Super high frequency continuous communication and positioning method for portable devices for hands-free access to motor vehicles

Abstract

The invention relates to a method and a system for communicating with and locating a portable device (T) by means of UHF, the portable device (T) being intended for "hands-free" access to a motor vehicle (V) on board of which a communication device (D) is present, the communication device (D) comprising a UHF transceiver (10), a power supply (Vcc) and at least one antenna (A), the motor vehicle (V) comprising a first arrangement in which the transceiver (10) is connected to the antenna (A) and a second arrangement in which the transceiver (10) is disconnected from the antenna (A) and then connected to an attenuation module (M1, M2, M3) located at a predetermined distance (L1, L2, L3) from the transceiver (10), the attenuation module (M1, M2, M3) comprising an impedance (Z1, Z2, Z3) with a predetermined value to ground, the predetermined distance (L1, L2, L3) between the transceiver (10) and the attenuation module (M1, M2, M3) and the predetermined value of the impedance (Z1, Z2, Z3) defining a location area (A1, A2, A3) for locating the portable device (T) in and around the motor vehicle (V). The method comprises the following steps: a) alternating (110) between the first arrangement and the second arrangement according to a predetermined ratio between the duration of activation of the first arrangement and the duration of activation of the second arrangement, b) maintaining the connection activity on the dedicated channel after the establishment of at least one dedicated data channel between the motor vehicle (V) and the portable device (T), c) configuring (120) the motor vehicle (V) to send at least one status request message (Mds) to the portable device (T) at at least one predetermined frequency and to receive at least one status confirmation message (Mcs) and configuring the portable device (T) to receive the status request message (Mds) and to send the status confirmation message (Mcs) to the motor vehicle (V) in response to the reception of the status request message (Mds), d) calculating (130) the reception success rate of the status request message (Mds) by the portable device (T), e) comparing (140) the reception success rate of the status request message (Mds) with a predetermined success rate, and f) locating the portable device (T) according to the result of the comparison.

Description

Technical Field

[0001] This invention relates to a system for communicating with and locating a portable device via ultra-high frequency (UHF) for "hands-free" access to a motor vehicle. Another subject of the invention is a method for implementing the system according to the invention. Background Technology

[0002] This invention is particularly applicable to systems for “hands-free” access to motor vehicles. A so-called “hands-free” access system allows authorized users to lock and / or unlock the ouvrant of their motor vehicle without using a key. To this end, the motor vehicle identifies and locates a badge or remote control carried by the user, and when the motor vehicle recognizes that the badge or remote control is associated with the motor vehicle and is located within the access area, the motor vehicle locks or unlocks its ouvrant.

[0003] Those skilled in the art are familiar with such "hands-free" access systems. They typically consist of an electronic control unit mounted in the vehicle, at least one radio frequency (RF) antenna located on the vehicle, and an identification remote control or badge carried by the user, which includes the RF antenna.

[0004] The exchange of identifiers between the badge and the vehicle via a radio frequency antenna enables the vehicle to recognize the badge and trigger the locking or unlocking of the unlocking mechanism.

[0005] Identifiers may be included in portable devices other than badges or remote controls, for example, in portable phones or watches.

[0006] Identifiers are typically exchanged via radio frequency (RF) waves and low frequency (LF) waves. The vehicle first sends an LF interrogation signal via its LF antenna, and if the badge is within the receiving area of ​​the signal, the badge sends back an RF presence message containing its identifier to the vehicle.

[0007] The badge is accurately located around the vehicle by measuring the strength of the LF signal received by the badge from the vehicle (via antennas and an electronic control unit). This measurement is commonly referred to as RSSI measurement (Received Signal Strength Indication, or a measurement of the received power of the signal received by the antennas). The positioning device onboard in the vehicle analyzes the power measurements of the signal received by the badge from each LF antenna of the vehicle to determine the badge's position relative to those LF antennas, i.e., relative to the vehicle.

[0008] This RSSI measurement enables the accurate positioning of badges around and inside a motor vehicle, allowing for the locking / unlocking of opening components, and also enabling the starting of the motor vehicle when the badge is detected inside the vehicle.

[0009] More and more portable devices, such as mobile phones, are now equipped with Bluetooth® or Bluetooth Low Energy (BLE) communication standards, which are ultra-high frequency (UHF) communications from 2400 MHz to 2480 MHz. The advantage of this communication standard is its universality, so it does not require country-specific approval (only “Bluetooth Low Energy” international certification is required), whereas the current RF / LF communication standards are the opposite, with their operating frequencies varying from country to country.

