A Hybrid Query Tree Protocol for Tag Collision Arbitration in RFID systems

In this paper, we propose a hybrid query tree protocol that combines a tree based query protocol with a slotted backoff mechanism. The proposed protocol decreases the average identification delay by reducing collisions and idle time. To reduce collisions, we use a 4-ary query tree instead of a binary query tree. To reduce idle time, we introduce a slotted backoff mechanism to reduce the number of unnecessary query commands. For static scenarios of tags, we extended the proposed protocol by adopting two phases. First, in
leaf

query

phase
for existing tags, the interrogator queries
leaf
-nodes directly to reuse query strings in the previous session. Second, in
root

query

phase
for new arriving tags, the interrogator starts the query process from the
roof
-node. Simulation reveals that the proposed protocol achieves lower identification delay than existing tag collision arbitration protocols regardless of whether tags are mobile or not.