• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2013.05a
• /
• pp.561-565
• /
• 2013

Due to the development of industrial networks, As an alternative to traditional fieldbus, fieldbus networks move to standard Ethernet that high data throughput and scalable technology. Hence we suggest transmission algorithm which satisfied requirements for hard-real time about periodic and aperiodic message based on general-purposed ethernet, and suggest scheduling algorithm for each message.

• Proceedings of the Korea Contents Association Conference
• /
• 2014.11a
• /
• pp.11-12
• /
• 2014

데드라인을 고려한 스케쥴러는 데드라인 내에 잡을 완료시키기 위해 노드의 실시간 I/O 부하, 데이터 지역성 등을 이용한다. 하지만 데드라인을 만족시키기 위한 기법이 오히려 노드부하를 야기하는 현상이 나타난다. 본 논문에서는 노드의 부하에 따라 맵리듀스 처리 성능이 저하되는 문제점을 해결하기 위해 새로운 스케줄링 기법을 제안한다. 제안하는 스케줄링 기법은 우선 순위에 의해 중지되는 작업의 발생을 감소시키기 위해 동일한 작업을 중복적으로 수행시키는 사행 작업(speculative task)를 처리한다. 맵리듀스 작업의 지연이나 취소를 방지시키기 위해 핫 데이터 청크를 성능이 우수한 노드에 복제한다.

• Journal of the Korean Society for Precision Engineering
• /
• v.9 no.4
• /
• pp.36-43
• /
• 1992

This paper presents a hierarchical real-time operation control and monitoring scheme of the FMS/CIM center which has been implemented at the Automation and Systems Research Institute of Seoul National University. The hierarchical structure of the whole scheme consists of three lavers. The upper layer is in charge of on-line scheduling, computer network control, shop-floor monitoring and command generation for AGV dispatching, machining, assembly, inspection, set-up, etc. The middle layer has six modules, which are installed in the FMS host computer with the upper layer and run on the multi-tasking basis. Each module is connected to one of six cell controllers distributed in the FMS model plant and transfers operation command down to each cell controller through the Ethernet/TCP-IP local area network. The lower layer is comprised of six cell control software modules for machining cell, assembly cell, inspection cell, set-up stations. AS/RS and AGV. Each cell controller reports the status of the manufacturing facilites to the middle layer as well as ecxecuting the appropriate sequence control of the manufacturing processes.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.7C
• /
• pp.592-600
• /
• 2012

In this paper, we proposed that decentralized frequency allocation scheme(DFAS) without network entry procedure between relays in mobile relay system. Frequency Indicator(FI) signal which is the reference signal of frequency division of each relay and Energy Detection(ED) region are defined. In addition, the mobile connected to the relay transmits the FI signal to neighbor relays in order to facilitate communication between relays. Finally, by using this scheme, the cell throughput improvement is confirmed.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.20 no.3
• /
• pp.1-16
• /
• 1995

Group collaborative systems are recently emerging to support a group of users engaged in common tasks such as group decision making, engineering design, group scheduling, or collaborative writing. This paper provides an change management framework for the group collaborative system to facilitate managing dependency relationship between shared objects and dependent user views, and coordinating change and propagation activities between the two in distributed computing environments. Specifically, the framework adopts an object-oriented database paradigm and presents several object constructs capturing dependency management and change notification mechanisms. First, it introduces change management mechanisms with transient shared objects and secondly, it extends them into presistent object computing environment by integrating transaction management mechanisms and change notification mechanisms. A prototype change management framework is developed on a commercial object-oriented database management system.

• Proceedings of the Korean Information Science Society Conference
• /
• 2004.04a
• /
• pp.505-507
• /
• 2004

IEEE 802.11 무선랜 표준에서 MAC(Media Access Control)은 동기와 비동기의 두 가지 타입의 서비스를 지원한다. 동기적 실시간 트래픽은 PCF(Point Coordination Function)에 의해서 폴링 엑세스 기법에 의해 처리된다. 비동기적 비실시간 트래픽은 CSMA/CA 프로토콜 기반의 DCF(Distributed Coordination function)에 의해 처리된다. 그래서 실시간 트래픽은 지연과 패킷손실에 민감하고 비실시간 트래픽은 에러와 처리율에 민감하기 때문에 적당한 트래픽 스케줄링 알고리즘이 설계되어질 필요가 있다. 하지만 IEEE 802.11 무선랜 표준은 실시간 트래픽을 효율적으로 서비스를 해주지 못하고 있다. 그래서 본 논문에서는 PCF 구간내에서 서비스를 받지 못한 실시간 트래픽 스테이션들을 DCF 구간에서 우선적으로 서비스함으로써 QoS를 향상시킬 수 있다.

