## 4 Experimental Validation of the Procedure  
In this section, the procedure is applied step-by-step considering an experimental example. The data reported in Ref. [24] are used, acquired using a Rohde & Schwarz FSP3 spectrum analyzer connected to a Keysight N6850A Broadband Omnidirectional antenna. The gNB is placed roughly 20 m above ground level, and the angular position of the measurement point with respect to the gNB is (\(\phi_{0}\simeq 0^{\circ}\), \(\theta_{0}\simeq 28^{\circ}\)). The antenna system is an mMIMO 64T64R operating with SU-MIMO. The basic information on the 5G signal is as follows:  
* Central frequency of the SSB: 3649.44 MHz;
* Bandwidth: \(B=80\) MHz;
* Numerology: \(\mu=1\);
* Duty cycle: \(F_{TDC}=0.743\). More details on the gNB and on the 5G signal can be found in [24]. We consider the MPE with a probability of 95% (\(prob=0.95\)). As a preliminary step, starting from the BERP and TERP of the AAS, the functions \(B(\theta,\phi)\) and \(T(\theta,\phi)\) (Figure 2) are obtained. From the plot of \(F_{beam}(\theta,\phi)\) (Figure 3), three different angular regions in which the functions show some degree of homogeneity are identified; the regions chosen in this example, indicated as colored rectangles in Figure 2, are as follows (in this example, quite large regions have been chosen; it is understood that it is possible to select narrower regions better centered on the measurement directions. ):  
* Region A: \(0^{\circ}\leq\theta\leq 12^{\circ}\), \(-40^{\circ}\leq\phi\leq 40^{\circ}\)
* Region B: \(12^{\circ}\leq\theta\leq 23^{\circ}\), \(-40^{\circ}\leq\phi\leq 40^{\circ}\)
* Region C: \(23^{\circ}\leq\theta\leq 30^{\circ}\), \(-40^{\circ}\leq\phi\leq 40^{\circ}\)  
In the right part of Figure 3, a contour plot of the \(F_{beam}(\theta,\phi)\) restricted to Region C is shown. The function exhibits a quite complex variation. As discussed in the text, the statistical approach allows the problems related to the exact value of the angular position of the UE to be mitigated. The three CDF curves associated with the three regions are calculated: the curves are shown in Figure 4 (Region A: blue curve, Region B: red curve; Region C: yellow curve). Regarding the measurements, the settings of the Spectrum Analyzer were as follows: span zero mode, RMS trace, central frequency 3649.44 MHz, and 1 MHz RBW. The plot of the SSBs power (in the absence of active UEs) is shown in Figure 5; the presence of an SSB burst [37] consisting of six SSBs is clearly visible. (After the SSB burst set there are four Tracking Reference Signals [26] signals, which are not of interest in the proposed MPE procedure. ); The highest power level of the SSBs is  
\[P_{SSB}^{SSB}=-44\text{ dBm},\]Applying the steps listed in the previous Section, we obtain \(E^{max\,SSB}=0.24\) V/m. The angular direction of the measurement point (i.e., \(\theta_{0}\simeq 28^{\circ},\phi_{0}\simeq 0^{\circ}\)) falls in Region C (yellow curve in Figure 4). Choosing 0.95 confidence, we have \(F_{beam}^{0.95}(\theta_{0},\phi_{0})\simeq 120\), i.e., \(\sqrt{F_{beam}^{0.95}(\theta_{0},\phi_{0})}\simeq 11\), and \(E_{5G}^{max\,0.95}=0.24\times 11=2.6\) V/m. The procedure indicates that the maximum field level in the measurement point is lower than 2.6 V/m in 95% of the positions of Region C.  
To validate this result, it is necessary to compare the MPE result (obtained from data acquired in absence-of-data-traffic condition) with the field actually radiated in the case of maximum data traffic load. In this regard, in the measurement session reported in [24], the communication system was forced to completely fill the frame using a UE terminal. Consequently, it was possible to obtain the maximum field value using Channel Power measurement. The measurement affected by the narrowest uncertainty ([24], Table 3, row 2) indicates a value of the maximum field level in the measurement position equal to \(1.72\pm 0.29\) V/m. The uncertainty range (expanded uncertainty, coverage factor \(k=2\)) of this measurement is plotted in Figure 6 as two green lines.