| 1. |
- Andersson, Björn, et al.
(författare)
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Exact admission-control for integrated aperiodic and periodic tasks
- 2007
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Ingår i: Journal of Computer and System Sciences. - : Elsevier BV. - 1090-2724 .- 0022-0000. ; 73:2, s. 225-241
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Tidskriftsartikel (refereegranskat)abstract
- Admission-controllers are used to prevent overload in systems with dynamically arriving tasks. Typically, these admission-controllers are based on sufficient (but not necessary) capacity bounds in order to maintain a low computational complexity. In this paper we present how exact admission-control for aperiodic tasks can be efficiently obtained. Our first result is an admission-controller for purely aperiodic task sets where the test has the same runtime complexity as utilization-based tests. Our second result is an extension of the previous controller for a baseload of periodic tasks. The runtime complexity of this test is lower than for any known exact admission-controller. In addition to presenting our main algorithm and evaluating its performance, we also discuss some general issues concerning admission-controllers and their implementation. (C) 2006 Elsevier Inc. All rights reserved.
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| 2. |
- Anthony, Richard, et al.
(författare)
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A Future Dynamically Reconfigurable Automotive Software System
- 2008
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Ingår i: Proceedings of the Elektronik im Kraftfahrzeug.
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Konferensbidrag (refereegranskat)abstract
- Embedded software systems in vehicles are of rapidly increasing commercial importance for the automotive industry. Current systems employ a static run-time environment; due to the difficulty and cost involved in the development of dynamic systems in a high-integrity embedded control context. A dynamic system, referring to the system configuration, would greatly increase the flexibility of the offered functionality and enable customised software configuration for individual vehicles, adding customer value through plug-and-play capability, and increased quality due to its inherent ability to adjust to changes in hardware and software. We envisage an automotive system containing a variety of components, from a multitude of organizations, not necessarily known at development time. The system dynamically adapts its configuration to suit the run-time system constraints.This paper presents our vision for future automotive control systems that will be regarded in an EU research project, referred to as DySCAS (Dynamically Self-Configuring Automotive Systems). We propose a self-configuring vehicular control system architecture, with capabilities that include automatic discovery and inclusion of new devices, self-optimisation to best-use the processing, storage and communication resources available, self-diagnostics and ultimately self-healing. Such an architecture has benefits extending to reduced development and maintenance costs, improved passenger safety and comfort, and flexible owner customisation.Specifically, this paper addresses the following issues: The state of the art of embedded software systems in vehicles, emphasising the current limitations arising from fixed run-time configurations; and the benefits and challenges of dynamic configuration, giving rise to opportunities for self-healing, self-optimisation, and the automatic inclusion of users’ Consumer Electronic (CE) devices. Our proposal for a dynamically reconfigurable automotive software system platform is outlined and a typical use-case is presented as an example to exemplify the benefits of the envisioned dynamic capabilities.
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| 3. |
- Anthony, Richard, et al.
(författare)
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Towards a Dynamically Reconfigurable Automotive Control System Architecture
- 2007
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Ingår i: Embedded System Design: Topics, Techniques and Trends. - Boston, MA : Springer US. - 9780387722573 ; , s. 71-84
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a vehicular control system architecture that supports self-configuration. The architecture is based on dynamic mapping of processes and services to resources to meet the challenges of future demanding use-scenarios in which systems must be flexible to exhibit context-aware behaviour and to permit customization. The architecture comprises a number of low-level services that will provide the required system functionalities, which include automatic discovery and incorporation of new devices, self-optimisation to best-use the processing, storage and communication resources available, and self-diagnostics. The benefits and challenges of dynamic configuration and the automatic inclusion of users' Consumer Electronic (CE) devices are briefly discussed and the self-management and control-theoretic technologies that will be used are described in outline. A number of generic use-cases have been identified, each with several specific use-case scenarios. To demonstrate the extent of the flexible reconfiguration facilitated by the architecture, some of these use-cases are described, each exemplifying a different aspect of dynamic reconfiguration.
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| 4. |
- Chen, DeJiu, et al.
(författare)
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An Architectural Approach to Autonomics and Self-management of Automotive Embedded Electronic Systems
- 2008
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Ingår i: 4th European Congress ERTS: Embedded Real Time Software 2008. - : SIA (Société des Ingénieurs de l'Automobile - French Automotive Engineers Society).
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Konferensbidrag (refereegranskat)abstract
- Embedded electronic systems in vehiclesare of rapidly increasing commercial importance forthe automotive industry. While current vehicularembedded systems are extremely limited and static,a more dynamic configurable system would greatlysimplify the integration work and increase quality ofvehicular systems. This brings in features likeseparation of concerns, customised softwareconfiguration for individual vehicles, seamlessconnectivity, and plug-and-play capability.Furthermore, such a system can also contribute toincreased dependability and resource optimizationdue to its inherent ability to adjust itself dynamicallyto changes in software, hardware resources, andenvironment condition. This paper describes thearchitectural approach to achieving the goals ofdynamically self-configuring automotive embeddedelectronic systems by the EU research projectDySCAS. The architecture solution outlined in thispaper captures the application and operationalcontexts, expected features, middleware services,functions and behaviours, as well as the basicmechanisms and technologies. The paper alsocovers the architecture conceptualization bypresenting the rationale, concerning the architecturestructuring, control principles, and deploymentconcept. In this paper, we also present the adoptedarchitecture V&V strategy and discuss some openissues in regards to the industrial acceptance.
