Radio Frequency IDentification
Antony Philip, University of Minnesota
Radio Frequency Identification (RFID) is an electronic identification technology that
allows an object, place, or person to be automatically identified at a distance without it
being in direct line-of-sight.
Radio frequency identification has been used since World War II to solve identification
and asset tracking problems. The first known use of RF Identification was during World
War II. The British Royal Air Force used the technology as an identification tool in its
Identify Friend/Foe (IFF) systems. Allied planes with an IFF transponder would respond
to queries from ground-based radars with a specific response. By the late 1970s, RFID
was used for the tracking of livestock. Individual cattle were tagged with their own
identification beacon. RF readers were placed at points of entry into barns, feeding stalls
and other locations. The ability to identify individual cows without human interaction
allowed better tracking of feeding and health irregularities. In the early 1980s, railroad
companies were using RFID to tag rail cars. This was among the first uses of RFID for
asset tracking over a large geographic area. An earlier initiative to do this with bar codes
failed due to poor read reliability in adverse weather conditions, high travel speeds and
direct sunlight. In the 1990s, RFID arrived in the suburban malls throughout the United
States as an enabling technology for Electronic Article Surveillance (EAS). RFID readers
positioned by store exits would trigger an alarm if an EAS tag passed through the field.
In many ways, the physical processes involved in RFID systems are the same across all
types of wireless communications systems, cordless telephones, or even baby monitors.
There is a transmission of an interrogator signal from an antenna to a transponder, and a
separate transmission of a reply from the transponder to a receiving antenna. Most
interrogator designs allow for a single antenna to be used for transmission and reception.
Figure 2. RFID Tags
Figure 3. RFID Reader
RFID tags, the computer chips embedded with products so they can be identified come in
a variety of shapes as shown in Figure 2. Tags can be active or passive depending on
how the chips are powered. Active tags have their own internal power source to power
the chip while passive tags do not. The majority of RFID tags in existence are of the
passive variety because they don’t need a battery to operate. Tag readers, such as the one
shown in Figure 3 generate a signal, creating an electromagnetic field. This causes the
RFID tag’s antenna to function as a voltage generator. The current generated in the tag
powers the chip, which modulates the radar cross-section of the tag and therefore its
reflected power. The modulation applied is usually specific to the tag, thereby allowing
information on that tag to be sent to the receiver. The simplest command results in the tag
sending back a signal containing a unique digital ID (e.g., the EPC-96 standard uses 96
bits). Once the id for the tag is read, the reader can send the data to the application
software for further processing. The application software then queries the information
about the id from its known data bases. This will give the history of the tag/product and
enables updating the database with the current spatial and temporal information about the
product. Sometimes, the tag may have an additional EEPROM memory which allows the
reader to write back instance specific information to the tag.
A typical RFID system may have the following:
• Hardware components
o Tags, programmed with binary data which respond to commands
propagated through the electromagnetic field
o Fixtures which attach the tag to the object being tracked
o Readers or integrators, which may have an integrated antenna to transmit
commands to tags and interpret the modulated results
o Network infrastructure, to allow communication between integrators and
the enterprise systems which evaluate the data read from the tags – This
could be RS-232, Ethernet or 802.11b wireless cards or proprietary
o Power infrastructure, to provide AC or DC power to the readers.
• Software / Middleware
o A reader, that can identify one or more tags are in the presence of a field.
It is useful to identify information such as the presence of a new tag or that
a tag which has been there is currently missing. But repeatedly reading
the same tag data may not be useful, so the events of interest need to be
defined by the upstream applications.
o A software middleware which adapts to the requirements of the upstream
applications and the varying reader protocols as explained in section 4
o Software systems to update and get information from companies’
enterprise systems like MRP, ERP, CRM, etc.
o Spatio-Temporal databases which can capture spatial and time information
of the data collected.
RFID has many potential applications, but the main beneficiary of this technology is the
global supply-chain management industry. Traditionally product identification was done
using bar codes and scanners. These bar-codes met the needs of the industry provided
that constraints in using them were met, namely that the barcodes were scanned by
operators or that products were carefully moved in an automated system so that bar codes
were visible. This method is not efficient and subject to errors. By contrast, products
which use RFID tags for identification can be read even if they are obscured by other
Figure 1. Retail Supply Chain
Figure 1 shows a typical supply chain maintained by retail stores such as Walmart to
support end customers who buy goods from them. The retailer buys goods from
distributors, who have warehoused goods they bought previously from manufacturers.
