## 2 Materials and Methods
### Scenario Description
As previously stated, future wireless communication systems such as 5G-NR or WLAN 802.11 ay will have benefits in several domains, such as the time domain with variable TDD schemes. In this sense, in TDD, the UL is separated from the DL by the allocation of different time slots within the same frequency band. \begin{table}
\begin{tabular}{c|c c c c c c} \hline \hline  & \multirow{2}{*}{**Conductivity (\(\sigma\)) (S/m)**} & \multicolumn{4}{c}{**Relative Permititivity (\(\epsilon_{r}\))**} \\ \cline{3-6}  & & \multicolumn{2}{c}{**Real Part (\(\epsilon^{\prime}\))**} & \multicolumn{2}{c}{**Imaginary Part (\(\epsilon^{\prime\prime}\))**} \\ \hline
**Frequency (GHz)** & 28 & 60 & 28 & 60 & 28 & 60 \\ \hline
**Material** & & & & & & \\ \hline Concrete & 0.48 & 0.89 & 5.31 & 5.31 & 0.31 & 0.26 \\ \hline Brick & 0.03 & 0.03 & 3.75 & 3.75 & 0.02 & 0.01 \\ \hline Plasterboard & 0.12 & 0.21 & 2.94 & 2.94 & 0.07 & 0.06 \\ \hline Wood & 0.16 & 0.37 & 1.99 & 1.99 & 0.10 & 0.11 \\ Glass & 0.22 & 0.56 & 6.27 & 6.27 & 0.14 & 0.17 \\ \hline Ceiling board & 0.02 & 0.05 & 1.5 & 1.5 & 0.01 & 0.01 \\ \hline Chipboard & 0.29 & 0.52 & 2.58 & 2.58 & 0.18 & 0.15 \\ \hline Floorboard & 0.39 & 1.11 & 3.66 & 3.66 & 0.25 & 0.33 \\ \hline Metal & \(10^{7}\) & \(10^{7}\) & \(1\) & 1 & \(6.4\times 10^{6}\) & 2.9 \(\times 10^{6}\) \\ Skin tissue & 73.22 & 210.52 & 28.54 & 11.97 & 0 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Material properties for the 3D ray launching simulations. \begin{table}
\begin{tabular}{l c c} \hline \hline \multicolumn{1}{c}{**Description**} & \multicolumn{2}{c}{**Value**} & **Ref** \\ \hline Number of AP * & 9 & \\ AP * antenna configuration & 64 & [50] \\ TX power per considered AP * beam & 15 dBm & [6,51] \\ AP * antenna element gain & 0 dBi & [6,51] \\ AP * azimuth beam width & 30\({}^{\circ}\) & [52] \\ AP * elevation beam width & 30\({}^{\circ}\) & [52] \\ Ftdd & 0.75 & [11,53] \\ UE antenna configuration & **8** & [50] \\ TX power per considered UE beam & 10 dBm & [23] \\ UE azimuth beam width & 65\({}^{\circ}\) & [51] \\ UE elevation beam width & 65\({}^{\circ}\) & [51] \\ UE antenna element gain & 0 dBi & [6,51] \\ Carrier frequency 5G/Wi-Fi 802.11 ay & 28/60 GHz & \\
3D-RL Angle Resolution & 0.4\({}^{\circ}\) & \\ Maximum number of reflections & 4 & \\ Maximum number of refractions & 1 & \\ Diffraction & Yes \\ Maximum number of diffractions/Diffracted ray angular resolution & 1/0.25\({}^{\circ}\) \\ Scenario size & \(18\times 47\times 7\) \\ Unitary volume analysis & 1 m \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Setting of the main input parameters for 5G and Wi-Fi 802.11 ay simulation setup in the considered scenario. From an exposure assessment point of view, the realistic maximum exposure should be proportional to the fraction of the DL transmission time to the total time given by [11]  
\[F_{\text{TDD}}=\frac{\text{DL : UL}}{\text{DL : UL}+1} \tag{5}\]  
where DL:UL denotes the DL/UL transmission configuration (ratio of DL transmission time to UL transmission time). In this paper, \(F_{\text{TDD}}\) = 0.75 is assumed as a reasonable value for future wireless communication systems [11]. In order to analyze the EMF exposure in the considered scenario, three different cases are considered for comparison purposes. These three cases are the following:  
* Case I: We consider that 100% of the users in the library are connected to 5G and no one to WLAN 802.11 ay, so we can assess EMF exposure only from the 5G communication system at 5G-FR2 (@28 GHz) in a crowded environment. * Case II: We consider that 100% of the users in the library are connected to WLAN 802.11 ay and no one to 5G, so we can assess EMF exposure only from the WLAN 802.11 ay (@60 GHz) communication system in a crowded environment. * Case III: We consider a case where both systems coexist, and 30% of the users are connected to 5G and 70% to WLAN 802.11 ay.