• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4269-4292
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• 2014

Currently, increasing numbers of access points (AP) are being deployed in enterprise offices, campuses and municipal downtowns for flexible Internet connectivity, but most of these access points are idle or redundant most of the time, which causes significant energy waste. Therefore, with respect to power conservation, applying energy efficient strategies in WIFI networks is strongly advocated. One feasible method is dynamically managing network resources, particularly APs, by powering devices on or off. However, when an AP is powered on, the device is initialized through a long boot time, during which period clients cannot be associated with it; therefore, the network performance would be greatly impacted. In this paper, based on a global view of an entire WLAN, we propose an AP selection technology, known as Temporary Access Selection (TAS). The criterion of TAS is a fusion metric consisting of two evaluation indexes which are based on throughput and battery life, respectively. TAS is both service and clients' preference specific through balancing the data rate, battery life and packet size. TAS also works well independently in traditional WLANs in which no energy efficient strategy is deployed. Moreover, this paper demonstrates the feasibility and performance of TAS through experiments and simulations with Network Simulator version 3 (NS3).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5209-5228
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• 2016

Device-to-device (D2D) communication underlaying cellular networks can bring significate benefits for improving the performance of mobile services. However, it hinges on elaborate resource sharing scheme to coordinate interference between cellular users and D2D pairs. We formulate a joint mode selection, link allocation and power control optimization problem for D2D communication sharing uplink resources in a multi-user cellular network and consider the efficiency and the fairness simultaneously. Due to the non-convex difficulty, we propose a three-step scheme: firstly, we conduct mode selection for D2D pairs based on a minimum distance metric after an admission control and obtain some cellular candidates for them. And then, a cellular candidate will be paired to each D2D pair based on fairness. Finally, we use Lagrangian Algorithm to formulate a joint power control strategy for D2D pairs and their reused cellular users and a closed-form of solution is derived. Simulation results demonstrate that our proposed algorithms converge in a short time. Moreover, both the sum rate of D2D pairs and the energy efficiency of cellular users are improved.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.3
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• pp.608-614
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• 2009

In wireless sensor networks, there are hundreds to thousands of small battery powered devices which are called sensors. As sensors have a limited energy resources, there is a need to use it effectively. A clustering based routing protocol forms clusters by distributed algorithm. Member nodes send their data to their cluster heads then cluster heads integrate data and send to sink node. In this paper we propose an energy efficient cluster-head selection algorithm. We have used some factors(a previous cluster head experience, a existence of data to transmit and an information that neighbors have data or not) to select optimum cluster-head and eventually improve network lifetime. Our simulation results show its effectiveness in balancing energy consumption and prolonging the network lifetime compared with LEACH and HEED algorithms.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.9
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• pp.1340-1346
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• 2022

In this paper, we consider a downlink non-orthogonal multiple access (NOMA) using multiple transmit antennas, where the transmit antenna selection scheme is used to reduce the system complexity. Thus, in this paper, we propose radio resource allocation and receiver selection schemes in order to improve the outage probability performance of the downlink NOMA system using the transmit antenna selection scheme. In particular, the receiver selection scheme is a method of grouping the receivers to improve the outage probability performance, and the radio resource allocation scheme is a method of allocating radio resources to each group in order to enhance the outage probability performance. In addition, through the computer simulation under the assumption of independent Rayleigh fading channels, we show that the proposed radio resource allocation and receiver selection schemes can improve the outage probability performance at the expense of the sum rate performance.

• Journal of the Korean Society for Library and Information Science
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• v.40 no.3
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• pp.233-262
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• 2006

This study is designed to identify the knowledge information resources of international organizations and the current situation and problems of gaining and using the information resources of international organizations. The researcher made a selection of a total of 115 organizations: 59 international organizations and Professional organizations under the jurisdiction of UN, 29 intergovernmental organizations, and 27 regional organizations. The questionnaire subjects were domestic university libraries. national libraries. and professional libraries of a certain size. The researcher took a look at the current collection situations of international organization information resources, the designation of trusted libraries. the subject areas of Possessed international organizational publications. the current situations of material management and use, the demand for international information resources. The findings will hopefully be used as basic materials for the service model of official international integrate information organization.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.9
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• pp.2590-2608
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• 2023

