (WPT) system with multiple n resonators. The method is based on ABCD matrices and allows transformation of the WPT system with multiple n resonators into a single two-port network system. The general maximum efficiency equation of a WPT system with multiple n resonators is derived using the ABCD matrix. Use of this equation allows placement of the relay resonators for maximum efficiency even though they are asymmetrical. The general maximum efficiency equation and the method of the optimum placement are verified by a full wave simulation. The results show that the method is useful for the analysis of a WPT system with relay resonators.

• 대한전기학회논문지:전력기술부문A
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• 제52권3호
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• pp.143-150
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• 2003

In this paper, we developed the window based monitoring system. This system offers the analysis of accidents in the power plants, the operating status of relays and the historical data with which the experts can offer the idea about the operation of the power system. And we can also monitor the status of the ACB and relay at a long distance by means of the function of communication in the digital protective relay itself. By means of the above functions, we developed the system, which is run after the diagnosis and maintenance of the electrical machines and an amount of data are realized by graphical method fitting the operating convenience of the users.

• IEIE Transactions on Smart Processing and Computing
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• 제2권2호
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• pp.67-76
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• 2013

Under an imperfect channel estimation, a Device-to-Device (D2D) communication framework based on MIMO relay technology is presented. The model consists of a D2D pair equipped with M antennas and a relay equipped with N antennas as well as a cellular user equipped with M antennas. The outage probability under different relaying protocols (i.e. AF and DF protocol) with and without considering a direct link was derived. The actual and theoretical outage probability of the five links under different antenna numbers was emulated. The number of user antennas and channel estimation error was analyzed carefully to determine their impact on the outage probability of a system. The simulation verified the theory analyses and the results showed that MIMO relaying improves the D2D communication system performance.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.15-18
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• 1998

Most existing FRADs support only permanent virtual circuit-based frame relay services. But several applications such as intranets, desktop video conferencing, remote access and voice applications typically do not require the dedicated bandwidth capabilities of PVCs because connections are only occasionally needed. So it drives the need of switched virtual circuit-based FRADs which offer potentail cost savings associated with dynamic bandwidth on demand connectivity. In this paper, we describe Frame Relay Network Access System(FNAS) that provides switched virtual circuit-based frame relay access for dial-up Internet services. The hardware configuration, software architecture and call processing flow of FNAS is explained.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.215-217
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• 2000

Protective relay play a crucial role in the proper operation of a power system, and the reliable transfer of electrical power. This paper deals with the design and implementation of a digital protective relay on a single chip. Implementation on the FPGA(Field Programmable Gate Array) of the chip of digital protective relay. This protective relaying chip monitors the frequency and the voltage and current of the power system. And report the voltage, the current. the frequency, active power and reactive power.