# Patent

## Title
Configuration of NFC routers for P2P communication

## Abstract

A method for configuring a first device for a near-field communication with a second device, wherein a peer-to-peer mode is selected if the second device draws the power supply of its circuits from a battery.

## Background
CROSS REFERENCE TO RELATED APPLICATION
This application claims priority to French Patent Application No. 13/51172, filed Feb. 12, 2013, which is hereby incorporated by reference to the maximum extent allowable by law.
BACKGROUND
1. Technical Field
The present disclosure generally relates to near-field communication systems and, more specifically, to the configuration of near-field communication devices for P2P (peer to peer) transmissions.
2. Discussion of the Related Art
More and more portable devices (smartphones, touch pads, etc.) are equipped with near-field communication devices (NFC).
Most often, such portable devices are capable of operating in two modes, respectively called card mode and reader mode. In card mode, the device operates as a contactless chip card to communicate with a near-field communication terminal (for example, another mobile device operating in reader mode). In reader mode, the device operates as a terminal and is capable of reading contactless cards (or another device operating in card mode), just as an electromagnetic transponder reader.
Electromagnetic transponder systems used in near-field communications are now well known. Their operation is based on the emission of a radio frequency radiation by the terminal or the reader to communicate with, and possibly to remotely supply, a transponder present in the field of the terminal. The transponder, when it is within the terminal range, captures this field and communicates by modulating the load that it forms on this field. A transponder is within the range when it is capable of exploiting the field, and possibly of extracting from this field a power sufficient for the operation of the circuits comprised therein. The terminal and the transponder are generally tuned to a same frequency.
When the device operates in reader mode, it most often has to remotely supply the transponder located within its range and with which it desires to communicate. Now, there exist different natures of transponders, from the simple passive electronic tag to more advanced transponders equipped with microprocessors. A transmission between a reader and a transponder thus generally begins with a search for the type of communication to be established between the two devices, that is, the communication standard to be respected.
The availability of devices capable of communicating in near field provides another possibility of communication, the peer-to-peer file exchange. Such a communication is performed according to an ISO-18092 (or ECMA 340; or NFC-Forum Digital Protocol) standard and is generally called F-type modulation. However, present processes for configuring an NFC device according to the type of modulation according to which it is to communicate may not be capable of detecting a need for a peer-to-peer communication.
SUMMARY
An embodiment overcomes all or part of the disadvantages of usual techniques for configuring a mobile near-field communication device according to the type of modulation according to which it is to communicate.
Another embodiment provides a configuration method capable of detecting a peer-to-peer communication need.
Another embodiment provides a solution compatible with usual processes for determining the communication type.
An embodiment provides a method for configuring a first device for a near-field communication with a second device, wherein a peer-to-peer mode is selected if the second device draws the power supply of its circuits from a battery.
According to an embodiment, the first device measures information representative of the current in an oscillating circuit for generating the field and compares it with a first threshold.
According to an embodiment, the peer-to-peer mode is selected if the value of said information is higher than said first threshold.
According to an embodiment, the peer-to-peer mode is selected if, further, the value of said information is higher than a second threshold higher than the first threshold.
According to an embodiment, if the value of said information is lower than said first threshold, the first device emits frames according to different modulation types and monitors the response of the second device.
According to an embodiment, the first device is initially configured for a communication according to an F-type modulation.
A device equipped with a near-field communication circuit, capable of implementing the method, is also provided.
The foregoing and other features and advantages will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a simplified view of a system of peer-to-peer communication by means of mobile near-field communication devices of the type to which the embodiments which will be described apply;
FIG. 2 is a simplified representation of a reader and of a transponder used in a near-field communication;
FIGS. 3A and 3B are timing diagrams illustrating the configuration of a reader on a modulation type;
FIG. 4 is a timing diagram of an example of configuration of the type of modulation of a near-field communication router;
FIG. 5 illustrates, in the form of a block diagram, an embodiment of a configuration method capable of detecting a peer-to-peer communication need;
FIGS. 6A and 6B illustrate the operation of the method of FIG. 5 in the absence of a peer-to-peer communication need;
FIGS. 7A and 7B illustrate the operation of the method of FIG. 5 in the presence of a peer-to-peer communication need.



