PROCEDURE FOR IMPLEMENTING AN NFC TRANSACTION

Description

Technical field

[0001] This description relates generally to electronic circuits and, more particularly, to electromagnetic transponders or electronic tags.

[0002] This description applies in particular to electronic devices incorporating a Near-Field Communication (NFC) circuit, more commonly referred to as NFC devices, and to the detection of the presence of such a device in the field of another device. Prior art

[0003] Electromagnetic transponder communication systems are becoming increasingly common, particularly since the development of near-field communication technologies. These systems typically exploit a radiofrequency electromagnetic field generated by an NFC device (terminal or reader) to detect and then communicate with another NFC device (card) within range.

[0004] Document US 2018 / 240097 describes an electronic device implementing a system for preventing duplicate wireless transactions.

[0005] Document US 2013 / 005242 describes an electronic device for reducing NFC multi-protocol interrogation time and power consumption. Summary of the invention

[0006] There is a need for improvement of NFC devices and their communication process.

[0007] One embodiment overcomes all or part of the drawbacks of known NFC devices. Brief description of the drawings

[0008] These and other features and advantages will be set forth in detail in the following description of particular embodiments given without limitation in relation to the attached figures, among which: there figure 1 represents, very schematically and in block form, an example of a near-field communication system of the type to which, by way of example, the described embodiments and implementations apply; figure 2 represents, schematically and in the form of blocks, an example of a near-field communication circuit; the figure 3 represents a timing diagram illustrating a mode of operation of an NFC device; the figure 4 illustrates, in a very schematic way, a mode of operation of the near field communication system illustrated in figure 1 ; there Figure 5 illustrates very schematically the operation of the described embodiments; and the figure 6 represents a flowchart illustrating a transaction process between two NFC devices. Description of the embodiments

[0009] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0010] For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been represented and are detailed.

[0011] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or be connected by means of one or more other elements.

[0012] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to the orientation of the figures.

[0013] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0014] There figure 1 represents, very schematically and in block form, an example of a near-field communication system of the type to which, by way of example, the described embodiments and implementations apply.

[0015] We arbitrarily assume the case of two similar electronic devices, for example two mobile phones, but what is described applies more generally to any system in which a reader, terminal or terminal radiates an electromagnetic field that can be picked up by a transponder. For simplicity, we will refer to NFC devices to designate electronic devices integrating one or more Near-Field Communication (NFC) circuits.

[0016] In the example shown, a first NFC device 100A (DEV1) is capable of communicating, by near-field electromagnetic coupling (EMF field), with a second NFC device 100B (DEV2). Depending on the applications, for communication, one of the NFC devices 100A, 100B operates in so-called reader mode while the other NFC device 100B, 100A operates in so-called card mode, or the two NFC devices 100A and 100B communicate in so-called peer-to-peer (P2P) mode.

[0017] Each NFC device 100A, 100B integrates a symbolized near-field communication circuit, in figure 1 , by a block 102A, 102B. The near-field communication circuits 102A and 102B each comprise various electronic elements or circuits for generating or detecting a radiofrequency signal using an antenna (not shown), for example modulation or demodulation circuits.

[0018] There figure 2represents, schematically and in block form, an example of a near-field communication circuit 200, the example of a circuit 200 being able to be included in a device 100A, 100B as described in relation to the figure 1 .

[0019] In the example shown, the circuit 200 comprises a near field communication controller 201 (NFC CONTROLLER), or NFC controller. The NFC controller 201 is, for example, an electronic chip or an electronic circuit adapted to implement near field communications.

[0020] In the example shown, the NFC controller 201 is connected to a central unit 202 (MAIN CPU). The central unit 202 is, for example, the central unit of the NFC device 100A, 100B and is, generally, in practice, a microcontroller.

[0021] According to an embodiment not shown, the NFC controller 201 is connected to a security element (secure element).

[0022] In the example shown, the NFC controller 201 is connected to a transmitting / receiving circuit 203 (Rx / Tx) or radiofrequency head. According to one embodiment, the controller 201 and the circuit 203 are part of the same integrated circuit. The circuit 203 is connected to an impedance matching circuit or network 205 (MATCHING NETWORK) comprising discrete external components, itself connected to an antenna 207 (ANTENNA).

[0023] The circuit 203 is adapted to convert the digital signals on the NFC controller side into modulated analog signals on the antenna side, and vice versa. The impedance matching circuit 205 is typically configured to maximize the amplitude of the signals likely to be transmitted or received by the NFC controller 201. In general, the circuit 205 is notably designed to adapt to electrical properties of the antenna 207.

