Determining when a portable key device is located on a front side or a back side

Abstract

A method for determining when a portable key device is located on a front side or a back side relative to a barrier fixed by an electronic lock is provided. The method is performed in a position determiner and comprises the steps of obtaining a channel impulse response, CIR, based on an impulse signal transmitted from the portable key device, the CIR being based on a plurality of samples of the impulse signal received by an antenna fixedly mounted relative to the electronic lock; and determining whether the portable key device is located on the front side or on the back side based on the CIR.

Description

Technical Field

[0001] This disclosure relates to the field of electronic locks, and more particularly to determining when a portable key device is positioned in front of or behind a barrier secured by an electronic lock. Background Technology

[0002] Locks and keys are evolving from traditional purely mechanical locks. Today, wireless interfaces exist for electronic locks, such as those that interact with portable key devices. For example, Radio Frequency Identification (RFID) has been used as a wireless interface.

[0003] When using RFID, the user needs to present the portable key device close to the reader connected to the lock. Furthermore, RFID requires a relatively large antenna in the reader next to the lock and consumes a significant amount of power. Notably, RFID requires the user to actively remove the portable key device (e.g., an RFID card or an NFC-enabled smartphone) and place it within centimeters of the lock. This is inconvenient and potentially insecure, as attackers can more easily steal the portable key device when it is presented to the lock for access control.

[0004] By using other short-range wireless communications with slightly longer ranges, such as Bluetooth Low Energy (BLE), Bluetooth, or UHF, portable key devices can remain in a pocket or handbag and still be used for access control. However, the increased range also introduces new problems. One issue arises if the lock unlocks whenever an authorized portable key device is within range: the electronic lock could be unintentionally unlocked when someone walks past it from the inside, allowing anyone to enter the restricted physical space.

[0005] By determining the position of the portable key device relative to the lock, it is possible to determine whether the portable key device (and therefore the user) is on the inside or outside. In this way, automatic access control can still be used, but a person walking on the inside will not trigger the unlocking process. Summary of the Invention

[0006] One objective is to improve the reliability of determining whether the portable key device is on the front or the rear side.

[0007] According to a first aspect, a method is provided for determining when a portable key device is located in front of or behind a barrier secured by an electronic lock. The method is performed in a position determiner and includes the steps of: obtaining a channel impulse response (CIR) based on pulse signals transmitted from the portable key device, the CIR being based on multiple samples of pulse signals received by an antenna fixed relative to the electronic lock; and determining whether the portable key device is located in front or behind based on the CIR.

[0008] The front side can be the side where the line of sight reaches the antenna, while the rear side is the side where the line of sight does not reach the antenna.

[0009] The steps of obtaining CIR may include obtaining a first CIR from a first antenna and a second CIR from a second antenna, in which case the determination step is based on determining the difference between the first CIR and the second CIR during the measurement period.

[0010] The difference between the first CIR and the second CIR can be determined by calculating the area between the envelopes of the first CIR and the second CIR during the measurement time period.

[0011] The difference between the first CIR and the second CIR can be determined by calculating the correlation between the envelope of the first CIR 30a and the envelope of the second CIR 30b during the measurement time period 32.

[0012] When the difference between the first CIR and the second CIR is greater than a threshold, this indicates that the portable key device is on the rear side, and when the difference between the first CIR and the second CIR is less than a threshold, this indicates that the portable key device is on the front side.

[0013] The steps can be determined based on the shape of the CIR during the measurement time period.

[0014] The determination steps can be based on comparing the energy of the CIR in a first time period with the energy of the CIR in a second time period, where both the first and second time periods are part of the measurement time period.

[0015] The determination step can be based on a machine learning model whose output is whether the portable key device is located in front or behind the barrier, and whose input is a CIR.

[0016] The pulse signal can be an ultra-wideband (UWB) signal.

