FR3053558A1 - METHOD FOR LOCATING AT LEAST ONE SECOND MOBILE TERMINAL AFTER AN EVENT RELATING TO A FIRST MOBILE TERMINAL LOCATED IN A SECOND TERMINAL ENVIRONMENT - Google Patents

Abstract

Method for locating at least one second mobile terminal following an event relating to a first mobile terminal located in an environment of the second terminal. This method comprises: - an interaction (E12) between the first terminal and a communication device located near the first terminal, the communication device being associated with a reference location information called "reference location"; following this interaction, an exchange (E14, E16) of acoustic signals between the first terminal and the second terminal; - determining (E18, E28, E30), from the exchange of signals, relative distance information known as "relative distance" of the second terminal relative to the first terminal; updating (E35) a previously obtained location of the second terminal, based on the reference location and the relative distance.

Description

Technical area

The invention relates generally to the geographic location of a mobile communication terminal, and more particularly to a method of locating a second mobile terminal following an event relating to a first mobile terminal located in an environment of the second terminal.

State of the art

Currently in the field of mobile telephony, communication terminals of the smartphone or smart phone type are very widespread, such as the iPhone ™ marketed by the company Apple. A smartphone can be defined as an advanced mobile phone with the functions of a personal digital assistant, a digital camera and a laptop. Data entry is most often done using a touch screen or, more rarely, a keyboard or stylus. According to the principle of a computer, it can execute various software / applications thanks to an operating system specially designed for mobiles, and therefore in particular provide functionalities in addition to those of conventional mobile phones such as: the agenda, television , calendar, web browsing, viewing and sending email, geolocation, dictaphone / tape recorder, calculator, compass, accelerometer, gyroscope, visual voicemail, digital mapping, etc.

With regard more particularly to the geolocation of a mobile terminal, various techniques exist for geographically locating a mobile terminal. Some solutions consist in using a geolocation module of the GPS type equipping the mobile terminal, but these solutions see their effectiveness reduced, even inoperative, in indoor environments ¹ ′ or constrained. Other solutions combine a location of the terminal obtained from wireless exchanges with a spatial reference system, for example a WiFi terminal, with the use of inertial sensors fitted to the terminal to evaluate movements of the terminal relative to the aforementioned spatial reference system ; however, the localization results obtained by this type of solution remain imprecise.

The invention aims in particular to improve the situation described above.

Statement of the invention

Thus, according to a first aspect, the invention relates to a method of locating at least a second mobile terminal following an event relating to a first mobile terminal located in an environment of the second terminal. According to the invention, such a method comprises:

an interaction between the first terminal and a communication device located near the first terminal, the communication device being associated with reference location information called reference location;

- Following this interaction, an exchange of acoustic signals between the first terminal and the second terminal;

- determining, from the exchange of signals, relative distance information called relative distance of the second terminal with respect to the first terminal;

- updating a location previously obtained from the second terminal, from the reference location and the relative distance.

Thanks to the aforementioned method, a simple exchange of acoustic signals between several mobile terminals in a determined area, following an interaction of one of the terminals with a device such as for example an NFC terminal or a device associated with a QR code, allows obtain a more precise location of the other terminals by taking advantage of the existence of a reference location consisting of a reliable location known beforehand to the communication device.

In the context of the present description, the term "communication device" means any mobile or fixed device capable of storing information such as electronic tags (tag in English), for example NFC, or tags of the QR code type, and of communicate with entities on a communication network; these can be, for example, terminals providing specific information or electronic portals for accessing places with controlled access. An interaction between a communication terminal and such a communication device within the meaning of the invention can be an exchange of data between the terminal and the device or simply a reading by the terminal of information on a passive medium associated with the device. (e.g. a QR code). Furthermore, according to the invention, an interaction between a terminal and such a communication device is a short-distance interaction (proximity interaction), typically within about fifty centimeters.

The invention can advantageously be implemented in closed spaces where communication by GPS is difficult or even impossible, such as parking lots or buildings.

According to a particular embodiment of the method according to the invention, the aforementioned exchange of signals between the first terminal and the second terminal, comprises the emission by the first terminal of a first acoustic signal in the environment; and, following the reception of the first signal by the second mobile terminal, the emission by the second mobile terminal of a second acoustic signal.

In this embodiment, the determination, from the exchange of signals, of the relative distance of the second terminal from the first terminal, comprises the estimation of the distance separating the first terminal from the second terminal from the speed propagation of the first and second signals in the environment, and at least the transmission time of the first signal between the first and the second terminal and the transmission time of the second signal between the second and the first terminal.

