WO2021001169A1

WO2021001169A1 - Method for determining at least one location for the improved reception of a backscattered ambient signal

Info

Publication number: WO2021001169A1
Application number: PCT/EP2020/067087
Authority: WO
Inventors: Romain FARA; Dinh Thuy Phan Huy
Original assignee: Orange
Priority date: 2019-07-01
Filing date: 2020-06-19
Publication date: 2021-01-07
Also published as: FR3098304B1; FR3098304A1

Abstract

The invention concerns a method for determining at least one location for receiving, by at least one receiver device (D_RX) associated with a zone (Z_T), an ambient radio signal backscattered by at least one transmitter device (D_TX), the transmitter device being associated with: - operating states, including at least one state termed "backscattering" and a state termed "non-backscattering", - a frequency band called "working band". Further, the method is implemented by the receiver device when the transmitter device is in the non-backscattering state and comprises, for at least one sub-band of the working band: - a step (E10) of travel of the receiver device in at least a part of said zone, - during the travel of the receiver device, a step (E20) of acquiring electromagnetic power measurements in said sub-band and at respective locations, - a step (E30) of comparing the measurements with a determined threshold, a location associated with a measurement being determined (E40) as being a receiving location if the measurement is less than said threshold.

Description

Title of the invention: Method for determining at least one location for improved reception of a backscattered ambient signal

Prior art

The present invention belongs to the general field of

telecommunications. It relates more particularly to a method for determining at least one location for the reception, by at least one receiving device, of an ambient radio signal intended to be backscattered by at least one transmitting device. It also relates to a method of communication between at least one transmitting device and at least one receiving device, by backscattering an ambient radio signal. The invention finds a particularly advantageous application, although in no way limiting, for applications of the "Internet of Things" type ("Internet of Things" or loT in Anglo-Saxon literature).

[0002] Ambient backscattering technology is well known today. The technical principles on which this technology is based are described, in particular, in the document by N. Van Huynh et al. titled "Ambient

Backscatter Communications: A Contemporary Survey ”, in IEEE

Communications Surveys & Tutorials, vol. 20, no. 4, pp. 2889-2922,

Fourthquarter 2018.

[0003] Conventionally, the backscattering of an ambient signal takes place between at least one transmitter device and at least one receiver device. Further, and as heretofore contemplated, said devices each occupy a fixed position.

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

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

[0007] To implement this technology, the transmitting device is equipped with at least one antenna configured to receive the ambient signal but also backscatter it to the receiving device.

[0008] The transmitter device is also associated with states of

operation, including at least one so-called "backscatter" state (the transmitting device backscattered the ambient signal) as well as an opposite state called "non-backscattering" (the transmitting device is transparent to the ambient signal). These states correspond to configurations in which said at least one antenna is connected to distinct impedances.

[0009] The receiver device, for its part, is configured to decode the signal

backscattered. However, and in practice, the implementation of this decoding can be deteriorated (decoding error, poor reception of the backscattered signal) due to the existence of interference at the level of the receiving device.

[0010] In fact, the transmitter and receiver devices are generally

positioned in a complex propagation environment comprising elements (walls, trees, ground, etc.) capable of generating reflections and diffractions of waves emitted by the source. Thus, and schematically, two types of signals reach the receiving device: the backscattered signal, the only carrier of the data useful for the implementation of ambient backscattering, as well as a signal coming directly from the source called “interfering signal”. and resulting from multiple reflections / diffractions of waves (by “directly”, one refers here to waves not resulting from the backscattered signal). On account of said reflections / diffractions, said interfering signal corresponds to a sum of waves which interfere with one another constructively or else destructively. Consequently, the power distribution generated by this interfering signal is not uniform and has areas where the power is locally maximum or, conversely, locally minimum. The areas where the power is locally maximum (respectively locally minimum) are areas where the interference level is the highest (respectively the lowest).

[0011] FIG. 1 schematically represents a distribution card of

electromagnetic power radiated by a source. Such a map was generated in a manner known per se by numerical simulation by considering a wave propagation model corresponding to a Rayleigh distribution.

Aspects related to the modeling of wave propagation are well known to those skilled in the art, and are therefore not repeated here.

[0012] In the example of Figure 1, said source corresponds to a tower of

television transmitting in a frequency band equal to [583 MHz, 590 MHz] Said card corresponds to a square with a side equal to 1 m25. The radiated power levels are represented using level lines, it being understood that the more an area of the map has lines that narrow, the more this area corresponds to a local minimum of radiated power.

[0013] As illustrated in Figure 1, the power distribution has a

plurality of local minima, and therefore ultimately also a plurality of local maxima. By way of example, zones Z_1, Z_2, Z_3 and Z_4, each comprising a local maximum of radiated power (power substantially equal to 5 dB), are indicated. Each zone Z_i, for i varying from 1 to 4, covers the portion of the map contained within the dotted curve surrounding the acronym “Z_i”. Two other zones Z_5 and Z_6, each comprising a local minimum of radiated power (power substantially equal to -6 dB), are also indicated, using arrows. Each zone Z_i, for i varying from 5 to 6, covers the portion of the map contained within the dotted curve pointed by the arrow associated with said zone Z i. Ultimately, the existence of areas where the level of interference is high, in addition to the fact that the transmitter and transmitter devices occupy fixed positions, proves to be problematic to ensure good

communication between these devices. Indeed, it is understood that if the receiving device occupies a position in a locally maximum power zone (for example one of the zones Z_1, Z_2, Z_3 or Z_4), the level of interference can be sufficiently high for the implementation decoding of the backscattered signal is compromised, thereby failing communication between the devices. To circumvent this problem, it has been proposed solutions implementing, at the level of the receiver device, signal processing techniques aimed at estimating, in a signal received by said receiver device, a component due to such interference . Once estimated, such a contribution is subtracted in order to keep only the signal useful for decoding, namely the backscattered signal. However, these techniques remain very complex to implement.

Disclosure of the invention

[0016] The present invention aims to remedy all or part of the

drawbacks of the prior art, in particular those set out above, by proposing a solution which makes it possible to determine a location of at least one receiving device, so as to prevent it from being able to decode, because

interference, a signal backscattered by at least one transmitting device, and thus optimize communication between these devices. To this end, and according to a first aspect, the invention relates to a method for determining at least one location for the reception, by at least one receiving device, of an ambient signal emitted in a frequency band, called “Transmission band”, and intended to be backscattered by at least one transmitting device to the receiving device, said transmitting device being associated with:

- operating states, including at least one so-called "backscattering" state as well as an opposite state called "non-backscattering", - a frequency band, called "working band", included in said transmission band,

said receiving device being associated with an area which is a function of said transmission band. In addition, said method is implemented by the receiving device when the transmitting device is in the non-backscattering state and comprises, for at least one sub-band of said working band:

- a step of traversing the receiving device in at least part of said zone,

- during the course of the receiving device, a step of acquiring measurements of electromagnetic power received by said receiving device, the measurements being acquired in said sub-band and in respective locations of said part,

a step of comparing said measurements with a determined threshold, a location associated with a measurement being determined as being a

reception location if said measurement is below said threshold.