[0017] According to a second aspect, a position determiner is provided for determining whether a portable key device is located in front of or behind a barrier secured by an electronic lock. The position determiner includes: a processor; and a memory storing instructions that, when executed by the processor, cause the position determiner to perform the following operations: obtaining a channel impulse response (CIR) based on pulse signals transmitted from the portable key device, the CIR being based on multiple samples of pulse signals received by an antenna fixed relative to the electronic lock; and determining whether the portable key device is located in front of or behind based on the CIR.

[0018] The front side can be the side where the line of sight reaches the antenna, in which case the rear side is the side where the line of sight does not reach the antenna.

[0019] Instructions for obtaining CIR may include instructions that, when executed by the processor, cause the position determiner to obtain a first CIR from a first antenna and a second CIR from a second antenna. In this case, instructions for determining include instructions that, when executed by the processor, cause the position determiner to determine the difference between the first CIR and the second CIR during the measurement period.

[0020] The difference between the first CIR and the second CIR can be determined by calculating the area between the envelopes of the first CIR and the second CIR during the measurement time period.

[0021] The difference between the first CIR and the second CIR can be determined by calculating the correlation between the envelope of the first CIR 30a and the envelope of the second CIR 30b during the measurement time period 32.

[0022] When the difference between the first CIR and the second CIR is greater than a threshold, this indicates that the portable key device is on the rear side, and when the difference between the first CIR and the second CIR is less than a threshold, this indicates that the portable key device is on the front side.

[0023] The instructions used for determination may include instructions that, when executed by the processor, cause the position determiner to determine the side based on the shape of the CIR during the measurement time period.

[0024] The instructions for determination may include instructions that, when executed by the processor, cause the position determiner to determine the side based on a comparison of the energy of the CIR in a first time period with the energy of the CIR in a second time period, in which case both the first and second time periods are part of a measurement time period.

[0025] The instructions for determining the location may include instructions that, when executed by the processor, cause the location determiner to determine the side based on a machine learning model whose output is whether the portable key device is located on the front or rear side relative to the barrier, and whose input is a CIR.

[0026] The pulse signal can be an ultra-wideband (UWB) signal.

[0027] According to a third aspect, a computer program is provided for determining whether a portable key device is located in front of or behind a barrier secured by an electronic lock. The computer program includes computer program code that, when executed on a position determiner, causes the position determiner to perform the following operations: obtaining a channel impulse response (CIR) based on pulse signals transmitted from the portable key device, the CIR being based on multiple samples of pulse signals received by an antenna fixed relative to the electronic lock; and determining whether the portable key device is located in front of or behind based on the CIR.

[0028] According to a fourth aspect, a computer program product is provided, comprising a computer program according to a third aspect and a computer-readable device having the computer program stored thereon.

[0029] Generally, unless otherwise expressly defined herein, all terms used in the claims shall be interpreted according to their ordinary meaning in the art. All references to “a / an / the element, device, component, apparatus, step, etc.” shall be explicitly interpreted as referring to at least one instance of the element, device, component, apparatus, step, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless expressly stated. Attached Figure Description

[0030] Now, with reference to the accompanying drawings, aspects and implementation methods will be described by way of example, in which:

[0031] Figure 1 This is a schematic diagram illustrating an electronic access control system as an environment in which the embodiments proposed herein can be applied;

[0032] Figure 2 It is shown Figure 1 A schematic diagram of the components of the position determiner;

[0033] Figures 3A to 3B This is a schematic graph showing the pulse signal from the portable key device and the corresponding channel pulse response;

[0034] Figure 4A and Figure 4B This is a schematic graph showing how CIR differs between different antennas;

[0035] Figure 5A and Figure 5B It is a schematic graph showing how CIR spreads differently when the portable key device is in front of or behind the position determiner;

[0036] Figure 6 This is a flowchart illustrating an implementation of a method for determining when a portable key device is positioned relative to the front or rear side of a barrier secured by an electronic lock; and

[0037] Figure 7 An example of a computer program product that includes a computer-readable device is shown. Detailed Implementation

[0038] Various aspects of this disclosure will now be described more fully below with reference to the accompanying drawings, in which certain embodiments of the invention are illustrated. However, these aspects may be implemented in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and so as to fully convey the scope of all aspects of the invention to those skilled in the art. Throughout the specification, the same reference numerals denote the same elements.

