Learn About RFID
What is RFID?
RFID — Radio Frequency Identification — is an Automatic Data Collection (ADC) technology that uses radio-frequency waves to transfer data between a reader and a movable item to identify, categorize, and track. RFID is fast, reliable, and does not require physical sight or contact between reader/scanner and the tagged item. This non-line of sight advantage means that tags can be read through a variety of substances such as snow, fog, ice, paint, dirt, grime, and other visually and environmentally challenging conditions. In these conditions, barcodes or other optically read technologies would be useless.
RFID tags can be read at very high speeds responding in less than 100
milliseconds and in challenging circumstances. Because of its
versatility and performance, RFID has become indispensable for a wide
range of automated data collection and identification applications that
would not be possible otherwise.
How do RFID Systems Work?
An RFID System consists of one or more RFID Tags, two or more
antennas, one or more interrogators, one or more host computers and the
appropriate software to transform the raw data into actionable
information.
In a basic RFID tag read operation — the reader initiates tag
collection and sends messages to all tags. All the tags in a reader's
field respond by transmitting their tag ID to the reader.
Then the reader forwards all collected Tag IDs to the main system
through a middleware platform that filters and aggregates data before
passing it on to other systems.
RFID tags can be read only (passive) or read-write (active). They can
be attached to almost anything including pallets, cases of product,
vehicles, company assets, high value electronics, livestock, pets,
apparel, luggage and even people. There are many different types of tags
with various characteristics. Some active RFID tags have high memory
capabilities of up to 512 kBytes or more. Some passive RFID tags are as
small as a thumbnail and some active RFID tags can be as large as a
brick. And the cost of tags can range from less than a quarter for
small, passive tags to $100 for advanced active tags with sensor and
security functionality.
Readers can be either fixed or mobile. Fixed readers can be installed
at any location, ideally where the tags frequently pass through such as
gates or chokepoints, at a point of sale, or in a warehouse. Mobile
readers are usually smaller, handheld devices with a tethered cable or
wireless communication.
There are six key characteristics of RFID that affect the
communication between a tag and reader: Range, Range Adjustment,
Propagation, Directionality, Multi-Tag Collection and Memory.
Range
Range is defined as the maximum distance for successful Tag-Reader
communication. Read range difference will vary and can be very-short,
short, or long.
- Very Short Range: approx. up to 60cm (2 ft)
- Short Range: approx. up to 5 m (16 ft)
- Long Range: approx. 100+ m (320+ ft)
Range Adjustment
Range Adjustment will also play a role in RFID tag read functionality.
Range adjustment is the ability to adjust range and is categorized as
very good or poor. Very good range adjustment can be fine-tuned to a
specific distance. Tag-Reader communication is guaranteed within the
specified range and tag-reader communication outside the range is
impossible. Whereas poor range adjustment cannot be adjusted well at
all. When there is a signal fall-off pattern or a reflection, tag-reader
communication in the physical area is not guaranteed.
Propagation
Propagation is the ability to perform tag-reader communication through
or around objects and material. With very good propagation, the radio
frequency can penetrate through objects allowing successful
communication between tag and reader. Plus, very good propagation allows
for penetration through water, liquids and human tissue and may even go
through metal. Whereas poor propagation works on in line-of-sight and
any obstacle such as a wall, people or vehicles between the tag and
reader will prevent any successful communication.
Directionality
Directionality is the ability to achieve directional RF coverage using
directional antennas. There are two types of directionality:
Omni-directional and Directional. Omni-directional coverage has similar
RF coverage in all directions. With directional coverage, the RF
coverage is much stronger in one specific direction.
Multi-tag collection
Multi-tag collection is the ability to quickly and reliably collect
large number of tags within a designated area.
Memory
Memory is key in RFID communication — it determines the read only,
read/write, or write once read many capabilities in the tag-reader
communication. Some tags have small memory size at 16 bits and others
have larger memory with 512 kBytes or more.
RFID also has various frequency ranges. Range determines the distance
of RF communication and what type of RFID technology should be used for
a specific implementation. Low-frequency (30 KHz to 500 KHz) systems
have short reading range and are commonly used in asset tracking and
security access implementations. High-frequency (850 MHz to 950 MHz and
2.4 GHz to 2.5 GHz) systems, offer long read ranges (greater than 90
feet) and high reading speeds. High-frequency systems are used for
railroad car tracking and automated toll collection.
