Method and system for generating at least one backscatter region of an ambient signal and / or for receiving a backscattered ambient signal

Abstract

The invention relates to a method for generating at least one area for backscattering ambient radio signals emitted by at least one source by at least one transmitter device to at least one receiver device and / or for generating at least one area for receiving said backscattered ambient signals by said receiver device. In addition, the method comprises: - a step of determining emission constraints, when said source complies with said emission constraints, for generating at least one area for backscattering and / or for generating at least one area for receiving, wherein in said at least one area for backscattering the received electromagnetic power is greater than a determined threshold value called "backscattering threshold", and in said at least one area for receiving the received electromagnetic power is less than a determined threshold value called "reception threshold", - a step of transmitting by said source in accordance with said emission constraints.

Description

Technical Field

[0001] The invention belongs to the general field of telecommunications. More specifically, the invention relates to a process for generating at least one backscattering area of ​​ambient radio signals emitted by at least one source to at least one receiver device by at least one transmitter device, and / or for generating at least one reception area of ​​said backscattered ambient signals by said receiver device. The invention also relates to a communication process between at least one transmitter device and at least one receiver device of ambient radio signals emitted by at least one source by backscattering. The invention is particularly advantageously, although by no means restrictively, suitable for use in applications of IOT type (“Internet of Things”). Background Art

[0002] The ambient backscatter technology is well known today. The technical principles on which it is based are described in particular in the document entitled “Ambient Backscatter Communications: A Contemporary Survey” by N. Van Huynh et al., IEEE Communications Surveys & Tutorials, Vol. 20, No. 4, pp. 2889-2922, 4th Quarter 2018.

[0003] In conventional terminology, backscattering of ambient signals is performed between at least one transmitter device and at least one receiver device occupying respective fixed positions.

[0004] The ambient signal in question corresponds to a radio signal emitted permanently or cyclically by at least one source in a given frequency band. For example, it can be a television signal, a mobile phone signal (3G, 4G, 5G), a Wi-Fi signal, a WiMAX signal, etc.

[0005] In order to communicate with a receiver device, a transmitter device utilizes the ambient signal to send data to the receiver device. More specifically, the transmitter device reflects the ambient signal to the receiver device (optionally by modulating it). The signal reflected in this way is called a "backscattered signal" and is intended to be decoded by the receiver device.

[0006] The fact that the transmitter device does not emit additional radio waves (in terms of waves other than those generated by the ambient signal) makes ambient backscatter technology particularly attractive. In fact, the energy cost of communication is optimized accordingly, which is particularly important in the current context of IoT, where every object in life can become a communication object.

[0007] To perform this technique, a transmitter device is equipped with at least one antenna that is configured to receive ambient signals but also to backscatter them to a receiver device. The receiver device itself is configured to decode the backscattered signals.

[0008] In view of this, and in practice, due to the areas within which the transmitter device and the receiver device are respectively located, it can be understood that the decoding is achieved.

[0009] In fact, the transmitter and receiver devices are usually located in a complex propagation environment that includes elements (walls, trees, ground, etc.) that may generate reflections and diffractions of the waves emitted by the source. In this way, and schematically, two types of signals arrive at the receiver device: the backscattered signal, the only carrier of data useful for performing environmental backscattering, and the signal that comes directly from the source called the "interference signal" and is generated by multiple reflections / diffraction of the wave ("direct" here means a wave that does not originate from the backscattered signal). Due to the so-called reflection / diffraction, the interference signal corresponds to the sum of waves that constructively interfere or destructively interfere with each other. Therefore, the distribution of the power generated by the interference signal is not uniform and exhibits areas where the power is locally maximum or, conversely, locally minimum. The area where the power is locally maximum (correspondingly, local minimum) is the area where the interference level is highest (correspondingly, minimum).

[0010] The uncontrolled distribution of these areas proves to be problematic in ensuring effective communication between transmitter and receiver devices which are conventionally arbitrarily arranged in close proximity to each other.

[0011] Indeed, if a receiver device is located in a local maximum power area, the interference level may be high enough to degrade the performance of the decoding of the backscattered signals (decoding errors, poor reception of the backscattered signals), thereby hindering communication between the devices.

[0012] Alternatively or additionally, if the transmitter device is located in an area of ​​local minimum of radiated power, the variation of the electromagnetic power received by the receiver device between the instants when the transmitter device backscatters and does not backscatter may fail to achieve a determined threshold value (referred to as the "power threshold"). Now, if this power threshold is indeed reached, it determines the effective performance of decoding. Summary of the invention

[0013] The object of the invention is to correct all or some of the disadvantages of the prior art, in particular those presented above, by proposing a solution which generates at least one area intended for a transmitter device and / or at least one area intended for a receiver device in order to prevent backscattered signals from being able to be decoded and thus improve communication by means of ambient backscatter between these devices.

[0014] For this purpose, and according to a first aspect, the present invention relates to a process for generating at least one backscattering area of ​​ambient radio signals emitted by at least one source to at least one receiver device by at least one transmitter device and / or for generating at least one reception area of ​​said backscattered ambient signals by said receiver device. In addition, said process comprises:

[0015] - a step for determining an emission constraint, for generating, when said source complies with said emission constraint, at least one backscattering zone in which the received electromagnetic power is greater than a determined threshold value, called “backscattering threshold”, and / or for generating at least one reception zone in which the received electromagnetic power is less than a determined threshold value, called “reception threshold”,

[0016] - a transmission step by said source for said emission constraints.

[0017] In this way, a backscattering zone such as that generated by the generation process of the present invention forms an area in which it is advantageous to position at least one transmitter device within the communication range by environmental backscattering. In fact, the present invention provides the possibility of generating a backscattering zone in which the received electromagnetic power is regulated, in particular to be greater than a backscattering threshold, which can be determined based on the power threshold. In this way, placing a transmitter device in a backscattering zone generated in this way increases the probability that the backscattered signal can be decoded. Therefore, this improves communication by environmental backscattering between a transmitter device and a receiver device.

[0018] In the case of a reception area such as that generated by the generation process of the present invention, the above advantages apply symmetrically. In fact, the present invention provides the possibility of generating a reception area in which the received electromagnetic power is regulated, in particular less than a reception threshold, which can be determined in order to prevent excessive interference levels. In this way, when fixing such a threshold, the aim is to prevent an area containing many interference instances (at least enough to make the decoding error rate exceed a given threshold) from being considered as an effective area for receiving backscattered signals. Therefore, placing a receiver device in a reception area generated in this way increases the probability that the backscattered signal can be decoded. Therefore, communication is improved by environmental backscattering between a transmitter device and a receiver device.

[0019] The generation process according to the invention is also notable in that emission constraints are determined in order to be exploited by the at least one source, the latter thus actively participating in the generation of the backscattering region and / or the reception region.

[0020] In certain embodiments, the generation process may also include one or more of the following features, taken alone or in all technically possible combinations.

[0021] In a first embodiment, the source is fixed and configured to transmit in a frequency band referred to as the "transmission bandwidth", the determining step comprises:

[0022] - at least one pilot sequence is transmitted to the source in a frequency band called "working band" and included in the transmission bandwidth and by at least one terminal whose location is intended to be included in the backscatter or reception area,

[0023] - estimating, by the source and assuming channel reciprocity, a propagation channel between the source and the terminal from the at least one received pilot sequence,

[0024] - calculating, by the source and from the estimated propagation channel, a precoder capable of generating, in the area of ​​the 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 to be included in the backscatter zone or in the reception zone,

[0025] The transmission constraints correspond to usage of the precoder by a source for transmission.

[0026] Advantageously, when a single terminal is considered, and:

[0027] - if the location of the terminal is intended to be included in the backscatter area, the precoder is of the maximum ratio transmission type;

[0028] - Otherwise, if the location of the terminal is intended to be included in the reception area, the precoder is capable of forming a power null.

[0029] Also advantageously, when considering at least two terminals, of which the position of a first terminal is intended to be included in the backscatter area and the position of a second terminal is intended to be included in the reception area, the precoder is calculated so as to be of the zero-forcing type.

[0030] This arrangement benefits from the generation of both backscattering areas and receiving areas. In this way, with transmitter and receiver devices placed in these areas, the present invention provides the possibility to further improve communication through ambient backscatter between these devices.

[0031] In a second embodiment, the source is fixed and configured to transmit in a frequency band referred to as the "transmission bandwidth", the determining step comprises:

[0032] - obtaining from said source a grid of beams respectively associated with the determined directions,

[0033] And, for each beam of the grid,

[0034] - transmissions by said source according to the direction of said beam,

[0035] - obtaining, during said transmission, in a frequency band called “working band” and included in the transmission bandwidth and by at least one terminal whose position is intended to be included in the backscatter or reception area, measurements of the electromagnetic power received by said terminal,

[0036] The determining step further comprises, once a measure of power is obtained for each beam:

[0037] - selection by said at least one terminal of a beam having a power measurement greater than said backscatter threshold or less than said reception threshold, according to which beam the location of said terminal is intended to be included in the backscatter or reception area,

[0038] - transmission by said at least one terminal to the source of an item of information indicating the selected beam,

[0039] The transmission constraints correspond to usage by the source of a beam selected for transmission based on the at least one information item.

