FR3094170A1 - METHODS AND SYSTEMS FOR LOCATING COMMUNICATING OBJECTS - Google Patents

Abstract

METHODS AND SYSTEMS FOR LOCATING COMMUNICATING OBJECTS Method for estimating by means of a mobile terminal (4) equipping a user (3) of the direction of arrival of a radio signal received by this mobile terminal, this method comprising the following steps: measuring, during a capture session, the power of the radio signal received by the mobile terminal at a plurality of measurement points around the user; determination of the measurement point among said plurality of measurement points around the user at which the measured power of the received radio signal is minimum, the direction starting in a horizontal plane from the determined measurement point towards the user being considered the direction of arrival of the received radio signal. Figure for the abstract: Figure 1

Description

METHODS AND SYSTEMS FOR LOCATING COMMUNICATING OBJECTS

The present invention relates to the technical field of methods and systems for locating an object communicating by short-range radio, and more particularly to methods and systems for estimating the direction of arrival of a short-range radio signal emitted by such communicating objects.

Here, “object communicating by short-range radio” means any device equipped with a radio transmitter implementing a short-range wireless communication standard, in particular of the Bluetooth, Wi-Fi, HiperLAN, or ZigBee type.

Due to their low power consumption and their extreme miniaturization, short-range radio transmitters are increasingly fitted to everyday objects, especially portable objects. These transmitters can, in fact, be provided as an integral part of these objects, or be annexed to them later. By way of example, the document US8847754 (Buchheim) describes an adhesive tag (or label), the size of a coin, using Bluetooth Low Energy communication, and which can be attached, by gluing, to a remote control. television, on a bunch of keys, on a suitcase, or on an item offered for sale.

Thus endowed with a communication capability, such objects can be located by a mobile terminal integrating a radio receiver of the same type as the radio transmitter, and located within the radio range of the latter.

To do this, methods for locating objects communicating by short-range radio are based on propagation parameters of the emitted radio signal, and not on an infrastructure and equipment dedicated to localization (such as GPS, GLONASS, or GALILEO) . These methods thus have the advantages, on the one hand, of dispensing with costly means in terms of resources and energy (most often, a GPS receiver in addition to wireless technology) and, on the other hand, of allowing location in both indoor and outdoor environments.

Among the metrics specific to the transmitted radio signal used for the location of the radio transmitter at short range, we cite the strength of the received signal (commonly referred to as "RSS" for Received Signal Strength , or also by "RSSI" for RSS Indicator ) , or the direction/angle of arrival of the received radio signal (commonly referred to as "DOA" for Direction of Arrival , or "AOA" for Angle of Arrival ).

By measuring the power of the radio signal received and applying a propagation model describing the attenuation of the power of the signal as a function of the distance travelled, it is possible to estimate the distance separating the transmitter from the receiver. The location information takes, in this case, the form of a zone centered on the position of the receiver.

The relevance of the RSS metric in radiolocation is thus directly linked to the precision in the measurement of the power of the received signal and to the relevance of the propagation model used. Indeed, an approximate measurement of the power of the received signal and/or the use of a non-representative model of the radio signal propagation environment directly impacts the accuracy of the location of the communicating object.

In addition, a control of the transmission power, implemented for example by means of the LMP protocol ( Link Manager Protocol ) of the Bluetooth standard, falsifies the relationship which could link the power of the received signal to the distance separating the transmitter from the short-range radio receiver, and therefore further limits the suitability of RSS-only tracking methods.

In addition, by measuring the strength of the radio signal received at different positions, it is possible to determine fairly roughly whether the radio receiver is approaching or moving away from the transmitter. It is, however, not possible to determine in which direction the source of the radio signal is, from only the power of the signal measured in a position of the receiver, information which would however be very useful for locating the radio transmitter faster.

Another drawback of the RSS metric (or the RSSI metric) is related to the difficulty of accurately modeling multipath propagation phenomena, which are very common in confined environments.

As for the metric of the direction (or angle) of arrival of the received radio signal, two approaches exist.

The first approach, based on spatial filtering, uses a rotating directional antenna (or a plurality of directional antennas arranged around an axis), configured to measure the received signal power at different angles. The direction of arrival of the radio signal is assumed to be the direction at which the strength of the received signal is maximum. The problem encountered with this approach is that the direction in which the power of the received signal is maximum is not necessarily, in the presence of the multipath propagation phenomenon, the direction in which the radio transmitter is located. In particular, because of destructive interference (for example, in a corridor similar to a tunnel), the power measured by a receiver oriented towards and in direct view of a radio transmitter is not, at certain positions with respect to the transmitter, not necessarily the largest relative to those measured at other orientations and/or positions of the radio receiver.