[0039] The implementation described herein determines when a portable key device is positioned in front of or behind a barrier (e.g., a door) based on channel impulse response (CIR). The impulse is transmitted by the portable key device, and the CIR is based on reception by an antenna fixed relative to the electronic lock. Whether the portable key device is in front or behind will affect the CIR received by the fixed antenna. This allows for convenient and reliable determination of front or behind, thereby enabling access control, for example, to be performed only when the portable key device is in front of the barrier (i.e., on the outside).

[0040] Figure 1 This is a schematic diagram illustrating an electronic access control system 10 as an environment in which the embodiments proposed herein can be applied. Access to the rear side 16 of the position determiner 1 is restricted by a selectively unlockable physical barrier 15. The physical barrier 15 is located between the rear side 16 and the front side 14 of the position determiner. The rear side 16 of the position determiner 1 is a restricted physical space, and the front side 14 of the position determiner 1 is an accessible physical space. Note that the front side 14 of the position determiner 1 may itself be a restricted physical space, but it is accessible relative to that particular position determiner 1. In other words, the rear side 16 of the position determiner 1 is inside the physical barrier 15, and the front side 14 of the position determiner is outside the physical barrier 15. The barrier 15 may be a door, gate, hatch, window, drawer, etc. A handle 17 or doorknob is provided to allow the barrier 15 to be opened once unlocked. An electronic lock 12 is provided to unlock or lock the barrier 15. The electronic lock 12 can be in an unlocked or locked state. The electronic lock 12 can be detached from but connected to the position determiner 1, or it can be part of the position determiner 1 (not shown). The barrier 15 is disposed in the surrounding fixed structure 11, such as a wall, fence, or vehicle.

[0041] The location determiner 1 includes one or more antennas 13. Each antenna is fixedly mounted relative to the electronic lock 12. Each antenna can be a directional antenna, where the gain varies depending on the direction of reception or transmission. In such a case, the antenna faces the front side 14 of the location determiner 1. This means that the antenna 13 has a line-of-sight with the portable key device in the front side 14 of the location determiner. Line-of-sight is interpreted in relation to line-of-sight wireless transmission in radio signal propagation. In other words, a thin plastic cover or similar material may be present to protect the antenna 13 from the spatial influence of the front side 14 of the location determiner 1. The direction in which the antennas 13a, 13b face is the direction in which signal reception and transmission best occur. Therefore, when the antenna is a directional antenna, the maximum gain of the antenna faces the front side 14. This can be achieved, for example, by providing a ground plane on the opposite side (rear side) of the antenna, as described below.

[0042] The front side 14 can be defined as the side of the position determiner that provides line-of-sight communication with the portable key device, and the rear side 16 can be defined as the opposite side, i.e., the side of the position determiner that does not provide line-of-sight communication with the portable key device.

[0043] The location determiner 1 is used to determine when a first portable key device 2a and a second portable key device 2b near any portable key device, such as an electronic lock 12, are located in front of or behind the location determiner 1. This determination is based on relative to the location determiner 1 and may be based, for example, on UWB (Ultra-Wideband) technology. UWB provides high accuracy in device positioning, but at the cost of relatively high energy consumption. Alternatively or additionally, the positioning module 13 may be based on other positioning technologies.

[0044] The electronic lock 12 can receive signals from or send signals to the portable key devices 2a to 2b via a communication channel, which may be a short-range wireless interface. The electronic lock 12 can use the same antenna 13 used by the position determiner 1 for the short-range wireless interface.

