Method for transmitting advertisement frame, method for establishing wireless link, electronic device and associated system thereof

Abstract

A first communication circuit mounted in an electronic device transmits an advertisement frame to a second communication circuit mounted in a vehicle. The second communication circuit operates according to consecutive cycles having a first predetermined duration, and each cycle includes a listening phase during which the second communication circuit is capable of detecting an electromagnetic signal, and an idle phase during which the second communication circuit is inactive. The method comprises the following steps:-the first communication circuit transmits (E4) an announcement frame (ADV1) at a first time (t1); determining (E6) a random value; -the first communication circuit transmits (E10) another advertisement frame (ADV2) at a second time (t2), which is separated from the first time by a second duration (At), which is determined according to a random value and is strictly comprised between two consecutive multiples of the first duration.

Description

Technical Field

[0001] The present invention generally relates to the field of wireless exchanges between on-vehicle systems, such as those provided on a vehicle, and electronic devices forming an identifier, for example, associated with the vehicle.

[0002] More specifically, the present invention relates to a method for transmitting broadcast packets, a method for establishing a wireless link, and associated electronic devices and systems. Background Art

[0003] PEPS (for "Passive Entry–Passive Start") systems are known, in which the implementation of functions (such as unlocking the vehicle doors or starting such a vehicle) depends on the presence, near the vehicle, of an electronic device forming a vehicle user identifier (usually carried by the user).

[0004] To this end, the vehicle and the identifier may be provided with communication circuits designed to establish a wireless data exchange link according to a communication protocol. Summary of the Invention

[0005] In this context, a method is proposed for transmitting a broadcast packet from a first communication circuit provided on an electronic device to a second communication circuit provided on a vehicle, where the second communication circuit operates in consecutive periods having a first predetermined duration, and each period includes a listening phase during which the second communication circuit is capable of detecting an electromagnetic signal and a sleep phase during which the second communication circuit is inactive. The method includes the following steps:

[0006] - The first communication circuit transmits a broadcast packet at a first time;

[0007] - Determine a random value;

[0008] - The first communication circuit transmits another broadcast packet at a second time separated from the first time by a second duration, the second duration being determined as a function of the random value and being strictly included between two consecutive multiples of the first duration.

[0009] Thus, the transmission times of two consecutive broadcast packets are not separated by a duration that is an exact multiple of the first duration (the duration of the operating period of the second communication circuit), such that the broadcast packets can be transmitted during the listening phase of the second communication circuit (vernier principle).

[0010] In addition, the second time for transmitting the broadcast packet designated as "other broadcast packet" above depends on the above-mentioned random value and will thus be different (except for some exceptions) from the corresponding transmission time used by another electronic device of the same design that may be nearby (for example, when two people each with a similar identifier approach the vehicle simultaneously). Therefore, interference is avoided in the case where two such electronic devices are present near the vehicle.

[0011] Other possible features, taken individually or in all technically possible combinations, are as follows, but are not limited to:

[0012] - The second duration, denoted as Δt, satisfies n.T 0 <Δt<(n + 1).T 0 , where T 0 is the first duration and n is an integer greater than or equal to 5 (or even an integer greater than or equal to 9);

[0013] - The method includes the step of determining the second duration by adding the duration of the listening phase (denoted below as t ON ) to the first duration T 0 multiplied by an integer (which can be a predetermined integer, such as greater than or equal to 10, or an integer that may depend on another random value) or subtracting the duration of the listening phase from the product;

[0014] - The method includes the step of determining the second duration by multiplying the first duration T 0 by a number that depends on the random value (the determination of the second duration may then include adding the duration of the listening phase t ON or a multiple of the duration of the listening phase to the result of the multiplication);

[0015] - The method includes the step of determining the second duration by adding the product of the duration of the listening phase t ON and a non-zero relative integer that depends on the random value to the product of the first duration T 0 and an integer (which can be a predetermined integer, such as greater than or equal to 10, or depends on another random value);

[0016] - For each of the said consecutive periods, the listening phase has a duration included between 5% and 30% of the first duration (that is, the duration t ON is included between 0.05.T 0 and 0.3.T 0 ).

