A Measurement Strategy to Assess the Optimal Design of an RFID-Based Navigation Aid

Different solutions have been proposed to address orientation in indoor/outdoor environments and among them, radio frequency identification (RFID)-based systems represent a strategic choice for its reduced complexity and cost. Widespread practices to validate the behavior of RFID-based systems use specific metrics related to the addressed application, while a general strategy to assess technical performances of the RFID-based system is lacking. In this paper, a novel measurement approach is proposed to perform optimal choices in developing an RFID-based orientation system and to impartially assess its technical performances. A multivariate measurement strategy is suggested to fully investigate performances of the system as a function of a set of operating quantities (user-tag distance, tag height, and intertag distance). An analysis is also proposed, which aims to assess the system performances in terms of sensitivity and specificity. Moreover, the use of a synthetic index, representing the overall behavior of the system under investigation is addressed. A case of study is presented. The system uses transparent RFID tags positioned in the environment and an embedded system including an RFID reader, as well as a dedicated module to convey audio messages to end-users. Results highlight that the device sensitivity improves in the case of a high intertag distance while the specificity decreases for short intertag distance, which is also confirmed by the synthetic index proposed. Specifically, an optimal tag height of 1 m has been estimated, while best performances are obtained in the case of intertag distance and user-tag distance belonging to ranges [1.50-2.50] m and [0.40-1.60] m, respectively.