It should be noted that the expression "sub-band" is defined here in the broad sense, and thus refers to a frequency band of width less than or equal to the width of the working band. Consequently, nothing excludes, according to a particular example of implementation, to consider a sub-band equal to the working band B_T.

[0019] Thus, the determination method according to the invention makes it possible to envisage a path of the receiving device within at least part of said zone. In other words, and unlike the methods of the state of the art, the receiving device is not forced to remain stationary and can advantageously move in order to detect at least one location in which the electromagnetic power received in a sub the band of the working band is low enough for the associated interference level to allow good communication by backscattering with the transmitter device to be envisaged.

[0020] It should also be noted that insofar as the process is implemented

when the ambient signal is not backscattered, said at least one location corresponds to a location in which the power generated by the interfering signal is below the threshold. In other words, the method according to the invention offers the possibility of optimizing the contribution of the backscattered signal, in terms of power received by the receiving device, when the transmitting device goes into a backscattering state.

[0021] The determination method according to the invention therefore offers the possibility, in the event that a location is effectively determined, to avoid the failure of communication between the transmitter device and the receiver device.

The invention thus advantageously overcomes the disadvantages presented by the solutions of the state of the art and which are linked to the stationarity of the transmitter and receiver devices.

In addition, the determination method according to the invention is particularly simple to implement in that it does not require the use of complex signal processing techniques, such as, for example, techniques which aim to estimate and removing, in a signal received by said receiving device, a component due to interference.

[0023] In particular embodiments, the method for determining at least one location may further include one or more of the following characteristics, taken in isolation or in any technically possible combination.

In particular embodiments, a plurality of sub-bands is considered, said sub-bands being distinct from one another, and at least the scanning and acquisition steps being iterated for each of said sub-bands.

The fact of considering sub-bands of the working band makes it possible to

discretize the latter, thus offering the possibility of finely detecting in the vicinity of which frequencies the level of interference is sufficiently low to envisage effective communication between the devices, it being understood that this level of interference varies as a function of the frequency considered for the acquisition of measurements.

In particular embodiments, said method comprises, when several locations have been determined and the transmitter device is in the non-backscattering state, a step of selecting, from among said locations, a location , known as "optimal location", including one associated electromagnetic power measurement is minimal among the power measurements associated with said locations.

Said optimal location therefore designates a location in which the

power received from the source is minimized, so that the level of interference will also be minimal when the receiving device occupies said optimal location to receive the backscattered signal in the sub-band associated with the extent to which the power is thus minimized. In this way, the communication between the transmitting and receiving devices will be optimized.

In particular modes of implementation, the path of the receiving device is carried out throughout the area.

[0029] Proceeding in this manner makes it possible to maximize the probability of finding a local minimum power during the journey of the receiving device. In fact, the more the route is carried out over a large area, the greater the probability of finding a local minimum power.

In particular modes of implementation, the path of the receiving device is carried out autonomously or in an assisted manner.

In particular modes of implementation, the measurements are acquired according to a determined time step or a determined distance step between each location in said part of the zone.

In particular embodiments, the transmitter device is associated with a determined pattern of operation over time corresponding to alternations between the non-backscattering state and said at least one backscattering state, the receiving device having knowledge of said operating diagram.

[0033] Such arrangements advantageously make it possible to facilitate the implementation of the determination method while the transmitter device is in the state of non-backscattering, without the need for an operator to intervene.

In particular modes of implementation, a plurality of transmitting devices is considered, the steps of said method being implemented when said transmitting devices are simultaneously in the non-backscattering state.

[0035] According to a second aspect, the invention relates to a process for

communication between at least one transmitting device and at least one receiving device, by backscattering an ambient radio signal transmitted in a frequency band, known as the "emission band", said transmitting device being associated with:

- operating states, including at least one so-called "backscattering" state as well as an opposite state called "non-backscattering",

- a frequency band, called "working band", included in said emission band.

said receiving device being associated with an area which is a function of said transmission band. In addition, said method comprises:

- a step of determining at least one location for reception according to a method according to the invention,

- when at least one location has been determined and the device

transmitter is in the non-backscattering state, a step of moving the receiving device in the area, so as to reach a fixed position depending on said at least one determined location,

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

a step of reception, by the receiving device and in the sub-band associated with a measurement from which said at least one location has been determined, of the backscattered ambient signal.

Thus, once at least one location has been determined, the receiving device can move to such a location in which it will occupy a fixed position, for example for a determined period of time, to receive the ambient signal backscattered by the transmitting device.

[0037] In particular embodiments, the communication method may further include one or more of the following characteristics, taken in isolation or in any technically possible combination.

[0038] In particular embodiments, when a location

optimal is determined, said fixed position corresponds to the position of the device receiver when it has carried out the minimum electromagnetic power measurement associated with said optimal location, reception taking place in the sub-band associated with said minimum power measurement.

In particular modes of implementation, the steps of determining at least one location, of moving the receiving device so as to reach a fixed position, of backscattering and of reception are iterated on a recurring basis.

[0040] Such arrangements make it possible to take into account the variability of

the environment in which the transmitting device and the receiving device are positioned.

[0041] Typically, elements capable of reflecting and / or diffracting the

waves from the ambient signal can see their respective positions modified in the environment close to the transmitting and receiving devices. By way of purely illustrative example, if the transmitter and receiver devices are placed in an apartment room and a piece of furniture is moved, a location previously determined as suitable for backscattering may no longer be suitable. By “no longer suitable”, we refer here to the fact that the power level can no longer be lower than the threshold, the power distribution having been modified due to the movement of the cabinet.

[0042] Thus, the fact of considering a recurring implementation of the

communication according to the invention advantageously allows the receiving device to adapt to an environment likely to evolve.

[0043] According to a third aspect, the invention relates to a computer program comprising instructions for implementing a method of

determining at least one location according to the invention or a communication method according to the invention when said program is executed by a computer.

[0044] According to a fourth aspect, the invention relates to a recording medium readable by a computer on which is recorded a computer program according to the invention. According to a fifth aspect, the invention relates to a receiver device for receiving an ambient radio signal transmitted in a frequency band, called the "transmission band", and intended to be backscattered by at least one transmitter device to said receiving device, said transmitting device being associated with:

- a frequency band, called "working band", included in said emission band,

In addition, said receiving device is associated with an area that is a function of said transmission band and comprises:

- means of movement in said zone,

- acquisition means, configured to acquire measurements of electromagnetic power received by said receiving device, the measurements being acquired in at least one sub-band of said working band and in respective locations of said zone,

- a comparison module, configured to compare measurements

respectively associated with said locations with a determined threshold,

- A determination module, configured to determine, when one of said measurements is below said threshold, that the location associated with said measurement is a location for receiving the ambient signal intended to be backscattered.

