## 4 Discussion  
In this study, the environmental radiofrequency (RF) electromagnetic field (EMF) exposure was evaluated in a commercial fifth generation (5G) new radio (NR) network in and around Bern, Switzerland. To this end, the time-averaged actual (\(E_{ang}\)) and extrapolated maximum electric-field levels (\(E_{max}\)) attributed to an NR signal were assessed at 22 positions in the vicinity of four NR base stations, using the methods described in [13]. At each site, the specifications of the NR channel (bandwidth of 100 MHz) and its 'always-on' broadcast signal (the synchronization signal block (SSB), with center frequency \(SS_{REF}\) 3604.8 MHz and subcarrier spacing 30 kHz) were identified. Then, the electric-field strengths per resource element (\(E_{RE}\)) allocated to either the SSB or the physical downlink shared channel (PDSCH, the downlink traffic signals) were measured, after which they  
Figure 9: Scatterplot of the maximum electric-field strength \(E_{max}\), extrapolated using Equation (2) and based on the field strength per resource element of the PDSCH, versus the maximum time-averaged electric-field strength \(E_{agg}\), measured during 100% downlink traffic directed towards the UE. The locations were grouped by their relative position to the NR base station: within (blue dots) or outside its scanning range (red dots). Markers with a white X depict positions in non-line-of-sight. were both extrapolated to \(E_{max}\)--using for \(E_{RE,SSB}\) the antenna patterns provided by the radio equipment manufacturer (Equation (1))--considering the worst-case scenario of a continuously full PDSCH-allocated channel bandwidth (i.e., '100% downlink'), and also taking into account the experimentally derived time division duplex (TDD) factor of 0.74. Finally, the \(E_{max}\) values were compared to the \(E_{avg}\) values that were measured while inducing a 100% downlink traffic stream to a user equipment (UE) using the iPerf3 application. Without inducing any downlink traffic, the actual exposure levels were very low, with a maximum of just 0.05 V/m (Figure 7), and the contribution to the environmental RF exposure was small (Table 1). A similar value of 5 \(\mu\)W/m\({}^{2}\) or 0.04 V/m for the exposure to the SSB was found in [16]. When a maximum downlink load was generated towards a UE on the same line as the measurement probe with respect to an NR base station, \(E_{avg}\) increased to maximally 0.4 V/m, which still only contributed 9.5% to the total environmental RF exposure as measured at the four investigated sites (Table 1). Furthermore, the highest extrapolated maximum field level \(E_{max}\) observed in the network was 0.6 V/m. Finally, the highest normalized (to an antenna input power of 1 W) \(E_{avg}\) was found at a distance of 190 m from an NR base station, although there was a large variation between field levels at about this distance. Despite some differences in the measurement settings and measurement positions, the exposure levels measured with the SRM-3006 and FSV spectrum analyzer were in good agreement. It is important to note that the reported values are specifically true for the Swisscom commercial 5G NR network in Bern, Switzerland, as it was at the time of the measurements (July 2020). The MaMIMO base stations were characterized by codebook-based beamforming configured with eight CSI-RS ports (with only azimuthal beam steering) and limited input powers \(P_{in}\) (in fact, the maximum was 8.1 W) due to the restrictive exposure limits that apply in Switzerland. In commercial NR networks in other areas or countries, \(P_{in}\) may very well be much higher. Extrapolating the electric-field levels measured in this study to a common maximum \(P_{in}\) of 200 W, maximum \(E_{avg}\) and \(E_{max}\) (based on Equation (1)) values of respectively 4.3 V/m (0.05 W/m\({}^{2}\)) and 4.9 V/m (0.06 W/m\({}^{2}\)) were obtained, i.e., exposure levels 150-200 times below the ICNIRP reference level of 10 W/m\({}^{2}\) (61 V/m) at 3.5 GHz [3].