• The KIPS Transactions:PartC
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• v.14C no.7
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• pp.571-582
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• 2007

Vehicular ad-hoc networks is temporarily established through inter-vehicle communication without any additional infrastructure aids. It requires a immediate message propagation because it mainly deals with critical traffic information such as traffic accidents. The distance-based broadcast scheme is one of the representative broadcast schemes for vehicular ad-hoc network. In this scheme, a node to disseminate messages is selected based on a distance from a source node. However, a message propagation delay will be increased if the relay nodes are not placed at the border of transmission range of the source node. In particular, when the node density is low, the message propagation delay is getting longer. In this paper, we propose a time-window reservation based relay node selection scheme. A node receiving the alert message from the source node has its time-window and randomly selects its waiting time within the given time-window range. A proportional time period of the given time-window is reserved in order to reduce the message propagation delay. The experimental results show that the proposed scheme has shorter message propagation delay than the distance-based broadcast scheme irrespective of node density in VANET. In particular, when the node density is low, the proposed scheme shows about 26% shorter delay and about 46% better performance in terms of compound metric, which is a function of propagation latency and network traffic.

• KIPS Transactions on Software and Data Engineering
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• v.4 no.4
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• pp.151-160
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• 2015

Internet-of-Things(IoT) is the computing environment to provide valuable services by interacting with multiple devices, where diverse devices are connected within the existing Internet infrastructure and acquire context information by sensing. As the concern of IoT has been increased recently, most of the industries develop many IoT devices. And, many people are focused on the IoT application that is utilizing different technologies, which are sensor network, communication technologies, and software engineering. Developing on-ground IoT application is especially even more active in progress depending on increasing of on-ground IoT devices because it is possible for them to access dangerous and inaccessible situation. However, There are a few studies related IoT. Moreover, since on-ground IoT application, which is different from typical software application, has to consider device's characteristics, communication, and surround condition, it reveal challenges, decreasing reliability. Therefore, in this paper, we analyze reliability challenges related to maturity and fault tolerance, one of reliability attributes, occurring in developing on-ground IoT applications and suggest the effective solutions to resolve the challenges. To verify proposed the challenges and solutions, we show result that is applying the solutions to applications. By presenting the case study, we evaluate the effectiveness of applying the solutions to the application.

• International Journal of Highway Engineering
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• v.20 no.2
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• pp.45-55
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• 2018

PURPOSES : This study aims to survey and analyze the status of the design and completion documents output delivery system in public construction projects in order to assess the problems of the Ministry of Land, Infrastructure and Transport (MOLIT)'s electronic delivery system, with a focus on roads and rivers, and to offer improvement measures. METHODS : This study first surveys and analyzes laws and existing study trends with regard to the design and completion documents output delivery system in public construction projects. It further analyzes the status of the output delivery system in public construction projects, including roads, rivers, expressways, water resources, and railroads. In addition, a comparative analysis of the current electronic delivery system of MOLIT and Korea Expressway Corporation in the road field is conducted, and the problems and improvement measures for MOLIT's electronic output delivery system are presented. This study seeks to analyze problems and prepare improvement measures with regard to road and river public construction projects, as ordered by MOLIT's five regional offices. RESULTS : This study sought to prepare the electronic output delivery system with regard to public construction projects and present the analysis of its major problems and improvement measures in four categories: "the preparation of electronic design documents output delivery system improvement measures including inspection and delivery," "preparation of guidelines, systems, etc., concerning electronic design documents," "preparation of improvement measures for the construction project management system and electronic design document support tools", and "linking of MOLIT's electronic output delivery system with relevant agencies and the expansion thereof to local governments." CONCLUSIONS : This study analyzed the current status and problems of the MOLIT's electronic output delivery system in the field of road and river construction projects, and presented corresponding improvement measures. This study is expected to address the problems of the MOLIT's electronic output delivery system, and to provide the foundation for the preparation of an efficient electronic output delivery system for design and completion documents. In addition, this study is expected to boost the quality and utilization of the electronic design documents output, and to exchange, share, and link construction information among relevant agencies so as to prepare the foundation for sharing construction information.

