2.1. Advantages of RFID
The advantages of RFID can be broadly
into the following two types:
. These advantages are immediately realizable with the technology products that exist today.
. These advantages are either available in some form today or will be available as improved features in the future as the technology matures.
These are not official terminologies, but are used for the sake of convenience and to aid in better understanding of a benefit. The following list covers both of these advantage types, and the rest of this chapter describes how much benefit is available today versus how much will be available in the future:
. An RFID tag can be read without any physical contact between the tag and the reader.
. The data of a read-write (RW) RFID tag can be rewritten a large number of times.
Absence of line of sight
. A line of sight is
not required for an RFID reader to read an RFID tag.
Variety of read ranges
. An RFID tag can have a read ranges as small as few inches to as large as more than 100 feet.
Wide data-capacity range
. An RFID tag can store from a few bytes of data to virtually any amount of data.
Support for multiple tag reads
. It is possible to use an RFID reader to automatically read several RFID tags in its read zone within a short period of time.
. RFID tags can sustain rough operational environment conditions to a fair extent.
. Besides being a carrier and transmitter of data, an RFID tag can be designed to perform other
(for example, measuring its
conditions, such as temperature and pressure).
The following, although often touted as a benefit of RFID, is
The following sections discuss the previously listed advantages in detail.
An RFID tag does
need to establish physical contact with the reader to transmit its data, which proves advantageous from the following perspectives:
No wear and tear
. Absence of physical contact means there is no wear and tear on the readers as well as on the tags for reading and writing data.
down of operations
. Existing operations do not have to slow down to bear the extra overhead of bringing a reader physically into contact with a tag. Establishing such a physical contact can sometimes
. In a scenario in which tagged cases of items are moving at a rapid speed on a conveyer belt, there is a high chance that a reader will fail to maintain a physical contact with such a moving box, resulting in a missed tag read. As a result, had RFID been contact-based, it could not have been applied satisfactorily in a large number of business applications (such as supply-chain applications and so on).
Automatic reading of several tags in a short period of time
. Had RFID been contact-based, the number of tags read by a reader would have been limited by the number of tags it could touch at a particular time. To increase this number, the reader's physical dimensions need to be increased, resulting in a higher-cost, clumsy reader.
In summary, RFID instantly offers several benefits just by being contactless. In addition, this is clearly a current advantage of the technology.
2.1.2. Writable Data
RW RFID tags that are currently available can be rewritten from 10,000 times to 100,000 times or more! Although the use of these types of tags is currently limited compared to
write once, read many
(WORM) tags, you can use these tags in custom applications where, for example, time-stamped data about the tagged object might need to be stored on the tag locally. This
that the data will be available even in absence of a back-end connection. In addition, if a tag (that is currently attached to an object) can be recycled, the original tag data can be overwritten with new data, thus allowing the tag to be reused. Although writable tags might seem like an advantage, they are not widely used today because of the following reasons:
Business justification of tag recycling
. Virtually all business cases that involve tag recycling impact business operations. For example, the following must be
in: how tags are going to be collected from the existing objects, when they are going to be collected, how these are going to be re-introduced to the operations, additional resources and overhead required, and so on. Unless the tag is active or semi-active and is expensive, in most situations, generally, tag recycling does not make business sense.
. How can tags safeguard accidental and malicious overwriting of data by valid and rogue readers when in use? If the application is used outside an enterprise in an uncontrolled environment, the security implications multiply many times. Even if such a tag is used within the four walls of an enterprise, the issue of security remains. To satisfactorily address this issue, additional hardware, setup, and processes might be necessary; this, in
, can result in high implementation costs that might prove unjustifiable. Currently, it seems as if RW tags will continue to be used within the specific secure bounds of an enterprise.
Necessity of dynamic
. If most of the RW tag applications are going to be used
inside the four walls of an enterprise, there is a high degree of probability of the presence of a network and the ability to access the back-end system through this network. Therefore, using the unique tag ID, the back end can store the data without any need to write this data on the tag itself. Also, process changes can be made to handle exceptional conditions when the network is downfor example, generally critical manufacturing facilities have two modes of operation, one automatic and one manual so that if the automatic mode of operation fails, the operators can switch to the manual mode without stopping production lines.
