Locating a mobile device using a vehicle

Abstract

Method for determining the position of a mobile device (20) in the interior of a vehicle (10) or in the vicinity of the vehicle (10), wherein a radio signal transmitted by the mobile device (20) with a carrier frequency assigned to a channel (32, 33, 34) of a selected radio technology is received by several antennas (11, 13, 15, 17) arranged in the interior of the vehicle (10), and wherein exactly one specific channel (32, 33, 34) of the radio technology is evaluated to determine the position of the mobile device (20), wherein at least one first antenna (11, 13, 15, 17) transmits a radio signal in several channels, and the radio signal transmitted by the at least one first antenna (11, 13, 15, 17) is received by at least one second antenna (11, 13, 15, 17), and wherein the position of the mobile device (20) is determined from the several Channels (32, 33, 34) the channel (32, 33, 34) is determined,in which the absolute difference between a calculated distance (12, 14, 16, 18, 51, 52, 53) of the at least one first antenna (11, 13, 15, 17) to the at least one second antenna (11, 13, 15, 17) and a known distance of the at least one first antenna (11, 13, 15, 17) to the at least one second antenna (11, 13, 15, 17), in particular averaged over several first and second antennas (11, 13, 15, 17), is minimal.

Description

[0001] The invention relates to a method for determining a position of a mobile terminal in an interior of a vehicle or in an environment of the vehicle, in which a radio signal which is transmitted by the mobile terminal with a carrier frequency assigned to a channel of a selected radio technology is received by at least one antenna attached to the vehicle.

[0002] For numerous applications, the most precise localization or positioning of a mobile unit is essential. Therefore, methods for determining the position of a mobile unit are of high economic relevance.

[0003] One well-known application is the location of a person using a mobile smartphone they carry. This can be helpful, for example, in a search for a missing or kidnapped person. However, the free choice of whereabouts is one of the so-called personal rights of every natural person. Therefore, a person's whereabouts are subject to their right of informational self-determination, meaning that the person must generally be able to permit or prohibit the determination of the location of a smartphone they carry.

[0004] Accordingly, DE 102 01 474 A1 discloses a method for authorizing a query of the position of a first terminal by a second terminal. If the first terminal is a mobile terminal located in a cell of a mobile network and communicating wirelessly with a base station of the mobile network defining the cell, the distance of the first terminal from the base station can be determined based on a reception level measured with an antenna of the base station.

[0005] A person's location also plays a crucial role in rescue operations. Only after the location of a person in need of assistance has been determined as precisely as possible can targeted rescue measures be carried out.

[0006] DE 101 03 034 A1 discloses a method for determining the position of a person seeking assistance. The person seeking assistance carries a GPS (Global Positioning System) terminal that is wirelessly connected to a messaging center, and a mobile terminal that is separate from the GPS terminal and wirelessly connected to the GPS terminal. The mobile terminal has an emergency call button, and the GPS terminal has a device for measuring the reception level of a radio signal from the mobile terminal. When an emergency call is made using the emergency call button, the GPS terminal can transmit both its position in the form of GPS coordinates and the measured reception level. The messaging center can calculate the distance between the mobile terminal and the GPS terminal from the reception level.In this way, the position of the person seeking help can be determined in the form of a radius around the transmitted position of the GPS terminal, even if the person seeking help has moved away from the GPS terminal and his position deviates from the position of the GPS terminal.

[0007] Even a mobile unit moving autonomously or at least partially autonomously must accurately determine its own position in order to correctly determine further movement towards a destination based on its current position.

[0008] DE 10 2014 002 150 B3 discloses a method for determining a position of a mobile unit, for example a vehicle, based on an image of the surroundings of the mobile unit, which image is captured by an optical sensor of the mobile unit, with a pre-stored image of the surroundings. A first position hypothesis for the position of the mobile unit is formed from the relative positions of specific objects within the captured image and the relative positions of the specific objects within an image of the surroundings pre-stored from a known position. Furthermore, further position hypotheses for the position of the mobile unit can be formed in a similar manner, for example, based on a plurality of reception levels of WLAN radio signals transmitted by antennas in the surroundings of the mobile unit, measured by the mobile unit.The position of the mobile unit is then determined by fusing the formed position hypotheses.

[0009] In all of the aforementioned methods, an antenna measures the reception level of a radio signal transmitted by a transmitter. From the measured reception level, a corresponding received signal strength indicator (RSSI) is then determined, which in turn allows the distance between the transmitter and the antenna to be calculated.

