WO2008132088A1

WO2008132088A1 - Tracking method and device, and related computer software product, storage medium and radiocommunication module

Info

Publication number: WO2008132088A1
Application number: PCT/EP2008/054829
Authority: WO
Inventors: Thierry Lys
Original assignee: Wavecom
Priority date: 2007-04-20
Filing date: 2008-04-21
Publication date: 2008-11-06
Also published as: FR2915343A1; FR2915343B1

Abstract

The invention relates to a tracking method implemented by a tracking device that comprises a radiocommunication module for receiving radiocommunication carriers. The method comprises: a configuration phase comprising the step of selecting (E1) reference carriers among carriers detected by the radiocommunication module in reference geographical position of the tracking device; a utilisation phase comprising the following steps for at least one current geographical position of the tracking device: determining (E3) the current carriers detected by the radiocommunication module; detecting a movement of the tracking device (E4, E5, E6) by comparing the current carriers with the reference carriers.

Description

Method and tracking device, computer program product, storage means and corresponding radio communication module.

1. Field of the invention

The field of the invention is that of radiocommunications and more particularly tracking devices (also called tracers, or "tracking" devices) comprising an electronic radiocommunication module. The aforementioned radiocommunication module complies with a radiocommunication standard such as in particular, but not exclusively, GSM ("Global System for Mobile" in English), GPRS ("Global Packet Radio Service" in English), UMTS ( «Universal Mobile Telecommunications

Service "), Wideband Code Division Multiple Access (WCDMA), WiFi (" Wireless Fidelity "), Bluetooth standard, ...

More specifically, the invention relates to a technique for detecting movements of such devices. The invention finds particular applications in the field of locating or monitoring objects or individuals.

Thus, the invention applies in particular, but not exclusively, to GSM / GPS location systems (or GSM / GPS tracking device), allowing, for example, to send to a remote operator an alert message containing a information on the position of a stolen vehicle, or to trigger a local alarm.

2. Solutions and disadvantages of the prior art

Currently, more and more users are using the new GSM location services (also called GSM geolocation services, or LBS for "Location Based Services").

GSM localization has many applications. The user can for example use it to find the nearest hotel or restaurant, to have tourist information about the place he visits. Concerned parents can locate their child at any time. Professionals can locate their vehicles, track personnel, deliveries and detect a potential problem (for example, a movement of a construction vehicle out of an area allowed).

We already know a lot of GSM localization techniques.

Among the different types of known techniques, a first technique, called CeIl-ID (cell identification, in French), consists of locating a tracking device comprising a radio communication module, for example a mobile terminal, from the address a BTS ("Base Transciever Station" in English, "base station" in French) on which is locked the mobile terminal.

A second known technique, called EOTD ("Enhanced Observed Time Difference" in English), is based on the principle that a mobile terminal sends a signal to the neighboring base stations that are synchronized with each other. By analyzing the signal travel times, the position is estimated.

The reciprocal system (the BTS send a signal to the mobile at the same time) is called TDO ("Time Difference of Arrival").

These GSM localization techniques have represented an important progress in the positioning of an object or an individual (as well as for the detection of the movement of an object related to the absolute space). However, they have a number of disadvantages. First of all, the techniques (GSM) of the aforementioned prior art require the determination of at least two successive absolute positions to detect a movement (which can be described as absolute movement). Motion detection is therefore not optimal.

Another disadvantage of these known techniques lies in the fact that, in order to obtain position information, they require the implementation of carrier decoding (in order to read a cell identifier contained in the carrier signal). Implementing such decoding is expensive in terms of computing resources and power consumption.

In addition, the inventors have found that the current techniques mentioned above have a certain number of disadvantages in certain situations, particularly in the context of a construction vehicle surveillance, by example a backhoe loader, using a GSM / GPS hybrid tracking system.

More precisely and as illustrated in FIG. 1, the GSM / GPS 100 tracking system, which is embedded on the backhoe loader (not shown), comprises a GPS location module 1 which cooperates with a GSM radio communication module 2. Generally GPS tracking (or location) is accomplished by receiving signals from several satellites in orbit. These geostationary satellites are capable of sending accurate absolute position information to users.

At the end of the day, before leaving the site, the driver of the backhoe switches on the GSM / GPS 100 tracking system. The GPS 1 and GSM 2 radio positioning modules are then activated. At the start of the system 100, the GPS location module 1 initially calculates an initial absolute position, corresponding to the place where the driver has parked the backhoe loader on the site, then transmits Sl this initial absolute position information to a module processing 3, which stores it for example in a memory (not shown).

