Field superposition method and system

Abstract

A method of wireless communication between a vehicle base station and a transponder is disclosed, the method comprising: i) driving, by the vehicle base station, a first and a second antenna on the vehicle using a first drive current, the first antenna being separated from the transponder by a part of the vehicle in which the vehicle base station is located; ii) detecting three separate vector components of the respective fields emitted by the first and second antennas and received at the transponder which are orthogonal to each other; iii) calculating a superposition factor for the first and second antennas; iv) driving the first and second antennas simultaneously; v) detecting three vector components of a superimposed signal received at the transponder comprising signals from both antennas which are orthogonal to each other; vi) determining whether two of the three detected vector components are above a threshold noise level; vii) repeating step iv) if less than two of the three detected vector components are above the threshold noise level; and viii) authenticating the transponder.

Description

Technical Field

[0001] This disclosure relates to wireless communication, and more specifically, to field superposition in wireless communication for ensuring source security. Background Technology

[0002] Some types of wireless communication systems employ transponders and base stations that communicate with each other. In one example, a wireless transponder can be used to enable passive keyless entry (PKE) for unlocking vehicle doors, or passive keyless start (PKG) for activating the ignition circuit. In each case, the wireless transponder communicates with the base station in the vehicle through a series of operations designed to authenticate the transponder and ensure that the transponder is within a limited distance of the vehicle.

[0003] PKE and PKG systems may be vulnerable to so-called relay attacks, in which signals transmitted by a transceiver in the vehicle are relayed by an attacker to and from a transponder, which may be located remotely, such as inside the vehicle owner's house or on the owner's person. An attacker can gain access to the vehicle by relaying signals between the transponder and the vehicle, thereby gaining entry and enabling the vehicle's ignition circuit.

[0004] One method to reduce the susceptibility to such relay attacks is to employ multiple antennas in the vehicle that collectively provide a challenge signal to the transponder. Upon receiving the challenge signal, the transponder uses three antennas arranged to receive signals in mutually orthogonal directions to determine the strength of the received signal in the three orthogonal directions. The transponder then responds by transmitting a coded signal containing the measurement value, and the vehicle's controller determines whether the vector information conforms to predetermined criteria based on the received signal, and only allows access to the vehicle, such as unlocking or enabling the ignition circuit, if the criteria are met. This system is disclosed in EP1189306A1.

[0005] Another method for reducing the susceptibility to relay attacks may involve generating superimposed signals from two or more antennas in the vehicle and determining whether a transponder is within physical range of the vehicle, as disclosed in, for example, EP2635059A1. In this system, first and second signals may be transmitted sequentially from first and second antennas, followed by a third signal from both antennas. The third signal needs to deliver at least two valid vector components higher than the noise level at the receiver (i.e., the transponder) to defend against relay attacks. If this criterion is not met, the vehicle controller determines the transponder response is invalid and does not allow access to the vehicle. The problem with this method is that in some cases, a valid transponder at a valid location (i.e., near the vehicle) may receive a superposition of signals that does not produce two or more vector components higher than the noise level, and the vehicle controller may improperly deny access. Summary of the Invention

[0006] According to a first aspect, a method for wireless communication between a vehicle base station and a transponder is provided, the method comprising:

[0007] i) Drive the first and second antennas on the vehicle using the vehicle base station with a first drive current, wherein the first antenna is separated from the transponder through the vehicle portion where the vehicle base station is located;

[0008] ii) Detect three separate vector components of the respective fields transmitted by the first and second antennas and received at the transponder that are orthogonal to each other;

[0009] iii) Calculate the superposition factor of the first and second antennas based on the individual vector components;

[0010] iv) The first drive current, multiplied by the calculated superposition factor, is used to drive the first and second antennas simultaneously using the same phase;

[0011] v) Detect the three mutually orthogonal vector components of the superimposed signal received at the transponder, which includes signals from the two antennas;

[0012] vi) Determine whether two of the three detected vector components are higher than the threshold noise level;

[0013] vii) If fewer than two of the three detected vector components are above the threshold noise level, then repeat step iv), wherein one of the first and second antennas is driven by the calculated superposition factor multiplied by the adjustment factor multiplied by the first drive current; and

[0014] viii) If two of the three detected vector components are higher than the threshold noise level, the transponder is authenticated in response to the detected superimposed vector components being within the error-based range of the sum of the individual vector components of each of the first and second antennas multiplied by the superposition factor of the first and second antennas, respectively.

