# Vegetation Loss Measurements for Single Alley Trees in Millimeter-Wave Bands
## 5 Discussion  
### Measurement Campaign Results Analysis  
Combining the theory presented in Section 2 with the results of the measurement campaign, one can observe a few facts.  
The geometry of the tree, including its density and distance between it and the next trees, has a significant impact on signal attenuation. The scattering of the coherent component is the dominant contributor (Table 3) when dealing with this type of vegetation area. A possible explanation for these large \((\sigma_{a}+\sigma_{s})\) values can be derived from the fact that in a foliage environment, all scattering obstacles are large compared to the millimeter wavelength. Behind large obstructions such as dense corona, deep shadows exist, and since the campaign was carried out over a path through maximum vegetation density, it is very likely that the RX antenna was placed in the shadow zones. Therefore, the measured data may indicate a higher value for \((\sigma_{a}+\sigma_{s})\) than one would obtain on average (measured in all spatial directions and by averaging the power received on these paths).  
It was observed that younger London plane trees could be a more serious obstacle when it comes to radio propagation attenuation. Additionally, it is important to mention that for a young London plane tree, the most characteristic element is that the value of the density of leaves is very high. This means that the tree canopy is clumped, creating highly scattered layers.  
It should be understood that the comparison of theory and experiments involves a certain amount of conjecture since the measured curves, as opposed to the smooth theoretical ones, show significant fluctuations. The RTE model has a priori assumptions and simplifications and is not fully identical to the experimental setup. It should be emphasized that the theoretical model applies to a forest half-space illuminated by a plane wave, whilst the incident beam has a finite cross section and trees have finite height. This  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline
**RTE Fitted Parameters** & \(\alpha\) & \(\gamma s\) & \(W\) & \((\sigma_{a}+\sigma_{s})\) \\ \hline
26 GHz measurement & 0.8366 & 359.9737 & 0.9634 & 1.4743 \\ \hline
28 GHz measurement & 0.8827 & 357.6472 & 0.9585 & 2.4831 \\ \hline
30 GHz measurement & 0.9509 & 356.9840 & 0.8401 & 2.0325 \\ \hline
32 GHz measurement & 0.8462 & 359.7209 & 0.9392 & 1.9761 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Tuning performed on the RTE solution using the data gathered during Scenario 1.  
Figure 22: All measurements and tuned models for Scenario 2.  
implies that losses due to radiation into the ground and air regions are not accounted for in the RTE model.  
In order to visualize these relationships, the comparison of the RTE theoretical values and measurements is presented in Figures 23 and 24.  
Further study is required in that field to seek novel methods that can simplify the mathematical description of phenomena or maintain the same level of complexity but may allow one to describe the huge number of different scenarios based on the theoretical model approach. This would be useful from the perspective of high-band RF planning for cellular networks.