Device for determining the distance from a transmitter to a receiver

Abstract

The invention relates to a device for determining the distance from a transmitter (6) to a receiver (8), wherein the transmitter and the receiver are arranged to communicate via a radio channel (10). The device comprises at least one measuring unit (2) which is arranged to measure reception level values ​​and flight time measurement values ​​of the radio channel. The device also comprises a processing unit (4) which is arranged to compare the measured value pairs of reception level values ​​and flight time measurement values ​​with stored value pairs of reception level values ​​and flight time measurement values, wherein the stored value pairs of reception level values ​​and flight time measurement values ​​are respectively associated with a respective one of the distances from the transmitter to the receiver, and the processing unit is arranged to determine the distance from the transmitter to the receiver based on the comparison result.

Description

Technical Field

[0001] The invention relates to a device for determining the distance from a transmitter to a receiver. Background Art

[0002] In various application cases, it may be necessary to determine the distance between a transmitter and a receiver. It is known to estimate the distance based on received signal level values ​​(received signal strength indicator, RSSI). In this case, a distance value can be assigned to each RSSI value by laboratory tests or by mathematical conversion. If a receiver measures a certain RSSI value, the receiver assumes that the distance to the transmitter is similar to the distance that existed in laboratory tests at the same RSSI value.

[0003] However, channel-related attenuation may occur in the transmitter. This channel-related attenuation of the radio channel between the transmitter and the receiver may change the RSSI value and thus hinder the successful conversion between the RSSI value and the distance value. The channel-related attenuation here depends strongly on the environmental conditions and the user behavior of the transmitter or the receiver. Therefore, the prediction about the distance based on this conversion is only an inaccurate estimate of the distance. It is precisely when the transmitter and / or the receiver is a mobile device, such as a smartphone, that the user-specific behavior may lead to a strong deviation between the real distance and the estimated distance. If the user carries his mobile device in his pocket, for example, the RSSI value may be greatly reduced, so that there is an estimated error of more than 100m between the real distance and the estimated distance.

[0004] In contrast, if only time-of-flight measurements are performed, the distance can only be determined within a small range of up to 20 m. Summary of the invention

[0005] It is therefore an object of the present invention to enable a more accurate estimation of the distance between a transmitter and a receiver over a larger range.

[0006] This object is achieved by a device according to the invention for determining the distance from a transmitter to a receiver.

[0007] Here, the transmitter and the receiver are configured to communicate via a radio channel. In order to improve the accuracy of determining the distance compared to previous systems, the device has at least one measuring unit, which is configured to measure a received level value (received signal strength indicator, RSSI) and a time of flight measurement value (time of flight: ToF) of the radio channel. In the time of flight measurement, the time interval between the emission of a signal and the reception of the signal is measured. The measurement of the received level value or the RSSI value can be carried out in different ways and often only contains an inaccurate relationship to the received signal energy. Ideally, however, the measurement of the RSSI value contains the power of the received useful signal.

[0008] The device further comprises a processing unit, which is configured to compare the measured value pair of reception level value and flight time measurement value with the stored value pair of reception level value and flight time measurement value. Here, the stored value pair of reception level value and flight time measurement value is respectively associated with a corresponding one of the distances from the transmitter to the receiver. The processing unit is further configured to determine the distance from the transmitter to the receiver based on the comparison result.

[0009] Unlike previous systems, which use only one RSSI value, i.e. a single reception level value, for determining the distance from a transmitter to a receiver, the device proposed here uses two different values, i.e. a reception level value and a flight time measurement value. The two different values ​​can improve the distance determination. In particular, when the RSSI value is affected by channel-related attenuation, the distance between the transmitter and the receiver can still be accurately determined by the associated flight time measurement value. The flight time measurement value can be used as a correction factor for the reception level value.

[0010] According to one specific embodiment, the stored value pairs are transmitter-specific. In this way, it is possible to take into account transmitter-specific properties, in particular user behaviors that influence the transmitter properties, when storing the value pairs. The determination of the distance can thus be further improved, since the transmitter-specific behaviors are also taken into account when determining the distance.

[0011] According to another embodiment, the processing unit is configured to determine the identity of the transmitter. If the identity of the transmitter is determined before determining the distance and measuring the reception level value and the flight time measurement value, the comparison can be determined directly based on a transmitter-specific value pair of the reception level value and the flight time measurement value. In particular, corresponding value pairs of the reception level value and the flight time measurement value can be stored for different transmitters, wherein a corresponding number of value pairs are selected based on the identity of the transmitter for determining the distance.

