Pushing The Range Limits Of Commercial Passive Rfids

This paper asks: "Can we push the prevailing range limits of commercial passive RFIDs?". Today's commercial passive RFIDs report ranges of 5-15 meters at best. This constrains RFIDs to be detected only at specific checkpoints in warehouses, stores and factories today, leaving them outside of communication range beyond these spaces. State-of-the-art approaches to improve the range of RFIDs develop new tag hardware that necessarily sacrifices some of the most attractive features of passive RFIDs such as their low cost, small form-factor or the absence of a battery.We present PushID, a system that exploits collaboration between readers to enhance the range of commercial passive RFID tags, without altering the tags whatsoever. PushID uses distributed MIMO to coherently combine signals across geographically separated RFID readers at the tags. In doing so, it resolves the chicken-or-egg problem of inferring the optimal beamforming parameters to beam energy to a tag without any feedback from the tag itself, which needs this energy to respond in the first place. A prototype evaluation of PushID with 8 distributed RFID readers reveals a range of 64-meters to the closest reader and a 7.4 x,1.2x and 1.6x improvement in range compared to state-of-the-art commercial readers and other two schemes [10, 33].