Since arriving tag
1101 responds to query 1 which staying tag 1001 responds to, query 1 causes a tag collision.
By expanding query 1 into query 10 and query 11, the reader recognizes both of two
con?¬‚icting tags quickly.
8.5.2 Query Deletion
In performing the procedure, the query insertion procedure enables only to expanding the
tree and therefore augments the number of leaf nodes in the tree. Since the number of
readable queries is the same as the number of tags, idle queries will proliferate and worsen
the reader??™s identi?¬?cation ability. It results from where readable queries are transformed
into idle queries by leaving tags. For fast tag identi?¬?cation, the query deletion procedure
removes unnecessary idle queries from CQ under the condition that CQ has bit strings
covering all branches in the tree.
Let l(q1q2 . . . qx) be the number of responses following query q1q2 . . . qx. Since the tag
responds to either q1q2 . . . qx0 or q1q2 . . . qx1 when its ID matches query q1q2 . . . qx,
l(q1q2 . . . qx) ?? l(q1q2 . . . qx0) ?? l(q1q2 . . . qx1):
When query q1q2 . . . qx is a collision query, l(q1q2 . . . qx) 2 since more than one response
follows the collision query. The node of collision query q1q2 . . . qx has two child nodes
which are a pair of node types as follows:
Reader??™s
transmission
1 00 010 011 10 11
0101
0110
1001 1001
1101 1101
Collision No response
0101 0110 1001 1101
Time
(a)
(b)
1 0
00 01 10 11
011 010
Tag 0101 Tag 0110
Tag 1001 Tag 1101
Idle
Readable
Collision
Tag
(0101)
Tag
(0110)
Tag
(1001)
Tag
(1101)
Reader??™s
reception
FIGURE 8.
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