Near Field Communication Interface & Protocol-2 (NFCIP-2) - Online Article

Near Field Communication Interface and Protocol-2 (NFCIP-2)

Brief history

In 2002, Ecma International formed Task Group 19 of Technical Committee 32 to specify Near Field Communication (NFC) signal interfaces and protocols. The NFC devices are wireless closely coupled devices communicating at 13,56 MHz.

The General Assembly of December 2002 adopted the Near Field Communication Interface and Protocol-1 (NFCIP-1) as ECMA-340.   Although ECMA-340 (NFCIP-1), ISO/IEC 14443 and ISO/IEC 15693 standards all specify 13,56 MHz as their working frequency, they specify distinct communication modes. These are defined as NFC, PCD, and VCD communication modes respectively.

This NFCIP-2 Standard specifies the mechanism to detect and select one communication mode out of those three possible communication modes. Furthermore, NFCIP-2 requires that subsequent behaviour be as specified in the standard specifying the selected communication mode.   TC32-TG19 applied minor editorial changes to Figure 1 and Clause 9 in their 7th meeting.

Scope

ECMA-340, ISO/IEC 14443 and ISO/IEC 15693 standards specify the RF signal interface, initialization, anti-collision and protocols for wireless interconnection of closely coupled devices and access to contactless integrated circuit cards operating at 13,56 MHz.

This Standard specifies the communication mode selection mechanism, designed to not disturb any ongoing communication at 13,56 MHz, for devices implementing ECMA-340 and the reader functionality for integrated circuit cards compliant to ISO/IEC 14443 or ISO/IEC 15693. This standard requires implementations to enter the selected communication mode as specified in the respective standard. The communication mode specifications, however, are outside the scope of this NFCIP-2 Standard.

Conformance

A conforming implementation complies with all the mandatory clauses in this Standard.

Normative References

Current applicable references should be used for the following:

     
  • ECMA-340 Near Field Communication - Interface and Protocol (NFCIP-1)
  •  
  • ISO/IEC 14443 Identification cards -- Contactless integrated circuit(s) cards -- Proximity cards
  •  
  • ISO/IEC 15693 Identification cards -- Contactless integrated circuit(s) cards -- Vicinity cards

Definitions

H Threshold

The minimum value of an external RF field that a NFCIP-2 device shall detect to not disturb ongoing communication by ensuring that its own RF field is switched off.

NFC Mode

The communication as specified in ECMA-340.

Operating Frequency (fc)

13, 56 MHZ +/- 7 kHz.

PCD

Proximity Coupling Device as specified in ISO/IEC 14443.

PCD Mode

The contactless communication between PCD and PICC as specified in ISO/IEC 14443.

VCD

Vicinity Coupling Device as specified in ISO/IEC15693.

VCD Mode

The contactless communication between VCD and VICC as specified in ISO/IEC 15693.

Conventions and notations

Names

The names of basic elements, e.g. specific fields, are written with a capital initial letter.

External RF field threshold value

NFCIP-2 devices shall detect external RF fields at the OPERATING FREQUENCY with a value higher than HTHRESHOLD while performing external RF field detection.   The value of HTHRESHOLD = 0,1875 A/m.

RF Field detection

In order to not disturb any communication on the OPERATING FREQUENCY, an NFCIP-2 device shall not switch on its RF field when it detects an external RF field.

Mode selection

Mode selection specifies the procedure for NFCIP-2 devices to select and subsequently enter one the NFC MODE, or the PCD MODE and VCD MODE.
  NFCIP-2 devices shall implement the following functions:

     
  1. Initiator and target as specified in ECMA-340;
  2.  
  3. PCD as specified in ISO/IEC 14443; and
  4.  
  5. VCD as specified in ISO/IEC 15693.

NFCIP-2 devices shall execute the following sequence

     
  1. The NFCIP-2 device shall have its RF field switched off.
  2.  
  3. If the NFCIP-2 device detects an external RF field, as specified in Clause 6, it shall select the NFC MODE.
  4.  
  5. If the NFCIP-2 device does not detect an external RF field it shall select the NFC MODE, or the PCD MODE or the VCD MODE.
  6.  
  7. If the NFCIP-2 device has selected the NFC MODE, it shall enter the NFC MODE.
  8.  
  9. NFCIP-2 devices that have selected either the PCD MODE or VCD MODE, shall perform RF detection, Initial RF generation.
     

RF Detection & Initial RF Generation

Any NFCIP-2 device having selected the PCD MODE or the VCD MODE shall continue the mode selection sequence and comply with the timing as specified below.

