• IEMEK Journal of Embedded Systems and Applications
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• v.10 no.4
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• pp.207-212
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• 2015

Wi-Fi Direct allows battery powered mobile devices to form a wireless ad hoc network. Since one member of the network called Group Owner (GO) takes the role of managing the network, the network lifetime is mainly affected by the energy efficiency of GO. Hence, Wi-Fi Direct defines power saving schemes that allow GO to save the energy by turning off its radio interface during the periods called absence periods. However, the Wi-Fi Direct specification does not specify how to set parameters (denoted by PS parameters) determining the schedule of the absence periods. In this paper, we therefore propose a novel traffic-aware power saving scheme for Wi-Fi Direct networks. In particular, the proposed scheme estimates the application-level traffic load and adaptively tunes the PS parameters according to the estimated value.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.10
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• pp.836-843
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• 2003

The automatic train control (ATC) system development project for the Automated Guideway Transit (AGT) system has high technical risk because the system is unmanned train control system using wireless technology which was unprecedented in train control industry of Korea. To overcome the technical risk during concept design phase of the ATC system development project, the integrated product team(IPT) carried out a reverse and reengineering process using a systems engineering design model. The generic systems engineering process is incorporated in the both reverse and reengineering process. As a result of the systems engineering effort, the IPT has built top layer systems engineering design model of the ATC subsystem. The purpose of this paper is to deliver the reverse and reengineering process which was used to develop the systems engineering design model of ATC system using a computer aided systems engineering tool. This study also shows that the model based reverse and reengineering process can reduce the technical risk by identifying the differences of requirement, functional and physical architecture between a reference system and a target system.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2649-2652
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• 2003

In this Paper, an Audio-Visual Teaching aid (AVTA) for use in a classroom and with Internet is presented. A system, which was designed and tested, consists of a wireless Microphone system, Text to Speech conversion Software, Noise filtering circuit and a Computer. An IBM compatible PC with sound card and Network Interface card and a Web browser and a voice and text messenger service were used to provide slightly delayed text and also voice over the internet for remote teaming, while providing scrolling text from a real time lecture in a classroom. The motivation for design of this system, was to aid Korean students who may have difficulty in listening comprehension while have, fairly good reading ability of text. This application of this system is twofold. On one hand it will help the students in a class to view and listen to a lecture, and on the other hand, it will serve as a vehicle for remote access (audio and text) for a classroom lecture. The project provides a simple and low cost solution to remote learning and also allows a student to have access to classroom in emergency situations when the student, can not attend a class. In addition, such system allows the student in capturing a teacher's lecture in audio and text form, without the need to be present in class or having to take many notes. This system will therefore help students in many ways.

• IEMEK Journal of Embedded Systems and Applications
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• v.3 no.4
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• pp.218-228
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• 2008

The convergence of broadcasting and telecommunication services is being accelerated by broadband networks, digital broadcasting and Web2.0. This paper describes the definition and service characteristics of IPTV as a representative of broadcasting and telecommunication convergence services. Especially, the changes of infrastructure and technology for IPTV2.0 are addressed in terms of the service features of mobility, intelligence and participation. IPTV2.0 shall be characterized by the open IPTV service based on Web2.0 and the mobile IPTV service over the heterogeneous networks employing various wireless/wired access technologies. The IP Multimedia Subsystem (IMS) and Service Delivery Platform (SDP) technologies are increasingly considered to support the personalization and openness. The mobility management technology is being evolved to provide QoS-guaranteed mobile communication services to users at anytime and anywhere. IPTV2.0 services and platforms are also anticipated to be core components to achieve knowledge-based ubiquitous society. IPTV2.0 contents are required to be integrated with the enhanced metadata to efficiently support search, selection, convergence and delivery of the contents. Moreover, those contents shall be enhanced to provide the scalable services which is adaptable to the network status and user preferences. Therefore, the networking technologies for IPTV2.0 should tightly cooperate with application services and adaptive contents. Those technologies will be developed to construct the ubiquitous content service platform considering the evolution of networks and various converged services.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.3 no.2 s.5
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• pp.9-17
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• 2004

In this paper, we examine the MIMO(Multiple Input Multiple Output) system in the point of mobile communication that is used for railway environment. First, under the radio environment, wireless channel characteristics are analyzed between moving train and base station, both assuming track side base stations and non-track side base stations. Next, the paper introduces the MIMO system which can be used to solve the problem of performance degradation in railway environment, and analyzes its performance in terms of channel capacity and diversity. We especially compares open-loop scheme with closed loop scheme at the diversity and analyses their performance according to antenna correlation. Finally, the we presents experimental result from the ESCORT project that was studied in railway environment with the MIMO system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.5
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• pp.1058-1076
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• 2013