DETAILED DESCRIPTION
The same elements have been designated with the same reference numerals in the different drawings, which have been drawn out of scale. For clarity, only those steps and elements which are useful to the understanding of the embodiments which will be described have been shown and will be detailed. In particular, the circuits for generating communication frames according to the different standards (or types) have not been detailed, the described embodiments being compatible with usual standards. Further, the generation of polling requests by a near-field communication device has not been detailed either, the described embodiments being here again compatible with usual devices.
FIG. 1 very schematically shows an example of a near-field communication system of the type to which the embodiments which will be described apply. In this example, two mobile devices 1 and 1′, of smartphone or tablet type, are capable of communicating with each other in near field mode. In a very simplified manner, these devices comprise various electronic circuits symbolized by a block 12 or 12′ in dotted lines, a battery 14 or 14′ for powering these circuits and peripherals (for example, a touch screen 16 or 16′) and a near-field communication circuit 18 or 18′ (NFC router) connected to an antenna 19 or 19′. The representation of FIG. 1 is very simplified and other circuits, pieces of equipment, or interfaces may equip devices 1 and 1′.
FIG. 2 is a partial simplified representation of devices 1 and 1′ illustrating the operation, considering that device 1 acts as a terminal or reader and that device 1′ acts as a transponder (card). Terminal 1 generates an electromagnetic field for transponders 1′ capable of being present in this field and of capturing this field to establish a communication with the reader.
Reader 1 comprises various electronic circuits (symbolized by a block 20 in FIG. 2) for processing the data to be transmitted and received (circuits 12 and 18, FIG. 1), and for generating a radio frequency signal (for example, at the 13.56-MHz frequency) intended to be amplified by an amplifier 24 before driving an oscillating circuit (antenna 19 or inductive element L1 and capacitive element C1). In the example of FIG. 1, a series oscillating circuit is assumed, inductive elements L1 and capacitive element C1 being series-connected between the output of amplifier 14 and the ground. The representation of FIG. 1 is simplified on the reader side and other circuits may be present.
The oscillating circuit of reader 1 generates a high-frequency electromagnetic field capable of being captured by transponders 1′ present in this field.
A transponder 1′ generally comprises a resonant circuit, formed of an antenna or inductance L2 and of a capacitive element C2, most often, in parallel. For an operation in card mode, remotely supplied by the terminal, the voltage across this oscillating circuit is rectified (rectifying bridge 26) to generate a D.C. voltage V2 for powering the various circuits (symbolized by a block 22 in FIG. 2) of the transponder (circuits 12′ and 18′, FIG. 1). Further, the radio frequency signal, or an image thereof, is sampled towards block 22 (input IN) to demodulate the messages received from the terminal and interpret them. The transmission, in the transponder-to-reader direction, is performed by modulating the load formed by the transponder circuits on the electromagnetic field generated by the reader. It is generally spoken of a retromodulation (most often resistive or capacitive). Such a retromodulation is symbolized in FIG. 1 by an output OUT of circuit 22 connected across the oscillating circuit.
The oscillating circuit of the device operating in reader mode (for example, 1) generates a high-frequency electromagnetic field capable of being sensed by the transponder(s) 1′ present in this field. The transmission in the reader-to-transponder direction is performed by modulating the carrier amplitude. The transmission, in the transponder-to-reader direction, is performed by modulating the load formed by the transponder circuits on the electromagnetic field generated by the reader.
The general operation of an electromagnetic transponder system is known and will not be detailed any further.
Generally, as long as no transponder (or device in card mode) has been detected in the field of the terminal (or device in reader mode), the latter periodically emits a polling frame. Indeed, it is not desirable for the reader to permanently emit for obvious power consumption reasons. Between polling frames, the device in reader mode may also switch to the card mode in order to, in case another device is present, respond thereto.
FIGS. 3A and 3B are timing diagram illustrating the operation of the system during such polling frames T and for the configuration of the communication type.
Frames T comprise, for reader 1, periodically emitting a train of alternations of the radio frequency carrier (for example, 13.56 MHz) with no modulation (signal S24 at the output of amplifier 24, FIG. 2). The frame duration is relatively short (typically, approximately ranging from 1 to 2 μs).
