• The KIPS Transactions:PartC
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• v.16C no.2
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• pp.183-188
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• 2009

Wireless sensor networks will be broadly deployed in the real world and widely utilized for various applications. A prerequisite for secure communication among the sensor nodes is that the nodes should share a session key to bootstrap their trust relationship. The open problems are how to verify the identity of communicating nodes and how to minimize any information about the keys disclosed to the other side during key agreement. At any rate, any one of the existing schemes cannot perfectly solve these problems due to some drawbacks. Accordingly, we propose a new pre-distribution scheme with the following merits. First, it supports authentication services. Second, each node can only find some indices of key spaces that are shared with the other side, without revealing unshared key information. Lastly, it substantially improves resilience of network against node capture. Performance and security analyses have proven that our scheme is suitable for sensor networks in terms of performance and security aspects.

• The KIPS Transactions:PartC
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• v.9C no.1
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• pp.79-88
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• 2002

Transcoding proxy strategy has been widely used as a means to reduce the delay in retrieving Web pages over wireless mobile data service networks. However, this strategy has the serious drawbacks of being a potential point of failure or a bottleneck of the service. We developed a distributed proxy server system in which multiple proxy servers are installed at geographically dispersed locations and share the workloads among them by serving mobile hosts only within assigned regions. A new handoff message protocol to enable handoffs between proxies as the mobile hosts move between regions is proposed. According to the proxy server handoff protocol, a client agent at the mobile horst requests a proxy server to start handoff processing by which two proxy servers synchronize distilled data belonging to a HTTP session that must be maintained across the handoff. Also, we introduce the architecture of the proxy server and the client agent that handles the proxy server handoff. Finally, we evaluate the proposed system through performance test.

• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.875-882
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• 2002

The active packets unlike traditional IP packets should be executed at each active node along their path. To execute the active program at each active node, the active packets for an active program should go through the same active nodes and all packets are delivered without any loss. This paper presents the new active engine for every active packet which execute an active program to be routed through the same intermediate active nodes and to be delivered reliably. Proposed active engine requires fewer changes to existing IP protocols and guarantees the reliable delivery of the active packets. Moreover, even if the sender does not have any information about the intermediate nodes every active packet is routed through the same intermediate active nodes. The simulation results show that proposed active engine achieves an efficient transmission with high data delivery and low communication overhead compared with the other existing transmission protocols.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.3
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• pp.285-289
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• 2004

Recently, due to the high development of the internet, needs for multimedia streams such as digital audio and video is increasing much more. In case of transmitting multimedia streams using the User Datagram Protocol (UDP), it may cause starvation of TCP traffic on the same transmission path, thus resulting in congestion collapse and enormous delay because UDP does not perform TCP-like congestion control. Because of this problem, diverse researches are being conducted on new transmission schemes and protocols intended to efficiently reduce the transmission delay of real-time multimedia streams and perform congestion control. The TCP-friendly congestion control schemes can be classified into the window-based congestion control, which uses the general congestion window management function, and the rate-based congestion control, which dynamically adjusts transmission rate by using TCP modeling equations and the like. In this paper, we suggest the square-root congestion avoidance algorithm with the hybrid TCP-friendly congestion control scheme which the window-based and rate-based congestion controls are dealt with in a combined way. We apply the proposed algorithm to the existing TEAR. We simulate the performance of the proposed TEAR by using NS, and the result shows that it gives better improvement in the stability needed for providing congestion control than the existing TEAR.

• Journal of the Society of Disaster Information
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• v.10 no.2
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• pp.254-262
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• 2014

KISStool is developed and established by KIGAM, in order to link and share the earthquake data easily with institutes related, this study includes the development of a KISStool program format and protocol supporting Kit. The Kit has functions such as transforming and sending a seismic data. The functions of the kit are implemented in modules, which are running on the realtime basis. The firmware is embedded into the Kit, which transforms the seismic data into the formats, miniSEED and QSCD20. These data are sent to KISStool program. We have confirmed the results of the data transforming, transmissions and storage functions are conducted normally, the speed of transmission shows same level when comparing with a standard system. We expect that the firmware developed in this study will have high usability not only for linking with KISStool program through being embedded into incompatible digitizers, but also for improving performance of older ones.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.192-197
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• 2002

