Cooperation between two methods of geolocating a terminal in a wireless communication system

Abstract

The invention relates to a method (100) for geolocating a terminal (20i) via an access network of a wireless communication system. The invention relies on cooperation between a first geolocation method and a second geolocation method, as well as on controlling an operating mode of the terminals (20). When a terminal (20, 20i) is configured in a first operating mode, it allows the access network to estimate (102) the terminal's position using the first geolocation method. The positions estimated by the first geolocation method are used to train (103) the machine learning algorithm of the second geolocation method. Once the algorithm is trained, it then becomes possible to estimate (104) the geographic position of a terminal (20i) even if it is not in the first operating mode.The first geolocation method is more precise than the second geolocation method, but it requires greater energy consumption and / or radio resources for the terminals (20). Figure for the abstract: Fig. 3.

Description

Title of the invention: Cooperation between two methods of geolocation of a terminal of a wireless communication system Field of the invention

[0001] The present invention belongs to the field of geolocation of a terminal of a wireless communication system. The invention applies particularly well to the geolocation of connected objects of the loT type (English acronym for “Internet Of Things”) or of the M2M type (English acronym for “Machine-to-Machine”). State of the art

[0002] There are currently many solutions for obtaining the geographic position of a terminal at the level of an access network of a wireless communication system.

[0003] For example, the terminal may have a GPS receiver ("Global Positioning System" in the English literature) enabling it to determine its geographical position. The terminal may then transmit a message indicating this geographical position to the access network of the wireless communication system. Satellite geolocation is particularly precise, but it suffers from several drawbacks, in particular the cost and power consumption involved in integrating and using a GPS receiver in an object. In addition, transmitting a message including the geographical position of the terminal to the access network also has a negative impact on the power consumption of the terminal. This is particularly true for an IoT or M2M type communication system in which a message transmitted by a terminal must be as short as possible due to the strong constraints on throughput and power consumption.Also, GPS-type satellite geolocation methods are known to have relatively low response rates in closed or covered areas (e.g., in hangars, buildings, or densely wooded areas). "Response rate" is defined as a ratio of the number of times a position could actually be determined to the number of times an attempt was made to determine a position.

[0004] There are also geolocation methods based on a database making the association between an identifier of a transmitting device (for example a WiFi or Bluetooth access point) and the geographical position of the transmitting device. In such a method, a terminal detects an identifier of the transmitting device (the identifier is for example included in a message sent by the transmitting device on a beacon signal). The terminal can then transmit the detected identifier to the access network. The access network can then query a geolocation server comprising a database with a table associating identifiers of transmitting devices with their respective geographical positions. The geolocation server can then determine the geographical position associated with said transmitting device, then send this information to the access network. The geographical position of the transmitting device corresponds to an estimated geographical position of the terminal. The geographical position of the terminal can possibly be refined according to a power level with which the beacon signal is received by the terminal. It is also possible to estimate the geographical position of the terminal according to the geographical position of several neighboring transmitting devices whose identifiers the terminal has detected.However, these geolocation methods also require high power consumption from the terminals to listen for beacon signals and to transmit the identifiers of detected neighboring transmitting devices. Furthermore, these methods generally have relatively low response rates in areas with low population density and / or economic activity.

[0005] It is also known to estimate, at the access network level, the geographical position of a terminal based on messages transmitted by said terminal and received by one or more base stations of the access network. Such arrangements make it possible in particular to save energy on the terminal side and to reduce the cost of the terminal by simplifying it (it is in fact no longer necessary to integrate a GPS receiver or a WiFi or Bluetooth module at the terminal level).

[0006] For example, when the same message is received by several base stations with geographical positions known a priori, then the geographical position of said terminal can be estimated by comparing the reception power levels (“Received Signal Strength Indicator” or RSSI in the English literature) of the message on each of the base stations. However, many parameters (obstacles, multiple paths, etc.) can influence the reception power level of the message by a base station, so that the geographical position of the terminal thus estimated is not always very precise.

[0007] The geographical position of the terminal can also be estimated by comparing the arrival times (“Time of Arrival” or TOA in the English literature) and / or the arrival frequencies (“Frequency of Arrival” or FOA in the English literature) of the message for different base stations. However, this involves synchronizing the base stations with each other in time and / or frequency, and the accuracy of estimating the geographical position depends on the accuracy with which the base stations are synchronized. For applications of the IoT and / or M2M type, it is generally not desirable to implement fine synchronization of the base stations together as this would increase the complexity and manufacturing cost of the access network.

[0008] Other geolocation methods rely on machine learning techniques. Concretely, this involves building, during a calibration phase, a database that associates with known geographical positions a radio signature corresponding to all the RSSI levels measured for a terminal at a known position for a set of base stations in the system. Then, during a search phase, a radio signature observed for a terminal located at an unknown position is compared to all the signatures in the database in order to estimate the position of the terminal from the position(s) corresponding to the most similar signature(s). However, these methods generally suffer from a lack of geolocation precision, and they present fairly strong constraints in terms of complexity (capacity and computing time), particularly in the case where the geographical area to be covered is vast.In addition, it is necessary to carry out a calibration phase regularly to keep the database up to date. Statement of the invention

[0009] The present invention aims to remedy all or part of the drawbacks of the prior art, in particular those set out above, by proposing a solution bringing together two different geolocation methods having advantages and disadvantages that differ from each other.