• Journal of Korea Water Resources Association
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• v.47 no.8
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• pp.671-684
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• 2014

Change point analysis is a efficient tool to understand the fundamental information in hydro-meteorological data such as rainfall, discharge, temperature etc. Especially, this fundamental information to change points to future rainfall data identified by reasonable detection skills can affect the prediction of flood and drought occurrence because well detected change points provide a key to resolve the non-stationary or inhomogeneous problem by climate change. Therefore, in this study, the comparative study to assess the performance of the 3 change point detection skills, cumulative sum (CUSUM) method, Bayesian change point (BCP) method, and segmentation by dynamic programming (DP) was performed. After assessment of the performance of the proposed detection skills using the 3 types of the synthetic series, the 2 reasonable detection skills were applied to the observed and future rainfall data at the 5 rainfall gauges in South Korea. Finally, it was suggested that BCP (with 0.9 posterior probability) could be best detection skill and DP could be reasonably recommended through the comparative study. Also it was suggested that BCP (with 0.9 posterior probability) and DP detection skills to find some change points could be reasonable at the North-eastern part in South Korea. In future, the results in this study can be efficiently used to resolve the non-stationary problems in hydrological modeling considering inhomogeneity or nonstationarity.

• Journal of the Korean Association of Geographic Information Studies
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• v.22 no.4
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• pp.158-168
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• 2019

Korea Hydrographic and Oceanographic Agency(KHOA) carried out a research project named 'Marine Fisheries Infrastructure Construction and Technology Training for the Philippines' as part of the 1st Official Development Assistance(ODA) from 2015 to 2018. It is preparing for the 2nd ODA project which will begin in 2020. Besides, recently, the Philippines is paying attention to marine territory management and response capability due to problems such as the sea-level rise and coastal erosion caused by climate change. Therefore, before 2nd ODA to the Philippines, this study analyzed the vertical ocean model on the vertical datum in Korea and suggests the direction of development of the vertical ocean modeling system for the vertical datum in the Philippines using the observed data from the permanent tide station which was built by the Philippines ODA research project over the last four years. Moreover, as a pilot study, the Sulu Sea in the Philippines was selected and analyzed by harmonic analysis method. At each tide station, constants for correction had been computed. And the grid-based tidal model was constructed based on this study. As a result of the study, similar tidal characteristic were observed when the prediction and the measured tide were compared by applying the constants for correction between two station in the sea area with similar tidal level. These results could be used as basic data for the 2nd ODA to the Philippines, and contributed to construct and maintain a close cooperation and friendship between Korea and the Philippines.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.2
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• pp.55-68
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• 2014

Some infrastructure these days is usually constructed under the ground for it to not interfere the foot-traffic of pedestrians, and thus, it is difficult to visually confirm the accurate location of the site where the establishments must be buried. These technical difficulties increase the magnitude of the problems that could arise from over-reliance on the experience of the worker or a mere blueprint. Such problems include exposure to flood and collapse. This paper proposes a constructor-oriented visualization system via mobile gadgets in general construction sites with occluded structures. This proposal is consisted with three stages. First, "Stage of detecting manhole and extracting features" detects and extracts the basis point of occluded structures which is unoccluded manhole. Next, "Stage of tracking features" tracks down the extracted features in the previous stage. Lastly, "Stage of visualizing occluded constructions" analyzes and synthesizes the GPS data and 3D objects obtained from mobile gadgets in the previous stages. This proposal implemented ideal method through parallel analysis of manhole detection, feature extraction, and tracking techniques in indoor environment, and confirmed the possibility through occluded water-pipe augmentation in real environment. Also, it offers a practical constructor-oriented environment derived from the augmented 3D results of occluded water-pipings.

