• Journal of Communications and Networks
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• v.13 no.4
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• pp.319-326
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• 2011

Beamforming techniques have been successfully utilized for traffic channels in order to solve the interference problem. However, their use for control channels has not been sufficiently investigated. In this paper, a (semi-) centralized beamforming strategy that adaptively changes beam patterns and controls the total transmit power of cells is proposed for the performance enhancement of the common channel in hierarchical cell structure (HCS) networks. In addition, some examples of its practical implementation with low complexity are presented for two-tier HCS networks consisting of macro and pico cells. The performance of the proposed scheme has been evaluated through multi-cell system-level simulations under optimistic and pessimistic interference scenarios. The cumulative distribution function of user geometry or channel quality has been used as a performance metric since in the case of common control channel the number of outage users is more important than the sum rate. Simulation results confirm that the proposed scheme provides a significant gain compared to the random beamforming scheme as well as conventional systems that do not use the proposed algorithm. Finally, the proposed scheme can be applied simultaneously to several adjacent macro and pico cells even if it is designed primarily for the pico cell within macro cells.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.12
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• pp.4617-4632
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• 2021

IEEE 802.11ax is a protocol being developed for high-density Wireless Local Area Networks (WLAN). Several algorithms have been proposed to improve the level of spatial reuse applied in IEEE 802.11ax. However, these algorithms are tentative and do not specify how to select the transmit power and carrier sense threshold in practice; It is unclear when and why the tuned parameters lead to better network performance. In this paper, we restricted the scale of transmit power tuning to prevent the case of backfire in which spatial reuse will result in transmission failure. If the restrictions cannot be satisfied, spatial reuse will be abandoned. This is why we named the proposed scheme as Arbitration based Spatial Reuse (ASR). We quantified the network performance after spatial reuse, and formulate a corresponding maximum problem whose solution is the optimal carrier sense threshold and transmit power. We verified our theoretical analysis by simulation and compared it with previous studies, and the results show that ASR improves the throughput up to 8.6% compared with 802.11ax. ASR can avoid failure of spatial reuse, while the spatial reuse failure rate of existing schemes can up to 36%. To use the ASR scheme in practice, we investigate the relation between the optimal carrier sense threshold and transmit power. Based on the relations got from ASR, the proposed Relation based Spatial Reuse (RSR) scheme can get a satisfactory performance by using only the interference perceived and the previously found relations.

• KNOM Review
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• v.22 no.2
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• pp.39-47
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• 2019

There are several big data-driven advanced research activities such as meteorological climate information, high energy physics, astronomy research, satellite information data, and genomic research data on KREONET. Since the performance degradation occurs in the environment with the existing network security equipment, methods for preventing the performance degradation on the high-performance research-only network and for high-speed research collaboration are being studied. In addition, the recent issue of quantum computers has been a threat to security using the existing encryption system. In this paper, we construct quantum cryptography-based communication network through environment construction and high-performance transmission test that build physical security through quantum cryptography-based communication network in end-to-end high-speed research network. The purpose of this study is to analyze the effect on network performance when performing physical encryption and to use it as basic data for constructing high-performance research collaboration network.

• Journal of Korea Society of Digital Industry and Information Management
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• v.9 no.3
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• pp.1-12
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• 2013

Illegal software use have been abroad through online (internet) and offline (CD, DVD, USB, etc.). It infringes intellectual property rights and weakens the will to software development. Also, it generates the software errors and virus intrusion in PC. It hinders national software industry and induces the personal and national trade friction. Many group (company, office, organization, institution, etc.) have been realized the prohibition of illegal software use. But, it is too hard to monitor and control illegal software use. In this paper, we propose a method of software management in a group. A software module of client agency is installed in all PC of the group. A main server of the software management controls the all of the PC through the communication. The server blocks the install of illegal software, permits the install / use of honest goods software, monitors the license (term, amount) in all the PC. The system prevents errors of illegal software use, all cuts the virus intrude through the illegal software, improves the performance of PC relatively.

• Journal of the Korea Society of Computer and Information
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• v.22 no.9
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• pp.155-161
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• 2017

As the e-marketplace becomes the core of management activities, researches on motivation, transaction type, strategy, satisfaction, risk management, performance evaluation, etc. have been actively studied, but the factors influencing actual utilization have not been fully. Especially, the factors that affect the intention of the users are limited without consideration of internal environment, external environment, e-marketplace characteristics such as operating rules, characteristics of the company to be used. In order to derive the determinants of B2B e-marketplace use, this study was conducted to examine the relationship between internal environment, external environment, e-marketplace characteristics as independent variables, intention of use as dependent variable, participation qualification, The results were as follows. First, the previous study limited the determinants of intention to use to either internal or external, but this study presented an integrated model that considers both factors. Second, the characteristics of companies participating in e-marketplace were identified by using participation qualification and activity scope as control variables.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.110-120
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• 2014

