# Mechanism to Estimate Effective Spectrum Availability Inside Smart Buildings
## 6 Conclusions  
In this paper, the use of a mechanism to determine the ESA inside an SB was shown. This ESA mechanism allows the feasibility of providing proprietary or public services using SR-CRWS inside an SB to be determined in a fast and accurate way, considering that the results were estimated within a CI with a probability of 0.95.  
The results obtained indicate that, due to the configuration of the deployment of the PU, no SB reaches 100% ESA efficiency and that the last two floors of the buildings cannot be used for the operation of an CR-based SS. However, those last two floors could be dedicated to the SB control rooms.  
Although the mechanism for obtaining the ESA found results for a specific TV channel, it can be said that the spatial availability would be approximately the same for all TV channels if the transmission was made from a single tower, as is the case in several large cities. If not, the results will vary depending on the locations of the BSs.  
Within the ESA zone, two or more SR-CRWS could use the same spectrum availability because the SSs support interference up to a given SNR, that is, they self-regulate the use of spectrum availability. However, to differentiate their transmission from the BS transmission, they must use a differentiating element, such as a beacon that identifies all SSs.  
As time passes, the spectrum shortage would also threaten the current spectrum bands authorized for the new systems. For this reason, encouragement of the spatial availability of the spectrum is needed if the operation conditions are met. Building interiors are suitable places for reusing unused  
Figure 14: ESA gain for each \(p\)-story SB, starting from \(d=0.5\) km.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \(d\psi\) & **40** & **50** & **60** & **70** & **80** & **90** & **100** \\ \hline
**0.5** & 1.00 & 1.23 & 1.42 & 1.57 & 1.70 & 1.79 & 1.86 \\
**1** & 1.16 & 1.41 & 1.65 & 1.84 & 2.01 & 2.14 & 2.24 \\
**2** & 1.31 & 1.61 & 1.92 & 2.17 & 2.38 & 2.54 & 2.67 \\
**4** & 1.49 & 1.85 & 2.20 & 2.51 & 2.76 & 2.97 & 3.14 \\
**8** & 1.68 & 2.08 & 2.46 & 2.84 & 3.16 & 3.43 & 3.64 \\
**16** & 1.84 & 2.28 & 2.72 & 3.15 & 3.55 & 3.86 & 4.12 \\
**32** & 1.97 & 2.46 & 2.94 & 3.42 & 3.87 & 4.25 & 4.58 \\ \hline \hline \end{tabular}
\end{table}
Table 3: ESA gain mapping.  
frequencies, both spatially and temporally. For this reason, SBs could be designed to obtain the desired ESA, which can be achieved by varying the heights and distances from the BS.  
This proposed mechanism specifically determines the spectrum spatial availability, so future work in this area should aim to predict the temporary availability of the spectrum inside buildings based on the measurement campaigns and the use of Deep Learning models.  
Conceptualization, W.M. and F.N.; methodology, W.M.; software, W.M. and E.C.; validation, W.M. and E.C.; formal Analysis, W.M. and F.N.; investigation, W.M. and J.R.; data curation, W.M. and E.C.; writing--original draft preparation, W.M.; writing--review and editing, J.R. and F.N.; visualization, W.M.; supervision, F.N. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.