When the NFCIP-2 device detects an external RF field, as specified in Clause 7, during the time TIDT + n × TRFW it shall recommence the mode selection procedure that is specified in Clause 8.

If the NFCIP-2 device does not detect an external RF field during the timeTIDT + n × TRFW, it shall switch on its RF field, and enter the selected communication mode. StartTIDTn * TRFWTIRFGTRFWRF On Data or Command

ISO/IEC 14443

ISO/IEC 14443 defines a proximity card used for identification that usually uses the standard credit card form factor defined by ISO/IEC 7810 ID-1. Other form factors also are possible. The standard was developed by the Working Group 8 of Subcommittee 17 in ISO's/IEC's Joint Technical Committee 1. The Radio Frequency Identification (RFID) reader uses an embedded microcontroller (including its own microprocessor and several types of memory) and a magnetic loop antenna that operates at 13.56 MHz (RFID frequency). More recent ICAO standards for machine-readable travel documents specify a cryptographically signed file format and authentication protocol for storing biometric features (photos of the face, fingerprints, and/or iris).
  ISO/IEC 14443 consists of four parts and describes two types of cards: type A and type B. The main differences between these types concern modulation methods, coding schemes (Part 2) and protocol initialization procedures (Part 3). Both type A and type B cards use the same transmission protocol described in Part 4. The transmission protocol specifies data block exchange and related mechanisms:

     
  1. Data block chaining
  2.  
  3. Waiting time extension
  4.  
  5. Multi-activation

ISO/IEC 14443 uses following terms for components:

 

PCD: Proximity coupling device (or reader)

 

PICC: Proximity integrated circuit card

The Calypso (RFID) standard complies with ISO/IEC 14443 part 1, 2, 3 and 4 type B. MIFARE cards comply with ISO/IEC 14443 part 1, 2 and 3 type A. LEGIC cards comply with ISO/IEC 14443 part 1, 2 and 3 type A. Biometric passports comply with ISO/IEC 14443. All RFID credit cards that have been publicly evaluated use ISO/IEC 14443 type B. This RFID Type is used in the American Express BLUE credit card line.

ISM Band

The industrial, scientific and medical (ISM) radio bands were originally reserved internationally for the use of RF electromagnetic fields for industrial, scientific and medical purposes other than communications. In general, communications equipment must accept any interference generated by ISM equipment
  The ISM bands are defined by the ITU-R in 5.138, 5.150, and 5.280 of the Radio Regulations. Individual countries' use of the bands designated in these sections may differ due to variations in national radio regulations. Because communication devices using the ISM bands must tolerate any interference from ISM equipment, these bands are typically given over to uses intended for unlicensed operation, since unlicensed operation typically needs to be tolerant of interference from other devices anyway. In the United States of America, ISM uses of the ISM bands are governed by Part 18 of the FCC rules, while Part 15 Subpart B contains the rules for unlicensed communication devices, even those that use the ISM frequencies. Thus, designers of equipment for use in the United States in the ISM bands should be familiar with the relevant portions of both Part 18 and Part 15 Subpart B of the FCC Rules.

The ISM bands defined by the ITU-R are (bands in italics are subject to local acceptance):

     
  • 6.765–6.795 MHz (centre frequency 6.780 MHz)
  •  
  • 13.553–13.567 MHz (centre frequency 13.560 MHz)
  •  
  • 26.957–27.283 MHz (centre frequency 27.120 MHz)
  •  
  • 40.66–40.70 MHz (centre frequency 40.68 MHz)
  •  
  • 433.05–434.79 MHz (centre frequency 433.92 MHz) in Region 1
  •  
  • 902–928 MHz (centre frequency 915 MHz) in Region 2
  •  
  • 2.400–2.500 GHz (centre frequency 2.450 GHz)
  •  
  • 5.725–5.875 GHz (centre frequency 5.800 GHz)
  •  
  • 24–24.25 GHz (centre frequency 24.125 GHz)
  •  
  • 61–61.5 GHz (centre frequency 61.25 GHz)
  •  
  • 122–123 GHz (centre frequency 122.5 GHz)
  •  
  • 244–246 GHz (centre frequency 245 GHz)

For many people, the most commonly encountered ISM device is the home microwave oven operating at 2.45 GHz. However, in recent years these bands have also been shared with license-free error-tolerant communications applications such as wireless LANs and cordless phones in the 915 MHz, 2450 MHz, and 5800 MHz bands. Because licensed devices already are required to be tolerant of ISM emissions in these bands, unlicensed low power uses are generally able to operate in these bands without causing problems for licensed uses. Note that the 915 MHz band should not be used in countries outside Region 2, except those that specifically allow it such as Australia and Israel, especially those that use the GSM-900 band for cell phones. The ISM band is also widely used for Radio-frequency identification (RFID) applications with the most commonly used band being the 13.56 MHz band used by systems compliant with ISO/IEC 14443 including those used by biometric passports and contactless smart cards.

