There are many different ways to identify
objects, animals, and people. Why use RFID? People have been counting
inventories and tracking shipments since the Sumerians invented the lost
package. Even some of the earliest uses of writing grew from the need to
identify shipments and define contracts for goods shipped between two persons
who might never meet.[*] Written tags and name badges work fine for identifying
a few items or a few people, but to identify and direct hundreds of packages an
hour, some automation is required.
The bar code is probably the most familiar
computer-readable tag, but the light used to scan a laser over a bar code
imposes some limitations. Most importantly, it requires a direct "line of
sight," so the item has to be right side up and facing in the right
direction, with nothing blocking the beam between the laser and the bar code.
Most other forms of ID, such as magnetic
strips on credit cards, also must line up correctly with the card reader or be
inserted into the card reader in a particular way. Whether you are tracking
boxes on a conveyor or children on a ski trip, lining things up costs time.
Biometrics can work for identifying people,
but optical and fingerprint recognition each require careful alignment, similar
to magnetic strips. Facial capillary scans require you to at least face the
camera, and even voice recognition works better if you aren't calling your
passphrase over your shoulder.
RFID tags provide a mechanism for
identifying an item at a distance, with much less sensitivity to the
orientation of the item and reader. A reader can "see" through the
item to the tag even if the tag is facing away from the reader.
RFID has additional qualities that make it
better suited than other technologies (such as bar codes or magnetic strips)
for creating the predicted "Internet of Things."[*] One cannot, for
instance, easily add information to a bar code after it is printed, whereas
some types of RFID tags can be written and rewritten many times. Also, because
RFID eliminates the need to align objects for tracking, it is less obtrusive.
It "just works" behind the scenes, enabling data about the
relationships between objects, location, and time to quietly aggregate without
overt intervention by the user or operator.
[*] This term was originally attributed to
the Auto-ID Center. We will discuss both this term and the Auto-ID Center in
more detail later in this book.
To summarize, some of the benefits of RFID
include the following:
Alignment is not necessary
A scan does not require line of sight. This
can save time in processing that would otherwise be spent lining up items.
High inventory speeds
Multiple items can be scanned at the same
time. As a result, the time taken to count items drops substantially.
Variety of form factors
RFID tags range in size from blast-proof
tags the size of lunch boxes to tiny passive tags smaller than a grain of rice.
These different form factors allow RFID technologies to be used in a wide variety
of environments.
Item-level tracking
Rewritability
Some types of tags can be written and
rewritten many times. In the case of a reusable container, this can be a big
advantage. For an item on a store shelf, however, this type of tag might be a
security liability, so write-once tags are also available.
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