• 한국정보통신설비학회:학술대회논문집
• /
• 2008.08a
• /
• pp.379-383
• /
• 2008

Cognitive Radio (CR) technology is proposed for using the unused spectrum band efficiently because of the spectrum scarcity problems. Spectrum sensing is one of the most challenging issues in cognitive radio system. In this paper, we focus on the signal detection of WiBro system band. As most of the modulated signals can be treated as cyclostationary random process, we can detect the signal of the OFDM signals in WiBro system. OFDM symbols using WiBro system have several pilot subcarriers and periodic pilots have cyclostationary characteristic. To improve of the detection performance, we get diversity gain using multiple antennas.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.6 no.1
• /
• pp.287-304
• /
• 2012

Spectrum sensing is an important functionality for cognitive users to look for spectrum holes before taking transmission in dynamic spectrum access model. Unlike previous works that assume perfect knowledge of the SNR of the signal received from the primary user, in this paper we consider a realistic case where the SNR of the primary user's signal is unknown to both fusion center and cognitive radio terminals. A Kalman filter based adaptive Takagi and Sugeno's fuzzy system is designed to make the global spectrum sensing decision based on the observed energies from cognitive users. With the capacity of adapting system parameters, the fusion center can make a global sensing decision reliably without any requirement of channel state information, prior knowledge and prior probabilities of the primary user's signal. Numerical results prove that the sensing performance of the proposed scheme outperforms the performance of the equal gain combination based scheme, and matches the performance of the optimal soft combination scheme.

• Korean Journal of Child Studies
• /
• v.31 no.4
• /
• pp.139-157
• /
• 2010

This study investigated the cognitive process of 5-year-old children, with a particular focus on gender, monthly age, and their tendencies towards hyperactivity through the performance of the Cognitive Assessment System (CAS; Das & Naglieri, 1997). The children with tendencies towards hyperactivity were identified based on Conners Teachers' Rating Scale (CTRS). The subjects were 75 five-year-old children in Seoul and surrounding metropolitan areas. Data were analyzed by means of descriptive statistics, an independent sample t-test, Pearson's correlation coefficient, one-way ANOVA, and by K-mean cluster analysis. Our results were as follows : (1) The CAS and CTRS' sub-factors were correlated negatively, except the positive correlation between planning factor and hyperactivity factor. (2) Girls exhibited significantly higher CAS scores in planning & sequential processing than boys. (3) The upper monthly age group (68-71 months) showed significantly higher score in terms of planning than the lower monthly age group (60-63 months). (4) The CAS scores of the children with tendencies towards hyperactivity was lower than that of normal children. (5) The CAS profile of 5-year-old children was divided into 4 groups with distinctive characteristics by means of K-mean cluster analysis.

• Asia pacific journal of information systems
• /
• v.25 no.3
• /
• pp.500-518
• /
• 2015

The present research aims to identify the relationship between trust and distrust in an online business environment. To clarify the concepts, cognitive-affective personality system theory was introduced, through which five types of psychological units were proposed. In developing the research model based on the theory, technical effectiveness of the system and content truthfulness of the website were selected as two key stimuli for the coding process of online users. Trust and distrust were selected as mediating factors that generate consequent behaviors. Finally, purchase intention served as a final dependent variable. Assuming that trust and distrust emerge in psychologically different stages, this study hypothesized the mutual causal relationship between trust and distrust, indicating that the relationship will be determined by their contextual emphasis on each dimension. To validate, a survey was conducted with 307 online shopping mall users. Results show that stimuli were more significantly associated with trust. Trust is therefore a more cognitive construct than distrust, and the path from trust to distrust is stronger than that from distrust to trust. This finding implies that the cognitive aspect of trust is stronger than that of distrust. Distrust is rather more affectively emerging than trust.

