Battery-Less LoRaWAN Communications using Energy Harvesting: Modeling and Characterization
Carmen Delgado, José María Sanz, Chris Blondia, Jeroen Famaey
TL;DR
This work tackles battery-less IoT by modeling LoRaWAN Class A devices powered solely by energy harvesters and capacitors, producing an analytical Markov Chain framework to evaluate uplink and downlink performance under realistic energy and transmission constraints. The model integrates harvester, capacitor, and load dynamics with LoRaWAN timing (two RX windows and SF-dependent airtime) to estimate PDR and DL reception probabilities, enabling rapid exploration of capacitor size, turn-on threshold, and harvest-rate settings. Key findings show battery-less LoRaWAN is feasible under proper configuration; downlink in RX2 and larger payloads impose stringent energy demands, while small downlink packets and careful turn-on thresholds improve reliability. The results highlight practical design guidelines for capacitor sizing and threshold control, with significant implications for scalable, maintenance-free IoT deployments in energy-scarce environments; future work includes experimental validation and dynamic threshold adaptation.
Abstract
Billions of 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 the future IoT. As an alternative, battery-less devices run on long-lived capacitors charged using energy harvesters. The small energy storage capacity of capacitors results in an intermittent on-off behaviour. 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 battery-less LoRaWAN devices for uplink and downlink transmissions and we evaluate their performance in terms of the parameters that define the model (i.e., device configuration, application behaviour and environmental conditions). Results show that LoRaWAN battery-less communications are feasible if choosing the proper configuration (i.e., capacitor size, turn-on voltage threshold) for different application behaviour (i.e., transmission interval, UL/DL packet sizes) and environmental conditions (i.e., energy harvesting rate). Since downlink in the second reception window highly affects the performance, only small DL packet sizes should be considered for these devices. Besides, a 47 mF capacitor can support 1 Byte $SF7$ 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 Byte $SF7$ transmissions every 9~s.