[0024] The near-field communication circuit 200 may further comprise other elements, such as one or more volatile or non-volatile memories, or various circuits implementing other functions, symbolized in figure 2 by a single block 209 (FCT).

[0025] During communication between NFC devices 100A and 100B ( figure 1 ), the radio frequency signal generated by one of the NFC devices is picked up by the other NFC device within range.

[0026] We arbitrarily consider, as illustrated in figure 1, that the first NFC device 100A emits an electromagnetic field (EMF) to initiate communication with the second NFC device 100B. The EMF field is picked up by the second NFC device 100B, and more particularly by its antenna 207. A coupling is then formed between the respective oscillating circuits of the NFC devices. This coupling results in a variation of the charge constituted by the circuits of the NFC device 100B on the oscillating circuit for generating the EMF field of the NFC device 100A.

[0027] In practice, for a communication, a corresponding variation in phase and / or amplitude of the emitted field is detected by the device 100A, which then starts an NFC communication protocol with the device 100B.

[0028] Once the NFC device 100A has detected the presence of the NFC device 100B in its field, it begins a communication establishment procedure involving the transmission of requests by the NFC device 100A and responses by the NFC device 100B.

[0029] In the applications covered by this description, when an NFC device is not communicating, it is switched to so-called low power mode, or sleep mode, in order to reduce the energy consumed. When an NFC device is in sleep mode, it remains capable of detecting the presence of a field generated by a reader (by being woken up by it). However, it does not then emit polling frames to detect a card within range.

[0030] There figure 3 represents a timing diagram illustrating a mode of operation of an NFC device.

[0031] The timeline illustrated in figure 3comprises two successive parts I and II, part I corresponding to operation when the sounder device (poller, in English) is in normal mode and part II corresponding to operation when the sounder device is in standby mode.

[0032] According to the embodiment illustrated in figure 3 , in normal mode (part I), the sounder device transmits periodic interrogation frames 301, during which it generates a field intended for devices in card mode which are within range (Poll mode). The frames 301 are spaced by intervals 303 during which the device is in listening mode (listener, in English) for a device in reader mode within range of which it is located.

[0033] For example, each frame 301 begins with a 304 interrogation (Listening) during which the sounder device interrogates its environment to find out if a card following a "tag talks first" (TTF) protocol is within range.

[0034] The interrogation of the card is followed by several bursts of transmission (burst, in English) 305. A single frame 301 is, for example, made up of a succession of five bursts of transmission 305 each configured in a different type of modulation technology. In other words, during a frame 301, the sounder device successively implements five bursts of transmission 305 each representative of a type of modulation technology. These bursts 305 make it possible to know whether a card of the technology considered is within range.

[0035] The types of technologies targeted by the 305 salvos are technologies of the reader-talk-first (RTF) type and are successively the ACM technology (Techno ACM), the two types A (Techno A) and B (Techno B) of the ISO 14443 standard, the FeliCa 212 kbps or 424 kbps (Techno F) type of the ISO 18092 standard and the technology known as "Vicinity cards" or ISO 15693 standard (Techno V).

[0036] Both types A and B correspond to the technology associated with the ISO IEC FDIS 14443-2:2020 standard "Radio frequency power and signal interface" in which: a. Type A is characterized by the fact that the reader uses 100% Amplitude Shift Keying (ASK) and modified Miller bit coding, and b. Type B is characterized by the fact that the reader uses 10% Amplitude Shift Keying (ASK) and Non Return to Zero (NRZ) bit coding.

[0037] Both Felica 212 kbps and Felica 424 kbps types correspond to the technology associated with the ISO IEC 18092:2013 standard "Information technology - telecommunication and information exchange between systems - Near Fields communication - interface and protocol (NFCIP-1)" in which: a. the Felica 212 kbps type is characterized by the fact that the player uses 10% amplitude shift keying and Manchester bit coding, and b. the Felica 424 kbps type is characterized by the fact that the player uses 10% amplitude shift keying and Manchester bit coding and the bit period is halved.

[0038] According to the implementation method illustrated in figure 3, each of the transmission bursts 305 is followed by a waiting time 307 (Waiting response). During the waiting time 307, the sounder device waits for the response of an NFC device in its field. If the sounder device detects a response after one of the bursts 305, this means that a device of the technology of the burst considered is present in the field. If the sounder device does not detect a response after one of the bursts 305, this means that there is no device of the technology of the burst considered in the field.

