METHOD FOR ACTIVATING A VEHICLE FUNCTION AND ASSOCIATED ACTIVATION DEVICE

Abstract

The invention relates to a method for activating a vehicle function by means of an activation device (D) comprising at least three ultra-high frequency transceivers capable of communicating with a portable access device (SD), the method comprising the following steps: Arranging the transceivers around each opening defining an access zone, Activating communication between the transceivers and the device, Receiving the signals and measuring the power of the received signal by each transceiver, Calculating a power difference between the transceivers located around the same opening, Comparing said differences with thresholds, Locating said device within an access zone based on the results of said comparisons, Selecting said corresponding pair of transceivers, Activating communication with the selected transceivers, and deactivating the other transceivers.Location of said equipment with said pair of transmitters / receivers; activation of the vehicle function, if the equipment is located in the predetermined area. Figure for the abbreviation: Fig. 1.

Description

Title of the invention: METHOD FOR ACTIVATING A VEHICLE FUNCTION AND ASSOCIATED ACTIVATION DEVICE technical field

[0001] The invention relates to a method for activating a vehicle function and an associated vehicle function activation device. The invention relates particularly to the field of hands-free vehicle access, i.e., unlocking and locking the vehicle doors, but not exclusively. The invention can be applied to functions that can be activated once the user's position is determined in an area near the vehicle. Functions that can be activated even before the user unlocks their vehicle may include switching on a welcome light (also called "welcome lighting"), or pre-setting radio stations, etc. Previous technique

[0002] In a motor vehicle, it is known to use vehicle function activation devices capable of detecting the presence of a user's hand or foot and thus enabling the locking or unlocking of all or part of the vehicle's openings, for example, the doors or the trunk. For example, detecting the presence of a user's hand on or in front of a door handle, coupled with the recognition of an identifier of a "hands-free" access device worn by that user, allows these openings to be locked and unlocked.

[0003] A so-called "hands-free" access system for a motor vehicle allows an authorized user to lock and / or unlock the vehicle's doors without having to physically press buttons on a key. To do this, the vehicle identifies a portable device, such as a badge, remote control, or even a key, carried by the user. If the badge, remote control, or key is located within a predetermined area around or inside the vehicle and is identified as belonging to the vehicle, then the vehicle automatically locks / unlocks its doors according to the user's intention, without the user having to physically handle a key.

[0004] To do this, when the user approaches the vehicle, communication is established over a wireless communication link between the "hands-free" access equipment, for example an electronic badge or a smartphone, and the vehicle function activation device to authenticate said access equipment using its identifier.

[0005] To this end, the activation device includes at least one radio frequency antenna enabling the reception of the identifier sent by the "hands-free" access equipment. The activation device is connected to an electronic control unit of the vehicle ("ECU": English abbreviation for "Electronic Control Unit") to which it transmits the identifier.

[0006] According to the prior art, the access equipment is generally an electronic badge. The signal received by the activation device's antenna, including the access equipment identifier, is transmitted via RF (Radio Frequency) or LF (Low Frequency) waves. The precise location of the wearable device around the vehicle is achieved by measuring the intensity of the LF signal received by the wearable device (via the antennas and the electronic control unit) from the vehicle, more commonly known as RSSI (Received Signal Strength Indication) measurements.The power of each signal received by the portable equipment from each antenna of the plurality of LF antennas located on the vehicle V is received and analyzed by an activation device, onboard in the vehicle, which thus determines, by triangulation, the position of the portable equipment relative to said LF antennas, i.e. relative to the vehicle.

[0007] Depending on the location of the portable equipment identified by the vehicle, in said location zones certain actions specific to said location zones are automatically carried out, unlocking / locking or prior activation of the interior lighting (also called "welcome lighting" in English).

[0008] Nowadays, however, it is increasingly common to use a mobile phone for authentication functions, thus avoiding the need for a dedicated electronic badge and reducing the number of devices required. Most mobile phones do not have RF or LF communication capabilities. It therefore becomes necessary to adapt the hands-free access and / or start system to a vehicle so that it can also work with a mobile phone equipped with other communication standards, such as, for example, Ultra Wideband (UWB), Bluetooth Low Energy (BLE), or Wi-Fi (wireless fidelity), and not only via radio waves and low frequencies (RF, LF). Ultra Wideband (UWB), in particular, is a radio modulation technique based on the transmission of very short pulses, often less than a nanosecond. Thus, the bandwidth can reach very high values.