This embodiment has the advantage of simply using the propagation of acoustic signals in the air and the use of microphones and speakers fitted to the terminals to simply carry out the exchange of these signals. It is therefore an efficient and economical technical solution since it uses elements (microphone and speaker) already present in the communication terminals.

According to particular characteristics of implementation of this process:

- The estimation of the distance separating the first terminal from the second terminal uses a technique based on a metric measurement of ETOA type (elapsed time between the two time-of-arrivals) applied to the first and second acoustic signals. This effective technique is clearly explained in the document noted BeepBeep in the context of this presentation and detailed below in the description, in conjunction with FIG. 3.

- The step of updating a geographic location of the second terminal from the reference location and the relative distance, includes obtaining by the second terminal the reference location; then determining a geographic circle centered on a first point corresponding to said reference location and radius corresponding to said relative distance; and the actual updating of the geographic location of the second terminal from the aforementioned geographic circle.

- Updating the geographic location of the second terminal includes determining a second point on the aforementioned geographic circle, this second point being the point closest to the geographic location, the geographic coordinates of this second point constituting a new geographic location of the second terminal.

According to other characteristics of embodiment of the invention:

- A geographic location, previously obtained, of the second terminal, is a location obtained beforehand by a geolocation module equipping the second terminal;

- the communication device located near the first terminal, is an NFC terminal type equipment or equipped with a QR code type code, associated with a precisely known geographic location.

According to a particular embodiment of the method of the invention, during the interaction between the first terminal and the communication device located near the first terminal, the following steps are implemented:

- transmission by the first terminal via a communication network of presence information from the first terminal to a location server;

- reception, in return, of the location server, of an acoustic signature characteristic of the communication device and defining the first acoustic signal.

The use of such an acoustic signature (or sound pattern) for the first signal unambiguously identifies the device with which the interaction with the first terminal occurred.

According to another exemplary embodiment, it is the acoustic signature linked to the first signal transmitted by the first terminal which enables the second terminal to identify the communication device, and to obtain the corresponding reference location.

According to a particular embodiment of the invention, the method comprises an operation of registering each communication terminal with the location server when the terminal is located in an area in which there is a communication device whose reference location is managed by the server; the recording operation comprising:

- the transmission to the server by the terminal of its last location;

- the transmission by the server to the terminal of the acoustic signature defining the first acoustic signal;

- the regular updating of a last location with the server by the terminal when the location of the terminal has changed beyond a predefined threshold.

According to a particular embodiment, the method according to the invention comprises:

- the calculation by the first terminal of a first delay representative of the time elapsed between the reception in the first terminal of the first signal and the second signal;

- the transmission by the first terminal of the first delay to at least one second terminal;

- the calculation by at least a second terminal of a second delay representative of the time elapsed between the reception in the second terminal of the first signal and the second signal;

- determining in the second terminal, from the first delay and the second delay, the relative distance of the second terminal from the first terminal;

- updating a location of the second terminal, previously obtained, from the reference location and the relative distance.

Taking into account the first and second delays mentioned above for the calculation of the relative distance between the first terminal and the second terminal, advantageously overcomes time differences between the respective clocks of each of the terminals for the calculation of the aforementioned delays. Consequently, this technique improves the accuracy of the relative distance thus obtained.

According to a particular embodiment of the invention, when several second terminals are located in the area covered by the location server, and following an interaction between the first terminal and a communication device located near the first terminal, the server localization sends each of the second terminals a specific delay to be observed before the emission of a second acoustic signal to the first terminal.

This characteristic makes it possible to avoid, in particular when second terminals are located substantially the same distance from the first terminal, that return signals (second signals) transmitted by these second terminals are received simultaneously by the first terminal, which would make their discrimination and their difficult processing by the first terminal.

According to a second aspect, the invention relates to a communication terminal (first terminal within the meaning of the method according to the invention) comprising:

- An interaction module with a communication device located near the terminal, the communication device being associated with reference location information called reference location;

an acoustic signal transmission / reception module adapted to transmit at least a first acoustic signal following this interaction, and to receive in response at least a second acoustic signal coming from at least one second communication terminal in the environment of which the communication terminal is located;

a module for calculating a first delay representative of the time elapsed between the reception in the terminal of the first signal and the second signal;

a module for transmitting the first delay to at least one second terminal in order to allow the second terminal to determine relative distance information known as the relative distance of the second terminal relative to the communication terminal.