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| 5. |
- Chen, DeJiu, et al.
(författare)
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Developing a Context-aware Architecture in DySCAS
- 2007
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Konferensbidrag (refereegranskat)abstract
- Software systems in vehicles are of rapidly increasing commercial importance for the automotive industry. Current vehicular embedded systems exhibit a fixed software structure and the possibilities for software upgrades are limited. Due to increasing expectations of context-awareness, dependability, flexibility, cost efficiency and time-to-market; we argue that it is now necessary to enable advanced features that are based on dynamic configuration.To reach the goals of dynamically self-configuring automotive systems, we propose an architecture which is currently being developed in the EC funded DySCAS project. We describe the proposed architecture, with a focus on its support for adaptive behavior. To illustrate the type and extent of adaptability achievable, a set of generic use case classes are briefly described and the requirements they place on the architecture and in particular the adaptive aspects, are discussed.The architecture is based on a distributed hierarchical control and decision strategy, which through the policy-based middleware functions and underlying technologies allows separation-of-concerns, on-line reconfiguration, seamless connectivity, plug-and-play capability, and also increased dependability and resource optimization. Decision points are concerned with both application and resource aspects and are dispersed throughout a distributed platform, allowing the embedding of numerous policies to make context-aware decisions whilst avoiding excessive complexity. The approach is scalable and provides additional freedom for engineers to define the dynamic configuration characteristics.The developed architecture is so far on a functional level and has been validated against system requirements. Current work concentrates on defining the corresponding software architecture, considering automotive platforms and constraints.
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| 6. |
- Claesson, Vilgot, 1968, et al.
(författare)
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The Event-Triggered and Time-Triggered Medium-Access Methods
- 2003
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Ingår i: Proceedings - 6th IEEE International Symposium on Object-Oriented Real-Time Distributed Computing, Hakodate, Japan, 14-16 May 2003. - 0769519288 ; , s. 131-134
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Konferensbidrag (refereegranskat)abstract
- The processes of accessing a shared communication media have been extensively researched in the dependability and real-time area. For embedded systems, the primary approaches have revolved around the event-triggered and the time-triggered paradigms. In this paper, our goal is to objectively and quantitatively outline the capabilities and limitations of each of these paradigms. The event-triggered approach is commonly perceived as providing high flexibility, while the time-triggered approach is expected to provide for a higher degree of predictable communication access to the media. We have quantified the spread of their differences, and provide a summary discussion about suggested best usage for each approach. The focus of our work is on the response times of the communication system, and also on the schedulability of the communication system in collaboration with tasks in the nodes.
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| 7. |
- Ekelin, Cecilia, 1973, et al.
(författare)
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A Lower-Bound Algorithm for Load Balancing in Real-Time Systems
- 2004
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Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 3540226672 ; 3144, s. 146-158
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Konferensbidrag (refereegranskat)abstract
- We study the problem of finding a safe and tight lower-bound on the load-balancing objective often found in real-time systems. Our approach involves the formulation of the Multiple Bounded Change-Making Problem which we efficiently solve by using a new symmetry-breaking algorithm. An experimental evaluation shows that the computed lower-bound is optimal in more than 70% of the cases and is able to find more than four times as many decidedly optimal solutions.
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| 8. |
- Ekelin, Cecilia, 1973, et al.
(författare)
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A Lower-Bound Algorithm for Minimizing Network Communication in Real-Time Systems
- 2002
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Ingår i: International Conference on Parallel Processing, 2002. Proceedings.. - 0190-3918. - 0769516777
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a pseudo-polynomial-time lower-bound algorithm for the problem of assigning and scheduling real-time tasks in a distributed system such that the network communication is minimized The key feature of our algorithm is translating the task assignment problem into the so called k-cut problem of a graph, which is known to be solvable in polynomial time for fixed k. Experiments show that the lower bound computed by our algorithm in fact is optimal in up to 89% of the cases and increases the speed of an overall optimization algorithm by a factor of two on average.
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| 9. |
- Ekelin, Cecilia, 1973
(författare)
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An Optimization Framework for Scheduling of Embedded Real-Time Systems
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Embedded real-time systems - appearing in products such as cars and mobile phones - are nowadays common in our everyday lives. Despite this fact, the design process of such systems is still cumbersome due to the large variety of design constraints that must be considered to ensure a safe operation of the system. In particular, present scheduling techniques - that analyze the timing behavior of the system - typically assume a too limited model to truly represent the system. In addition, to make the system cost-effective its design should be optimized regarding performance measures such as resource utilization, energy consumption and robustness. Unfortunately, optimization in general is very time-consuming process, often without guarantee that the best solution will be found. This thesis addresses these problems by proposing a scheduling framework that not only enables arbitrary design constraints to be modelled but also allows for design optimization. The framework is based on constraint programming, and this thesis presents how the problem of scheduling embedded real-time systems can be modeled and solved using this technique. In addition, a number of novel techniques for reducing the runtime of the optimization algorithm are presented. This includes the identification and exclusion of symmetries in the solution space as well as fast and tight estimates of how good a solution may get. Finally, this thesis contains a performance comparison between the proposed framework and other state-of-the-art scheduling algorithms. The evaluation shows that both the quality of the solutions and the optimization time is improved over previous approaches - in many cases the order of the solution time is reduced from minutes to seconds.
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| 10. |
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