Distance measurement system, communication station, and distance measurement method

Abstract

Provided are a distance measurement system, a communication station, and a distance measurement method capable of setting a measurement frequency on the basis of a measured distance, thereby enabling high-precision distance measurement. A distance measurement system is provided with a first communication station and a second communication station, the second communication station having: a distance measurement unit for performing distance measurement processing for measuring the distance to the first communication station on the basis of the result of bidirectional transmission of a signal between the second communication station and the first communication station; and a frequency setting unit that sets, on the basis of the distance measured by the distance measuring unit, the frequency at which the distance measuring unit performs the distance measuring process.

Description

Technical Field

[0001] The present disclosure relates to a ranging system, a communication station and a ranging method. Background Art

[0002] Conventionally, there is a positioning time interval control device that controls the time interval for measuring a position. The positioning time interval control device includes: an acquisition unit that acquires the moving state and moving speed of a mobile terminal device; and a positioning time interval setting unit that sets the time interval for measuring the position (distance) of the mobile terminal device and the time interval for outputting the position information obtained by the measurement, based on the moving state and moving speed of the mobile terminal device obtained by the acquisition unit. The positioning time interval setting unit changes the time interval when the moving state and / or moving speed of the mobile terminal device changes. The mobile terminal device acquires the position information of the mobile terminal device at the time interval set by the positioning time interval setting unit and outputs the position information. The higher the moving speed of the mobile terminal device, the longer the time interval for measuring the position of the mobile terminal device and the time interval for outputting the position information obtained by the measurement are set by the positioning time interval setting unit (for example, refer to Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2011 / 102151 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, the conventional positioning time interval control device does not change the frequency of measuring (ranging) the distance to the mobile terminal device according to the distance to the mobile terminal device, and therefore cannot perform high-precision ranging of the mobile terminal device.

[0008] Therefore, an object of the present invention is to provide a distance measurement system, a communication station and a distance measurement method, which can set the measurement frequency according to the measured distance, thereby enabling high-precision distance measurement.

[0009] Means for solving problems

[0010] The ranging system of an embodiment of the present disclosure includes a first communication station and a second communication station, wherein the second communication station has: a ranging unit that performs ranging processing, and the ranging processing measures the distance between the second communication station and the first communication station based on the result of bidirectional signal transmission between the second communication station and the first communication station; and a frequency setting unit that sets the frequency of the ranging processing performed by the ranging unit according to the distance measured by the ranging unit.

[0011] Effects of the Invention

[0012] By being able to set the measurement frequency according to the measured distance, it is possible to provide a distance measurement system, a communication station, and a distance measurement method capable of performing high-precision distance measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 1 is a diagram showing an example of the configuration of a vehicle 10 and a smartphone 20 on which the distance measuring devices 100 and 200 according to the first embodiment are respectively mounted.

[0014] Figure 2 This is a diagram showing an example of the configuration of distance measuring devices 100 and 200 according to Embodiment 1.

[0015] Figure 3A This is a diagram for explaining an example of the outline of the overall processing of the distance measuring devices 100 and 200 .

[0016] Figure 3B This is a diagram for explaining an example of the frequency of distance measurement processing.

[0017] Figure 4A This is a flowchart showing an example of processing executed by the distance measuring devices 100 and 200 .

[0018] Figure 4B This is a flowchart showing an example of processing executed by the distance measuring devices 100 and 200 .

[0019] Figure 5 This is a diagram showing an example of a configuration in which a distance measuring system 300M according to a modified example of the first embodiment is applied to a speaker system.

[0020] Figure 6 This is a diagram showing an example of the configuration of distance measuring devices 100 and 200 according to the second embodiment.

[0021] Figure 7 This is a diagram showing an example of a position where distance measurement information is stored in an advertisement signal.

[0022] Figure 8 1 is a diagram showing an example of reception information and distance measurement information received by the distance measuring device 100 .

[0023] Fig. 9 This is a diagram showing an example of the calculation results of the evaluation points.

[0024] Fig.10 2 is a sequence diagram showing an example of processing executed by the distance measuring devices 100 and 200 .

[0025] Fig.11 2 is a flowchart showing an example of specific processing contents of the process 1. The process 1 is executed by the distance measuring device 100 .

[0026] Fig.12 This is a flowchart showing an example of the specific processing content of the process 2.

[0027] Fig.13 It is a diagram showing an example of calculation of a predicted position. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of a ranging system, a communication station, and a ranging method to which the present disclosure is applied will be described.

[0029] <Implementation Method 1>

[0030] Figure 1 1 is a diagram showing an example of a vehicle 10 and a smartphone 20 on which the distance measuring devices 100 and 200 according to the first embodiment are respectively mounted. Figure 2 1 is a diagram showing an example of the configuration of the distance measuring devices 100 and 200 according to Embodiment 1. A system including the distance measuring devices 100 and 200 is a distance measuring system 300 .

[0031] Here, as an example, a method in which the distance measuring device 100 is installed in a smart entry system mounted on a vehicle 10 and the distance measuring device 200 is installed in a smartphone 20 is described. The smartphone 20 functions as a smart key for the smart entry system of the vehicle 10. As an example, the distance measuring devices 100 and 200 perform data group communication via BLE (Bluetooth (registered trademark) Low Energy).

[0032] The distance measuring device 100 is an example of a first communication station, and the distance measuring device 200 is an example of a second communication station. Here, as an example, the following method is described: since the vehicle 10 is parked and not moving, the distance measuring device 100 is a fixed station that does not move, and the distance measuring device 200 is a mobile station that can move along with the movement of the holder of the smartphone 20. The fixed station is not limited to the parked vehicle 10, and may be, for example, a building, etc. However, the distance measuring device 100 is not limited to a fixed station, and may also be mobile.

[0033] In addition, as an example, the vehicle 10 is equipped with an automatic parking assistance system, and the distance measuring device 100 is included in the automatic parking assistance system. The automatic parking assistance system is a system that allows the vehicle 10 to autonomously park at a parking position or to autonomously leave the parking position by remotely sending instructions to the vehicle 10 from the smartphone 20 using wireless communication.

[0034] At least one of the distance measuring device 100 of the vehicle 10 and the distance measuring device 200 of the smartphone 20 measures the distance between the vehicle 10 and the smartphone 20, and the locks of the doors, trunk, etc. of the vehicle 10 are unlocked when the distance measured by the distance measuring device 100 or 200 is an appropriate distance.

[0035] Here, as an example, it is assumed that the distance measuring device 200 of the smartphone 20 performs distance measuring processing to measure the distance, and notifies the distance measuring result to the distance measuring device 100 of the vehicle 10. As an example, the distance measuring devices 100 and 200 have the same configuration.

[0036] <Configuration of Distance Measuring Device 100>

[0037] The distance measuring device 100 includes three antennas 110 , a communication unit 120 , and an MCU (Micro Controller Unit) 130 .

