2a. This is due to the fact that the binary tree protocol adopts the
probabilistic approach of exploiting random numbers and does not use information on
staying tags. As shown in Figure 8.2b, under the query tree protocol, tag 1 causes the same
number of collisions with other staying tags again. The query tree protocol also does not
consider collisions by staying tags though it differs from the binary tree protocol in the
sense of exploiting tag IDs.
When tag collision occurs in tag identi?¬?cation of tree-based protocols, colliding tags need
to retransmit their IDs. Resolution of tag collisions consumes the tag??™s limited energy and
causes additional identi?¬?cation delay. Therefore, eliminating interstaying tag collisions can
shorten the total delay for tag identi?¬?cation and reduces the tag??™s communication overhead.
To prevent collisions between staying tags, adaptive splitting protocols start the
splitting procedure from several tag sets; each of the sets has one staying tag at most. They
are still simple and recognize all tags quickly.
8
7
6
5
4
3
2
1
0
3 8 10 11 18 21 22 23
Tag??™s virtual ID
No. of collisions
One frame
Next frame
25 26 29 35 46 48
(a)
7
6
5
4
3
2
1
0
8 21 22 25
Tag??™s virtual ID
No. of collisions
One frame
Next frame
26 29 48
(b)
FIGURE 8.2
Collisions between staying tags in tree-based protocols.
Pages:
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293