Method for implementing NFC transactions

Abstract

Various embodiments of the present disclosure relate to methods for implementing NFC transactions. The present disclosure relates to methods implemented by a first NFC device, wherein a transaction is established with a second NFC device configured in reader mode when a signal level received by the first device configured in card mode reaches a first threshold value based on a modulation technology type of the second device.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to French patent application No. 2103038, filed on March 25, 2021, entitled “Procédé de mise en oeuvre d'une transaction NFC” (Method for implementing an NFC transaction). Technical Field

[0003] The present disclosure relates generally to electronic circuits and, more particularly, to electromagnetic transponders or electronic tags.

[0004] The present disclosure has particular applicability to electronic devices incorporating near field communication (NFC) circuitry, commonly referred to as NFC devices, and to detecting the presence of such a device in the field of another device. Background Art

[0005] Especially due to the development of near field communication technology, communication systems based on electromagnetic transponders are becoming more and more common. These systems generally use the radio frequency electromagnetic field generated by an NFC device (e.g., a terminal or reader) to detect another NFC device (e.g., a card) within range and then communicate with it. Summary of the Invention

[0006] One or more embodiments of the present disclosure provide an improved NFC device and a communication method thereof.

[0007] One embodiment addresses all or some of the disadvantages of known NFC devices.

[0008] One embodiment provides a method implemented by a first NFC device in which a transaction is initiated with a second NFC device configured in reader mode when a signal level received by the first device configured in card mode reaches a first threshold based on a modulation technology type of the second device.

[0009] In one embodiment, the first device is configured to initiate a transaction with a second NFC device configured in reader mode when a signal level received by the first device configured in card mode reaches a first threshold based on the modulation technology type of the second device.

[0010] According to one embodiment, initiating a transaction is preceded by a step of determining, by the first device, the modulation technology type of the second device.

[0011] According to one embodiment, the first threshold corresponds to a received signal strength indicator threshold.

[0012] According to one embodiment, the value of the first threshold for each modulation technique type of the second device is stored in a non-volatile memory of the first device.

[0013] According to one embodiment, the following steps are performed before initiation:

[0014] detecting, by the first device, a field transmitted by a second NFC device configured in reader mode; and

[0015] When the received signal level reaches a second threshold, the first device is switched to a card mode.

[0016] According to one embodiment, the determining step occurs before the detecting step.

[0017] According to one embodiment, the second threshold is lower than the first threshold.

[0018] According to one embodiment, the second threshold corresponds to a threshold of an ISO 14443B type technique.

[0019] According to one embodiment, the second threshold corresponds to a threshold of the FeliCa technology.

[0020] According to one embodiment, the first device exits the interrogation mode of its environment when the received signal level reaches a third threshold value that is lower than the second threshold value.

[0021] According to one embodiment, the second device is of ISO 14443B type, and the first threshold corresponds to a minimum signal threshold for initiating a transaction in ISO 14443B technology.

[0022] According to one embodiment, the second device is of ISO 14443A type, and the first threshold corresponds to a minimum signal threshold for initiating a transaction in ISO 14443A technology.

[0023] According to one embodiment, the second device is of the FeliCa 212 type and the first threshold corresponds to a minimum signal threshold for initiating a transaction in the FeliCa 212 technology.

[0024] According to one embodiment, the second device is of the FeliCa 424 type and the first threshold corresponds to a minimum signal threshold for initiating a transaction in the FeliCa 424 technology.

[0025] According to one embodiment, the first device is a smartphone.

[0026] According to one embodiment, the second device is a transport ticket reader terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above features and advantages and other features and advantages will be described in detail in the following description of specific embodiments given by way of illustration and not limitation with reference to the accompanying drawings, in which:

[0028] Figure 1 Examples of near field communication systems of the type to which the described embodiments and implementation modes apply are shown in a very schematic manner and by way of example in the form of block diagrams.

[0029] Figure 2 An example of a near field communication circuit is schematically shown in block diagram form.

[0030] Figure 3 Figure 2 shows a timing diagram illustrating the operating modes of an NFC device.

[0031] Figure 4 Very schematically illustrated Figure 1 The operating mode of the near field communication system is shown.

