• Smart Media Journal
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• v.9 no.3
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• pp.71-79
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• 2020

Mobile network is used by many users worldwide for diverse services, including phone-call, messaging and data transfer over the Internet. However, this network may experience massive damage if it is exposed to cyber-attacks or denial-of-service attacks via wireless communication interference. Because the mobile network is also used as an emergency network in cases of disaster, evaluation or verification for security and safety is necessary as an important nation-wide asset. However, it is not easy to analyze the mobile core network because it's built and serviced by private service providers, exclusively operated, and there is even no separate network for testing. Thus, in this paper, a virtual mobile network is built using OpenAirInterface, which is implemented based on 3GPP standards and provided as an open source software, and the structure and protocols of the core network are analyzed. In particular, the S1AP protocol messages captured on S1-MME, the interface between the base station eNodeB and the mobility manager MME, are analyzed to identify potential security threats by evaluating the effect of the messages sent from the user terminal UE to the mobile core network.

• The Journal of the Korea Contents Association
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• v.6 no.1
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• pp.114-125
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• 2006

Since wireless Internet services and small mobile communication devices come into wide use as well as the use of GPS is rapidly growing, researches on moving object, whose location information shifts sequently in accordance with time interval, are being carried out actively. Especially, the researches on vehicle moving object are applied to Advanced traveler information system, vehicle tracking system, and distribution transport system. These systems are very useful in searching previous positions, predicted future positions, the optimum course, and the shortest course of a vehicle by managing historical data of the vehicle movement. In addition, vehicle historical data are used for distribution transport plan and vehicle allocation. Vehicle historical data are stored at regular intervals, which can have a pattern. For example, a vehicle going repeatedly around a specific section follows a route very similar to another. If historical data of the vehicle with a repeated route course are stored at regular intervals, many redundant data occur, which result in much waste of storage. Therefore this thesis suggest a vehicle historical data store scheme for vehicles with a repeated route course using similar trajectory which efficiently store vehicle historical data.

• The Journal of the Korea Contents Association
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• v.8 no.5
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• pp.19-28
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• 2008

In this paper, we implemented an intelligent home service robot system which alerts users to danger by wireless internet platforms for interoperability(WIPI) of a cellular phone. This paper discusses the three parts of the system: robot, middleware and mobile system. First, the robot consists of a gas sensor, a fire detector, ultrasonic sensors, motors, a camera and a Bluetooth module. The robot perceives various danger circumstances. Second, the middleware connects the robot and the mobile system. It monitors the robot and sends emergency notification SMS message to the user's cellular phone if in danger. Third, the mobile system sends commands which control the robot using TCP/IP protocol. The proposed scheme is to control the sensors of the robot part through Atmega 128 processor, and the robot and middleware parts will be installed in the household, and will be controled by mobile part from the outside.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.90-94
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• 2007

The conventional single-reference station positioning is affected by systematic errors such as ionospheric and tropospheric delay, so that the rover must be located within 10 km from the reference station in order to acquire centimeter-level accuracy. The medium-range real-time kinematic has been proven feasible and can be used for high precision applications. However, the longer of the baseline, the more of the time for resolving the integral ambiguity is required. This is due to the fact that systematic errors can not be eliminated effectively by double-differencing. Recently, network approaches have been proposed to overcome the limitation of the single-reference station positioning. The real-time systematic error modeling can be achieved with the use of GPS network. For expanding the effective range and decreasing the density of the reference stations, Land Survey Bureau, Ministry of the Interior in Taiwan set up a national GPS network. In order to obtain the high precision positioning and provide the multi-goals services, a GPS network including 66 stations already been constructed in Taiwan. The users can download the corrections from the data center via the wireless internet and obtain the centimeter-level accuracy positioning. The service is very useful for surveyors and the high precision coordinates can be obtained real time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.935-942
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• 2006

The performance of ROF systems can be severely degraded due to nonlinear effects in the channel. Also, Orthogonal Frequency Division Multiplex(OFDM), as a standard for broadband wireless and mobile internet networks, is being proposed for deployment with ROF systems to facilitate the total performance of a system. In this paper, at first, the performance of the OFDM-based RoF system with a Mach-Zehnder(MZ) modulator distortion effects has been analyzed at 5.8GHz. Evaluation of mean-squared error of the proposed OFDM-RoF system was carried out to compare with the conventional single carrier system based RoF link after the modulator distortion case and also for fixed signal to noise ratio(SNR) of 20dB using undistorted OFDM signal. Nominal and offset baising pre-distortion techniques are applied in proposed system to linearize the OFDM-RoF link. Finally, a comparison between the aforementioned pre-distortion techniques applied showed important observation in terms of distortion-free dynamic range and SNR to choose offset pre-distortion technique for our proposed system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3C
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• pp.426-435
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• 2004