[0045] Optionally, the electronic lock 12 includes a separate unit for communicating with and evaluating access to portable key devices 2a to 2b, also referred to as an access control reader. In this example, there is a first portable key device 2a and a second portable key device 2b. The portable key devices 2a to 2b can be implemented using any suitable means that can be carried by a user and used by the electronic lock 12 to evaluate whether access is permitted by communicating via a communication channel. The portable key device may include a digital encryption key for electronic authentication.

[0046] Portable key devices 2a to 2b are typically carried or worn by a user and can be implemented as smartphones, wearable devices, remote keys, etc. In this example, the first portable key device 2a is carried by the first user 4a, and the second portable key device 2b is carried by the second user 4b. The first user 4a and the first portable key device 2a are located on the front side 14 of the position determiner 1 (i.e., on the outside of the electronic lock 12), and the second user 4b and the second portable key device 2b are located on the rear side 16 of the position determiner (i.e., on the inside of the electronic lock 12).

[0047] The short-range wireless interface between the portable key devices 2a to 2b and the electronic lock 12 is a radio frequency (RF) wireless interface, and can employ, for example, Bluetooth Low Energy (BLE), Bluetooth, ZigBee, Radio Frequency Identification (RFID), any IEEE 802.11 standard, any IEEE 802.15 standard, etc. Using the communication channel, the portable key devices 2a to 2b can be authenticated, and authorization determination (access control) can be performed by the electronic lock 12 or an access control reader. Communication via the short-range wireless interface can be encrypted.

[0048] When access is granted via access control of electronic lock 12, electronic lock 12 is set to the unlocked state. When electronic lock 12 is in the unlocked state, barrier 15 can be opened, and when electronic lock 12 is in the locked state, barrier 15 cannot be opened. In this way, access to the rear side 16 of position determiner 1 is controlled by electronic lock 12. It should be noted that electronic lock 12 can be installed in the fixed structure 11 via physical barrier 15 (as shown) or installed in the physical barrier 15 itself (not shown).

[0049] The electronic lock 12 can perform access control on any portable key devices 2a to 2b presented to it. However, according to the embodiment presented herein, access is only permitted after the portable key device 2a is determined to be in front of the location determiner 14. The reason for this is that if the electronic lock 12 permits access whenever a portable key device is within communication range, a second portable key device 2b in the restricted physical space 16 (i.e., on the inside) could cause the electronic lock 12 to unlock when the second user 5 walks by without intending to unlock the electronic lock 12 to open the barrier. Then, an unauthorized person could open the barrier 15 and enter the restricted physical space 16.

[0050] The electronic lock optionally includes communication capabilities to connect to the server 6 of the electronic access control system 10 via network 5. The network can be a wide area network such as the Internet, and the portable key devices 2a to 2b can connect to the wide area network, for example, via WiFi (e.g., any IEEE 802.11x standard) or cellular networks such as LTE (Long Term Evolution), next-generation mobile networks (5G), UMTS (Universal Mobile Telecommunications System) using W-CDMA (Wideband Code Division Multiplexing), etc.

[0051] Figure 2 It is shown Figure 1 A schematic diagram of the components of the position determiner 1. The processor 60 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions 67 stored in memory 64, which can therefore be a computer program product. Alternatively, the processor 60 can be implemented using an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), etc. The processor 60 can be configured to execute the following references. Figure 6 The method described.

[0052] Memory 64 may be any combination of random access memory (RAM) and / or read-only memory (ROM). Memory 64 also includes permanent storage devices, such as magnetic storage, optical storage, solid-state storage, or even remotely mounted memory, any one or a combination thereof.

[0053] A data memory 66 is also provided for reading and / or storing data during the execution of software instructions in the processor 60. The data memory 66 can be any combination of RAM and / or ROM.

[0054] The location determiner 1 also includes an I / O interface 62 for communicating with external and / or internal entities. Optionally, the I / O interface 62 also includes a user interface. In this embodiment, the location determiner 1 includes two separate antennas 13a and 13b. However, the location determiner can be implemented with any suitable number of antennas.

