• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2012년도 한국컴퓨터종합학술대회논문집 Vol.39 No.1(D)
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• pp.283-284
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• 2012

최근 무선 네트워크의 사용이 증가하고 전송하는 데이터의 크기가 증가함에 따라 광대역 무선 네트워크에 대한 연구가 진행되고 있다. 광대역 무선 네트워크 기술인 IEEE 802.16j MMR(Mobile Multi-hop Relay)은 높은 전송률과 셀 영역 확장을 목표로 하는 기술로써 RS(Relay Station)를 통하여 멀티 홉을 지원한다. 본 논문에서는 IEEE 802.16j MMR 환경에서 링크 상태를 고려하여 동적으로 라우팅 주기를 조절하는 기법을 제안한다. 제안하는 라우팅 주기 조절 기법을 통해 경로 복구 지연시간을 최소화 하고 네트워크 자원 소모의 효율성을 높인다. 시뮬레이션을 통하여 제안하는 기법이 네트워크 성능을 향상시킬 수 있음을 확인하였다.

• Journal of Communications and Networks
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• 제16권1호
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• pp.26-35
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• 2014

We consider multiple-input multiple-output decode-and-forward relay systems in Rayleigh fading channels under the partial channel state information (CSI) that the channel statistics of the source-relay (SR) link and the instantaneous CSI of the source-destination and relay-destination links are known at the destination. In this paper, we propose a new near maximum likelihood (near-ML) decoder with two-level pairwise error probability (near-ML-2PEP) which uses the average PEP instead of the exact PEP. Then, we theoretically prove that the near-ML and near-ML-2PEP decoders achieve the maximum diversity, which is confirmed by Monte Carlo simulations. Moreover, we show that the near-ML-2PEP decoder can also achieve the maximum diversity by substituting the average PEP with the values that represent the error performance of the SR link.

• 대한교통학회지
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• 제6권1호
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• pp.5-16
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• 1988

Development is given to an optimal network design method using continuous design variables. Modified Hooke-and-Jeeves algorithm is implemented in order to solve nonlinear programming problem which is approximately equivalent to the real network design problem with system efficiency crieteria and improvement cost as objective function. the method was tested for various forms of initial solution, and dimensions of initial step size of link improvements. At each searching point of evaluating the objective function, a link flow problem was solved with user equilibrium principles using the Frank-Wolfe algorithm. The results obtained are quite promising interms fo numbers of evaluation, and the speed of convergence. Suggestions are given to selections of efficient initial solution, initial step size and convergence criteria. An approximate method is also suggested for reducing computation time.

• Journal of Communications and Networks
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• 제16권2호
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• pp.146-154
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• 2014

This paper proposes a bandwidth-aware localized-routing algorithm that is capable of sensing the available spectrum bands within a two-hop neighboring for choosing the highly opportunistic routes. A mixed-integer linear programming (MILP) is utilized to formulate the optimization problem. Then, the proposed algorithm is used to determine the maximum bandwidth possible of link pairs via a bandwidth approximation process of relaxed variables. Thereby, the proposed algorithm can allow selected routes corresponding to maximum bandwidth possible between cognitive radio (CR) users through link pairs in cognitive radio networks. By comparing the solution values to previous works, simulation results demonstrate that the proposed algorithm can offer a closed-optimal solution for routing performance in cognitive radio networks. The contribution of this paper is achieved through approximately 50% throughput utilized in the network.

• 한국통신학회논문지
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• 제34권5A호
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• pp.421-428
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• 2009

Inter-cell coordination has been an emerging issue for mitigating inter-cell interference in broadband wireless access networks such as IEEE802.16 and 3GPP LTE (Long Term Evolution). This paper proposes uplink/downlink hybrid inter-cell coordination patterns for a TDD (Time Division Duplex)/MC-CDMA (Multi-Carrier Code Division Multiple Access) system. For the performance analysis, closed forms of inter-cell interferences are derived when uplink and downlink transmissions coexist over a multi-cell environment. In the analysis, we find an optimal ratio of downlink transmit powers of BSs (Base Stations) based on the target outage probability and the performance according to ratios of uplink/downlink transmit powers of MSs (Mobile Stations)/BSs is explored. Our numerical results show that interference mitigation utilizing the characteristics of the uplink and downlink power ratio is very effective in improving system performance in terms of QoS.