[0009] Approaching the access equipment close to the activation device (less than 2m) and recognizing the identifier received by the computer, coupled or not with the detection of the presence of the user's hand, allows the door to be locked or unlocked.

[0010] The disadvantage of such a process using high or ultra-high frequency lies in the need for the vehicle to accurately locate the position of the user.

[0011] Recently, localization methods using the phase of Bluetooth signals have been developed, also called "Bluetooth Channel Sounding" in English or channel sounding process in French.

[0012] Unlike traditional techniques such as using power with RSSI (Received Signal Strength Indication), or measuring the time of flight of signals, using phase in Bluetooth allows for more precise measurements of the distance between the vehicle and the user. By analyzing the phase of the signals received across the entire Bluetooth frequency band, it is possible to improve the accuracy of user location.

[0013] However, this localization method is significantly impacted in a reflective propagation environment, i.e., an environment containing obstacles located around the vehicle. The Bluetooth signals are then reflected off these obstacles, and their phase value is affected, thus distorting the distance measurement.

[0014] It is therefore known to remedy this drawback by classifying or categorizing Bluetooth transmitters and receivers according to a quality indicator in order to use only transmitters and receivers whose emitted waves do not undergo, for example, reflection on obstacles.

[0015] The quality indicator is estimated using an algorithm for processing the signal received after a Bluetooth communication phase used to locate the portable equipment for the first time.

[0016] Not only is the Bluetooth communication phase time-consuming, as it uses the entire communication band, i.e. 72 channels each with a width of 1MHz, and requires 72 continuous exchanges between the vehicle and the access equipment, but also the algorithm used to classify / categorize the transmitters and receivers is very complex and time-consuming as well.

[0017] It takes between 300ms and 500ms per transceiver to be "classified", i.e. 2 seconds if four Bluetooth transceivers are on board the vehicle, in order to enable a second, more precise localization of the user around the vehicle.

[0018] The invention proposes a vehicle function activation method that overcomes the aforementioned drawbacks, more specifically an activation method that locates the user around the vehicle more quickly and reliably. Description of the invention

[0019] The invention relates to a method for activating a vehicle function by means of an activation device intended to be installed on a motor vehicle, the device comprising at least three ultra-high frequency transceivers capable of communicating with a portable access device worn by a user, the vehicle function being triggered by the detection of the presence of said portable device in a predetermined zone around the vehicle and by authentication of said device, the method being remarkable in that it comprises the following steps: a. Prior arrangement of the transceivers on either side of the vehicle's openings, thus forming a pair, each pair of transceivers defining an access zone around said corresponding opening, b. Activation of ultra-high frequency communication between the transceivers and the access device and authentication of said device. c. Reception of signals by the transceivers from the access equipment and measurement by each transceiver of the power of the received signal, d. Calculation, for each pair of transmitter-receivers located on either side of the same opening, of a value representing the difference in power of the received signal between said transmitter-receivers. e. Comparisons of said calculated differences with predetermined power difference thresholds, f. Location of said equipment within the access zone defined by a pair of transmitter-receivers based on the results of said comparisons, g. Selection of said transmitter-receiver pair corresponding to the access zone, h. Activation of ultra-high frequency communication only with the selected transceiver pair, and deactivation of the other transceivers, i. Localization of said equipment by ultra-high frequency communication with the activated transceiver pair, j. Activation of the vehicle function, if the said equipment is located in the predetermined area around the vehicle.

[0020] Preferably the power difference thresholds are four in number, consisting of two different values ​​and their opposites.

[0021] Advantageously, the location of the access equipment relative to the predetermined area is achieved by ultra-high frequency channel scanning.

[0022] The invention also relates to any vehicle function activation device intended to be installed on a motor vehicle, said device comprising at least three ultra-high frequency transceivers capable of communicating with a portable access device worn by a user, the function being triggered by detection of the presence of said portable device in a predetermined area around the vehicle and by authentication of said device, the device being notable in that the transceivers are arranged on either side of the vehicle's openings, thus forming a pair, and in that it further comprises: a. Means for authenticating said access device, b. Means for measuring, by each transceiver, the power of the received signal, c. Calculation methods for each pair of transmitter-receivers located on either side of the same aperture, based on a value representing the difference in power of the received signal between said transmitter-receivers, d. Means of comparing said differences calculated with predetermined power difference thresholds, e. Means of locating said equipment within an access zone defined by a pair of transceivers based on the results of said comparisons f. Means for selecting said pair of transmitter-receivers corresponding to the access zone, g. And means of activating ultra-high frequency communication only with the said selected pair of transmitters and receivers, and deactivating the other transmitters and receivers, h. Means of locating said equipment by ultra-high frequency communication with the activated transceiver pair, i. Means of activating the vehicle function depending on the location of said equipment in relation to the predetermined area around the vehicle.