[0055] To avoid ambiguity in the concepts presented in this paper, other components of the position determiner 1 have been omitted.

[0056] Figures 3A to 3B This is a schematic graph showing the UWB pulse signal 29 from the portable key devices 2a and 2b and the corresponding channel impulse response (CIR). The horizontal axis represents time, and the vertical axis represents amplitude.

[0057] exist Figure 3AThe image shows a UWB pulse signal 29 from a portable key device, which is generated and transmitted from the portable key device. The UWB pulse signal 29 can be transmitted by the portable key device based on a command triggered by a position determiner.

[0058] exist Figure 3B The diagram shows CIR 30. In this case, CIR 30 is how the UWB pulse signal 29 is received by one of the antennas 13a and 13b of the position determiner. Due to attenuation, reflection, absorption, antenna shape, and other radio environmental factors, CIR 30 differs in shape from the UWB pulse signal 29.

[0059] Since the radio environmental factors are significantly different if the UWB pulse signal is received from the front side 14 under line-of-sight conditions and if the UWB pulse signal is received from the rear side 16, the CIR can be used to determine whether the transmitter of the UWB pulse signal 29 (i.e., the portable key device) is located in front of the position determiner 14 or rear of the position determiner 16.

[0060] Figure 4A and Figure 4B This is a schematic graph illustrating how the CIR differs between different antennas. A first CIR 30a is shown, which is the envelope of the signal received by the first antenna. A second CIR 30b is shown, which is the envelope of the signal received by the second antenna.

[0061] exist Figure 4A In the diagram, a portable key device based on a UWB pulse signal 29 transmitted from the front side 14 is shown, comprising a first CIR 30a and a second CIR 30b. It can be seen that the first CIR 30a and the second CIR 30b are very similar and follow each other very well during the measurement period 32. When the UWB pulse signal 29 is received from the front side 14, there is a line of sight to the antenna. In this case, the difference between the CIR shapes of the two antennas is very small.

[0062] exist Figure 4B The portable key device based on transmitting UWB pulse signals from the rear side 16 shows a first CIR 30a and a second CIR 30b. In this case, the radio signal will experience different radio environments and be affected by different reflections and absorptions, resulting in a significant difference in the shape between the first CIR 30a and the second CIR 30b.

[0063] Based on how well the CIRs 30a to 30b match when the portable key device is on the front side 14 or the rear side 16, the position determiner 1 can deduce that if the difference between the CIR shapes of the two antennas 13a and 13b is less than a threshold, the portable key device is on the front side 14, and if the difference between the CIR shapes of the two antennas 13a and 13b is greater than a threshold, the portable key device is on the rear side.

[0064] Figure 5A and Figure 5B This is a schematic graph illustrating how the CIR spreads differently depending on whether the portable key device is in front of or behind the position determiner. A first CIR 30a is shown, which is the envelope of the signal received by the first antenna. A second CIR 30b is shown, which is the envelope of the signal received by the second antenna. Here, the measurement period 32 includes a first time period 33a and a second time period 33b. The first time period 33a and the second time period 33b do not need to cover the entire measurement period 32. In one embodiment, the first time period 33a and the second time period 33b do not overlap. The first time period 33a and the second time period 33b can be fixed to a pre-configured duration, for example, starting when the CIR is greater than a certain amplitude, and the second time period 33b follows the first time period 33a for the pre-configured duration. Alternatively, the first time period and the second time period can be dynamically determined based on predetermined rules.

[0065] exist Figure 5A In the middle, a portable key device based on UWB pulse signal 29 transmitted from the front side 14 is shown with a first CIR 30a and a second CIR 30b.

[0066] Here, there is a line of sight between the portable key device and the antenna, in which case the CIR reflects the UWB pulse signal 29 quite well. When the portable key device is on the front side 14, a greater amount of energy is received in the first time period 33a than in the second time period 33b. The energy can be defined as the integral of the CIR under discussion over the time period, i.e., the area under the CIR.

