# False Positive RFID Detection Using Classification Models
## 3 Dataset and Feature Extraction
Various other tag movements close to the gate were also conducted and labelled as false positive, and random static tags were placed within the configured read range and also labelled as false positive. In total, 1624 unique data readings were collected, with 1130 false positives and the remainder true positive. Each reading consisted of tag id, date and time, and RSS value. The minimum, maximum, and average number of tags read during a data gathering session where 17, 240, and 69.23, respectively. Figure 3 shows RSS readings for a typical data gathering session. The ALR-9900+ reader does not provide the unit of measure for the RSSI; therefore, we have presented signal quality (%) as secondary y-axis. First, we investigated the minimum as well as maximum values of RSSI during our experiment, they were 432 and 37,131, respectively. Based on this information, the real value of RSSI was then converted into signal quality (%). The maximum RSS for tags moved through the gate was larger than for static tags (Figure 3a). RSS increased when tags passed through the gate, achieving maximum when the tags were closest to the antenna. In contrast, static tags had relatively constant RSS, since the distance between the antenna and static tag was fixed. This particular case shows a static tag located relatively distant from the reader, hence RSS was low. Figure 3b shows RSS histograms for typical static tags and those moved through the gate. Static tags tended to have small variance, whereas tags moved through the gate tag tended to exhibit heavy-tailed distribution. Figure 3c shows the case for a static tag located a relatively close distance to the RFID reader. The static tag generated a non-constant RSS, being relatively stable but reducing when other products being moved through the gate blocked the antenna signal (the worker as well as the boxes). Once the worker and boxes complete passing the gate, the static tag RSS became stable again. Consequently, closer static tags tended to generate histograms with higher variance and maximum RSS values compared to more distant tags (Figure 3b), as shown in Figure 3d. However, closer static tags still tended to have lower variance and light-tailed distributions compared with tags moved through the gate. Figure 2: Data gathering: (**a**) Possible tag movements and static tag locations, (**b**) example tag movement through the gate, and (**c**) data gathering program to record tag RSS, etc. Figure 3e shows a typical RSS distribution for a tag moved close to the gate, which is quite similar to that for tags moved through the gate. For both tags, RSS increased as they moved closer to the antenna, then decreased as the distance increased. However, maximum RSS for tags moved close to the gate was lower than for tags moved through the gate, since the antenna did not directly face the tags moved close to the gate. Figure 3f compares typical histograms for tags moved close to and through the gate. Although the histograms are similar, tags moved through the gate tag exhibited higher variance and more heavy-tailed distributions compared to tags moved close to the gate. Since RSS depends on the distance between the antenna and tag, closer tags generated larger RSS. Therefore, RSS attributes provide important data to classify RFID readings, and have been utilized in previous studies to identify RFID readings with high performance accuracy [20; 21; 22]. Table 1 shows the nine relevant statistical features extracted from RSS to help distinguish between true and false positives. Figure 3: Typical tag RSS and corresponding histogram: (**a,b**) Relatively distant static and through the gate, (**c,d**) relatively close static and through the gate, and (**e,f**) close to the gate and through the gate. During data gathering, the worker loaded several boxes with attached tags on the trolley and performed different RFID readings (i.e., true and false positives) (Figure 2b). To generate a complex dataset, the worker followed different speeds and paths.