Radio Frequency Identification (RFID)
Connect802 can help with the selection and system design for many
manufacturer's equipment for RFID data backhaul as well as for
Wi-Fi RFID tagging and Real-Time Location Services.
If you have questions, please don't hesitate to call us today! We'll be happy to provide you with any technical explanation that you need to help you assure a successful wireless networking deployment.
RFID is a technology whereby "tags" replace conventional UPC bar codes as a way to identify a product in inventory, a fixed asset, or any other object by reading the tag with a radio signal. Wi-Fi enters the picture as a back-haul infrastructure for the RFID readers to use to communicate to a central database system.
A Brief Description of Radio Frequency Identification (RFID) Technology
In a nutshell, RFID works like this: A radio-sensitive "tag" is placed on an item. The tag could be concealed in an adhesive label, affixed to the shirt collar tag on an item of clothing, attached to the packaging for a product, or even injected under the skin of a dog or a cat (or a human - as is being offered by a sports club in Brazil to uniquely identify members!) When an RFID "reader" scans the tag a pulse of radio energy is sent out and the tag sends back the inventory control number. In its essence, RFID is "wireless UPC bar coding". But there's more...
While "read-only RFID tags" are simply read, "read-write RFID tags" can have their information content updated by the reader. This is being proposed by Toyota whereby they would place a read-write tag under the VIN number plate in 2005 vehicles and the complete maintenance history of the vehicle would be encoded on the tag.
Suffice it to say, there is a significant amount of discussion taking place regarding people's right to privacy and the potential for RFID technology to track a person's purchases, and even their physical location. The State of California passed a law in 2004 restricting the information content of an RFID tag to that of a static UPC bar code. While it's uncertain how far RFID technology will go towards documenting private information there's no question that the RFID tag will replace the UPC bar code over time. Some of the advantages of using Radio Frequency Identification are:
The ability to scan and identify an entire shopping cart full of merchandise without removing individual items.
The ability to locate a "lost" product in a warehouse or a "lost" piece of equipment on a corporate campus.
The ability to track a person's or vehicle's location inside a building when GPS (Global Positioning System) signals can't be received.
The ability to read tag information from up to 30-feet away without having to "scan" anything with a laser, the way a UPC bar code scanner is required to do today.
RFID Is Not a Wi-Fi Radio Standard
The key thing to remember, relative to Connect802, is that RFID is not a Wi-Fi technology. The radio standards for RFID are unrelated to those of 802.11 (although there is RFID specified in the 2.4 GHz band also used by 802.11b/g).
"If RFID isn't a Wi-Fi technology, why is being discussed in a 'Just the Facts' page?"
There's every reason to expect RFID tagging to completely replace the common UPC bar codes found on essentially every product sold in every retail store around the world. The RFID readers (referred to as "RFID interrogators") may be handheld, they may be mobile (attached, for example, to a fork lift in a warehouse), or they may be fixed (at a point-of-sale location, on a door frame for entry control, or on a warehouse loading dock door to track inventory as it enters and leaves the warehouse). Here's the key thought: The RFID readers must have a way to communicate back to the in-building network to send information to, and receive information from the central database system that understands what to do with the identification information read from the tags.
The communication link between the RFID reader and the in-building network is the 802.11 Wi-Fi network infrastructure. That's the link between RFID and Wi-Fi. It means that the Wi-Fi network will have to be designed to provide sufficient capacity and throughput and sufficient RF signal coverage, to support the use of whatever types of RFID readers are in use. In addition, the Wi-Fi network will probably be used for data communications, web browsing, email, and possibly wireless Voice-over-IP telephony. This is where Connect802 enters into the picture, providing RF design services through the Connect EZ Predictive RF CAD Design to make sure the Wi-Fi wireless LAN does its job supporting RFID, data, voice, and possibly even streaming video for security cameras.
To provide a perspective
on how RFID works you
are invited to read this
'Just the Facts' tutorial.
To build a Wi-Fi backhaul
network to support the
connection of RFID interrogators
/ readers to the in-building
or corporate campus network,
you're invited to call
Connect802 in California
at (925) 552-0802.
When you are considering
implementing an RFID
solution for vehicle
yard management, equipment
yard management, asset
tracking, reusable transport
item tracking, personnel
monitoring or as part
of your maintenance and
repair process you'll
need to involve a professional
RFID solutions provider.
