• International journal of advanced smart convergence
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• v.9 no.2
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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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• v.10 no.1
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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.

• Journal of the Ergonomics Society of Korea
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• v.32 no.6
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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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• v.10 no.3
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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.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.3
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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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• v.10 no.3
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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.

• Journal of the Ergonomics Society of Korea
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• v.31 no.1
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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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• 2009.02a
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• pp.673-676
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• 2009

In this paper, we describe CAMAR Companoin, a context-aware mobile AR system that provides a user-adaptive assistance with an augmented picture according to the user's context in smart space. It recognizes physical objects and tracks the movement of those objects with a camera embodied to a mobile device. CAMAR Companion observes a mobile user's context, which is sensed by various kinds of sensors in environments, and infers user preference for the content in the situation. It recommends multimedia content relevant to the user's context. It overlays selected content over associated physical objects and enables the user to experience the content in a user-centric manner. Furthermore, we have developed the prototype to illustrate how our system could be used for a mobile user's well-being care applications in smart home environments. In this application, we found that our system could perceive a user preference even though a user's context is changed dynamically, and then adapt the multimedia content with respect to the user's context effectively. As such, the proposed user-adaptive system has the potential to play an important role in developing customized user interfaces in mobile devices.

• Journal of Advanced Navigation Technology
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• v.19 no.4
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• pp.311-317
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• 2015

This paper is a study on how to develop service robots can easily complex software development services robot control system. User created contents based on the robot control system developed in this study is a robot drive control circuit, a sensor data processing, the status, the monitoring systems and modular system to configure the service robot operation screen from a user perspective and that can control the service robot operation As in the text-based features that can be operated to have freedom to the robot control service content. In addition, the user has the advantage that changes position by the development as well as user created contents desired by the user operating the robot control GUI (graphic user interface) also changes are possible. As a result, the service robot operator to offer a way to make the service robot can be conveniently presented in a user's point of view how to enable the development of the service robot.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.26 no.6
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• pp.1493-1504
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• 2016

As cyber threats have been increased over the Internet, the invasions of personal information are constantly occurring. A malicious user can access the Web site as a normal user using leaked personal information and does illegal activities. This paper proposes an effective method which authenticates a genuine user with real-time. The method use the user's profile which is a record of user's behavior created by Membership Analysis(MA) and Markov Chain Model(MCM). In addition to, user's profile is augmented by a Time Weight(TW) which reflects the user's tendency. This method can detect a malicious user who camouflage normal user. Even if it is a genuine user, it can be determined as an abnomal user if the user acts beyond the record profile. The result of experiment showed a high accuracy, 96%, for the correct user.