• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4145-4164
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• 2016

Energy harvesting is an increasingly attractive source of power for cellular networks, and can be a promising solution for green networks. In this paper, we consider a cellular network with power beacons powering multiple mobile terminals with microwave power transfer in energy beamforming. In this network, the power beacons are powered by grid and renewable energy jointly. We adopt a dual-level control architecture, in which controllers collect information for a core controller, and the core controller has a real-time global view of the network. By implementing the water filling optimized power allocation strategy, the core controller optimizes the energy allocation among mobile terminals within the same cluster. In the proposed green energy cooperation paradigm, power beacons dynamically share their renewable energy by locally injecting/drawing renewable energy into/from other power beacons via the core controller. Then, we propose a new water filling optimized green energy cooperation management strategy, which jointly exploits water filling optimized power allocation strategy and green energy cooperation in cellular networks. Finally, we validate our works by simulations and show that the proposed water filling optimized green energy cooperation management strategy can achieve about 10% gains of MT's average rate and about 20% reduction of on-grid energy consumption.

• Journal of Communications and Networks
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• v.14 no.4
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• pp.374-384
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• 2012

Utilizing artificial noise (AN) is a good means to guarantee security against eavesdropping in a multi-inputmulti-output system, where the AN is designed to lie in the null space of the legitimate receiver's channel direction information (CDI). However, imperfect CDI will lead to noise leakage at the legitimate receiver and cause significant loss in the achievable secrecy rate. In this paper, we consider a delayed feedback system, and investigate the impact of delayed CDI on security by using a transmit beamforming and AN scheme. By exploiting the Gauss-Markov fading spectrum to model the feedback delay, we derive a closed-form expression of the upper bound on the secrecy rate loss, where $N_t$ = 2. For a moderate number of antennas where $N_t$ > 2, two special cases, based on the first-order statistics of the noise leakage and large number theory, are explored to approximate the respective upper bounds. In addition, to maintain a constant signal-to-interferenceplus-noise ratio degradation, we analyze the corresponding delay constraint. Furthermore, based on the obtained closed-form expression of the lower bound on the achievable secrecy rate, we investigate an optimal power allocation strategy between the information signal and the AN. The analytical and numerical results obtained based on first-order statistics can be regarded as a good approximation of the capacity that can be achieved at the legitimate receiver with a certain number of antennas, $N_t$. In addition, for a given delay, we show that optimal power allocation is not sensitive to the number of antennas in a high signal-to-noise ratio regime. The simulation results further indicate that the achievable secrecy rate with optimal power allocation can be improved significantly as compared to that with fixed power allocation. In addition, as the delay increases, the ratio of power allocated to the AN should be decreased to reduce the secrecy rate degradation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1238-1259
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• 2019

Saving energy is a big challenge for Wireless Sensor Networks (WSNs), which becomes even more critical in large-scale WSNs. Most energy waste is communication related, such as collision, overhearing and idle listening, so the schedule-based access which can avoid these wastes is preferred for WSNs. On the other hand, clustering technique is considered as the most promising solution for topology management in WSNs. Hence, providing interference-free clustering is vital for WSNs, especially for large-scale WSNs. However, schedule management in cluster-based networks is never a trivial work, since it requires inter-cluster cooperation. In this paper, we propose a clustering method, called Interference-Free Clustering Protocol (IFCP), to partition a WSN into interference-free clusters, making timeslot management much easier to achieve. Moreover, we model the clustering problem as a multi-objective optimization issue and use non-dominated sorting genetic algorithm II to solve it. Our proposal is finally compared with two adaptive clustering methods, HEED-CSMA and HEED-BMA, demonstrating that it achieves the good performance in terms of delay, packet delivery ratio, and energy consumption.

