Method for processing a radio signal, and associated device

Abstract

The invention relates to a method for processing a radio signal emitted by an emitter device (DSo) and backscattered by a transmitter device (DTx), the method comprising the following steps, implemented by a receiver device (DRx) following receipt of the backscattered signal: obtaining, from the backscattered signal, an identification datum identifying the transmitter device and a digital signature of a datum relating to the identification datum, said signature being associated with a management entity managing the emitter device; and processing the backscattered signal based on the identification datum identifying the transmitter device if the signature is valid.

Description

Description Title of the invention: Method for processing a radio signal and associated device Technical field

[0001] The present invention belongs to the general field of telecommunications. It relates more particularly to a method for processing a radio signal emitted by a transmitting device and backscattered by a transmitting device, and a receiving device configured to implement this processing method.

[0002] It also relates to a method for generating a digital signature associated with a transmitting device configured to backscatter a radio signal, and a control device configured to implement this method for generating a digital signature.

[0003] The present invention also relates to a general method for controlling a backscattered signal comprising the steps of the method for processing a backscattered signal and the method for generating a digital signature, as well as a communication system comprising the receiving device, the transmitting device and the controlling device.

[0004] The invention finds a particularly advantageous, although in no way limiting, application for applications of the “Internet of Things” (IoT) type, in particular in the context of so-called “device-to-device communications” (D2D communications). Prior art

[0005] Ambient backscatter communication technology is now well known. The technical principles underlying this technology are described, among others, in the document: “Ambient Backscatter Communications: A Contemporary Survey”, N. Van Huynh, D. Thai Hoang, X. Lu, D. Niyato, P. Wang, D. In Kim, IEEE Communications Surveys & Tutorials, vol. 20, no. 4, pp. 2889-2922, Fourth Quarter 2018.

[0006] Conventionally, backscattering of an ambient signal occurs between a transmitting device and a receiving device. The ambient signal in question corresponds to a radio signal emitted, permanently or recurrently, in a given frequency band by a source distinct from said transmitting and receiving devices. For example, it may be a television signal, a mobile telephone signal (3G, 4G, 5G, B5G (acronym for "Beyond 5G")), a Wi-Fi signal, a WiMax signal, etc.

[0007] To communicate with the receiving device, the transmitting device uses the ambient signal to send data to said receiving device. More specifically, the transmitting device reflects the ambient signal towards the receiving device by modulating it, by selectively connecting an antenna which equips it with distinct impedances. The signal thus reflected is called a "backscattered signal", and is intended to be decoded by the receiving device (i.e. the receiving device extracts from the backscattered signal information transmitted by the transmitting device, for example in the form of bits).

[0008] The fact that no additional radio waves (in the sense of a wave other than that from the ambient signal) are emitted by the transmitting device makes ambient backscattering technology particularly attractive. Indeed, the energy cost of communication is thus reduced, which is particularly important in the current context of the IoT where every object in everyday life is intended to become a communicating object. In particular, such communication finds an application today in D2D type communications in which it is a question of implementing, in addition to traditional modes of communication (upstream / downstream mode in which a terminal / base station transmits data to a base station / terminal), another mode, called "backscattering mode", in which two terminals communicate with each other by ambient backscattering.The addition of this backscattering mode advantageously allows the network used for traditional modes to be unloaded, and therefore frequency resources to be saved.

[0009] The fact remains that conventional use of ambient backscatter communication technology is carried out without any verification of the identity or authenticity of the transmitting device. This security in the transmission of signals proves to be all the more complex when the transmitting device is not equipped with data processing means, such as cryptographic means. Disclosure of the invention

[0010] 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 identify a transmitting device, and to ensure that the identified transmitting device has been validly declared to the telecommunications operator.

[0011] To this end, and according to a first aspect, the invention relates to a method for processing a radio signal emitted by a transmitting device and backscattered by a transmitting device, the method comprising the following steps, implemented by a receiving device following reception of the backscattered signal:

[0012] – obtaining, from the backscattered signal, an identification data item for the transmitting device and a digital signature of a data item relating to the identification data item, said signature being associated with a management entity of the transmitting device; and,

[0013] – processing of the backscattered signal based on the identification data of the transmitting device if the signature is valid.

[0014] As discussed in more detail below, the identification data of the transmitting device corresponds, for example, to an identifier of this transmitting device.

