• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.10
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• pp.17-26
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• 2004

This paper proposes JBSTBC (Joint Beamforming Space-Time Block Coding) scheme for MIMO (Multi-Input Multi-Output) communication systems. To enhance the order of spatial diversity in presence of deteriorative fading correlations as well as inter-substream interferences, the proposed JBSTBC method employs joint eigen-beamforming technique together with the BOLD (block-ordered layered detector) for MIMO-STBC. In order to confirm superiority of the proposed JBSTBC method, the computer simulations are conducted in highly correlated fading situations with providing detailed mathematical derivations for clarifying functionality of the proposed scheme.

• Journal of information and communication convergence engineering
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• v.12 no.2
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• pp.67-74
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• 2014

In multi-hop communication systems, two-way relaying is one of the solutions to mitigate the spectral efficiency loss caused by a half-duplex transmission. In this paper, a simple two-way relaying scheme is proposed for two-hop two-user multiple input multiple output (MIMO) systems. In the proposed system, a base station and a relay station (RS), both equipped with two antennas, form a point-to-point MIMO channel, while the RS and two single-antenna mobile users form a point-to-multipoint multiuser (MU)-MIMO channel. Numerical examples show that the proposed system achieves a significant sum rate gain as compared to a one-way relaying system as the distance between a relay and the two users decreases. We also show that although we can expand the proposed scheme to more than two users, its performance gain as compared to that of one-way relaying decreases with an increase in the number of users.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.4
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• pp.747-749
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• 2017

In this paper, we propose a novel precoder selection technique for maximum-likelihood (ML) detected spatially multiplexed multiple-input multiple-output (MIMO) systems. Previous precoder selection techniques were designed without considering UEP, however the proposed technique is designed considering multi-antenna unequal error protection (UEP). Simulations demonstrate the improved multi-antenna UEP performance by the proposed technique.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.5
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• pp.505-508
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• 2006

This paper presents a new analytical approach for designing multiloop PI controllers for disturbance rejection in multivariable processes with time delay. The proposed method is based on IMC-PID design approach. To overcome a sluggish load response by dominant pole in the process, the IMC filter is modified to compensate the dominant pole effect. Based on the modified IMC filter, an analytical tuning rule for multiloop PI controller is driven by extending the generalized IMC-PID method for single input/single output (SISO) systems [1] to multi input/multi output (MIMO) systems. Simulation results show that the proposed method gives a satisfactory load performance as well as servo performance in the multiloop system.

• Journal of Communications and Networks
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• v.8 no.3
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• pp.275-285
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• 2006

Suitable for multi-input multi-output (MIMO) communications, the joint beamforming space-time block coding (JBSTBC) scheme is proposed for high-speed downlink transmission. The major functionality of the scheme entails space-time block encoder and joint transmit and receive eigen-beamformer (EBF) incorporating with block-ordered layered decoder (BOLD), and its operating principle is described in this paper. Within these functionalities, the joint EBFs will be utilized for decorrelating fading channels to cause an enhancement in the spatial diversity gain. Furthermore, to fortify the capability of layered successive interference cancellation (LSIC) in block-ordered layered decoding process, this paper will develop a simple ad-hoc transmit power discrimination scheme (TPDS) based on a particular power discrimination function (PDF). To confirm the superior behavior of the proposed JBSTBC scheme employing ad-hoc TPDS, computer simulations will be conducted under various channel conditions with the provision of detailed mathematical derivations for clarifying its functionality.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.481-489
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• 1993

The charge distribution is calculated to analyze the quasi-static impedance of periodic interdigital transducer taking into account the effect of infinite neighboring electrodes. The charge distribution can be represented by the element factor and array factor. The radiation conductance, susceptance and static capacitance of the input and output IDT's with arbitrary voltages are obtained by the charge distribution. The impedance of apodized IDT, is analyzed by multi-track model in which IDT is represented by the parallel connection of the uniform tracks. The calculated input and output impedances are in good agreement with the experimental results.