During the entire operating time of the system 100, the processing module 3 receives current absolute position information transmitted by the GPS location module 1. The processing module 3 compares the current absolute position received with the initial absolute position (stored in memory), so that if the current absolute position is different from the initial absolute position, then there is an absolute movement of the backhoe and the processing module 3 generates an alert signal S2.

The alert signal S2 is then transmitted to the GSM radio communication module 2. The GSM radiocommunication module 2 then switches to an alert mode, in which it transmits to a remote operator an alert message containing information relating to the current position of the backhoe loader.

The major disadvantage of the aforementioned GPS / GPS tracking system lies in the fact that the GPS location module is permanently on. Thus, the power consumption of such a system is not optimal. In addition, the GPS system is a stochastic system whose measurement accuracy can vary by several tens of meters, depending on the thickness of atmospheric layers. As a result, the GPS location module can calculate a current absolute position that is different from the initial absolute position, while the backhoe has not moved.

To remedy these problems, it is traditionally envisaged to associate a GPS location module and one or more motion detectors, for example accelerometers.

As illustrated in FIG. 2, this solution of the prior art consists of waking up the GPS location module 1 '(which is placed in a rest mode after the system 200 starts) when the accelerometers 4 detect a relative movement. The operation of the tracking system GSM / GPS 200, after awakening of the GPS location module 1 ', is identical to the operation of the tracking system GSM / GPS 100 which has been described in connection with Figure 1. The conditioned activation of the module GPS location 1 'thus allows to optimize the power consumption of the system and make it less sensitive to the erratic movements of satellites and jitter phenomena.

However, this known solution has the disadvantage of implementing one or more motion detectors which are expensive and sensitive to vibrations.

3. Objectives of the invention

The invention particularly aims to overcome these disadvantages of the prior art.

More specifically, an objective of the invention, in at least one of its embodiments, is to provide a tracking technique that is simple and effective to implement, especially in terms of detecting a displacement of a device. tracking.

Another object of the invention, in at least one of its embodiments, is to provide such a technique, which is particularly well suited to the detection of relative motion.

Another object of the invention, in at least one of its modes of embodiment, is to provide such a technique, which does not require carrier decoding operations to be performed by the GSM radio module.

The invention, in at least one of its embodiments, is also intended to provide such a technique that does not require the use of expensive motion detectors, in particular to activate a location module (GPS for example).

In other words, an object of the invention, in at least one of its embodiments, is to provide a compact GSM / GPS hybrid tracking system with low power consumption.

The invention, in at least one of its embodiments, also aims to provide such a technique that is inexpensive and compatible with all existing radiocommunication modules.

4. DESCRIPTION OF THE INVENTION In a particular embodiment of the invention, there is provided a tracking method implemented by a tracking device comprising a radio communication module allowing the reception of radiocommunication carriers. The method comprises: a configuration phase comprising a step of selecting the carrier N (s), said carrier (s) of reference, among carriers detected by the radiocommunication module in a reference geographical position of the tracking device with N≥l; a phase of use, comprising the following steps, for at least one current geographical position of the tracking device: * determination of carriers, said current carriers, detected by the radiocommunication module in said current geographical position of the tracking device; detection of a displacement of the tracking device outside a geographical reference zone comprising said reference geographical position, by comparison of the current carriers with the reference carrier (s). Thus, the invention is based on a completely new and inventive approach to the relative motion detection of a tracking device. Indeed, the invention is based on the comparison of carriers, without decoding thereof.

The invention therefore consists in obtaining a reference spectrum, formed by one or more reference carriers, and then detecting a modification of the reference spectrum. Thus, the relative motion detection according to the invention is conditioned by the fact that the radiocommunication module, in a given current position, receives new carriers or no longer receives one or more reference carriers. It should be noted that this is also a result of knowing that the radiocommunication module no longer receives any carrier.

It is also noted that the radiocommunication carriers can be transmitted by base stations of a radio communication network (for example GSM, UMTS, etc.) or by specific antennas (for example an antenna of a remote operator transmitting an tag according to the WiFi standard). According to the invention, the selection of the reference carriers can be performed automatically or manually by a user (via a man / machine interface).

