• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2003년도 Proceeding
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• pp.236-242
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• 2003

ATM ABR service controls network traffic using feedback information on the network congestion situation in order to guarantee the demanded service qualities and the available cell rates. In this paper we apply the control method using queue length prediction to the formation of feedback information for more efficient ABR traffic control. If backward node receive the longer delayed feedback information on the impending congestion, the switch can be already congested from the uncontrolled arriving traffic and the fluctuation of queue length can be inefficiently high in the continuing time intervals. The feedback control method proposed in this paper predicts the queue length in the switch using the slope of queue length prediction function and queue length changes in time-series. The predicted congestion information is backward to the node. NLMS and neural network are used as the predictive control functions, and they are compared from performance on the queue length prediction. Simulation results show the efficiency of the proposed method compared to the feedback control method without the prediction. Therefore, we conclude that the efficient congestion and stability of the queue length controls are possible using the prediction scheme that can resolve the problems caused from the longer delays of the feedback information.

• 한국통신학회논문지
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• 제34권11B호
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• pp.1225-1233
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• 2009

기업이나 대학 등 대규모 기관들은 고속 네트워크를 구축하여 운영하고 있다. 이와 같은 고속 엔터프라이즈 네트워크 내에서 네트워크 이용률(utilization)이 저조함에도 불구하고 종단간 성능은 네트워크 속도에 비하여 상당히 저조하다. 이러한 원인은 특정 장비에서 아주 작은 시간에 트래픽이 폭주하는 미세폭주(micro-congestion)가 발생하기 때문이다. 미세폭주는 패킷손실(Packet Loss)나 지연(Delay), 패킷역전(Packet Reordering)을 발생시키고 이것이 성능 저하의 원인이 된다. 본 논문에서는 미세폭주를 발생하는 시점을 검출하는 방법과 미세폭주를 검출한 시점에 트래픽을 수집하여 패킷손실, 지연, 패킷역전과 트래픽의 특성과의 상관관계 분석하여 성능저하를 발생시키는 미세폭주의 특성을 규명한다.

• 한국정보과학회논문지:정보통신
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• 제41권4호
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• pp.186-191
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• 2014

네트워크 코딩은 시스템에서 전송되는 패킷 개수를 줄여 성능향상을 줄 수 있기 때문에 기존 연구들은 네트워크 코딩 기회를 극대화하는 점에만 집중하였다. 하지만 각 소스노드가 채널상황을 고려하여 코딩을 수행하는 중간노드로 최대한 높은 속도로 전송하기 때문에 혼잡을 발생시킬 수 있다. 따라서 본 연구에서는 채널상황과 혼잡을 고려하여 이득이 확실한 경우에만 기회적으로 네트워크 코딩을 수행하는 기법을 제안했다. 중간노드는 코딩할 수 있는 네트워크 코딩 조합 중에서 데이터 손실과 혼잡을 최소화하고 전송횟수를 줄일 수 있는 목적함수를 동적프로그래밍을 통해 구하고 최적의 코딩 조합을 선택한다. 퀄넷 시뮬레이터를 활용한 성능평가를 통해 제안하는 기법이 기존 연구들에 비해서 최대 20% 성능향상이 있음을 증명했다.

• 한국통신학회논문지
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• 제28권5B호
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• pp.427-434
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• 2003

본 논문은 TCP-Reno등의 TCP 등에서 사용되는 다른 혼잡 제어 알고리즘보다 에러가 많은 무선 환경에 더욱 강인한 향상된 TCP 혼잡 제어 알고리즘을 제안한다. 제안하는 알고리즘은 혼잡 윈도우 크기를 패킷 에러율과 현 TCP의 상태가 fast recovery 혹은 slow start 상태에 있느냐에 따라 결정한다. 시뮬레이션을 통해 제안하는 알고리즘의 유효성을 보여 주며, 여러 TCP 혼잡 제어 알고리즘들과 혼잡 윈도우 크기와 효율과 같은 성능 지표 관점에서 비교하였다. 제안하는 알고리즘은 다른 알고리즘보다 높은 PER하에서는 높은 효율을 가지며, 낮은 PER하에서는 비슷한 효율을 가진다.

