• 한국정보과학회논문지:정보통신
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• 제29권5호
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• pp.524-532
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• 2002

인터넷이 급속하게 발달함에 따라 네트워크 사용자는 텍스트 기반의 서비스에서 멀티미디어 서비스 사용을 위한 고속의 네트워크를 요구하고 있다. 또한 네트워크 사용자는 인터넷 IP 주소 부족을 해결하기 위한 네트워크 변환 기술(NAT)이나 외부 망으로부터 내부 망을 보호하기 위한 방화벽(Firewall)과 같은 Layer 3에서의 라우팅 기술을 요구하고 있다. 그러나 현재 라우터 기반의 알고리즘에서는 멀티미디어 서비스를 지원하거나 사용자의 요구조건을 충족시키면서 혼잡상황 및 불공정성을 해결하기 위한 방법을 가지고 있지 않다. 본 논문에서는 Layer 3의 라우팅 기술인 네트워크 변환 기술을 이용하여 혼잡상황을 효과적으로 해결하는 MFRED(Multiple Fairness RED) 알고리즘을 제안하였다. MFRED 알고리즘은 비반응 플로우(unresponsive flow)와 TCP와 같은 플로우(TCP-like flow) 사이에 불공정성 문제를 해결하였다. 그리고, 이 알고리즘은 혼잡 상황에 덜 민감하고 혼잡 상황의 원인이 되는 플로우로부터 혼잡상황에 민감한 플로우를 공정하게 잘 보호하도록 동작한다.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1995년도 춘계공동학술대회논문집; 전남대학교; 28-29 Apr. 1995
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• pp.316-323
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• 1995

This paper presents an image processing technique to get traffic information such as vehicle volume, velocity, and occupancy for measuring the traffic congestion rate. To obtain these information, two horizontal lines are previously set on the screen. A moving vehicle is detected using the gray level difference on each line, and also template matching method at night. Threshold values are determined by sampling pavement grey level, and updated dynamically to cope with the change of ambient light conditions. These technique is successfully used to calculate vehicle volume, occupancy, and velocity. This study can be applied to traffic signal control system for minimizing traffic congestion in urban areas.

• 대한안전경영과학회지
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• 제13권1호
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• pp.127-131
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• 2011

Even if there are no causing factors such as car crash and road works, traffic congestion come from traffic growth on the road. In this case, estimation of traffic flow helps find the solution of traffic congestion problem. In this paper, we present a optimization model which used on traffic equilibrium problem and studied the problem of inverting shortest path sets for complex traffic system. And we also develop pivotal decomposition algorithm for reliability function of complex traffic system. Several examples are illustrated.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2145-2157
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• 2018

Congestion Management (CM) is an attractive research area in the electrical power transmission with the power compensation abilities. Reconfiguration and the Flexible Alternating Current Transmission Systems (FACTS) devices utilization relieve the congestion in transmission lines. The lack of optimal power (real and reactive) usage with the better transfer capability and minimum cost is still challenging issue in the CM. The prediction of suitable place for the energy resources to control the power flow is the major requirement for power handling scenario. This paper proposes the novel optimization principle to select the best location for the energy resources to achieve the real-reactive power compensation. The parameters estimation and the selection of values with the best fitness through the Symmetrical Distance Travelling Optimization (SDTO) algorithm establishes the proper controlling of optimal power flow in the transmission lines. The modified fitness function formulation based on the bus parameters, index estimation correspond to the optimal reactive power usage enhances the power transfer capability with the minimum cost. The comparative analysis between the proposed method with the existing power management techniques regarding the parameters of power loss, cost value, load power and energy loss confirms the effectiveness of proposed work in the distributed renewable energy systems.

• 한국통신학회논문지
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• 제40권7호
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• pp.1377-1384
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• 2015

본 논문에서는 혼잡상황에서 발생할 수 있는 비디오 프레임 손실을 방지하기 위한 자원 관리 기법을 제안하였다. WiMedia 프로토콜은 고속의 전송속도를 지원하기 때문에, 선박 네트워크(ship area network)등과 같은 환경에서 고속의 전송률을 요구하는 실시간 멀티미디어 서비스 제공과 같은 응용분야에 적합하다. 하지만, 혼잡 상황에서는 프레임의 중요도에 관계없이 프레임을 파기하기 때문에, 동영상 전송 품질의 저하의 원인이 되기도 한다. 본 논문에서는 기존의 WiMedia 프로토콜에서는 혼잡상황을 적절하게 대처하지 못하여 발생하는 네트워크 성능저하를 해결하는 자원 관리 기법을 제안하였다.