[0032] Figure 5 illustrates very schematically the operation of the described embodiment; and

[0033] Figure 6 Figure 1 shows a flow chart illustrating a transaction process between two NFC devices. DETAILED DESCRIPTION

[0034] Similar features are denoted by similar reference numerals in the various figures. Specifically, common structural and / or functional features in various embodiments may have the same reference numerals and may be provided with the same structure, dimensions, and material properties.

[0035] For clarity, only operations and elements that are useful for understanding the embodiments described herein are illustrated and described in detail.

[0036] Unless otherwise stated, when reference is made to two elements being connected together, this means a direct connection without any intervening elements other than conductors, and when reference is made to two elements being coupled together, this means the two elements may be connected or they may be coupled via one or more other elements.

[0037] In the following disclosure, unless otherwise stated, when referring to absolute position qualifiers, such as terms "front", "back", "top", "bottom", "left", "right", etc., or referring to relative position qualifiers, such as terms "above", "below", "higher", "lower", etc., or referring to orientation qualifiers, such as "horizontal", "vertical", etc., please refer to the orientation shown in the figures.

[0038] Unless otherwise indicated, the expressions "about," "approximately," "substantially," and "on the order of" mean within 10%, preferably within 5%.

[0039] Figure 1 Examples of near field communication systems of the type to which the described embodiments and implementations are applied by way of example are shown very schematically in block diagram form.

[0040] The case of two similar electronic devices (e.g., two cell phones) is arbitrarily assumed, 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 refer to an NFC device as an electronic device that incorporates one or more near-field communication (NFC) circuits.

[0041] In the example shown, a first NFC device 100A (DEV1) is capable of communicating with a second NFC device 100B (DEV2) via electromagnetic coupling in a near field (e.g., an electromagnetic field; EMF field). According to the present application, for communication, one of the NFC devices 100A, 100B operates in a so-called reader mode, while the other NFC device 100B, 100A operates in a so-called card mode, or the two NFC devices 100A and 100B communicate in a so-called peer-to-peer (P2P) mode.

[0042] Each NFC device 100A, 100B incorporates Figure 1 Near field communication circuits 102A and 102B are shown in FIG. Each of the near field communication circuits 102A and 102B includes various electronic components or circuits, such as modulation or demodulation circuits, for generating or detecting radio frequency signals using an antenna (not shown).

[0043] Figure 2 An example of a near field communication circuit 200 is schematically shown in block diagram form, where the example circuit 200 may be included in relation to Figure 1 In the devices 100A, 100B described.

[0044] In the example shown, the circuit 200 includes a near field communication controller 201 (NFC controller) or NFC controller. The NFC controller 201 is, for example, a microchip or an electronic circuit capable of near field communication.

[0045] In the example shown, NFC controller 201 is connected to central processing unit 202 (MAIN CPU). MAIN CPU 202 is, for example, the CPU of NFC devices 100A, 100B and is typically a microcontroller in practice. As used herein, the term "connected" includes the meanings of "physical connection," "electrical connection," or "communication connection" according to the relevant embodiments described in this disclosure. In some embodiments, connection may mean both "physical connection and electrical connection." In other embodiments, communication connection may mean that one or more components are connected using various communication schemes, including wired communication, wireless communication such as NFC, WiFi, Bluetooth, cellular, and the like.

[0046] According to one embodiment not shown, the NFC controller 201 is connected to a secure element.

[0047] In the example shown, NFC controller 201 is connected to transmit / receive circuitry 203 (Rx / Tx) or a radio frequency head. According to one embodiment, controller 201 and transmit / receive circuitry 203 are part of the same integrated circuit. Transmit / receive circuitry 203 is connected to an impedance matching circuit or network 205 (MATCHING NETWORK) comprising discrete external components, which in turn is connected to antenna 207 (ANTENNA).

[0048] The transmit / receive circuit 203 is capable of converting digital signals at the NFC controller end into modulated analog signals at the antenna end, and vice versa. The impedance matching circuit 205 is generally configured to increase or maximize the amplitude of the signal that can be transmitted or received by the NFC controller 201. Typically, the impedance matching circuit 205 is specifically designed to match the electrical characteristics of the antenna 207.