According to an advantageous aspect of the invention, each carrier is defined by its frequency. The configuration phase includes a step of determining the power level with which each reference carrier is detected. In the use phase, there is positive displacement detection in case of verification, for each of at least M reference carrier (s), with l≤M≤N, of at least one of the following conditions: current carriers have the same frequency as said reference carrier; one of the current carriers has the same frequency as said reference carrier and is detected with a power level verifying a predetermined relationship to the power level with which said reference carrier has been detected. The present invention covers a first case in which displacement detection is done only by the analysis of the carrier frequencies. In in other words, it is checked whether the radiocommunication module always receives the carriers at the reference carrier frequencies, if this is not the case then it is estimated that a displacement is detected.

The invention also covers a second case in which the displacement detection is done by analyzing the carrier frequencies and the power levels. In other words, it is checked whether the radiocommunication module always receives the carriers at the reference carrier frequencies, if this is not the case then it is estimated that a displacement is detected, otherwise it is verified, for each carrier frequency of reference, if the power level of the current carrier is less than a first determined threshold or greater than a second determined threshold. According to the invention, the first and second thresholds are calculated (automatically or manually set by the user) from the power level of the reference carrier. By way of example, the first threshold may be equal to one hundredth of the power level of the reference carrier and the second threshold equal to one hundred times the power level of the reference carrier. In another variant, it is possible to envisage having first and second thresholds equal to the power level of the reference carrier. In the latter case, if the power level of the current carrier is different from the power level of the reference carrier, then it is estimated that a displacement is detected.

It is furthermore possible to envisage detecting displacement by analyzing an average of carrier power levels.

In a preferred embodiment of the invention, in the case of positive displacement detection, the use phase comprises a step of transmitting an alert signal by the radiocommunication module.

The warning signal according to the invention makes it possible, for example, to activate one or more alert modules external to the tracking device, such as audible alarms, means for specific SMS alert transmissions, deactivation means the engine of the vehicle on which the tracking device is embarked, etc.

Advantageously, in the case of positive detection of displacement, the phase of use comprises a step of activating a location module included in the tracking device.

Thus, the invention is based on a completely new and inventive approach for the activation of a location module (GPS for example). Indeed, the invention is based on the comparison of carriers, which therefore requires no motion detector (accelerometer for example).

In a first particular embodiment of the invention, the activation step of the location module is followed by the following steps: obtaining, with the location module, at least one absolute location information; transmission by the radiocommunication module of an alert message comprising said at least one absolute location information.

In a second particular embodiment of the invention, the activation step of the location module is followed by the following steps: obtaining, with the location module, at least one absolute location information; checking said displacement with the aid of said at least one absolute location information; - in case of positive verification, transmission by the radiocommunication module of an alert message.

Preferably, the step of selecting the N reference carrier (s) is performed in descending order of reception power level by the radiocommunication module. Advantageously, said method is implemented in said radiocommunication module.

In another embodiment, the invention relates to a computer program product downloadable from a communication network and / or recorded on a computer readable medium and / or executable by a processor, said computer program product comprising instructions program code for implementing the aforementioned tracking method, when said program is running on a computer.

In another embodiment, the invention relates to a storage medium, possibly completely or partially removable, readable by a computer, storing a set of instructions executable by said computer to implement the aforementioned tracking method.

In another embodiment, the invention relates to a tracking device comprising a radio communication module for receiving radiocommunication carriers. This device comprises: configuration means comprising carrier selection means (N) said reference carrier (s), among carriers detected by the radiocommunication module in a reference geographical position of the tracking device with N≥l; means for use, comprising, for at least one current geographical position of the tracking device: means for determining carriers, called current carriers, detected by the radiocommunication module in said current geographical position of the tracking device; means for detecting a displacement of the tracking device outside a geographical reference zone comprising said reference geographical position, by comparison of the current carriers with the reference carrier (s).

More generally, the tracking device according to the invention comprises means for implementing the tracking method as described above (in any one of its various embodiments).

In another embodiment, the invention relates to a radiocommunication module for receiving radiocommunication carriers and can be included in a tracking device.

This module comprises: - configuration means comprising means for selecting

N carrier (s), called reference carrier (s), among carriers detected by the radiocommunication module in a reference geographical position of the tracking device, with N≥1; means for use, comprising, for at least one current geographical position of the tracking device: means for determining carriers, called current carriers, detected by the radiocommunication module in said current geographical position of the tracking device; means for detecting a displacement of the tracking device outside a geographical reference zone comprising said reference geographical position, by comparison of the current carriers with the reference carrier (s).

