• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.12
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• pp.1298-1306
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• 2014

In this paper, we use the ECMA-392 standard, the first cognitive radio networks to meet the demand for IT services in the ship. And, we investigate about the conflicts of devices that support multi-hop network based on the ECMA-392. Therefore, we propose the resolution scheme of CRP reservation conflicts to solve this. The current CRP reservation approaches does not solve the CRP reservation conflicts of ECMA-392 between devices that move at a distance of three hops. Therefore, it is not possible to guarantee the QoS of real time services such as multimedia streaming. So, we provide a new CRP reservation scheme to avoid conflict through a new 2-hop CRP Availability IE and the change of CRP Control field. From the simulation results, we know that the proposed method of 3 hops CRP reservation conflicts resolution improves the throughput of device.

• Journal of Korea Water Resources Association
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• v.51 no.8
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• pp.703-711
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• 2018

Water distribution system (WDS) pipe bursts are caused from excessive pressure, pipe aging, and ground shift from temperature change and earthquake. Prompt detection of and response to the failure event help prevent large-scale service interruption and catastrophic sinkhole generation. To that end, this study proposes a improved Western Electric Company (WECO) method to improve the detection effectiveness and efficiency of the original WECO method. The original WECO method is an univariate Statistical Process Control (SPC) technique used for identifying any non-random patterns in system output data. The improved WECO method multiples a threshold modifier (w) to each threshold of WECO sub-rules in order to control the sensitivity of anomaly detection in a water distribution network of interest. The Austin network was used to demonstrated the proposed method in which normal random and abnormal pipe flow data were generated. The best w value was identified from a sensitivity analysis, and the impact of measurement frequency (dt = 5, 10, 15 min etc.) was also investigated. The proposed method was compared to the original WECO method with respect to detection probability, false alarm rate, and averaged detection time. Finally, this study provides a set of guidelines on the use of the WECO method for real-life WDS pipe burst detection.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.89-97
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• 2012

In recent years, efficient energy management technologies are required, as environmental problems have emerged worldwide. In response to this, smart home services focused on efficient energy management technology seems to be emerging. And the integration of technology of user-oriented real-time energy monitoring and control systems is required. In this paper, we present a location-based green home service using smart phones for efficient energy management in a house. We design a green home network system to apply the green home service, and implement an integrated gateway system which connects and controls each appliance in a house. We develop appliance control services and indoor location services on smart phones, and determine whether user's occupancy of each room by measuring the location according to the variation of signal strength. In order to evaluate the performance of the energy savings, we have set up the scenarios of energy usage pattern and have compared the energy variation resulting from the application of the indoor location services with smart meters. A comparison of energy usage demonstrated that the energy saving of a house with the proposed location-based green home service was down up to 30%.

• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.34-41
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• 2011

At present wireless internet access service is available through the 3G network, mobile WiMAX and WiFi anytime and anywhere. In this environment where there are various networks, users should be able to select specific networks depending on different situations. And it is necessary to provide mobility support between homogeneous and between heterogenous networks. Given this situation, the many proposals have been presented to link 3G, which has the largest service area among various networks, with mobile WiMAX(IEEE 802.16e), or with WiFi(IEEE 802.11). But, recently, with the increasing volume of wireless internet use and wireless internet data, due to the advents of net-book, e-book and smart phone, the service area of WiFi and mobile WiMAX has rapidly expanded. Especially, the availability of real-time application such as internet phone has led to the relative shrinking of the proportion of 3G mobile communication network giving conventional voice service, and enlargement of those of wireless internet access networks like WiFi and mobile WiMAX. This paper suggests a handover scheme based on PMIPv6, whitch support mobility between WiFi and mobile WiMAX, and minimizes handover delay. In this scheme, the mobile node has a dual stack structure composed of two interfaces-WiFi and mobile WiMAX. Since WiFi dose not support mobility, it is suggested that the mobile node have the capacity to deal with handover signaling between gateway in case of handover between homogeneous networks. This handover scheme, suggested comparing with current handovers between homogeneous networks, has proved, in its analytic evaluation, to be able to reduce handover, transmission, and signaling overhead.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.1-11
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• 2020

As an important basic building block of the smart grid environment, smart meter provides real-time electricity consumption information to the utility. However, ensuring information security and privacy in the smart meter data aggregation process is a non-trivial task. Even though the secure data aggregation for the smart meter has been a lot of attention from both academic and industry researchers in recent years, most of these studies are not secure against internal attackers or cannot provide data integrity. Besides, their computation costs are not satisfactory because the bilinear pairing operation or the hash-to-point operation is performed at the smart meter system. Recently, blockchains or distributed ledgers are an emerging technology that has drawn considerable interest from energy supply firms, startups, technology developers, financial institutions, national governments and the academic community. In particular, blockchains are identified as having the potential to bring significant benefits and innovation for the electricity consumption network. This study suggests a distributed, privacy-preserving, and simple secure smart meter data aggregation system, backed up by Blockchain technology. Smart meter data are aggregated and verified by a hierarchical Merkle tree, in which the consensus protocol is supported by the practical Byzantine fault tolerance algorithm.