[0040] Advantageously, at least two terminals are considered, including a first terminal whose position is intended to be included in the backscatter area and a second terminal whose position is intended to be included in the reception area, so that if the beams selected by the first terminal and the second terminal, respectively, are consistent, the transmission constraint corresponds to the use of a beam common to the first terminal and the second terminal.

[0041] In a third embodiment, the source is fixed and configured to transmit in a frequency band referred to as the "transmission bandwidth", the determining step comprises:

[0042] - obtaining, by the source and by at least one terminal whose location is intended to be included in the backscatter or reception area, a codebook comprising a plurality of precoders,

[0043] - transmitting, by said source, at least one determined pilot sequence to said at least one terminal,

[0044] - estimating, by the at least one terminal, a propagation channel between the source and the terminal from the at least one received pilot sequence,

[0045] And, for each precoder in the codebook,

[0046] - calculating, by said at least one terminal and as a function of said precoder, a value of electromagnetic power theoretically received by said terminal via the estimated propagation channel and in a frequency band called "operating band" and included in the transmission bandwidth,

[0047] The determining step further comprises, once the power value according to each precoder is calculated:

[0048] - selecting, by the at least one terminal, a precoder having a power value greater than the backscatter threshold or less than the reception threshold according to whether the location of the terminal is intended to be included in the backscatter area or the reception area,

[0049] - transmission by said at least one terminal to the source of an information item indicating the selected precoder,

[0050] The transmission constraints correspond to usage by the source of a precoder selected for transmission based on the information item.

[0051] Advantageously, at least two terminals are considered, including a first terminal whose position is intended to be included in the backscatter area and a second terminal whose position is intended to be included in the reception area, so that if the precoders selected by the first terminal and the second terminal, respectively, are consistent, the transmission constraint corresponds to the use of a precoder common to the first terminal and the second terminal.

[0052] In a fourth embodiment, the source comprises a directional antenna configured to transmit in a frequency band referred to as a "transmission bandwidth" and the directional antenna is associated with a travel area, the determining step comprises:

[0053] - travel of said source in at least a part of said travel area,

[0054] - transmission by said source of at least one pilot sequence in at least one placement in at least one determined direction of said directional antenna during the travel of said source,

[0055] - obtaining, during said transmission, in a frequency band called “working band” and included in the transmission bandwidth and by at least one terminal whose position is intended to be included in the backscatter or reception area, measurements of the electromagnetic power received by said terminal,

[0056] The determining step further comprises: once the travel of the source is completed,

[0057] - selecting, by the at least one terminal, a placement and an antenna direction associated with said placement, for which a power measurement is greater than said backscatter threshold or less than a reception threshold, according to which placement and the antenna direction associated with said placement the location of the terminal is intended to be included in a backscatter or reception area,

[0058] - transmission by said at least one terminal to the source of an information item indicating the chosen antenna placement and orientation,

[0059] The emission constraints correspond to the use by the source of a placement and direction selected for transmission based on the at least one information item.

[0060] Advantageously, at least two terminals are considered, including a first terminal whose position is intended to be included in the backscatter area and a second terminal whose position is intended to be included in the reception area, so that if the antenna placement and orientation selected by the first terminal is consistent with the antenna placement and orientation selected by the second terminal, the transmission constraint corresponds to the use of the placement and antenna orientation that are common to the first and second terminals.

[0061] According to a second aspect, the invention relates to a communication process between at least one transmitter device and at least one receiver device by backscattering of ambient radio signals emitted by at least one source,

[0062] The process includes:

[0063] - steps for generating at least one backscattering area and / or for generating at least one receiving area based on the process as described above,

[0064] - positioning the transmitter device in the backscatter area if the transmitter device is not already positioned in the backscatter area, and / or positioning the receiver device in the reception area if the receiver device is not already positioned in the reception area,

[0065] - a step of backscattering said ambient signal by said transmitter device,

[0066] - A step of receiving backscattered ambient signals by said receiver device.

[0067] In this way, once at least one backscattering area and / or at least one receiving area has been determined, the transmitter device and the receiver device can advantageously be appropriately positioned in these areas. The communication established between these devices is of excellent quality, in particular when at least one backscattering area and at least one receiving area are generated.

[0068] In certain embodiments, the steps for generating, locating, backscattering, and receiving are iterated cyclically.

[0069] Such an arrangement takes into account the variability of the environments in which the transmitter and receiver devices are located.

[0070] According to a third aspect, the invention relates to a computer program comprising instructions for performing at least a part of a generation process according to the invention or at least a part of a communication process according to the invention, when said program is executed by a computer.

[0071] According to a fourth aspect, the present invention relates to a computer-readable recording medium, in which a computer program according to the present invention is recorded.

[0072] According to a fifth aspect, the invention relates to a system comprising components configured to perform a generating process according to the invention or components configured to perform a communicating process according to the invention.

[0073] Another object of the invention is a source comprising means of software and / or hardware configured to execute a generation process such as that mentioned above.

[0074] The object of the present invention is also a source comprising:

[0075] -Components for determining launch constraints;

[0076] - Transmission means of an ambient radio signal, wherein the influence of said transmission constrained generates, relative to said emission constraints, at least one first area in which the received electromagnetic power is greater than a determined threshold value called "backscatter threshold" and / or at least one reception area in which the received electromagnetic power is less than a determined threshold value called "reception threshold".

[0077] In an embodiment, the source is configured to transmit in a frequency band referred to as a "transmission bandwidth", and the means for determining is configured to:

[0078] - assuming channel reciprocity, estimating the propagation channel between a source and at least one terminal whose location is intended to be included in the backscatter or reception area, from at least one pilot sequence transmitted by said at least one terminal in a frequency band called "working band" included in the transmission bandwidth,

[0079] - calculating, as a function of the estimated propagation channel, a precoder capable of generating, in the area of ​​the terminal, an electromagnetic power greater than the backscatter threshold or less than the reception threshold, according to which the position of the terminal is intended to be included in the backscatter area or in the reception area,

[0080] The transmission constraints correspond to usage of the precoder by the source for transmission.

[0081] In an embodiment, the source is fixed and configured to transmit in a frequency band referred to as the "transmission bandwidth", the means for determining is configured to:

[0082] - obtaining a grid of beams respectively associated with the determined directions,

[0083] - for each beam of the grid, transmitting according to the direction of the beam,

[0084] - obtaining, from at least one terminal whose position is intended to be included in the backscatter or reception area, an item of information indicating the beam selected by said at least one terminal,

[0085] The transmission constraints correspond to usage by the source of a beam selected for transmission based on the at least one information item.

[0086] In an embodiment, the source is fixed and configured to transmit in a frequency band referred to as the "transmission bandwidth", the means for determining is configured to:

[0087] - obtaining a codebook comprising a plurality of precoders,

[0088] - sending at least one determined pilot sequence to at least one terminal which is also a recipient of the codebook, the location of said at least one terminal being intended to be included in the backscatter or reception area,

[0089] - receiving an information item sent by said at least one terminal, said information item indicating a precoder selected by said at least one terminal,

[0090] The transmission constraints correspond to usage by the source of a precoder selected for transmission based on the information item.

[0091] In an embodiment, the source comprises a directional antenna configured to transmit in a frequency band referred to as a "transmission bandwidth", the source is associated with a travel area, and the means for determining is configured to:

[0092] - transmitting at least one pilot sequence in at least one placement in at least one determined direction of said directional antenna during the travel of said source in at least a part of said travel area,

[0093] - receiving an item of information sent by at least one terminal, the item of information indicating a placement chosen by the terminal and an antenna direction associated with said placement, the location of said at least one terminal being intended to be included in the backscatter or reception area,

[0094] The emission constraints correspond to the use by the source of a placement and direction selected for transmission based on the at least one information item. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] Other characteristics and advantages of the invention will emerge from the following description made with reference to the accompanying drawings, which illustrate exemplary embodiments without any limiting character, in which:

[0096] Figure 1 Schematically illustrates a specific embodiment of a communication system by ambient backscatter according to the present invention;

[0097] Figure 2schematically illustrates a part of an exemplary embodiment of a transmitter device of a communication system according to the present invention;

[0098] Figure 3 A specific embodiment of a generation system according to the invention is schematically illustrated;

[0099] Figure 4 The main steps of the process of generating at least one backscattering area of ​​an ambient signal and / or at least one receiving area of ​​a backscattered ambient signal according to the present invention are illustrated in the form of a flow chart;

[0100] Figure 5 Schematically illustrates Figure 4 A first specific embodiment of the generation process of;

[0101] Figure 6 Schematically illustrates Figure 4 A second specific embodiment of the generation process of;

[0102] Figure 7 Schematically illustrates Figure 4 A third specific embodiment of the generation process of;

[0103] Figure 8 Schematically illustrates Figure 4 A fourth specific embodiment of the generation process of;

[0104] Fig. 9 The main steps of the communication process according to the present invention are illustrated in the form of a flow chart. DETAILED DESCRIPTION

[0105] Figure 1 A specific embodiment of a communication system 10 by ambient backscatter according to the present invention is schematically illustrated.

