| 1. |
- Bohlin, Markus, et al.
(författare)
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Safe Shared Stack Bounds in Systems with Offsets and Precedences
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The paper presents two novel methods to bound the stack memory used in preemptive, shared stack, real-time systems. The first method is based on branch-and-bound search for possible preemption patterns, and the second one approximates the first in polynomial time. The work extends previous methods by considering a more general taskmodel, in which all tasks can share the same stack. In addition, the new methods account for precedence and offset relations. Thus, the methods give tight bounds for a large set of realistic systems. The methods have been implemented and a comprehensive evaluation, comparing our new methods against each other and against existing methods, is presented. The evaluation shows that our exact method can significantly reduce the amount of stack memory needed. In our simulations, a decrease in the order of 40% was typical, with a runtime in the order of seconds. Our polynomial approximation consequently yields about 20% higher bound than the exact method.
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| 2. |
- Hansen, Ewa, 1973-
(författare)
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Centralized Routing for Prolonged Network Lifetime in Wireless Sensor Networks
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis centralized routing methods for wireless sensor networks have been studied. The aim has been to prolong network lifetime by reducing the energy consumed by sensor-node communication.Wireless sensor networks are rapidly becoming common in application areas where information from many sensors is to be collected and acted upon. The use of wireless sensor networks adds flexibility to the network, and the cost of cabling can be avoided.Wireless sensor networks may consist of several hundreds of small devices, equipped with sensors (e.g. acoustic, seismic or image) that form a wireless network. Each sensor node collects information from its surroundings and sends it to a base station, either from sensor node to sensor node, or directly to the base station.We have made simulations that show that asymmetric communication with multihop extends the lifetime of large wireless sensor networks. We have also investigated the usefulness of enforcing a minimum separation distance between cluster heads in a cluster based wireless sensor network. The results show that our sensor network performs up to 150% better when introducing a minimum separation distance between cluster heads. The simulations also show that the minimum separation distance resulting in the lowest energy consumption in our network varies with the number of clusters. We have also made an initial study of maximum lifetime routing in sparse wireless sensor networks to be able to see how different heuristic routing algorithms influence the energy consumption of individual sensor nodes, and thus the lifetime of a sparse sensor network. We have also compared the maximum lifetime of the heuristic algorithms to the maximum lifetime of an optimal routing solution. These simulations showed that for some types of applications the choice of heuristic algorithm is more important to prolong network lifetime, than for other types of applications.
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| 3. |
- Hänninen, Kaj
(författare)
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Efficient Memory Utilization in Resource Constrained Real-Time Systems
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents design and run-time techniques for efficient memory utilization in embedded real-time systems. The proposed techniques give developers means to reduce the memory consumption in the systems. Altogether, this gives possibilities to increases the added value of industrial systems, in the sense that more features can be fitted on existing hardware.The thesis begins by presenting the results of a series of interviews concerning common requirements in development of embedded real-time systems. Based on these results, the thesis presents a novel component model for development of resource constrained real-time systems. The model supports efficient memory usage through stack sharing and is formal enough to enable predictability of the resulting stack usage. To provide run-time support for stack sharing, the thesis presents an integration of the stack sharing strategy in an operating system for the component model. To determine the resulting memory usage under stack sharing, a novel analysis method is presented. In an evaluation, the thesis show that the analysis method is both fast and that it gives tight bounds on the resulting stack usage, which makes it suitable for industrial use. The thesis ends with a presentation showing the integration of the proposed analysis technique in an integrated development environment.The proposed techniques have been integrated in the commercial tool Rubus-ICE from Arcticus Systems. The techniques will be available for developers in the upcoming release of Rubus-ICE.
