• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권3호
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• pp.446-458
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• 2013

Recently, energy-efficient cellular transmission has received considerable research attention to improve the energy efficiency of wireless communication. In this paper, we consider a cellular network consisting of one base station (BS) and multiple user terminals and explore the network coding for enhancing the energy efficiency of cellular downlink transmission from BS to users. We propose the network coded cellular transmission scheme and conduct its energy consumption analysis with target outage probability and data rate requirements in Rayleigh fading environments. Then, the energy efficiency in Bits-per-Joule is further defined and analyzed to evaluate the number of bits delivered per Joule of energy cost. Numerical results show that the network coded cellular transmission significantly outperforms the traditional cellular transmission in terms of energy efficiency, implying that given a Joule of energy cost, the network coded cellular transmission scheme can deliver more bits than the traditional cellular transmission.

• 기술혁신학회지
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• 제3권3호
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• pp.36-52
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• 2000

This study takes an issue of efficiency analysis in the presence of network effect utilizing the DEA (Data Envelopment Analysis) framework. Network effect has important policy implication for the regulation of local monopolies which undertake their business through physical network, such as electricity, natural gas, local telephony, etc. If the difference in spatial condition between companies is not controlled properly, the performance comparison and associated incentive regulation bear significant bias. In this study, we propose a methodology to measure the true managerial or technical efficiency apart from efficiency difference accruing from the difference in spatial condition. A series of modified DEA efficiency models are combined to investigate the extent of exogenous and endogenous efficiency component in the Korean natural gas distribution companies. Empirical results show that the network effect plays significant role in determining superficial performance difference.

• 한국IT서비스학회지
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• 제13권4호
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• pp.93-107
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• 2014

Interests on collaborative research and academic relationship among researchers have been increased. Collaborative researchers can maximize productivity, time and cost savings, and reduce the risk of research. An empirical study on the research productivity of co-authors' network and review efficiency of the reviewer network was conducted based on co-author networks and reviewer networks in Korea Society of IT Service. This study aims to find the characteristics of the co-author and reviewer networks, and to analyze research productivity and review efficiency in order to draw some implications. The meaning of interactions among professional groups was analyzed. Research productivity index was calculated using 728 authors' papers submitted to the society. In order to verify the effects of indicators of social network analysis on research productivity and review efficiency, correlation and regression analyses were used. As a result, the indicators of network centrality did not affect the review efficiency, but affect the research productivity.

• Journal of Communications and Networks
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• 제18권5호
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• pp.713-724
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• 2016

Energy consumption has become a main problem of sustainable development in communication networks and how to communicate with high energy efficiency is a significant topic that researchers and network operators commonly concern. In this paper, an energy-efficient multicast algorithm in multi-hop wireless networks is proposed aiming at new generation wireless communications. Traditional multi-hop wireless network design only considers either network efficiency or minimum energy consumption of networks, but rarely the maximum energy efficiency of networks. Different from previous methods, the paper targets maximizing energy efficiency of networks. In order to get optimal energy efficiency to build network multicast, our proposed method tries to maximize network throughput and minimize networks' energy consumption by exploiting network coding and sleeping scheme. Simulation results show that the proposed algorithm has better energy efficiency and performance improvements compared with existing methods.

• 산업경영시스템학회지
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• 제43권3호
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• pp.87-94
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• 2020

In this study, the factors affecting the efficiency of 48 projects of private R&D institutes were analyzed using the Tobit model. Influencing factors were selected as open R&D network size, IT industry, interaction between R&D network size and IT industry, and type of R&D network cooperation. As a result of Tobit analysis, the R&D network size, the IT industry, and the type of R&D network cooperation were found to be significant. The larger the open R&D network size, the lower the efficiency, and the IT industry showed lower R&D efficiency than other industries. In addition, cooperation with universities and research institutes showed lower R&D efficiency than cooperation with companies. As a result of these studies, companies will be able to select and focus on cooperation with the outside in relations and investment allocation.

