• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.9
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• pp.1243-1249
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• 2018

In this paper, we propose a scheme that tunes the backoff period for enhancing the system throughput with estimating the number of devices in IEEE 802.15.4 slotted carrier sense multiple access with collision avoidance (CSMA/CA) networks. Since each device does not sense the channel always in IEEE 802.15.4 slotted CSMA/CA networks, a personal area network (PAN) coordinator is used to estimate the number of active devices. The PAN coordinator broadcasts an optimal backoff period for the estimated number of devices through a beacon frame. In order to estimate the number of devices in run time, a simple moving average filter is utilized. We show the performance of our proposed scheme in terms of the estimated number of devices and the system throughput. The simulation results show that our proposed scheme can obtain higher system throughput than the IEEE 802.15.4 standard.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.12
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• pp.955-963
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• 2017

Nowadays, fintech becomes the key technology of the mobile banking and payments. Financial market is moved to fintech-based non-face-to-face trade/payment from traditional face-to-face process in Korea. Core of this transition is the smartphones, which have several sensitive sensors for personal identifications such as fingerprint and iris recognition sensors. But it has some originated security risks by data path attacks, for instance, hacking and pharming. Multi-level certification and security systems are applied to avoid these threats effectively, while these protections can be cause of some inconvenience for non-face-to-face certifications and financing processes. In this paper, I confirmed that it have sensible differences correspond with the data connection paths such as WiFi networks and mobile communication networks of the smartphones, and I propose a gradual certification method which alleviates the inconvenience by risk-level definitions of the data-paths.

• Journal of Korea Game Society
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• v.11 no.6
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• pp.13-22
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• 2011

In the digital media environment, the convergence is in the progress creating the new service and contents by users and developing the new needs of users by the service and contents as well. Social games are actualizing the new meaning of convergence. shows not only a new situation blurring the boundary of work and leisure, labor and playing and private and public sector, but how meaningful it is to make connection of social interactions and social assets a solid network. As the most popular social game text, reveals how the personal connections and personal networks constructs the social capital by making the ritual communication more interesting and flexible to the social gamers.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.3
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• pp.18-26
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• 2011

Social network services whose users increase rapidly is the online services that reflect social network. They are used for various purposes such as strategy of election, commercial advertisement and marketing, educational information sharing and exchange of medical knowledge and opinions. These services make users form social networks with other users who have common interests and expand their relationships by releasing their personal information and utilizing other users' social networks. However, the social network services based on open and sharing of information raise various security threats such as violation of privacy and phishing. In this paper, we propose a group key management scheme and protocols using key rings to protect communication of small groups in social network services.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2008.10b
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• pp.479-491
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• 2008

A "task network" is a type of social network that consists of experts who exchange professional help and advice regarding executing tasks. In this study, we investigate the task network used within the IS department of a national bank in Korea. We identify how this network moderates the influence of computer-mediated communication (CMC) technology on an individual s task performance. Size, density, and centrality were measured as the characteristics of a personal task networks. Size equates to the total number of colleagues who work with a specific member for a certain project. Density is the ratio of the number of actual relationships to the total number of available relationships. Centrality defines whether an individual s position is in the exact center of whole network, and is measured by betweenness centrality, meaning the position one member holds between others in a network. Our findings conclude that the conditions - the larger the size of the task network, the smaller its density and the higher its level of centrality - lead to more benefits of using CMC media. Further, this positive effect of CMC is more noticeable when it provides synchronicity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.3
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• pp.623-628
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• 2009

The emergence of compact and low-power wireless communication sensors and actuators in the technology supporting the ongoing miniaturization of processing and storage allows for entirely the new kinds of embedded systems. These systems are distributed and deployed in environments where they may have been designed into a particular control method, and are often very dynamic. Collection of devices can communicate to achieve a higher level of coordinated behavior. Wireless sensor nodes deposited in various places provide light, temperature, and activity measurements. Wireless sensor nodes attached to circuits or appliances sense the current or control the usage. Together they form a dynamic and multi-hop routing network connecting each node to more powerful networks and processing resources. Wireless sensor networks are a specific-application and therefore they have to involve both software and hardware. They also use protocols that relate to both applications and the wireless network. Wireless sensor networks are consumer devices supporting multimedia applications such as personal digital assistants, network computers, and mobile communication devices. Wireless sensor networks are becoming an important part of industrial and military applications. The characteristics of modem embedded systems are the capable of communicating adapting the different operating environments. In this paper, We designed and implemented sensor network system which shows through host PC sensing temperature and humidity data transmitted for wireless sensor nodes composed wireless temperature and humidity sensor and designs sensor nodes using embedded system with the intention of studying USN.

• Journal of the Korea Convergence Society
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• v.5 no.1
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• pp.29-34
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• 2014

It appeared with the development of IT skills to help the social network SNS(Social Network Service) on the online form. Many people around the world and in the business environment changes is the emergence of social networks are bringing. And the rapid development of the idea, but are insignificant for the security threats that are used by many people in many companies, and social network services. In addition, although it is true that this connection is increased from the number of mobile machines to the development of M2M, that is not recognized for that vulnerability. To evaluate and identify vulnerabilities against security threats and countermeasures for the SNS access the social network on the M2M After looking for privacy and in the present.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.15-18
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• 2004

A high data rate Wireless Personal Area Networks (WPAN) system is a hot issue in wireless communication communities and being standardized. Multi-band Orthogonal Frequency Division Multiplexing (MB-OFDM) is one of the candidates for WPAN standard. In this paper, we discuss the PLCP (Physical Layer Convergence Protocol) structure for MB-OFDM. Also we evaluate the performance of two signal detection algorithms, which are the method of cross-correlation with the original preamble and the signed preamble. The latter has a low complexity with a little degradation.

• ETRI Journal
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• v.36 no.3
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• pp.374-384
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• 2014

To achieve high-speed (giga-bit) connectivity for short-range wireless multimedia applications, the millimeter-wave (mmWave) wireless personal area networks with directional antennas are gaining increased interest. Due to the use of directional antennas and mmWave communications, the probability of non-interfering transmissions increases in a localized region. Network throughput can be increased immensely by the concurrent time allocation of non-interfering transmissions. The problem of finding optimum time allocation for concurrent transmissions is an NP-hard problem. In this paper, we propose two enhanced versions of previously proposed multi-hop concurrent transmission (MHCT) schemes. To increase network capacity, the proposed schemes efficiently make use of the free holes in the time-allocation map of the MHCT scheme; thus, making it more compact.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.616-620
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• 2006

IEEE 802.15.4 is designed for low-rate wireless personal area networks (LR_WPAN) and it attempts to provide a low data rate, low power, low cost wireless networking on the device-level communication. In this paper, I have established a realistic environment for the effect of collision in nonbeacon-enabled mode and beacon enabled mode. The data throughput and delivery ratio are investigated as the performance metrics.