[0039] Each of the five bursts 305 is preceded by a guard interval 309 (Guard time) during which the sounder device configures the protocol of said burst 305 in the desired technology.

[0040] According to the embodiment illustrated in figure 3, when the device is in standby mode (part II), it "probes" its environment by short periodic emission pulses 311. Two pulses 311 are, for example, separated by an interval 303 similar to that of operation in normal mode. A pulse 311 corresponds to a short field emission by the sounder device to detect a possible device configured in card mode present in its field. In the event of such a detection, the sounder device then comes out of standby and then switches to normal mode. The detection implements an analysis of the electrical quantities specific to these pulses such as the amplitude or the phase, these quantities varying if a device configured in card mode is nearby.

[0041] According to one embodiment, each frame 301 has a duration of between 60 ms and 80 ms and each pulse 311 has a duration of the order of 30 µs.

[0042] During frames 301 and pulses 311, detection of a field emitted by a device configured in proximity reader mode is impossible.

[0043] According to an example application, the described embodiments relate to transport systems and, more particularly, to the validation of transport tickets stored in a telephone, for example a smartphone. Thus, in this example application, the first NFC device is a telephone and the second NFC device is a terminal or a terminal for validating or reading transport tickets.

[0044] There figure 4 illustrates, in a very schematic way, a mode of operation of the near field communication system illustrated in figure 1 .

[0045] More specifically, the figure 4 illustrates a near field communication system comprising a telephone 401 and a validation terminal 403.

[0046] In practice, when validating a transport ticket, a user brings his telephone 401 close to the validation terminal 403. The telephone 401 listens to its environment. The telephone 401 implements the operation described in relation to the figure 3 .

[0047] It is assumed that the validation terminal 403 is within range of the telephone 401 when the distance between the two devices is less than or equal to a distance d, that is to say it is assumed that the signal level of the validation terminal 403 received by the telephone 401 exceeds a certain threshold hereinafter called the standby exit threshold. The standby exit threshold is, for example, defined and stored in the internal memory of the telephone 401.

[0048] However, even when it is within range of the terminal 403, the telephone 401 cannot detect it during the frames 301. The detection of the validation terminal 403 by the telephone 401 is then delayed by a duration corresponding approximately to that of a frame 301.

[0049] This offset causes a delay in establishing communication between the telephone 401 and the validation terminal 403.

[0050] To overcome this problem, we could think: interrupting an interrogation frame 301 when the telephone 401 detects, outside the transmission phases, a received signal intensity greater than an anti-collision threshold (less than the standby exit threshold); switching the telephone 401 into card mode and establishing a communication when the telephone 401 detects a received signal intensity greater than a standby exit threshold; then detecting the type of technology of the terminal 403.

[0051] However, we would then be led to base ourselves on the technology whose signal-to-noise ratio or SNR (from the English "Signal-to-Noise Ratio"), allowing to correctly decode any response received from the card, is the highest to calculate the exit threshold from standby, the technology of terminal 403 not being known when the communication is established. This would lead in practice to choosing type A of the 14443 technology.

[0052] The embodiments described below provide for avoiding the choice of the worst case and for setting the communication establishment threshold according to the type of technology of the terminal 403.

[0053] There Figure 5 illustrates, in a very schematic manner, the operation of the embodiments described.

[0054] More particularly, the embodiments provide: when the value of the detected external field (External field detector thresholds) exceeds an anticollision threshold (Collision avoidance threshold), to interrupt the reader mode which has the effect of preventing any field emission whether according to a 301 frame or a 311 frame ( figure 3 ) implemented by the telephone 401; when the value of the detected external field exceeds a wake-up threshold, to wake up the telephone 401 ( figure 4 ) from standby mode and switch it to card mode, the standby exit threshold being based on one of the technologies 14443 type B, 18092 type Felica 212 kbps or 18092 type Felica 414 kbps; to determine the technology of terminal 403 ( figure 4); to set a communication threshold according to the technology of terminal 403; and when the value of the detected external field exceeds the previously set communication threshold (RSSI_B threshold, RSSI_F212 threshold, RSSI_F424 threshold, RSSI_A threshold), to start a transaction with terminal 403, following the protocol of the technology of terminal 403.

[0055] The communication threshold is preferably a minimum threshold for a transaction to take place in the technology in question.

