## 2 Methodology and Data Collection
### Measurements and Data Collection Procedure  
In order to represent typical O2I links, received signal-strength measurements were carried out in two universities in Chile with similar scenarios: the engineering campus of Universidad Diego Portales (UDP) in Santiago, and the main campus of Universidad Tecnica Federico Santa Maria (USM) in Valparaiso. This measurement campaign was employed in [6] to research a completely different objective than the one addressed in this study; here we only employ the NLOS O2I samples. In seeking to analyze NLOS links, the samples collected in the measurement campaigns described two types of links reported in Table 1. Table 2 details the scenarios for measurement campaigns and the NLOS O2I samples collected. \begin{table}
\begin{tabular}{c c c} \hline \hline
**NLOS Link** & **Description** \\ \hline Same side (SS) & The transmitter and receiver system share the same street \\ Opposite side (OS) & The transmitter and receiver system are placed on opposing sides of the street \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Measurement Campaign non-line-of-sight (NLOS) Links. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Scenario**} & \multicolumn{4}{c}{**Outdoor 1**} & \multicolumn{2}{c}{**Indoor**} \\ \cline{2-5}  & **Street** & **Street** & **Surroundings** & **No.** & **Rooms** \\  & **Width** & **Length** & & **Rooms** & **Width** \\ \hline \hline \multirow{3}{*}{UDP} & \multirow{3}{*}{2I m} & \multirow{3}{*}{89 m} & Concrete buildings with different floor heights and a few trees with \(\approx\)6 m in height & \multirow{3}{*}{2} & \multirow{3}{*}{6 m} \\  & & & & & \\ \cline{1-1} \cline{4-5} \cline{7-7}  & & & Three-story concrete buildings of uniform shape with 6 m2 windows & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Measurement Campaign Scenarios. In Figure 1, a basic layout of both scenarios is illustrated; for same side (SS) links, the transmitter system was always placed on the sidewalk 0.7 m away from the building wall, and for opposite side (OS) links, it was moved directly across the street from its previous location. Throughout the different transmitter system settings, it was located at a 5 m height with a 60\({}^{\circ}\) depression angle to the wall. The transmitter power of the system was 17.8 dBm (\(P_{\text{tx}}\)) at a 3.5 GHz continuous wave (CW) and it consisted of a vertically polarized directional patch antenna with 10.2 dB gain (\(G_{\text{tx}}\)), 60\({}^{\circ}\) azimuth and elevation half-power beamwidths. The received power was recorded by a narrowband receiver connected to a vertically polarized half-wavelength dipole with a 2.4 dB gain (\(G_{\text{rx}}\)). The receiver bandwidth of 200 KHz allowed it to capture any frequency dispersion affecting the CW transmission. In all field measurements the received power was at least 20 dB above the receiver noise floor of \(-\)123 dB. For the sampling process the receiver antenna was placed on a computer-controlled rotating arm involving measurements of 6\({}^{\circ}\) (or 0.105 rad) angular increments on circles of radius 0.4 m at each receiver placement. For each angular position 25 consecutive power samples were collected, in order to verify consistency and averaging, and to remove residual temporal fades, which did not fluctuate by more than \(\pm\)0.5 dB due to the narrowband static environment. Then, these consecutive samples were averaged to account for the first power sample value and to continue to the next angular position until 60 possible angular positions were completed in a 360\({}^{\circ}\) circle. Finally, 60 received signal power samples were collected at each receive location, as illustrated in Figure 2. Regarding receiver locations, a total of 308 and 108 sample locations were reported for the O2I NLOS USM and UDP scenarios, respectively. Considering the angular increments as \(\theta\) and the circle radius as \(r\) in Figure 3 the resulting separation distance is illustrated.