• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.06a
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• pp.249-251
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• 2013

해상교통안전에 영향을 미치는 여러 가지 해상 개발사업으로 인하여 발생할 수 있는 항해안전의 위험요인을 전문적으로 측정하고 평가하는 것으로 '해상교통안전진단제도'가 있다. 이제도의 주요 평가항목에는 해상교통 현황조사, 해상교통 현황측정, 해상 교통시스템 적정성 평가 및 해상교통 안전대책이 있다. 특히 해상교통 현황측정의 세부 항목 중에는 진단 대상 항만 또는 항로가 추정된 미래의 해상교통량을 수용할 수 있는지를 평가하고 필요 시 관련 해역의 교통 흐름을 조정할 목적으로 수행하는 해상교통혼잡도 평가 있다. 이 연구는 현재 교통혼잡도 평가를 위한 미래 해상교통량 추정기법의 문제점의 현황과 이를 개선하여 신뢰도 있는 교통량 예측이 가능한 통계기법을 개발하고자 하는 것이다.

• The KIPS Transactions:PartC
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• v.12C no.5 s.101
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• pp.733-740
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• 2005

In this paper, we propose an approach to transport layer mobility support leveraging the SCTP extension dubbed dynamic address reconfiguration in IPv6 networks. Timing issues related to the end-to-end address management, and a novel error recovery mechanism associated with a handover are discussed. The proposed error recovery mechanism is analyzed and compared to that of the plain SCTP to show that it reduces the handover latency and error recovery time.

• International Journal of Highway Engineering
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• v.10 no.1
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• pp.145-154
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• 2008

The purpose of this study is to evaluate the quality of on-line departure time-based link travel time estimates. For this, accuracy (i.e. estimation error) and timeliness (i.e. degree of time lag) are proposed as MOE of the quality of on-line link travel time estimates. Then the relationship between quality of link travel time estimates and link length and level of congestion is analyzed. It was found that there is trade-off between the accuracy and timeliness of link travel time estimates. The estimation error was modeled to consist of two components: one is systematic error and the other is mean square error which reflects level of congestion. further, time lag was again segmented into three parts for the analysis purpose. There are minimum one, congestion-related one, and update interval-related one. From the real-world data using AVI system, it was revealed that regardless of the link length and level of congestion, 10 minutes of time lag occurs in general.

• Journal of the Korea Society for Simulation
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• v.20 no.1
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• pp.61-67
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• 2011

Smart TV System will lead to drastic change of communication and media industries as one of the emerging next generation network services. However, when the number of concurrent users increases rapidly, the issue of service quality degradation occurs because providing services to many users simultaneously stresses both the server and the network. The server limitation can be circumvented by deploying server clusters. but the network limitation is far less easy to cope with, due to the difficulty in determining the cause and location of congestion and in provisioning extra resources. In order to alleviate these problems, a number of schemes have been developed. Prior works mostly focus on reducing user-centric performance metrics of individual connection, such as the round-trip time(RTT), downloading time or packet loss rate, but tend to ignore the network loads caused by the concurrent connections or global network load balance. In this work, we make an in-depth investigation on the issue of user grouping for massive Smart TV services through simulations on actual Internet test-bed, PlanetLab.

• Journal of Korean Society of Transportation
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• v.17 no.5
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• pp.69-78
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• 1999

This paper defines the reliable based route choice Principle and formulates the reliability based equilibrium traffic assignment using the Principle. The reliability is defined as the difference of travel demand and capacity using the interference theory of the system engineering. An efficient solution a1gorithm based on Frank-Wo1fe algolithm is Presented to calculate and compare the reliability based traffic assignment with conventional travel time based assignment using small and large scaled road networks. The results show that reliability based traffic assignment converges to equilibrium solution in a reasonable computing time. The equilibrium link flows between reliability and travel time based traffic assignment differ each other in the sense that reliability based assignment is assigned based on the maximum difference of travel demand and link capacity whilst travel time based is assigned on the shortest travel time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.6
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• pp.1208-1216
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• 2015

In this paper, we use WiMedia WLP-based networks to meet the demand for IT services of a ship. If a mobile node moves to a congested base station of a new subnetwork, we will propose a scheme for improving performance of radio link of existing communicating mobile nodes. An old base station denotes packets stored during a handover. And, a proposed buffer management determines to discard the buffered packets in accordance with congestion degree at the congested new base station. Simulation results show that the proposed buffer management scheme improves link utilization in congested wireless links.

