Low-Power Circuits and Energy-Aware Protocols for Connecting Batteryless Sensors

Removing batteries from the Internet of Things (IoT) devices is a big innovative step towards green operation and sustainability. Batteryless IoT operates by only harvesting the surrounding ambient energy and achieving low environmental impact. As the harvested energy may be irregular and transient, batteryless devices operate intermittently due to frequent arbitrary power failures. Intermittent operation prevents reliable communication among transiently-operated IoT devices. Exploiting ultra-low-power physical layer technologies does not guarantee reliable wireless communication since nodes can still fail during data transmission due to the random nature of energy availability. This paper presents the main characteristics, challenges, and existing solutions in transiently-powered communication, including our recent efforts in this domain. We summarize existing hardware designs and protocol solutions that support overcoming the challenge of intermittent operation during wireless communication. We emphasize that the key insight to achieving reliable communication is to share the energy status of the batteryless nodes, allowing for energy-aware data packet communication. Our experimental results show that energy-aware communication completely avoids data and energy loss due to intermittent operation and enhances the network throughput by three times. Finally, we provide open challenges for future research to draw the attention of the wireless communication community to this new field.