[0106] The communication system 10 comprises a source SO equipped with at least one directional antenna and configured to transmit via said directional antenna a radio signal called "ambient signal" in a frequency band called "transmission bandwidth". Said ambient signal is for example emitted permanently. Alternatively, the transmission is performed cyclically.

[0107] For the rest of the description, and as Figure 1 As shown, the situation where the ambient signal is emitted by only a single source is considered to be in no way limiting. However, there is no restriction on the number of sources that can be considered within the scope of the present invention, since these sources emit in corresponding bandwidths whose intersection is not empty and also intersects with the determined frequency band, as described in more detail below.

[0108] "Radio signal" here refers to electromagnetic waves that are extended wirelessly and whose frequencies are included in the traditional spectrum of radio waves (a few hertz to tens of gigahertz).

[0109] The remainder of the description focuses more specifically, but by no means restrictively, on ambient signals from 4G mobile phones transmitted in the transmission bandwidth [811 MHz, 821 MHz].

[0110] However, it should be noted that the present invention is still applicable to other types of radio signals, such as, for example, mobile phone signals other than 4G (e.g., 2G, 3G, 5G), Wi-Fi signals, WiMAX signals, DVB-T signals, etc. In general, a person skilled in the art knows how to determine which transmission signals may be considered for the source SO according to the embodiments contemplated and described in detail hereinafter.

[0111] The communication system 10 further comprises a transmitter device D_TX and a receiver device D_RX, each configured to communicate with each other via ambient backscatter from an ambient signal emitted by a source SO.

[0112] In the rest of the description, and as Figure 1 In the embodiment shown in FIG. 1 , a communication system 10 is considered in a non-limiting manner to include 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 communication systems including a plurality of transmitter devices and / or a plurality of transmitter devices.

[0113] In a manner known per se, communication by ambient backscattering comprises the use of ambient signals by a transmitter device D_TX to send data to the receiver device D_RX. More specifically, the transmitter device D_TX (respectively, the receiver device D_RX) is configured to perform a process from the ambient signal (respectively, from the backscattered signal) aimed at backscattering the ambient signal (respectively, aimed at decoding the backscattered signal) by performing a backscattering process (respectively, a decoding process).

[0114] For this purpose, the transmitter device D_TX (respectively, the receiver device D_RX) comprises, for example, one or more processors and memory components (magnetic hard drive, electronic memory, optical disk, etc.) in which data and computer programs are stored in the form of a set of program code instructions to be executed to perform the backscattering process (respectively, the decoding process).

[0115] Alternatively or additionally, the transmitter device D_TX (respectively, the receiver device D_RX) also includes a circuit of the FPGA, PLD type, etc. or a programmable logic circuit, and / or an application-specific integrated circuit (ASIC), and / or a group of discrete electronic components, etc., suitable for performing the backscatter process (respectively, the decoding process).

[0116] In other words, the transmitter device D_TX (respectively, the receiver device D_RX) comprises a set of components configured for software (specific computer program) and / or hardware (FPGA, PLD, ASIC, etc.) for performing a backscattering process (respectively, a decoding process).

[0117] Specific aspects regarding the transmission of data by backscattering to the receiver device D_RX and regarding the decoding technique implemented by the latter are known to the person skilled in the art and are outside the scope of the present invention. Therefore, they will not be described in further detail here.

[0118] The wave transmitted by the signal considered in the present invention is composed of Figure 1 . More specifically, arrows F_1 and F_2 illustrate the waves of the ambient signal emitted by the source SO. The wave shown by arrow F_1 is backscattered by the transmitter device D_TX, and the wave of the backscattered signal is shown here by arrow F_3. The wave shown by arrow F_2 is not backscattered itself, but reaches the receiver device D_RX directly. Only the wave shown by arrow F_3 carries the data that the receiver device D_RX aims to decode.

[0119] It should be noted that Figure 1 is given purely illustratively. In this way, it does not, for example, include elements of waves that may reflect or diffract ambient signals. In this sense, Figure 1 Meaning a simplified version of the environment in which the transmitter D_TX and receiver D_RX devices are located. However, it should be remembered that this environment usually has a complex configuration and in reality comprises elements (walls, trees, ground, etc.) capable of generating such reflections and diffractions.

[0120] Figure 2 Schematically illustrates Figure 1 Detailed view of an exemplary embodiment of a transmitter device D_TX of FIG. 1 (components configured as software and / or hardware are not shown here). The configuration of such a transmitter device D_TX is known to a person skilled in the art.

[0121] like Figure 2As shown, the transmitter device D_TX is equipped with an antenna 111 which is configured in a manner known per se to receive ambient signals but also to backscatter them to the receiver device D_RX. It should be noted that there is no restriction on the number of antennas that may be mounted on the transmitter device D_TX.

[0122] exist Figure 2 In the example of , the antenna is constructed so as to present a larger dimension substantially equal to half the wavelength associated with the frequency F_C contained in the transmission bandwidth. More specifically, the frequency F_C considered here is the center frequency of the transmission bandwidth [811 MHz, 821 MHz], i.e. 816 MHz. In this way, the larger dimension of the antenna 111 is substantially equal to 18 cm.

[0123] In practice, the transmitter device D_TX is associated with a frequency band called "influential bandwidth", which corresponds to the frequency band in which the antenna 111 is able to receive / backscatter signals. Figure 2 In the example given, the affected bandwidth corresponds to a frequency interval centered on the frequency F_C and its amplitude is equal to the switching frequency F_E of the transmitter device D_TX. The switching frequency F_E corresponds to the frequency at which the transmitter device D_TX transitions between different operating states, as described in detail later. In other words, the affected bandwidth is equal to [F_C-F_E / 2, F_C+F_E / 2].

[0124] For example, the switching frequency F_E is equal to 1 MHz and the affected bandwidth is then equal to [815.5 MHz, 816.5 MHz]. Obviously, the affected bandwidth is included in the transmission bandwidth associated with the source SO. Due to this inclusion, the affected bandwidth is defined as the "operating band". The "operating band" here refers to the fact that the transmitter device D_TX is compatible with the source SO and can therefore in particular be backscattered for any frequency included in the operating band.

[0125] However, it is not excluded that other values ​​of the frequencies F_C and F_E are considered (for example, a frequency F_E between 10 Hz and 1 MHz). However, it is clear that in order for the transmitter device D_TX to be able to backscatter ambient signals, the influential bandwidth should have a non-empty intersection with the transmission bandwidth, so that the operating frequency band corresponds to this intersection. In this way, if the transmitter device D_TX is configured so as to be associated with an influential bandwidth containing the transmission bandwidth, the operating frequency band of the transmitter device D_TX is defined to be equal to the transmission bandwidth.

[0126] The transmitter device D_TX is also associated with operating states, in particular a state called "backscatter" (the transmitter device D_TX backscatters ambient signals) and an opposite state called "non-backscatter" (the transmitter device D_TX is transparent to ambient signals). These states correspond to configurations in which the antenna 111 is connected to a single impedance. In the case of the backscatter state, this is typically a positive impedance, or even zero, and in the case of non-backscatter, on the contrary, this is typically a theoretically infinite impedance.

[0127] For example, and if Figure 2 As shown, the transmitter device D_TX comprises two switches 112, 113, which are configured so that they can be connected to the antenna 111 according to their respective positions (e.g., an impedance I_1 equal to 0 ohms or equal to R ohms, where R is a strictly positive finite value). When at least one of the switches 112, 113 is not connected to the impedance I_1, the antenna 111 is in a configuration called "open circuit" corresponding to the non-backscattering state.

[0128] Thus, the receiver device D_RX is configured as:

[0129] - receiving an ambient signal emitted by the source SO, including in particular the possible reflections and diffractions experienced by the waves of this signal due to elements placed in the environment containing the transmitter D_TX and receiver D_RX devices,

[0130] - Receive the backscattered signal from the transmitter device D_TX.

[0131] For this purpose, the receiver device D_RX comprises at least one receiving antenna. It should be noted that there are no restrictions on the number of antennas that can be installed on the receiver device D_RX. Figure 1 In the embodiment of the present invention, the receiver device D_RX is a smart phone.