[0010] For this purpose, and according to a first aspect, the present invention proposes a method for geolocating a terminal, called a “terminal of interest”, of a wireless communication system with an access network of said wireless communication system. The method comprises the following steps: - a determination of a criterion for bringing the terminal of interest into and / or out of a first operating mode, - an estimate, for each of a plurality of messages received by the access network from the terminal of interest, and possibly from other terminals of the wireless communication system, of a geographical position of the terminal at the origin of the message with a first geolocation method, each message of said plurality of messages being of a first type and being sent when the terminal at the origin of the message is in the first operating mode, - training of a machine learning algorithm of a second geolocation method from messages of the first type and associated geographic positions estimated with the first method of geolocation, said machine learning algorithm being trained to estimate the geographic position of a terminal from a message of a second type sent by the terminal when it is not in the first operating mode, - once the machine learning algorithm of the second geolocation method is trained, an estimation of the geographical position of the terminal of interest with the second geolocation method from a message of the second type sent by the terminal of interest.

[0011] The invention is based on cooperation between a first geolocation method and a second geolocation method, as well as on control of an operating mode of the terminals. When a terminal is configured in the first operating mode, it allows the access network to estimate the position of the terminal with the first geolocation method. The first geolocation method may in particular be based on determining, using a geolocation server, the geographical position of one or more neighboring transmitting devices (for example WiFi or Bluetooth access points) detected by the terminal. Other geolocation methods could however be implemented as the first geolocation method. For example, the geographical position of a terminal could be determined by the terminal using a receiver of a satellite positioning system and then transmitted to the access network.According to another example, the terminal could transmit to the access network measurements made by the terminal using one or more sensors (accelerometer, gyroscope, magnetometer, altimeter, pressure or temperature sensor, etc.) in order to allow the access network to estimate the position of the terminal. According to yet another example, the terminal could explicitly transmit to the access network a time and / or a frequency of arrival of a radio signal received by the terminal (geolocation method based on TOA and / or FOA with measurements made by the terminal).

[0012] The positions estimated by the first geolocation method make it possible to train the automatic learning algorithm of the second geolocation method. It then becomes possible, once the algorithm has been trained, to estimate the geographical position of a terminal even if it is not in the first operating mode.

[0013] The first geolocation method is generally more accurate than the second geolocation method. However, the first geolocation method generally requires higher energy consumption for the terminals. The second geolocation method can in fact be based on metadata associated with any message received from a terminal whose geographical position is to be estimated (for example, levels of power with which the message was received by base stations of the access network). No particular operation specific to geolocation is then required by the terminal for the second geolocation method (the message on which the second geolocation method is based may in particular have been sent for a purpose other than that of geolocating the terminal, and sending a classic message whose primary objective is not to geolocate the terminal is not considered to be an operation specific to geolocation).

[0014] It should be noted that the trade-off between geolocation accuracy and energy consumption is not necessarily the only trade-off that can be considered to favor one or the other of the two geolocation methods. Other criteria may be taken into account, such as response rate, radio resource utilization, etc.

[0015] The criterion for bringing the terminal of interest into the first operating mode and / or for bringing the terminal of interest out of the first operating mode may be defined according to whether a precise position of the terminal of interest is required or whether an approximate position of the terminal of interest is sufficient, according to the need to reduce the energy consumption of the terminal of interest, according to the possibility or not of using the first geolocation method, according to the need or not of training the automatic learning algorithm of the second geolocation method, according to whether the terminal is moving or not, etc.

[0016] In particular embodiments, the invention may further comprise one or more of the following characteristics, taken individually or in any technically possible combination.

[0017] In particular modes of implementation, the message of the first type explicitly contains a parameter used by the first geolocation method.

[0018] This means, for example, that the message comprises a set of bits encoding data transported by the message, and at least part of said bits encodes a parameter used by the first geolocation method.

[0019] It should be noted, however, that the first geolocation method might not require an explicit parameter, for example if the first method is based on a measurement by the access network of an arrival time and / or a frequency of arrival of the message for different base stations.

[0020] In particular modes of implementation, the parameter is at least part of an identifier of a transmitting device detected by the terminal at the origin of the transmission of the message of the first type.

[0021] The transmitting device corresponds for example to a WiFi or Bluetooth access point, or to an RFID tag (acronym for “Radio Frequency Identification”).

[0022] In one variant, the parameter could also correspond to a geographical position determined by the terminal using a receiver of a GPS-type satellite positioning system. According to another variant, the parameter could also correspond to a geographical position estimated by the terminal using measurements made by one or more sensors of the terminal. According to yet another variant, the parameter could also correspond to a set of measurements made by the terminal using one or more sensors (accelerometer, gyroscope, magnetometer, altimeter, pressure or temperature sensor, etc.). The parameter could also correspond to a time, a direction and / or a frequency of arrival of a radio signal received by the terminal (geolocation method based on TOA and / or FOA with measurements made by the terminal).

[0023] In particular modes of implementation, the message of the second type does not explicitly contain information used by the second geolocation method.