[0049] The near field communication circuit 200 may further include other elements, such as one or more volatile or non-volatile memories, or various circuits implementing other functions. Figure 2 209 (FCT).

[0050] When the NFC devices 100A and 100B ( Figure 1 ) when communicating between NFC devices, a radio frequency signal generated by one of the NFC devices is picked up by another NFC device found within range.

[0051] like Figure 1 As shown, it is arbitrarily assumed that a first NFC device 100A emits an electromagnetic field (EMF) to initiate communication with a second NFC device 100B. The EMF field is picked up by the second NFC device 100B, more specifically by its antenna 207. Coupling then occurs between the respective oscillating circuits of the NFC devices. This coupling results in a change in the load formed by the circuit of the NFC device 100B on the EMF field generated by the oscillating circuit of the NFC device 100A.

[0052] In practice, for communication, device 100A detects corresponding changes in the phase and / or amplitude of the transmitted field and then initiates the NFC communication protocol with device 100B.

[0053] Once the NFC device 100A detects the presence of the NFC device 100B in its field, it initiates a communication establishment process involving a request transmission by the NFC device 100A and a response by the NFC device 100B.

[0054] In the applications targeted by this disclosure, when an NFC device is not communicating, it is switched to a so-called low-power mode or sleep mode to reduce power consumption. When an NFC device is in sleep mode, it is still able to detect the presence of a reader-generated field (by being woken up by the reader). However, it does not transmit polling frames to detect cards within range.

[0055] Figure 3 Figure 2 shows a timing diagram illustrating one mode of operation of an NFC device.

[0056] Figure 3 The timing diagram represented in includes two consecutive parts I and II, part I corresponding to the operation when the poller is in normal mode, and part II corresponding to the operation when the poller is in sleep mode.

[0057] according to Figure 3 In the illustrated embodiment, in normal mode (part 1), the polling device transmits periodic polling frames 301 during which it generates fields to map mode devices within range (polling mode). The frames 301 are separated by intervals 303 during which the device is in listener mode for devices in range that are in reader mode.

[0058] For example, each frame 301 begins with an inquiry 304 (listen), where the sounder device interrogates its environment to determine if a tag-to-flight (TTF) card is within range.

[0059] The card's inquiry is followed by several bursts 305. A single frame 301, for example, consists of five consecutive transmission bursts 305, each configured with a different type of modulation technology. In other words, during frame 301, the sounder device performs five consecutive transmission bursts 305, each representing a modulation technology type. These bursts 305 indicate whether a card of the technology in question is in range.

[0060] In some embodiments, the technology type targeted by burst 305 is the reader-announced Reader Talk First (RTF) type technology, which is followed by ACM technology (Techno ACM), two types A (Techno A) and B (Techno B) of the ISO 14443 standard, FeliCa type 212 kbps or 424 kbps (Techno F) of the ISO 18092 standard, and the technology known as "proximity card" or ISO 15693 standard (Techno V). For example, Type A is characterized by the reader using 100% amplitude shift keying (ASK) and modified Miller bit encoding; Type B is characterized by the reader using 10% amplitude shift keying and non-return-to-zero (NRZ) bit encoding.

[0061] Both FeliCa 212kbps and FeliCa 424kbps types correspond to the technologies associated with ISO IEC 18092:2013 "Information technology — Telecommunications and information exchange between systems — Near field communication — Interface and protocol (NFCIP-1)", where:

[0062] The FeliCa 212kbps type is characterized by the reader using 10% displacement amplitude modulation and Manchester bit encoding; and

[0063] The FeliCa 424kbps type is characterized in that the reader uses 10% shift amplitude modulation and Manchester bit encoding, and the bit period is halved.

[0064] according to Figure 3 In the illustrated implementation, each transmission burst 305 is followed by a wait time 307 (wait for response). During wait time 307, the sounder device waits for a response from an NFC device in its field. If the sounder device detects a response after one of the bursts 305, it means that a device of the technology in that burst is present in the field. If the sounder device does not detect a response after any burst 305, it means that no device of the bursting technology is present in the field.