The direction in which the radio transmitter is located is estimated, according to a second approach, by calculating the angle of arrival of the signals received at the level of a plurality of radio receivers, arranged in an array of uniformly spaced antennas. The estimation of the direction of arrival is based, in this case, on the phase difference between the signals measured by two successive antennas of the network.

The accuracy of this approach depends, among other things, on the number and sensitivity of the antennas used. Hence the constraints weighing on the deployment of this method, preventing its large-scale use.

An object of the present invention is to provide methods and systems for estimating the direction of arrival of a radio signal, suitable for consumer applications.

Another object of the present invention is to propose methods and systems for locating an object communicating by radio at short range, the reliability of which is acceptable, with regard to the means invested.

Another object of the present invention is to provide methods for estimating the direction in which a connected object is located, with respect to the current position and orientation of the user.

Another object of the present invention is to provide a method of locating, by means of a mobile terminal such as a smartphone, a connected object.

Another object of the present invention is to provide a method for assisting in the location of a connected object, based on the power of the signals emitted by this connected object and received by a mobile terminal in a given position.

Another object of the present invention is to propose a cooperative localization method of a target connected object.

To this end, it is proposed, first, a method of estimating, by means of a mobile terminal equipping a user located at a position in a predefined environment, the direction of arrival of a radio signal received by this mobile terminal, this radio signal being emitted in this environment by a short-range radio transmitter, this method comprising the following steps:

measurement, during a capture session, of the power of the radio signal received by the mobile terminal, at a plurality of measurement points around the user;

determination of the measurement point among said plurality of measurement points around the user at which the measured power of the radio signal received is minimum, the direction starting in a horizontal plane from the determined measurement point towards the user being considered the direction of arrival of the received radio signal at the user's position in the environment.

Various additional features may be provided, alone or in combination:

said plurality of measurement points are at regular angular intervals around the user;

said plurality of measurement points comprises a measurement point in front of the user, a measurement point to the left of the user, a measurement point behind the user, a measurement point to the right of the user;

to measure the power of the radio signal received by the mobile terminal at a plurality of measurement points around the user, the estimation method further comprises a step of rotating the user on himself;

the mobile terminal is kept, during the capture session, substantially fixed relative to the body of the user;

the estimation method further comprises a step of indicating to the user the direction of arrival of the received signal considered to be the direction in which the short-range radio transmitter is located.

Secondly, a method for locating a short-range radio transmitter emitting a radio signal in a predefined environment is proposed, this method comprising the following steps:

estimation, by means of a mobile terminal equipping a user located at a first position in said environment, of the direction of arrival of said radio signal received by the mobile terminal according to the methods presented above;

estimation, by means of a mobile terminal equipping a user located at a second position in said environment, of the direction of arrival of said radio signal received by the mobile terminal according to the methods presented above;

estimating the position of the radio transmitter as being at the intersection of the estimated direction of arrival at said first position and the estimated direction of arrival at said second position.

In some implementations, several users are each provided with a mobile terminal connected to a central server, each mobile terminal being able to communicate to this server its position in the environment and an identifier of a communicating object provided with said radio transmitter emitting said radio signal, the location of the communicating object thus being achieved in a cooperative manner by involving several users.

Advantageously, the central server estimates the position of the communicating object by having available data for estimating the position of the radio transmitter obtained at two different positions of at least one user provided with a mobile terminal.

Thirdly, a mobile terminal intended to equip a user located in a position in a predefined environment and configured to estimate the direction of arrival of a radio signal received by this mobile terminal, this mobile terminal comprising:

a short-range radio receiver, capable of measuring, during a capture session, the power of the radio signal received at a plurality of measurement points around the user;

a processor, configured to determine the measurement point among said plurality of measurement points around the user at which the measured power of the received radio signal is minimum, the direction extending in a horizontal plane from the determined measurement point towards the user being considered to be the direction of arrival of the radio signal received at the position of the user in the environment.

The mobile terminal advantageously further comprises a motion sensor, configured to associate an azimuth with each of the measurement points.

It is proposed, fourthly, a computer program product implemented on a memory medium, capable of being implemented within a computer processing unit and comprising instructions for the implementation of one of the methods presented above.

