• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.687-708
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• 2017

The machine-to-machine (M2M) communication is featured by tremendous number of devices, small data transmission, and large uplink to downlink traffic ratio. The massive access requests generated by M2M devices would result in the current medium access control (MAC) protocol in LTE/LTE-A networks suffering from physical random access channel (PRACH) overload, high signaling overhead, and resource underutilization. As such, fairness should be carefully considered when M2M traffic coexists with human-to-human (H2H) traffic. To tackle these problems, we propose an adaptive Slotted ALOHA (S-ALOHA) and time division multiple access (TDMA) hybrid protocol. In particular, the proposed hybrid protocol divides the reserved uplink resource blocks (RBs) in a transmission cycle into the S-ALOHA part for M2M traffic with small-size packets and the TDMA part for H2H traffic with large-size packets. Adaptive resource allocation and access class barring (ACB) are exploited and optimized to maximize the channel utility with fairness constraint. Moreover, an upper performance bound for the proposed hybrid protocol is provided by performing the system equilibrium analysis. Simulation results demonstrate that, compared with pure S-ALOHA and pure TDMA protocol under a target fairness constraint of 0.9, our proposed hybrid protocol can improve the capacity by at least 9.44% when ${\lambda}_1:{\lambda}_2=1:1$and by at least 20.53% when ${\lambda}_1:{\lambda}_2=10:1$, where ${\lambda}_1,{\lambda}_2$ are traffic arrival rates of M2M and H2H traffic, respectively.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.328-333
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• 2004

Railway is huge traffic system which is operated organically combining all the elements; vehicle, track, electric power, signal/communication, operation, etc. Safety level has ben improved steadily by learning lessons from past accident. But with rapid progress in high-speed, massive, high-frequency transit fresh idea of accident prevention is now in order. In quest of effective and efficient countermeasure, we aim to establish an adequate safety evaluation/management method. Our proposals are basic concept relating to safety analysis of fatal accidents, AHP of Saaty, Fuzzy AHP.

• Proceedings of the KSR Conference
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• 2003.10a
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• pp.192-198
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• 2003

Railway is huge traffic system which is operated organically combining all the elements; vehicle, track, electric power, signal/communication, operation, etc. Safety level has been improved steadily by learning lessons from past accident. But with rapid progress in high-speed, massive, high-frequency transit fresh idea of accident prevention is now in order. In quest of effective and efficient countermeasure, we aim to establish an adequate safety evaluation/management method. Our proposals are basic concept relating to safety analysis of fatal accidents, AHP of Saaty, Fuzzy AHP.

• Proceedings of the IEEK Conference
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• 2002.06a
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• pp.247-250
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• 2002

It is predicted that the existing backbone network has encountered its limit due to massive growth in data traffic. Perhaps new WDM methods utilizing optical fibers are desirable. Also to assure reliance of the network detour routes fur collision recovery must be considered. But due to the redundancy occurred by allocating bandwidths to the detour route, the efficiency of the link my decline. In this paper, we designed a detour route to minimize the redundancy.

• Journal of electromagnetic engineering and science
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• v.14 no.4
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• pp.353-359
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• 2014

Recently, the use of mobile devices has increased, and mobile traffic is growing rapidly. In order to deal with such massive traffic, cognitive radio (CR) is applied to efficiently use limited-spectrum resources. However, there can be multiple communication systems trying to access the white space (unused spectrum), and inevitable interference may occur to cause mutual performance degradation. Therefore, understanding the effects of interference in CR-based systems is crucial to meaningful operations of these systems. In this paper, we consider a long-term evolution (LTE) system using additional spectra by accessing the TV white space, where low-power devices (LPDs) are licensed primary users, in addition to TV broadcasting service providers. We model such a heterogeneous system to analyze the co-existence problem and evaluate the interference effects of LPDs on LTE user equipment (UE) throughput. We then present methods to mitigate the interference effects of LPDs by 'de-selecting' some of the UEs to effectively increase the overall sector throughput of the CR-based LTE system.

