Experimental evaluation of in-vehicle RF-EMF induced by IoT devices of smart parking systems and other wireless technologies

Abstract

This study empirically investigates the impact of Internet of Things (IoT) devices in urban settings on human exposure to radiofrequency electromagnetic fields (RF-EMF). It addresses a notable research gap by presenting a systematic evaluation of RF-EMF exposure from a specific IoT implementation. The novelty of this work lies in its dedicated focus on LoRaWAN and its provision of a comparative analysis with other wireless technologies. Measurements were performed in a vehicle with a LoRaWAN device at 868 MHz, moving in several urban environments (university and street parking sites), for three cases: inside and outside a regular (petrol engine) vehicle, and inside an electric (engine). Power density was measured with a broadband probe, covering all current bands of wireless technologies (from 0.79 GHz to 5.85 GHz). The main goal was to determine the potential change in EMF level during the stay of a person in a car that uses IoT devices for monitoring the availability of parking lots and other possible services. As expected, values were very low compared with ICNIRP’s Guidelines (the strictest reference value in the whole measured band is 4 W/m²). In the LoRaWAN band, the highest temporal variation of the average power density fluctuated between 5.16 µW/m² and 35.37 µW/m², this system contributing only with around 0.02 % of the total power. The measured values fit well a Log-Normal Distribution. The observed low exposure levels and compliance with ICNIRP’s Guidelines (the maximum value is 14.63 dB below ICNIRP’s threshold) support the safe deployment of LoRaWAN based parking systems.