Tag A, tag B, and tag D choose 0 as their counter value and make one
group. On the other hand, tag C chooses 1 as its counter value and makes another group. In
the next reading slot, the former group tries to transmit and a collision occurs. The reader
Query
Medium Collision
Slot
Tag 011
0 l 1 1 l 00,01 1 l 01,10,11 01 l 10,11 10l1,010,011 11 l 010,011 011 l 110,111 110 l 111 111
010l
011,110,111 ?†
Tag 001
Tag 010
Tag 001
Tag 010
Tag 011
Tag 110
Tag 111
Tag 001
Tag 010
Tag 011
Tag 110
Tag 111
Tag 001
Tag 010
Tag 011
Tag 110
Tag 111
Tag 010
Tag 011
Tag 110
Tag 111
Tag 010
Tag 011
Tag 110
Tag 111
Tag 010
Tag 010
Tag 011
Tag 011
Tag 110
Tag 111
Tag 110
Tag 111
Tag 011
Tag 110
Tag 111
Tag 110
Tag 111 Tag 111
Tag 110
Tag 111
Collision Collision Tag 001 Tag 010 Tag 011 Tag 110 Tag 111 Collision Collision Collision
FIGURE 9.3
An example of tag identi?¬?cation using the query tree protocol with ?¬?ve tags.
Comparative Performance Analysis of Anticollision Protocols in RFID Networks 165
informs tags of the result of current reading slot. Tag C which has nonzero value of its
counter increases its counter value by 1. Tag A, tag B, and tag D generate random number
and add it to their counter value. Since tag A and tag B have the counter??™s value of 0, they
perform transmission and a collision occurs. Tag C and tag D which have nonzero value of
their counter increase their counter value by 1.
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