[0015] As is known, a digital signature is a cryptographic mechanism that guarantees the authenticity and integrity of electronic data, as well as the identity of the signatory. In the context of the invention, the digital signature is associated with a management entity of the issuing device, and therefore guarantees the identity of this management entity. The data signed electronic data includes, for example, the identifier of the transmitting device, or a result of applying a function to the identifier of the transmitting device.

[0016] Generally speaking, it is considered that the steps of a process should not be interpreted as being linked to a notion of temporal succession.

[0017] In particular embodiments, the treatment method may further comprise one or more of the following characteristics, taken individually or in all technically possible combinations.

[0018] In particular embodiments, the processing method further comprises a step of verifying the validity of the signature, implemented by the receiving device.

[0019] In particular embodiments, the obtaining step further comprises obtaining at least one characterization data item of the transmitting device different from the identification data item, and the method further comprises a verification, by the receiving device and from the at least one characterization data item, whether the transmitting device is a valid device.

[0020] The use of characterization data makes it possible to ensure the authenticity of the transmitting device, and a fortiori to ensure that the transmitting device has not been duplicated without the telecommunications operator being notified.

[0021] In particular embodiments, the at least one characterization data item comprises data representative of a use of the transmitting device, and the verification that the transmitting device is a valid device comprises a verification that the use of the transmitting device corresponds to a desired use.

[0022] The data representing a usage makes it possible to protect against duplication of a transmitting device without the telecommunications operator being notified, for a use of the duplicated transmitting device different from that of the initial transmitting device.

[0023] This data also allows the receiving device to filter the backscattered signals received, in order to process only those whose use corresponds to the desired use.

[0024] In particular embodiments, the at least one characterization data item comprises data representative of a location of the transmitting device, and the verification that the transmitting device is a valid device comprises a verification that the transmitting and receiving devices have compatible locations.

[0025] For the purposes of the invention, it is considered that the transmitter and receiver devices have compatible locations when they have the same location or when the respective locations of the transmitter and receiver devices are adapted to the range of the backscattered signal. Thus, the locations of the transmitter and receiver devices are compatible when these two devices are, for example, located in the same area (e.g., in the same portion of space), or at a distance less than a threshold value from this area (e.g., 1 kilometer).

[0026] The data representing a location makes it possible to protect against duplication of a transmitting device without the telecommunications operator being notified for use of the duplicated transmitting device in a location different from that in which the initial transmitting device is installed.

[0027] In particular modes of implementation, the digital signature is generated by encryption of a first fingerprint using a private encryption key associated with said management entity, the first fingerprint being generated as a function of the identification data, and the processing method further comprises a verification of the validity of said signature including the following steps, implemented by the receiving device:

[0028] – decryption of the signature obtained using a public key associated with said private key, so as to obtain the first fingerprint;

[0029] – generation of a second fingerprint based on the identification data obtained from the backscattered signal; and,

[0030] – a comparison of the first and second fingerprints, said signature being valid if the first and second fingerprints are identical.

[0031] As is well known, a fingerprint (sometimes called a "digital fingerprint") refers to a piece of digital data smaller than the data it identifies. It typically results from the application of a hash function. In a way known in itself, a hash function transforms data of arbitrary size into data of fixed size, called a "digest". A cryptographic hash function must also have the property of being non-reversible, resistant to falsification – and the slightest modification of the message must then result in a different digest – and resistant to collisions – and two different messages must then not result in the same digest. The "Secure Hash Algorithm" functions SHA-1, SHA-2 or MD5 (Message Digest 5) are examples of cryptographic hash functions.

[0032] In particular embodiments, the first fingerprint is further generated as a function of the at least one characterization data item, and the method further comprises obtaining the at least one characterization data item from the backscattered signal, and the second fingerprint is further generated as a function of the at least one characterization data item obtained.

[0033] In particular embodiments, the first and second fingerprints are generated by applying a cryptographic hash function to a concatenation of the identification data and the at least one characterization data.

[0034] In particular modes of implementation, the management entity of the transmitting device corresponds to a telecommunications operator responsible for managing the transmitting device or to a certification authority affiliated with said telecommunications operator.

[0035] In particular embodiments, the obtaining step further comprises obtaining a time validity range associated with the transmitting device.

[0036] The time validity range helps to protect against the reuse of a valid identifier on a new transmitting device, for example after the initial transmitting device has been destroyed. This feature is particularly advantageous when biodegradable transmitting devices are deployed.

