Read only and read-write RFID tags

RFID tags may be able to either perform as a read only RFID tag, or they may be a read-write Radio Frequency Identification tag. In view of the cost of manufacturing different types against the quantities made and the differences between the two, most RFID tags today are the read-write variety, and for applications where only a read function is required, the write ability is not used.

Read only radio frequency identification tags are typically programmed either in the factory. Data included will be a unique identifier and other specified data that cannot be changed.

Read-write RFID tags normally contain an area where data cannot be altered – this is often a segregated secure read-only area in the memory. Again this will include a unique identifier, and other data that may be required. The writeable area can then be used to contain data that may be required. For example if the RFID tag is used with a container, it can contain details of the container contents, etc. This area of memory within the RFID tag can be re-written many times.

RFID backscatter coupling

RFID backscatter coupling or RFID backscattering uses the RF power transmitter by the tag reader to energise the tag. Essentially they “reflect” back some of the power transmitted by the reader, but change some of the properties, and in this way send back information to the reader.

Using RFID backscatter or RFID backscattering, some tags achieve their data transmission by changing the properties of the tags themselves, while others switch a load resistor in and out of the antenna circuit.

RFID backscatter coupling operates outside the near field region, and the radio signal propagates away from the RFID reader. When the signal reaches the RFID tag, this interacts with the ingoing signal and some energy is reflected back towards the RFID reader. The way in which the signal is reflected back depends upon the properties of the tag (or any other object for that matter). Factors such as the cross sectional area, and the antenna properties etc within the tag all have an effect. In particular the antenna will pick-up and re-radiate energy, and the way this energy is re-radiated is dependent upon the antenna properties – by changing factors such as adding or subtracting a load resistor across the antenna, the re-radiated signal properties can be changed.

Over short ranges, the amount of power reaching the tag from the reader is sufficient to allow operation of small low current circuits within the tag. This can be used to drive an electronic switch, e.g. a FET that can switch an antenna load resistor in and out of circuit. This will effectively modulate the returned signal and allow data to be passed back to the reader.

In order to allow transmission and reception of a signal at the same time, a directional coupler is often used to allow the received signal to be separated from the transmitted on. Additionally the reader must be able to detect the modulation in the presence of a host of other reflections, although these will normally be stable and not modulated in any way.

Active RFID

The original tags that were used in the shopping electronic surveillance tags was purely passive – the next step in the RFID history was to develop active tags.

As happens in the development of technology, several people were working on similar types of development around the same time, each with their own approach or result. In one development a US patent was granted for an active RFID tag with a rewritable memory in January 1973.

Also in the 1970s the Los Alamos National Laboratories started to develop a system to track the transportation of nuclear materials securely and safely. The system included a variety of readers and transponders attached to the vehicles carrying the materials. These would then enable the truck to be identified at various points along its route.

In another development in the RFID history, again at Los Alamos, but in the agricultural department needed to devise a system that would allow individual cows to be identified. A system was devised that enabled a passive transponder was injected under the skin of the cow. The RFID was based at a frequency of around 125 kHz transponder drew power from the reader, reflecting back a “backscatter” signal that was modulated with the cow identification information.

While the low frequencies of 125 kHz were initially used, systems around the 13.56 MHz license free frequencies were also developed. The use of the higher frequency allowed for higher data rates and longer ranges to be achieved.

UHF RFID history

While RFID had previously been focussed on lower frequencies where the technology was cheaper, the advantages of the UHF frequency spectrum started to be employed in the early 1990s. Experiments were undertaken by IBM who then trialled them with Wal-mart. However the technology was sold on to Internec and they were able to commercialise the technology.

The main drawback to large scale commercialisation was the lack of standards. Several processes started to come together to ensure proper standardisation that would allow the grown and widespread use of RFID.

In 1999 a number of organisations set up the Auto-ID Center at the Massachusetts Institute of Technology. This enabled common standards to be set up.