[0017] The present invention also provides a method for establishing a wireless link between a first communication circuit disposed on an electronic device and a second communication circuit disposed on a vehicle, comprising the following steps:

[0018] - Implementing the method for transmitting broadcast packets as described above by the first communication circuit;

[0019] - Detecting, by the second communication circuit, one of the broadcast packets during a listening phase;

[0020] - Transmitting, by the second communication circuit, a connection request in response to the detected broadcast packet;

[0021] - Establishing a connection between the first communication circuit and the second communication circuit.

[0022] Correspondingly, the present invention provides an electronic device, which includes a control unit and a first communication circuit. The first communication circuit is designed to transmit broadcast packets to a second communication circuit disposed on a vehicle. The second communication circuit operates in consecutive periods having a first predetermined duration, and each period includes a listening phase and a sleep phase. During the listening phase, the second communication circuit is capable of detecting an electromagnetic signal, and during the sleep phase, the second communication circuit is inactive. Wherein, the control unit is designed to determine a random value, and determine a second duration as a function of the random value that is strictly included between two consecutive multiples of the first duration. And wherein, the first communication circuit is designed to transmit a broadcast packet at a first time, and transmit another broadcast packet at a second time separated from the first time by the second duration.

[0023] Finally, the present invention provides a system, which includes the electronic device just mentioned and a vehicle-mounted system including a second communication circuit.

[0024] Of course, various features, variations, and embodiments of the present invention can be combined with each other in various combinations, as long as they are not incompatible or mutually exclusive with each other. Description of the Drawings

[0025] The following description with reference to the accompanying drawings given by way of non-limiting examples will allow a clear understanding of what the present invention includes and how to implement the present invention.

[0026] In the drawings:

[0027] Figure 1 The main elements of the system in which the present invention can be implemented are schematically shown;

[0028] Figure 2 An example of a method for transmitting broadcast packets that can be implemented within the system framework of Figure 1 is shown; and

[0029] Figure 3An example of a method for establishing a wireless link is shown. Detailed implementation

[0030] Figure 1 The main elements of a system in which the present invention can be implemented are schematically shown.

[0031] Such a system includes a vehicle 10 (here a motor vehicle) and an electronic device 20 acting as an identifier, such as a key or a badge for accessing the vehicle 10 (or, as a variant, a user terminal, such as a multifunctional mobile phone or a "smartphone", which is provided with the right to access the vehicle 10).

[0032] The vehicle 10 is provided with an on-vehicle system 15, which particularly includes an electronic control unit 11 and a communication circuit 12.

[0033] The electronic control unit 11 includes, for example, a microprocessor and at least one memory, such as a rewritable non-volatile memory. This memory particularly stores program instructions, which, when executed by the microprocessor, allow the electronic control unit 11 to implement the methods described below with reference to Figure 3 the description. The memory can also store values or parameters used during these methods.

[0034] The memory of the electronic control unit 11 also stores a key K (which has been written into the electronic control unit 11, for example, during the manufacturing process of the electronic control unit 11).

[0035] As a variant, the electronic control unit 11 can be implemented in the form of an application-specific integrated circuit (or ASIC).

[0036] The communication circuit 12 is designed to establish a wireless link with other electronic devices, in this case, a link of the "low energy Bluetooth" (or "BLE") type. Therefore, the communication circuit 12 is particularly designed to transmit and receive electromagnetic signals (generally, at a frequency higher than 1 MHz or even 500 MHz), in this case, in the 2.4 GHz band.

[0037] As a result of a command received, for example, from the electronic control unit 11, the communication circuit 12 performs a continuous operating cycle with a predetermined duration T 0 and / or each operating cycle includes a listening phase and a sleep phase, during which the communication circuit 12 is able to detect electromagnetic signals during the listening phase and is inactive during the sleep phase. In other words, the operation of the communication circuit 12 is periodic, and each operating cycle (predetermined duration T 0 ) includes a listening phase and a sleep phase as defined above. The sleep phase makes it possible to reduce the average power consumption of the communication circuit 12 and thus the average power consumption of the on-vehicle system 15.

