# BLE RSS Measurements Dataset for Research on Accurate Indoor Positioning
## 4 Usage Examples
### Beacon Deployment, Estimations Positions and Robustness  
For Wi-Fi-based positioning, is it acknowledged that a high Wi-Fi routers density in the target area benefits the positioning accuracy. A large beacon density is also positive for BLE-based positioning [47]. Despite their cost is lower and their deployment is easier than for Wi-Fi routers, largely increasing the number of beacons for a deployment is usually not practical. The choice of the amount of beacons and their placement depends on factors like deployment restrictions in the target area, the beacon range, the positioning method, and environment obstacles. Beacon deployment choice has been addressed in literature [11; 48; 49], showing the complexity of the problem and only a few placement guidelines. The beacon deployments used in the provided database are dense in the two zones, so that subsets of the deployed beacons can be considered alternative deployments. The scripts shipped with the data allow the selection of several alternative deployments that we considered interesting. Figure 8 shows the location estimations and their accuracy using the WC and FP methods for three distinct beacon deployments. The first deployment (Figure 8a) considers all beacons deployed in the Library zone. The positioning methods used a window of size 2 for buffering (for improved results), and the estimations were performed only for test points. Notice that the value for \(k\) parameter of the FP method is lower than the one used in previous experiments, despite that the new \(k\) value provides a worse accuracy metric value. The new \(k\) value was chosen to avoid a further concentration of the estimates in the center of the zone. The second deployment (Figure 8b) reduces the number of beacons to nine, and the accuracy drops in \(\approx\)1 m in the two methods. Notice that the FP estimated positions remain concentrated in the center area. The WC estimated positions, however, change and there are wide areas near the borders and away from beacons where the WC method is unable to place estimations. The third deployment (Figure 8c) also has only nine beacons, but no beacon was placed in the left and right sides of the area. The WC method is further unable to make proper position estimations for samples in areas near the sides. The absence of beacons near the boundary of the target area does not affect the FP method in this experiments. The FP accuracy is improved in the third deployment, because this new layout decrease mean distance of beacons to collection points and thus, the number of beacons detected in training and test fingerprints is higher. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Mean**} & \multicolumn{4}{c}{**Last**} \\ \hline  & \multicolumn{2}{c}{**Library**} & \multicolumn{2}{c}{**Geotec**} & \multicolumn{2}{c}{**Library**} & \multicolumn{2}{c}{**Geotec**} \\ \hline Windows size & FP & WC & FP & WC & FP & WC & FP & WC \\ none & 4.46 & 3.46 & 4.16 & 3.44 & 4.46 & 3.46 & 4.16 & 3.44 \\
2 & 3.77 & 2.58 & 3.91 & 2.69 & 3.85 & 2.56 & 3.93 & 2.69 \\
3 & 3.43 & 2.32 & 3.49 & 2.59 & 3.41 & 2.35 & 3.52 & 2.49 \\
4 & 2.95 & 2.29 & 3.38 & 2.61 & 3.03 & 2.31 & 3.47 & 2.45 \\
5 & 2.83 & 2.28 & 3.34 & 2.48 & 2.87 & 2.30 & 3.55 & 2.37 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Buffering results using data for the A5 phone and power \(-\)12 dBm. For realistic comparisons, position estimation were only computed for test sets in WC. The BLE beacons are battery-powered devices and thus, unless active monitoring and fast replacements are done, the situation where two or more beacons are not broadcasting at a given time is likely to happen when the power in their batteries is close to the time of exhaustion. The Figure 9 presents the robustness of WC and FP methods to situations where one to six beacons stop broadcasting. The WC method has better accuracies than the FP method, as we had previously seen, but it is also more affected by beacon disconnections.