# LoS Theoretical and Experimental MIMO Study from 1-40 GHz in Indoor Environments
## 5 Comparison with Ray-Tracing Simulations
### Propagation Mechanisms Analysis  
In addition, the ray-tracing tool allows a comprehensive analysis of the significance of the included propagation mechanisms. For instance, the percentage of the simulated power of each one of the propagation mechanisms can be finely assessed as depicted in Figure 13. The antenna gain of transmitter and receiver of each path was not included to show only the channel effects.  
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Position** & **Simulated (ns)** & **Measured (ns)** & **Acc. (\%)** \\ \hline
1 & 16.20 & 17.32 & 93.51 \\
2 & 17.06 & 17.32 & 98.46 \\
3 & 18.44 & 18.57 & 99.30 \\
4 & 14.46 & 16.35 & 88.44 \\
5 & 13.36 & 14.94 & 89.49 \\
6 & 12.35 & 13.07 & 94.47 \\
7 & 8.14 & 8.36 & 97.34 \\
8 & 9.76 & 9.94 & 98.15 \\
9 & 11.45 & 10.95 & 95.43 \\
10 & 8.05 & 9.19 & 87.60 \\
11 & 5.59 & 6.17 & 90.60 \\
12 & 3.67 & 3.87 & 94.65 \\
13 & 7.92 & 8.52 & 92.92 \\
14 & 5.29 & 5.52 & 95.75 \\ - & - & Mean & 94.00 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Comparison between the measured and simulated mean delay between 1 GHz and 40 GHz.  
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**Position** & **Simulated (ns)** & **Measured (ns)** & **Diff. (dB)** \\ \hline
1 & 63.45 & 63.68 & 0.23 \\
2 & 63.77 & 63.43 & 0.34 \\
3 & 63.76 & 63.87 & 0.11 \\
4 & 62.69 & 61.68 & 1.01 \\
5 & 62.40 & 61.79 & 0.61 \\
6 & 62.15 & 60.79 & 1.36 \\
7 & 60.60 & 57.79 & 2.81 \\
8 & 60.71 & 59.01 & 1.70 \\
9 & 62.12 & 60.42 & 1.70 \\
10 & 60.29 & 59.66 & 0.63 \\
11 & 57.86 & 56.44 & 1.42 \\
12 & 55.12 & 53.45 & 1.67 \\
13 & 60.29 & 59.50 & 0.79 \\
14 & 57.42 & 55.95 Of course, the main propagation mechanism is the direct ray since all positions correspond to LoS situations. Apart from the direct ray, the main propagation mechanism is the reflection, although the diffraction represents an important percentage of the total power. The diffuse scattering power is smaller than the reflected and diffracted power, but it is still significant and increases with distance. The weaker mechanisms are those composed of a combination of a single reflection and a single diffraction.  
The percentage of power of each propagation mechanism was also extracted for the WRC'15/19 as shown in Figures 14-16 for the 3.3-4.99 GHz, 24.25-27.5 GHz, and 37-40 GHz bands, respectively. The results clearly demonstrate that the contribution of the LoS decreases with distance, whereas that of reflection and diffraction increases. This trend is clearly shown in all central frequencies. Furthermore, it can be observed that diffuse scattering is much less frequency dependent and should not be omitted when simulating low-mmW radio channels as reported in an earlier work at 60 GHz [32]. These results show that the radio channel becomes more simplistic at higher frequencies enabling the use of efficient simulation approaches such as ray-tracing.  
Figure 14: Percentage of power of different propagation mechanisms for all positions when the frequency is 4.145 GHz, central frequency of the band 3.3–4.99 GHz.  
Figure 13: Percentage of power of different propagation mechanisms for all positions when the frequency is 20.5 GHz.