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| 4. |
- Hänninen, Kaj, 1970-
(författare)
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Introducing a Memory Efficient Execution Model in a Tool-Suite for Real-Time Systems
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis shows how development of embedded real-time systems can be made more efficient by introduction of an memory efficient execution model in a commercial development suite. To identify the need of additional support for execution models in development tools, the thesis investigate by a series of interviews, the common requirements in development of industrial embedded real-time systems. The results indicate that there exist functionality in industrial systems that could be more efficiently implemented in other execution models than the currently supported ones. The thesis then presents how use of multiple execution models (hybrid scheduling) can reduce processor utilization in real-world applications. Furthermore, the thesis presents an integration of an memory efficient execution model in an industrially used real-time operating system. In addition, the thesis describes an efficient technique to analyze memory consumptions of functionality executing under the introduced execution model.Embedded computers play an important role in peoples everyday life. Nowadays, we can find computers in product such as microwave ovens, washing machines, DVD players, cellular phones and cars, to mention a few examples. For example, a modern car may have more than 70 embedded control units handling functionality such as airbags, anti-lock braking, traction control etc. In addition, there is a clear trend indicating that the amount of computer controlled functionality in products will continue to increase. Many of today’s embedded systems are resource constrained and the software for them is developed for a few execution models. Even though researchers has proposed a numerous number of different execution models for embedded real-time systems, in practice however, only a few of the proposed execution models are supported in industrial development tools. This implies that developers often force fit functionality to be executed under these models, resulting in poor resource utilization and increasing complexity in software.
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| 5. |
- Hänninen, Kaj, et al.
(författare)
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Introducing a Plug-In Framework for Real-Time Analysis in Rubus-ICE
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we present the development of a plug-in framework for integration of real-time analysis methods in the Rubus Integrated Component Environment (Rubus-ICE). We also present the implementation, and evaluate the integration, of two state of the art analysis techniques (i) response-time analysis for tasks with offsets and (ii) shared stack analysis, as plug-ins, in the Rubus-ICE framework.The paper shows that the proposed framework is well suited for integration of complex analysis methods. However, experience also show that analysis methods are not easily transferred from an academic environment to industry. The main reason for this, we believe, originates from differences in requirements and assumptions between industry and academia.
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| 6. |
- Mäki-Turja, Jukka, et al.
(författare)
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Efficient Development of Real-Time Systems Using Hybrid Scheduling
- 2005
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Ingår i: Proceedings of the 2005 International Conference on Embedded Systems and Applications, ESA'05. - 9781932415537 ; , s. 53-59
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper will show how advanced embedded realtime systems, with functionality ranging from time-triggered control functionality to event-triggered user interaction, can be made more efficient. Efficient with respect to development effort as well as run-time resource utilization. This is achieved by using a hybrid, static and dynamic, scheduling strategy. The approach is applicable even for hard real-time systems since tight response time guarantees can be given by the response time analysis method for tasks with offsets. An industrial case study will demonstrate how this approach enables more efficient use of computational resources, resulting in a cheaper or more competitive product since more functionality can be fitted into legacy, resource constrained, hardware.
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| 7. |
- Mäki-Turja, Jukka, 1967-
(författare)
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Engineering Strength Response-Time Analysis : A Timing Analysis Approach for the Development of Real-Time Systems
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vid utvecklingen av datorsystem som är en del av en större produkt, som t.ex. styrsystemet i en bil, ett flygplan eller medicinsk utrustning, ställs det ofta mycket hårda krav på säkerhet och tillförlitlighet. En av målsättningarna är även att hålla nere produkt- och utvecklingskostnaden, samtidigt som man vill öka kundnyttan genom att öka innehållet, dvs. funktionaliteten.Ökningen i antalet funktioner, och komplexiteten den medför, ställer krav på bättre utvecklingsmetoder, -modeller och -verktyg. Att analysera svarstider genom s.k. responstidsanalys (RTA) är ett sätt att kunna garantera systemets tidsbeteende innan produkten tas i drift. I denna avhandling presenteras nya tekniker som syftar till att förbättra existerande RTA-metoder, vilket konkret leder till följande förbättringar:q Precisionen i de beräknade svarstiderna blir avsevärt högre än tidigare (typiskt ca 15% kortare responstider).q Analyserna kan göras avsevärt snabbare än tidigare (typiskt ca 100 ggr snabbare än tidigare).Genom att kombinera dessa två helt oberoende tekniker, behöver man ej offra precision för snabb analys eller vice versa. Det bästa av två världar uppnås i en och samma analysmetod; snabb analystid och precisa svarstider. Högre precision i svarstider möjliggör antingen ökad funktionalitet inom ramen för en given produktkostnad, eller en lägre kostnad för en given funktionalitet. Snabbare analysmetoder innebär att utvecklingsverktyg nu kan använda RTA i praktiken även för riktigt stora system med hundratals, ja även tusentals, funktioner.Speciellt säkerhetskritiska tillämpningar som måste vara oerhört säkra och tillförlitliga, och många gånger måste genomgå en dyr och tidskrävande certifieringsprocess, kan dra nytta av RTA. En stor del av svensk exportindustri såsom Volvo, Saab, och ABB utvecklar realtidssystem för vilka denna forskning skulle kunna vara av strategisk betydelse.