[0024] In particular embodiments, the machine learning algorithm is trained to associate a signature of a message with a geographic position. The signature comprises, for each of a plurality of base stations of the access network, a measurement of a power level with which said message is received by said base station.

[0025] In particular embodiments, the transmission of a message of the second type requires fewer radio resources, and / or less electrical energy for the terminal of interest, than the transmission of a message of the first type.

[0026] In particular modes of implementation, the criterion is defined by a configuration stored by the terminal of interest to make it enter and / or exit the first operating mode depending on predetermined periods of time.

[0027] In particular embodiments, the criterion for bringing the terminal of interest into and / or out of the first operating mode depends on an indication provided by a sensor of the terminal of interest.

[0028] In particular modes of implementation, the indication relates to: - the start or the end of a mobility phase of the terminal of interest, and / or - to an alert triggered by the fact that a measurement made by the sensor is greater than or less than a predetermined threshold, and / or - upon detection of an impossibility of forming a message of the first type.

[0029] In particular modes of implementation, the criterion for bringing the terminal of interest into and / or out of the first operating mode is defined by the access network and sent to the terminal of interest by the access network in a configuration message on a downlink communication link.

[0030] The configuration message allows, for example, the terminal of interest to be entered in the first operating mode during a learning period programmed by the access network. According to another example, the configuration message makes it possible to put the terminal of interest into the first operating mode when its position is to be known precisely. According to yet another example, the configuration message can be sent to the terminal of interest based on an estimate of a quality level of the geolocation of said terminal by the second geolocation method, etc.

[0031] The configuration message can be sent by point-to-point link (“unicast” in the English literature) or by broadcast. The broadcast can be local to a particular geographical area.

[0032] According to a second aspect, the present invention relates to a computer-readable recording medium comprising instructions which, when executed by a computer, cause the latter to implement the steps of the method according to any of the preceding embodiments.

[0033] According to a third aspect, the present invention relates to a server of an access network of a wireless communication system. The server is configured to: - estimate, for each of a plurality of messages received by the access network from a terminal of interest and possibly from one or more other terminals of the wireless communication system, a geographical position of the terminal at the origin of the message with a first geolocation method, each message of said plurality of messages being of a first type and being transmitted when the terminal at the origin of the message is in a first operating mode, - training a machine learning algorithm of a second geolocation method from the messages of the first type and the associated geographical positions estimated with the first geolocation method, said machine learning algorithm being trained to estimate the geographical position of a terminal from a message of a second type sent by said terminal when it is not in the first operating mode, - determine a criterion for entering and / or exiting the terminal of interest from the first operating mode, - send a configuration message to said terminal of interest to make it enter and / or exit the first operating mode according to the criterion thus determined, - once the machine learning algorithm of the second geolocation method is trained, estimate the geographic position of the terminal of interest with the second geolocation method from a message of the second type sent by the terminal of interest.

[0034] In particular embodiments, the invention may further comprise one or more of the following features, taken individually or in any technically possible combination.

[0035] In particular embodiments, the message of the first type explicitly contains a parameter used by the first geolocation method.

[0036] In particular embodiments, the parameter is an identifier of a transmitting device detected by the terminal at the origin of the transmission of the message of the first type.

[0037] In particular embodiments, the message of the second type does not explicitly contain information used by the first geolocation method.

[0038] In particular embodiments, the machine learning algorithm is trained to associate a signature of a message with a geographic position, said signature comprising, for each of a plurality of base stations of the access network, a measurement of a power level with which said message is received by said base station.

[0039] In particular embodiments, the criterion for bringing the terminal of interest into and / or out of the first operating mode is determined as a function of predetermined learning periods, or as a function of a level of urgency for geolocating the terminal of interest, or as a function of an estimation of a level of quality of the geolocation of said terminal of interest by the second geolocation method.

[0040] According to a fourth aspect, the present invention relates to an access network comprising a server according to any one of the preceding embodiments.

[0041] In particular embodiments, the access network is a low-power wireless wide area network.

[0042] According to a fifth aspect, the present invention relates to a Terminal of a wireless communication system, configured to: - determine a criterion for entering and / or exiting a first operating mode, - only when the terminal is in the first operating mode, transmit to the access network a message of a first type explicitly containing a parameter intended to be used by the access network to geolocate the terminal using a first geolocation method, - when the terminal is not in the first operating mode, send to the access network a message of a second type which can be used by the access network to geolocate the terminal using a second method of geolocation, the transmission of the message of the second type requiring less radio resources, and / or less electrical energy than the transmission of the message of the first type. Presentation of figures

[0043] The invention will be better understood on reading the following description, given by way of non-limiting example, and made with reference to Figures 1 to 3 which represent:

[0044] [Fig-1] a schematic representation of an exemplary embodiment of a system of wireless communication,

[0045] [Fig.2] a schematic representation of an example of embodiment of a terminal,

[0046] [Fig.3] a schematic representation of the main stages of a method of implementation implementation of a process for geolocating a terminal.

[0047] In these figures, identical references from one figure to another designate identical or similar elements. For reasons of clarity, the elements represented are not necessarily on the same scale, unless otherwise stated.

[0048] Detailed description of an embodiment of the invention

[0049] [Fig.l] schematically represents a wireless communication system 10, comprising terminals 20 and an access network 30 comprising several base stations 31.