This article proposes a spectrum sharing method which can avoid the mutual interference in both primary and secondary systems. The two systems make them a priority to use two single-dimension orthogonal signals, the real and imaginary pulse amplitude modulation signals, if the primary system is not in outage with this use. A secondary transmitter is selected to be the primary relay and the active secondary source to perform this. This allows a simultaneous spectrum access without any mutual interference. Otherwise, the primary system attempts to use a full two-dimensional signal, the quadrature amplitude modulation signal. If there is no outage with respect to this use, the secondary spectrum access is not allowed. When both of the previous attempts fail, the secondary system is allowed to freely use the spectrum two whole time slots. The analysis and simulation are provided to analyze the outage performance and they validate the considerable improvement of the proposed method as compared to the conventional one.

• Information Systems Review
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• v.17 no.1
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• pp.65-92
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• 2015

Driven by the development of information technologies, information system (IS) use has been common even in military organizations. In particular, field artillery is currently using the Battalion Tactical Commanding System-A1 (BTCS-A1) to improve fire support. The use of BTCS-A1 makes fire-commanding processes simple and autonomous, which leads to shorten time to support fire. Although BTCS-A1 has been considered as a helpful system, there still exists some dispute regarding its effectiveness and impact on task performance. By conceptualizing BTCS-A1 use as appropriation, this study investigates how BTCS-A1 appropriation promotes task performance. We also hypothesize that IS quality, organizational pressure (institutional pressure and supervisor influence), and team climate (team learning climate and team empowerment climate) increase the appropriation. Survey results show that organizational pressure and team climate promote BTCS-A1 appropriation, which improves users' task performance. However, effect of IS quality is not significant. Theoretical and practical implications are presented.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.9
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• pp.4624-4644
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• 2019

With the development of films, games and animation industry, analysis and reuse of human motion capture data become more and more important. Human motion segmentation, which divides a long motion sequence into different types of fragments, is a key part of mocap-based techniques. However, most of the segmentation methods only take into account low-level physical information (motion characteristics) or high-level data information (statistical characteristics) of motion data. They cannot use the data information fully. In this paper, we propose an unsupervised framework using both low-level physical information and high-level data information of human motion data to solve the human segmentation problem. First, we introduce the algorithm of CFSFDP and optimize it to carry out initial segmentation and obtain a good result quickly. Second, we use the ACA method to perform optimized segmentation for improving the result of segmentation. The experiments demonstrate that our framework has an excellent performance.

• Journal of Internet Computing and Services
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• v.20 no.5
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• pp.67-77
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• 2019

Today, companies are making efforts to improve the performance of workers by utilizing various IT-based mobile and internet devices. In pharmaceutical companies, salespeople are using the e-brochure to search for diverse expertise in real time. Through the e-brochure, pharmacists and doctors can be provided with the information they need, thereby increasing confidence in pharmaceuticals and salespeople. Salespeople can also use e-brochures to improve their work performance and to be more satisfied with their jobs. This study examines which functions of e-brochures satisfy salespeople and what attitudes to the e-brochures they need to have. This paper explains the effect of satisfaction and attitude to the e-brochures on job satisfaction through self-efficacy with statistical analysis. As a statistical result, the functions of e-brochures (professional knowledge, massive amount of data, easy searching, information updates, and the reflection of feedback) and attitudes to the e-brochures (importance, intention to use, belief in improvement, efficacy to use, and negative cognition) influence on self-efficacy of salespeople. Further, self-efficacy has mediating effects on the relationship between the functions of e-brochures / attitudes to e-brochures and job satisfaction. Exceptionally, the mediating effect of self-efficacy was not significant in relation to information updates / reflection of feedback and job satisfaction. These results will explain what functions should be focused for the future development of e-brochures. It will also suggest what attitudes the salespeople should have about e-brochures. Through these efforts, salespeople will be able to utilize new technology of e-brochures to satisfy their jobs and improve their performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.10A
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• pp.1756-1763
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• 2001

In this paper, we propose an ATM-LAN IWU(interworking unit) with threshold based dynamic bandwidth allocation scheme. We analyze a discrete-time based finite queueing model with deterministic service times in order to investigate the performance of the proposed scheme. It is known that the arrival process of IP packets is bursty. So we use an MMPP(Markov Modulated Poisson Process) to model the bursty input traffic. As performance measures, we obtain the packet loss probability and the mean packet delay. We present some numerical results to show the effects of the thresholds on the performance of the DBAS(dynamic bandwidth allocation scheme).