[0037] According to a second aspect, the invention relates to a method for generating a digital signature associated with a transmitting device configured to backscattering a radio signal emitted by a transmitting device, the method comprising the following steps, implemented by a control device of a management entity of the transmitting device:

[0038] – a reception, from a management device of a manager of said transmitting device, of data identifying the transmitting device; and,

[0039] – generation of a digital signature from a fingerprint generated based on the identification data.

[0040] The control device corresponds, for example, to a remote server administered by a telecommunications operator, this operator also operating, for example, the previously mentioned transmitting device. The transmitting device is, for its part, administered by a transmitting device manager typically ensuring the management of a group of transmitting devices.

[0041] In particular embodiments, the reception further comprises a reception of at least one characterization data item of the transmitting device different from the identification data item, and the digital signature is further generated based on the at least one characterization data item.

[0042] According to a third aspect, the invention relates to a receiving device configured to implement the processing method previously mentioned.

[0043] According to a fourth aspect, the invention relates to a control device configured to implement the method for generating a digital signature previously mentioned.

[0044] According to a fifth aspect, the invention relates to a communication system comprising a transmitting device configured to transmit a radio signal, a transmitting device configured to backscatter the radio signal, the receiving device according to the third aspect and the control device according to the fourth aspect.

[0045] According to a sixth aspect, the invention relates to a computer program comprising instructions for implementing the method of processing a backscattered radio signal, when said program is executed by a processor.

[0046] According to a seventh aspect, the invention relates to a computer-readable recording medium on which the computer program according to the sixth aspect is recorded.

[0047] According to an eighth aspect, the invention relates to a computer program comprising instructions for implementing the method for generating a digital signature, when said program is executed by a processor.

[0048] According to a ninth aspect, the invention relates to a computer-readable recording medium on which the computer program according to the eighth aspect is recorded. Brief description of the drawings

[0049] 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 character. In the figures:

[0050] [Fig.1A] Figure 1A is a first example of a communication system in which a general method for controlling a backscattered signal is implemented;

[0051] [Fig.1B] Figure 1B is a second example of a communication system in which a general method of controlling a backscattered signal is implemented;

[0052] [Fig.1C] Figure 1C is a third example of a communication system in which a general method of controlling a backscattered signal is implemented;

[0053] [Fig.2A] Figure 2A represents modules embedded in a receiving device, according to an exemplary implementation of the invention;

[0054] [Fig.2B] Figure 2B represents modules embedded in a control device, according to an exemplary implementation of the invention;

[0055] [Fig.3A] Figure 3A represents an example of hardware architecture of a receiving device;

[0056] [Fig.3B] Figure 3B represents an example of hardware architecture of a control device;

[0057] [Fig.4] Figure 4 illustrates, in the form of a flowchart, the main steps of a general method for controlling a backscattered signal, according to an exemplary implementation of the invention. Description of the embodiments

[0058] Figure 1A is a first example of a communication system in which a general method of controlling an ambient signal emitted by a transmitting device (DSo) and backscattered by a transmitting device (DTx) is implemented.

[0059] As illustrated in Figure 1A, the communication system comprises a transmitting device, also called a "source" DSo, configured to transmit, according to a transmission frequency included in a given frequency band called the "transmission band", a radio signal called the "ambient signal". This signal is "ambient" from the point of view of the transmitting device (DTx), but as mentioned below, no limitation is attached to the signal considered in the context of the present invention, which can correspond to any radio signal transmitted by an electronic device. The transmission of the ambient signal is carried out, for example, permanently or recurrently.

[0060] For the remainder of the description, and as illustrated by Figure 1A, the case where the ambient signal is emitted by only a single source is considered in a non-limiting manner. The choice of considering a single source is made here for the purpose of simplifying the description only. Also, no limitation is attached to the number of sources that can be considered within the scope of the present invention, the following developments being in fact generalizable without difficulty by those skilled in the art in the case of a plurality of sources.

[0061] By "radio signal" we mean an electromagnetic wave propagating by non-wireless means, whose frequencies are included in the traditional spectrum of radio waves (from a few hertz to several hundred gigahertz).

[0062] As a non-limiting example, the ambient signal is a 4G mobile telephone signal emitted in the transmission band [811 MHz, 821 MHz] by the DSo source.

[0063] It should however be specified that the invention remains applicable to other types of radio signals, such as for example a mobile telephone signal other than 4G (for example 2G, 3G, 5G, B5G), a Wi-Fi signal, a WiMax signal, a DVB-T signal ("Digital Video Broadcasting – Terrestrial"), etc. In general, no limitation is attached to the ambient radio signal which can be considered within the scope of the present invention, since the latter can be used to communicate by ambient backscattering.