[0038] <Antenna 110>

[0039] The antenna 110 is connected to the communication unit 120 and receives a signal transmitted from the distance measuring device 200 of the smartphone 20. Figure 1 , the distance measuring device 100 includes three antennas 110, but the distance measuring device 100 may include more than four antennas 110. The three antennas 110 are configured such that two are arranged on a first axis of two mutually orthogonal axes, two are arranged on a second axis of two mutually orthogonal axes, and one of these antennas is arranged on both the first axis and the second axis.

[0040] <Communication Department 120>

[0041] The communication unit 120 includes an AFE (Analog Front End), an AD (Analog to Digital) converter, etc., performs signal processing such as AD conversion on the signal received by the antenna 110 from the distance measuring device 200 , and outputs the signal to the MCU 130 .

[0042] <mcu130>

[0043] MCU130 has a main control unit 131, a signal strength measuring unit 132, a permission judging unit 133, a transceiver processing unit 134, a distance measuring unit 135, an angle measuring unit 136, a frequency setting unit 137, and a memory 138. As an example, MCU130 is implemented by a microcomputer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and an internal bus. The main control unit 131, the signal strength measuring unit 132, the permission judging unit 133, the transceiver processing unit 134, the distance measuring unit 135, the angle measuring unit 136, and the frequency setting unit 137 represent the functions of the program executed by MCU130 as functional blocks. In addition, the memory 138 functionally represents the memory of MCU130.

[0044] <Main Control Unit 131>

[0045] The main control unit 131 is a processing unit that manages the entire MCU 130 , and performs processing other than processing executed by the signal strength measuring unit 132 , the permission determining unit 133 , the transmission and reception processing unit 134 , the distance measuring unit 135 , the angle measuring unit 136 , and the frequency setting unit 137 .

[0046] <Signal Strength Measurement Unit 132>

[0047] The signal strength measuring unit 132 measures RSSI (Received Signal Strength Indicator) indicating the signal strength of the advertisement signal received from the distance measuring device 200 via the communication unit 120, and outputs the RSSI to the permission determination unit 133. Since the RSSI of the advertisement signal output by the distance measuring device 200 is proportional to the distance between the distance measuring devices 100 and 200, if the RSSI of the advertisement signal output by the distance measuring device 200 is measured in advance at a plurality of distances, the distance between the distance measuring devices 100 and 200 can be estimated based on the RSSI measured by the signal strength measuring unit 132 by interpolation processing or the like.

[0048] <Permission determination unit 133>

[0049] The permission determination unit 133 determines whether to permit the distance measuring device 100 to communicate with the distance measuring device 200 under BLE based on the RSSI of the advertisement signal measured by the signal strength measuring unit 132, and performs a permission determination process to generate a permission signal if the communication connection is permitted. More specifically, the permission determination unit 133 permits the distance measuring unit 235 of the distance measuring device 200 to perform the distance measurement process when the signal strength measured by the signal strength measuring unit 132 is greater than a predetermined strength. The permission signal is sent from the main control unit 131 to the distance measuring device 200.

[0050] <Transmission and Reception Processing Unit 134>

[0051] The transceiver processing unit 134 transmits and receives signals with the transceiver processing unit 234 of the distance measuring device 200 in order to obtain data such as the round trip time, phase difference, and frequency component of the signal required for the distance measuring unit 135 of the distance measuring device 100 or the distance measuring unit 235 of the distance measuring device 200 to perform distance measurement. In the first embodiment, as an example, the distance measurement process of calculating the distance between the distance measuring devices 100 and 200 is performed by the distance measuring unit 235 of the distance measuring device 200, and is not performed by the distance measuring unit 135 of the distance measuring device 100. Therefore, when the distance measuring unit 235 of the distance measuring device 200 performs distance measurement, the transceiver processing unit 134 performs the following auxiliary processing according to the processing of the transceiver processing unit 234.

[0052] When the distance measuring unit 235 of the distance measuring device 200 performs distance measurement based on the RTT (Round Trip Time) format, the transceiver processing unit 134 receives a signal for RTT from the transceiver processing unit 234 of the distance measuring device 200 via the antenna 110, and then returns the signal for RTT from the antenna 110 to the transceiver processing unit 234 of the distance measuring device 200. In this case, the transceiver processing unit 134 can use one of the three antennas 110 to receive and send signals.

[0053] When the distance measuring unit 235 of the distance measuring device 200 performs distance measurement based on the TOA (Time of Arrival) format, the transceiver processing unit 134 transmits and receives signals with the transceiver processing unit 234 of the distance measuring device 200. In this case, the transceiver processing unit 134 may transmit and receive signals using one of the three antennas 110. The transceiver processing unit 134 measures the phase of the signal received from the distance measuring device 200, and sends data indicating the measured phase to the distance measuring device 200.

[0054] In addition, when the angle measurement unit 236 of the ranging device 200 performs angle measurement based on the AOA (Angle of Arrival) format, the transceiver processing unit 134 receives the signal received from the ranging device 200 through the three antennas 110, measures the phase difference when the three antennas 110 receive the signal, and sends data representing the measured phase difference to the ranging device 200.

[0055] <Distance measuring unit 135>

[0056] The ranging unit 135 can perform ranging processing based on the RTT format and ranging processing based on the TOA format. In the first embodiment, since the ranging unit 235 of the ranging device 200 performs ranging processing (processing of calculating the distance), the ranging unit 135 does not perform ranging processing. The ranging processing based on the RTT format and the ranging processing based on the TOA format will be described later. Here, as an example, in order to illustrate the mode in which the ranging devices 100 and 200 have the same structure, the MCU 130 of the ranging device 100 has the ranging unit 135, but the MCU 130 of the ranging device 100 may not have the ranging unit 135.

[0057] <Angle measurement unit 136>

[0058] The angle measuring unit 136 can perform angle measurement processing of measuring the elevation angle and azimuth angle of the position of the distance measuring device 200 relative to the distance measuring device 100 in the polar coordinate system in the AOA format using the three antennas 110. However, in the first embodiment, as an example, the angle measuring unit 136 of the distance measuring device 100 does not perform the angle measurement processing, and the angle measuring unit 236 of the distance measuring device 200 performs the angle measurement processing, so the angle measuring unit 136 does not perform the angle measurement processing. In addition, the MCU 130 of the distance measuring device 100 may not have the angle measuring unit 136.

[0059] <Frequency Setting Unit 137>

[0060] When the distance measuring unit 135 performs the distance measuring process, the frequency setting unit 137 sets the frequency of the distance measuring unit 135 performing the distance measuring process according to the distance measured by the distance measuring process performed by the distance measuring unit 135. However, in the first embodiment, as an example, the distance measuring unit 135 of the distance measuring device 100 does not perform the distance measuring process, and the distance measuring unit 235 of the distance measuring device 200 performs the distance measuring process, so the frequency setting unit 137 does not perform the process of setting the frequency. In addition, the MCU 130 of the distance measuring device 100 may not have the frequency setting unit 137.

[0061] <Memory 138>

[0062] The memory 138 stores programs and data required for the main control unit 131 , the signal strength measuring unit 132 , the permission determining unit 133 , the transmission and reception processing unit 134 , the distance measuring unit 135 , the angle measuring unit 136 , and the frequency setting unit 137 to execute processing.