In particular embodiments, said receiving device

comprising a control module, configured to control, when at least one location for reception has been determined, a movement of the receiving device in the area, so as to reach a fixed position depending on said at least one determined location.

[0047] According to a sixth aspect, the invention relates to a communication system comprising at least one receiver device according to the invention and at least one transmitter device.

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

[Fig. 1] FIG. 1 schematically represents an electromagnetic power distribution card radiated by a source corresponding to a television tower;

[Fig. 2] Figure 2 shows schematically, in its environment and in a particular embodiment, a communication system 10 according to the invention;

[Fig. 3] FIG. 3 schematically shows a partial view of an exemplary embodiment of a D_TX transmitter device of the communication system according to the invention;

[Fig. 4] FIG. 4 shows, in flowchart form, the main steps of a method for determining at least one location for the reception of a backscattered ambient signal according to the invention;

[Fig. 5] FIG. 5 diagrammatically represents a preferred embodiment of the determination method of FIG. 4;

[Fig. 6] FIG. 6 shows, in flowchart form, the main steps of a communication method according to the invention.

Description of embodiments

FIG. 2 schematically shows, in its environment and in a particular embodiment, a communication system 10 according to the invention.

The communication system 10 comprises a D_TX transmitter device which remains fixed, as well as a D_RX receiver device.

In the remainder of the description, and as illustrated by the embodiment of FIG. 2, it is considered in a nonlimiting manner that the communication system 10 comprises a single transmitter device D_TX and a single receiver device D_RX. It should however be specified that the invention is also applicable to a communication system comprising a plurality of transmitting devices and / or a plurality of transmitting devices.

The operation of the communication system 10 is based on the

ambient backscattering technology. This technology consists, in a manner known per se, in the backscattering, by the transmitter device D_TX and towards the receiver device D_RX, of an ambient radio signal emitted in a determined frequency band, called "emission band". In other words, to communicate with the receiver device D_RX, the transmitter device D_TX uses said ambient signal to send data to said receiver device D_RX. More particularly, the transmitter device D_TX reflects the ambient signal towards the receiver device D_RX, possibly by modulating it. The signal thus reflected is called a “backscattered signal”, and is intended to be decoded by the receiver device D_RX.

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

The ambient signal corresponds to a radio signal emitted, permanently or even recurrently, by at least one source 20. For the remainder of the description, and as illustrated by FIG. 2, we consider so in no way limiting the case where the ambient signal is emitted by only one source. No limitation is however attached to the number of sources that can be considered in the context of the present invention, since these sources transmit in respective bands whose intersection is not empty and which also intersects an associated frequency band. to the D_TX transmitter device, as described below in more detail.

By "radio signal", we refer here to a wave

electromagnetic propagating by wireless means, the frequencies of which are included in the traditional spectrum of waves

radio (a few hertz to several hundred gigahertz). The remainder of the description is more specifically, but in no way limiting, a UHF ambient signal (acronym for the expression "Ultra High Frequencies") emitted by a television tower in the transmission band [583 MHz, 590 MHz]

It should however be noted that the invention remains applicable to any type of radio signal, such as for example a mobile telephone signal (for example 3G, 4G, 5G), a Wi-Fi signal, a WiMax signal, a DVB-T signal, etc.

Furthermore, no limitation is attached to the structural forms that can be taken respectively by the source 20 and the receiver device D_RX. By way of non-limiting examples, the following configurations are

possible (depending, of course, on the transmission band considered):

- the source 20 is a base station, and the receiver device D_RX is a smartphone,

- the source 20 is a smartphone, and the receiving device D_RX is a base station,

- the source 20 is a smartphone, and the receiving device D_RX is also a smartphone,

the source 20 is a domestic gateway (also called an “Internet box”) emitting a Wi-Fi signal, and the receiving device D_RX is a smartphone.

The waves conveyed by the signals considered in the present invention are conceptually represented by wavy arrows in FIG. 2. More particularly, the arrows F_1 and F_2 represent waves of the ambient signal emitted by the source 20. The waves represented by the arrow F_1 are backscattered by the transmitter device D_TX, and the waves of the backscattered signal are here represented by the arrow F_3. The waves represented by the arrow F_2 are for their part not backscattered and reach the receiving device D_RX directly. It should also be noted that only the waves represented by the arrow F_3 transport the data that the receiver device D_RX is intended to decode.

It should be noted that Figure 2 is given purely for illustration. Thus, it does not include, for example, any element capable of reflecting or diffracting the waves of the ambient signal. In this sense, Figure 2 is intended to be a version simplified environment in which the D_TX transmitter and D_RX receiver devices are located. It should nevertheless be borne in mind that this

The environment is generally of complex configuration and comprises, in practice, elements (walls, trees, ground, etc.) capable of generating such reflections and diffractions.

As mentioned previously, the transmitter device D_TX and the receiver device D_RX are respectively configured in order to communicate with each other by ambient backscattering.

[0062] Figure 3 schematically shows a partial view of an exemplary embodiment of the D_TX transmitter device of Figure 2. The configuration of such a D_TX transmitter device is known to those skilled in the art.

As illustrated in Figure 3, the D_TX transmitter device is equipped with an antenna 111 configured, in a manner known per se, to receive the ambient signal but also backscatter it to the D_RX receiver device. It should be noted that no limitation is attached to the number of antennas that can equip the D_TX transmitter device.

[0064] In the example of Figure 3, said antenna is constructed so as to

have a larger dimension substantially equal to half the wavelength associated with a frequency F_C included in the emission band. More particularly, the frequency F_C considered here is the center frequency of the emission band [583 MHz, 590 MHz], or 586.5 MHz. Thus, said largest dimension of the antenna 111 is substantially equal to 25 cm.

In practice, the transmitter device D_TX is associated with a band

frequency, called “influence band”, which corresponds to the frequency band in which the antenna 111 is able to receive / backscatter signals. Thus, in the example given above with reference to FIG. 3, said influence band corresponds to a frequency interval centered on said frequency F_C, and whose amplitude is equal to a sampling frequency F_E applied by an analog / digital converter equipping the D_TX transmitter device with signals likely to be received. In other words, said influence band is equal to [F_C - F_E / 2, F_C + F_E / 2] For example, said sampling frequency is equal to 1 MHz, and the influence band is then equal to [585.5 MHz, 587.5 MHz] It is then noted that the influence band is included in the emission band associated with the source 20. Due to this inclusion, said influence band is qualified as “working band” B_T. By “working band”, reference is made here to the fact that the transmitter device D_TX is compatible with the source 20, namely that the backscatter can be carried out for any frequency included in said working band B_T.