Radio-Frequency Identification

Radio-frequency identification (RFID) is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders.

An RFID tag is an object that can be applied to or incorporated into a product, animal, or person for the purpose of identification using radio waves. Some tags can be read from several meters away and beyond the line of sight of the reader.

Most RFID tags contain at least two parts. One is an integrated circuit for storing and processing information, modulating and demodulating a (RF) signal, and other specialized functions. The second is an antenna for receiving and transmitting the signal. Chip less RFID allows for discrete identification of tags without an integrated circuit, thereby allowing tags to be printed directly onto assets at a lower cost than traditional tags.

Today, RFID is used in enterprise supply chain management to improve the efficiency of inventory tracking and management. However, growth and adoption in the enterprise supply chain market is limited because current commercial technology does not link the indoor tracking to the overall end-to-end supply chain visibility. Coupled with fair cost-sharing mechanisms, rational motives and justified returns from RFID technology investments are the key ingredients to achieve long-term and sustainable RFID technology adoption.

RFID Tags

An RFID tag used for electronic toll collection.  RFID tags come in three general varieties:- passive, active, or semi-passive (also known as battery-assisted). Passive tags require no internal power source, thus being pure passive devices (they are only active when a reader is nearby to power them), whereas semi-passive and active tags require a power source, usually a small battery.

The diagram shows a typical backscatter scheme for RFID tags, which are powered using the energy contained in the requesting wave from the reader device.

Passive

Passive RFID tags have no internal power supply. The minute electrical current induced in the antenna by the incoming radio frequency signal provides just enough power for the CMOS integrated circuit in the tag to power up and transmit a response. Most passive tags signal by backscattering the carrier wave from the reader. This means that the antenna has to be designed both to collect power from the incoming signal and also to transmit the outbound backscatter signal. The response of a passive RFID tag is not necessarily just an ID number; the tag chip can contain non-volatile data, possibly writable EEPROM for storing data.
  Passive tags have practical read distances ranging from about 10 cm (4 in) with near-field (ISO 14443), up to approximately 10 meters (33 feet) with far-field (ISO 18000-6) and can reach up to 600 feet (183 meters) when combined with a phased-array. Basically, the reading and writing depend on the chosen radio frequency and the antenna design/size. Due to their simplicity in design they are also suitable for manufacture with a printing process for the antennas. The lack of an onboard power supply means that the device can be quite small: commercially available products exist that can be embedded in a sticker, or under the skin in the case of low frequency (LowFID) RFID tags.

Active

Unlike passive RFID tags, active RFID tags have their own internal power source, which is used to power the integrated circuits and to broadcast the response signal to the reader. Communications from active tags to readers is typically much more reliable (i.e. fewer errors) than from passive tags due to the ability for active tags to conduct a "session" with a reader.

Active tags, due to their onboard power supply, also may transmit at higher power levels than passive tags, allowing them to be more robust in "RF challenged" environments with humidity and spray or with RF-dampening targets (including humans and cattle, which contain mostly water), reflective targets from metal (shipping containers, vehicles), or at longer distances: Generating strong responses from weak reception is a sound approach to success. In turn, active tags are generally bigger (due to battery size) and more expensive to manufacture (due to price of the battery). However, their potential shelf life is comparable, as self-discharge of batteries competes with corrosion of aluminated printed circuits.

Many active tags today have operational ranges of hundreds of meters, and a battery life of up to 10 years. Active tags may include larger memories than passive tags, and may include the ability to store additional information received from the reader.

Semi-Passive

Semi-passive tags are similar to active tags in that they have their own power source, but the battery only powers the microchip and does not power the broadcasting of a signal. The response is usually powered by means of backscattering the RF energy from the reader, where energy is reflected back to the reader as with passive tags. An additional application for the battery is to power data storage.