[0063] <Configuration of Distance Measuring Device 200>

[0064] The distance measuring device 200 includes three antennas 210, a communication unit 220, and an MCU 230. Each antenna 210 is connected to the communication unit 220 to receive a signal transmitted from the distance measuring device 100. Figure 1 2 , the distance measuring device 200 includes three antennas 210, but the distance measuring device 200 may include more than four antennas 210. The three antennas 210 are configured such that two are arranged on a first axis of two mutually orthogonal axes, two are arranged on a second axis of two mutually orthogonal axes, and one of these antennas is arranged on both the first axis and the second axis.

[0065] As an example, the distance measuring device 200 has the same configuration as the distance measuring device 100. That is, the antenna 210, the communication unit 220, and the MCU 230 are respectively the same as the antenna 110, the communication unit 120, and the MCU 130 of the distance measuring device 100. However, in the first embodiment, the distance measuring device 200 does not perform RSSI measurement and connection permission judgment, and the distance measuring device 200 performs distance measurement processing, angle measurement processing, and frequency setting processing. Therefore, in the first embodiment, the operations of the distance measuring devices 100 and 200 are different. The following describes the MCU 230.

[0066] <mcu230>

[0067] The MCU 130 includes a main control unit 231, a signal strength measuring unit 232, a permission determining unit 233, a transceiver processing unit 234, a distance measuring unit 235, an angle measuring unit 236, a frequency setting unit 237, and a memory 238. The main control unit 231, the signal strength measuring unit 232, the permission determining unit 233, the transceiver processing unit 234, the distance measuring unit 235, the angle measuring unit 236, the frequency setting unit 237, and the memory 238 are respectively the same as the main control unit 131, the signal strength measuring unit 132, the permission determining unit 133, the transceiver processing unit 134, the distance measuring unit 135, the angle measuring unit 136, the frequency setting unit 137, and the memory 138 of the MCU 130 of the distance measuring device 100.

[0068] Main control unit 231, signal strength measuring unit 232, permission determination unit 233, transmission and reception processing unit 234, distance measuring unit 235, angle measuring unit 236, and frequency setting unit 237 represent functions of programs executed by MCU 230 as functional blocks. Memory 238 functionally represents memory of MCU 230.

[0069] <Main Control Unit 231>

[0070] The main control unit 231 is a processing unit that manages the entire MCU 230 and performs processing other than the processing executed by the signal strength measuring unit 232 , the permission determination unit 233 , the transmission and reception processing unit 234 , the distance measuring unit 235 , the angle measuring unit 236 , and the frequency setting unit 237 .

[0071] <Signal Strength Measurement Unit 232>

[0072] The signal strength measuring unit 232 can measure the RSSI of the advertisement signal received from the distance measuring device 100 via the communication unit 220, similarly to the signal strength measuring unit 132 of the distance measuring device 100. However, in the first embodiment, the signal strength measuring unit 132 of the distance measuring device 100 measures the RSSI, so the MCU 230 of the distance measuring device 200 may not include the signal strength measuring unit 232.

[0073] <Permission determination unit 233>

[0074] The permission determination unit 233 determines whether to permit the communication connection of the ranging device 200 under the BLE of the ranging device 200 based on the RSSI of the advertisement signal measured by the signal strength measurement unit 232, similarly to the permission determination unit 133 of the ranging device 100, and can generate a permission signal if the communication connection is permitted. However, in the first embodiment, the permission determination unit 133 of the ranging device 100 performs the permission determination process, so the MCU 230 of the ranging device 200 may not have the permission determination unit 233.

[0075] <Transmission and Reception Processing Unit 234>

[0076] The transmission and reception processing unit 234 transmits and receives signals with the distance measuring device 100 in order to obtain data such as phase difference and frequency component required for the distance measuring unit 235 and the angle measuring unit 236 to measure the distance and angle.

[0077] The transceiver processing unit 234 transmits and receives signals with the transceiver processing unit 134 of the distance measuring device 100 in order to obtain data such as the round trip time, phase difference, and frequency component of the signal required for the distance measuring unit 235 to perform the distance measuring process. That is, the distance measuring unit 235 performs the distance measuring process together with the transceiver processing unit 134 of the distance measuring device 100. In this way, the distance measuring unit 235 performs the distance measuring process together with the transceiver processing unit 134 of the distance measuring device 100, which means that the distance measuring device 200 performs the distance measuring process together with the distance measuring device 100. In addition, the transceiver processing unit 234 transmits and receives signals with the transceiver processing unit 134 of the distance measuring device 100 in order to obtain the signal required for the angle measuring unit 236 to perform the angle measuring process. That is, the angle measuring unit 236 performs the angle measuring process together with the transceiver processing unit 134 of the distance measuring device 100. In this way, the angle measuring unit 236 performs the angle measuring process together with the transmission and reception processing unit 134, which means that the distance measuring device 200 performs the angle measuring process together with the distance measuring device 100.

[0078] The distance measurement process for calculating the distance between the distance measuring devices 100 and 200 is performed by the distance measuring unit 235 of the distance measuring device 200, and is not performed by the distance measuring unit 135 of the distance measuring device 100. In addition, the angle measurement process is performed by the angle measurement unit 236 of the distance measuring device 200, and is not performed by the angle measurement unit 136 of the distance measuring device 100. Therefore, when the distance measuring unit 235 and the angle measurement unit 236 perform the distance measurement process and the angle measurement process, respectively, the transmission and reception processing unit 234 performs the following auxiliary processes according to the processes of the distance measuring unit 235 and the angle measurement unit 236.

[0079] When the ranging unit 235 performs ranging in the RTT format, the transceiver processing unit 234 transmits a signal for RTT to the ranging device 100 via the antenna 210. When the signal for RTT is received from the ranging device 100, the round-trip time, which is the time required from transmission to reception, is measured and output to the ranging unit 235. The transceiver processing unit 234 may use one of the three antennas 110 to transmit and receive the signal for RTT.

[0080] When the distance measuring unit 235 performs distance measurement based on the TOA format, the transceiver processing unit 234 transmits TOA signals of multiple frequencies in both directions with the transceiver processing unit 134 of the distance measuring device 100. In this case, the transceiver processing unit 234 may use one of the three antennas 110 to transmit the TOA signal. The transceiver processing unit 234 measures the phase of the TOA signal received from the distance measuring device 100, obtains the round-trip phase difference of the TOA signal of each frequency using the data indicating the phase received from the distance measuring device 200, and outputs the data indicating the phase difference for each of the multiple frequencies to the distance measuring unit 235.

[0081] When the angle measuring unit 236 performs angle measurement based on the AOA format and when the distance measuring unit 235 performs distance measurement based on the TOA format, data indicating the phase difference when the three antennas 210 receive from the distance measuring device 100 is output to the angle measuring unit 236 .

