Near field communication, or NFC, is a set of short-range wireless technologies, typically requiring a distance of 4 cm or less. NFC operates at 13.56 MHz and at rates ranging from 106 kbit/s to 848 kbit/s. NFC always involves an initiator and a target; the initiator actively generates an RF field that can power a passive target. This enables NFC targets to take very simple form factors such as tags, stickers, key fobs, or cards that do not require batteries. NFC peer-to-peer communication is of course possible, where both devices are powered. According to the NFC Forum, the three main uses of NFC currently are “sharing, pairing, and transaction.” Global companies are interested in NFC’s ability to provide pervasive marketing, simplify processes, and facilitate contactless payment for goods.
NFC tags contain simple data or elaborate instructions that enable them to perform such functions as unlocking doors, paying for goods, launching phone calls or exchanging data between users. The majority of tags for consumer applications are read-only. However, NFC tags can also be read and rewriteable. They can be custom-encoded by their manufacturers or use the specifications provided by the NFC Forum, an industry association charged with promoting the technology and setting key standards. The tags can securely store personal data such as debit and credit card information, loyalty program data, PINs and networking contacts, among other information. The NFC Forum defines four types of tags which provide different communication speeds and capabilities in terms of configurability, memory, security, data retention and write endurance. Tags currently offer between 96 and 512 bytes of memory.
Specifications
- As with proximity card technology, near-field communication uses magnetic induction between two loop antennas located within each other's near field, effectively forming an air-core transformer. It operates within the globally available and unlicensed radio frequency ISM band of 13.56 MHz. Most of the RF energy is concentrated in the allowed 14 kHz bandwidth range, but the full spectral envelope may be as wide as 1.8 MHz when using ASK modulation.
- Theoretical working distance with compact standard antennas: up to 20 cm (practical working distance of about 4 centimetres)
- Supported data rates: 106, 212, 424 or 848 kbit/s
- There are two modes:
- Passive communication mode: The initiator device provides a carrier field and the target device answers by modulating the existing field. In this mode, the target device may draw its operating power from the initiator-provided electromagnetic field, thus making the target device a transponder.
- Active communication mode: Both initiator and target device communicate by alternately generating their own fields. A device deactivates its RF field while it is waiting for data. In this mode, both devices typically have power supplies.
- NFC employs two different codings to transfer data. If an active device transfers data at 106 kbit/s, a modified Miller coding with 100% modulation is used. In all other cases Manchester codingis used with a modulation ratio of 10%.
- NFC devices are able to receive and transmit data at the same time. Thus, they can check for potential collisions if the received signal frequency does not match with the transmitted signal’s frequency.
Applications
NFC technology is intended mainly for use in mobile phones. There are currently three specific uses for NFC according to the NFC Forum:
- Reader/writer mode: the NFC device is active and reads a passive RFID tag. Example: smart posters.
- P2P mode: two NFC devices exchange data. Example: virtual business cards or digital photos.
- Card emulation: the NFC device behaves like an existing contactless card and can be used with existing technology infrastructures.
there are many other application for NFC...
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