A Nonclairvoyant Real-Time Scheduler for Ambient Energy Harvesting Sensors

International audienceAmbient energy harvesting also known as energy scavenging is the process where energy is obtained from the environment, converted, and stored to power small devices such as wireless sensors. We present a variant of EDF scheduling algorithm called EH-EDF (Energy Harvesting-Earliest Deadline First). Decisions are taken at run-time without having prior knowledge about the future energy production and task characteristics. We gauge the performance of EH-EDF by means of simulations in order to show its benefits .W eevaluat ean dcompar esevera lvariant so fEH-ED Fi nterm so fpercentag eo ffeasibl etas ksets .Metric ssuc ha saverage length of the idle times are also considered. Simulations tend to demonstrate that no online scheduler can reach optimality in a real-time energy harvesting environment

Partitioned EDF Scheduling in Multicore systems with Quality of Service constraints

International audienceIn this paper we study the partitioned EDF scheduling in a homogeneous multiprocessor environment with Quality of Service (QoS) constraints. The system considered here is a real-time multiprocessor system assumed to be powered by rechargeable batteries. We address the issue of how to best partition a set of firm real-time tasks that can occasionally skip one instance according to a predefined QoS threshold. The main goal is to minimize the energy consumption of the system while offering solutions with respect to transient energy starvation situations the system can experiment. The contribution of the paper is twofold. First, we present a schedulability analysis of firm multiprocessor task sets under QoS constraints. Second we propose new partitionning heuristics integrating skips. The evaluation is conducted from several points of view (minimization of the total processor number, maximization of the spare capacity on each processor)

Importance of the traffic model in the reliability estimation of highway bridges

Road bridges are exposed to stochastic traffic loadings that are not simply determined. The international codes for the design and assessment of highway bridges provide some standard trucks that can be used in the design process. Knowing that the traffic can vary considerably from one bridge to another, standard trucks may lead to poorly estimate the reliability in the assessment process. So, the sensitivity of the reliability indices to the load models will be discussed, on one hand by considering the standard truck given by the French Fascicule 61 and on the other hand by adopting real vehicle data from existing weigh-in-motion station. A set of reinforced concrete bridges will be used for the application

Uniprocessor Scheduling for Real-Time Energy Harvesting Applications

Energy management is a central problem in real-time systems design, in particular for embedded wireless devices. Whereas a great number of work was carried out in order to minimize the energy consumption and maximize the lifetime achieved as in classical battery operated devices, few studies have been devoted to emerging harvesting systems which need to operate perennially thanks to the environmental energy. In such systems, the consumed energy comes at the same time from the computing nodes and the supports of transmission/reception. In this book, we focus on systems that receive their energy from an environmental source (for example, solar energy). Under these assumptions, the objective is to ensure a perennial functioning of the real-time system that must be able to operate indefinitely in the respect of its timing requirements. So the problem we have to deal with is: How can we schedule tasks so as to guarantee their timing constraints perpetually by suitably exploiting both the processor and the available ambient energy

Stratégies d’ordonnancement temps réel pour les systèmes embarqués autonomes en énergie

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Towards multiprocessor scheduling in distributed real-time systems under energy constraints

International audiencePerformance boosting has been a highly important goal in system designs in the past decades. Not until recently, energy efficiency becomes another critical feature being pursued in a wide variety of products, especially for battery powered devices. Various studies have been conducted for energy efficient systems techniques. The most adopted ones are Dynamic Voltage Scaling (DVS) and Dynamic Power Management (DPM). However, all the previous research have disregarded an important aspect of these devices, namely rechargeability of the batteries. Several studies have explored the problem of scheduling real-time tasks in a monoprocessor rechargeable system. This paper summarizes the state of art research results of uniprocessor real-time systems under energy constraints. Then, we extend our work to deal with the problem of scheduling real-time tasks in a monoprocessor rechargeable systems