• Smart Media Journal
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• v.9 no.1
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• pp.9-15
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• 2020

Recently there have been increasing attempts to apply blockchains to businesses and public institutions. Blockchain is a distributed shared ledger with excellent transparency and security of data and through consensus algorithm, the same data can be shared to all nodes in order. In this paper, Modified PBFT which does not modify the PBFT consensus algorithm is proposed. MPBFT is able to tolerate Byzantine faults on a private blockchain on an asynchronous network. Even with the increase of participating nodes, the network communication cost can be effectively maintained. Modified PBFT takes into account the characteristics of an asynchronous network environment where node-to-node trust is guaranteed. In response to the client's request, PBFT performed the entire participation broadcast several times, but Modified PBFT enabled consensus and authentication through the 2 / N leader. By applying the Modified PBFT consensus algorithm, the broadcast process can be simplified to maintain the minimum number of nodes for consensus and to efficiently manage network communication costs.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.495-501
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• 2013

This paper describes a flexible wireless telemetering system using a mesoscale cantilever sensor, which is microfabricated with a patterned thin Ni-Cu foil on a resin substrate. The dynamic validation of the sensor has been conducted in a flow. The wireless telemetry is used to obtain data regarding the oscillating flows. It is shown that the sensor is nearly independent of the environmental temperature and is suitable for application to primary healthcare and diagnostic devices. It can be easily integrated with other modules for measuring physiological parameters, e.g., blood pressure, oxygen saturation, and heart rate, to increase the convenience and reliability of diagnosis. The precision and reliability of the sensor are also dependent on the design of the analog front-end and noise reduction techniques. It is shown that the present system's minimum interval between packet transmissions is ~16 ms.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.2
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• pp.51-58
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• 2017

Because of safety and security, Surveillance camera market is growing. Accordingly, Study on video recognition and tracking is also actively in progress, but There is a limit to identify object by obtaining the information of object identified and tracked. Especially, It is more difficult to identify multiple objects in open space like shopping mall, airport and others utilized surveillance camera. Therefore, This paper proposed adding object identification function by using RFID to existing video-based object recognition and tracking system. Also, We tried to complement each other to solve the problem of video and RFID based. Thus, through the interaction of system modules We propose a solution to the problems of failing video-based object recognize and tracking and the problems that could be cased by the recognition error of RFID. The system designed to identify the object by classifying the identification of object in four steps so that the data reliability of the identified object can be maintained. To judge the efficiency of this system, this demonstrated by implementing the simulation program.

• Journal of IKEEE
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• v.10 no.1 s.18
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• pp.30-39
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• 2006

The TCP protocol can provide some reliability using sliding window mechanism for data transmission, flow control, and congestion control. However, TCP has some limitations in that it has basically been designed solely for wired communication environments. If traditional TCP protocol is used also in wireless networks, the end-to-end data transmission performance degrades dramatically due to frequent packet losses caused by transmission errors and hand-offs. While there have been some research efforts on TCP enhancements considering the mobility of wireless communication devices, in this paper we propose a new method to improve the TCP performance by combining the Snoop and the Freeze-TCP methods. In the proposed scheme, the TCP end-to-end semantics is maintained and no changes of existing protocols in sending systems or in routers are required. It has the advantage of simple implementation because TCP code changes are limited to mobile devices for applying the Freeze-TCP and it requires only to add Snoop modules in base stations. Accordingly, the proposed scheme can operate well in the existing networks. Finally, in this study, we compared the performance of the proposed scheme with traditional TCP, other approaches through simulations using ns-2.

• The Transactions of the Korea Information Processing Society
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• v.6 no.8
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• pp.2158-2170
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• 1999

It has been required more reliable communication on processes and improvement of system performance as distributed systems using multicast protocol became widespread. In distributed environment maintaining data consistency through asynchronous execution of processes and coordinating the activities of them would occurs. This paper proposes a total ordering algorithm, TORMP, in order to resolve these problems. TORMP takes advantage of multicast protocol and uses an effective token passing method. It reduces a process delaying time before transmitting its message by multicasting a token simultaneously to every process that initiates the request of the message. Moreover, the processes receiving the token start multicasting the message at the same time, which causes to cut down the overall transmission dely. In case that one process sends a message, TORMP hardly uses the procedure of controlling for ordering. It gives fairly the right of sending messages to all processes in a group with utilizing vector clock. In TORMP, unlike other algorithms, the number of packets generated during ordering process does not depend on the number of processes.

