• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.3
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• pp.675-683
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• 1996

CAC, UPC, NPC, cell level QoS and congestion control is required to assign efficiently channels's BW and to prevent networks from congestion. In the CAC algorithm, each user defines characteristics of input traffic when channels are set up and network based on this parameters determines the acception or rejection of the required BW. The CAC control mechanism is classified into the centralized BW allocation mechanism and the distributed BW Allocation mechanism according to the function and position of CAC processor allocating BW. In this paper, in contrast with esisted the distributed BW allocation mechanism which assumes the required BW of input traffic as constant, we assume input traffic & serices as bulk probability distribution in order to analyze performance more precisely.

• Journal of the Korea Society of Computer and Information
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• v.4 no.4
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• pp.140-147
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• 1999

ABR uses the extra network resource more efficiently which uses not the guaranteed service in ATM and supports the best effort which the characteristics of application is bursty and maximum transfer rate is high. Switches for using ABR flow control differentiate EFCI switches (which supply only the congestion state information) from ER switches (which supply fair rate to source). This paper analyses the switches operation technique for efficiently managing ABR traffic in case which the network mixes EFCI switches and ER switches in ATM.

• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.3
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• pp.63-80
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• 2007

This study is a generalization of 'stable dynamics' recently suggested by Nesterov and de Palma[29]. Stable dynamics is a new model which describes and provides a stable state of congestion in urban transportation networks. In comparison with user equilibrium model that is common in analyzing transportation networks, stable dynamics requires few parameters and is coincident with intuitions and observations on the congestion. Therefore it is expected to be an useful analysis tool for transportation planners. An equilibrium in stable dynamics needs only maximum flow in each arc and Wardrop[33] Principle. In this study, we generalize the stable dynamics into the model with multiple traffic classes. We classify the traffic into the types of vehicle such as cars, buses and trucks. Driving behaviors classified by age, sex and income-level can also be classes. We develop an equilibrium with multiple traffic classes. We can find the equilibrium by solving the well-known network problem, multicommodity minimum cost network flow problem.

• Proceedings of the Korea Society for Simulation Conference
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• 2005.11a
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• pp.125-129
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• 2005

As metropolitan areas are rapidly growing in both population and physical size, so too has the problem of traffic congestion. Magnifying this is the limited financial resources and lack of road corridor space available to juggle the many competing demands. High Occupancy Vehicle (HOV) facilities have been implemented in an attempt to alleviate the problem of growing congestion while considering the issue of limited funding and lack of physical space. HOV lanes may increase the efficiency of a road corridor by maximising its person carrying capacity. These facilities are meant to provide priority treatment to HOVs, thereby luring people to choose a transport mode with a higher occupancy than the single occupant vehicle (SOV), such as buses or carpools. This paper analyze the issues surrounding HOV lanes, their effect, problems and their evaluation by using Intergration, that is Traffic Simulation Software, when HOV lanes be implemented in the Olympic Highway.

• Journal of Communications and Networks
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• v.8 no.3
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• pp.351-359
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• 2006

In this article, we present a new slow-start variant, which improves the throughput of transmission control protocol (TCP) Vegas. We call this new mechanism Gallop-Vegas because it quickly ramps up to the available bandwidth and reduces the burstiness during the slow-start phase. TCP is known to send bursts of packets during its slow-start phase due to the fast window increase and the ACK-clock based transmission. This phenomenon causes TCP Vegas to change from slow-start phase to congestion-avoidance phase too early in the large bandwidth-delay product (BDP) links. Therefore, in Gallop-Vegas, we increase the congestion window size with a rate between exponential growth and linear growth during slow-start phase. Our analysis, simulation results, and measurements on the Internet show that Gallop-Vegas significantly improves the performance of a connection, especially during the slow-start phase. Furthermore, it is implementation feasible because only sending part needs to be modified.

• Journal of applied mathematics & informatics
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• v.18 no.1_2
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• pp.455-464
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• 2005

In this paper, we analyze a queueing system with overload control by arrival rates. This paper is motivated by overload control to prevent congestion in telecommunication networks. The arrivals occur dependent upon queue length. In other words, if the queue length increases, the arrivals may be reduced. By considering the burstiness of traffics in telecommunication networks, we assume the arrival to be a Markov-modulated Poisson process. The analysis by the embedded Markov chain method gives to us the performance measures such as loss and delay. The effect of performance measures on system parameters also is given throughout the numerical examples.

