Once again about RFID

In the last post, an overview article was published concerning proximity technology and its use in everyday life. Today we will continue this topic, dedicating the main part of the conversation to the international system of product identification GTAG.
Terminology
In the last article, we mainly used the term proximity. In a broader sense and given the many new applications, the term RFID - Radio Frequency IDentification is becoming more and more common, which literally translates as "radio frequency identification." This term is more correct, as with the increase in the reading range of contactless tags, the meaning of the word proximity (close) begins to lose its original meaning.
The term GTAG is completely familiar only to specialists. It is derived from the phrase Global TAG, which can be translated as a “global label.” Why global? Because specialists of the whole world work on this standard, and this standard is proposed not as European or American, but as a global one. The main provisions of the standard have already been developed, the element base has been developed and the implementation of this technology has begun.


GTAG vs. Barcodes
Bar coding has long been part of our daily lives. We are used to the fact that in the supermarket the basket we typed is quickly driven through the checkout due to the bar codes on the goods. Bar coding is used in tickets to stadiums and cinemas, for marking goods, components for production, and so on. At a certain level of development of technology, this has become a panacea for many ills. But the progress is inexorably moving, and today the technology of bar codes is not satisfied in many respects, and RFID technology begins to crowd out it.
Look at table 1 in order to understand that the new technology has much more advantages than disadvantages! The main disadvantage is the price, but the mass application and improvement of production will quite quickly reduce this difference at times.
Pay attention to the first row in the table. The ability to work simultaneously with dozens of tags - this is not provided by any other identification system. For example, you can put on the table under which the reader is installed, a pack of books and magazines along with your reader's ticket, which also implanted a RFID tag. Within seconds, information will be read and written to the library database. How does this work? Let's try to figure it out.

Anti-collision mechanism
In the last article, we talked about the principle of operation of a simple proximity reader, used in most access control systems. RFID tag readers with rewrite capability and anti-collision mechanism are a bit more complicated. Compare Figure 1 below and the corresponding figure in the previous issue of the journal.
If the simplest proximity reader continuously radiates energy, and the card in its field also responds continuously with its code, then overwriting identifiers use a more complex interactive mode, that is, the reader can transmit a command by modulating the radiated energy. The list of commands, as a rule, includes commands like “transfer factory number”, “transfer byte from memory with address X”, “write byte into memory at address Y”, “go into silence mode”. It is the last command that is used to resolve conflicts when there are several tags in the field of the reader simultaneously.

Figure 1. Tag-reader dialog
To implement the tag-reader interactive mode of operation, a modulator appears in the reader that controls the flow of energy emitted by the reader. A decoder and a modulator control circuit are added to the label respectively.
There are several anti-collision algorithms; each has its own advantages and disadvantages in such parameters as the recognition time for a given number of tags, the complexity of implementation, and so on. The easiest-to-implement algorithm, called “free running,” is illustrated in Figure 2a. It is based on the fact that all tags generate responses at random intervals, due to which there will always come a moment when only one tag answers the reader.
At times T1, T3 and T6 there is an overlay of responses from marks 1 and 3, 1 and 2, 2 and 3, respectively. The reader determines this by the fact that due to the imposition of signals, the checksums of the responses of the tags do not converge. At times T2, T4 and T5, there are no collisions, and the reader identifies the tags in the following order: label 2, label 3, label 1. By the time T6, all three tags are read.

Figure 2. Anticollision Algorithms
Figure 2b shows the dialogue algorithm “switch off”. It is based on the principle that a “turn off” command is sent to the tag that has already been read, which is executed by the tag until the power fails (that is, until the tag is removed from the reader's field). From figure 2b it can be seen that the collision, in contrast to figure 2a, takes place only at time T1. Then label 2 is read, the command “turn off” is sent to it, and at times T3 and T6 it is no longer a source of collisions. At time T3, label 1 is read, a shutdown command is also sent to it, and the last one is read at time T4, label 3.
As can be seen from the figure, “switch off” works faster than “free running”, because over time there are fewer and fewer tags left in the field of the reader. The great advantage of the “switch off” algorithm is that, under certain conditions, we can even count tags with the same code. The intermediate position between “free running” and “switch off” is occupied by the “slow down” algorithm, in which the tags are not turned off from the poll, but transferred to the mode of rarer answers.
There is also a group of so-called fast (or accelerated) algorithms providing for turning off unnecessary tags before the end of the adoption of a code from one of the tags, but we will not make the presentation more difficult with technical details. Just below we give the dependence of the read time of a given number of identifiers for different anticollision algorithms (Figure 3).