[0023] Preferably, the location means locate the access equipment relative to the predetermined area and include ultra-high frequency channel probing means.

[0024] The invention relates to any computer program product comprising program code instructions and included in an activation device according to any one of the above characteristics and suitable for performing the steps of: a. Activation of ultra-high frequency communication between the transceivers and the access equipment, and authentication of said equipment, b. Reception of signals by the transceivers from the access equipment and measurement by each transceiver of the power of the received signal, c. Calculation, for each pair of transmitter-receivers located on either side of the same opening, of a value representing the difference in power of the received signal between said transmitter-receivers. d. Comparisons between said calculated differences and predetermined power difference thresholds, e. Location of said equipment within an access zone defined by a pair of transmitter-receivers based on the results of said comparisons, f. Selection of said pair of transmitters / receivers corresponding to the access zone, g. Activation of ultra-high frequency communication only with the selected transceiver pair, and deactivation of other transceiver pairs, h. Localization of said equipment by ultra-high frequency communication with the activated transceiver pair, i. Activation of the vehicle function, if the said equipment is located in the predetermined area around the vehicle.

[0025] Finally, the invention also relates to any motor vehicle comprising an activation device according to any one of the characteristics listed above. Brief description of the drawings

[0026] Other features and advantages of the invention will become apparent from the following description. This description is purely illustrative and should be read in conjunction with the accompanying drawings, in which:

[0027] [Fig.1]: [Fig.1] is a schematic representation of a motor vehicle equipped with a device for activating a vehicle function according to the invention,

[0028] [Fig.2]: [Fig.2] is a schematic representation of an activation device according to the invention,

[0029] [Fig.3]: [Fig.3] is a schematic representation of the four zones location around the vehicle determined according to the activation method of the invention,

[0030] [Fig.4]: [Fig.4] illustrates a scenario of a user located near a door side of the vehicle,

[0031] [Fig. 5]: [Fig. 5] illustrates a scenario of a user located near the safe of the vehicle,

[0032] [Fig.6]: [Fig.6] is a flowchart representing the different steps of the process activation according to the invention. Description of the implementation methods

[0033] Figure 1 illustrates a motor vehicle V equipped with an activation device D according to the invention.

[0034] Device D comprises four Bluetooth Low Energy BLE transceivers El, E2, E3, E4, capable of communicating at a frequency between 2.402 GHz and 2.480 GHz with a portable access device (SD) such as, for example, a smartphone.

[0035] The four transmitter-receivers E1, E2, E3, E4 are electronically connected to a central control unit 10 intended to manage communication between the vehicle V and the access equipment.

[0036] If the SD access equipment determined through Bluetooth communication is located in a predetermined area Z0 around the vehicle V and if it is authenticated as an access equipment authorized to access the vehicle, then the vehicle function, such as unlocking the doors, is activated.

[0037] This is known from the prior art.

[0038] As explained previously, the disadvantage of the process of activating a vehicle function using Bluetooth communication lies in the inaccuracy of locating the SD access equipment, which requires a time-consuming step of classifying or categorizing the transceivers according to their Bluetooth communication quality in order to use only those that are the most accurate.

[0039] The invention proposes to remedy this. The invention proposes a device D and a method for activating a vehicle function that eliminates this Bluetooth classification / categorization step.

[0040] For this purpose, according to the invention, the transmitter-receivers El, E2, E3, E4 are located on either side of the openings 01, 02, 03, 04 present on the vehicle V. This is illustrated in [Fig.1].

[0041] For example, the first transmitter-receiver El and the second transmitter-receiver E2 are located on either side of a first opening 01 which corresponds to the front left door, driver's side.

[0042] The second transmitter receiver E2 and the third transmitter receiver E3 are located on either side of a second opening 02 which corresponds to the rear trunk of the vehicle V.

[0043] And finally the third transmitter receiver E3 and the fourth transmitter receiver E4 are located on either side of a third opening 03 which corresponds to the front right door, 03 passenger side.

