We present 2V-DBP-SNAP, an algorithm that allows hard real-time tasks in an embeddedreal-time control system to read a snapshot of a number of data elements in a real-time database. Furthermore, 2V-DBP-SNAP allows th...
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We present 2V-DBP-SNAP, an algorithm that allows hard real-time tasks in an embeddedreal-time control system to read a snapshot of a number of data elements in a real-time database. Furthermore, 2V-DBP-SNAP allows these data elements to be shared with soft real-time tasks, which access them using a database query language, and with other hard real-time tasks that use database pointers. 2V-DBP-SNAP allows temporal behavior and memory consumption to be accurately predicted. Introducing snapshot transactions is beneficial for embedded control-systems, such as for engine control in an automotive system, since a snapshot of the state of the environment can be collected, e.g., the state of all cylinders in the engine. 2V-DBP-SNAP is lightweight and predictable, both with respect to computational and memory overhead, and is therefore highly suited for resource constrained systems.
We present a real-time scheduling algorithm called VCUA, for tasks whose execution times are functions of their starting times. We model such variable execution times with variable cost functions (or VCFs). the algori...
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We present a real-time scheduling algorithm called VCUA, for tasks whose execution times are functions of their starting times. We model such variable execution times with variable cost functions (or VCFs). the algorithm considers application activities that are subject to time/utility function time constraints, VCFs, and the scheduling objective of assuring that the maximum interval between any two consecutive successful completions of jobs of a task must not exceed a specified bound, and maximizing the system's total utility. We establish that VCUA achieves optimal timeliness during under-loads, and identify the conditions under which timeliness assurances hold. Our simulation experiments illustrate VCUA's effectiveness and superiority.
In recent years, there has been much research on ubiquitous computing, including context aware computingthat is an important field in ubiquitous computing. the primary focus of this paper is on context modeling. We s...
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In recent years, there has been much research on ubiquitous computing, including context aware computingthat is an important field in ubiquitous computing. the primary focus of this paper is on context modeling. We study the characteristics of context and so the requirements on the modeling. Besides, we also take into account the development requirements of next generation context-aware application. We study the context modeling approaches of some famous existing projects and find that few models meet all these requirements. In this paper, we propose a comprehensive model, which meets these requirements. We implement this model in a middleware called Scudware.
In this paper, the enhanced collision resolution algorithm, referred as high priority binary exponential backoff (h-BEB) is analyzed. Such algorithm provides high priority traffic separation, enabling the support of r...
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In this paper, the enhanced collision resolution algorithm, referred as high priority binary exponential backoff (h-BEB) is analyzed. Such algorithm provides high priority traffic separation, enabling the support of real-time communication in shared Ethernet networks. It allows multiple Ethernet standard devices to coexist in the same network segment with one h-BEB enhanced station, imposing higher priority for the transfer of h-BEB related traffic. the simulation analysis shows that the h-BEB algorithm guarantees values for boththe average access delay and the related standard deviation, that are significantly smaller for the h-BEB station than for the BEB stations.
Advanced micro-architectural features such as caches and branch prediction mechanisms supporting speculative execution are becoming commonplace within modern microprocessors. For developers of real-timesystems, these...
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Advanced micro-architectural features such as caches and branch prediction mechanisms supporting speculative execution are becoming commonplace within modern microprocessors. For developers of real-timesystems, these mechanisms present predictability problems. Previous work has demonstrated accurate analysis for instruction caches, data caches, and branch prediction mechanisms are possible. However, the integration of these individual analysis methods is difficult to do without large increases in computational complexity or the introduction of pessimism regarding the worst-case execution time (WCET) estimate. In this paper, we discuss how a previously published analysis method for branch predictors can be integrated with instruction pipeline analysis.
On-demand broadcast is an attractive data dissemination method for mobile and wireless computing. In this paper, we propose a new online preemptive scheduling algorithm, called PRDS that incorporates the urgency, the ...