• Convergence Security Journal
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• v.16 no.5
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• pp.41-48
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• 2016

In this paper we propose a new method of security visualization, VisFlow, using traffic flows to solve the problems of existing traffic flows based visualization techniques that were a loss of end-to-end semantics of communication, reflection problem by symmetrical address coordinates space, and intuitive loss problem in mass of traffic. VisFlow, a simple and effective security visualization interface, can do a real-time analysis and monitoring the situation in the managed network with visualizing a variety of network behavior not seen in the individual traffic data that can be shaped into patterns. This is a way to increase the intuitiveness and usability by identifying the role of nodes and by visualizing the highlighted or simplified information based on their importance in 2D/3D space. In addition, it monitor the network security situation as a way to increase the informational effectively using the asymmetrical connecting line based on IP addresses between pairs of nodes. Administrator can do a real-time analysis and monitoring the situation in the managed network using VisFlow, it makes to effectively investigate the massive traffic data and is easy to intuitively understand the entire network situation.

• Journal of Korean Society of Transportation
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• v.22 no.7 s.78
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• pp.33-40
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• 2004

This study aims to provide guidelines for the selection of on-street parking spot on local streets considering conditions of surrounding area and characteristics of traffic generation. This guideline provides the method which determine required roadway width for planning and design of local streets. It is necessary to identify factors for the location selection analysis. This research team selects 12 case study areas to investigate traffic environment on the sites for this analysis. Most of factors which influence on-street parking are found to have a qualitative data format except traffic volume and pedestrian movement data. Quantification theory II which is known to be suitable for qualitative analysis has been applied to identify the meaningful variables for dependent variable. In addition, discriminant analysis has performed to verify the correlation for each variable with hit ratio. Road width, traffic volume, street traders and their heavy packages, and illegally parked vehicle are found to be most significant factors for selection of on-street parking location. Therefore, it is necessary to consider traffic volume generated from massive residential complex and traffic volume for outside and above-mentioned factors for installation of on-street parking facility in the case of new road construction or road width widen.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.3
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• pp.667-678
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• 2016

Due to a development of the cable/wireless network infra, the traffic as big as unable to compare with the past is being served through the internet, the traffic is increasing every year following the change of the network paradigm such as the object internet, especially the traffic of about 1.6 zettabyte is expected to be distributed through the network in 2018. As the network traffic increases, the performance of the security infra is developing together to deal with the bulk terabyte traffic in the security equipment, and is generating hundreds of thousands of security events every day such as hacking attempt and the malignant code. Efficiently analyzing and responding to an event on the attack attempt detected by various kinds of security equipment of company is one of very important assignments for providing a stable internet service. This study attempts to overcome the limit of study such as the detection of Tor network traffic using the existing low-latency by classifying the anonymous network by means of the suggested algorithm about the event detected in the security infra.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.4
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• pp.124-133
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• 2021

The airline industry has been growing steadily since 2016 with more than 100 million air passengers, renewing the largest number of air passengers every year. Increasing air demand leads to an increase in air traffic in limited airspace, increasing the likelihood of accidents between aircraft. Due to the massive human and material damage caused by a single mistake, aviation safety is being heavily focused around the world to efficiently use limited airspace. Studies related to various human factors are underway as most of the aviation accidents are found to be caused by human factors, but research on human factors by controllers is insufficient while they are active in terms of control and operation. Given that 82% of air accidents caused by controllers are caused by human error, the importance of management of human error and changes in perception are urgently needed. This study aims to understand the seriousness of the controller's human error by analyzing the accident cases caused by the controller's human error using TEM to identify threats and errors and derive common human factors.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3309-3328
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• 2017

The application of Internet of Things (IoT) in the next generation cellular networks imposes a new characteristic on the data traffic, where a massive number of small packets need to be transmitted. In addition, some emerging IoT-based emergency services require a real-time data delivery within a few milliseconds, referring to as ultra-low latency transmission. However, current techniques cannot provide such a low latency in combination with a mice-flow traffic. In this paper, we propose a dynamic resource reservation schema based on an air-interface slicing scheme in the context of a massive number of sensors with emergency flows. The proposed schema can achieve an air-interface latency of a few milliseconds by means of allowing emergency flows to be transported through a dedicated radio connection with guaranteed network resources. In order to schedule the delay-sensitive flows immediately, dynamic resource updating, silence-probability based collision avoidance, and window-based re-transmission are introduced to combine with the frame-slotted Aloha protocol. To evaluate performance of the proposed schema, a probabilistic model is provided to derive the analytical results, which are compared with the numerical results from Monte-Carlo simulations.