Slower operating speed
. A tag write is often slower than a tag read operation. Therefore, an application that does tag rewrites has a good possibility of being slower compared to an application that does tag reads only.
These issues might seem daunting to the reader. However, it is
possible that some RFID applications exist for which using RW tags makes good business as well as technical sense. An example of such an application is monitoring the production quality control of a bottling operation for a medical drug. First, RW RFID tags are attached to empty bottles, which are then washed in hot water and sanitizing solutions,
, and subsequently go through a series of steps before the drug is placed in these bottles and sealed. It is assumed that the tags are sturdy enough to withstand the various processing steps. At each processing step, the parameters of the processsuch as temperature, humidity, and so onare written to the tags. When the sealed bottles roll off the assembly line, their associated tag data is automatically read by quality control systems. This way, any processing step that fell short of the minimum requirements can be
, and the overall quality of the bottling process can be quantized.
This is a current advantage of RFID that also offers future advantages in terms of better data security and improved technology.
2.1.3. Absence of Line of Sight
The absence of line of sight is probably the most distinguishing feature of RFID. An RFID reader can read a tag
obstructing materials that are RF-
for the frequency used. For example, if a tag is placed inside a cardboard box, a reader operating in UHF can read this tag even if this box is sealed on all the sides! This capacity proves useful for inspecting the content of a container
opening it. This feature of RFID has privacy rights infringement implications, however. If a person is carrying some tagged items in a bag, an RFID reader can (
) read the tagged item data without this person's consent. If this person's personal information is associated with the tagged item data (at the point of sale by the merchant, for example), it might be possible to access this information (using a suitable application) without the person's
or knowledge, which might
a privacy rights infringement. To prevent this, a reader should not read these tags after sale is completed unless explicitly needed or authorized by the buyer. There are multiple ways to achieve this objective (see Chapter 5, "Privacy Concerns"). Note that in some situations, a line of sight is needed to help configure the tag read distance, reader energy, and reader antenna to counter the environmental impact. These situations involve UHF tags and the presence of a large amount of RF-reflecting materials, such as metal, in the operating environment giving rise to multipath (see Chapter 1, "Technology Overview"). For example, consider a machinery tool production line where virtually everything is made of metal. A large amount of RF energy from the readers installed in this environment gets reflected from the objects in the environment. In this case, to achieve a good read accuracy, a tag and a reader must be placed so that there is no
This is a current advantage of RFID. It is possible that future improvements in the technology can bypass some of the hurdles faced by the presence of RF-
materials between the reader and the tag. Therefore, this is a future benefit, too.
2.1.4. Variety of Read Ranges
(LF) passive RFID tag generally has a read distance of a few inches; for a passive
(HF) tag, this distance is about 3 feet. The reading distance of an
(UHF) passive tag is about 30 feet. A UHF (for example, 433 MHz) active tag can be read at a distance of 300 feet and an active tag in the gigahertz range can have a reading distance of more than 100 feet. These reading distances are usually realized under ideal conditions. Therefore, the actual tag-reading distance of a real-world RFID system can be substantially less than these
. For example, the reading distance of 13.56 MHz tags in general do not exceed a few inches. This wide array of reading distances makes it possible to apply RFID to a wide variety of applications. Whereas the LF read distance passive tags are
suited for security, personnel identification, and electronic payments, to
a few, you can use HF passive tags for smart-shelf applications; passive UHF for supply-chain applications, tracking, and many other types of applications; and, finally, you can use passive tags in the microwave ranges for anti-counterfeiting. You can use active and semi-active tags in these frequency ranges for tracking, electronics toll payment, and almost limitless other possibilities. As you can understand, RFID has virtually an unlimited spectrum of current and possible applications.
Today, the tags for every frequency type are commercially available. In addition, the location of an active or a passive tag can be associated with a reader that reads this tag. Therefore, if a reader installed at a certain dock door of a warehouse reads a tag in its read zone, the location of this tag can be assumed to be this dock door at the time of reading. This location information can then be made available through a private or public (for example, Internet) network over a wide geographical area. As a result, the tag can be tracked thousands of miles away from its actual location. Future improvements of the technology will have limited impact on this aspect because the entire range of reading distances is currently available using direct (that is, a reader) and indirect (that is, a network) means. Hence, this feature is a current advantage of RFID.