According to a third aspect, the invention relates to a communication terminal (second terminal within the meaning of the method according to the invention), this terminal comprising:

an acoustic signal transmission / reception module adapted to transmit a second acoustic signal in response to the reception of a first acoustic signal from a first communication terminal, following an interaction between the first terminal and a device communication located near the first terminal, the communication device being associated with reference location information called reference location;

- a module for obtaining said reference location;

a module for calculating a second delay representative of the time elapsed between the reception in the second terminal of the first signal and the second signal;

- a reception module from the first terminal of a first delay representative of the time elapsed between the reception in the first terminal of the first signal and the second signal;

a module for determining, from the first and from the second delay, a relative distance information item known as the relative distance of the second terminal with respect to the first terminal;

a module for updating a location of the second terminal, previously obtained, from the reference location and the relative distance.

In practice, according to a particular implementation of the method, the reference location is transmitted by the server to each of the "second terminals" within the meaning of the invention.

According to a fourth aspect, the invention relates to a location server, for the implementation of a location method as briefly explained above, this server comprising a module for managing reference locations associated respectively with a set of devices communication systems located in a specific geographic area, the management module being configured to:

- transmit a reference location linked to a communication device of the above-mentioned assembly to at least one terminal located in the area, as well as an acoustic signature characteristic of the communication device and defining an acoustic signal to be exchanged between at least two terminals located in the area, following the interaction of a terminal with the communication device considered;

- regularly update the latest locations received from terminals registered in the server for the geographic area.

According to a fifth aspect, the invention relates to a system for locating at least one second mobile terminal following an event relating to a first mobile terminal located in an environment of the second terminal, the system comprising:

- at least one communication device associated with reference location information known as reference location, located in a determined geographical area;

- at least one location server as briefly explained above;

- At least a first communication terminal and at least a second communication terminal, as briefly explained above.

In practice, the means constituting the invention and in particular the functional modules briefly described above which are implemented by a communication terminal or a location server according to the invention, and which allow the implementation of a method for locating a terminal, according to the invention, are essentially implemented in software form, that is to say one or more computer programs stored in one or more memories, of RAM (Random Access Memory), ROM (Read) type. Only Memory) or magnetic type (hard drive for example), and executed by a processor incorporated in the terminal and / or the server considered, as the case may be.

Consequently, according to a last aspect, the present invention also relates to a computer program stored on an information medium for the implementation of all or part of the steps of a method of locating a communication terminal, according to the invention, when the program is executed by a processor of a computer system.

In particular, such a program can be incorporated into an operating system of a communication terminal according to the invention, or be a software module distinct from the operating system, installed in the terminal and accessible mainly by the operating system. , to implement the functionalities of the method according to the invention.

Such a computer program according to the invention can use various programming languages, and include programs in the form of source code, object code, or of intermediate code between source code and object code, such as in a partially compiled form, or in any other desirable form.

Finally, the invention also relates to an information recording medium readable by a computer, and comprising instructions of a computer program in accordance with the invention. Such a recording medium can be constituted by any entity or device capable of storing such a program. For example, the support may include a storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or also a removable recording means such as a USB key or a recording means. magnetic, such as a hard drive. On the other hand, a program or software module according to the invention can in particular be downloaded over a network of the Internet type.

The advantages provided by a location server, a communication terminal or a computer program, according to the invention, as briefly explained above, are identical to or contribute to those mentioned above in relation to the method of location of 'a communication terminal according to the invention, and will therefore not be recalled here.

Brief description of the figures

Other characteristics and advantages of the present invention will emerge from the detailed description which follows, which refers to the appended drawings in which:

- Figure 1 illustrates a network environment in which the present invention is implemented, according to one embodiment;

- Figure 2 shows the hardware architecture of a terminal location server, or a communication terminal, according to the invention; and

- Figure 3 shows in flowchart the main steps of a method of locating at least a second mobile terminal following an event relating to a first mobile terminal located in an environment of the second terminal, according to one embodiment of the invention.

Detailed description of the invention

FIG. 1 represents a network environment in which the present invention is implemented according to an embodiment. In this network environment, a system according to the invention for improved location of a communication terminal is implemented.