[0010] Therefore, the hands-free access system needs to be adapted to work with Bluetooth® or Bluetooth Low Energy (BLE) communication standards, instead of relying solely on radio frequency waves and low frequency waves (RF / LF).

[0011] The advantage of Bluetooth® or Bluetooth Low Energy (BLE) communication standards is that they enable a relatively large communication range of approximately 250m around a vehicle. However, it cannot detect the presence of portable devices at shorter distances. This is, for example, when a portable device is located a few centimeters away from a vehicle and the user wants to unlock the vehicle. However, this usage is possible with existing RF and LF wave-switched communication devices. In fact, the RSSI measurement of Bluetooth signals is very inaccurate and varies greatly depending on the surrounding environment (noise, interference), making it difficult to determine whether a portable device is 5m, 10m, 40m, or further away. Therefore, specific calibration is required to suit the specific characteristics of each portable device.

[0012] Therefore, starting a motor vehicle using Bluetooth® or Bluetooth Low Energy (BLE) communication is also difficult, as starting is only authorized when the portable device is inside the vehicle and a few centimeters from the vehicle's UHF antenna. However, given the considerable variability in the characteristics of portable devices, detecting such a portable device a few centimeters from the UHF antenna is impossible.

[0013] Document FR3040551B1 proposes an ultra-high frequency (UHF) positioning device for portable devices, which enables the mitigation of these drawbacks. UHF refers to the radio spectrum band between 300 MHz and 3000 MHz, i.e., wavelengths between 1 m and 0.1 m.

[0014] More precisely, the existing UHF positioning device enables the detection of portable devices at distances ranging from a few centimeters to a few meters around a motor vehicle and at a few centimeters from the UHF antenna mounted on the vehicle. This makes “hands-free” activation possible using Bluetooth® or Bluetooth Low Energy (BLE) communication standards, which was previously impossible with these communication standards in the prior art.

[0015] Therefore, such as Figure 1a The prior art positioning device D shown includes a power supply Vcc for powering a transceiver 10, which is electrically connected to at least one antenna A via a wire 20A. Furthermore, the prior art positioning device D includes at least one attenuation module M1 on the (transmit / receive) communication wire 20 between the transceiver 10 and the antenna A. Finally, the prior art positioning device D also includes a control component 30 for controlling the attenuation module M1 and a determining component 40 for determining the location of the portable device.

[0016] Therefore, the prior art positioning device D enables the range of ultra-high frequency waves to be "downgraded" from the prior art's maximum range of 250m to approximately a few centimeters, so as to accurately define the positioning area of ​​the portable device in and around the motor vehicle.

[0017] However, the effect of this degradation is that it makes wide-range communication between portable devices and motor vehicles (i.e., when the portable device is outside the location area) no longer possible.

[0018] However, some uses require that the functions of the vehicle be triggered before the user approaches the vehicle. For example, this could be the vehicle's remote control functions, such as locking / unlocking opening parts, turning on the heating, defrosting, or starting the engine. Summary of the Invention

[0019] This invention proposes an ultra-high frequency communication system that can mitigate this drawback. Attached Figure Description

[0020] Further features and advantages of the invention will become more apparent from the following description. This description is purely illustrative and should be read with reference to the accompanying drawings, in which:

[0021] As described above Figure 1a The prior art positioning device D is schematically shown.

[0022] Figure 1b A first embodiment of the positioning device according to the present invention is illustrated schematically.

[0023] Figure 1c A second embodiment of the positioning device according to the present invention is illustrated schematically.

[0024] Figure 2 The system S according to the present invention is illustrated schematically.

[0025] Figure 3a The first construction of the prior art positioning device D is schematically shown.

[0026] Figure 3b The second construction of the prior art positioning device D is schematically shown.

[0027] Figure 3c The third configuration of the prior art positioning device D is schematically shown.

[0028] Figure 4 The diagram schematically illustrates the positioning area of ​​a portable device for positioning in and around a motor vehicle, according to the prior art positioning device D.

[0029] Figure 5 The graph shows the attenuation of UHF waves (in decibels) as a function of a predetermined distance.

[0030] Figure 6 The method of carrying out the present invention is illustrated schematically.