[0012] In order to determine the identity of the transmitter, the processing unit may be configured to receive verification information from the transmitter. The verification information may be exchanged between the transmitter and the receiver via a suitable radio protocol. For example, the verification information may be exchanged between the transmitter and the receiver as an encryption key.

[0013] According to another embodiment, the measuring unit is configured to measure the reception level value simultaneously with the measurement of the time-of-flight measured value. The measurements of the values ​​are carried out simultaneously or at least in close temporal proximity. In this way, measured value pairs of the reception level value and the time-of-flight measured value that occur at the same or substantially the same time can be determined for the transmitter.

[0014] The measuring unit can also be arranged to perform n measurements on the value pairs of the reception level value and the flight time measurement value. These n measurements can be used by the processing unit to determine and store the transmitter-specific probability relationship for the value pairs of the reception level value and the flight time measurement value. The probability relationship can be determined, for example, by a histogram, a statistical average, a minimum value calculation / maximum value calculation or the like.

[0015] By establishing such a transmitter-specific probabilistic relationship between reception level values ​​and time-of-flight measured values, the influence of device-specific and user-specific characteristics of the radio channel for the respective transmitter and the environmental conditions in which the transmitter resides can be detected and evaluated statistically. As the number of measurements of reception level values ​​and time-of-flight measured values ​​increases, the processing unit is thus able to determine or estimate the distance of the receiver from the transmitter with increasing accuracy.

[0016] According to another embodiment, the processing unit is configured to calculate the distance between the transmitter and the receiver within a first range (e.g. up to 20 m), and the processing unit is configured to estimate the distance between the transmitter and the receiver within a second range (e.g. 20 to 100 m) based on the stored probability relationship. Thus, a determination can be made over a larger distance range by the combination of reception level values ​​and time-of-flight measurement values. The time-of-flight measurement values ​​can be used to determine the distance within a nearby range of up to about 20 m. By means of the reception level values, the measurement range of the time-of-flight measurement can be extended to a larger range, for example to a range of up to about 100 m, by extrapolating the probability relationship to a larger range.

[0017] In order to further improve the determination of the distance, the processing unit can be configured to adjust the stored probability relationship at predetermined intervals or continuously. In this way, changes in the characteristics of the transmitter (for example when a user places the transmitter in the housing or removes it from the housing) can be taken into account in the future for determining the distance.

[0018] The determination or estimation of the distance can be determined using currently measured reception level values ​​and flight time measurement values ​​and stored transmitter-specific reception level values ​​and flight time measurement values ​​and stored probability statistics of reception level values ​​and flight time measurement values. In this case, an extrapolation function, such as a Taylor approximation, can be used to estimate based on the current values ​​and the stored values: what is the current distance. In particular, when specific values ​​have been stored only for the nearby range, the distance can be determined by such an extrapolation function also in a larger range, for example in a range where only RSSI values ​​are present.

[0019] For example, a histogram can be used to estimate with what probability a certain distance exists for the current RSSI value of the transmitter. In addition, a quality assessment criterion for the statistical significance of the histogram can be used. By means of the quality assessment criterion, individual values ​​can be classified as unimportant or important for the distance. If there are a plurality of measurements with a plurality of value pairs, the estimation of the distance is thus improved. In this case, the device can be implemented as a self-learning system.

[0020] The measuring unit may also be configured to implement the measurement of the reception level value via an ultra-wideband connection (UWB), and / or the measuring unit may be configured to implement the measurement of the time of flight measurement value via a BLE connection. By combining the two measurements in the range of up to 20 m, these measurements may be converted to a distance for a range of 20 m to 100 m. The overlapping range of 0 m to 20 m between the time of flight measurement and the RSSI measurement may be approximated by a functional relationship and extrapolated to a value range of 20 m to 100 m. In this way, distance measurements exceeding 20 m may be implemented.

[0021] According to another embodiment, the transmitter is a mobile device and / or the receiver is a motor vehicle. For example, the device can be used to unlock a motor vehicle, wherein the distance from the transmitter (i.e. the mobile device) to the receiver (i.e. the motor vehicle) is used to determine whether the user is already within the range of the motor vehicle and should therefore unlock the motor vehicle. The mobile device can be, for example, a mobile phone, a smartphone, a PDA, a tablet computer, etc. In addition, the receiver can be adjusted based on the determination of the distance from the transmitter to the receiver. If the receiver is a motor vehicle, for example, the motor vehicle can be adjusted individually, such as seat adjustment, etc., based on the distance determination.