The network environment comprises a network NW which may be according to the chosen embodiment, a wireless network called ^3rd generation - for example according to the UMTS standard (Universal Mobile Telecommunications System) -, or a mobile network said 4 ^th generation - for example compliant with the LTE standard (Long Term Evolution). This NW network allows interconnection with an IP (Internet Protocol) network, not shown in Figure 1.

The network environment represented in FIG. 1 comprises a geographical zone Z in which there are two communication devices (B1, B2); these are, for example, wireless communication equipment of the NFC (Near Field Communication) terminal type or having a QR code. Each communication device is associated with a precisely known geographic location and designated by reference location in the context of this description.

In the zone Z of the network environment are also present four communication terminals T1-T4, here mobile terminals, the operation of which is detailed below.

The network environment also includes an SVR location server connected to the NW network. The SVR server conventionally has a hardware architecture of a computer, as represented in FIG. 2, which represents the hardware architecture not only of a server according to the invention but also of a terminal (first or second) according to the invention.

The SVR location server thus comprises a processor 20, a rewritable non-volatile memory 21, a ROM (Read-only memorized) 22 memory, a RAM (Random-access memorized) 23 and a communications module COM. The COM communications module allows the SVR server to communicate if necessary with the terminals B1-B2 and with the mobile terminals T1-T4. The read-only memory 22 of the location server SVR constitutes a recording medium according to the invention, readable by the processor 20 and on which is recorded a computer program PG1 according to the invention comprising instructions therefore the execution causes the implementation of the steps of the method for locating a terminal, according to the invention, which are implemented in the server. The steps of the method according to the invention are detailed below in relation to FIG. 3.

The computer program PG1 of the server SVR notably comprises a module for managing reference locations associated respectively with a set of communication devices (here terminals B1 and B2) located in the geographical area Z. This location management module is configured in particular to transmit to a communication terminal such as terminals T1-T4, a reference location linked to a communication device (terminal B1) as well as an acoustic signature characteristic of this communication device, this acoustic signature defining a signal acoustics to be emitted by a terminal considered following an interaction (INT) of the terminal considered with this device (B1). The location management module is also configured to regularly update the latest locations received from the terminals (T1-T4) registered with the SVR server for the geographical area Z managed by the server.

Still in FIG. 1, the T1-T4 mobile terminals are equipped with software modules, installed natively, or installed on demand (by downloading a software application), in order to implement a method of locating terminals according to the invention. In addition, each of the mobile terminals (T1-T4) is conventionally equipped with a microphone (MC) and a speaker (HP).

As explained above, the implementation of a method according to the invention allows the location of at least one second mobile terminal (T2-T4) following an event relating to a first mobile terminal (T1) located in an environment (zone Z) of the second terminal (T2-T4). More particularly, in the example illustrated in FIG. 1, the method comprises an acoustic signal exchange phase (S1 ₂ ; S2!; SL; S2 ₂ ), detailed below, between the first terminal (T1) and the second terminal (T2), following an interaction (INT) between the first terminal (T1) and the terminal (B1) located near the first terminal (T1), the terminal B1 being associated with a reference location; then according to the method, a relative distance from the second terminal relative to the first terminal is determined from this signal exchange; updating of a previously obtained location of the second terminal (T2) is then carried out from the reference location and the relative distance.

Consequently, a communication terminal according to the invention comprises a computer program PG1 (FIG. 2), that is to say a set of functional software modules, among which, when the terminal considered exercises the function of first terminal within the meaning of the invention, there are in particular the following functional modules:

- An interaction module with a communication device located near the terminal, the communication device being associated with reference location information called reference location;

an acoustic signal transmission / reception module adapted to transmit at least a first acoustic signal following this interaction, and to receive in response at least a second acoustic signal coming from at least one second communication terminal in the environment of which the communication terminal is located;

a module for calculating a first delay representative of the time elapsed between the reception in the first terminal of the first signal and the second signal;

a module for transmitting the first delay to the second terminal in order to allow the second terminal to determine relative distance information known as the relative distance of the second terminal relative to the first terminal.

When the communication terminal considered operates as a second terminal 'within the meaning of the invention, the aforementioned computer program comprises in particular the following modules:

an acoustic signal transmission / reception module adapted to transmit a second acoustic signal in response to the reception of a first acoustic signal from a first communication terminal, following an interaction between the first terminal and a device communication located near the first terminal (the communication device being associated with a reference location);

a module for calculating a second delay representative of the time elapsed between the reception in the second terminal of the first signal and the second signal;

- a reception module from the first terminal of the first delay mentioned above;

a module for determining, from the first and the second delay, a relative distance from the second terminal relative to the first terminal;

- a module for obtaining the reference location, for example from the location server;

a module for updating a location of the second terminal, previously obtained, from the reference location and the relative distance.

