Monitoring Urban Environment through Wireless Sensor Nodes Powered by Mobile RF Sources

The pervasive deployment of Internet of Things (IoT) devices is considered a fundamental brick in the transition towards the Smart City. Small, interconnected, battery-less transceivers, capable of harvesting energy from Radio Frequency (RF) communications are envisioned as a green solution to realize this transition. In this paper, we investigate the possibility of setting up an urban monitoring application through battery-less IoT sensors deployed alongside a road and capable of scavenging energy from mobile wireless sources like traveling vehicles. The proposed Energy Harvesting (EH) model has been derived from experimental measurements, and combined with a vehicular traffic simulator in order to obtain a realistic input power pattern, which takes into account the variable speed and the trajectory of the vehicles. On top of this, a low-energy wireless communication protocol, inspired by the Long Range (LoRa) stack, has been developed, which prescribes periodic data transmission to a remote Access Point (AP). Extensive simulations have been carried out to highlight the impact of several parameters, including storage capacity, load current, data rate, packet size, RF sources intensity and mobility, on the overall system throughput. The obtained results confirm the feasibility of the approach; furthermore, they show that while the peculiar nature of the energy source would make it advantageous to send small packets at higher pace, the opposite strategy (larger packets at lower pace) becomes preferable when the overhead cost is taken into account.