NFC Near Field Communication - Background
As mobile phones are increasingly becoming a must-have tool in people's daily lives, telecom operators and mobile phone manufacturers are beginning to think about whether mobile phones can be used not only for making calls, but also for more daily life services. Imagine that the mobile phone will replace some cards carried by modern people, such as credit cards, loyalty cards, transportation cards, etc., to help people complete transportation tickets, pay bills, point shopping and other services, and can talk between two mobile phones. Download music, exchange images and synchronize communication functions, the phone can also read smart posters, download entertainment information and more. These features are not only attractive to consumers, but will also greatly expand the application and sales market for mobile phones. The birth and application of NFC-Near Field Communication Technology will make this possible.
Introduction to NFC
• NFC (Near Field Communication) is a short-range non-contact communication method that combines non-contact sensing (RFID) and wireless connection technology to operate in the 13.56 Mhz band with a transmission distance of approximately 10 CM.
• The transmission speed is currently 106Kbit/s, 212Kbit/s or 424Kbit/s, which can be increased to around 1Mb in the future.
• It is not only compliant with ISO18092, ISO21481, ECMA (340, 352 and 356) and ETSI TS 102 190 standards, but is also compatible with non-contact smart card infrastructures that are widely used with ISO14443A and B standards. Such as Philips' MIFARE technology and Sony's Felica technology.
• Compared with other short-range wireless communication technologies, NFC is safer and has shorter response time, so it is very suitable as an e-wallet technology in a wireless transmission environment, and the transaction is fast and secure.
• Because NFC is compatible with existing contactless smart card technology, it is now supported by more and more vendors and becomes the official standard.
• In addition to payment functions, NFC technology provides easy, secure, fast and automatic communication between devices. For example, NFC can help people exchange information between different devices, such as music, information, photos, video clips, etc., and can also purchase new information content.
How NFC works
• NFC-enabled devices can exchange data in active or passive mode.
• In passive mode: A device that initiates NFC communication, also known as an NFC originating device (master device), provides an RF field (RF-field) throughout the communication process, as shown in Figure 2. It can select one of 106kbps, 212kbps or 424kbps to send data to another device. The other device, called the NFC target device (slave device), does not have to generate a radio frequency field, but uses load modulation technology to transmit data back to the initiating device at the same speed. This communication mechanism is compatible with non-contact smart cards based on ISO14443A, MIFARE and FeliCa. Therefore, in passive mode, NFC-initiated devices can detect and connect contactless smart cards or NFC target devices with the same connection and initialization process. .
• In active mode: Each device must generate its own RF field when it wants to send data to another device. As shown in Figure 1, both the initiating device and the target device generate their own RF fields for communication. This is the standard mode for peer-to-peer network communication and allows for very fast connection settings.
• As shown in Figure 2, mobile devices operate primarily in passive mode, which significantly reduces power consumption and extends battery life. During an application session, the NFC device can switch its role between the initiating device and the target device. With this feature, devices with low battery levels can require passive mode to act as the target device instead of the initiating device.
Suppose there is a voltage source, whether it is DC or AC, low frequency or high frequency, it has a basic indicator of voltage. When this voltage source is loaded, the magnitude of the load will have a more or less effect on the voltage of the power supply. The voltage of the voltage source is varied by the variation of the load, which is the basic method of load modulation. The above is exemplified by a voltage source. The source can also be of current source, frequency, phase, temperature, etc., when the source's own frequency, phase, and temperature are changed by changing the source load (size, frequency, etc.). The method of generating corresponding changes, etc., can be called load modulation. Load modulation is the process or effect that causes some or some of the parameters of the source to change accordingly, taking advantage of some differences in the load or changes in the load. Load modulation is utilized in radio frequency card (or tag) identification systems. The antenna (or coil) of the RF card is the load of the reader antenna (or coil). The RF card changes the parameters of the antenna loop (such as resonance and detuning), so that the reader end is modulated, thus achieving a weak The energy transfer from the RF card to the reader.
Three working modes of NFC
1) Card mode: refers to the use of contactless mobile payment, such as shopping malls, transportation and other applications, the user only needs to close the mobile phone close to the card reader, and then the user only needs to enter a password to confirm the transaction or directly receive the transaction. For example, access control, tickets, tickets, etc. In this way, the card is powered by the RF field of the contactless reader, even if the phone is dead.
