• International journal of advanced smart convergence
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• 제9권2호
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• pp.68-75
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• 2020

Non-orthogonal multiple access (NOMA) has gained the significant attention in the fifth generation (5G) mobile communication, which enables the advanced smart convergence of the artificial intelligence (AI), the internet of things (IoT), and many of the state-of-the-art technologies. Recently, correlated superposition coding (SC) has been proposed in NOMA, to achieve the near-perfect successive interference cancellation (SIC) bit-error rate (BER) performance for the stronger channel users, and to mitigate the severe BER performance degradation for the weaker channel users. In the correlated SC NOMA scheme, the stronger channel user BER performance is even better than the perfect SIC BER performance, for some range of the power allocation factor. However, such excessively good BER performance is not good for the user-fairness, i.e., the more power to the weaker channel user and the less power to the stronger channel user, because the excessively good BER performance of the stronger channel user results in the worse BER performance of the weaker channel user. Therefore, in this paper, we propose the power splitting to establish the user-fairness between both users. First, we derive a closed-form expression for the power splitting factor. Then it is shown that in terms of BER performance, the user-fairness is established between the two users. In result, the power splitting scheme could be considered in correlated SC NOMA for the user-fairness.

• Journal of Communications and Networks
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• 제10권1호
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• pp.28-37
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• 2008

In this paper, we investigate the problem of minimizing the average transmission power of users while guaranteeing the average delay constraints in time-varying uplink channels. We design a scheduler that selects a user for transmission and determines the transmission rate of the selected user based on the channel and backlog information of users. Since it requires prohibitively high computation complexity to determine an optimal scheduler for multi-user systems, we propose a low-complexity scheduling scheme that can achieve near-optimal performance. In this scheme, we reduce the complexity by decomposing the multiuser problem into multiple individual user problems. We arrange the probability of selecting each user such that it can be determined only by the information of the corresponding user and then optimize the transmission rate of each user independently. We solve the user problem by using a dynamic programming approach and analyze the upper and lower bounds of average transmission power and average delay, respectively. In addition, we investigate the effects of the user selection algorithm on the performance for different channel models. We show that a channel-adaptive user selection algorithm can improve the energy efficiency under uncorrelated channels but the gain is obtainable only for loose delay requirements in the case of correlated channels. Based on this, we propose a user selection algorithm that adapts itself to both the channel condition and the backlog level, which turns out to be energy-efficient over wide range of delay requirement regardless of the channel model.

• 대한인간공학회지
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• 제32권6호
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• pp.557-563
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• 2013

Objective: This study introduces user experience measurement and its application for senior friendly products. Background: Measuring user experience for senior friendly product is very important for its design, but the measurement is not easy. Method: This study was focused on case studies for user experience measurement and its application for senior friendly product. Mobile patient lift and four wheeled walker that assist the old's mobility were studied. User experience was measured through interview and observation method. Result: From measuring the user experience, some usability issues were identified for the products. A method to apply QFD(quality function deployment) in design process was proposed. A design prototype was also developed considering user experience. Conclusion: User experience measurement for senior friendly products is key process for user centered design. Application: The method and result of this study can be applied to user experience measurement and design of senior friendly product.

• International journal of advanced smart convergence
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• 제10권3호
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• pp.1-9
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• 2021

In the Internet of Thing (IoT) framework, massive machine-type communications (MMTC) have required large spectral efficiency. For this, non-orthogonal multiple access (NOMA) has emerged as an efficient solution. Recently, a non-successive interference cancellation (SIC) NOMA scheme has been implemented without loss. This lossless NOMA without SIC is achieved via correlated superposition coding (SC), in contrast to conventional independent SC. However, conventional minimum high-correlated SC for only 2-user NOMA schemes was investigated in the lossless 2-user non-SIC NOMA implementation. Thus, this paper investigates a 3-user low-correlated SC scheme, especially for an inflated achievable sum rate, with a design of 3-user low-correlated SC. First, we design the 3-user low-correlated SC scheme by taking the minimum sum rate between 3-user SIC NOMA and 3-user non-SIC NOMA, both with correlated SC. Then, simulations demonstrate that the low correlation in the direction of the first user's power allocation inflates the sum rate in the same direction, compared to that of conventional minimum high-correlated SC NOMA, and such inflation due to low correlation is also observed similarly, in the direction of the second user's power allocation. Moreover, we also show that the two low correlations of the first and second users inflates doubly in the both directions of the first and second users' power allocations. As a result, the proposed 3-user low-correlated SC could be considered as a promising scheme, with the inflated sum rate in the future fifth-generation (5G) NOMA networks.