[0064] The communication system also comprises a transmitter device DTx and a receiver device DRx respectively configured to communicate with each other by ambient backscattering from the ambient signal emitted by the source device DSo. It should be noted that, in accordance with the invention, the source device DSo, the transmitter device DTx and the receiver device DRx are distinct from each other.

[0065] Generally speaking, no limitation is attached to the structural forms that can be taken respectively by the source device DSo and the receiver device DRx. As non-limiting examples, the following configurations are conceivable depending on the working frequency band considered:

[0066] – the source device DSo is a cell phone, for example a smartphone, and the receiver device DRx is a base station,

[0067] – the source device DSo and the receiver device DRx are both cell phones, for example smartphones,

[0068] – the source device DSo is a home gateway (also called an “Internet box”) emitting a Wi-Fi signal, and the receiver device DRx is a cell phone, for example a smartphone, etc.

[0069] In the remainder of the description, and as illustrated by FIG. 1A, it is considered in a non-limiting manner that the communication system comprises a single transmitter device DTx and a single receiver device DRx. It should however be specified that the invention is also applicable to a communication system comprising a plurality of transmitter devices and / or a plurality of receiver devices, the developments necessary for such a generalization being able to be implemented without difficulty by the person skilled in the art.

[0070] In a manner known per se, communication by ambient backscattering consists of the exploitation of the ambient signal, by the transmitter device DTx, to send information data to the receiver device DRx, such as for example identification data specific to said transmitter device DTx.

[0071] In the present embodiment, the DTx transmitter device is equipped with an antenna (not shown in FIG. 1) configured, in a manner known per se, to receive the ambient signal, but also to backscatter it towards the DRx receiver device. It should however be noted that the invention remains applicable in the case where the DTx transmitter device comprises a plurality of antennas (sometimes also called "antenna elements").

[0072] In a particular implementation, the DTx transmitter device is a reconfigurable intelligent surface (RIS) whose electrical and magnetic properties can be modified to control the reflection of electromagnetic waves. The specificities of reconfigurable intelligent surfaces are for example described in the articles “Reconfigurable Intelligent Surface-Aided Wireless Communications: Adaptive Beamforming and Experimental Validations”, MM Amri & Al., IEEE Access, vol. 9, pp. 147442-147457, 2021; and, “Reconfigurable Intelligent Surfaces: A signal processing perspective with wireless applications”, E. Björnson & Al., in IEEE Signal Processing Magazine, vol.39, no.2, pp.135-158, March 2022.

[0073] The wave paths carried by the signals considered in the present invention are represented by dotted arrows in this figure 1A. More particularly:

[0074] – a first path refers to a wave coming from the source device DSo and arriving directly (i.e. without being backscattered by the transmitter device DTx) to the receiver device DRx;

[0075] – a second path refers to a wave coming from the source device DSo and whose backscattering by the transmitter device DTx reaches the receiver device DRx.

[0076] The transmission of the backscattered signal by the DTx transmitter device is carried out by variation of the backscattering of the ambient signal, this variation being based on the possibility that the DTx transmitter device has of modifying the impedance presented to the antenna which equips it, depending on the information data to be transmitted.

[0077] An information datum intended to be transmitted by the transmitting device DTx, by means of the backscattered signal, is conventionally encoded by means of a set of symbols, comprising for example a so-called "high" symbol (bit of value "1"), or a so-called "low" symbol (bit of value "0"). The transmission of such an information datum can therefore be carried out by alternating between said backscattering and non-backscattering states, each of said states being dedicated to the transmission of a symbol of a particular type (for example high symbol for the backscattering state and low symbol for the non-backscattering state, or vice versa). In other words, an information datum is transmitted to the receiving device DRx by modulation of the waves of the ambient signal (i.e. by "backmodulation").

[0078] It is important to note that the invention is not limited to this ideal case in which only two states, respectively perfectly backscattering and perfectly non-backscattering, would be considered. Indeed, the invention also remains applicable in the case where the first and second states are not perfectly backscattering / non-backscattering, since the variation of the backscattered waves is perceptible by the DRx receiver device.

[0079] Figure 1B is a second example of a communication system in which a general method of controlling a backscattered signal is implemented.

[0080] As illustrated in Figure 1B, the source device DSo takes the form of a base station, and the receiver device DRx that of a cell phone. This example considers the case of downlink radio links. More precisely, the base station emits a wave that reaches the cell phone directly; and emits a wave that is backscattered by the transmitter device DTx before reaching the cell phone.

