Multi-Antenna UHF RFID Reader Utilizing Stimulated Rate Tolerance

One of the main potentials for improved bulk reading speed in UHF radio frequency identification (RFID) systems is collision recovery, i.e., the recovery of signal collisions on the channel caused by unwanted simultaneous replies of the RFID tags. State-of-the-art collision recovery methods typically rely on quasi perfect channel state information (CSI), which is difficult to achieve using existing UHF RFID standards. In addition, these methods neglect the rate tolerance, i.e., the unknown bit-rate of the tag replies. In this paper, we will show that this rate tolerance can be used for improving the performance of RFID readers. We also show that we can further improve the performance if we furthermore artificially stimulate this rate tolerance. Using our approach we also do not face the difficulty of unknown CSI. Our new approach is compatible with the existing EPCglobal Class-1 Gen-2 RFID standard. Simulation results indicate that the new approach is able to reduce the time for reading a bulk by 8% compared to a maximum likelihood receiver. Using additional rate tolerance stimulation, this gain increases up to 25%. Furthermore, we can easily combine our approach with multiple antennas for improved performance, without any significant effect on the complexity of our decoding algorithms.