Your solutions provider
will have the software
and RFID readers that
will collect tag data
and Connect802 will provide
the Wi-Fi wireless infrastructure
to carry that data back
to the central software
system. Companies like
Retail Anywhere provide
of Sale Software to give you the ability
to easily integrate an
RFID solution into your
current operating methods.
An Overview of RFID Technology
The Evolution of RFID Technology
Universal Product Code (UPC) barcode labels are inadequate for the sophisticated requirements of today's supply chain management systems. Barcodes may be extremely cheap, but their stumbling block is their low storage capacity and the fact that they cannot be reprogrammed. The technically optimal solution would be the storage of data in a silicon chip. The most common form of electronic data carrying device in use in everyday life is the chip card based upon a contact field (telephone chip card, bank cards). However, the mechanical contact used in the chip card is often impractical. A contactless transfer of data between the data carrying device and its reader is far more flexible. In the ideal case, the power required to operate the electronic data carrying device would also be transferred from the reader using contactless technology. Because of the procedures used for the transfer of power and data, contactless ID systems are called RFID systems (Radio Frequency Identification).
RFID (Radio Frequency Identification) is used in all areas of automatic data capture allowing contactless identification of objects using RF. With applications ranging from secure internet payment systems to industrial automation and access control, RFID technology solutions are receiving much attention in the research and development departments of large corporations. RFID is a major growth are in auto ID, allowing emergency vehicles to safely trip traffic signals, and providing the technology behind contactless smart cards, "autopiloting" cars, and production automation.
The RFID Transponder / Interrogator System
An RFID system contains two basic components:
The RFID transponder (referred to as a "tag") located on the object to be identified
The RFID interrogator / detector (referred to as a "reader" or "scanner") which sends pulses of RF energy to activate the tag, and then read the resulting response from the tag
A reader typically contains a high frequency module (transmitter and receiver), a control unit and a coupling element to the transponder. In addition, 802.11 Wi-Fi radios are often included with the reader to allow communication to a central database or control software system.
The transponder, which represents the actual data carrying device of an RFID system, normally consists of a coupling element and an electronic microchip. When the transponder, which does not usually possess its own voltage supply (battery), is not within the response range of a reader it is totally passive. The transponder is only activated when it is within the response range of a reader. The power required to activate the transponder is supplied to the transponder through the coupling unit (contactless) in the form of a timing pulse and data.
Passive and Active RFID Tags
There are two basic designs for RFID tags: passive tags and active tags. Passive tags obtain power from the interrogation pulse from the reader. They use this power to send back their information message. Because they have no battery they essentially last forever and can't wear out. A passive RFID tag is very little more than a loop of antenna with the most basic circuitry. Active tags have a battery. Because of this they are able to respond with a signal that can travel perhaps as much as 50-feet or more to a remote reader.
Tag and Reader Coupling and Data Transfer
There are two basic methods for acquiring information from the RFID tag: inductive coupling and backscatter coupling. Inductively coupled transponders are almost always operated passively. This means that all the energy needed for the operation of the microchip has to be provided by the reader. For this purpose, the reader's antenna coil generates a strong, high frequency electro-magnetic field, which penetrates the cross-section of the coil area and the area around the coil. Because the wavelength of the frequency range used (< 135 kHz: 2400 m, 13.56 MHz: 22.1 m) is several times greater than the distance between the reader's antenna and the transponder, the electro-magnetic field may be treated as a simple magnetic alternating field with regard to the distance between transponder and antenna. In the language of electromagnetic wave theory we refer to this as "near field coupling".
Near-field coupling is the electromagnetic effect that occurs within roughly 1-wavelength of a radiating element. In the near-field the energy field fluctuates outward from the radiating element, and then back in to the radiating element in a "push - pull" manner. Beyond the near-field the electromagnetic energy simply radiates outwards (never "back in") and the power drops off based on the inverse-square law ("twice as far away = 1/4 as powerful"). Consequently, the RFID reader and the tag become part of a bi-directional electromagnetic system in which energy can be exchanged and, thereby, information can be exchanged.
