NFC Tutorial : Understanding NFC Protocol Stack, Working, Frame and Modes
Near Field Communication (NFC) is a short-range wireless communication technology that has revolutionized how devices interact in various industries, from payments to data sharing. This NFC tutorial guide covers protocol stack, working principles, frame structure and different communication modes.
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
Fig:1 NFC Network
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
Fig:2
The figure depicts protocol stack of NFC 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
Fig:3
The 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.
Conclusion
NFC technology simplifies wireless communication by utilizing a well structured NFC protocol stack and various operational modes. Its intuitive working principles and frame structure make it ideal for a range of applications, from simple data transfers to complex secure transactions. This NFC tutorial is very useful for beginners who would like to understand how NFC enables secure and efficient data exchange in close proximity.