• Journal of Communications and Networks
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• v.8 no.4
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• pp.451-460
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• 2006

Since low earth orbit (LEO) satellite constellations have important advantages over geosynchronous earth orbit (GEO) systems such as low propagation delay, low power requirements, and more efficient spectrum allocation due to frequency reuse between satellites and spotbeams, they are considered to be used to complement the existing terrestrial fixed and wireless networks in the evolving global mobile network. However, one of the major problems with LEO satellites is their higher speed relative to the terrestrial mobile terminals, which move at lower speeds but at more random directions. Therefore, handover management in LEO satellite networks becomes a very challenging task for supporting global mobile communication. Efficient and accurate methods are needed for LEO satellite handovers between the moving footprints. In this paper, we propose a new seamless handover management scheme for LEO satellites (SeaHO-LEO), which utilizes the handover management schemes aiming at decreasing latency, data loss, and handover blocking probability. We also present another interesting handover management model called satellite mobility pattern based handover management in LEO satellites (PatHO-LEO) which takes mobility pattern of both satellites and mobile terminals into account to minimize the handover messaging traffic. This is achieved by the newly introduced billboard manager which is used for location updates of mobile users and satellites. The billboard manager makes the proposed handover model much more flexible and easier than the current solutions, since it is a central server and supports the management of the whole system. To show the performance of the proposed algorithms, we run an extensive set of simulations both for the proposed algorithms and well known handover management methods as a baseline model. The simulation results show that the proposed algorithms are very promising for seamless handover in LEO satellites.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.8
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• pp.667-673
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• 2014

In a smart shipyard area, it is possible to integrate a variety of ship modules from separate sites into a final ship construction by using mobile applications. In this paper, we proposed the LTE femtocell network configuration which is applicable to sub shipyard, the traffic exchange method with shipyard headquarter and offload method to separate the general traffic. We defined the mode change in a femtocell gateway for supporting offload for general traffic between the main server in shipyard headquarter and sub shipyard, the offload data managements and message definition. We check the transmitted/received message flow in the wireless link, and consider the performance of the proposed method using state the transition diagram. It is expected that our results can improve the productivity within a smart shipyard by mobile communications and LTE femtocell network.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.128-134
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• 2016

IoT devices including smart devices are connected with internet, thus they have security threats everytime. Particularly, IoT devices are composed of low performance MCU and small-capacity memory because they are miniaturized, so they are likely to be exposed to various security threats like DoS attacks. In addition, in case of IoT devices installed for a remote place, it's not easy for users to control continuously them and to install immediately security patch for them. For most of IoT devices connected directly with internet under user's intention, devices exposed to outside by setting IoT gateway, and devices exposed to outside by the DMZ function or Port Forwarding function of router, specific protocol for IoT services was used and the devices show a response when services about related protocol are required from outside. From internet search engine for IoT devices, IP addresses are inspected on the basis of protocol mainly used for IoT devices and then IP addresses showing a response are maintained as database, so that users can utilize related information. Specially, IoT devices using HTTP and HTTPS protocol, which are used at usual web server, are easily searched at usual search engines like Google as well as search engine for the sole IoT devices. Ill-intentioned attackers get the IP addresses of vulnerable devices from search engine and try to attack the devices. The purpose of this study is to find the problems arisen when HTTP, HTTPS, CoAP, SOAP, and RestFUL protocols used for IoT devices are detected by search engine and are maintained as database, and to seek the solution for the problems. In particular, when the user ID and password of IoT devices set by manufacturing factory are still same or the already known vulnerabilities of IoT devices are not patched, the dangerousness of the IoT devices and its related solution were found in this study.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.4
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• pp.41-52
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• 2008

Ubiquitous service environment is poor in reliability of connection and has a high probability that the intrusion and the system failure may occur. Therefore, in the environment, the capability of a system to collectively accomplish its mission in spite of active intrusions and various failure scenarios, that is, the survivability of services are needed. In this paper, we analyze the Jgroup/ARM framework that was developed in order to help the development of fault- tolerant Jini services. More importantly, we propose an intrusion-tolerant Jini service architecture to satisfy the security availability and quality of services on the basis of the analysis. The proposed architecture is able to protect a Jini system not only from faults such as network partitioning or server crash, but also from attacks exploiting flaws. It is designed to provides performance enough to show a low response latency so as to support seamless service usage. Through the experiment on a test-bed, we have confirmed that the architecture is able to provide high security and availability at the level that degraded services quality is ignorable.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.6
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• pp.584-593
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• 2012