Concerning communication devices, as said previously, it can be equipment such as NFC terminals or any type of equipment with which a mobile terminal can come into contact when it is in contact with the equipment considered or a few centimeters from it, for example to read an NFC tag with a reader fitted to the terminal. Such a communication device can also be integrated into an electronic access portal, the opening of which is triggered by near field communication (NFC) between a mobile terminal and the device.

The communication terminals targeted by the invention can be located at a fixed or variable position (if the terminal is portable) but in all cases they are associated with a precisely known geographic location, and for each terminal managed by the server SVR location, this location is stored and updated with the SVR server.

FIG. 3 represents in the form of a flowchart the main steps of a method for locating at least one second mobile terminal following an event relating to a first mobile terminal located in an environment of the second terminal, according to the embodiment of the invention illustrated in Figure 1.

As illustrated in FIG. 3, the implementation of the method according to the invention begins with a prior operation E10 of recording each communication terminal present in the zone Z controlled by the location server SVR. In the example of FIG. 1, when a terminal T1-T4 incorporating a location application according to the invention, detects the presence of a communication terminal B1 or B2, the terminal identifies itself with the server and transmits to it its last location or geographic position. Depending on the embodiment chosen, provision may be made for each of the terminals identified with the server to communicate with the server in order to regularly update its last location, when the location of the terminal has changed beyond a predefined threshold.

Each of the terminals communicates with the server using wireless communication technology, for example Wi-Fi technology, which defines a set of wireless communication protocols governed by the standards of the IEEE 802.11 group.

In the embodiment chosen, following the registration of a terminal considered with the SVR server, the server transmits to the terminal an acoustic signature which defines, for a given terminal such as B1 (FIG. 1), the type of sound signal to be transmitted in its environment by a terminal following an interaction with the terminal in question.

Furthermore, in the chosen embodiment, following the identification of a terminal considered with the SVR server, the server transmits to the terminal the reference location associated with the terminal whose presence is detected by the terminal.

According to another embodiment, it can be provided as a variant that it is the terminal (first terminal T1) which interacts with a terminal (B1, B2) of the zone Z which transmits the reference location of the terminal to the other terminals (second terminals T2T4).

Returning to FIG. 3, in step E12, the terminal T1 (first terminal) interacts with the terminal B1 located nearby, for example by reading an NFC label by the terminal T1. As mentioned previously, the terminal B1 is associated with reference location information called reference location, stored and updated in the server. During the above-mentioned interaction, the terminal T1 transmits presence information to a location server SVR and receives in return from the server, in this example, the reference location linked to the terminal B1 and, where appropriate, a acoustic signature characteristic of terminal B1. We can provide, according to another exemplary embodiment, that the terminal T1 has beforehand this reference location without it being necessary for the server to communicate it following the interaction.

In step E14, the terminal T1 emits by means of its speaker HP a first sound signal S1, in its environment. This first sound signal propagates in zone Z and is received, on the one hand, by the microphone of each of the terminals T2, T3 and T4 situated at that time in zone Z, and on the other hand, by the microphone of terminal T1 (S1 ₂ denotes the signal S1 which is picked up by the microphone of terminal T2). The following process being the same for each of the terminals T2, T3 and T4, only the operations implemented in the terminal T2 will be described below.

In step E16, the terminal T2 receives via its microphone MC the signal S1 (denoted S1 ₂ ), coming from the terminal T1. The reception of the signal S1 ₂ in the terminal T2 triggers, via the application according to the invention installed in the terminal, the emission by the loudspeaker of the terminal T2 of a second sound signal S2.

In the embodiment described, this second signal has the same characteristics, that is to say the same acoustic signature - as the first signal, this acoustic signature being characteristic of the terminal with which the interaction takes place.

The second signal S2 is received on the one hand, by the microphone of the terminal T2 (denoted S2 ₂ ) and is on the other hand received by the microphone of the terminal T1 (denoted S2Ù, as illustrated in FIG. 1.

In step E18 which follows, the terminal T2 calculates a delay representative of the time elapsed between the instant of reception by its microphone of the first signal S1 (S1 ₂ ) and the second signal S2 (denoted S2 ₂ ).