[0010] Methods for determining a position using radio technology are described in US 2016 / 0320469 A1 in connection with keyless access to a vehicle, in WO 2017 / 181050 A1 for the purpose of authorizing a mobile terminal and in DE 11 2014 001 445 T5 for warning against theft of an object carried in a vehicle.

[0011] US 2011 / 0195699 A1 describes a method in which the functionality of a mobile device is restricted when the position of the mobile device in a vehicle is determined. The restriction concerns, for example, blocking text input to effectively protect a vehicle driver from dangerous distraction caused by the mobile device.

[0012] A radio signal from a mobile device that complies with a specific radio technology has a so-called carrier frequency, which is usually assigned to an ISM frequency band (Industrial, Scientific and Medical Band) reserved for the specific radio technology. For example, the 2.4 GHz band is reserved for the common radio technologies WLAN and Bluetooth. The ISM frequency band is often divided into several numbered channels, each of which is assigned a specific carrier frequency. As is usual, a channel is understood to be a frequency range that is narrow compared to the width of the ISM frequency band. Depending on the specific radio technology, a reception strength value is determined from several reception levels in a frequency spectrum or from a reception level averaged across several channels.

[0013] If multiple mobile devices are located in the interior of a vehicle or in the vehicle's surroundings, each transmitting radio signals on different channels of an ISM frequency band, this can negatively impact the determination of a reception strength value, for example, due to interference in the peripheral areas of neighboring channels. A reception strength value determined under these conditions can exhibit sudden changes over time, resulting in corresponding jumps in the calculated distance. Such fluctuations can only be partially removed from the determined reception strength value using special filters, such as a Kalman filter or a particle filter.

[0014] The invention is therefore based on the object of providing an improved method for determining the position of a mobile terminal in the interior of a vehicle or in the surroundings of the vehicle, which avoids the described disadvantages and enables precise localization of the mobile terminal. Furthermore, the object of the invention is to provide a vehicle suitable for implementing the method according to the invention.

[0015] The invention relates to a method for determining a position of a mobile terminal in the interior of a vehicle or in the surroundings of the vehicle, in which a radio signal transmitted by the mobile terminal using a carrier frequency assigned to a channel of a selected radio technology is received by at least one antenna mounted on the vehicle. Although the invention is described with reference to a vehicle, it does not necessarily require a vehicle. For example, the described method can easily be implemented for the interior of a building or the like.

[0016] In the method according to the invention, a specific radio technology channel is evaluated to determine the position of the mobile device. Unlike other methods, no frequency spectrum or multiple radio technology channels are evaluated. Instead, the evaluation is limited to a specific radio technology channel.

[0017] Furthermore, according to the invention, the radio signal transmitted by the mobile device is received by several antennas arranged in the interior of the vehicle. The more antennas used to determine the position of the mobile device, the more precise the determined position. With more than three antennas, the position of the mobile device is overdetermined. However, overdetermination can contribute to further increasing the precision of the determined position of the mobile device.

[0018] In a further preferred embodiment, a reception level associated with each antenna is measured in the specific channel for several antennas, in particular for each antenna, and a reception strength value (Received Signal Strength Indicator, RSSI) is determined from the measured reception level. A reception level can be easily measured, and a reception strength value can be easily determined from the measured reception level using the formula RSSI(P)=RSSI(P0)−10 n log10(P / P0) calculated. Where RSSI(P) is the reception strength value, P is the reception level measured by the antenna in mW, n is a so-called path loss exponent which is determined depending on the environment and usually assumes a value between 2 and 4, P0 is a reception level measured in mW at a reference distance from the mobile device, and RSSI(P0) is the associated reference reception strength value. The reception strength value is usually given in dB (decibels) and is negative. It can be understood as the distance-dependent attenuation of a radio signal transmitted by the mobile device. Advantageously, reception levels assigned to each antenna can also be measured in several separate channels for several antennas, in particular for each antenna.

[0019] In other embodiments, a distance of the mobile device from the antenna associated with the determined reception strength value is calculated from at least one, in particular each, determined reception strength value. Calculating a distance from a reception strength value is a simple task. The more distances calculated for a mobile device, the more accurately its position can be determined.

