• 한국인터넷방송통신학회논문지
• /
• 제12권4호
• /
• pp.31-36
• /
• 2012

본 논문에서는 인지무선통신에서 중요한 기술 중 하나인 스펙트럼 센싱의 Hidden node의 문제나 셀룰라 시스템에서 셀 경계에서 CPE(Customer Premises equipments)의 낮은 SNR(Signal to Noise Ratio)로 인한 센싱 성능 저하를 해결하기 위해 CPE들의 협력 릴레이 기법을 사용한 협력 스펙트럼 센싱을 제안하고 검출확률 성능을 분석한다. 송신단과 수신단 사이의 릴레이(Relay) 적용된 협력 스펙트럼 센싱은 가상의 공간 다이버시티이득(Spatial Diversity Gain)을 얻을 수 있어 센싱 성능이 향상된다. 협력 통신 기법 중 다중안테나를 적용한 AF(Amplify and Forward) 고정형 중계기를 사용하여 다이버시티이득을 얻는 시스템 모델을 제안하고, 검출 성능 향상을 분석한다.

• Asia pacific journal of information systems
• /
• 제8권1호
• /
• pp.43-64
• /
• 1998

Cooperative query answering is a research effort to develop a fault-tolerant and intelligent database system using the semantic knowledge base constructed from the underlying database. Such knowledge base has two aspects of usage. One is supporting the cooperative query answering process for providing both an exact answer and neighborhood information relevant to a query. The other is supporting ongoing maintenance of the knowledge base for accommodating the changes in the knowledge content and database usage purpose. Existing studies have mostly focused on the cooperative query answering process but paid little attention to the dynamic knowledge base maintenance. This paper proposes a multi-level knowledge representation framework called Knowledge Abstraction Hierarchy(KAH) that can not only support cooperative query answering but also permit dynamic knowledge maintenance, On the basis of the KAH, a knowledge abstraction database is constructed on the relational data model and accommodates diverse knowledge maintenance needs and flexibly facilitates cooperative query answering. In terms of the knowledge maintenance, database operations are discussed for the cases where either the internal contents for a given KAH change or the structures of the KAH itself change. In terms of cooperative query answering, four types of vague queries are discussed, including approximate selection, approximate join, conceptual selection, and conceptual join. A prototype system has been implemented at KAIST and is being tested with a personnel database system to demonstrate the usefulness and practicality of the knowledge abstraction database in ordinary database application systems.

• 한국위성정보통신학회논문지
• /
• 제7권1호
• /
• pp.7-12
• /
• 2012

본 논문에서는 인지무선통신에서 중요한 기술 중 하나인 스펙트럼 센싱의 Hidden node의 문제나 셀룰라 시스템에서 셀 경계에서 CPE(Customer-Primise equipments)의 낮은 SNR(Signal to Noise Ratio)로 인한 센싱 성능 저하를 해결하기 위해 CPE들의 협력릴레이 기법을 사용한 협력 스펙트럼 센싱을 제안하고 검출확률 성능을 분석한다. 송신단과 수신단 사이의 릴레이(Relay) 적용된 협력 스펙트럼 센싱은 가상의 공간 다이버시티이득(Spatial Diversity Gain)을 얻을 수 있어 센싱 성능이 향상된다. 협력 통신 기법 중 AF(Amplify and Forward)와 DF(Decoded and Forward)방식이 대표적이다. 따라서 이 두가지 협력통신 기법을 적용하여 협력스펙트럼 센싱의 검출확률의 성능을 비교하고 분석한다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권12호
• /
• pp.5898-5916
• /
• 2018

In this paper, the downlink performance of multi-cell distributed antenna systems (DAS) with a single user in each cell is investigated. Assuming the channel state information is available at the transmitter, four transmission modes are formulated as combinations of remote antenna units (RAUs) selection and cooperative transmission, namely, non-cooperative transmission without RAU selection (NCT), cooperative transmission without RAU selection (CT), non-cooperative transmission with RAU selection (NCT_RAUS), and cooperative transmission with RAU selection (CT_RAUS). By using probability theory, the cumulative distribution function (CDF) of a user's signal to interference plus noise ratio (SINR) and the system ergodic capacity under the above four modes are determined, and their closed-form expressions are obtained. Furthermore, the system energy efficiency (EE) is studied by introducing a realistic power consumption model of DAS. An expression for determining EE is formulated, and the closed-form tradeoff relationship between spectral efficiency (SE) and EE is derived as well. Simulation results demonstrate their consistency with the theoretical analysis and reveal the factors constraining system EE, which provide a scientific basis for future design and optimization of DAS.

• Educational Technology International
• /
• 제6권1호
• /
• pp.103-119
• /
• 2005

This study investigated to designand implement web-based collaborative learning system Co-Net and map out students' learning procedure using the system, based upon Student Team Achievement Division (STAD Slavin, 1990, 1996). There are technical process and instructional considerations to be made during the design process. The former are those that concern equipment requirements and specifications and include Ease of Use, Speed of Access, and Flexibility. On the other hand, instructional considerationsare concerned with the delivery and access of instructional materials and their outcomes on learners. They are cooperative interactions within groups and group heterogeneity, learner control, group incentives, individual accountability, equal opportunity for earning high scores and contributing to group effort, task specialization, and competition among groups. A web site for a virtual learning environment designed and built by the authors and known as Co-Net is then explained along with the whole process learners inside the environment. The main page of Co-Net consists of 15 menus to implement cooperative learning process. The cooperative learning activities using 15 menus are composed of six phases (1) preparation of the new knowledge (2) presentation of the new knowledge (3) knowledge assimilation and application (4) team and individual evaluation (5) team and individual recognition Throughout the five phases, the appropriate use of cooperative learning techniques has been shown to have both academic and social benefits to learners.