• 한국정밀공학회지
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• 제16권10호
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• pp.126-131
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• 1999

Up until now, it is said that no satisfactory computer solutions have been found for synthesizing four-bar linkage based on the prescribed coupler link curve. In our study, an algorithm has been developed to improve the design synthesis of four-bar linkage automatically generating prescribed path by using B-spline interpolation. The suggested algorithm generates the desired coupler curve by using B-spline interpolation, and hence the generated curve approximates as closely as to the desired curve representing coupler link trajectory. Also, when comparing each generated polygon with the control polygon, rapid comparison by applying convex hull concept. finally, optimization process using ADS is incorporated into the algorithm based on the 5 precision point method to reduce the total optimization process time. As for examples, three different four-bar linkages were tested and the results showed the effectiveness of the algorithm.

• 한국통신학회논문지
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• 제23권9A호
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• pp.2165-2172
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• 1998

Existing premises telecommucation wiring ad been installed for efficient telephone service. But premises wiring is currently ready to be reused as media for wideband digital services and Fiber-to-the-curb architecture. Electrical properties of premises wiring link have not characateized above frequencies for voice service. Accurte measurement of these characteristics are exssential for studies fof wideband ditital transmission system. On the other hand, the transmission qualities of premises wiring have been known to be worst in telecommunications access networks. So the knowledge of premises wiring sturucture as well as electrical properties is needed to improve the performance of premises wiring. In this paper, the structure of premises wiring is described in detail and electrical characteristics (characteristic impedance, SRL, attnuation, NEXT) about premises cables and stelecommucations link of representative apartment complex sare measured and naalyzed ove r16MHz range which is UTP Cat3 bandwidth.

• 반도체디스플레이기술학회지
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• 제5권3호
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• pp.11-16
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• 2006

A low cost PDP sustain power supply is proposed based on flyback topology. By using Boundary Conduction Method(BCM) to control input current regulation, DCM condition can be met under all load conditions. Another feature of the proposed method is that a excessive voltage stress due to the link voltage increase can be suppressed by removing link capacitor and suggest new 'Level-shifting switch driver'. this new gate driver is improved 66% of efficiency than switching loss of a existed push-pull amplifier. The proposed converter is tested with a 400W(200V-2A output) prototype circuit.

• 한국안전학회지
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• 제16권4호
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• pp.65-73
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• 2001

This paper is a study on the fatigue analysis using BS5400 Part10(1980), code of practice for fatigue for a double link type level luffing jib crane which has been operated since the crane was built in 1985 at a domestic pier. South Korea. In addition, on the basis of the design lift due to fatigue analysis and the number of cracks detected from the nondestructive test the structural reliability and the residual life of the crane is predicted by evaluating the expected development of detectable fatigue oracle during the next five to ten years using Paris's Law for predicting fatigue crack growth and Gaussian probability density function to be reasonable for stress ranges below the mean values determined by laboratory tests. The statistical data used for the analysis of the structural reliability and life expectancy is given in the above referred code.

• 한국통신학회논문지
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• 제16권6호
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• pp.498-508
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• 1991

본 논문은 비트레벨에서, 3 - 상태 마코프체인의 모델을 사용한 종단대 종단 디지털 접속부에서의 개개 링크들의 에러성능을 평가하는 성능 분석 알고리즘을 표현했다. 링크모델은 개개링크의 버스트에러를 제안했으며, 또한 그것은 여러가지 개개링크들을 연결시키는 방법과 종단대 종단 디지털 접속부에 대한 모델을 추출하는 방법을 나타냈다. 이 결과적인 종단대 종단 모델이 주어진 블럭크기에 대한 비트에러율과 블럭에러와 같은 성능 파라미터를 계산하는데 사용될 수 있다.