[0065] Each of the five bursts 305 is preceded by a guard time 309 during which the sounder device configures the protocol of the burst 305 in the desired technique.

[0066] according to Figure 3 In the embodiment shown, when the device is in standby mode (part II), it "sounds" its environment by transmitting short, periodic pulses 311. Two pulses 311 are separated, for example, by a gap 303, similar to normal mode operation. Pulses 311 correspond to short field emissions from the sounder device to detect the presence of a possible device configured in card mode in its field. In the event of such a detection, the sounder device then exits standby and switches to normal mode. The detection analyzes the electrical quantities specific to these pulses (such as amplitude or phase), which will be different if a device configured in card mode is nearby.

[0067] According to one embodiment, each frame 301 has a duration between 60 ms and 80 ms and each pulse 311 has a duration of approximately 30 μs.

[0068] During frame 301 and pulse 311, it is not possible to detect the field emitted by the device configured in proximity reader mode.

[0069] According to an application example, the described embodiment is directed to a transportation system, and more specifically to the verification of a transportation ticket stored in a phone (e.g., a smartphone). Thus, in this example application, the first NFC device is a phone, and the second NFC device is a terminal for verifying or reading a transportation ticket.

[0070] Figure 4 The diagram is shown in a very schematic way Figure 1 The operating mode of the near field communication system shown in .

[0071] More specifically, Figure 4 A near field communication system including a phone 401 and a verification terminal 403 is illustrated.

[0072] In fact, when validating a transportation ticket, the user brings his phone 401 close to the validation terminal 403. The phone 401 is monitoring its surroundings. Figure 3 Describes the operation.

[0073] When the distance between the two devices is less than or equal to distance d, it is assumed that verification terminal 403 is within range of phone 401. For example, it is assumed that the signal level 401 received by the phone from verification terminal 403 exceeds a certain threshold, hereinafter referred to as the standby threshold. The standby threshold is, for example, defined and stored in the internal memory of phone 401.

[0074] However, even though it is within range of terminal 403, phone 401 is unable to detect it during frame 301. Detection of authentication terminal 403 by phone 401 is then delayed by approximately the time of frame 301.

[0075] This delay causes a delay in establishing communication between the phone 401 and the verification terminal 403 .

[0076] To alleviate this problem, you can consider:

[0077] When the phone 401 detects a received signal strength greater than the anti-collision threshold (less than the standby threshold) outside the transmission phase, the inquiry frame 301 is interrupted;

[0078] When the phone 401 detects that the received signal strength is greater than the standby threshold, the phone 401 is switched to the card mode and a call is established; then

[0079] The technology type of the terminal 403 is detected.

[0080] However, this would then lead to relying on the technique that has the highest SNR (Signal to Noise Ratio) that allows correct decoding of any response received from the card, the technique of the terminal 403 not being known at the time of communication establishment. This would lead to the choice of the 14443-A technique in practice.

[0081] The embodiments described below provide for avoiding worst-case selection and setting a communication establishment threshold based on the technology type of the terminal 403 .

[0082] Figure 5 The operation of the described embodiments is illustrated in a very schematic manner.

[0083] More specifically, the embodiments provide:

[0084] When the value of the detected external field (external field detector threshold) exceeds the collision avoidance threshold, the reader mode is interrupted, which has the effect of frame 301 or frame 311 ( Figure 3 ) prevent any field emission effects;

[0085] When the value of the detected external field exceeds the wake-up threshold, the phone 401 ( Figure 4 ) Exiting standby mode and switching it to card mode, the wake-up threshold is based on FeliCa technology or 14443-B technology;

[0086] Determine the technology of terminal 403 ( Figure 4 );

[0087] Setting a communication threshold based on the technology of terminal 403; and

[0088] When the value of the detected external field exceeds the previously set communication thresholds (RSSI_B threshold, RSSI_F212 threshold, RSSI_F424 threshold, RSSI_A threshold), a transaction with the terminal 403 is initiated according to the protocol of the terminal 403 technology.

[0089] The communication threshold is preferably the minimum threshold at which a transaction occurs in the technology.

