# Path Loss Measurements and Model Analysis in an Indoor Corridor Environment at 28 GHz and 38 GHz
## 3 Path Loss Measurements and Models
### NLOS Measurement Evaluation: Study Results and Discussion  
The CI and FI models for both vertical-to-vertical (V-V) and vertical-to-horizontal (V-H) antenna polarizations were evaluated using NLOS measurements. It is clear that, compared to the 28 GHz frequency band, the reflection from the corridor's walls--made of dry concrete and bricks--is more difficult when the values of the PLE in both the V-V and V-H are maximum at 38 GHz. Plots for the measured values, CI, FI, and FSPL models for the V-V and V-H in the 38 GHz and 28 GHz frequency bands are shown in Figures 16 and 17, respectively. The PLEs of the 28 GHz in V-V and V-H antenna polarizations differ, with the PLE for the V-H polarization increasing by about 0.445. The standard deviation of 0.78 decibels was approximately the same for both polarizations. The PLE in the 38 GHz situation was 2.8207 in the V-V polarization, increased by 0.6475 in the V-H polarization, and a notable increase was observed in the value of the standard deviation, which rose from 1.6283 to 2.9396 dB. The changes in the PLE and standard deviation were caused by changes in the antenna polarization due to different wave guiding effects, diffraction, and reflections at the two antenna polarizations, culminating in constructive interference of the multiple signal components that reached the receiver in both cases. \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{3}{c}{28 GHz LOS communication scenario} \\ \hline  & V–V polarization & V–H polarization \\ PLE (\(n\)) & 2.2254 & 2.9790 \\ \(\sigma_{min}^{CI}\) [dB] & 1.7718 & 1.3425 \\ \(\alpha_{FI}\) [dB] & 58.8294 & 59.9354 \\ \(\beta_{FI}\) & 2.1537 & 3.0540 \\ \(\sigma_{min}^{FI}\) [dB] & 1.7431 & 1.3008 \\  & 38 GHz LOS communication scenario & \\  & V–V polarization & V–H polarization \\ PLE (\(n\)) & 2.7801 & 3.1978 \\ \(\sigma_{min}^{CI}\) [dB] & 3.1874 & 4.1001 \\ \(\alpha_{FI}\) [dB] & 60.5444 & 62.1883 \\ \(\beta_{FI}\) & 3.1461 & 3.6625 \\ \(\sigma_{min}^{FI}\) [dB] & 2.7439 & 3.5455 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The LOS comparative study results at 28 and 38 GHz frequencies. Figure 16: Path loss versus distance at 28 GHz for the NLOS scenario and V–V polarization. When considering the 38 GHz frequency, the higher value of PLE and standard deviation indicated that there was a low wavelength and a higher path loss at a higher frequency. Figures 18 and 19 display the plots for both V-V and V-H antenna polarizations. The floating intercept values (\(\beta\)) at 28 GHz were 1.0558 and 0.9722, which were approximately the same in V-V and V-H. However, at 38 GHz, the floating intercept value rose to 2.7254 in V-V polarization and 3.3064 in V-H polarization. Figure 17: Path loss versus distance at 28 GHz for the NLOS scenario and V–H polarization. Figure 18: Path loss versus distance at 38 GHz for the NLOS scenario and V–V polarization. Furthermore, the values of \(\sigma_{min}^{CI}\) in the 28 GHz frequency band had a sharp increase in both polarizations when compared to the value in the LOS scenario. The value was 8.1287 for (V-V) and 10.4790 for (V-H), while the 38 GHz values increased slightly from 1.6822 (V-V) to 3.0257 (V-H). This indicates that the signal performance in the NLOS was better in the 38 GHz frequency band when compared to the 28 GHz in both polarizations (although the contrast occurred for the LOS situations). The rate of increase in penetration losses at 28 GHz was higher in the NLOS than 38 GHz (a similar behavior occurred in the experimental analysis by [69,77]). This behavior is seen in the plotting of the path losses shown in Figures 16 and 17 for 28 GHz, and in Figures 18 and 19 for 38 GHz. The behaviors of the curves (of CI path losses for 28 and 38 GHz in the NLOS for V-V antenna polarization) in Figure 20 were strikingly similar. This demonstrates that the path loss follows nearly the same patterns at both frequencies, albeit with a higher value at 38 GHz.