• Journal of Information Processing Systems
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• v.14 no.5
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• pp.1272-1285
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• 2018

The paper presents a novel embedded multifunctional media sever (EMMS) for mobile devices to receive various media programs. Being different from other contemporary system research, the paper mainly studies how to design a reception solution for terrestrial digital television (DTV) on mobile devices and how to enable mobile devices can receive DTV program, enjoy video-on-demand (VOD), achieve video surveillance and relay Internet video program via local Wi-Fi simultaneously. In the system design, we integrate broadcasting-terrestrial DTV tuner, streaming media re-transmission system, VOD disk, video camera and access interface to the Internet into EMMS, which can either receive terrestrial DTV radio signals and demodulate out digital transport stream (TS), or can read streaming media bit-stream from VOD disk, surveillance camera or access interface to the Internet. The experimental results show the proposed system is stable and quality-efficient. Comparing with the other systems, the proposed system has the least packet loss rate and response time.

• The Journal of Korea Robotics Society
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• v.2 no.3
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• pp.212-220
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• 2007

This paper proposes a method of avoiding obstacles and tracking a moving object continuously and simultaneously by using new concepts of virtual tow point and fuzzy danger factor for differential wheeled mobile robots. Since differential wheeled mobile robot has smaller degree of freedom to control and are non-holonomic systems, there exist multiple solutions (trajectories) to control and reach a target position. The paper proposes 'fuzzy danger factor' for obstacles avoidance, 'virtual tow point' to solve non-holonomic object tracking control problem for unique solution and three kinds of fuzzy logic controller. The fuzzy logic controller is policy decision controller with fuzzy danger factor to decide which controller's result is more valuable when the mobile robot is tracking a moving object with obstacles to be avoided.

• The Journal of Korea Robotics Society
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• v.2 no.3
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• pp.221-226
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• 2007

A robust position-sensing system is proposed in this paper for ubiquitous mobile robots which move indoor as well as outdoor. The Differential GPS (DGPS) which has position estimation error of less than 5 m is a general solution when the mobile robots are moving outdoor, while an active beacon system (ABS) with embedded ultrasonic sensors is selected as an indoor positioning system. The switching from the outdoor to indoor or vice versa causes unstable measurements on account of the reference and algorithm changes. To minimize the switching time in the position estimation and to stabilize the measurement, a robust position-sensing system is proposed. In the system, to minimize the switching delay, the door positions are stored and updated in a database. The reliability and accuracy of the robust positioning system based on DGPS and ABS are verified through the real experiments using a mobile robot prepared for this research and demonstrated.

• Journal of information and communication convergence engineering
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• v.9 no.1
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• pp.64-68
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• 2011

On the limited urban area, precise measurement of meteorological data is not easy for the cost problem. The facilities collecting the data require high installment costs. The mobile sources can be a solution in city region. For example, a public bus on which some meteorological sensors are installed can act as moving information gathering station. The information is gathered on a server and aggregated to generate useful information for smart phone application. To implement the services, several obstacles are exists. This paper studies on a design of this mobile meteorological information service system for urban area.

• Journal of Digital Contents Society
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• v.11 no.4
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• pp.453-461
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• 2010

Specifying and designing the election algorithm in mobile ad hoc distributed systems is very difficult task. It is because mobile ad hoc systems are more prone to failures than conventional distributed systems. The aim of this paper is to propose a specification and design of the election algorithm in a specific ad hoc mobile computing environment. For this aim, we specify and design an election algorithm in this paper. In addition, we formally verify it and show that it is correct. This solution is based on the nodes detection algorithm that is a classical one for synchronous distributed systems.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.1012-1019
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• 2016

A robust control intended for a nonholonomic mobile robot is considered to guarantee good tracking a desired trajectory. The main drawbacks of the mobile robot model are the existence of nonholonomic constraints, uncertain system parameters and un-modeled dynamics. in order to overcome these drawbacks, we propose a robust control based on Lyapunov theory associated with sliding-mode control, this solution shows good robustness with respect to parameter variations, measurement errors, noise and guarantees position and velocity tracking. The global asymptotic stability of the overall system is proven theoretically. The simulation results largely confirm the effectiveness of the proposed control.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1259-1262
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• 2004

Detecting environmental hazards and monitoring remote terrain are among many sensor network applications. In case of fire detection, it is significantly valuable to monitor fire-spot's shape and trend in time. Mobile ad hoc sensor nodes right round are responsible for sensoring, processing and networking packets, or even launching extinguisher. In this paper, we proposed a ring-oriented Multicast architecture based on "Fisheye State Routing" (MFSR) to organize a group of mobile ad hoc sensor nodes in a multicast way. It is familiar with traditional mesh-based multicast protocol [1] in mobile ad hoc network, trying to concentrates on efficiency and robustness simultaneously. Certain applications-based solution for hazards is proposed, quantitative results including architecture and recovery algorithms of MFSR are also investigated in this paper.

• ETRI Journal
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• v.44 no.6
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• pp.966-976
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• 2022

Optical wireless communication, or free space optics, is a promising solution for backhauls in sixth-generation mobile systems. However, the susceptibility of optical links to weather conditions has led to FSO links being furnished with radio frequency (RF) backups. These Hybrid FSO/RF systems provide enhanced link availability but lead to RF resource wastage. Cognitive radio technology, in contrast, is well known for its optimal use of RF resources and may be combined with an FSO link to create a Cognitive Hybrid FSO/RF system. This work uses such a system to analyze a configuration for a mobile backhaul in sixth-generation mobile systems. This configuration can seamlessly coexist with established large scale RF cellular networks. The performance of this configuration is analyzed with respect to outage probability and average bit error by considering the impact of optical channel turbulence, misalignment loss, RF interference, and noise. Mathematical closed-form expressions are verified by simulations.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.190-199
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• 1993

In this study a three-axes mobile robot which has two independently controlled driving wheels and a function of simultaneously steering the driving wheels has been developed. Two-motion modes of the mobile robot, the first is a differential velocity motion of two driving wheels and the second is a equal driving and steering motion, have been analyzed and the kinematic and dymanic analyses about the each motion mode have been carried out. As a result of dynamic analysis, the torque used on a motor control and acceleration have been derived explicitly. Hence, a computation time is saved effectively and a real time control of the mobile robot considering the dynamics has become possible. Through a simulation the results considering the dynamics have been compared with that no regarding the dynamics and the possibility of real-time control has been proved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.2
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• pp.102-113
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• 2014

Present communication and network environment have been moving rapidly toward wireless and mobile base from existing wired internet base. This change of trend influences greatly on business methods accordingly. Therefore many enterprises are trying hard to adopt mobile business in order to gain competitive edge of their products and they are in need of more effective and stable mobile solutions. However, the method of establishing optimal mobile computing environment and how to handle existing business process and use vast amount of database are still needed. Therefore this paper tries to realize a mobile middleware system as a mobile business establishment supporting tool that could link various computational resource on wired internet with wireless LAN, mobile phone network, and mobile devices. To accomplish that specific goal, this paper provides a powerful tool of mobile and wireless application data access that could expand the line of business already set up in general enterprises easily and rapidly into mobile environment. When this suggested solution is applied in the field of industry, it can economically change legacy business process into mobile environment without having to change existing logic and resources at all.