[0050] The terminals 20 are adapted to transmit messages on an uplink to the access network 30. Each base station 31 is adapted to receive the messages from a terminal 20 when said terminal 20 is within its range. Conventionally, a message transmitted by a terminal 20 comprises an identifier of the terminal 20. Each message received by a base station 31 is for example transmitted to a server 32 of the access network 30, possibly accompanied by other information such as an identifier of the base station 31 which received it, the reception power level of said received message, the time of arrival of said message, the frequency at which the message was received, etc. The server 32 processes for example all the messages received from the different base stations 31.

[0051] The wireless communication system 10 may be unidirectional, that is to say that it only allows message exchanges on the uplink from the terminals 20 to the access network 30. However, nothing precludes, according to other examples, allowing bidirectional exchanges. Where appropriate, the access network 30 is also adapted to transmit, via the base stations 31, messages on a downlink to the terminals 20, which are adapted to receive them.

[0052] The exchanges of messages on the uplink to the access network 30 use a first wireless communication protocol.

[0053] In particular embodiments, the first wireless communication protocol is a low-power wireless wide area network (LPWAN) communication protocol. Such a wireless communication system is a long-range access network (greater than one kilometer, or even greater than a few tens of kilometers), with low energy consumption (for example, energy consumption during the transmission or reception of a message of less than 100 mW, or even less than 50 mW, or even less than 25 mW), and whose data rates are generally less than 1 Mbits / s. Such wireless communication systems are particularly suitable for loT or M2M type applications.

[0054] In an IoT or M2M type communication system, the data exchanges are essentially unidirectional, in this case on an uplink from the terminals 20 to the access network 30 of the wireless communication system 10. In order to minimize the risks of losing a message transmitted by a terminal 20, the planning of the access network is often carried out in such a way that a given geographical area is covered simultaneously by several base stations 31, such that a message transmitted by a transmitting device 20 can be received by several base stations 31.

[0055] In the remainder of the description, it is considered by way of non-limiting example that the first wireless communication protocol is a low-power, ultra-narrowband wireless wide area network communication protocol. By "ultra narrow band" ("Ultra Narrow Band" or UNB in ​​the English literature), it is meant that the instantaneous frequency spectrum of the radio signals emitted by the terminals has a frequency width of less than two kilohertz, or even less than one kilohertz.

[0056] A terminal 20 is also adapted to receive messages transmitted by at least one transmitting device 40, which is located in the vicinity of said terminal 20. The messages transmitted by the transmitting device 40 use a second wireless communication protocol, different from the first wireless communication protocol. It should be noted that the transmitting device 40 can be entirely independent of the wireless communication system 10, and it does not need to support the first wireless communication protocol.

[0057] In the example considered and illustrated in [Fig.l], the terminal 20a is in proximity to two transmitting devices 40 from which it can receive messages. The terminal 20i is in priority to another transmitting device 40 from which it can receive messages.

[0058] In particular embodiments, the second wireless communication protocol has a range less than the range of the first wireless communication protocol. It should be noted, however, that it is also possible, according to other examples, to have a second wireless communication protocol whose range is not in- lower than that of the first wireless communication protocol.

[0059] The second wireless communication protocol is for example a wireless local area network communication protocol (“Wireless Local Area Network” or WLAN in the English literature), for example of the WiFi type (IEEE 802.11 standards), etc., or a wireless personal area network communication protocol (“Wireless Personal Area Network” or WP AN in the English literature), for example of the Bluetooth or BLE type (English acronym for “Bluetooth Low Energy”, “Bluetooth à basse consommation” in French), etc. According to yet another example, the second wireless communication protocol may be a short-distance communication protocol based for example on NFC technology (English acronym for “Near Field Communication”, “communication en champ proche” in French) or on RFID technology (English acronym for “Radio Frequency Identification”, “identification par radiofréquences” in French).

[0060] A geolocation server 50 comprises a database, called a “geolocation database”, comprising a table storing identifiers of transmitting devices 40. Each transmitting device identifier 40 is associated in the table with at least one item of position information representative of the geographical position of the transmitting device 40.

[0061] An identifier of a transmitting device 40 corresponds for example to a MAC address of the transmitting device 40 (MAC is the acronym for “Media Access Control”). Other parameters could however play the role of identifier for a transmitting device 40, such as for example an SSID (an acronym for “Service Set IDentifier”) or a BSSID (an acronym for “Base Service Set IDentifier”) of a WiFi access point, an identifier of a Bluetooth or BLE access point, an identifier of an RFID tag, etc.

[0062] The position information may be directly coordinates (longitude, latitude and possibly altitude) of a geographical position of the transmitting device 40. The position information may however also be contextual information making it possible to estimate the geographical position of the transmitting device 40, such as for example a postal address, a store name, a name of a district, region or country, etc.

[0063] The geolocation server 50 is for example connected to the server 32 of the access network 30 by an internet connection.

[0064] [Fig.2] schematically represents an example of an embodiment of a terminal 20.

[0065] As illustrated by [Fig.2], the terminal 20 comprises a first communication module 21 adapted to exchange messages with the base stations 31 according to the first wireless communication protocol. The first communication module 21 is for example in the form of a radio circuit comprising equipment (antenna, amplifier, local oscillator, mixer, analog filter, etc.).

