# BLE RSS Measurements Dataset for Research on Accurate Indoor Positioning
## 3 The BLE RSS Database  
The provided database is openly available at [PERSON] et al. (2018). It contains a dataset for the Library zone (\(D_{l}\)) and another dataset for the Geotec zone (\(D_{g}\)). Each dataset is composed of four sets: RSS values, positions, times and identifiers sets. A set of RSS values is defined as:  
\[R_{(p\cdot s)\times a}=\left\{r_{i,j}\right\}, \tag{1}\]  
where \(p\) is the number of points (unique triplets of the 2D coordinates and the direction the subject was facing), \(s\) is the number of samples per unique triplet collected in the zone, \(a\) is the number of beacons deployed in the zone, and \(r_{i,j}\) is the BLE RSS value measured in dBm (or a non-detection value of 100) for the \(j\)-th beacon (column) at the \(i\)-th fingerprint (row). The operation \((p\cdot s)\) represent the product between two real numbers. Remember from Section 2 that a fingerprint is composed by the RSS values associated to beacon advertisements detected in a 1-s time window. A set of times is defined as:  
\[T_{(p\cdot s)\times a}=\left\{t_{i,j}\right\}, \tag{2}\]  
where \(t_{i,j}\) is the timestamp when a \(j\)-th beacon RSS value was measured (or a non-detection value of 0) during the time period corresponding to the \(i\)-th fingerprint. The timestamp is relative to the device boot and it represents the number of nanoseconds elapsed until the advertisement was detected. A set of positions is defined as:  
\[L_{(p\cdot s)\times 2}=\left\{(x_{i},y_{i})\right\}, \tag{3}\]  
where \(x_{i}\), \(y_{i}\) are the (\(x\),\(y\)) local coordinates where the \(i\)-th fingerprint was collected. The local coordinates were designed taken a given position in the target zone as the coordinates origin (represented by  
Figure 3: Geotec office zone. In (**a**), green diamonds, orange circles and the magenta asterisk represent the position of beacons, collection locations and the local coordinates origin, respectively. The blue horizontal-lines-filled rectangles represent tall furniture that create NLOS situations. In (**b**), a shot to show how beacons were deployed in the ceiling tiles.  
magenta asterisks in Figures 2a and 3a) and assuring that 1 unit of distance represents 1 m of actual distance in the zone. A set of identifiers is defined as:  
\[ID_{(p\cdot s)\times 1}=\{id_{i}\}, \tag{4}\]  
where \(id_{i}\) is a number that uniquely identifies the \(i\)-th fingerprint in the whole database. The number format contains information that allows determining membership information of the fingerprint, as shown in the example of Figure 4. The membership information is harnessed by the supporting scripts provided along with the database for fingerprint selection.  
The files in the database are organized in three folders: the RSS measurements and their labels (\"rss\"), the BLE beacon deployment positions (\"dep\"), and the geometries of obstacles (shelves and pillars) found inside the collection area (\"obs\"). The name of every file includes an indication of the zone its information refers to: \"lib\" for the Library zone and and \"geo\" for the Geotec zone. The RSS values, positions, times and identifiers sets of a zone are each stored in a file whose name includes \"rss\", \"crd\", \"tms\", or \"ids\", respectively. The \(i\)-th row of each of them holds the respective information of the \(i\)-th fingerprint collection in the zone.