A Hashing-based Anti-Collision Algorithm for RFID Tag Identification

Anti-collision algorithms are responsible for fast and energy efficient identification of RFID tags. They can be classified in Tree or Aloha based. To exploit benefits of both approaches, in this paper, we present a hybrid anti-collision algorithm. We assume that each tag stores a unique product identifier (ID) and the output of a hash function applied to that ID, which is shorter than the entire ID. With the proposed algorithm, in a first step, the reader, exploiting a Query Tree approach, queries the tags trying to identify each tag ID with the corresponding digest. When a hash collision is revealed, a second step, based on Framed Slotted Aloha Protocol, is used by the reader to identify only tag IDs with same digest. Numerical results have shown that the developed method, when using the most general Electronic Product Code scheme for tags addressing, improves performance in terms of mean identification delay with respect to query based protocols. Moreover, it gets about the same performance of the Binary Tree protocol, but overcoming its principal drawbacks.