EP4008135A1

EP4008135A1 - Method and system for generating at least one zone for the backscattering of an ambient signal and/or for receiving a backscattered ambient signal

Info

Publication number: EP4008135A1
Application number: EP20756935.1A
Authority: EP
Inventors: Romain FARA; Dinh Thuy Phan Huy
Original assignee: Orange SA
Current assignee: Orange SA
Priority date: 2019-08-02
Filing date: 2020-07-29
Publication date: 2022-06-08
Also published as: WO2021023928A1; FR3099670A1; CN114731182A; US11777572B2; US20220286171A1

Abstract

The invention concerns a method for generating at least one zone for backscattering, by at least one transmitter device and to at least one receiver device, an ambient radio signal emitted by at least one source, and/or for generating at least one zone for receiving, by the receiver device, said backscattered ambient signal. In addition, the method comprises: - a step of determining an emission constraint making it possible, when it is complied with by the source, to generate at least one zone for backscattering in which the electromagnetic power received is greater than a determined threshold, called "backscattering threshold", and/or to generate at least one zone for receiving in which the electromagnetic power received is less than a determined threshold, called "reception threshold", - a step of emission, by said source, in compliance with said emission constraint.

Description

Title of the invention:

PROCESS AND SYSTEM FOR GENERATING AT LEAST ONE ZONE FOR THE

BACK BROADCAST OF AN AMBIENT SIGNAL AND / OR FOR THE RECEPTION OF A

BACKSCATTERED AMBIENT SIGNAL

Prior art

The present invention belongs to the general field of telecommunications. It relates more particularly to a method for generating at least one zone for backscattering, by at least one transmitting device and towards at least one receiving device, of an ambient radio signal transmitted by at least one source, and / or for generating. at least one zone for the reception, by said receiver device, of said backscattered ambient signal. It also relates to a method of communication between at least one transmitting device and at least one receiving device, by backscattering an ambient radio signal transmitted by at least one source. The invention finds a particularly advantageous application, although in no way limiting, for applications of the "Internet of Things" type ("Internet of Things" or loT in Anglo-Saxon literature).

[0002] Ambient backscattering technology is well known today. The technical principles on which this technology is based are described, in particular, in the document by N. Van Huynh et al. titled “Ambient Backscatter Communications: A Contemporary Survey”, in IEEE Communications Surveys & Tutorials, vol. 20, no. 4, pp. 2889-2922,

Fourthquarter 2018. [0003] Conventionally, the backscattering of an ambient signal takes place between at least one transmitting device and at least one receiving device occupying respective fixed positions.

[0004] The ambient signal concerned corresponds to a radio signal transmitted, permanently or else recurrently, by at least one source in a given frequency band. For example, it can be a TV signal, a mobile phone signal (3G, 4G, 5G), a Wi-Fi signal, a WiMax signal, etc. To communicate with a receiver device, a transmitter device uses the ambient signal to send data to said receiver device. More particularly, the transmitter device reflects the ambient signal towards the receiver device, optionally by modulating it. The signal thus reflected is called a “backscattered signal”, and is intended to be decoded by the receiving device.

[0006] The fact that no additional radio waves (in the sense of a wave other than that resulting from the ambient signal) are emitted by the transmitting device makes the ambient backscattering technology particularly attractive. Indeed, the energy cost of a communication is thus optimized, which is particularly important in the current context of the IoT where every object of everyday life is intended to become a communicating object.

[0007] To implement this technology, the transmitter device is equipped with at least one antenna configured to receive the ambient signal but also backscatter it to the receiving device. The receiving device, on the other hand, is configured to decode the backscattered signal.

[0008] This being the case, and in practice, the implementation of this decoding may be compromised due to the areas within which the transmitter device and the receiver device are respectively positioned. [0009] In fact, the transmitter and receiver devices are generally positioned in a complex propagation environment comprising elements (walls, trees, ground, etc.) capable of generating reflections and diffractions of waves emitted by the source. Thus, and schematically, two types of signals reach the receiving device: the backscattered signal, the only carrier of the data useful for the implementation of ambient backscattering, as well as a signal coming directly from the source called “interfering signal”. and resulting from multiple reflections / diffractions of waves (by "directly", one refers here to waves not resulting from the backscattered signal). On account of said reflections / diffractions, said interfering signal corresponds to a sum of waves which interfere with one another constructively or else destructively. As a result, the power distribution generated by this interfering signal is not uniform and presents areas where the power is locally maximum or well, conversely, locally minimal. The areas where the power is locally maximum (respectively locally minimum) are areas where the interference level is the highest (respectively the lowest).

[0010] The fact that the distribution of these areas is not controlled proves to be problematic in ensuring effective communication between the transmitter device and the receiver device which are traditionally arranged arbitrarily in the vicinity of one another.

[0011] In fact, if the receiving device is located in an area of locally maximum power, the interference level may be high enough for the implementation of the decoding of the backscattered signal to be deteriorated (decoding error, poor reception of the signal. backscattered signal), causing communication between devices to fail.

Alternatively, or in addition, if the transmitting device is located in an area where the radiated power is locally minimum, the variation in electromagnetic power received by the receiving device, between times when the transmitting device backscattered and not not backscattered, may not reach a determined threshold, called "power threshold". However, reaching this power threshold conditions the effective implementation of the decoding.

Disclosure of the invention

The object of the present invention is to remedy all or part of the drawbacks of the prior art, in particular those set out above, by proposing a solution which makes it possible to generate at least one zone intended for a transmitter device and / or at least one zone intended for a receiving device, so as to prevent the backscattered signal from being decoded, and thus improve communication by ambient backscattering between these devices.

To this end, and according to a first aspect, the invention relates to a method for generating at least one zone for backscattering, by at least one transmitting device and towards at least one receiving device, of a radio signal ambient transmitted by at least one source, and / or generation of at least one zone for the reception, by said receiving device, of said backscattered ambient signal. In in addition, said method comprises:

a step of determining an emission constraint making it possible, when it is complied with by the source, to generate at least one zone for backscattering in which the electromagnetic power received is greater than a determined threshold, called "backscatter threshold ", And / or generate at least one zone for reception in which the electromagnetic power received is less than a determined threshold, called" reception threshold ",

- an emission step, by said source, subject to said emission constraint.

[0015] Thus, an area for backscattering, as generated by the generation method of the invention, forms an area in which it is advantageous to position at least one transmitter device in the context of an ambient backscattering communication. Indeed, the invention offers the possibility of generating a zone for backscattering within which the received electromagnetic power is adjusted, namely here greater than a backscatter threshold which can be determined as a function of said power threshold. Thus, by placing a transmitter device in an area for the backscatter thus generated, the probability that the backscatter signal can be decoded is increased. Communication by ambient backscattering between a transmitting device and a receiving device is therefore improved.

[0016] The aforementioned advantages apply symmetrically to the case of a zone for reception as generated by the generation method of the invention. Indeed, the invention offers the possibility of generating a zone for reception within which the electromagnetic power received is adjusted, namely here below a reception threshold which can be determined so as to avoid an excessive level of interference. important. Thus, by setting such a threshold, the objective is to prevent an area in which there is a lot of interference, at least enough so that the decoding error rate exceeds a given threshold, from being considered a valid area. for receiving the backscattered signal. Therefore, by placing a receiving device in a reception area thus generated, the probability that the backscattered signal can be decoded is increased. Communication by ambient backscattering between a transmitting device and a receiving device is therefore improved. The generation method according to the invention is also remarkable in that the emission constraint is determined so as to be used by said at least one source, the latter therefore participating actively in the generation of a area for backscattering and / or area for reception.

[0018] In particular modes of implementation, the generation method may further include one or more of the following characteristics, taken in isolation or in any technically possible combination.

[0019] In a first mode of implementation, the source is fixed and is configured to transmit in a frequency band, called "emission band", the determination step comprising:

a transmission, in a frequency band, called the “working band” and included in the transmission band, and by at least one terminal whose position is intended to be included in a zone for backscattering or for reception, d '' at least one pilot sequence to the source,

- an estimate, by the source and under the assumption of channel reciprocity, of a propagation channel between the source and said terminal from said at least one pilot sequence received,

a calculation, by the source and as a function of the estimated propagation channel, of a precoder capable of generating at said terminal an electromagnetic power greater than the backscattering threshold or less than the reception threshold depending on whether the position of the terminal is intended for be included in a zone for backscattering or for reception, said emission constraint corresponding to the use by the source of said precoder for sending.