[0090] For example, for all terminal technology types, the standby threshold corresponds to the communication threshold for the technology type with the highest signal-to-noise ratio required for reader decoding, e.g., the technology type requiring the minimum signal-to-noise ratio. For example, for all terminal technology types, the standby output threshold corresponds to the communication threshold for the FeliCa technology type or the 14443-B technology type. Preferably, the standby output threshold corresponds to the communication threshold for the 14443-B technology type.

[0091] Therefore, by determining the terminal 403 technology by the phone 401 before communicating and initiating the RSSI for the terminal 403 technology, communication can now begin without waiting for the worst case scenario.

[0092] The embodiment then allows time savings when establishing communication between phone 401 and terminal 403. Specifically, the lower the signal-to-noise ratio of the terminal 403 technology, the more significant the time savings. For example, the time saved by 14443-B technology when establishing communication between phone 401 and terminal 403 will be greater than the time saved by establishing communication between phone 401 and terminal 403 using FeliCa technology.

[0093] Embodiments also avoid communication errors at range limits.In fact, in some embodiments, communication is established only when the signal level allows for a given technology.

[0094] More generally, what I just explained about traffic ticket validation applies to any type of application where similar issues arise, such as contactless payment applications, product information reading, access control, and so on. For all of these applications, communication speed is crucial. For all of these applications, the speed of communication between devices is important.

[0095] Figure 6 Figure 1 shows a flow chart illustrating a transaction process between two NFC devices.

[0096] Figure 6 The flowchart shown begins with a step of checking (block 601, VBAT > VBATDET) whether the charge level of the phone's battery (VBAT) is greater than a previously determined battery limit value (VBATDET) and stored in the phone's internal memory. The battery limit value is, for example, between 2.4V and 3.2V. The battery limit value can be configured, for example, in steps of 0.2V. This condition is checked, for example, by a voltage monitoring circuit VBAT present in the phone.

[0097] After step 601, Figure 6 The flowchart described in FIG. 1 is as the distance d ( Figure 4 ) decreases (block 603, distance d decreases). The method relies on detecting the external field and its value when the distance d decreases.

[0098] If, after step 601, the phone leaves the range of the verification terminal at any time, for example, if the phone leaves the verification terminal so that the terminal is no longer within the range of the phone, the phone returns to the so-called polling phase, achieving the combined Figure 3 Describes the operation.

[0099] Otherwise, step 601 is followed by a loop in which the RSSI (Received Signal Strength Indicator) of the detected external field is monitored until the field value is greater than or equal to a threshold value, 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 below the value of threshold A (output N of block 605), the phone remains in the so-called polling state. As soon as the phone approaches the terminal and the value of the detected external field exceeds the value of threshold A (output Y of block 605), the phone stops its so-called polling phase (block 607, stop polling).

[0100] Step 607 is followed by a loop in which the detected external field is monitored until its value is greater than or equal to a threshold value referred to as 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 below the value of threshold B (output N of block 609), the phone remains in standby mode. Once the phone approaches the terminal and the value of the detected external field exceeds the value of threshold B (output Y of block 609), the phone enters card emulation mode (block 611, card emulation activation).

[0101] Step 611 is followed by step 613, in which the terminal's technology type is identified based on the query frame received from the terminal (Identifying Technology Type). This identification of the terminal's technology type then allows the communication threshold, or threshold C, to be set accordingly in step 615 (Setting Threshold C), from which the phone will respond to the terminal. Threshold C is set based on a value stored in the non-volatile memory of the phone's central unit 202. In practice, the value of Threshold C is stored in the phone's non-volatile memory for each modulation technology used to authenticate the terminal.

[0102] Step 615 is followed by a loop in 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 below the value of threshold C (output N of block 617), communication or a transaction between the phone and the terminal is not established (the terminal continues to send inquiry frames). Once the phone approaches the terminal and the value of the detected external field exceeds the value of threshold C (output Y of block 617), the phone begins communicating or transacting with the terminal using a protocol corresponding to the technology type of the terminal (block 619, start transaction). Because the communication threshold is based on the technology type of the terminal, communication is activated as quickly as possible while the phone is moving toward the terminal. This speed helps reduce the number of incomplete communications.