[0081] Figure 1C is a third example of a communication system in which a general method of controlling a backscattered signal is implemented.

[0082] As illustrated in Figure 1C, the source device DSo takes the form of a cell phone, and the receiver device DRx that of a base station. This example considers the case of uplink radio links. More precisely, the cell phone emits a wave that reaches the base station directly; and emits a wave that is backscattered by the transmitter device DTx before reaching the base station.

[0083] Figure 2A schematically represents modules embedded in a DRx receiver device, such as the DRx receiver device of Figures 1A to 1C, according to an exemplary implementation of the invention.

[0084] As illustrated in Figure 2A, the DRx receiver device comprises a MOD_OB module for obtaining identification data and a digital signature and a MOD_PROC processing module whose functionalities are described with reference to Figure 3A.

[0085] Figure 3A represents an example of hardware architecture of a DRx receiver device. As illustrated by Figure 3A, the DRx receiver device has the hardware architecture of a computer. Thus, the DRx receiver device comprises, in particular, a processor 1, a random access memory 2, a read-only memory 3 and a non-volatile memory 4. It further comprises a communication module 5.

[0086] The read-only memory 3 or the non-volatile memory 4 of the DRx receiver device constitutes a recording medium as proposed, readable by the processor 1 and on which is recorded a computer program PROG_Rx executed by the DRx receiver device, comprising instructions for the execution of steps of the signal processing method as proposed below. The PROG_Rx program defines one or more functional modules of the DRx receiver device, which rely on or control the hardware elements 1 to 5 cited above, and which include in particular:

[0087] – a MOD_OB module for obtaining, from the backscattered signal, identification data for the transmitting device and a digital signature of data relating to the identification data, said signature being associated with a management entity of the transmitting device; and,

[0088] – a MOD_PROC module for processing the backscattered signal based on the identification data of the transmitting device, this MOD_PROC module being called if the signature is valid.

[0089] Furthermore, the DRx receiver device may also comprise other modules, in particular for implementing particular modes of the method for processing a backscattered signal, as described in more detail later.

[0090] Figure 2B schematically represents modules embedded in a DCTRL control device of a management entity of the transmitting device, according to an exemplary implementation of the invention.

[0091] As illustrated in Figure 2B, the DCTRL control device comprises a MOD_RX reception module and a MOD_GEN module for generating a digital signature, the functionalities of which are described with reference to Figure 3B.

[0092] Figure 3B represents an example of hardware architecture of a DCTRL control device. As illustrated by Figure 3B, the DCTRL control device has the hardware architecture of a computer. Thus, the DCTRL control device comprises, in particular, a processor 1, a random access memory 2, a read-only memory 3 and a non-volatile memory 4. It further comprises a communication module 5.

[0093] The read-only memory 3 or the non-volatile memory 4 of the DCTRL control device constitutes a recording medium as proposed, readable by the processor 1 and on which is recorded a computer program PROG_CTRL executed by the DCTRL control device, comprising instructions for the execution of steps of the method for generating a digital signature as proposed below. The program PROG_CTRL defines one or more functional modules of the control device DCTRL control, which rely on or control the hardware elements 1 to 5 cited above, and which include in particular:

[0094] – a MOD_RX module for receiving, from a management device of a manager of said transmitting device, data identifying the transmitting device; and,

[0095] – a MOD_GEN module for generating a digital signature from a fingerprint generated based on the identification data.

[0096] Furthermore, the DCTRL control device may also include other modules, in particular to implement particular modes of the method for generating a digital signature, as described in more detail later.

[0097] Figure 4 illustrates, in flowchart form, the main steps of a general method for controlling a backscattered signal, according to an exemplary implementation of the invention.

[0098] As illustrated in Figure 4, the general method for controlling a backscattered signal comprises a first step S300 of transmitting, to a control device DCTRL, a request to obtain a signature for a certain transmitting device. This step S300 is implemented by an electronic device DP under the control of the transmitting device manager. The request comprises an ID_DTx data item identifying the transmitting device DTx for which the signature is desired, an ID_AREA data item representing a location of this transmitting device DTx, and an ID_USE data item representing a use envisaged for this transmitting device DTx. This request is received by the MOD_RX module of the control device DCTRL during a step S400.

[0099] In the remainder of the description, it is considered in a non-limiting manner that the request for obtaining relates only to a single DTx transmitter device. However, it should be specified that the invention is also applicable in the case where the request for obtaining relates to a plurality of DTx transmitter devices, the developments necessary for such an adaptation being able to be implemented without difficulty by the person skilled in the art.