[0056] For example, for all types of terminal technology, the exit threshold from standby corresponds to the communication threshold of the most efficient type of technology in terms of signal-to-noise ratio required for its decoding by the reader, i.e. the type of technology that requires the smallest value of the signal-to-noise ratio. For example, for all types of terminal technology, the exit threshold from standby corresponds to the communication threshold of the Felica 212 kbps or 424 kbps type of 18092 technology or of type B of 14443 technology. Preferably, the exit threshold from standby corresponds to the communication threshold of type B of 14443 technology.

[0057] Thus, thanks to the determination of the technology of the 403 terminal, prior to communication, by the 401 telephone and the setting of the RSSI required for the technology of the 403 terminal, it is now possible to start a communication without waiting for the worst case.

[0058] The embodiments then allow a time saving in establishing communication between the telephone 401 and the terminal 403. In particular, the time saving is all the greater as the signal-to-noise ratio of the technology of the terminal 403 is low. For example, the time saving for establishing communication between the telephone 401 and a terminal 403 of type B of the 14443 technology will be greater than the time saving for establishing communication between the telephone 401 and a terminal 403 of the 18092 FeliCa 212 kbps or 424 kbps technology.

[0059] The embodiments also make it possible to avoid communication errors at the limit of range. Indeed, communication is only established if the signal level allows it for a given technology.

[0060] More generally, what has just been explained in relation to the validation of transport tickets applies to all types of applications in which similar problems arise, for example, contactless payment applications, reading of product information, access control, etc. For all these applications, the speed of communication between devices is important.

[0061] There figure 6 represents a flowchart illustrating a transaction process between two NFC devices.

[0062] The organization chart illustrated in figure 6begins with a step in which it is checked (Block 601, VBAT > VBATDET) whether the phone's battery (VBAT) has a charge greater than a previously determined limit battery value (VBATDET) stored in the phone's internal memory. The limit battery value is, for example, between 2.4 V and 3.2 V. The limit battery value is, for example, configurable in steps of 0.2 V. This condition is, for example, checked by a VBAT voltage monitoring circuit present in the phone.

[0063] Following step 601, the flowchart described in figure 6 takes place as the distance d ( figure 4 ), representative of the distance between the telephone and the terminal, decreases (block 603, Decrease of distance d). This method is based on the detection of the external field and its value during the decrease of the distance d.

[0064] If, after step 601, the telephone leaves the range of the validation terminal at any time, i.e. if the telephone moves away from the validation terminal so that the terminal is no longer within range of the telephone, the telephone returns to a so-called polling phase implementing the operation described in relation to the figure 3 .

[0065] Step 601 is otherwise followed by a loop during which the detected external field RSSI (Received Signal Strength Indicator) is monitored until the value of the field is greater than or equal to the value of a threshold called the anti-collision threshold or threshold A (block 605, External field level ≥ Threshold A). As long as the value of the detected external field remains lower than the value of threshold A (output N of block 605), the telephone remains in the so-called polling state. As soon as, as the telephone approaches the terminal, the value of the detected external field exceeds the value of threshold A (output Y of block 605), the telephone stops its so-called polling phase (block 607, Stop Polling).

[0066] Step 607 is followed by a loop during which the detected external field is monitored until its value is greater than or equal to the value of a threshold called the standby exit threshold or threshold B (block 609, External field level ≥ Threshold B). As long as the value of the detected external field remains lower than the value of threshold B (output N of block 609), the telephone remains in standby. As soon as, as the telephone approaches the terminal, the value of the detected external field exceeds the value of threshold B (output Y of block 609), the telephone switches to a card emulation mode (block 611, Card emulation activation).

[0067] Step 611 is followed by a step 613 during which the technology type of the terminal is identified (Identify technology type), from the interrogation frame received from the terminal. The identification of the technology type of the terminal then makes it possible to configure, during a step 615, the communication threshold or threshold C as a function of this (Set up of threshold C) from which the telephone will respond to the terminal. The threshold C is configured from values stored in the non-volatile memory of the central unit 202 of the telephone. Indeed, for each type of modulation technology of the validation terminals, a value of the threshold C is stored in the non-volatile memory of the telephone.

[0068] Step 615 is followed by a loop during which the detected external field is monitored until its value is greater than or equal to the value of threshold C (block 617, External field level ≥ Threshold C). As long as the value of the detected external field remains lower than the value of threshold C (output N of block 617), the communication or transaction between the telephone and the terminal is not established (the terminal continues to transmit interrogation frames). As soon as, as the telephone approaches the terminal, the value of the detected external field exceeds the value of threshold C (output Y of block 617), the telephone starts a communication or a transaction with the terminal in the protocol corresponding to the protocol of the terminal's technology type (block 619, Start transaction). Since the communication threshold is based on the terminal's technology type, the communication is activated as early as possible during the telephone's movement towards the terminal.This speed helps to reduce the number of incomplete communications.