• 한국경영과학회지
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• 제34권1호
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• pp.61-83
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• 2009

This study developed a variable demand traffic assignment model by stable dynamics. Stable dynamics, suggested by Nesterov and do Palma[19], is a new model which describes and provides a stable state of congestion in urban transportation networks. In comparison with the user equilibrium model, which is based on the arc travel time function in analyzing transportation networks, stable dynamics requires few parameters and is coincident with intuitions and observations on congestion. It is therefore expected to be a useful analysis tool for transportation planners. In this study, we generalize the stable dynamics into the model with variable demands. We suggest a three stage optimization model. In the first stage, we introduce critical travel times and dummy links and determine variable demands and link flows by applying an optimization problem to an extended network with the dummy links. Then we determine link travel times and path flows in the following stages. We present a numerical example of the application of the model to a given network.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.121.1-121
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• 2001

Congestion control is a critical issue in TCP networks, Recently, active queue management (AQM) was proposed for congestion control at routers. The random early detection RED algorithm is widely known in the AQM algorithms, We present an adaptive nonlinear RED (NRED) algorithm, which has nonlinear drop probability profile. The proposed algorithm enhanced the performance of the RED algorithm by the self-parameterization based on the traffic load Furthermore, the proposed algorithm can effectively adapt itself between he RED and the drop-tail queue management by adopting proper nonlinearity in the drop probability profile. Through simulation, we show the effectiveness of the proposed algorithm comparing with the drop-tail and the original RED algorithm.

• 대한전기학회논문지:전력기술부문A
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• 제55권11호
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• pp.447-452
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• 2006

This paper presents a scheme to solve the congestion problem with phase-shifting transformer(PST) controls and power generation controls using linear programming method. A good design of PST and power generation control can improve total transfer capability(TTC) in interconnected systems. This paper deals with an application of optimization technique for TTC calculation. Linear programming method is used to maximize power flow of tie line subject to security constraints such as voltage magnitude and real power flow in interconnected systems. The results are compared with that of repeat power flow(RPF) and sequential quadratic programming(SQP). The proposed method is applied to 10 machines 39 buses model systems to show its effectiveness.

• 정보처리학회논문지C
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• 제9C권4호
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• pp.513-522
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• 2002

기존의 end-to-end 방식에서는 네트워크 내부에서 혼잡(congestion)이 발생했을 경우 각 전송자가 즉시 알아 낼 수 없기 때문에 일정시간 동안 수신된 패킷(packet)의 순서에 대한 정보로 흔잡이 발생했는지에 대해 추론하는 것이다. 이와 같은 방법은 RTT(Round Trip Time)가 커지면 혼잡이 발생할 경우 전송자가 전송 양을 줄인다 해도 이미 전송된 패킷들로 인하여 흔잡이 가중되며 전체적인 TCP 동기화 (TCP Global synchronization) 현상을 피할 수 없게 된다. 반면 네트워크 내부에서 직접적으로 정보를 얻거나 처리를 해 줄 수 있다면 혼잡 발생과 동시에 처리가 가능함으로 기존 방식보다 처리율이 향상될 것이다. 본 논문에서는 액티브 라우터의(Active Network) 피드백 메커니즘을 이용하여 네트워크 내부 정보를 각 전송자가 이용할 수 있도록 하기 위해 라우터와의 통신을 이용하였으며, 코어 라우터의 큐 모듈은 RED(Random Early Detection)를 응용하여 ACC의 누락 메커니즘을 개선하였다. ACC를 확장한 메커니즘인 EACC(Enhanced Active Congestion Control)를 제시하고 모의실험을 통해 기존의 혼잡제어나 ACC(Active Congestion Control)보다 성능이 향상됨을 보여준다.

• Journal of Electrical Engineering and Technology
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• 제4권4호
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• pp.467-475
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• 2009

Congestion management is one of the technical challenges in power system deregulation. This paper presents single objective and multi-objective optimization approaches for optimal choice, location and size of Static Var Compensators (SVC) and Thyristor Controlled Series Capacitors (TCSC) in deregulated power system to improve branch loading (minimize congestion), improve voltage stability and reduce line losses. Though FACTS controllers offer many advantages, their installation cost is very high. Hence Independent System Operator (ISO) has to locate them optimally to satisfy a desired objective. This paper presents optimal location of FACTS controllers considering branch loading (BL), voltage stability (VS) and loss minimization (LM) as objectives at once using GA. It is observed that the locations that are most favorable with respect to one objective are not suitable locations with respect to other two objectives. Later these competing objectives are optimized simultaneously considering two and three objectives at a time using multi-objective Strength Pareto Evolutionary Algorithms (SPEA). The developed algorithms are tested on IEEE 30 bus system. Various cases like i) uniform line loading ii) line outage iii) bilateral and multilateral transactions between source and sink nodes have been considered to create congestion in the system. The developed algorithms show effective locations for all the cases considered for both single and multiobjective optimization studies.