[0066] The terminal 20 also comprises a second communication module 22 adapted to receive messages transmitted by the transmitting device of interest 40, according to the second wireless communication protocol. The second communication module 22 is for example in the form of a radio electric circuit comprising equipment (antenna, amplifier, local oscillator, mixer, analog filter, etc.).

[0067] Furthermore, the terminal 20 also comprises a processing circuit 23, connected to the first communication module 21 and to the second communication module 22. The processing circuit 23 comprises, for example, one or more processors and storage means (magnetic hard disk, electronic memory, optical disk, etc.) in which a computer program product is stored, in the form of a set of program code instructions to be executed to implement all or part of the steps of a method for geolocating the terminal (the geolocation method will be detailed later with reference to [Fig. 3]).

[0068] The server 32 of the access network 30 also comprises one or more processors and storage means in which a computer program product is stored, in the form of a set of program code instructions to be executed to implement all or part of the steps of the method for geolocating a terminal.

[0069] The server 32 of the access network 30 is notably configured to implement a first method of geolocation of a terminal of interest 20i. In this first geolocation method, the terminal of interest 20i detects, for at least one neighboring transmitting device 40, an identifier of the transmitting device 40 (the identifier is for example included in a message transmitted by the transmitting device 40 on a beacon signal received by the terminal of interest 20i). The terminal of interest 20i can then transmit the detected identifier to the server 32 of the access network 30. The server 32 can then query the geolocation server 50. The geolocation server 50 can then determine the geographical position associated with said transmitting device 40, then send this information to the server 32 of the access network 30. The geographical position of the transmitting device 40 corresponds to an estimated geographical position of the terminal of interest 20i.The geographical position of the terminal can optionally be refined based on a power level with which the beacon signal is received by the terminal of interest 20i.

[0070] It is also possible, for this first geolocation method, to estimate the geographical position of a terminal as a function of the geographical position of several neighboring transmitting devices 40 whose identifiers the terminal has detected. This is the case, for example, for the terminal 20a in the example illustrated in [Fig.l].

[0071] This first geolocation method can be repeated for different messages comprising one or more identifiers of transmitting devices 40 transmitted by the terminal of interest 20i and possibly by one or more other terminals 20, 20a of the wireless communication system 10.

[0072] A terminal 20 may be configured to enter a first operating mode and / or to exit the first operating mode. When a terminal 20 is in the first operating mode, the terminal 20 is configured to detect one or more identifiers of neighboring transmitting devices 40 and to transmit them in one or more messages to the access network 30.

[0073] A message addressed by a terminal 20 to the access network 30 and comprising at least part of a transmitting device 40 detected by said terminal 20 is a message of a first type. In the example considered, a message of the first type therefore explicitly contains a parameter used by the first geolocation method. This explicit parameter corresponds to at least part of a transmitting device identifier 40. It is for example coded on a set of bits. The transmission of a message of the first type by a terminal 20 has a negative impact on the energy consumption of the terminal and on the use of radio resources (in the spectral domain and / or in the time domain) of the wireless communication system 10. Furthermore, when a terminal 20 is in the first operating mode, it consumes electrical energy to listen to the beacon signals of the detected transmitting devices 40.

[0074] The server 32 of the access network 30 is also configured to implement a second method of geolocation of the terminal of interest 20i. This second geolocation method is based on a machine learning algorithm trained to estimate the geographical position of the terminal of interest 20i from a message sent by said terminal of interest 20i and from a reference database constructed from the messages of the first type and the associated geographical positions estimated with the first geolocation method.

[0075] The reference database associates, for example, with each geographical position estimated with the first geolocation method a radio signature

[0076] corresponding to the different power levels with which the message of the first type was received by different base stations 31 of the access network 30.

[0077] Once the machine learning algorithm is trained, it becomes possible to estimate the geographic position of the terminal of interest 20i using the second geolocation method. For this, a radio signature of interest is de completed from a message sent by the terminal of interest. The radio signature of interest is then compared to all the signatures in the reference database. The geographic position of the terminal of interest 20i can then be estimated from the position(s) corresponding to the signature(s) in the reference database that most closely resemble(s) the radio signature of interest.

[0078] The accuracy of the second geolocation method is generally less good than the accuracy of the first geolocation method, in particular if the geographical area to be covered is vast and / or if the number of data in the reference database is not sufficiently large (it should however be noted, as indicated previously, that the invention could also be applied to a case where the geolocation method of the second method is as good as, or even better than, the accuracy of the first geolocation method).

[0079] However, the second geolocation method has the advantage that any type of message sent by the terminal of interest 20i can be used to estimate the position of the terminal of interest 20i. In particular, this message does not have to explicitly contain information used by the second geolocation method. Indeed, in the example considered, the second geolocation method is based on the power levels with which the base stations 31 of the access network 30 received the message, and not on explicit information contained in the message. No particular operation specific to geolocation is then required by the terminal of interest 20i for the second geolocation method (the message on which the second geolocation method is based may in particular have been sent for a purpose other than that of geolocating the terminal).To estimate the position of the terminal of interest 20i, the second geolocation method can therefore be based on a message of a second type sent by the terminal of interest 20i when it is not in the first operating mode (it should however be noted that nothing prevents the sending of a message of the second type when the terminal is in the first operating mode). In the example considered, the sending of a message of the second type requires fewer radio resources and less electrical energy for the terminal of interest 20i, than the sending of a message of the first type.

