What is NFC?
NFC is a standards-based technology used to provide short range wireless connectivity technology that carry secure two-way interactions between electronic devices. Communications are established in a simple way, not requiring set-up by users as in the case of many other wireless communications. As such NFC enables users to perform contactless transactions, access digital content and connect electronic devices by touching devices together.
NFC near field communication provides contactless communication up to distances of about 4 or 5 centimeters. In this way there communications are inherently more secure because devices normally only come into contact and hence communication when the user intends this.
As no physical connectors are used with NFC near field communication, the connection is more reliable and does not suffer problems of contact wear, corrosion and dirt experienced by systems using physical connectors.
NFC utilizes inductive-coupling, at a frequency of 13.56 MHz - a licence free allocation in the HF portion of the radio spectrum.
NFC is a form of RFID, but it has a specific set of standards governing its operation, interface, etc. This means that NFC equipment, and elements from a variety of manufacturers can be used together. The NFC standards determine not only the contactless operating environment, but also the data formats and data transfer rates.
NFC technology RF interface :
NFC near field communication is a wire-less technology, using radio frequencies. It operates at a frequency of 13.56 MHz within the globally available and unregulated 13.56 MHz frequency band. As a result no licenses are required for operation on these frequencies.
In addition to this the radio transmissions using NFC are half duplex as the same channel is used for both transmit and receive. Also to prevent two devices transmitting together, they operate what is termed a listen before talk protocol. The devices may only transmit if they previously listen to check that no other devices are transmitting. In view of the short ranges involved, the protocol used by NFC need not be as comprehensive as that used for other wireless protocols.
Connection is made between two NFC devices when they are brought together so there is no difficulty in associating two devices. This occurs when the two devices are brought to less than about 4 centimeters of one another, although actual distances will depend upon a variety of factors, and figures of 20 centimetres for the maximum communications distance have been seen. In this way a simple wave or touch can establish an NFC connection. Because the transmission range is so short, NFC-enabled transactions are inherently secure.
To provide the standard interfaces, the underlying layers of NFC technology follow the normal ISO standards.
NFC technology data transfer :
The data transfer rate may be either 106, 212 or 424 kbps. The application itself sets up the initial communication speed, but it may be changed later dependent upon the communication environment and the requirements.
NFC technology device types :
The NFC near field communication standard defines two types of NFC device. These are known as the Initiator and Target of the communication. As the names imply, the initiator is the device that initiates the communication and it controls the data exchanges. The Target device is the one that responds to the requests from the Initiator.
The NFC near field communication standard defines two different modes of operation:
In addition to the NFC modes of operation, three communication modes are also defined:
NFC standards and capability :
With Near Field Communications set to become widely accepted in many applications, the system has been standardized by a number of globally accepted standards bodies. NFC has standards accepted by ISO (18092), ECMA (340) and ETSI. Additionally NFC is compatible with Philips' MIFARE® (ISO 14443 A) and Sony's FeliCa smart card protocols.
NFC RF signal parameters:
NFC uses the global 13.56 MHz allocation as this is an unlicensed radio frequency ISM band.
Using ASK - amplitude shift keying, as the format for the NFC modulation, most of the RF energy is concentrated in the allowed 14 kHz bandwidth, although the sidebands may extend out as far as ± 1.8 MHz