• Journal of Communications and Networks
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• v.4 no.4
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• pp.336-343
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• 2002

A major challenge for next generation mobile communication is capturing the system architecture’s complexity with all its internal and external dependencies. Seamless integration of heterogeneous environments in all system parts is a key requirement. Moreover, future systems have to consider the different evolution cycles of individual system parts. Among those, services are expected to change the fastest. With respect to these considerations, we propose an overall architecture for next generation mobile communication systems. It covers all system parts from wireless transmission to applications including network and middleware platform. Our approach focuses on adaptability in terms of recon- figurability and programmability to support unanticipated system evolution. Therefore, we consider abstraction layers which consist of adaptable cooperating components grouped by open platforms rather than rigid system layers. In addition to that, we introduce cross-layer cooperation allowing an efficient use of the available resources. Specific scenarios illustrate the feasibility of our approach.

• Journal of Digital Convergence
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• v.3 no.2
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• pp.59-71
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• 2005

Nowadays, it is not unusual to buy and sell goods, service and information through the internet. As a result of rapid development of Information Technology(IT), business through the internet can be done without time Limitations, place restrictions and product limitations. However, internet shopping has been restricted a lot due to the need for physical connections to the internet in order to search for information and order what we want, and this is one of the biggest problems to the busy people of the 21st century. Therefore it is very natural to use mobile phones to do shopping through wireless internet easily and conveniently whilst on the move. The purpose of this research is to find out characteristics of mobile phone users in UK, Japan and Korea and 1) main aims of the mobile phone use, 2) reasons for ease of use of mobile phones, 3) favourite types of a mobile phone, 4) psychological stability of mobile phone users, 5) problems of mobile phone use, 6) purchase goods/services via mobile phone in the future. The research method used is questionnaire survey The research results will suggest how to take actions to promote mobile commerce in the future.

• Journal of Korea Society of Digital Industry and Information Management
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• v.11 no.4
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• pp.61-68
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• 2015

MANET has various vulnerability in wireless network and is more vulnerable in security because central management is not performed. In particular, routing attack may decrease performance of the overall network because the mobile node acts as a router. In this paper, we proposed authentication technique for improving the reliability of the network by increasing the integrity of the routing control packet and blocking effectively attacks that occur frequently in the inside. The proposed technique is consisted of two authentication methods of ZCN and N2N. ZCN authentication method is to elect CA nodes and monitor the role of the CA nodes. N2N authentication method is for an integrity check on the routing packets between nodes. Index key is determined by combining the hop count value to shared key table issued from CA in order to increase the robustness of the internal attack. Also, the overhead of key distribution was reduced by distributing a shared key to nodes certificated from CA. The excellent performance of the proposed method was confirmed through the comparison experiments.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.1
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• pp.57-66
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• 2019

Drones, which are used in various fields, are vulnerable to various security threats such as physical deodorization attacks and information leakage attacks because they operate in an unmanned environment and use wireless communication with weak security. In particular, research is needed to prevent damages such as leakage of stored information and unauthorized use due to illegal drone deodorization. In this paper, we propose a context - aware drone control mechanism that protects stored internal information and prevents unauthorized use when the drones are illegally deactivated. We also demonstrated the feasibility of the proposed mechanism as a prototype implementation and experiment.

• Journal of the Korea Convergence Society
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• v.6 no.4
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• pp.1-7
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• 2015

This study is a case study of the research study and education with high school students of natural sciences. Recent development of the Internet of Things (IoT) based on the subject of various studies exist. This study is one of the most portable communication devices of these infancy, yet students were easy to define the molding process of contacting a pager that can go along way in making research topics. We called a pager. Today, it is given a large and complex smart mobile communication devices that can be used for big data. Prior pagers are taught the meaning of the first mobile communication means in our lives were given device. The internal structure is relatively simple and is thought to function relatively simple, just suitable as a teaching practices of high school students with an interest in science and engineering universities. This study can see all of the mechanical, electronic information contents of the radio pager in a relatively simple analysis of the injection molding ONE CAVITY analysis. Furthermore, the students also rated good educational practices that give meaning to remind the convergence training on mass production and process automation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.11
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• pp.1060-1073
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• 2013

In this paper, we present a cluster-based routing scheme for efficiently delivering data to group mobile users by extracting and clustering mobile user group simply from beacon message information in wireless ad-hoc networks. First, we propose an online-clustering mechanism that uses a local neighbor table on each node by recursively transmitting to neighbor nodes, and forms a group table where a set of listed nodes are classified as group members, without incurring much overhead. A node that appears the most frequently from neighbor tables throughout the network is selected as the cluster-head node, serving as a data gateway for the intra-cluster. Second, we design an inter-cluster routing that delivers data from stationary data sources to the selected cluster-head node, and a intra-cluster routing to deliver from the cluster-head node to users. Simulation results based on ns-2 in the ad-hoc networks consisting of 518 stationary nodes and 20 mobile nodes show that our proposed clustering mechanism achieves high clustering accuracy of 96 % on average. Regarding routing performance, our cluster-based routing scheme outperforms a naive one-to-one routing scheme without any clustering by reducing routing cost up to 1/20. Also, our intra-cluster routing utilizing a selected cluster-head node reduces routing cost in half as opposed to a counterpart of the intra-cluster routing through a randomly-selected internal group member.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.253-256
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• 2009