[0015] The advantage of the method described above is that it can take into account the existence of a 'black hole', which is a region in which the transponder can determine that the superimposed signals actually cancel each other out, leaving only a signal with a vector in only one direction, which would otherwise prevent authentication from occurring.

[0016] The adjustment factor can increase or decrease the signal strength value transmitted from one of the first and second antennas by, for example, 10% or more. The adjustment factor can, for example, increase or decrease the signal strength value transmitted from one of the first and second antennas by up to about 30%, 50%, or up to 75%.

[0017] The method may further include unlocking the vehicle and / or activating the vehicle's ignition circuit after authenticating the transponder.

[0018] In some cases, step iv) may be repeated no more than once. If, after repeating the steps, there is still no more than one detected vector component above the threshold noise level, the likelihood that the transponder is actually in a valid position is extremely low.

[0019] In other examples, if, after repeating step iv), fewer than two of the three detected vector components are above the threshold noise level, the adjustment factor can be changed and step iv) repeated again. In such cases, considering that the probability of the transponder being in an effective position after the required number of vector components has not yet been identified is extremely low, step iv) can be repeated no more than twice.

[0020] According to a second aspect, a system for wireless authentication of a transponder is provided, the system comprising:

[0021] Base station, said base station is installed on a vehicle; and

[0022] First and second antennas, which are connected to the base station and mounted at separate locations on the vehicle.

[0023] The base station is configured to:

[0024] i) Drive the first and second antennas using a first drive current;

[0025] ii) Detecting a signal from the transponder, the signal encoding three mutually orthogonal vector components of the corresponding fields transmitted by the first and second antennas and received at the transponder;

[0026] iii) Calculate the superposition factor of the first and second antennas based on their individual vector components;

[0027] iv) The first and second antennas are driven simultaneously using the calculated superposition factor multiplied by the first drive current and the same phase.

[0028] v) Detecting a signal from the transponder, the signal encoding three mutually orthogonal vector components of a superimposed signal including signals received at the transponder from the two antennas;

[0029] vi) Determine whether two of the three detected vector components are above the threshold noise level;

[0030] vii) If fewer than two of the three detected vector components are above the threshold noise level, then repeat step iv), wherein one of the first and second antennas is driven by the calculated superposition factor multiplied by the adjustment factor multiplied by the first drive current; and

[0031] viii) If two of the three detected vector components are higher than the threshold noise level, the transponder is authenticated in response to the detected superimposed vector components being within the error-based range of the sum of the individual vector components of each of the first and second antennas multiplied by the superposition factors of the inner and outer antennas, respectively.

[0032] The adjustment factor can increase or decrease the signal strength value transmitted from one of the first and second antennas by, for example, 10% or more. The adjustment factor can, for example, increase or decrease the signal strength value transmitted from one of the first and second antennas by up to 30%, 50%, or up to 75%.

[0033] The base station can be configured to unlock the vehicle and / or activate the vehicle's ignition circuit after authenticating the transponder.

[0034] In some examples, the base station may be configured to repeat step iv) no more than once.

[0035] In other examples, if, after repeating step iv), fewer than two of the three detected vector components are above the threshold noise level, the base station may be configured to change the adjustment factor and repeat step iv) again. In such cases, the base station may be configured to repeat step iv) no more than twice.

[0036] According to a third aspect, a computer program including instructions is provided, which, when executed, cause a processor of a vehicle base station to perform the method according to the first aspect.