The high-altitude and mobility characteristics of unmanned aerial vehicles (UAVs) have made them a key element of new radio systems, particularly because they can exceed the limits of terrestrial networks. However, at high altitudes, UAVs can be significantly affected by intercell interference at a high line-of-sight probability. To mitigate this drawback, we propose an algorithm that selects the optimal beam to reduce interference and maximize transmission efficiency. The proposed algorithm comprises two steps: constructing a user-location-based fingerprint database according to the user types presented herein and cooperative beam selection. Simulations were conducted using cellular cooperative downlink systems for analyzing the performance of the proposed method, and the signal-to-interference-plus-noise cumulative distribution function and spectral efficiency cumulative distribution function were used as performance analysis indicators. Simulation results showed that the proposed algorithm could reduce the effect of interference and increase the performance of the desired signal. Moreover, the algorithm could efficiently reduce overheads and system cost by reducing the amount of resources required for information exchange.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.9
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• pp.3151-3168
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• 2021

Internet of Things (IoT) connects several objects with embedded sensors and they are capable of exchanging information between devices to create a smart environment. IoT smart devices have limited resources, such as batteries, computing power, and bandwidth, but comprehensive sensing causes severe energy restrictions, lowering data quality. The main objective of the proposal is to build a hybrid protocol which provides high data quality and reduced energy consumption in IoT sensor network. The hybrid protocol gives a flexible and complete solution for sensor selection problem. It selects a subset of active sensor nodes in the network which will increase the data quality and optimize the energy consumption. Since the unused sensor nodes switch off during the sensing phase, the energy consumption is greatly reduced. The hybrid protocol uses Dijkstra's algorithm for determining the shortest path for sensing data and Ant colony inspired variable path selection algorithm for selecting active nodes in the network. The missing data due to inactive sensor nodes is reconstructed using enhanced belief propagation algorithm. The proposed hybrid method is evaluated using real sensor data and the demonstrated results show significant improvement in energy consumption, data utility and data reconstruction rate compared to other existing methods.

• Journal of the Korean Society for Library and Information Science
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• v.37 no.2
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• pp.27-56
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• 2003

The school library media specialists offer the users assistance in using information resources and instructional media by assessing, evaluating and selecting the most appropriate materials for the present educational situation in school. The format of the information media and the scope of the media center collection have constantly been changed by information technology. Media specialist has to know the selection criteria to be capable of providing any media format in the technological society, particularly of providing instruction software(courseware), multimedia, hypermedia and digital reference service to maintain the school library media center as one of the user oriented educational information centers. This paper presents the selection criteria for the instruction media by media format as one of the useful guidelines to the media specialist.

• The Journal of Industrial Distribution & Business
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• v.6 no.2
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• pp.17-24
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• 2015

Purpose - The main goals of this study are (1) to study the information sources used the most by customers of Islamic banks; and (2) to compare this with conventional bank customers. Research design, data, and methodology - 125 Islamic bank customers and 125 conventional bank customers were surveyed. The study employed two independent sample tests. Additionally, an exploratory study was conducted to support the quantitative analysis. Result - The results show that Islamic bank customers use personal as well as marketing information sources more intensely than conventional bank customers, although the result differences were not significant. Specifically, customers of Islamic banks use certain personal resources (parents and friends) and marketing information (marketers)intensely than conventional bank customers. Conclusion - The study revealed that friends and parents are the most important information sources for the selection of the Islamic bank. In addition, based on the resources used, Islamic banking customers can be classified as traditional and religious communities. Therefore, the most effective customer communications will be through Islamic groups such as Islamic social institutions and Islamic educational institutions.

• Journal of the Korean Society for Library and Information Science
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• v.44 no.2
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• pp.5-27
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• 2010

The purpose of this research is to examine the characteristics and problems of OASIS, a web archive, developed and operated by the National Library of Korea, and then to propose how to improve the quality of its contents. An analysis of the contents in 'Literature' and 'Social Sciences' in the OASIS website shows problems, including low quality of some contents, lack of balance in subjects and creators/publishers, duplicate collections of web documents and web sites, lack of currency and evidence of unique or scholarly value of collected web resources, etc. Suggested are the use of 'real-name' of subject specialists to ensure their responsibilities in selection process and the addition of metadata elements to evidence the appropriate application of selection criteria.