[0103] For example, threshold C corresponds to the first threshold, threshold B corresponds to the second threshold, and threshold A corresponds to the third threshold.

[0104] One advantage of the described embodiments and implementation modes is that they allow saving time when establishing communication between a first NFC device and a second NFC device configured in reader mode.

[0105] Another advantage of the described embodiments and modes of implementation is that they allow establishing communication in the technical protocol of a device configured in reader mode.

[0106] A further advantage of the described embodiments and modes of implementation is that they allow reducing the number of incomplete communications.

[0107] Various embodiments and variations have been described. Those skilled in the art will appreciate that certain features of these embodiments may be combined and that other variations will readily occur to those skilled in the art.

[0108] Ultimately, actual implementation of the embodiments and variations described herein is within the capabilities of a person skilled in the art based on the functional description provided above.

[0109] A method implemented by a first NFC device (401) can be summarized as including: establishing a transaction (619) with a second NFC device (403) configured in reader mode when a signal level received by the first device configured in card mode reaches a first threshold (C) based on a modulation technology type of the second device.

[0110] The first device (401) can be summarized as including initiating a transaction (619) with a second NFC device (403) configured in reader mode when a signal level received by the first device configured in card mode reaches a first threshold (C) based on a modulation technology type of the second device.

[0111] Establishing the transaction (619) may be preceded by a step of determining (613) by the first device the modulation technology type of the second device.

[0112] The first threshold (C) may correspond to a received signal strength indicator threshold.

[0113] The value of the first threshold (C) for each modulation technique type of the second device may be stored in a non-volatile memory of the first device (401).

[0114] The establishment may be preceded by the following steps: detecting by the first device (401) a field emitted by a second NFC device configured in reader mode; and switching (611) the first device to card mode when the received signal level reaches a second threshold (B).

[0115] The determining step (613) may occur before the detecting step.

[0116] The second threshold (B) may be smaller than the first threshold (C).

[0117] The second threshold (B) may correspond to a threshold of an ISO 14443B type technique.

[0118] The second threshold (B) may correspond to a threshold of the FeliCa technology.

[0119] When the received signal level reaches a third threshold (A) that is lower than the second threshold (605), the first device (401) may exit the interrogation mode (607) of its environment.

[0120] The second device (403) may be of ISO 14443B type, and the first threshold (C) corresponds to the minimum signal threshold for setting up a transaction in ISO 14443B technology.

[0121] The second device (403) may be of ISO 14443A type, and the first threshold (C) corresponds to a minimum signal threshold for establishing a transaction in ISO 14443A technology.

[0122] The second device (403) may be of FeliCa 212 type, and the first threshold (C) corresponds to a minimum signal threshold for establishing a transaction in FeliCa 212 technology.

[0123] The second device (403) may be of FeliCa 424 type, the first threshold (C) corresponding to a minimum signal threshold for establishing a transaction in FeliCa 424 technology.

[0124] The first device (401) may be a smartphone.

[0125] The second device (403) may be a transportation ticket reading terminal.

[0126] In some embodiments, a method implemented by a first NFC device (401) configured in card mode can be summarized to include initiating a transaction (619) with a second NFC device (403) configured in reader mode.

[0127] The method comprises the step of determining (613) by a first device (401) a modulation technique type of a second device (403) from among several modulation technique types.

[0128] The method comprises the step of comparing the signal level received by the first device with a first threshold (C) according to the type of modulation technique of the second device (403), communication being established when the signal level is above the first threshold.

[0129] In some embodiments, the first device (401) can be generally configured to determine a modulation technology type of the second device (403) among several modulation technology types, compare a level of a received signal with a first threshold (C) based on the modulation technology type of the second device (403), and establish a transaction (619) with the second NFC device (403) configured in reader mode when the signal level received by the first device configured in card mode reaches the first threshold (C).

[0130] The various embodiments described above can be combined to provide further embodiments.

[0131] These and other changes can be made to the embodiments in light of the above detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and claims, but should be construed to include all possible embodiments and the full scope of equivalents to which such claims are entitled. Therefore, the claims are not limited by this disclosure.

