AB symmetry

A technique in which after a tag is inventoried, it changes its state from A to B or from B to A.

Active tags

Tags that are able to transmit radio frequency (RF) signals to the environment without being near an interrogation zone or without needing power of some sort from an outside source.

Air interface protocol

A protocol that defines the rules of communication between tags and interrogators. The air interface protocol includes rules for encoding, modulation, and anticollision, as well as for reading and writing to a tag and other operations. The protocol usually does not define the tag architecture or encoding capacity of the tag.

ALOHA protocol

Developed by the University of Hawaii, this protocol was originally intended to avoid data collision in early LANs. ALOHA mode is based on a node not transmitting and receiving data packets all at once, but instead switching these functions based on time. If a collision occurs, the node transmits the data packet after a random delay.


A feature of smart readers that uses polls tags by using certain algorithms to prevent tag collisions (two or more tags responding at the exact same time).

Application-specific integrated circuit (ASIC)

An integrated circuit (IC) customized for a particular use, rather than intended for general-purpose use.

Asynchronous algorithm

Also known as a probabilistic algorithm, an anticollision method based on tags responding at randomly generated times. This method includes several specific protocols, including the ALOHA protocol.


A method of encoding that has been used by tags under the ISO standards but is now supported by Generation 2 as well. This type of encoding is very fast but susceptible to interference; therefore, it is not usually used in the dense reader mode of operation.


A performance level that can be used to assess the impact of individual changes on performance and offer insight into the most effective test sequence.


Broadcasting a tag's information to the environment at regular intervals.

Bi-static antenna

An antenna composed of two separate antennas: one for transmitting the RF signal to the tag and one for receiving the signal from the tag.

Critical boundary

The outer edge of the interrogation zone (IZ), where you do not want to read any tags. This is critical to determine, because you may have a forklift with tag items driving by, or a printer printing RFID tags, or something similar, and you wouldn't want to pick up those stray tags.

Data protocol

A protocol that specifies the size and structure of the tag memory, tag data formatting and length, and the means of storing, accessing, and transferring information.

Dense reader mode

A mode in which readers are able to operate in an environment with many other readers present and are able to avoid or reduce the risk of interference.

Deterministic algorithm

See Synchronous algorithm.

Differential time of arrival (DTOA)

DTOA is a method where a tag sends a signal to the environment, and the tag's location is calculated based on the difference in time it takes the signal to travel from the tag to each access point.

Direct thermal

A printing method that requires heat-sensitive RFID media and no printing ribbon. Information is printed as the printhead applies heat directly onto a heat-sensitive label.

DoD Construct

An identifier defined by the U.S. Department of Defense (DoD) used to encode the 96-bit Class 1 tag that is being shipped to the U.S. DoD, if the supplier has a Commercial and Government Entity (CAGE) code.

Dwell time

Also referred to as time in beam , dwell time ensures tags are read by the interrogation zone by considering the time when the tags are present in the zone.

CompTIA RFID+ Study Guide Exam RF0-101, includes CD-ROM
CompTIA RFID+ Study Guide Exam RF0-101, includes CD-ROM
Year: 2006
Pages: 136 © 2008-2017.
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