Alleviating Slot Collisions in UHF RFID Systems

One of the main obstacles for low latency bulk reading in UHF RFID systems is collision occurrence. State-of-the-art high-speed identification methods mostly rely on collision recovery techniques or collision avoidance algorithms. Collision recovery can be done by enhancing the physical layer capabilities to support this feature. Usually, the probability of collision occurrence can be reduced by carefully optimizing the frame length and accurately estimating the number of tags in the interrogation area. In this paper, bulk reading time is reduced by detecting collisions in tag replies. More precisely, the RFID reader identifies slot types using the tag replies spectrum and the deviation in tag data rates which is known as rate tolerance. This novel reader feature distinguishes two types of collided slots; identified collided slots with shorter duration as compared to the non-identified ones. Hence, our technique drastically improves RFID tag reading times. Our experimental results show that the proposed technique can reduce bulk reading times by 10% compared to conventional receivers at SNR greater than 20dB.