Also the International Standards Organisation, ISO introduced standards for the different elements of RFID from tags to readers and writers, etc.

Another milestone in RFID history occurred when suppliers started to take RFID seriously and in January 2005, Wal-Mart required its top 100 suppliers to apply RFID labels to all shipments.

The history of RFID has shown a steady development in RFID technology. Having its routes in the earliest days of electrical science and then radio, RFID history has come out of developments such as radar and IFF. Now RFID is a technology in its own right which is widely used and showing massive benefits to industry and society as a whole.


Using NFC data is exchanged by two inductively coupled coils — one per appliance — generating an magnetic field with a frequency of 13.56 MHz. The field is modulated to facilitate data transfers. For the communication one device acts as the initiator (starting the communication) whereas the other device operates in target mode (waiting for the initiator). Thus not more than two devices can be evolved in the communication.
The rolls of the devices — initiator and target — are assigned automatically during the listen-before-task concept which is part of the mode switching of NFC. In general each NFC device acts in target mode. Periodically the device switches into initiator mode in order to scan the environment for NFC targets (= polling) and then falls back into target mode. If the initiator finds a target an initiation sequence is submitted to establish the communication and then starts exchanging data.
NFC distinguishes two operation modes for communication: passive and active mode.
Passive Mode
In passive mode only the device that starts the communication (the initiator) produces the 13.56 MHz carrier field. A target introduced to this field may use it to draw energy but must not generate a carrier field at its own. The initiator transfers data by directly modulating the field, the target by load-modulating it. In both directions the coding complies with ISO14443 or FeLiCa, respectively. This mode enables NFC-devices to communicate with existing contactless smart cards. The term load modulation describes the influence of load changes on the initiator’s carrier field’s amplitude. These changes can be perceived as information by the initiator. Depending on the size of the coils, ranges up to 10 cm and data rates of 106, 212, and 424 kBit/sec are possible.
Active Mode
When in active mode, both appliances generate an RF field. Each side transmits data by modifying its own field, using an Amplitude Shift Keying (ASK) modulation scheme. Advantages compared to passive mode is a larger operating distance (up to 20 cm) and higher transmission speeds (eventually over 1 MBit/sec). To avoid collisions only the sending device emits a electromagnetic field; the receiving entity switches off its field while listening. If necessary these roles can change as often as needed.
Usecases and Applications
An NFC compliant device offers the following modes of communication:
Reader/Writer Mode: In Reader/Writer mode an NFC system acts as an ordinary reader for contactless smart cards. If two or more cards are present in the reader’s carrier field one is selected using an anti-collision algorithm. NFC also takes care of sensing whether the chosen card is ISO 14443-A/B or FeLiCa compliant. The method used for anti-collision is dependent on the type of card detected. This mode causes the NFC device to act as an active device. From an application’s view there is no difference between a conventional and an emulated terminal, accesses to the contactless token proceed equally.
Operating in this mode, the NFC device can read and alter data stored in NFC compliant passive (without battery) transponders. Such tags can be found on e. g. SmartPoster allowing the user to retrieve additional information by reading the tag with an NFC device. Depending on the data stored on the tag, the NFC device takes an appropriate action without any user interaction. If e. g. an URI was found on the tag the handset would open a web browser.
Card Emulation Mode: Tag emulation mode is the reverse of reader/writer mode: A contactless token is emulated. Now the device acts soley in passive mode. Due to the fact that the card is only emulated it is possible to use one NFC wdevice to act on behalf of several „real“ smart cards. Which card is presented to the reader depends on the situation and can be influenced by software. Additionally an NFC device can contain a secure element to store the information for the emulated card in a secure way.
In this case an external reader cannot distinguish between a smart card and an NFC device in card emulation mode. This mode is useful for contactless payment and ticketing applications for example. Actually, an NFC enabled handset is capa-ble of storing different contactless smartcard applications in one device.
Peer-to-Peer Mode: This mode is specific to NFC. After having established a link between the two participants (the method is equal to ISO 14443-A) a transparent protocol for data exchange can be started. The data block size can be chosen freely, with an MTU (maximum transmission unit) limited to 256 bytes. Main purpose of this protocol is to enable the user to send his/her own data as soon as possible (i. e. after a few milliseconds). In a peer-to-peer session either both initiator and target can be in active mode or initiator in active and target in passive mode. This helps the target to reduce its energy consumption and is therefore especially useful if the initiator is a stationary terminal (e. g. a ticket counter) and the target a mobile device (e. g. a mobile phone).
The NFC peer-to-peer mode (ISO 18092) allows two NFC enabled devices to establish a bidirectional connection to exchange contacts, bluetooth pairing information or any other kind of data. Cumbersome pairing processes are a thing of the past thanks to NFC technology. To establish a connection a client (NFC peer-to-peer initiator) is searching for a host (NFC peer-to-peer target) to setup a connection. Then the Near Field Communcation Data Exchange Format (NDEF) is used to transmit the data.