• Journal of Korean Society of Transportation
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• v.32 no.6
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• pp.567-578
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• 2014

The study suggested a method to improve analysis accuracy such that the interactive effects of transportation changes between outside and inside of sub-areas were sequentially considered in the analysis by linking a macroscopic network analysis and a microscopic traffic simulation. A dynamic O/D estimation method was developed for practical implement of sub-area microscopic simulation analysis by using the results of macroscopic network analysis, the results of selected link analysis at the cordon line of the sub-area, departure time data of household travel survey, timely observed traffic volume data at the cordon. This estimated dynamic O/D for the sub-area made it possible to analyze traffic phenomena in details. Various detailed phenomena such as traffic queues, delay at intersection, and conflicts between vehicles, which is impossible to be grasped through a macroscopic analysis, can be analyzed with the dynamic microscopic traffic analysis. Through implementing an empirical study and validation, the study provided a reference result about accuracy of a microscopic traffic simulation of a sub-area to help its application for real transportation policy analysis.

• Science of Emotion and Sensibility
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• v.5 no.2
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• pp.29-34
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• 2002

Our previous studies investigated that narrow field of view (FOV : 50˚) and slow navigation speed decreased the frequency of occurrence and severity of cybersickness during immersion in the virtual reality (VR). It would cause a significant reduction of cybersickness if it were provided cybersickness alleviating virtual environment (CAVE) using biofeedback method whenever subject underwent physiological agitation. For verifying the hypothesis, we constructed a real-time cybersickness detection and feedback system with artificial neural network whose inputs are electrophysiological parameters of blood pulse volume, skin conductance, eye blink, skin temperature, heart period, and EEG. The system temporary provided narrow FOV and decreased speed of navigation as feedback outputs whenever physiological measures signal the occurrence of cybersickness. We examined the frequency and severity of cybersickness from simulator sickness questionnaires and self-report in 36 subjects. All subjects experienced VR two times in CAVE and non-CAVE condition at one-month intervals. The frequency and severity of cybersickness were significantly reduced in CAVE than non-CAVE condition. Virtual environment of narrow FOV and slow navigation provided by electrophysiological features based artificial neural network caused a significant reduction of cybersickness symptoms. These results showed that efficiency of a cybersickness detection system we developed was relatively high and subjects expressed more comfortable in the virtual navigation environment.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.1
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• pp.7-13
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• 2018

In the current study, we proposed an optimized brain-computer interface (BCI) which employed blind source separation (BBS) approach to remove noises. Thus motor imagery (MI) signal and steady state visual evoked potential (SSVEP) signal were easily to be detected due to enhancement in signal-to-noise ratio (SNR). Moreover, a combination between MI and SSVEP which is typically can increase the number of commands being generated in the current BCI. To reduce the computational time as well as to bring the BCI closer to real-world applications, the current system utilizes a single-channel EEG signal. In addition, a convolutional neural network (CNN) was used as the multi-class classification model. We evaluated the performance in term of accuracy between a non-BBS+BCI and BBS+BCI. Results show that the accuracy of the BBS+BCI is achieved $16.15{\pm}5.12%$ higher than that in the non-BBS+BCI by using BBS than non-used on. Overall, the proposed BCI system demonstrate a feasibility to be applied for multi-dimensional control applications with a comparable accuracy.

• Journal of the Korean Association of Geographic Information Studies
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• v.7 no.2
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• pp.78-86
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• 2004

Recently GPS and mobile GIS technologies based on LBS(location based service) have played an important role as DSS(decision supporting system) for domestic forest fire extinguishment policies. In this study forest fire extinguishments information management system based on mobile GIS technique was designed to seize the exact location on wireless network so that it helps to guide the safe and efficient extinguishments affairs and provide the extinguishments environment toward ground fighting teams and the central forest government in real time. Moreover, possibly to operate this system, the foundation technologies by the name of '.gci' such as the spatial data compression method, the spatial data transmission method over wireless network and the spatial analysis interface on PDA should be mainly considered. Especially, in this study the spatial data compression method having high compression rate from 51% to 62% for each polygon, line, and point data, without the loss of data was developed.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.6
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• pp.41-50
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• 2011

This article is concerned with the technology to provide car driver the car's status which are composed of car trouble code in car engine and many sensors. In addition, it installs vehicle diagnostic programs on wireless communication's portable device, for example, Smart phone, PDA, PMP, UMPC. As a result, this is to provide car manager with many information of car sensors when we go to car maintenance. it can monitor relevant information on vehicle by portable device in real time, alert drivers with specific messages and also enable them to address abnormalities immediately. Moreover, the technology could help the drivers who perhaps don't know very well about their vehicles to drive safely and economically as well; the reason is because the whole system is composed of just Vehicle-information collecting device and personal wireless communication's portables and transfers the relating data to server computers through wireless network in order to handle information on vehicles. This technology make us monitor vehicle's running, failure and disorder by using wireless communication's portable device. Finally, this study system is composed of a lot of application to display us the car's status which get car's inner sensor information while driving a car.