[0038] Predetermined duration T of the operating cycle 0 For example, it is between 10 ms and 200 ms, here it is 100 ms.

[0039] In each operating cycle, the duration of the listening phase is, for example, between 5% and 30% of the operating cycle. The duration t of the listening phase is illustrated below ON . (The duration t ON Thus, in this case, it is between 0.05.T 0 and 0.3.T 0 ).

[0040] An electronic device 20, which is usually carried by a user of the vehicle 10, is used as an identifier for authorizing and / or permitting the control of certain functions of the vehicle 10 (such as unlocking the doors of the vehicle 10), especially when it is close to the vehicle 10. The electronic device 20 may also include control buttons that the user can use to control at least some of the aforementioned functions or other functions of the vehicle 10.

[0041] The electronic device 20 includes a control unit 21 and a communication circuit 22.

[0042] The control unit 21 is implemented, for example, by a microprocessor and at least one memory (such as a rewritable non-volatile memory). This memory stores, in particular, program instructions that, when executed by the microprocessor, allow the control unit 21 to implement the methods described below with reference to Figure 2 and / or the methods described below with reference to Figure 3 . The memory may also store values or parameters used during these methods.

[0043] The memory of the control unit 21 also stores, additionally, a key K. In the case where the electronic device 20 forming the identifier is a badge (or key) for entering the vehicle, the key K has been, for example, written into the memory of the control unit 21 during the manufacture of the identifier 20. In the variant mentioned above, where the electronic device 20 forming the identifier is a user terminal, the key K has been, for example, received from a remote server and stored during the registration phase of the service for controlling vehicle functions via the user terminal.

[0044] Note that, in the embodiments described here, the key K stored in the memory of the control unit 21 is the same as the key K stored in the memory of the electronic control unit 11. However, as a variant, for example, in the case of using public key infrastructure (or PKI), the key K stored in the memory of the control unit 21 may be different from the key K stored in the memory of the electronic control unit 11.

[0045] As a variant, the control unit 21 can be implemented in the form of an application-specific integrated circuit.

[0046] The communication circuit 22 is designed to establish a wireless link (in this case of the "Low Energy Bluetooth" or "BLE" type) via the aforementioned communication circuit 12 with other electronic devices, in particular with the electronic control unit 11 of the vehicle 10. Thus, the communication circuit 22 itself is also designed to transmit and receive electromagnetic signals (usually having a frequency higher than 1 MHz or even 500 MHz), in this case in the 2.4 GHz frequency band.

[0047] As described below, by means of the wireless link that can be established between the communication circuit 12 of the on-vehicle system 15 of the vehicle 10 and the communication circuit 22 of the electronic device 20, data can be exchanged between the electronic control unit 11 of the on-vehicle system 15 of the vehicle 10 and the control unit 21 of the electronic device 20.

[0048] The electromagnetic signals exchanged between the communication circuits 12, 22 can also be used to evaluate the distance by which the electronic device is separated from the vehicle 10 (precisely the distance by which the communication circuits 12, 22 are separated), as described below.

[0049] Figure 2 An exemplary method for transmitting a broadcast packet is shown, which can be implemented within the framework of the system just described.

[0050] A broadcast packet is an electromagnetic signal, for example located in a predefined frequency band and / or having a predefined shape according to the communication protocol used (in this case the BLE protocol).

[0051] The method starts at step E2, during which the control unit 21 commands the communication circuit 22 to transmit a broadcast packet ADV1 at time t 1 The broadcast packet ADV1 is, for example, the first broadcast packet transmitted after the electronic device 20 is restarted (e.g., after it is powered on), and time t 1 is, for example, a predefined time of the restart process.

[0052] Thus, in step E4, the communication circuit 22 transmits the broadcast packet ADV1 at time t 1 according to the BLE protocol.

[0053] The method continues to step E6, during which the control unit 21 determines a random value a, for example, in the case described here, by calling a dedicated function (random draw function) within the microprocessor forming the control unit 21.

