Analysis of the variability of RSSI values for active RFID-based indoor applications

Radio frequency identi cation (RFID) technology-based indoor localisation solutions have been widely adapted by many industries. An important factor a ecting the performance of RFID applications is the received signal strength indication (RSSI) values. Indoor setting and layout may have direct e ects on the RSSI variability, which, in turn, a ect the robustness of RFID applications outcomes. E ects of di erent environmental factors on RSSI values for RFID tags have been observed and reported in previous literature; however, there is a lack of research that addresses the e ects of such parameters on RSSI values in a holistic and quanti ed manner. In this study, 2 di erent test scenarios are used to compare and assess the relationships between the RSSI values and system parameters for active RFID tags in indoor applications. These parameters include: 1) type of materials that tags are attached to, 2) obstructions between tags and an antenna, 3) relative elevation between tags and an antenna, and 4) relative orientation of tags and an antenna. The e ect of each parameter was evaluated by statistical analyses. The Shapiro{Wilk, Bartlett s, Levene s, Kruskal{Wallis, Mann{Whitney, and Games{Howell tests were conducted. The results show that the data groups for all of the system parameter tests were nonnormally distributed and heterogeneous. Based on the Mann{Whitney test results, U values for comparisons of RSSI values in both test beds were found to be 0.00 for all of the system parameters. The results indicate that di erent system parameters caused variations in RSSI values as well as the detectability rates. Nevertheless, di erent test beds changed the in uence of each parameter on the RSSI values. It is concluded that testing environment is a prominent parameter that a ects the results and uctuations in the RSSI values, and that the detectability rates cannot be attributed to any speci c parameter that has been included in this study.