2.1.5. Wide Data-Capacity Range
A typical passive tag can contain a few bits to hundreds of bits for data storage. Some passive tags can carry even more data. For example, the ME-Y2000 series (also known as
) passive, RW
tag from Maxell (see Figure 2-1) operating in the 13.56 MHz range can carry up to 4 K bytes of data within its 2.5 mm x 2.5 mm space.
Figure 2-1. HF tag from Maxell Corporation of America.
Reprinted with permission from Maxell Corporation of America
An active tag has no theoretical data-storage limit because the physical dimensions and capabilities of an active tag are not limited, provided this tag is
There are two approaches to use an RFID tag for an application. The first one stores only a unique identification number on the tag, analogous to a "license plate" of an automobile that uniquely identifies the tagged item; the second one stores both a unique identification number and data
to the tagged object. A large number of unique identifiers can be generated with a relatively small number of bits. For example, using 96 bits, a total of 80,000 trillion trillion unique identifiers can be generated (see Chapter 10, "Standards")! So, a relatively small number of bits are sufficient to tag virtually any type of object in the world. However, some applications might choose to store additional data on a tag locally. The advantage of storing this data locally is that no access to a networked database is required to retrieve the object data using its unique identifier as a key, an advantage that proves useful if the tagged object is going to be moved around in areas where the presence of network access to an object database is either not available or undesirable. Even when such a network connection is available, the associated application is such that it must not be impacted by a network
or delay. Therefore, one of the benefits of storing data locally on the tags is that the resulting application can be made largely independent of a back-end system. However, such a scheme has drawbacks compared to a "license plate" type of approach. First, data security needs to be addressed so that tag data can
overwritten by a valid reader nor by a rogue reader intentionally. The transmission time necessary for a high data capacity tag to transmit all its data bits correctly to a reader can be several times more compared to just transmitting the unique identifier. In addition, an increase in data transmission leads to an increase in error rate of transmission. A high memory capacity tag will be more expensive than the tags that can store only a unique identifier. Therefore, just because it is available, using a high memory capacity tag in an application does
seem like a good idea unless the application
demands it (
true for applications that have a hard time limit to perform a specific task). An active tag, however, can use a large data-storage capacity to support its custom tasks. A small amount of which, most probably containing the results of these tasks, might end up getting transmitted by this tag (which is
acceptable because this data is dynamic and can only be determined by the tag itself by scanning its environment).
This is a future benefit. Most of the passive tags available on the market today are constrained in memory
. These tags are used in "license plate" types of applications, and therefore they prove quite adequate for the task at hand. More high memory capacity tags will become available in the future.
2.1.6. Support for Multiple Tag Reads
Support for multiple tag reads ranks as one of the most important benefits of RFID. Using what is called an
, an RFID reader can automatically read several tags in its read zone in a short period of time. Generally, using this scheme a reader can uniquely identify a few to several tags per second depending on the tag and the application. This benefit allows the data from a collection of tagged objects, whether stationary or in motion (within the reader limits), to be read by a reader, thus obviating any need to read one tag at a time. Consider, for example, one of the classic tasks of a financial institution: counting a stack of currency notes to determine its total count and value. Assuming these notes have proper RFID tags, the data from these currency tags can be read using an RFID reader, which can then be used to determine the total count and the value of the notes in aggregate in a very short period of time, automatically. This method is much more efficient compared to the traditional counting techniques. Now consider another classic example: loading a truck with cases of merchandise at a shipping dock and receiving it at a receiving dock. Currently, for these types of applications, either the boxes are not inventoried at all during shipping time (they are, however, inventoried most of the time at the receiving dock) or they are inventoried using bar codes (which is manual and
). As a result, business might lose a considerable amount of inventory annually due to
or incur a high recurrent overhead in the cost of labor. If RFID tags can be applied to the boxes before they are shipped, a stationary reader placed near a loading truck can read all the boxes, automatically, when these boxes are being loaded into this truck. Thus, the business can have an accurate list of items being shipped to a distributor or a retailer. In addition, significant labor costs were saved by eliminating manual scanning of the labels, which would have been unavoidable if a technology such as bar code had been used instead. The data collected from these tags can be checked against the actual order to verify whether a box should be loaded into this truck (thus reducing the number of invalid shipments). As you can understand, this particular RFID advantage can speed up and streamline existing business operations considerably.
