## 3 Results and Discussion
### Measurement Results  
A complete campaign of the measurements was performed in the library scenario under analysis to validate the enhanced simulation tool for RF-EMF exposure assessment at 28 and 60 GHz following the previously described measurement guidelines in Section 2.3. Figures 14 and 15 present the received power comparison between the experimental measurements and the 3D-RL simulation at the 28 and 60 GHz operating frequencies, respectively, along the different radials of the transmitter antenna beamforming (see Figure 8 for reference) when the transmitter was placed on the first floor. In this case, most of the measurements were performed under line-of-sight (LOS) conditions, but the measurements performed within the bookshelves were done under non-line-of-sight (NLOS) conditions (the indoor environment within the bookshelves can be seen in Figure 3). LOS conditions can be considered as a higher risk situation in terms of the nonionizing radiation exposure levels. As it can be seen from the comparisons, the simulation and measurements were in good agreement for both cases. Table 6 shows the differences between the measurements and simulation estimations for both frequencies at each linear distribution radial, ranging from 1.20-3.59 dB for the 28 GHz frequency band to 1.40-5.09 dB for the 60 GHz frequency band. This difference reflects both uncertainties in the measurements and assumptions made in computing. The maximum level of power using the Max Hold function in the handheld spectrum analyzer was used for the measurement results when compared to the simulations. However, we experimentally observed in the campaign of measurements that they fluctuated, with an average value of approximately 2.5 dB. Figure 13: E-field and Power density distribution levels of the XY bi-dimensional plane at the working spaces at head height of seated people on the first floor of the library for Case III HD: (**a**) E-field and (**b**) power density. Figure 14: Experimental measurements and 3D-RL simulation comparison at 28 GHz frequency along the different linear radial distributions R\({}_{1}\),..., R\({}_{11}\) depicted in Figure 8. \begin{table}
\begin{tabular}{c c c} \multicolumn{3}{c}{**Difference Sim. vs. Meas. (dB)**} \\ \hline
**Frequency** & **28 GHz** & **60 GHz** \\ \hline Radials Figures 14 and 15 & & \\ \hline R1 & 1.52 & 1.84 \\ R2 & 1.55 & 2.18 \\ R3 & 1.30 & 1.84 \\ R4 & 1.48 & 3.23 \\ R5 & 1.71 & 1.40 \\ R6 & 1.67 & 3.88 \\ R7 & 3.59 & 1.89 \\ R8 & 2.42 & 5.09 \\ R9 & 1.20 & 2.38 \\ R10 & 1.51 & 4.13 \\ R11 & 1.20 & 4.50 \\ \hline Measurement Points Figure 16 & 0.86 & 2.64 \\ TOTAL Difference (mean) & 1.67 & 2.92 \\ \hline \end{tabular}
\end{table} 
Table 6: Differences between the measurements and simulation for the different linear distribution radials presented in Figures 14 and 15 and the measurements points of Figure 16.  
Figure 15: Experimental measurements and 3D-RL simulation comparison at 60 GHz frequency along the different linear radial distributions R\({}_{1}\),..., R\({}_{11}\) depicted in Figure 8.  
Moreover, Figure 16 presents the experimental measurements and 3D-RL comparisons for both frequencies (28 and 60 GHz) at the different points represented in Figure 9 when the transmitter was placed on the second floor of the scenario (see Figure 9 for reference). In this case, all measurement points were under LOS conditions. When comparing LOS condition measurement spatial points, it did not mean that we compared only the LOS component, since, although they were under LOS conditions, we also detected multipath components, which could be from different phenomena, such as a reflected, transmitted or diffracted field. The in-house enhanced simulation EMF exposure software considered the full three-dimensional characteristics of the scenario at the geometry level and clutter location, as well as the dispersive properties by means of the conductivity and relative permittivity, of all the obstacles within the environment.