Figure 3. The effectiveness of anti-collision algorithms
Global accounting and control = GTAG
So, the GTAG project. The International Product Numbering Association of EAN International and the Council on the Uniform Code of the USA and Canada Uniform Code Council, Inc. actively participate in its development. (UCC) - leading organizations in the field of automatic identification. Today, the basic standard is ISO 15693, which defines the interface between the reader and the tag. Compliance with this standard will allow different manufacturers of tags and readers to ensure the mutual compatibility of products, which in itself is a powerful incentive for the wide dissemination of technology.
Now GTAG has three frequency bands: traditional 13.56 MHz, 860-930 MHz and 2.45 GHz. Note that the range of 125 kHz for future applications is no longer considered due to the low exchange rate, which does not ensure the transfer of large amounts of information in a short time. Figure 4 shows why it is supposed to use not one, but just three frequency ranges. Each of them in certain conditions has its own advantages and disadvantages over the others.

Figure 4. RFID system parameters versus frequency
Instead of an abstract listing of possible areas of application, we will talk today about some of the projects already implemented, based on RFID tags.
Users of the Italian postal system can expect significant improvements in the speed and accuracy of the delivery of correspondence through the use of RFID technology - I-Code tags that mark mail bags. When sorting mail on the conveyor, everything happens automatically in real time due to the fact that reading tags occurs almost instantaneously with any orientation of the bags, even if the tags are located inside the bag with the mail.
The system, called FastTrack, is one of the first large projects in the field of correspondence delivery based on RFID technology.
The new largest library in Singapore, Woodland, opened in April 2001, uses RFID tags to identify its more than half a million books, tapes and CD stock. The ELiMS ™ (Electronic Library Management System) system developed by ST LogiTrack allows you to keep on-line records of all publications from the library collection, search them on racks using hand readers, instantly issue and receive publications, because using RFID technology you can read simultaneously up to 30 tags per second. At the same time, RFID tags serve security purposes. This system will “allow” to take out books or CDs taken for use, but will not allow other editions, paintings and other items to be taken out.
Moreover, automated points of delivery of the received literature or tapes, located at the metro stations, provide reception and write-off of the received publications from the subscriber without calling the library.
RFID tags are revolutionizing the baggage handling technology of air passengers. The world's first large-scale experimental system of such a plan since the end of last year has been tested by British Airways on flights flying from Heathrow to Munich and Manchester.
Each piece of baggage is marked similar to the paper tag used today, in which there is a crystal and an RFID tag antenna between the paper layers. Since the contents of the tag are reprogrammed over the radio channel, all the necessary information is entered into it - the flight number, departure date, additional information about the passenger. If necessary, additional information (for example, on transit flights) is also entered on the fly. Baggage is sorted on the conveyor automatically, which speeds up the process and completely eliminates errors.
Given the annual growth in air travel by 6%, the use of a new technology is the only solution to speeding up processes and increasing the reliability of baggage handling. In addition, for safety purposes, RFID technology, used simultaneously in airline tickets, allows for the shortest possible time to determine the correspondence between the passengers who arrived on board and the luggage loaded onto the aircraft.
In April of this year in Germany, all small vessels began to equip RFID tags. Of the 660,000 operated boats and yachts, only 560,000 are registered and insured, the remaining 100,000 are operated without registration. The old registration system (inscription on board the ship) is not very reliable because it can be easily forged. In addition, she herself does not carry information about the state of the vessel, its owner, and so on.
Implantation of RFID tags into the design of a boat or yacht allows the police, using a hand-held reader, not only to identify the vessel, but also to obtain additional information about its condition and owner, and it is almost impossible to fake such a tag.
In the spring of 2002, the largest German manufacturer of wooden doors, Nickel, introduced a system for automating the production, storage and shipment of products using I-Code tags. Technical solutions are developed and implemented by the company MOBA, specializing in the field of identification.
Before the introduction of I-Code, stickers with a barcode were used in the production process, which were erased, torn off and scratched during the production process, which made it impossible to use them. Remotely implanted RFID tags that are implanted at the initial stage of production into the door cavity are not affected by these factors and ensure the 100% reliability of the automated control system.
The Museum of Fine Arts in Rotterdam, a collection of which includes paintings by Rembrandt, Renoir, Picasso and other famous masters, in April 2002 introduced a system for marking all canvases using technology-based labels.
I-code. At the same time, the museum staff solved several problems at once:
authentic identification of works of art, performed by a hidden method;
protection against theft, since the picture protected by the label, even when hidden, will be detected when attempting to carry out;
simplicity of work with the fund, since the selection of the necessary pictures from the vaults, for example, to be sent to exhibitions, is easily automated.
The system was designed and installed by HELICON Conservation Support b.v.
Reports of new and new applications of RFID technology in various large projects appear regularly.
Instead of conclusion
The RFID theme is limitless. For those who want to get more detailed information on the state of the RFID market, it is recommended that you familiarize yourself with the selection of materials from the id.Magazine electronic magazine http://www.idpress.ru. Experts will find enough information on the site of the leader in the production of components of RFID systems - Philips Semicondactors (http://www.semiconductors.philips.com/markets/identification). Also, interesting materials can be found on the website of Russian companies MicroEM http://www.microem.ru and the NKT Group of Companies http://www.smartcard.ru/rfid.