• 환경정책연구
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• 제14권2호
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• pp.27-47
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• 2015

투입 산출변수의 외생적 흐름에 기초한 전통적인 자료포락분석은 생산활동의 모든 내부과정을 'black box'로 간주하며 각 생산단계의 상호작용에 대한 정보를 고려하지 못한 한계를 지닌다. 이에 생산과정을 세분화하고 각 생산단계의 효율성을 연계하여 추정하는 Network DEA 방식이 최근 활발히 적용되고 있으며 특히 환경효율성의 추정과정을 생산 및 저감활동으로 구분한 연구가 대표적이다. 본고는 한국의 51개 산업단지를 대상으로 Network DEA에 기초한 환경효율성 추정을 시도하였으며, 분석결과 추정치의 변별력, 비효율의 발생단계, 기타 외생변수와의 통계적 관련성 등의 관점에서 전통적 DEA 추정결과에 비해 우수한 점을 확인할 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권5호
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• pp.1333-1353
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• 2012

The robustness of a network is usually measured by error tolerance and attack vulnerability. Significant research effort has been devoted to determining the network design with optimal robustness. However, little attention has been paid to the problem of how to improve the robustness of existing networks. In this paper, we investigate how to optimize attack tolerance and communication efficiency of an existing network under the limited link addition. A survival fitness metric is defined to measure both the attack tolerance and the communication efficiency of the network. We show that network topology reconfiguration optimization with limited link addition (NTRLA) problem is NP-hard. Two approximate solution methods are developed. First, we present a degree-fitness parameter to guide degree-based link addition method. Second, a preferential configuration node-protecting cycle (PCNC) method is developed to do trade-off between network robustness and efficiency. The performance of PCNC method is demonstrated by numerical experiments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권3호
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• pp.1599-1610
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• 2019

Intelligent services have expanded as Internet of Things (IoT) technology has evolved and new requirements emerge to accommodate various services. One new requirement is transmitting data over long distances with low-power. Researchers have developed low power wide area (LPWA) network technology to satisfy the requirement; this can improve IoT network infrastructure and increase the range of services. However, network coverage expansion causes several problems. The traffic load is concentrated at a specific gateway, which causes network congestion and leads to decreased transmission efficiency. Therefore, the approach proposed in this paper attempts to recognize and then avoid congestion through gateway channel hopping. The LPWA network employs multiple channels, so wireless channel hopping is available in a gateway. Devices that are not delay sensitive wait for the gateway to reappear on their wireless channel; delay sensitive devices change the wireless channel along the hopping gateway. Thus, the traffic load and congestion in each wireless channel can be reduced improving transmission efficiency. The proposed approach's performance is evaluated by computer simulation and verified in terms of transmission efficiency.

• 무역학회지
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• 제47권6호
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• pp.135-171
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• 2022

This study is to find out how psychological characteristics and management capabilities of small manufacturers influence business performance through parameters including self-efficiency, network, and collaboration strategies. The survey was implemented between December 26, 2017 and January 15, 2018. The final 439 valid questionnaires were collected and used for analysis. The results were followed. First, the relationship between psychological characteristics and self-efficiency, and the path coefficient for psychological characteristics and network were significant. Second, management capabilities was related to self-efficiency, and the path factor for managing capability and network relationships was significant. Lastly, the path coefficients for self-efficiency and collaboration strategies were not significant, and the path coefficients for network and collaboration strategies were significant.

• 기술혁신학회지
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• 제13권4호
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• pp.794-816
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• 2010

평가위원간 네트워크가 국가연구개발사업의 효율성과 어떠한 영향을 가지는 것인가에 대한 의문을 해소하고자 본 연구는 국가연구개발사업 중 대형사업으로 분류되는 원자력연구개발사업의 2007년 및 2008년간 평가위원의 네트워크를 분석하고 이를 효율성 분석과 연계하여 고찰하여 보았다. 분석을 위해 2개년간 평가에 참여한 평가위원의 기초 자료를 수집하고 효율성 분석을 위해 국가연구개발사업 성과보고서에 제시된 통계치를 토대로 자료포락분석을 활용하였다. 분석 결과 평가위원간 네트워크 정도가 미약할 수록 사업의 효율성이 상대적으로 높게 나타났는데, 이는 사업의 효율성은 연구자가 도출하는 연구 업적도 중요하지만 평가시 섭외되는 평가위원간의 네트워크를 고려하여야 함을 의미한다. 이러한 연구는 그간 평가의원 구성에 있어 전문성 외에도 평가위원간 네트워크를 고려하여야 함을 제시하였다는 점에서 의미를 찾을 수 있다.