# BLE RSS Measurements Dataset for Research on Accurate Indoor Positioning
## 4 Usage Examples
### Positioning Accuracy
There is no notable accuracy difference between the results using data for powers \(-12\) dBm and \(-4\) dBm. Across the explored power configurations and collection smartphones, the WC method has larger maximum positioning errors than the FP method, but for percentiles below 75, the WC method provides lower positioning errors. The used smartphone may have an important impact on the positioning accuracy, and very weak transmission powers should be avoided. The positioning accuracy for fingerprinting is low, even below that reported in a previous study for Wi-Fi in the same environment [24]. However, it should be noticed that BLE is more affected by fast fading than Wi-Fi (its known solution is addressed later) and that the test locations for [PERSON] et al. [24] included locations closer to the training locations than those from the BLE data described in this paper. Figure 7: Positioning accuracy. For (**a,b**), data was captured in the Library zone. For (**c,d**), data was captured in the Geotec zone. In the two positioning methods, WC and FP, a parameter \(k\) should be set up before testing the method goodness for positioning. For WC, the \(k\) parameter represents the number of the most strongly detected beacons whose positions are considered in the operational fingerprint. For FP, it is the number of most similar training fingerprints whose positions are considered. We tested the impact of the value of \(k\) on the accuracy of the WC method for the Library zone, but the difference among several \(k\) values was negligible as long as the value was above 3. Therefore, and considering the detection delays issue explored in the previous section, three configurations were tested:  
* All: all beacons detected in a fingerprint are used. All estimations are used to compute the accuracy metric. * K10: \(k\) = 10, (10 was the \(k\) value providing the best accuracy). Take notice that the number of beacons detected in a fingerprint can be lower than 10. All estimations are used to compute the accuracy metric. * KF10: \(k\) = 10. Estimations for samples with less than 10 detected beacons are considered unfeasible and thus, not used to compute the accuracy metric. Table 4 shows the results of applying the previous three configurations on the positioning accuracy. Setting a \(k\) value has no significant influence on the WC's accuracy for this environment. Notice that in the Library zone there was no beacon whose detection range was larger than the others because of the the environment's layout. As presented in the result for configuration KF10, the accuracy for samples with 10 or more detected beacons are better than the rest of samples. The positioning method could be adapted so that it does not provide estimations for the latter samples, or so that it associates to a position estimation a certainty indicator based on the number of beacons detected for a sample. For the FP method (using \(k\) = 72), the number of detected beacons is relevant for both the fingerprints that are collected for training and for the operational (test) fingerprints. Table 5 presents how the accuracy in FP correlates with the number of coincident beacons that were detected in both the operational and training fingerprints. Notice how the number of coincident beacons is low (or very low for the case of A5) and the accuracy is lower than the one obtained with WC. The results of the Pearson correlation test between the positioning error and the number of coincident beacons for each test sample are presented in the last two rows of Table 5. The correlation is large and significant for the BQ and S6 smartphones, and large but not significant for the A5 smartphone. This correlation may explain why the accuracy for FP is lower than for WC, and that a solution for detection delays should be applied to both training and operational fingerprints. There is a known solution to the detection delays: create measurement windows [11].