[0054] Then, in step E8, the control unit 21 commands the communication circuit 22 to transmit a broadcast packet ADV2 at a time t 1 separated from the first time t by a duration Δt 2 The duration Δt is determined as a function of the random value a and is strictly included within a predetermined duration T0 Between two consecutive multiples of (the duration of each operating cycle of the communication circuit 12 as described above).

[0055] In other words, the duration Δt separating the time t 1 of the transmission packet ADV1 and the time t 2 of the transmission packet ADV2 depends on the random value a and satisfies:

[0056] n.T 0 < Δt < (n + 1).T 0 , where n is an integer greater than or equal to 2, preferably an integer greater than or equal to 5.

[0057] In fact, the duration Δt can be determined according to one of the methods now proposed. In these examples, it is considered that the random value a determined in step E6 is included between 0 and 1 (that is, obtained by random sampling in the interval [0, 1]).

[0058] According to the first possible method, the duration Δt is determined as follows:

[0059] Δt = m.T 0 + t ON , if a > 0.5,

[0060] Δt = m.T 0 - t ON , if a ≤ 0.5,

[0061] where m is a predetermined integer (greater than or equal to 3, preferably greater than or equal to 6), and where, as already indicated, t ON is the duration of each listening phase.

[0062] According to the second possible method, the duration Δt is determined as follows:

[0063] Δt = m.T 0 + 2.t ON , if a > 0.5,

[0064] Δt = m.T 0 + t ON , if a ≤ 0.5,

[0065] where m is a predetermined integer (greater than or equal to 2, preferably greater than or equal to 5), and where, as already indicated, t ON is the duration of each listening phase.

[0066] According to the third possible method, the duration Δt is determined as follows:

[0067] Δt = INT(5 + 5a).T 0 + tON

[0068] where INT is the "integer part" function, and where, as already indicated, t ON is the duration of each listening phase.

[0069] According to a fourth possible embodiment, step E6 further includes determining another random value b, and the duration Δt is determined as follows:

[0070] Δt = INT(5 + 5a).T 0 + t ON , if b > 0.5,

[0071] Δt = INT(5 + 5a).T 0 - t ON , if b ≤ 0.5.

[0072] Then, in step E10, the communication circuit 22 transmits the broadcast packet ADV2 at time t 2 according to the BLE protocol.

[0073] The method can then return to step E6 in order to transmit a new broadcast packet.

[0074] By means of the method just described, two consecutive broadcast packets are transmitted at respective times separated by a duration Δt that satisfies the conditions set forth above for the broadcast packet ADV2, i.e., the duration Δt depends on a random value (which can be different for each transmitted packet) and is strictly included between two consecutive multiples of a predetermined duration T 0 (the pair of consecutive multiples in question may be different from packet to packet).

[0075] Thus, for each transmitted broadcast packet ADV i, the duration Δt separating the transmission of the broadcast packet ADV i from the previous packet satisfies:

[0076] n.T 0 < Δt < (n + 1).T 0 , where n is an integer greater than or equal to 2, and preferably greater than or equal to 5 (as already indicated, n can vary from broadcast packet to broadcast packet).

[0077] Thus, compared to the provisions made for the listening phases of the communication circuit 12, the broadcast packets are transmitted less frequently, which makes it possible to reduce the power consumption at the electronic device 20.

[0078] In addition, the broadcast packets are not transmitted in the same period as the repetition period T 0 of the listening phases, in order to ensure that a broadcast packet appears during a listening phase (possibly after transmitting several broadcast packets) (vernier principle).

[0079] Finally, the transmission time of the broadcast packet (during step E8) depends on a random value (determined in step E6), such that electronic devices 20 of the same type and two electronic devices of the same design (e.g., this is the case when two users of a vehicle each carry two similar identifiers) will transmit the broadcast packet at different times (except for some exceptions), which makes it possible to avoid interference between these two electronic devices in their exchange with the communication circuit 12 provided on the vehicle.

[0080] The above-mentioned broadcast packets ADV1, ADV2 are of the ADV_IND type in this case: these are broadcast packets indicating connection availability and are not specifically targeted at a communication partner (or "connectable undirected broadcast event").