• 한국정보시스템학회지:정보시스템연구
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• 제33권2호
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• pp.125-142
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• 2024

Purpose The purpose of this study is to identify and analyze the key factors influencing congestion in the in-out transportation at port container terminals, and to design of a predictive model for in-out congestion based on these analysis. This study focused on architecting a deep learning-based predictive model. Design/methodology/approach This study was conducted through the following methodology. First, hypotheses were established and data were analyzed to examine the impact of vessel schedules and external truck schedules on in-out transportation. Next, explored time series forecasting models to a design the architecture for deep learning-based predictive model. Findings According to the empirical analysis results, this study confirmed that vessel schedules significantly affect in-out transportation. Specifically, the volume of transportation increases as the vessel arrival/departure time and the cargo cutoff time approach. Additionally, significant congestion patterns in transportation volume depending on the day of the week and the time of day were observed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권1호
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• pp.41-60
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• 2018

Recently, road traffic congestion is becoming a serious urban phenomenon, leading to massive adverse impacts on the ecology and economy. Therefore, solving this problem has drawn public attention throughout the world. One new promising solution is to take full advantage of vehicular ad hoc networks (VANETs). In this study, we propose a new traffic congestion detection and quantification method based on vehicle clustering and fuzzy assessment in VANET environment. To enhance real-time performance, this method collects traffic information by vehicle clustering. The average speed, road density, and average stop delay are selected as the characteristic parameters for traffic state identification. We use a comprehensive fuzzy assessment based on the three indicators to determine the road congestion condition. Simulation results show that the proposed method can precisely reflect the road condition and is more accurate and stable compared to existing algorithms.

• 디지털산업정보학회논문지
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• 제18권2호
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• pp.9-16
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• 2022

The nodes constituting the vehicle ad hoc network (VANET) are vehicles moving along the road and road side units (RSUs) installed around the road. The vehicle ad hoc network is used to collect the status, speed, and location information of vehicles driving on the road, and to communicate with vehicles, vehicles, and RSUs. Today, as the number of vehicles continues to increase, urban roads are suffering from traffic jams, which cause various problems such as time, fuel, and the environment. In this paper, we propose a method to solve traffic congestion problems on urban roads and demonstrate that the method can be applied to solve traffic congestion problems through performance evaluation using two typical protocols of vehicle ad hoc networks, AODV and GPSR. The performance evaluation used ns-2 simulator, and the average number of traffic jams and the waiting time due to the average traffic congestion were measured. Through this, we demonstrate that the vehicle ad hoc-based traffic congestion management technique proposed in this paper can be applied to urban roads in smart cities.

• International Journal of Contents
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• 제7권1호
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• pp.8-13
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• 2011

For energy-efficiency in Wireless Sensor Networks (WSNs), when a sensor node detects events, the sensing period for collecting the detailed information is likely to be short. The lifetime of WSNs decreases because communication modules are used excessively on a specific sensor node. To solve this problem, the TARP decentralized network packets to neighbor nodes. It considered the average data transmission rate as well as the data distribution. However, since the existing scheme did not consider the energy consumption of a node in WSNs, its network lifetime is reduced. In this paper, we propose an energy awareness congestion control scheme based on genetic algorithms in WSNs. The proposed scheme considers the remaining amount of energy and the transmission rate on a single node in fitness evaluation. Since the proposed scheme performs an efficient congestion control, it extends the network lifetime. In order to show the superiority of the proposed scheme, we compare it with the existing scheme through performance evaluation. It is shown that the proposed scheme enhances the data fairness and improves the network lifetime by about 27% on average over the existing scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제2권6호
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• pp.333-351
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• 2008

Transmission control protocols have to overcome common problems in wireless networks. TCP employing both packet loss discrimination mechanism and available bandwidth estimation algorithm, known as the good existing solution, shows significant performance enhancement in wireless networks. For instance, TCP New Jersey which exhibits high throughput in wireless networks intends to improve TCP performance by using available bandwidth estimation and congestion warning. Even though it achieves 17% and 85% improvements in terms of goodput over TCP Westwood and TCP Reno, respectively, we further improve it by exploring maximized available bandwidth estimation, handling bit-error-rate error recovery, and effective adjustment of sending rate for retransmission timeout. Hence, we propose TCP NJ+, showing that for up to 5% packet loss rate, it outperforms other TCP variants by 19% to 104% in terms of goodput when the network is in bi-directional background traffic.

• JSTS:Journal of Semiconductor Technology and Science
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• 제11권4호
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• pp.344-350
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• 2011

Higher integrated density in 3D ICs also brings the difficulties of routing, which can cause the routing failure or re-design from beginning. Hence, precise congestion estimation at the early physical design stage such as floorplan is beneficial to reduce the total design time cost. In this paper, an effective estimation method of routing congestion is proposed for 3D ICs at floorplan stage. This method uses synthesized virtual signal nets, power/ground network and clock network to achieve the estimation. During the synthesis, the TSV location is also under consideration. The experiments indicate that our proposed method had small difference with the estimation result got at the post-placement stage. Furthermore, the comparison of congestion maps obtained with our method and global router demonstrates that our estimation method is able to predict the congestion hot spots accurately.