• Proceedings of the Korean System Dynamics Society
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• 2004.08a
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• pp.109-128
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• 2004

The complexity of information and communication policy has been increasing due to its rapid changes and its expansions toward various fields. I used the2001, 2002 and 2003 White Papers on MIC(Ministry of Information and Communication Republic of Korea) as a reference and the Vensim PLE program to create a causal map. According to my analysis, no major feedback loop was found among the information and communication policies. Thus, it was impossible to conduct a causal map analysis on these policies. The causal map analysis is usually employed to understand a complex mechanism of entire policies by finding feedback loops among them. A lack of feedback loops makes it impossible to conduct the causal map analysis and means that the mechanism of such policies is even more complex to understand. The most important conclusion is that to consider feedback thought among the policies based on the systems thinking before making the policies.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.711-711
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• 2006

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5098-5103
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• 2012

This study examines the effect of information systems through communication and process competency to increase customer relationship competency. This study focuses on the effect of information systems which help internal customers for their work to satisfy the external customers. Based on the data collected by KRIVET and the Ministry of employment and labor, information systems, communication, process competency, and customer relationship competency are examined. The result showed that information system has an influence on communication and process competency, significantly. Process competency affect customer relationship competency positively while communication does not. However, communication has a positive influence on process competency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.3
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• pp.1083-1097
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• 2018

This paper presents a novel range-free localization algorithm based on quantum particle swarm optimization. The proposed algorithm is capable of estimating the distance between two non-neighboring sensors for multi-hop heterogeneous wireless sensor networks where all nodes' communication ranges are different. Firstly, we construct a new cumulative distribution function of expected hop progress for sensor nodes with different transmission capability. Then, the distance between any two nodes can be computed accurately and effectively by deriving the mathematical expectation of cumulative distribution function. Finally, quantum particle swarm optimization algorithm is used to improve the positioning accuracy. Simulation results show that the proposed algorithm is superior in the localization accuracy and efficiency when used in random and uniform placement of nodes for heterogeneous wireless sensor networks.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.5
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• pp.861-871
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• 2017

There is a Korean proverb that learns old things and learns new things from it. This study analyzes the change of the policy governance system in the field of information and communication since 2008 and outlines the future directions. The launch of the Korea Communications Commission (KCC), which combines the Ministry of Information and Communication and the Korea Broadcasting Commission in 2008, and the separation of the Korea Communications Commission and Ministry of Science, ICT and Future Planning in 2013, were systematic responses to the policy environment. Recent changes in the ICT environment, such as the advent of the fourth industrial revolution and the intelligence information society, call for an organizational timely response. In the future, it will be very important to set the scope of ICT policy, the establishment of a dedicated organization, the strengthening of the regulatory system, and the role of the government and the market.

• Journal of Information Technology Services
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• v.13 no.3
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• pp.111-128
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• 2014

President Park Geun-hye Administration has established the Ministry of Science, ICT and Future Planning (MSIP) to build a creative economy using Information and Communication Technology (ICT). July 2, 2013, The National Assembly has legislated the special act on the ICT promotion and convergence so called special ICT Act. This special ICT Act has reduced the legal basis through legislative process and departmental agreement. Therefore many experts worried that since the MSIP's key functions and roles are being reduced, there will be a limit to the MSIP's endeavor for the advancement of science technology and the ICT promotion and convergence. The establishment of the Agency, together with the formation of 'IT Strategy Committee', is considered to be one of the core items of the Special Act on ICT. MSIP originally planned to integrate the ICT R&D functions scattered across many governmental organizations, including Korea Communications Agency (KCA), KEIT and Korea Creative Contents Agency (KOCCA), into the Agency to separate the national ICT R&D from private R&D and streamline the process of 'discovery-selection-evaluation-commercialization'. The analytical results in this study are supposed to the establishment of efficient ICT governance systems as the practical strategies to actively cope with the changes of ICT convergence environment. It is also expected to the revision on the special ICT Act in the ICT budget and governance. Therefore, MSIP should cover research and development (R&D) as well as major ICT promotion functions to a creative economy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.4
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• pp.1020-1041
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• 2024

With the development of covert communication technologies, the number of covert communication technologies using blockchain as a carrier is increasing. However, using the transaction amount of digital currency as a carrier for covert communication has problems such as low embedding rate, large consumption of transaction amount, and easy detection. In this paper, firstly, by experimentally analyzing the distribution of bitcoin transaction amounts, we determine the most suitable range of amounts for matrix decomposition. Secondly, we design a novel matrix decomposition method that can successfully decompose a large amount matrix into two small amount matrices and utilize the elements in the small amount matrices for covert communication. Finally, we analyze the feasibility of the novel matrix decomposition method in this scheme in detail from four aspects, and verify it by experimental comparison, which proves that our scheme not only improves the embedding rate and reduces the consumption of transaction amount, but also has a certain degree of resistance to detection.