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On-demand broadcast is an attractive data dissemination method for mobile and wireless computing. In this paper, we propose a new online preemptive scheduling algorithm, called PRDS that incorporates the urgency, the data size and the number of pending requests for real-time on-demand broadcast system. Furthermore, we use pyramid preemption to optimize performance and reduce overhead. We have done a series of simulation experiments to evaluate the performance of our algorithm as compared with other previously proposed methods under a range of scenarios. the experimental results show that our algorithm can substantially outperform other algorithms without jeopardizing other performance metrics, such as response time and stretch.
this paper considers the problem of hard real-time fixed priority scheduling of sporadic graph tasks on a uniprocessor. We study feasibility conditions based on the computation of the worst case response times of the ...
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this paper considers the problem of hard real-time fixed priority scheduling of sporadic graph tasks on a uniprocessor. We study feasibility conditions based on the computation of the worst case response times of the graph tasks. A sporadic graph task associated to an application is characterized by a set of subtasks under precedence constraints. We investigate the late deadline constraint. We extend already published papers established in the preemptive case to the nonpreemptive case and to the hybrid case of an application composed of preemptive and nonpreemptive subtasks.
Designing and constructing real-time distributed industrial vision systems (RT-DIVS) from scratch is very complicated task. RT-DIVS has conflicting requirements such as reasonable development cost, ease of use, reusab...
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Designing and constructing real-time distributed industrial vision systems (RT-DIVS) from scratch is very complicated task. RT-DIVS has conflicting requirements such as reasonable development cost, ease of use, reusable code and high performance. the success key in building such systems is to recognize the need for middleware software. Middleware plays a major role in developing distributed systems efficiently. real-time publish-subscribe (RTPS) model is one of the latest developments in real-time middleware technologies. Network data distribution service (NDDS) is RTPS middleware developed by real-time innovation (RTI). NDDS is widely used in real-time distributed and embeddedsystems for mission critical applications. the research work presented in this paper discusses the employment of NDDS for RT-DIVS and the advantages of NDDS's quality of service (QoS) policies in covering the requirements of RT-DIVS. An experimental test set-up is used to verify the NDDS's performance for RT-DIVS. Tests results show that RTPS middleware (and NDDS specifically) is suitable for soft and firm timelines requirements for distributed industrial vision systems.
Common language infrastructure (CLI) has been introduced as a core technology of Microsoft .NET. It enables "writing in multiple languages, running in multiple platforms" by providing virtual execution syste...
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Common language infrastructure (CLI) has been introduced as a core technology of Microsoft .NET. It enables "writing in multiple languages, running in multiple platforms" by providing virtual execution system (VES), common intermediate language, and common type system etc. the advantages of using CLI, including portability, compactness, and interoperability, could benefit the productivity of application software development and deployment. However, for embeddedreal-timesystems, the applications' time-constraints cannot be satisfied easily due to several features of CLI runtime environment, such as thread priority, thread scheduling, garbage collection etc. In this paper, we aim to have a garbage collection mechanism applicable on real-timeapplications in CLI and other virtual machine environments. We achieve the goal by making the pause time of garbage collection operations predictable, and the invocation of garbage collection and applications schedulable. A cost model based on measured WCET is established to predict the execution time and overhead of garbage collection operations.
the run-time power consumption model for multimedia application routines in an embedded system is developed in this paper. A wide range of benchmarks for these routines such as image, video and speech coding algorithm...
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the run-time power consumption model for multimedia application routines in an embedded system is developed in this paper. A wide range of benchmarks for these routines such as image, video and speech coding algorithms are examined extensively to characterize their power consumption behavior. then, based on this study, a run-time power consumption model is proposed to achieve fast and accurate power usage estimation, where the model depends on the specific application routine involved as well as the applied voltage and the operating frequency. It is demonstrated that the developed model is able to predict the cumulative energy consumption of validating sequences with little error. Finally, this model is validated with a commercial VLIW processor by checking its actual power consumption behavior.
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