• 산업경영시스템학회지
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• 제42권3호
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• pp.39-51
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• 2019

This paper is an exploratory study to investigate the influence of characteristics of local government web-sites on user satisfaction and trust. The objective of this research is to identify the characteristics of local government web-sites influencing on user satisfaction and trust, and determine how they affect user satisfaction and trust. From the literature review, we identify four characteristics which are expected to influence on user satisfaction: technical, information, customer-oriented, and work-performing characteristics. In addition, we develop research model that the four characteristics are expected to affect user satisfaction and trust via users' perceived values. The results of the research are as follows. The technical, customer-oriented, and work-performing characteristics significantly affects perceived values, which significantly affected user satisfaction and trust. Perceived value is partially mediated by user satisfaction in affecting user trust. The characteristics of local government web-sites affecting perceived values differed partially by the purpose of visitor. As for the personal goal, the technical, customer-oriented, and work-performing characteristics significantly affect perceived values, with the technical and customer-oriented characteristics having more significant effects. As for the business goal, the technical, information, work-performing characteristics significantly affected perceived values, with information characteristics having more significant effects.

• International journal of advanced smart convergence
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• 제10권3호
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• pp.17-25
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• 2021

As a new paradigm in non-orthogonal multiple access (NOMA), correlated superposition coding (CSC) has gained an attention in the literature of NOMA, in contrast to standard independent superposition coding (ISC). In the conventional 3-user CSC scheme, it has been reported that the average allocated power can be reduced, owing to an introduced correlation between transmitted signals. Thus, this paper proposes a 3-user cross CSC scheme with purely-imaginary correlation coefficients. First, we derive the achievable data rates of the proposed 3-user cross CSC scheme, for each of the three users. Then, simulations demonstrate that for the proposed 3-user cross CSC scheme, the achievable data rates of the first and second users increase greatly and slightly, respectively, whereas the achievable data rate of the third user decreases little, compared to those of the conventional 3-user CSC scheme. In addition, we also show that the sum rate of the three users of the proposed 3-user cross CSC scheme is much larger than that of the three users of the conventional 3-user CSC scheme. As a result, the proposed 3-user cross CSC scheme could be a solution to the problem of the reduction of the average allocated total power in the conventional 3-user CSC scheme toward the fifth-generation (5G) NOMA mobile networks.

• 대한인간공학회지
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• 제31권1호
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• pp.109-116
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• 2012

Objective: The aim of this study is to present a solution to problems in the services provided by the general hospitals by creating a user-centric environment through analyzing the User Journey Map and the User Context. Background: The rapid growth in aging population and the monopolization of superior medical staffs by the general hospitals increased demand for the general hospitals in Korea. But, often services provided by the general hospitals are provider-centric and low quality. Method: This study examines problems in the services provided by the general hospitals by analyzing the User Journey Map through stakeholder interviews(contextual interviews) and on-site observation. Based on the contextual analysis of the user(i.e. the patient), this study proposes new and improved user-centric services to be provided by the general hospitals. Results: Ten new user-centric services proposed by this study are: (1) "Booklet on Success Story", (2) "FAQs by Doctor", (3) "Designated Nurse", (4) "Patient Interview Record Card", (5) "Close relationship between doctor & patient", (6) "Thank You Notice Board", (7) "Step by Step", (8) "Green Cap", (9) "Patient Kit", (10) "RFID Direction Display System". Conclusion: The service design for the general hospitals proposed by this study is an important case-study on improving the environment of the general hospitals from provider(medical staffs)-centric to user(patents and its family)-centric. Application: This study is expected to be used in various areas to improve existing system(products and/or services) to be more user-centric.