[0031] For illustrative purposes, the accompanying drawings may not be to scale, especially regarding thickness. Detailed Implementation

[0032] The system according to the invention proposes adding wide-range communication capabilities to existing positioning devices. In this way, the portable device and the motor vehicle can communicate with each other to remotely control the motor vehicle, while enabling the motor vehicle to accurately locate the portable device in and around the vehicle.

[0033] Therefore, in Figure 2 In this invention, the system S includes a prior art device D, a microcontroller-type computer 50, and a portable device T.

[0034] Figure 1a Positioning device D is shown. Positioning device D includes:

[0035] - Power supply Vcc,

[0036] - An ultra-high frequency transceiver, more precisely a Bluetooth® or Bluetooth Low Energy (BLE) transceiver 10, which includes printed circuitry.

[0037] - At least one antenna A.

[0038] exist Figure 1aIn the positioning device D, at least one attenuation module M1 is also included on the (transmit / receive) communication cable 20 between the transceiver 10 and the antenna A. The positioning device D also includes a control component 30 for controlling the attenuation module M1 and a determining component 40 for determining the location of the portable device.

[0039] Figure 1a Multiple attenuation modules are shown, connected in series on communication line 20: first attenuation module M1, second attenuation module M2, and third attenuation module M3. For example... Figure 2 As shown, the positioning device D also includes:

[0040] - A control unit 30 for controlling, for example, multiple attenuation modules M1, M2, M3 integrated in transceiver 10; and

[0041] - A determining component 40 for determining the location of the portable device, which is electrically connected to the transceiver 10 and a control component 30 for controlling the attenuation module.

[0042] Each attenuation module, namely the first attenuation module M1, the second attenuation module M2, or the third attenuation module M3, is located at a predetermined distance from the transceiver 10. In this example, the distances are respectively the first distance L1, the second distance L2, and the third distance L3.

[0043] Each attenuation module, namely the first attenuation module M1, the second attenuation module M2, or the third attenuation module M3, further includes:

[0044] - Switching components, such as switches, namely, first switch S1, second switch S2, and third switch S3; and

[0045] - Impedances, namely first impedance Z1, second impedance Z2 and third impedance Z3, each impedance having a predetermined value and being electrically grounded.

[0046] The predetermined values ​​of the first impedance Z1, the second impedance Z2, and the third impedance are all equal to each other, and each impedance has a value of 50Ω, for example, between 0 and 100kΩ.

[0047] Control unit 30 is configured to actuate each attenuation module M1, M2, M3, and each switching unit S1, S2, S3 is configured to select one of the following two positions:

[0048] - In the first position, the transceiver 10 or the preceding attenuation modules M1, M2 are disconnected from the antenna A or the subsequent attenuation modules M2, M3, and the transceiver 10 or the preceding attenuation module is electrically connected to impedances Z1, Z2, Z3 associated with the switching component.

[0049] - Second position, wherein switching components S1, S2, S3 electrically connect transceiver 10 or the previous attenuation module M1, M2 to antenna A or the subsequent attenuation module M2, M3.

[0050] Each switching component (first switch S1, second switch S2, and third switch S3) thus enables the transceiver 10 to be disconnected from the antenna A and enables the transceiver 10 to be connected to an associated attenuation module (first attenuation module M1, or second attenuation module M2, or third attenuation module M3), that is, to connect the transceiver 10 to an impedance (first impedance Z1, or second impedance Z2, or third impedance Z3), which is electrically grounded, has a predetermined value, and is located at a predetermined distance from the transceiver 10 (at a first distance L1, a second distance L2, and a third distance L3, respectively).

[0051] For example, in Figure 3a In this configuration, the first switch S1 is in the first position, electrically connecting the transceiver 10 to the first impedance Z1 of the first attenuation module M1, located at a first distance L1 from the transceiver 10. In this first configuration, the transceiver 10 emits a UHF signal that propagates through the printed circuitry of the transceiver 10, causing the printed circuitry to resonate at that frequency. The UHF signal also propagates through the communication line 20 to the first impedance Z1 and then to ground. The maximum range of the UHF wave thus generated by the positioning device D depends on the first predetermined distance L1 between the first attenuation module M1 and the transceiver 10, and a predetermined value of the first impedance Z1. In this first configuration, the values ​​of the first distance L1 and the first impedance Z1 are selected such that the range of the emitted UHF wave is limited to a first positioning area A1 located within the motor vehicle V (see...). Figure 4 ).

