• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.16 no.4
• /
• pp.35-40
• /
• 2008

There are many studies indicate that human is one of the major contributing factors to the aviation accident. To this end, the Human Factor of pilots and in flight operations has been a popular subject to be studied, however, not of the air traffic controllers. Recently, some States have started studying Human Errors in Air Traffic Control field, removal of the potential errors in advance and prevention of the similar errors. This study analyzed Human Errors in air traffic control in terms of LOSA of airlines, which has been actively studied. This study will contribute to safe Flight Operation and Air Traffic Control.

• Journal of Korean Society of Transportation
• /
• v.14 no.2
• /
• pp.223-237
• /
• 1996

Based on the traffic and accident data collected on a 4.2km (2.6mile) section of Interstate highway 35W in Minneapolis the relationship between traffic operation variables and safety measures is investigated. An aggregate specification that could be integrated into an urban freeway safety prediction methodology is proposed as a multiple regression model. The specification includes lane occupancy and volume data, which are the control parameters commonly used because they can be measured in real time. The primary variables that appear to affect the safety of urban freeway are : vehicle-miles of travel, entrance ramp volumes and the dynamic effect of queue building. The potential benefits of freeway traffic control strategies on freeway safety are also investigated via a simulation study. It was concluded that improvement of urban freeway safety is achievable by traffic control strategies which homogenize traffic conditions areound critical occupancy values.

• The Journal of the Korea Contents Association
• /
• v.14 no.3
• /
• pp.451-462
• /
• 2014

In this paper, Coordinated Semi-Actuated Signal Control algorithm was developed and evaluated. According to the analysis of simulation, the coordinated semi-actuated signal control led to reduced vehicle delay as the difference of traffic volume between major and minor streets was getting bigger. But when there was relatively high traffic volume, or the equivalent amount of traffic volume on major and minor streets, optimized pre-timed signal control was verified to lower delay times compared to coordinated semi-actuated signal control; however, it might increase pedestrian delay. Therefore, the coordinated semi-actuated signal control should be implemented at intersections where traffic volume is relatively low.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.34S no.11
• /
• pp.25-33
• /
• 1997

The end-to-end rate-based control mechanism is used for the flow control of the ABR service to allow much more flexibility in ATM switching system. To accommodate the ABR service effciently many algorithms such as EFCI, EPRCA, ERICA, and CAPC2 have been proposed for the switch algorithm. ABR cells and related RM cells are received at the ATM switch fabric transparently without any processing. And then cells received from the traffic source are queued in the ABR buffer of switching system. The ABR buffer usually has some thresholds for easy congestion control signal transmission. Whatever we use, therefore, these can be many ABR traffic control algorithms to implement the ABR transfer capability. The genertion of congestion indicate signal for ABR control algorithms is determined by ABR buffer satus. And ABR buffer status is determined by ABR cells transfer ratio in ATM switch fabrics. In this paper, we presented the functional structures for control of the ABR traffic capability, proposed the readout scheduling, cell slot allocation of output link and the buffer allocation model for effective ABR traffic guranteeing with considering CBR/VBR traffics in ATM switch. Since the proposed readout scheduling scheme can provide more avaliable space to ABR buffer than existing readout scheduling scheme, generation rate of a SEND signal, that is, BCN signal in destination node can be increased for ABR call connection. Therefore, the proposed scheme, in this paper, can be appropriate as algorithm for effective ABR traffic service on output link of ATM switching node.

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 1991.10a
• /
• pp.179-182
• /
• 1991

In this paper, we survey traffic control issues for the B-ISDN based on the ATM. We first investigate traffic descriptors to represent the characteristics of various ATM traffics in a standardized form. Also, we examine key issues related to the connection admission control, usage parameter control, network parameter control, priority control, and congestion control.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.3 no.6
• /
• pp.575-596
• /
• 2009