[0132] In general, no constraints are attached to the structural forms that can be taken by the source SO and the sink device D_RX, respectively, except those related to the transmission bandwidth considered. As non-limiting examples, the following configurations are possible:

[0133] - the source SO is a smartphone and the receiver device D_RX is a base station,

[0134] - the source SO is a smartphone and the sink device D_RX is also a smartphone,

[0135] - The source SO is a home gateway (or "Internet in a box") transmitting Wi-Fi signals, and the receiver device D_RX is a smartphone.

[0136] In this embodiment, the transmitter device D_TX and the receiver device D_RX are located in the backscattering area Z_TX and the receiving area Z_RX, respectively (for illustration only, Figure 1 The corresponding delimitation of the areas Z_TX and Z_RX is illustrated with dots in FIG.

[0137] "Backscatter / reception area" refers here to an area which is specifically and advantageously generated according to the invention so that the transmitter device D_TX (respectively the receiver device D_RX) is located there. The way in which these areas are generated is described in detail below.

[0138] As a non-limiting example, such backscatter / reception areas correspond to known geographical areas that are frequented, in particular during one or more periods of the day. This is for example a restaurant, a commercial area, a station dedicated to a means of transport (subway, bus, train, etc.), a conference room, etc. Furthermore, in order to make the tracking of the areas generated in this way easier, the areas generated in this way can advantageously be indicated by visual marking means, such as, for example, an indication panel with a written mention of the nature of the area in question.

[0139] Furthermore, in addition to the communication system 10, the present invention relates to a generation system 100 configured to generate such a backscattering / reception area to ensure that the transmitter device and the receiver device are located there.

[0140] Figure 3 A specific embodiment of the system 100 for generating according to the present invention is schematically illustrated.

[0141] like Figure 3 As shown, the system 100 for generating includes sources corresponding to the sources SO of the communication system 10 described previously.

[0142] The generation system 100 also includes two terminals, specifically:

[0143] - a first terminal M_TX, the location of which is intended to be included in the zone Z_TX;

[0144] - A second terminal M_RX, the location of which is intended to be comprised in the zone Z_RX.

[0145] The remaining description focuses more specifically but in a non-limiting manner on the case where both terminals M_TX and M_RX are cellular phones (eg smartphone type). However, it is not excluded to consider other types of terminals, such as tablet computers, digital personal assistants, personal computers, etc.

[0146] According to the invention, the source SO and the first terminal M_TX and the second terminal M_RX are configured to carry out a process aimed at generating the zones Z_TX, Z_RX, thus performing a process of generating said zones Z_TX, Z_RX.

[0147] For this purpose, the source SO (respectively the first terminal M_TX / the second terminal M_RX) comprises, for example, one or more processors and memory means (magnetic hard drive, electronic memory, optical disk, etc.) in which data and computer programs are stored in the form of a set of program code instructions to be executed in order to at least partially perform the generation process.

[0148] Alternatively or additionally, the source SO (respectively, the first end terminal M_TX / the second end terminal M_RX) also includes one or more programmable logic circuits and / or application-specific integrated circuits (ASICs) of FPGA, PLD type, etc. and / or a group of discrete electronic components, etc., which are suitable for at least partially performing the generation process.

[0149] In other words, the source SO (respectively the first terminal M_TX / the second terminal M_RX) comprises a set of components configured as software (specific computer program) and / or hardware (FPGA, PLD, ASIC, etc.) for at least partially performing the generation process.

[0150] For the rest of the description, it is by no means restrictively considered that the first terminal M_TX and the second terminal M_RX occupy respective fixed positions in the environment of the source SO. However, it is not excluded to consider that at least one of said terminals M_TX, M_RX is mobile within said environment.

[0151] Figure 4 The main steps of the generation process according to the present invention are shown in the form of a flow chart.

[0152] like Figure 4 As shown, the generation process includes:

[0153] - a step E1 for determining the emission constraint C_TX for generating the backscattering zone Z_TX and the reception zone Z_RX when the source SO complies with the emission constraint C_TX,

[0154] - A transmission step E2 of said source SO for said emission constraints C_TX.

[0155] According to the invention, during step E1 , emission constraints C_TX are determined so that, when the source SO emits, the electromagnetic power received in the zone Z_TX is greater than a determined threshold value, called “backscatter threshold” S_TX.

[0156] In fact, it is known to those skilled in the art that decoding of the backscattered signal can only be performed when the variation of the electromagnetic power received by the receiver device D_RX between the moments of backscattering and not backscattering by the transmitter device, known as the “power contrast” C_P, reaches a determined threshold value known as the “power threshold” S_P. Such a power threshold S_P is defined, for example, as a function of a determined decoding error rate and as a function of the reception noise on the side of the receiver device D_RX.

[0157] In this way, it is important that the transmitter device D_TX is able to occupy a position where the power radiated by the source SO is sufficient so that the power contrast C_P evaluated by the receiver device D_RX increases and so that the power threshold S_P is finally reached.

[0158] In practice, the power contrast C_P can be evaluated according to the following formula:

[0159] C_P=|P_R–P_NR|.

[0160] 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 backscattering state (respectively, the non-backscattering state). In this way, the condition according to which decoding can be performed is reflected here by C_P>S_P. Therefore, it is clear that reaching the threshold S_P depends on the spread between P_R and P_NR.

[0161] However, it should be noted that even if decoding can theoretically be performed as soon as C_P>S_P, this does not exclude imposing stricter decoding conditions 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 that stricter conditions are imposed improves the quality of communication between the transmitter device D_TX and the receiver device D_RX.

[0162] In any case, the backscatter threshold S_TX is determined according to the power threshold S_P. A person skilled in the art knows how to fix the threshold S_TX from which the area for backscattering can be considered. For example, the threshold S_TX is chosen to be sufficiently high, for example greater than the power threshold S_P.

[0163] In this way, placing the transmitter device D_TX in the zone Z_T increases the probability that the backscattered signal can be decoded, and this improves the communication via ambient backscatter between devices.

[0164] According to the invention, the transmission constraint C_TX is also determined such that the electromagnetic power received in the zone Z_RX is less than a determined threshold value, called “reception threshold” S_RX.

[0165] The threshold S_RX considered here is usually determined according to the determined decoding error rate and the reception noise considered to be tolerable on the receiver device D_RX side. Generally, a person skilled in the art knows how to fix a threshold S_RX from which (i.e. below which) a placement for reception can be considered.

[0166] In this way, fixing such a threshold S_RX means that the aim is to prevent areas containing many interference instances, at least enough for the decoding error rate to exceed a given threshold, or areas to be considered valid for the reception of backscatter signals.

[0167] For example, the threshold S_RX is selected to be sufficiently low, for example in the interval [-6dB, -2dB], more specifically in the interval [-6dB, -4dB].

[0168] In this way, placing the receiver device D_RX in the zone Z_RX increases the probability that the backscattered signal can be decoded, and this improves the communication via ambient backscatter between the devices.

[0169] The rest of the description aims at describing in detail different embodiments of the generation process and, more specifically, different embodiments of the determination step E1 .

[0170] Figure 5 Schematically illustrates Figure 4 A first specific embodiment of a generation process of wherein the source SO is fixed and configured to send data with high spectral efficiency due to the formation of beams (also called "beamforming").

[0171] like Figure 5 As shown, in this first embodiment, the step E1 for determining consists in transmitting E1_10 at least one pilot sequence to the source SO in the operating frequency band and by each of the terminals M_TX, M_RX.

[0172] The transmissions respectively associated with the first terminal M_TX and the second terminal M_RX are for example synchronous. Alternatively, these transmissions are asynchronous.

[0173] The determination step E1 also comprises estimating E1_11 the propagation channel CA_TX, CA_RX between the source SO and each terminal M_TX, M_RX from the received pilot sequences, by the source SO and assuming channel reciprocity.

[0174] The estimation of the propagation channel in a wireless network is a classical operation known to those skilled in the art, and therefore will not be described in further detail here. It is based in particular on sending the sequence comprising pilot symbols on the propagation channel to be estimated. The assumption of reciprocity for estimating the channel is also known to those skilled in the art, who then understand that the communication context between the M_TX, M_RX terminals and the source SO for sending / receiving pilot sequences corresponds to TDD mode (the acronym for "time division duplex").

[0175] Finally, the step E1 for determining also comprises calculating, by the source SO and as a function of the estimated propagation channels CA_TX, CA_RX, E1_12 a precoder capable of generating, in the area of ​​the first terminal M_TX, an electromagnetic power greater than the backscatter threshold S_TX and, in the area of ​​the second terminal M_RX, an electromagnetic power less than the reception threshold S_TX. More specifically, in this first embodiment, the precoder is of the zero-forcing type (or "zero-forcing" ZF).

[0176] In a manner known per se, such a precoder ZF simultaneously focuses at least a portion of the radiation of the source SO onto the first terminal M_TX and eliminates the presence of radiation in the region of the second terminal M_RX.

[0177] It should also be noted that setting a ZF type precoder for generating a power level greater than a backscatter threshold S_TX in the area of ​​the first terminal M_TX and less than a reception threshold S_TX in the area of ​​the second terminal M_RX is a procedure known in the art.

