• Journal of Communications and Networks
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• v.18 no.4
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• pp.589-599
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• 2016

Most existing resource management problem models arise from the original desire of allocating resources in either a user-centric or network-centric manner. The difference between their objectives is obvious: user-centric methods attempt to optimize the utility of individual users, whereas network-centric models intend to optimize the collective utilities of the entire network. In this paper, from the above two aspects, we analyze the robust power control problem in device-to-device (D2D) communication underlaying cellular networks, where two types of channel uncertainty set (e.g., ellipsoidal and column-wise) are considered. In the user-centric method, we formulate the problem into the form of a Stackelberg game, where the energy efficiency (EE) of each user is the ingredient of utility function. In order to protect the cellular user equipment's (CUE) uplink transmission, we introduce a price based cost function into the objectives of D2D user equipment (DUE). The existence and uniqueness of the game with the influence of channel uncertainty and price are discussed. In the network-centric method, we aim to maximize the collective EE of CUEs and DUEs. We show that by the appropriate mathematical transformation, the network-centric D2D power control problem has the identical local solution to that of a special case of the user-centric problem, where price plays a key role. Numerical results show the performance of the robust power control algorithms in the user-centric and network-centric models.

• KIISE Transactions on Computing Practices
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• v.21 no.5
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• pp.379-386
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• 2015

We propose a novel user-perceived performance optimization framework for the Android platform that takes advantage of the user-centric response time analysis. To this end, we propose a new definition of response time, which we call the user-centric response time, as a metric for the quality of user-perceived performance of the smartphone application. In this paper, we describe the design and implementation of an on-line user-centric response time analyzer for Android-based smartphones, which provides smartphone application developers with valuable insight for user-perceived performance optimization. We implemented the user-centric response time analyzer on the Android platform, version 4.0.4 (ICS) running on a Galaxy Nexus smartphone. From our experimental results, the proposed user-centric response time analyzer accurately estimates user-centric response times with an accuracy of 92.0% compared to manually measured times with less than 1% performance penalty. In order to evaluate the efficiency of the proposed framework, we were able to reduce the user-centric response time of the target application by up to 16.4% based on the evaluation results by the proposed framework.

• 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.

• The Journal of Korean Institute for Practical Engineering Education
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• v.2 no.1
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• pp.164-173
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• 2010

In recent decades, focuses on usability and emphases on user-centric design have become more prevalent in the field of software design. However, it is not always easy for engineers and computer scientists to think in the users' shoes. Human-computer interaction (HCI) is a field of study that focuses on creating technologies easier and more intuitive for the users. This paper is based on teaching HCI skills to undergraduate computer science students in a software application design course. Specifically, this paper employs: first, the HCI skills taught to the students; second, the tendencies and challenges of the students in creating user-centric applications; and lastly, suggestions based on our findings to promote HCI in developing user-friendly software. While more firm conclusions shall be reserved for more formal empirical studies, the findings in this paper still offer implications and suggestions for promoting user-centric approach for software designers and developers in the technology industry.

• Journal of information and communication convergence engineering
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• v.9 no.2
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• pp.177-182
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• 2011

Considerations for user-centric environments are regarded as essential for the successful deployment of convergence services in BcN. Event driven service (EDS) is regarded as a typical convergence service converging different functions of multiple service providers to support user-centric environments. This paper first describes the deployment model and service scenario of EDS, a convergence service for user-centric environments in BcN. The user-centric environments stimulates the unified identifier management, namely unified identification (U-ID), to enable users to be provided convergence services without awareness of multiple providers. Then the designed structure and implementation results are given.

• ETRI Journal
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• v.31 no.4
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• pp.399-407
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• 2009

In this paper, we present a robust $H_{\infty}$ distributed power control scheme for wireless CDMA communication systems. The proposed scheme is obtained by optimizing an objective function consisting of the user's performance degradation and the network interference, and it enables a user to address various user-centric and network-centric objectives by updating power in either a greedy or energy efficient manner. The control law is fully distributed in the sense that only its own channel variation needs to be estimated for each user. The proposed scheme is robust to channel fading due to the immediate decision of the power allocation of the next time step based on the estimations from the $H_{\infty}$ filter. Simulation results demonstrate the robustness of the scheme to the uncertainties of the channel and the excellent performance and versatility of the scheme with users adapting transmit power either in a user-centric or a network-centric efficient manner.

• Journal of Korea Society of Digital Industry and Information Management
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• v.7 no.4
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• pp.101-110
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• 2011

The change of digital convergence service environment converted the subject of design into user -centric one instead of developer-centric one, and changed the existing design environment focused on product development into the new user -centric design environment. Accordingly, GUI considering user's usability come to take big shares in those contents being used for multimedia equipments. However, as the present educational contents provide complex interface due to its design produced based on the existing e-learning system, they have many problems in that they don't consider user's usability. Thus this paper aimed to analyze actual examples through GUI elements of educational contents being used for multimedia equipments and attempt to suggest some directions for development. additionally, consider the various characteristics of digital convergence environment and educational contents, and try to set up strategic directions possible to utilize user'-centric interface elements more usefully and properly at the time to produce designs.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.296-305
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• 2015

Coupled schemes between service-oriented architecture (SOA) and Web 2.0 have recently been researched. Web-based content providers and telecommunications company (Telecom) based Internet protocol television (IPTV) providers have struggled against each other to accommodate more three-screen service subscribers. Since the advent of Web 2.0, more abundant reproduced content can be circulated. However, because according to increasing device's resolution and content formats IPTV providers transcode content in advance, network bandwidth, storage and operation costs for content management systems (CMSs) are wasted. In this paper, we present a user centric CMS for open IPTV, which integrates SOA and Web 2.0. Considering content popularity based on a Zipf-like distribution to solve these problems, we analyze the performance between the user centric CMS and the conventional Web syndication system for normalized costs. Based on the user centric CMS, we implement a social Web TV with device-aware function, which can aggregate, transcode, and deploy content over social networking service independently.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.3
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• pp.37-50
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• 2009

With the increase of number of internet services due to development of internet, it becomes a critical issue to appropriately manage the personal information about user's identity, that is ID information that service providers collect in terms of user's convenience improvement and privacy protection. But the existing ID information management models are service provider-centric or they insufficiently provide ID information management functions, so that they have not been satisfying user's requirement. In this paper, by establishing user-centric concept in we information management, we propose the new user-centric ID information management model in which user can make use of the internet service more conveniently and eventually enhance user's privacy.

• 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.