[0100] The ID_AREA data representing a location of this DTx transmitter device typically corresponds to an area identifier in which the DTx transmitter device must be deployed. This is for example a location area identifier ("Location Area Identity" in English terminology) for example defined in section 4.1 of the 3GPP TS 23.003 version 18.3.0 specification, published in September 2023; the tracking area identifier ("Tracking Area Identity" in English terminology) for example defined in section 19.4.2.3 of the 3GPP TS 23.003 specification, "Numbering, addressing and identification", version 18.3.0, published in September 2023 – the notion of "tracking area" being described in particular in the article "Tracking Area Update and Paging in 5G Networks: a Survey of Problems and Solutions", Alsaeedy, AAR, Chong, EKP, Mobile Netw Appl 24, pages 578–595, published in October 2018 –; a department number; a postal code, etc.

[0101] The ID_USE data representing a use can take different values ​​predetermined by the telecommunications operator, for example "1" for use in terms of location management, "2" for use in terms of logistics monitoring, etc.

[0102] Then, during a step S410, the MOD_GEN module of the DCTRL control device generates an STO signature based on the identification data ID_DTx, the ID_AREA data representing a location and the ID_USE data representing a use. According to a particular implementation, the control device generates a fingerprint of the concatenation of these three data, by applying a cryptographic hash function ^^^^^^ℎ . For the record, a hash function transforms data of any size into data of fixed size. A cryptographic hash function must also have the property of being non-reversible, resistant to falsification and collisions. The STO signature is then generated by applying an encryption of the fingerprint with a private encryption key ^^ ^^^^^^^^ of the telecommunications operator.

[0103] The method further comprises a step S420 during which the control device DCTRL transmits this STO signature to the electronic device DP under the control of the transmitting device manager, and which is received by this electronic device DP during a step S310.

[0104] Then, during a step S320, the electronic device DP transmits this signature STO to the transmitter device DTx, and which is received by this transmitter device DTx during a step S100. Alternatively, the transmission step S320 is not implemented, and the signature is then stored in memory 3 of the transmitter device DTx during its manufacture.

[0105] The general method for controlling a backscattered signal further comprises a step S110, implemented by the transmitter device DTx for backscattering an ambient signal emitted by a source device DSo. More specifically, as explained in the article "Ambient Backscatter Communications: A Contemporary Survey", N. Van Huynh, D. Thai Hoang, X. Lu, D. Niyato, P. Wang, D. In Kim, IEEE Communications Surveys & Tutorials, vol.20, no.4, pp.2889-2922, Fourthquarter 2018", the transmitter device DTx backscatters the ambient signal in a time-modulated manner to transmit its message. In the most basic implementation example (reported in the same reference), the DTx transmitter device communicates by means of two strands of a dipole antenna connected to a radio-frequency switch and a microcontroller controlling the switch and having in memory the binary sequence to be transmitted.During a symbol period, to transmit a binary symbol '0', the switch disconnects the two strands so that the antenna is almost transparent to ambient signals, and backscatters a low or no amount of signal. To transmit a binary symbol '1', the switch connects the two strands of the antenna so that the antenna reradiates the incident ambient signal, i.e., backscatters a higher amount of signal. The SIG_So signal emitted by the source device DSo propagates to the receiver device DRx via several propagation paths, including a path reflected by DTx. The SIG signal received by the receiver device DRx is the sum of the signals received via all these paths, including the path reflected by DTx.The SIG signal is therefore over-modulated in time by DTx and carries the ID_DTx data identifying the DTx transmitting device, the ID_AREA data representing a location, the ID_USE data representing a use and the STO signature.

[0106] This backscattered SIG signal is received by the DRx receiver device during a step S200. Then, during a step S205, the MOD_OB module of the DRx receiver device extracted from the received signal, the ID_DTx identification data of the transmitting device, the ID_AREA data, the ID_USE data and the STO signature.

[0107] The validity of the STO signature extracted in step S205 is verified by the receiving device DRx in a step S210. More precisely, the receiving device DRx decrypts the signature obtained in step S205 using the public key ^^ ^^^^^^of the telecommunications operator, so as to obtain a digital fingerprint, called the first fingerprint. Then it generates a digital fingerprint, called the second fingerprint, by applying the cryptographic hash function ^^^^^^ℎ to the data ID_DTx, ID_AREA, and ID_USE obtained in step S205 from the backscattered SIG signal. According to a particular implementation, the receiving device DRx generates a fingerprint of the concatenation of these three data, by applying the cryptographic hash function ^^^^^^ℎ to this concatenation. Finally, the receiving device DRx compares the first and second fingerprints, and determines that the STO signature is valid if the first and second fingerprints are identical.

