• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.4
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• pp.781-788
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• 2017

This paper proposes a new algorithm for comparing amplitude between multiple digital input signals and its digital logic architecture. After simultaneously comparing multiple inputs, the proposed algorithm can provide the information of the largest (or smallest) value among them by using a simple digital logic function. The drawback of the method is to increase hardware resource. To overcome this we propose a reuse method of the overlapped logic operation. The proposed method focuses on enhancing the operational clock frequency, in other words decreasing combinational delay time. After implementing the comparing method with HDL (hardware description language), we experiment on it with environment of Cyclone III EP3C40F324A7 FPGA of Altera Inc. In case of 4 input signals, it can increase the operational speed as mush as 1.66 times with 1.20 times the hardware resource. In case of 8, it can also have 2.29 times the clock frequency and 2.15 times the hardware resource.

• The KIPS Transactions:PartC
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• v.9C no.3
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• pp.439-444
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• 2002

In this paper, we present both the link budget analysis according to system parameters and the cell coverage according to transmitter power and modulation scheme of digital MMDS among the wireless CATV system methods which is bated on the wireless internet service. Also, in this paper, we present C/I and number of subscriber according to splitting cell. In this paper, the cell coverage of which obtain the results according to both transmitter power from 0dBW to -9dBW and modulation scheme of QPSK, 16QAM and 64QAM based on link budget was analysis for system parameter of digital MMDS was able to provide from maximum 134km to minimum 4.3km. Also, in this paper, the number of subscriber of which obtain the results according to polarization wave, frequency of frequency reuse and C/I in 4. 6 and 8 sectors was able to provide from maximum 5,200DSI to minimum 1,300DSI.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.195-200
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• 2017

Due to the rapid development of Internet technology, qualities of Web services are steadily improving and the Web database systems are actively employed to efficiently manage proper informations in various fields. In this paper, we propose a Web database system for the efficient material management for reusing construction materials. The proposed Web-based management system is operated using the spring framework, after constructing a database based on the collected data including tag ID, Location, Material, State, and Cycle, using the RFID(: Radion Frequency IDentification) system equipped with a location estimation module. Recently, the processing problem for a large amount of the residues generated at the demolition stage of various buildings is magnified in the construction site. The proposed Web-based construction material management system is expected for improving the processing problem as increasing the reusability and for reducing the construction cost as efficiently managing the construction materials for the reuse.

• The Journal of the Acoustical Society of Korea
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• v.36 no.1
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• pp.39-48
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• 2017

CDMA (Code Division Multiple Access) is promising medium access control schemes for underwater acoustic sensor networks because of its robustness against frequency-selective fading and high frequency-reuse efficiency. In this paper, we design diversity schemes of underwater CDMA transceiver for the forward and reverse links. User data are multiplexed by Walsh code and a pseudo random noise code acquisition process is added for phase error correction before decoding the user data at the receiver. Then, the diversity reception using equal gain combining and maximal ratio combining is performed in order to minimize performance degradation caused by rich multipath fading of underwater acoustic channel. We evaluated the performance of diversity transceiver through lake experiment, which was performed at Lake Kyungcheon, Mungyeong city using two transmitters and two receivers placed 460 m apart at an average depth of 40 m. The lake experiment results show that user data are recovered with error-free in both of the forward and reverse links.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5C
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• pp.351-360
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• 2008

In cellular mobile radio systems with frequency reuse, the interference signals degrade the channel estimation and signal detection performance due to the low signal-to-interference ratio near coverage boundaries. When the preamble pilot sequences from different cells are orthogonal or located in disjointed positions, they can be used for multi-cell channel estimation and interference cancellation. In time-varying channels caused by Doppler spread, data pilot symbols are needed for channel estimations. However, data pilot symbols are usually located in identical positions for the overhead reduction, which degrades the channel estimation performance. In this paper, we demonstrate a significant amount of performance improvement is achieved by multiplying different pseudonoise(PN) sequences to the data pilot symbols from adjacent interference cells. In particular, for detection scheme using maximal ratio combining(MRC) and inter-cell spatial demultiplexing(ISD), quantitative performance gain of spectral efficiency for different values of Doppler frequency and interference power is presented.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.29 no.4
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• pp.35-55
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• 2018

The purpose of this study is to suggest how to activate the school library by examining how the users' perceive teacher librarians. For this purpose, questionnaires and in-depth interviews were conducted for students in 10 middle and high schools in Seoul and Gyeonggi. Analyses lead to these findings: the image types of teacher librarians were classified as professional image, active image, and simple-work image. Multiple regression analysis was used to examine the effect of teacher librarians images on school library user satisfaction. In order to enhance the teacher librarians images and school library user satisfaction, it is necessary to strive to cultivate the active attitude and professionalism of teacher librarians. Also, as the frequency of use is lower, the teacher librarians' images are viewed as simple work. Therefore, it is required to consider various reading events and reading education to raise the frequency of use. This study shows that the teacher librarians' images have a positive effect on school library users' satisfaction and suggests improvement plan for school library activation.

