• Proceedings of the Korean Society of Computer Information Conference
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• 2014.01a
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• pp.347-348
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• 2014

최근 급증하는 교통 혼잡으로 인해 시간적/물질적 손실이 크게 발생하고 있다. 이러한 교통난 해소는 시설투자만으로는 근본적인 해결책이 될 수 없다는 판단 하에 지난 수년간 보다 정확한 교통량을 예측하기 위해 시계열 기반의 다양한 교통량 예측 모델들이 개발 되어 왔다. 그러나 시계열 기반의 모델들은 회귀분석을 통해 과거 교통량을 분석하고 과거의 교통패턴이 미래에도 지속적으로 연장된다는 가정 하에 연구되었기 때문에 실시간으로 급변하는 불규칙한 교통 패턴에 대한 예측의 신뢰성을 떨어트린다. 또한 시계열 기반의 예측 기법은 어떠한 회귀분석 모델을 사용하는지에 따라 성능의 차이가 많이 나타나기 때문에 회귀분석 모델 선택이 중요하다. 이러한 제약을 극복하기 위해 본 논문에서는 은닉 마르코프 모델(Hidden Markov model)을 이용해 동적인 교통 패턴에 따라 현재 상황에 맞는 회귀분석 모델을 선택하는 신뢰도 높은 교통량 예측 시스템을 제안한다.

• Journal of Internet Computing and Services
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• v.8 no.5
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• pp.125-132
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• 2007

Transmission mechanisms that include an available bandwidth estimation algorithm and a packet loss differentiation scheme, in general, exhibit higher TCP performance in wireless networks. TCP New Jersey, known as the best existing scheme in terms of goodput, improves wireless TCP performance using the available bandwidth estimation at the sender and the congestion warning at intermediate routers. Although TCP New Jersey achieves 17% and 85% improvements in goodput over TCP Westwood and TCP Reno, respectively, we further improve TCP New Jersey by exploring improved available bandwidth estimation, retransmission timeout, and recovery mechanisms. Hence, we propose TCP New Jersey PLUS (shortly TCP NJ+), showing that under 1% packet loss rate, it outperforms 3% by TCP New Jersey and 5% by TCP Wes1wood. In 5% packet loss rate, a characteristic of high bit-error-rate wireless network, it outperforms other TCP variants by 19% to 104% in terms of goodput even when the network is in bi-directional congestion.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6B
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• pp.895-900
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• 2010

As the diverse telecommunication services have been developed, network designers need to prevent congestion which may be caused by properties of timecorrelation and burstiness, and unpredictable statistical fluctuation of traffic streams. This paper considers the leaky bucket scheme with combined control of arrival and token rates, in which the arrival rate and the token generation interval are controlled according to the queue length. By using the embedded Markov chain and the supplementary variable methods, we obtain the queue length distribution as well as the loss probability and the mean waiting time.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.11
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• pp.1-8
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• 2001

Adaptive and Strict Packet Dropping mechanism we proposed in this paper drops adaptively packets for the congestion control, as predicting traffic pattern between each cycle. Therefore the proposed mechanism makes up for the drawback of RIO mechanism and minimizes the wastes of the bandwidth being capable of predicting in Dynamic and Strict Packet Dropping (DSPD) mechanism. And we executed a simulation and analyzed the throughput and packet drop rate based on the Sending Drop Precedence changing dynamically depending on the network traffic and compared RIO and the DSPD. The results show that the proposed mechanism provides better performance on drop precedence levels and stricter drop precedence policy for AF class than RIO and the DSPD mechanism.

• Journal of Korean Society of Transportation
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• v.25 no.5
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• pp.135-148
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• 2007

Understanding the relation between characteristics of an accident and its duration is crucial for the efficient response of accidents and the reduction of total delay caused by accidents. Thus the objective of this study is to model accident duration using an AFT metric model. Although the log-logistic and log-normal AFT models were selected based on the previous studies and statistical theory, the log-logistic model was better fitted. Since the AFT model is commonly used for the purpose of prediction, the estimated model can be also used for the prediction of duration on freeways as soon as the base accident information is reported. Therefore, the predicted information will be directly useful to make some decisions regarding the resources needed to clear accident and dispatch crews as well as will lead to less traffic congestion and much saving the injured.