[0108] If the signature is invalid (choice "N"), the receiver device DRx implements a step S240 during which it ignores the backscattered signal SIG. According to a particular implementation, the receiver device DRx also transmits, to the control device DCTRL, an indication that a SIG signal has been detected from a transmitter device having the identifier ID_DTx and including an invalid STO signature.

[0109] If, on the other hand, the signature is valid (choice "Y"), the DRx receiver device implements a step S220 to verify that the use of the DTx transmitter device corresponds to a use desired or expected by this DRx receiver device.

[0110] If the transmitting device DTx backscatters a signal whose use does not correspond to that expected by the receiving device DRx (choice "N"), the receiving device DRx implements step S240 during which it ignores the backscattered signal SIG.

[0111] If, on the other hand, the transmitter device DTx backscatters a signal whose use corresponds to that expected by the receiver device DRx (choice "Y"), the receiver device DRx implements a step S230 during which it verifies that the transmitter device DTx and itself have compatible locations. For this, the receiving device DRx compares a location of the transmitting device DTx determined from the ID_AREA data representative of a location obtained in step S205, and its own location.

[0112] If the DRx receiver device is for example inside the area identified by ID_AREA, or at a distance less than a predetermined threshold value (for example 1 kilometer) from the area, identified by ID_AREA, it is then considered that the DTx transmitter and DRx receiver devices have compatible locations, and the device then implements a step S250 (choice "Y").

[0113] If, on the other hand, the transmitter DTx and receiver DRx devices do not have compatible locations, the receiver DRx device then implements step S240 during which it ignores the backscattered signal SIG. According to a particular implementation, the receiver DRx device also transmits, to the control device DCTRL, an indication that a SIG signal has been detected coming from a transmitter device having the identifier ID_DTx and not having the location initially declared by the manager during its enrollment.

[0114] According to a particular implementation, a time validity range associated with said DTx transmitter device is also obtained during step S205, and the general control method then comprises a step (not shown) of verifying the validity of the backscattered signal as a function of this validity range.

[0115] Finally, the general method for controlling a backscattered signal therefore comprises step S250 during which a processing of the backscattered signal is implemented which takes into account the identification data ID_DTx obtained in step S205.

[0116] Different processing operations may be envisaged within the framework of this invention, such as the indoor positioning of the DRx receiver device. In this case, according to a first exemplary implementation, the DRx receiver device consults a spatial representation of the structure (building, house, etc.) in which it is located and including for example different ID_DTx identifiers of DTx transmitter devices, and determines, from the ID_DTx identifier obtained in step S205, its own position.

[0117] According to a second example of implementation, the DRx receiver device transmits, to a remote server, one or more ID_DTx identifiers of transmitting devices having backscattered signals detected by this same DRx receiver device, which in return provides it with its own location. The server determines the location of the DRx receiver device by comparing the received ID_DTx identifier(s) with a pre-recorded list of mapped ID_DTx identifiers (i.e., those which have known geographical positions and are stored in memory).

[0118] Object or person tracking can also be implemented as part of the processing of this backscattered GIS signal. In this case, the DTx transmitter device is, for example, fixed to the object to be tracked. Each time it passes close (e.g., a few meters) to a smartphone (also called a "multifunction mobile") connected to the network and geolocated, it is detected and the location of the smartphone is associated with it. In an example implementation illustrated in Figure 1C, the smartphone corresponds to the DSo source device and the DRx receiver device corresponds to a base station. In another example implementation illustrated in Figure 1B, the DSo source device corresponds to a base station and the DRx receiver device to a smartphone.The DRx receiver device then transmits, during step S250, to a remote server, one or more identifiers ID_DTx of transmitter devices having backscattered signals detected by this same DRx receiver device, as well as location information for the DRx receiver device. The server then records in an object tracking database the fact that the object(s) associated with the DTx transmitter device have been detected near the provided location.

[0119] The invention has been described so far in the case where the identification data ID_DTx, the data ID_AREA and the data ID_USE are considered, but the invention nevertheless remains applicable in the particular case where only the identification data ID_DTx is considered for the generation of the digital signature by the control device and for determining whether the processing of the backscattered signal must be carried out by the receiving device (DRx). The invention nevertheless also remains applicable in the case where the identification data ID_DTx and one of the two data ID_AREA and ID_USE are considered for the generation and determination indicated above.