[0020] Advantageously, when a single terminal is considered, and:

- If the position of said terminal is intended to be included in a zone for backscattering, said precoder is of the maximum ratio transmission type;

- Or, if the position of said terminal is intended to be included in a zone for reception, said precoder is capable of forming power zeros.

Also advantageously, when at least two terminals are considered, including a first terminal whose position is intended to be included in a zone for backscattering as well as a second terminal whose position is intended to be included in a zone for reception, said precoder is calculated so as to be of the forcing to zero type.

[0022] Such arrangements make it possible to simultaneously benefit from the generation of a zone for backscattering and of a zone for reception.

Thus, by placing transmitter and receiver devices in these areas, the invention offers the possibility of further improving the ambient backscatter communication between these devices.

[0023] In a second mode of implementation, the source is fixed and is configured to transmit in a frequency band, known as the "emission band", the determination step comprising:

- Obtaining, by the source, a grid of beams respectively associated with determined directions, and, for each beam of said grid,

- an emission, by the source, in the direction of said beam,

- during said transmission, an acquisition, in a frequency band, called “working band” and included in the transmission band, and by at least one terminal whose position is intended to be included in a zone for backscattering or for the reception of an electromagnetic power measurement received by said terminal, said determining step also comprising, once the power measurements have been acquired for each beam:

a selection, by said at least one terminal, of a beam for which the power measurement is greater than said backscattering threshold or below said reception threshold depending on whether the position of said terminal is intended to be included in a zone for backscattering or for reception,

a transmission, by said at least one terminal and to the source, of information indicating the selected beam, said emission constraint corresponding to the use by the source, on the basis of said at least one item of information, of a beam selected to transmit.

Advantageously, at least two terminals are considered, including a first terminal whose position is intended to be included in a zone for backscattering and a second terminal whose position is intended to be included in a zone for reception. , so that if the bundles respectively selected by the first and second terminals coincide, the emission constraint corresponds to the use of the beam common to said first and second terminals.

[0025] In a third mode of implementation, the source is fixed and is configured to transmit in a frequency band, known as the "emission band", the determination step comprising:

- obtaining, by the source as well as by at least one terminal whose position is intended to be included in an area for backscattering or for reception, of a code book comprising a plurality of precoders,

- a transmission, by the source and to said at least one terminal, of at least one determined pilot sequence,

- an estimate, by said at least one terminal, of a propagation channel between the source and said terminal from said at least one pilot sequence received, and, for each precoder of the codebook,

- a calculation, by said at least one terminal and as a function of said precoder, of an electromagnetic power value theoretically received by said terminal through the estimated propagation channel and in a frequency band, called

"Working band" and included in the emission band, said determining step also comprising, once the power values following each precoder have been calculated:

a selection, by said at least one terminal, of a precoder for which the power value is greater than said backscattering threshold or below said reception threshold depending on whether the position of said terminal is intended to be included in a zone for backscattering or for reception,

a transmission, by said at least one terminal and to the source, of information indicating the selected precoder, said emission constraint corresponding to the use by the source, on the basis of said information, of a selected precoder to send.

Advantageously, at least two terminals are considered, including a first terminal whose position is intended to be included in a zone for backscattering and a second terminal whose position is intended to be included in a zone for reception. , so that if the precoders respectively selected by the first and second terminals coincide, the emission constraint corresponds to the use of the precoder common to said first and second terminals.

In a fourth mode of implementation, the source comprises a directional antenna configured to transmit in a frequency band, called "emission band", and is associated with a displacement zone, the determination step comprising:

- a path of the source in at least part of said displacement zone,

- during the path of the source, an emission, by the source and in at least one location, of at least one pilot sequence following at least one determined direction of the directive antenna,

- during said transmission, an acquisition, in a frequency band, called “working band” and included in the transmission band, and by at least one terminal whose position is intended to be included in a zone for backscattering or for the reception of an electromagnetic power measurement received by said terminal, said determining step also comprising, once the path of the source has been completed,

a selection, by said at least one terminal, of a location and an antenna direction associated with said location for which the power measurement is greater than said backscatter threshold or less than the reception threshold depending on whether the position of said terminal is intended to be included in a zone for backscattering or for reception,

a transmission, by said at least terminal and to the source, of information indicating the location and direction of the selected antenna, said emission constraint corresponding to the use by the source, on the basis of said au minus one piece of information, a location and a direction selected to transmit.

Advantageously, at least two terminals are considered, including a first terminal whose position is intended to be included in a zone for backscattering and a second terminal whose position is intended to be included in a zone for reception. , so that if the antenna location and direction selected by the first terminal coincide with the location and the antenna direction selected by the second terminal, the emission constraint corresponds to the use of the location and the antenna direction common to said first and second terminals.

[0029] According to a second aspect, the invention relates to a method of communication between at least one transmitting device and at least one receiving device, by backscattering an ambient radio signal transmitted by at least one source, said method comprising:

- a step of generating at least one zone for backscattering and / or generating at least one zone for reception according to a method according to any one of claims 1 to 10,

a step of positioning said transmitting device in an area for backscattering if said transmitting device is not already positioned in an area for backscattering and / or positioning said receiving device in an area for receiving if said receiving device is not is not already positioned in an area for reception,

- a step of backscattering, by the transmitting device, of the ambient signal,

a step of reception, by the receiving device, of the backscattered ambient signal.

[0030] Thus, once at least one zone for backscattering and / or at least one zone for reception has been determined, the transmitter and receiver devices can be advantageously positioned in an appropriate manner in these zones. The communication established between these devices is of excellent quality, especially when at least one area for backscattering and at least one area for reception are generated.

In particular modes of implementation, the steps of generation, positioning, backscattering and reception are iterated on a recurring basis.

[0032] Such arrangements make it possible to take into account the variability of the environment in which the transmitter device and the receiver device are positioned. According to a third aspect, the invention relates to a computer program comprising instructions for the implementation of at least part of a generation method according to the invention or of at least part of a communication method according to the invention when said program is executed by a computer.

[0034] According to a fourth aspect, the invention relates to a recording medium readable by a computer on which is recorded a computer program according to the invention.

According to a fifth aspect, the invention relates to a system comprising means configured to implement a generation method according to the invention or means configured to implement a communication method according to the invention.

Brief description of the drawings

[0036] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an exemplary embodiment thereof without any limiting nature. In the figures:

[Fig. 1] FIG. 1 schematically represents a particular embodiment of an ambient backscattering communication system according to the invention;

[Fig. 2] Figure 2 schematically shows a partial view of an embodiment of a transmitter device of the communication system according to the invention;

[Fig. 3] FIG. 3 schematically represents a particular embodiment of a generation system according to the invention;

[Fig. 4] FIG. 4 represents, in the form of a flowchart, the main steps of a method for generating at least one zone for the backscattering of an ambient signal and / or at least one zone for the reception of a backscattered ambient signal according to the invention;

[Fig. 5] FIG. 5 diagrammatically represents a first particular mode of implementation of the generation method of FIG. 4; [Fig. 6] FIG. 6 schematically represents a second particular mode of implementation of the generation method of FIG. 4;

[Fig. 7] FIG. 7 schematically represents a third particular mode of implementation of the generation method of FIG. 4;

[Fig. 8] FIG. 8 schematically represents a fourth particular embodiment of the generation method of FIG. 4;

[Fig. 9] FIG. 9 represents, in the form of a flowchart, the main steps of a communication method according to the invention.

Description of embodiments

[0037] Figure 1 schematically shows a particular embodiment of an ambient backscattering communication system 10 according to the invention.

The communication system 10 comprises a source SO equipped with at least one directional antenna and configured to transmit, via said directional antenna and in a frequency band called "emission band", a radio signal called "ambient signal" . Said ambient signal is for example emitted permanently. Alternatively, the broadcast is carried out on a recurring basis.

For the remainder of the description, and as illustrated by FIG. 1, we consider in no way limiting the case where the ambient signal is emitted by only one source. No limitation is however attached to the number of sources that can be considered in the context of the present invention, since these sources transmit in respective bands whose intersection is not empty and which also intersects a determined frequency band. , as described below in more detail.

By "radio signal", we refer here to an electromagnetic wave propagating by wireless means, the frequencies of which are included in the traditional spectrum of radio waves (a few hertz to several hundred gigahertz). The remainder of the description relates more specifically, but in no way limiting, an ambient 4G mobile telephone signal emitted in the transmission band [811 MHz, 821 MHz]

It should however be specified that the invention remains applicable to other types of radio signals, such as for example a mobile telephone signal other than 4G (for example 2G, 3G, 5G), a Wi-Fi signal, a WiMax signal, a DVB-T signal, etc. In general, a person skilled in the art knows how to determine which emission signals can be considered for the source SO according to the modes of implementation envisaged for and detailed below.