The DIAMETER protocol provides Authentication, Authorization, and Accounting (AAA) transactions across the Internet. SIP(Session Initiation Protocol) will be used for new types of signaling, such as instant messaging and application level mobility across networks. And SIP will be a major signaling protocol for next generation wireless networks. But the Digest authentication scheme is not using a secure method of user authentication in SIP, and it is vulnerable to man-in-the-middle attacks or dictionary attacks. This study focused on designing a SIP proxy for interworking with AAA server with respect to user authentication and security analysis. We compared and analyzed the security aspects of the scenarios and propose two proposals that a response which include the user address and password-based mutual authentication and key agreement protocol. It is claimed to be more secure against common attacks than current scenarios.

• Journal of Korea Spatial Information System Society
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• v.7 no.3 s.15
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• pp.13-24
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• 2005

This paper proposes a model for the location information grading policy. Location information grading policy is that government would give a public notice of criterion for location information quality, and location information operators should elucidate the grade of provided location information. As the quality grade of services is provided in the 'terms of use' with the detailed quality specification and quality range, the user can understand the quality of location information, and can select more suitable service for their purposes. Additionally, the qualiy grading policy can enforce the location information operators and location service providers to support more stable and reliable service quality. In this paper, we propose the model of location information grades, the typical classification of quality, and the realitic policy applying model. Recent enacted 'Location Information Law' are expected to activate korean information market. In this situation, proposed location information grading policy take a role in protecting location privacy and improving the reliability of location information services.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5834-5840
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• 2013

Along with the development of high-speed, wired and wireless Internet technology, various harmful images in a form of photos and video clips have become prevalent these days. In this paper, we suggest a method of automatically detecting adult images by extracting woman's nipple areas which represent obscenity of the image. The suggested algorithm first segments skin color areas in the $YC_bC_r$ color space from input images and extracts nipple's candidate areas from the segmented skin areas through the suggested nipple map. We then select real nipple areas by using geometrical information and determines input images as harmful images if they contain nipples. Experimental results show that the suggested nipple map-based method effectively detects adult images.

• Journal of the Korea Society of Computer and Information
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• v.12 no.2 s.46
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• pp.9-19
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• 2007

In recent, development of wireless internet technology gradually has increased multimedia application in mobile device. Specially, application of grand capacity multimedia contents has increased in mobile environment gradually. MPEG-7 can search multimedia data using various type. But in restricted grand capacity of multimedia, MPEG-7 is used to be limited in desktop computer system mostly. Therefore, management of grand capacity multimedia data has become very important researching topic in mobile environment, and so embedded DBMS based on MPEG-7 for multimedia data management in client-server environment is needed. The system supports restricted hardware resource for multimedia application in mobile device. In this paper, we propose a method for MPEG-7 data clustering that included MPEG-7 data property. On the base of the clustering result, we also develop the embedded multimedia database management system based on MPEG-7 scheme(EMDS:MPEG-7 Scheme Based Embedded Multimedia Database Management System) in mobile device such as PDA.

• Journal of KIISE:Information Networking
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• v.32 no.6
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• pp.723-731
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• 2005

Wide spread deployment of infrastructure WLANs has made Wi Fi an integral part of today's Internet access technology. Despite its crucial role in affecting end to end performance, past research has focused on MAC protocol enhancement, analysis and simulation based performance evaluation without sufficient consideration for modeling inaccuracies stemming from inter layer dependencies, including physical layer diversity, that significantly impact performance. We take a fresh look at IEEE 802.11 WLANs, and using experiment, simulation, and analysis demonstrate its surprisingly agile performance traits. Contention based MAC throughput degrades gracefully under congested conditions, enabled by physical layer channel diversity that reduces the effective level of MAC contention. In contrast, fairness and jitter significantly degrade at a critical offered load. This duality obviates the need for link layer flow control for throughput improvement but necessitates traffic control for fairness and QoS. We use experimentation and simulation in a complementary fashion, pointing out performance characteristics where they agree and differ.