Glossary Of Rfid Terms -- Q
In the Gen 2 air interface protocol, Q is a parameter that a reader uses to regulate the probability of tag response. A reader commands tags in an inventory round to choose a random number between zero and 2^Q; a tag may be successfully singulated if no other tags choose the same random number (a "collision"). Larger Q values decrease the probability of collision, but require the reader to spend more time during singulation.
An RFID tag that can be read only occasionally with the interrogator output at full power, or which can only be read at very close range.