Other characteristics and advantages of the invention will appear more clearly and concretely on reading the following description of embodiments, which is made with reference to the appended drawings in which:

schematically illustrates methods and systems for estimating, according to various embodiments, the direction of arrival of a radio signal emitted by a communicating object and received by a mobile terminal;

schematically illustrates methods and systems for estimating, according to various embodiments, the direction of arrival of a radio signal emitted by a communicating object and received by a mobile terminal;

schematically illustrates components included in a mobile terminal, according to various embodiments;

schematically illustrates the steps of a method for locating a communicating object, according to various embodiments.

Referring to Figure 1, a communicating object 1 is displayed. This communicating object 1 comprises a portable object 11 , such as a watch, an earphone, a toy, an external hard drive, a t-shirt, a USB key, a key ring, a book, a backpack , a handbag, a telephone, a beacon, a wallet, a toolbox, a suitcase, a bracelet, a hands-free kit, or more generally any other portable object.

The communicating object 1 further comprises a short-range radio transmitter 12. This radio transmitter 12 can take the form of a tag, a chip, or a label. The short-range radio transmitter 12 can be originally provided with the portable object 11 , or be linked to it later by the end user of the portable object 11 .

The communicating object 1 is, in one embodiment, one of the connected objects which, with the advent of the Internet of objects, are more and more numerous.

The short-range radio transmitter 12 is preferably compact compared to the portable object 11 and has reduced power consumption.

The short range radio transmitter 12 is configured to transmit radio waves on a regular basis. The power and/or the sending frequency and/or the content of these signals is/are, in one embodiment, configurable remotely. The transmitted signal can include any information relating to the communicating object 1 (i.e. to the portable object 11 and/or to the radio transmitter 12 ), such as an address (an IP address, an address MAC for example), an identifier, a serial number, a manufacturer's name, a brand, the owner of the communicating object 1 .

The short range radio transmitter 12 includes, in some embodiments, a Bluetooth transmitter. This Bluetooth transmitter can be of class 1, 2 or 3, the ranges of which are, respectively, of the order of 100m, 10m and 1m.

As a variant or in combination, the short-range radio transmitter 12 preferably comprises a Bluetooth Low Energy (or Bluetooth SMART) transmitter oriented to very low energy consumption.

As a variant or in combination, the radio transmitter 12 comprises a Zigbee transmitter (based on the IEEE 802.15.4 standard).

As a variant or in combination, the short-range radio transmitter 12 comprises a Wi-Fi (Wireless Fidelity) transmitter or a Hiperlan transmitter.

The communicating object 1 is placed in an environment 2 . The range of the radio transmitter 12 at least partially covers the environment 2 .

The environment 2 is, in one embodiment, an interior environment, such as a workshop, a warehouse, a store, an office, a room, a corridor, a bedroom, or a hall. Alternatively, the environment 2 is an outdoor environment, such as a courtyard, a park, a garden, a parking lot, a field, a pedestrian street, or any urban outdoor environment.

The environment 2 is, in one embodiment, a place where a user 3 spends most of his time and where communicating objects 1 are intended to be there most often.

The user 3 is equipped with a mobile terminal 4 comprising, as displayed in FIG. 2, a short-range radio receiver 41 , capable of picking up and measuring the radio signal emitted by the short-range radio transmitter 12 scope. The short-range radio receiver 41 is of the same type as the radio transmitter 12 . Thus, whether the radio signal emitted is a Wi-Fi, and/or Bluetooth, and/or ZigBee signal, the short-range radio receiver 41 is capable of picking up this signal.

To estimate the direction of arrival of the signal transmitted by the short-range radio transmitter 12 and received at the position of the user 3 by the short-range radio receiver 41 , the user 3 performs a rotation on himself, by carrying the mobile terminal 4 with it . This rotation is approximately 360 °, that is to say a complete tower 5.

To do this, the user 3 holds the mobile terminal 4 in front of him close to his body and performs a turn (or a rotation) 5 on himself, so that his body can shield the communicating object 1 when it is, during its rotation, between the mobile terminal 4 and the communicating object 1 .

When the user 3 is between the communicating object 1 and the mobile terminal 4 , the radio signal received undergoes an additional attenuation (compared to measurements where the body of the user 3 does not obstruct the propagation of the radio signal between the radio transmitter 12 and the radio receiver 41 ), due to the body mass of the user 3 whom he encounters in his journey. This information is used to estimate the direction of arrival of the received radio signal. In other words, the energy absorbed by the body mass of the user 3 is, here, used to estimate the direction of arrival of the received radio signal.

