# Mechanism to Estimate Effective Spectrum Availability Inside Smart Buildings
## 4 Interference Model Validation
### C1 Interference Condition Model Validation  
Then, we proceeded to validate the propagation models used to determine the interference condition C1. The power levels obtained from both scenarios--a shortbuilding and a tall building--were used separately for C1 validation by comparing these results with the power levels that would be obtained using each of the three propagation models. The three outdoor propagation models proposed were used to evaluate the \(L_{outside}\) values, as explained in Section 3.  
In the case of the small building, the comparisons of the measured and simulated power values are shown in Figures 6 and 7, where the values of the interference \(I_{BS-SS}\) can be appreciated. In those figures, the FRIS model is represented by the blue line; the COST-WI model, by the cyan line; and the EGLI model, by the red line, and the black line represents the measured power levels.  
As expected, Figures 6 and 7 show that the front apartments received higher levels of interference than the apartments located in the middle of the building or at the back of it. Additionally, the interference levels increased with height, which is predictable since as the height of the measurement point increased, the receiver device further approached the broadcast site, according to the scenario proposed.  
Figure 5: (**a**) Locations of and separation distance between the Torres de la Merced building (point A) and the 25 UHF TV base station (BS) (point B); (**b**) Partial view of Torres de la Merced building.  
Figure 6: Simulated and measured interference levels received in the apartments located in the front of the small building that presents a line of sight (LOS) with the transmission system.  
Additionally, it was observed that the EGLI propagation model best approximated the interference levels measured. On the contrary, the WI and FRIIS models presented significant variation in the interference level on the lower floors of the building, because they did not consider heights for their determination. However, the three propagation models tended to exhibit similar behavior when the height of the floors approached the height of the SB antenna.  
Moreover, the interference levels from the measurement campaign were lower than those simulated. This was due to the characteristics of the proposed scenario, because the simulation did not account for all of the real stationary obstacles, such as furniture, or those in motion, such as people inside the building.  
For the tall building, the power values measured inside the building and the values simulated by the three propagation models under study are compared in Figure 8.  
Figure 8: Simulated and measured power levels received in the long building.  
Figure 7: Simulated and measured interference levels received in the apartments located in the middle sector of the small building.  
In Figure 8, the power values found by simulation varied sharply on the 16 th floor, because the obstruction of the attached building was considered. The behavior simulated using the FRIIS and COST-WI models showed quasi-constant values in the two sections of the building, while the EGLI model showed increasing behavior. It can be verified that, as in the small building, the behavior of the EGLI model was more adequate than that of the other models in the sector containing the lower floors.  
To establish the best-simulated behavior, an analysis of the correlation coefficients of the measurements was performed for each of the models under study. Table 1 shows the values of the correlation coefficients, where it can be seen that all of the simulated propagation models correlate quite well with the measurements made.  
Table 1 shows that the propagation model with the highest correlation coefficient is the EGLI. For this reason, and in line with the proposed objectives, for the remainder of this study, only the EGLI model was considered for the \(L_{outside}\) component in the implementation of C1.