• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.239-243
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• 2011

In wireless ad-hoc network, the detection of link breakage and re-establishing the route path causes lots of network overhead and results in communication delay. In the LBN method, the node causing a link breakage actively sends a message to neighbors so that they can instantly start re-establishing process of new path. In this paper we describe the result of network simulation we performed using NS2 to show the effectiveness of LBN method.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.11
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• pp.141-149
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• 2013

IETF 6LoWPAN standard technique has been studied in IoT environment to support the IPv6 packet communication. 6LoWPAN protocol for transmission of packets mainly in the AODV routing protocol and a variety of extended techniques have been investigated. In particular, consisting of nodes with limited resources in a network error occurs when the 6LoWPAN reliable data transfer and fast routing method is needed. To this end, in this paper, we propose resilient routing protocol and extension of IETF LOAD algorithm, for optimal recovery path, More specifically, the optimal recovery path setup algorithm, signal flow, and detailed protocols for the verification of the reliability of packet transmission mathematical model is presented. The proposed protocol techniques to analyze the performance of the NS-3 performance through the simulation results that is end-to-end delay, throughput, packet delivery fraction and control packet overhead demonstrated excellence in comparison with existing LOAD.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.40-41
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• 2007

$SnO_2$ nanowires are used at the nanoscale level for the electrical transduction of the gas interaction with these sensing materials. We report on a study of high sensitivity and fast NOx gas sensor. We focused on improving the response time and refresh time by growth nanowires on the trench structure of Si substrate as air path. To improve refresh time we applied the trench structure with depth of $10\;{\mu}m$ by the inductively coupled plasma reactive ion etching(ICP-RIE). The fabricated device was measured at temperature of $200{\sim}300^{\circ}C$. The sensor exhibit ultra-fast and reversible electrical response (t90% ~4 s for response and ~3 s for recovery).

• Journal of KIISE:Databases
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• v.27 no.2
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• pp.216-226
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• 2000

This paper suggests a new access path, hashed B-tree which is an efficient access method for integrity checking. Hashed B-tree is based on the observation that most query patterns in enforcing integrity constraints are point queries. Hashed B-tree compresses the key by hashing procedure, which reduces the height of tree and results in fast node search. This method has the advantages such as it can be implemented easily and use the B-tree concurrency control and recovery algorithm with minor modifications.

• Journal of KIISE:Information Networking
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• v.31 no.6
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• pp.595-607
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• 2004

Networks often evolve to provide a host with multiple access points to the Internet. In this paper, we propose a transport layer load distribution mechanism utilizing the multiple network interfaces simultaneously. We specifically propose an extension of Stream Control Transmission Protoco1 (SCTP) to have load sharing over multiple network interfaces. We named the particular service provided by the Proposed load sharing mechanism to be LS (Load Sharing) mode service. LS mode service is based on the following four key elements: (i) the separation of flow control and congestion control, (ii) congestion window based striping, (iii) redundant packet retransmission for fast packet loss recovery, (iv) a novel mechanism to keep track of the receiver window size with the SACKS even if they arrive out-of-order. Through simulations, it is shown that the proposed LS mode service can aggregate the bandwidth of multiple paths almost ideally despite of the disparity in their bandwidth. When a path with a delay of 100% greater is utilized as the second path, the throughput is enhanced about 20%.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.2
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• pp.186-190
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• 2008

This paper analyzes previous work on publish/subscribe in mobile ad-hoc networks with respect to collaboration methods among distributed event brokers. Our experiments suggest that approaches building event delivery structures are suitable for a scenario where there are events of various types each of which is consumed by a few subscribers. However, these approaches based on independent periodic exchange of network topology information may fail to reflect the up-to-date information when building event delivery paths. For this reason they do not correctly recover a broken path caused by node mobility, which results in lower event delivery rates. This paper proposes a scheme for building and maintaining event delivery paths based on advertisements initiated by and hence propagated from the root node. This guarantees correct recovery of event delivery paths within each period. Our experiments show that, our proposed scheme gives a better event delivery ratio with lower overhead.

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.3
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• pp.336-343
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• 2002

Nowadays, after appearance of wireless network the existent internet environment is changing into the united wire/wireless network. But the present TCP regards all of the packet losses on transmission as the packet tosses due to the congestion. When it is applied on the wireless path, it deteriorates the end-to-end TCP throughput because it regards the packet loss by handoff or bit error as the packet loss by the congestion and it reduces the congestion window. In this paper, for solving these problems we propose the method that controls the performance of TCP on the wireless link by extending ECN which is used as a congestion control mechanism on the existent wire link. This is the method that distinguished the packet loss due to the congestion from due to bit error or handoff on the wireless network, so it calls the congestion control mechanism only when there occurs the congestion in the united wire/wireless network.

• Progress in Superconductivity
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• v.7 no.2
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• pp.114-119
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• 2006

High critical current density, high n value, multiple faults endurances, and fast recovery characteristics of YBCO thin films are very attractive characteristics for developing resistive type superconducting fault current limiters. But due to the limited current and voltage ratings of one YBCO module, it is needed to construct series and parallel module connections for high capacity electric networks. Especially for distribution network, more than 30 units should be connected in series to meet voltage level. So in order to construct distribution-level superconducting fault current limiter, simultaneous quench in one YBCO thin films should be realized, and furthermore, quench should be occurred in all fault current limiting units equally to avoid local heating and failures. In this paper, we proposed optimum design of YBCO thin films for fault current limiting module and technical method using shunt resistor to achieve simultaneous quench between multi current limiting units. From the analytical and the experimental results, optimal current path and thickness of shunt material was determined for YBCO thin films and shunt resistor between modules was developed. Finally, 14 kV one phase resistive fault current limiter using multi YBCO thin films was constructed and it was possible to get satisfactory test results.