The communication system 10 also includes a D_TX transmitter device and a D_RX receiver device respectively configured to communicate with each other by ambient backscattering from the ambient signal emitted by the source SO.

In the remainder of the description, and as illustrated by the embodiment of FIG. 1, it is considered in a non-limiting manner that the communication system 10 comprises a single transmitter device D_TX and a single receiver device D_RX. However, it should be noted that the invention is also applicable to a communication system comprising a plurality of transmitting devices and / or a plurality of transmitting devices.

In a manner known per se, communication by ambient backscattering consists of the use of the ambient signal, by the transmitter device D_TX, to send data to said receiver device D_RX. More particularly, the D_TX transmitter device (respectively the D_RX receiver device) is configured to perform, from the ambient signal (respectively from the backscattered signal), processing aimed at backscattering said ambient signal (respectively aimed at decoding said backscattered signal) , by implementing a backscattering method (respectively a decoding method).

For this purpose, the transmitter device D_TX (respectively the receiver device D_RX) comprises for example one or more processors and storage means (magnetic hard disk, electronic memory, optical disk, etc.) in which data is stored. and a program computer, in the form of a set of program code instructions to be executed to implement the backscattering method (respectively the decoding method).

[0047] Alternatively or in addition, the transmitter device D_TX

(respectively the receiver device D_RX) also comprises one or more programmable logic circuits, of FPGA, PLD type, etc., and / or specialized integrated circuits (ASIC), and / or a set of discrete electronic components, etc. adapted to implement the backscattering method (respectively the decoding method).

In other words, the transmitter device D_TX (respectively the receiver device D_RX) comprises a set of means configured in software (specific computer program) and / or hardware (FPGA, PLD, ASIC, etc.) to implement the backscattering method (respectively the decoding method).

The specific aspects concerning the transmission of data by backscattering to the receiver device D_RX, as well as those relating to the decoding techniques implemented by the latter, are known to those skilled in the art and go beyond the scope of present invention. Therefore, they are not detailed here further.

The waves conveyed by the signals considered in the present invention are conceptually represented by wavy arrows in FIG. 1. More particularly, the arrows F_1 and F_2 represent waves of the ambient signal emitted by the source SO. The waves represented by the arrow F_1 are backscattered by the transmitter device D_TX, and the waves of the backscattered signal are here represented by the arrow F_3. The waves represented by the arrow F_2 are for their part not backscattered and reach the receiving device D_RX directly. Only the waves represented by the arrow F_3 carry the data that the receiver device D_RX is intended to decode.

It should be noted that Figure 1 is given purely for illustration. Thus, it does not include, for example, any element capable of reflecting or diffracting the waves of the ambient signal. In this sense, Figure 1 is intended to be a simplified version of the environment in which the transmitter devices are located. D_TX and D_RX receiver. It should nevertheless be borne in mind that this environment is generally of complex configuration and comprises, in practice, elements (walls, trees, ground, etc.) capable of generating such reflections and diffractions.

Figure 2 schematically shows a partial view of an embodiment of the D_TX transmitter device of Figure 1 (the means configured in software and / or hardware are not shown). The configuration of such a D_TX transmitter device is known to those skilled in the art.

As illustrated in Figure 2, the D_TX transmitter device is equipped with an antenna 111 configured, in a manner known per se, to receive the ambient signal but also backscatter it to the D_RX receiver device. It should be noted that no limitation is attached to the number of antennas that can equip the D_TX transmitter device.

[0054] In the example of Figure 2, said antenna is constructed so as to have a larger dimension substantially equal to half the wavelength associated with a frequency F_C included in the emission band. More specifically, the frequency F_C considered here is the center frequency of the emission band [811 MHz, 821 MHz], or 816 MHz. Thus, said largest dimension of the antenna 111 is substantially equal to 18 cm.

In practice, the D_TX transmitter device is associated with a frequency band, called the "influence band", which corresponds to the frequency band in which the antenna 111 is able to receive / backscatter signals. Thus, in the example given above with reference to FIG. 2, said influence band corresponds to a frequency interval centered on said frequency F_C, and whose amplitude is equal to a switching frequency F_E of the transmitter device D_TX. Said switching frequency F_E corresponds to a frequency at which the transmitter device D_TX passes between distinct operating states, as is detailed later. In other words, said influence band is equal to [F_C - F_E / 2, F_C + F_E / 2]

For example, said switching frequency F_E is equal to 1 MHz, and the influence band is then equal to [815.5 MHz, 816.5 MHz] It is then noted that the influence band is included in the emission band associated with the source SO. Because of this inclusion, said influence band is qualified as a “working band”. By “working band”, reference is made here to the fact that the transmitter device D_TX is compatible with the source SO, namely that the backscatter can be carried out for any frequency included in said working band.

However, nothing excludes considering other values for the frequencies F_C and F_E (for example an F_E frequency between 10 Hz and 1 MFIz). It is nevertheless evident that in order for the transmitter device D_TX to be able to backscatter the ambient signal, said influence band should intersect non-empty with said transmission band, the working band therefore corresponding to at this intersection. Thus, if the D_TX transmitter device is configured to be associated with an influence band containing the emission band, then the working band of said D_TX transmitter device is defined as being equal to said emission band.

The D_TX transmitter device is also associated with operating states, namely a so-called "backscatter" state (the D_TX transmitter device backscaters the ambient signal) as well as an opposite state called "non-backscattering" (the D_TX transmitter device is transparent to the ambient signal). These states correspond to configurations in which said antenna 111 is connected to distinct impedances. This is typically a positive or even zero impedance in the case of a backscattering state, and conversely a theoretically infinite impedance in the case of the non-backscattering state.

For example, and as illustrated by Figure 2, the transmitter device D_TX comprises two switches 112, 113 configured so as to be able to connect to the antenna 111, according to their respective positions, an impedance l_1, by example equal to 0 Ohms, or even equal to R Ohms where R is a finite strictly positive value. When at least one of the switches 112, 113 is not connected to the impedance I_1, the antenna 111 is in a so-called “open circuit” configuration corresponding to said non-backscattering state. The receiver device D_RX, for its part, is configured for:

- receive the ambient signal emitted by the source SO, including in particular any reflections and diffractions undergone by the waves of this signal due to elements placed in the environment in which the D_TX transmitter and D_RX receiver devices are located,

- receive the backscattered signal from the D_TX transmitter device.

To this end, said D_RX receiver device comprises at least one reception antenna. It should be noted that no limitation is attached to the number of antennas that can equip the D_RX receiver device. For example, in the embodiment of FIG. 1, the receiver device D_RX is a smartphone.

In general, no limitation, other than that related to the transmission band considered, is attached to the structural forms that can be taken respectively by the source SO and the receiver device D_RX. By way of non-limiting examples, the following configurations can be envisaged:

- the SO source is a smartphone, and the D_RX receiver device is a base station,

- the SO source is a smartphone, and the D_RX receiver device is also a smartphone,

the source SO is a domestic gateway (also called an “Internet box”) transmitting a Wi-Fi signal, and the receiving device D_RX is a smartphone.

In the present embodiment, the transmitter device D_TX and the receiver device D_RX are respectively positioned in a zone Z_TX for backscattering and in a zone Z_RX for reception (the respective boundaries of the zones Z_TX and Z_RX are shown, to purely by way of illustration, dotted in figure 1).

By "zone for backscattering / reception", we refer here to a zone specifically and advantageously generated according to the invention so that the transmitter device D_TX (respectively the receiver device D_RX) is positioned there. The way in which these zones are generated is detailed below.

By way of non-limiting example, such an area for backscattering / reception corresponds to a geographical area known to be very frequented, especially during one or more periods of the day. This is for example a restaurant, a shopping area, a station dedicated to a mode of transport (metro, bus, train, etc.), a meeting room, etc. Moreover, in order to facilitate the identification of an area thus generated, it can be advantageously indicated by visual identification means, such as for example an indicator panel bearing a written mention relating to the nature of the zone considered.

[0066] Also, in addition to the communication system 10, the invention relates to a generation system 100 configured to generate such zones for backscatter / reception, with the objective that transmitter and receiver devices are positioned therein.

[0067] Figure 3 schematically shows a particular embodiment of said generation system 100 according to the invention.

As illustrated by FIG. 3, the generation system 100 comprises a source corresponding to the source SO of the communication system 10 described above.