Inductive Coupling in the Near-Field
A small part of the emitted field penetrates the antenna coil of the transponder, which is some distance away from the coil of the reader. By induction, a voltage is generated in the transponder's antenna coil. This voltage is rectified and serves as the power supply for the data carrying device (microchip). A capacitor is connected in parallel with the reader's antenna coil, the capacitance of which is selected such that it combines with the coil inductance of the antenna coil to form a parallel resonant circuit, with a resonant frequency that corresponds with the transmission frequency of the reader. Very high currents are generated in the antenna coil of the reader by resonance step-up in the parallel resonant circuit, which can be used to generate the required field strengths for the operation of the remote transponder.
Inductively coupled systems are based upon a transformer-type coupling between the primary coil in the reader and the secondary coil in the transponder. This is true when the distance between the coils does not exceed 0.16 wavelength , so that the transponder is located in the near field of the transmitter antenna
Backscatter Coupling in the Far-Field
Outside the radius of the near-field the interrogation pulse from the reader propagates outwards, never giving energy back to the radiating element. This RF signal travels outwards and encounters the antenna element in the tag. We know from the field of RADAR technology that electromagnetic waves are reflected by objects with dimensions greater than around half the wavelength of the wave. The efficiency with which an object reflects electromagnetic waves is described by its reflection cross-section. Objects that are in resonance with the wave front that hits them, as is the case for antenna at the appropriate frequency for example, have a particularly large reflection cross-section.
An electromagnetic field propagates outwards from from the reader's antenna and a small proportion of that field (reduced by free space attenuation) reaches the transponder's antenna. The power is supplied to the antenna connections as HF voltage and after rectification by diodes this can be used as turn on voltage for the deactivation or activation of the power saving "power-down" mode. The voltage obtained may also be sufficient to serve as a power supply for short ranges.
A proportion of the incoming RF energy is reflected by the antenna and reradiated outwards. The reflection characteristics (= reflection cross-section) of the antenna can be influenced by altering the load connected to the antenna. In order to transmit data from the transponder to the reader, a load resistor connected in parallel with the antenna is switched on and off in time with the data stream to be transmitted. The strength of the signal reflected from the transponder can thus be modulated (a technique referred to as modulated backscatter).
The signal from the transponder is radiated into free space. A small proportion of this signal is picked up by the reader's antenna. The reflected signal therefore travels into the antenna connection of the reader in the "backwards direction" and can be decoupled using a directional coupler and transferred to the receiver input of a reader. The "forward" signal of the transmitter, which is stronger by powers of ten, is to a large degree suppressed by the directional coupler.
Avoiding Interference in RFID Systems
The need to exercise care with regard to other radio services significantly restricts the range of suitable operating frequencies available to an RFID system. For this reason, it is usually only possible to use frequency ranges that have been reserved specifically for industrial, scientific or medical applications or for short range devices. These are the frequencies classified worldwide as ISM frequency ranges (Industrial-Scientific-Medical) or SRD frequency ranges, and they can also be used for RFID applications.
Frequency ranges for RFID-Systems
Frequency Band, Coupling, and Applications
Allowed field strength / transmission power
< 135 kHz
low frequency, inductive coupling
6.765 .. 6.795 MHz
medium frequency (ISM), inductive coupling
7.400 .. 8.800 MHz
medium frequency, used for EAS (electronic article surveillance) only
13.553 .. 13.567 MHz
medium frequency (13.56 MHz, ISM), inductive coupling, wide spread usage for contactless smartcards (ISO 14443, MIFARE, LEGIC, ..)., smartlabels (ISO 15693, Tag-It, I-Code, ..). and item management (ISO 18000-3).
26.957 .. 27.283 MHz
medium frequency (ISM), inductive coupling, special applications only
UHF (ISM), backscatter coupling, rarely used for RFID
10 .. 100 mW
868 .. 870 MHz
UHF (SRD), backscatter coupling, new frequency, systems under development
500 mW, Europe only
902 .. 928 MHz
UHF (SRD), backscatter coupling, several systems
4 W - spread spectrum, USA/Canada only
2.400 .. 2.483 GHz
SHF (ISM), backscatter coupling, several systems, (vehicle identification: 2.446 .. 2.454 GHz) Potential for 802.11b/g interference
4 W - spread spectrum, USA/Canada only,
500 mW, Europe
5.725 .. 5.875 GHz
SHF (ISM), backscatter coupling, rarely used for RFID. Potential for 802.11a and WiMAX 802.16 interference
4 W USA/Canada,
500 mW Europe
An RFID tag (and the associated reader) work in accordance with the rules of some particular air interface. Essentially an air interface corresponds to a row in the table above. It's the set of physical rules that define how the electromagnetic signals will work and how they'll convey bits. Standards must also specify the way data is structured and the way to represent a unique tag ID.