[0082] <Distance measuring unit 235>

[0083] The distance measuring unit 235 can perform distance measuring processing based on the RTT format and distance measuring processing based on the TOA format. When performing the distance measuring processing based on the RTT format, the distance measuring unit 235 calculates the distance between the distance measuring devices 100 and 200 based on the data indicating the round-trip time obtained from the transmission and reception processing unit 234 .

[0084] When performing the ranging process based on the TOA format, the ranging unit 235 obtains data indicating the phase difference of each of the multiple frequencies from the transmission and reception processing unit 234, and calculates the distance between the ranging devices 100 and 200 based on the relationship between the multiple phase differences and the frequencies. The distance calculated in the TOA format is much more accurate than the distance calculated in the RTT format.

[0085] <Angle measurement unit 236>

[0086] The angle measuring unit 236 uses the three antennas 210 to measure the elevation angle and azimuth angle of the position of the distance measuring device 100 relative to the distance measuring device 200 in the polar coordinate system in the AOA format. The angle measuring unit 236 measures the elevation angle and azimuth angle in the AOA format based on the phase difference when the three antennas 210 receive the signal transmitted from the distance measuring device 100. The phase difference when the three antennas 210 receive the signal is a first phase difference when the two antennas 210 located on the first axis receive the signal, and a second phase difference when the two antennas 210 located on the second axis receive the signal. The angle measuring unit 236 calculates the azimuth angle representing the position of the distance measuring device 100 relative to the distance measuring device 200 based on the ratio of the first phase difference to the second phase difference. In addition, the angle measuring unit 236 calculates the elevation angle representing the position of the distance measuring device 100 relative to the distance measuring device 200 based on the azimuth angle and the first phase difference or the second phase difference. In the angle measurement process of the AOA format, the elevation angle and the azimuth angle in the polar coordinate system of the position of the distance measuring device 100 relative to the distance measuring device 200 can be measured.

[0087] <Frequency Setting Unit 237>

[0088] The frequency setting unit 237 sets the frequency of the ranging process performed by the ranging unit 235 according to the distance measured by the ranging process performed by the ranging unit 235. The frequency of performing the ranging process indicates the number of times the ranging process is performed within a specified unit time (for example, 60 seconds) or the time interval for performing the ranging process. A high frequency of performing the ranging process indicates that the number of times the ranging process is performed within a specified unit time is large, in other words, the time interval for performing the ranging process is short.

[0089] When the distance between the distance measuring devices 100 and 200 is far, the frequency of performing the distance measurement process may be low. This is because the smartphone 20 equipped with the distance measuring device 200 is far away from the vehicle 10 equipped with the distance measuring device 100, and therefore it is difficult to consider that the holder of the smartphone 20 immediately unlocks the doors or the trunk of the vehicle 10. In addition, when the distance between the distance measuring devices 100 and 200 is close, the frequency of performing the distance measurement process is increased. This is because since the smartphone 20 is close to the vehicle 10, the holder of the smartphone 20 may immediately unlock the doors or the trunk of the vehicle 10. Therefore, the shorter the distance measured by the distance measuring unit 235, the higher the frequency is set by the frequency setting unit 237. As to how the frequency setting unit 237 sets the frequency measured by the distance measuring unit 235 according to the distance, use Figure 4A as well as Figure 4B The flowchart is described later.

[0090] <Memory 238>

[0091] The memory 238 stores programs and data required for the main control unit 231 , the signal strength measuring unit 232 , the permission determination unit 233 , the transmission and reception processing unit 234 , the distance measuring unit 235 , the angle measuring unit 236 , and the frequency setting unit 237 to execute processing.

[0092] Furthermore, the main control unit 231 obtains the position of the distance measuring device 100 relative to the distance measuring device 200 based on the distance obtained by the distance measuring unit 235 and the angle (elevation angle and azimuth angle) obtained by the angle measuring unit 236 .

[0093] <Overview of overall processing>

[0094] Figure 3A 1 is a diagram for explaining an example of an overview of the overall processing of the distance measuring devices 100 and 200 . Figure 3B FIG. 1 is a diagram illustrating an example of the frequency of ranging processing. Figure 3A , a state in which a holder of the smartphone 20 is walking toward the vehicle 10 is shown. Figure 3B In FIG. 1 , the frequency of distance measurement processing performed by the distance measuring devices 100 and 200 is shown in time series. Figure 3B In the figure, the distance measuring device 100 is an Anchor (fixed station), the distance measuring device 200 is a Tag (mobile station), and the horizontal axis is the time axis.

[0095] like Figure 3A As shown, as an example, threshold values ​​of 60 m (an example of distance 3), 30 m (an example of distance 2), and 10 m (an example of distance 1) are set for the distance between the distance measuring device 100 and the distance measuring device 200 mounted on the vehicle 10. In addition, the distance 2 is an example of the first prescribed distance, and the distance 1 is an example of the second prescribed distance.

[0096] In addition, the frequency (time interval) of the RSSI measurement process of the signal strength measurement unit 132 or the ranging process based on the RTT format or TOA format of the ranging unit 135 is set according to the distance between the ranging devices 100 and 200. Hereinafter, time interval 1, time interval 2, and time interval 3 are used. Time interval 1 is the shortest, and time interval 3 is the longest. That is, the relationship of time interval 1 < time interval 2 < time interval 3 holds. If time interval 1, time interval 2, and time interval 3 are expressed by frequency, they are high frequency, medium frequency, and low frequency, respectively.

[0097] <When the distance between the distance measuring devices 100 and 200 is longer than 60 m>

[0098] For example, when the distance between the distance measuring devices 100 and 200 is longer than 60 m, the distance measuring unit 235 of the distance measuring device 200 does not perform distance measurement processing, and the signal strength measuring unit 132 of the distance measuring device 100 only measures the RSSI of the advertising signal output by the distance measuring device 200. The RSSI measurement is performed at the longest time interval 3. Since the distance between the distance measuring devices 100 and 200 is far enough, it is difficult to consider that the owner of the smartphone 20 immediately unlocks the door and trunk of the vehicle 10. In such a situation, by not performing distance measurement processing, the power consumption of the distance measuring devices 100 and 200 can be reduced.

[0099] In addition, since the signal strength measuring unit 132 of the distance measuring device 100 measures only the RSSI of the advertisement signal, the processing load of the distance measuring devices 100 and 200 is small, and thus the responsiveness of the distance measuring devices 100 and 200 can be improved. In particular, when there are multiple distance measuring devices 200, it is useful for the distance measuring device 100 to have high responsiveness.

[0100] <When the distance between the distance measuring devices 100 and 200 is less than 60 m and longer than 30 m>

[0101] In addition, as an example, when the distance between the distance measuring devices 100 and 200 is less than 60m and longer than 30m, the distance measuring unit 235 of the distance measuring device 200 performs the distance measuring process in the RTT format at the time interval 3 (low frequency). The distance measuring process at the longest time interval 3 is the low frequency distance measuring process. As an example, the low frequency distance measuring process Figure 3B As shown in the upper part of FIG. 1 , the time interval for performing the distance measurement process is very long. As an example, the time interval 3 is 100 seconds.

