• The KIPS Transactions:PartC
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• v.16C no.5
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• pp.653-660
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• 2009

A research for middleware of WSN can provide sensor applications with avoiding tight coupling of hardware, ease of development, and abstract data access. However, previous works have some limitations which should install their own middleware onto the all sensor nodes resulting in computational and communication overhead. In order to address it, we proposed a virtual sensor overlay network, called TinyONet-Lite which introduced virtual sensors to model a virtual counterpart of physical sensors. These virtual sensors dynamically grouped into an overlay network, Slice, which provides middleware services. We implemented TinyONet-Lite on mote class hardware with TinyOS. In accordance with experiments and comparison with existing researches, TinyONet-Lite was proved to show advantages of extensibility, dynamic service composition and reducing overhead.

• Journal of the Korea Society of Computer and Information
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• v.11 no.6 s.44
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• pp.289-298
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• 2006

Many researches are going on with regard to issues and problems related to mobile database systems, which are caused by the weak connectivity of wireless networks, the mobility and the portability of mobile clients. Mobile computing satisfies user's demands for convenience and performance to use information at any time and in any place, but it has many problems to be solved in the aspect of data management. The purpose of our study is to design Mobile Continuous Query Processing System(MCQPS) to solve problems related to database hoarding, the maintenance of shared data consistency and the optimization of logging, which are caused by the weak connectivity and disconnection of wireless networks inherent in mobile database systems under mobile client server environments. We proved the superiority of the proposed MCQPS by comparing its performance to the C I S(Client-Intercept-Slaver) model. In Addition, we experiment on proposed index structure and methodology in various methods.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.2
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• pp.1-8
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• 2011

Traffic congestion is a source of significant economic and social costs in urban areas. Intelligent Transportation Systems (ITS) are a promising means to help alleviate congestion by utilizing advanced sensing, computing, and communication technologies. This paper proposes and investigates a basic and advanced ITS framework Advanced Traveler Information System (ATIS) using wireless Vehicle to Roadside (Centralized ATIS model: CA model) and Vehicle to Vehicle (DeCentralized ATIS model: DCA model) communication and assuming an ideal communication environment in the typical $6{\times}6$ urban grid traffic network. Results of this study indicate that an ATIS using wireless communication can save travel time given varying combinations of system characteristics: traffic flow, communication radio range, and penetration ratio. Also, all tested metrics of the CA and DCA models indicate that the system performance of both models is almost identical regardless of varying traffic demand and penetration ratios. Therefore, DCA model can be a reasonable alternative to the fixed infrastructure based ATIS model (CA model).

• Journal of the HCI Society of Korea
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• v.3 no.1
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• pp.1-7
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• 2008

Recently researchers have studied mobile physiological sensing device. However, previous works focused on multiple and real time physiological sensing method, instead of aesthetic shape of sensing devices, sensing comfort during monitoring and sensing reliability against the hand motion artifact. In this work, we propose a stone shaped physiological sensing device to monitor the physiological status in a daily life which maximize the aesthetic feeling and sensing comfort and sensing reliability. We proposed stepwise user centered design process for user centric physiological sensing device and evaluated appropriate sensing positions against the hand motion artifacts and pressure from sensors. From the usability test and experiments, we verified the proposed sensing device provides the aesthetic appeals, sensing comfort and sensing reliability. We expect that this work can be applied in the various health care applications in near future.

• The Journal of Korean Association of Computer Education
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• v.11 no.3
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• pp.91-99
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• 2008

In recent years, wireless networks have been widely deployed and the use of mobile devices has been popularized. As a result, mobile devices are increasingly considered as a resource of the Grid However, there are some problems such as unstable wireless communication and disconnection of mobile devices caused by movement in Mobile Grid Therefore, a scheduling method allocating jobs to the mobile devices should progressively deal with this problem The existing scheduling methods in Mobile Grid have mainly focused on the connection time of mobile devices. The connection time of mobile devices shows typically a regular pattern according to a user's living environments such as vacation/class in school, weekday/weekend in work, and so on. In this paper, we analyze statistics information for the utilization patterns of mobile devices and propose global and local scheduling methods for Mobile Grid, based on the analyzed utilization patterns.