Referring to Figure 3, the direction of arrival, at the position of the user 3 , of the radio signal transmitted by the radio transmitter 12 at short range of the communicating object 1 is determined by analyzing the variation of the power of the radio signal received at a plurality of measurement points 51 around the user 3 . This direction of arrival of the radio signal received is determined by the measurement point 51 of the mobile terminal 4 around the user 3 at which the measured power of the radio signal received is the weakest.

The direction of arrival of the radio signal received is estimated to be the direction in which the communicating object 1 is located, from the position of the user 3 in the environment 2 .

Contrary to known methods, the estimation of the direction in which the communicating object 1 is located is based, here, on the invisibility (the masking, the obstruction, or the concealment) for the radio receiver 41 of the radio transmitter 12 . The presence of an obstacle (in this case, the body of the human user 3 ) is, in fact, used to estimate the direction of arrival of the received radio signal.

The attenuation of the radio signal by the body mass of the user 3 is, here, used to estimate the direction of arrival of the received radio signal.

For this, the user 3 triggers, in a position of the environment 2 , a session for capturing the radio signal emitted by the radio transmitter 12 at short range, and then performs a turn 5 on itself.

In one embodiment, a capture session is launched only when the power of the received radio signal is between two predefined values.

During the capture session, the user 3 keeps the mobile terminal 4 stationary with respect to his body, so that the mobile terminal 4 keeps approximately the same orientation and the same distance with respect to the body of the user 3 during its rotation on itself. As a result, during a capture session, the mobile terminal 4 traverses a substantially circular path, centered on the user 3 .

During this capture session, with reference to FIG. 2, a processor 42 , included in the mobile terminal 4 , memorises, while the user performs a turn 5 on himself, measurements of the power of the radio signal received by the radio receiver 41 at different measurement points 51 of the mobile terminal 4 around the user 3 . These measurements of the power of the radio signal received (RSS in dBm or, in an equivalent way, the RSSI in dB) are stored in a memory 43 . In one embodiment, the powers of the radio signal received are stored in association with the measurement points 51 around the user 3 at which they are measured.

These measuring points 51 can be defined by:

a relative azimuth (relative to the orientation of the user 3 when launching a capture session for example) or absolute (relative to geographic north for example), or

an orientation relative to the orientation of the user 3 when launching a capture session, of the front, left, right or behind type.

The measurement points 51 around the user 3 at which measurements are stored are, in one embodiment, determined by dividing 360 degrees by the total number of measurements stored.

During a capture session, the communicating object 1 is assumed to be kept fixed relative to the position of the user 3 . It is also assumed that environment 2 (ie the propagation channel) is, during the capture session, static or quasi-static. The rotation of the user 3 on himself during a session for capturing the radio signal emitted by the communicating object 1 takes place all other things being equal (ceteris paribus), ie. with no nearby moving object that could interfere with the radio signal emitted. When, during a capture session, a relatively slow change in relation to the duration of this capture session occurs in environment 2 (for example, movement of communicating object 1 or any other object present in environment 2 ), the propagation channel is assumed to be static.

While the user 3 performs a turn 5 on himself, the mobile terminal 4 picks up the radio waves emitted from the communicating object 1 and regularly records the power of the radio signal received.

The measurement points 51 are at regular angular intervals (for example, every x degrees, where x is a real between 0° and 90° in the azimuth plane), around the user 3 . When the speed of rotation of the user 3 is substantially constant during the capture session, the memorized measurements are therefore carried out at regular time intervals. Otherwise, the measurements are stored so that they are taken by the radio receiver 41 at measurement points 51 substantially uniformly distributed around the user 3 . The speed of rotation of the user 3 on himself is, in the latter case, taken into account to order the storage of the measurements taken.

In one embodiment, the power of the received radio signal is measured and stored at predefined measurement points 51 around the user 3 , without him having to turn on himself. The user 3 positions the mobile terminal 4 for a predefined time at different measurement points 51 around him, for example in front of him, to his left, behind him, and to his right and, possibly, at any other intermediate positions.

In one embodiment, the radio receiver 41 continuously measures the strength of the received radio signal. Alternatively, radio receiver 41 measures the strength of the radio signal upon request from processor 42 .

Furthermore, when the radio signal is transmitted periodically and not continuously, the transmission period of the short-range radio transmitter 12 is also taken into account by the processor 42 so as to have sufficient observations. the strength of the radio signal received around the user 3 . Preferably, at least four measurements of the power of the radio signal received, respectively, in front, to the right, behind and to the left of the user 3 , are stored.