A tag reader transmits an interrogation pulse. Will the tag respond and, if it does, will the data structure for the information being conveyed be consistent with what's expected by the reader? The goal of the various RFID standards organizations is to make it possible for tags and readers to work together properly. As it turns out, there are different priorities for different types of RFID adopters and different standards have evolved for these groups.
JTC 1/SC 31: Automatic Identification and Data Collection Techniques ("Where's the lost child at the amusement park?")
(ISO = "International Standards Organization", JTC = "Joint Technical Committee"; a sub-group within the ISO)
Definitions and descriptions of Radio Frequency Identification (RFID) that you might find on the web:
A typical RFID system consists of a tag, a reader, and some sort of data processing equipment, such as a computer. The reader sends a request for identification information to the tag. The tag responds with the respective information, which the reader then forwards to the data processing device. The tag and reader communicate with one another over an RF channel. In some systems, the link between the reader and the computer is wireless.
Radio Frequency Identification; a type of electronic identification that uses radio frequency signals to read on-vehicle tags for AVI and AVC.
Radio frequency identification (ID). RFID tags are small integrated circuits connected to an antenna, which can respond to an interrogating RF signal with simple identifying information, or with more complex signals depending on the size of the IC.
Refers to the technology that uses devices attached to objects that transmit data to an RFID receiver. These devices can be large pieces of hardware the size of a small book like those attached to ocean containers or very small devices inserted into a label on a package. RFID has advantages over bar codes such as the ability to hold more data, the ability to change the stored data as processing occurs, does not require line-of-sight to transfer data and is very effective in harsh environments where bar code labels won't work.
A method for uniquely identifying an object using a tag or module that carries a unique ID number, or code. Identification can be made using wireless (RF, or radio-wave) connection, meaning no line-of-sight or physical contact is needed.
An alternative to bar coding. Advantages include data capacity, read/write capability, and no line-of-sight requirements.
Radio frequency identification tags (RFID) are the successor to the Universal Product Code -- that row of lines that grocery scanners read. An RFID tag is a small silicon chip with a small antenna. The tag responds to the energy given off by an RFID-tag reader with a signal.
RFID tags do not require a line of sight to scan items, and they can identify each item individually, rather than generically. This means that goods in warehouses, in trucks, and on trains can be tracked more easily and more intelligently. Manufacturers can learn in near-real time when and where their goods have been sold. Pharmacists can make sure that expired drugs go into the trash, not into patients.
RFID will squeeze inefficiency out of the systems that deliver consumer goods, bringing us more of what we want and need, at lower prices, with higher quality and better safety.
NCITS 256 defines a standard for Radio Frequency Identification (RFID) for use in item management. This standard is intended to allow for compatibility and to encourage interoperability of products for the growing RFID market in the United States. Because the U.S. Federal Communications Commission (FCC) regulations do not restrict physical configuration options, this is an enabling standard that supports and promotes several RFID implementations without making conclusions about the relative technical merits of any available option for any possible application.
The Air Interface Standards of ISO/IEC JTC 1/SC 31 are contained in the various Parts of ISO/IEC 18000, Radio-frequency Identification Standard for Item Management -- Air Interface. These are:
Part 1, Generic Parameters for Air Interface Communication for Globally Accepted Frequencies
Part 2, Parameters for Air Interface Communication below 135 kHz.
Part 3, Parameters for Air Interface Communication at 13.56 MHz.
Part 4, Parameters for Air Interface Communication at 2.45 GHz.
Part 5, Parameters for Air Interface Communication at 5.8 GHz.
Part 6, Parameters for Air Interface Communication - UHF Frequency Band
Each of these frequencies have differing operating parameters, and performance considering antenna design, power levels and other parameter are held comparable, including the active/passive nature of the tag. Different RFID technologies within the different parts or frequencies may result in different performance and parameter trade-offs. This may cover the redundancy or reliability to operate as intended under adverse environmental conditions such as noise or interference or other physical environment variations.