IN-SITU 5G NR BASE STATION EXPOSURE OF THE GENERAL PUBLIC: COMPARISON OF ASSESSMENT METHODS.

New measurement methods and equipment for correct 5G New Radio (NR) electromagnetic field (EMF) in-situ exposure assessment of instantaneous time-averaged exposure (Eavg) and maximum extrapolated field exposure (Emax) are proposed. The different options are investigated with in-situ measurements around 5G NR base stations (FR1) in different countries. The maximum electric field values satisfy the ICNIRP 2020 limit (maximum 7.7%). The difference between Emax and Eavg is <3 dB for the different measurement equipment at multiple sites in case there is only self-generated traffic. However, in a more realistic scenario, Eavg cannot be used to assess the exposure correctly due to influence of other users as the spatial distribution of user equipment (UE) influences Eavg, while Emax is not affected. However, when multiple UEs are collocated, there is no influence of the number of UEs. A broadband measurement can give a first impression of the RF-EMF exposure up to 700 m, but is not enough to assess the 5G-NR exposure.

Prediction of RF-EMF exposure levels in large outdoor areas through car-mounted measurements on the enveloping roads.

Knowledge of spatial and temporal trends in the environmental exposure to radiofrequency electromagnetic fields (RF-EMF) is a key prerequisite for RF-EMF risk assessment studies attempting to establish a link between RF-EMF and potential effects on human health as well as on fauna and flora. In this paper, we determined the validity of RF exposure modelling based on inner-area kriging interpolation of measurements on the surrounding streets. The results vary depending on area size and shape and structural factors; a Spearman coefficient of 0.8 and a relative error of less than 3.5dB are achieved on a data set featuring a closed measurement ring around a decently sized area (1km(2), with an average minimum distance of the encircled area to the ring of less than 100m), containing mainly low, detached buildings. In larger areas, additional inner-area sampling is advised, lowering the average minimum distance between sampled and interpolated locations to 100m, to achieve the same level of accuracy.

Do car-mounted mobile measurements used for radio-frequency spectrum regulation have an application for exposure assessments in epidemiological studies?

Knowing the spatial and temporal trends in environmental exposure to radiofrequency electromagnetic fields is important in studies investigating whether there are associated health effects on humans and ecological effects on plants and animals. The main objective of this study is to assess whether the RFeye car-mounted mobile measurement system used for radio frequency spectrum monitoring in The Netherlands and the United Kingdom could be of value in assessing exposure over large areas as an alternative to measuring exposure with personal exposure meters or using complex modelling techniques. We evaluated the responses of various body-worn personal exposure meters in comparison with the mobile measurement system for spectrum monitoring. The comparison was restricted to downlink mobile communication in the GSM900 and GSM1800 frequency bands. Repeated measurements were performed in three areas in Cambridge, United Kingdom and in three areas in Amersfoort, The Netherlands. We found that exposure assessments through the car-mounted measurements are at least of similar quality to exposure modelling and better than the body worn exposimeter data due to the absence of the shielding effect. The main conclusion is that the mobile measurements provide an efficient and low cost alternative particularly in mapping large areas.

Calibration and uncertainties in personal exposure measurements of radiofrequency electromagnetic fields.

In the past 5 years radiofrequency personal exposure meters have been used to characterize the exposure during daily activities. We found from calibration tests for the 12 frequency bands of the EME Spy 121 exposimeter in a Gigahertz Transverse Electromagnetic cell and an Open Area Test Site, that these measurements tend to underestimate the actual exposure. Therefore, a maximum frequency-dependent correction factor of 1.1-1.6 should be applied to the electric field. This correction factor consists of three multipliers correcting for calibration, elevation arrival angle, and influence of the body. The calibration correction factor should be determined per exposimeter, as the maximum range of response between exposimeters in a frequency band is 2.4 dB. Since the range of response for different elevation angles could reach 10.2 dB, a strict protocol for wearing the exposimeter during fieldwork should be followed to be able to compare and combine measurements made by different persons in the same microenvironments. Because the influence of the body depends on the azimuth angle of arrival, it may lead to an over- or underestimation. Thus, the body correction factor is an average over the angles and should only be applied in activities involving movement through the full 360° range of random angles of arrival.