# BLE RSS Measurements Dataset for Research on Accurate Indoor Positioning
## 4 Usage Examples
### Environment and Device: Signal Intensities and Advertisements Loss  
The environment influence relates not only to the presence or absence of line-of-sight between beacons and a smartphone. As presented in Figure 5, the drop in signal strength as the distance to a beacon increases is more significant in the Library zone than in Geotec as a result of a dense bookshelf placement. In the Geotec zone there are only four tall shelves and the height of other furniture pieces is below the altitude at which a person usually holds a smartphone, thus, the shelves do not significantly influence the reported beacon RSS. Figure 4: Example of membership information extracted from an identifier. The fingerprint tagged by this identifier is the 2 nd fingerprint captured for the 105 th point of campaign number 3 (Library zone). The smartphone used is the \(\mathrm{BQ}\) and beacons were advertising at a power level of \(-12\) dBm. Table 2 shows how, apart from the transmission power, the range (or detectability) of the beacons depends on the measurement smartphone and the deployment environment. The first row indicates the maximum detected value for a beacon at any collection point. For the Library zone, the signals strengths reported by the S6 smartphone were weaker than those reported by the A5 smartphone. The A5 smartphone was able to detect stronger signals in the Library than in Geotec. Despite the non-existence of line-of-sight situations in the Library, the minimum distance (3D) between collection points and beacons is smaller than in Geotec. The second row (MDP70) displays the maximum distance at which a beacon was spotted with a signal strength over \(-70\) dBm. The distances are consistent with the maximum reported RSS. The third row (MDHT) presents the maximum distance at which a beacon was consistently detected (in more than half of fingerprints) at a collection point. The S6 smartphone was notably better at detecting beacon advertisements, despite it registered weaker values of RSS. BLE beacons can be usually configured to send advertisements at given time intervals. It is however known that the times between two consecutive detections, as reported by a smartphone, are usually higher than the interval setting configured in the beacons [11; 20]. It is not only that advertisements are lost if the receptor is beyond the beacon range, or that some (tiny) extra processing time is added, but that some smartphones are unable to properly detect all advertisements. Figure 6a shows the detection delays as registered by the smartphone A5 for beacon 1 in the Library zone. All beacons were configured to advertise every 200 ms, but the number of two consecutive advertisements detected with a time difference of about 200 ms is very low. Figure 6b shows that the smartphone A5 has a low detection capability when compared to the BQ and S6 smartphones. It is also known that for the 2.4 GHz networks, closer distances to an emitter correlate to higher variance in reported RSS. It has also been stated that closer distances to a beacon correlate to a lower detection delays [41]. Table 3 shows the results of exploring the presence of the latter correlation for the A5 smartphone. The correlation was individually tested for each beacon, and Table 3 only presents the \(\rho\) and \(p\)-value for the beacon with the most interesting values. The results are not conclusive, but they hint that the distance to a beacon is not a relevant factor for advertisement detection delays. Also, given that consecutive measurements in a point have the same collection direction, orientation is likely to have only a small influence on detection delays for our settings and analyses. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Library (S6)** & **Library (A5)** & **Geotec (A5)** \\ \hline Max detected RSS (dBm) & \(-52\) & \(-33\) & \(-44\) \\ MDP70 (m) & \(0.47\) & \(3.92\) & \(2.75\) \\ MDHT (m) & \(4.50\) & \(1.47\) & \(1.16\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Beacons detection range.