• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.2
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• pp.550-565
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• 2018

Cognitive radio technology is still the key technology of future mobile communication systems. Previous studies have focused on improving spectrum utilization and less energy consumption. In this paper, we propose an Overhead Reduced Scheme (ORS) for green cooperative spectrum sensing. Compared to traditional cooperative sensing scheme, ORS scheme divides the sensing time into three time slots and selects the best multi-mode user to report decisions. In consideration of reporting channel deviation, we derive closed-form expressions for detection probability and false alarm probability of ORS scheme based on Rayleigh fading channel. Simulation results show that ORS scheme can improve the perception accuracy while reducing the perceived delay and energy consumption in the process of perception, so as to realize the green communication.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.5
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• pp.2357-2380
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• 2019

In this paper, we investigate the impact of hardware impairments (HWIs) on the performance of a downlink massive MIMO system. We consider a single-cell system with maximum ratio transmission (MRT) as precoding scheme, and with all the HWIs characteristics such as phase noise, distortion noise, and amplified thermal noise. Based on the system model, we derive closed-form expressions for a typical user data rate under two scenarios: when a common local oscillator (CLO) is used at the base station and when separated oscillators (SLOs) are used. We also derive closed-form expressions for the downlink transmit power required for some desired per-user data rate under each scenario. Compared to the conventional system with ideal transceiver hardware, our results show that impairments of hardware make a finite upper limit on the user's downlink channel capacity; and as the number of base station antennas grows large, it is only the hardware impairments at the users that mainly limit the capacity. Our results also show that SLOs configuration provides higher data rate than CLO at the price of higher power consumption. An approach to minimize the effect of the hardware impairments on the system performance is also proposed in the paper. In our approach, we show that by reducing the cell size, the effect of accumulated phase noise during channel estimation time is minimized and hence the user capacity is increased, and the downlink transmit power is decreased.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.267-270
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• 2005

An RFID patch antenna for metallic object has been designed. The effects of variation of distance between the tag antenna and ground of the antenna have been studied. Various dielectric constants, thickness, permittivity, width of transmission line and length of transmission line have been used to design the better tag antenna for metallic object.

• 한국공간정보시스템학회:학술대회논문집
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• 2003.11a
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• pp.98-103
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• 2003

환경이 하나의 도시계획 요소로 작용하고 있는 상황에서 기후요소인 바람을 도시계획시 고려하여, 기존의 도시계획과는 다른 관점을 제시해 주는 분석시스템이다. 기상자료 및 해당 도면의 속성자료를 토대로 GRID분석과 Kriging보간 알고리즘을 구현하여 대상지역의 온도분포 및 바람흐름, 바람통로를 찾아내고자 하였다. 기후지도를 이용하여 주요 바람길을 파악할 수 있으며 대상지내 신선한 공기가 시작되는 녹지들을 추출하여 녹지계획의 핵으로 정한다. 녹지의 핵으로부터 각각의 녹지로 연결되는 바랑의 길을 분석하여 도시계획업무추진 시 바랑통로가 단절된 곳이나 단절된 계획이 있는 곳을 파악한다. 그리고 바람통로를 위해서 보존할 곳과 올바른 바람을 유도할 곳 등을 생성한다. 또한 본 연구에서는 열섬현상이 빈번히 발생하는 대구시를 대상지로 정하여 Landsat TM영상을 활용 도시의 열섬현상을 분석하고 시스템을 통해 제작된 기후지도를 활용한 열섬 현상 저감방안도 모색하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.9
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• pp.4541-4554
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• 2019

This paper proposes a planar projection DV-hop location algorithm (PTCDV-hop) based on the LED semi-angle at half power (SAHP, which accounts for LED SAHP characteristics in visible light communication (VLC)) and uses the DV-hop algorithm for range-free localization. Distances between source nodes and nodes positioned in three-dimensional indoor space are projected onto a two-dimensional plane to reduce complexity. Circles are structured by assigning source nodes (projected onto the horizontal plane of the assigned nodes) to be centers and the projection distances as radii. The proposed PTCDV-hop algorithm then determines the position of node location coordinates using the trilateral-weighted-centroid algorithm. Simulation results show localization errors of the proposed algorithm are on the order of magnitude of a millimeter when three sources are used. The PTCDV-hop algorithm has higher positioning accuracy and stronger dominance than the traditional DV-hop algorithm.

