• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.5
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• pp.1063-1070
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• 2015

In this paper, we propose a distributed user scheduling with transmit power control based on the amount of generating interference to other base stations (BSs) in multi-cell multi-input multi-output (MIMO) networks. Assuming that the time-division duplexing (TDD) system is used, the interference channel from users to other cell BSs is obtained at each user. In the proposed scheduling, each user first generates a transmit beamforming vector by using singular value decompositon (SVD) over MIMO channels and reduces the transmit power if its generating interference to other BSs is larger than a predetermined threshold. Each BS selects the user with the largest effective channel gains among users, which reflects the adjusted power of users. Simulation results show that the proposed technique significantly outperforms the existing user scheduling algorithms.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.7
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• pp.1597-1601
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• 2013

Multiple antenna technique is attracting attention as a core technology for next-generation mobile communication systems to accommodate explosively increasing mobile data traffic. Especially, recent researches focus on multi-user multiple input multiple output (MU-MIMO) system where base stations are equipped with several tens of transmit antennas and transmit data to multiple terminals (users) simultaneously. To enhance the performance of MU-MIMO systems, we, in this paper, propose an adaptive user selection algorithm which adaptively selects a user set according to varying channel states. According to Monte-Carlo based computer simulations, the performance of proposed scheme is significantly improved compared to the conventional scheme without user selection and approaches that of exhaustive search-based optimal scheme. On the other hand, the proposed scheme can reduce the computational complexity to $K/(2^K-1)$ compared to the optimal scheme where K denotes the number of total users.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.1
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• pp.114-121
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• 2022

In this paper, we consider a user centric clustering in order to guarantee the performance of the users in cell free multiple-input multiple-output (MIMO) network. In the user centric clustering scheme, by using large scale fading coefficients of the connected access points (APs), each user decides own cluster with the APs having the higher the large scale fading coefficients than threshold value compared to the highest large scale fading coefficient. In the determined user centric clusters, the APs design the beamformers and power allocations in the distributed manner and the APs cooperatively transmit data to users by using beamformers and power allocations. In the simulation results, we verify the performance of user centric clustering in terms of the spectral efficiency and we also find the optimal threshold value in the given configuration.

• Journal of Digital Convergence
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• v.13 no.11
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• pp.337-348
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• 2015

Touch input method is unintended difficulties regarding touch and input have increased with touch input methods when compared to using a mouse for input in previously existing menus. This study attempted to analyze usability evaluations according to form and size changes of minimal button forms in button menus. This attempted to verify possibilities through more effective applications of the quantitative performance prediction evaluation model through comparative analysis of Fitts' Law, the representative model of the regression model formula and the interface human performance evaluation method, so that applications can be made in interface designs of touch input methods. Therefore it was significant in that it made reflections on design with consideration given to use user times according to button forms and size changes that can be applied to touch screens.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.4
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• pp.545-558
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• 2020

The gaze-based input provides feedback to confirm that the typing is correct when the user types the text. Many studies have already demonstrated that feedback can increase the usability of gaze-based inputs. However, because the information of the typed text is revealed through feedback, it can be a target for shoulder-surfing attacks. Appropriate feedback needs to be used to improve security without compromising the usability of the gaze-based input using the original feedback. In this paper, we propose a new gaze-based input method, FFI(Fake Flickering Interface), to resist shoulder-surfing attacks. Through experiments and questionnaires, we evaluated the usability and security of the FFI compared to the gaze-based input using the original feedback.