[0022] Furthermore, a method for determining the distance from a transmitter to a receiver is proposed, wherein the transmitter and the receiver are configured to communicate via a radio channel. The method comprises the following steps: measuring a reception level value and a flight time measurement value of the radio channel; comparing the measured value pairs of the reception level value and the flight time measurement value with stored value pairs of the reception level value and the flight time measurement value, wherein the stored value pairs of the reception level value and the flight time measurement value are each associated with a respective one of the distances from the transmitter to the receiver; and determining the distance from the transmitter to the receiver based on the comparison result.

[0023] The embodiments and features described for the proposed device apply correspondingly to the proposed method.

[0024] Furthermore, a computer program product is proposed, which has a program code which is designed to cause the execution of the method explained above on a computer.

[0025] The computer program product, for example a computer program element, can be provided or supplied, for example, as a storage medium, for example a memory card, a USB stick, a CD-ROM, a DVD or in the form of a downloadable file by a server in the network. This can be achieved, for example, in a wireless communication network by transmitting a corresponding file with the computer program product or the computer program element.

[0026] Other possible embodiments of the present invention also include the combinations not explicitly mentioned of the features or embodiments described above or below with respect to each embodiment. Here, those skilled in the art may also add individual aspects as improvements or supplements to the corresponding basic forms of the present invention.

[0027] Further advantages and advantageous embodiments are given in the description, the drawings and the claims. In particular, the individual feature combinations given in the description and the drawings are purely exemplary, so that the individual features can also exist individually or in combination in other ways. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be described in more detail below with the aid of the embodiments shown in the drawings. The embodiments and the combinations shown in the embodiments are only exemplary and should not limit the scope of protection of the present invention. The scope of protection is limited only by the attached claims.

[0029] In the attached picture:

[0030] Figure 1 A schematic block diagram showing a system having an apparatus for determining a distance between a transmitter and a receiver;

[0031] Figure 2a graph showing an estimate of the distance between two transmitters after one measurement; and

[0032] Figure 3 A graph showing the distance measurements for two transmitters after 100 measurements. DETAILED DESCRIPTION

[0033] In the following, identical elements or elements having the same functional effect are denoted by the same reference numerals.

[0034] Figure 1 A system 100 is shown having a transmitter 6 and a receiver 8. The transmitter 6 and the receiver 8 can communicate via a radio channel 10. The transmitter 6 can be, for example, a mobile device such as a smartphone. The receiver 8 can be, for example, a motor vehicle or a part of a motor vehicle.

[0035] A device 1 is provided for determining the distance between the transmitter 6 and the receiver 8. The device 1 can be integrated with the receiver 8, for example, in a motor vehicle. Based on the distance between the transmitter 6 and the receiver 8, the receiver 8 or a device connected to the receiver, for example, a motor vehicle, can be adjusted. The determined distance can be used to unlock the motor vehicle when the transmitter 6 is within a defined distance range relative to the receiver 8.

[0036] In order to determine the distance between the transmitter 6 and the receiver 8, the device 1 has one or more measuring units 2. The measuring unit 2 is configured to measure a reception level value and a flight time measurement value of a radio channel 10 between the transmitter 6 and the receiver 8. In a flight time measurement, the time interval between the emission of a signal until the signal is received is measured. Ideally, the measurement of the reception level value or RSSI value includes the power of the received useful signal.

[0037] Based on this pair of measured values, the processing unit 4 can determine the distance between the transmitter 6 and the receiver 8. For this purpose, the measured value pair consisting of the reception level value and the flight time measurement value is compared with the already stored value pairs of the reception level value and the flight time measurement value. The stored value pairs are respectively associated with a corresponding distance from the transmitter 6 to the receiver 8. Based on the comparison result, the processing unit can determine the distance from the transmitter 6 to the receiver 8.

[0038] In particular, the device 1 can be used as a self-learning system. In this case, the measuring unit 2 measures the reception level value and the flight time measurement value continuously or at a determined interval simultaneously or substantially simultaneously. The processing unit 4 can determine the transmitter-specific probability relationship for the value pair of the reception level value and the flight time measurement value based on these n measurements and store the relationship. If new flight time measurement values ​​and reception level values ​​are measured, the processing unit 4 can further refine the probability relationship. As the number of measurements of the reception level value and the flight time measurement value increases, the processing unit 4 can determine the distance from the receiver 8 to the transmitter 6 with higher accuracy.

[0039] By establishing such a transmitter-specific probabilistic relationship between reception level values ​​and flight time measurement values, the influence of device-specific and user-specific properties of radio channel 10 for the respective transmitter 6 and of the environmental conditions in which transmitter 6 is located can be statistically detected and estimated.

[0040] This is Figure 2 and Figure 3 It is shown in, where Figure 2 On the one hand, the actual distances of the first transmitter to the receiver and the second transmitter to the receiver are shown as curves S1 , S2 , and also a prediction VS1 for transmitter S1 and a prediction VS2 for transmitter S2 after a measurement of RSSI values ​​and reception level values.