[0020] In a further embodiment, noise from a determined reception strength value or a calculated distance is removed using a filter, in particular a Kalman filter. Kalman filters take into account the temporal progression of a reception strength value to smooth out strong fluctuations. This takes into account the fact that excessively strong fluctuations in a very short period of time are very likely not caused by a corresponding actual change in the position of the mobile device.

[0021] In a preferred embodiment, the radio signal transmitted by the mobile device is received by exactly four antennas, each arranged at known distances from one another in the vehicle's interior. The position of the mobile device is determined from the calculated distances to the four antennas. Four antennas can be arranged particularly symmetrically in the vehicle's interior and can ensure good coverage of the vehicle's interior and the surrounding area.

[0022] According to the invention, a radio signal is transmitted by at least one first antenna in a plurality of channels, and the radio signal transmitted by the at least one first antenna is received by at least one second antenna, and the channel is determined from the plurality of channels in which an absolute difference between a calculated distance of the at least one first antenna to the at least one second antenna and a known distance of the at least one first antenna to the at least one second antenna, in particular averaged over a plurality of first and second antennas, is minimal. The absolute difference can be calculated using the formula D=1n(n−1)∑i≠jn|dij,ber−dij,bek| where D is the averaged absolute difference, n is the number of first and second antennas involved, i is the index of at least one first antenna, j is the index of at least one second antenna, d ij,berthe calculated distance between the at least one first antenna and the at least one second antenna and d ij,bek the known distance between the at least one first antenna and the at least one second antenna. In other words, the channel is selected in which the calculated distances between the antennas best match the known distances between the antennas. In this way, the antennas themselves are used to calibrate the method.

[0023] In the event of interference on the specific channel, at least one alternative channel can be additionally determined from the multiple channels. The at least one alternative channel preferably corresponds to the next largest difference, for example, the second smallest difference averaged across the multiple antennas. If interference occurs on the specific channel, the system can immediately switch to the at least one alternative channel, and the process can continue with the alternative channel.

[0024] In a preferred embodiment, the Bluetooth standard is chosen as the wireless technology. The Bluetooth standard is a widely used short-range wireless technology for short-range devices (SRDs), which is very common in vehicles, for example, to connect a mobile device to a vehicle's infotainment system. However, other known or future short-range wireless technologies are also within the scope of the invention.

[0025] The invention also relates to a vehicle which is configured to determine a position of a mobile terminal which is arranged in an interior of the vehicle or in an environment of the vehicle and transmits a radio signal with a carrier frequency assigned to a channel of a selected radio technology, by means of at least one antenna mounted on the vehicle and receiving the radio signal transmitted by the mobile terminal, in particular in a method according to the invention. Alternatively, several separate radio technology channels can be used, in which overlaps in peripheral areas are excluded. With such a vehicle, the position of a mobile terminal in an interior of the vehicle or in an environment of the vehicle can be determined very precisely.

[0026] In a preferred embodiment, the vehicle comprises several, in particular four, antennas, each of which is arranged symmetrically to the left and right of a central longitudinal axis of the interior extending in a front-rear direction of the vehicle, and to the front and rear of a central transverse axis of the interior extending perpendicular to the central longitudinal axis, and / or the at least one antenna is designed as a Bluetooth antenna (Bluetooth beacon). The described arrangement is advantageous not least with regard to the seating positions of the usually maximum of four vehicle occupants and thus the positions of the respective mobile devices, but also provides optimal coverage of the vehicle's surroundings.

[0027] The invention is illustrated schematically in the drawings using embodiments and will be further described with reference to the drawings. It shows: Fig. 1 shows a schematic plan view of an embodiment of a vehicle according to the invention; Fig. 2 shows a diagram showing a subdivision of a frequency band reserved for various short-range wireless radio technologies into several channels; Fig. 3 in a function graph for three different positions of a mobile terminal, a reception strength value in a temporal development; Fig. 4 in a function graph three distances, each of which consists of the Fig. 3 shown reception strength values ​​are calculated, in a temporal development; Fig. 5 in a function graph a Fig. 3 shown reception strength value in a temporal development together with a reception strength value filtered by means of a Kalman filter in a temporal development.

[0028] Fig. 1 shows a schematic plan view of an embodiment of a vehicle 10 according to the invention. The vehicle 10 has four antennas 11, 13, 15, 17 designed as Bluetooth antennas (Bluetooth beacons). The antennas 11, 13, 15, 17 are each arranged symmetrically to the left and right of a central longitudinal axis of the interior extending in a front-rear direction of the vehicle 10, and to the front and rear of a central transverse axis of the interior extending perpendicular to the central longitudinal axis. A mobile terminal 20 is arranged in the vehicle 10 and is spaced 12, 14, 16, 18 from the antennas 11, 13, 15, 17, respectively.