This paper introduces an AVP (Automated Valet Parking) system which applies an autonomous driving concept into the current PAS (Parking Assistant System). The present commercial PAS technology is limited into vehicle. It means vehicle only senses and controls by and for itself to assist the parking. Therefore, the present PAS is restricted to simple parking events. But AVP includes wider parking events and planning because it uses infra-sensor network as well as vehicle sensor. For the realization of AVP, the commercial steering system of a compact vehicle was modified into steer-by-wire structure and various sensors like LRF (Long Range Finder) and camera were installed in a parking area. And local & global server decides where and when the vehicle can go and park in the testing area after recognized the status of environment and vehicle from those sensors. GPS solution was used to validate the AVP performance. More various parking situations, vehicles and obstacles will be considered in the next research stages based on these results. And we expect this AVP solution with more intelligent vehicles can be applied in a big parking lot like a market, an amusement park, etc.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.209-218
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• 2017

Healthcare services can be provided through a number of independent service platforms for measurement of vital signs, diagnosis and prevention of diseases, and Information and communication technology(ICT) such as internet and mobile are converged to provide health information to users at anytime and anywhere, and it is in the center of the IoT(Internet of things). Accordingly, in this paper, we designed IoT based urination management system and evaluate the performance. A low - power Zigbee network was constructed for the configuration of the urination management system. The implemented capacitive diaper sensor was operable for the duration of 2,000 hours. We also built a database server using Raspberry Pi, a tiny embedded device, and stored the collected data to verify the data through an Android-based mobile application. The proposed urination management system can be utilized not only for the older patients, but also for the infants.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.6
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• pp.72-81
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• 2013

In this paper, we propose the architecture and user interaction mechanism to implement N-Screen services on Multi-Vision System (MVS) that are not supported in existing systems. N-Screen services enable users to control the MVS displays through any of their devices and share contents among MVS displays and user's active-devices with service continuation at any location. We provide N-Screen interactive services on MVS by introducing N-Screen interaction & session management server and agent. Furthermore, we present some examples of the protocols such as application launching, user interaction for service control and visualcasting to support N-Screen services. In addition, we explain the N-Screen service scenarios for providing split sessions on user's active-devices and launching metadata content on any of his devices at any location supported by these protocols. The simulation result demonstrates the feasibility and performance improvement of the proposed visualcasting mechanisms.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.1-7
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• 2013

Big data management is becoming increasingly important in both industry and academia of information science community. One of the important categories of big data generated from software systems is log data. Log data is generally used for better services in various service providers and can also be used as information for qualification. This paper presents a big data management architecture specialized for log data. Specifically, it provides the aggregation of log messages sent from multiple clients and provides intelligent functionalities such as analyzing log data. The proposed architecture supports an asynchronous process in client-server architectures to prevent the potential bottleneck of accessing data. Accordingly, it does not affect the client performance although using remote data store. We implement the proposed architecture and show that it works well for processing big log data. All components are implemented based on open source software and the developed prototypes are now publicly available.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.111-117
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• 2006

Developing a home network and a ubiquitous infrastructure requires various communication techniques and devices with more advanced hardware. With this development, increasing realtime access to multimedia data results in rapid degradation of qualify for multimedia playback. This paper presents a traffic allocation technique based on MPP(Media Preference for Presentation) that can steadily maintain multimedia playback quality by adaptively allocating streaming traffic requested from clients with different playback performances. Media preference is defined in accordance with content popularity and playback performance of client devices. Through experiments when requested stream data exceeds processing ability of a midea server, the proposed allocation technique shows 10% quality improvement comparing to the system without applying the proposed allocation technique.

• Journal of Digital Contents Society
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• v.10 no.4
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• pp.649-657
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• 2009

Usually, The data transmission processing efficiency of the distributed system running on high speed networks depends on the system architecture and the data transmission processing system. In order to secure the real-time rate and the system reliability, the real-time distributed simulation system on the distributed environment has tried to satisfy the performance required by the data transmission processing system. However, the client/server-based data transmission processing system in the real-time simulation system has been difficult to satisfy the system stability, extensibility and maintenability, especially when system changes. So, it is natural to study another improved data transmission processing system to solve the problems at the existing real-time simulation system. After analyzing the existing real-time simulation system, this paper will propose the improved real-time data transmission system by using Software Design Pattern, which enhances extensibility, interoperability, reusability and maintenability of the system.