• Journal of the Korea Society for Simulation
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• v.27 no.3
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• pp.45-52
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• 2018

We consider the busy period of an M/G/1/K queueing system with queue-length-dependent overload control policy. A variant of an oscillating control strategy that was recently analyzed by Choi and Kim (2016) is considered: two threshold values, $L_1({\leq_-}L_2)$ and $L_2({\leq_-}K)$, are assumed, and service rate and arrival rate are adjusted depending on the queue length to alleviate congestion. We investigate the busy period of an M/G/1/K queue with two overload control policies, and present the formulae to obtain the expected length of a busy period for each control policy. Based on the numerical examples, we conclude that the variability and expected value of the service time distribution have the most influence on the length of a busy period.

• KIISE Transactions on Computing Practices
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• v.21 no.11
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• pp.727-732
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• 2015

These days, many researchers are working on Future Internet and a new networking paradigm called Software Defined Networking draws a great attention. In this paper, we redefine Software Defined Networking as Service Defined Networking which means that packets are categorized according to types of services. By using Service Defined Networking, we are not only dealing with the way to utilize the network resources efficiently but we also propose an algorithm to minimize the waiting time for packets to be delivered. This proposed algorithm can solve the delay problem, one of the most significant problems caused by network congestion. Also, since we are adopting Service Defined Networking, network resource utilization can be improved compared to the existing network.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.1
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• pp.86-99
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• 2021

One of the methods to alleviate traffic congestion is to increase the efficiency of the roads by providing traffic condition information on road user and distributing the traffic. For this, reliability must be guaranteed, and quantitative real-time traffic speed prediction is essential. In this study, and based on analysis of traffic speed related to traffic conditions, historical data correlated with traffic flow were used as input. We developed an LSTM model that predicts speed in response to normal traffic conditions, along with a CNN-LSTM model that predicts speed in response to incidents. Through these models, we try to predict traffic speeds during the hour in five-minute intervals. As a result, predictions had an average error rate of 7.43km/h for normal traffic flows, and an error rate of 7.66km/h for traffic incident flows when there was an incident.

• Journal of the Korea Society of Computer and Information
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• v.14 no.9
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• pp.147-156
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• 2009

The aim of this study is to propose an integrated press system design for traffic information service by multi-connecting traffic information services which are now being serviced by each different requirements for the press service and by providing advanced traveler information service which organically user oriented design such as traffic broadcast, news, journal, semantic web and also related traffic ontology as well as road traffic information. For the objective, the status of domestic and foreign traffic information supply system was analyzed and then the requirements by media were reviewed. Then, by analyzing the system implementation method and the implementation system the method of implementing such the system was suggested. The design method suggested in this study enabled the information users to utilize a variety of traffic information through intervening between the necessary and sufficient conditions of information users and information suppliers. Throughout the result of this study, for the users who used the integrated transport, the efficient space movement and the economic using value was improved. Providing the traffic information through the press media will become useful information to road drivels, and it is effected that the traffic volume will be dispersed and the traffic jam will be relieved owing to the supply of traffic information to the press.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.47-60
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• 2017

Car sharing, which is considered as a good example of innovation in the transportation sector, is a type of use in which a plurality of people share a single vehicle for a short period of time. It is divided into various types, NFP (Not For Profit) operated by a non-profit organization, B2C (Business to Customer), which is operated by a company, and Peer to Peer (P2P), which is directly connected to an individual. Among them, P2P car sharing is a method of sharing personal vehicles owned by individuals. It has the merit of reducing traffic congestion and providing for efficient traffic demand management by reducing the purchase rate of additional vehicles and minimizing the number of idle ones. This study examines the introduction of P2P car sharing in order to develop a traffic demand management policy and facilitate the transition to a sustainable transportation system. The spatial extent of the study consisted of apartment complexes in Seoul. In apartment complexes, it is possible to minimize the level of expenditure, such as operating expenses, by utilizing the APT management office and there is no difficulty in securing the necessary parking space. Therefore, apartment complexes were selected as the spatial range.