2) Peer-to-peer communication mode: that is, wireless data exchange, linking two NFC-enabled devices, enabling point-to-point data transmission, such as downloading music, exchanging pictures, or synchronizing device address books. Therefore, through NFC, multiple devices such as digital cameras, PDAs, computers, and mobile phones can perform wireless hutongs and exchange data or services.
3) Card reader mode: It is used as a contactless card reader, for example, reading information from a poster or an electronic tag of an exhibition information.
Several implementations of NFC technology
(1) NFC mobile phone solution
• The NFC function chip and antenna in this solution are independent of other parts of the phone and the SIM card, but the NFC module shares the battery with the phone. When the battery is powered, the NFC module can work in active, passive, and bidirectional modes; when the battery is powered off, it can only work in passive mode, which is equivalent to an ordinary card. The mobile phone switch has no effect on the NFC module, ie the NFC function can also be used when the phone is turned off. There are two ways to achieve this: one is to customize the mobile phone, integrate the antenna on the mobile phone battery or the motherboard, so that the NFC application and the mobile phone are integrated, the work is stable and reliable, but the mobile phone needs to be replaced; the second is to connect the antenna directly to the NFC chip, and then The battery is placed close to the battery and the back cover of the phone, so the user does not need to change the phone.
• The shortcomings of this solution: the reliability of the antenna connection is not high; in addition, there are special requirements for the internal size of the mobile phone, and the increase of the antenna affects the portability of the mobile phone.
• Advantages of this solution: The card compatibility of different technologies and different credit card issuers is good. There are many cases in the world, and the application technology is relatively mature, which is more suitable for the pilot project. Nokia's 6131 mobile phone is based on this.
(2) Dual interface SIM card solution
• The solution is based on the 13.56MHz SIM Pass standard. It is a dual-interface smart SIM card that supports contactless applications. It also implements the functions of a normal mobile phone SIM card. It does not affect contactless when answering calls and sending and receiving text messages. operating.
• The two implementations are basically the same as the NFC solution: one is to customize the mobile phone; the other is to connect the antenna directly to the SIM card and place it between the battery and the back cover of the mobile phone, so that only the SIM card can be replaced, and the cost is reduced. Low reliability and high requirements on the size of mobile phones. This solution occupies the C4 and C8 interfaces, which are used for high-speed data downloads and may affect future high-speed over-the-air applications.
(3) NFC solution with USIM card security
• This solution separates the application layer and the underlying functions, placing NFC application important data and security controls on the SIM card, and placing the NFC function chip in the phone. The NFC master chip communicates with the SIM card through the SWP/HCI protocol, and does not occupy the original pins that are intended for large-capacity cards. The application Midlet communicates with the SIM card via the standard ISO7816 protocol. When the user replaces the SIM card, the existing transaction data can be taken away to achieve complete machine card separation.
RFID and NFC
Ø NFC evolved from the integration of contactless radio frequency identification (RFID) and interoperability technologies, combining inductive card readers, inductive cards and point-to-point functions on a single chip to identify and interact with compatible devices over short distances. Data exchange. Originally a simple merger of RFID technology and network technology, this technology has evolved into a short-range wireless communication technology, and the development trend is quite rapid.
Ø Like RFID, NFC information is also transmitted through the electromagnetic induction coupling of the radio frequency part of the spectrum, but there is still a big difference between the two. First of all, NFC is a wireless connection technology that provides easy, secure and fast communication. Its transmission range is smaller than that of RFID. The transmission range of RFID can reach several meters or even tens of meters, but because NFC adopts unique signal attenuation technology, Compared with RFID, NFC has the characteristics of close distance, high bandwidth and low energy consumption. Second, NFC is compatible with existing contactless smart card technology and has become the official standard supported by more and more major vendors. Once again, NFC is a close-range connection protocol that provides easy, secure, fast, and automatic communication between devices. Compared to other connections in the wireless world, NFC is a close-range, private communication method. Finally, RFID is more widely used in production, logistics, tracking, and asset management, while NFC plays a huge role in access control, public transportation, and mobile payment.