• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.5
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• pp.2416-2432
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• 2017

In this paper, we investigate the security performance for cooperative networks over Nakagami-m fading channels. Based on whether the channel state information (CSI) of wiretap link is available or not, optimal relay selection (ORS) and suboptimal relay selection (SRS) schemes are considered. Also, multiple relays combining (MRC) scheme is considered for comparison purpose. The exact and asymptotic closed-form expressions for secrecy outage probability (SOP) are derived and simulations are presented to validate the accuracy of our proposed analytical results. The numerical results illustrate that the ORS is the best scheme and SRS scheme is better than MRC scheme in some special scenarios such as when the destination is far away from the relays. Furthermore, through asymptotic analysis, we obtain the closed-form expressions for the secrecy diversity order and secrecy array gain for the three different selection schemes. The secrecy diversity order is closely related to the number of relays and fading parameter between relay and destination.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.1
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• pp.269-281
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• 2014

Compared to hiding information into digital image, hiding information into digital text file requires less storage space and smaller bandwidth for data transmission, and it has obvious universality and extensiveness. However, text files have low redundancy, so it is more difficult to hide information in text files. To overcome this difficulty, Wang et al. proposed a reversible information hiding scheme using left-right and up-down representations of Chinese characters, but, when the scheme is implemented, it does not provide good visual steganographic effectiveness, and the embedding and extracting processes are too complicated to be done with reasonable effort and cost. We observed that a lot of traditional and simplified Chinese characters look somewhat the same (also called lookalike), so we utilize this feature to propose a novel information hiding scheme for hiding secret data in lookalike Chinese characters. Comparing to Wang et al.'s scheme, the proposed scheme simplifies the embedding and extracting procedures significantly and improves the effectiveness of visual steganographic images. The experimental results demonstrated the advantages of our proposed scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.1
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• pp.114-130
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• 2021

With the drastic growth of Information and Communication Technology (ICT) industry, global energy consumption is exponentially increased by mobile communications. The huge energy consumption and increased environmental awareness have triggered great interests on the research of dynamic distribution of cell user and traffic, and then designing the energy efficient cellular network. In this paper, we explore the temporal and spatial characteristics of human mobility and traffic distribution using real data set. The analysis results of cell traffic illustrate the tidal effect in temporal and spatial dimensions and obvious periodic characteristics which can be used to design Base Station (BS) dynamic with sleeping or shut-down strategy. At the same time, we designed a new Cell Zooming and BS cooperation mode. Through simulation experiments, we found that running in this mode can save about 35% of energy consumption and guarantee the required quality of service.

• 대한공업교육학회지
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• v.32 no.1
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• pp.134-152
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• 2007

This study deals with the development of computer program which can restrict students to access to the unallowable web sites during the Internet based class. Our suggested program can find the student's access list to the unallowable sites, display it on the teacher's computer screen. Through the limitation of the student's access, teacher can enhance the efficiency of class and fulfill his educational purpose for the class. The use of our results leads to the effective and safe utilization of the Internet as the teaching tools in the class. Meanwhile, the typical method is to turn off the LAN (Local Area Network) power in order to limit the student's access to the unallowable web sites. Our program has been developed on the Linux operating systems in the small network environment. The program includes following five functions: the translation function to change the domain name into the IP(Internet Protocol) address, the search function to find the active students' computers, the packet snoop to capture the ongoing packets and investigate their contents, the comparison function to compare the captured packet contents with the predefined access restriction IP address list, and the restriction function to limit the network access when the destination IP address is equal to the IP address in the access restriction list. Our program can capture all passing packets through the computer laboratory in real time and exactly. In addition, it provides teacher's computer screen with the all relation information of students' access to the unallowable sites. Thus, teacher can limit the student's unallowable access immediately. The proposed program can be applied to the small network of the elementary, junior and senior high school. Our research results make a contribution toward the effective class management and the efficient computer laboratory management. The related researches provides teacher with the packet observation and the access limitation for only one host, but our suggested program provides teacher with those for all active hosts.

