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Cellular Networking Perspectives

David Crowe’s Wireless Telecom Magazine Articles

Q1’2004 Issue

Radio Frequency Identification (RFID): Tag, You’re It!

Radio Frequency Identification (RFID) uses radio waves to communicate the identity of a tagged book, lab coat, Dalmatian, DVD, license plate, speed-skater, gas cylinder, crate of toothpaste, microwave oven or even a VIP customer at a nightclub. RFID covers a wide range of capabilities, with major differences in the speed of reading, distance at which tags can be read, amount of data that can be stored and the ability to update information in the tag. There are many different, mainly proprietary, RFID systems, often with little more in common than that the tag is cheap, and communicates using radio waves.

RFID provides a more sophisticated alternative to older methods of identification, even though it is often more expensive than the tags it replaces. RFID benefits are seen through greater efficiency in the organization, savings in labour costs, and reductions in the error rate.

Applications

In an industrial laundry, RFID tags help separate cleaned laundry by client, reducing person-power requirements. Because the tags can be embedded in each garment, they are more robust than bar codes. The extra costs of the tags can quickly be recouped in a few washings.

In a public library, RFID replaces not only the bar code, but also the anti-theft strip. RFID tags can be attached to racers at athletic events, providing for automated and more accurate timing. ‘Smart shelves’ at a grocery or department store contain an RFID reader that, by regular scanning, can determine when products are placed on the shelf, and when it they are removed. This can help reduce loss through theft and make restocking more efficient.

Shipments of goods may be placed on pallets that while away their time reading the RFID information of all the goods placed on them. At a later time, they will communicate that information, which can be used to inform the manufacturer, purchaser and the shipping company of the progress of the goods.

There are many vehicular applications for RFID. License plates can be made fraud resistant by embedding an RFID tag. Other tags can be used to simplify processing by frequent users of automated toll highways (such as Highway 407), bridges (such as the Confederation bridge) and border crossings. RFID tags built into cars can provide a more tamper-resistant identity than a stamped metal vehicle identification number. Gasoline can be paid for with an RFID fob at some gas stations, such as Esso’s Speedpass.

People may even be tracked by RFID under special circumstances. Prisoners under house arrest may be monitored by an RFID reader that will generate an alarm if the tag leaves a defined area (presumably still attached to the convict). Employee tags can be RFID, as this technology eases the opening of doors in a facility, but also ensures that high security areas are not breached by unauthorized employees.

Many Canadians already have a ‘microchip’ inserted into their pet, in case it becomes lost. This is an RFID device. The pound can then identify a lost pet, contact a company that maintains a database of pet identification numbers, and then hopefully reunite Flossie with Aunt Bessie. Cows may be tagged due to the Mad Cow scare, to enable more efficient tracking and identification. A posh nightclub in Barcelona, Spain, is allowing its best patrons to pay for admission or drinks by just a wave of their hand, when the hand contains an RFID implant.

RFID Types

At their simplest, ‘passive’ RFID tags are powered by induction due to a magnet in the ‘antenna’ of an RFID reader. The motion of the magnetic field as the reader is waved past the tag induces an electrical current, which powers the tiny logic circuit in the tag, which then emits a radio signal containing the identification number, a string of from 32 to 128 bits. Radio transmission is usually in the 100-500 KHz range, and the tags can only be read with the reader a few inches away.

More sophisticated ‘active’ tags are more expensive, but can overcome many of the limitations of passive tags. They often have a built in battery, and can receive a command over the radio link, as well as use it to transmit. These systems usually operate in the 850-950 MHz or 2.4-5.8 GHz range. They can store significantly larger amounts of data – up to megabytes worth in some cases – can transmit it much faster, and sometimes can receive commands to update their memory as well.

Active RFID tags can be read individually by transmitting their identification number, plus a command. However, this is only useful when you know the number of the tag. What is sometimes more useful is to read multiple tags without knowing the ID of any of them. This is often done with a ‘tree-walking’ algorithm. The reader will transmit a short prefix and all tags that match will respond. It will then add one more bit to the prefix, which splits the group of tags into two. Eventually it will address an individual tag. This allows efficient reading of a group of tags with unknown ids. For example, if there were two tags with 4-bit codes of 0110 and 0001, the reader would first transmit a “1” and get no response, then a “0” and get multiple responses, then “01” and get only a single response. Knowing that more tags still remain unread (because of the multiple responses when the first bit was set to 0), the reader will broadcast “00” and get a single response from 0001. Now it knows that all tags have been read with four read/write cycles, even though there are 16 possible combinations of four-bit identification numbers. With identification numbers that are 32 bits or longer, the savings are exponentially larger.

