• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.3
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• pp.91-99
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• 2009

Development of high-speed Internet services and the increased supply of mobile devices have become the key factor for the acceleration of ubiquitous technology. WiBro system, formed with lP backbone network, is a MBWA technology which provides high-speed multimedia service in a possibly broader coverage than Wireless LAN can offer. Wireless telecommunication environment needs not only mobility support in Layer 2 but also mobility management protocol in Layer 3 and has to minimize handover latency to provide seamless mobile services. In this paper, we propose a fast cross-layer handover scheme based on signal strength prediction in WiBro environment. The signal strength is measured at regular intervals and future value of the strength is predicted by Exponential Smoothing Method. With the help of the prediction, layer-3 handover activities are able to occur prior to layer-2 handover, and therefore, total handover latency is reduced. Simulation results demonstrate that the proposed scheme predicts that future signal level accurately and reduces the total handover latency.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.7
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• pp.1597-1603
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• 2004

Recently many corporations are introducing web services which supports mutual smooth information exchange without depending on platform or programming language and new distributed computing environment based on U standard technology and internet standard protocol such as HTTP. However they are suffering difficulty in interoperability because of the problem of version inconsistency of standards supported by platforms that each vender offers. To solve these interoperability problem, although WS-I is progressing a consecutive standardization work by method of that offer Basic Profile and Usage Scenario, it is in the state that the domestic research connected with this is not sufficient yet. Accordingly, this treatise constructed interoperability Test framework by developing web services on the basis of different platform from books information retrieval services that can easily be come with and simulated and verified the interoperability by applying WS-I Basic Profile.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.3
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• pp.713-718
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• 2011

The advancement of computer network technology, coupled with the growing prevalence of Internet, is promoting ubiquitous computing, also called next-generation computing paradigm, as an important study field that many researches are joining and undergoing. In this paper, as the support technology for creating ubiquitous computer environment, we design the SSDLbased on XMLwhich is used for sending and receiving data by USN application service in a standardized form. A ref model, with no regard to different platforms or implementation languages, is proposed in our research on the basis of web service so that most of unspecified users could apply the standardized protocol designed for sensor data to real sensor data in various application environments based on the designed language. Therefore, through this research we can take advantage of acquisition of USN-based technology and technology draft related to application service.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.2885-2890
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• 2014

Localization of a sensor network node using machine learning has been recently studied. It is easy for Support vector machines algorithm to implement in high level language enabling parallelism. Raspberrypi is a linux system which can be used as a sensor node. Pi can be used to construct IP based Hadoop clusters. In this paper, we realized Support vector machine using python language and built a sensor network cluster with 5 Pi's. We also established a Hadoop software framework to employ MapReduce mechanism. In our experiment, we implemented the test sensor network with a variety of parameters and examined based on proficiency, resource evaluation, and processing time. The experimentation showed that with more execution power and memory volume, Pi could be appropriate for a member node of the cluster, accomplishing precise classification for sensor localization using machine learning.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.175-182
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• 2018

As Internet of things with a large number of nodes emerges, wireless-power communication networks (WPCN) based on a random access protocol needs to be investigated. In the random access-based WPCN, a terminal accessing later in given random access (RA) slots can harvest more energy before transmission and thus can transmit data with higher power and achieve higher throughput if the access is successful. On the basis of this property, the proposed random access control protocol gives the terminals priority and distinguishes the RA slots according to the priority level, so that a near terminal with access point allows to access preferentially other than a remote terminal. This operation decreases the throughput of near terminal and increases the throughput of remote terminal, and then, the doubly near-far problem in WPCN is resolved and the user fairness is improved. Results show that the proposed random access control improves both channel throughput and user fairness according to the priority level.

• The KIPS Transactions:PartC
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• v.10C no.7
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• pp.885-890
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• 2003

The Core Base Tree (CBT) multicast routing architecture is a multicast routing protocol for the internet. The CBT establishes a single shared tree for a multicast connection. The shared tree Is rooted at a center node called core. The location of the core may affect the cost and performance of the CBT. The core placement method requires the knowledge of the network topology In this Paper, we propose a simple and effective method for selecting the core. This method requires the distance vector information. in addition, we used results that calculated sample correlation coefficient. And then we select suitable routing algorithm according to member's arrangement states in muliticast group. we select core node that have minimum average cost or PIM-SM protocol is selected. The performance of this method is compared with several other methods by extensive simulations (i.e mean delay, maximum delay, and total cost). Our results shows that this method for Selecting Core is very effective.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.2014-2025
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• 2015

Wireless Sensor Networks (WSNs) are special network which has purpose of usage for gathering information of certain area and observing situation. WSNs consist of small nodes with sensing event such as temperature, movement or certain objects. The sensor has the capabilities to collect data and route data back to the sink. The sensors route data either to other sensors or back to a sink in one direction. That is, traditional WSNs communicate asymmetrically. However, under the new paradigm of the Internet of Things (IoTs) or Cyber Physical system (CPS), WSNs have potential to be used as important area. So, more research is necessary to communicate with each moving objects symmetrically in WSNs. In this paper, we proposed symmetric communication scheme among mobile objects in wireless sensor network. Simulation results show that our scheme is superior th the existing ones in terms of energy consumption and transmission success ratio.

• Journal of the Korea Society of Computer and Information
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• v.13 no.7
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• pp.181-188
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• 2008

Nowadays, WiMAX which provides internet service with a middle and low speed serves more function and is wider than Wi-Fi. While they solve the security risks as subscribers do handover by subscriber's re-certification procedure as the Network range is getting wider, there are more security problems making the problems of electric-power consumption and delay. This paper suggests a handover mechanism which simplify the subscriber's re-certification procedure and prevents a security problem as doing handover for solving the problem of delay and the rate of processing. The mechanism can cooperate with PKI structure to increase flexibility and security and minimize network re-entry procedure or re-certification procedure by providing continual service. As a result. the mechanism's throughput as the number of subscribers is lower than IEEE 802.16e and the mechanism proves that it is secure from the attack of man-in-the-middle and reply as doing handover.

• Journal of the Korea Society of Computer and Information
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• v.13 no.7
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• pp.213-220
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• 2008

In a distributed processing environment composed of many independent systems connected by networks, it is very important and difficult to make time synchronization between the systems. Especially in the USN environment the time synchronization is still more difficult than in general distributed processing environment because energy is limited and communication function is feeble. Even though of these difficulties, the USN environment requires higher precision of time synchronization. We of the typical applications requesting very strict time synchronization in USN is TDMA MAC. This paper proposes and evaluates a new time synchronization protocol HTSP(Hierarchical Time Synchronization Protocol) which is an advanced version of the FTSP(Flooding Time Synchronization Protocol) published recently. The time synchronization precision of the HTSP is equal to that of the FTSP, but the energy consumption of the HTSP is lower than that of the FTSP owing to the reduced number of broadcast messages. The simulation results show that the energy consumption of the HTSP is only 74% of that of the FTSP.

• Journal of Digital Convergence
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• v.13 no.5
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• pp.219-226
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• 2015

OTP(One Time Password) is for user authentication of Internet banking and users should carry their security card or OTP generator to use OTP. If they lost their security card or OTP generator, there is at risk for OTP leak. This paper suggests a new User Authentication Framework using personal health information from diverse technology of u-Health. It will cover the problem of OTP loss and illegal reproduction A User Authentication Framework is worthy of use because it uses various combinations of user's physical condition which is inconstant. This protocol is also safe from leaking information due to encryption of reliable institutes. Users don't need to bring their OTP generator or card when they use bank, shopping mall, and game site where existing OTP is used.