Contrary to popular belief, a reader can communicate with only
tag in its read zone at a time. If more than one tag attempts to communicate to the reader at the same time, a
occurs. A reader has to resolve this collision to properly identify all the tags in its read zone. Therefore, a reader imposes rules on communication so that only one tag can communicate to the reader at a time, during which period the other tags must
silent. This is what
an anti-collision algorithm (see Chapter 5, "Privacy Concerns"). Note that there is a difference between reading a tag's data in response to an anti-collision command versus reading a tag's data completely. In the former case, only certain data bits of a tag are read; whereas in the latter, the complete set of data bits of a particular tag are read. In addition, there is a theoretical as well as practical limitation on how many tags can be identified by a reader within a certain period of time.
This is a current benefit, but it is possible that future improvements in RFID reader technology might substantially increase the number of tags that can be identified per second (within the theoretical and practical limits).
A passive RFID tag has few moving
and can therefore be made to withstand environmental conditions such as heat, humidity,
(to a fair degree). For example, some passive tags can survive
from 40°F to 400°F (40° C to 204°C). Generally, these tags are made depending on the operating environment of a specific application. Today,
single tag can withstand
these environmental conditions. An active and semi-active tag that has
electronics with a battery is generally more susceptible to damage compared to a passive tag. A tag's ruggedness almost always
This is a current benefit because tags with a variety of resistance to operating environments are available. However, plenty of room exists for improvement, and as the tag technology
, it is expected that more tags will be available that can better resist
environments than their present-day counterparts. Therefore, this can also be called a future benefit.
2.1.8. Perform Smart Tasks
The on-board electronics and power supply of an active tag can be used to perform specialized tasks such as monitoring its surrounding environment (for example, detecting motion). The tag can then use this data to dynamically determine other parameters and transmit this data to an available reader. For example, suppose that an active tag is attached to a
item for theft detection. Assume that this active tag has a built-in motion sensor. If someone attempts to move the asset, the tag senses movement and starts broadcasting this event into its surroundings. A reader can receive this information and forward the information to a theft-detection application, which in turn can sound an alarm to alert the personnel. It might seem that by just taking off the tag from the asset and then
the tag back where it was (while taking the asset away) would fool the tag into thinking that the asset is stationary again. However, it is possible for such a tag to sense that it is no longer attached to the asset. The tag can then send another type of broadcast message to signify this event.
This aspect of RFID has the greatest potential for improvement as active tags with specialized functionalities are becoming available. Hence, this can be called a future benefit.
2.1.9. Read Accuracy
In the media, the read accuracy of RFID is mentioned variously as "very accurate," "100 percent accurate," and so on, but no objective study shows how accurate RFID reads really are. It would definitely be desirable to back up such accuracy statements with hard data, because no technology can offer 100 percent read accuracy in every operating environment all the time. Factors on which RFID read accuracy depends include the following:
. Which frequency tags are being used, the tag antenna design, and so on can have a
on the read accuracy of an RFID system.
. The composition of the object, how it is packed, the packing material, and so on play important roles in determining the readability and hence the read accuracy. Also note that impact of this factor depends on the frequency of the RFID system used.
. Interference from existing mobile equipment, electrostatic
(ESD), the presence of metal and liquid bodies, among other factors, can pose a problem for read accuracy in the UHF and microwave frequencies.
. Tag orientation and placement relative to the reader antennas can significantly impact read accuracy.
Another issue with RFID is what are called
. In this situation, a random but seemingly valid tag data is recorded by the reader for a brief period of time. After this time, the tag data can no longer be read by the reader! The problem arises when a reader receives incorrect data from a tag, which might happen for various reasons (such as a poorly
error-correcting protocol). Phantom reads are "
" in the supplier system. Incorrect installations might also give rise to this
. In general, phantom reads are not an issue. However, this shows that the objective determination of RFID accuracy is not easy, that it depends on several factors. It is possible for the accuracy rates of two identical RFID systems used in different environments to
. It might not always be possible to increase the read accuracy and degree of automation of highly automated systems that are in existence today.
This is a current benefit because several applications generally do show sufficient accuracy to meet business requirements. However, the read accuracy of RFID has good potential to improve as improved tags, readers, and antennas become available in the future. Therefore, this can also be called a future benefit.