Approaching user exposure assessment using broadband versus frequency-selective methods: IEEE 802.11ax mobile device emitted field

We have approached user exposure to EMF originated from an IEEE 802.11ax client (mobile phone) by using both broadband and frequency selective measurement instrumentation. All the measured field strengths were situated below the ICNIRP and IEEE reference levels for public safe exposure. Higher field levels were observed during file upload followed by file download and then video streaming. Following, we propose an original algorithm for similarity evaluation of the two measurement system readings based on cross-correlation and dynamic time warping (DTW) algorithm. We observed clear differences between probes in general, and between their ability to correctly follow the field strengths amplitude time dynamic. The proposed algorithm offers a series of advantages compared to traditional response time investigation. While the temporal response of the used broadband field probe appears to be adequate for 802.11ax signals, the amplitude resolution exhibits a serious drawback for measuring low field levels associated with some Wi-Fi applications like video streaming.