The generation system 100 also includes two terminals, namely:

- a first terminal M_TX whose position is intended to be included in the zone Z_TX;

- a second M_RX terminal whose position is intended to be included in the Z_RX zone.

The remainder of the description relates more specifically, but in a nonlimiting manner, to the case where the two terminals M_TX and M_RX are both cellular telephones, for example of the smartphone type. However, nothing excludes considering terminals of another type, such as a tablet, a personal digital assistant, a personal computer, etc.

According to the invention, the source SO as well as said first and second terminals M_TX, M_RX are configured to perform processing aimed at generating the zones Z_TX, Z_RX, by implementing a method for generating said zones Z_TX, Z_RX . To this end, the source SO (respectively the first terminal M_TX / the second terminal M_RX) comprises for example one or more processors and storage means (magnetic hard disk, electronic memory, optical disk, etc.) in which stored are data and a computer program, in the form of a set of program code instructions to be executed to implement, at least in part, the generation method.

Alternatively or in addition, the source SO (respectively the first terminal M_TX / the second terminal M_RX) also includes one or more programmable logic circuits, of FPGA, PLD, etc. type, and / or specialized integrated circuits (ASIC) , and / or a set of discrete electronic components, etc. adapted to implement, at least in part, the generation method.

In other words, the source SO (respectively the first terminal M_TX / the second terminal M_RX) comprises a set of means configured in software (specific computer program) and / or hardware (FPGA, PLD, ASIC). , etc.) to implement, at least in part, the generation method.

For the remainder of the description, it is considered in no way limiting that the first terminal M_TX and the second terminal M_RX occupy respective fixed positions in the environment of the source SO. However, nothing excludes considering that at least one of said terminals M_TX, M_RX is mobile within said environment.

[0076] FIG. 4 represents, in the form of a flowchart, the main steps of the generation process according to the invention.

As illustrated by Figure 4, said generation method comprises:

- a step E1 of determining an emission constraint C_TX allowing, when it is respected by the source SO, to generate the zone Z_TX for the backscattering as well as the zone Z_RX for the reception,

a step of sending E2, by said source SO, subject to said emission constraint C TX. According to the invention, the emission constraint C_TX is determined, during step E1, so that, when the source SO emits, the electromagnetic power received in the zone Z_TX is greater than a determined threshold , known as “backscatter threshold” S_TX.

It is in fact known to those skilled in the art that the decoding of the backscattered signal can only be implemented if the variation in electromagnetic power received by the receiver device D_RX, between times when the backscattered transmitter device and not not backscattered, and called “power contrast” C_P, reaches a determined threshold, called “power threshold” S_P. Such a power threshold S_P is for example defined on the basis of a determined decoding error rate as well as the reception noise on the receiving device side D_RX.

Thus, it is important that the transmitter device D_TX can occupy a location in which the power radiated by the source SO is sufficient, so as to increase the power contrast C_P evaluated by the receiver device D_RX, and so that the threshold power S_P is finally reached.

In practice, the power contrast C_P can be evaluated according to the following formula:

C_P = | P_R - P_NR |.

In this formula, PR (respectively PNR) corresponds to the power received by the receiver device D_RX when the transmitter device D_TX is in the backscatter state (respectively in the non-backscatter state). Thus, a condition according to which the decoding can be carried out here results in C_P> S_P. It is therefore understandable that reaching the threshold S_P depends on the difference between P_R and P_NR.

It should however be noted that although the decoding can be theoretically implemented as soon as C_P> S_P, nothing excludes a more restrictive decoding condition from being imposed on the receiver device D_RX, such as for example C_P> N ^* S_P where N is a real number strictly greater than 1. The fact of imposing a more restrictive condition makes it possible to increase the quality of communication between the transmitting devices D_TX and receiver D RX. In any event, the backscattering threshold S_TX is determined as a function of said power threshold S_P. Those skilled in the art know how to set a threshold S_TX from which a zone can be considered for backscattering. For example, said threshold S_TX is chosen sufficiently high, for example greater than the power threshold S_P.

Thus, by placing the transmitter device D_TX in the zone Z_TX, the probability that the backscattered signal can be decoded is increased, and thus the communication by ambient backscattering between the devices is improved.

According to the invention, the emission constraint C_TX is also determined so that the electromagnetic power received in the zone Z_RX is less than a determined threshold, called the "reception threshold" S_RX.

The S_RX threshold considered here is typically determined as a function of a determined decoding error rate as well as a reception noise considered admissible on the D_RX receiver device side. In general, a person skilled in the art knows how to set an S_RX threshold above which (i.e. below which) a location can be considered for reception.

Thus, by setting such a threshold S_RX, the objective is to prevent an area in which there is a great deal of interference, at least enough for the decoding error rate to exceed a given threshold, from being considered as a valid area for receiving the backscattered signal.

For example, said S_RX threshold is chosen sufficiently low, for example in the range [-6 dB, -2dB], more particularly in the range [-6 dB, -4 dB]

Thus, by placing the receiver device D_RX in the zone Z_RX, the probability that the backscattered signal can be decoded is increased, and thus the communication by ambient backscattering between the devices is improved.

The remainder of the description aims to detail different modes of implementation of the generation method, and more particularly of the determination step E1.

FIG. 5 diagrammatically represents a first particular mode of implementation of the generation method of FIG. 4 in which the source SO is fixed and configured to emit data with high spectral efficiency thanks to the formation of beams (also called “beamforming” in the English literature).

As illustrated by FIG. 5, the determination step E1 comprises, in this first embodiment, a transmission E1_10, in the working band and by each of the terminals M_TX, M_RX, at minus one pilot sequence to the SO source.

The transmissions respectively associated with the first terminal M_TX and with the second terminal M_RX are for example synchronized. Alternatively, these broadcasts are out of sync.

The determination step E1 also includes an estimate E1_11, by the source SO and under the assumption of channel reciprocity, of a propagation channel CA_TX, CA_RX between the source SO and each of the terminals M_TX, M_RX from the pilot sequences received.

Estimation of a propagation channel in a wireless network is a conventional operation known to those skilled in the art, and therefore not detailed here further. It is based in particular on the sending of said sequences comprising pilot symbols on the propagation channel that it is sought to estimate. The reciprocity assumption for estimating the channel is also known to those skilled in the art who therefore understand that the communication context between the terminals M_TX, M_RX and the source SO, for sending / receiving the pilot sequences , corresponds to a TDD mode (acronym of the Anglo-Saxon expression "Time Division Duplex").

Finally, the determination step E1 also includes a calculation E1_12, by the source SO and as a function of the estimated propagation channels CA_TX, CA_RX, of a precoder capable of generating at the level of the first terminal M_TX a higher electromagnetic power at the backscattering threshold S_TX, as well as at the level of the second terminal M_RX, an electromagnetic power lower than the reception threshold S_TX. More particularly, in this first embodiment, said precoder is of the zero forcing type (or ZF for “Zero Forcing” in the English literature). In a manner known per se, such a ZF precoder makes it possible to obtain, simultaneously, a focusing of at least part of the radiation from the source SO towards the first terminal M_TX, as well as an absence of radiation at the source. second level M_RX terminal.

It should also be noted that the parameterization of a ZF type precoder in order to generate at the level of the first terminal M_TX a power level greater than the backscatter threshold S_TX, as well as a power level less than the threshold of S_TX reception at the second terminal M_RX is a process known from the state of the art.

According to such an implementation, each zone Z_TX, Z_RX then takes, for example, substantially the shape of a circle centered on the terminal M_TX, M_RX associated and whose radius is of the order of a quarter of the wavelength associated with the frequency F_C.

[0100] Ultimately, the emission constraint C_TX corresponds to the use by the source SO, during emission step E2, of said precoder to send.

[0101] FIG. 6 schematically represents a second particular embodiment of the generation method of FIG. 4 in which the source SO is fixed and configured to emit data with high spectral efficiency thanks to the formation of beams (" beamforming ”).

[0102] For the implementation of this second mode, each M_TX, M_RX terminal includes acquisition means configured to acquire, in the working band, electromagnetic power measurements received by said M_TX, M_RX terminal.

[0103] Conventionally, said acquisition means comprise an acquisition chain connected to a sensitive element configured to provide an analog electrical signal representative of the measured electromagnetic power. In the present exemplary embodiment, said sensitive element corresponds to a reception antenna equipping the terminal M_TX, M_RX.

[0104] Said acquisition chain comprises for example an acquisition card configured to condition said electrical signal. The packaging implemented by the acquisition card comprises for example, in a manner known in itself, amplification and / or filtering and / or current-power conversion. In general, the configuration of such acquisition means is well known to those skilled in the art, and is therefore not detailed here further.