Current Directions

RFID got a boost recently when both Wal-Mart and the U.S. Department of Defence indicated that they would require all products they purchase to be tagged. Their dream, and that of many other companies, is for the RFID tag to be read at various places from the manufacturing plant, trans-shipping operations, warehouses and at the retail store until finally being deactivated at checkout. This will give unprecedented visibility along the supply chain.

Microsoft is heavily involved, an indication that RFID is about to hit the big time. They announced the formation of the Microsoft Radio Frequency Identification Council in April 2004. They are not alone. Competitors such as Oracle and IBM have their own plans to support networks and software for RFID.

There are a number of challenges to this dream, however. One is that the use of a common tag for many products can require the integration of a company’s databases, and often that is a more significant undertaking than expected. It will require companies to exchange more information, requiring more sophisticated and secure inter-working. Standardization has been the bane of RFID. According to AIM, the Association for Automatic Identification and Mobility, a trade association for RFID vendors, “The lack of open systems’ interchangeability has severely crippled RFID industry growth as a whole, and the resultant technology price reductions that come with broad-based inter-industry use.”

There has been some progress. ISO standards 11784/11785 have been developed for the identification of animals, and ANSI X3T6 has written a standard for 2.45 GHz RFID tag operation. Canada is now getting into the act, with a new standardization effort known as JTC1/SC31 for the “Automatic identification and data capture techniques,” which was kicked off with a call for company participation in December, 2003.

Privacy and Security

One of the biggest challenges to RFID, especially in the retail chain, is the customer perception that these tags will be used to track them. Companies had best deal with the perception before it becomes an enforced reality. The U.S. Federal Trade Commission held a workshop in June 2004 and is inviting further comments, particularly on issues of security and privacy.

The tracking abilities of RFID are not great, due to the limited range of most readers. Wal-Mart claims that its tags can be read from no more than 15 feet away and Esso’s Speedpass tags are readable from only up to a few inches. Because of this, and incompatibilities between proprietary tag types, it would be difficult for an unscrupulous company to keep a database of products that were sold, and then surreptitiously monitor people as they walked by their store. This would violate any number of privacy laws and gather information of questionable quality. However, consumers may still be nervous, so the easiest way to deal with the perception is to provide a mechanism to remove or completely disable the RFID device at checkout, and to make sure that the devices are clearly visible on products that do still have them on when they leave the store.

Another misperception is that every item will be tagged with RFID when, often, it is only pallets and boxes that are tagged. This is true for the Wal-Mart initiative, for example. When the consumer purchases an individual item, it might not be tagged, especially if its cost is relatively small, because the expense of tracking such low cost items is simply too great.

RSA, the well known security company, has proposed a device that jams RFID readers by responding to every request with a partial identification. This would mean, for example, that four billion operations would be required to read 32-bit tags, even if only 3 of them were in the vicinity. The blocker merely responds affirmatively to every request with an identification prefix, forcing the reader to search every branch of the tree.

Privacy concerns may put the brakes on thoughts of using one tag for multiple purposes. A single tag on a vehicle to replace the license plate, vehicle identification number and automated toll gates could easily be misused, especially if the multiple databases containing the tag’s id number were interconnected, or all accessible by the same organization. Even stand-alone databases must be protected from intrusion, with accesses logged so that unauthorized use by insiders can be tracked down.

Price, Price, Price

Tags seem quite cheap, often being in the 50 cent range (although prices go much higher for more sophisticated tags), but the industry’s goal is to produce a simple tag for 5 cents. At this price it would be feasible to embed tags in just about any consumer product. The “RFID Journal” has estimated that manufacturing volumes and technological advances will allow this price point to be met in 2007. That is 5 US cents, but perhaps by 2007, it will be the same as 5 Canadian cents.

Companies that use RFID are going to have to devote resources to defuse privacy and security concerns. If consumers start to believe, for example, that US $20 bills contain secret RFID chips, because of a story published on a website, despite the impossibility of concealing them, they will have no trouble believing that every product they purchase from a company that uses RFID will contain such tags, and that the main purpose is to track them. Any attempt at secrecy will only be interpreted as having something to hide. It is better to provide simple, factual information, so that the sting can be taken out of rumors that will inevitably circulate as this technology suffuses through retail industries.

RFID tags are not pie in the sky. They are already all around us. In the future there will be many more of them, in just about everything we purchase except, I hope, in fresh fruit and vegetables. Standardization will occur gradually, as large organizations mandate compatibility for all their vendors. Smaller organizations will find that taking advantage of the cheaper, mass-produced tags will be more cost-effective, leading to a gradual reduction in the number of tags that perform essentially the same function. There will never be a day when one RFID tag does everything, simply because the range of applications and environments is too great.

About the Author

David Crowe is a wireless standards and technology consultant based in Calgary. He can be reached at David.Crowe@cnp-wireless.com.