5. List of figures

Other features and advantages of the invention will emerge more clearly on reading the following description of a preferred embodiment, given as a simple illustrative and nonlimiting example, and the appended drawings, among which: FIG. 1 , already commented on in relation to the prior art, presents the simplified diagram of a conventional GSM / GPS hybrid tracking system; - Figure 2, also commented in connection with the prior art, shows the simplified diagram of a GSM / GPS hybrid tracking system with motion detectors; Figure 3 shows the simplified diagram of a tracking device according to a particular embodiment of the invention; FIG. 4 represents a flowchart illustrating a particular embodiment of the method according to the invention, in the case where the selection of the reference carriers is carried out by the tracking device; and FIG. 5 shows the simplified structure of a particular embodiment of a radiocommunication module according to the invention. 6. Detailed description The general principle of the invention is based on the detection of a displacement of a tracking device comprising a radio communication module, based on a comparison of carriers detected by the radiocommunication module. As already indicated, the invention successively implements a comparison of frequencies and a comparison of power levels.

The tracking method according to the invention is implemented either in the aforementioned radiocommunication module, or in a dedicated processing module, included in the tracking device. For the sake of simplification of the description, throughout the remainder of this document, reference will be made to the particular case where the tracking method of the invention is implemented in a dedicated processing module, cooperating with a module of radiocommunication allowing the reception of GSM carriers. Of course, the invention applies to any other type of carrier, in particular, but not exclusively, to carriers transmitted by specific antennas (in the WiFi standard, etc.).

In the remainder of this document, it is assumed that the tracking device of the invention is embedded in a construction vehicle (backhoe for example).

A tracking device 300 according to a particular embodiment of the invention will now be described with reference to FIG.

In this embodiment, the tracking device 300 according to the invention comprises: processing means 31 specific to the invention; a GSM 32 radiocommunication module specific to the invention; and a GPS location module 33 of conventional type per se.

In an alternative embodiment, it is possible to combine the processing means 31 and the GSM radiocommunication module 32 in the same housing.

The processing means 31 comprise a memory 310 in which are stored reference carriers, received (that is to say detected) by the GSM radio communication module 32 in a geographical position of reference of the tracking device 300, and detection means 320 of a displacement of the tracking device.

As will be seen in the remainder of the description, the detection means 320 comprise first comparator means 3201 making it possible to compare carrier frequencies and second comparator means 3202 making it possible to compare carrier power levels.

In more detail, at the end of the day, before leaving the building site, the driver of the backhoe switches on the tracking device 300 (according to a variant of use, the system can be constantly lit). The GSM radiocommunication module 32 and the processing means 31 are then activated. At startup (referenced "instant t0" in Figure 3), the GPS location module 33 is placed in a rest mode. At time t0, the device 300 (which is loaded on the backhoe loader) is in a reference geographical position. In this reference position, the radiocommunication module GSM 32 receives carrier GSM (also called BCCH tags in GSM terminology) Pl (Fl ₅ Nl), P2 (F2, N2) and P3 (F3, N3) via an antenna 34 Each of the detected GSM carriers (P1, P2 and P3) is characterized by a carrier frequency (F1, F2 and F3) and a power level (N1, N2 and N3).

In the present embodiment, the processing means 31 implement a reference carrier selection algorithm which can be expressed as follows: among the detected GSM carriers P1, P2 and P3, selection of the two carriers having the levels highest power. This selection is made in descending order of power level. In the example described, consider the following relation: N1>N2> N3. For the rest of the description, Pl (Fl ₅ Nl) and P2 (F2, N2) are therefore taken as reference carriers. The reference carriers Pl (Fl ₅ Nl) and P2 (F2, N2) are then stored in the memory 310.

Note that in another particular embodiment, the driver can himself select, via a man / machine interface located for example in the vicinity of the dashboard of the backhoe loader, reference carriers among the detected GSM carriers P1, P2 and P3. After registering the reference carriers in the memory 310, at a time tθ + 1, the GSM radio module 32 receives via the antenna 34 common carriers P4 (F4, N4) and P5 (F5, N5). The latter are transmitted to the detection means 320. In a first step, the first comparison means 3201 verify whether the number of current carriers is equal to the number of reference carriers stored in the memory 310.

In case of inequality, the detection means 320 indicate to the GSM radio module 32 that a displacement of the tracking device 300 is detected. The radiocommunication module 32 then generates an alert signal S3. The alert signal S3 is transmitted to the GPS location module 33. Upon receipt of this alert signal S3, the GPS location module 33 switches from the idle mode to a work mode; in other words GPS is enabled. Thus, the GPS location module 33 obtains via an antenna 35 an absolute location information, then transmits it to the radio communication module 32. The radio communication module 32 then transmits via the antenna 34 an alert message comprising the information of absolute location of the GPS. In an alternative embodiment, it is possible to condition the sending of the alert message by verifying the movement of the device 300 using the absolute location information.

