# 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 maximum upper value of PLE (3.47) in this investigation, however, was recorded at 38 GHz for V-H polarization. Practically all of the PLE values for the LOS in this study had FSPL exponents higher than 2. This demonstrated that there were few hints of depolarization at 28 GHz for V-V, 28 GHz for V-H, 38 GHz V-V, and 38 GHz V-H. In the FI model, the frequency-dependent \(\alpha^{\rm FI}\) model had a value of 58.83 dB (V-V) that varied slightly with the free space path loss (FSPL) at 1 m for 28 GHz, which was 61.4 dB. In the V-H, however, the value was 59.94. At 1 m, the FSPL at 38 GHz was 64 dB. However, the V-V value obtained in this study was 60.54 and the V-H value was 62.19. The lowest range in the literature [46] was at a frequency of 6.5 GHz (in an indoor corridor environment, with a value of 40.7) and the highest was at 73 GHz, with a value of 101.1, as recorded in [39]. At 4.5 GHz for V-V polarization, the slope value \(\beta^{\rm FI}\) had the lowest value of 2.16; however, the lowest value of our experiment was 2.16 for 28 GHz V-V polarization. The value of \(\sigma^{\rm CI}\) and \(\sigma^{\rm FI\,min}\) in both the lower and higher ranges was also consistent with the mean values in all of the literature studies taken into consideration. The highest value of \(\beta^{\rm FI}\) was recorded at [77] for a frequency of 28 GHz. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & \multicolumn{3}{c}{LOS} \\ \hline Frequency & Polarization & CI & & \multicolumn{3}{c}{FI} \\ (GHz) & Polarization & _PLE (m)_ & \(\sigma^{\rm CI}\) [dB] & \(\alpha^{\rm FI}\) [dB] & \(\beta^{\rm FI}\) & \(\sigma^{\rm FI\,min}\) [dB] \\ \hline
28 & V–V & 2.2254 & 1.7718 & 58.8294 & 2.1537 & 1.7431 \\  & V–H & 2.9790 & 1.3425 & 59.9354 & 3.0540 & 1.3008 \\
38 & V–V & 2.7801 & 3.1874 & 60.5444 & 3.1461 & 2.7439 \\  & V–H & 3.1978 & 4.1001 & 62.1883 & 3.6625 & 3.5455 \\  & & NLOS & & & \\
28 & V–V & 2.8815 & 8.1287 & 81.8470 & 1.0558 & 0.7872 \\  & V–H & 3.3303 & 10.4790 & 87.8146 & 0.9722 & 0.7796 \\
38 & V–V & 2.8207 & 1.6822 & 65.1057 & 2.7254 & 1.6283 \\  & V–H & 3.4682 & 3.0257 & 65.8500 & 3.3064 & 2.9396 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Single-frequency CI and FI path loss model parameters for all measured frequencies in the indoor channels. \begin{table}
\begin{tabular}{c c c} \hline \hline  & V–V polarization & V–H polarization \\ PLE (\(n\)) & 2.8815 & 3.3303 \\ \(\sigma^{CI}_{min}\) [dB] & 8.1287 & 10.4790 \\ \(\alpha_{FI}\) [dB] & 81.8470 & 87.8146 \\ \(\beta_{FI}\) & 1.0558 & 0.9722 \\ \(\sigma^{\rm FI}_{min}\) [dB] & 0.7872 & 0.7796 \\  & \(38\) GHz NLOS communication scenario & \\  & V–V polarization & V–H polarization \\ PLE (\(n\)) & 2.8207 & 3.4682 \\ \(\sigma^{CI}_{min}\) [dB] & 1.6822 & 3.0257 \\ \(\alpha_{FI}\) [dB] & 65.1057 & 65.8500 \\ \(\beta_{FI}\) & 2.7254 & 3.3064 \\ \(\sigma^{F}_{min}\) [dB] & 1.6283 & 2.9396 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The NLOS comparative study results in 28 and 38 GHz frequencies. \begin{table}
\begin{tabular}{l c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Ref. **} & **Dist. (m.)** & **Fee. Range** & **Fee. ** & **Range** & **Dimers. (m)** & **Materials Make** & **Sec. ** & _PLE (o)_ & \(\alpha^{\rm{T}}\)**[dB]** & \(\alpha^{\rm{T}}\)**[dB]** & \(\beta^{\rm{T}}\)** & \(\alpha^{\rm{T}}\)**[dB]** \\  & & **(KGL)** & **Pol. ** & **Ew. ** & **Dimers. (m)** & **Materials Make** & **Sec. ** & _PLE (o)_ & \(\alpha^{\rm{T}}\)**[dB]** & \(\alpha^{\rm{T}}\)**[dB]** & \(\beta^{\rm{T}}\)** & \(\alpha^{\rm{T}}\)**[dB]** \\ \hline
[9] & 4.1-21.3 & 28-73.5 & V-V & Indoor office & \(39.3\times 27\times 65.9\) & \  
The lowest range of the PLE value, which was 1.97 at 4.5 GHz frequency V-V [51], was lower in the NLOS scenario than our 2.384 estimate. Our PLE's greatest value, 3.47, was less than the number in the highest range, 73 GHz [39]. These findings demonstrate that our study remains consistent with previous studies in the literature. The rise in signal degradation, particularly with a higher frequency, is a clear NLOS indicator.