The collision cycle defers tag identi?¬?-
cation and the tag??™s communication is pure overhead. The reader sends a query
(or a feedback) conducting the split of the set including con?¬‚icting tags.
In a tree of an identi?¬?cation frame, only a node of a collision cycle has two child nodes
because a set is split into two subsets in the collision cycle. Consequently, all intermediate
nodes in the tree correspond to collision cycles and all the leaf nodes correspond to either
readable cycles or idle cycles. Tag identi?¬?cation in tree-based protocols is coincident with a
tree search starting at the root of the tree for ?¬?nding nodes of readable cycles. The
performance of tag identi?¬?cation is in?¬‚uenced signi?¬?cantly by how ef?¬?ciently it splits
the tag set.
8.2.1 Binary Tree Protocol
The binary tree (BT) protocol [20??“25] uses random binary numbers generated by colliding
tags for the splitting procedure. The tag has a countervalue initialized to 0 at the beginning
of the frame. The tag transmits ID when the countervalue is 0. Therefore, all tags, at the
beginning of the frame, form one set and transmit concurrently. The reader transmits
a feedback to inform tags of the occurrence of tag collision. According to the reader??™s
feedback, all tags change their countervalues. The tag randomly selects a binary number
when its transmission causes collision (i.
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