Real-time scheduling for energy harvesting sensors

Energy harvesting is the conversion of ambient energy into electricity to power small devices such as wireless sensors, making them self-sufficient. The electrical energy used to power them is variable over time and limited by the capacity of the energy storage (battery or ultra-capacitor). In general, these embedded devices have to adhere to real-time constraints expressed in terms of deadlines. In this paper, we present power management and scheduling solutions for energy harvesting systems having real-time constraints such as most of wireless sensors. We show how to answer questions like the following: When should the system use energy? When should it be idle and recharge the energy storage? We review the main properties of a scheduler known as Earliest Deadline with Energy Guarantee (EDeg) and we report results of an experimental study.