• Korean Journal of Computational Design and Engineering
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• v.17 no.6
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• pp.417-425
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• 2012

In recent years, great attention has been paid to using simple physical objects as tangible objects to improve user interaction in augmented reality (AR) environments. In this paper, we address AR-based user interaction using tangible objects, which has been used as a key component for virtual design evaluation of engineered products including digital handheld products. We herein consider the use of two types (product-type and pointer-type) of tangible objects. The user creates input events by touching specified parts of the product-type object with the pointer-type object, and the virtual product reacts to the events by rendering its visual and auditory contents on the output devices. The product-type object is used to reflect the geometric shape of a product of interest and to determine its position and orientation in the AR environment. The pointer-type object is used to recognize the reference position of the pointer (or finger) in the same environment. The rapid prototype of the product is employed as a good alternative to the product-type object, but various alternatives to the pointer-type object can be considered according to fabrication process and touching mechanism. In this paper, we present four alternatives to the pointer-type object and investigate their strong and weak points by performing experimental comparison of their various aspects including interaction accuracy, task performance, and qualitative user experience.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.957-962
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• 2005

Today, the elderly is increasing gradually in the Republic of Korea society and this problem will be more serious in the near future. Therefore, engineering support for aged people is required. We are establishing a new field of healthcare engineering for elderly people and aiming to support for aged people and disabled people using adaptive control and instrument technology. In this paper, the goal is to implement the shared control of a robot mobility aid for the elderly. As using this type of assistive technology to be useful by its intended user community, it supports elderly people and handicapped people to live independently in their private homes. The interface transforms the force applied by the user into the robot's motion. Devices like buttons, joysticks, and levers already exist for relaying user input; however, they require hand displacement that would loosen or otherwise release the user's hold. Such interfaces make operation very difficult and potentially unsafe. Therefore, we propose a shared control system. It's safe more than joysticks and buttons. The shared control is a means of registering the user's intention through physical interaction. It's an important component in the development of robotic elderly assistant. The concept of shared control describes a system which is two or more independent control systems. We are using that the three component blocks consist of pressure sensor (flexible force sensor), circuit of measurement and transfer function. Experimental trials of this paper have been tested at the indoor environment. The robot is able to know the user intended direction through haptic device were logged along with the robot's force sensor.

• Journal of Digital Contents Society
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• v.18 no.1
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• pp.63-70
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• 2017

Recently, as user feedback such as social reading become active, demand has been increased on e-book contents making which is based on user feedback. However, to reflect the user feedback onto the e-book, direct coding is required, which was difficult to the author who was not good at programming. To resolve this problem, Block assembly style feedback editor system, using Blockly was developed. This editor enables to reflect the user feedback by area allocation, component allocation, block editing, and code generating insertion, contrary to the existing way of programming realization in which direct coding was required for input, processing and output separately. This system was developed by using HTML. Javascript, PHP, and Codeigniter. Block editing is enabled to do provision and assembly of blocks by Blockly. The function of code generation & insertion allows to insert the Library function code. Through this system, the general users who are not capable of coding also can reflect feedback without doing actual coding.

• Journal of the Korea Computer Graphics Society
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• v.23 no.3
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• pp.39-46
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• 2017

This study proposes a gaze-based user interface to provide user oriented interaction suitable for the virtual reality environment on mobile platforms. For this purpose, a mobile platform-based three-dimensional interactive content is produced, to test whether the proposed interface increases user satisfaction through the interactions in a mobile virtual reality environment. The gaze-based interface, the most common input method for mobile virtual reality content, is designed by considering two factors: the field of view and the feedback system. The performance of the proposed gaze-based interface is analyzed by conducting experiments on whether or not it offers motives for user interest, effects of enhanced immersion, differentiated formats from existing ones, and convenience in operating content.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.119-126
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• 2011

As a software component for computer game, the physics engine simulates objects' movement according to the laws of physics. This paper introduces a design and implementation of mobile game on the Android platform, where we used JBox2D physics engine library and Android graphics APIs. We borrowed the key idea of this game from Crayon Physics which is known as a famous PC game. This game starts with no way from user character to destination character. The game user has to make a way to destination character from user character by creating polygon objects between them. The user wins when user character meets destination character. However, the game user has to decide the time to create objects and their shapes well because all objects in this game are governed by the laws of physics. As an important thing of this paper, we introduced into this game new input methods of LCD touch and sensors embedded in mobile devices but not in PCs. Game users can create objects by drawing polygons with LCD touch and move objects or characters according to sensor values from accelerator sensors by tilting the mobile device.