[0037] A computer program may be provided that, when executed on a computer, causes the computer to configure the computer to include any device comprising the circuitry, controllers, sensors, filters, or means disclosed herein, or to perform any of the methods disclosed herein. The computer program may be a software implementation, and the computer may be considered any suitable hardware, including digital signal processors, microcontrollers, and implementations in read-only memory (ROM), erasable programmable read-only memory (EPROM), or electrically erasable programmable read-only memory (EEPROM), as are non-limiting examples. The software implementation may be an assembler.

[0038] The computer program may be provided on a computer-readable medium or may be implemented as a transient signal, which may be a physical computer-readable medium, such as an optical disc or storage device. This transient signal may be a network download, including an internet download.

[0039] These and other aspects of the invention will become apparent from the embodiments described below, and will be illustrated with reference to the embodiments described below. Attached Figure Description

[0040] The embodiments will be described by way of example only, in which:

[0041] Figure 1 An example wireless system with field superposition is shown;

[0042] Figure 2 A wireless car system with field superposition is shown;

[0043] Figure 3 A schematic diagram illustrating the vector components of the received signal;

[0044] Figure 4 The ac diagram illustrates the superposition of vector components of signals from the first and second antennas.

[0045] Figure 5 The diagram shows the superposition of vector components of signals from the first and second antennas, where one signal is adjusted to avoid zero vector components in the superimposed signal; and

[0046] Figure 6 A schematic flowchart illustrating an example method for authenticating wireless transponders using field overlay.

[0047] It should be noted that the figures are illustrative and not drawn to scale. For clarity and convenience in the illustrations, the relative dimensions and proportions of the parts in these figures have been shown by enlarging or reducing them in size. The same reference numerals are generally used to refer to corresponding or similar features in modified and different embodiments. Detailed Implementation

[0048] Figure 1 An example wireless system 100 with field superposition is shown. System 100 includes first and second antennas 110 and 120, which may be a main antenna 110 and an internal antenna 120, respectively. Antennas 110 and 120 transmit signals from a base station / controller 130 to a remote transponder 140. The internal antenna 120 is shielded, for example, by a vehicle housing or other components, to prevent direct access by the transponder 140.

[0049] Base station 130 drives main antenna 110 and internal antenna 120, and transponder 140 detects signals from the antennas, including the vector components of each signal. Transponder 140 transmits encrypted information characterizing these detected signals back to base station 130, which uses the information to generate a field superposition factor for driving each antenna. Base station 130 further encrypts the superposition factor and sends it to transponder 140.

[0050] Then, base station 130 applies a corresponding superposition factor to simultaneously drive each antenna. Transponder 140 detects the superimposed signal, which is used in conjunction with the superposition factor to determine whether the superimposed signal, comprising the combined signal from each antenna, is within an error factor. In some embodiments, the superimposed signal is authenticated by determining whether each of the three vector components (e.g., x, y, and z) is within the error factor of the vector. If the combined signal is within the error factor, the transponder is authenticated. This authentication can be used, for example, to operate or enable a system, such as an entry / locking mechanism or an ignition mechanism. Alternatively, calculations for authenticating the signal can be performed at one or both the transponder and the base station, where the transponder transmits information characterizing the received signal to the base station for such calculations as in the latter example.

[0051] Figure 2 An example wireless automotive system 200 with field superposition is shown. System 200 includes a base station 250 within a vehicle 210, an external first antenna 220, and an internal second antenna 222. An optional external third antenna 224 is located opposite the first antenna 220 relative to the vehicle 210. The positioning of the respective antennas can be varied to suit different embodiments and applications to different types of vehicles 210, wherein the positioning of both the vehicle and the antenna is an example of numerous vehicle and antenna configurations (where the first antenna 222 is shielded).

[0052] The first and second antennas 220 and 222 are each configured to transmit a signal detectable by a transponder 240 within an indicated driver detection area 230, which may be, for example, within the range of a door handle of the vehicle 210. When in use, an external fourth antenna 226 may also be configured to transmit a signal to the transponder 240 within the driver detection area 230.

