RFID - F.A.Q
Automatic identification, or auto ID for short, is the broad term given to a host of technologies that are used to help machines identify objects. Auto identification is often coupled with automatic data capture. That is, companies want to identify items, capture information about them and somehow get the data into a computer without having employees type it in. The aim of most auto-ID systems is to increase efficiency, reduce data entry errors, and free up staff to perform more value-added functions, such as providing customer service. There are a host of technologies that fall under the auto-ID umbrella. These include bar codes, smart cards, voice recognition, some biometric technologies (retinal scans, for instance), optical character recognition, and radio frequency identification (RFID).
Radio frequency identification, or RFID, is a generic term for technologies that use radio waves to automatically identify people or objects. There are several methods of identification, but the most common is to store a serial number that identifies a person or object, and perhaps other information, on a microchip that is attached to an antenna (the chip and the antenna together are called an RFID transponder or an RFID tag). The antenna enables the chip to transmit the identification information to a reader. The reader converts the radio waves reflected back from the RFID tag into digital information that can then be passed on to computers that can make use of it.
The RFID system consists of an tag, which consists of a microchip ip with a coiled antenna, and an interrogator/reader with an antenna. The reader emits electromagnetic waves that form a magnetic field when they "couple" with the antenna on the RFID tag. A passive RFID tag powers the microchip's circuits by drawing the power from this magnetic field. The microchip then modulates the waves that the tag sends back to the reader and the reader converts the new waves into digital data.
RFID uses the low-end of the electromagnetic spectrum. The waves coming from readers are no more dangerous than the waves coming to your car radio.
RFID is not necessarily "better" than bar codes. The two are different technologies and have different applications, which sometimes overlap. The big difference between the two is bar codes are line-of-sight technology. That is, a scanner has to "see" the bar code to read it, which means people usually have to orient the bar code towards a scanner for it to be read. Radio frequency identification, by contrast, doesn’t require line of sight. RFID tags can be read as long as they are within range of a reader. Bar codes have other shortcomings as well. If a label is ripped, soiled or falls off, there is no way to scan the item. And standard bar codes identify only the manufacturer and product, not the unique item. The bar code on one milk carton is the same as every other, making it impossible to identify which one might pass its expiration date first.
Probably not. Bar codes are inexpensive and effective for certain tasks. It is likely that RFID and bar codes will coexist for many years.
RFID is a proven technology that's been around since at least the 1970s. Up to now, it's been too expensive and too limited to be practical for many commercial applications. But if tags can be made cheaply enough, they can solve many of the problems associated with bar codes. Radio waves travel through most non-metallic materials, so they can be embedded in packaging or encased in protective plastic for weather-proofing and greater durability. And tags have microchips that can store a unique serial number for every product manufactured around the world.
Many companies have invested in RFID systems to get the advantages they offer. These investments are usually made in closed-loop systems—that is, when a company is tracking goods that never leave its own control. That’s because all existing RFID systems use proprietary technology, which means that if company A puts an RFID tag on a product, it can’t be read by Company B unless they both use the same RFID system from the same vendor. But most companies don’t have closed-loop systems, and many of the benefits of tracking items come from tracking them as they move from one company to another and even one country to another.
Another problem is cost. RFID readers typically cost $1,000 or more. Companies would need thousands of readers to cover all their factories, warehouses and stores. RFID tags are also fairly expensive – 20 cents or more – which makes them impractical for identifying millions of items that cost only a few dollars (see below).
The Passive tags cost a magnitude less than Active tags. The Passive tags can cost as little as 30 cents or even less if bought in bulk Active tags - those with a battery - can cost far more. Some Active tags even come with temperature or pressure sensors built in, which cost more than $100
Just as your radio tunes in to different frequency to hear different channels, RFID tags and readers have to be tuned to the same frequency to communicate. RFID systems use many different frequencies, but generally the most common are low- (around 125 KHz), high- (13.56 MHz) and ultra-high frequency, or UHF (850-900 MHz). Microwave (2.45 GHz) is also used in some applications. Radio waves behave differently at different frequency, so you have to choose the right frequency for the right application
Different frequencies have different characteristics that make them more useful for different applications. For instance, low-frequency tags are cheaper than ultra high frequency (UHF) tags, use less power and are better able to penetrate non-metallic substances. They are ideal for scanning objects with high-water content, such as fruit, at close range. UHF frequencies typically offer better range and can transfer data faster. But they use more power and are less likely to pass through materials. And because they tend to be more "directed," they require a clear path between the tag and reader. UHF tags might be better for scanning boxes of goods as they pass through a bay door into a warehouse. It is probably best to work with a consultant, integrator or vendor that can help you choose the right frequency for your application.
Most countries have assigned the 125 kHz or 134 kHz area of the radio spectrum for low-frequency systems, and 13.56 MHz is used around the world for high-frequency systems. But UHF RFID systems have only been around since the mid-1990s and countries have not agreed on a single area of the UHF spectrum for RFID. Europe uses 868 MHz for UHF and the U.S. uses 915 MHz. Until recently, Japan did not allow any use of the UHF spectrum for RFID, but it is looking to open up the 960MHz area for RFID. Many other devices use the UHF spectrum, so it will take years for all governments to agree on a single UHF band for RFID. Government’s also regulate the power of the readers to limit interference with other devices. Some groups, such as the Global Commerce Initiative, are trying to encourage governments to agree on frequencies and output. Tag and reader makers are also trying to develop systems that can work at more than one frequency, to get around the problem.