RFID Technology Standards

Depending on the standard use, these cards are either proximity cards (according to ISO 14443) or vicinity cards (according to ISO 15693). Both standards use the so popular RFID Technology, so I’ll talk about that first. RFID standard for Radio Frequency Identification. The technology bases in the inductive coupling of two coils/antennas. Depending on the antennas and the power used to generate the electro mangentic field, distances starting from some centimeters up to several meters can be briged by using RFID Technology. There are several different frequencies used in the RFID Industry, popular ones are: 125 kHz, 13,56 Mhz (used by ISO14443, ISO15693, ISO18092) or 900 Mhz. In an RFID System there is usually an active reader, that generates the electro mangentic field and a passive transponder (tag, smartcard) that is powered by this field (and thus needs no battery). After the passive part is powered, the communication is established and both parties can exchange data. The active part (reader) emitting the field is also called initiator where as the passive one (waiting for the initiator) is called target. So far for the electro magenetic stuff (from a very basic, theoretical side) and back to the smartcards.
As already mentioned both proximity and vinicity card use 13,56 Mhz and therefore are compatible on the very low (physical) layer of communcation. ISO 15693 actually is not considered by the NFC Forum – the standardization body for NFC – thus, I will not give further details on this standard. During the standardization of ISO 14443 the two major players (Infineon, Philips; now NXP) could not agree on a modulation schema, thus there are two different one: ISO 14443-A (Philips, now NXP & Co.) and ISO 14443-B (Infineon & Co. ). There are several popular products using ISO 14443, like the RFID Passport. One of the most widely used RFID Card is Mifare. Mifare is not compliant to ISO 14443 on all levels (only 1 – 3) as it implements a proprietary cipher. Several public transport Systems, like London (Oyster) or Hongkong (Octopus) use Mifare. The cipher actually was broken in 2008. In Japan Sony has introduced its one contactless Smartcard: Felcia; there it is used for Payment & Public Transport (Suica). Felcia is neither ISO14443-A nor –B. NFC Devices in the further should be able to overcome all this different smartcard standards and should be able to talk to any of these contactless smartcards or reader.