[0102] The ranging process in the RTT format is as follows: the ranging device 200 sends a signal for RTT to the ranging device 100 once, and the ranging device 100 that receives the signal for RTT returns the signal for RTT to the ranging device 200 once, thereby finding the distance between the ranging devices 100 and 200 based on the round-trip time of the signal for RTT between the ranging devices 100 and 200. Since the ranging devices 100 and 200 only send the signal for RTT one by one, the processing load of the ranging devices 100 and 200 is small, and the ranging process can be performed in a short time. However, compared with the ranging in the TOA format, the ranging accuracy is low.

[0103] The distance between the distance measuring devices 100 and 200 is relatively far, and it is difficult to consider that the owner of the smartphone 20 immediately unlocks the door and trunk of the vehicle 10. Therefore, when the distance measured in the RTT format is less than 60m and longer than 30m, the distance measurement process in TOA, which is part of the authentication process, is not performed, and the distance measurement process in the RTT format with a small processing load in the distance measuring devices 100 and 200 is performed, thereby reducing the power consumption of the distance measuring devices 100 and 200. In addition, it is difficult to consider that the owner of the smartphone 20 immediately unlocks the door and trunk of the vehicle 10, and the necessity of the authentication process is low, so the authentication process including TOA is not performed, and the power consumption of the distance measuring devices 100 and 200 is reduced.

[0104] In addition, since the processing load of the distance measuring devices 100 and 200 is small, it is possible to improve the responsiveness of the distance measuring devices 100 and 200. In particular, when there are a plurality of distance measuring devices 200, it is useful for the distance measuring device 100 to have high responsiveness.

[0105] <When the distance between the distance measuring devices 100 and 200 is less than 30 m and longer than 10 m>

[0106] In addition, as an example, when the distance between the distance measuring devices 100 and 200 is less than 30 m and longer than 10 m, the distance measuring unit 235 of the distance measuring device 200 performs distance measurement processing based on the TOA format at time interval 2 (medium frequency). The distance measurement at time interval 2 is a distance measurement with medium frequency. Figure 3B As shown in the middle section, the time interval for ranging processing at medium frequency is 2. Figure 3B The low-frequency time interval 3 shown in the upper section is shorter than Figure 3B The high-frequency time interval 1 shown in the lower section of is long. As an example, the time interval 2 is 10 seconds.

[0107] In addition, when the distance between the ranging devices 100 and 200 is less than 30 m and longer than 10 m, the angle measuring unit 236 measures the elevation angle and the azimuth angle in the form of AOA at a time interval of 2 (medium frequency) based on the phase difference when the signal sent from the ranging device 100 is received by the three antennas 210.

[0108] When the distance obtained by the TOA-based ranging is less than 30m and longer than 10m, it is still difficult to consider that the holder of the smartphone 20 immediately unlocks the door and trunk of the vehicle 10. This is because, if the moving speed of a person is assumed to be about 1m / s to 4m / s, it is assumed that if the distance is longer than 10m, it will take several seconds for the holder of the smartphone 20 to reach the vehicle 10. The ranging in the TOA-based ranging transmits signals of multiple frequencies in both directions between the ranging devices 100 and 200, so the processing load of the ranging devices 100 and 200 is relatively large, but by reducing the frequency of ranging processing, it is possible to reduce the power consumption of the ranging devices 100 and 200 and improve the responsiveness. In addition, especially when there are multiple ranging devices 200, it is useful for the ranging device 100 to have high responsiveness. In addition, when the distance obtained by the TOA-based ranging is less than 30m and longer than 10m, the elevation angle and azimuth angle are measured by the AOA-based with a medium frequency.

[0109] <When the distance between the distance measuring devices 100 and 200 is less than 10 m>

[0110] In addition, as an example, when the distance between the distance measuring devices 100 and 200 is less than 10 m, the distance measuring unit 235 of the distance measuring device 200 performs distance measurement processing based on the TOA format at time interval 1 (high frequency). The distance measurement at time interval 1 is high frequency distance measurement. As an example, high frequency distance measurement, such as Figure 3B As shown in the lower part of the figure, the time interval for ranging processing is Figure 3B The low frequency and the medium frequency shown in the upper and middle sections of are short, and the ranging process is repeatedly performed without almost waiting. As an example, the time interval 1 is 0.1 seconds.

[0111] In addition, when the distance between the distance measuring devices 100 and 200 is less than 10m, the angle measuring unit 236 measures the elevation angle and the azimuth angle in AOA format at a time interval of 1 (high frequency) based on the phase difference when the three antennas 210 receive the signal sent from the distance measuring device 100.

[0112] If the distance obtained by TOA ranging is less than 10 m, the owner of the smartphone 20 may immediately unlock the doors and trunk of the vehicle 10. Therefore, the frequency of TOA ranging processing is increased, authentication processing is performed at a high frequency, and the elevation angle and azimuth angle are measured at a high frequency in AOA format.

[0113] <Flowchart>

[0114] Figure 4A as well as Figure 4B FIG. 2 is a flowchart showing an example of processing performed by the distance measuring devices 100 and 200. Figure 4A as well as Figure 4B In FIG. 1 , the process of the distance measuring device 100 is shown in the left half, and the process of the distance measuring device 200 is shown in the right half, so that the relationship between the processes of the distance measuring devices 100 and 200 is also described.

[0115] When the process starts, first, the distance measuring device 200 as a tag transmits an advertisement signal (step S201). In one example, the process of the distance measuring devices 100 and 200 starts when the distance measuring device 200 transmits a start notification to the distance measuring device 100 and the distance measuring device 100 receives the start notification.

[0116] The distance measuring device 200 as the anchor receives the advertisement signal and measures the RSSI (step S101 ). The RSSI is measured by the signal strength measuring unit 132 .

[0117] The distance measuring device 100 estimates the distance between the distance measuring devices 100 and 200 based on the measured RSSI, and determines whether the estimated distance is equal to or less than the distance 3 (step S102). This process is executed by the permission determination unit 133. As an example, the distance 3 is 60 m.

[0118] When the distance measuring device 100 determines that the estimated distance is equal to or less than the distance 3 (S102: Yes), it generates a permission signal and transmits it to the distance measuring device 200 (step S103). The permission determination unit 133 generates the permission signal.

[0119] If the distance measuring device 100 determines in step S102 that the estimated distance is not less than the distance 3 (S102: No), the flow returns to step S101. This is to receive the advertisement signal again and re-measure the RSSI.

[0120] When the ranging device 100 sends the permission signal to the ranging device 200, it sends a measurement start notification of the RTT-format ranging process to the ranging device 200 (step S104). The measurement start notification of the RTT-format ranging process is a notification indicating that the RTT-format ranging process is performed. As an example, the transmission and reception processing unit 134 of the ranging device 100 performs the processing of step S104.

[0121] When the distance measuring device 100 transmits the measurement start notification of the RTT-based distance measuring process, the distance measuring device 100 executes the RTT-based distance measuring process together with the distance measuring device 200 (step S105). As an example, the transmission and reception processing unit 134 of the distance measuring device 100 executes the process of step S105.

