• Journal of Internet Computing and Services
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• v.7 no.5
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• pp.13-24
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• 2006

Context aware computing is an emerging paradigm to achieve ubiquitous computing environments by enabling computer systems to understand their situational contexts. A context aware system uses context to provide relevant information and services to the user depending on the user's task. In this paper, we propose an ontology based context aware modeling methodology that transmits low level contexts acquired by directly accessing various sensors in the physical environments to high level contexts. With these high level contexts, context aware application can provides proactive and intelligent services using ECA (Event Condition Action) rules. We implemented a presentation service in smart office environment.

• Information Systems Review
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• v.11 no.1
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• pp.197-215
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• 2009

As the ubiquitous technology has been widespread, the u-service development driven by the private sector is increasing these days. In this paper, a new development methodology of interactive u-services for a mixed-use complex in u-City is proposed. The current state-of-the-art IT, Web2.0, assumes that information must be communicated in both way, not only from service provides to users but also from users to service providers. Here the user-driven u-service will be utilized for service providers to customize user services. By this interactive u-service paradigm, the information users become the information providers so that the mixed-use complex will take advantage of massive information. Also, admitting that the mixed-use complex is limited in terms of the space size, the network effect of information and shared contents created through the interactive u-services can be maximized.

• ETRI Journal
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• v.45 no.5
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• pp.887-898
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• 2023

Aerial base stations (ABSs) seem promising to enhance the coverage and capacity of fifth-generation and upcoming networks. With the flexible mobility of ABSs, they can be positioned in air to maximize the number of users served with a guaranteed quality of service (QoS). However, ABSs may be overloaded or underutilized given inefficient placement, and user association has not been well addressed. Hence, we propose a three-dimensional ABS placement scheme with a delay-QoS-driven user association to balance loading among ABSs. First, a load balancing utility function is designed based on proportional fairness. Then, an optimization problem for joint ABS placement and user association is formulated to maximize the utility function subject to statistical delay QoS requirements and ABS collision avoidance constraints. To solve this problem, we introduce an efficient modified gray wolf optimizer for ABS placement with a greedy user association strategy. Simulation results demonstrate that the proposed scheme outperforms baselines in terms of load balancing and delay QoS provisioning.

• ETRI Journal
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• v.30 no.3
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• pp.421-431
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• 2008

In this paper, we offer a new technique to discover frequent spatiotemporal patterns from a moving object database. Though the search space for spatiotemporal knowledge is extremely challenging, imposing spatial and timing constraints on moving sequences makes the computation feasible. The proposed technique includes two algorithms, AllMOP and MaxMOP, to find all frequent patterns and maximal patterns, respectively. In addition, to support the service provider in sending information to a user in a push-driven manner, we propose a rule-based location prediction technique to predict the future location of the user. The idea is to employ the algorithm AllMOP to discover the frequent movement patterns in the user's historical movements, from which frequent movement rules are generated. These rules are then used to estimate the future location of the user. The performance is assessed with respect to precision and recall. The proposed techniques could be quite efficiently applied in a location-based service (LBS) system in which diverse types of data are integrated to support a variety of LBSs.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.306-320
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• 2015

Due to an explosive growth in services running in different datacenters, there is need for service selection and routing to deliver user requests to the best service instance. In current solutions, it is generally the client that must first select a datacenter to forward the request to before an internal load-balancer of the selected datacenter can select the optimal instance. An optimal selection requires knowledge of both network and server characteristics, making clients less suitable to make this decision. Information-Centric Networking (ICN) research solved a similar selection problem for static data retrieval by integrating content delivery as a native network feature. We address the selection problem for services by extending the ICN-principles for services. In this paper we present Queue and Latency, a network-driven service selection algorithm which maps user demand to service instances, taking into account both network and server metrics. To reduce the size of service router forwarding tables, we present a statistical method to approximate an optimal load distribution with minimized router state required. Simulation results show that our statistical routing approach approximates the average system response time of source-based routing with minimized state in forwarding tables.

