## 3 Results
### Maximum Exposure  
#### 3.2.1 Electric-Field Strength per Resource Element  
To determine the electric-field strength per RE allocated to SSB (\(E_{RE,SSB}\)) and PDSCH (\(E_{RE,PDSCH}\)), zero-span measurements were performed with the FSV at the SSB's center frequency of 3604.8 MHz (Figure 3) with a resolution bandwidth of 1 MHz. At an SCS of 30 kHz (as determined in the previous section), the average power received per subcarrier, \(P_{sc}\), can be calculated from the measurement samples \(P_{meas}\) using  
\[P_{sc}=P_{meas}-10\log_{10}\frac{RBW}{SCS}=P_{meas}-15.23\;\mathrm{dB}. \tag{3}\]  
Whereas for the SSB symbols, the average power per resource element \(P_{RE}\) is equal to \(P_{sc}\), as all subcarriers within the measured bandwidth were allocated to the SSB at these time instances, in the case of PDSCH, \(P_{RE}\geq P_{sc}\), since the actual allocation is unknown.  
Each successive trace of roughly 1 s measured by the FSV was post-processed such that the samples were aligned with the 5G NR frame structure and stacked per SSB period of 20 ms ('waterfall diagram' [13]). This post-processing step, which is illustrated in Figure 4, enables one to distinguish between the SSB (which is four Orthogonal Frequency Duplexing Multiplexing (OFDM) symbols long) and the PDSCH resources. In this case, there was only one cell-wide SSB, i.e., the narrow band with a length of four symbols within the first of two slots of the first subframe '0' (on the far left of Figure 4). The PDSCH-allocated symbols, on the other hand, form multiple thicker bands each consisting of four successive slots, with 10 (in the case of a special 'S' slot) or 14 symbols (a normal downlink 'D' slot). The varying color and sometimes gaps in Figure 4 further illustrate the varying allocation of PDSCH resources within the measured bandwidth. Furthermore, from Figure 4 the TDD pattern 'DDDSU' can be observed (where an 'S'-slot contains 10 downlink symbols) and a TDD factor \(f_{TDD}\) of 0.74 is obtained.  
For each field component \(k\) (\(k=X,Y,Z\)), \(P_{k,RE,SSB}\) was determined as the median of the identified SSB samples, whereas \(P_{k,RE,PDSCH}\) required an additional post-processing  
Figure 4: ‘Waterfall diagram’ plot [13] of a zero-span trace of 1.1 s (55 \(\times\) 20 ms) measured with the FSV setup in a 1 MHz-bandwidth around the SSB center frequency. Successive pairs of NR frames (i.e., 2 \(\times\) 10 ms, with each frame containing 20 slots (two per subframe) of 14 Orthogonal Frequency Duplexing Multiplexing (OFDM) symbols) are stacked on top of each-other. The four-symbol long SSB is visible on the left. The other bands show a clear DDDSU pattern, with three downlink (D) slots, one special (S) slot (which contains 10 downlink symbols), and one (empty) uplink (U) slot.  
step: for each PDSCH slot (identified using the aforementioned 'waterfall' method [13]) the median power of the slot's symbols was retained, after which the highest Gaussian was determined in the distribution of these median powers [13]--using the findpeaks command in Matlab. The electric-field values per RE and per component \(E_{k,RE}\) were obtained using the antenna factor (AF) and cable losses of the measurement equipment and the vector sum of the components then resulted in the total \(E_{RE}\)[13]. Figure 5 shows the two resulting \(E_{RE}\) for each measurement position. For PDSCH resources, the highest \(E_{RE}\) was 0.012 V/m, for SSB resources 0.008 V/m. The difference in \(E_{RE}\) (assumed due to the difference in antenna gain) was generally about 4 dB, in particular in LOS and within the BS radio scanning range. Outside the scanning range, there was more variation, ranging between 1 dB and 8 dB. The \(E_{RE}\) values were the lowest at the two NLOS positions, one within and one outside the scanning range, with differences of 0.5 and 2.8 dB, respectively. However, in NLOS, the measured signals were very close to the noise level, which resulted in a higher uncertainty.