[0080] The invention advantageously relies on controlling the first operating mode of the terminals 20 in order to advantageously make the first geolocation method and the second geolocation method cooperate. When a terminal is configured in the first operating mode, it allows the access network to estimate the position of the terminal with the first geolocation method. The positions estimated by the first geolocation method make it possible to train the automatic learning algorithm of the second geolocation method. It then becomes possible, once the algorithm has been trained, to estimate the geographic position of a terminal even if it is not in the first operating mode.

[0081] The criterion for bringing the terminal of interest into the first operating mode and / or for bringing the terminal of interest 20i out of the first operating mode may be defined, for example, according to whether a precise position of the terminal of interest 20i is required or whether an approximate position of the terminal of interest 20i is sufficient. When a precise position of the terminal of interest 20i is required, it is appropriate to bring the terminal of interest 20i into the first operating mode so that it detects neighboring transmitting devices 40 and transmits the detected identifiers in order to allow precise geolocation of the terminal of interest 20i with the first geolocation method.When an approximate position of the terminal of interest 20i is sufficient, it is appropriate to take the terminal of interest 20i out of the first operating mode in order to save the energy consumed by the terminal of interest 20i and / or optimize the use of the radio resources of the communication system 10.

[0082] The criterion for bringing the terminal of interest into and / or out of the first operating mode may also be defined according to the need to reduce the energy consumption of the terminal of interest.

[0083] The criterion for bringing the terminal of interest into and / or out of the first operating mode may also be defined according to whether or not it is possible to use the first geolocation method. For example, if it is known that the terminal of interest 20i cannot be able to detect a neighboring transmitting device 40, it is appropriate to bring the terminal of interest 20i out of the first operating mode.

[0084] The criterion for bringing the terminal of interest 20i into and / or out of the first operating mode may also be defined according to the need or not to train the automatic learning algorithm of the second geolocation method. For example, if the number of data in the reference database is not sufficient, or if there is a risk that this data is obsolete, then it is appropriate to bring the terminal of interest 20i into the first operating mode so that it emits messages of the first type which will make it possible to update the reference database.

[0085] The criterion for bringing the terminal of interest 20i into and / or out of the first operating mode may be defined by a predetermined configuration stored by the terminal of interest 20i.

[0086] The criterion may in particular be defined as a function of predetermined time periods. For example, the terminal of interest 20i may be configured to enter / exit the first operating mode at regular intervals, or at recurring and increasingly less frequent intervals, etc.

[0087] According to another example, the criterion for bringing the terminal of interest 20i into and / or out of the first operating mode may depend on an indication provided by a sensor of the terminal of interest 20i. This indication may in particular relate to the start or end of a mobility phase of the terminal of interest 20i (it is for example advantageous to promote precise geolocation by activating the first operating mode at the start or end of a mobility phase of the terminal). The sensor used to determine the start or end of a mobility phase of the terminal of interest 20i may be an accelerometer. It may indeed be advantageous to favor one or the other of the two geolocation methods depending on whether the terminal of interest is moving or not.In particular, in the example considered where the first geolocation method is based on collaboration with transmitting devices, it may be advantageous to favor geolocation via the first geolocation method when the terminal is stationary, and favor geolocation via the machine learning algorithm of the second geolocation method when the terminal is in motion. According to another example, if the first geolocation method is based on a GPS receiver embedded in the terminal, it may be advantageous to favor geolocation via the first geolocation method when the terminal is in motion, and favor geolocation via the machine learning algorithm of the second geolocation method when the terminal is stationary.

[0088] This indication may also relate to an alert triggered by the fact that a measurement taken by the sensor is greater than or less than a predetermined threshold (need to obtain precise geolocation of the terminal by activating the first operating mode when an alert is detected).

[0089] The criterion for bringing the terminal of interest 20i into and / or out of the first operating mode may also be defined by the access network 30 and sent to the terminal of interest 20i by the access network 30 in a configuration message over a downlink communication link. The criterion may in particular be determined as a function of predetermined learning periods, or as a function of a level of urgency for geolocating the terminal of interest 20i, or as a function of an estimation of a level of quality of the geolocation of the terminal of interest 20i by the second geolocation method (for example, if the precision is insufficient, it is appropriate to bring the terminal into the first operating mode to obtain a more precise geolocation of the terminal with the first geolocation method, and / or to enrich the reference database of the second geolocation method).

[0090] The configuration message can be sent by point-to-point link (“unicast”) or by broadcast. The broadcast can be local to a particular geographic area.

[0091] [Fig. 3] schematically represents the main steps of an example of implementation of a method 100 according to the invention for geolocating a terminal of interest 20i in a communication system 10 such as that described with reference to [Fig. 1].

[0092] The method 100 comprises a step 101 of determining a criterion for bringing the terminal of interest 20i into and / or out of the first operating mode. This criterion can be determined as described previously. The choice of a particular method for determining this criterion is only a variant of the invention.