[0052] exist Figure 3b In the first position, the first switch S1 is in the second position, which electrically connects the transceiver 10 to the second attenuation module M2. The second switch S2 is in the first position, which electrically connects the first attenuation module M1, which is itself connected to the transceiver 10, to the second impedance Z2, which is located at a second distance L2 from the transceiver 10.

[0053] In this example, the value of the second impedance Z2 is equal to the value of the first impedance Z1, and the second distance L2 is greater than the first distance L1.

[0054] In this second configuration of the positioning device D, the range of the emitted UHF wave is larger than that of the first configuration, and it defines an outer area near the motor vehicle V, referred to as the second positioning area A2. The second positioning area A2 is centered on the motor vehicle V, is larger than the first positioning area A1, and covers the first positioning area A1 (see...). Figure 4 ).

[0055] exist Figure 3c In the first position, the first switch S1 and the second switch S2 are in the second position. The second switch S2 is electrically connected to the second attenuation module M2 of the transceiver 10 via the first switch and electrically connected to the third impedance Z3. The third switch S3 is in the first position, and it electrically connects the second attenuation module M2 (i.e., the transceiver 10) to the third impedance Z3, which is located at a third distance L3 from the transceiver 10.

[0056] In this example, the value of the third impedance Z3 is equal to the value of the second impedance Z2, and the third distance L3 is greater than the second distance L2.

[0057] In this third configuration of the positioning device D, the range of the emitted UHF wave is greater than that of the second configuration, and it defines a third positioning area A3, that is, an area centered on the motor vehicle V, larger than the second positioning area A2, and covering the first and second positioning areas A1 and A2 (see...). Figure 4 ).

[0058] Finally, the fourth configuration includes switching all switches S1, S2, and S3 to the second position, in which case the transceiver 10 is connected to the antenna A, and the transmission range of the positioning device D is maximized, equal to the range of Bluetooth® or Bluetooth Low Energy (BLE).

[0059] Of course, the values ​​of the first, second, and third impedances Z1, Z2, and Z3 can vary from one another depending on the desired size of the location area.

[0060] exist Figure 4 In the example, a portable device T, such as a mobile phone, is located in the third location area A3.

[0061] When the positioning device D is in the third configuration and sends an identification request via UHF wave, the portable device T located in the third positioning area A3 receives the identification request from the transceiver 10 and then sends its identifier back to the transceiver 10.

[0062] The identifier received by the transceiver is transmitted to a determining component 40 for determining the location of the portable device t. When the determining component 40 is connected to the control component 30, it receives information related to the configuration of the positioning device D, more specifically, information related to the position of the switching component, and therefore information related to the target positioning area (in this example, the third positioning area A3). If the received identifier corresponds to the identifier of the portable device T paired with the motor vehicle V, the identifier is considered valid, and the positioning component 40 infers that the portable device T exists in the third positioning area A3.

[0063] The control unit 30, transceiver 10, and determining unit 40 may be software components integrated into a control unit (not shown) of the type BCM (Body Control Module, or electronic module for controlling the vehicle body).

[0064] Figure 5 The graph illustrates the attenuation of the UHF wave at each distance (Li), in decibels (dBi). Each distance (Li) represents the first distance L1, the second distance L2, and the third distance L3 (between the transceiver 10 and the first attenuation module M1, the second attenuation module M2, and the third attenuation module M3). Corresponding to each distance L1, L2, and L3 are the UHF wave attenuations dB1, dB2, and dB3, and the positioning areas A1, A2, and A3 of the portable device T.

[0065] The following formula gives the attenuation dBi of a UHF wave with respect to distance Li:

[0066] Mathematical expression 1 DBi = A × ln(Li) + B

[0067] Or equivalent:

[0068] Mathematical formula 2

[0069] in:

[0070] Mathematical Formula 3

[0071] Li: Pre-determined distance

[0072] DBi: Attenuation, measured in decibels.

[0073] A: A coefficient greater than zero.

[0074] f: Transmission frequency

[0075] ε PCB The relative permittivity of the printed circuit of positioning device D.

[0076] ε AIR The dielectric constant of air.

[0077] c: speed of light.

[0078] Therefore, determining the range of the portable device T will depend on the sensitivity of the portable device T and Figure 5 The attenuation curve. In practice, when the signal power received by the portable device T becomes lower than the sensitivity of the portable device T, the portable device T is no longer within the range of the transceiver 10.