[0122] The distance measuring device 200 determines whether a permission signal is received within a specified time from the transmission of the advertisement signal (step S202). As an example, the specified time is 0.01 seconds. If a permission signal is not received within the specified time, it becomes a timeout. As an example, the main control unit 231 of the distance measuring device 200 performs the processing of step S202.

[0123] If the distance measuring device 200 determines that the permission signal is received within the predetermined time (S202: Yes), it receives the measurement start notification of the distance measuring process in the RTT format (step S203). As an example, the main control unit 231 of the distance measuring device 200 executes the process of step S203.

[0124] If the distance measuring device 200 determines in step S202 that the permission signal has not been received within the predetermined time (S202: No), the flow returns to step S201. This is to resend the advertisement signal and re-process.

[0125] When the distance measuring device 200 receives the measurement start notification of the distance measuring process in the RTT format, it performs the distance measuring process in the RTT format together with the distance measuring device 100 (step S204). The process of step S204 is a process performed integrally with the process of step S105 performed by the distance measuring device 100, and is performed by the transceiver processing unit 134 of the distance measuring device 100, the transceiver processing unit 234 of the distance measuring device 200, and the distance measuring unit 235. Specifically, the transceiver processing unit 234 transmits a signal for RTT, and the transceiver processing unit 134 returns a signal for RTT. Based on the round-trip time obtained by the transceiver processing unit 234, the distance measuring unit 235 measures the distance between the distance measuring devices 100 and 200 in the RTT format. In the process of step S204, the distance between the distance measuring devices 100 and 200 is calculated by the distance measuring process in the RTT format.

[0126] When the RTT-based distance measurement process of steps S105 and S204 is completed, the distance measuring device 200 determines whether the measured distance is equal to or less than distance 2 (step S205 ). As an example, the process of step S205 is executed by the frequency setting unit 237 of the distance measuring device 200 .

[0127] If the distance measuring device 200 determines that the measured distance is not less than the distance 2 (S205: No), the time interval for performing the distance measurement is set to the time interval 3 (step S206A). If the measured distance is not less than the distance 2, since the measured distance is the distance 3, the time interval 3 corresponding to the distance 3 is set. As an example, the processing of step S206A is performed by the frequency setting unit 237 of the distance measuring device 200.

[0128] In addition, if the distance measuring device 200 determines in step S205 that the measured distance is less than distance 2 (S205: Yes), the time interval for performing distance measurement is set to time interval 2 (step S206B). When the measured distance is less than distance 2, the measured distance is distance 2 or distance 1, so it is temporarily set to time interval 2 equivalent to distance 2. As an example, the processing of step S206B is performed by the frequency setting unit 237 of the distance measuring device 200.

[0129] When the distance measuring device 200 finishes the process of step S206A or S206B, it transmits the interval data indicating the time interval set in step S206A or S206B to the distance measuring device 100 (step S207). As an example, the main control unit 231 of the distance measuring device 200 executes the process of step S207.

[0130] The distance measuring device 100 receives the interval data from the distance measuring device 200 (step S106). As an example, the main control unit 131 of the distance measuring device 100 executes the process of step S106.

[0131] The distance measuring device 100 determines whether the time interval indicated by the interval data received in step S106 is time interval 2 (step S107 ). As an example, the main control unit 131 of the distance measuring device 100 executes the process of step S107 .

[0132] If the distance measuring device 100 determines that the time interval represented by the received interval data is not time interval 2 (S107: No), the standby time in the distance measuring device 100 is set to time interval 3 (step S108A). As an example, the main control unit 131 performs the processing of step S108A. If the distance measuring device 100 ends the processing of step S108A, the flow returns to step S101. This is to restart from the measurement of RSSI.

[0133] In addition, if the distance measuring device 100 determines in step S107 that the time interval represented by the received interval data is time interval 2 (S107: Yes), the standby time in the distance measuring device 100 is set to time interval 2 (step S108B). If the distance measuring device 100 ends the processing of step S108B, the flow enters step S109. As an example, the main control unit 131 executes the processing of step S108B.

[0134] The distance measuring device 100 sends a measurement start notification of the distance measuring process in the TOA format and the angle measuring process in the AOA format to the distance measuring device 200 (step S109). The measurement start notification of the distance measuring process in the TOA format and the angle measuring process in the AOA format is a notification indicating that the distance measuring process in the TOA format and the angle measuring process in the AOA format are performed. As an example, the transmission and reception processing unit 134 of the distance measuring device 100 performs the processing of step S109.

[0135] When transmitting the measurement start notification of the TOA ranging process and the AOA angle measurement process, the ranging device 100 executes the TOA ranging process (step S110) together with the ranging device 200. As an example, the transmission and reception processing unit 134 of the ranging device 100 executes the process of step S110.

[0136] The distance measuring device 200 receives the measurement start notification of the distance measuring process in the TOA format and the angle measuring process in the AOA format (step S208 ). As an example, the main control unit 231 of the distance measuring device 200 executes the process of step S208 .

[0137] When the distance measuring device 200 receives the measurement start notification of the distance measuring process in the TOA format and the angle measuring process in the AOA format, it performs the distance measuring process in the TOA format together with the distance measuring device 100, and performs the angle measuring process in the AOA format when receiving the signal from the distance measuring device 100 (step S209). The distance measuring process in the process of step S209 is a distance measuring process performed integrally with the process of step S110 performed by the distance measuring device 100, and is performed by the transceiver processing unit 134 of the distance measuring device 100, the transceiver processing unit 234 of the distance measuring device 200, and the distance measuring unit 235. Specifically, the transceiver processing unit 234 sequentially transmits signals of multiple frequencies for TOA, the transceiver processing unit 134 sequentially returns signals of the same frequency for TOA, and the transceiver processing unit 134 transmits phase data indicating the phase when the signal is received to the distance measuring device 200. In addition, the AOA-format angle measurement processing in the processing of step S209 is a process of measuring a first phase difference and a second phase difference when the ranging device 200 receives a signal for TOA from the ranging device 100, and measuring an azimuth and an elevation angle representing the position of the ranging device 100 relative to the ranging device 200 based on the first phase difference and the second phase difference.

[0138] Furthermore, the distance measuring device 200 transmits data indicating the distance and angle obtained by the distance measuring process and the angle measuring process in step S209 to the distance measuring device 100. The transmission of such data may be performed by the transmission and reception processing unit 234 as an example.

[0139] The distance measuring unit 235 of the distance measuring device 200 obtains the round-trip phase difference obtained by adding the phase when the transmission and reception processing unit 234 receives the signal from the distance measuring device 100 and the phase indicated by the phase data received from the distance measuring device 100 for each frequency. The distance measuring unit 235 measures the distance between the distance measuring devices 100 and 200 in the TOA format based on the relationship between the multiple frequencies and the round-trip phase difference at each frequency. In the process of step S209, the distance between the distance measuring devices 100 and 200 is calculated by the distance measurement process in the TOA format. The accuracy of the distance measurement in the TOA format is much higher than the accuracy of the distance measurement in the RTT format. In addition, in the process of step S209, the angle measuring unit 236 of the distance measuring device 200 measures the elevation angle and the azimuth angle in the AOA format at a time interval 1 (high frequency) based on the phase difference when the TOA signal sent from the distance measuring device 100 is received by the three antennas 210.

