• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.52-63
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• 2009

The problem of scheduling simply periodic task systems upon a uniform multiprocessor is considered. Partitioning of periodic task systems requires solving the bin-packing problem, which is known to be intractable (NP-hard in the strong sense). This paper presents a global scheduling algorithm which transforms a given simply periodic task system into another using a "task-splitting" technique. Each transformed simply periodic task system is guaranteed to be successfully scheduled upon any uniform multiprocessor using a partitioned scheduling algorithm. It is proven that the proposed algorithm achieves the theoretical maximum utilization bound upon any uniform multiprocessor platform.

• The Journal of the Korea Contents Association
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• v.7 no.1
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• pp.83-93
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• 2007

In this paper, we address a power-aware scheduling algorithm for a mixed real-time system which consists of periodic and sporadic tasks, each of which is characterized by its minimum period, worst-case execution requirement and deadline. We propose a dynamic voltage scaling algorithm called DVSMT(DVS for mixed tasks), which dynamically scales down the supplying voltage(and thus the frequency) using on-line distribution of the borrowed resources when jobs complete while still meeting their deadlines. With this scheme, we could reduce more energy consumption. As the proposed algorithm can be easily incorporated with RTOS(Real-Time Operating System), it is applicable for handhold devices and sensor network nodes that use a limited battery power. Simulation results show that DVSMT saves up 60% more than the existing algorithms both in the periodic-task and mixed-task systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8B
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• pp.509-520
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• 2007

In this paper, we propose a real-time sensor node platform that guarantees the real-time scheduling of periodic and aperiodic tasks through a multitask-based software decomposition technique. Since existing sensor networking operation systems available in literature are not capable of supporting the real-time scheduling of periodic and aperiodic tasks, the preemption of aperiodic task with high priority can block periodic tasks, and so periodic tasks are likely to miss their deadlines. This paper presents a comprehensive evaluation of how to structure periodic or aperiodic task decomposition in real-time sensor-networking platforms as regard to guaranteeing the deadlines of all the periodic tasks and aiming to providing aperiodic tasks with average good response time. A case study based on real system experiments is conducted to illustrate the application and efficiency of the multitask-based dynamic component execution environment in the sensor node equipped with a low-power 8-bit microcontroller, an IEEE802.15.4 compliant 2.4GHz RF transceiver, and several sensors. It shows that our periodic and aperiodic task decomposition technique yields efficient performance in terms of three significant, objective goals: deadline miss ratio of periodic tasks, average response time of aperiodic tasks, and processor utilization of periodic and aperiodic tasks.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06a
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• pp.170-172
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• 2012

실시간 시스템(real-time system)은 논리적 연산을 일정한 시간적 제약 하에서 수행하는 시스템이다. 시간적 제약을 충족하도록 주기적 태스크(periodic task)를 스케줄(schedule)할 때 일반적으로 태스크 오프셋(initial offset)이 0 이거나 고정된 것으로 가정한다. 그러나 오프셋에 약간의 유연성을 허용함으로써 태스크들의 평균 응답 시간을 줄일 수도 있다. 이 논문에서는 주기적 태스크의 오프셋을 주어진 허용 범위 안에서 선택하여 평균 응답 시간(response time)을 최적화할 수 있음을 보이고, 임의의 태스크 집합에 대하여 최적 오프셋이 존재하는 좁은 범위를 제시한다.

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.101-113
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• 2018

Systems such as military inspection equipment which it is important to acquire and evaluate data in real-time should be able to real-time processing at the operating system level. As technology advances, there is a demand for replacing existing equipment with mobile device, but mobile devices with Android are not suitable for systems requiring real-time performance. On Android, garbage collection ensures free memory, while other tasks are interrupted while this task is performed, which cannot guarantee periodicity of particular tasks. In this paper, we designed and implemented a structure to control execution garbage collection of Android to solve this problem. Real-time performance is ensured by controlling garbage collection during the time required for real-time operation, and RTiK(Real-Time implanted Kernel) is applied to ensure real-time performance on Android. In order to evaluate the performance, we measured the call period of the 5ms period task, and, only 34.31% of the task was guaranteed before the control, but the task period of 98.18% was satisfied through control, providing real-time performance to Android.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.04a
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• pp.58-60
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• 2014