[0178] According to such an implementation, each zone Z_TX, Z_RX, for example, substantially takes the form of a circle centred on the associated terminal M_TX, M_RX and whose radius is of the order of a quarter of the wavelength associated with the frequency F_C.

[0179] The emission constraint C_TX ultimately corresponds to the usage by the source SO of said precoder for sending during the transmission step E2.

[0180] Figure 6 Schematically illustrates Figure 4 A second specific embodiment of the generation process of , in which the source SO is fixed and configured to send data with high spectral efficiency due to the formation of beams ("beamforming").

[0181] In order to implement this second mode, each terminal M_TX, M_RX comprises acquisition means configured to acquire, in the operating frequency band, a measure of the electromagnetic power received by said terminal M_TX, M_RX.

[0182] In conventional terms, the acquisition means comprise an acquisition chain connected to a sensitive element configured to provide an electrical analog signal representative of the electromagnetic power measured. In this exemplary embodiment, the sensitive element corresponds to a receiving antenna mounted on the terminal M_TX, M_RX.

[0183] The acquisition chain comprises, for example, an acquisition card configured to condition the electrical signal. The conditioning performed by the acquisition card comprises, for example, amplification and / or filtering and / or current-to-power conversion in a manner known per se. Generally, the configuration of such acquisition components is well known to those skilled in the art and is therefore not described in further detail here.

[0184] like Figure 6 As shown, in this second embodiment, the determination step E1 comprises obtaining E1_20 by the source SO a grid G_F (labeled G_F(1), G_F(2), etc.) of beams respectively associated with the determined directions.

[0185] The direction of the beam G_F(i) corresponds to a combination of directions in space, which can be shown algebraically in the form of a vector representation. Such a vector associated with the beam G_F(i) itself represents a precoder which, when used for transmission by the source SO, focuses the transmission in the direction of the beam G_F(i) in question. Furthermore, by adopting the above vector representation, the grid of beams G_F can be shown in the form of a matrix.

[0186] For example, the beams G_F(i) of the grid are determined by means of a discrete Fourier transform ("DFT", discrete Fourier transform) method. This method is described, for example, in the following document: "DFT beamforming for more accurate estimation of signal DOA and application to improve DS / CDMA receiver performance", TBVu, Electronic Letters, Vol. 36, No. 9, pp. 834-836, 2000.

[0187] In a particular exemplary embodiment, the grid G_F of the beams is predetermined. For example, the grid G_F is stored (in the form of a matrix) in a memory component attached to the source SO, such as, for example, a database stored on a server. Since these attached memory components are separate from the memory components of the source SO, obtaining the grid G_F of the beams corresponds to transmitting the grid to the source SO via the communication components installed on the source SO. Once the grid G_F is sent, the source SO stores it in its memory component.

[0188] There are no restrictions on the configuration of the communication means of the grid G_F capable of transmitting beams, which may be wired or wireless and may use any known type of transmission protocol.

[0189] Alternatively, the grid G_F of the beams is determined directly by the source SO. For example, obtaining the grid G_F of the beams corresponds to calculating, by the source SO, the coefficients of a matrix associated with said grid G_F.

[0190] Once the grid of beams G_F is obtained, for each beam G_F(i) of the grid G_F, the determination step E1 also comprises:

[0191] - transmission E1_21 by the source SO according to the direction of the beam G_F(i),

[0192] - during said transmission E1_21 , obtaining E1_22 , in the operating frequency band and by each of the terminals M_TX, M_RX, measurements P_TX(i), P_RX(i) of the electromagnetic power received by said terminals M_TX, M_RX.

[0193] exist Figure 6 In the second embodiment shown, the determination step E1 also includes: once the power measurement is obtained for each beam, each terminal M_TX, M_RX of the beam G_F(i), G_F(j) selects E1_23 beam G_F(i), G_F(j), and the power measurement P_TX(i), P_RX(j) of the beam G_F(i), G_F(j) is greater than the backscatter threshold S_TX or less than the reception threshold S_RX. According to the beam G_F(i), G_F(j), the position of the terminal M_TX, M_RX is intended to be included in the backscatter area Z_TX or to be used to receive Z_RX.

[0194] Preferably, if a number of power measurements P_TX(i) obtained by the first terminal M_TX (respectively, a number of power measurements P_RX(j) obtained by the second terminal M_RX) are greater than a backscatter threshold S_TX (respectively, less than a reception threshold S_RX), then the beam selected from the beams associated with said measurements corresponds to the beam whose associated power measurement is the largest (respectively, whose power measurement is the smallest).

[0195] However, it is not excluded to consider randomly selecting a beam by the first terminal M_TX (respectively the second terminal M_RX), where appropriate, from among the beams whose associated power measurement is greater than the backscatter threshold S_TX (respectively less than the reception threshold S_TX).

[0196] The determination step E1 also comprises transmitting E1_24, by each of the terminals M_TX, M_RX to the source SO, an item of information INFO indicating the selected beam. The transmission E1_24 is done for example via a signalling message that may be defined in a telecommunication standard.

[0197] Such an information item INFO generally corresponds to the index i of the selected beam G_F(i).

[0198] Finally, in the second embodiment, if the beams respectively selected by the first terminal M_TX and the second terminal M_RX are consistent (for example, the indices of the selected beams are equal), the transmission constraint C_TX corresponds to the use of the beam common to the first terminal M_TX and the second terminal M_RX for transmission by the source SO during the transmission step E2 and based on the information item INFO.

[0199] It should be noted that if the beams selected by the first terminal M_TX and the second terminal M_RX, respectively, are not identical, the transmission constraint C_TX corresponds to the use by the source SO of one or the other of said selected beams.

[0200] Figure 7 Schematically illustrates Figure 4 A third specific embodiment of the generation process of , in which the source SO is fixed and configured to send data with high spectral efficiency due to the formation of beams ("beamforming").

[0201] like Figure 7 As shown, in this third embodiment, the determination step E1 comprises obtaining E1_30 by the source SO and by each of the terminals M_TX, M_RX a codebook L_C (referred to as "codebook") comprising a plurality of precoders (referenced L_C(1), L_C(2), etc.).

[0202] The fact that the combined precoders L_C(i) are considered within a codebook L_C is known to the skilled person who usually refers to telecommunication standards to obtain access to such a codebook L_C. In this way, in this exemplary embodiment (ambient signals for mobile phones 4G), the codebook L_C is provided by a standard such as that defined in the document "3GPP TS 36.211 V15.5.0 (2019-03)".

[0203] The codebook L_C is for example stored in additional memory means of the source SO and the terminal M_TX, M_RX, such as a database stored on a server. Since these additional memory means are different from the memory means of the source SO and the terminal M_TX, M_RX, obtaining the codebook L_C corresponds to sending the codebook to the source SO and the terminal M_TX, M_RX through the communication means installed respectively on the source SO and the terminal M_TX, M_RX. Once the codebook L_C is sent, the source SO and the terminal M_TX, M_RX store it in their respective memory means.

[0204] There is no limitation on the configuration of the communication component capable of transmitting the codebook L_C, and the communication component may be wired or wireless, and may use any type of known transmission protocol.

[0205] The determination step E1 also comprises the transmission E1_31 by the source SO to each of the terminals M_TX, M_RX of at least one pilot sequence.

[0206] For example, the transmissions respectively associated with the first terminal M_TX and the second terminal M_RX are synchronized. Alternatively, these transmissions are not synchronized.

[0207] The determination step E1 also comprises estimating E1_32, by each of the terminals M_TX, M_RX, from the received pilot sequence, a propagation channel CA_TX, CA_RX between the source SO and said terminal M_TX, M_RX.

[0208] As mentioned above, estimating the propagation channel in a wireless network from a pilot sequence is a classic operation known to those skilled in the art, and thus will not be described in further detail here.

[0209] Once the propagation channel CA_TX, CA_RX has been estimated between the source SO and the terminals M_TX, M_RX, the determination step E1 further comprises: for each precoder L_C(i) of the codebook L_C, each of the terminals M_TX, M_RX and based on the precoder L_C(i) calculates E1_33 the value of the electromagnetic power Pt_TX(i), Pt_RX(i) theoretically received by the terminal M_TX, M_RX in the working frequency band and via the propagation channel estimated for the terminal M_TX, M_RX.

[0210] In other words, when the calculation is completed, each terminal M_TX, M_RX is associated with a determined number of power values ​​Pt_TX(i), Pt_RX(i), which is equal to the number of precoders L_C(i) recorded in the codebook L_C.

[0211] It should be noted that a person skilled in the art knows how to perform such calculation of the theoretical power received according to the considered precoder.

