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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.

In the present article we propose a solution based on Software Defined Radio for isotropic, real-time, and simultaneous measurement of six channels corresponding to six field probes (electric and magnetic). The measurement system is much needed for exposure evaluation campaigns conducted in the near field of emitting devices (mobile phone, WLAN router, etc.). However, the use of an SDR pose other problems that need careful and precise solving, to report accurate field levels. To this extent, in this work we present the calibration of an instrument model USRP N310 in the n78 5G (3.5-3.7 GHz) frequency band. The instrument response is investigated for a 5G-like signal, namely a 20 MHz wide, LTE-A, OFDM signal. The instrument sensitivity is analysed in function of the used channel bandwidth and compared to a mid-range swept spectrum analyser sensitivity. The frequency and amplitude response of the instrument are commented on. Results suggest suitability of the instrument for the proposed measurement system. To increase the accuracy of the measured field levels a quick frequency response calibration is indicated before each measurement campaign.

We offer a preliminary description and evaluation of an Android application that can be used to characterize user exposure to electromagnetic fields emitted by an 802.11ax mobile device. The system used consists of a DUT (Device Under Test - Huawei P40 Pro) connected to a wireless router. A measurement system composed of a small isotropic antenna connected to a spectrum analyzer and remotely controlled via a custom designed Python application was used to measure the field strength. Higher field levels were observed during file upload as compared to file download. Based on the measurements recorded by the Android application we performed an analysis of the field changes according to the number of transmitted/received bits and RSSI. We observed direct field strength variation with upload/download speed. We have also introduced the dosimetric indicator of power density/unit of information and proved its validity in highlighting different usage profiles. Further investigations have to be carried out in order to provide large scale data on Wi-Fi user exposure in the case of realistic operating scenarios.

Frequencies higher than 3 GHz are today of extreme interest for the agile human exposimetry. Current approach proposes and demonstrates the capability of a statistic method to report 4G/4G+ wireless applications usage impact on the human factor by providing results regarding: a) energy density accumulation rate in air near the emitting device (instantaneous and average); b) observation of peculiarities of time-distribution of emitted field strengths during certain wireless application/device/network/moment in time of usage.

Wi-Fi network devices emit electromagnetic radiation which is of interest for human exposure safety. Based on the quasi-stochastic time-variability of such signals emitted in two different protocols belonging to the 4th and the 5th generations, namely IEEE 802.11 - n and ac, we demonstrate here that specific temporal patterns can be extracted from the time series, if we use the representation of Poincare plots. Practically, the main parameters of the Poincare ellipses are different for the two communication protocols, directions of data transmission and bandwidths used. When energy density per transferred bit was computed, it was also revealed that there is a linear relationship between this one and the Poincare ellipse area. Based on the mean electric field strengths measured near a Wi-Fi device by directly collecting the amplitude probability density traces of the emitted powers, one can extract the features of short- and long-term exposure profile variations in different wireless data transmission configurations.

The measurement of realistic exposure levels of quasi - stochastic signals from the IEEE 802.11ac communication standard was achieved by applying the complementary cumulative distribution function mode of a real - time spectrum analyzer connected to a laptop. Statistics were used to highlight the differences between the data transfer directions.

The paper investigates the accuracy of assessing exposure to radiation emitted by sources specific to the IEEE 802.11n communication standard by two methods. The first one is based on weighing of the maximum power channel measured in the frequency domain and the second one uses the complementary cumulative distribution function (CCDF) acquisition mode of a real-time spectrum analyzer. It has been demonstrated that the CCDF method is much proper to be applied in the case of the quasi-stochastic signals such as WLAN's.

The paper investigates the possibility of using Software Defined Radio (SDR) platforms in assessing exposure to electromagnetic radiation emitted by sources specific to 3G and 4G generations. Critical parameters of SDR platforms that can limit their performance are the sampling frequency and the receiving resolution of the analog to digital converter (ADC). The performed tests showed that the 8-bit ADC resolution has an influence on the amplitude’s dynamic range, i.e. when evaluating exposure to high-level signals (greater than -40 dBm), the accuracy is consistently diminished. The sampling frequency influences the bandwidth of the channel, and broadband signals (e.g. 20 MHz – in case of 4G) impose requirements for the performance of the SDR platform. For an average-priced SDR platform, such as HackRF One, measurements can be conducted with an acceptable accuracy at most on 5 MHz bandwidths.

The paper aims to analyze the electromagnetic field components in the near field of a high frequency (HF) emission antenna. The typical case of a dipole antenna emitting Near Vertical Incident Skywave (NVIS) HF signals at two emitting frequencies (3.6 MHz and 7.1 MHz) and at 100 W input power is being discussed. The measurements have highlighted the places around the antenna where the field levels are high, from the perspective of safe exposure to electromagnetic radiation. Thus, it was found that on a line situated just beneath and parallel to the emitting antenna, the electric field strength may exceed the safety limit recommended for the population by ICNIRP guidelines. The magnetic field component however was lower than the limit in all considered cases.