In practice, this is the calculation of a metric known by the acronym ETOA (elapsed time between the two time-of-arrivals) and described precisely in the following document:

BeepBeep: A High-Accuracy Acoustic-Based System for Ranging and Localization Using COTS Devices - Chunyi Peng; Guobin Shen; Yongguang Zhang - ACM Transactions on Embedded Computing Systems, Vol. 11, No. 1, Article 4, Publication date: March 2012.

More precisely, the calculation of an ETOA is described in the aforementioned document in sections 3.1 and 3.2 (see in particular equation (7) section 3.1).

Thus in step E18, the terminal T2 calculates an ETOA value ₂ i with:

ETOA ₂ , = t ₂ (S2 ₂ ) -t ₂ (S1 ₂ ) where t ₂ (S2 ₂ ) indicates the instant of reception of the signal S2 by the microphone of the terminal T2 and t ₂ (S1 ₂ ) indicates the instant of reception of the signal S1 by the microphone of the terminal T2.

Similarly, the reception of the signal S1 respectively by the terminal T3 and the terminal T4 triggers the emission, by the loudspeaker of each of these terminals, of an acoustic signal S3 and an acoustic signal S4 respectively (steps E20 and E24). The steps E20 and E24 are then followed respectively, as for the terminal T2, by the steps E22 and E26 for calculating an ETOA delay concerning each of these terminals with respect to the reception of the signal S1 and the transmission / reception of a signal S3 and S4 respectively:

ETOA ₃ , = t ₃ (S3 ₃ ) - t ₃ (S1 ₃ ) where t ₃ (S3 ₃ ) denotes the instant of reception of the signal S3 by the microphone of the terminal T3 and t ₃ (S1 ₃ ) denotes the instant receiving the signal S1 by the microphone of the terminal T3;

ETOA ₄ , = t ₄ (S4 ₄ ) - t ₄ (S1 ₄ ) where t ₄ (S4 ₄ ) indicates the instant of reception of the signal S4 by the microphone of the terminal T4 and t ₄ (S1 ₄ ) indicates the instant of reception of the signal S1 by the microphone of the terminal T4.

In step E28, following the reception of each of the sound signals S2, S3, S4 respectively transmitted by the terminals T2, T3 and T4, the calculation module of the terminal T1 determines a value of ETOA from the reception of each S2-S4 signals:

ETOA, ₂ = 1 (81,) - 1 (82,)

ETOA, ₃ = t, (S1,) - 1 (S3,)

ETOA, ₄ = ti (S1i) -l (S4,) where ti (S11) indicates the instant of reception of the signal S1 by the microphone of the terminal T1 and 1 (Sx,) indicates the instant of reception of the signal Sx by the microphone of terminal T1, with x = 2, 3, 4.

Still at step E28, once the ETOA, _X values (x = 2, 3, 4) calculated by the terminal T1, these values are then transmitted respectively to the terminals T2, T3, T4, for example directly by type of communication Bluetooth from terminal to terminal, or via the SVR server.

In steps E30, E32 and E34, each of the terminals T2, T3, T4, after reception respectively of the corresponding ETOA value transmitted by the terminal T1, calculates the distance (here designated by relative distance) between the terminal considered and the terminal T1 by applying the following equations:

- for terminal T2 (step E30): £> ₂₁ = | £ 7Ύλ4 ₁₂ - ET0A ₂₁ \ · c / 2 + K

- for terminal T3 (step E32): £> ₃₁ = | £ T04 ₁₃ - ET0A ₃₁ \ · c / 2 + K

- for terminal T4 (step E34): D ₄₁ = \ ET0A ₁₄ - ET0A ₄₁ \ · c / 2 + K where c is the speed of sound and K is a constant.

Reference may be made to the BeepBeep document cited above, in particular page 4: 6, fig. 3 and equation (III), to obtain more details on the calculation of the type of relative distance between two terminals.

Finally, in steps E35, E36 and E37, each of the terminals T2, T3 and T4 updates a location of the terminal considered, previously obtained, from the reference location - that is to say the location of the terminal B1 - and of the corresponding relative distance calculated respectively in the preceding steps E30-E34.

According to an exemplary embodiment, a geographic location previously obtained for a terminal such as the terminal T2, T3 or T4 is a location obtained beforehand by a geolocation module equipping the terminal considered. Furthermore, the reference location linked to the terminal (B1) is transmitted to the various terminals (T2-T4), according to the embodiment chosen, by the SVR server when entering these terminals in zone Z.