As illustrated by FIG. 6, the determination step E1 comprises, in this second mode of implementation, obtaining E1_20, by the source SO, of a grid G_F of beams (denoted G_F (1 ), G_F (2), etc.) respectively associated with determined directions.

[0106] A beam direction G_F (i) corresponds to a combination of directions in space, such a combination being able to be translated algebraically in the form of a vector representation. Such a vector associated with a beam G_F (i) represents in itself a precoder which, when it is used by the source SO to transmit, makes it possible to focus the emission in the direction of the beam G_F (i) considered. Also, by adopting the above-mentioned vector representation, the beam grid G_F can be represented in the form of a matrix.

[0107] For example, the beams G_F (i) of the grid are determined by means of a discrete Fourier transform ("DFT", standing for Discrete Fourier Transform in the English literature). Such a method is for example described in the document: “DFT beamforming for more accurate estimate of signal DOA with application to improving DS / CDMA receiver performance”, T. B. Vu, Electronic Letters, vol. 36, no. 9, pp. 834-836, 2000.

In a particular example of implementation, the beam grid G_F is predetermined. For example, said grid G_F is stored (in the form of a matrix) in storage means annexed to the source SO, such as for example a database stored on a server. These additional storage means being distinct from the storage means of the source SO, obtaining the beam grid G_F corresponds to a transmission from said grid to the source SO by communication means equipping the latter. Once said G_F gate has been transmitted, the source SO stores it in its storage means. No limitation is attached to the configuration of the means of communication suitable for transmitting the beam grid G_F, which can be wired or wireless, as well as using any type of known transport protocol.

[0110] Alternatively, the beam grid G_F is determined directly by the source SO. For example, obtaining the beam grid G_F corresponds to a calculation of the coefficients of the matrix associated with said grid G_F by the source SO.

[0111] Once the beams grid G_F has been obtained, the determination step E1 also comprises, for each beam G_F (i) of the grid G_F:

- an emission E 1 _21, by the source SO, according to the direction of the beam G_F (i),

- during said transmission E 1 _21, an acquisition E1_22, in the working band, and by each of the terminals M_TX, M_RX, of an electromagnetic power measurement P_TX (i), P_RX (i) received by said terminal M_TX , M_RX.

In the second mode of implementation illustrated by FIG. 6, said step of determining E1 also comprises, once the power measurements have been acquired for each beam, a selection E1_23, by each terminal M_TX, M_RX, of a beam G_F (i), G_F (j) for which the power measurement P_TX (i), P_RX (j) is greater than said backscatter threshold S_TX or less than said reception threshold S_RX depending on whether the position of said terminal M_TX, M_RX is intended to be included in an area for Z_TX backscattering or for Z_RX reception.

Preferably, if several power measurements P_TX (i) acquired by the first terminal M_TX (respectively several power measurements P_RX (j) acquired by the second terminal M_RX) are greater than the backscatter threshold S_TX (respectively less than the threshold of reception S_RX), the selected beam, from among the beams associated with said measurements, corresponds to the beam for which the associated power measurement is maximum (respectively for which the power measurement is minimum).

However, nothing excludes considering a random selection, by the first terminal M_TX (respectively the second terminal M_RX), of a beam from among the beams whose associated power measurements are greater than the threshold. backscatter S_TX (respectively below the reception threshold S_TX) if applicable.

[0115] The determination step E1 further comprises a transmission E1_24, by each of the terminals M_TX, M_RX and to the source SO, of information INFO indicating the selected beam. The E1_24 transmission takes place, for example, via a signaling message that can be defined in a telecommunications standard.

[0116] Such information INFO typically corresponds to the index i of the selected beam G_F (i).

Finally, in said second mode of implementation, if the beams respectively selected by the first and second terminals M_TX,

M_RX coincide (for example the indices of the selected beams are equal), the emission constraint C_TX corresponds to the use by the source SO, during the emission step E2 and on the basis of said information INFO, of the beam common to said first and second terminals M_TX, M_RX to transmit.

It is noted that if the beams respectively selected by the first and second terminals M_TX, M_RX do not coincide, the emission constraint C_TX then corresponds to the use, by the source SO, of one or the other of said selected beams.

[0119] FIG. 7 schematically represents a third particular embodiment of the generation method of FIG. 4 in which the source SO is fixed and configured to emit data with high spectral efficiency thanks to the formation of beams (" beamforming ”).

[0120] As illustrated by FIG. 7, the determination step E1 comprises, in this third mode of implementation, obtaining E1_30, by the source SO as well as by each of the terminals M_TX, M_RX, of a L_C code book (also called “codebook” in Anglo-Saxon literature) comprising a plurality of precoders (denoted L_C (1), L_C (2), etc.).

The fact of considering L_C (i) precoders united within an L_C code book is well known to those skilled in the art who typically refers to a standard telecommunications to have access to such a code book L_C. Thus, in the present example of implementation (ambient signal of 4G mobile telephony), the codebook L_C is provided by a standard as defined in the document:

"3GPP TS 36.211 V15.5.0 (2019-03)". [0122] Said code book L_C is for example stored in storage means annexed to the source SO and the terminals M_TX, M_RX, such as for example a database stored on a server. These additional storage means being distinct from the storage means of the source SO and of the terminals M_TX, M_RX, obtaining the code book L_C corresponds to a transmission of said book to the source SO as well as to the terminals M_TX, M_RX by means of communication respectively equipping the latter. Once the code book L_C has been transmitted, the source SO and the terminals M_TX, M_RX stores it in their respective storage means.

[0123] No limitation is attached to the configuration of the means of communication suitable for transmitting the L_C codebook, which can be wired or wireless, as well as using any type of known transport protocol.

[0124] The step of determining E1 also comprises a transmission E1_31, by the source SO and to each of the terminals M_TX, M_RX, of at least one pilot sequence. The transmissions respectively associated with the first terminal M_TX and with the second terminal M_RX are for example synchronized. Alternatively, these broadcasts are out of sync.

[0126] The step of determining E1 also comprises an estimate E1_32, by each of the terminals M_TX, M_RX, of a propagation channel CA_TX, CA_RX between the source SO and said terminal M_TX, M_RX from the pilot sequences received.

[0127] As mentioned previously, the estimation of a propagation channel in a wireless network, from pilot sequences, is a conventional operation known to those skilled in the art, and therefore not detailed here any further. before. Once the propagation channels CA_TX, CA_RX have been estimated between the source SO and the terminals M_TX, M_RX, the determination step E1 also comprises, for each precoder L_C (i) of the code book L_C, a calculation E1_33, by each of the terminals M_TX, M_RX and as a function of said precoder L_C (i), of an electromagnetic power value Pt_TX (i), Pt_RX (i) theoretically received by said terminal M_TX, M_RX in the working band and through the estimated propagation channel for this terminal M_TX, M_RX.

In other words, at the end of said calculations, each terminal M_TX, M_RX is associated with a determined number of power values Pt_TX (i), Pt_RX (i), this number being equal to the number of precoders L_C (i) recorded in the L C.

[0130] It should be noted that a person skilled in the art knows how to implement such calculations of theoretical received power as a function of a considered precoder.

In the third mode of implementation illustrated by FIG. 7, said step of determining E1 also comprises, once said power values according to each precoder have been calculated, a selection E1_34, by each terminal M_TX, M_RX, of a precoder L_C (i), L_C (j) for which the power value Pt_TX (i), Pt_RX (j) is greater than said backscatter threshold S_TX or less than said reception threshold S_RX depending on whether the position of said terminal is intended to be included in an area for Z_TX backscattering or for Z_RX reception.

[0132] Preferably, if several power values Pt_TX (i) calculated by the first terminal M_TX (respectively several power measurements Pt_RX (j) calculated by the second terminal M_RX) are greater than the backscatter threshold S_TX (respectively less than the threshold of reception S_RX), the selected precoder, from among the precoders associated with said values, corresponds to the precoder whose associated power value is maximum (respectively whose power value is minimum).

However, nothing excludes considering a random selection, by the first terminal M_TX (respectively the second terminal M_RX), of a precoder among the precoders whose associated power values are greater. at the S_TX backscattering threshold (respectively less than the S_TX reception threshold) if applicable.

[0134] The determination step E1 further comprises a transmission E1_35, by each of the terminals M_TX, M_RX and to the source SO, of information INFO indicating the selected precoder. The E1_35 transmission takes place, for example, via a signaling message that can be defined in a telecommunications standard.

[0135] Such information INFO typically corresponds to the index i of the selected precoder L_C (i).