[0053] Vehicle 210 shields its internal second antenna 222 from external transponders, making signals from the internal second antenna 222 undetectable by the transponder in the driver detection area 230. For example, glass, metal, or other components of vehicle 210 may distort signals transmitted by the internal antenna 222, preventing the transponder 240 from directly detecting signals generated at the antenna 222.

[0054] For example, transponder 240 is shown placed in driver detection area 230, representing an exemplary interaction with system 200. Optionally, transponder 240 is part of the system and is used to transmit signals to base station 250 in vehicle 210 via one or two antennas 220 and 222 (or 224 in implementation). Figure 1 In system 100, base station 250 is connected to each of antennas 220, 222 (and 224, 226 in implementation) to transmit and receive signals via the antennas.

[0055] Base station 250 (e.g., circuitry within vehicle 210) drives antennas 220 and 222 with an initial transmission current for each antenna (e.g., the current may differ if the antennas are subsequently driven). A signal with a corresponding vector component corresponding to each antenna 220 and 222 is detected at a transponder (e.g., 240) and said signal (e.g., encrypted) is transmitted back to the base station in vehicle 210. The base station uses the detected vector component of each antenna 220 and 222 along with a random field strength value (high enough to account for noise / error) to generate a field strength factor to apply to the corresponding signal subsequently driven in each of the antennas.

[0056] Then, base station 250 drives antennas 220 and 222 simultaneously and in the same phase using the current of each antenna, the current corresponding to the field strength factor of the antenna multiplied by the initial current previously applied to the antenna. The superimposed signal detected at the transponder is processed with error data corresponding to the respective antenna and the known field strength factor of each antenna to determine the authenticity of transponder 240. This authenticity can be determined, for example, by determining whether transponder 240, which receives and processes the signal, is within the driver detection region 230 or receives a signal detected by a relay transponder within the detection region. For example, if transponder 240 is a relay transponder and transponder 250 is actually authenticated for vehicle 210 but outside the driver detection region 230, relay transponder 240 cannot generate a field from each antenna with the corresponding vector value.

[0057] Further details of the method of authentication using superimposed transponders are disclosed in EP2498226A2. Figure 1 and 2 The above paragraph is derived from EP2498226A2.

[0058] Figure 3 The diagram schematically illustrates how a vector 301, representing the strength and direction of a signal, can be divided into three components, x, y, and z, along corresponding mutually orthogonal axes, with vector 301 representing the geometric sum of the three components.

[0059] Figure 4a, b, and c schematically illustrate the effect of superposition of signals transmitted by the first and second antennas, which may be, for example, Figure 2 The first and second antennas 220, 222 or of the example system 200 shown in the figure Figure 1 The system 100 shown includes first and second antennas 110 and 120. In each case, the signal shown is received by transponders 240 and 140 located at unknown positions relative to the antennas. The signal 401 from the first antenna is superimposed with the signal 402 from the second antenna to produce a superimposed signal 403. Because the y-components of the first and second signals 401 and 402 are sufficiently close in magnitude, the components effectively cancel each other out, resulting in a zero y-component in the superimposed signal 403. In fact, if the superimposed signal results in a component below a threshold noise level, a zero result will be produced. Therefore, the resulting superimposed signal 403 actually contains only two components, in this case, in the x and z directions.

[0060] In some cases, more than one component of the first and second signals 401, 402 may be canceled out, resulting in zero components on both axes and only a single resulting component. According to the authentication process mentioned above, this would be interpreted as a relay station attack, and the transponder would fail to be authenticated. Depending on the specific field pattern generated by the antenna location, vehicle configuration, and surrounding environment, there may be multiple relative positions and orientations where the transponder fails to be authenticated due to the superposition of signals producing only a component along one axis.

[0061] To account for the possibility of a “black hole” where the transponder cannot be authenticated if the response from the transponder results in fewer than two components exceeding the detected threshold noise level, additional operational sequences may be included in the method for authenticating the transponder.

