Since
the reader, however, cannot estimate the number of tags precisely, the guarantee of
recognizing all tags must be taken into consideration in the design of the tag
anticollision protocol.
. The reader has to recognize tags promptly. Since an object with a tag is potentially
mobile, tag identi?¬?cation must keep pace with the object??™s velocity. If tag identi-
?¬?cation is carried out slower than the object??™s velocity, the reader cannot recognize
it and the RFID system fails in monitoring or tracking.
. The tag should be recognized while consuming a small amount of resource. Since
the passive tag is supplied with power by the reader??™s signal, tag??™s available power
is limited. In addition, the tag has low computational capability and limited
memory. Thus, the tag anticollision protocol must load the tag with the least
possible communication and computation overheads.
This chapter introduces tree-based tag anticollision protocols and adaptive splitting
protocols [32], an adaptive query splitting (AQS) protocol and an adaptive binary splitting
(ABS) protocol, which are enhanced versions of tree-based protocols by suppressing the
occurrence of tag collisions and shortening tag identi?¬?cation delay. For decreasing tag
collisions, adaptive splitting protocols adaptively decide the starting point of the
tag identi?¬?cation by using information on the previous identi?¬?cation process in an environment
where the reader executes tag identi?¬?cation repeatedly for object monitoring and
140 RFID Handbook: Applications, Technology, Security, and Privacy
tracking.
Pages:
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285