No. Radio waves bounce off metal and are absorbed by water at ultra-high frequencies. That makes tracking metal products or those with high water content problematic, but good system design and engineering can overcome this shortcoming. Low- and high-frequency tags work better on products with water and metal. In fact, there are applications in which low-frequency RFID tags are actually embedded in metal auto parts to track them.
Active RFID tags have a battery, which is used to run the microchip's circuitry and to broadcast a signal to a reader (the way a cell phone transmits signals to a base station). Passive tags have no battery. Instead, they draw power from the reader, which sends out electromagnetic waves that induce a current in the tag's antenna. Semi-passive tags use a battery to run the chip's circuitry, but communicate by drawing power from the reader. Active and semi-passive tags are useful for tracking high-value goods that need to be scanned over long ranges, such as railway cars on a track, but they cost a dollar or more, making them too expensive to put on low-cost items. Companies are focusing on passive UHF tags, which cost under a 50 cents today in volumes of 1 million tags or more. Their read range isn't as far -- typically less than 20 feet vs. 100 feet or more for active tags -- but they are far less expensive than active tags and can be disposed of with the product packaging.
It depends on the vendor and the application, but typically a tag would carry no more than 2KB of data—enough to store some basic information about the item it is on. Companies are now looking at using a simple "license plate" tag that contains only a 96-bit serial number. The simple tags are cheaper to manufacture and are more useful for applications where the tag will be disposed of with the product packaging.
Microchips in RFID tags can be read-write or read-only. With read-write chips, you can add information to the tag or write over existing information when the tag is within range of a reader, or interrogator. Read-write tags usually have a serial number that can't be written over. Additional blocks of data can be used to store additional information about the items the tag is attached to. Some read-only microchips have information stored on them during the manufacturing process. The information on such chips can never been changed. Other tags can have a serial number written to it once and then that information can't be overwritten later.
One problem encountered with RFID is the signal from one reader can interfere with the signal from another where coverage overlaps. This is called reader collision. One way to avoid the problem is to use a technique called time division multiple access, or TDMA. In simple terms, the readers are instructed to read at different times, rather than both trying to read at the same time. This ensures that they don't interfere with each other. But it means any RFID tag in an area where two readers overlap will be read twice. So the system has to be set up so that if one reader reads a tag another reader does not read it again.
Another problem readers have is reading a lot of chips in the same field. Tag collision occurs when more than one chip reflects back a signal at the same time, confusing the reader. Different vendors have developed different systems for having the tags respond to the reader one at a time. Since they can be read in milliseconds, it appears that all the tags are being read simultaneously
The read range of passive tags (tags without batteries) depends on many factors: the frequency of operation, the power of the reader, interference from metal objects or other RF devices. In general, low-frequency tags are read from a foot or less. High frequency tags are read from about three feet and UHF tags are read from 10 to 20 feet. Where longer ranges are needed, such as for tracking railway cars, active tags use batteries to boost read ranges to 300 feet or more
Yes. International standards have been adopted for some very specific applications, such as tracking animals. Many other standards initiatives are under way. The International Organization for Standardization (ISO) is working on standards for tracking goods in the supply chain using high-frequency tags (ISO 18000-3) and ultra-high frequency tags (ISO 18000-6). EPCglobal, a joint venture set up to commercialize Electronic Product Code technologies, has its own standards process, which was used to create bar code standards. EPCglobal intends to submit EPC protocols to ISO so that they can become international standards.
There are many different RFID vendors with different areas of expertise. RFID Journal has compiled a searchable database and director of vendors around the world
RFID is used for everything from tracking cows and pets to triggering equipment down oil wells. It may sound trite, but the applications are limited only by people's imagination. The most common applications are tracking goods in the supply chain, reusable containers, high value tools and other assets, and parts moving to a manufacturing production line. RFID is also used for security (including controlling access to buildings and networks) and payment systems that let customers pay for items without using cash.
Yes. Some companies are combining RFID tags with sensors that detect and record temperature, movement, even radiation. One day, the same tags used to track items moving through the supply chain may also alert staff if they are not stored at the right temperature, if meat has gone bad, or even if someone has injected a biological agent into food.
Software agents are basically autonomous applications that automate decision making by establishing a set of rules. For instance, if X happens, do Y. They are important to RFID because humans will be overwhelmed by the amount of data coming from RFID tags and the speed at which it comes (real-time in many cases). So agents will likely be used to automate routine decisions and alert employees when a situation requires their attention. SAP and a company called BiosGroup are working on an automated replenishment system in which software agents would make decisions when trends indicate a product will be out of stock.
Most passive RFID tags simply reflect back waves from the reader. Energy harvesting is a technique in which energy from the reader is gathered by the tagged, stored momentarily and transmitted back at a different frequency. This method may improve the performance of passive RFID tags dramatically.