[0081] The broadcast packets ADV1, ADV2, ADVi transmitted by the communication circuit 22 of the electronic device 20 may include data, in particular the identification data ID of the electronic device 20.

[0082] Figure 3 An example of a method for establishing a wireless link between the communication circuit 12 provided on the vehicle and the communication circuit 22 of the electronic device 20 forming an identifier is shown.

[0083] The method starts with the communication circuit 22 of the electronic device 20 transmitting a broadcast packet according to what has just been Figure 2 described.

[0084] When the vehicle 10 is close enough to the electronic device 20 (which typically occurs when the carrier of the electronic device 20 approaches the vehicle 10), the communication circuit 12 of the in-vehicle system 15 of the vehicle 10 detects (and thus receives) one of the broadcast packets ADVi and thus indicates to the electronic control unit 11 the arrival of the broadcast packet ADVi (step E12). In this step, the communication circuit 12 may also transmit the data that may be included in the broadcast packet ADVi (in particular the identification data ID of the electronic device 20) to the electronic control unit 11.

[0085] Then, in step E14, the electronic control unit 11 may command the communication circuit 12 to respond to the broadcast packet ADVi transmitted by the electronic device 20, typically by transmitting a connection request CONN_REQ to the communication circuit 22 of the identifier 20 (step E16).

[0086] According to a possible embodiment, a connection request CONN_REQ is transmitted by the communication circuit 12 (upon the command of the electronic control unit 11), which may however depend on the presence of the identification data ID of the electronic device 20 in a list of previously paired identifiers (this list is stored in the memory of the electronic control unit 11, and the identification data of a given electronic device is added to this list through a specific pairing process).

[0087] In step E18, the communication circuit 22 of the electronic device 20 receives the connection request CONN_REQ. Thus, in step E20, according to the communication protocol under discussion (here the BLE protocol already mentioned), a wireless link can be established between the in-vehicle system 15 and the identifier 20 by establishing a connection between the communication circuit 12 of the in-vehicle system 15 and the communication circuit 22 of the identifier 20.

[0088] Within the framework of this connection established according to the communication protocol under discussion, as already pointed out, time slots dedicated to data exchange between the communication circuit 12 of the in-vehicle system 15 and the communication circuit 22 of the electronic device 20 are provided (for example during steps E22 to E30 described below).

[0089] According to a possible embodiment, the data exchanged between the electronic device 20 and the in-vehicle system 15 is encrypted during their exchange between the communication circuit 12 of the in-vehicle system 15 and the communication circuit 22 of the electronic device 20 (usually through a cryptographic encryption algorithm, using for example the key K shared by the electronic control unit 11 and the control unit 21 as already pointed out). The encryption used is provided, for example, in the context of the data exchange protocol D under discussion, here the BLE protocol.

[0090] Still referring to Figure 3 , the possible data exchange between the electronic device 20 and the in-vehicle system 15 will now be described.

[0091] During step E22, the electronic control unit 11 of the in-vehicle system 15 determines a value CH (for example by random extraction) and commands the communication circuit 12 to transmit this value CH via the established wireless link (between the communication circuit 12 and the communication circuit 22), and thus to the electronic device 20 (that is, actually to the control unit 21). As described below, this value CH is used as a challenge in a challenge-response exchange in order to verify that the electronic device 20 indeed has the key K.

[0092] The control unit 21 receives the value CH via the communication circuit 22 (step E24).

[0093] During step E26, the control unit 21 applies a cryptographic processing algorithm (such as an encryption algorithm) using the key K to the value CH in order to obtain a response RS for the in-vehicle system 15.

[0094] The control unit 21 then commands (step E28) the communication circuit 22 to transmit the response RS via the wireless link established (between the communication circuit 12 and the communication circuit 22), and thus to the electronic control unit 11.

[0095] Accordingly, in step E30, the electronic control unit 11 receives the response RS via the communication circuit 12.

[0096] Accordingly, the electronic control unit 11 can verify the received response RS in step E32, here by applying a cryptographic processing algorithm, such as a decryption algorithm, to the response RS using the key K, and by verifying whether the obtained result is indeed the same as the value CH sent in step E22.