[0067] exist Figure 5B In the middle, a portable key device based on UWB pulse signal 29 transmitted from the rear side 16 is shown with a first CIR 30a and a second CIR 30b.

[0068] In this scenario, the UWB pulse signal is reflected and absorbed by different materials before being received by the antenna. This diffuses the UWB pulse signal, resulting in a more dispersed energy distribution of the CIR over time compared to when the portable key device is on the front side.

[0069] In other words, when the portable key device is on the rear side 16, the energy of the CIR in the second time period 33b is more similar to the amount of energy of the CIR in the first time period 33a.

[0070] Therefore, the side of the portable key device can be determined by evaluating the reference between the energy of the CIR in the first time period 33a and the energy of the CIR in the second time period 33b. This reference can be for each CIR or a combination of CIRs. It should be noted that more than two time periods can exist. For example, three time periods can exist, and one or more energy ratios between different time periods can be used to determine which side the portable key device is located on.

[0071] Figure 6 This is a flowchart illustrating an embodiment of a method for determining when portable key devices 2a, 2b are located relative to the front side 14 or rear side 16 of the barrier 15 secured by the electronic lock 12. The method is implemented in a position determiner 1. The front side 14 can be defined as the side where the position determiner's line of sight reaches the antennas 13, 13a, 13b, and the rear side 16 can be defined as the side where the line of sight does not reach the antennas 13, 13a, 13b.

[0072] In step 40 of obtaining the CIR, the position determiner obtains one or more CIRs 30a, 30b, 30c based on pulse signals 29 transmitted from portable key devices 2a, 2b. Each CIR 30a, 30b, 30c is based on multiple samples of pulse signals 29 received by corresponding antennas 13, 13a, 13b. As mentioned above, each antenna 13, 13a, 13b is fixedly mounted relative to the electronic lock 12.

[0073] This step may include obtaining a first CIR 30a from a first antenna 13a and a second CIR 30b from a second antenna 13b.

[0074] In step 42 of the side determination, the position determiner determines whether the portable key devices 2a, 2b are located on the front side 14 or the rear side 16 based on the CIR. This determination takes into account the shape of the CIR, not just finding the first peak. For example, the determination may consider the measurement period 35 of the CIR containing at least two peaks. The side determination is based on the shape of the CIR during the measurement period 32.

[0075] When the first CIR 30a and the second CIR 30b are obtained in the preceding step 40, the determination of the side can be based on determining the difference between the first CIR and the second CIR over the measurement time period, such as Figure 4A and Figure 4B As shown and as described above.

[0076] The difference between the first CIR and the second CIR can be determined by calculating the area between the envelope of the first CIR 30a and the envelope of the second CIR 30b during the measurement time period 32.

[0077] The difference between the first CIR and the second CIR can be determined by calculating the correlation between the envelope of the first CIR 30a and the envelope of the second CIR 30b during the measurement time period 32.

[0078] In determining the side, when the difference between the first CIR and the second CIR is greater than a threshold, this can indicate that the portable key devices 2a and 2b are on the rear side 16. Similarly, when the difference between the first CIR and the second CIR is less than a threshold, this can indicate that the portable key devices 2a and 2b are on the front side 14.

[0079] In one implementation, the determination of the side is based on comparing the energy of the CIR in a first time period 33a with the energy of the CIR in a second time period 33b, where both the first time period 33a and the second time period 33b are part of a measurement time period. This is in Figures 5A to 5B It is shown in the diagram and described above.

[0080] Optionally, the determination of the side is based on a machine learning model whose output is whether the portable key device is located on the front or rear side relative to the barrier, and whose input is a CIR.

