• Journal of Korea Society of Industrial Information Systems
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• v.11 no.2
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• pp.98-102
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• 2006

Recent development of Information Technology, the ubiquitous computing environment is on the rise. At the same time, RFID technology and its related applications are actively investigated. In this paper, a portable merchandise information providing system using cheap wireless transmission module is developed in order to overcome the mobility limitation of the wired RFID system. The TRF6901 chipset of 900MHz band from TI is used for the wireless transmission module and the MPS430F149 is used for the MPU. It is expected that the developed system can be applied to numerous innovative wireless applications such as library circulation desk for lending service and automated door system for entrance control.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10a
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• pp.167-171
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• 2006

무선 센서 네트워크는 유비쿼터스 컴퓨팅에서 생활 환경과 컴퓨터 사이의 중계자 역할을 하는 매우 중요한 연구 분야이다. 매우 제약적인 자원 환경에서 동작하여야 하는 센서 노드의 동작 환경적 특성 때문에 제한된 자원을 효율적으로 관리할 수 있는 센서 노드용 운영체제가 요구된다. 센서 노드는 제약적인 자원을 가지고 있지만 데이터 수집, 데이터 프로세싱, 다른 노드로부터 수신된 데이터의 전달 등 여러 가지 작업들이 동시에 발생된다. 기존의 범용 센서네트워크 운영체제에서는 극도로 제한된 자원을 최대한 효율적으로 사용할 수 있는 방법에 대하여 주로 연구해 왔다. 무선 센서 네트워크의 응용 범위가 점차 넓어지고 있다. 방사능 감지와 같이 실시간성을 요구하는 응용분야들이 생겨나기 시작하면서 센서 네트워크에서도 실시간성의 필요성이 대두되게 되었다. 실시간 센서 네트워크 연구 분야에서 실시간 통신 프로토콜의 연구 결과가 발표되고 있지만, 실시간 운영체제의 지원없이 완전한 실시간성을 보장하기 힘들다. 하지만 센서 노드용 실시간 운영체제에 대한 연구는 아직까지 활발히 진행되지 않고 있다. 본 논문에서는 정시성을 보장하는 분산 객체 모델인 TMO를 센서네트워크의 제한된 자원 환경에 알맞도록 경량화 시킨 $\mu$TMO 모델을 제시하고, 센서 노드용 운영체제에 $\mu$TMO 모델 을 적용하여 실시간성 지원에 따른 오버헤드를 감소시킨 실시간 센서 네트워크 운영체제의 구조를 제안한다.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.9
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• pp.690-694
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• 2009

In this paper, we propose a hybrid MAC architecture for reducing energy consumption and maximizing network lifetime in wireless sensor networks. For this purpose, the hybrid MAC architecture is proposed for energy efficient by combining inter-cell TDMA and intra-cell CSMA scheme. Based on the ns-2 simulation result, we prove that the proposed architecture improves energy efficiency as compared with CSMA and TDMA.

• Journal of KIISE:Databases
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• v.33 no.1
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• pp.117-128
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• 2006

In this paper, we propose a streaming method for XML data that supports energy-efficient processing of queries over the stream in mobile clients. We propose new stream organizations for XML data which have different kinds of addresses to related data in a stream. We describe event-driven stream generation algorithms for the proposed stream structures and provide search algorithms for simple XML path queries which leverage the access mechanisms incorporated in the stream. Experimental results show that our approaches can effectively improve the tuning time performance of user queries in a wireless broadcasting environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.588-591
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• 2009

In ubiquitous computing GIS services, it is possible to use the spatio-temporal data anytime through the mobile device. GIS services regularly update use the latest spatio-temporal data to provide the most suitable services. For this situation, update data is distributed to CD or wired networks update services. However, this method has problem to propagate update data to users as taking long time. In this paper, suggests a synchronization system which propagate update data to users for reducing processing time efficiently. This synchronization system collects update data in the field and synchronizes server with collected data to use mobile devices by real time. For this system, I design and materialize synchronization module which updates update data and wireless network module.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.16-19
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• 2010

최근 무선 컴퓨팅 환경과 무선 단말기관련 기술의 발전으로 인해 모바일 애드혹 네트워크관련 연구가 활발하게 이루어지고 있다. 모바일 애드혹 네트워크에서는 노드들이 자유롭게 이동하기 때문에 네트워크가 빈번하게 분리되며, 이로 인해 데이터 접근성 저하문제가 발생한다. 기존 연구에서는 데이터 접근성이 저하되는 문제를 해결하기 위해 다양한 복제본 할당 기법이 연구되었다. 그러나, 지금까지 연구된 복제본 할당기법들은 모바일 애드혹 네트워크 환경의 제한된 자원으로 인한 노드들의 이기적인 행동에 대해 고려하지 않았다. 본 논문은 모바일 애드혹 네트워크 상의 노드들이 자신의 이득을 위해 협력이 아닌 이기적인 행동을 택하게 되는 과정을 게임이론을 통해 설명하고, 수익함수 조절을 통해 노드들의 이기적인 행동을 억제할 수 있는 방안을 제시한다.

• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.241-248
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• 2006

Mobile computing has such characteristics as portability, wireless network, mobility, etc. These characteristics cause various problems to mobile terminals like frequent disconnection, high error rate, and varying network status. These problems motivate us to develop an adaptive error control mechanism for supporting multimedia service in mobile computing environment. In this paper, we propose the Adaptive Error Control(AEC) scheme using client's buffer size and current error rate. After categorizing the status into four groups according to client's buffer size and current error rate, this scheme applies an appropriate error control scheme to each status. In this scheme, thresholds of buffer size and error rate are determined by the data transmission time, play rate and average VOP size, and by the probability of error for a sequence of packets. The performance of proposed scheme is evaluated by flaying MPEG-4 files on an experimental client/server environment, respectively. The results show that error correcting rate is similar to other schemes while the time for correcting error reduce a little. In addition, the size of data for correcting error is decreased by 23% compared with FEC and Hybrid FEC, respectively. Theses results demonstrate that the proposed scheme is more suitable in mobile computing environment with small bandwidth and varying environment than existing schemes.

• Journal of Korea Society of Industrial Information Systems
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• v.16 no.2
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• pp.85-97
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• 2011

Wireless sensor networks have emerged as one of the key enabling technologies for ubiquitous computing since wireless intelligent sensor nodes connected by short range communication media serve as a smart intermediary between physical objects and people in ubiquitous computing environment. We recognize the wireless sensor network as a massively distributed and deeply embedded system. Such systems require concurrent and asynchronous event handling as a distributed system and resource-consciousness as an embedded system. Since the operating environment and architecture of wireless sensor networks, with the seemingly conflicting requirements, poses unique design challenges and constraints to developers, we propose a very new operating system for sensor nodes based on finite state machine. In this paper, we clarify the design goals reflected from the characteristics of sensor networks, and then present the heart of the design and implementation of a compact and efficient state-driven operating system, SenOS. We describe how SenOS can operate in an extremely resource constrained sensor node while providing the required reactivity and dynamic reconfigurability with low update cost. We also compare our experimental results after executing some benchmark programs on SenOS with those on TinyOS.

• Archives of design research
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• v.17 no.1
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• pp.49-62
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• 2004

Due to the recent surge of wireless Internet and concurrent development of the end user terminal devices having standardized graphical user interface(GUI) and unified operation mechanism for better interactivity in information representation and ease of use, various efforts on the improvement of GUI is widely recognized as one of the key factors that will usher in the next stages of the wireless Internet for the users. Especially, improved usability along with unique visual effect are considered to be the key elements for GUI considering the rapid improvement of the resolution and color on the end user handset devices; thus, the study and research on the subject of GUI is expected to increase along with the wireless Internet using smart phones. User interface of the wires Internet end user handsets will have a definite and significant effect on the user interaction as well as productivity. Domestically, wireless Internet service providers and GUI design companies are making various efforts in producing a common GUI models for standardized operation scheme and improved graphical display capabilities of the hand phones, PDAs and smart phones. In the study, Nokia 3650 model and Microsoft Orange SPV model were chosen as test devices for usability comparison and data collection to collect directional benchmark data in developing next generation smart phone user interface integrating PDAs and phones. The mail purpose of this study is to achieve the most efficient user accessibility to WAP menu through intensive focus on developing WIPI WAP menu having most effective usability for the users in their twenties and thirties. The result of this study can also be used as the base research materials for WAP service development, VM browser development and PDA browser development. The result of this study along with the evaluation model is expected to provide effective analysis materials on the subject of user interface to the developers of the wireless Internet user devices, GUI designers and service planners while short listing key factors to consider in developing smart phones therefore serving as the GUI guideline of WIPI phones.

• The Journal of the Convergence on Culture Technology
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• v.5 no.1
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• pp.401-407
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• 2019

SDN(Softeware Defined Networking) has emerged to address the rapidly growing demand for cloud computing and to support network virtualization services. Therefor many companies and organizations have taken SDN as a next-generation network technology. However, unlike the wired network where the SDN is originally designed, the SDN in the wireless network has a restriction that it can not provide the mobility of the node. In this paper, we extended existing openflow protocol of SDN and developed SDN-based network platform, which enables the SDN controller to manage the radio resources of its network and support the mobility of the nodes. The mobility support function of this paper has the advantage that a node in the network can move using its two or more wireless interfaces by using the radio resource management function of the SDN controller. In order to test the functions implemented in this paper, we measured parameters related to various transmission performance according to various mobile experiments, and compared parameters related to performance using one wireless interface and two interfaces. The SDN-based network platform proposed in this paper is expected to be able to monitor the resources of wireless networks and support the mobility of nodes in the SDN environment.