• ETRI Journal
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• v.32 no.5
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• pp.665-675
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• 2010

Recent research on mobile Internet protocol television and digital right management (DRM) interconnections has focused on multimedia technologies designed to enhance content scalability and adaptive content distribution. However, due to the architectural and scalable limitations, recent systems are not flexible and securable with respect to their adaptive content distribution and protective policy management. Therefore, we propose a content protective multi-agent platform that provides secure multimedia services, correlation management, pattern-based management, and multi-source multi-use (MsMu)-based services. Our architecture, supported by DRM, lets us create a rich set of MsMu-based content protection and seamless multimedia services through the extension of one source multi-use (OsMu)-based content services. We have verified our platform, which provides scalable and securable services with a 17% lower service response time by using a testbed.

• Journal of the Korea Computer Industry Society
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• v.2 no.11
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• pp.1453-1464
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• 2001

Explosive growth of Internet populations results performance degradations of web service. Popular web sites cannot provide proper level of services to many requests, and such poor services cannot give user a satisfaction. Web caching, the remedy of this problem, reduces the amount of network traffic and gives fast response to user. In this paper, we analyze the characteristics of web cache traffics using traces of NLANR(National Laboratory for Applied Network Research) root caches and Education network cache in Seoul National University. Based on this analysis, we suggest a method of prefetching and we discuss the gains of our prefetching. As a result, we find proposed prefetching enhances hit rate up to 3%, response time up to 5%.

• Journal of Communications and Networks
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• v.14 no.1
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• pp.15-20
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• 2012

As Internet protocol and wireless communications have developed, the number of different types of mobile services has increased gradually. Existing priority-computing schemes cannot satisfy the dynamic requirements of supporting multiple services in future wireless communication systems, because the currently used factors, mainly user priority, are relatively simple and lack relevancy. To solve this problem and provide the desired complexity, dynamic behavior, and fairness features of 3G and beyond 3G mobile communication systems, this paper proposes a novel cross-layer dynamic integrated priority-computing scheme that computes the priority based on a variety of factors, including quality of service requirements, subscriber call types, waiting time, movement mode, and traffic load from the corresponding layers. It is observed from simulation results that the proposed dynamic integrated priority scheme provides enhanced performance.

• Proceedings of the Korea Contents Association Conference
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• 2008.05a
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• pp.547-550
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• 2008

Recently, changes in the environment of user-centric internet service such as blog, UCC and IPTV and ubiquitous computing based on web service are needed to high availability system platform. High availability system is to provide safe service continuously even if system failure occurs in clustering system at the network. And it is necessary to synchronize data for reliable service in high availability system. In this paper, I implement DRBD(Disk Replicated Block Device) which is synchronization technique for data of local disks in high availability system.

• International journal of advanced smart convergence
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• v.8 no.3
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• pp.115-122
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• 2019

Recent and ongoing discoveries of mycoviruses with new properties demand the development of an appropriate research infrastructure to analyze their evolution and classification. In particular, the discovery of negative-sense single-stranded mycoviruses is worth noting in genome types in which double-stranded RNA virus and positive-sense single-stranded RNA virus were predominant. In addition, some genomic properties of mycoviruses are more interesting because they have been reported to have similarities with the pathogenic virus family that infects humans and animals. Genetic information on mycoviruses continues to accumulate in public repositories; however, these databases have some difficulty reflecting the latest taxonomic information and obtaining specialized data for mycoviruses. Therefore, in this study, we developed a bioinformatics-based pipeline to efficiently utilize this genetic information. We also designed a schema for data processing and database construction and an algorithm to keep taxonomic information of mycoviruses up to date. The pipeline and database (termed 'mycoVDB') presented in this study are expected to serve as useful foundations for improving the accuracy and efficiency of future research on mycoviruses.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9B
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• pp.802-812
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• 2008

This paper proposes QoS Model which has tested and analyzed the capabilities of provisioning multimedia service in high speed Internet environment. We have tested quality measurement test for VoIP/MoIP, VoD, IPTV services and analyzed the level of QoS and QoS degradation by constructing test laboratory consisted of 46 subscribers which provided by 3 telecom operators. Besides, We propose QoS Model to apply for BcN application based on analysis result and prove proposed model by constructing test lab in KOREN environment. It is expected that telecom will use this results as a valuable information to construct All-IP network based on NGN(NGN:Next Generation Network).This paper proposes QoS Model which has tested and analyzed the capabilities of provisioning multimedia service in high speed Internet environment. It is expected that telecom will use this results as a valuable information to construct All-IP network based on NGN.