Determination of maximal RF exposure to 5G massive MIMO base stations under non-line-of-sight conditions: part 1 : theoretical and numerical investigations

This paper addresses misestimations of RF exposure found in measurements at 5G massive MIMO base stations under non-line-of-sight conditions. One possible cause is incorrectly determined gain correction factors, which are used for extrapolating the measured SSB exposure to the maximal possible exposure. Plausibility considerations based on geometrical optics are used to identify corresponding scenarios; here, the measurement points are in places where the envelopes of the traffic and broadcast beams are not identical and the exposure is dominated by reflections. Numerical simulations also show an increasingly locally small-scale varying field distribution. A verification of these considerations by measurement is successfully done in part 2.