• Proceedings of the Korea Society for Simulation Conference
• /
• 1998.10a
• /
• pp.90-94
• /
• 1998

한국전력공사 전력연구원은 10년간의 시뮬레이터 개발 경험을 바탕으로 Windows(NT)환경의 시뮬레이터 개발 툴인 Powersim을 독자적으로 개발하고 이를 이용하여 화력발전소 DCS(Distributed Control System) 검증용 시뮬레이터를 개발하고 있다. PowerSim은 GMB(Graphic Model Builder)를 갖춘 국내 최초의 시뮬레이터 개발툴로 다양한 발전소 기기모델과 강사조작반기능을 갖추고 있다. PowerSim은 완벽한 GUI (Graphic User Interface)환경을 지원하여 User가 Icon Drag 방식으로 시뮬레이션 도면(SimDiagram)을 그리면 그래픽 에디터에서 출력된 각종 기기의 접속상태를 나타내는 Netlist를 변환기가 처리하여 기기의 연결상태를 정규화하고 Scheduler는 기기모델(일종의 Subroutine)을 Netlist에 맞게 Scheduling하여 Executive에서 실행 가능한 형태로 만드는 모든 과정이 자동화되어 있다. 따라서, 개발자는 발전소 P&ID(Pipe and Instrument Drawing)에 기초하여 Simdiagram을 그리고 발전소 데이터를 입력하는 것만으로 실시간 시뮬레이터를 구현할 수 있다. 본 논문에서는 PowerSim의 개요와 GMB(Graphic Model Builder) 및 강사조작반에 적용된 GUI 환경과 실시간 Executive에 대해 다룬다.

• Proceedings of the IEEK Conference
• /
• 2003.11c
• /
• pp.191-194
• /
• 2003

In IEEE 802.11b, Medium Access Control Sublayer consists of DCF (Distributed Coordination Function) and PCF (Point Coordination Function). DCF provides contention based services and PCF provides contention free services for QoS satisfaction. DCF uses CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) as an access protocol. And PCF uses Polling Scheme. In this paper, a modified New-PCF, which gives weights to channels with heavier traffic load, was suggested. NS-2 simulations were conducted to compare the service performances with original DCF, PCF and the modified New-PCF respectively. Simulation results has shown the increased overall throughput with the proposed New-PCF compared with other cases.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.5 no.2
• /
• pp.185-192
• /
• 2010

A P2P technology in distributed environments is very useful in the respect that persons to have resources efficiently share the resources. A P2P system is caused as follows : resource search, resource transmission, resource transmission again and then excessively occurred network traffic. To improve performance about this a lot of studies is proceeding. One of this various study's directions to improve performance is recently come to a field to improve usability as such person. At this point this study is proposed P2P group search algorithm to improve usability.

• Journal of Communications and Networks
• /
• v.14 no.5
• /
• pp.554-565
• /
• 2012

In this paper, we study a cross-layer and end-to-end optimization problem for the integrated wireless and wireline network that consists of one wireline core network and multiple wireless access networks. We consider joint end-to-end flow control/distribution at the transport and network layers and opportunistic scheduling at the data link and physical layers. We formulate a single stochastic optimization problem and solve it by using a dual approach and a stochastic sub-gradient algorithm. The developed algorithm can be implemented in a distributed way, vertically among communication layers and horizontally among all entities in the network, clearly showing what should be done at each layer and each entity and what parameters should be exchanged between layers and between entities. Numerical results show that our cross-layer and end-to-end optimization approach provides more efficient resource allocation than the conventional layered and separated optimization approach.