• Journal of Internet of Things and Convergence
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• v.8 no.3
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• pp.29-40
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• 2022

The aim of this study was to analyze research trends of social service quality from 2007 to 2020 based on text mining and topic modeling. Our focus was to provide foundational materials for social service improvement by discovering the latent meaning of relevant research papers. We collected 97 scholarly articles on social service, social welfare service, and quality from RISS, and implemented two segments of text mining analysis. Our results showed that the first section included 38 papers and the second 59, indicating 6.9 articles annually. Word frequency results demonstrated that the common keywords of both sections were 'service', 'quality', 'social service', 'satisfaction', 'users', 'quality control', 'reuse', 'policy', 'voucher', etc. TF-IDF suggested that 'social service', 'satisfaction', 'users', 'customer satisfaction', 'revisiting', 'voucher', 'quality', 'assisted living facility', 'quality control', 'community service investment business', etc., were represented in both categories. Lastly, topic modeling analysis revealed that the first segment displayed 'types of care services', 'service costs', 'reuse', 'users based', and 'job creation', whereas the second presented 'service quality', 'public value', 'management system of human resources', 'service provision system', and 'service satisfaction'. Future directions of social service quality were discussed based on the results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5C
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• pp.527-539
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• 2009

In this paper, we propose an asynchonous ICI (Inter-Cell Interference) mitigation techniques for 3GPP LTE MIMO-OFDMA down-link receiver. An increasing in symbol timing misalignments may occur relative to sychronous network as the result of BS (Base Station) timing differences. Such symbol synchronization errors that exceed the guard interval or the cyclic prefix duration may result in MAI (Multiple Access Interference) for other carriers. In particular, at the cell boundary, this MAI becomes a critical factor, leading to degraded channel throughput and severe asynchronous ICI. Hence, many researchers have investigated the interference mitigation method in the presence of asynchronous ICI and it appears that the knowledge of the SCM (Spatial Covariance Matrix) of the asynchronous ICI plus background noise is an important issue. Generally, it is assumed that the SCM estimated by using training symbols. However, it is difficult to measure the interference statistics for a long time and training symbol is also not appropriate for MIMO-OFDMA system such as LTE. Therefore, a noise reduction method is required to improve the estimation accuracy. Although the conventional time-domain low-pass type weighting method can be effective for noise reduction, it causes significant estimation error due to the spectral leakage in practical OFDM system. Therefore, we propose a time-domain sinc type weighing method which can not only reduce the noise effectively minimizing estimation error caused by the spectral leakage but also implement frequency-domain moving average filter easily. By using computer simulation, we show that the proposed method can provide up to 3dB SIR gain compared with the conventional method.

• Journal of IKEEE
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• v.13 no.4
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• pp.75-81
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• 2009

The cellular system in the next generation decreases the range of transmission of a signal as well as increases the rate of transmission adapting the method of multi-hop relaying with the relay. However, the fact of decreasing the range of transmission with the method of multi-hop relaying means increasing interferential amount in the outer cell; therefore, the deployment of the relay can affect to the function of the cellular system. In this thesis, the deployment of the relay is determined for the maximum rate of transmission, based on the transmission power of the relay and the variation of interferential amount. The condition to determine the deployment of the relay is analyzed with the mathematical model; in addition, its performance is verified through the result of a simulation. Based on the analysis of this thesis, the established deployment and transmission power of the relay to minimize the average outage probability exist. Furthermore, the relay contributes to enlargement of capacity of cells, decreasing the average outage probability in the situation of less severe interference between cells with reuse of frequency. However, the relay should be restrained in use in the situation of severe interference between cells due to the fact that the outage probability of inter-cells can be increased.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.850-857
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• 2013

The objective of this paper is to provide service continuity based on an efficient subchannel allocation in OFDMA systems. The resource management for handover are necessary to maintain the QoS requirements of different multimedia applications because the service continuity may be defected by some delay and information loss. Therefore we propose two subchannel management schemes applied to OFDMA systems. Firstly, a superposition allocation of interference subchannels is achieved by modifying a frequency reuse scheme, using co-subchannel interference principle. Secondly for handover applications, we suggest a novel subchannel reservation scheme to adjust the number of allocated channels, depending on the different characteristics and diverse quality of mobile multimedia applications. Simulation results show that the total throughput for the proposed method is increased up to 20% at average and peak arrivals and the handover failure rate is decreased to about 25%, as compared to the conventional method.