[0062] Figure 5 The effect of applying an adjustment factor to one of the signals transmitted by the antennas is illustrated schematically. In this case, the signal 502 from the second antenna is reduced in magnitude, for example, by about 50%, while the signal 501 from the first antenna remains at the same level as before. The resulting superimposed signal 503 now has components above the noise level on all three orthogonal axes. Therefore, the resulting signal transmitted from the transponder to the base station enables the transponder to be authenticated and allowed access to the vehicle.

[0063] The signal from the second antenna can be reduced by decreasing the current supplied from the base station to the antenna. Alternatively, the signal can be increased to provide the same effect. The magnitude difference between the currents supplied to the second antenna can be at least 10%, and can be as high as about 30%, 50%, or up to 75%.

[0064] Figure 6This diagram illustrates a series of steps involved in an example method for authenticating a transponder, with the left-hand side indicating operations performed at the base station and antenna, and the right-hand side indicating operations performed by the transponder. In a first step 601, a first transmission 621 is initiated from the first antenna. At 602, this transmission 621 is received by the transponder, which then responds by transmitting a signal 622 encoding the vector components of the received signal. At 603, this signal 622 is received by the first antenna. In step 604, a second transmission 623 is initiated from the second antenna. At 605, this second transmission 623 is received at the transponder, which then responds by transmitting a signal 624 encoding the vector components of the received signal. At step 606, this signal 624 is received by the second antenna. Then, at step 607, the base station calculates a superposition factor for the first and second antennas based on the individual vector component information received from the transponder, and at step 608, multiplies the calculated superposition factor by the drive currents used for the first and second transmissions, respectively, driving the first and second antennas simultaneously with the same phase, thereby transmitting a superimposed signal 625 to the transponder. At 609, the transponder detects the superimposed signal, and the transponder subsequently responds by transmitting a signal 626 encoded with the vector components of the received signal, which is received at the base station at 610. In step 611, the base station determines whether two of the three detected vector components are above a threshold noise level. If fewer than two of the three detected vector components are above the threshold noise level, step 608 is repeated, where one of the first and second antennas is driven by a calculated superposition factor multiplied by an adjustment factor multiplied by a first drive current. If two of the three detected vector components are above the threshold noise level, in step 612, in response to the detected superimposed vector components being within an error-based range of the sum of the individual vector components of each of the first and second antennas multiplied by the superposition factors of the first and second antennas, the base station authenticates the transponder. The base station can then unlock the vehicle and / or enable the vehicle's ignition circuit.

[0065] If it is unlikely that repeating step 608 with the adjustment factor will result in the two detected vector components exceeding the threshold noise level, the base station may change the adjustment factor and repeat the step. Otherwise, the base station may refuse to authenticate the transponder, and the process begins again.

[0066] By reading this disclosure, those skilled in the art will understand other variations and modifications. Such variations and modifications may involve equivalent and other features that are already known in the field of wireless communications and can be used as substitutes for or supplements to the features already described herein.

[0067] Although the appended claims are directed to specific combinations of features, it should be understood that the scope of the disclosure of this invention also includes any novel feature or combination of novel features or any generalization of such novel features as expressly or implicitly disclosed herein, regardless of whether such novel feature relates to the same invention as currently claimed in any of the claims or whether such novel feature alleviates any or all of the same technical problems as those alleviated by this invention.

[0068] Features described in the context of a single embodiment may also be provided in combination in a single embodiment. Conversely, for the sake of brevity, various features described in the context of a single embodiment may also be provided individually or in any suitable sub-combination. The applicant hereby reminds that new claims may be made for such features and / or combinations of such features during the examination of this application or any other application derived therefrom.

[0069] For completeness, the term "comprising" does not exclude other elements or steps, the term "a" or "an" does not exclude that a plurality of, a single processor or other unit may perform the functions of the several components described in the claims, and the reference numerals in the claims should not be construed as limiting the scope of the claims.

