• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.573-577
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• 2005

Recently there are increasing needs for Internet and various kinds of contents. These traffics for various contents need more amount of data to provide high-quality information and require various QoS depending on the characteristics of contents. However, current Internet service supports BE (Best Effort) service only, therefore IntServ (Integrated Service) scheme and DiffServ (Differentiated Service) scheme are represented to support QoS in IP layer. Moreover, while wireless Internet is getting popular, MAC(Medium Access Control)is also becoming important. This is due to the fact that wireless access, resource allocation and packet scheduling, which are done in another layers before, are performed in MAC layer in many new wireless systems. This paper describes new scheme that provides QoS taking into account the traffic characteristics over Mobile IPv6 network based on IEEE 802.11e EDCF and evaluates the performance through computer simulation.

• Journal of Communications and Networks
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• v.13 no.5
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• pp.499-510
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• 2011

Any server offering a routing service in the Internet would naturally be in competition for clients, and clients may need to utilize service from a specific server in order to achieve a desired result. We study the various properties of this competition, such as the fraction of route requests handled by a routing service provider and the fraction of total revenue obtained. As the routing service providers (i.e., servers or routers in this context) compete, they may alter behavior in order to optimize one of the above properties. For example, a service provider may lower the price charged for its service, in order to increase the number of clients served. Our models are based on servers offering a routing service to clients within representative network topologies based on actual Internet sub-graphs. These models provide, a framework for evaluating competition in the Internet. We monitor key aspects of the service, as several variables are introduced into the models. The first variable is the fraction of client requests that will pay more for a better quality route. The remaining requests are normal client requests that are satisfied by the most economical route. The second variable is the fraction of servers who choose to lower service prices in order to maximize the number of client requests served. As this fraction increases, it is more likely that a server will lower the price. Finally, there are some resource constraints applied to the model, to increase the difficulty in providing a routing solution, i.e., to simulate a realistic scenario. We seek to understand the effect on the overall network, as service providers compete. In simple cases, we show that this competition could have a negative impact on the overall efficiency of a service. We show that the routing variety present in the larger models is unable to mask this tendency and the routing service performance is decreased due to competition.

• The KIPS Transactions:PartD
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• v.14D no.5
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• pp.501-508
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• 2007

Simulation system was introduced and used a lot in the fields of aviation, vessel, and medical treatment. 3D Simulation system has been used quite insufficiently as it requires a lot of system resource and huge amount of computer calculation. As the graphic card performance and simulation function developed, however, PC based simulation has been activated and is verified of its possibility as an educational software. However, educational institutions need to invest huge amount of budget and manpower to purchase and maintain CT Equipment. For such a reason, educational institutions entrust their students to hospitals for indirect experience of operation or for mere observation. This study, therefore, developed a CT Virtual reality education system with which medical CT Equipment can be directly operated in PC based 3D Virtual environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.510-513
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• 2006

Mobile Ad-hoc networks have recently attracted a lot of attention in the research community as well as in industry. Although the previous research mainly focused on various of Ad-hoc in routing we consider, in this paper, how to efficiently support applications such as variable Geocasting basd on Ad-hoc networks. The goal of a geocasting protocol is deliver data packets to a group of nodes that are located within a specified geocasting region. Previous research that support geocast service in mobilie computing based on Ad-hoc have the non-optimization problem of data delivery path, overhead by frequent reconstruction of the geocast tree, and service disruption problem. In this paper, we propose the mobility pattern based geocast technique using variable service range according to the mobility of destination node and resource reservation to solve this problem. The experimental results show that our proposed mechanism has improved performance than previous research.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.330-334
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• 2017

Container-based virtualization reduces performance overhead compared with other virtualization technologies and guarantees an isolation of each virtual execution environment. So, it is being studied to block access to host resources or container resources for sandboxing in restricted system resource like embedded devices. However, because security threats which are caused by security vulnerabilities of the host OS or the security issues of the host environment exist, the needs of the technology to prevent an illegal accesses and unauthorized behaviors by malware has to be increased. In this paper, we define additional access permissions to access a virtual execution environment newly and control them in kernel space to protect attacks from illegal access and unauthorized behaviors by malware and suggest the Container Access Control to control them. Also, we suggest a way to block a loading of unauthenticated kernel driver to disable the Container Access Control running in host OS by malware. We implement and verify proposed technologies on Linux Kernel.