However, nothing excludes considering other values for the frequencies F_C and F_E. It is nevertheless evident that in order for the transmitter device D_TX to be able to backscatter the ambient signal, said influence band should intersect non-empty with said transmit band, the working band B_T corresponding from then at this intersection. Thus, if the transmitter device D_TX is configured so as to be associated with an influence band containing the transmission band, then the working band B_T of said transmitter device D_TX is defined as being equal to said band

resignation.

The transmitter device D_TX is also associated with states of

operation, namely a state called "backscattering" (the device

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

For example, and as illustrated in Figure 3, the transmitter device comprises two switches 112, 113 configured so as to be able to connect to the antenna 111, according to their respective positions, an impedance l_1, for example equal to 0 Ohms, or even equal to R Ohms where R is a finite strictly positive value. When at least one of the switches 112, 113 is not connected to the impedance I_1, the antenna 111 is in a so-called “open circuit” configuration corresponding to said non-backscattering state. In addition, the D_TX transmitter device is configured to perform, from the ambient signal received via its antenna 111 and when it is in the backscatter state, processing aimed at backscattering said ambient signal, by implementing a backscattering process.

For this purpose, the transmitter device D_TX comprises for example one or

several processors and storage means (magnetic hard disk, electronic memory, optical disk, etc.) in which data and a computer program are stored, in the form of an assembly

of program code instructions to be executed to initiate the backscattering process.

Alternatively or in addition, the D_TX transmitter device also includes one or more programmable logic circuits, of FPGA, PLD, etc. type, and / or specialized integrated circuits (ASIC), and / or a set of discrete electronic components, etc. adapted to implement the method of

backscattering.

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

Aspects specifically related to the implementation of the method of

backscattering (processing of the ambient signal, modulation, etc.) are outside the scope of the present invention, and are also known to those skilled in the art. Therefore, they are not detailed here further.

The receiver device D_RX, for its part, is configured for:

- receive the ambient signal emitted by the source 20, including in particular the

any reflections and diffractions undergone by the waves of this signal due to elements placed in the environment in which the D_TX transmitter and D_RX receiver devices are located,

- receive the backscattered signal from the D_TX transmitter device.

For this purpose, said D_RX receiver device comprises at least one reception antenna. It should be noted that no limitation is attached to the number of antennas that can equip the D_RX receiver device. The receiver device D_RX is also associated with a zone Z_T determined as a function of said transmission band. Such a zone Z_T

corresponds to a geographical space within which the D_RX receiver device can move from an initial location that it occupies, to find a location in which the distribution of power radiated by the source 20 is locally minimal.

Said zone Z_T is for example defined at the time of the design of the

D_RX receiver device.

Alternatively, said zone Z_T is defined while the receiver device D_RX already occupies a position in situ, depending on a type of source from which it is desired to backscatter the ambient signal. To this end, a message comprising information defining said zone Z_T can be transmitted, for example by an operator, to the receiver device D_RX.

Preferably, said zone Z_T has at least one dimension

substantially equal to half the wavelength associated with a frequency included in the emission band, preferably a frequency corresponding to the center frequency of said emission band. The fact of considering such a value for said at least one dimension results from the fact that the local minima of the power distribution radiated by the source 20 (such as for example those associated with zones Z_5 and Z_6 in FIG. 1) are on average two with two separated by a distance equal to half the wavelength associated with the center frequency of the transmission band. It is therefore understood that the fact of considering a zone Z_T having at least one such dimension advantageously allows the receiver device D_RX to maximize the probability of finding a local minimum during a movement in said zone Z_T.

By way of non-limiting example, such a zone Z_T is illustrated in FIG. 1. In this example, the frequency considered in the transmission band is said frequency F_C, so that said at least one dimension of the zone Z_T is equal to 25 cm. More particularly, the zone Z_T corresponds here to a square whose side length is equal to 25 cm. In addition, the receiver device D_RX occupies an initial location corresponding to the center of this square. We note that this initial location is determined independently of any a priori knowledge of the power distribution radiated by the source 20.

[0082] Nothing excludes however, following other examples not detailed here, from

consider an area of a shape other than a square, as well as having one or more (or even all) dimensions less than or greater than half the wavelength associated with a frequency included in the emission band. In addition, no limitation is attached to the initial location occupied by the receiving device D_RX within the Z_T area. For example, in the case where the zone Z_T is a square, said initial location may correspond to a corner of this square.

The D_RX receiver device further comprises movement means (not shown in the figures) in said Z_T zone, and more broadly in the entire environment in which the D_TX transmitter and D_RX receiver devices are located.

For example, said displacement means comprise means

drive, such as at least one electric motor, as well as guide means, such as wheels. However, nothing excludes considering other training means, such as a heat engine, as well as other guidance means, such as caterpillars.

Preferably, the D_RX receiver device takes the form of a robot comprising an electric motor and wheels. For example, such a robot is intended to operate in a hangar in which are stored

goods, these goods being likely to be extracted from the hangar, one by one, in order to be dispatched following consumer orders. Said D_TX transmitter device, for example of the computer type, is able to keep up to date the inventory of the stock of goods in the hangar. Therefore, the data backscattered to the receiver device D_RX can be

representative, at a given instant, of a part of said inventory, this part relating to an area of the hangar in which the receiver device D_RX moves. The receiver device D_RX also comprises acquisition means configured to acquire, in at least one location of said zone Z_T, electromagnetic power measurements received by said receiver device D_RX, said measurements being respectively acquired in at least one sub - band of said working band B_T.

It should be noted that the expression "sub-band" is defined here in the broad sense, and thus refers to a frequency band of width less than or equal to the width of the working band B_T. Consequently, nothing excludes considering a sub-band equal to the working band B_T.

[0088] Conventionally, said acquisition means comprise an acquisition chain connected to a sensitive element configured to provide an analog electrical signal representative of the measured electromagnetic power. In the present exemplary embodiment, said sensitive element corresponds to a reception antenna fitted to the receiver device D_RX.

Said acquisition chain comprises for example an acquisition card

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

[0090] It should be noted that the acquisition means are configured to perform

acquiring power measurements in both the non-backscattering state and the backscattering state of the D_TX transmitter device.

In a particular embodiment, the transmitter device D_TX is associated with a determined pattern of operation over time corresponding to alternations between the non-backscattering state and the backscattering state. For example, determined durations are allocated respectively to the non-backscattering state and to the backscattering state, the transmitter device D_TX operating according to said states as a function of said allocated durations. It should be noted that such an operating diagram is for example defined in a telecommunications standard. Furthermore, in this particular embodiment, the receiver device D_RX is aware of said operating diagram. This knowledge comes for example from one or more data representative of said operating diagram and stored by the receiver device D_RX. These data are for example transmitted to the receiver device D_RX by an operator or else by the transmitter device D_TX itself.