[0069] For example, threshold C corresponds to a first threshold, threshold B corresponds to a second threshold and threshold A corresponds to a third threshold.

[0070] An advantage of the described embodiments and implementations is that they allow time to be saved in establishing communication between a first NFC device and a second NFC device configured in reader mode.

[0071] Another advantage of the described embodiments and implementations is that they allow communication to be established in the protocol of the technology of the device configured in reader mode.

[0072] Yet another advantage of the described embodiments and implementations is that they reduce the number of incomplete communications.

[0073] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art.

[0074] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

1. A method implemented by a first near field communication NFC device (401), for establishing (619) a transaction with a second NFC device (403) configured in reader mode, comprising, in order: - a step (607) of stopping a mode of polling its surroundings, in which is the first NFC device, being first configured in reader mode, when the signal level, received from the second NFC device, reaches a first threshold (A); - a step of switching (611) the first device to card mode when the received signal level reaches a second threshold (B), higher than first threshold (A); - a step of determining (613), by the first device (401), the type of modulation technology of the second device (403) from among several types of modulation technology; and - a step of comparing the level of the signal received by the first device (401) to a third threshold (C), depending on the type of modulation technology of the second device (403), the communication being established when the signal level is higher than the third threshold.

2. A first device (401) configured to perform the following steps, in order: - stopping a mode of polling its surroundings in which it is in reader mode when the level of the signal received from a second near field communication NFC device, configured in reader mode, reaches a first threshold (A); - switching to a card mode when the level of the signal received from the second NFC device reaches a second threshold (B), higher than first threshold (A), - determining the type of modulation technology of the second NFC device (403), among several types of modulation technology; - comparing the level of the received signal to a third threshold (C), depending on the type of modulation technology of the second NFC device (403), and - establishing a transaction (619), with the second NFC device (403) when the level of the signal received by the first device, configured in card mode, reaches a third threshold (C).

3. The method according to claim 1, or the first device according to claim 2, wherein the first threshold (C) corresponds to a received signal strength indicator threshold.

4. The method according to claim 1 or 3, or the first device according to claim 2 or 3, wherein a value of the first threshold (C), for each type of modulation technology of the second device, is stored in a non-volatile memory of the first device (401).

5. The method according to any one of claims 1, 3 or 4, or the first device according to any one of claims 2 to 4, wherein the establishment is preceded a step of detection, by the first device (401), of a field emitted by the second NFC device configured in reader mode.

6. The method or first device according to claim 5, wherein the determining step (613) occurs before the detecting step.

7. The method or first device according to any of claim 1 to 6, wherein the second threshold (B) is less than the first threshold (C).

8. The method or first device according to any one of claims 1 to 7, wherein the second threshold (B) corresponds to the threshold of ISO 14443 type B technology.

9. The method or first device according to any one of claims 1 to 7, wherein the second threshold (B) corresponds to a threshold of 18092 type FeliCa 212kbps or 424kbps technology.

10. The method according to any one of claims 1, 3 to 9 or the first device according to any one of claims 2 to 9, wherein the second device (403) is of the ISO 14443 type B technology, the first threshold (C) corresponding to a minimum signal threshold required for the setting of a transaction in ISO 14443 type B technology.

11. The method according to any one of claims 1, 3 to 9 or the first device according to any one of claims 2 to 9, wherein the second device (403) is of the ISO 14443 type A technology, the first threshold (C) corresponding to a minimum signal threshold required for the setting of a transaction in ISO 14443 type A technology.

12. The method according to any one of claims 1, 3 to 9 or the first device according to any one of claims 2 to 9, wherein the second device (403) is of the 18092 type FeliCa 212 kbps technology, the first threshold (C) corresponding to a minimum signal threshold required for the setting of a transaction in 18092 type FeliCa 212 kbps technology.

13. The method according to any one of claims 1, 3 to 9 or the first device according to any one of claims 2 to 9, wherein the second device (403) is of the 18092 type FeliCa 424 kbps technology, the first threshold (C) corresponding to a minimum signal threshold required for the setting of a transaction in 18092 type FeliCa 424 kbps technology.

14. The method according to any one of claims 1, 3 to 13 or the first device of any one of claims 2 to 13, wherein the first device (401) is a smartphone.

15. The method according to any one of claims 1, 3 to 14 or the first device according to any one of claims 2 to 14, wherein the second device (403) is a transport ticket reading terminal.