Information Technology Reference
In-Depth Information
handheld devices and resemble the pricing guns or barcode scanners used in
supermarkets. Readers can also be fixed in place (e.g., in doorways or at vehicle toll
gateways) and even hidden, e.g., embedded into ceilings or walls [ 32 ].
10.6.4
RFID Frequency Allocation
RFID is fundamentally based on wireless communication, making use of radio
waves, which form part of the electromagnetic spectrum (i.e., frequencies from 300
kHz to 3 GHz). It operates in an unlicensed spectrum space referred as ISM
(Industrial, Scientific, and Medical). The exact frequencies that constitute ISM may
vary depending on the regulations in different countries, Table 10.4 .
Low-frequency (LF) tags operate at less than 135 kilohertz (kHz), which typically
means short-range uses, like animal identification and anti-theft systems (RFID-
embedded automobile keys). System that operates at 13.56 megahertz (MHz) is char-
acterized as high frequency (“HF”), which means longer read range. Scanners can read
multiple HF tags at once and at a faster rate than LF tags. The third frequency, Ultra-
High Frequency (“UHF”), operates at around 900 MHz, and it can be read at longer
distances, which outside the laboratory environment range between 3 and possibly
15 ft. However, UHF tags are more sensitive to environmental factors like water, which
absorb the tag's energy and thus block its ability to communicate with a reader.
RFID systems based on LF and HF frequencies make use of near-field communica-
tion and the physical property of inductive coupling from a magnetic field. The reader
creates a magnetic field between the reader and the tag and this induces an electric cur-
rent in the tag's antenna, which is used to power the integrated circuit and obtain the ID.
Table 10.4 RFID frequency allocation
Types
Used frequencies
Comment
Low Frequency (LF)
125-134 kHz (Europe,
North America and
Japan)
• Shortreadrange(<0.5m)
• Lesssensitivetointerference
• Lessexpensive
High Frequency (HF)
13.56 MHz (Europe,
North America,
Australia, and Japan
at very similar power
levels)
• Readrange(<1m)
• HigherspeedthanLF
Ultra High Frequency
(UHF) - non microwave
860-930 MHz (EU and
USA)
• Readrange(upto3m)
950-956 MHz (Japan)
• Limitedabilitytoreadtags
with high water or metal
content
Ultra High Frequency
(UHF) - microwave
2.45 GHz (used by IEEE
802.11b and 802.11g
WLAN and Bluetooth
systems)
• Offerthehighestdataread
rates
• Mostexpensive
 
Search WWH ::




Custom Search