A real-time feedback scheduler for environmental energy with discrete voltage/frequency modes

• We address the problem of real-time scheduling inherent to energy harvesting real-time systems.
• We propose a feedback scheduler for energy harvesting systems (FS-EH) in a soft real-time context on a DVFS processor.
• This solution computes the CPU speed with taking into account the energy levels and the executions time variability.
• The proposed approach shows experimentally a good compromise between the available energy and the processor workload.

This paper proposes a feedback scheduler for energy harvesting systems (FS-EH) in a soft real-time context on a DVFS processor. This scheduler reduces the processor speed in proportion to the available energy in the batteries and the processor utilization. The goal is to experimentally maximize the battery life while minimizing the deadline miss ratio. When the battery is full, the harvested energy is wasted, therefore the system could use the processor at full speed. This is accounted for in FS-EH by using the processor at full speed when the available energy is over a given threshold. Otherwise, the processor speed is set proportionally to the available energy and instantaneous processor utilization. We experimentally show that FS-EH performs better, in terms of energy consumption, quality of control and deadline miss rate than other scheduling algorithms proposed in this context.

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