5
2
2.5
3
No. of reading cycles
Binary
Query
AQS
ABS
0 1 2 3 4 5
Maximum MPF (m/frame)
6 7 8 9 10
(c)
FIGURE 8.8
Impact of tag mobility on tag identi?¬?cation. (a) Collisions. (b) Idle cycles. (c) Identi?¬?cation delay.
154 RFID Handbook: Applications, Technology, Security, and Privacy
values by the number of recognized tags. When tags move at low speed, adaptive splitting
protocols outperform the binary tree protocol and the query tree protocol considerably.
Tags would like to be staying tags, and AQS and ABS block collisions between staying tags
completely because they do not allocate more than one staying tag to a set. Especially, they
achieve collisionless tag identi?¬?cation when the maximum MPF is 0. As tags move faster,
the performance of AQS and ABS deteriorates. When the maximum MPF is >6 m=frame,
AQS has longer delay than the query tree protocol. When the tag mobility has high
speed, there are fewstaying tags and collisions between staying tags at the binary tree protocol
and the query tree protocol hardly occur. Additionally, AQS and ABS generate idle cycles
because leaving tags increase and leaving tags make idle cycles. Hence, AQS and ABS show
the performance similar to the binary tree protocol and the query tree protocol at high speeds.
8.7.3 Impact of the Similarity of ID
For the purpose of another comparison, we evaluate the impact of the similarity among
IDs.
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