However, nothing excludes considering that the D_TX transmitter device is not associated with any specific operating diagram. For example, the change from the backscatter state to the non-backscatter state (and vice versa) is performed in an operator-assisted manner, depending on specific communication needs between devices. Again, knowledge of the state (backscatter or non-backscatter) of said D_TX transmitter device, by the D_RX receiver device, may come from a message transmitted to said D_RX receiver device, this message comprising data representative of the state. For example, this message is transmitted by an operator or else by the D_TX transmitter device itself.

In any event, and according to the invention, the D_RX receiver device is able to perform processing (for example a determination method as described later) when the D_TX transmitter device is in the non-state. backscattering. In other words, the D_RX receiving device can perform such processing synchronizing with periods when the D_TX sending device is in the non-backscattering state.

The D_RX receiver device is also configured to perform, on the basis of power measurements acquired in at least one location, processing aimed at determining at least one location for the reception of the backscattered signal, by implementing all or part steps of a method for determining said at least one location.

For this purpose, the receiver device D_RX comprises for example one or

several processors and storage means (magnetic hard disk, electronic memory, optical disk, etc.) in which data and a computer program are stored, in the form of an assembly program code instructions to be executed to implement at least part of the steps of the determination method.

Alternatively or in addition, the D_RX receiver device also comprises one or more programmable logic circuits, of FPGA, PLD, etc. type, and / or specialized integrated circuits (ASIC), and / or a set of discrete electronic components, etc. suitable for implementing all or part of the steps of the determination method.

In other words, the D_RX receiver device comprises a set of means configured in software (specific computer program) and / or hardware (FPGA, PLD, ASIC, etc.) to implement all or part steps of the determination process.

In addition to allowing the determination of at least one location for reception, said means configured in software and / or hardware also make it possible to control the movement of the D_RX receiver device.

[0100] To this end, these means comprise for example a control module (not shown in the figures) configured to generate control commands.

displacement of the receiving device D_RX. Such commands can be generated regardless of the state (backscatter or non-backscatter) of the D_TX transmitter device.

[0101] For example, said commands are generated without assistance. In other words, the D_RX receiver device is able to move around the Z_T zone autonomously, that is to say without the intervention of an operator.

[0102] Alternatively, the control of the receiver device D_RX is carried out from

a manner assisted by an operator who generates remote control signals, these control signals then being transmitted to said receiver device D_RX which moves according to the data conveyed in these signals. For this purpose, the receiver device D_RX comprises for example communication means for receiving said control signals, said signals then being processed by the control module. These communication means are based, in a manner known per se, on a communication interface capable of exchanging data between said operator and said receiving device D_RX. No limitation is attached to the nature of this communication interface, which can be wired or wireless, so as to allow the exchange of data according to any protocol known to those skilled in the art (Ethernet, Wifi, Bluetooth, 3G, 4G, 5G, etc.). Nothing excludes either considering, according to another example, that said control signals are received by a reception antenna of the receiver device D_RX.

For the remainder of the description, it is considered in no way limiting that the operation of the receiver device D_RX is provided by an electrical energy that the latter is able to store.

[0104] For example, said electrical energy is contained in a battery

electrical device integrated into said receiver device D_RX, and can be recharged for example by means of solar panels equipping said receiver device D_RX, or else by capacitive effect, so that the receiver device D_RX is energetically autonomous. Alternatively, the recharging of said battery is carried out via a connection to the domestic electrical network.

[0105] However, nothing excludes considering other types of energy, such as fossil fuel, for example, especially in the case where the D_RX receiver device is equipped with a heat engine. Finally, nothing excludes considering an energy mix (electrical and thermal) either.

[0106] In other words, and in general, no limitation is attached to the energy considered for the operation of the D_RX receiver device, or even to the way in which this energy is obtained by the latter.

[0107] In addition, and as mentioned above, the receiver device D_RX is configured to perform processing aimed at decoding the backscattered signal, by implementing a decoding method.

To this end, and according to characteristics identical to those described above in the case of the means for implementing the determination method, the receiver device D_RX also comprises a set of means configured in a software manner (program of specific computer) and / or hardware (FPGA, PLD, ASIC, etc.) to implement said decoding method. The aspects specifically related to the implementation of the decoding method are outside the scope of the present invention, and are also known to those skilled in the art. Therefore, they are not detailed here further.

[0110] FIG. 4 represents, in flowchart form, the main steps of the method for determining at least one location according to the invention.

[0111] Said method of determining is implemented by the D_RX receiver device when the D_TX transmitter device is in the non-backscattering state.

[0112] It is recalled here that the non-backscattering state corresponds to a configuration in which the antenna 111 of the D_TX transmitter device is in the open circuit configuration. Also, for the implementation of the determination method, no limitation is attached as to whether the D_TX transmitter device is in operation or not (ie the energy necessary for the operation of the D_TX transmitter device is in use or no), as long as it is in the non-backscattering state.

[0113] Said method of determination comprises several steps. In its general principle, it consists in carrying out, for at least one sub-band of the working band B_T, electromagnetic power measurements at locations in the Z_T zone when the receiving device D_RX performs a route, in order to be able to locate a location in which the electromagnetic power generated by the source 20 is sufficiently low, thus limiting the presence of interference liable to cause the decoding of a signal backscattered by the transmitter device D_TX to fail.

For the remainder of the description, and purely by way of illustration, it is considered that the distribution of power radiated by the source 20 at the time when the determination method is implemented conforms to the distribution shown in FIG. 1. It is also considered that the zone Z_T associated with the receiving device D_RX corresponds to that indicated in FIG. 1.

[0115] It is also considered that the receiver device D_RX occupies, before the implementation of said determination method, an initial location corresponding to the center of the square forming the zone Z_T. However, it should be noted that no limitation is not attached to the location of said initial location within, or else along the border, of said zone Z_T.

The method will now be described by taking the configuration in which several sub-bands SB_1, SB_2, ... are considered within the working band B_T to carry out acquisitions of electromagnetic power measurements.

[0117] However, no limitation is attached to the number of sub-bands

that can be considered. Thus, the invention remains applicable in the case where a single sub-band is considered, this sub-band also possibly being equal to the working band B_T.

[0118] Said sub-bands SB_1, SB_2 ... are distinct from one another.

Preferably, said sub-bands SB_1, S B_2 ... form a partition of the working band B_T. Such arrangements make it possible to optimize the discrimination of the measurements between them, with a view to determining a reception location, as described later.

[0119] For example, the width of a sub-band SB_i is equal to 100 kHz. No limitation is attached to the width that can be considered for an SB_i sub-band. Further, such a width may be prescribed by a telecommunications standard.

[0120] It should be noted that the choice consisting in considering sub-bands forming a partition of the working band B_T does, however, constitute only one variant of the implementation of the invention. Thus, nothing excludes considering sub-bands which partially overlap.

[0121] As illustrated by FIG. 4, said method of determining comprises, for a band SB_i considered among the sub-bands SB_1, SB_2, ..., several steps including a step E10 of traversing the receiver device D_RX in the au minus a part of the zone Z_T.