[0079] Corresponding to the first distance L1 is a stronger first attenuation dB1 of the emitted UHF wave range, thus defining a first positioning area A1.

[0080] Corresponding to the second distance L2 is a second attenuation dB2 that is weaker than the first attenuation, which defines a second positioning area A2 that is larger than the first positioning area A1.

[0081] Corresponding to the third distance L3 is a smaller attenuation dB3 of the wave range, thus defining a third positioning area A3 that is larger than the second positioning area A2.

[0082] Therefore, we have: A1 < A2 < A3 and L1 < L2 < L3, where Z1 = Z2 = Z3.

[0083] For example, if Z1 = Z2 = Z3 = 50Ω, and L1 = 2mm, L2 = 10mm, L3 = 30mm are set, then the maximum range of the UHF wave for each positioning area is approximately equal to:

[0084] - For the positioning area A1, it is 1 meter.

[0085] - For the positioning area A2, it is 5 meters.

[0086] - For the positioning area A3, it is 10 meters.

[0087] Therefore, the positioning device D enables the portable device T to be located in at least one positioning area A1 through ultra-high frequency waves, that is, through Bluetooth® or Bluetooth Low Energy (BLE). This is achieved by disconnecting the transceiver 10 from the antenna A and connecting the transceiver 10 to the attenuation module M1 or M2 or M3 located at a predetermined distance L1, L2, or L3 from the transceiver 10, and the attenuation module M1 or M2 or M in which the impedance Z1, Z2, Z3 of the ground connection has a predetermined value. The predetermined distances L1, L2, L3 between the transceiver 10 and the attenuation module M1 or M2 or M3 and the predetermined values of the impedance Z1, Z2, Z3 define the positioning areas A1, A2, A3 for locating the portable device T in and around the motor vehicle V.

[0088] In one example, the positioning device D includes a plurality of attenuation modules M1, M2, M3.

[0089] In this example, the plurality of attenuation modules M1, M2, M3 enables the change of the predetermined distance between the transceiver 10 and the attenuation modules M1, M2, M3 and / or the predetermined values of the impedance Z1, Z2, Z3 in order to define several positioning areas A1, A2, A3 for locating the portable device T in and around the motor vehicle V, that is, a plurality of UHF wave emission areas with different sizes, so as to accurately locate the portable device T in and around the motor vehicle V.

[0090] Figure 1b An embodiment of the invention is illustrated, wherein the positioning device D includes two communication lines 20, 20'. In practice, the first communication line 20 electrically connects the transceiver 10 to the antenna A, while the second communication line 20' connects the transceiver 10 to at least one attenuation module M1. In this arrangement, the switching component S1 is set to its first position, and the control component 30 is configured to alternate the electrical connection of the transceiver 10 with the first communication line 20 and the second communication line 20'. The effect of this arrangement is to separate the transmission chains for short-range and long-range communication. For this purpose, the first communication line 20 is dedicated to long-range communication, and the second communication line 20' is dedicated to short-range communication.

[0091] In one example of this implementation, such as Figure 1c As shown, the positioning device D includes two antennas A and A'. The first antenna A is adapted to produce vertical or horizontal polarization, while the second antenna A' is adapted to produce polarization orthogonal to that produced by the first antenna A. In practice, a first communication line 20 electrically connects the transceiver 10 to antennas A and A'. Using orthogonal polarization on antennas A and A' improves signal reception at the portable device T.

[0092] In a variant of this embodiment (not shown), the positioning device D includes a third communication line 20'. In practice, the third communication line 20'' electrically connects the transceiver 10 to the antenna A'.

[0093] Therefore, the prior art positioning device D cleverly enables the "downgrading" of the range of ultra-high frequency (Bluetooth® or Bluetooth Low Energy (BLE)) waves, reducing it from the maximum range of 250m in the prior art to approximately a few centimeters, in order to accurately define the positioning area of ​​the portable device T in and around the motor vehicle V. Using this positioning method, it is now possible to locate the portable device T in the motor vehicle V via Bluetooth® or Bluetooth Low Energy (BLE) to authorize "hands-free" starting.

[0094] However, the effect of this degradation is that it makes wide-range communication between the portable device T and the motor vehicle V impossible, i.e., when the portable device T is outside the location area.