• Journal of Korean Society of Transportation
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• v.17 no.1
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• pp.173-185
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• 1999

The purpose of this study is to develope a forecasting model to implement short-term Congestion Management Program (CMP) based on TDM strategies in Seoul. The CMP is composed of three elements: 1) setting a goal of short-term traffic management. 2) developing a model to forecast the impacts of TDM alternatives, and 3) finding TDM measures to achieve the goal To Predict the impacts of TDM alternatives, a model called SECOMM (SEoul COngestion Management Model) is developed. The model assumes that trip generation and distribution are not changing in a short term, and that only mode split and traffic assignment are affected by TDM. The model includes the parameter values calibrated by a discrete mode choice model, and roadway and transit networks with 1,020 zones. As a TDM measure implement, it affects mode choice behavior first and then the speeds of roadway network. The chanced speed again affects the mode choice behavior and the roadway speeds. These steps continue until the network is equilibrated. The study recommends that CMP be introduced in Seoul, and that road way conditions be monitored regularly to secure the prediction accuracy of SECOMM. Also, TDM should be the major Policy tools in removing short-term congestion problems in a big city.

• Journal of Korean Institute of Industrial Engineers
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• v.13 no.2
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• pp.65-77
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• 1987

Congestion occurs whenever users interfere with each other, while competing for scarce resources. In a congested market, such as a telecommunication service market, users of telecommunication services incur costs in using the service in addition to the price. The user's own time costs involved in learning to use the service, waiting for the service, and making use of the service are typically greater than the price of telecommunication services. A market equilibrium analysis is performed in which a method for user demand aggregation is developed. The effects of price changes on user demands and market demands for congested services are examined. It is found that total market demands may increase as the price for less-congested services increase under certain demand conditions. This suggests that a nonuniform pricing scheme for a congested service may improve the utilization of the congested system. The sign of price cross-elasticity for congested services is show to vary with demand conditions. A possible complementary property of congested services is found and the implication of such a property is discussed. It is argued that such a complementary property may lead to a cross subsidy in a market with congestion. Finally, comparisons between uniform pricing and nonuniform pricing policies are made. A specific numerical example is given to show that a nonuniform pricing policy may be Pareto superior to a uniform pricing policy.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.159-164
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• 2005

Recently, it has demanded high-speed digital circuits as information increase. Therefore, electromagnetic characteristics of compact microwave circuit occurred importantly. And, the effect of the imperfect ground plane on the signal integrity and influence of coupling between two parallel lines for high-speed digital transmission line on the printed circuit board is investigated by FDTD simulations in 3-D electromagnetic analysis method. The results of FDTD simulation are compared with the ADS simulation in commercial software, analyzed lumped element of modeling and electromagnetic wave's radiation of slot as frequency. As a consequence, when the slot in the ground plane is under microstrip line, it has much effect on propagation of wave.

• Journal of the Korean Institute of Navigation
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• v.15 no.3
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• pp.13-24
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• 1991

This paper aims to determining the optimal capacity of Pusan port in view point of Container Physical Distribution cost. It has been established a coast model of the container physical distribution system in Pusan port is composed of 4 sub-systems and in-land transport system. Cargo handling system, transfer & storage system and in-land transport system, and analyzed the cost model of the system. From this analysis, we found that the system had 7 routes including in-land transport by rail or road and coastal transport by feeder ship between Pusan port and cargo owner's door. Though railway transport cost was relatively cheap, but, it was limited to choose railway transport routes due to the introducing of transport cargo allocation practice caused by shortage of railway transport capacity. The physical distribution ost for total import & export container through Pusan port was composed of 4.47% in port entring cost, 12.98% in cargo handling cost, 7.44% in transfer & storage cost and 75.11% in in-land transport cost. Investigation in case of BCTOC verified the results as follows. 1) The optimal level of one time cargo handling was verified 236VAN (377TEU) and annual optimal handling capacity was calculated in 516, 840VAN(826, 944TEU) where berth occupancy is $\rho$=0.6 when regardless of port congestion cost, 2) The optimal level of one time cargo handling was verified 252VAN (403TEU) and annual optimal handling capacity was calculated in 502, 110VAN (803, 376TEU) where berth occupancy is $\rho$=0.58 when considering of port congestion cost.