If no transponder is present in the field (left-hand portion of the timing diagrams of FIGS. 3A and 3B), the electromagnetic field is not disturbed and voltage V1 across capacitor C1, or an image of the current in the oscillating circuit of the reader, takes a value V1IDLE, called idle value, during frame T. Idle value means a value corresponding to a time when no transponder is present in the field.
When a transponder is present in the electromagnetic field, a voltage develops across its oscillating circuit. On the reader side, the power sampling by the transponder reflects as a lowering of the current in the oscillating circuit, and thus of voltage V1 down to a threshold detection value V1DET. Such a variation is detected by the reader, which can then start a communication with the transponder. Such a communication starts with a process for determining the type of transponder present in the field of the reader, that is, an identification of the type of modulation to be used for the transmission. This phase, generally called activity loop (AL) and defined, for example, as a polling loop in the NFC-Forum Activity 1.0 specification, is illustrated by a block in the timing diagram of FIG. 3A.
The detection of the lowering of voltage V1 is for example performed by a dedicated transponder detection circuit (Tag Detector) having the function of detecting a disturbance of the field emitted by device 1, that is, in practice, the presence of an antenna in its field.
FIG. 4 is a simplified block diagram of the steps of a phase for determining the transponder type (Activity Loop) which follows the detection of the presence of a transponder.
After a step 41 of initialization (NIT) of different variables, the reader starts by sending a request according to a first modulation type, and then, in the absence of any response from the transponder, switches to another type, and so on.
In NFC routers, radio communications are based on standards respecting a carrier frequency of approximately 13.56 MHz. Transmissions from the terminal to the transponder are mainly amplitude-modulated according to four families or types set by ISO standard 14443, designated as TYPE A, TYPE B, TYPE F, and 15693. The different types can be distinguished, among others, by the transmission rate, the carrier modulation index, and the data coding.
In the example of FIG. 4, the terminal starts by emitting in type A and watches whether it receives a response from the transponder (block 42, type A?). If it does, (output Y of block 42), it configures its modulator for type A (block 43, A) and the activity loop stops (block 44, OUT) and the transmission can start. If the transponder does not respond to the type-A modulation (and is thus not compatible with this type of modulation), the terminal or reader attempts to communicate by using type B (block 45, type B?). If it receives a response (output Y of block 45), it configures its modulation for type B (block 46, B) and the transmission can start. If it does not (output N of block 45), it attempts to communicate by using type F (block 47, type F?). If the transponder accepts type F (output Y of block 47), the terminal switches to this type of modulation (block 48, F). If it does not (output N of block 47), the terminal considers that the transmission cannot be established (block 49, ERR) and returns to an initial polling frame generation state T.
Other methods for determining the modulation type may be used in an activity loop. For example, the activity loop may start with an attempt to detect a type B or a type F.
Such a configuration is not capable of configuring two mobile devices and their NFC routers for a peer-to-peer operation (P2P).
In a peer-to-peer communication, and especially a communication in so-called passive peer-to-peer mode between two devices, one is called “initiator” (that which desires to send a file to the other) and the other is called “target”. The communication respects the reader-card operation, that is, one of the two devices operates in reader mode and the other operates in card mode. To simplify the following description, initiator 1 is considered as being configured in reader mode and target 1′ is considered as being configured in card mode. However, the inverse is possible.
Peer-to-peer communications are desired according to type F. Indeed, most telecommunications operators do not desire for a peer-to-peer communication to be established according to type A or B. Now, with usual activity loops, if the device in card mode responds on type A and does not support protocol ISO-18092 (output Y of block 42), the configuration loop stops and there is no way to switch to another standard. The peer-to-peer communication is then impossible.
Even by starting a configuration phase on a type-B detection, the problem remains the same: in the case where the modulation on type B or on type A is accepted, the configuration will not reach type F.