According to another embodiment, this reference location can be already stored beforehand in each of the terminals, this is in particular possible in the case where the communication devices considered have a fixed location. One can also envisage, according to another embodiment, that it is the terminal T1 which transmits the reference location of the terminal B1 to the other terminals (T2-T4), following the interaction with the terminal B1.

When the terminals considered are mobile, according to an exemplary embodiment, provision may be made for the last reference location associated with a terminal considered to be transmitted by the server to the terminals after the terminal has been moved or periodically, for example.

According to the embodiment chosen and described, updating a geographical location of a second terminal such as the terminal T2, T3 or T4 from the reference location and the relative distance, first comprises the determination of a geographic circle C (O, D) centered on a first geographic point O corresponding to the reference location of the terminal, and of radius corresponding to the relative distance (D) calculated in steps E30-E34 between the terminal T1 and the terminal T2, T3 or T4 considered. Next, updating the geographic location of the terminal considered (T2-T4) includes determining a second point on the aforementioned geographic circle, this second point being the point closest to the (last) geographic location of the terminal. . The geographic coordinates of this second point then constitute a new geographic location of the terminal considered T2-T4.

The new location thus obtained for the terminal considered is then transmitted to the location server SVR.

In the case where several communication devices (B1, B2) are activated by interaction with a respective first communication terminal (T1, T1 ') in the same area (Z), at the same time or in a sufficiently short time interval for that a second terminal T2 can receive a first sound signal (S1, S1 ') coming from each of the two terminals (T1, T1') interacting with one of the two terminals, then this second terminal can in accordance with the invention determine for each of the two bounds (B1, B2) activated a geographic circle, C1 (O1, D1) and C2 (O2, D2), as explained above. In this case, a new location for the terminal T2 in question may be chosen as being a point belonging to the intersection of the two aforementioned circles.

According to a more elaborate embodiment of the invention, in the case where several terminals T1-T4 have been registered with the location server SVR to signal their presence in the zone Z managed by the server, then it is expected that, following to an interaction between one of the terminals (T1) (first terminal in the sense of the invention) with a communication device (B1), the server implements a timing of the second acoustic signals (S2-S4) transmitted by the terminals (T2-T4) (second terminals within the meaning of the invention) following the reception of the first signal (S1) transmitted by the first terminal (T1), this in order to prevent acoustic signals from returning (S2-S4 ) are received at the same time by the microphone of the first terminal (T1).

More specifically, the SVR server transmits to each terminal of the zone in question a time delay or delay value to be respected which takes into account the position of each of the second terminals relative to the first terminal, before emitting an acoustic response signal (second signal S2) in response to a first signal (S1) sent by the terminal (T1) having interacted with a terminal. According to an exemplary embodiment, each of the timing values is chosen as being the smallest multiple of time units such that the sum of the propagation times of the return signals (S2) and the timing value chosen does not coincide with a timer value already used, i.e. already transmitted to a terminal in the area.

Claims (15)