[0093] The method 100 comprises a step 102 of estimating, for each of a plurality of messages received by the access network 30 from the terminal of interest 20i, and possibly from other terminals 20, 20a, a geographical position of the terminal at the origin of the message with the first geolocation method. Each message of said plurality of messages is a message of the first type sent when the terminal at the origin of the message is in the first operating mode.

[0094] The method 100 comprises a step 103 of training the automatic learning algorithm of the second geolocation method. This training is done from the messages of the first type and the associated geographical positions estimated with the first geolocation method. The automatic learning algorithm is trained to estimate the geographical position of a terminal from any message sent by the terminal (and in particular a message of the second type which does not include explicit information for geolocation). Furthermore, the automatic learning algorithm can be trained to determine an accuracy with which the geographical position of the terminal has been estimated. This accuracy can in particular be used as a criterion for entering and / or exiting the terminal of interest from the first operating mode.

[0095] Once the machine learning algorithm of the second geolocation method is trained, the method 100 comprises a step 104 of estimating the geographical position of the terminal of interest 20i with the second geolocation method. This estimation 104 can in particular be carried out from a message of the second type sent by the terminal of interest 20i when it is not in the first operating mode.

[0096] The above description clearly illustrates that, through its various characteristics and their advantages, the present invention achieves the set objectives. In particular, the control of the first operating mode of the terminals advantageously makes it possible to intelligently cooperate the first geolocation method and the second geolocation method to reduce the energy consumption of the terminals and / or the radio resources of the communication system.

[0097] It should be noted that the implementation and embodiment modes considered above have been described as non-limiting examples, and that other variants are therefore conceivable.

[0098] The present invention finds in particular a particularly advantageous application, although in no way limiting, in the geolocation of connected objects of the loT or M2M type with an LPWAN type network. However, nothing excludes considering other types of wireless wide area network (WWAN). For example, the first wireless communication protocol could be a standardized communication protocol of the UMTS (Universal Mobile Telecommunications System), LTE (Long Term Evolution), LTE-Advanced Pro, 5G, etc. type.

[0099] The invention has been described by considering that the first method of geolocation of a terminal 20 is based on the determination of the geographical position of one or more neighboring transmitting devices 40 detected by the terminal using a geolocation server 50.

[0100] Other geolocation methods could however be implemented as a first geolocation method. For example, the geographical position of a terminal 20 could be determined by the terminal using a receiver of a satellite positioning system and then transmitted to the access network 30. According to another example, the terminal could transmit to the access network measurements made by the terminal using one or more sensors (accelerometer, gyroscope, magnetometer, altimeter, pressure or temperature sensor, etc.) in order to allow the access network to estimate the position of the terminal. According to yet another example, the terminal could transmit to the access network a time and / or a frequency of arrival of a radio signal received by the terminal (geolocation method based on TOA and / or FOA with measurements made by the terminal).

[0101] It should also be noted that there is no requirement that messages of the first type necessarily include an explicit parameter relating to the geographical position of the terminal 20 (for example, if the first geolocation method is a geolocation method based on TOA and / or FOA with measurements carried out by the access network 30).

[0102] The invention has been described by considering that the second geolocation method uses a machine learning algorithm based on radio signatures representative of the power levels with which a message is received by different base stations 31 of the communication system 10. However, nothing would prevent the machine learning algorithm from being based on other characteristics of a message transmitted by a terminal 20. For example, the following characteristics can be taken into account: time or frequency of reception of the message at the different base stations, identifiers of the base stations having received the message, etc.

[0103] Also, different types of machine learning algorithms are conceivable. These can be classification algorithms as well as regression algorithms. The choice of a particular machine learning algorithm for the second geolocation method is only a variant of the invention.

[0104] It should also be noted that not all terminals 20 of the communication system 10 necessarily need to support the first operating mode. Indeed, it is possible to train the automatic learning algorithm of the second geolocation method with only a portion of the terminals 20 of the access network 30 that support the first operating mode. As soon as the automatic learning algorithm is trained, it becomes possible to geolocate a terminal that does not support the first operating mode using the second geolocation method.

[0105] As mentioned previously, nothing prevents the sending of a message of the second type when the terminal is in the first operating mode. Also, nothing prevents the estimation of the position of a terminal with the second geolocation method based on a message of the first type sent by said terminal. In this case, it becomes possible to estimate the position of the terminal from the message of the first type not only with the first geolocation method, but also with the second geolocation method. Such arrangements can make it possible to compare the positions estimated with each method in order to determine a more precise position from the two estimated positions, and / or to improve the precision of one or other of the methods, etc.Such provisions can also improve the response rate for the geolocation of the terminal (for example, if in certain cases only one of the two methods can determine the position of the terminal, it is useful to be able to estimate the position of the terminal with both methods).

