# Feature Importances: A Tool to Explain Radio Propagation and Reduce Model Complexity
## 3 Problem Description and Model Used
### Features and the Associated Propagation Mechanisms
\begin{table}
\begin{tabular}{c c l} \hline \hline
**Number** & **Name** & **Description** \\ \hline
**1** & _LOS\_1a_ & The distance (h\({}_{1}\)) of the top of the tallest building of the first segment, from the point at which the building intersects the LOS ray, between Tr and R \\ \hline
**2** & _LOS\_1b_ & The distance d\({}_{1}\) of the tallest building of the first segment from the transmitter \\ \hline
**3** & _LOS\_1c_ & The length, l\({}_{1}\), of the tallest building of the first segment \\ \hline
**4** & _LOS\_2a_ & The distance (h\({}_{2}\)) of the top of the tallest building of the second segment, from the point at which the building intersects the LOS ray, between Tr and R \\ \hline
**5** & _LOS\_2b_ & The distance d\({}_{2}\) of the tallest building of the second segment from the transmitter \\ \hline
**6** & _LOS\_2c_ & The length, l\({}_{2}\), of the tallest building of the second segment \\ \hline
**7** & _LOS\_3a_ & The distance (h\({}_{3}\)) of the top of the tallest building of the third segment, from the point at which the building intersects the LOS ray, between Tr and R \\ \hline
**8** & _LOS\_3b_ & The distance d\({}_{3}\) of the tallest building of the first segment from the transmitter \\ \hline
**9** & _LOS\_3c_ & The length, l\({}_{3}\), of the tallest building of the third segment \\ \hline
**10** & _Buildings:_ & The total number of the buildings which interrupt the LOS path. \\ \hline
**11** & _SSL\_1_ & The height of the building (or the existence of a street) 10m right from the receiver \\ \hline
**12** & _SSL\_2_ & The height of the building (or the existence of a street) 10 m left from the receiver \\ \hline
**13** & _SSL\_3_ & The height of the building (or the existence of a street) 10 m above the receiver \\ \hline
**14** & _SSL\_4_ & The height of the building (or the existence of a street) 10 m below the receiver \\ \hline
**15** & _SSL\_5_ & The height of the building (or the existence of a street) 10 m left and above the receiver \\ \hline
**16** & _SSL\_6_ & The height of the building (or the existence of a street) 10 m left and below the receiver \\ \hline
**17** & _SSL\_7_ & The height of the building (or the existence of a street) 10 m right and above the receiver \\ \hline
**18** & _SSL\_8_ & The height of the building (or the existence of a street) 10 m right and below the receiver \\ \hline
**19** & _Tr\_x_ & X\_coordinate of the transmitter \\ \hline
**20** & _Tr\_y_ & Y\_coordinate of the transmitter \\ \hline
**21** & _R\_x_ & X\_coordinate of the receiver \\ \hline
**22** & _R\_y_ & Y\_coordinate of the receiver \\ \hline
**23** & _Distance_ & The distance between transmitter and receiver in the xy plane \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The 23 features used. Figure 3: Features 19 to 23 refer only to the positions of the transmitter and the receiver, and the distance between them. They do not depend on the built-up profile of the area in question. Table 1 summarizes and describes all features. It is apparent that information regarding the map of the area is needed to calculate the values corresponding to each feature. This could either be obtained through specific databases, or through a combination of OpenStreetMap [19] (which provides the footprints of the buildings) and the open source software QGIS (which provides the heights of the buildings).