[0122] Such a path of the receiver device D_RX allows the latter to scan at least in part the zone Z_T with the objective of discovering there at least one location in which the power radiated by the source 20 is sufficiently high. low so that the receiving device D_RX can decode the signal that will be backscattered.

The term “journey” is used here to refer to an exploration phase, this phase possibly comprising a continuous movement (that is to say without stopping within said part) between initial and final locations respectively in in which the receiving device D_RX is fixed, or else which can be produced in a fractional manner (that is to say with one or more intermediate stops within said part before reaching a final location).

[0124] In a particular mode of implementation, the path of the device

D_RX receiver is carried out autonomously, that is to say without external assistance. For example, said receiver device D_RX is configured to analyze the environment in which it is located, in order to detect any obstacles that it can therefore bypass. Such detection is typically implemented by means of imaging means (for example a camera) fitted to the D_RX receiver device, as well as by processing implemented by said D_RX receiver and aimed at analyzing images obtained with said means imaging. Such treatments are well known to those skilled in the art, and are therefore not detailed here further.

In another particular mode of implementation, the path of the receiver device D_RX is performed in an assisted manner, for example by an operator able to remotely control the movements of the receiver device D_RX.

Whatever the mode of implementation considered (autonomous or assisted), the path of the receiver device D_RX can take place along a determined path, such as for example a spiral, a line, in slots, etc.

[0127] Alternatively, the displacement of the receiver device D_RX can be carried out in a non-deterministic manner.

In general, no limitation is attached to the path followed by the receiver device D_RX.

Furthermore, said part of the zone Z_T is for example configured so as to include the initial location of the receiver device D_RX. [0130] By way of illustration, and with reference to FIG. 1, said part corresponds to one half (for example the right half) of the square formed by the zone Z_T. Thus, the initial location belongs to the boundary of said part.

[0131] Alternatively, said part does not include the initial location, so that the receiver device D_RX performs a preliminary movement in order to reach said part which is then traversed.

[0132] In general, no limitation is attached to the shape presented by said part of the Z_T zone. In addition, the path of the receiver device D_RX can be carried out for a determined duration which can be configured, so that the shape of said part can depend on this determined duration.

In a particular mode of implementation, the displacement of the receiver device D_RX is carried out throughout the zone Z_T. Proceeding in this way makes it possible to maximize the probability of finding a local minimum power during the travel of the receiving device D_RX.

The determination method also comprises, for said sub-band SB_i, during the path of the receiver device D_RX, a step E20

acquisition of electromagnetic power measurements Pi_1, Pi_2, ... received by said receiving device D_RX. Said measurements P1_i, P2_i, ... are acquired in said sub-band SB_i and in respective locations E1_i, E2_i, ... of said part of zone Z_T.

In other words, for a location EjJ (j being an integer index greater than or equal to 1) considered, a measurement PjJ is acquired in the sub-band SB_i. A map is thus obtained, called a "acquisition map", grouping the measurements made in said part of the zone Z_T for said sub-band SB_i.

[0136] Acquisitions are preferably carried out at standstill (phase

fractional exploration). In other words, during its journey, the receiver device D_RX marks stops as soon as it wishes to acquire, at a location EjJ, electromagnetic power measurements.

However, nothing excludes considering that said measurements P1J, P2J, ... are acquired while the receiver device D_RX is in motion. In a particular example of implementation, if a plurality of locations is considered during the acquisition step E20, the measurements are acquired according to a determined time step, for example configurable, between each location in said part of the Z_T zone. To do this, the receiver device D_RX moves for example at constant speed.

[0139] According to another example, or else in addition to the preceding one in which a determined time step is considered, and when several locations are considered during step E20, the measurements are acquired according to a determined distance step, for example configurable, between each location in said part of zone Z_T.

[0140] The number of EjJ locations considered for the SB_i sub-band

corresponds for example to a determined number for example configurable. However, it should be noted that there is no limitation on the number of EjJ locations that can be considered. Thus, the invention remains applicable in the situation where only one location is considered for said sub-band SB J.

[0141] In addition, nothing excludes considering that one of said power measurements PjJ is acquired in the SBJ sub-band and in the initial location when the receiver device D_RX is stopped.

The determination method also comprises, for said sub-band SBJ, a step E30 of comparing the measurements PjJ respectively associated with said locations with a determined threshold S_D.

This comparison step E30 is implemented here by a comparison module fitted to the receiver device D_RX. It should be noted that although this step E30 is described here as being implemented when said transmitter device D_TX is in the non-backscattering state, nothing excludes considering, according to a particular embodiment, that said module comparison is also able to perform such a comparison during a backscattering state.

The threshold S JD considered here for the comparison is typically determined as a function of a determined decoding error rate as well as a reception noise considered admissible on the receiving device side D_RX. Of a In general, those skilled in the art know how to set a threshold S_D from which a location can be considered for reception.

[0145] Thus, by setting such a threshold S_D, the objective is to prevent a location in which there is a great deal of interference, at least sufficiently so that the decoding error rate exceeds a given threshold, from being considered. as a valid location for receiving the backscattered signal.

[0146] For example, said threshold S_D is chosen sufficiently low, for example in the range [-6 dB, -2dB], more particularly in the range [-6 dB, -4 dB]

The comparison carried out during step E30 is for example implemented each time a power measurement is acquired in the sub-band SB_i.

[0148] Alternatively, said comparison is implemented once a determined duration of the journey has elapsed and / or when a determined number of locations EjJ has been reached during the journey (for example when all the measurements P1_i, P2_i , ... respectively associated with said locations EjJ have been acquired), said measurements being in this case stored by the receiver device D_RX during its journey.

[0149] According to yet another alternative, or else in addition to the preceding alternatives, said comparison is carried out once all the part of the zone Z_T, or even all of said zone Z_T where applicable, has been traversed.

[0150] Consequently, for said SBJ sub-band, and during a step E40 of the

method of determination, a location EjJ associated with an acquired measurement PjJ is determined as being a reception location, said measurement PjJ is below said threshold S_D.

This determination step E40 is implemented here by a determination module fitted to the receiver device D_RX. It should be noted that although this step E40 is described here as being implemented when said transmitter device D_TX is in the non-backscattering state, nothing excludes considering, according to a particular embodiment, that said module determination is also able to make such a determination during a backscattering state. [0152] This therefore involves sorting among the locations E1_i, E2_i, ... in which power measurements have been acquired.

According to an exemplary implementation, when the comparison of the measurements P1_i, P2_i, ... with the threshold S_D is performed each time a power measurement is acquired, the determination step E40 is stopped as soon as when an acquired measurement is determined below the threshold S_D.

Thus, in this example, if the first measurement P1_i acquired by the receiver device D_RX in the sub-band SB_i is carried out in its initial location, and if this measurement P 1 _i is less than the threshold S_D, said receiver device remains motionless.

