Method for activating a function of a vehicle

1. A method for activating a function of a vehicle from a portable access device borne by a user, said vehicle comprising a plurality of detection devices, each detection device comprising a presence detector, an antenna and an associated transceiver module able to communicate with the access device over an ultra-high-frequency communication link via said antenna, said transceiver module being electrically connected to an on-board computer in the vehicle, said method comprising:

authenticating the access device by the vehicle,

measuring the received signal strength of signals exchanged between the access device and the transceiver modules,

detecting, by one of the detectors, of human presence, the transceiver module associated with said detector then being called “main module” and the other transceiver modules being called “secondary modules”,

sending, to the computer, by the detection device comprising the main module, a human presence detection message,

sending, to the computer, by each detection device comprising a secondary module, the signal strength measurement performed between the access device and said secondary module,

receiving, by the computer, the signal strength measurements sent by the secondary modules and of the human presence detection message,

determining, by the computer, a position of the access device from the received signal strength measurements,

activating a function of the vehicle when the computer has received the detection message and the position of the authenticated access device is determined as being within a predetermined proximity zone around the vehicle,

wherein the signal strength measurement performed between the access device and the main module is either compensated or ignored.

2. The method as claimed in claim 1 , further comprising calculating, by the main module, a compensated signal strength value from the signal strength measurement performed between the access device and said main module and:

sending, to the computer, by the detection device comprising the main module, said compensated value,

receiving, by the computer, said compensated value,

the computer then using this compensated value and the measurements received from the secondary modules to determine the position of the access device, the activation of a function of the vehicle being performed only when the computer has received the detection message and the position of the authenticated access device is determined as being in a predetermined proximity zone around the vehicle.

3. The method as claimed in claim 1 , said method further comprising sending, to the computer, by the detection device comprising the main module, the signal strength measurement that is performed and, when the computer has received the detection message, calculating, by the computer, a compensated signal strength value based on the signal strength measurement received from the main module, the computer then using this compensated value and the measurements received from the secondary modules to determine the position of the access device.

4. The method as claimed in claim 2 , wherein the compensated value corresponds to a sum of the signal strength measurement performed between the access device and the main module and a predetermined value.

5. The method as claimed in claim 1 , wherein the signal strength measurements are performed by the access device.

6. The method as claimed in claim 1 , wherein the signal strength measurements are performed by the transceiver modules.

7. The method as claimed in claim 1 , wherein the position of the access device is determined through triangulation using the signal strength measurements received by the computer.

8. The method as claimed in claim 1 , wherein the access device ( 20 ) communicates with each of the transceiver modules over a Bluetooth® communication link.

9. A motor vehicle comprising:

a plurality of detection devices, each detection device comprising:

a presence detector,

an antenna and

an associated transceiver module able to communicate over an ultra-high-frequency communication link via said antenna with an access device associated with the vehicle and borne by a user, said transceiver module being able to measure or to receive a received signal strength measurement of signals exchanged between said access device and said transceiver module, the transceiver module associated with a presence detector detecting human presence then being called “main module” and the other transceiver modules being called “secondary modules”,

said detection device being electrically connected to at least one on-board computer in the vehicle and being able to send a presence detection message to said computer, and

at least one computer electrically connected to the plurality of detection devices and able to:

authenticate the access device,

receive a detection message from one of the detection devices,

receive signal strength measurements sent by the transceiver modules,

determine a position of the access device from the received signal strength measurements,

activate a function of the vehicle following the reception of a detection message and when the position of the authenticated access device is determined as being within a predetermined proximity zone around the vehicle,

wherein one or the other of the main module or the computer is able to compensate or to ignore the signal strength measurement performed between the access device and the main module.

10. A system for activating a function of a vehicle, comprising a vehicle as claimed in claim 9 and an access device borne by a user of the vehicle, able to authenticate itself with said vehicle and to communicate with the transceiver modules of the detection devices over an ultra-high-frequency communication link.

11. The method as claimed in claim 3 , wherein the compensated value corresponds to a sum of the signal strength measurement performed between the access device and the main module and a predetermined value.