Claims

1. A method for implementing an NFC transaction, comprising: receiving, by a first near field communication (NFC) device, a first signal from a second NFC device, and exiting a polling mode by the first NFC device in response to a level of the first signal exceeding a first threshold; receiving, by the first NFC device, a second signal from the second NFC device, and switching, by the first NFC device, to operate in card mode in response to the second signal exceeding a second threshold value that is higher than the first threshold value; determining, by the first NFC device, a type of modulation technology of the second NFC device from a plurality of types of modulation technologies, and setting a third threshold value depending on the type of modulation technology; receiving, by the first NFC device configured in card mode, a third signal; as well as Based on the level of the third signal reaching the third threshold, a transaction is initiated between the first NFC device and the second NFC device configured in reader mode. The method of claim 1 , wherein the third threshold corresponds to a received signal strength indicator threshold.

3. The method according to claim 1, comprising: For each type of modulation technique of the second NFC device, a value of the third threshold is stored in a non-volatile memory of the first NFC device.

4. The method according to claim 2, comprising: detecting, by the first NFC device, a field emitted by the second NFC device configured in reader mode, The detecting and the switching are performed before initiating the transaction between the first NFC device and the second NFC device. The method of claim 4 , wherein the determining step occurs before the detecting step. The method according to claim 1 , wherein the second threshold is smaller than the third threshold. The method according to claim 1 , wherein the second threshold corresponds to a threshold of ISO 14443 Type B technique.

8. The method according to claim 1, wherein The second NFC device is of ISO 14443B type, and the third threshold corresponds to a minimum signal threshold for setting a transaction based on the ISO 14443B technology.

9. A device for implementing NFC transactions, comprising: Near field communication circuit; as well as an antenna coupled to the near field communication circuit, the antenna being operable to receive signals; wherein the near field communication circuit is in operation, receiving a first signal from a second NFC device, and exiting the polling mode in response to a level of the first signal exceeding a first threshold; receiving a second signal from the second NFC device and switching to operating in the card mode in response to the second signal exceeding a second threshold value that is higher than the first threshold value; determining a type of modulation technology of the second NFC device from a plurality of types of modulation technology, and setting a third threshold value depending on the type of modulation technology; and When the level of the third signal received by the antenna reaches a third threshold, initiating a transaction with the second NFC device, Wherein, the device is configured in card mode, and the second NFC device is configured in reader mode.

10. The apparatus according to claim 9, comprising: The memory is operable to store a value of the third threshold for each type of modulation technology of the second NFC device.

11. The apparatus according to claim 9, wherein The near field communication circuit in operation: A field transmitted by the second NFC device configured in reader mode is detected. 12 . The apparatus according to claim 9 , wherein the second threshold corresponds to a threshold of FeliCa technology. 13 . The device according to claim 9 , wherein the second NFC device is of ISO 14443A type, and the third threshold corresponds to a minimum signal threshold for establishing a transaction based on the ISO 14443A technology.

14. A system for implementing NFC transactions, comprising: a first NFC device; a second NFC device communicatively coupled to the first NFC device; wherein the first NFC device is in operation, receiving a first signal from the second NFC device, and exiting the polling mode in response to a level of the first signal exceeding a first threshold; receiving a second signal from the second NFC device and switching to operating in the card mode in response to the second signal exceeding a second threshold value that is higher than the first threshold value; determining a type of modulation technology of the second NFC device from a plurality of types of modulation technology, and setting a third threshold value depending on the type of modulation technology; as well as When the level of the received signal reaches the first threshold, a transaction with the second NFC device is initiated.

15. The system according to claim 14, comprising: The memory is operable to store a value of the third threshold for each type of modulation technology of the second NFC device. 16 . The system of claim 15 , wherein the second NFC device is of FeliCa 212 type, and the third threshold corresponds to a minimum signal threshold based on establishing a transaction in FeliCa 212 technology. 17 . The system of claim 15 , wherein the second NFC device is of FeliCa 424 type, and the third threshold corresponds to a minimum signal threshold based on establishing a transaction in FeliCa 424 technology.

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