[0140] When the TOA distance measurement process and the AOA angle measurement process of steps S110 and S209 are completed, the distance measuring device 200 determines whether the measured distance is less than or equal to distance 1 (step S210 ). As an example, the process of step S210 is executed by the frequency setting unit 237 of the distance measuring device 200 .

[0141] If the distance measuring device 200 determines that the measured distance is not less than the distance 1 (S210: No), the time interval for performing the distance measurement is set to the time interval 2 (step S211A). If the measured distance is not less than the distance 1, the measured distance is longer than the distance 1 and less than the distance 2, and therefore is set to the time interval 2. As an example, the processing of step S211A is performed by the frequency setting unit 237 of the distance measuring device 200.

[0142] In addition, if the distance measuring device 200 determines in step S210 that the measured distance is less than distance 1 (S210: Yes), the time interval for performing distance measurement is set to time interval 1 (step S211B). When the measured distance is less than distance 1, it is set to time interval 1. As an example, the processing of step S211B is performed by the frequency setting unit 237 of the distance measuring device 200.

[0143] When the distance measuring device 200 finishes the process of step S211A or S211B, it transmits the interval data indicating the time interval set in step S211A or S211B to the distance measuring device 100 (step S212). As an example, the main control unit 231 of the distance measuring device 200 executes the process of step S212.

[0144] The distance measuring device 100 receives the interval data from the distance measuring device 200 (step S111). As an example, the main control unit 131 of the distance measuring device 100 executes the process of step S111.

[0145] The distance measuring device 100 determines whether the time interval indicated by the interval data received in step S111 is time interval 1 (step S112 ). As an example, the main control unit 131 of the distance measuring device 100 executes the process of step S112 .

[0146] If the distance measuring device 100 determines that the time interval represented by the received interval data is not time interval 1 (S112: No), the waiting time in the distance measuring device 100 is set to time interval 2 (step S113A). The process of step S113A is executed by the main control unit 131. If the distance measuring device 100 ends the process of step S113A, the flow returns to step S104. This is to restart the distance measuring process in the RTT format.

[0147] If the distance measuring device 100 determines in step S112 that the time interval indicated by the received interval data is time interval 1 (S112: Yes), the distance measuring device 100 sets the standby time in the distance measuring device 100 to time interval 1 (step S113B). The process of step S113B is executed by the main control unit 131.

[0148] After the process of step S113B is finished, the distance measuring device 100 determines whether to finish the process (step S114). The end is, for example, when the authentication process is completed. The process of step S114 is executed by the main control unit 131. In the authentication process, the distance and angle data obtained by the distance measuring device 200 and sent to the distance measuring device 100 in the distance measuring process and angle measuring process of step S209 are used.

[0149] If the distance measuring device 100 determines that the process is not to be completed (S114: No), the process returns to step S109. This is to perform the distance measurement process of the TOA format and the angle measurement process of the AOA format at a high frequency of the time interval 1.

[0150] If the distance measuring device 100 determines that the process is finished (S114: Yes), it sends a notification of the completion of the series of processes to the distance measuring device 200 (step S115). If the distance measuring device 100 sends a notification of the completion to the distance measuring device 200, the series of processes are finished (end).

[0151] When receiving the termination notification from the distance measuring device 100 , the distance measuring device 200 terminates a series of processes (Terminate).

[0152] <Effect>

[0153] The distance measuring system 300 of the first embodiment includes the distance measuring device 100 and the distance measuring device 200, wherein the distance measuring device 200 includes: a distance measuring unit 235 that performs distance measuring processing based on the result of the distance measuring device 200 transmitting signals bidirectionally with the distance measuring device 100 to measure the distance between the distance measuring device 200 and the distance measuring device 100; and a frequency setting unit 237 that sets the frequency of the distance measuring unit 235 performing the distance measuring processing according to the distance measured by the distance measuring unit 235. Therefore, the frequency of the distance measuring unit 235 performing the distance measuring processing can be set according to the distance measured by the distance measuring unit 235.

[0154] Therefore, by being able to set the measurement frequency according to the measured distance, it is possible to provide a distance measurement system 300 capable of high-precision distance measurement. In addition, since the measurement frequency is set according to the measured distance, the power consumption of the distance measurement devices 100 and 200 can be reduced according to the measured distance.

[0155] In addition, the distance measuring device 200 can move relative to the distance measuring device 100. Therefore, when the distance between the distance measuring devices 100 and 200 changes due to the movement of the distance measuring device 200 relative to the distance measuring device 100, the measurement frequency can be set according to the measured distance, thereby providing the distance measuring system 300 capable of high-precision distance measurement.

[0156] In addition, the shorter the distance measured by the distance measuring unit 235 is, the higher the frequency is set by the frequency setting unit 237. Therefore, the shorter the distance between the distance measuring devices 100 and 200 is, the higher the frequency setting unit 237 can perform the distance measurement process. Therefore, it is possible to provide a distance measuring system 300 that can perform distance measurement at a higher frequency as the distance between the distance measuring devices 100 and 200 is shorter. In addition, the longer the distance measured is, the lower the measurement frequency is set, and thus the longer the distance measured is, the lower the power consumption of the distance measuring devices 100 and 200 can be reduced.

[0157] In addition, the distance measuring device 100 includes: a signal strength measuring unit 132 that performs a signal strength measuring process of measuring the signal strength (RSSI) of a signal received from the distance measuring device 200; and a permission determination unit 133 that permits the distance measuring unit 235 of the distance measuring device 200 to perform the distance measuring process when the signal strength measured by the signal strength measuring unit 132 is greater than a predetermined strength. Therefore, when the RSSI of the signal transmitted by the distance measuring device 200 is greater than a predetermined value and the distance measuring device 200 is close to the distance measuring device 100 to a certain extent, the distance measuring unit 235 can perform the distance measuring process, and when the RSSI of the signal transmitted by the distance measuring device 200 is less than a predetermined value, the distance measuring process can be omitted. When the distance between the distance measuring devices 100 and 200 is sufficiently far, it is difficult to assume that the holder of the device (for example, the smartphone 20) equipped with the distance measuring device 200 is in immediate contact with the device (for example, the vehicle 10) equipped with the distance measuring device 100. In such a situation, by not performing the distance measurement process as part of the authentication process of the distance measuring device 200 , the power consumption of the distance measuring devices 100 and 200 can be reduced.

