3D Modeling for Propagation of UHF-RFID Tags’ Signals in an Indoor Environment

Indoor positioning systems are used to locate people or objects inside buildings. Several technologies are used for this purpose like Infrared, Global Navigation Satellite System (GNSS), Inertial Measurement Unit (IMU), Radio Frequencies, etc. Radio Frequency IDentification (RFID) is one of these technologies. Further, interference, multipath, obstacles lead to a complex spatial propagation of the signal. This paper aims to examine the coverage of RFID tags operating at 433 MHz in two different scenarios. The first one includes a single UHF RFID tag. The second introduces a constellation of tags which is a group of tags placed over a circle. The improvement in (tag-reader) distance error while using constellation is presented. Moreover, the measurement’s procedure characterized the propagation of signals in a complex indoor environment. According to experimental validations, performance of simulations based on the 3D ray-tracing method is obviously illustrated. The measured and simulated data present a good agreement between each other; this encourages the use of the simulated propagation model for indoor localization algorithms.