NFC Tutorial: Understanding Near Field Communication

Near Field Communication (NFC) is a short-range wireless technology similar to RFID. This tutorial will cover various aspects of NFC, including how it works, its modulation and coding techniques, differences between NFC tags and readers, tag types, NFC-A/B/F signalling, and comparisons with other wireless technologies like Bluetooth, Wi-Fi, and RFID.

How NFC Works

NFC operates by leveraging the electromagnetic fields around an RF antenna. These fields are categorized into two regions: the near field and the far field. The near field is the area close to the antenna (up to 2D²/λ), while the far field is the region further away.

NFC has gained popularity for short-distance communication (within a few millimeters) with low data rates (a few kbits/sec). NFC protocols are based on RFID standards, as outlined in ISO/IEC 18092. This technology is used in a wide range of contactless applications such as:

• Access control in railways and offices
• Healthcare
• Information exchange
• Payments
• Consumer electronics

NFC is fundamentally a point-to-point communication method that always requires an initiator and a target.

NFC Communication Modes

There are two primary communication modes based on power:

• Active Communication: Both the initiator and the target generate electromagnetic fields alternately to communicate.
• Passive Communication: The target draws power from the NFC reader. This mode is convenient for creating NFC targets using stickers without needing a battery.

Inductive Coupling

NFC devices operate based on inductive coupling. Induction is the generation of electric current by passing a wire through a magnetic field (H). NFC devices have coils built-in, and when a magnetic field from another NFC device interacts with these coils, it generates power, initiating data transmission via radio waves. This power is shared between the target and initiator.

NFC Operating Modes

Image: NFC modes

NFC technology features three operating modes:

• Reader/Writer: Compliant with ISO/IEC 14443 and FeliCa specifications. In this mode, an NFC device can read tags integrated into smart posters or stickers.
• Peer to Peer: Compliant with ISO/IEC 18092. Devices are self-powered, communicate with each other, and share information. This mode allows users to exchange Bluetooth or WLAN link establishment parameters, as well as data like digital photos or virtual business cards.
• Card Emulation: Data stored on a smart card is read by an NFC reader. This mode is used for applications like ticketing, payments, purchases, and transit access control. The NFC device communicates with the reader like a smart card, enabling two-way communication.

NFC Frequency and Data Rates

NFC operates in the unlicensed ISM frequency band at 13.56 MHz, supporting data rates of 106 Kbps, 212 kbps, and 424 Kbps. It uses a bandwidth of 14KHz to map data onto the RF carrier, and the sidebands of the NFC RF modulated spectrum can extend up to +/- 1.8MHz.

NFC Applications

Image: NFC USIM

NFC has a wide variety of applications, facilitated by NFC-enabled mobile phones and smart cards:

• Transportation: Used at airports and railways for pass gates, retrieving information from smart posters and kiosks, and paying for bus or taxi fares.
• Automotive: Adjusting seat positions, opening doors, paying parking fees.
• Office: Entry and exit access, exchanging business cards, logging into PCs, printing with copiers.
• Restaurant: Paying via credit card, earning loyalty points, using coupons, and sharing information among NFC users.
• Entertainment: Used at theaters and stadiums for pass entrance and accessing event information.
• Mobile Applications: Downloading and personalizing applications, checking usage history, and remotely locking phones.

All NFC-compliant products use the N-Mark, a global symbol for recognition and acceptance of NFC-compatible devices.

NFC Tag Types

There are four NFC tag types: Tag 1, Tag 2, Tag 3, and Tag 4.

• Type 1 Tag: Based on ISO/IEC 14443A, these tags are read/write capable with a memory size between 96 bytes and 2 KB. The memory can be write-protected, and they support a data rate of 106 kbps. An example is the Innovision Topaz.
• Type 2 Tag: Also based on ISO/IEC 14443A, these tags are read/write protected and write protectable. The memory size ranges from 48 bytes to 2 KB, and they support a data communication speed of 106 kbps. NXP manufactures these tags, available as NXP Mifare Ultralight.
• Type 3 Tag: Based on JIS X 6319-4 and popular in Japan, these tags can be read & re-writable or read-only, configured during manufacturing. They offer a memory size of up to 1 MB and support a data rate of 212 kbps. An example is the Sony Felica.
• Type 4 Tag: Compliant with ISO/IEC 14443 (A or/and B), these tags are pre-configured at manufacturing and can be read & rewritable or read-only. They support a maximum memory size of 32 KB and a data communication speed of 106 Kbps. Communication requires APDU as per ISO 7816-4.

NFC Signalling Types

There are three signalling types used in NFC communication: NFC-A, NFC-B, and NFC-F. These types facilitate communication between initiators and targets or between readers and tags.