If energy from the reader is collected and stored to emit a response in the future, the tag is operating active.  Whereas in passive tags the power level to power up the circuitry must be 100 times stronger than with active or semi-active tags, also the time consumption for collecting the energy is omitted and the response comes with shorter latency time. The battery-assisted reception circuitry of semi-passive tags leads to greater sensitivity than passive tags, typically 100 times more. The enhanced sensitivity can be leveraged as increased range (by one magnitude) and/or as enhanced read reliability (by reducing bit error rate at least one magnitude).
  The enhanced sensitivity of semi-passive tags places higher demands on the reader concerning separation in more dense population of tags. Because an already weak signal is backscattered to the reader from a larger number of tags and from longer distances, the separation requires more sophisticated anti-collision concepts, better signal processing and some more intelligent assessment of which tag might be where. For passive tags, the reader-to-tag link usually fails first. For semi-passive tags, the reverse (tag-to-reader) link usually collides first.

Semi-passive tags have three main advantages: greater sensitivity than passive tags; longer battery powered life cycle than active tags; they can perform active functions (such as temperature logging) under their own power, even when no reader is present for powering the circuitry.

Unique Features

What makes the communication between the devices so easy is that the NFC protocol provides some features not found in other general-purpose protocols.
  First of all, it is a very short-range protocol. It supports communication at distances measured in centimeters. The devices have to be literally almost touched to establish the link between them. This has two important consequences:

     
  1. The devices can rely on the protocol to be inherently secured since the devices must be placed very close to each other. It is easy to control whether the two devices communicate by simply placing them next to each other or keeping them apart.
  2.  
  3. The procedure of establishing the protocol is inherently familiar to people: you want something to communicate – touch it. This allows for the establishment of the network connection between the devices be completely automated and happen in a transparent manner. The whole process feels then like if devices recognize each other by touch and connect to each other once touched.

Another important feature of this protocol is the support for the passive mode of communication. This is very important for the battery-powered devices since they have to place conservation of the energy as the first priority. The protocol allows such a device, like a mobile phone, to operate in a power-saving mode – the passive mode of NFC communication. This mode does not require both devices to generate the RF field and allows the complete communication to be powered from one side only. Of course, the device itself will still need to be powered internally but it does not have to “waste” the battery on powering the RF communication interface.

Also, the protocol can be used easily in conjunction with other protocols to select devices and automate connection set-up. As was demonstrated in the examples of use above, the parameters of other wireless protocols can be exchanged allowing for automated set-up of other, longer-range, connections. The difficulty in using long-range protocols like Bluetooth or Wireless Ethernet is in selecting the correct device out of the multitude of devices in the range and providing the right parameters to the connection. Using NFC the whole procedure is simplified to a mere touch of one device to another.

Bluetooth

Bluetooth is a wireless protocol utilizing short-range communications technology facilitating data transmission over short distances from fixed and/or mobile devices, creating wireless personal area networks (PANs). The intent behind the development of Bluetooth was the creation of a single digital wireless protocol, capable of connecting multiple devices and overcoming issues arising from synchronization of these devices. Bluetooth uses a very robust radio technology called frequency hopping spread spectrum. It chops up the data being sent and transmits chunks of it on up to 75 different frequencies. In its basic mode, the modulation is Gaussian frequency shift keying (GFSK). It can achieve a gross data rate of 1 Mb/s. Bluetooth provides a way to connect and exchange information between devices such as mobile phones, telephones, laptops, personal computers, printers, GPS receivers, digital cameras, and video game consoles over a secure, globally unlicensed Industrial, Scientific, and Medical (ISM) 2.4 GHz short-range radio frequency bandwidth. The Bluetooth specifications are developed and licensed by the Bluetooth Special Interest Group (SIG). The Bluetooth SIG consists of companies in the areas of telecommunication, computing, networking, and consumer electronics.

NFC vs. Bluetooth

NFC and Bluetooth are both short-range communication technologies which have recently been integrated into mobile phones. The significant advantage of NFC over Bluetooth is the shorter set-up time. Instead of performing manual configurations to identify Bluetooth devices, the connection between two NFC devices is established at once (under a tenth of a second). To avoid the complicated configuration process, NFC can be used for the set-up of wireless technologies, such as Bluetooth. The maximum data transfer rate of NFC (424 Kbit/s) is slower than Bluetooth (721 Kbit/s). With less than 20 cm, NFC has a shorter range, which provides a degree of security and makes NFC suitable for crowded areas where correlating a signal with its transmitting physical device (and by extension, its user) might otherwise prove impossible. In contrast to Bluetooth, NFC is compatible with existing RFID structures. NFC can also work when one of the devices is not powered by a battery (e.g. on a phone that may be turned off, a contactless smart credit card, a smart poster, etc.).

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