• Journal of Engineering Education Research
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• v.22 no.5
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• pp.49-55
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• 2019

Folded structure is widely applied in various engineering fields. Many of the Japanese folding fans in the Edo era (1603-1868) have been successfully blended with the processing technology of "natural materials" that is the origin of Japan's "Monodzukuri" (craftsmanship) and its application "artistic originality". The charm of a fan lies in the diversity of stereoscopic expression not born in plane representation. For example, the effects of folds, the expression of the front and back sides flowing from the front to the back by double-sided description, and the two-layer effect of raising the backside from the surface using the permeability of Japanese paper, the calculated depiction are also seen. Moreover, by handling the fan, it also produced an illusion effect which skillfully calculated the change due to movement of the viewpoint. Students experience the natural materials such as Japanese paper, bamboo and starch paste, which are the materials of paint and fan at the time, and processing method, and know the difference with the current one. This study is to verify the effectiveness of engineering education which gains experience by making concrete fans and to understand deeply this traditional technology with the artistry of a Japanese fan at the same time. And we can learn from the characteristics of the fan to Japan's history and culture.

• Journal of electromagnetic engineering and science
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• v.19 no.1
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• pp.20-30
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• 2019

A wide-band multiple-input multiple-output (MIMO) antenna with dual-band (2.4 and 5 GHz) operation is proposed for premium indoor access points (IAPs). Typically, an omni-directional pattern is used for dipole antennas and a directional radiation pattern is used for patch antennas. In this paper, both antenna types were used to compare their performance with that of the proposed $2{\times}2$ MIMO antenna. We simulated and measured the performance of the MIMO antenna, including the isolation, envelope correlation coefficient (ECC), mean effective gain (MEG) for the IAPs, and the throughput, in order to determine its communication quality. The performance of the antennas was analyzed according to the ECC and MEG. The proposed antenna has sufficient performance and excellent characteristics, making it suitable for IAPs. We analyzed the communication performance of wireless networks using the throughput data of a typical office environment. The network throughput of an 802.11n device was used for the comparison and was conducted according to the antenna type. The results showed that the values of the ECC, MEG, and the throughput have unique characteristics in terms of their directivity, antenna gains, isolation, etc. This paper also discusses the communication performance of various aspects of MIMO in multipath situations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.6A
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• pp.341-350
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• 2003

In this paper, we evaluate the performance of a moving average (MA) channel estimation filter when space-time block coding transmit diversity (STBC-TD) is applied to the wideband direct sequence code division multiple access (WCDMA) forward link. And we present the infinite impulse response (IIR) filter scheme that can reduce the required memory buffer and the channel estimation delay time. This paper also compares the performance between MA filter scheme and IIR filter scheme in various Rayleigh fading channel environments through the bit error rate (BER) and the frame error rate (FER). Extensive computer simulation results show that transmission with STBC-TD provides a significant gain in performance over no transmit diversity technique, particularly at pedestrian speeds. If STBC-TD technique is employed in the channel estimator based on MA filter, it provides considerable performance gains against Rayleigh fading and reduces the optimum filter tap number. Consequently, the channel estimation delay time and the complexity of the receiver are reduced. In addition, the channel estimator based on IIR filter has the advantages such as little memory requirement and no delay time compared to the MA scheme. However, IIR filter coefficients is very sensitive to the mobile speed change and it exerts a serious influence upon the performance. For that reason, it is important to set uP the optimum IIR filter coefficients.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.95-103
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• 2009

An efficient symbol time synchronization scheme for IEEE 802.11n MIMO-OFDM based WLAN systems using cyclic shift diversity (CSD) preamble is proposed. CSD is used to prevent unintentional beamforming when the same preamble signal is transmitted through transmit antennas. However, it is difficult to find a proper starting-point of the OFDM symbol with the conventional algorithms because of time offset by multi-peaks which are result from cross-correlation of received CSD preamble with a known short training symbol. In addition, the performance of symbol time sync. is affected by AGC and packet detection position. In this paper, an optimal symbol time synch. algorithm which is composed of the boundary detection scheme between LTS and OFDM symbols, the verification scheme for enhancement of boundary detection accuracy, and the SNR-varying threshold estimation scheme is proposed. Simulation result show that the proposed algorithm has performance gains of 4.3dB in SNR compared to the conventional algorithms at the rate of 1% sync. failure probability for $2{\times}2$ MIMO-OFDM system and 18dB at 0.1% when maximum frequency offset exists. It also can be applied to $4{\times}4$ MIMO-OFDM system without any modification. Hence, it is very suitable for MIMO-OFDM WLAN systems using CSD preamble.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.8
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• pp.1785-1796
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• 2015

In this paper, we investigate achieving the full diversity order and power gains in case of using OSTBCs and quasi-OSBCs in the x channel system with interference alignment with more than 2 antennas at each terminal. A slight degradation is remarked in the case of quasi-OSTBCs. In terms of receiver structure, we show that due to the favorable structure of the channel matrices, the simple zero-forcing receiver achieves the full diversity order, while the interference cancellation receiver leads to degradations in performance. As compared to the conventional scheme, simulation results demonstrate that our proposed schemes achieve 14dB and 16.5dB of gain at a target bit error rate (BER) of 10^-4 in the case of OSTBCs with 3 and 4 antennas at each terminal, respectively, while achieving the same spectral efficiency. Also, a gain of 10dB is achieved at the same target BER in the case of quasi-OSTBC with 4 antennas at each terminal.