In one embodiment, when the number of measurements of the power of the radio signal received stored during a capture session is less than a predefined number, a new capture session is required, in order to be able to estimate the direction of arrival of the radio signal received.

In one embodiment, the user is informed via an indication means 44 included in the mobile terminal 4 , of the minimum duration of a session for capturing the radio signal emitted by the communicating object 1 . The indication means 44 is capable of emitting an audible signal, a visual signal (screen or light), or a vibration indicating the duration or the time remaining in the duration of a capture session.

In one embodiment, when a capture session is launched by the user 3 , the processor 42 requests, via the radio receiver 41 , the radio transmitter 12 to transmit a regular signal of a predefined amplitude and/or or at predefined time intervals.

It should be noted that, when the mobile terminal 4 and the communicating object 1 do not know each other, the mobile terminal 4 launches a procedure aimed at discovering/detecting the communicating objects 1 within range (for example, an "Inquiry » when the radio standard used is Bluetooth). Otherwise, the mobile terminal 4 proceeds to establish a connection with the communicating object 1 whose address is known for the mobile terminal 4 (via, for example, a “Page” type procedure when the radio standard used is Bluetooth). The mobile terminal 4 preferably indicates to the user 3 the communicating objects 1 within range, as well as information concerning them (address, identifier, name, brand, power or power level of the received signal, reception frequency, the time since the last reception for example). The user 3 is thus informed of the presence in the vicinity of a communicating object 1 .

In another embodiment, a search procedure (of the “Inquiry” type) for communicating objects 1 and the selection of an object from those detected is carried out prior to a capture session, either by the user 3 or automatically by the mobile terminal 4 .

The mobile terminal 4 comprises, in one embodiment, a motion sensor (such as an accelerometer and/or a gyroscope and/or magnetometer, and/or a camera and/or a laser sensor, and/or a compass) , connected to processor 42 . This movement sensor is configured to pick up the movement of the mobile terminal 4 . Equipped with a clock and the motion sensor, the mobile terminal 4 makes it possible to calculate the speed of rotation, during a capture session, of the user 3 on himself.

In another embodiment, the motion sensor is configured to capture, during a capture session, the direction of rotation of the user 3 on himself (i.e. from the left to the right or right to left). Alternatively, the user 3 provides, via input means (buttons, mouse, touch screen for example) the direction of his rotation on himself, or more generally the direction of travel of the measurement points 51 to which measurements of the radio signal received are stored.

In another embodiment, the motion sensor is configured to associate an azimuth with each of the measurement points 51 . The azimuth is defined relative to the initial orientation of the user, when starting a capture session.

In one embodiment, the mobile terminal 4 indicates to the user 3 , via the indicating means 44 , the appropriate rotation speed on itself during a capture session (for example, in the form of a progress bar on a screen, a voice message or a vibration speed to indicate that the current rotational speed is too fast, not fast enough, or adequate).

The user's maximum spin speed during a capture session can be determined from:

the number of transmissions per unit time of the radio signal by the short-range radio transmitter 12; and or

data from motion sensors included in the mobile terminal 4 .

The measurements of the power of the radio signal received at a plurality of measurement points 51 around the user 3 are, in one embodiment, normalized with respect to the average power of the memorized measurements. As a variant, the stored powers are normalized with respect to the maximum value among the powers stored at a plurality of measurement points 51 around the user 3 .

In one embodiment, to estimate the direction of arrival of the radio signal received, a representation in polar coordinates of the stored powers makes it possible to identify the measurement point 51 at which the power of the radio signal received is the weakest.

A relatively strong attenuation of the power of the radio signal received at a measurement point 51 around the user 3 is interpreted by the processor 42 as being caused by the masking of the communicating object 1 by the user 3 (i.e. .d. at this measurement point 51 , the received radio signal is at least partially blocked by the body mass of the user 3 ). At this measurement point 51 , the communicating object 1 is behind the user 3 (when the user holds the mobile terminal 4 in front of him). In other words, the processor 42 considers that a relatively large attenuation in the power of the radio signal received corresponds to the measurement point 51 where the body of the user 3 is between the radio transmitter 12 and the radio receiver 41 .

More generally, the processor 42 determines the measurement point 51 around the user 3 at which the power of the radio signal received is the weakest. The direction of arrival of the radio signal received is that which starts in a horizontal plane (in particular, the transverse plane of the body of the user 3 ) from the measurement point 51 determined towards the user 3 .