• The KIPS Transactions:PartB
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• v.13B no.5 s.108
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• pp.507-514
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• 2006

Various application systems are developed using RFID as a part of ubiquitous computing, and it is expected that RFID chip will become wide-spread for the distribution industry especially. Efficient and efact intelligent-type of warehouse management system is essential for small-to-medium-sized enterprises in the situation having a trouble in the viewpoint of expense and manpower. In this paper, we implement small-scale warehouse management system using log-based context awareness technology. This system is implemented to be controlled on web, configuring clients to control RFID readers and building up DBMS system in a server. Especially, it grasps user's intention of storing or delivering based on toE data for the history of user's access to the system and it reports user's irregular pattern of warehouse use and serves predictive information of the control of goods in stock. As a result, the proposed system can contribute to enhance efficiency and correctness of small-scale warehouse management.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.2
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• pp.102-110
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• 2012

ZigBee networks developed for low power and short range communication are being used as home network solution for ubiquitous computing. However, as smart phones and tablet PCs have been widely used, WLANs which use same frequency with ZigBee networks have been increasingly used. Therefore, radio frequency interference causes many problems. To solve radio frequency interference problem among ZigBee networks and WLANs, many researches focus on designing interference minimization schemes in ZigBee networks. However, existing schemes have problems that have waste of resource for detecting interference, and have unnecessary time to avoid interference. In this paper, we propose an interference minimization scheme to solve radio frequency interference in ZigBee networks. The proposed scheme detects interference using ACK mechanism to reduce waste of resource, and avoids interference using table driven channel hopping scheme which is faster than existed schemes. The performance of proposed interference minimization scheme is evaluated by using OPNET simulator. Through the simulation result, we prove that proposed scheme has faster channel hopping than existing schemes.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.9
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• pp.17-26
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• 2011

Many types of services appear in a ubiquitous environment promulgated by the evolution of web service technology with the advances in wireless network technologies and mobile computing devices. These services differ according to their location environments, such as home, office, airport, and exhibition. It is required that a different set of services dynamically drops into the mobile user's device depending on their context and the distributed localized services are efficiently managed to seamlessly provide these localized services to the user. This paper proposes an Autonomic Service Composition System (ASCS) to provide useful services to the user with minimal or no effort for service selection. ASCS seamlessly installs the programs of localized services in the user's mobile device. It automatically provides localized services to users that are in the local service zone. Also ASCS can manage distributed localized services remotely and efficiently. ASCS is composed of a Remote Manager, Service Gateway, and Mobile Device. The prototype implementation uses 802.11b Wireless Network and Bundles using the OSGi Framework.

• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.923-930
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• 2004

Wireless sensor networks is a core technology of ubiquitous computing which enables the network to aware the different kind of context by integrating exiting wired/wireless infranet with various sensor devices and connecting collected environmental data with applications. However it needs an energy-efficient approach in network layer to maintain the dynamic ad hoc network and to maximize the network lifetime by using energy constrained node. Cluster-based data aggregation and routing are energy-efficient solution judging from architecture of sensor networks and characteristics of data. In this paper. we propose a new distributed clustering algorithm in using distance from the sink. This algorithm shows that it can balance energy dissipation among nodes while minimizing the overhead. We verify that our clustering is more en-ergy-efficient and thus prolongs the network lifetime in comparing our proposed clustering to existing probabilistic clustering for sensor network via simulation.

• The KIPS Transactions:PartD
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• v.12D no.4 s.100
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• pp.521-530
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• 2005

Many researches are going on with regard to issues and problems related to mobile database systems, which are caused by the weak connectivity of wireless networks, the mobility and the Portability of mobile clients. Mobile computing satisfies user's demands for convenience and Performance to use information at any time and in any Place, but it has many Problems to be solved in the aspect of data management. The purpose of our study is to design Mobile Query Processing System(MQPS) to solve problems related to database hoarding, the maintenance of shared data consistency and the optimization of logging, which are caused by the weak connectivity and disconnection of wireless networks inherent in mobile database systems under mobile client-server environments. In addition, we proved the superiority of the proposed MQPS by comparing its performance to the C-I-S(Client-Intercept- Server) model.