1. Method for locating at least a second mobile terminal (T2) following an event relating to a first mobile terminal (T1) located in an environment of the second terminal, the method comprising: - An interaction (E12) between the first terminal (T1) and a wireless communication device (B1) located near the first terminal, the communication device being associated with reference location information called reference location; - Following said interaction, an exchange (E14, E16) of acoustic signals between the first terminal and the second terminal; the determination (E18, E28, E30), from the exchange of signals, of relative distance information known as the relative distance of the second terminal with respect to the first terminal; - updating (E35) a location previously obtained from the second terminal, from said reference location and said relative distance. 2. Method according to claim 1, in which: the exchange of signals between the first terminal and the second terminal, comprises the emission by the first terminal of a first acoustic signal in said environment; and following the reception of the first signal by the second mobile terminal, the transmission by the second mobile terminal of a second acoustic signal; the determination, from said exchange of signals, of said relative distance of the second terminal with respect to the first terminal, comprises the estimation of the distance separating the first terminal from the second terminal from the propagation speed of the first and second signals in the environment, and at least the transmission time of the first signal between the first and the second terminal and the transmission time of the second signal between the second and the first terminal. 3. Method according to claim 2, in which the estimation of said distance separating the first terminal from the second terminal uses a technique based on a measurement of metrics of ETOA type (elapsed time between the two time-of-arrivals) applied to the first and second acoustic signals. 4. Method according to any one of claims 1 to 3, in which the updating of a geographic location of the second terminal from said reference location and said relative distance, includes: - the obtaining by the second terminal of said reference location; - determining a geographic circle centered on a first point corresponding to said reference location and radius corresponding to said relative distance; - updating of said geographic location of the second terminal from said geographic circle. 5. Method according to claim 4, in which the updating of said geographic location of the second terminal comprises the determination of a second point on said geographic circle, this second point being the point closest to said geographic location, the coordinates of said second point constituting a new geographic location of the second terminal. 6. Method according to any one of the preceding claims, in which a geographic location, previously obtained, of the second terminal, is a location obtained beforehand by a geolocation module equipping the second terminal. 7. Method according to any one of the preceding claims, in which the communication device located near the first terminal is equipment of the NFC terminal type or having a QR Code type code associated with a known geographical location. precise. 8. Method according to any one of claims 2 to 7, in which during the interaction between the first terminal and the communication device located near the first terminal, the following steps are implemented: - Transmission by the first terminal via a communication network of presence information from the first terminal to a location server; - reception, in return, of the location server, of an acoustic signature characteristic of the communication device and defining said first acoustic signal. 9. Method according to any one of claims 2 to 8, comprising: - the calculation by said first terminal of a first delay representative of the time elapsed between the reception in the first terminal of the first signal and the second signal; - the transmission by said first terminal of said first delay to said at least one second terminal; - the calculation by said at least one second terminal of a second delay representative of the time elapsed between the reception in said second terminal of the first signal and of the second signal; - determining in said at least one second terminal, from said first delay and said second delay, said relative distance of said second terminal with respect to the first terminal; - updating a location of said at least one second terminal, previously obtained, from said reference location and said relative distance. 10. The method of claim 8 or 9, comprising an operation of registering each communication terminal with the location server when said terminal is located in an area in which is located a communication device whose reference location is managed by said server; said recording operation comprising: - the transmission to the server by the terminal of its last location; - the transmission by the server to the terminal of the acoustic signature defining said first acoustic signal; - the regular updating of a last location with the server by the terminal when the location of the terminal has changed beyond a predefined threshold. 11. Method according to any one of claims 8 to 10, comprising, when several second terminals are located in the area covered by the location server, and following an interaction between the first terminal and a communication device located near the first terminal, the sending by the server to each of the second terminals of a specific time limit to be observed before the emission of a second acoustic signal intended for said first terminal. 12. Communication terminal (T1) characterized in that it comprises: - An interaction module with a communication device located near the terminal, the communication device being associated with reference location information called reference location; an acoustic signal transmission / reception module adapted to transmit at least a first acoustic signal following said interaction, and to receive in response at least a second acoustic signal coming from at least one second communication terminal in the the environment in which said communication terminal is located; a module for calculating a first delay representative of the time elapsed between the reception in the first terminal of the first signal and the second signal; a module for transmitting said first delay to said at least one second terminal in order to allow said at least one second terminal to determine relative distance information, said relative distance of said at least one second terminal with respect to said terminal. 13. Communication terminal (T2-T4) characterized in that it comprises: an acoustic signal transmission / reception module adapted to transmit a second acoustic signal in response to the reception of a first acoustic signal from a first communication terminal, following an interaction between the first terminal and a device communication located near the first terminal, the communication device being associated with reference location information called reference location; - a module for obtaining said reference location; a module for calculating a second delay representative of the time elapsed between the reception in said terminal of the first signal and the second signal; - a reception module from the first terminal of a first delay representative of the time elapsed between the reception in the first terminal of the first signal and the second signal; a module for determining, from said first delay and from said second delay, a relative distance information item known as the relative distance of said terminal with respect to the first terminal; a module for updating a location of said terminal, previously obtained, from said reference location and said relative distance. 14. Location server (SVR), for the implementation of a location method according to any one of claims 1 to 11, comprising a reference location management module respectively associated with a set of communication devices located in a geographic area, said management module being configured to: transmitting a reference location linked to a communication device of said set to at least one terminal located in said zone, as well as an acoustic signature characteristic of said communication device and defining an acoustic signal to be exchanged between at least two terminals located in said zone, following the interaction of a terminal with said communication device; - regularly update the latest locations received from terminals registered in said server for said geographic area. 15. Computer program implemented in a communication terminal or in a server on a communication network, said program comprising instructions whose execution by a processor of the terminal or of the server, causes the execution of all or part steps of a method according to any one of claims 1 to 11.