The goods are manufactured using parts from the suppliers. As materials move from the
initial supplier in the chain to the end-customer, value and costs are added at each node.
Businesses strive to make their supply chains more efficient by improving the
information sharing throughout the supply chain in order to optimize profit based on
supply and demand. Introducing RFID tags and readers in the supply chain can greatly
increase the productivity, reduce chances for mistakes and improve the overall efficiency
of this supply chain system.
RFID technology began receiving tremendous coverage in the media in the early 1990s
because of successful applications such as ExxonMobil’s credit card linked Speed Pass,
north eastern states EZPass toll collection system, and the US Department of Defense’s
asset tracking during the second Gulf War. At the same time, RFID began to attract
negative publicity from privacy advocacy groups because of its potential as a powerful
data mining tool. In recent years, concerns about privacy have threatened to predominate
over news of positive applications. Ohkubo et al.  argue that to be successful as a
technology, RFID applications should give clear, tangible value to the average consumer.
This will compensate for whatever loss of privacy fears they may have. Consumers tend to
accept the risk of being tracked if they feel it’s worth the benefits the application provides. So
the key to a successful RFID application is how it considers the equation from the
consumer’s point of view. To alleviate this privacy concern EPCGlobal specifies a ‘kill’
function for the tag, allowing the end-user the opportunity to remove the tag-id from the
Despite these concerns in the marketplace over privacy, the list of popular applications of
RFID has grown to include:
• Electronic Product Code (EPC) tags for products stored in a store
• Embedded tags in library books to track check-in, check-out of books
• Traffic toll collection (such as EZPass)
• Passports and other IDs
• Pet identification
• Semiconductor factory lot tracking
• Livestock tracking
• Measuring reach and network routing of water and sediment by tracking RFID’ed
One natural extension for RFID is RFID with sensing capability. Adding this facilitates
the collection of sensor derived data on the product it is tagging along. Some of the
applications of RFID with sensor are
• Measuring physical parameters such as temperature and acceleration. This
includes some of the well-known applications like detecting the temperature
changes for frozen poultry and detecting the acceleration changes in packaging
for sensitive equipment such as computers, artwork, etc.
• Harmful agents such as biological, nuclear, chemical monitoring. This is an
application of interest especially after the events of 9/11.
RFID data can be integrated into spatial databases to develop powerful applications. Tag
readers can be considered as one of the information provider node in a spatial database
application framework. Tag reader provides both spatial and temporal information for a
product it read. In a retail environment this facilitates spatio-temporal queries and
facilitates demand forecasting.
The RFID industry faces a number of challenges, both technical and non-technical, to
widespread adoption of RFID technology.
The tag-reader cannot communicate effectively with a tag that is oriented
perpendicular to the reader antenna. As we can see this limits RFID usage to
applications such as ‘one scan identification’ of all products in a shopping basket.
This problem can be mitigated by using multiple readers oriented in many
directions. However, using multiple readers requires additional synchronization
and merging of results.
• Reader Coordination and Signal Processing
Most RFID readers are not designed to operate in the presence of another reader
that is also scanning for tags. Standards are needed to define a protocol to allow
these systems to share the available bandwidth. Further improvements can be
made when interpreting the tag signals received at the reader, intelligently
filtering out noise.
• Product Packaging Independence
RFID tag information can be disrupted by materials in the product it is
identifying. Since tags use RF circuits, it is possible to attenuate the signals if they
are placed next to products made of metals such as food cans.
• Multiple Standards
Because of cost trade-offs, national frequency use restrictions, and politics
multiple standards are used within countries and around the world.
• Data Formats
Although the data format returned by read-only tags is defined by standards, the
writable tags provide flash memory that customers can use in a proprietary way.
Standardizing this data format will facilitate inter-operability. An XML-based
format might be adopted for this purpose.