Facing limited network resources such as bandwidth and processing capability, the Internet will have congestion from time to time. In this paper, we propose a scheme to maximize the total utility offered by the network to the end user during congested times. We believe the only way to achieve our goal is to make the scheme application-aware, that is, to take advantage of the characteristics of the application. To make our scheme scalable, it is designed to be class-based. Traffic from applications with similar characteristics is classified into the same class. We adopted the RED queue management mechanism to adaptively control the traffic belonging to the same class. To achieve the optimal utility, the traffic belonging to different classes should be controlled differently. By adjusting link bandwidth assignments of different classes, the scheme can achieve the goal and adapt to the changes of dynamical incoming traffic. We use the control theoretical approach to analyze our scheme. In this paper, we focus on optimizing the control on two types of traffic flows: TCP and Simple UDP (SUDP, modeling audio or video applications based on UDP). We derive the differential equations to model the dynamics of SUDP traffic flows and drive stability conditions for the system with both SUDP and TCP traffic flows. In our study, we also find analytical results on the TCP traffic stable point are not accurate, so we derived new formulas on the TCP traffic stable point. We verified the proposed scheme with extensive NS2 simulations.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.28 no.2
• /
• pp.75-89
• /
• 2003

Media Access Control (MAC) Protocol in IEEE 802.11 Wireless LAN standard supports two types of services, synchronous and asynchronous. Synchronous real-time traffic is served by Point Coordination Function (PCF) that implements polling access method. Asynchronous nonreal-time traffic is provided by Distributed Coordination Function (DCF) based on Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol. Since real-time traffic is sensitive to delay, and nonreal-time traffic to error and throughput, proper traffic scheduling algorithm needs to be designed. But it is known that the standard IEEE 802.11 scheme is insufficient to serve real-time traffic. In this paper, real-time traffic scheduling and admission control algorithm is proposed. To satisfy the deadline violation probability of the real time traffic the downlink traffic is scheduled before the uplink by Earliest Due Date (EDD) rule. Admission of real-time connection is controlled to satisfy the minimum throughput of nonreal-time traffic which is estimated by exponential smoothing. Simulation is performed to have proper system capacity that satisfies the Quality of Service (QoS) requirement. Tradeoff between real-time and nonreal-time stations is demonstrated. The admission control and the EDD with downlink-first scheduling are illustrated to be effective for the real-time traffic in the wireless LAN.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.9A
• /
• pp.2184-2196
• /
• 1998

Admission control is one of the most important congestion control mechanism to be executed at the call set up phase by regulating traffic into a network in a preventive way. An efficient QOS evaluation or bandwidth estimation method is required for call admission to be decided in real time. In this paper, we spropose a computtionally simple approximation method of estimating cell loss probability and mean cell delay for admission control of both delay sensitive and loss sensitive calls. Mixed input queueing system, where a new call combines with the existing traffic, is used as a queueing model for QOS estimation. Also traffic parameters are suggested to characterize both a new call and existing traffic. Aggregate traffic is approximated by a renewal process with these traffic parameters and then mean delay and cell loss probability are detemined using appropriate approximation formulas. The accuracy of this approximation approach is examined by comparing their results with exact analysis or simulation results of vrious mixed unput queueing systems. Based on this QOS estimation method, call admission control scheme which is traffic independent and computable in yeal time are proposed.

• Journal of IKEEE
• /
• v.26 no.4
• /
• pp.590-595
• /
• 2022

When a train is delayed because of a disturbance, the time interval deviation between successive trains increases, and high frequency metro lines can become unstable. Thus, it is necessary to control the traffic regularity to prevent any such instability. In this paper, we propose a simple but effective traffic regulation algorithm that gurantees system stability. In the proposed method, the control algorithm for running time is designed using a discrete traffic model where control input is determined from a linear combination of departure time deviations and control input of the preceding train to ensure an optimal time interval between successive trains. The results of the computer simulation are also given to demonstrate the validity of the proposed algorithm.

• International Journal of Automotive Technology
• /
• v.1 no.2
• /
• pp.61-69
• /
• 2000

This paper will address the basic requirements for realizing a stop and go cruise control system. Issues discussed comprise: functional, sensor and basic HMI requirements, primary characterization of naturalistic stop & go driving, and the basic approach of the transformation of situational knowledge in an elementary controller.