1. 실시간 모니터링 -온실 내부환경의 계측장치로 모듈화된 단일 칩 마이크로프로세서를 이용한 하우스 모니터를 개발하였다. 개발된 다수의 하우스 모니터는 RS-485통신을 이용하여 개발된 프로토콜을 통하여 그룹 모니터와 통신하면서 계측 데이터를 전송하였고 안정된 계측 성능을 보였다. 또한 그룹 모니터는 하우스모니터로부터 수신한 데이터를 인터넷 환경 TCP/IP 통신에 의해 서버에 정보를 전송하고 데이터베이스 서버에 저장할 수 있었다. 2. 클라이언트 서버 모델 -클라이언트 모니터를 통하여 허용된 사용자들은 해당 온실의 상황을 원격지에서 파악할 수 있는 있었다. 또한 분산환경 기술을 이용하여 서버를 경유하여 데이터베이스 서버에서 데이터 셋을 가져와 과거 재배 사례 등을 조회 및 이용 가능하였다. 이는 전문가에게 접근을 허용함으로써 재배에 관한 지원이 가능하도록 하였다. 데이터 베이스 시스템으로 연계하여 온실환경 정보를 분석하는 것이 가능하였다. 3. 기대효과 및 나아가야 할 방향 -개발된 시스템을 식물 공장 내 작물의 재배환경을 데이터베이스화하여 재배사례 데이터베이스를 형성하고 작물이 가장 잘 자라는 최적 재배 환경을 연구하여 고품질의 작물 재배에 이용될 수 있다. 또한 식물공장의 운전실적, 환경 조건, 환경 조절비용 등의 분석에 효율적으로 이용될 수 있을 것으로 예상되며 각 환경인자들과의 관계를 구명하는데 도움을 줄 것이다. 축적된 작물의 재배 사례 데이터베이스를 이용하여 작물 특성 및 재배 연구에 도움을 줄 수 있을 것이다. 제어 장치들의 운영실적을 분석함으로써 제어 시스템의 효율적이고 경제적인 제어가 가능하도록 할 수 있을 것이다. 이들이 모두 완성되면 전문가 및 전문가 시스템으로부터 지원을 받는 지능형 식물공장이 가능할 것이다. 본 연구에서 개발한 계측 모듈 및 데이터베이스 시스템은 실제 농가에 설치된 전용선을 이용하여 실증 실험을 통해 수정·보완하여야 할 것이다. 또한 시설원예분야에서 있어서 통신체계에 대한 표준화 연구가 수행되어 앞으로 개발될 다른 시스템들과의 호환성을 갖도록 해야 할 것이다. 앞으로 온실의 경영 및 관리 데이터베이스를 개발하여 첨단온실의 통합 관리 및 정보 시스템을 구축하여야 할 것이다. 또한, 시설원예의 환경 설계의 기준을 적용할 수 있도록 하여야 할 것이다.

• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.51-59
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• 2011

To support seamless IPTV services in IP-based wireless network, delay or interruption time must be minimized because noticeable interruption will make IPTV service users unhappy. A number of protocols have been proposed for solving mobility problem. However effective seamless handover mechanism to support mobile IPTV services yet to be solved. Mobile WiMAX offers a wireless solution in the access networks that can support IPTV services. Goal of this paper is to identify some reasons of delay time during handover process in an IPv6 capable Mobile WiMAX and to perform handover delay of some optimization scenarios given by existing standardization and proposed improvement.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.12
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• pp.692-703
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• 2004

Communication induced checkpointing (CIC) is one of the checkpointing techniques to provide fault tolerance for distributed systems. Independent checkpoints that each distributed process produces without coordination are likely to be useless. Useless checkpoints, which cannot belong to any consistent global checkpoint sets, induce nondeterminant rollback. To prevent the useless checkpoints, CIC forces processes to take additional checkpoints at proper moment. The number of those forced checkpoints is the main source of failure-free overhead in CIC. In this paper, we present two new CIC protocols which satisfy 'No Z-Cycle (NZC)'property. The proposed protocols reduce the number of forced checkpoints compared to the existing protocols with the drawback of the increase in message delay. Our simulation results with the synthetic data show that the proposed protocols have lower failure-free overhead than the existing protocols. Additionally, we show that the classical 'index-based checkpointing' protocols are inefficient in constructing the consistent global cut in distributed executions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.304-309
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• 2004

Recently, the needs for multimedia stream such as digital audio and video in the Internet has increased tremendously. Unlike TCP, the UDP protocol, which has been used to transmit streaming traffic thorough the Internet, does not apply any congestion control mechanism to regulate the data flow thorough the shared network And it leads to congestion collapse of the Internet and results in long-term transmission delay. To avoid any adverse effect on the current Internet functionality, a now protocol of modification or addition of some functionality to perform congestion control and to reduce huge transmission delay in transmitting of multimedia stream are in study. TCP-friendly congestion control mechanism is classified into two : one is window-based congestion control scheme using general window management functionalities, the other is rate-based congestion control scheme using TCP modeling equation. In this paper, we propose an algorithm for improving the transmitting rate on a hybrid TCP-friendly congestion control scheme combined with widow-based and late-based congestion control for multimedia stream. And we also simulate the performance of improved TEAR implementation using NS. With He simulation results, we show that the improved TEAR can provide better fairness and lower rate fluctuations than TCP.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.510-513
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• 2006

Mobile Ad-hoc networks have recently attracted a lot of attention in the research community as well as in industry. Although the previous research mainly focused on various of Ad-hoc in routing we consider, in this paper, how to efficiently support applications such as variable Geocasting basd on Ad-hoc networks. The goal of a geocasting protocol is deliver data packets to a group of nodes that are located within a specified geocasting region. Previous research that support geocast service in mobilie computing based on Ad-hoc have the non-optimization problem of data delivery path, overhead by frequent reconstruction of the geocast tree, and service disruption problem. In this paper, we propose the mobility pattern based geocast technique using variable service range according to the mobility of destination node and resource reservation to solve this problem. The experimental results show that our proposed mechanism has improved performance than previous research.