[0095] However, some applications require that the functions of the vehicle V be triggered before the user approaches the vehicle V. For example, this could be a remote control function of the vehicle V, such as locking / unlocking opening parts, turning on the heating, defrosting, or starting the engine.

[0096] Therefore, in this invention, the computer 50 is configured to cause the switching components S1, S2, S3 to alternate between the first position and the second position according to a predetermined ratio between the activation duration of the first position and the activation duration of the second position.

[0097] In this way, the portable device T and the motor vehicle V can communicate with each other to remotely control the motor vehicle V, while enabling the motor vehicle V to accurately position the portable device T in and around the motor vehicle V.

[0098] In one example, the activation duration of the first position and the activation duration of the second position are respectively equivalent to "1 / 3" and "2 / 3" of the total activation duration of the first and second positions.

[0099] In another example, the activation duration of the first position and the activation duration of the second position are respectively equivalent to "1 / 2" and "1 / 2" of the total activation duration of the first and second positions.

[0100] Of course, other values ​​for the activation duration of the first position and the activation duration of the second position can be envisioned without requiring substantial modifications to the present invention.

[0101] Furthermore, in this invention, such as Figure 2 As shown, after establishing at least one dedicated data channel (“connection mode”) between the motor vehicle V and the portable device T, the system S is further configured as follows:

[0102] - The motor vehicle V sends at least one status request message Mds to the portable device T at at least one predetermined frequency, and the motor vehicle V receives at least one status confirmation message Mcs from the portable device T.

[0103] - The portable device T receives a status request message Mds, and in response to receiving the status request message Mds, the portable device T sends a status confirmation message Mcs to the motor vehicle V.

[0104] In a particular implementation, the predetermined frequency depends on the activation duration of the first position and / or the activation duration of the second position.

[0105] In the first example, the predetermined frequency depends on the activation duration of the first position. Therefore, a predetermined function can be defined that relates the predetermined frequency to the activation duration of the first position, such that the predetermined frequency corresponds to the activation duration of a given first position.

[0106] In the second example, the predetermined frequency depends on the activation duration of the second position. To this end, a predetermined function can be defined that relates the predetermined frequency to the activation duration of the second position, such that the predetermined frequency corresponds to the activation duration of a given second position.

[0107] In the third example, the first predetermined frequency depends on the activation duration of the first position, and the second predetermined frequency depends on the activation duration of the second position.

[0108] Therefore, in this third example, when the activation duration of the first position and the activation duration of the second position are respectively equivalent to "1 / 3" and "2 / 3" of the total activation duration of the first position and the second position, the first predetermined frequency enables the status request message Mds that can be sent to the portable device T to be twice the second predetermined frequency.

[0109] Furthermore, in this third example, when the activation duration of the first position and the activation duration of the second position are respectively equivalent to "1 / 2" and "1 / 2" of the total activation duration of the first position and the second position, the first predetermined frequency and the second predetermined frequency enable the same number of status request messages Mds to be sent to the portable device T.

[0110] Of course, other values ​​for the first and second predetermined frequencies can be conceived without requiring substantial modifications to the present invention.

[0111] In a particular embodiment where the transceiver 10 includes a communication interface according to the Bluetooth® or Bluetooth Low Energy (BLE) protocol, the vehicle V is also configured to send a status request message Mds in a frame, which is selected between a so-called advertising signaling frame and a data frame.

[0112] In retrospect, in UHF communication systems, it is typically stipulated that at least one dedicated channel must be established between two devices before data frames are transmitted. Therefore, by using data frames, the present invention does not require modification to the Bluetooth® or Bluetooth Low Energy (BLE) protocol to enable the transmission of data frames after a dedicated data channel has been established between the motor vehicle V and the portable device T.

[0113] Furthermore, those skilled in the art will understand that advertising frames are intended to signal to other devices that data exchange is now possible. In the Bluetooth Low Energy (BLE) protocol, advertising frames are not transmitted after a dedicated data channel is established between two devices. Therefore, this invention requires a slight modification to the Bluetooth Low Energy (BLE) protocol to enable the transmission of advertising frames after a dedicated data channel is established between the vehicle V and the portable device T.

[0114] The message exchange mechanism using acquittement proposed in this invention maintains connection activity on the dedicated channel.

[0115] In practice, in UHF communication systems, the dedicated channel is disconnected if no messages are exchanged between two devices within a predetermined time period. For example, in some UHF communication systems, the predetermined time period is set to approximately 30 seconds.

