• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4B
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• pp.675-682
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• 2000

In this paper, we propose a new scheduling algorithm called the Adaptive Weighted Round Robin with Delay Tolerance (AWRR/DT). The proposed scheme is based on the per-class queueing mechanism in which a number of connections of similar characteristics are multiplexed into one class-queue. Traffic classes of the proposed method are classified into a single non-real-time traffic class and other real-time traffic classes. The proposed scheme determines the weights of classes according to the input traffic and delay characteristics of each class at the beginning of every cycle. Furthermore, this scheme incorporates a cell discarding method to reduce the QoS degradation that may be incurred by congestion of networks. We have evaluated the proposed scheme through discrete-event simulation. Simulation results indicate that the proposed scheme can reduce the average delay of non-real-time class while maintaining the QoS of real-timeclasses. The proposed algorithm can be effectively applied to high-speed networks such as ATM networks.

• The Journal of the Korea Contents Association
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• v.8 no.12
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• pp.53-62
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• 2008

The Election paradigm can be used as a building block in many practical problems such as group communication, atomic commit and replicated data management where a protocol coordinator might be useful. The problem has been widely studied in the research community since one reason for this wide interest is that many distributed protocols need an election protocol. However, despite its usefulness, to our knowledge there is no work that has been devoted to this problem in a mobile ad hoc computing environment. Mobile ad hoc systems are more prone to failures than conventional distributed systems. Solving election in such an environment requires from a set of mobile nodes to choose a unique node as a leader based on its priority despite failures or disconnections of mobile nodes. In this paper, we describe a solution to the election problem from mobile ad hoc computing systems. This solution is based on the Group Membership Detection algorithm.

• The Journal of the Korea Contents Association
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• v.8 no.10
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• pp.54-63
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• 2008

With the improvement of computer performance in Mobile Environments, the users demand for the multimedia player is getting higher, which will be the major force behind the wide distribution of the media player that allows several moving pictures to run simultaneously using multiple windows on the screen. Products that adopted the same method used for a single moving picture and yet support the several moving pictures simultaneously emerged; however, they are not immune from problems. In this paper, we propose method to solve the problems of blinking, play prioritization processor and semi-transparent processor that occur when appling several moving pictures to the method used for a single moving picture and suggested the possible solutions. Taking it one step further, it focused on design and implementation of the media player that allows several moving pictures using overlapping and overlay technique by recognizing the biggest problem, which is that the above media play is not supported when playing several moving pictures simultaneously.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.684-690
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• 2010

Most of the existing SoCs have shared bus architecture which always has a bottleneck state. The more IPs are in an SOC, the less performance it is of the SOC, Therefore, its performance is effected by the entire communication rather than CPU speed. In this paper, we propose cross-bar switch bus architecture for the reduction of the bottleneck state and the improvement of the performance. The cross-bar switch bus supports up to 8 masters and 16 slaves and parallel communication with architecture of multiple channel bus. Each slave has an arbiter which stores priority information about masters. So, it prevents only one master occupying one slave and supports efficient communication. We compared WISHBONE on-chip shared bus architecture with crossbar switch bus architecture of the SOC platform, which consists of an OpenRISC processor, a VGA/LCD controller, an AC97 controller, a debug interface, a memory interface, and the performance improved by 26.58% than the previous shared bus.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.3
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• pp.33-38
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• 2013

Smart phones that are equipped with various types of sensors can monitor human beings, and their social activities and environments. Smart phone sensing systems are inevitable to lose sensing data at a certain region. It is more severe effect on opportunistic sensing because this sensing scheme is designed to read values from sensors when the state of numberous users meets pre-defined conditions. In this paper, we suggested an estimation model of missing data considering features of smart phone sensing to solve lower quality of collected data. This proposed model does not only reflect a temporal and spatial correlation, but also give high priority to participants who provide high quality data to improve the accuracy of estimated values. The experimental results show that our scheme is more accurate than previous scheme.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4877-4883
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• 2012

As a basic research for revitalization of cycling that is emerging as a means of green transportation, this study aims to analyze the impact of neighbourhood environmental factor perceived by the local residents on cycling satisfaction as the concern for energy and environmental issues is increasing. For this, a survey was conducted through a questionnaire to the residents in Sangju-si and the impact of the perceived neighbourhood environmental factor to cycling satisfaction with ordered logit model was analyzed. The result showed that the factors such as quality of bicycle lane, quality of bicycle conveniences, accessibility of major conveniences, safety of cycling and amenity of street made a significant impact on cycling satisfaction. Based on such result, this study suggested the considerations to be made in designing a cycling environment.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.2
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• pp.1-11
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• 2010

The provision of warning information on upcoming hazards leading to potential crash occurrence is a significant countermeasure to prevent crashes on the highway. This study presents a methodology for selecting more effective warning messages using a multi-criteria value function. The understandability, preference level, and message reading time were used as measures of effectiveness (MOE) for messages. Expert judgements were incorporated into the value function by analytical hierarchical process (AHP) technique. Field experiments to evaluate the warning messages were conducted in a testbed section on the Jungboo-Naeryuk freeway. The proposed methodology would be a useful tool to support the design of various traffic information messages.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.853-858
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• 2019

One of the methods which can enhance the efficiency of railroad network is construction of interconnection branch line for several route to share one railway. In Korea, this method already has been implemented or excuted as project level. This study suggests a network design model and a solution algorithm to choice most proper site to construction it and determine the priority of branch lines which can be considered in planning level, not project level. The model is a non-linear optimization program which minimize total cost-construction cost, operating cost and passengers' travel cost. The decision variables are a binary variable to explain whether construction or not and its direction and a integer variable of the frequencies of travel routes. The solution algorithm-problem solution and route choice and also the result of implementation for example network are suggested. This result can be more advanced after application in real network and calibration of parameters.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.6
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• pp.159-164
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• 2016

This paper proposes an improved superframe structure with one : N situation of the network as a target for efficiency battery and communication performance used in the existing standard IEEE 702.15.4 MAC layer. The proposed superframe transforms and adds a two structures. First, we add the proposed scheduling interval after the arrival of the beacon. Second, we change to a structure in which one of the contention access period is divided into two. The contention access period and the contention-free access period of active portion are divided according to the LQI value of the device. Through this system-level simulation written by $c{^+^+}$, as a results show that the battery consumption and transmission performance has been increased.

• Journal of Korea Multimedia Society
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• v.2 no.3
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• pp.329-338
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• 1999

In this paper we propose a WATM MAC protocol called DTDD/PS (Dynamic Time Division Duplex using Poll/Select scheme). The idea of the DTDD/PS protocol is based that a radio cell is considered as queueing system. The MAC controller in base station is charged in coordinating terminals for the QoS requirement from each terminal. For that reason, terminals send it's own dynamic parameter represented its status, and controller controls the access of terminals and assigns time slots dynamically using received parameters. Therefore this system can satisfy the QoS of real-time service in wireless environments. To evaluate DTDD/PS protocol simulations are executed. In 25Mbps channel capacity, the voice and data coexist traffic situation, as the total number of terminal is increased, the delay of data terminals is increased rapidly. But the case of only increasing data terminals, the number of supported voice terminals is not varying. Therefore we can expect that DTDD/PS protocol can applied to multimedia traffic effectively.