[0212] exist Figure 7In the third embodiment shown, the determination step E1 also includes: once the power value according to each precoder is calculated, each terminal M_TX, M_RX selects E1_34 precoder L_C(i), L_C(j) according to whether the position of the terminal is intended to be included in the backscatter area Z_TX or the reception area Z_RX, and for the precoder L_C(i), L_C(j), the power value Pt_TX(i), Pt_RX(j) is greater than the backscatter threshold S_TX or less than the reception threshold S_RX.

[0213] Preferably, if a number of power values ​​Pt_TX(i) calculated by the first terminal M_TX (respectively, a number of power measurements Pt_RX(j) calculated by the second terminal M_RX) are greater than a backscatter threshold S_TX (respectively, less than a reception threshold S_RX), the precoder selected from the precoders associated with said values ​​corresponds to the precoder whose associated power value is the largest (respectively, whose power value is the smallest).

[0214] However, it is not excluded that, where appropriate, the first terminal M_TX (respectively the second terminal M_RX) is considered to randomly select a precoder from among the precoders whose associated power values ​​are greater than the backscatter threshold S_TX (respectively less than the reception threshold S_TX).

[0215] The determination step E1 also comprises the transmission E1_35 by each of the terminals M_TX, M_RX to the source SO of an information item INFO indicating the selected precoder. The transmission E1_35 is done for example via a signalling message that may be defined in a telecommunication standard.

[0216] Such an information item INFO generally corresponds to the index i of the selected precoder L_C(i).

[0217] Finally, in the third embodiment, if the precoders respectively selected by the first terminal M_TX and the second terminal M_RX are consistent (for example, the indices of the selected precoders are equal), the transmission constraint C_TX corresponds to the use of the precoder for transmission that is common to the first terminal M_TX and the second terminal M_RX by the source SO during the transmission step E2 and based on the information item INFO.

[0218] It is noted that if the precoders selected by the first terminal M_TX and the second terminal M_RX, respectively, are not identical, the transmission constraint C_TX corresponds to the use of one or the other of the precoders by the source SO.

[0219] So far, the present invention has been described by considering that the source SO is fixed. However, the present invention is not limited to this configuration of the source SO.

[0220] Figure 8 Schematically illustrates Figure 4 A fourth specific embodiment of the generation process of , wherein the source SO is capable of moving and is configured to send data directionally.

[0221] In order to implement the fourth mode, each terminal M_TX, M_RX includes a display similar to that in the second embodiment ( Figure 6 ) within the scope of the invention.

[0222] The source SO comprises a directional part of the directional antenna. In this way, via its directional part, the source SO is able to modify the direction in which the directional antenna points, even if the source SO does not modify its position. Such directional parts are of a type known per se, such as for example an electric motor dedicated to said direction.

[0223] Furthermore, in order to implement said fourth mode, the source SO comprises displacement means (not shown in the figures) in its surroundings.

[0224] For example, the displacement means include drive means, such as at least one electric motor, and guide means, such as wheels. However, other drive means, such as thermomotors, and other guide means, such as tracks, are not excluded.

[0225] Preferably, the source SO takes the form of a robot comprising a motor and wheels.

[0226] Besides the fact of being able to generate at least one backscatter zone Z_TX and / or at least one reception zone Z_RX, the component configured as software and / or hardware installed on the source SO also manipulates its movement.

[0227] For this purpose, these means comprise, for example, a control module (not shown in the figures) configured to generate displacement commands for the source SO.

[0228] For example, the command is generated without assistance. In other words, the source SO is able to move autonomously, ie without intervention of an operator.

[0229] Alternatively, the manipulation of the source SO is done in an assisted manner by an operator who remotely generates command signals, which are then sent to the source SO, which moves according to the data transmitted in these signals. For this purpose, the source SO comprises, for example, communication means for receiving said command signals, which are then processed by the control module. As known per se, these communication means are supported on a communication interface capable of exchanging data between said operator and the source SO. There is no restriction on the nature of this communication interface, which may be wired or wireless, so as to allow the exchange of data according to any protocol known to those skilled in the art.

[0230] For the rest of the description, it is by no means restrictively considered that the operation of the source SO is ensured by the electrical energy that can be stored.

[0231] For example, the electrical energy is contained in a battery integrated into the source SO, and the battery can be recharged, for example, by means of a solar panel mounted on the source SO or by capacitive effect, making the source SO autonomous in terms of power. Alternatively, the recharging of the battery is done via a link to the household grid.

[0232] However, it is not excluded to consider other types of energy, such as fossil energy for example, in particular if the source SO is equipped with a thermal generator. Finally, it is not excluded to consider a mixture of energies (electrical and thermal).

[0233] In other words, and in general, there are no constraints on the energy considered for operation of the source SO, or even on the way in which this energy is obtained by the source SO.

[0234] Furthermore, the source SO is associated with a zone called "travel zone" Z_D within which the source SO can move.

[0235] The travel zone Z_D generally corresponds to a geographical area (on the ground) defined according to the radiation pattern of the directional antenna mounted on the source SO. More specifically, when the source SO is fixed, and according to the radiation pattern of the directional antenna, a first coverage area (respectively, a second coverage area) corresponding to a geographical area with a radiation power greater than the backscatter threshold S_TX (respectively, less than the reception threshold S_RX) can be determined. Of course, it should be understood that once the travel of the source SO is completed according to a sufficient distance, the first coverage area (respectively, the second coverage area) may evolve during the travel. In addition, and in practice, the travel zone Z_D is defined so as to present a larger size that is greater than or equal to the maximum value between the maximum size of the first coverage area and the maximum size of the second coverage area.

[0236] However, it is not excluded to consider a travel zone Z_D whose maximum size is defined differently, for example as being greater than or equal to the sum of the maximum size of the first coverage area and the maximum size.

[0237] Generally, there are no constraints on the way of defining the travel zone Z_D. For example, based on or not based on the radiation pattern, multiple parameters can be taken into account, such as, for example, the operating power autonomy of the source SO, the configuration of the environment in which the source SO is located (obstacles, etc.), the prediction of the presence density of transmitter D_TX and / or receiver D_RX devices, etc.

[0238] like Figure 8As shown, the determination step E1 comprises a movement E1_40 of the source SO in at least a portion of the zone Z_D.

[0239] This travel of the source SO allows the source SO to at least partially scan the zone Z_D with the purpose of testing the placement and orientation of antennas from which at least one backscatter zone Z_TX and / or at least one reception zone Z_RX can be generated.

[0240] "Travel" here refers to the exploration phase, and such phases may include continuous travel (i.e., without stops within the portion) between initial placement and final placement, respectively, wherein the source SO is fixed, or may be carried out in stages (i.e., with one or more intermediate stops within the portion before reaching the final placement).

[0241] In certain exemplary embodiments, the travel of the source SO is performed autonomously, i.e., without external assistance. For example, the source SO is configured to analyze the environment in which it is located to detect any possible obstacles that it can then bypass. Such detection is typically performed thanks to imaging components (e.g., cameras) mounted on the source SO and thanks to processing performed by the source SO aimed at analyzing images obtained using the imaging components. Such processing is well known to those skilled in the art and is therefore not described in further detail here.

[0242] In another particular exemplary embodiment, the traveling of the source SO is performed in an assisted manner, for example by an operator who is able to remotely control the movement of the source SO.

[0243] Regardless of the implementation considered (autonomous or assisted), the travel of the source SO may be performed according to a determined trajectory (such as, for example, a spiral, a line, a groove, etc.).

[0244] Alternatively, the shifting of the source SO may be performed via a non-deterministic method.

[0245] Typically, there are no constraints on the trajectory followed by the source SO.

[0246] Furthermore, said portion of the zone Z_D is, for example, configured so as to comprise an initial placement of the source SO.

[0247] Alternatively, the portion does not include an initial placement, causing the source SO to make a previous run in order to connect the portion that is subsequently run.

[0248] Typically, no constraints are imposed on the form presented by said portion of the zone Z_D. Furthermore, the travel of the source SO may be performed within a determined time period, which may be set such that the form of said portion may depend on the determined time period.

[0249] In a particular exemplary embodiment, the travel of the source SO is performed throughout the zone Z_D. Doing so in this manner maximizes the number of possible placements and directions tested during the entire generation process.

[0250] During the travel of the source SO, the determination step E1 also includes the transmission E1_41 of at least one pilot sequence by the source SO in at least one placement A(i) in at least one determined direction D(i, j) of the directional antenna (i and j are integers greater than or equal to 1).

[0251] A direction D(i, j) of a directional antenna is usually expressed in the form of a pair of angular coordinates representing the azimuth and elevation of the antenna, respectively. It should 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 placements A(i) considered (i.e., for a given index i, index j is greater than or equal to i).

[0252] In a particular embodiment, the number of directions D(i, j) considered during transmission E1_41 is strictly greater than the number of placements A(i) considered. For this purpose, the direction of the directional antenna is modified due to the directional components described above. For example, in placement A(i), the source SO transmits a pilot sequence in several directions, the corresponding elevation components of which are all identical, but the corresponding azimuth components are phased according to a spacing equal to one degree so as to cover a determined angular sector, for example an angular sector equal to [0°, 360°].