• Journal of Astronomy and Space Sciences
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• v.13 no.2
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• pp.52-66
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• 1996

In this paper, we present the design methodology of KASCOM(KAIST satellite computer), the experimental on-board computer system of KITSAT-2. The design of the on-board computer system should consider the following constraints: operational throughput, fault tolerant input-output, low power, size, weight, and radiation hardness. KASCOM is designed to satisfy these constraints. This paper also presents the implementation and testing details of KASCOM. Finally, the in-orbit operational results are presented. The results show that about 2 SEU errors occur for the program memory(1Mbit SRAM) in a day, while 3.7 SEU errors occur for the data memory(4Mbit SRAM). This implies that high-integrated memories are more susceptible to the radiation environment than low-integrated memories.

• Journal of Internet Computing and Services
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• v.16 no.2
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• pp.7-17
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• 2015

To provide scalability, wireless sensor network has cluster-based architecture. Wireless sensor network can be implemented based on the IEEE 802.15.4 which is exploited in 2.4GHz ISM frequency band. Since this frequency band is used for various data communication, network status of wireless sensor networks frequently changes according to wireless environment. Thus, wireless channel selection to avoid reduction of transmission efficiency is required. This paper estimates network status using the information that a cluster-head collects in a cluster. Through objective function with throughput, RSSI level and reliability as input parameters, this paper proposes proper wireless channel selection. Simulation results show that the proposed method maintains transmission efficiency even though network status changes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.5
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• pp.39-43
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• 2020

In this paper, we propose the multi-channel interference cancellation algorithm for visible light communication (VLC) in smart building. The VLC system is communication technology using visible rays that come out in Light Emitting Diode (LED) device. It has energy curtailment effect and possible to use in ubiquitous network service applications. When a large number of users communicate indoors, the performance can be reduced due to channel interference. To remove interference, at the first, the minimum mean square error (MMSE) scheme as interference cancellation methods used, and then the successive interference cancellation (SIC) is applied to obtain additional diversity gain and improve interference cancellation performance. Indoor VLC channel model is employed. The performance is evaluated in terms of bit error rate (BER). From the simulation results, it is confirmed that the proposed scheme has better BER performance compared to the previous systems. As a result, the proposed interference cancellation improves the signal quality of VLC systems by effectively removing the channel noise. The results of the paper can be applied to VLC for smart building and general communication systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.193-197
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• 2015

Recently, the new issues for the safety and the information delivery system in the ship are raised. The deployment and the efficient algorithms of deploying the wireless sensor networks instead of using the built-in wired networks or the setup of the new wired networks is more desirable than the deployment of the wired networks in a ship after its final production since it can reduce the cost and the time of the brand new wired networks by reshaping some of the internal structure of the ship. In this paper, the shipboard signal propagation measurement system based on the signature sequence-three way slave mode are designed and its measureed data are analysed after measuring the signal propagation characteristics. Consequently, it is expected that the reliable and cost-effective signal measurement system with the three way algorithm for the deployment of the shipboard wireless networks can be achieved.

• The KIPS Transactions:PartD
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• v.8D no.6
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• pp.715-722
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• 2001

In recent years, we recognize a new paradigm in the development process：From object oriented development, to the development process which has focused on the use of standard components. In recent years a lot of research related to the component-based development has been done, especially in business domain. but still there are many open and unresolved problems in this area. such as established development process for a distributed environment, formal process, infrastructure for COTS, development and management tool considering maintenance to guarantee a proper treatment of components. It also required a service and an application integration for component. In this paper, we propose cooperative information systems (CIS) that supports component based development. It must address for component based systems to achieve their full potential. We identify a set of CIS organized 3-tier which is a presentation layer, business logic layer and data control layer. We also discuss the specific roles and activities for the layers. we also define the behavior and managed information for business logic layer as core level. As an illustration of the CIS, we present a successful considerations which is widely helpful to user when they make decision in component development and assemble. Also, we expect to component reusability and efficiency in business domain.