• 한국HCI학회:학술대회논문집
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• 한국HCI학회 2009년도 학술대회
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• pp.673-676
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• 2009

본 논문에서는 스마트 공간에서 모바일 사용자의 맥락 정보에 따라 개인화된 콘텐츠를 증강시키는 맥락 인식 모바일 증강 현실 시스템인 CAMAR Companion을 소개한다. 이는 모바일 기기에 부착된 카메라를 이용하여 스마트 공간의 오브젝트를 인식하고 인식된 오브젝트의 움직임을 추적한다. 그리고 여러 가지 센서들로부터 획득된 정보를 통합하여 모바일 사용자의 변화하는 맥락 정보를 실시간으로 인식한다. 또한 모바일 사용자의 맥락 정보 히스토리를 기반으로 해당 맥락에 대한 사용자의 프로파일, 특히 사용자가 선호하는 콘텐츠 혹은 맥락에 용이한 콘텐츠에 대한 정보를 추론한다. 그리고 모바일 기기를 통해 제공되는 콘텐츠를 사용자의 맥락에 적절한 형태로 디스플레이하거나 물리적 오브젝트에 증강시킴으로써 사용자에게 용이한 형태의 콘텐츠를 제공한다. 더 나아가 제안한 시스템을 기반으로 스마트 홈 환경에서의 사용자 맥락 정보에 따라 개인화된 콘텐츠를 증강 시켜주는 맥락 인식 모바일 증강 현실 정보 도우미를 구현하였다. 이는 사용자의 변화하는 맥락 정보를 실시간으로 인식하고 해당 맥락에 대한 사용자의 프로파일을 동적으로 추론하여 사용자로 하여금 개인화된 증강 콘텐츠를 경험할 수 있도록 하였다. 궁극적으로 이를 통하여 모바일 기기에서 개인화된 사용자 인터페이스를 개발하는 데 있어 제안한 맥락 인식 모바일 증강 현실 시스템의 응용 가능성을 확인하고자 한다.

• 한국항행학회논문지
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• 제19권4호
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• pp.311-317
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• 2015

본 논문에서는 서비스 로봇 제어 시스템의 복잡한 소프트웨어 개발을 손쉽게 하기 위한 서비스 로봇 콘텐츠 개발 방법에 관한 연구이다. 본 연구에서 개발된 User created contents 기반 로봇 제어 시스템은 로봇 구동 제어회로, 센서 데이터 처리, 상태 표시, 모니터링 시스템 등을 모듈화 하여 사용자 입장에서 서비스 로봇 운용 화면을 구성하고 서비스 로봇을 운용 제어할 수 있는 시스템으로써 텍스트 기반에서 서비스 로봇 제어 콘텐츠를 자유롭게 운용할 수 있는 특징을 가진다. 또한, 사용자는 개발된 User created contents 를 이용하여 위치 변경뿐만 아니라 사용자가 원하는 로봇 운영 제어 GUI (graphic user interface) 도 변경이 가능하다는 장점을 가지고 있다. 결과적으로, 서비스 로봇 운용자가 사용자 입장에서 편리하게 서비스 로봇 콘텐츠를 만들 수 있는 방법을 제안하여 서비스 로봇의 개발을 활성화하는 방법을 제시하였다.

• 정보보호학회논문지
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• 제26권6호
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• pp.1493-1504
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• 2016

인터넷을 통한 사이버 위협이 증대됨에 따라 개인정보 침해도 지속적으로 발생하고 있다. 악의적인 사용자들은 유출된 개인정보를 도용하여 정상 사용자처럼 해당 웹사이트를 접근하고 불법적인 행동을 할 수 있다. 본 논문에서는 이러한 불법 사용자의 접근을 실시간으로, 효과적으로 탐지하기 위해 정상 사용자의 웹사이트 평시 사용 패턴을 멤버십 분석(membership analysis)과 마르코프 체인 모델(markov chain model)을 기반으로 프로파일링 함으로써, 정상 사용자를 판별하는 방법을 제안한다. 아울러 이러한 프로파일에 시간적인 특성, 즉 시간 가중치(time weight)를 적용하여, 시간적으로 변하는 사용자의 행동을 사용자의 프로파일에 반영한다. 이에 따라 시간에 따른 사용자의 성향을 반영한 결과를 얻을 수 있다. 본 연구를 통해 생성한 사용자별 프로파일을 기반으로 개인정보를 도용한 악의적인 사용자를 적발할 수 있고, 정상적인 사용자이더라도 민감한 정보에 접근하는 것을 방지할 수 있다. 본 연구를 적용한 결과, 정상 사용자에 대해 96%의 높은 판별 정확도를 보여주었다.