NFC Tag Types

The NFC Forum has agreed on the following four NFC tag types.
Type 1:Type 1 Tag is based on ISO/IEC 14443A. This tag type is read and re-write capable. The memory of the tags can be write protected. Memory size can be between 96 bytes and 2 Kbytes. Communication Speed with the tag is 106 kbit/sec. Example: Innovision Topaz
Type 2: Type 2 Tag is based on ISO/IEC 14443A. This tag type is read and re-write capable. The memory of the tags can be write protected. Memory size can be between 48 bytes and 2 Kbytes. Communication Speed with the tag is 106 kbit/sec. Example: NXP Mifare Ultralight, NXP Mifare Ultralight
Type 3:Type 3 Tag is based on the Japanese Industrial Standard (JIS) X 6319-4. This tag type is pre-configured at manufacture to be either read and re-writable, or read-only. Memory size can be up to 1 Mbyte. Communication Speed with the tag is 212 kbit/sec. Example: Sony Felica
Type 4:Type 4 is fully compatible with the ISO/IEC 14443 (A \& B) standard series. This tag type is pre-configured at manufacture to be either read and re-writable, or read-only. Memory size can be up to 32 KBytes; For the communication with tags APDUs according to ISO 7816-4 can be used. Communication speed with the tag is 106 kbit/sec. Example: NXP DESfire, NXP SmartMX with JCOP.)
Mifare Classic is not an NFC forum compliant tag, although reading and writing of the tag is supported by most of the NFC devices as they ship with an NXP chip. The specifications for the tag types are available for free from the NFC-Forum website.
NFC data exchange format (NDEF)
The NFC forum has defined a structure for writing data to tags or exchanging it between two NFC devices. The format is called NDEF. A so called NDEF record can contain multiple different RTD. A RTD is an information set for a single application, as an RTD may only contain an isolated information such as text, a URI, a business card or pairing information for other technologies. The different RTD specifications are available from the NFC Forum website.

RFID in Documents

Documents have been a part of human history even before the invention of paper. Every recorded transaction generates a document and these are preserved for varying lengths of time depending on their importance. Documents that establish or seek to dispute identity and ownership or are a permanent record of important events and transactions, especially documents generated by the government and statutory authorities, need to be kept safely often over a person’s lifetime. Even secure electronic documents are based on physical documents that are inherently unsecure.

While archival documents are largely confined in secure areas with limited access only to researchers, other important documents such as legal, financial and health records are often retrieved from time to time and handled by various people before being returned to storage. Institutions such as banks and insurance companies, and agencies such as document custodial services have in their possession huge quantities of important documents that require frequent reference. Similarly law courts handle millions of case papers and files in the course of their proceedings.

It is therefore imperative that the security of these documents is also ensured during their movement and transfer from the storeroom to the courtroom, office or any other place of examination and scrutiny. Physical documents can be misplaced, damaged, tampered or destroyed, and this loss can have serious consequences. Locating a particular document amongst a pile of similar records is also time-consuming. Without efficient document management, this is akin to searching for a needle inside a haystack.

RFID tracking of documents provides real-time visibility on a large-scale, which is not possible through other methods. Tags affixed to each document and file allow efficient remote monitoring and live tracking that is not dependent on either line-of-sight visibility or individual manual scrutiny. Since each tagged document and file can be uniquely identified within a stack of files that are read simultaneously by the RFID reader, the savings in time and effort are enormous. Document movement from one location to another is automatically verified by RFID readers at each transit location till it reaches its final destination. The system therefore establishes and ensures that a chain of custody is maintained throughout document storage, issue, movement and receipt, with a similar process occurring when the document is returned to storage. This in turn automatically creates an audit trail that provides a history of document custody.

RFID thus provides automated compliance, eliminates human error, bias and mischief, and ensures transparency in operations with the highest accuracy. Automated tracking enables automated alarms that are triggered in real-time whenever a tagged document is sought to be retrieved from custody by an unauthorized person or taken to a wrong or unauthorized location. Since each tagged document has its own unique digital identity, it can be easily searched and referenced in a database, and its physical location on a rack and shelf known to the system. This also allows an alarm to be triggered when a particular document tag from within a database list of a bunch of outgoing or incoming files cannot be read by the RFID reader since the document is missing from the bunch. If the document or file has only been misplaced, it is easily located when its RFID tag is automatically read on another rack or shelf.

