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An Overview of RFID

Radio frequency identification (RFID) is a technique that uses radio waves to track and identify people, animal, objects, and shipments. This is done by the principle of modulated backscatter. The term “backscatter” is referring to the reflection of the radio waves striking the RFID tag and reflecting back to the transmitter source with its stored unique identification information.

What makes up the RFID System?

The RFID system consists of two things:

The reader (transceiver) transmits radio waves, which activates (turns on) an RFID tag. The tag then transmits modulated data, containing its unique identification information stored in the tag, back to the reader. The reader then extracts the data stored on the RFID tag. The RFID idea dates back to 1948, when the concept of using reflected power as a means of communication was first proposed. The 1970s saw further development in RFID technology—in particular, a UHF scheme that incorporates rectification of the RF signal for providing power to the tag.

Development of RFID technology

Development of RFID technology significantly increased in the 1990s. Applications included toll collection that allowed vehicles to pass through tollbooths at highway speeds while still being able to record data from the tag.

Today, RFID technology is being used to track inventory shipments for major commercial retailers, the transportation industries, and the Department of Defense. Additionally, RFID applications are being used in Homeland Security in tracking container shipments at border crossings. Additionally, RFID is being incorporated into WLAN computer networks to keep better track of inventory. Wireless technologies are becoming more important for the enterprise. RFID technology is being used as a wireless means for asset tracking and as a result is placing more importance on its role in the network. The tracking technology is even being extended to tracking Wi-Fi devices within the WLAN infrastructure.

RFID Parameters

There are three parameters that define an RFID system. These include the following:

Powering the Tag

RFID tags are classified in three ways based on how they obtain their operating power. The three classifications are passive, semi-active, and active:

Frequency of Operation

The RFID tags must be tuned to the reader’s transmit frequency to turn on. RFID systems typically use three frequency bands for operation, LF, HF, and UHF:

Communications (Air Interface) Protocol

The air interface protocol adopted for RFID tags is Slotted Aloha, a network communications protocol technique similar to the Ethernet protocol. In a Slotted Aloha protocol, the tags are only allowed to transmit at predetermined times after being energized. This technique reduces the chance of data collisions between RFID tag transmissions and allows for the reading of up to 1000 tags per second. (Note: This is for high-frequency tags.) The operating range for RFID tags can be up to 30 meters. This means that multiple tags can be energized at the same time, and a possible RF data collision can occur. If a collision occurs, the tag will transmit again after a random back-off time. The readers transmit continuously until there is no tag collision.


Published on Tue 21 August 2012 by Rolf Gupta in Networking with tag(s): rfid