The short range of the wireless standard is typical for NFC. NFC data transmission is only possible when the sender and receiving antennas are located in direct proximity with each other. In practice, the operational distance between two NFC devices is below 10 centimeters. For example, NFC-compatible payment cards have to be held directly against the card reader. Only then can transactions be made. The limited range is intended to prevent unintended connections and plays an important role in the security of the wireless standard.
In principal, two modes of communication are conceivable with NFC wireless transmission: passive and active mode. While passive mode only permits one-way communication in which an NFC device retrieves data from another, active mode allows mutual communication.
- Passive mode: In the passive mode, active NFC readers are used to read passive transponders. The antenna of the active device thereby generates a high-frequency, alternating electromagnetic field. If a passive transponder enters the range of the high-frequency field, it is supplied with energy for a short time. Passive transponders themselves do not generate a feedback signal, instead the data is transmitted by modulating the inquiry signal. This mode is used for contactless payments, for example. These transponders can now be found in most debit and credit cards.
- Active mode: If both the initiator of the wireless transmission as well as the target device are able to transmit NFC signals, transmission in the active mode is possible. Active NFC devices have their own energy source. During communication, the devices involved generate their own high-frequency, alternating fields to transmit data, and deactivate them when waiting for a response.
Data transmission via NFC is relatively limited at 106, 212 or 424 kbit/s. For data-intensive applications, NFC technology is therefore usually combined with wireless standards like Bluetooth – in order to make the pairing of Bluetooth devices easier, for example. Wi-Fi connections can also be established faster and more easily using NFC technology. When NFC connection data is stored on an NFC transponder, users only need to read the data using an NFC phone to connect to the network. This makes entering the Wi-Fi key manually unnecessary.