• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 심포지엄 논문집 정보 및 제어부문
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• pp.59-61
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• 2004

Researches about scheduling distributed real-time systems have some weak points, not scheduling both sporadic and periodic tasks and messages or being unable to guaranteeing the end-to-end constraints due to omitting precedence relations between sporadic tasks. This paper describes the application model of sporadic tasks with precedence constraints in a distributed real-time system. It is shown that existing scheduling methods such as Rate Monotonic scheduling are not proper to be applied to the system having sporadic tasks with precedence constraints. So this paper proposes an end-to-end laxity-based priority assignment algorithm which considers the practical laxity of a task and allocates a proper priority to a task.

• 한국정보과학회논문지:시스템및이론
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• 제29권4호
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• pp.201-212
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• 2002

본 연구에서는 다양한 실시간 스케줄링 알고리즘들을 구현할 수 있는 재구성 가능한 스케줄러모델을 제안한다. 제안 모델은 기본적인 작업(job) 디스패처(dispatcher)와 소프트웨어 타이머를 제공하는 하위 계층의 스케줄링 틀(framework)과 이를 기반으로 응용에 적합한 특정 스케줄링 알고리즘을 구현하는 상위 계층의 태스크 스케줄러로 구성된다. 시스템 개발자는 상하 구성 요소간 정보 교환을 위한 커널 내부 인터페이스만 준수한다면, 커널 하부 메커니즘과는 독립적으로 새로운 스케줄링 알고리즘을 구현할 수 있다. 한번 구현된 태스크 스케줄러는 향후 새로운 시스템 구축시 재사용 가능하다. 실시간 리눅스 (Real-Time Linux) (5)에 제안된 스케줄링 틀을 구현한 후, 이를 기반으로 대표적인 실시간 스케줄링 알고리즘들을 시험적으로 구현하여 보았다. 이를 통해 다양한 스케줄링 알고리즘들을 하부의 복잡한 커널 메커니즘 수정 없이 독립적으로 개발할 수 있음을 확인하였다. 또한 실험을 통해 두 단계 분리된 구조를 가진 제안 모델의 스케줄링 오버 헤드가 하나로 통합된 기존 일체형 스케줄러와 큰 차이가 없음을 확인할 수 있었다.

• 산업기술연구
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• 제18권
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• pp.139-148
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• 1998

Traditionally, the problems of manufacturing technology and manufacturing management have been treated independently. In this research, we endeavor to integrate the process planning and scheduling activities as an attempt to integrate the two realms. To draw up a plan of process planning and scheduling in real manufacturing environment is not an easy task because available time to plan could be limited and the shop status could change frequently. So we propose an architecture of integrated process planing and scheduling problem within the allowed time even if sheep situations change rather frequently. We argue that we can obtain a better and practical scheduling solution by dynamically changing the processing machines and operations as the shop condition changes. The proposed system takes the initial information for alternative machines and operations represented by an AND/OR graph as its input. Other informational inputs to the system are part order and shop statues. The system then generates new process plan and schedules during permitted time. Experimental results show that the proposed scheme provides a viable solution for real world scheduling problems.

• ETRI Journal
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• 제26권5호
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• pp.391-396
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• 2004

In this paper, we propose a packet scheduling discipline called packet loss fair scheduling, in which the packet loss of each user from different real-time traffic is fairly distributed according to the quality of service requirements. We consider an orthogonal frequency division multiple access (OFDMA) system. The basic frame structure of the system is for the downlink in a cellular packet network, where the time axis is divided into a finite number of slots within a frame, and the frequency axis is segmented into subchannels that consist of multiple subcarriers. In addition, to compensate for fast and slow channel variation, we employ a link adaptation technique such as adaptive modulation and coding. From the simulation results, our proposed packet scheduling scheme can support QoS differentiations while guaranteeing short-term fairness as well as long-term fairness for various real-time traffic.

