Dedicated RF Power Transfer for Wirelessly-Powered Wearable Medical Sensors

We investigate the possibility of wirelessly charging autonomous wearable sensors for patient health-monitoring through dedicated power transfer from Power Beacons (PB). We propose a novel strategy for transmitting energy beams towards patients, where sensors emit a charging request based on a battery lower threshold and receive energy till the battery reaches an upper threshold. These energy beams are steered towards the patient's smartphone rather than towards the sensor, relieving the need for tracking the PB-sensor channel at only negligible performance loss. Furthermore, as PBs cannot serve all requiring sensors simultaneously, we compare different scheduling algorithms, jointly with the battery thresholds and the energy beam width. For the examined configurations, results show that the energy outage probability is slightly affected by the scheduling policy, and most of the energy is harvested from non-intended beams. We show that the strategy for energy-beam transmission should be adjusted to the sensor location on the human body and the patient's velocity for better performance. Finally, proposing new strategies minimizing the waiting duration can be used as a guideline to reduce the energy outage.