• Longer Range
In practice most of the lower-frequency RFID systems can read tags at a
maximum distance of about a meter. Reliable longer-range systems should
become possible and expand the usefulness of RFID in warehouses and other
• Lowering Manufacturing Costs
Lowering tag and system costs would likely further the adoption of RFID,
particularly for item-level tagging. Industry currently aims to bring down the cost
of a tag to 5 cents to enable large scale adoption for individual product tracking.
• RFID with sensor
RFIDs with sensors have several unique problems. First of all, packaging a
sensing material with a tag chip is difficult. Also, the sensors need to operate in a
condition in which it gets power only when the tag is being read.
• Privacy And Customer Pushback
As noted earlier in section 3, many consumers fear misuse of their personal
information, if the items they bought are tracked after its sale. If early adopters of
the technology do not address these issues successfully, they may well face
customer pushback and loss of sales.
To address these challenges, RFID stakeholders began to work with MIT and other
universities to create the Auto-ID Center in the late 1990s. Founding members included
several hardware and software component manufacturers, system integrators and a
number of product manufacturers and distribution chain participants. The overall goal
was to drive the adoption of RFID. In 2003, the administrative function of the center was
spun off into an organization called EPCGlobal, while the university research
components continued under Auto-ID Labs. EPCGlobal works towards the goal of
driving RFID adoption in several ways. Each targets one or more of the challenges
presented by the industry structure or specifics of the technology.
First and foremost, EPCGlobal establishes and promotes standards for the automatic
identification of items in the supply chain of any company, industry and country. EPC is
an acronym for “Electronic Product Code”. The EPC number is a compact numerical
naming convention to uniquely identify items in the supply chain. When an EPC-
compliant tag responds to an interrogator, it usually transmits its EPC number. Current
versions of the EPC contain either 64 or 96 bits, and store four pieces of information:
• A Header that identifies the format and version of this EPC
• A Manager Number to identify the company associated with the product
• An Object Class, identifying a product type unique to that company
• A Serial Number which uniquely identifies the item
The software standards serve to meet the supply chain coordination challenges. The
Physical Markup Language (PML) which is an XML standard offers a common
vocabulary for communicating information about items across the entire supply chain.
PML is extensible, meaning that additional attributes can be appended as needed. Object
Naming Service (ONS) provides for the translation of tag data into useable information
about the manufacturer and product. There are already many companies working with
RFID technologies and more are being added to this list every day. An important role of
the EPCGlobal consortium is to provide a single voice for the industry. The consortium
provides a forum for all the value chain actors to interact. EPCGlobal maintains a
relationship with the Auto-ID Labs at several universities worldwide. The labs conduct
research into various aspects of RFID systems, and continue to publish research. Through
this relationship, EPCGlobal can help shape the direction of research in order to address
obstacles adoption of RFID technology.
RFID technology can provide considerable value to industry and ultimately to the end
user. The technical challenges listed in section 5 may be overcome in the coming years
but the privacy concern will remain unless the industry makes a concerted effort to
alleviate it. Another major challenge is integrating the vast amount of data generated in
these readers with existing databases. The data generated is about individual products
whose product life-cycle is kept in the database. Since the data generated is of a spatio-
temporal nature, spatial database technologists can play a crucial role in mining that data
to give valuable information.
1. Eckfeldt, B., ., “What does RFID do for the consumer”, Communications of the
ACM, Vol 48 , No 9, pp 77-79, 2005
2. Landt, J., "The history of RFID", IEEE Potentials, Vol.24, no.4, pp. 8- 11, Oct-
3. Ohkubo, M., Suzuki, K., Kinoshita, S., “RFID privacy issues and technical
challenges”, Communications of the ACM, Vol 48 , No 9, pp 66-71, 2005
4. Sarma, S., “Integrating RFID”, ACM Queue, Vol 2, No 7, pp 50-57, 2004
5. Want, R., “The magic of RFID”, ACM Queue, Vol 2, No 7, pp 40-48, 2004
6. Want, R., "Enabling ubiquitous sensing with RFID," Computer , vol.37, no.4, pp.
84- 86, 2004
7. EPCGlobal Website, http://www.epcglobalinc.org/