There are various RFID technologies available today. These include:
Very Short Range Passive RFID, Short Range Passive RFID, Active Beacon,
Two-way Active, and Real-time Locating Systems (RTLS). The frequency
- Very Short Range Passive RFID can communicate a distance up to 60
centimeters. Due to this very short range, applications are limited to
barcode-like "chokepoint" scenarios such as reading items on conveyor
belts, manual or human involvement with handheld scanning and assets
that are processed one at a time.
- Short Range RFID communicates a distance up to 3.5 meters. This
increased chokepoint distance accommodates a greater variety of
scenarios such as identifying assets that are moved by forklifts
through a warehouse or crates that are transported from one slot to
another. However, significant issues still remain with the shorter
range. 915 MHz is the only band providing short range with passive
tags and this band is not available in Europe today. Plus, the time to
collect multiple tags increases with the number of tags to collect,
reducing the speed assets are allowed travel. Due to the short range,
multiple readers are required for good coverage in chokepoint area and
adding readers will increase deployment costs.
- Active Beacon Long Range RFID communicates a distance of 50 to 100
meters. With this long range, a chokepoint implementation is difficult
or impossible. For example, assets on a conveyor belt cannot be
distinguished from assets sitting in storage and applications are
therefore limited to scenarios of continuous tag collection such as
taking inventory when collecting all tag data is required or
searching for a specific tag. With Active Beacon RFID - there is no
ability to write to the tag.
- Two-Way Active RFID tags have long range communication at a
distance of 50 to 100 meters. Again with this long range, chokepoint
implementation is difficult or impossible and applications are
therefore limited to scenarios of continuous or on-demand tag
collection.
- Real-Time Location Systems (RTLS) have long range communication of
50 to 100 meters. RTLS has the ability to locate tags to within 10
feet but resolution decreases in crowded environments and it is
difficult to translate the data information to a logical location such
as the specific parking slot a trailer might be located. It is not
possible to write to the tag due to the long range distance and also
involves a costlier infrastructure due to the number of readers
required and the expensive processing equipment.
Below is a summary of the RFID Technologies available today:
|
Technology |
Advantages |
Disadvantages |
| Very short range passive |
- Very low-cost tag
-
Global frequency |
- Requires significant
process changes
-
Limited multi-tag capability |
| Short
range passive |
- Low-cost tag
-
Sufficient range for dock doors and similar portals |
- No global frequency
-
Many readers/antennas required for coverage
-
Slow multi-tag collection |
| Active beacon |
- Low-cost active
-
Wide area monitoring |
- Limited chokepoint/portal
capability
-
No means of disabling beacon (air cargo) |
| Two-way
active |
- Highly reliable
communication
-
Support for advanced functionality (memory, sensors) |
- Expensive tag
-
Limited chokepoint/portal capability |
| RTLS |
- Physical finding/ locating
-
Wide area monitoring |
- Very expensive
infrastructure
-
Precision does not support "logical" locating (e.g. specific parking
slot) |
RFID tags are categorized as either active or passive. Active RFID
tags typically have both read and write capabilities so tag data can be
rewritten and/or modified. Active RFID tags can transmit specific data
or instructions to a reader (where the tag has been or important
information about the items in the container). A passive tag can not
actively send information —
it is read only. Plus, active tags are
powered by an internal battery which gives them a longer read range.
Passive RFID tags operate without a separate external power source and
obtain operating power generated from the reader. They have shorter read
ranges than active tags and require a higher-powered reader. Read-only
tags are typically passive and are programmed with a unique set of data
(usually 32 to 128 bits) that cannot be modified. Passive tags are
lighter, have smaller form factors and are less expensive then the more
powerful active tags.
Active and Passive RFID are two fundamentally different technologies,
each with unique advantages. While often considered competing
technologies, they actually complement each other, balancing cost and
capability. Active and Passive RFID offer tremendous potential for
combined use within many applications, including air cargo and
intermodal cargo management. Along with technical performance and
regulatory issues, this opportunity for combined use must also be
considered when selecting a frequency for Active RFID.
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