In other words, the direction of arrival of the radio signal received is identical (respectively, opposite) to the orientation of the user 3 when the measurement point 51 determined is behind (respectively, in front of) him. Likewise, the direction of arrival of the received radio signal is oriented towards the right (respectively, towards the left) of the user 3 when the determined measurement point 51 is to his left (respectively, to his right).

The direction in which the communicating object 1 is located is considered to be that of the arrival of the received radio signal.

At the end of a capture session, the mobile terminal 4 indicates, via the indication means 44 , intended for the user 3 , the estimated direction in which the communicating object 1 is located.

In one embodiment, the estimated direction in which the communicating object 1 is located from the current position of the user 3 is represented in the form of a directional beam starting from the position of the user 3 . The width of the directional beam can vary depending on:

the distance between the mobile terminal 4 and the user's body 3 , making it possible to increase or reduce the obstacle to the received radio signal;

the number of measurement points 51 around the user 3 at which measurements are stored, the directional beam being all the finer as the number of these points increases.

The estimated direction in which a communicating terminal 1 sought by the user 3 is located is indicated in a relative manner with respect to the initial orientation of the user, at the start of the capture session (also equal to the orientation end of the user after doing one or more 5 turns on himself). It is, in this case, formulated in a relative manner with respect to the initial orientation as follows: "the communicating object 1 is in front of you", "the communicating object 1 is on your left", "the 'communicating object 1 is to your right', 'communicating object 1 is behind you', or more generally, 'communicating object 1 is in the direction of approximately x degrees from your current orientation' where x is a real taking a value between 0° and 360°.

As a variant, the estimated direction of arrival is indicated in a relative manner with respect to the geographic north direction indicated by a compass included in the mobile terminal 4 . As a result, advantageously, the user is not, in this case, bound by his orientation at the start of the session or at the end of the capture session.

As a variant, the estimated direction in which a communicating terminal 1 sought by the user 3 is located is indicated to him based on data retrieved from sensors fitted to the mobile terminal 4 (accelerometers, gyrometers, magnetometers, compasses).

In one embodiment, the user 3 provides the mobile terminal 4 with information to be taken into consideration for estimating the direction in which the communicating object 1 is located. This information includes:

the body mass of the user 3 (height and weight) influencing the attenuation of the radio signal received;

the type of clothing or objects worn (bulletproof vest with ceramic plate, backpack with computer, for example) that may create an additional obstruction to the radio signal.

In one implementation, this information is provided to the mobile terminal 3 , via a software application.

In one embodiment, a calibration of the mobile terminal 4 is carried out taking into account the following variables:

the transmission power of the radio transmitter 12 . This transmission power can be observed when pairing the communicating object 1 or more generically by testing each class of the radio transmitter 11 ;

the type of the mobile terminal 4 (a smartphone, phablet, tablet, model, reference of the radio receiver) and/or of the radio receiver 41 .

In one embodiment, and in order to improve the relevance of the estimated direction of arrival of the radio signal received, the user 3 performs more than one turn on himself, in order to memorize a greater number of measurements.

More generally, the method for estimating the direction of arrival of the radio signal received (considered to be the direction in which a communicating object 1 is located from the current position of the user 3 ) comprises, with reference to the Figure 4, the following steps:

measurement and storage (step 10 ) of the power of the radio signal received at a plurality of measurement points 51 around the user 3 , in particular by performing a turn by this user 3 while carrying the mobile terminal 4 with him ;

determination (step 20 ) of the measurement point 51 around the user 3 at which the power of the signal received is minimum, this measurement point corresponding to the presence of the user 3 between the mobile terminal 4 and the communicating object 1 ;

indication (step 30 ) to the user 3 of the direction in which the communicating object 1 is located, estimated that starting in a horizontal plane from the measurement point 51 determined towards the user 3 .

In one embodiment, while moving in the environment 2 in search of the communicating object 1 , the user 3 is invited to implement the method described above for estimating the direction in which finds the communicating object 1 as soon as the power of the signal received is between two predefined values. In other words, the mobile terminal 4 probes and regularly compares the power of the radio signal received and invites the user to launch a capture session as soon as the power of the signal is between two predefined power levels. This has the advantage of accelerating the procedure for discovering the communicating object 1 .

The location of the communicating object 1 is, in one embodiment, obtained from the estimated directions of arrival of the radio signal received, respectively, in a first position and in a second position of the environment 2 . The position of the communicating object 1 is estimated to be at the intersection of the estimated directions of arrival of the signal received at different positions of the environment 2 .

