• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.915-919
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• 2003

This paper presents a fuzzy-motion-control based tracking algorithm of mobile robots, which uses the geometrical information derived from the active stereo-vision system mounted on the mobile robot. The active stereo-vision system consists of two color cameras that rotates in two angular dimensions. With the stereo-vision system, the center position and depth information of the target object can be calculated. The proposed fuzzy motion controller is used to calculate the tracking velocity and angular position of the mobile robot, which makes the mobile robot keep following the object with a constant distance and orientation.

• Korean System Dynamics Review
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• v.2 no.2
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• pp.41-62
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• 2001

Perhaps, one of the typical emerging markets drawing tremendous attention from not only business professionals but also policy-makers would be the mobile Internet services. In recent years many research institutes reported their predictions on the growth of the mobile Internet services market, announcing that the market would show explosive growth and replace the wired Internet service market rapidly. Unfortunately, however, the reality we are facing at present is quite different from their expectations. The realized share of the mobile services in Korea last year has turned out remaining only about one percent of the total network service revenue. What are the reasons for the gap between the prospects and the reality? Starting from this question, this paper attempts to explore the generic pitfalls of the traditional number-crunching methods adopted thus far for the forecast of newly emerging market trends, and present an alternative by introducing systems thinking to the mobile Internet service market as an example, followed by its rationale as a new tool for forecasting and some reasoning about why traditional methods are no longer appropriate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.7
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• pp.1448-1458
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• 1997

In this paper the reverse link of the GLOBALSTAR-the representative CDMA LEO satellite system and LEO mobile satellite channel are developed by the SPW software simulation tool. And the performance of the system is evaluated. GLOBALSTAR is designed to give cellular-type service to hand-held user terminals through a constellation of 48 LEO satellites in circular orbites with 1414 Km altitude. Since LEO mobile satellite system communicates with mobile unit, it is suffered from severe multipath fading and shadowing. The fast mobility of LEO satellites makes the channel condition time vering. So, the LEO mobile satellite channel is different from land mobile channels. In this unique LEO satellite channel, it is shown that the performance of the GLOBALSTAR reverse link is varied according to the elevational angle, but this variation is overcome by satellite path diversity.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.3
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• pp.233-238
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• 2010

This paper describes a multi-mobile robot system with fuzzy rule based structure in collision avoidance. Collision avoidance is an important function to perform a given task collaboratively and cooperatively in multi-mobile robot environments. So the important but challenging problem is handled in this paper. Considered obstacles for collision avoidance between multi mobile robots are static, dynamic, or both of them at the same time. Using the fuzzy rule based structure, distance and angle from a robot to obstacles are described as fuzzy linguistic values and steering angle for the robot are updated from the collision environments. As a result, the multi-mobile robot can modify a global path from a robot itself to its own target. In addition, avoiding collision with static or dynamic obstacles for the robot system can be achieved. Simulation based experimental results are given to show usefulness of this method.

• Journal of Industrial Technology
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• v.27 no.A
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• pp.131-139
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• 2007

The recent advance in wireless network technologies has enabled the streaming media service on the mobile devices such as PDAs and cellular phones. Since the wireless network has low bandwidth channels and mobile devices are actually composed of limited hardware specifications, the transcoding technology is needed to adapt streaming media to given mobile devices. Futhermore owing to the diversity of bandwidth in the wireless network by reason of mobile users' movements and environments, it is difficult to provide stable QoS. In this paper, the autonomic multimedia transcoding system is proposed in order for users to provide network adaptive QoS. Our proposed system is based on the estimation of available bandwidth in wireless network for seamless multimedia streaming service. The proposed system is designed and implemented for various mobile clients. In experiments, we evaluate its seamless multimedia streaming and the adaptation transcoding bit rate according to the changes of bandwidth in wireless network.

• Spatial Information Research
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• v.10 no.4
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• pp.567-578
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• 2002

The success of gCRM depends on the availability of adequate, real-time data about customers' location and the provision of diverse value-added services utilizing it. In the existing gCRM systems, however, it seems that the positional precision of customers' location is very low, and further that the services based on real-time location data are not provided. In order to overcome these weaknesses and extend the limited scope of gCRM, we suggest a new design of gCRM system integrated with LBS. We also describe in some detail the system prototype for such an integration.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.350-354
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• 2008

IP-based mobile communication system is one of the key research items in the mobile networks for a long time. But, due to some technical issues and no need of markets, it is still not full-fledged. Recently, CDMA and WCDMA service providers want to introduce IP-based network connectivity. Even though their efforts, the main network intra-structure depends on ATM or HDLC technology. This article describes a good example of commercialization of IP-based mobile communication systems. Our research is not experimental system but a in-service system - replacing the existing equipments with new IP-based systems. In this paper, we introduce IP related technologies used in our research such as IP-based ATCA(Advanced Telecommunications Computing Architecture) platform, HA(High Availability) redundancy, IP multicast, network redundancy techniques, multi-link bundling and IP header compression. These are already well-known to internet domain. We mix them with mobile communication systems concretely.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.11 no.2
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• pp.95-102
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• 2011

In this paper, a Mobile Continuous Query Processing System (MCQPS) is designed to solve problems related to database hoarding, maintenance of shared data consistency, and optimization of logging. These problems are caused by weak connectivity and disconnection of wireless networks inherent in mobile database systems under mobile client-server environments. We show the superiority of the proposed MCQPS by comparing its performance to the Client-Intercept-Server (C-I-S) model. In addition, several experimental results show the effectiveness of our proposed indexing structure and methodology for real-time continuous queries.

• 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.

• Journal of the Korea Society for Simulation
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• v.19 no.4
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• pp.161-167
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• 2010

To realize the U-healthcare system, the mobile patient monitoring system is of the essence. In this monitoring system, a patient's real-time data on biometrics and location must be transferred to predeterminate destination server ceaselessly. As the number of mobile patients increases steadily or mobile patients are moving into some specific area, the load balancing solution to real-time data congestion problem is needed. In this paper, we propose a new mobile patient monitoring system with Torus topology where three layers are connected hierarchically and the intermediate layer takes charge of priority-based load balancing. For the formalized design and verification of proposed system, we describe the overall structure with connectivity among its components and implement major components in pseudo-code by adopting a system specification-based approach. This approach makes the design and verification of our mobile patient monitoring system more flexible and accurate.