NFC Tutorial | Tutorial on NFC Protocol | How NFC works

This NFC Tutorial covers Near Field Communication System basics. This tutorial on NFC protocol also describes NFC frame, NFC modes, how NFC works, NFC protocol stack and NFC test equipments.

What is NFC (Near Field Communication) ?

As mentioned NFC is the short form of Near Field Communication. It is a short range low data rate wireless communication technology operating at 13.56 MHz frequency. It is a contactless mode of communication using electromagnetic waves. This technology allows two devices housing NFC chip to communicate for various applications for example,
• Data communication between smartphones
• Verification of authenticated person having NFC ID card at the office by NFC reader in the door.
• Banking payments using NFC compliant credit card to enhance security
• Ticket booking at the airports
• Automatic running of scheduled features in the NFC phone.

Following table summarizes features of wireless NFC (Near Field Communication) technology.

Features NFC (Near Field Communication) Support
RF Carrier Frequency 13.56 MHz
Distance less than 10 cm
Data Rate 106 or 212 or 424 Kbps
NFC Network Devices Tags and Readers, NFC Tag vs Reader➤
NFC Tag Types Type 1 to 5, More on NFC tag types➤
Network configuration peer to peer
NFC Network Device Modes Card Emulation, Reader/Writer, Point to Point(active & passive)
two NFC device communication modes active-passive or active-active
connection establishment time Few seconds (approx. less than 0.1 sec)
Data Coding Schemes NRZ-L, Manchester, Modified Miller, Read More➤
Data Modulation Schemes ASK, BPSK
Collision mechanism (i.e. MAC) Anti-collision support
NFC Standards ISO 14443A/B, ISO 18092, JIS X6319-4

Table:1 NFC network features or NFC capability

There are three types of NFC forum specifications viz. NFC-A, NFC-B and NFC-F,
Refer features of NFC-A, NFC-B, NFC-F types➤.

How NFC works

how NFC works
Fig:1 NFC Network

Let us understand how NFC works as part of this NFC tutorial. As mentioned NFC network consists of two devices known as initiator device and target device. NFC tag can be active as well as passive device. NFC reader is always active device. These devices operate either in active-active or active-passive modes. In active-active mode, both the NFC devices will have their own power while in active-passive mode, passive device derive its power from received EM waves of the active device.

Basic mode of communication is half duplex in NFC, where in one NFC device transmits while other device receives. This is also referred as "Listen before Talk". Here one of the two NFC devices will function as initiator which first listen on channel and transmits only when no other signal is there on channel. Here Initiator polls the other devices which comes closer to it and the other NFC device referred as target listens and responds to initiator as per requested message.

NFC Network Modes-Card Emulation, Reader/Writer, Point to Point(Peer)

There are three modes in which NFC tag and reader works viz. Card Emulation, reader/writer and peer to peer (or point to point) as explained below.

NFC Card Emulation Mode:
In this mode, usually active device reads passive device.
EXAMPLE#1:ID card , NFC tag or NFC compliant ticket are read by NFC compliant active reader at office or railway stations.
EXAMPLE#2:Smart phone acts as smart card to allow booking of tickets or to perform online banking transactions or payments using credit card reader.

Following are the steps involved in card emulation mode:
• Step-1: NFC reader oscillates 13.56 MHz RF field. When the card comes near to the RF field, it gets power due to EM (Electro-magnetic) coupling and gets connected with the reader.
• Step-2: Reader sends commands using RF field.
• Step-3: Card responds to the reader as requested.

NFC Reader/Writer Mode:
In this mode, one device will be in reading mode and the other one will be in writing mode. They can be either active device or passive device.
Example#1:Product Authentication
Example#2:Smart advertising
Example#2:Device pairing

Following are the steps involved in reader/writer mode:
• Step-1: In read mode, NFC reader reads NFC tags either passive or active one.
• Step-2: In Write mode, one NFC device writes to the other NFC device.

NFC Peer to Peer (Point to Point):
In this mode, data is transmitted from one NFC device to the other NFC device in adhoc or peer to peer mode. Here any device can become initiator and the rest of the device will act as target to complete the connection establishment.
Example#1: smartphone to smartphone communication
Example#2: Automotive (in car operation)
Example#3: Social media applications or games

Following are the steps involved in peer to peer mode (active mode):
• Step-1: Both NFC smartphones establish pairing for data communication. Both have got power and their own RF fields.
• Step-2:Initiator sends commands by modulating RF field and switches off the RF field.
• Step-3:Target device responds to the initiator using its own RF field modulation.

NFC protocol stack

NFC protocol stack
Fig:2 NFC Protocol stack

The figure depicts simple NFC protocol stack in peer to peer mode. As shown it consists of application layer, data link layers (logical link control and media access control) and physical layer.
➨Application layer takes care of format of the data to be exchanged between NFC devices or between NFC device and Tags. NFC uses NDEF (NFC Data Exchange Format).
➨Data link layer takes care of different modes of operation and anti-collision mechanism. LLCP establishes communication between two peer devices.
➨Physical layer takes care of modulation, coding and RF related parameters such frequency, power etc.

NFC Frame Structure

NFC message format
Fig:3 NFC Frame

NFC frame uses special encapsulation format referred as NDEF (NFC Data Exchange Format). Each NFC device transmission is known as message. One message composed of one or more records. Each record consists of header part and payload part. Header part is made of identifier, length and type fields. Payload carry data or URL.

NFC Test Equipments

Refer NFC tester for NFC testing➤ and NFC Tools and Equipments➤ for more information.

This NFC tutorial is very useful for beginners as well as experts who would like to know all about NFC technology right from features till NFC testing including how NFC works in various modes. It covers link to useful NFC test equipments including NFC protocol analyzer.

NFC Tutorial Related Links

This Near Field Communication-NFC tutorial covers following sub topics very useful to understand NFC basics:
NFC basics    NFC Modulation and coding   NFC-A,NFC-B,NFC-F types    NFC vs RFID    difference between bluetooth,wifi,RFID and NFC    What is NFC on phone    Difference between NFC tag types    NFC Tag vs NFC Reader    NFC tester for NFC testing    NFC Tools and Equipments    NFC Security  

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