[0116] Therefore, in the prior art, when the positioning device D positions the portable device T in or around a moving vehicle V, no further exchange occurs between the portable device T and the vehicle V on the channel established between the two devices. Consequently, when the predetermined time period expires, the connection channel is disconnected, and the positioning process needs to be restarted. In other words, in the prior art, non-continuous positioning of the portable device T is performed. The disadvantage of this is that after the portable device T has been positioned, it is impossible to know whether the portable device T is still within the positioning area. In other words, if the portable device T moves after being positioned, it will be impossible to know this unless the positioning device D is reactivated to re-execute the positioning process, which requires sending a large number of synchronization messages.

[0117] The system S according to the invention advantageously enables the avoidance of such disconnection by means of a message exchange mechanism employing affirmative responses implemented after a dedicated data channel is established between the motor vehicle V and the portable device T, so as to enable continuous positioning of the portable device T.

[0118] In fact, in this invention, the positioning process is not interrupted because the system S implements a message exchange mechanism with affirmative response when the portable device T is located in or around the motor vehicle V and within the maximum range of the ultra-high frequency wave.

[0119] Furthermore, the system S is configured to measure the success rate of receiving status request messages Mds within a predetermined measurement period, and if the success rate of receiving status request messages Mds is high, the positioning device D is triggered to perform a positioning process.

[0120] In practice, in this invention, the computer 50 is constructed as follows:

[0121] - Calculate the success rate of receiving status request messages Mds by portable device T, and

[0122] - Compare the success rate of receiving the status request message Mds with the predetermined success rate in order to control the positioning device D to locate the portable device T.

[0123] In the first example, computer 50:

[0124] - Count the number of acknowledgment messages received at motor vehicle V, and

[0125] - Calculate the success rate of receiving status request messages (Mds) based on the number of acknowledgment messages received.

[0126] Therefore, if the motor vehicle V sends six status request messages Mds to the portable device T and receives four status confirmation messages Mcs from the portable device T within the predetermined measurement period, the success rate of receiving the status request messages Mds will be equal to "4 / 6", that is, approximately 66.66%.

[0127] In the second example:

[0128] - The portable device T counts the number of status request messages received.

[0129] - The portable device T adds the number of received status request messages to the status acknowledgment message Mcs, and

[0130] Computer 50 calculates the success rate of receiving status request messages Mds based on the number of received status request messages.

[0131] Therefore, if the motor vehicle V sends six status request messages Mds to the portable device T during the predetermined measurement period and the portable device T only receives two status request messages Mds, the success rate of receiving status request messages Mds will be equal to "2 / 6", or approximately 33.33%.

[0132] The present invention also relates to a method for implementing system S, such as Figure 6 As shown.

[0133] In method 100, two arrangements of the motor vehicle V are considered.

[0134] In the first arrangement, transceiver 10 is connected to antenna A, as described above.

[0135] In the second arrangement, the transceiver 10 is disconnected from the antenna A, and then the transceiver 10 is connected to the attenuation modules M1, M2, and M3 located at predetermined distances L1, L2, and L3 from the transceiver 10, as described above.

[0136] Then, in step 110, as described above, the first arrangement and the second arrangement are alternated according to a predetermined ratio between the activation duration of the first arrangement and the activation duration of the second arrangement.

[0137] Then, after establishing at least one dedicated data channel between the motor vehicle V and the portable device T in step 120:

[0138] - Configure the motor vehicle V to send at least one status request message Mds to the portable device T at at least one predetermined frequency and to receive at least one status confirmation message Mcs from the portable device T, and

[0139] - The portable device T is configured to receive a status request message Mds and, in response to receiving the status request message Mds, send a status confirmation message Mcs to the motor vehicle V.

[0140] In one example, as described above, the predetermined frequency depends on the activation duration of the first arrangement and / or the activation duration of the second arrangement.

[0141] In one particular implementation, at motor vehicle V,

[0142] - In step 130, calculate the success rate of the portable device T in receiving the status request message Mds, and

[0143] - In step 140, the success rate of receiving the status request message Mds is compared with a predetermined success rate in order to control the positioning device D to locate the portable device T.

[0144] In the first example of this particular implementation, as described above,

[0145] - Count the number of acknowledgment messages received at motor vehicle V, and

[0146] - The success rate of receiving status request messages (Mds) is calculated based on the number of acknowledgment messages received.