For this, the mobile terminal 4 temporarily stores, in one embodiment, the recent positions of the user 3 (provided by the user 3 or determined by the mobile terminal 4 ) at which a capture session has been carried out and the measurements memorized during these sessions and/or the estimated direction of arrival at these positions. It follows that the superposition of at least two directions of arrival respectively estimated at two different positions of the user 3 makes it possible to locate the communicating object 1 .

As a variant and without memorization by the mobile terminal 4 of the data relating to previous capture sessions, the user 3 interprets the estimated directions in which the communicating object 1 is located and which are indicated to him by the mobile terminal 4 , in order to deduce the location of the communicating object 1 .

To improve the relevance of the estimated position of the communicating object 1 , an estimation of the direction of arrival of the radio signal received at a plurality of positions of the user 3 in the environment 2 can be envisaged.

The positions of the user 3 at which capture sessions are launched are chosen so that the estimated directions of arrival are concurrent at an estimated point the position of the communicating object 1 . For this, a second position of the user 3 is chosen so that the straight line defined by the second position and a first position of the user 3 is not parallel with the direction of arrival estimated at the first position of the user 3 .

The mobile terminal 4 is, in one embodiment, an intelligent telephone (Smartphone), a phablet or a tablet. Such mobile terminals 4 are, in fact, most often equipped with a Bluetooth and/or Wifi receiver, a processor, a memory and an indication means (in particular, a display screen, an audio output and/or a vibrator), via which it is possible to indicate to the user 3 the estimated direction of arrival. These mobile terminals 4 further comprise movement and/or orientation sensors, or more generally inertial sensors. In this case, the methods described above are implemented by a software application.

In one embodiment, the location of a target communicating object 1 is carried out in a cooperative manner involving several users 3 .

In this case, the mobile terminal 4 is connected, through a wireless link, to a central server responsible for locating the communicating objects 1 . The central server is accessible via a wireless access point covering the environment 2 . This wireless access point is, in one embodiment, of the Wi-Fi type (a Wi-Fi hotspot whether public or private) or of the type of a mobile data network (a base station of a cellular network).

The mobile terminal 4 is configured to communicate to the central server the position in the environment 2 of the user 3 at which a capture session is launched and the direction of arrival of the signal received at this position (or the measurements stored during this session). The mobile terminal 4 is furthermore configured to communicate to the central server an identifier of the communicating object 1 .

In one embodiment, the measurements stored by the mobile terminal 4 during a capture session are transmitted to the central server, in order to obtain in return an estimate of the direction of arrival of the radio signal received. The memorized measurements are associated with the measurement points 51 around the user 3 .

In one embodiment, the central server is a mobile terminal 4 to which one or more other mobile terminals 4 can be directly or indirectly connected.

By having data obtained at two different positions of the environment 2 and concerning the same communicating object 1 , the central server is able to estimate, as explained above, the position of the communicating object 1 .

Consequently, in response to a request sent to it by a mobile terminal 4 or any other network node, the central server is capable of providing the estimated location of the communicating object 1 .

In another embodiment, the central server includes a list of target communicating objects 1 to be located by the mobile terminals 4 . For this, the central server broadcasts a notification to the mobile terminals 4 inviting them to participate in the location of a communicating object 1 . This notification includes information making it possible to uniquely identify the communicating object 1 .

As soon as a radio signal emitted by the target communicating object 1 is detected, the mobile terminal 4 invites the user 3 to launch a capture session. The data resulting from this session is then communicated to the central server.

From the data transmitted to it from mobile terminals 4 , the central server estimates and makes available the position of the communicating object 1 target.

Advantageously, such a service for the cooperative location of communicating objects 1 is greatly facilitated by the extensive use of short-range wireless communication standards (in particular, Bluetooth and Wi-Fi) and geolocation sensors (in particular, GPS) which now equip most smart phones.

Advantageously, the methods and systems described above for locating a communicating object 1 :

make it possible to dispense with an approximation of the propagation model specific to each location environment 2;

avoid passing several times next to the communicating object 1 to be located, to establish a two-dimensional map of the power of the radio signal received;

allow easy deployment and minimal maintenance of location systems, important criteria for consumer applications;

are suitable, on the one hand, for any connected object and, on the other hand, for most existing smartphones;

allow the location of connected objects in both indoor and outdoor environments;

are based on the measurement of the power of the radio signal received and on the natural phenomenon of attenuation of the radio signal by the human body, and therefore do not require sophisticated means.