On the other hand, in case of equality between the number of current carriers and the number of reference carriers, the first comparator means 3201 checks whether the current carriers have the same carrier frequencies as the reference carriers stored in the memory 310. negative verification case, ie if at least one of the frequencies

Fl and F2 of the reference carriers P1 and P2 are not equal to one of the frequencies F4 and F5 of the current carriers P4 and P5, then the detection means 320 indicate to the GSM radio module 32 that a displacement of the device tracking 300 is detected. As a result, an alert signal S3 is generated by the radiocommunication module 32, the GPS location module 33 is then activated by the alert signal S3, then an alert message including the GPS absolute location information is transmitted.

On the other hand, in the case of positive verification, that is, if the frequencies

Fl and F2 of the reference carriers P1 and P2 are equal to the frequencies F4 and F5 of the current carriers P4 and P5, while the second comparison means 3202 in turn verify whether the current carriers have the same power levels as the reference carriers. , at identical carrier frequencies.

For the rest of the description, the following relations are considered: F1 = F4; N1 = N4; F2 = F5 and N2> N5. In this example, the second comparison means 3202 compare the power level N1 of the first reference carrier P1 with the power level N4 of the first current carrier P4 (because F1 = F4), and the power level N2 of the second reference carrier P2 with the power level N5 of the second current carrier P5 (because F2 = F5). In this case, the second comparison means 3202 detect firstly that the power level N1 is equal to the power level N4, and secondly that the power level N2 is greater than the power level N5. The power levels N2 and N5 being different, the detection means 320 indicate to the GSM radio module 32 that a displacement of the tracking device 300 is detected. As a result, the radiocommunication module 32 generates the alert signal S3. The GPS location module 33, which is activated by the warning signal S3, transmits an absolute location information to the radiocommunication module 32. Finally, the radiocommunication module 32 transmits (for example to a remote operator) via its antenna. communication 34 an alert message including the GPS absolute location information.

FIG. 4 shows a flowchart illustrating a particular embodiment of the method according to the invention, in the case where the selection of the reference carriers is carried out by the tracking device 300. radiocommunication module 32, included in the tracking device 300 which is placed in a geographical position of reference, receives carriers for example from a terrestrial public network of a mobile operator (for example the GSM network operator SFR).

A configuration phase comprises a first step El, during which the processing means 31 implement a reference carrier selection algorithm. In a particular embodiment, the selection may consist of classifying the detected carriers in a decreasing order of power level, then selecting the first two carriers of this classification.

During a step E2, the two reference carriers selected in step E1 are stored in the memory 310 (included in the device 300). The following steps relate to a phase of use.

During a step E3, the radiocommunication module 32, included in the tracking device 300 which is placed in a current geographical position, receives current carriers. During this step, the radiocommunication module 32 transmits the detected current carriers to the displacement detection means 320.

During a step E4, the first comparison means 3201 (included in the detection means 320) check whether the number of current carriers

(detected in step E3) is equal to the number of reference carriers (stored in memory 310 in step E2). In case of positive verification, we go to a step E5, otherwise we go to a step E7 (a displacement of the device is detected).

In step E5, the first comparison means 3201 checks whether the current carriers (detected in step E3) have the same frequencies as the reference carriers (stored in the memory 310 in step E2). In case of positive verification, we go to a step E6, otherwise we go to step E7 (a displacement of the device is detected).

In step E6, the second comparison means 3202 checks whether the current carriers have, at identical carrier frequencies (that is to say those determined in step E5), the same power levels as the carriers. reference. In case of positive verification, it returns to step E3 (no movement of the device is detected), otherwise we go to step E7 (a displacement of the device is detected). Then, during step E7, the detection means 320 indicate to the radiocommunication module 32 that a displacement of the tracking device 300 is detected. During this step, the radiocommunication module 32 generates and transmits an alert signal S3 to the locating module 33. Finally, during a step E8, the locating module 33 switches from the idle mode to the working mode. The locating module 33 then transmits to the radiocommunication module 32 an absolute location information. Finally, the radiocommunication module 32 transmits (to a remote operator for example) an alert message including the absolute location information. FIG. 5 schematically shows the structure of a radiocommunication module 500 according to a particular embodiment of the invention, which comprises a memory 510, and a processing unit 520 equipped with a microprocessor μP, which is controlled by a computer program (or application) 530 implementing certain steps of the method according to the invention described in FIGS. 3 and 4. The processing unit 520 receives as input current carriers 540. The microprocessor μP processes these carriers, according to the instructions of the program 530, to obtain an alert signal 550.