[0044] The last opening 04 is the hood of the vehicle V, and the fourth and first transmitter receiver E4, E are located on either side of said hood.

[0045] It is important to note that each opening 01, 02, 03, 04 must be "framed" by two transmitter-receivers, on each side, in order for the activation method according to the invention to function.

[0046] Each pair of transmitter-receivers thus defines an access zone Z1, Z2, Z3, Z4 around said corresponding opening.

[0047] The transmitter-receiver pair consisting of the first and second El, E2 transmitter-receivers define a first access zone Zl around the first opening 01.

[0048] The transmitter-receiver pair consisting of the second and third opening E2, E3 transmitter-receivers define a second access zone Z2 around the second opening 02.

[0049] The transmitter-receiver pair consisting of the third and fourth opening E3, E4 transmitter-receivers define a third access zone Z3 around the third opening 03.

[0050] Finally, the transmitter-receiver pair consisting of the fourth and first E4 transmitter-receivers define a fourth access zone Z4, around the fourth opening 04.

[0051] According to the invention, the activation device D further comprises (see [Fig.2]): a. Means of authentication Ml of said SD access equipment, b. Measurement means M2 by each transmitter receiver El, E2, E3, E4 of a power of the received signal PE1, PE2, PE3, PE4; c. Calculation means M3 for each pair of transmitters (El, E2), (E2, E3), (E4, E3) (E4, El) receiver located on either side of the same opening 01, 02, 03, 04 of a power difference value API, AP2, AP3, AP4, of the signal received between said transmitters and receivers; d. Means of comparison M4 for each pair of transmitter-receivers of said difference calculated with a predetermined power difference threshold, SI, S2, e. Means of locating said SD equipment M5 within an access zone defined by a pair of transceivers based on the results of said comparisons f. Means of selecting M6 of said transmitter-receiver pair, g. And means of activating M7 ultra-high frequency communication only with said selected transceiver pair, and deactivating the other transceivers, h. Means of locating said equipment within the M8 access zone by means of ultra-high frequency communication with the activated transceiver pair, i. Means of activating M9 of the vehicle function depending on the location of said equipment in relation to the predetermined area around the vehicle.

[0052] The authentication means M1, the measurement means M2, the calculation means M3, the comparison means M4, the localization means M5, the selection means M6, the activation means M7, the localization means M8 and the activation means M9 are preferably in the form of software integrated into a microcontroller located in the central control unit 10.

[0053] The activation device D also includes a processor 100 and a memory 101 (see [Fig.2]); for example integrated into the central control unit 10, in which instructions are stored to configure the processor to execute certain particular processing, in particular to implement the steps of the vehicle function activation process, according to the embodiment as described below.

[0054] The authentication means M1 are capable of verifying that the identifier sent by the access equipment corresponds to an identifier stored as authorized to access the vehicle V

[0055] The measurement means M2 are capable of determining the power of the signal received by Bluetooth communication, i.e. the RSSI, for each transceiver.

[0056] The calculation means M3 are capable of calculating the power difference of the received signal between two transmitters and receivers El, E2, E3, E4 located on either side of the same opening 01, 02, 03, 04.

[0057] For example, as illustrated in [Fig.3].

[0058] A first API power difference is calculated between the power of the signal received by the first transmitter receiver PE1 and the power of the signal received by the fourth transmitter receiver PE4.

[0059] That is:

[0060] [Math.l] AP1 = PE1-PE4

[0061] Similarly, a second power difference AP2 is calculated between the power of the signal received by the second transceiver PE2 and the power of the signal received by the third transceiver PE3.

[0062] That is:

[0063] [Math.2] AP2 = P£2-P£3

[0064] A third power difference AP3 is calculated between the power of the signal received by the fourth transceiver PE4 and the power of the signal received by the third transceiver PE3.

[0065] That is:

[0066] [Math.3] AP3 = PE4-PE3

[0067] Finally, a fourth power difference AP4 is calculated between the power of the signal received by the first transmitter-receiver PE1 and the power of the signal received by the second transmitter-receiver PE2.

[0068] That is:

[0069] [Math.4] AP4 = PE1-PE2

[0070] The comparison means M4 then compare for each pair of transmitter-receivers, the power difference API, AP2, AP3, AP4, thus calculated with predetermined power difference thresholds SI, S2, -SI and -S2.

