Warehouse Management Systems (RFID)

Frequencies

RFID systems are available in a wide range of frequencies to suit various performance
needs. Frequency is an important factor in transmission range and speed. However,
bandwidth availability is regulated by telecommunications authorities in each country,
and not all frequencies are available for use throughout the world. This is an important
consideration when planning logistics and supply chain applications. Most tag
frequencies share the ISM (Industrial, Safety and Medical) bands. Compatibility
problems are gradually being solved through standardization efforts, particularly in
standards sponsored by the ISO.
Most RFID technology used in warehousing and distribution operates at either 13.56MHz
(high frequency), 860-930MHz (ultrahigh frequency, or UHF) or the 2.45GHz
(microwave) band. Still in use are 125 KHz low-frequency tags, which are used for
access control and vehicle identification. Standards that have been ratified or are in
development for material handling, logistics and supply chain applications are
concentrated in the UHF band and 13.56MHz. Wal-Mart, which will begin requiring its
100 largest suppliers to tag shipments with RFID, has specified the use of draft standards
in these frequency bands.
Here is a very brief overview of different RFID frequencies and their performance
characteristics.

Low Frequency

Low frequency is defined as between 100 and 500kHz. This frequency band is
inexpensive, with a short to medium read range and slower read speed. Typical
applications for low-frequency RFID are access control, animal identification, inventory
control and car anti-theft (immobilizing) systems. This is an attractive frequency band
because such systems do not need to be licensed in many countries. Read range with a
fixed station reader is usually less than 18 inches.

High Frequency

The high frequency, which some call intermediate, band encompasses the 10 to 15MHz
range, with 13.56MHz being the most common. Read range with a fixed station reader is
around 1 to 3 meters (3 to 10 feet), although the reading speed is higher than the lowfrequency
band. Sizing of the antennas and tags becomes more critical. More expensive
than low frequency, this band has the potential to become more cost-competitive through
volume purchase of tags. Typical applications here include access control and smart
cards. The first “smart labels” which are RFID tags embedded within adhesive bar code
labels, were produced at 13.56MHz, but are now also available in other frequencies.

Ultrahigh Frequency (UHF)

Ultrahigh-frequency RFID encompasses the 850 to 950MHz band and is frequently
championed for distribution and logistics applications. The American National Standards
Institute (ANSI) standard for RFID identification of returnable transport items, which
complements the ANSI MH10.8 bar code shipping label standard, specifies the 902-
928MHz band for item identification. The ePC specification (discussed later) supported
by Wal-Mart also utilizes the UHF band.
Read range, which as with all frequencies depends on tag size, power output and
interference, is up to 10 feet.

Microwave

Some RFID products are also produced in the microwave bandwidth, typically at either
2.45GHz or 5.8GHz. These products offer the highest data read rates., but are also more
expensive and have higher power requirements. These are often appropriate in
specialized applications.