• Journal of the Korea Society of Computer and Information
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• v.10 no.5 s.37
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• pp.161-170
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• 2005

The Certificate Revocation List(CRL) or the Online Certificate Status Protocol(OCSP)has been used to validate certificates. However, the CRL cannot validate certificates in realtime because of the Time-Gap problem and the OCSP server overloads in a large scale secure system. In addition, the client cannot access a wired LAN until the client has been authenticated by the authentication server on the IEEE 802. 1x framework. Therefore, the client cannot validate the authentication server's certificate using a certificate validation server. Thus, the client cannot authenticate the authentication server in realtime. To solve these problems this paper designed a secure system that can protect the content of communications and authenticate users in realtime on a wireless LAN The designed certificate validation protocol was proved that the stability and efficiency of the system was very high, the result of the validation had the presence, the speed of the validation was not affected by the system scale, the number of authorities user must trust was reduced to one, and the overload of the validation server was Protected. And the designed user authentication and key exchange protocols were Proved that the mutual authentication was possible in realtime and the fact of the authentication could be authorized by the CA because of using the authorized certificates.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.50-55
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• 2000

The United States has had the superiority in the global trading market, and focused on the deregulation, decentralization, and often competitiveness. Also, it has adhered to pluralistic and uncoordinated systems for its various standard related activities. But with the WTO TBT entering into force late in 1990s, international standards have become more important in the global telecommunication market. So it has been recognized that the progressive standard activity would lead to keep the superiority of the nation in global telecommunication market. Specially, as the EU has been most active in building an agreed-upon technical standards among Its members, the US has faced with a serious problem that it has lack of agreed-upon infrastructure for standards. Hence, to keep the leadership in international telecommunications market, now it has been focusing on the national approach to standardization activities through the governmental support. For the implementation of above purposes, it amended 2 Acts. One is the Telecommunication Act of 1996. The other is NTTAA(National Technology Transfer and Advancement Art) of 1996, which was enacted according to the 1995 report "Standards, Conformity Assessment, and Trade into the 21 Century" by )TRC(National Research Council). In this paper, we analyse the US legal system in telecommunication standardization field including above arts and their Implementing plans. And we suggest the need for the active system of government in our telecommunication standardization.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.2
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• pp.73-86
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• 2018

The increase in the number of private automobiles has incurred various traffic problems. Globally, studies on MaaS(Mobility as a Service) has already been initiated to mobilize the use of public transportation in reducing private passenger cars in roads. This study aims to analyze the passenger's optimal route considering the transfer between different transportation modes through simulation, and analyze the effect of available route through the connected transportation modes. Sejong Special Self-Governing City was chosen as the study area due to its extensive transportation network. As a result of the analysis, the predominant obtainable route is derived either from using public transportation (i.e. bus and subway) only or by bicycle. However, it is also possible to use the car sharing and public bicycle to reach their final destination efficiently when paths that can be traversed were more scrutinized. When various transportation information and location-based services are introduced in smart phone applications, they can provide very useful information to passengers, and also promote social problems such as traffic congestion and environmental issues in the future.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.8-14
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• 2020

Recently, there was an increasing demand for an integrated access control system which is capable of user recognition, door control, and facility operations control for smart buildings automation. The market available door lock access control solutions need to be improved from the current level security of door locks operations where security is compromised when a password or digital keys are exposed to the strangers. At present, the access control system solution providers focusing on developing an automatic access control system using (RF) based technologies like bluetooth, WiFi, etc. All the existing automatic door access control technologies required an additional hardware interface and always vulnerable security threads. This paper proposes the user identification and authentication solution for automatic door lock control operations using camera based visible light communication (VLC) technology. This proposed approach use the cameras installed in building facility, user smart devices and IoT open source controller based LED light sensors installed in buildings infrastructure. The building facility installed IoT LED light sensors transmit the authorized user and facility information color grid code and the smart device camera decode the user informations and verify with stored user information then indicate the authentication status to the user and send authentication acknowledgement to facility door lock integrated camera to control the door lock operations. The camera based VLC receiver uses the artificial intelligence (AI) methods to decode VLC data to improve the VLC performance. This paper implements the testbed model using IoT open-source based LED light sensor with CCTV camera and user smartphone devices. The experiment results are verified with custom made convolutional neural network (CNN) based AI techniques for VLC deciding method on smart devices and PC based CCTV monitoring solutions. The archived experiment results confirm that proposed door access control solution is effective and robust for automatic door access control.