Finally, in said third mode of implementation, if the precoders respectively selected by the first and second terminals M_TX,

M_RX coincide (for example the indices of the selected precoders are equal), the emission constraint C_TX corresponds to the use by the source SO, during the emission step E2 and on the basis of said information INFO, of the precoder common to said first and second terminals M_TX, M_RX to transmit.

It is noted that if the precoders respectively selected by the first and second terminals M_TX, M_RX do not coincide, the emission constraint C_TX then corresponds to the use, by the source SO, of one or the other of said selected precoders.

[0138] The invention has hitherto been written considering that the SO source is fixed. The invention is not, however, limited to such a configuration of the SO source.

FIG. 8 schematically represents a fourth particular mode of implementation of the generation method of FIG. 4 in which the source SO is able to move and configured to send data in a directional manner.

For the implementation of this fourth mode, each terminal M_TX, M_RX comprises acquisition means having technical characteristics identical to those described above in the context of the second mode of implementation (FIG. 6). [0141] The source SO comprises means for orienting the directional antenna.

Thus, the SO source is able, via its orientation means, to modify the direction in which the directional antenna points even though the SO source does not modify its position. Such orientation means are of a type known per se, such as for example an electric motor dedicated to said orientation.

[0142] In addition, for the implementation of said fourth mode, the source SO comprises means of movement (not shown in the figures) in the environment which surrounds it.

[0143] For example, said displacement means comprise drive means, such as for example at least one electric motor, as well as guide means, such as for example wheels. However, nothing excludes considering other training means, such as a heat engine, as well as other guidance means, such as caterpillars.

[0144] Preferably, the SO source takes the form of a robot comprising an electric motor and wheels.

[0145] In addition to allowing the generation of at least one Z_TX zone for backscattering and / or at least one Z_RX zone for reception, the software and / or hardware configured means equipping the source SO also make it possible to control its displacement.

To this end, these means include for example a control module (not shown in the figures) configured to generate commands for moving the source SO.

[0147] For example, said commands are generated without assistance. In other words, the source SO is able to move autonomously, that is to say without the intervention of an operator.

[0148] Alternatively, the control of the SO source is carried out in an assisted manner by an operator who generates remote control signals, these control signals then being transmitted to the SO source which moves according to the data conveyed in these signals. . To this end, the source SO comprises for example communication means for the reception of said signals of control, said signals then being processed by the control module. These communication means are based, in a manner known per se, on a communication interface capable of exchanging data between said operator and the source SO. No limitation is attached to the nature of this communication interface, which can be wired or wireless, so as to allow the exchange of data according to any protocol known to those skilled in the art.

For the remainder of the description, it is considered in no way limiting that the operation of the source SO is ensured by an electrical energy that the latter is able to store.

[0150] For example, said electrical energy is contained in an electric battery integrated into the SO source, and can for example be recharged by means of solar panels equipping said SO source, or else by capacitive effect, so that said SO source is energetically autonomous. Alternatively, the recharging of said battery is carried out via a connection to the domestic electrical network.

[0151] However, nothing excludes considering other types of energy, such as, for example, fossil energy, especially in the case where the SO source is equipped with a heat engine. Finally, nothing excludes considering an energy mix (electrical and thermal) either.

[0152] In other words, and in general, no limitation is attached to the energy considered for the operation of the SO source, or even to the way in which this energy is obtained by the latter.

In addition, the source SO is associated with a zone, called a "displacement zone" Z_D, within which it can move.

Said movement zone Z_D typically corresponds to a geographic zone (on the ground) defined from the radiation pattern of the directional antenna equipping the source SO. More particularly, it is possible to determine, when the source SO is fixed, and from the radiation pattern of said directional antenna, a first coverage area (respectively a second coverage) corresponding to a geographical area within which the radiated power is greater than the backscatter threshold S_TX (respectively less than the reception threshold S_RX). It will of course be understood that this first coverage area (respectively this second coverage area) is liable to change during a movement of the source SO, as soon as said movement is carried out over a sufficient distance. Also, and in practice, the displacement zone Z_D is defined so as to have a greater dimension greater than or equal to the maximum between the largest dimension of the first coverage area and the largest dimension of the second coverage area.

[0155] However, nothing excludes considering a displacement zone Z_D whose largest dimension is defined differently, for example as being greater than or equal to the sum of the largest upper dimension and the largest dimension of the first zone. cover.

[0156] In general, no limitation is attached to the way in which said movement zone Z_D is defined. For example, on the basis or not of the radiation pattern, a plurality of parameters can be taken into account, such as for example an energy autonomy of operation of the SO source, the configuration of the environment in which the source is located. SO (obstacles, etc.), forecasting a density of presence of D_TX transmitting devices and / or D_RX receivers, etc.

[0157] As illustrated by FIG. 8, the determination step E1 comprises a path E1_40 of the source SO in at least part of the zone Z_D.

[0158] Such a path of the source SO allows the latter to scan at least in part the zone Z_D with the objective of testing antenna locations and directions from which it is possible to generate at least one zone. Z_TX for backscattering and / or at least one Z_RX area for reception.

By "journey", we refer here to an exploration phase, this phase may include a continuous movement (that is to say without stopping within said part) between respectively initial and final locations in which the source SO is fixed, or else which can be carried out in a fractional manner (that is to say with one or more intermediate stops within said part before reaching a final location). In a particular example of implementation, the path of the source SO is carried out autonomously, that is to say without external assistance. For example, the source SO is configured to analyze the environment in which it is located, in order to detect any obstacles that it can therefore bypass. Such detection is typically implemented by means of imaging means (for example a camera) equipping the source SO, as well as by means of processing implemented by said source SO and aimed at analyzing images obtained with said means of imagery. Such treatments are well known to those skilled in the art, and are therefore not detailed here further.

In another particular example of implementation, the path of the source SO is carried out in an assisted manner, for example by an operator able to remotely control the movements of the source SO.

Whatever the implementation considered (autonomous or assisted), the path of the source SO can take place according to a determined path, such as for example a spiral, a line, in slots, etc.

[0163] Alternatively, the displacement of the source SO can be carried out in a non-deterministic manner.

In general, no limitation is attached to the path followed by the source SO.

[0165] Furthermore, said part of the zone Z_D is for example configured so as to include the initial location of the source SO.

[0166] Alternatively, said part does not include the initial location, so that the source SO performs a preliminary movement in order to join said part which is then traversed.

[0167] In general, no limitation is attached to the shape presented by said part of the zone Z_D. In addition, the path of the source SO can be carried out for a determined duration which can be parameterized, so that the shape of said part can depend on this determined duration.

In a particular example of implementation, the path of the source SO is carried out throughout the zone Z_D. Proceeding in this way allows maximize the number of locations and directions that can be tested during the generation process.

During the journey of the source SO, the determination step E1 also comprises an emission E1_41, by the source SO and in at least one location A (i), of at least one pilot sequence following at least one determined direction D (i, j) of the directional antenna (i and j are integers greater than or equal to 1).

[0170] A direction D (i, j) of the directional antenna is conventionally expressed in the form of a pair of angular coordinates representing respectively the azimuth and the elevation of the antenna. It will of course be understood that the number of directions D (i, j) considered during transmission E1_41 is greater than or equal to the number of locations A (i) considered (ie for a given index i, the index j is greater than or equal to i).

[0171] In a particular example of implementation, the number of directions D (i, j) considered during the emission E1_41 is strictly greater than the number of locations A (i) considered. To do this, the direction of the directional antenna is changed using the orientation means described above. For example, at a location A (i), the source SO emits pilot sequences in several directions whose respective elevation components are all identical, but whose respective azimuth components are scaled at a pitch equal to a degree of so as to cover a determined angular sector, for example an angular sector equal to [0 °, 360 °].

[0172] It should be noted that no limitation is attached to the number of emission directions that can be considered at a location A (i).

[0173] Furthermore, the E1_41 transmission of a pilot sequence is preferably carried out at a standstill (fractional exploration phase). In other words, during its journey, the source SO marks a stop at a location A (i) as soon as it wishes to transmit.

However, nothing excludes considering that an emission is carried out while the source SO is in motion. No limitation is attached to the number of locations A (i) that can be considered for transmitting pilot sequences. In addition, if a plurality of locations A (i) is considered, these locations A (i) can be separated by a determined distance step, for example configurable. They can also be separated by a determined time step, for example configurable, in which case the speed of the source 11 can be adjusted to comply with said time step.