[0097] If (and only if) the verification is correctly performed in step E32 (which indicates that the electronic device actually stores the key K), the electronic device 20 is authenticated by the electronic control unit 11; the electronic control unit 11 can then authorize certain actions, such as unlocking the vehicle 10.

[0098] In addition, the electronic control unit 11 and / or the control unit 21 can control (to the communication circuit 12 and / or the communication circuit 22 respectively) the transmission of electromagnetic signals and / or the execution of measurements (step E40) in order to evaluate the distance separating the communication circuit 12 from the communication circuit 22, for example according to what is described in the patent application disclosed in the reference FR 3 081 637.

Claims

1. A method for transmitting a broadcast packet from a first communication circuit (22) provided on an electronic device (20) to a second communication circuit (12) provided on a vehicle (10), wherein, the second communication circuit (12) operates in consecutive periods having a first predetermined duration, and each period includes a listening phase and a sleep phase. During the listening phase, the second communication circuit (12) is capable of detecting an electromagnetic signal, and during the sleep phase, the second communication circuit (12) is inactive. The method includes the following steps: - The first communication circuit (22) transmits (E4) a broadcast packet (ADV1) at a first time (t 1 ). - determining (E6) a random value; - at a second time (t 2 2 ) separated from the first time by a second duration (Δt), the first communication circuit (22) transmits (E10) another broadcast packet (ADV2), the second duration (Δt) being determined as a function of the random value and being strictly included between two consecutive multiples of the first duration.

2. The transmission method according to claim 1, wherein, The second duration, denoted as Δt, satisfies n.T 0 <Δt<(n + 1).T 0 , where T 0 is the first duration and n is an integer greater than or equal to 5.

3. The transmission method according to claim 1 or 2, including the step of determining (E8) the second duration (Δt) by adding the duration of the listening phase to the product of the first duration and an integer or subtracting the duration of the listening phase from the product according to the random value.

4. The transmission method according to claim 1 or 2, including the step of determining (E8) the second duration (Δt) by multiplying the first duration by a number depending on the random value.

5. The transmission method according to claim 1 or 2, including the step of determining (E8) the second duration (Δt) by adding the product of the duration of the listening phase and a non-zero relative integer depending on the random value to the product of the first duration and an integer.

6. The transmission method according to any one of claims 1 to 5, wherein, for each of the consecutive periods, the listening phase has a duration included between 5% and 30% of the first duration.

7. A method for establishing a wireless link between a first communication circuit (22) provided on an electronic device (20) and a second communication circuit (12) provided on a vehicle (10), including the following steps: - implementing, by the first communication circuit (22), the method for transmitting broadcast packets (ADV1, ADV2, ADVi) according to any one of claims 1 to 6; - detecting (E12) one of the broadcast packets (ADVi) by the second communication circuit (12) during the listening phase; - transmitting (E16) a connection request (CONN_REQ) by the second communication circuit (12) in response to the detected broadcast packet (ADVi); - establishing (E20) a connection between the first communication circuit (22) and the second communication circuit (12).

8. An electronic device (20), including a control unit (21) and a first communication circuit (22), the first communication circuit (22) being designed to transmit broadcast packets (ADV1, ADV2) to a second communication circuit (12) provided on a vehicle (10), the second communication circuit (12) operating in consecutive periods having a first predetermined duration, and each period including a listening phase and a sleep phase. During the listening phase, the second communication circuit (12) is capable of detecting an electromagnetic signal, and during the sleep phase, the second communication circuit (12) is inactive, wherein, The control unit (21) is designed to determine a random value and to determine a second duration (Δt) which is strictly included between two consecutive multiples of the first duration as a function of the random value, and Among them, the first communication circuit (22) is designed to transmit a broadcast packet (ADV1) at a first time (t 1 ) and transmit another broadcast packet (ADV2) at a second time (t 1 ) separated from the first time (t 2 ) by the second duration (Δt).

9. A system comprising an electronic device (20) as claimed in claim 8 and a vehicle system (15) comprising the second communication circuit (12).

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