Only by starting a phase on type F can a target accepting a peer-to-peer communication be identified. This would however exclude other type-F communications.
The inventors have observed that, on the card-mode device side, a peer-to-peer communication would generate another functional difference. Indeed, for a reader-card communication, the device operating in card mode is generally remotely supplied by the reader. Conversely, the peer-to-peer mode is generally only available if the devices draw the power necessary to their operation from their respective batteries.
Thus, it is provided that a first device (initiator or emitter) desiring to send a file in peer-to-peer mode to a second device (target or receiver) starts by verifying whether the target draws power from the generated field.
FIG. 5 is a simplified block diagram of an embodiment of such a starting phase.
After an initialization phase (block 51, INITI), the device operating in reader mode emits an electromagnetic field and watches whether the distant device consumes power or not (block 52, CONSO?). This amounts to determining, for example, whether voltage V1 across the capacitor of its oscillating circuit remains approximately at the level of antenna detection threshold value V1DET or decreases down to a threshold V1USE corresponding to a usage value. More generally, such a determination is performed on information representative of the current in the oscillating circuit of the reader.
In the presence of power consumption by the device in card mode (output Y of block 52), for example detected by the fact that voltage V1 is lower than threshold V1USE, this means that the device is not configured for a peer-to-peer mode. A usual activity loop (block 53, AL), for example, of the type illustrated in FIG. 4, is then carried out.
In the absence of power consumption detected at block 52 (output N), for example detected by the fact that voltage V1 ranges between thresholds V1USE and V1DET, this means that the target device is powered by its battery. It can be deduced that it is configured for a peer-to-peer transmission. Initiator 1 (block 54, P2P) then starts a peer-to-peer (P2P) communication.
According to a variation illustrated in dotted lines, initiator 1 which desires to start a peer-to-peer communication is initially configured for a transmission according to type F (block 55, TYPE F). This simplifies subsequent processings.
FIGS. 6A and 6B illustrate the operation of the method of FIG. 5 in the case where the target device is ready for a peer-to-peer communication.
FIGS. 7A and 7B illustrate this operation in the opposite case.
FIGS. 6A and 7A are timing diagrams schematically illustrating the value of voltage V1. FIGS. 6B and 7B are timing diagrams illustrating the corresponding processes implemented from the point of view of configuration CONF of the transmission type.
In the left-hand portion of these timing diagrams, the variation according to which the emitter device is pre-configured with TYPE F has been illustrated in dotted lines (block 55, FIG. 5).
In FIGS. 6A and 6B, device 1′ uses the power of its battery. During polling frames T, voltage V1 is influenced by the presence of the antenna (lower than level V1DET), but remains higher than threshold V1USE. Accordingly, on the side of device 1, it is known that a Type-F communication will be started in peer-to-peer mode. The configuration is performed correspondingly (right-hand portion of timing diagrams 6A and 6B).
In the case of FIGS. 7A and 7B, device 1′ samples power from the field emitted by device 1. Accordingly, voltage V1 falls below threshold V1USE, which enables to detect that the communication will not be of P2P type. In this case, device 1 starts a usual configuration loop of activity loop (AL) type.
An advantage of the described embodiments is that it is now possible to identify a peer-to-peer communication for a correct configuration of a mobile telecommunication device equipped with an NFC router.
Various embodiments have been described. Various alterations and modifications will occur to those skilled in the art. In particular, although reference has been made to the level of voltage V1, any other quantity enabling the terminal to detect whether the target device uses or not its battery may be used. For example, the results provided by a circuit for detecting a current variation in the antenna may be used. Further, the practical implementation of the described embodiments is within the abilities of those skilled in the art based on the functional indications given hereabove and by using usual computer tools for parameterizing the terminals. Indeed, the implementation of these embodiments requires no structural modification of mobile telecommunication devices.
Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and the scope of the present invention. Accordingly, the foregoing description is by way of example only and is not intended to be limiting. The present invention is limited only as defined in the following claims and the equivalents thereto.