• Korean journal of communication and information
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• v.35
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• pp.87-113
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• 2006

This study aims to theoretically examine the validity of argument that market-opening will improve the audience welfare of media and cultural contents. To accomplish its purpose, first of all, this study classifies the spectrum of approaches on cultural market-opening in Korea. Then, it examines, by the concept of public goods, whether market-opening can bring on economic gains for audience as consumer. Finally, this study inspects the profit and loss for audience as citizen which will be brought on by market-opening on the grounds of democratic value. As a result of this study, the improvement of economic efficiency and competence, the expansion of consumer‘s choices, the preservation of cultural value that the positive approach on market-opening is promising cannot be justified theoretically and logically. Therefore, at least in theoretically, the conclusion that market-opening cannot improve the audience welfare is deduced. However, the objection of market-opening cannot be related to the distorted protectionism of nation culture. On the contrary, this study suggests the condition of market-opening debate must be a opportunity to reconsider and reform of cultural diversity in Korea.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.121-126
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• 2015

This paper proposes a novel reconfigurable microstrip antenna based on alternating a perturbation structure to achieve circular polarization diversity. The proposed antenna consists of an annular ring microstrip radiator for simultaneously loading stub and slot perturbations which support right- and left-handed circular polarization senses and two PIN diodes for choosing the operating polarization sense. By controlling the states of two PIN diodes between perturbing slot and stub at one diagonal corner of the radiator, reconfigurable circular polarization senses of the proposed antenna are successfully obtained and alternated. The proposed antenna has been theoretically analyzed and experimentally demonstrated at 2.4 GHz of S-band for satellite communication system. The simulation and measurement results of the proposed antenna show in good agreement with the reflection coefficients, axial-ratios, realized antenna gains, and radiation patterns.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.69-76
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• 2016

In this paper, we investigate the system performance of a cooperative relaying system of Non-orthogonal multiple access (NOMA) with successive interference cancellation (SIC), which is considered promising application in fifth generation (5G) cellular networks. Previous studies have focused on the selected relays, however we include the maxmin relay selection and derive analytical outage probability of opportunistic incremental relaying systems. For the realistic mobile environment, the distributions of relays are modeled as a homogeneous Poisson point process (PPP). And maximal ratio combining (MRC) is adapted to improve the system performance at the destination node. Analytical results demonstrate the outage probability improves with the near/far user power ratio, and the cooperative relaying scheme can achieve low outage probability in comparison to the no relaying scheme. It is also conformed that the increase of the intensity of PPP cause higher gains of the spacial diversity and hence the performance improves.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.5
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• pp.313-322
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• 2020

A large volume of data will improve the robustness of deep learning models and avoid overfitting problems. In automatic tongue segmentation, the availability of annotated tongue images is often limited because of the difficulty of collecting and labeling the tongue image datasets in reality. Data augmentation can expand the training dataset and increase the diversity of training data by using label-preserving transformations without collecting new data. In this paper, augmented tongue image datasets were developed using seven augmentation techniques such as image cropping, rotation, flipping, color transformations. Performance of the data augmentation techniques were studied using state-of-the-art transfer learning models, for instance, InceptionV3, EfficientNet, ResNet, DenseNet and etc. Our results show that geometric transformations can lead to more performance gains than color transformations and the segmentation accuracy can be increased by 5% to 20% compared with no augmentation. Furthermore, a random linear combination of geometric and color transformations augmentation dataset gives the superior segmentation performance than all other datasets and results in a better accuracy of 94.98% with InceptionV3 models.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.541-546
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• 2004

Space-Time Coding(STC) is a technique that utilizes joint correlation of transmitted signals in both time and space domains. Through this approach, diversity and coding gains can be simultaneously obtained. In this paper, we use SPW simulation tool to implement the IEEE 802.11a system. Based on this system, OFDM system with STC and convolutional coder concatenated is implemented. The system performance is analyzed and compared with the performance of the IEEE 802.11a system. The simulation results show that the performance with concatenated codes at a data rate of 6Mbps shows approximately a 5dB gain over the system with the convolutional code only. At a data rate of 12Mbps, the performance with concatenated codes is further improved by approximately 6dB.