• Journal of Advanced Navigation Technology
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• v.23 no.5
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• pp.373-379
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• 2019

AeroMACS spectrum is a national resource internationally allocated by ITU at WRC-07. AeroMACS is an airport broadband mobile communication infrastructure based on WiMAX-based IEEE 802.16e that enables real-time video, graphics, voice, and high-speed data transmission. With the approval of ICAO's development technology standards in 2008, 50 airports in 11 countries have already completed the testing of D-TAXI or A-SMGCS technology using the AeroMACS infrastructure in 2019, starting in the United States in 2009. With many advantages in safety and convenience in terrestrial telecommunications operations, the system is becoming an area of performance improvement for airport operations in accordance with ICAO's ASBU plan. This paper examines the current status of domestic development of AeroMACS and lists service areas applicable to airlines and operators. It also seeks to promote safe and efficient next-generation airport mobile communication system services by presenting feasible partners management in the mobile area and use of aircraft communication systems for active technology development.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.8
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• pp.2827-2848
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• 2021

Mobile Crowdsourcing (MCS) has become an emerging paradigm evolved from crowdsourcing by employing advanced features of mobile devices such as smartphones to perform more complicated, especially spatial tasks. One of the key procedures in MCS is to collect answers from mobile users (workers), which may face several security issues. First, authentication is required to ensure that answers are from authorized workers. In addition, MCS tasks are usually location-dependent, so the collected answers could disclose workers' location privacy, which may discourage workers to participate in the tasks. Finally, the overhead occurred by authentication and privacy protection should be minimized since mobile devices are resource-constrained. Considering all the above concerns, in this paper, we propose a lightweight and privacy-preserving answer collection scheme for MCS. In the proposed scheme, we achieve anonymous authentication based on traceable ring signature, which provides authentication, anonymity, as well as traceability by enabling malicious workers tracing. In order to balance user location privacy and data availability, we propose a new concept named current location privacy, which means the location of the worker cannot be disclosed to anyone until a specified time. Since the leakage of current location will seriously threaten workers' personal safety, causing such as absence or presence disclosure attacks, it is necessary to pay attention to the current location privacy of workers in MCS. We encrypt the collected answers based on timed-release encryption, ensuring the secure transmission and high availability of data, as well as preserving the current location privacy of workers. Finally, we analyze the security and performance of the proposed scheme. The experimental results show that the computation costs of a worker depend on the number of ring signature members, which indicates the flexibility for a worker to choose an appropriate size of the group under considerations of privacy and efficiency.

• The Journal of Society for e-Business Studies
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• v.23 no.3
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• pp.51-64
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• 2018

Recently, the magnitude and frequency of the natural disaster have been increased, the damage has become severer. The importance of disaster response system to relieve the damage has arised continuously. This study has tried to develop the algorithm to solve the facility location and size problem in emergency logistics. A facility in the emergency logistics has various roles in victim care, casualty treatment, relief resource management and relief vehicle assistance. Moreover, the location of facility in emergency logistics has to consider the safety and reliability. To gather these information, information management system with IoT sensors are suggested. The location problem in this study also covers various features to response various demands in disaster. To solve this problem, this study suggested MIP based algorithm. Scenario based simulation experiments are conducted to verify the performance suggested algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.10
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• pp.1254-1260
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• 2019

Recently, 5G cellular systems have been attracted great attention as a key enabler for Industry 4.0. In this paper, we propose a novel random access based on pilot-assisted opportunistic transmission to support internet-of-things (IoT) scenario in cellular networks. A key feature of our proposed scheme is to enable each of IoT devices to attempt opportunistic transmission of its data packet in Step 3 with randomly selected uplink pilot signal. Both the opportunistic transmission and the pilot randomization in Step 3 are effective to significantly mitigate the occurrence of packet collisions. We mathematically analyze our proposed scheme in terms of packet collision probability and uplink resource efficiency. Through simulations, we verify the validity of our analysis and evaluate the performance of our proposed scheme. Numerical results show that our proposed scheme outperforms other competitive schemes.

• Journal of Korean Library and Information Science Society
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• v.52 no.2
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• pp.209-233
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• 2021

This study aims to obtain implications for educational information services for elementary school teachers by analyzing their information seeking behavior. The in-depth interview was carried out in-depth interviews with 11 elementary school teachers and it analyzed of the core roles and tasks of elementary school teachers, the required information and usage behavior of information sources. The study result showed that elementary school teachers perceived homeroom duties, teaching/learning activities, school duties, and other as their works and tasks, and the response to the importance of task performance was homeroom teacher, teaching-learning activities, school works, and other tasks. Also, elementary school teachers needed information in order of teaching-learning activities, homeroom teacher, school works and they used various information sources including web, interpersonal sources and book. Moreover, this study observed some factors that elementary school teacher mainly used web information source which other elementary school teacher developed and that they got teaching-learning materials from fellow teachers. Based on these findings, the author proposed teacher librarian share library based instruction materia in web resource, provide cooperative educational information service through learning community, and provide homeroom work material for elementary school teachers.