• 한국정보통신학회논문지
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• 제15권8호
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• pp.1820-1831
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• 2011

본 논문에서는 제한된 에너지 자원을 사용하는 센서 노드에서 실시간 및 비실시간 태스크의 실행이 요구되는 경우, 효율적인 전력 소비와 실시간 태스크의 마감시한 보장 및 비실시간 태스크의 향상된 평균 응답 시간을 제공하는 혼합 태스크 스케줄링 기법을 제안하였다. 제안한 혼합 태스크 스케줄링 기법은 기존 EDF 기반 DVS 스케줄링 기법, FIFO 기반 TinyOS 스케줄링 기법과 태스크 클러스터링 기반의 비선점형 실시간 스케줄링 기법과 성능을 비교하여 그 우수성을 검증하였다.

• 한국국방경영분석학회지
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• 제25권1호
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• pp.199-214
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• 1999

The Constructive Battle Simulation Model is very important to the recent military training for the substitution of the field training. However, real battlefield systems operate under real-time conditions, they are inherently distributed, concurrent and dynamic. In order to reflect these properties by the computer-based simulation systems which represent real world processes, we have been developing constructive simulation model for several years. Conventionally, scheduling and resource allocation activities which have timing constraints, we elaborated on these issues and developed the simulation system on commercially available hardware and operating system with lock-free resource allocation scheme and rate monotonic scheduling.

• 한국컴퓨터정보학회논문지
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• 제12권3호
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• pp.147-153
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• 2007

태스크 스케줄링은 여러 개의 수행 가능한 태스크 중에서 하나의 태스크를 선정하여 프로세서에 할당하는 중요한 역할을 한다. 실시간 시스템에서 경성 실시간 태스크를 적시에 스케줄링하지 못하면 시스템이 다운되는 최악의 상태가 발생하므로 실시간 시스템은 효율성, 자원 및 속도 등의 문제 외에도 시간 제약도 진지하게 고려해야 한다. 본 논문에서는 L-RE 좌표를 이용하여 실시간 다중프로세서 시스템에서의 새로운 우선순위 기준 스케줄링 알고리즘을 제안한다. L-RE 좌표 알고리즘은 태스크의 스케줄링 효율을 높이기 위해 고안 되었으며 우선순위를 할당하는데 데드라인과 함께 유휴시간을 고려하고 있다. 시뮬레이션 결과는 LR-E 알고리즘이 EDF보다 스케줄의 원활성을 높이고 또 LLF보다는 문맥교환 수를 줄일 수 있음을 보여준다.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.114-120
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• 2002

In a distributed real-time control system, it is essential to confirm the timing behavior of all tasks because these tasks of each real-time controller have to finish their processes within the specified time intervals called a deadline. In order to satisfy this objective, the timing analysis of a distributed real-time system such as shcedulability test must be performed during the system design phase. In this study, a simple application of CAN fur a vehicle body network system is formulated to apply to a holistic scheduling analysis, and the worst-case execution time (WCET) and the worst-case end-to-end response time (WCRT) are evaluated in the point of holistic system view.

• 제어로봇시스템학회논문지
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• 제18권4호
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• pp.302-307
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• 2012

Real-time systems perform periodic tasks and real-time aperiodic tasks such as alarm processing. Especially the periodic tasks included in control systems such as robots have precedence relationships among them. This paper proposes a new scheduling algorithm based on topological sort and residual time. The precedence relationships among periodic tasks are translated to the priorities of the tasks using topological sort algorithm. During the execution of the system the proposed scheduling algorithm decides on whether or not a newly arrived real-time aperiodic task is accepted based on residual time whenever the aperiodic task such as alarm is arrived. The proposed algorithm is validated using examples.

• Journal of Computing Science and Engineering
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• 제9권2호
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• pp.108-117
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• 2015

Interrupt handling is generally separated from process scheduling. This can lead to a scheduling anomaly and priority inversion. The processor can interrupt a higher priority process that is currently executing, in order to handle a network packet reception interruption on behalf of its intended lower priority receiver process. We propose a new network interrupt handling scheme that combines interrupt handling with process scheduling and the priority of the process. The proposed scheme employs techniques to identify the intended receiver process of an incoming packet at an earlier phase. We implement a prototype system of the proposed scheme on Linux 2.6, and our experiment results show that the prototype system supports the predictable real-time behavior of higher priority processes even when excessive traffic is sent to lower priority processes.