Time-Efficient Tag Identification in Blocker-Assisted RFID Systems

In RFID systems, the privacy problem has attracted increasing attention as the tags have extremely limited on-chip resources and may blindly respond to unauthorized readers. To protect the privacy, one widely used solution is to deploy one or more blocker tags to collide the RF signal sent from protected tags all the time. In this paper, we investigate the problem of tag identification in privacy-sensitive RFID systems when we have the authorized reader(s). Due to the presence of blocker tags, the tag identification becomes more challenging since the protected tags and blocker tags will always respond concurrently, leading to unreconciled collisions. To overcome this challenge, we in this paper propose three efficient tag identification protocols IIP, SIP, and SUIP, which meet three application requirements: privacy, accuracy, and efficiency. IIP iteratively deactivates blocking tags as well as labeling genuine tags, and finally identifies tags by avoiding all the unreconciled collisions. On top of IIP, SIP further avoids the slot waste by carrying out a filter to separate genuine tags from others in advance. Furthermore, SUIP can identify the incremental unknown tags in an efficient way. It separates the incremental unknown tags from others by using a filter with improved performance and puts forward a collision reconciliation technique to accelerate the identification process. Simulation results demonstrate that our protocols are able to guarantee any identification accuracy in a privacy-protected way.