• The KIPS Transactions:PartC
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• v.10C no.1
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• pp.39-44
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• 2003

The network performance gets down during congestion periods to solve the problem effectively. A RED(Random Earl Detection) algorithm of the queue management algorithm is proposed and IETF recommends it as a queue management. A RED algorithm controls a congestion aspect dynamically. In analyzing parameters when static value of parameter is set in the gateway cannot be handled the status of current network traffic properly We propose the Effective RED algorithm to solve with the weakness of RED In this algorithm the maximum drop probability decides to accept or drop the interning packets, is adjusted dynamically on the current queue state for controlling the congestion phase effectively in the gateway. This algorithm is confirmed by computer simulation using the NS(Network Simulator)-2.

• The Journal of the Korea institute of electronic communication sciences
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• v.1 no.2
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• pp.102-109
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• 2006

In this paper, we improve the performance of bidirectional TCP connection over end-to-end network that uses transfer rate-based flow and congestion control. The sharing of a common buffer by TCP packets and acknowledgement has been known to result in an effect called ack compression, where acks of a connection arrive at the source bunched together, resulting in unfairness and degraded throughput. The degradation in throughput due to bidirectional traffic can be significant. For example, even in the simple case of symmetrical connections with adequate window size, the connection efficiency is improved about 20% for three levels of background traffic 2.5Mbps, 5.0Mbps and 7.5Mbps. Otherwise, the throughput of jitter is reduced about 50% because round trip delay time is smaller between source node and destination node. Also, we show that throughput curve is improved with connection rate algorithm which is proposed for TCP congestion avoidance as a function of aggressiveness threshold for three levels of background traffic 2.5Mbps, 5Mbps and 7.5Mbps.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5D
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• pp.611-617
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• 2009

With advanced technologies applied to transportation, realtime traffic information has been necessary for not only drivers but also agencies. In normal, traffic conditions have been represented to three levels according to congestion: "free", "slow", and "jammed". Those categories and criteria are set up for traffic management even though traffic information is provided for drivers. This study examines how drivers feel current congestion levels and delves into traffic categories and criteria which they recognize. To collect data for drivers' recognition, a survey of freeway travellers is conducted answering the question about traffic flow speed from video image on a freeway section. In the result of the survey, the surveyee preferred a 4-level traffic condition including "delayed" to 3-level traffic condition. As its criteria, 20 km/h, 50 km/h, and 75 km/h were obtained. These results are expected to contribute to building more appropriate traffic information for drivers and providing an operational guideline for Traffic Monitering Centers.

• Journal of the Economic Geographical Society of Korea
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• v.22 no.4
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• pp.576-591
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• 2019

This study attempts to analyze the effects of distance-accessibility to the complex shopping mall of 'Lotte Mall-Suwon', located at the old central and catchment district of the Suwon station in the Province of Gyeonngi, on the prices of its neighboring apartments within the Gwonseon-gu of Suwon City by using the hierarchical and linear-difference in difference regression method. The results of the analysis are as follows. First, before construction the effects of distance-accessibility show the U-shaped pattern, suggesting that the negative external effects of noise and traffic congestion around the Suwon Station affected the prices of its neighboring apartments within the Gwonseon-gu of Suwon City. Second, the effects of distance-accessibility at different times, such as the construction period and after the opening, are statistically significant only in the latter, indicating the reverse U-shaped pattern unlike before the opening. This means that after the opening of the complex shopping mall its external effects as a leisure and convenience space have a positive effect on the prices of its neighboring apartments within the Gwonseon-gu of Suwon City. Third, the effects of distance-accessibility is at an inflection point around 1.6-1.7 kilometers, which means that the U-shaped distance-decay pattern before construction, while the reverse U-shaped pattern is shown after the opening of opening. The latter implies that apartments that are very close to the mall within the Gwonseon-gu of Suwon City enjoy relatively small positive externalities. Therefore, they are exposed to some negative external effects of noise and traffic congestion, but apartments with some distance apart within the Gwonseon-gu of Suwon City maximize those positive externalities. These results suggest that the effects to distance-accessibility are different from location to location.