Claims

Claims

1. Method for processing a radio signal emitted by a transmitter device (DSo) and backscattered by a transmitter device (DTx), the method comprising the following steps, implemented by a receiver device (DRx) following reception (S200) of the backscattered signal: − obtaining (S205), from the backscattered signal, an identification data item (ID_DTx) of the transmitter device and a digital signature (STO) of a data item relating to the identification data item (ID_DTx), said signature being associated with a management entity of the transmitter device (DSo); and, − processing (S250) of the backscattered signal as a function of the identification data item (ID_DTx) of the transmitter device if the signature is valid.

2. Processing method according to claim 1, wherein the obtaining step (S205) further comprises obtaining at least one characterization data (ID_AREA, ID_USE) of the transmitting device (DTx) different from the identification data (ID_DTx), and the method further comprises a verification (S210, S220), by the receiving device (DRx) and from the at least one characterization data (ID_AREA, ID_USE), whether the transmitting device (DTx) is a valid device.

3. Processing method according to claim 2, wherein the at least one characterization data comprises a data (ID_USE) representative of a use of the transmitting device (DTx), and the verification that the transmitting device (DTx) is a valid device comprises a verification (S220) that the use of the transmitting device (DTx) corresponds to a desired use.

4. Processing method according to claim 2 or 3, wherein the at least one characterization data item comprises a data item. (ID_AREA) representative of a location of the transmitting device (DTx), and verifying that the transmitting device (DTx) is a valid device includes verifying (S230) that the transmitting (DTx) and receiving (DRx) devices have compatible locations.

5. Processing method according to one of claims 1 to 4, wherein the digital signature is generated by encrypting a first fingerprint using a private encryption key associated with said management entity, the first fingerprint being generated as a function of the identification data (ID_DTx), and the method further comprises a verification (S230) of the validity of said signature (STO) including the following steps, implemented by the receiving device (DRx): − a decryption of the signature (STO) obtained using a public key associated with said private key, so as to obtain the first fingerprint; − a generation of a second fingerprint as a function of the identification data (ID_DTx) obtained from the backscattered signal; and, − a comparison of the first and second fingerprints, said signature being valid if the first and second fingerprints are identical.

6. Processing method according to claim 5 in combination with claim 2, the first fingerprint being further generated as a function of the at least one characterization data (ID_AREA, ID_USE), the method further comprising obtaining the at least one characterization data (ID_AREA, ID_USE) from the backscattered signal, and the second fingerprint is further generated as a function of the at least one characterization data (ID_AREA, ID_USE) obtained.

7. Processing method according to claim 6, wherein the first and second fingerprints are generated by applying a cryptographic hash function to a concatenation of the identification data (ID_DTx) and the at least one characterization data (ID_AREA, ID_USE).

8. Processing method according to one of claims 1 to 7, in which the management entity of the transmitting device (DSo) corresponds to a telecommunications operator in charge of managing the transmitting device (DSo) or to a certification authority affiliated with said telecommunications operator.

9. Processing method according to one of claims 1 to 8, in which the obtaining step (S205) further comprises obtaining a time validity range associated with said transmitting device (DTx).

10. Method for generating a digital signature (STO) associated with a transmitter device (DTx) configured to backscatter a radio signal emitted by a transmitter device (DSo), the method comprising the following steps, implemented by a control device (DCTRL) of a management entity of the transmitter device (DSo): − a reception (S400), from a management device (DP) of a manager of said transmitter device (DTX), of an identification data item (ID_DTX) of the transmitter device; and, − a generation (S410) of a digital signature (STO) from a fingerprint generated as a function of the identification data item (ID_DTX).

11. Method for generating a digital signature according to claim 10, the reception (S400) further comprising a reception of at least one characterization data (ID_AREA, ID_USE) of the transmitter device (DTx) different from the identification data (ID_DTx), and the digital signature (STO) being further generated as a function of the at least one characterization data (ID_AREA, ID_USE).

12. Receiving device (DRx) configured to implement the processing method according to one of claims 1 to 9.

13. Control device (DCTRL) configured to implement the method for generating a digital signature (STO) according to claim 10 or 11.

14. Communication system comprising a transmitter device (DSo) configured to transmit a radio signal, a transmitter device (DTx) configured to backscatter said radio signal, the receiver device (DRx) according to claim 12 and the control device (DCTRL) according to claim 13.

Images