What exactly is tag collision, and how is it avoided?
Virtually all RFID transponders support some kind of anti-collision algorithm. Tag collision is when two tags try to respond to signals from a reader at the same time. The reader cannot differentiate the signals and, without an anti-collision algorithm, would not be able to interrogate either tag, rendering the system useless any time that more than one tag was in the read field.
There are a variety of methods for preventing tag collisions, but all do essentially the same thing: They make it possible for tags to respond to a reader one at a time. The algorithm used is usually part of the air-interface protocol standard—the “language” that tags and readers use to communicate.
—Mark Roberti, Founder and Editor, RFID Journal
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