• Journal of the Korea Computer Industry Society
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• v.2 no.3
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• pp.309-320
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• 2001

According to the increasing of the cars, road traffic confused. If we estimate the traffic confusion use of statistical research, road traffic improved considerably. This paper analysis element that affected a expressway speed and investigate the mutual relation. For the accomplish it, we construct the DB for traffic of a expressway and applied a hypothesis to road traffic DB, we obtain the results from a various method with Data Mining operation.

• Proceedings of the KOR-KST Conference
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• 2007.11a
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• pp.315-322
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• 2007

신호교차로 교통사고는 90년대 이후 도시가 발달하고 산업이 고도화됨에 따라 교통 혼잡 문제와 함께 심각한 사회문제로 대두되고 있다. 특히 신호교차로의 교통사고는 인적요인, 차량요인, 환경적 요인 등이 복합적으로 작용하여 발생하는데, 교통량의 집중과 도로의 기하구조, 운전자 과실 등이 교통사고의 주요 인자로 작용하고 있다. 본 연구에서 교통사고 예측모형을 개발하기 위해서 2003년부터 2006년도까지 실제 경기도의 신호교차로에서 발생한 교통사고자료를 기초로 하였다. 구체적으로는 시내가 아닌 지방부 성격을 지닌 일반국도를 대상으로 하였다. 지방부 일반국도의 신호교차로 교통사고 분석에 단순통계분석과 다중회귀분석을 사용하였다. 사고와 관계가 높은 신호주기, 방향별 접근 교통량, 회전교통량 둥과 같은 도로, 교통, 운영조건들로 변수를 정하여 교통사고 예측모형을 도출하였다. 본 연구에서는 도로조건, 교통조건, 운영조건들과 사고와의 관계를 이용하여 경기도 일반국도의 신호교차로 교통사고예측모형을 개발하였고, 이는 지방부 성격을 지닌 교차로에 적용이 가능하다고 판단된다.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.7
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• pp.794-798
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• 2010

Assuming that a wireless link is mostly used at the network edge and the wireless NIC driver keeps monitoring the error rate of its link, this paper proposes an enhanced TCP congestion control, TCP-L (TCP Link-Aware). TCP-L predicts true congestion losses occurred inside the wired link area by utilizing the wireless link error rate. As a result, it mitigates performance degradation caused from TCP congestion control actions when segments losses occur in a wireless link. Experimental results show that TCP-L provides better performance and fairness in lossy wireless links than existing TCP congestion control schemes. Our approach utilizing the characteristic of the link at TCP could be well adapted to new wireless environments such as Cognitive Radio and ACK-less IEEE 802.11, where a frame may be delivered with a very long delay or lost in the link.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.126-134
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• 2006

Traditional TCP implementations have the under-utilization problem in large bandwidth delay product networks especially during the startup phase. In this paper, we propose a delay-based congestion control(DCC) mechanism to solve the problem. DCC is subdivided into linear and exponential growth phases. When there is no queueing delay, the congestion window grows exponentially during the congestion avoidance period. Otherwise, it maintains linear increase of congestion window similar to the legacy TCP congestion avoidance algorithm. The exponential increase phase such as the slow-start period in the legacy TCP can cause serious performance degradation by packet losses in case the buffer size is insufficient for the bandwidth-delay product, even though there is sufficient bandwidth. Thus, the DCC uses the RTT(Round Trip Time) status and the estimated queue size to prevent packet losses due to excessive transmission during the exponential growth phase. The simulation results show that the DCC algorithm significantly improves the TCP startup time and the throughput performance of TCP in large bandwidth delay product networks.

• Journal of Korean Society of Transportation
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• v.27 no.4
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• pp.77-89
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• 2009

With an increasing number of cars in Korea, the government is constantly providing roads and their related facilities. However the fundamental problems of cities like the structure of cities and the environment of roads make the traffic congestion of downtowns. To solve this problem the construction of toll roads such as tunnels and bridges is increasing but use rates of drivers is low. With more tolls required, less persons will use the roads. Thus this study is to consider offering discounted charges when using the two or more toll roads together. This study analyzes the impact that discounted charges would bring to the demand. In the meantime we looks into what the proper range should be for the discount. The results of this study are expected to be used as basis for the introduction of a discount system in the future.