The determination step E1 also comprises, during said transmission E1_41, an acquisition E1_42, in the working band, and by each of the terminals M_TX, M_RX, of an electromagnetic power measurement P_TX (i), P_RX (i) received by said terminal M_TX, M_RX.

In the fourth mode of implementation illustrated by FIG. 8, said step of determining E1 also comprises, once the path of the source SO has been completed, a selection E1_43, by each terminal M_TX, M_RX, of a location A (m), A (k) and an antenna direction D (m, n), D (k, I) associated with said location A (m), A (k) for which the power measurement P_TX ( i), P_RX (k) is greater than said backscatter threshold S_TX or less than said reception threshold S_RX depending on whether the position of said terminal M_TX, M_RX is intended to be included in a zone for Z_TX backscatter or for Z_RX reception.

[0178] Preferably, if several power measurements P_TX (m) acquired by the first terminal M_TX (respectively several power measurements P_RX (k) acquired by the second terminal M_RX) are greater than the backscattering threshold S_TX (respectively less than the threshold of reception S_RX), the selected antenna location and direction, among the locations and directions associated with said measurements, correspond to the location and direction for which the associated power measurement is maximum (respectively for which the power measurement is minimum ).

However, nothing excludes considering a random selection, by the first terminal M_TX (respectively the second terminal M_RX), of a location and a direction among the locations and directions whose measurements of associated power are greater than the S_TX backscatter threshold (respectively less than the S_RX reception threshold) where applicable.

[0180] Furthermore, the determination step E1 comprises a transmission E1_44, by each of the terminals M_TX, M_RX and to the source SO, of information INFO indicating the location and direction selected. The E1_44 transmission takes place, for example, via a signaling message that can be defined in a telecommunications standard.

Finally, in said fourth embodiment, if the antenna location and direction selected by the first M_TX terminal coincide with the antenna location and direction selected by the second M_RX terminal, the constraint transmission C_TX corresponds to the use by the source SO, during the transmission step E2 and on the basis of said information INFO, of the location and direction of the antenna common to said first and second terminals M_TX, M_RX to send.

It is noted that if the locations and / or directions respectively selected by the first and second terminals M_TX, M_RX do not coincide, the emission constraint C_TX then corresponds to the use, by the source SO, of the antenna location and direction selected by either of said terminals M_TX, M_RX.

[0183] The invention has been described so far by considering only two terminals, namely the first terminal M_TX and the second terminal M_RX. The invention nevertheless remains applicable to a number of terminals other than two. Thus, nothing excludes considering the configuration according to which the generation system 100 consists of the source SO and one or more terminals for backscattering (respectively one or more terminals for reception).

[0184] Thus, and with regard more particularly to the first mode of implementation (Figure 5), nothing excludes considering an alternative in which only one terminal would be considered. According to this alternative, the calculation E1_12 of the precoder is carried out so as to allow the generation, at said terminal, of an electromagnetic power:

- greater than the backscattering threshold if the position of said terminal is intended for be included in a Z_TX zone for backscattering, or - less than the reception threshold if the position of said terminal is intended to be included in a Z_RX zone for reception.

[0185] For example, if the position of said terminal is intended to be included in a Z_TX zone for backscattering, said precoder is of the maximum ratio transmission type (or MRT for “Maximum Ratio Transmission” in the English literature). In other words, said MRT precoder is intended to be used so that the source SO focuses essentially towards said terminal in order to generate maximum power there.

Conversely, if the position of said terminal is intended to be included in a Z_RX zone for reception, said precoder is for example suitable for forming power zeros. Such a precoder is well known to those skilled in the art, and essentially consists in allowing the source SO to generate signals of opposite signs (and therefore capable of canceling each other out) at the level of the terminal considered for reception. For example, we can cite the scientific publication: "Null forming method by phase control of selected array elements using plane-wave synthesis", I. Chiba, S. Mano, Antennas and Propagation Society Symposium, pp. 70-73, 1987.

[0187] In addition, when several terminals of the same type are considered (for backscattering or for reception), nothing excludes considering that the respective positions of all or part of said terminals of the same type are intended for be included in the same zone (for backscattering or for reception depending on the type of terminals considered). Alternatively, the respective positions of the terminals are intended to be included in areas distinct from each other.

[0188] Furthermore, the invention has also been described so far by considering modes of implementation of the generation method based on the use of one or more terminals M_TX, M_RX. Proceeding in this way advantageously makes it possible to configure the source SO, via the determination of the emission constraint C_TX, to be transmitted in a specific manner (precoder of a particular type, selection of a precoder or of a beam from among a plurality of precoders or beams) according to the positions occupied by the terminals M_TX, M_RX during the determination step E1. The terminal or terminals M_TX, M_RX thus play the role of support for causing the source SO to be transmitted in a specific manner. In other words, when the terminal (s) M_TX, M_RX are used during the generation process, the determination step E1 aims to “teach” the source SO how the latter must send in order to generate one or more zones. Z_TX, Z_RX.

[0189] However, nothing excludes considering other modes of implementation of the generation method in which no terminal is used.

[0190] For example, in the case where the source SO is fixed and is configured to emit data with high spectral efficiency thanks to the formation of beams ("beamforming"), the determination step E1 may include obtaining, by the source SO, of a predetermined precoder implementing a discrete Fourier transform (as mentioned above in the description given with reference to FIG. 6), said emission constraint corresponding to the use by the source SO of said precoder to transmit during the transmission step E2. In this example, the location of the Z_TX zone or zones for backscattering or Z_RX for reception is not conditioned by the presence of one or more terminals. Since the precoder is entirely predetermined, it is possible to know in advance (for example via numerical simulations) the distribution of electromagnetic power in the environment surrounding the SO source. Thus, the positioning of a Z_TX zone for backscattering and / or of a Z_RX zone for reception is conditioned here by said power distribution. In practice, in this embodiment, a zone Z_TX for backscattering is typically chosen so as to be illuminated by the main emission lobe of the source SO, or even by a secondary lobe of sufficient power. A zone Z_RX for reception is typically chosen so as not to be illuminated by the emission lobes of the source SO.

[0191] Furthermore, according to another aspect, the invention also relates to a method of communication by ambient backscattering between the transmitter device D_TX and the receiver device D_RX. Said communication method is advantageously based on the generation method described above in order to allow efficient communication between these devices within the communication system 10 as described above. FIG. 9 represents, in the form of a flowchart, the main steps of the communication method according to the invention. Said communication method is detailed here, by way of illustration, with reference to the communication system 10 as described previously (FIG. 1).

[0193] As illustrated by FIG. 9, said communication method firstly comprises a step H1 of generating the Z_TX zone for backscattering and of generating the Z_RX zone for reception according to the method of generating the l 'invention.

[0194] Once said areas have been generated, the communication method comprises a step H2 of positioning said D_TX transmitter device in the Z_TX area for backscattering if said D_TX transmitter device is not already positioned there, and of positioning said D_RX receiver device. in zone Z_RX for reception if said receiving device D_RX is not already positioned there.

[0195] No limitation is attached to the way in which said positioning is carried out. For example, in the case where said devices D_TX, D_RX take the general form of a smartphone and that said zones Z_TX, Z_RX are identified by means of indicator panels, the respective users of the devices D_TX, D_RX are responsible for positioning the latter in according to the indications of said panels.

[0196] Once the positioning step H2 has been carried out, the communication method comprises a step H3 of backscattering, by the transmitter device D_TX, of the ambient signal emitted by the source SO (ie the transmitter device D_TX goes from the state of non-backscattering in the backscatter state if it was not in this state before). It also comprises a step H4 of reception, by the receiver device D_TX, of the ambient signal backscattered by the transmitter device D_TX.

In a particular mode of implementation (not shown in FIG. 9), said steps of generation H1, positioning H2, backscattering H3 and reception H4 are iterated recurrently. The fact of carrying out these steps recurrently makes it possible to take into account the variability of the environment in which the transmitter device D_TX and the receiver device D_RX are positioned.

[0199] For example, said steps are iterated periodically, for example once a day in an environment in which the power distribution generated by the source SO is stable, or even more, for example once every hour if the power distribution is likely to change substantially every hour.

Claims

[Claim 1] Method for generating at least one zone (Z_TX) for backscattering, by at least one transmitting device (D_TX) and towards at least one receiving device (D_RX), of an ambient radio signal transmitted by at least a source (SO), and / or generating at least one zone (Z_RX) for the reception, by said receiving device (D_RX), of said backscattered ambient signal, said method comprising:

- a step (El) of determining an emission constraint (C_TX) allowing, when it is complied with by the source (SO), to generate at least one zone (Z_TX) for the backscattering in which the electromagnetic power received is greater than a determined threshold, called “backscattering threshold” (S_TX), and / or generate at least one zone (Z_TX) for reception in which the electromagnetic power received is less than a determined threshold, known as “reception threshold "(S_RX),

- an emission step (E2), by said source (SO), subject to said emission constraint (C_TX).