[0147] In the second example of this particular implementation, as described above,

[0148] - Count the number of status request messages received at the portable device T.

[0149] - Add the number of received status request messages to the status acknowledgment message Mcs, and

[0150] - The success rate of receiving status request messages (Mds) is calculated based on the number of status request messages received.

Claims

1. System for communicating with and locating a portable device for "hands-free" access by means of UHF, the system comprising a UHF locating device which is on-board in a motor vehicle, and comprising: - a power supply, - a UHF transceiver comprising a printed circuit connected to: - an antenna connected by a first communication line, - a computer, the UHF locating device further comprising: - a second communication line, on which at least one attenuation module, said at least one attenuation module being located at a predetermined distance from the transceiver, comprising a switching component and an impedance having a predetermined value, and being grounded, - a control component for controlling said at least one attenuation module, - a determination component for determining the location of the portable device, electrically connected to the transceiver and to the control component for controlling the attenuation module, the switching component having: - a first position in which the transceiver is disconnected from the antenna and electrically connected to the impedance associated with said switching component via the second communication line, - a second position in which the switching component electrically connects the transceiver to the antenna via the first communication line, wherein the computer is configured to alternate the switching component between the first position and the second position according to a predetermined ratio between the duration of activation of the first position and the duration of activation of the second position, establishing at least one dedicated data channel between the motor vehicle and the portable device.

2. The system of claim 1, wherein, After establishing said at least one dedicated data channel between the motor vehicle and the portable device and maintaining the connection active on the dedicated channel, the system is further configured to: - the motor vehicle sending at least one status request message to the portable device at at least one predetermined frequency, and the motor vehicle receiving at least one status confirmation message from the portable device, and - the portable device receiving said at least one status request message, and the portable device sending said at least one status confirmation message to the motor vehicle in response to receiving said at least one status request message.

3. The system of one of claims 1 to 2, wherein, The UHF transceiver comprises a communication interface according to or Bluetooth Low Energy, BLE, protocol.

4. The system of claim 1, wherein, The motor vehicle is further configured to send the status request message in a frame selected between a signaling frame and a data frame.

5. The system of claim 1, wherein, The locating device further comprises a second antenna, the antenna being adapted to produce a vertical or horizontal polarization, while the second antenna is adapted to produce a polarization which is orthogonal to the polarization produced by the antenna.

6. Method implemented with a system for communicating with and locating a portable device for "hands-free" access by means of UHF according to one of claims 1 to 5, the portable device being for "hands-free" access to a motor vehicle, the motor vehicle being on-board a communication device comprising a UHF transceiver, a power supply and at least one antenna, the motor vehicle comprising a first arrangement in which the transceiver is connected to the antenna and a second arrangement in which the transceiver is disconnected from the antenna and then connected to an attenuation module located at a predetermined distance from the transceiver, the attenuation module comprising an impedance which is grounded and has a predetermined value, the predetermined distance between the transceiver and the attenuation module and the predetermined value of the impedance defining a location area in and around the motor vehicle for locating the portable device, the method being characterized in that: a) alternating between the first arrangement and the second arrangement according to a predetermined ratio between the duration of activation of the first arrangement and the duration of activation of the second arrangement, b) maintaining connection activity on the dedicated channel after the establishment of at least one dedicated data channel between the motor vehicle and the portable device, c) making the following configurations a. configuring the motor vehicle to send at least one status request message to the portable device at at least one predetermined frequency and to receive at least one status confirmation message, b. configuring the portable device to receive the status request message and to send the status confirmation message to the motor vehicle in response to receiving the status request message, d) calculating a reception success rate of the status request message by the portable device, e) comparing the reception success rate of the status request message with a predetermined success rate, f) positioning the portable device as a function of the result of the comparison.

7. The method of claim 6, wherein, The predetermined frequency depends on the activation duration of the first arrangement and / or the activation duration of the second arrangement.

8. The method of claim 6 or 7, wherein, The motor vehicle - counts the number of status confirmation messages received, and - calculates the reception success rate of the status request message on the basis of the number of status confirmation messages received.

9. The method of claim 6 or 7, wherein, The portable device - counts the number of status request messages received, - adds the number of status request messages received to the number of status confirmation messages, and - calculates the reception success rate of the status request message on the basis of the number of status request messages received.

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