This paper describes a core generator (FFT_Core_Gen) which generates Verilog HDL models of 8 different FFT/IFFT cores with $N=64{\times}2^k$($0{\leq}k{\leq}7$ for OFDM-based communication systems. The generated FFT/IFFT cores are based on in-place single memory architecture, and use a hybrid structure of radix-4 and radix-2 DIF algorithm to accommodate various FFT lengths. To achieve both memory reduction and the improved SQNR, a conditional scaling technique is adopted, which conditionally scales the intermediate results of each computational stage, and the internal data and twiddle factor has 14 bits. The generated FFT/IFFT cores have the SQNR of 58-dB for N=8,192 and 63-dB for N=64. The cores synthesized with a $0.35-{\mu}m$ CMOS standard cell library can operate with 75-MHz@3.3-V, and a 8,192-point FFT can be computed in $762.7-{\mu}s$, thus the cores satisfy the specifications of wireless LAN, DMB, and DVB systems.

• Earthquakes and Structures
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• v.19 no.1
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• pp.29-44
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• 2020

The effectiveness and the sensitivity of a Wireless impedance/Admittance Monitoring System (WiAMS) for the prompt damage diagnosis of two single-storey single-span Reinforced Concrete (RC) frames under cyclic loading is experimentally investigated. The geometrical and the reinforcement characteristics of the RC structural members of the frames represent typical old RC frame structure without consideration of seismic design criteria. The columns of the frames are vulnerable to shear failure under lateral load due to their low height-to-depth ratio and insufficient transverse reinforcement. The proposed Structural Health Monitoring (SHM) system comprises of specially manufactured autonomous portable devices that acquire the in-situ voltage frequency responses of a network of twenty piezoelectric transducers mounted to the RC frames. Measurements of external and internal small-sized piezoelectric patches are utilized for damage localization and assessment at various and increased damage levels as the magnitude of the imposed lateral cycle deformations increases. A bare RC frame and a strengthened one using a pair of steel crossed tension-ties (X-bracing) have been tested in order to check the sensitivity of the developed WiAMS in different structural conditions since crack propagation, damage locations and failure mode of the examined frames vary. Indeed, the imposed loading caused brittle shear failure to the column of the bare frame and the formation of plastic hinges at the beam ends of the X-braced frame. Test results highlighted the ability of the proposed SHM to identify incipient damages due to concrete cracking and steel yielding since promising early indication of the forthcoming critical failures before any visible sign has been obtained.

• Journal of the Korean Society of Physical Medicine
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• v.15 no.1
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• pp.77-84
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• 2020

PURPOSE: This study compared the activities of the trunk muscles during crutch walking to determine which of the crutch length measurements is most beneficial. METHODS: Twenty young women volunteered to participate in this study. After adjusting crutch length, the participants performed a three-point walking with nondominant leg limited in weight bearing. This study used six crutch length measurements: (1) Height-40.6cm, (2) Height'.77, (3) Olecranon-to-finger length, (4) Axillary-toheel length, (5) Arm-span length-40.6cm, and (6) Arm-span length'.77. The EMG activities of the internal oblique (IO), rectus abdominis (RA), multifidus (MF), and erector spinae (ES), muscles on the weight bearing side were monitored using wireless surface EMG. RESULTS: The EMG activities of the RA and ES appeared to be significantly different among the crutch length measurements (p<.05). The post-hoc test showed that the 'Arm-span length-40.6cm' was significantly greater in the RA activity when compared to the 'Height'.77' and 'Axillary-to-heel length' measurements, and in the ES activity when compared to 'Height'.77' measurements. Furthermore, IO/RA and MF/ES ratios showed significant differences among the crutch length measurements (p<.05). In the post-hoc test, significant difference was observed between 'Olecranon-to-finger length' and 'Arm-span length-40.6cm' for the IO/RA ratio, and between 'Height'.77' and 'Olecranon-to-finger length' and between 'Height'.77' and 'Arm-span length-40.6cm' measurement for the MF/ES ratio. CONCLUSION: These findings suggest that the 'Height'.77' measurement is relatively advantageous to optimize the activities of trunk muscles during the crutch walking, and allow simple measurements of the crutch length.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.7
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• pp.1401-1410
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• 2017

Cryptographic synchronization which synchronizes internal state of cryptographic algorithm and ciphertext stream between an encryptor and a decryptor affects the quality of secure communication. If there happens a synchronization loss between a transmitter and a receiver in a secure communication, the output of the receiver is unintelligible until resynchronization is made. Especially, in the secure communication on a wireless channel with high BER, synchronization performance can dominate its quality. In this paper, we proposed a novel and noise robust synchronization signal generation method as well as its detection algorithm. We generated a synchronization signal in the form of a masking structure based on the maximal length sequence, and developed a detection algorithm using a correlation property of the maximal length sequence. Experimental results have demonstrated that the proposed synchronization signal outperforms the conventional concatenated type synchronization signal in a noisy environment.