[Claim 2] A method according to claim 1, in which the source (SO) is fixed and is configured to transmit in a frequency band, called “transmission band”, the step (El) of determining comprising:

- an emission (E1_10), in a frequency band, called the “working band” and included in the emission band, and by at least one terminal (M_TX, M_RX) whose position is intended to be included in a zone for backscattering (Z_TX) or for reception (Z_RX), of at least one pilot sequence to the source,

- an estimate (El_ll), by the source and under the assumption of channel reciprocity, of a propagation channel (CA_TX, CA_RX) between the source and said terminal (M_TX, M_RX) from said at least one pilot sequence received ,

- a calculation (El_12), by the source and as a function of the estimated propagation channel (CA_TX, CA_RX), of a precoder capable of generating at said terminal an electromagnetic power greater than the threshold of backscatter or less than the reception threshold depending on whether the position of the terminal is intended to be included in a zone for backscattering or for reception, said transmission constraint (C_TX) corresponding to the use by the source of said precoder to transmit.

[Claim 3] A method according to claim 2, wherein only one terminal is considered, and:

- if the position of said terminal is intended to be included in a zone (Z_TX) for backscattering, said precoder is of the maximum ratio transmission (MRT) type;

- Or, if the position of said terminal is intended to be included in a zone (Z_RX) for reception, said precoder is capable of forming power zeros.

[Claim 4] The method of claim 2, wherein at least two terminals are considered, including a first terminal (M_TX) whose position is intended to be included in an area (Z_TX) for backscattering as well as a second terminal (M_RX) whose position is intended to be included in a zone (Z_RX) for reception, said precoder being of the forcing to zero (ZF) type.

[Claim 5] The method of claim 1, in which the source (SO) is fixed and is configured to transmit in a frequency band, called “transmission band”, the step (El) of determining comprising:

- obtaining (E1_20), by the source, of a grid (G_F) of beams respectively associated with determined directions, and, for each beam of said grid (G_F (i)),

- an emission (El_21), by the source, in the direction of said beam,

- during said transmission, an acquisition (E1_22), in a frequency band, called "working band" and included in the transmission band, and by at least one terminal (M_TX, M_RX) whose position is intended for be included in a zone for backscattering (Z_TX) or for reception (Z_RX), of an electromagnetic power measurement (P_TX (i), P_RX (i)) received by said terminal, said determining step (El) also comprising, once the power measurements have been acquired for each beam:

a selection (E1_23), by said at least one terminal, of a beam for which the power measurement is greater than said backscatter threshold (S_TX) or less than said reception threshold (S_RX) depending on whether the position of said terminal is intended to be included in an area for backscattering or for reception,

a transmission (E1_24), by said at least one terminal and to the source, of information (INFO) indicating the selected beam, said emission constraint (C_TX) corresponding to the use by the source, on the basis of of said at least one item of information, of a beam selected to transmit.

[Claim 6] A method according to claim 5, wherein at least two terminals are considered, including a first terminal (M_TX) whose position is intended to be included in an area (Z_TX) for backscattering as well as a second terminal ( M_RX) whose position is intended to be included in a zone (Z_RX) for reception, so that if the beams respectively selected by the first and second terminals coincide, the emission constraint (C_TX) corresponds to the use of the beam common to said first and second terminals.

[Claim 7] The method of claim 1, in which the source (SO) is fixed and is configured to transmit in a frequency band, called “transmission band”, the step (El) of determining comprising:

- obtaining (El_30), by the source as well as by at least one terminal (M_TX, M_RX), the position of which is intended to be included in a zone for backscattering (Z_TX) or for reception (Z_RX), of a code book (L_C) comprising a plurality of precoders (L_C (i)),

- A transmission (E1_31), by the source and to said at least one terminal, of at least one determined pilot sequence,

- an estimate (E1_32), by said at least one terminal, of a propagation channel (CA_TX, CA_RX) between the source and said terminal (M_TX, M_RX) from said at least one pilot sequence received, and, for each precoder in the codebook,

- a calculation (E1_33), by said at least one terminal and as a function of said precoder, of an electromagnetic power value (Pt_TX (i), Pt_RX (i)) theoretically received by said terminal through the estimated propagation channel and in a frequency band, called the “working band” and included in the transmission band, said determining step (El) also comprising, once the power values following each precoder have been calculated:

- a selection (E1_34), by said at least one terminal, of a precoder for which the power value is greater than said backscatter threshold (S_TX) or lower than said reception threshold (S_RX) depending on whether the position of said terminal is intended to be included in an area for backscattering or for reception,

a transmission (E1_35), by said at least one terminal and to the source, of information (INFO) indicating the selected precoder, said emission constraint (C_TX) corresponding to the use by the source, on the basis of of said information, of a precoder selected to transmit.

[Claim 8] A method according to claim 7, wherein at least two terminals are considered, including a first terminal (M_TX) whose position is intended to be included in an area (Z_TX) for backscattering as well as a second terminal ( M_RX) whose position is intended to be included in a zone (Z_RX) for reception, so that if the precoders respectively selected by the first and second terminals coincide, the transmission constraint (C_TX) corresponds to the use of the precoder common to said first and second terminals.

[Claim 9] The method of claim 1, in which the source (SO) comprises a directional antenna configured to transmit in a frequency band, called the “emission band”, and is associated with a displacement zone (Z_D), l 'step (El) of determination comprising:

- a path (El_40) of the source in at least part of said displacement zone (Z_D),

- during the course of the source, an emission (El_41), by the source and in at least one location (A (i)), of at least one pilot sequence following at least one direction (D (i, j)) determined of the directional antenna,

- during said transmission, an acquisition (E1_42), in a frequency band, called “working band” and included in the transmission band, and by at least one terminal (M_TX, M_RX) whose position is intended for be included in a zone for the backscattering (Z_TX) or for the reception (Z_RX), of an electromagnetic power measurement (P_TX (i), P_RX (i)) received by said terminal, said determining step (El) comprising also, once the path of the source is completed,

- a selection (E1_43), by said at least one terminal, of a location (A (m), A (k)) and of an antenna direction (D (m, n), D (k, l )) associated with said location for which the power measurement is above said backscattering threshold (S_TX) or below the reception threshold (S_RX) depending on whether the position of said terminal is intended to be included in a zone for backscattering or for reception ,

a transmission (E1_44), by said at least terminal and to the source, of information (INFO) indicating the location and direction of the selected antenna, said emission constraint (C_TX) corresponding to the use by the source, based on said at least one piece of information, of a location and direction selected to transmit.

[Claim 10] A method according to claim 9, in which at least two terminals are considered, including a first terminal (M_TX) whose position is intended to be included in an area (Z_TX) for backscattering as well as a second terminal ( M_RX) whose position is intended to be included in an area (Z_RX) for reception, so that if the antenna location and direction selected by the first terminal coincide with the antenna location and direction selected by the second terminal, the emission constraint (C_TX) corresponds to the use of the location and the antenna direction common to said first and second terminals.

[Claim 11] Method of communication between at least one transmitting device (D_TX) and at least one receiving device (D_RX), by backscattering of an ambient radio signal transmitted by at least one source (SO), said method comprising:

- a step (Hl) of generating at least one zone (Z_TX) for the backscattering and / or generating at least one zone (Z_RX) for reception according to a method according to any one of claims 1 to 10,

a step (H2) of positioning said transmitting device in an area for backscattering if said transmitting device is not already positioned in an area for backscattering and / or positioning said receiving device in an area for reception if said device receiver is not already positioned in an area for reception,

- a step (H3) of backscattering, by the transmitting device, of the ambient signal,

- a step (H4) of reception, by the receiving device, of the backscattered ambient signal.

[Claim 12] The method of claim 11, wherein the steps of generating (H1), positioning (H2), backscattering (H3) and receiving (H4) are iterated repeatedly.

[Claim 13] A computer program comprising instructions for implementing at least part of a generation method according to any one of claims 1 to 10 or at least part of a generation method. communication according to any one of claims 11 to 12 when said program is executed by a computer.

[Claim 14] A computer readable recording medium on which a computer program according to claim 13 is recorded.

[Claim 15] A system comprising means configured to implement a generation method according to any one of claims 1 to 10 or means configured to implement a communication method according to any one of claims 11 to 12.