[0041] The circles drawn around the curves S1 and S2 show the reception level values ​​measured for the transmitter S1 and the transmitter S2. As can be seen, the reception level value measurements fluctuate strongly around the actual distances S1, S2. Based on only one measurement of the reception level value and the flight time measurement value, a corresponding prediction VS1, VS2 is possible, but the prediction is only accurate up to a distance of about 15 to 20 m. In a larger distance range, the prediction VS1, VS2 becomes very inaccurate.

[0042] However, the distance estimate becomes more accurate as the number of measurements increases, e.g. Figure 3 100 times. The actual distance curves S1 and S2 are also shown here. The predictions VS1 and VS2 are clearly close to the actual curves here. As shown by the circles, the measurement of the reception level values ​​varies strongly around the actual curves S1 and S2. However, since the reception level values ​​are always measured together with the flight time measurement values ​​and integrated into the probability relationship, the prediction can be improved for other reception level values. It can be said that the flight time measurement values ​​are used as correction factors for the reception level values.

[0043] Furthermore, the combination of reception level values ​​and flight time measurements enables determinations over a greater distance range, such as also in Figure 2 and Figure 3 As shown in . For distances greater than 20 m, the estimation of the distance is extended to a larger range by extrapolating the probability relationship. In this larger range, only reception level values ​​can be measured. However, here, too, the estimation of the distance by extrapolation improves with an increasing number of measurements of the value pair consisting of reception level value and flight time measurement, as becomes apparent by the predictions VS1, VS2.

[0044] Therefore, the device proposed here can improve the determination of the distance between the transmitter and the receiver by using two different values, namely the flight time measurement value and the reception level value. In this case, the determination of the distance becomes more accurate as the number of measurements increases.

[0045] Reference numerals list

[0046] 1 device

[0047] 2 measuring units

[0048] 4 processing units

[0049] 6 Transmitters

[0050] 8 Receivers

[0051] 10 radio channels

[0052] 100 systems

[0053] S1, S2 transmitter

[0054] VS1, VS2 prediction

Claims

1. A device (1) for determining the distance from a transmitter (6) to a receiver (8), wherein: The transmitter (6) and the receiver (8) are arranged to communicate via a radio channel (10), The device (1) is characterized in that the device (1) has at least one measuring unit (2) which is configured to measure reception level values ​​and flight time measurement values ​​of the radio channel (10), and the device (1) has a processing unit (4) which is configured to compare the measured value pairs of reception level values ​​and flight time measurement values ​​with stored value pairs of reception level values ​​and flight time measurement values, the stored value pairs of reception level values ​​and flight time measurement values ​​being respectively associated with a respective distance from the transmitter (6) to the receiver (8), and the processing unit (4) is configured to determine the distance from the transmitter (6) to the receiver (8) based on the comparison result, The measuring unit (2) is configured to perform n measurements of a pair of reception level values ​​and a flight time measurement value for a specific transmitter, the processing unit (4) is configured to determine and store a transmitter-specific probability relationship for the pair of reception level values ​​and the flight time measurement value based on the n measurements of the pair of reception level values ​​and the flight time measurement value, and the processing unit (4) is configured to determine the distance by extrapolating the probability relationship within a range in which only reception level values ​​can be measured.

2. The device according to claim 1, wherein: The stored value pairs are transmitter-specific.

3. The device according to claim 1 or 2, wherein: The processing unit (4) is arranged to determine the identity of the transmitter (6).

4. The device according to claim 3, wherein: The processing unit (4) is arranged to receive authentication information from a transmitter (6).

5. The device according to claim 1 or 2, wherein: The measuring unit (2) is configured to carry out the measurement of the reception level value simultaneously with the measurement of the flight time measurement value.

6. The device according to claim 1 or 2, wherein: The processing unit (4) is configured to calculate the distance between the transmitter (6) and the receiver (8) within a first range, and the processing unit is configured to estimate the distance between the transmitter (6) and the receiver (8) within a second range based on the stored probability relationship.

7. The device according to claim 1 or 2, wherein: The processing unit (4) is configured to adjust the stored probability relationship at predetermined intervals or continuously.

8. The device according to claim 1 or 2, wherein: The measuring unit (2) is configured to carry out the measurement of the reception level value via an ultra-wideband connection, and / or the measuring unit is configured to carry out the measurement of the flight time measurement value via a BLE connection.

9. The device according to claim 1 or 2, wherein: The transmitter (6) is a mobile device and / or the receiver (8) is a motor vehicle.

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