Document tracking through RFID ensures that the current location of any document within the premises is immediately known to the system administrator and all other authorized persons at any given moment. It enables easy and accurate retrieval from storage and also identifies the current custodian of the file at its current location in transit. With the number of documents exponentially increasing all the time, document tracking and management through RFID is a fast growing market that provides the most reliable method of ensuring both security as well as prompt and accurate retrieval of documents. RFID tracking of documents brings efficiency in time savings and cost savings in a previously inefficient and lethargic sector, thereby improving compliance, productivity and performance, resulting in improved services to customers and the common man.

RFID in School Children

The safety and security of school children is a serious concern for parents and school officials. Students on their way to school and back are without parental or direct school supervision, and it is essential for guardians to know where and when these young children have got on and off the school bus, whether they have boarded the correct bus, and that they have arrived at school safely.

RFID tracking embedded within student IDs along with remote vehicle monitoring through GPS/GPRS enables easy and efficient management of students travelling in school buses, by ensuring that children have been picked up at their designated bus stop by the correct bus, and have also actually reached school instead of playing truant. The system has built-in alerts that notify the bus attendant if the child attempts to get on the wrong bus or fails to get off the bus. This ensures that little children are not left behind in the bus if they have fallen asleep. Bus tracking through remote monitoring of vehicle route ensures that bus drivers adhere to the specfied route and timings, halt at every pick-up and drop-off bus stop within a pre-determined geo-fenced area, and have responded to alerts.

The system enables messaging that is triggered through RFID Tag that informs guardians if the student gets off at an earlier bus stop, or the bus has been delayed due to traffic. When GPS tracking is available to parents, live status updates of school bus whereabouts can be received by them on their cellphones. They can then view when the school bus is about to arrive, so that they can be at the bus stop to pick up their children.

RFID can also be efficiently deployed by schools to individually monitor the food being served to each student and ensure that it is in accordance with each child’s individual health requirements. Foods which trigger allergies or are temporarily disallowed can be precluded from erroneous selection by the child. RFID tagged student IDs also simplify and automate library check-in and check-out, as well as monitor access to areas having restricted timings such as laboratories, computer rooms and gyms.

Identity cards with embedded RFID can be issued to school staff, bus drivers and attendants. Parents and guardians can also be issued such IDs to ensure that only authorized persons can pick-up students directly from the school premises.

Tracking of very young children in school and on the school bus, is an facility that provides safety and security to students, while providing assurance and peace of mind to their parents, and is fast becoming a necessity in an increasingly turbulent world.

RFID in Library

Libraries all over the world are moving away from the traditional model of using barcodes to scan and check out books. While this method has been around since the advent of barcodes almost 40 years ago, rapidly evolving technology has meant that more efficient, streamlined library management solutions have been developed. The most recent technology, one that many of the largest libraries in the world have already switched over to, is Radio Frequency Identification Device (RFID).

This involves affixing a tiny RFID tag onto each book, which allows it to be read by readers stationed across the library. The advantage of this technology over barcodes is that RFID technology does not require a direct line of sight. Thus, multiple books can be detected and checked out simultaneously, instead of having to scan every individual book. In addition, patrons can check their books out themselves, instead of relying on a librarian. This gives the librarian more time to help out other library members, and it lets patrons check their books out faster.

RFID also acts as a security guard on the premises, alerting the guards if a book leaves the library without being checked out. Thus, one single technology, RFID, can replace the existing bar code technology for checkout, as well as the EM technology for theft detection.

RFID also helps in re-shelving, since wrongly shelved books can be instantly identified without needing a line of sight read. Patrons searching for books can also find books much faster using a handheld RFID scanner, instead of having to manually look through the shelves.

Finally, RFID also lets patrons return a book anytime they want. This is because the RFID chip in the book can be identified by the reader in the book drop box, and the returned book can be recorded. A librarian does not need to be physically present to collect the returned book, and so the library effectively stays open 24/7.

Given the many advantages that RFID has over traditional technology that is used in libraries today, many large libraries all over the world such as the Seattle Public Library in America and the Shenzen Library in China have already switched over to RFID.