We consider cyclic real-time applications built using nearly autonomous components. These components can run on any of the available hosts subject to certain constraints. The hosts in the system are allowed to be hete...
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ISBN:
(纸本)9781479964994
We consider cyclic real-time applications built using nearly autonomous components. These components can run on any of the available hosts subject to certain constraints. The hosts in the system are allowed to be heterogeneous and they can have different cycle times for realtime execution. Given a set of component based applications and a set of available hosts, we propose a solution for the problem of finding an optimum deployment. The deployment problem can be reduced to the problem of finding feasible static schedules for each host in the system that satisfy the real-time periodic execution requirements of all the applications. We propose a deterministic algorithm for finding static schedules for all the hosts in the system. The approach models the possible partial schedules at each step as nodes in a virtual tree. A breadth first traversal is conducted to construct the tree and complete the schedule. A node is removed from the tree if it cannot lead to a correct schedule. If more than one solutions are possible then the 'best' solution is selected based on the optimization criteria.
This paper addresses modelling and assessing of worst-case execution times of tasks in a distributedreal-timesystem. The presented case study is based on a stress test system for power semiconductors. Typical distri...
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ISBN:
(纸本)9781728157306
This paper addresses modelling and assessing of worst-case execution times of tasks in a distributedreal-timesystem. The presented case study is based on a stress test system for power semiconductors. Typical distributedsystems involve inherent inter-dependencies that have to be handled with minimized delays. Studying the computing task's timing behavior becomes necessary to understand the timing violations. Modelling the temporal behaviour of the system using probabilistic Worst-Case Execution time (WCET) analysis aids to overcome the timing faults. This paper focuses on (1) the study of the temporal behaviour through the execution time profile of the distributed hard realtimesystem;(2) the statistical analysis by performing probability distribution modelling on the measured data. Measurement-based probabilistic timing analysis is an emerging and reliable method used to arrive at industry quality estimates. This method is used here in the paper to carry out temporal validation of the real-time computing tasks on our case study.
FlexRay is a high-bandwidth protocol that supports hard-deadline periodic and sporadic traffic in modern in-vehicle communication networks. The dynamic segment of FlexRay is used for transmitting hard deadline sporadi...
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FlexRay is a high-bandwidth protocol that supports hard-deadline periodic and sporadic traffic in modern in-vehicle communication networks. The dynamic segment of FlexRay is used for transmitting hard deadline sporadic messages. In this paper, we describe an algorithm to minimize the duration of the dynamic segment in a FlexRay cycle, yielding better results than existing algorithms in the literature. The proposed algorithm consists of two phases. In the first phase, we assume that a sporadic message instance contends for service with only one instance of each higher-priority message. The lower bound provided by the first phase serves as the initial guess for the number of mini-slots used in the second phase, where an exact scheduling analysis is performed. In the second phase, a sporadic message may contend for service with multiple instances of each higher-priority message. This two-phase approach is efficient because the first phase has low overhead and its estimate greatly reduces the number of iterations needed in the second phase. We conducted experiments using the dataset provided in the literature as well as the SAE benchmark dataset. The experimental results demonstrate superior bandwidth minimization and computational efficiency compared to other algorithms.
This study proposes a method to handle unrecoverable data using a formula called Bezier curve. The proposed method suggests the possibility to approximate the damaged data, which have been processed by the error corre...
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This study proposes a method to handle unrecoverable data using a formula called Bezier curve. The proposed method suggests the possibility to approximate the damaged data, which have been processed by the error correction scheme. The proposed method works on the real-time distributed system which retransmission is considered as unsuitable solution to manage the overall networked system. By using the Bezier curve, the transmitted unrecoverable data are reconstructed again by using the functional approximation. This method provides a smoothing effect on damaged data that usually are normalised on real-time transmission of PROFIBUS. Three differences Bezier curve methods are compared in PROFIBUS data, four-points (FP) method, two-points two-degrees method and four-degrees (FD) method. Simulation results show that all three Bezier curve methods can approximate data in PROFIBUS. FD has higher computation complexity compared with others. However, FD compensates with its data size which is only half of FP method.
A significant problem with no simple solutions in current real-time literature is analyzing the end-to-end schedulability of tasks in distributedsystems with cycles in the task graph. Prior approaches including netwo...
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A significant problem with no simple solutions in current real-time literature is analyzing the end-to-end schedulability of tasks in distributedsystems with cycles in the task graph. Prior approaches including network calculus and holistic schedulability analysis work best for acyclic task flows. They involve iterative solutions or offer no solutions at all when flows are non-acyclic. This paper demonstrates the construction of the first generalized closed-form expression for schedulability analysis in distributed task systems with non-acyclic flows. The approach is a significant extension to our previous work on schedulability in Directed Acyclic Graphs. Our main result is a bound on end-to-end delay for a task in a distributedsystem with non-acyclic task flows. The delay bound allows one of several schedulability tests to be performed. Using the end-to-end delay bound, we extend the delay composition algebra developed for acyclic distributedsystems in prior work, to handle loops in the task graph as well. Evaluation shows that the schedulability tests thus constructed are less pessimistic than prior approaches for large distributedsystems.
In this paper we present major technical requirements far designing and developing future distributed multimedia information system using Internet technology. The key requirements of this system are to allow users to ...
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In this paper we present major technical requirements far designing and developing future distributed multimedia information system using Internet technology. The key requirements of this system are to allow users to search, access, and communicate multimedia documents consisting of text, audio, video, and image. We emphasize the role of object oriented technology for information management and real-time communication protocols to guarantee QoS. We pre sent a reference architecture for Web-based realtimedistributed multimedia system which provides several functionalities including real-time streaming, multimedia indexing and searching, and distributed object management.
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