• Journal of Auto-vehicle Safety Association
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• v.14 no.4
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• pp.91-99
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• 2022

In Korea, various studies on autonomous vehicles are being conducted with the aim of commercializing the fully autonomous driving (Lv.4) on major roads in 2027. Currently, the communication between non-autonomous vehicles and road users is made with gestures, eye contact, and verbal signals. In the case of autonomous vehicles in the future, autonomous vehicles should communicate instead of drivers. Recently, V2H communication technology (communication technology between autonomous vehicles and road users) is being developed. This study shows technology priorities using the KANO model in caution (warning) and traffic (concession) situations. As a result, a total of six attractive quality technologies were analyzed: technology to provide dark warning information in a display graphic; technology to provide dark warning information in a projection graphic; technology to provide light concession information in a display graphic; technology to provide dark concession information in a display graphic. In the future, it will investigate the preference of users in providing V2H information by road situation. It will be used as a V2H design priority.

• International Journal of Knowledge Content Development & Technology
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• v.10 no.2
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• pp.7-18
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• 2020

Communication is a process involving a group of interrelated elements working together for the purpose of information transfer. This paper discusses information retrieval as a communication process in the 21st century library. The difficulties associated with access to recorded knowledge through bibliographic control devices have been exacerbated by the interposition of additional encoding processes in the library and further decoding by the users. In addition, the innovation of internet/web has revolutionized the means and mode of communication process in the library by flooding information seekers with information and creating an illusion of self-sufficiency in many users. With these changes in information seeking behaviour and pattern, a cybernetic approach to information retrieval has emerged emphasizing adaptive control mechanisms and feedback processes. This paper argues that libraries should strive to continuously remain relevant by keeping abreast with changes in the behavior of information users. To this end, this paper proposes apomediatic-cybernetic model of communication, which illustrates information retrieval processes for the 21st-century library.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.4
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• pp.1020-1041
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• 2024

With the development of covert communication technologies, the number of covert communication technologies using blockchain as a carrier is increasing. However, using the transaction amount of digital currency as a carrier for covert communication has problems such as low embedding rate, large consumption of transaction amount, and easy detection. In this paper, firstly, by experimentally analyzing the distribution of bitcoin transaction amounts, we determine the most suitable range of amounts for matrix decomposition. Secondly, we design a novel matrix decomposition method that can successfully decompose a large amount matrix into two small amount matrices and utilize the elements in the small amount matrices for covert communication. Finally, we analyze the feasibility of the novel matrix decomposition method in this scheme in detail from four aspects, and verify it by experimental comparison, which proves that our scheme not only improves the embedding rate and reduces the consumption of transaction amount, but also has a certain degree of resistance to detection.

• International Journal of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.304-310
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• 2023

With the development of information and communication technology, modern people are receiving various benefits, and knowledge and use of information and communication technology are becoming essential qualities in modern people's lives. There are people who do not enjoy the rich benefits of this information and communication society, and the so-called 'digital divide' acts as an obstacle that prevents the information and communication from enjoying a rich life. Currently, there are four major information underprivileged classes in Korea, the disabled, the elderly, low-income class and farmers and fishermen, respectively. The purpose of this study is to identify the current status of the digital divide for the low-income class and to analyze the causes of the digital divide. To this end, in this study, we analyze statistics on digital divide at the national level and analyzed the digital divide of low-income class from three perspectives: information access, information capability, and information use. As a result of the analysis, it was found that the lack of information capability was the biggest cause of the digital divide, and in particular, information management ability was the most insufficient among information capabilities.

• Journal of Information Technology Services
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• v.17 no.4
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• pp.1-19
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• 2018

Effective internal communication is known to have a positive impact on business performance, but there is a lack of research on the effects of online channels for workplace communication. This study using regression analysis examines how task-technology fit, information richness, self-efficacy, perceived ease of use, and perceived usefulness related to online communication channels affect not only the satisfaction with the tools but also the effectiveness of them. Additionally, we verify how the organizational culture of online and offline communication shows the control effect. As a result, all five variables were positively correlated with internal communication channels satisfaction, and we found that the organizational culture of online and offline communication controls the relationship between online communication channels satisfaction and effectiveness.