• Journal of Korea Multimedia Society
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• v.7 no.6
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• pp.781-790
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• 2004

This paper presents a fourth-order cumulants based iterative algorithm for blind channel equalization. It is robust with respect to the existence of heavy Gaussian noise in a channel and does not require the minimum phase characteristic of the channel. In this approach, the transmitted signals at the receiver are over-sampled to ensure the channel described by a full-column rank matrix. It changes a single-input/single-output (SISO) finite-impulse response (FIR) channel to a single-input/multi-output (SIMO) channel. Based on the properties of the fourth-order cumulants of the over-sampled channel outputs, the iterative algorithm is derived to estimate the deconvolution matrix which makes the overall transfer matrix transparent, i.e., it can be reduced to the identity matrix by simple reordering and scaling. Both a closed-form and a stochastic version of the proposed algorithm are tested with three-ray multi-path channels in simulation studies, and their performances are compared with a method based on conventional second-order cumulants. Relatively good results are achieved, even when the transmitted symbols are significantly corrupted with Gaussian noise.

• Journal of the Ergonomics Society of Korea
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• v.33 no.3
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• pp.241-253
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• 2014

Objective: The objective of this study was to examine multi-modal interaction effects of input-mode switching on the use of smart phones. Background: Multi-modal is considered as an efficient alternative for input and output of information in mobile environments. However, there are various limitations in current mobile UI (User Interface) system that overlooks the transition between different modes or the usability of a combination of multi modal uses. Method: A pre-survey determined five representative tasks from smart phone tasks by their functions. The first experiment involved the use of a uni-mode for five single tasks; the second experiment involved the use of a multi-mode for three dual tasks. The dependent variables were user preference and task completion time. The independent variable in the first experiment was the type of modes (i.e., Touch, Pen, or Voice) while the variable in the second experiment was the type of tasks (i.e., internet searching, subway map, memo, gallery, and application store). Results: In the first experiment, there was no difference between the uses of pen and touch devices. However, a specific mode type was preferred depending on the functional characteristics of the tasks. In the second experiment, analysis of results showed that user preference depended on the order and combination of modes. Even with the transition of modes, users preferred the use of multi-modes including voice. Conclusion: The order of combination of modes may affect the usability of multi-modes. Therefore, when designing a multi-modal system, the fact that there are frequent transitions between various mobile contents in different modes should be properly considered. Application: It may be utilized as a user-centered design guideline for mobile multi modal UI system.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1127-1136
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• 2017

This paper proposes a new soft switching dual input converter for renewable energy systems. Multi-input converters are produced by combining discrete converters. These converters reduce the number of circuit elements, cost, volume and weight of the converter and provide a constant output power in different weather conditions. Furthermore, soft switching techniques can be applied to increase efficiency. In this paper, a Zero Voltage Transition (ZVT) dual input boost converter is presented. Only one auxiliary circuit is used to provide the soft switching condition for all of the semiconductor elements. The proposed converter, which is simulated by ORCAD software, is theoretically analyzed. To confirm the validity of the theoretical analysis, a prototype of proposed converter was constructed. Simulation and experimental results confirm the theoretical analysis. An efficiency comparison shows a one percent improvement at nominal loads.

• Journal of Internet of Things and Convergence
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• v.9 no.2
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• pp.71-76
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• 2023

In this paper, we propose a smoothed received signal strength indicator (RSSI)-based distance estimation using deep neural network (DNN) for accurate distance estimation in an environment where a single receiver is used. The proposed scheme performs a data preprocessing consisting of data splitting, missing value imputation, and smoothing steps to improve distance estimation accuracy, thereby deriving the smoothed RSSI values. The derived smoothed RSSI values are used as input data of the Multi-Input Single-Output (MISO) DNN model, and are finally returned as an estimated distance in the output layer through input layer and hidden layer. To verify the superiority of the proposed scheme, we compared the performance of the proposed scheme with that of the linear regression-based distance estimation scheme. As a result, the proposed scheme showed 29.09% higher distance estimation accuracy than the linear regression-based distance estimation scheme.