Claims

1. Claims Method (100) for geolocating a terminal (20), called "terminal of interest (20i)" of a wireless communication system (10) with an access network (30) of said wireless communication system (10), said method (100) comprising: - a determination (101) of a criterion for bringing the terminal of interest (20i) into and / or out of a first operating mode, - an estimation (102), for each of a plurality of messages received by the access network (30) from the terminal of interest (20i), and possibly from other terminals (20, 20a) of the wireless communication system (10), of a geographical position of the terminal at the origin of the message with a first geolocation method, each message of said plurality of messages being of a first type and being sent when the terminal at the origin of the message is in the first operating mode, - training (103) a machine learning algorithm of a second geolocation method from the messages of the first type and the associated geographical positions estimated with the first geolocation method, said machine learning algorithm being trained to associate a signature of a message with a geographical position, said signature comprising, for each of a plurality of base stations (31) of the access network (30), a characteristic relating to the reception of said message by said base station (31), in order to be able to estimate the geographical position of a terminal from a message of a second type transmitted by the terminal when it is not in the first operating mode, - once the machine learning algorithm of the second geolocation method is trained, an estimation (104) of the geographical position of the terminal of interest (20i) with the second geolocation method from a message of the second type sent by the terminal of interest (20i).

2. Method (100) according to claim 1 in which the message of the first type explicitly contains a parameter used by the first geolocation method, that is to say that data transported by the message of the first type encodes information used by the first geolocation method.

3. Method (100) according to claim 2 wherein the parameter is at least part of an identifier of a transmitting device (40) detected by the terminal (20a) at the origin of the transmission of the message of the first type.

4. Method (100) according to one of claims 1 to 3 in which the message of the second type does not explicitly contain information used by the second geolocation method, that is to say that no information used by the first geolocation method is encoded in data transported by the message of the first type.

5. Method (100) according to one of claims 1 to 4 wherein said characteristic relating to the reception of a message by a base station (31) is a power level with which said message is received by said base station (31).

6. Method (100) according to one of claims 1 to 5 in which the transmission of a message of the second type requires less radio resources, and / or less electrical energy for the terminal of interest (20i), than the transmission of a message of the first type.

7. Method (100) according to one of claims 1 to 6 in which the criterion is defined by a configuration stored by the terminal of interest (20i) to make it enter and / or exit the first operating mode according to predetermined time periods.

8. Method (100) according to one of claims 1 to 6 wherein the criterion for entering and / or exiting the terminal of interest (20i) from the first operating mode depends on an indication provided by a sensor of the terminal of interest (20i).

9. Method (100) according to claim 8 in which the indication relates to: - the start or the end of a mobility phase of the terminal of interest (20i), and / or - an alert triggered by the fact that a measurement carried out by the sensor is greater than or less than a predetermined threshold, and / or - to a detection of an impossibility of forming a message of the first type.

10. Method (100) according to one of claims 1 to 9 wherein the criterion for bringing the terminal of interest (20i) into and / or out of the first operating mode is defined by the access network (30) and sent to the terminal of interest (20i) by the access network (30) in a configuration message on a downlink communication link.

11. A computer-readable recording medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method (100) according to any one of claims 1 to 10.

12. Server (32) of an access network (30) of a wireless communication system (10), said server (32) being configured to: - estimate, for each of a plurality of messages received by the access network (30) from a terminal of interest (20i) and possibly from one or more other terminals (20, 20a) of the wireless communication system (10), a geographical position of the terminal at the origin of the message with a first geolocation method, each message of said plurality of messages being of a first type and being transmitted when the terminal at the origin of the message is in a first operating mode, - train an automatic learning algorithm of a second geolocation method from the messages of the first type and the associated geographical positions estimated with the first geolocation method,said machine learning algorithm being trained to associate a signature of a message with a geographical position, said signature comprising, for each of a plurality of base stations (31) of the access network (30), a characteristic relating to the reception of said message by said base station (31), in order to be able to estimate the geographical position of a terminal from a message of a second type sent by said terminal when it is not in the first operating mode, - determining a criterion for bringing the terminal in and / or out, of interest (20i) of the first operating mode, - sending a configuration message to said terminal of interest (20i) to make it enter and / or exit the first operating mode according to the criterion thus determined, - once the automatic learning algorithm of the second geolocation method is trained, estimating the geographical position of the terminal of interest (20i) with the second geolocation method from a message of the second type sent by the terminal of interest (20i).

13. Server (32) according to claim 12 in which the message of the first type explicitly contains a parameter used by the first geolocation method, that is to say that data transported by the message of the first type encodes information used by the first geolocation method.

14. Server (32) according to claim 13 in which the parameter is an identifier of a transmitting device detected by the terminal (20a) at the origin of the transmission of the message of the first type.

15. Server (32) according to one of claims 12 to 14 in which the message of the second type does not explicitly contain information used by the first geolocation method, that is to say that no information used by the first geolocation method is encoded in data transported by the message of the first type.

16. The server (32) of claim 15 wherein said characteristic relating to the reception of a message by a base station (31) is a power level with which said message is received by said base station (31).

17. Server (32) according to one of claims 12 to 16 wherein the criterion for bringing the terminal of interest (20i) into and / or out of the first operating mode is determined as a function of predetermined learning periods, or as a function of a level of urgency for geolocating the terminal of interest (20i), or as a function of an estimation of a level of quality of the geolocation of said terminal of interest (20i) by the second geolocation method.

18. An access network (30) comprising a server (32) according to any one of claims 12 to 17.

19. The access network (30) of claim 18, said access network (30) being a low-power wireless wide area network.

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