임베디드 소프트웨어는 국방, 항공 우주, 자동차와 같이 다양한 응용분야에서 그 중요성이 부각되고 있다. 이와 함께 시스템 자원의 효율성을 높이고 응용 소프트웨어 간 안전한 실행환경을 제공하기 위해서 자원 파티셔닝의 필요성이 강조되고 있다. 최근 임베디드 시스템의 응용 분야가 다양해지면서 주기적인 파티션과 함께 비주기적인 파티션들에 대한 요구가 증가하고 있다. 하지만 기존 시스템들은 비주기적인 파티션은 고려하고 있지 않거나, 주기적인 파티션에 비해서 우선순위가 낮게 취급하고 있다. 이러한 문제를 해결하기 위해서 본 논문은 높은 우선순위의 비주기적인 태스크 그룹을 지원하기 위한 구조를 제안하고, 리눅스의 cgroup 프레임워크를 확장하여 구현한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.5
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• pp.783-791
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• 2006

In e-Trade, Real-Time System(RTS) plays a very important role. Each task is set with limited time, and appointed regulations must be followed because it can be greatly damaged if it cannot be executed in limited time. In e-Trade, the scheduling possibility techniques generally use periodical tasks; however, it is necessary to study more stable prediction scheduling possibility algorithm by using other task timing conditions and non-periodical task scheduling tasks. This study proposed an algorithm to increase the prediction possibility using individual task utilization rate, and presented scheduling possibility conditions using existing whole task utilization rate and the proposed algorithm.

• Journal of KIISE:Software and Applications
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• v.26 no.2
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• pp.241-250
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• 1999

Gomaa에 의해 제안된 CODARTS(Concurrent Design Approach for Real-Time System)방법론은 COBRA(Concurrent Object-based Real-Time Analysis)을 사용하여 실시간 시스템의 행동 모델을 개발하고 행동 모델에서 병렬 태스크 구조로 변환하는 데 도움을 주는 태스크 구성 지침을 제공한다. CODARTS에서는 태스크 구성 지침을 RTSA(Real-Time System Analysis)표기법으로 표현된 행동 모델에 적용하여 태스크를 구성한다. 그러나 RTSA 표기법에는 태스크를 구성하는데 필요한 실행 성질 및 주기, 이벤트의 병렬성 및 순서와 같은 정보들을 기술하지 않기 때문에 직접 태스크 구성 지침을 적용하는 것은 어렵다. 본 논문에서는 CODARTS 방법론의 분석단게에서 태스크 구성에 필요한 정보를 통합적으로 나타낼 수 있는 STS (Specification for Task Structuring)를 제안한고 이를 이용하여 태스크를 자동적으로 구성할 수 있는 알고리즘과 적용 예제를 보인다.

• Journal of Korean Library and Information Science Society
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• v.49 no.3
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• pp.407-428
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• 2018

Metadata standard is very important element to describe a digital resource in the records lifecycle. Metadata standard is influenced by the purpose and content of tasks that are performed to a resource. But it does not reflect a task-centric viewpoint to cover the whole records-lifecycle because metadata is defined and designed from a resource-centric viewpoint. In other words, to cover the whole records-lifecycle using metadata, it is necessary to properly select and combine metadata property from a task-centric viewpoint. Therefore, we proposed a task-centric metadata application profile that can combine and select appropriate metadata properties according to requirements and tasks performed on resource.

• The KIPS Transactions:PartA
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• v.11A no.7 s.91
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• pp.483-488
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• 2004

For real-time applications, the underlying operating system (0S) should support timeliness guarantees of real-time tasks. However, most of current operating systems do not provide timely management facilities in an efficient way. There could be two approaches to support timely management facilities for real-time applications: (1) by modifying 0S kernel and (2) by Providing a middleware without modifying 0S. In our approach, we adopted the middleware approach based on the TMO (Time-triggerred Message-triggered Object) model which is a well-known real-tine object model. The middleware, named TMSOM (TMO Support Middleware) has been implemented on various OSes such as Linux and Windows XP/NT/98. In this paper, we mainly consider TMOSM implemented on Linux(TMOS/Linux). Although the real-time schedul-ing aIgorithm used in current TMOSM/Linux can produce an efficient real-time schedule, it can be improved for periodic real-time tasks by considering several factors. In this paper, we discuss those factors and propose an improved real-time scheduling algorithm for periodic real-time tasks, In order to simulate the performance of our algorithm, we measure timeliness guarantee rate for periodic real-time tasks. The result shows that the performance of our algorithm is superior to that of existing algorithm. Additionally, the proposed algorithm can improve system performance by making the structure of real-time middleware simpler.