Wirelessly Retrieving Phase and RSSI of UHF RFID using Commodity SDR Sniffer

This paper demonstrates the retrieval of relative phase and RSSI from UHF RFID tag responses using a noncoherent low-cost commodity software-defined radio sniffer. Two common scenarios have been considered: (i) when the tag is stationary and (2) when the tag is moving. The retrieved results have been verified by a commercial RFID reader. Overall, the standard deviations in phase and RSSI estimations in the two cases are up to 8.1° and 0.61 dB respectively. In addition, the phase ambiguity has been increased to 360° by taking the sign of the tag data into account. The approach will enable a range of SIMO approaches to tag localisation using existing RFID readers and multiple sniffers.