How can you pay by just tapping?

Have you used the new “touch and pay” feature of Alipay? Have you ever wondered what the principle behind it is?

In fact, the technology behind this is called NFC . This technology has a long history. Today we will learn what NFC is and how it works.

What is NFC?

NFC is short for Near Field Communication, which refers to a short-range wireless communication technology . Its working principle is based on radio frequency identification (RFID) technology, but NFC is different from traditional RFID in that it has two important features: First, short-range communication. The communication distance of NFC is very short, generally within a few centimeters. This feature makes it highly secure and avoids long-distance signal interference and eavesdropping ; second, two-way communication. NFC can not only read information, but also actively send information, supporting two-way data exchange. This makes NFC more flexible than traditional one-way RFID in some applications.

Image source: [6]

In addition, the operating frequency of NFC technology is usually 13.56 MHz, and the standard data transmission rate is 106kbps to 424kbps. The transmission rate is moderate and sufficient to support most common application scenarios.

How NFC works

The working principle of NFC can be summarized as a simple " transmit and receive ". Specifically, NFC devices communicate with each other through electromagnetic fields. When two NFC-enabled devices are close enough, they exchange information through electromagnetic waves. NFC devices usually consist of a transmitter and a receiver:

Image source: [7]

In active mode, NFC devices actively send signals to communicate with other devices. Mobile phones or other devices will transmit signals through NFC chips and wait for the receiver's response. In passive mode, NFC devices do not actively send signals, but use the electromagnetic field from other devices to power and respond to signals. Passive mode is commonly used for devices such as cards and tags. For two-way mode, two NFC devices can send and receive information to each other. This mode is often used for pairing or file transfer between devices.

NFC applications in mobile phones

NFC technology is widely used, covering almost every field of our lives. Here are some common NFC applications:

1

Mobile Payment

Mobile payment is one of the most well-known applications of NFC. Nowadays, using mobile phones to make payments has become a part of daily life. Through the NFC function, smartphones can quickly establish a connection with payment terminals (such as POS machines) to complete the payment process.

For example, when using apps such as Alipay, WeChat Pay, and Apple Pay, the phone only needs to be close to the payment device to complete the payment. This is because the NFC chip in the phone exchanges information with the POS machine through near-field communication to achieve fund transfer.

During the payment process, the NFC chip in the mobile phone acts as an "electronic wallet", storing bank card information or payment account information, encrypting and authenticating it to ensure the security of the payment process.

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2

Electronic access control

NFC technology is also widely used in electronic access control systems. Many modern office buildings, hotel rooms and other places have begun to use NFC as a replacement for access control cards. Simply bring an NFC-enabled phone close to the access control device to complete the identity verification and unlock the door. This method is not only convenient and fast, but also reduces the risk of losing traditional access control cards.

Image source: [5]

3

Bluetooth pairing

NFC also plays an important role in Bluetooth pairing. When you want to pair your phone with Bluetooth headsets, speakers, car systems and other devices, the traditional pairing process requires manual password entry or device selection. When using NFC, you only need to bring your phone and Bluetooth device close together, and the device will automatically recognize and complete the pairing, which greatly simplifies the operation process and improves convenience.

Image source: [2]

4

Smart labels and information exchange

NFC tags (also called NFC tag cards, NFC stickers) are devices that exchange information with mobile phones and other devices through NFC. NFC tags are widely used in smart advertising, ticketing systems, product information queries, etc. For example, you can see some billboards or product labels embedded with NFC chips in stores. Users only need to bring their phones close to the tags to obtain detailed product information, promotions, anti-counterfeiting and traceability information, etc.

Image source: [8]

In addition, NFC tags can also be used to store some simple information or settings. For example, in a home automation system, you can stick an NFC tag on the door and use your phone to scan the tag to control smart home devices, such as turning on lights, adjusting air conditioning temperature, etc.

5

Data exchange and file sharing

NFC technology can also be used for fast data exchange between devices. In some devices, users can quickly exchange contacts, photos, music files and other data simply by bringing two NFC-enabled phones close together. Compared with Bluetooth, this method is faster and simpler to operate, and is particularly suitable for fast transfer of small files.

Image source: [2]

6

Identity Authentication and Electronic Tickets

NFC can also be used for identity authentication, electronic documents and electronic ticketing. For example, the public transportation systems in some countries and regions support NFC tickets. Passengers only need to bring their mobile phones close to the card swiping device to quickly complete the ticket verification. In addition, NFC technology is also used in some high-security occasions, such as access cards, ID cards, electronic passports and other identity authentication scenarios.

Image source: [4]

References

[1]https://mp.weixin.qq.com/s/OSeQxztKnW6qs3z8lHpLhw

[2]https://mp.weixin.qq.com/s/g-GgKhRG4e0UuZuVcKUOyQ

[3]https://mp.weixin.qq.com/s/LveBIvnCWg_8lCINH3zR-g

[4]https://mp.weixin.qq.com/s/Ar-YrOtTIpXwIld2t-d1dw

[5]https://mp.weixin.qq.com/s/Vqa5CsW0VvXzahQnhhxCGg

[6]https://mp.weixin.qq.com/s/FRKbkAs8Q3SxJPjvdC-frQ

[7]https://mp.weixin.qq.com/s/EFulsF5P6-Dr_pRAvQnGsw

[8]https://mp.weixin.qq.com/s/vXoPUZHu24cBHmTg0qaM6w

[9] Wang Peiyi, Ju Xinxin, Zhao Junyan, et al. Design and application of one-card system based on NFC technology[J]. Wireless Internet Technology, 2021, 18(18): 50-51.

[10] Mobile phone “transformed” into a bus card? Unveiling the NFC function for you [J]. Instrument and Meter User, 2020, 27(01):104.

Planning and production

Source｜Lixkp Science (ID: lxkp-cstam)

Editor: Yang Yaping

Proofread by Xu Lailinlin