[0029] The vehicle 10 is configured to determine a position of the mobile terminal 20, which transmits a radio signal with a carrier frequency assigned to a channel 32, 33 of the Bluetooth standard, by means of the four antennas 11, 13, 15, 17 attached to the vehicle 10 and receiving the radio signal transmitted by the mobile terminal 20, to evaluate exactly one specific channel 32, 33 of the Bluetooth standard.

[0030] Fig. 2 shows in a diagram 30 a subdivision of an ISM frequency band 31 reserved for various short-range wireless radio technologies (Bluetooth, WLAN) into several Bluetooth data channels 32, Bluetooth advertising channels 33 and WLAN channels 34. The frequency band comprises, in steps of 2 MHz, several carrier frequencies between 2402 MHz and 2480 MHz, each of which is assigned to a channel 32, 33, 34.

[0031] In the method according to the invention, the mobile terminal 20 transmits a radio signal with a carrier frequency assigned to a channel 32, 33 of the Bluetooth standard. The radio signal is received by the antennas 11, 13, 15, 17. To determine a position of the mobile terminal 20 in the interior of the vehicle 10, precisely one specific channel 32, 33 of the Bluetooth standard is evaluated.

[0032] For each antenna 11, 13, 15, 17, a reception level associated with that antenna is measured. In the next step, a reception strength value 41, 42, 43 is determined from the measured reception level.

[0033] Fig. 3 shows in a function graph 40 for three different positions of the mobile terminal 20 a reception strength value 41, 42, 43 in a temporal development.

[0034] Subsequently, from each determined reception strength value 41, 42, 43, a distance 51, 52, 53 of the mobile terminal 20 from the antenna 11, 13, 15, 17 assigned to the determined reception strength value 41, 42, 43 is calculated.

[0035] Fig. 4 shows in a function graph 50 three distances 51, 52, 53, each of which is derived from the Fig. 3 shown reception strength values ​​41, 42, 43 are calculated, in a temporal development.

[0036] Any noise from the determined reception strength values ​​41, 42, 43 is then removed using a Kalman filter.

[0037] Fig. 5 shows in a function graph 60 the Fig. 3 shown reception strength value 61 in a temporal development. The reception strength value 61 corresponds to the Fig.4 and is shown together with a reception strength value 62 filtered by a Kalman filter. Due to the effect of the Kalman filter, the reception strength value 61, which fluctuates sharply downwards in a very short period of time, is smoothed out.

[0038] After removing the noise from the determined reception strength values ​​41, 42, 43, the position of the mobile terminal 20 is determined from the respectively calculated distances 12, 14, 16, 18 to the four antennas 11, 13, 15, 17.

[0039] To calibrate the method, exactly one channel 32, 33 is selected from the ISM frequency band 31. For this purpose, a radio signal is transmitted from at least one first antenna 11, 13, 15, 17 in several channels 32, 33, and the radio signal transmitted by the at least one first antenna 11, 13, 15, 17 is received by at least one second antenna 11, 13, 15, 17. Then, from the plurality of channels 32, 33, the channel 32, 33 is determined in which an absolute difference between a calculated distance 12, 14, 16, 18 of the at least one first antenna 11, 13, 15, 17 to the at least one second antenna 11, 13, 15, 17 and a known distance of the at least one first antenna 11, 13, 15, 17 to the at least one second antenna 11, 13, 15, 17 averaged over a plurality of first and second antennas 11, 13, 15, 17 is minimal.

[0040] The method according to the invention offers the advantage that the position of the terminal device 20 can be determined very precisely. This makes the method suitable for very diverse applications, only a few of which are listed below as examples.

[0041] First, for example, a driver of the vehicle 10 and other occupants of the vehicle 10 can be distinguished based on their respective terminal devices 20. Apart from that, pedestrians in the vicinity of the vehicle 10 can also be precisely located if they carry a mobile terminal device 20 with them.

[0042] Another useful application of the method according to the invention is the reliable identification of one of several garage doors arranged next to each other, for example, the garage doors of a double garage, when the garage doors are configured to transmit radio signals. This allows the exact garage door in front of which the vehicle 10 is parked to be opened automatically.

