Batteryless LoRaWAN Communications Using Energy Harvesting: Modeling and Characterization

Billions of Internet-of-Things (IoT) devices are deployed worldwide and batteries are their main power source. However, these batteries are bulky, short lived, and full of hazardous chemicals that damage our environment. Relying on batteries is not a sustainable solution for future IoT. As an alternative, batteryless devices run on long-lived capacitors charged using energy harvesters. The small energy storage capacity of capacitors results in an intermittent on-off behavior. LoRaWAN is a popular low-power wide-area network technology used in many IoT devices and can be used in these new scenarios. In this work, we present a Markov model to characterize the performance of batteryless LoRaWAN devices for uplink and downlink (UL/DL) transmissions and we evaluate their performance in terms of parameters that define the model (i.e., device configuration, application behavior, and environmental conditions). Results show that LoRaWAN batteryless communications are feasible if choosing the proper configuration (i.e., capacitor size and turn-on voltage threshold) for different application behavior [i.e., transmission interval, UL/DL packet sizes (PSs)], and environmental conditions (i.e., energy harvesting rate). Since DL in the second reception window highly affects the performance, only small DL PSs should be considered for these devices. Besides, a 47-mF capacitor can support 1 B SF7 transmissions every 60 s at an energy harvesting rate of 1 mW. However, if no DL is expected, a 4.7-mF capacitor could support 1 B SF7 transmissions every 9 s.