[0071] For example, Sl=5 dB, -Sl=-5dB, S2=10 dB, and -S2=-10 dB.

[0072] In this case, the comparison means M4 compare: a. APIs with IF and -IF values, b. AP2 to Sl and to - Sl, c. AP3 at S2 and -S2, d. AP4 to S2 and to -S2.

[0073] The location means M5 locate said equipment SD in relation to the access zones Z1, Z2, Z3, Z4 defined by the transmitter-receiver pairs (respectively (E1, E2), (E2, E3), (E3, E4), (E4, E1)) according to the result of said comparisons.

[0074] More specifically, and as illustrated in [Fig. 3], if

[0075] [Math.5] AP1< -SI

[0076] Then the SD access equipment is located in the access zone Z3 defined by the third opening 03.

[0077] If:

[0078] [Math.6] AP1>S1 And [Math.6] AP2>S1

[0079] Then the SD access equipment is located in the access zone ZI defined by the first opening 01.

[0080] If:

[0081] [Math.7] AP3>S2^ AP4>S2

[0082] Then the SD access equipment is located in the access zone Z4 defined by the fourth opening 04.

[0083] And finally, yes:

[0084] [Math.8] AP3< -S2 And [Math.8] AP4< -S2

[0085] Then the SD access equipment is located in the access zone Z2 defined by the second opening 02.

[0086] Depending on the access zone in which the SD access equipment is located, the selection means M6 then select the pair of transmitter-receivers defining said access zone.

[0087] Then, the M7 ultra-high frequency activation means activate the pair of transmitter-receivers thus selected in ultra-high frequency communication and deactivate the pairs of transmitter-receivers furthest from the SD access equipment, i.e. the pairs of transmitter-receivers defining the access zones other than the access zone in which the SD access equipment is located.

[0088] This is illustrated in figures 4 and 5.

[0089] In [Fig.4], we have:

[0090] [Math.9] AP1< -SI

[0091] Consequently, the SD access equipment is located in the access zone Z3 defined by the third opening 03, i.e., the user U is near the front passenger-side door of the vehicle V. In this case, the transceivers that remain active in ultra-high frequency communication are the third and fourth transceivers E3, 4. The first and second transceivers E1, E2 are then deactivated.

[0092] In [Fig.5], we have:

[0093] [Math. 10] P3>S2 And [Math. 10] AP4>S2

[0094] Consequently, the SD access equipment is located in the access zone Z4 defined by the third opening 04, i.e. that the user U is located near the rear trunk of the vehicle V. In this case, the transceivers that remain activated in ultra high frequency communication are the first and fourth transceivers El, 4. The third and second transceivers E3, E2 are then deactivated.

[0095] The M8 location means then precisely locate the SD access equipment within said access zone using ultra-high frequency communication. More specifically, this location is achieved by "Bluetooth Channel Sounding." This Bluetooth channel sounding location method is known in the prior art and will not be detailed here.

[0096] The vehicle function activation means M9 then triggers the unlocking (or locking) depending on the location of the access equipment relative to a predetermined zone Z0 allowing remote unlocking or locking of the "hands-free" type.

[0097] It should be noted that the invention applies from at least three transmitter-receivers E1, E2, E3 on board the vehicle V and located on either side of an opening 01, 02.

[0098] By calculating the difference in received power, for example AP4, AP2 between the two pairs formed by three transmitters and by comparing it to the threshold values ​​S2, SI and -SI, -S2, it is possible to know if the access equipment SD is in front of the first opening 01 or in front of the second opening 02 and thus activate only the two transmitter-receivers which are on each side of said opening and deactivate the third transmitter-receiver.

[0099] The method of activating a vehicle function, illustrated in [Fig.6], will now be described.

[0100] In a preliminary step (not shown in [Fig.6]) at least four transmitter-receivers El, E2, E3, E4 are placed on either side of each opening 01, 02, 03, 04 of the vehicle V. Each pair of transmitters thus placed on or in the vehicle V defines an access zone Z1, Z2, Z3, Z4 around the corresponding opening.

[0101] Then in a first step El, all four transceivers are activated in Bluetooth communication in order to communicate with a hands-free SD access device worn by the user U (see [Fig. 1]).

[0102] During this first step El, the signals are sent back by the access equipment SD to the transceivers El, E2, E3, E4.

[0103] Still during this step, the Bluetooth signals from the SD access equipment are received by the four transceivers. And each transceiver measures the strength of the signal it receives, i.e., the "RSSI" or "Received Signal Strength Indication".

