# Investigations on Millimeter-Wave Indoor Channel Simulations for 5G Networks
## 4 Results and Discussion
Table 7 presents the mean RMS delay spread (DS) over the investigated frequencies; mean RMS-DS is inversely proportional/decreases as frequency increases; this is because, as frequency increases, the signal power drops rapidly, especially for NLOS scenarios, due to higher path loss and high dispersion and penetration losses. Therefore, signals travel shorter distances and fall below receiver sensitivity. The directional antenna focuses the radiation in specific directions, which reduces the effect of multipath and, therefore, the traveling time will be shorter. In LOS scenarios, using a directional and omnidirectional antenna will have bigger RMS-DS results since the directional antenna provides signals that travel further distances and the omnidirectional antenna can collect rays from the surroundings. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**28 GHz**} & \multicolumn{2}{c}{**39 GHz**} & \multicolumn{2}{c}{**60 GHz**} & \multicolumn{1}{c}{**73 GHz**} \\ \hline \multirow{5}{*}{NLOS} & Our paper & 4.36 & 4.88 & 4.51 & 4.71 \\ \cline{2-5}  & [22] & 4.4 & - & - & 5.3 \\ \cline{2-5}  & [23] & 2.8 & - & - & - \\ \cline{2-5}  & [24] & 2.2 & - & 5.7 & - \\ \cline{2-5}  & [39] & 3.3 & - & - & - \\ \hline \multirow{5}{*}{LOS} & Our paper & 1.48 & 1.5 & 1.54 & 1.6 \\ \cline{2-5}  & [22] & 1.7 & - & - & 1.6 \\ \cline{2-5}  & [23] & 1.9 & - & - & - \\ \cline{2-5}  & [24] & 1.5 & - & & - \\ \cline{2-5}  & [25] & 1.8 & - & - & - \\ \cline{2-5}  & [26] & - & 1.2 & - & - \\ \cline{2-5}  & [27] & - & - & 1.2 & - \\ \cline{2-5}  & [40] & 1.6 & - & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 6: PLE comparison with the published literature. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Freq. (GHz)**} & \multicolumn{2}{c}{**Dir-Dir**} & \multicolumn{2}{c}{**Omni-Omni**} & \multicolumn{2}{c}{**Dir-Omni**} \\ \cline{2-7}  & **NLOS** & **LOS** & **NLOS** & **LOS** & **NLOS** & **LOS** \\ \hline
28 & 2.57 & 2.24 & 6.76 & 10.66 & 5.38 & 11.66 \\ \hline
39 & 2.21 & 1.46 & 4.11 & 8.37 & 3.31 & 9.31 \\ \hline
60 & 1.95 & 1.65 & 3.27 & 4.46 & 2.57 & 4.94 \\ \hline
73 & 2.25 & 2.87 & 3.64 & 9.36 & 2.38 & 9.98 Figure 5 presents the probability plot of RMS-DS for NLOS scenarios using different antenna configurations, as seen in the fact that RMS-DS decreases at higher frequencies, as observed in [27]. The difference between recorded values using a directional and omnidirectional antenna is observable. For example, at 28 GHz, the probability for DS to be less or equal to 5 ns is 0.9 (using directional channels (Dir-Dir)) and 0.4 (using omnidirectional channels (Omni-Omni)); similarly, the probability is 0.95 (Dir-Dir) and 0.6 (Omni-Omni) at 39 GHz, 0.85 (using Dir-Dir) and 0.75 (using Omni-Omni) at 60 GHz, and 0.85 (using Dir-Dir) and 0.65 (using Omni-Omni) at 73 GHz. Omnidirectional channels have more propagation paths and, hence, longer DS. This difference is visible in LOS scenarios, as seen in Figure 6. Figure 6 displays the probability of the omnidirectional and directional RMS-DS for LOS scenarios; as seen, using directional antennae at both ends, the RMS-DS is less than 5 ns for almost 90% of the cases, while, for omnidirectional channels, the percentages were less than 30% for most of the examined frequencies. Figures 7 and 8 present the number of clusters and the number of rays/cluster for NLOS scenarios, respectively, using omnidirectional, directional, and directional-omidirectional radiation patterns. The number of ray clusters follows the Poisson distribution; while the number of clusters follows a decaying exponential distribution. For omnidirectional channels, the majority of rays come in three clusters or less, while, for directional channels, the majority of rays come in five clusters or less. When using directional-omidirectional antenna patterns, rays come in four clusters or fewer, which is more than the case of the omnidirectional channels and less than the case of the directional channels.