[0253] It should be noted that there is no constraint on the number of transmission directions that can be considered in placement A(i).

[0254] Furthermore, the transmission E1_41 of the pilot sequence is preferably performed in idle time (subdivided probing phase). In other words, during its progress, the source SO marks a stop in the placement A(i) as soon as it wants to send.

[0255] However, it is not excluded to consider transmission while the source SO is in motion.

[0256] There is no additional constraint on the number of placements A(i) that can be considered for sending the pilot sequence. Furthermore, if multiple placements A(i) are considered, these placements A(i) can be separated by spacings of a certain distance that can be set, for example. They can also be separated by a pitch of a certain time that can be set, for example, in which case the speed of the source 11 can be adjusted to comply with the time pitch.

[0257] The determination step E1 also comprises obtaining E1_42 a measurement of the electromagnetic power P_TX(i), P_RX(i) received by the terminals M_TX, M_RX, in the operating frequency band and by each of the terminals M_TX, M_RX, during said transmission E1_41.

[0258] exist Figure 8 In the fourth embodiment shown, the determination step E1 also includes: once the travel of the source SO is completed, each terminal M_TX, M_RX selects E1_43 a placement A(m), A(k) and an antenna direction D(m, n), D(k, l) associated with the placement A(m), A(k), wherein the power measurement P_TX(i), P_RX(k) is greater than the backscatter threshold S_TX or less than the reception threshold S_RX, and according to the placement A(m), A(k) and the antenna direction D(m, n), D(k, l), the position of the terminal M_TX, M_RX is intended to be included in the backscatter Z_TX or reception Z_RX area.

[0259] Preferably, if a number of power measurements P_TX(m) obtained by the first terminal M_TX (correspondingly, a number of power measurements P_RX(k) obtained by the second terminal M_RX) are greater than a backscatter threshold S_TX (correspondingly, less than a reception threshold S_RX), the antenna placement and orientation selected from the placements and orientations associated with the measurements corresponds to the placement and orientation with which the associated power measurement is maximum (correspondingly, the power measurement is minimum).

[0260] However, it is not excluded that, where appropriate, a placement and an orientation are randomly selected by the first terminal M_TX (respectively the second terminal M_RX) from placements and orientations whose associated power measurements are greater than the backscatter threshold S_TX (respectively less than the reception threshold S_RX).

[0261] Furthermore, the determination step E1 comprises transmitting E1_44, by each of the terminals M_TX, M_RX to the source SO, an item of information INFO indicating the chosen placement and direction. The transmission E1_44 is for example performed via a signalling message that may be defined in a telecommunication standard.

[0262] Finally, in said fourth embodiment, the transmission constraint C_TX corresponds to the use of placement and antenna direction for transmission that is common to said first terminal M_TX and said second terminal M_RX by the source SO during the transmission step E2 and based on said information item INFO, if the antenna placement and direction selected by the first terminal M_TX is consistent with the antenna placement and direction selected by the second terminal M_RX.

[0263] Note that the transmission constraint C_TX corresponds to the use by the source SO of the placement and antenna direction selected by one or the other of the terminals M_TX, M_RX if the placement and / or direction respectively selected by the first terminal M_TX and the second terminal M_RX are inconsistent.

[0264] So far, the invention has been described by considering only two terminals (specifically, a first terminal M_TX and a second terminal M_RX). However, the invention is still applicable to a plurality of terminals different from two. In this way, it is not excluded to consider a configuration in which the generation system 100 is constituted by a source SO and by one or more backscatter terminals (correspondingly, one or more receiving terminals).

[0265] In this manner, and more particularly with respect to the first embodiment ( Figure 5 ), without excluding the consideration of an alternative solution that would take into account a single terminal. According to this alternative solution, the calculation E1_12 of the precoder is performed so as to allow the generation in the area of ​​said terminal of electromagnetic power:

[0266] if the terminal's position is intended to be included in a backscatter zone Z_TX, is greater than a backscatter threshold, or

[0267] - less than the reception threshold if the terminal's position is intended to be included in the reception zone Z_RX.

[0268] For example, if the location of the terminal is intended to be included in the backscatter zone Z_TX, the precoder is of the type with maximum ratio transmission (or MRT with "maximum ratio transmission"). In other words, the precoder MRT is intended to be used so that the source SO is substantially focused on the terminal to generate maximum power.

[0269] If, on the contrary, the location of the terminal is intended to be included in the reception zone Z_RX, the precoder is, for example, capable of forming a power null. Such precoders are well known to those skilled in the art and essentially consist of causing the source SO to generate signals of opposite signs (and thus capable of cancelling each other) in the area of ​​the receiving terminal under consideration. As an example, the following scientific publication may be cited: "Zero formation method by phase control of selected array elements using plane wave synthesis", I. Chiba, S. Mano, Symposium of the Antenna and Propagation Society, pp. 70-73, 1987.

[0270] Furthermore, when considering several terminals of the same type (for backscattering or for reception), it is also not excluded that the respective positions of all or some of said terminals of the same type are intended to be included in the same area (for backscattering or reception according to the type of terminal considered). Alternatively, the respective positions of the terminals are intended to be included in areas different from each other.

[0271] Furthermore, the invention has been described so far by considering an embodiment based on a generation process using one or more terminals M_TX, M_RX. In this way, the source SO is advantageously configured to transmit specifically (a specific type of precoder, a precoder or beam selected from a plurality of precoders or beams) according to the position occupied by one or more terminals M_TX, M_RX during the determination step E1 via the determination of the emission constraint C_TX. Therefore, one or more terminals M_TX, M_RX play a supporting role so that the source SO transmits specifically. In other words, when one or more terminals M_TX, M_RX are used during the generation process, the determination step E1 is intended to "teach" the source SO the way in which the latter must transmit to generate one or more zones Z_TX, Z_RX.

[0272] However, it is not excluded that other embodiments of the generation process are considered in which no terminal is used.

[0273] For example, in the case where the source SO is fixed and configured to transmit data with high spectral efficiency due to the formation of beams (“beamforming”), the determination step E1 may comprise obtaining, by the source SO, a predetermined precoder that performs a discrete Fourier transform (as described above in reference to Figure 6 ), the emission constraint corresponds to the use of the precoder for transmission by the source SO during the transmission step E2. In this example, the location of (multiple) backscatter or reception Z_TX or Z_RX areas is not constrained by the presence of one or more terminals. Since the precoder is completely predetermined, the distribution of electromagnetic power in the environment around the source SO can be known in advance (for example via digital simulation). In this way, the positioning of the backscatter area Z_TX and / or the reception area Z_RX is here regulated by the power distribution. In practice, in this embodiment, the backscatter area Z_TX is usually selected so as to be illuminated by the main transmission lobe of the source SO, or by a secondary lobe of sufficient power. Therefore, the reception area Z_RX is usually selected not to be illuminated by the transmission lobe of the source SO.

[0274] Furthermore, according to another aspect, the invention also relates to a communication process by ambient backscatter between a transmitter device D_TX and a receiver device D_RX. Said communication process is advantageously based on the previously described generation process to allow efficient communication between these devices within a communication system 10 such as previously described.

[0275] Fig. 9 The main steps of the communication process according to the present invention are shown in the form of a flow chart. Here, by way of illustration, reference is made to a communication system 10 ( Figure 1 ) to describe the communication process in detail.

[0276] like Fig. 9 As shown, the communication process first comprises a step H1 for generating a backscattering zone Z_TX and for generating a reception zone Z_RX according to the generation process of the present invention.

[0277] Once the area is generated, the communication process comprises a step H2 for positioning the transmitter device D_TX in the backscatter area Z_TX if the transmitter device D_TX is not already positioned in the backscatter area Z_TX, and for positioning the receiver device D_RX in the reception area Z_RX if the receiver device D_RX is not already positioned in the reception area Z_RX.

[0278] There are no additional constraints in the way in which said positioning is performed. For example, in the case where said device D_TX, D_RX takes the general form of a smartphone and said zones Z_TX, Z_RX are identified by means of an indication panel, the respective user of the device D_TX, D_RX is responsible for locating these zones Z_TX, Z_RX according to the indications of said panel.

[0279] Once the positioning step H2 is completed, the communication process comprises a step H3 of backscattering by the transmitter device D_TX of the ambient signals emitted by the source SO (i.e. the transmitter device D_TX passes from the non-backscattering state to the backscattering state, unless it was previously in this state). It also comprises a step H4 of reception of the backscattered ambient signals of the transmitter device D_TX by the receiver device D_TX.

[0280] In a specific embodiment ( Fig. 9 ), the steps for generating H1, positioning H2, backscattering H3 and receiving H4 are cyclically iterated.