[0104] Then in a second step E2, for each pair of transmitter-receivers located on either side of the same opening, a value of the difference in the power of the received signal between the two said transmitter-receivers is calculated.

[0105] A first API power difference is calculated between the power of the signal received by the first transmitter receiver El and the power of the signal received by the fourth transmitter receiver E4.

[0106] Either

[0107] [Math.l] AP1 = PE1-PE4

[0108] Similarly, a second power difference AP2 is calculated between the power of the signal received by the second transceiver E2 and the power of the signal received by the third transceiver E3.

[0109] That is:

[0110] [Math.2] AP2 = PE2-PE3

[0111] A third power difference AP3 is calculated between the power of the signal received by the fourth transceiver E4 and the power of the signal received by the third transceiver E3.

[0112] That is:

[0113] [Math.3] AP3 = PE4-PE3

[0114] Finally, a fourth power difference AP4 is calculated between the power of the signal received by the first transceiver El and the power of the signal received by the second transceiver E2.

[0115] That is:

[0116] [Math.4] AP4 = PE1-PE2

[0117] In a third step E3, the power differences thus calculated are compared to predetermined power difference thresholds SI, S2, -SI, -S2.

[0118] These power difference thresholds consist of two values ​​SI, S2, each applied to the emitter-receiver pairs located on the two opposite sides of the vehicle and their opposites -SI, -S2 applied to the other emitter-receivers located on the two other opposite sides of the vehicle V. This is illustrated in [Fig.3].

[0119] In this case, a. API is compared to SI and to-SI, b. AP2 is compared to Sl and -Sl, c. AP3 is compared to S2 and -S2, d. AP4 is compared to S2 and to -S2.

[0120] In particular, the following comparisons are verified:

[0121] [Math.5] A PI < -SI And [Math.5] AP2< -SI

[0122] [Math.6] AP1>S1 And [Math.6] AP2>S1

[0123] [Math.7] kP3>S2et AP4>52

[0124] [Math.8] AP3< -S2 And [Math.8] AP4< -S2

[0125] During a fourth step E4, based on the comparisons made above, the SD access equipment is located in one of the access zones Z1, Z2, Z3 or Z4.

[0126] In this case, if one of the above conditions is verified, then the SD access equipment is located in an access zone defined by the transceivers for which the comparison of received power with one of the predetermined thresholds is verified.

[0127] This has been explained previously.

[0128] Once the SD access equipment has been located in one of the four access zones, then in the fifth step E5, the pair of transmitter-receivers Ei, Ej defining the access zone in which the SD access equipment has been located is selected.

[0129] Then at the sixth step E6, only the transmitter-receiver pair defining this particular access zone are activated in Bluetooth communication, the other transmitter pairs are then deactivated and no longer transmit in Bluetooth.

[0130] At the seventh step E7, the SD access equipment is located relative to the predetermined zone Z0 solely by means of the pair of transmitter-receivers thus selected.

[0131] This localization step is carried out using the "Bluetooth Channel Sounding" method, which is known to those skilled in the art.

[0132] In the next step, E8, it is determined whether the SD access equipment is located in the predetermined zone Z0.

[0133] If the SD access equipment is located in the predetermined zone Z0 allowing remote activation of certain vehicle functions, then said functions are activated (step E9), such as, for example, but not limited to, unlocking or locking the vehicle openings V.

[0134] On the contrary, if the SD access equipment is not located in the predetermined zone Z0 around the vehicle V, then no function is activated, and the process returns to the first step El.

[0135] The invention therefore makes it possible ingeniously to locate the access equipment around the vehicle quickly, reliably and robustly, thus overcoming the disadvantages of the prior art.