## Claims

1. A method, comprising:
determining, by a first near-field communication device, whether a second near-field communication device is self-powered; and
selecting, by the first near-field communication device, a mode of communication with the second near-field communication device based on the determination of whether the second near-field communication device is self-powered, wherein the determining comprises:
measuring, by the first near-field communication device, information representative of a current in an oscillating circuit generating a communication field; and
comparing, by the first near-field communication device, the measured information with a first threshold indicative of whether the second near-field communication device is drawing power from the communication field.

2. The method of claim 1 wherein a peer-to-peer mode of communication is selected by the first near-field communication device when a value of said measured information is higher than said first threshold.

3. The method of claim 1 wherein a peer-to-peer mode of communication is selected by the first near-field communication device when a value of said measured information is lower than a second threshold and higher than said first threshold.

4. The method of claim 1 wherein when a value of said measured information is higher than said first threshold, the method comprises:
emitting, by the first near-field communication device, frames according to different modulation types; and
monitoring, by the first near-field communication device, a response of the second near-field communication device to the emitted frames.

5. The method of claim 1, comprising:
setting a default communication mode of the first near-field communication device to type-F modulation.

6. A near-field communication device, comprising:
an oscillating circuit, which, in operation generates a communication field; and
processing circuitry coupled to the oscillating circuit, wherein the processing circuitry, in operation:
determines whether a second near-field communication device is self-powered; and
selects a mode of near-field communication with the second near-field communication device based on the determination of whether the second near-field communication device is self-powered, wherein the processing circuitry, in operation:

measures information representative of a current in the oscillating circuit; and
compares the measured information with a first threshold indicative of whether the second near-field communication device is extracting power from the communication field.

7. The device of claim 6 wherein the processing circuitry, in operation, selects a peer-to-peer mode of communication when a value of said measured information is higher than said first threshold.

8. The device of claim 6 wherein the processing circuitry, in operation, selects a peer-to-peer mode of communication when a value of said measured information is lower than a second threshold and higher than said first threshold.

9. The device of claim 6 wherein, in operation, when a value of said measured information is higher than said first threshold, the processing circuitry:
emits frames according to different modulation types; and
monitors a response of the second near-field communication device to the emitted frames.

10. The device of claim 6 wherein, in operation, the processing circuitry selects an initial communication mode of type-F modulation.

11. The device of claim 6, comprising:
a battery; and
a touchscreen.

12. A device, comprising:
one or more inputs to couple to an oscillating circuit; and
processing circuitry coupled to the one or more inputs, wherein the processing circuitry, in operation:
determines whether a second near-field communication device is self-powered; and
selects a mode of near-field communication with the second near-field communication device based on the determination of whether the second near-field communication device is self-powered, wherein the processing circuitry, in operation:

measures information representative of a current in the oscillating circuit; and
compares the measured information with a first threshold indicative of whether the second near-field communication device is extracting power from a communication field generated by the oscillating circuit.

13. The device of claim 12 wherein the processing circuitry, in operation, selects a peer-to-peer mode of communication when a value of said measured information is higher than said first threshold.

14. The device of claim 12 wherein the processing circuitry, in operation, selects a peer-to-peer mode of communication when a value of said measured information is lower than a second threshold and higher than said first threshold.

15. The device of claim 12 wherein, in operation, when a value of said measured information is higher than said first threshold, the processing circuitry:
emits frames according to different modulation types; and
monitors a response of the second near-field communication device to the emitted frames.

16. The device of claim 12 wherein, in operation, the processing circuitry selects an initial communication mode of type-F modulation.

17. The device of claim 12, comprising:
the oscillating circuit.