Numerical and Experimental Characterization of Wrist-Fingers Communication Link for RFID-Based Finger Augmented Devices

Radio frequency-identification finger-augmented devices (R-FAD) identify a particular wearable technology suitable to turn the human fingers into enhanced sensing surfaces to restore lost senses in impaired people as well as to augment the existing ones. The communication channel of R-FAD, involving a reader's antenna placed onto the wrist and tag antennas stuck onto the fingers, is here characterized in the UHF radio frequency identification (RFID) band by means of both numerical simulations, accounting for several options of the system, and an experimental campaign with volunteers asked to reproduce natural gestures of the hands. The study identifies the most appropriate placement of the devices and, above all, it quantifies the robustness of the link against the human variability. The channel follows a lognormal cumulative probability law indicating that the minimum required power to establish a reliable RFID link is 18-27 dBm depending on the chip sensitivity. Measurements finally revealed a remarkable correlation of the minimum required power from the reader with the volume of the hand.