[0081] Optionally, the proposed method can be combined with angle of arrival (AHA) measurement to improve accuracy. AHA measurement is based on the time difference between the two antennas 13a and 13b receiving the UWB signal. The AHA defines the direction from the antenna to the portable key device. For example, in one embodiment, if the distance is determined to be less than a threshold distance, and the AHA is within a predetermined range, and the above method indicates that the portable key device is on the outside (i.e., the front), access can be permitted (if the portable key device is authenticated and authorized for access).

[0082] Figure 7 An example of a computer program product 90 including a computer-readable device is shown. A computer program 91 may be stored on this computer-readable device, which can cause a processor to perform methods according to the embodiments described herein. In this example, the computer program product is in the form of a removable solid-state memory (e.g., a Universal Serial Bus (USB) drive). As mentioned above, the computer program product can also be implemented in the memory of a device, for example... Figure 6Computer program product 64. Although computer program 91 is schematically shown herein as part of removable solid-state storage, computer program may be stored in any manner suitable for computer program product—such as another type of removable solid-state storage, or optical discs such as CD (compressed disc), DVD (digital versatile disc), or Blu-ray disc.

[0083] The foregoing has primarily described various aspects of this disclosure with reference to some embodiments. However, as will be readily understood by those skilled in the art, other embodiments besides those disclosed above may also be within the scope of the invention as defined by the appended claims. Therefore, while various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes and are not intended to be limiting, wherein the true scope and spirit are indicated by the appended claims.

Claims

1. A method for determining when a portable key device (2a, 2b) is located on the front (14) or rear (16) side of a barrier (15) secured by an electronic lock (12), the method being performed in a position determiner (1) and comprising the steps of: (40) Channel impulse response (CIR) (30a, 30b, 30c) is obtained based on the pulse signal (29) transmitted from the portable key device (2a, 2b), the CIR (30a, 30b, 30c) being based on multiple samples of the pulse signal (29) received by the antenna (13, 13a, 13b) fixed relative to the electronic lock (12); and Based on the CIR, determine (42) whether the portable key device (2a, 2b) is located on the front side (14) or on the rear side (16). The step of obtaining (40) the CIR includes obtaining a first CIR from a first antenna and a second CIR from a second antenna, and the step of determining (42) is based on determining the difference between the first CIR and the second CIR during the measurement period, wherein both the first antenna and the second antenna face the front side.

2. The method according to claim 1, wherein, The front side (14) is the side from which the line of sight reaches the antenna (13, 13a, 13b), and the rear side (16) is the side from which the line of sight does not reach the antenna (13, 13a, 13b).

3. The method according to claim 1, wherein, The difference between the first CIR and the second CIR is determined by calculating the area between the envelopes of the first CIR and the second CIR during the measurement time period.

4. The method according to any one of claims 1 to 3, wherein, The difference between the first CIR and the second CIR is determined by calculating the correlation between the envelope of the first CIR (30a) and the envelope of the second CIR (30b) during the measurement time period (32).

5. The method according to any one of claims 1 to 3, wherein, A difference between the first CIR and the second CIR greater than a threshold indicates that the portable key device (2a, 2b) is on the rear side (16), and a difference between the first CIR and the second CIR less than a threshold indicates that the portable key device (2a, 2b) is on the front side (14).

6. The method according to any one of claims 1 to 3, wherein, The determination step is based on the shape of the CIR during the measurement time period.

7. The method according to any one of claims 1 to 3, wherein, The determination step is based on comparing the energy of the CIR in the first time period (33a) with the energy of the CIR in the second time period (33b), wherein the first time period (33a) and the second time period (33b) are both part of the measurement time period.

8. The method according to any one of claims 1 to 3, wherein, The determination step is based on a machine learning model whose output is whether the portable key device is located on the front or the rear side relative to the barrier, and whose input is the CIR.