[0155] Proceeding in this way not only makes it possible to determine a

location so that the backscattered signal can be decoded by the D_RX receiver device, but also optimize the power consumption of the D_RX receiver device.

[0156] The steps of the method have been described up to now by considering a single sub-band SB_i among the sub-bands SB_1, SB_2, ... of the working band B_T.

[0157] Also, in the present mode of implementation of the determination method, once the steps of path E10, acquisition E20, comparison E30 as well as the determination E40 of at least one location have been executed for one of said sub-bands, they are iterated for each of the remaining sub-bands. In other words, said sub-steps are iterated as many times as the number of sub-bands.

[0158] The choice consisting in iterating all the steps of the process when

several sub-bands are considered, however, only constitutes a variant implementation of the invention. For example, the comparison steps E30 and / or determination E40 can be executed once all the routes have been carried out (iterations of step E10) and all the measurements have been acquired during these routes (iterations of l 'step E20).

In general, performing such iterations makes it possible in particular to obtain acquisition cards for each of the sub-bands of the working band. B_T. The fact of considering several sub-bands advantageously makes it possible to finely discriminate the frequencies of the working band B_T as a function of the interference levels respectively associated with each of them. Indeed, it is known that the level of power received at a location, and therefore ultimately the level of interference at this location, varies as a function of the frequency considered to acquire measurements.

It should be noted that the locations considered during the different iterations can for example coincide with one another. In other words, in this example, the acquisition maps include measurements acquired at identical locations from one iteration to the next. However, nothing excludes considering separate locations, in whole or in part, from one iteration to another.

By way of illustrative example, and with reference to FIG. 1, ten sub-bands, all of the same width equal to 200 kHz so as to form a partition of the interval [585.5 MHz, 587.5 MHz], are considered. According to this example, the receiver device D_RX traverses, for each sub-band, the entire part corresponding to the right half of the square formed by the zone Z_T, and carries out acquisitions at a distance step equal to 2 cm between each location.

Furthermore, in this example, the comparison of the measurements acquired is carried out once the ten paths of the receiver device D_RX have been carried out. At the end of the process, the receiver device D_RX has determined two reception locations respectively located within the zones Z_5 and Z_6.

[0162] FIG. 5 diagrammatically represents a preferred mode of implementation of the determination method of FIG. 4.

In this preferred embodiment, and as illustrated by FIG. 5, said determination method comprises, when several locations have been determined as being locations for reception, a selection step E50, from among said reception locations, of a location, called “optimal location” E_OPT, of which the associated power measurement is minimum among the power measurements associated with said reception locations.

Said optimal location E_OPT therefore designates a location in which the power received from the source 20 is minimized, so that the probability that interference is generated there is also minimal when the receiver device D_RX occupies said optimum location E_OPT for receiving the backscattered signal. In this way, the communication between the D_TX, D_RX devices is optimized.

Returning to the illustrative example mentioned above, and in which two locations have been determined in the zones Z_5 and Z_6, the optimal location E_OPT selected corresponds for example finally to the location associated with the zone Z_5.

[0166] The invention also relates to a method of communication between the

D_TX transmitter device and D_RX receiver device.

[0167] FIG. 6 represents, in the form of a flowchart, the main steps of said communication method.

[0168] As illustrated by FIG. 6, said backscattering method firstly comprises a step F10 of determining at least one location for reception.

[0169] Such a determination step F10 is carried out in accordance with the determination method described above.

[0170] Subsequently, and when at least one reception location has been determined and the transmitter device D_TX is in the non-backscattering state, said backscattering method comprises a step F20 of moving the receiver device D_RX in the zone Z_T, so as to reach a fixed position POS_F which is a function of said at least one determined location.

[0171] For example, said fixed position POS_F corresponds to a position identical to that occupied by the receiver device D_RX when it has carried out the measurement associated with said at least one determined location. By "identical position", it should be understood that, if the receiver device D_RX is equipped with several antennas, the relative positions (in terms of geographical coordinates) of said antennas, when the receiver device D_RX reaches said fixed position POS_F, correspond exactly to the positions relative antennas at the time when the measurement associated with said at least one location was acquired. The choice of such a fixed position POS_F constitutes only one variant of implementation of the invention. For example, the receiving device D_RX can occupy a fixed position POS_F according to which the position (in terms of geographical coordinates) of its center of gravity is identical to the position of its center of gravity when the measurement associated with said at least one location has been acquired. Although there is a correspondence concerning the position of the center of gravity, the relative positions of the antennas for said fixed position may nevertheless differ from the relative positions of the antennas at the time when the measurement associated with said at least one location was acquired.

[0173] It should be noted that if several locations are determined, the fixed position POS_F is for example a function of the position of the receiver device D_RX when it has carried out the electromagnetic power measurements associated with any of said determined locations.

[0174] Preferably, when an optimal location E_OPT is selected, said fixed position POS_F is identical to the position of the transmitter device D_TX when it has performed the electromagnetic power measurement associated with said optimal location E_OPT.

[0194] Once the receiver device D_RX has reached said fixed position POS_F, the communication method comprises a step F30 of backscattering, by the transmitter device D_TX, of the ambient signal. To do this, said D_TX device changes from the non-backscattering state to the backscattering state.

[0176] Furthermore, the communication method also includes a step F40 of reception, by the receiver device D_RX and in the sub-band associated with a measurement from which said at least one location has been determined, of the backscattered ambient signal .

[0177] Returning to the preferred example described above, in which a

optimal location E_OPT is selected, reception takes place in the sub-band associated with the minimum power measurement.

[0178] Preferably, the backscattering steps F30 and reception F40 are implemented simultaneously. However, nothing excludes considering a time shift between said steps F30 of backscattering and F40 of reception. However, it is implied that the D_TX and receiver D_RX communicate with each other as soon as the periods during which the backscattering steps F30 and reception F40 are

respectively implemented overlap at least partially.

In a particular mode of implementation, the steps of determining F10 of at least one location, of displacement F20 of the transmitter device so as to reach a fixed position POS_F, of backscattering F30 and of reception F40 are iterated in a manner recurring.

The fact of performing these steps recurrently makes it possible to take into account the variability of the environment in which the transmitter device D_TX and the receiver device D_RX are positioned.

[0181] For example, said steps are iterated periodically, for example once a day in an environment in which the power distribution is stable, or even more, for example once every hour if the power distribution is likely to evolve substantially every hour.

[0182] The invention has been described up to now considering that the device

Transmitter D_TX was associated with a single backscatter state as well as a single non-backscatter state. The invention nevertheless remains applicable in the case where the transmitter device D_TX is associated with a plurality of control states.

backscattering, these states being distinct from one another in that they are implemented thanks to respective impedances which are distinct from one another. It will of course be understood that the non-backscattering state itself remains unique.

[0183] Those skilled in the art know how to adapt the configuration of the D_TX transmitter device as represented in FIG. 3 to take into consideration several backscattering states. For example, with reference to FIG. 3, several impedances that are distinct from one another can be arranged in parallel between the switches 112, 113.