• Journal of Korean Society of Transportation
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• v.18 no.5
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• pp.83-97
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• 2000

The traffic management schemes through traffic signal control and information provision could be effective when the link-level data and trip-level data were used simultaneously in analysis Procedures. But, because the trip-level data. such as origin, destination and departure time, can not be obtained through the existing surveillance systems directly. It is needed to estimate it using the link-level data which can be obtained easily. Therefore the objective of this study is to develop the model to estimate O-D demand using only the link flows in highway network as a real time. The methodological approaches in this study are kalman filer, least-square method and normalized least-square method. The kalman filter is developed in the basis of the bayesian update. The normalized least-square method is developed in the basis of the least-square method and the natural constraint equation. These three models were experimented using two kinds of simulated data. The one has two abrupt changing Patterns in traffic flow rates The other is a 24 hours data that has three Peak times in a day Among these models, kalman filer has Produced more accurate and adaptive results than others. Therefore it is seemed that this model could be used in traffic demand management. control, travel time forecasting and dynamic assignment, and so forth.

• Journal of Korean Society of Transportation
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• v.31 no.3
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• pp.65-73
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• 2013

Exclusive median bus lanes were installed to mitigate congestions on urban traffic networks. However, capacity analysis of signalized intersections having exclusive median bus lanes have not been provided in current capacity analysis process(analyses). This study aims to develop a method of capacity analysis for lane groups consisting of only buses at the signalized intersections having exclusive median bus lanes. Finding basic saturation flow rates for buses is critical since the operational characteristics between automobiles and buses are fairly different. A total of 8 intersections in Seoul were chosen as study sites. Saturation headways, distances between bus-stop and stopline, and grades of each approach were measured at the sites. It was found that the basic saturation headway and the basic saturation flow rate of buses were 3.27 s/veh and 1,100pc/h/ln, respectively. Adjustment factor for upstream bus-stop locations was estimated with 0.50 and 0.75 when the distances between bus-stop and stopline are 20m and 70m, respectively. This study explains that bus saturation flow rates are decreased in half if the bus stop locates within 20 meters from stop lines.

• Journal of Korean Society of Transportation
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• v.35 no.6
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• pp.511-524
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• 2017

This study aims to evaluate the availability of ABM (Active-Based Model), FEATHERS, as a policy evaluation tool. To achieve the goal, scenario analysis on flexible working policy was conducted to measure its impact on activity-travel behavior. As a consequence, there seems no significant change in worker's daily life, other than mitigating traffic congestion due to decreasing commuting travel in the rush hour. The result of VKT (vehicle kilometers traveled) shows an opposite pattern according to given household/individual constraints. The scenario analysis on telecommuting indicates a decreasing trend in both travel frequency and distance because of the diminished number of commuting trips. As the activity space of telecommuters is shifted to a residential area, there are more short-distance trips by using non-motorized transport, which leads to decrease in VKT (using a private vehicle). Thus, the sensitivity of VKT by population groups varies due to transport mode shift (between personal and another mode) and growing non-work trips (using a private mode). This study found few things. First, it is necessary to evaluate the details of policy impact by population groups since it can be varied depending on household/individual characteristics. Second, the case study shows a promising performance of ABM as policy measurement that provides reality in policy evaluation. Third, ABM allows us to do more accurate analysis (i.e. time-series analysis by population groups) of policy assessment than those of FSM (Four-Step Model). Lastly, a further effort in data collection, literature review, and expert survey should be made to enhance the accuracy and confidence of future research.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.12
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• pp.34-43
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• 2007

Recently, in addition to the sharp increase of mobile nodes, various kinds of wireless technologies are available for mobile nodes. If IPv6 technology is applied to the network, multi-homing terminals which have several public IP addresses on one interface will be common. Accordingly, there are many research activities on mobility management for multi-interface, multi-homming nodes. In this paper we propose an extended fast handover mechanism for multi-interface MIPv6 environments that uses multi-interface FBU (MFBU) message instead of the existing FBU message. The MFBU message has the "tunnel destination" mobility option that points a specific tunnel destination other than NAR, and "T" flag that indicates the existence of tunnel destination option. The proposed mechanism can improve the TCP performance by mitigating packet reordering during FMIPv6 handover that can cause unnecessary congestion control due to 3 duplicate ACKs. In this paper, we implemented a multi-Interface MIPv6 simulator by extending a single-interface MIPv6 simulator in NS-2, and showed that the performance of TCP traffic is improved by using the proposed multi-interface fast MIPv6.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1017-1028
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• 2006

Japanese railroad companies continued growing by developing diversification based on a railroad enterprise. However, after entering in the 1990s, the diversification model of a railroad company reached the management limit. Under economic depression, A decrease in the birthrate and aging progressed and passenger transport changed to the downward tendency. Nevertheless, since railroad investment was expanded, railroad achievements got worse and price competitiveness with JR East Japan became weak. But the achievements of a diversification section got worse compared with the railroad enterprise. Therefore, group management was thought as important and enterprise reorganization was developed.