The WBAN(Wireless Body Area Network) supplies mobile convenience to our medical services. But if we have few effective control variables across this service deployment, the hidden distortions or defects of the system might threaten the lives and rights of the stakeholders. Therefore we need to increase the service credibility, to get WBAN effective. This study proposes a governance mechanism using feasible variables that are currently in use in practices in WBAN environments against medical incidents. Control variables were tested in Seoul National University hospital and related medical industries of South Korea. We assume that WBAN systems would be open based on integrating patients, medical employees and law enforcements to get smart theater operations against medical incidents by implementing proposed MJA(Multilateral Joint Analysis) model. MJA model also contributes to the convergence of computer systems and medical services by demonstrating flexible SOA(Service Oriented Architecture) dashboard of healthcare services with credibility factors in medicine. The important components in MJA model across WBAN, were found to be "Safety, Accuracy and Reliability" in priority order. Factor analysis, correlations and ANOVA were used to evaluate this model and an IT dashboard with a realization of mobile application, was used to support participants' decision-making.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.8
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• pp.3852-3864
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• 2016

Patients' health data is very sensitive and the access to individual's health data should be strictly restricted. However, many data consumers may need to use the aggregated health data. For example, the insurance companies needs to use this data to setup the premium level for health insurances. Therefore, privacy-preserving data aggregation solutions for health data have both theoretical importance and application potentials. In this paper, we propose a privacy-preserving health data aggregation scheme using differential privacy. In our scheme, patients' health data are aggregated by the local healthcare center before it is used by data comsumers, and this prevents individual's data from being leaked. Moreover, compared with the existing schemes in the literature, our work enjoys two additional benefits: 1) it not only resists many well known attacks in the open wireless networks, but also achieves the resilience against the human-factor-aware differential aggregation attack; 2) no trusted third party is employed in our proposed scheme, hence it achieves the robustness property and it does not suffer the single point failure problem.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.1
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• pp.17-27
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• 2018

We propose a new approach to control a biped robot motion based on iterative learning of voice command for the implementation of smart factory. The real-time processing of speech signal is very important for high-speed and precise automatic voice recognition technology. Recently, voice recognition is being used for intelligent robot control, artificial life, wireless communication and IoT application. In order to extract valuable information from the speech signal, make decisions on the process, and obtain results, the data needs to be manipulated and analyzed. Basic method used for extracting the features of the voice signal is to find the Mel frequency cepstral coefficients. Mel-frequency cepstral coefficients are the coefficients that collectively represent the short-term power spectrum of a sound, based on a linear cosine transform of a log power spectrum on a nonlinear mel scale of frequency. The reliability of voice command to control of the biped robot's motion is illustrated by computer simulation and experiment for biped walking robot with 24 joint.

• Proceedings of the Korea Contents Association Conference
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• 2006.11a
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• pp.70-74
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• 2006

In this paper, We propose the real-time monitor and control mechanism based-on web service for intelligent robot called URC(Ubiquitous Robotic Companion). URC is intelligent robot designed to interact with external digital device that can communicate through wire or wireless. In this paper, we designed the result of this study into the target robot called NETTORO and proved its practical worth. we optimized web-service technology in Embedded system environment so that can monitor and control indoors in remote place through acquired information from various sensors / actuators and then we designed. Also, we described command port to WSDL, so that can apply variously such as web server or application program in AXIS engine through gSOAP transmission protocol.

• Journal of Ubiquitous Convergence Technology
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• v.2 no.2
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• pp.67-77
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• 2008

Representation of various types of information in an interactive virtual reality environment on mobile devices had been an attractive and valuable research in this new era. Our main focus is presenting spatial indoor location sensing information in 3D perception in mind to replace the traditional 2D floor map using handheld PDA. Designation of 3D virtual reality by Virtual Reality Modeling Language (VRML) demonstrates its powerful ability in providing lots of useful positioning information for PDA user in real-time situation. Furthermore, by interpolating portal culling algorithm would reduce the 3D graphics rendering time on low power processing PDA significantly. By fully utilizing the CC2420 chipbased sensor nodes, wireless sensor network was established to locate user position based on Received Signal Strength Indication (RSSI) signals. Implementation of RSSI-based indoor tracking method is low-cost solution. However, due to signal diffraction, shadowing and multipath fading, high accuracy of sensing information is unable to obtain even though with sophisticated indoor estimation methods. Therefore, low complexity and flexible accuracy refinement algorithm was proposed to obtain high precision indoor sensing information. User indoor position is updated synchronously in virtual reality to real physical world. Moreover, assignment of magnetic compass could provide dynamic orientation information of user current viewpoint in real-time.