• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.3
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• pp.371-378
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• 2016

The most important things in real-time systems are that a system guarantees to meet its deadline and to operate in its predictable range. When we design a real-time system, we need to verify whether the system can meet its deadline through schedulability analysis. There are several kinds of schedulability analysis technique for fixed priority scheduling systems. But as we all know, we can't perform schedulability analysis in design time because we can't estimate upper bounds on execution time of each task. So we used a similar real-time system to estimate upper bounds on execution time for our system, and then we performed schedulability analysis and verified that our system designed can meet its deadline.

• International journal of advanced smart convergence
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• v.8 no.1
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• pp.9-17
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• 2019

In this article, we present a performance enhancement scheme for mobile applications by adopting persistent memory. The proposed scheme supports the deadline guarantee of real-time applications like a video player, and also provides reasonable performances for non-real-time applications. To do so, we analyze the program execution path of mobile software platforms and find two sources of unpredictable time delays that make the deadline-guarantee of real-time applications difficult. The first is the irregular activation of garbage collection in flash storage and the second is the blocking and time-slice based scheduling used in mobile platforms. We resolve these two issues by adopting high performance persistent memory as the storage of real-time applications. By maintaining real-time applications and their data in persistent memory, I/O latency can become predictable because persistent memory does not need garbage collection. Also, we present a new scheduler that exclusively allocates a processor core to a real-time application. Although processor cycles can be wasted while a real-time application performs I/O, we depict that the processor utilization is not degraded significantly due to the acceleration of I/O by adopting persistent memory. Simulation experiments show that the proposed scheme improves the deadline misses of real-time applications by 90% in comparison with the legacy I/O scheme used in mobile systems.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.103-109
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• 2019

The automotive electronic system should provide a method that can be safely performed by loading a number of application programs having time constraints in several electronic control devices. In this paper, we propose a timing protection mechanism for AUTOSAR, which is a real - time operating system specification for automotive field, in order to observe the deadline of each task when scheduling real - time tasks. We propose a dynamic non-preemption algorithm to guarantee a flexible deadline for fixed priority or dynamic priority tasks, and a location where execution time can be monitored for errors, and suggest ways to implement the AUTOSAR time protection mechanism.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.3
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• pp.337-344
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• 2000

In this paper, we define a Process Algebra ACSMR(Algebra of Communicating Shared Multiple Resources) for system specification and verification using multiple resources. ACSMR extends a concept of multiple resources in ACSR that is a branch of formal methods based on process algebra. We'll show that two specification and verification examples. One is the specification of system behavior in multiprocessor using EDF(Earliest-Deadline-First) which is a scheduling algorithm of a real-time system. The other is the specification of describing timing analysis and resources restriction in a super scalar processor using multiple ports registers.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.7
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• pp.363-369
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• 2000

To flexibly evaluate performance and reliability of an electric power system in the aspect of the real-time system which is intrinsically characterized by stringent timing constraints fails catastrophically if its control input is not updated by its digital controller computer within a certain time limit called the hard deadline, we propose fuzzy-random variables and build a discrete event model embedded with fuzzy-random variables. Also, we adapt fuzzy-variables to a path-space approach, which derives the upper and lower bounds of reliability by using a semi-Markov model that explicitly contains the deadline information. Consequently, we propose certain formulas of state automata properly transformed by fuzzy-random variables, and present numerical examples applying the formulas as well.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.5
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• pp.236-244
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• 2001

디스크배열 또는 RAID 시스템은 저렴한 비용으로 대용량 저장공간을 제공할 수 있으나, VOD 서비스와 같은 대규모 멀티미디어 서비스에 대해서는 아직 충분한 입출력 속도를 지원하지 못하고 있다. 보다 높은 대역폭을 지원하기 위해 다수의 디스크 컨트롤러를 채용한 다중 디스크배열에서 스트라이프를 전체 디스크에 효과적으로 분산시키기 위한 수직 스트라이핑 모델이 이용되고 있다. VOD 서비스 이용자가 고품질의 동영상을 감상하기 위해서는, 응용프로그램이 요청한 마감시간까지 저장장치에 기록되어 있는 데이터를 읽어와야 한다. 본 논문에서는 효과적이 VOD 서비스 지원을 위해, 다중 디스크배열에서 각 디스크 컨트롤러의 지역 요청큐로 분산된 입출력 요청들을 스케쥴링하여 마감시간 초과율(deadline miss rate)을 줄이기 위한 알고리즘을 제안한다. 이 알고리즘은 VOD 서버와 같이 데이터 읽기 작업이 많은 멀티미디어 서비스에 적합하도록 설계되었다. 시뮬레이션 결과, 제안된 알고리즘이 마감시간 초과율을 평균 41.5% 감소시킴을 알 수 있었다.

• Journal of Internet Computing and Services
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• v.8 no.1
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• pp.71-78
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• 2007

In this paper, an effective task scheduling scheme was proposed for the flexible real time LINUX systems with the selection between EDF(earliest deadline first) and RMS(rate monotonic scheduling). It was known that many task scheduling schemes were analyzed according to the characteristics of scheduling schemes and the guarantee of an earliest deadline scheduler for process utilities.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4451-4466
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• 2014

We present joint radio selection and relay scheme that delivers data from a source to a sink in heterogeneous stationary sensor networks consisting of various radio interfaces. The proposed scheme finds the optimal relay nodes and their corresponding radio interfaces that minimize energy consumption throughout the network while satisfying the end-to-end packet deadline requirement. We formulate the problem of routing through radio interface selection into binary integer programs, and obtain the optimal solution by solving with an optimization solver. We examine a trade-off relationship between energy consumption and packet delay based on network level simulations. We show that given the end-to-end deadline requirement, our routing algorithm finds the most energy-efficient routing path and radio interface across mesh hops. We demonstrate that the proposed routing scheme exploits the given packet delivery time to turn into network benefit of reducing energy consumption compared to routing based on single radio interface.

• ETRI Journal
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• v.32 no.3
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• pp.422-429
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• 2010

We present guaranteed dynamic priority assignment schemes for multiple real-time tasks subject to (m, k)-firm deadlines. The proposed schemes have two scheduling objectives: providing a bounded probability of missing (m, k)-firm constraints and maximizing the probability of deadline satisfactions. The second scheduling objective is especially necessary in order to provide the best quality of service as well as to satisfy the minimum requirements expressed by (m, k)-firm deadlines. We analytically establish that the proposed schemes provide a guarantee on the bounded probability of missing (m, k)-firm constraints. Experimental studies validate our analytical results and confirm the effectiveness and superiority of the proposed schemes with regard to their scheduling objectives.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04a
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• pp.687-690
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• 2002

In this paper, we present a novel semaphore implementation scheme which shortens finish time of high priority tasks and improves reliability of a system. The real-time systems have time constraints. Especially, the task with hard real-time constraints must meet its deadline. Consequently, managing shared resources is considered guaranteeing mutual exclusion as well as meeting task's deadline under unfavorable condition. According to the number and sort of the locked semaphores under the event occurred, this paper presents the reduction of the finish time of high priority task by decision whether the context switched or not. The experimental results show that the proposed method gives performance improvements in finish time of high priority tasks of about 11% over zuberi[4] method.