SDR readers for Gen2 RFID and backscatter sensor networks

Abstract

Scatter radio has emerged as a key enabling technology for low-cost and large scale ubiquitous sensing. Radio frequency identification (RFID) tags/sensors utilize scatter radio technology to transfer sensed information to readers, typically employing Gen2, the industrial RFID protocol. This work offers a complete software-defined radio Gen2 reader, based on GNU Radio and USRP2 commodity software defined radio (SDR) platform. In sharp contrast to prior art, a single radio front end card is used with coherent detection and optimal exploitation of the FM0 line coding memory. The reader can act as a research tool to experiment with state-of-the-art signal processing algorithms and RFID devices. The two tag collision problem is studied and problems that arise in a real world system, such as channel estimation and tag symbol synchronization are highlighted. Experimental measurements are conducted and it is shown that the reader can identify a commercial, passive UHF RFID tag up to 6 meters with acceptable reliability. In addition, it is shown that collision recovery algorithms can increase performance of the implemented reader. Furthermore, an implementation of a SDR reader for a wireless backscatter sensor network (BSN) is presented. The developed reader implements noncoherent frequency shift keying (FSK) detection. The reader can decode multiple tags in real time and achieves communication ranges with semi-passive tags/sensors up to 130 meters.