Claims

1. Demands Method of activating a vehicle function by means of an activation device (D) intended to be installed on a motor vehicle (V), the device (D) comprising at least three ultra-high frequency transceivers (E1, E2, E3, E4) capable of communicating with a portable access device (SD) worn by a user (U), the vehicle function being triggered by detection of the presence of said portable device (SD) in a predetermined zone around the vehicle (ZO) and by authentication of said device, the method being characterized in that it comprises the following steps: a. Prior arrangement of the transmitter-receivers (E1, E2, E3, E4) on either side of the vehicle's openings (O1, O2, O3, O4), thus forming a pair, each pair of transmitter-receivers defining an access zone (Z1, Z2, Z3, Z4) around said corresponding opening, b. Activation of ultra-high frequency communication between the transceivers (El, E2, E3, E4) and the access equipment (SD) and authentication of said equipment (step El), c. Reception of signals by the transceivers (E1, E2, E3, E4) from the access equipment (SD) and measurement by each transceiver of the power of the received signal (PE1, PE2, PE3, PE4) (step E1), d. Calculation for each pair of transmitter-receivers located on either side of the same opening of a value of difference in power of the received signal (API, AP2, AP3, AP4) between said transmitter-receivers (step E2), e. Comparisons of said calculated differences with predetermined power difference thresholds (SI, -SI, S2, -S2) (step E3), f. Location of said equipment in the access zone (Z1, Z2, Z3, Z4) defined by a pair of transmitter-receivers according to the result of said comparisons, (step E4) g. Selection of said transmitter-receiver pair corresponding to the access zone, (step E5) h. Activation of ultra-high frequency communication only with said transceiver pair selected, and deactivation of the other transceivers (step E6), i. Location of said equipment by ultra high frequency communication with the activated transceiver pair (step E7), j. Activation of the vehicle function, if said equipment is in the predetermined zone (ZO) around the vehicle, (steps E8 and E9).

2. Activation method according to the preceding claim, characterized in that the power difference thresholds are four in number, consisting of two different values ​​(SI, S2) and their opposites (-S1,-S2).

3. Activation method according to claim 1 or 2, characterized in that the localization of the access equipment (SD) relative to the predetermined area is carried out by ultra-high frequency channel scanning.

4. Activation device (D) for a vehicle function intended to be installed on a motor vehicle (V), said device comprising at least three ultra-high frequency transceivers (E1, E2, E3, E4) capable of communicating with a portable access device (SD) worn by a user (U), the function being triggered by detection of the presence of said portable device (SD) in a predetermined zone (ZO) around the vehicle and by authentication of said device, the device being characterized in that the transceivers (E1, E2, E3, E4) are arranged on either side of the vehicle's openings, thus forming a pair, and in that it further comprises: a. Authentication means (M1) for said access device, b. Measurement means (M2) by each transceiver of a power of the received signal (PE1, PE2, PE3, PE4), c.Calculation means (M3) for each pair of transmitter-receivers located on either side of the same opening of a value of difference in power of the received signal (API, AP2, AP3, AP4) between said transmitter-receivers,. d. Means of comparison (M4) of said differences calculated with predetermined power difference thresholds (SI, -SI, S2, -S2), e. Means of locating said equipment (SD) in an access zone (Z1, Z2, Z3, Z4) defined by a pair of transceivers according to the result of said comparisons f. Means for selecting said pair of transmitter-receivers corresponding to the access zone, g. And means for activating (M7) ultra-high frequency communication only with said selected transceiver pair, and deactivating the other transceivers, h. Means of locating said equipment by ultra-high frequency communication with the activated transceiver pair, i. Means of activating (M9) the vehicle function according to the location of said equipment in relation to the predetermined area around the vehicle.

5. Activation device (D), according to the preceding claim, characterized in that the location means (M5) locate the access equipment relative to the predetermined area and include ultra-high frequency channel probing means.

6. A computer program product comprising program code instructions and included in an activation device according to any one of claims 4 or 5, characterized in that it is adapted to perform the steps of: a. Activation of ultra-high frequency communication between the transceivers and the access equipment and authentication of said equipment (step El), b. Reception of signals by the transceivers from the access equipment and measurement by each transceiver of the power of the received signal (step El), c. Calculation for each pair of transmitter-receivers located on either side of the same opening, with a value of

7. difference in the power of the received signal between said transmitters and receivers (step E2), d. Comparisons between said calculated differences and predetermined power difference thresholds (step E3), e. Location of said equipment in an access zone defined by a pair of transmitter-receivers according to the result of said comparisons, (step E4) f. Selection of said pair of transmitters / receivers corresponding to the access zone, (step E5) g. Activation of ultra-high frequency communication only with the selected transceiver pair, and deactivation of the other transceiver pairs (step E6), h. Localization of said equipment by ultra-high frequency communication with the activated transceiver pair (step E7), i. Activation of the vehicle function, if the said equipment is located in the predetermined area around the vehicle (steps E8 and E9). Motor vehicle (V), characterized in that it comprises an activation device according to any one of claims 4 or 5.

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