# Mechanism to Estimate Effective Spectrum Availability Inside Smart Buildings
## 5 ESA Model Performance  
Once the propagation models with the measurement campaigns inside the buildings had been validated, both the EGLI model for the outdoor path in the C1 interference model and the MWM model in the C2 interference model were set up under the conditions outlined in Section 3 to implement the mechanism for obtaining the ESA. In this section, the analysis of the ESA mechanism's performance is performed using the parameters shown in Table 2. The first analysis of the results refers to the ESA per floor (ESAF), and then an analysis was performed for the entire SB to obtain the ESA. The ESAF behavior for two SBs is shown in Figure 11. The results indicate high levels of ESAF on the lower floors of both SBs, and these values decreased slowly as the height of the building increased. On the two last floors, the ESAF dropped sharply to zero, as can be seen in Figure 11. In other words, this figure indicates that SR_CRWS devices cannot be used on the two last floors of the SB because they are located very close to the rooftop and could interfere with the PUs represented by the building's receiving system mounted on the rooftop. The high amount of ESAF on the lower floors was because C1 was fulfilled in most of the apartments, and it decreased in the upper floors because the power levels were higher there. On the other hand, on the last floors of the SB, C2 prevailed over C1, so the availability dropped to zero on the top floor of each building. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Definition** & **Qty/Unit** \\ \hline \(H_{BS}\) & tower height & 400 m \\ \(H_{B}\) & building height & 400 m \\ \(Hp\) & floor height & 4 m \\ \(d_{D}\) & apartment width & 4 m \\ \(d_{SB}\) & building width & 80 m \\ \(p\) & number of floors & 20–100 floors \\ \(N\) & apartments/floor & 400 \\ \(P_{BS}\) & primary system (PS) power & 32 dB \\ \(P_{TH}\) & threshold power & \(-76\) dB \\ \(f\) & frequency & 639 MHz \\ \(d\) & SB to BS distance & 0.5–32 Km \\ \(P_{SS}\) & secondary system (SS) power & 20 dBm \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation parameters. Figure 10: Comparison of power of simulated interference levels using Multi-Wall Model (MWM) and power measurements made on the rooftop of the small building, including the bounds of CI = 95%. For the case of an SB with 40 floors, which is shown in Figure 11, the ESAF dropped abruptly across the last four floors, from 55% of apartments available on the 36 th floor to no apartments available on the 39 th floor. In the case of the 20-story SB, the ESAF began to decrease from the 17 th floor, falling rapidly to be null on the 19 th floor. The behavior of the ESAF for a 100-story building is shown in Figure 12. The effects of the contribution of the reflected rays in the five-ray model can be appreciated when simulating an SB that has more than 50 floors. As expected, the ESAF was high on the lower floors and began to decrease slowly in the upper floors, but after the 50 th floor, the ESAF decreased rapidly until reaching zero on the 99 th floor. Figure 11: Effective Spectrum Availability per floor (ESAF) behavior for a 20-story SB and for a 40-story SB. \(d=1\) Km. Figure 12: ESAF behavior for a 100-story SB, \(d=1\) Km. The rapid decrease in the ESAF occurred because the contribution of the reflected ray began to become significant, and this was because the highest floors of all the SBs were closer to the BS of the primary system. In other words, the power contribution of the rays reflected in the neighboring buildings was high enough to reduce the ESAF. The analysis below focuses on the ESA results for various SBs, whose behavior was related to the SB height and distance to BS.