• KEPCO Journal on Electric Power and Energy
• /
• 제6권3호
• /
• pp.279-284
• /
• 2020

This paper presents the conceptual design of a cooperative control with Energy Management System (EMS) and Distribution Management System (DMS). This control enables insufficient reactive power reserve in a power transmission system to be supplemented by surplus reactive power in a power distribution system on the basis of the amount of the needed reactive power reserve calculated by the EMS. This can be achieved, because increased numbers of microgrids with distributed energy resources will be installed in the distribution system. Furthermore, the DMS with smart control strategy by using surplus reactive power in the distribution system of the area has been gradually installed in the system as well. Therefore, a kind of hierarchical voltage control and cooperative control scheme could be considered for the effective use of energy resources. A quantitative index to evaluate the current reactive power reserve of the transmission system is also required. In the paper, the algorithm for the whole cooperative control system, including Area-Q Indicator (AQI) as the index for the current reactive power reserve of a voltage control area, is devised and presented. Finally, the performance of the proposed system is proven by several simulation studies.

• 수산경영론집
• /
• 제32권1호
• /
• pp.99-123
• /
• 2001

The relatively recent emphasis on a total allowable catch(TAC) system is placing new demands on fisheries management. Korean fisheries law has provided recently for implementation of the TAC based on fishery management system, in order to conserve and manage fisheries resources rationally in its exclusive economic zone(EEZ). In 1998, the TAC system was first applied to Korean fisheries. This TAC system is currently undergoing a second trial period, having been put under the system for 20012002 and continuous trial basis until the complete settlement of EEZ system agreement among three countries, Korea, China and Japan. The TAC system implementation needs are sophisticated information collection, analysis and modeling that will continue to increase and require the high management resources. In addition, data on social and economic impacts on TAC system is sometimes inadequate. The implementation of the TAC system provides a unique opportunity to examine the limits of management information and resources, and to solve the problems in Korean fisheries management system, These limits and problems are complicated by an inadequate biologically and economically information and insufficient management resources. Government and fisheries cooperatives must be cooperated in the management process in order to minimize its conflicts and maximize commitment to sustain fishery development. Recognition of the ineffectiveness and its potential consequences leads to the adoption of the cooperative-based co-management approach in implementation of TAC system. In 1998, the TAC system was first applied to Korean fisheries, where traditional fishery management has consisted mainly of technical measures and input controls. The QMS of TAC system has been implemented in the form of cooperative-based co-management framework. This QMS framework was chosen to overcome many difficulties and limits that a competitive TAC system would impose on Korean traditional fisheries management. The implementation of the QMS of TAC system provides a unique opportunity to examine the limits of management information and resources, and to solve the problems in Korean fisheries management system.

• 컴퓨터교육학회논문지
• /
• 제11권6호
• /
• pp.95-102
• /
• 2008

본 연구에서 SDG를 사용한 교육 퍼즐구현을 통하여 협동학습을 컴퓨터교육에 적용하였다. SDG란 하나의 컴퓨터 디스플레이에 다중 입력장치로 협동적인 작업을 할 수 있는 시스템을 말한다. SDG 기반의 협동학습을 통해 학습자들은 협동 학습을 수행하게 된다. SDG를 이용한 협동학습이 단일 디바이스를 이용한 개별 학습보다 우월하다는 기존의 연구가 있다. 이를 바탕으로 협동학습을 이용한 퍼즐게임을 구현하였다.

• Journal of Communications and Networks
• /
• 제12권1호
• /
• pp.11-18
• /
• 2010

Diversity-multiplexing tradeoff (DMT) is an efficient tool to measure the performance of multiple-input and multiple-output (MIMO) systems and cooperative systems. Recently, cooperative multicast system with wireless network coding stretched tremendous interesting due to that it can drastically enhance the throughput of the wireless networks. It is desirable to apply DMT to the performance analysis on the multicast system with wireless network coding. In this paper, DMT is performed at the three proposed wireless network coding protocols, i.e., non-regenerative network coding (NRNC), regenerative complex field network coding (RCNC) and regenerative Galois field network coding (RGNC). The DMT analysis shows that under the same system performance, i.e., the same diversity gain, all the three network coding protocols outperform the traditional transmission scheme without network coding in terms of multiplexing gain. Our DMT analysis also exhibits the trends of the three network coding protocols' performance when multiplexing gain is changing from the lower region to the higher region. Monte-Carlo simulations verify the prediction of DMT.

• 한국지능시스템학회:학술대회논문집
• /
• 한국퍼지및지능시스템학회 1996년도 추계학술대회 학술발표 논문집
• /
• pp.323-326
• /
• 1996

In this paper, we propose a new method of the communication system for cooperative behavior and control in a collective autonomous mobile robots. A communication function among the collective robots is essential to intelligent cooperation. In general, global communication is effective for small number of robots. However when the number of robot goes on increasing, this becomes difficult to be realized because of limited communication capacity and increasing amount of information to handle. And also the problems such as communication interference and improper message transmission occur. So we propose local communication system based on infrared sensor to realize the cooperative behavior and control as the solution of above problem. It is possible to prevent overflow of information and exchange of complex information by combining communicate a specific robot. At last we verify the effectiveness of the proposed communication system from example of cooperative behavior.