9. The method according to any one of claims 1 to 3, wherein, The pulse signal is an ultra-wideband (UWB) signal.

10. A position determiner (1) for determining whether a portable key device (2a, 2b) is located on the front side or the rear side relative to a barrier secured by an electronic lock (12), the position determiner (1) comprising: Processor (60); as well as Memory (64), which stores instructions (67), which, when executed by the processor, cause the position determiner (1) to perform the following operations: The channel impulse response (CIR) is obtained based on the pulse signal transmitted from the portable key device, the CIR being based on multiple samples of the pulse signal received by an antenna fixedly mounted relative to the electronic lock; as well as Based on the CIR, determine whether the portable key device (2a, 2b) is located on the front side or the rear side; The instructions for obtaining the CIR include instructions (67) that, when executed by the processor, cause the position determiner (1) to obtain a first CIR from the first antenna and a second CIR from the second antenna, and the instructions for determining include instructions (67) that, when executed by the processor, cause the position determiner (1) to determine the difference between the first CIR and the second CIR during the measurement period, wherein both the first antenna and the second antenna face the front side.

11. The position determiner (1) according to claim 10, wherein, The front side (14) is the side from which the line of sight reaches the antenna (13, 13a, 13b), and the rear side (16) is the side from which the line of sight does not reach the antenna (13, 13a, 13b).

12. The position determiner (1) according to claim 10, wherein, The difference between the first CIR and the second CIR is determined by calculating the area between the envelopes of the first CIR and the second CIR during the measurement time period.

13. The position determiner (1) according to any one of claims 10 to 12, wherein, The difference between the first CIR and the second CIR is determined by calculating the correlation between the envelope of the first CIR (30a) and the envelope of the second CIR (30b) during the measurement time period (32).

14. The position determiner (1) according to any one of claims 10 to 12, wherein, A difference between the first CIR and the second CIR greater than a threshold indicates that the portable key device (2a, 2b) is on the rear side (16), and a difference between the first CIR and the second CIR less than a threshold indicates that the portable key device (2a, 2b) is on the front side (14).

15. The position determiner (1) according to any one of claims 10 to 12, wherein, The instructions for determination include instructions (67) that, when executed by the processor, cause the position determiner (1) to determine the side based on the shape of the CIR during the measurement time period.

16. The position determiner (1) according to any one of claims 10 to 12, wherein, The instructions for determination include instructions (67) that, when executed by the processor, cause the position determiner (1) to determine the side based on a comparison of the energy of the CIR in a first time period (33a) with the energy of the CIR in a second time period (33b), wherein the first time period (33a) and the second time period (33b) are both part of the measurement time period.

17. The position determiner (1) according to any one of claims 10 to 12, wherein, The instructions for determination include, when executed by the processor, instructions (67) to cause the position determiner (1) to determine the side based on a machine learning model whose output is whether the portable key device is located on the front side or the rear side relative to the barrier, and whose input is the CIR.

18. The position determiner (1) according to any one of claims 10 to 12, wherein, The pulse signal is an ultra-wideband (UWB) signal.

19. A computer program product (64, 90) comprising a computer program (67, 91) and a computer-readable device, the computer program being stored on the computer-readable device, the computer program being configured to determine whether a portable key device (2a, 2b) is located on the front or rear side relative to a barrier secured by an electronic lock (12), the computer program comprising computer program code that, when executed on a position determiner (1), causes the position determiner (1) to perform the following operations: The channel impulse response (CIR) is obtained based on a pulse signal transmitted from the portable key device, the CIR being based on multiple samples of the pulse signal received by an antenna fixedly mounted relative to the electronic lock; and Based on the CIR, determine whether the portable key device (2a, 2b) is located on the front side or the rear side; in, The computer program code for obtaining the CIR includes computer program code that, when executed on the position determiner (1), causes the position determiner (1) to obtain a first CIR from the first antenna and a second CIR from the second antenna, and wherein the computer program code for determining includes computer program code that, when executed on the position determiner (1), causes the position determiner (1) to determine the difference between the first CIR and the second CIR during the measurement time period, wherein both the first antenna and the second antenna face the front side.

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