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| 8. |
- Mäki-Turja, Jukka, et al.
(författare)
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Fast and Tight Response-Times for Tasks with Offset
- 2005
-
Ingår i: Proceedings - Euromicro Conference on Real-Time SystemsVolume 2005, 2005. - 9780769524009 ; , s. 127-136
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In previous work, we presented a tight approximate response-time analysis for tasks with offsets. While providing a tight bound on response times, the tight analysis exhibits similarly long execution times as does the traditional methods for calculating response-times for tasks with offsets. The existing method for fast analysis of tasks with offsets is not applicable to the tight analysis. In this paper we extend the fast analysis to handle the distinguishing trait of the tight analysis; continuously increasing interference functions. Furthermore, we provide another speedup; by introducing pessimism in the modelling of interference at certain points, we speed up the convergence of the numerical solving for response-times without increasing the pessimism of the resulting response-times. The presented fast-and-tight analysis is guaranteed to calculate the same response-times as the tight analysis, and in a simulation study we obtain speedups of more than two orders of magnitude for realistically sized tasks sets compared to the tight analysis. We also demonstrate that the fast-and-tight analysis has comparable execution time to that of the fast analysis. Hence, we conclude that the fast- and-tight analysis is the preferred analysis technique when tight estimates of response-times are needed, and that we do not need to sacrifice tightness for analysis speed; both are obtained with the fast-and-tight analysis.
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| 9. |
- Möller, Anders
(författare)
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Software Component Technologies for Heavy Vehicles
- 2005
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Control-systems for heavy vehicles have advanced from an area where Industrial Requirements on Component Technologies for Embedded Systemsmainly mechanic and hydraulic solutions were used, to a highly computerised domain using distributed embedded real-time computer systems. To cope with the increasing level of end-customer demands on advanced features and functions in future vehicle systems, sophisticated development techniques are needed. The development techniques must support software in numerous configurations and facilitate development of systems with requirements on advanced functionality, timeliness, and safety-criticality. In order to meet these requirements, we propose the use of component-based software engineering. However, the software component-technologies available on the market have not yet been generally accepted by the vehicular industry. In order to better understand why this is the case, we have conduced a survey - identifying the industrial requirements that are deemed decisive for introducing a component technology. We have used these requirements to evaluate a number of existing component technologies, and one of our conclusions is that none of the studied technologies is a perfect match for the industrial requirements. In addition, we have implemented and evaluated the novel component model SaveCCM, which has been designed for safety-critical automotive applications. Our evaluation indicates that SaveCCM is a promising technology which has the potential to fulfil the industrial requirements. However, tools are still immature and incomplete. In the final part of this work, we propose the use of monitored software components, as a general approach for engineering of embedded systems. In our approach, a component's execution is continuously monitored and experience regarding the behaviour is accumulated. As more and more experience is collected the confidence in the component grows.
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| 10. |
- Neander, Jonas, et al.
(författare)
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Prolonging Network Lifetime in Long Distance Sensor Networks using a TDMA Scheduler
- 2007
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we present a Time Division Multiple Access (TDMA) scheduler for the Asymmetric communication and ROuting in Sensor networks architecture (AROS). The scheduler enables dynamic network configurations of the AROS architecture. We show that asymmetric multihop communication with dynamic network configurations in AROS prolongs the lifetime of sensor nodes in long distance networks compared to the LEACH architecture.
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