• Korean Journal of Cognitive Science
• /
• v.16 no.3
• /
• pp.213-224
• /
• 2005

To develop a cognitive system with the flexibility and breadth of human reasoning, it's very important to construct a large scale knowledge base which includes commonsense knowledge as well as expert knowledge. This paper introduces a cognitive system which provides a commonsense reasoning for everyday physical phenomena using qualitative reasoning. It is difficult to apply previous qualitative reasoning to commonsense reasoning since it provides reasoning based on abstract concepts which are apart from everyday real world concepts. Our research provides commonsense reasoning based on sketches and real world concepts by integrating qualitative reasoning and general large scale Cyc knowledge base. Our system has been implemented and tested on various examples.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.3
• /
• pp.249-257
• /
• 2013

Recently, data traffic is significantly increased by high rate data service. As a result, radio spectrum is considered one of the most scarce and valuable resources for wireless communications. For the solution of this problem, cognitive radio(CR) has been proposed as an efficient means to opportunistic spectrum sharing between primary (licensed) users and cognitive radio users. In this paper, user selection scheme in CR networks is proposed for additional consideration of secondary system. The proposed user selection scheme mitigates interference to primary user by using orthogonal channel vectors while improves performance of secondary system. Simulation results show that the proposed scheme achieves 1.62bps/Hz higher average throughput of whole system than one of the existing scheme.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.1A
• /
• pp.66-74
• /
• 2007

Cognitive Radio system can guarantee available channel whenever, wherever by sensing surrounding channel condition. Therefore, there is a strict rule that have to use allocated channel efficiently without any interference from incumbent User. In this paper, to avoid interference which can occur during uplink transmission in CR system, we propose reporter using scheme which informs incumbent user's situation to adjacent cell to limit channel usage. Therefore, we can use more channel in each cell without interference. With this scheme we can expect better throughput using more channel in a large space with same resource.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.4B
• /
• pp.704-712
• /
• 2010

Recently, the lack of the frequency have been emerged due to the use of various wireless terminals. To find solutions for obtaining new frequency resources and for avoiding an interference, a cognitive radio technology have focused on as the new technology that can use the whitespace in TV broadcasting band. In this paper, the Cognitive Radio terminal system for whitespace in TV band is first introduced. The purpose of the CR terminal platform is to evaluate the feasibility of the unlicensed wireless service in the TV band. Then, we design and develop the software for Sensing MAC applied the cognitive radio terminal system. The developed Sensing MAC software based on IEEE 802.22 specification can be aware of using the whitespace in TV band that operates on cognitive radio terminal system. Finally, we have tested for evaluating the sensing MAC module.

• Journal of Korean Academy of Oral Health
• /
• v.41 no.2
• /
• pp.96-101
• /
• 2017

Objectives: The aim of this study was to investigate the relationship between cognitive function and occlusal status in elderly individuals. Methods: A total of 162 individuals aged 65 years and older, who attended the senior citizen center in Daegu city, were included after consent for participation in the study was obtained. The Korean version of the Mini-Mental State Examination (MMSE-K) was used to evaluate the level of cognitive function. Occlusal status was determined using the T-scan $III^{(R)}$ system. All collected data were analyzed by ${\chi}^2$ test, t-test, one way ANOVA, and linear regression analysis using SPSS version 23.0 for Windows. Results: There was a significant relationship between the cognitive function and the use of dentures. Individuals with posterior occlusal status had higher MMSE-K scores than those with anterior occlusal status. There was a positive correlation between the cognitive function and posterior occlusal force. Conclusions: These results suggest that occlusal status was associated with cognitive function in the elderly individuals. Active national policies to improve occlusal condition in the elderly population are needed.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.6
• /
• pp.2926-2945
• /
• 2017

In geo-location database oriented spectrum sharing system, the entire geographic area is divided into meshes to classify, store and delivery the cognitive information. In this paper, we propose a flexible polygon mesh division scheme to reduce the number of meshes. Hence the cognitive information can be reduced correspondingly. Besides, polygon mesh can approximate the real environment and reduce the error of cognitive information because the edges of polygon are selected along the boundaries of the networks. We have designed the polygon approximation algorithm and have analyzed the relation between the error and the number of polygon's edges. Finally, the simulation results are provided to verify the algorithm and analysis. The polygon mesh division scheme in this paper provides an efficient approach for cognitive information organization in database oriented spectrum sharing system.