[0043] If a mobile terminal 20 can be reliably located in the interior of the vehicle 10 or in the surroundings of the vehicle 10, a locking state of the vehicle 10 can also be automatically controlled. A specific mobile terminal 20 located outside the vehicle 10 can trigger an automatic unlocking of the vehicle 10. Conversely, a mobile terminal 20 located inside the vehicle 10 can prevent an automatic locking of the vehicle 10. LIST OF REFERENCE SYMBOLS: 10 vehicles 11 Antenna 12 distance 13 Antenna 14 Distance 15 Antenna 16 distance 17 Antenna 18 distance 20 mobile devices 30 Diagram 31 frequency band 32 Bluetooth data channels 33 Bluetooth advertising channel 34 WLAN channels 40 Function graph 41 Reception strength value 42 Reception strength value 43 Reception strength value 50 Function graph 51 distance 52 distance 53 distance 60 function graph 61 Reception strength value 62 filtered reception strength value

Claims

[1] A method for determining a position of a mobile terminal (20) in an interior of a vehicle (10) or in an environment of the vehicle (10), in which a radio signal transmitted by the mobile terminal (20) with a carrier frequency assigned to a channel (32, 33, 34) of a selected radio technology is received by a plurality of antennas (11, 13, 15, 17) arranged in an interior of the vehicle (10), and in which, to determine the position of the mobile terminal (20), precisely one specific channel (32, 33, 34) of the radio technology is evaluated, wherein at least one first antenna (11, 13, 15, 17) transmits a radio signal in each of several channels, and the radio signal transmitted by the at least one first antenna (11, 13, 15, 17) is received by at least one second antenna (11, 13, 15, 17). and in which the channel (32, 33, 34) is determined from the plurality of channels (32, 33, 34),in which an absolute difference between a calculated distance (12, 14, 16, 18, 51, 52, 53) of the at least one first antenna (11, 13, 15, 17) to the at least one second antenna (11, 13, 15, 17) and a known distance of the at least one first antenna (11, 13, 15, 17) to the at least one second antenna (11, 13, 15, 17), in particular averaged over a plurality of first and second antennas (11, 13, 15, 17), is minimal. [2] Method according to claim 1, in which in the specific channel (32, 33, 34) for a plurality of antennas (11, 13, 15, 17), in particular each antenna (11, 13, 15, 17), at least one reception level assigned to the antenna (11, 13, 15, 17) is measured and a reception strength value (41, 42, 43) is determined from the measured reception level. [3] Method according to claim 2, in which a distance (12, 14, 16, 18, 51, 52, 53) of the mobile terminal (20) from the antenna (11, 13, 15, 17) associated with the determined reception strength value (41, 42, 43) is calculated from at least one, in particular each, determined reception strength value (41, 42, 43). [4] Method according to claim 3, wherein a noise of a determined reception strength value (61) or a calculated distance (12, 14, 16, 18, 51, 52, 53) is removed by means of a filter, in particular a Kalman filter. [5] Method according to one of claims 1 to 4, in which the radio signal transmitted by the mobile terminal (20) is received by exactly four antennas (11, 13, 15, 17), which are each arranged at known distances from one another in the interior of the vehicle (10), and the position of the mobile terminal (20) is determined from the respectively calculated distances to the four antennas (11, 13, 15, 17). [6] Method according to one of claims 1 to 5, wherein the Bluetooth standard is selected as the radio technology. [7] Vehicle (10) which is configured to determine a position of a mobile terminal (20) which is arranged in an interior of the vehicle (10) or in an environment of the vehicle (10) and transmits a radio signal with a carrier frequency assigned to a channel (32, 33, 34) of a selected radio technology, by means of at least one antenna (11, 13, 15, 17) attached to the vehicle (10) and receiving the radio signal transmitted by the mobile terminal (20) to evaluate exactly one specific channel (32, 33, 34) of the radio technology in a method according to one of claims 1 to 6. [8] Vehicle according to claim 7, with several, in particular four antennas (11, 13, 15, 17), which are each arranged symmetrically to a central longitudinal axis of the interior extending in a front-rear direction of the vehicle (10) on the left and right and to a central transverse axis of the interior extending perpendicular to the central longitudinal axis on the front and rear, and / or in which the at least one antenna (11, 13, 15, 17) is designed as a Bluetooth antenna.

Images