[0184] Furthermore, the invention has also been described so far by considering a single transmitter device D_TX. The invention nevertheless remains applicable in the case where a plurality of transmitting devices D_TX is considered.

For example, when a plurality of D_TX transmitting devices are

considered, the steps of the method for determining at least one location (browse step E10, acquisition step E20, comparison step E30, determination step E40, and selection step E50 if applicable) are implemented by the receiver device D_RX when said transmitter devices D_TX are simultaneously in the non-backscattering state. To ensure such simultaneity, said D_TX transmitting devices are for example synchronized with each other by GPS (acronym for the English expression "Global Positioning System") and each observe the same non-backscattering duration according to a period which is also theirs. common, such a duration and such a period being for example defined in a telecommunications standard. Preferably, said D_TX transmitting devices backscatter the ambient signal simultaneously (step F30).

[0185] It is clear to those skilled in the art that the arrangements described above in the case where several synchronized D_TX transmitting devices are considered apply regardless of the number of D_RX receiving devices considered. Preferably, when several D_RX receiver devices are considered, the reception step F40 is executed for each of said D_RX receiver devices simultaneously with the step F30 of

backscattering.

Claims

[Claim 1] Method for determining at least one location for the reception, by at least one receiving device (D_RX), of an ambient signal transmitted in a frequency band, called the “transmission band”, and intended to be backscattered by at least one transmitting device (D_TX) to the receiving device (D_RX), said transmitting device (D_TX) being associated with:

- a frequency band, called "working band", included in said transmission band,

said receiver device (D_RX) being associated with a zone (Z_T) which is a function of said transmission band,

said method being implemented by the receiving device (D_RX) when the transmitting device (D_TX) is in the non-backscattering state and comprising, for at least one sub-band (SBJ) of said working band:

- a step (E10) for traversing the receiving device (D_RX) in at least part of said zone (Z_T),

- during the path of the receiving device (D_RX), a step (E20) of acquiring measurements of electromagnetic power (PjJ) received by said receiving device (D_RX), the measurements being acquired in said sub-band (SBJ) and at respective locations (EiJ) of said part,

a step (E30) of comparing said measurements with a determined threshold (S_D), a location associated with a measurement being determined (E40) as being a reception location if said measurement is below said threshold.

[Claim 2] A method according to claim 1, wherein a

a plurality of sub-bands is considered, said sub-bands being distinct from one another, and at least the scanning (E10) and acquisition (E20) steps being iterated for each of said sub-bands.

[Claim 3] A method according to any one of claims 1 to 2, said method comprising, when several locations have been determined and the transmitting device (D_TX) is in the non-backscattering state, a step (E50) of selecting, from among said locations, a location, called an “optimal location” (E_OPT), of which an associated electromagnetic power measurement is minimal among the power measurements associated with said locations.

[Claim 4] Method according to any one of claims 1 to 3, in which the path of the receiving device (D_RX) is carried out in the entire area (Z_T).

[Claim 5] A method according to any one of claims 1 to 4, in which the path of the receiving device (D_RX) is carried out autonomously or in an assisted manner.

[Claim 6] A method according to any one of claims 1 to 5, wherein the measurements are acquired according to a determined time step or a determined distance step between each location in said part of the area (Z_T).

[Claim 7] A method according to any one of claims 1 to 6, in which the transmitter device (D_TX) is associated with a determined pattern of operation in time corresponding to alternations between the state of "non-backscattering" and said at least one state of "

backscattering ”, the receiving device (D_RX) having knowledge of said operating diagram.

[Claim 8] A method according to any one of claims 1 to 7, wherein a plurality of transmitter devices (D_TX) are considered, the steps (E10, E20, E30, E40, E50) of the method being implemented when said transmitting devices (D_TX) are simultaneously in the non-backscattering state.

[Claim 9] Method of communication between at least one transmitting device (D_TX) and at least one receiving device (D_RX), by backscattering an ambient radio signal transmitted in a frequency band, called “transmission band”, said device transmitter (D_TX) being associated at :

- a frequency band, called "working band", included in said transmission band,

said receiver device (D_RX) being associated with a zone (Z_T) which is a function of said transmission band, and said method comprising:

- a step (F10) of determining at least one location for reception according to a method according to any one of claims 1 to 8,

- when at least one location has been determined and the transmitting device (D_TX) is in the non-backscattering state, a step (F20) of moving the receiving device (D_RX) into the area (Z_T), so in reaching a fixed position (POS_F) depending on said at least one determined location,

- a step (F30) of backscattering, by the transmitter device (D_TX), of the ambient signal,

a step (F40) of reception, by the receiving device (D_RX) and in the sub-band associated with a measurement from which said at least one location has been determined, of the backscattered ambient signal.

[Claim 10] A method according to claim 9, wherein, when an optimum location (E_OPT) is determined, said fixed position corresponds to the position of the receiving device (D_RX) when it has made the minimum electromagnetic power measurement associated with said said fixed position. optimal location (E_OPT), the reception taking place in the sub-band associated with said minimum power measurement.

[Claim 11] A method according to any one of claims 9 to 10, wherein the steps of determining (F10) at least one

location, displacement (F20) of the receiving device (D_RX) so as to reach a fixed position (POS_F), backscattering (F30) and reception (F40) are iterated repeatedly.

[Claim 12] A computer program comprising instructions for implementing a method for determining at least one location according to any one of claims 1 to 8 or a communication method according to any of claims 9 to 11 when said program is executed by a computer.

[Claim 13] A computer readable recording medium on which is recorded a computer program according to claim 12.

[Claim 14] Receiver device (D_RX) for receiving an ambient radio signal transmitted in a frequency band, called the “transmission band”, and intended to be backscattered by at least one transmitting device (D_TX) to said receiving device (D_RX), said transmitter device (D_TX) being associated with:

- a frequency band, called "working band", included in said transmission band,

said receiving device (D_RX) being associated with a zone (Z_T) which is a function of said transmission band and comprising:

- means of movement in said zone (Z_T),

- acquisition means, configured to acquire measurements of electromagnetic power received by said receiver device (D_RX), the measurements being acquired in at least one sub-band of said working band and in respective locations of said zone (Z_T ),

- a comparison module, configured to compare the measurements respectively associated with said locations with a determined threshold,

a determination module, configured to determine, when one of said measurements is below said threshold, that the location associated with said measurement is a location for receiving the ambient signal intended to be backscattered.

[Claim 15] Receiver device (D_RX) according to claim 14, said receiver device (D_RX) comprising a pilot module, configured to control, when at least one location for reception has been. determined, a displacement of the receiving device (D_RX) in the zone (ZT), so as to reach a fixed position (POS_F) depending on said at least one determined location.

[Claim 16] A communication system comprising at least one receiver device (D_RX) according to any one of claims 14 to 15 and at least one transmitter device (D_TX). j