Claims (12)

Method for estimating, by means of a mobile terminal ( 4 ) fitted to a user ( 3 ) who is at a position in a predefined environment (2 ), the direction of arrival of a radio signal received by this mobile terminal ( 4 ), this radio signal being emitted in this environment ( 2 ) by a short-range radio transmitter ( 12 ), this method comprising the following steps: measurement, during a capture session, of the power of the radio signal received by the mobile terminal ( 4 ) at a plurality of measurement points ( 51 ) around the user ( 3 ); determination of the measurement point ( 51 ) among said plurality of measurement points ( 51 ) around the user ( 3 ) at which the measured power of the received radio signal is minimum, the direction starting in a horizontal plane from the measurement point ( 51 ) determined towards the user ( 3 ) being considered the direction of arrival of the radio signal received at the position of the user ( 3 ) in the environment ( 2 ). Method according to claim 1, characterized in that said plurality of measuring points ( 51 ) are at regular angular intervals around the user ( 3 ). Method according to claim 1 or 2, characterized in that said plurality of measurement points ( 51 ) comprises a measurement point ( 51 ) in front of the user ( 3 ), a measurement point ( 5 ) to the left of the user ( 3 ), a measuring point ( 51 ) behind the user ( 3 ), a measuring point ( 51 ) to the right of the user ( 3 ). Method according to any one of the preceding claims, characterized in that it comprises, for measuring the power of the radio signal received by the mobile terminal ( 4 ) at a plurality of measurement points ( 51 ) around the user ( 3 ), a user rotation step ( 3 ) on itself. Method according to the preceding claim, characterized in that the mobile terminal ( 4 ) is maintained, during the capture session, substantially fixed relative to the body of the user ( 3 ). Method according to any one of the preceding claims, characterized in that it further comprises a step of indicating ( 30 ) to the user ( 3 ) the direction of arrival of the received signal considered to be the direction in which is the radio transmitter ( 12 ) at short range. Method for locating a short-range radio transmitter (12 ) emitting a radio signal in a predefined environment (2 ), this method comprising the following steps: estimation by means of a mobile terminal ( 4 ) equipping a user ( 3 ) being at a first position in said environment ( 2 ) of the direction of arrival of said radio signal received by the mobile terminal ( 4 ) according to a method according to any one of claims 1 to 6; estimation by means of a mobile terminal ( 4 ) equipping a user ( 3 ) located at a second position in said environment of the direction of arrival of said radio signal received by the mobile terminal ( 4 ) according to a method according to one any of claims 1 to 6; estimating the position of the radio transmitter ( 12 ) as being at the intersection of the estimated direction of arrival at said first position and the estimated direction of arrival at said second position. Method according to claim 7, characterized in that several users ( 3 ) are each provided with a mobile terminal ( 4 ) connected to a central server, each mobile terminal ( 4 ) being able to communicate to this server its position in the environment ( 2 ) and an identifier of a communicating object ( 1 ) provided with said radio transmitter ( 12 ) emitting said radio signal, the location of the communicating object ( 1 ) thus being carried out in a cooperative manner by involving several users ( 3 ) . Method according to Claim 8, characterized in that the central server estimates the position of the communicating object ( 1 ) by having available data for estimating the position of the radio transmitter ( 12 ) obtained at two different positions of at least least one user ( 3 ) provided with a mobile terminal ( 4 ). Mobile terminal ( 4 ) intended to equip a user ( 3 ) located in a position in an environment ( 2 ) predefined and configured to estimate the direction of arrival of a radio signal received by this mobile terminal ( 4 ), this terminal mobile ( 4 ) comprising: a short-range radio receiver (41 ) capable of measuring, during a capture session, the power of the radio signal received at a plurality of measurement points ( 51 ) around the user ( 3 ); a processor ( 42 ) configured to determine the measurement point ( 51 ) among said plurality of measurement points ( 51 ) around the user ( 3 ) at which the measured power of the received radio signal is minimum, the direction starting in a plane horizontal of the measurement point ( 51 ) determined towards the user ( 3 ) being considered to be the direction of arrival of the radio signal received at the position of the user ( 3 ) in the environment ( 2 ). Mobile terminal ( 4 ) according to the preceding claim, further comprising a motion sensor configured to associate an azimuth with each of the measurement points ( 51 ). Computer program product implemented on a memory medium, capable of being implemented within a computer processing unit and comprising instructions for implementing an estimation method according to one of Claims 1 to 6, or for the implementation of a location method according to any one of claims 7 to 9.