• Korean Management Science Review
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• v.32 no.4
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• pp.175-192
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• 2015

Due to the emergence of open innovation driven by development of network service technologies and convergence in ICT service industry, It is necessary for ICT service firms to examine their capabilities for open innovation. The purpose of this paper is to empirically examine determinants affecting open innovation in Korean ICT service industry. In order to analyze, this paper uses logistic and multiple regression models based on survey data of Korean ICT service firms. Estimation results show that external network for collaboration is positive on the technological innovation activity regardless of the innovation type. Specifically, user networks are significant in all types of technology innovation, revealing that it is important to innovation activities of the ICT service firms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.3831-3851
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• 2015

This paper is concerned with the problem of joint resource allocation and user-pairing in virtual MIMO SC-FDMA systems to improve service quality of experience (QoE). No-reference logarithmic model is introduced to quantify service experience for each user and the objective is to maximize sum of all user's mean of score (MOS). We firstly formulate the optimal problem into an S-dimensional (S-D) assignment problem. Then, to solve this problem, the modified Lagrangian relaxation algorithm is deduced to obtain the suboptimal result of joint user-paring and subchannel allocation. The merits of this solution are as follows. First, the gap between its results and the global optimal one can be quantified and controlled by balancing the complexity and accuracy, which merit the other suboptimal algorithms do not have. Secondly, it has the polynomial computational complexity and the worst case complexity is O(3LN³), where L is the maximum iteration time and N is the number of subchannels. Simulations also prove that our proposed algorithm can effectively improve quality of experience and the gap between our proposed and the optimal algorithms can be controlled below 8%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.8
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• pp.4212-4226
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• 2019

In this paper, a design and implementation for direct deal distribution platform is proposed to bypass the complex traditional distribution structure of agricultural market, as one of the fields where distribution patterns have changed. In the case of domestic agricultural distribution, demand and supply are unstable since the sales market is excessively concentrated in the designated wholesale market. Besides sales must go through multiple stages of distribution leading to problems in freshness and stability of agricultural products and downward pressure on profit margins for producers. To solve the above mentioned issues, we propose a cloud service convergence direct deal distribution platform based on asynchronous-driven Node.js. The proposed platform can facilitate a variety of direct trading functions and also access to visualization information related to agricultural products, which may increase user confidence at an intermediary-free direct transactions platform. First, we describe the requirements of intermediary-free direct transactions of agricultural products and transaction entities. Next the database structure and transaction functions are designed and then implemented according to those requirements. Finally, an API based cloud convergence service structure is designed to provide the analyzed information to ensure a trustworthy system.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.3
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• pp.341-351
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• 2021

Recently, user-driven privacy control technology, such as distributed ID management, has been gaining attention. However, the existing blockchain-based access control studies have not provided a sufficient level of privacy control method to users. This paper proposes a method that combines permissioned blockchain technology and a recent privacy control standard. To allow users to participate in privacy control, a token-based user access control service that conforms to the UMA2 standard was applied to the blockchain dApp. By combining the blockchain and UMA2, the proposed method provides a user-centered privacy control function that the existing blockchain could not provide. In addition, we solved the problem of privacy, security, and availability of entities, which are the disadvantages of UMA2.

• Journal of Science and Technology Studies
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• v.15 no.1
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• pp.245-279
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• 2015

The new innovation model that deals with agenda as sustainability, quality of life, societal challenges is emerging as NIS(National Innovation System) is needed to transit to post catch-up and creativity. To achieve this objective, there is a growing need for enhancing usage of ICT, end-user's needs, prolification of R&D results and social impact. Living Lab is the new innovation model that end-user's participation, co-work/network within actors and usage of user's experience and This study deal with Living Lab related R&D of ICT-based service from co-work with end-users. Example cases are Turku Archipelago Living Lab in Finland, and Living Lab projects in EU, EIT ICT Labs and ELLIOT. And the focus of case analysis is that reflection of user's needs and experience, and aspect of ICT usage.