[0281] The fact of performing these steps cyclically takes into account the variability of the environment in which the transmitter device D_TX and the receiver device D_RX are located.

[0282] For example, the steps are iterated periodically, for example once a day in an environment where the distribution of power generated by the power source SO is stable, or more frequently, for example once an hour if the distribution of power may evolve substantially hourly.

Claims

1. A method for generating at least one backscattering zone Z_TX of ambient radio signals emitted by at least one source SO by at least one transmitter device D_TX to at least one receiver device D_RX and / or for generating at least one reception zone Z_RX of ambient signals backscattered by said receiver device D_RX, the method comprising: - a step E1 of determining an emission constraint C_TX, of generating, when the source SO complies with said emission constraint C_TX, at least one backscatter zone Z_TX, and / or of generating at least one reception zone Z_TX, in which the electromagnetic power received by said at least one transmitter device D_TX is greater than a determined threshold value, called "backscatter threshold" S_TX, and in which the electromagnetic power received by said receiver device D_RX is less than a determined threshold value, called "reception threshold" S_RX, - Step E2 of transmission by said source SO of said emission constraint C_TX.

2. The method according to claim 1, wherein: The source SO is fixed and configured to transmit in a frequency band called "transmission bandwidth", the step E1 for determining comprises: - the transmission E1_10 of at least one pilot sequence to the source in a frequency band called "working band" and included in the transmission bandwidth and by at least one terminal (M_TX, M_RX) whose position is intended to be included in the backscatter zone Z_TX or in the reception zone Z_RX, - estimating E1_11 the propagation channel (CA_TX, CA_RX) between said source and said terminal (M_TX, M_RX) from said at least one pilot sequence received by said source and assuming channel reciprocity, - calculating, by said source and as a function of the estimated propagation channel (CA_TX, CA_RX), an E1_12 precoder capable of generating, in the area of ​​said terminal, an electromagnetic power greater than said backscatter threshold or less than said reception threshold, according to which the position of said terminal is intended to be included in the backscatter area or in the reception area, The transmit constraint C_TX corresponds to the usage of the precoder by the source for transmission.

3. The method according to claim 2, wherein a single terminal is considered and: if the location of the terminal is intended to be included in a backscatter zone Z_TX, the precoder is of the Maximum Ratio Transmission MRT type; - Otherwise, if the location of the terminal is intended to be included in a reception zone Z_RX, the precoder is capable of forming a power null.

4. The method according to claim 2, wherein: Considering at least two terminals, including a first terminal M_TX whose position is intended to be included in the backscatter zone Z_TX and a second terminal M_RX whose position is intended to be included in the reception zone Z_RX, the precoder is of the zero forcing ZF type.

5. The method according to claim 1, wherein: The source SO is fixed and configured to transmit in a frequency band called "transmission bandwidth", the step E1 for determining comprises: - a grid G_F of beams respectively associated with the determined directions obtained E1_20 by the said source, And, for each beam G_F(i) of the grid, - a transmission E1_21 by said source according to the direction of said beam, - during said transmission, in a frequency band called "working band" and included in the transmission bandwidth and by at least one terminal (M_TX, M_RX) whose position is intended to be included in the backscatter zone Z_TX or for reception Z_RX, obtaining E1_22 measurements of the electromagnetic power (P_TX(i), P_RX(i)) received by said terminal, The determination step E1 also comprises, once a power measurement has been obtained for each beam: - selection by said at least one terminal of a beam having an E1_23 power measurement greater than said backscatter threshold S_TX or less than said reception threshold S_RX, according to which beam the position of said terminal is intended to be included in the backscatter or reception area, - transmission by said at least one terminal to said source of an information item INFO indicating the selected beam, E1_24, The transmission constraint C_TX corresponds to the use by the source of the beam selected for transmission based on the at least one information item.

6. A method according to claim 5, wherein at least two terminals are taken into account, including a first terminal M_TX whose position is intended to be included in the backscatter zone Z_TX and a second terminal M_RX whose position is intended to be included in the reception zone Z_RX, so that if the beams selected by the first terminal and the second terminal respectively are consistent, the transmission constraint C_TX corresponds to the use of a beam common to the first terminal and the second terminal.

7. The method according to claim 1, wherein: The source SO is fixed and configured to transmit in a frequency band called "transmission bandwidth", the step E1 for determining comprises: - obtaining E1_30 a codebook L_C comprising a plurality of precoders L_C(i) by said source and by at least one terminal (M_TX, M_RX) whose position is intended to be included in the backscatter zone Z_TX or in the reception zone Z_RX, - transmitting E1_31 at least one determined pilot sequence by said source to said at least one terminal, - estimating E1_32, by said at least one terminal, from said at least one received pilot sequence, a propagation channel (CA_TX, CA_RX) between said source and said terminal (M_TX, M_RX), And, for each precoder of the codebook, - calculation by said at least one terminal and according to said precoder of the value of the electromagnetic power (Pt_TX(i), Pt_RX(i)) theoretically received by said terminal via the estimated propagation channel and in a frequency band called "working band" and included in the transmission bandwidth, The determination step E1 also comprises, once the power value according to each precoder is calculated: - selection by said at least one terminal of a precoder having an E1_34 power value greater than said backscatter threshold S_TX or less than said reception threshold S_RX, according to which the location of said terminal is intended to be included in the backscatter or reception area, - transmission by said at least one terminal to said source of an information item INFO indicating the selected precoder E1_35, The transmission constraint C_TX corresponds to the use by the source of a precoder selected for transmission based on the information item.

8. A method according to claim 7, wherein at least two terminals are taken into account, including a first terminal M_TX whose position is intended to be included in the backscatter zone Z_TX and a second terminal M_RX whose position is intended to be included in the reception zone Z_RX, so that if the precoders selected by the first terminal and the second terminal respectively are consistent, the transmission constraint C_TX corresponds to the use of a precoder common to the first terminal and the second terminal.

9. The method according to claim 1, wherein: The source SO comprises a directional antenna configured to transmit in a frequency band called "transmission bandwidth" and associated with a travel zone Z_D, the determination step E1 comprises: - a movement E1_40 of said source in at least a portion of said movement zone Z_D, - transmission E1_41 of at least one pilot sequence by said source in at least one placement A(i) in at least one determined direction D(i, j) of said directional antenna during the travel of said source, - during said transmission, obtaining E1_42, in a frequency band called "working band" and included in the transmission bandwidth, by at least one terminal (M_TX, M_RX) whose position is intended to be included in the backscatter zone Z_TX or in the reception zone Z_RX, measurements of the electromagnetic power (P_TX(i), P_RX(i)) received by said terminal, The step E1 for determining also comprises: once the travel of the source is completed, - selection by said at least one terminal of a placement (A(m), A(k)) and an antenna direction (D(m,n), D(k,l)) associated with said placement, for which a power measurement is greater than said backscatter threshold S_TX or less than a reception threshold S_RX, according to which the location of said terminal is intended to be included in a backscatter or reception area, - transmission by said at least one terminal to said source of an information item INFO indicating the chosen placement and orientation of the antenna, E1_44, The transmission constraint C_TX corresponds to the use by the source of the placement and direction selected for transmission based on the at least one information item.

10. A method according to claim 9, wherein at least two terminals are taken into account, including a first terminal M_TX whose position is intended to be included in the backscatter zone Z_TX and a second terminal M_RX whose position is intended to be included in the reception zone Z_RX, so that if the antenna placement and orientation selected by the first terminal are consistent with the antenna placement and orientation selected by the second terminal, the transmission constraint C_TX corresponds to the use of a placement and antenna orientation that is common to the first terminal and the second terminal.

11. A method of communication between at least one transmitter device D_TX and at least one receiver device D_RX by backscattering of ambient radio signals emitted by at least one source SO, The method comprises: - a step H1 of generating at least one area backscatter Z_TX and / or generating at least one reception area Z_RX based on the method according to any one of claims 1 to 10, - a step H2 of positioning the transmitter device in the backscattering area if the transmitter device is not already positioned in the backscattering area, and / or positioning the receiver device in the receiving area if the receiver device is not already positioned in the receiving area, - a step H3 of backscattering said ambient signal by said transmitter device, - Step H4 of receiving, by said receiver device, the backscattered ambient signal.

12. The method according to claim 11, wherein: The steps for generating H1 , locating H2 , backscattering H3 and receiving H4 are iterated cyclically.

13. A computer-readable recording medium having a computer program recorded thereon, the computer program comprising instructions for executing at least a portion of the method according to any one of claims 1 to 10 or at least a portion of the method according to any one of claims 11 to 12 when the program is executed by a computer.

14. A system for generating at least one backscatter region of an ambient signal and / or for receiving a backscattered ambient signal, comprising components configured to perform the method according to any one of claims 1 to 10 or components configured to perform the method according to any one of claims 11 to 12.

15. A source SO comprising software and / or hardware components configured to perform the method according to any one of claims 1 to 12.

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