Although the invention has been described above in relation to a limited number of embodiments, the skilled person, upon reading the present description, will understand that other embodiments can be imagined without departing from the present invention. of the present invention.

In particular, the analysis of the power levels can consist in: checking whether the power level of the current carrier is lower than a first determined threshold or greater than a second determined threshold; - check whether the power level of the current carrier is different from the power level of the reference carrier; checking whether the average power levels of the current carriers are different from the average power levels of the reference carriers; -

Claims

1. Tracking method implemented by a tracking device (300) comprising a radio communication module (32) for receiving radiocommunication carriers, characterized in that it comprises: - a configuration phase comprising a step (El ) selection of N carrier (s), said reference carrier (s), among carriers detected by the radiocommunication module in a reference geographical position of the tracking device, with N≥l; a phase of use, comprising the following steps, for at least one current geographical position of the tracking device: determination of carriers, called current carriers, detected by the radiocommunication module in said current geographical position of the device of tracking; detection (E4, E5, E6, E7) of a displacement of the tracking device outside a geographical reference zone comprising said reference geographical position, by comparison of the current carriers with the reference carrier (s).

2. Method according to claim 1, characterized in that each carrier is defined by its frequency, in that the configuration phase comprises a step of determining the power level with which each reference carrier is detected, and in that, in the use phase, there is positive displacement detection in case of verification, for each of at least M reference carrier (s), with l≤M≤N, of at least one of the following conditions: current carriers have the same frequency as said reference carrier; one of the current carriers has the same frequency as said reference carrier and is detected with a power level verifying a predetermined relationship to the power level with which said reference carrier has been detected.

3. Method according to any one of claims 1 and 2, characterized in that, in case of positive displacement detection, the use phase comprises a step of transmitting an alert signal by the radiocommunication module.

4. Method according to any one of claims 1 and 2, characterized in that, in case of positive displacement detection, the use phase comprises a step (E8) of activation of a location module included in the tracking device.

5. Method according to claim 4, characterized in that the activation step of the location module is followed by the following steps: obtaining, with the location module, at least one absolute location information; transmission by the radiocommunication module of an alert message comprising said at least one absolute location information.

6. Method according to claim 4, characterized in that the activation step of the location module is followed by the following steps: obtaining, with the location module, at least one absolute location information; checking said displacement using said at least one absolute location information; in case of positive verification, transmission by the radiocommunication module of an alert message.

7. Method according to any one of claims 1 to 6, characterized in that the step of selecting the N reference carrier (s) is performed in descending order of receiving power level by the radiocommunication module.

8. Method according to any one of claims 1 to 7, characterized in that it is implemented in said radiocommunication module (32).

9. Computer program product downloadable from a communication network and / or recorded on a computer readable medium and / or executable by a processor, characterized in that it comprises program code instructions for implementing the method according to at least one of claims 1 to 8, when said program is executed on a computer.

10. Storage medium, possibly completely or partially removable, readable by a computer, storing a set of instructions executable by said computer to implement the method according to at least one of claims 1 to 8.

11. Tracking device (300) comprising a radiocommunication module (32) for receiving radiocommunication carriers, characterized in that it comprises: configuration means comprising means for selecting N carrier (s), said ( s) reference carrier (s), among carriers detected by the radiocommunication module in a reference geographical position of the tracking device, with N≥1; means of use, comprising, for at least one current geographical position of the tracking device: means for determining carriers, called current carriers, detected by the radiocommunication module in said current geographical position of the tracking device; means for detecting a displacement of the tracking device outside a geographical reference zone comprising said reference geographical position, by comparison of the current carriers with the reference carrier (s).

12. Radiocommunication module (32) for receiving radiocommunication carriers and which can be included in a tracking device (300), characterized in that it comprises: configuration means comprising means for selecting the carrier N (s) said reference carrier (s), among carriers detected by the radiocommunication module in a reference geographical position of the tracking device, with N≥1; means of use, comprising, for at least one current geographical position of the tracking device:

means for determining carriers, called current carriers, detected by the radiocommunication module in said current geographical position of the tracking device;

means for detecting a displacement of the tracking device outside a geographical reference zone comprising said reference geographical position, by comparison of the current carriers with the reference carrier (s).