Claims

1. A method for wireless communication between a vehicle base station (130) and a transponder (140), characterized in that, The method includes: i) The first and second antennas (110, 120) on the vehicle are driven by the first driving current through the vehicle base station (130), wherein the first antenna (110) is separated from the transponder (140) through the vehicle part where the vehicle base station (130) is located; ii) Detect three separate vector components of the respective fields that are orthogonal to each other, transmitted by the first and second antennas (110, 120) and received at the transponder (140); iii) Calculate the superposition factor of the first and second antennas (110, 120) based on the individual vector components; iv) The first and second antennas (110, 120) are driven simultaneously using the calculated superposition factor multiplied by the first drive current and the same phase. v) Detect the three mutually orthogonal vector components of the superimposed signal received at the transponder (140), which includes signals from the two antennas (110, 120); vi) Determine whether two of the three detected vector components are higher than the threshold noise level; vii) If fewer than two of the detected three vector components are above the threshold noise level, then repeat step iv), wherein the second antenna (120) is driven by the calculated superposition factor multiplied by the adjustment factor multiplied by the first drive current, while the first antenna (110) is driven by the same first drive current as before; and viii) If two of the three detected vector components are higher than the threshold noise level, the transponder (140) is authenticated in response to the detected superimposed vector components being within the error-based range of the sum of the individual vector components of each of the first and second antennas multiplied by the superposition factor of the first and second antennas, respectively.

2. The method according to claim 1, characterized in that, The adjustment factor increases or decreases the signal strength value transmitted from one of the first and second antennas by 10% or more.

3. A system (200) for wireless authentication of a transponder (240), characterized in that, The system (200) includes: Base station (250), said base station (250) is mounted on vehicle (210); and First and second antennas (220, 222), which are connected to the base station (250) and mounted at separate locations on the vehicle (210), The base station (250) is configured to: i) Drive the first and second antennas (220, 222) using the first drive current; ii) Detecting a signal from the transponder (240) that encodes three mutually orthogonal vector components of the corresponding fields transmitted by the first and second antennas (220, 222) and received at the transponder (140); iii) Calculate the superposition factor of the first and second antennas (210, 220) based on the vector components; iv) The first and second antennas (220, 222) are driven simultaneously using the calculated superposition factor multiplied by the first driving current and the same phase. v) Detecting a signal from the transponder (240) that encodes three mutually orthogonal vector components of a superimposed signal comprising signals received at the transponder (240) from the two antennas (220, 222); vi) Determine whether two of the three detected vector components are higher than the threshold noise level; vii) If fewer than two of the detected three vector components are above the threshold noise level, then repeat step iv), wherein the second antenna (222) is driven by the calculated superposition factor and adjustment factor multiplied by the first drive current, while the first antenna (220) is driven by the same first drive current as before; and viii) If two of the three detected vector components are higher than the threshold noise level, the transponder (140) is authenticated in response to the detected superimposed vector components being within the error-based range of the sum of the individual vector components of each of the first and second antennas multiplied by the superposition factors of the inner and outer antennas, respectively.

4. The system (200) according to claim 3, characterized in that, The adjustment factor increases or decreases the signal strength value transmitted from one of the first and second antennas by 10% or more.

5. The system (200) according to claim 4, characterized in that, The adjustment factor increases or decreases the signal strength value transmitted from one of the first and second antennas by up to 30%.

6. The system (200) according to claim 4, characterized in that, The adjustment factor increases or decreases the signal strength value transmitted from one of the first and second antennas by 50%.

7. The system (200) according to claim 4, characterized in that, The adjustment factor increases or decreases the signal strength value transmitted from one of the first and second antennas by up to 75%.

8. The system (200) according to claim 3 or 4, characterized in that, The base station (250) is configured to unlock the vehicle after authenticating the transponder.

9. The system (200) according to claim 3 or 4, characterized in that, The base station is configured to repeat step iv) no more than once.

10. The system (200) according to claim 3 or 4, characterized in that, If, after repeating step iv), fewer than two of the three detected vector components are above the threshold noise level, the base station is configured to change the adjustment factor and repeat step iv again.

11. The system (200) according to claim 10, characterized in that, The base station is configured to repeat step iv) no more than twice.

12. A computer-readable medium including instructions, characterized in that, When the instruction is executed, it causes the processor of the vehicle base station to perform the method according to claim 1 or 2.

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