[0158] In addition, if the distance between the distance measuring device 100 becomes less than the first predetermined distance (distance 2), the distance measuring unit 235 measures the distance between the distance measuring device 100 in the TOA format based on the relationship between the round-trip phase difference and the multiple frequencies obtained by the distance measuring device 100 and the distance measuring device 200 bidirectionally sending the signals of multiple frequencies. Therefore, when the distance between the distance measuring devices 100 and 200 is short to a certain extent (less than the distance 2), the distance can be measured with high accuracy in the TOA format. In addition, the distance measurement processing in the TOA format has many processing steps in order to obtain the relationship between the round-trip phase difference and the multiple frequencies, so the power consumption of the distance measuring devices 100 and 200 increases. By performing the distance measurement processing with large power consumption in a limited manner when the distance between the distance measuring devices 100 and 200 becomes less than the distance 2, the power consumption of the distance measuring devices 100 and 200 can be reduced.

[0159] In addition, when the distance between the distance measuring unit 235 and the distance measuring device 100 is not less than the first predetermined distance (distance 2), the distance between the distance measuring device 100 and the distance measuring device 200 is measured in the RTT format based on the round-trip time when the distance measuring device 100 and the distance measuring device 200 make a round trip. Therefore, when the distance between the distance measuring devices 100 and 200 is medium short, the distance between the distance measuring devices 100 and 200 can be roughly measured in the RTT format. In addition, the RTT format ranging process only requires a round trip of the signal between the distance measuring devices 100 and 200 once, and can be performed with less power consumption than the TOA format ranging process, so when the distance between the distance measuring device 100 is not less than the first predetermined distance (distance 2), by using the RTT format ranging process, the power consumption of the distance measuring devices 100 and 200 can be reduced.

[0160] In addition, if the distance between the distance measuring device 100 is less than the first predetermined distance (distance 2), the frequency setting unit 237 sets the frequency of the distance measuring unit 235 to perform the distance measurement process to be higher than when the distance between the distance measuring device 100 is not less than the first predetermined distance. Therefore, when the distance between the distance measuring devices 100 and 200 is not less than the first predetermined distance, the distance measurement can be performed at a low frequency by the RTT type distance measurement process, and when the distance between the distance measuring devices 100 and 200 is less than the first predetermined distance (distance 2), the distance measurement can be performed at a high frequency by the TOA type distance measurement process. When the distance between the distance measuring devices 100 and 200 is not less than the first predetermined distance, the necessity of the distance measurement is low, so by using the RTT type distance measurement process with low power consumption and reducing the frequency of performing the distance measurement process, further low power consumption can be achieved. When the distance between the distance measuring devices 100 and 200 is equal to or less than the first predetermined distance (distance 2), the necessity for distance measurement is high, so by frequently performing distance measurement using a TOA-type distance measurement process with high distance measurement accuracy, high-precision distance measurement can be realized frequently.

[0161] In addition, when the distance between the distance measuring device 100 becomes less than the second predetermined distance (distance 1) shorter than the first predetermined distance, the frequency setting unit 237 sets the frequency of the distance measuring unit 235 to perform the distance measurement process to be higher than when the distance between the distance measuring device 100 is not less than the second predetermined distance. Therefore, when the distance between the distance measuring devices 100 and 200 is less than the first predetermined distance (distance 2), the frequency of performing the distance measurement process in the TOA format can be changed according to whether it is less than the distance 1, and when the distance measuring device 200 approaches the distance measuring device 100 to less than the distance 1, the distance between the distance measuring devices 100 and 200 can be measured with high frequency and high accuracy in the TOA format. In addition, when the distance between the distance measuring devices 100 and 200 is less than the first predetermined distance (distance 2), the frequency of performing the distance measurement process is changed according to whether it is less than the distance 1, so that when it is farther than the distance 1, the power consumption of the distance measuring devices 100 and 200 can be reduced.

[0162] In addition, the distance measuring device 200 includes a plurality of antennas 210, and the distance measuring device 200 further includes an angle measuring unit 236. The angle measuring unit 236 performs an angle measurement process for measuring an angle indicating the position of the distance measuring device 100 relative to the distance measuring device 200 based on a phase difference when the plurality of antennas 210 of the distance measuring device 200 receive signals from the distance measuring device 100 when the distance measuring device 100 and the distance measuring device 200 bidirectionally transmit signals of a plurality of frequencies. Therefore, the angle (azimuth and elevation) of the distance measuring device 100 relative to the distance measuring device 200 can be obtained.

[0163] In addition, the distance measuring system 300 includes a distance measuring device 100 and a distance measuring device 200, wherein the distance measuring device 100 or the distance measuring device 200 has: a distance measuring unit (135 or 235) that performs distance measuring processing, and the distance measuring processing measures the distance between the distance measuring device 100 and the distance measuring device 200 based on the result of the distance measuring device 100 and the distance measuring device 200 sending signals in both directions; and a frequency setting unit (137 or 237) that sets the frequency of the distance measuring processing performed by the distance measuring unit (135 or 235) according to the distance measured by the distance measuring processing. Therefore, the frequency of the distance measuring processing performed by the distance measuring unit (135 or 235) can be set according to the distance measured by the distance measuring unit (135 or 235).

[0164] Therefore, by being able to set the measurement frequency according to the measured distance, it is possible to provide a distance measurement system 300 capable of high-precision distance measurement. In addition, since the measurement frequency is set according to the measured distance, the power consumption of the distance measuring devices 100 and 200 can be reduced according to the measured distance. In addition, the distance measuring unit (135 or 235) and the frequency setting unit (137 or 237) can be located in any one of the distance measuring device 100 and the distance measuring device 200.

[0165] The communication station (distance measuring device 200) of the first embodiment is a communication station (distance measuring device 200) as a distance measuring device 200 capable of communicating with the distance measuring device 100, and the distance measuring device 200 includes: a distance measuring unit 235 that performs distance measuring processing based on the result of the distance measuring device 200 transmitting signals bidirectionally with the distance measuring device 100, and a frequency setting unit 237 that sets the frequency of the distance measuring unit 235 performing the distance measuring processing according to the distance measured by the distance measuring unit 235. Therefore, the frequency of the distance measuring unit 235 performing the distance measuring processing can be set according to the distance measured by the distance measuring unit 235.

[0166] Therefore, by being able to set the measurement frequency according to the measured distance, it is possible to provide the distance measuring device 200 capable of performing high-precision distance measurement.

[0167] The distance measurement method of the first embodiment is a distance measurement method in a distance measurement system 300 including a distance measurement device 100 and a distance measurement device 200, and performs a distance measurement process for measuring the distance between the distance measurement device 100 and the distance measurement device 200 based on the result of bidirectional signal transmission between the distance measurement device 100 and the distance measurement device 200, and sets the frequency of performing the distance measurement process according to the distance measured by the distance measurement process. Therefore, the frequency of performing the distance measurement process by the distance measurement unit 235 can be set according to the distance measured by the distance measurement unit 235.

[0168] Therefore, by being able to set the measurement frequency according to the measured distance, it is possible to provide a distance measurement method capable of performing high-precision distance measurement.

[0169] In the above description, the distance measuring device 100 measures the RSSI of the advertisement signal transmitted by the distance measuring device 200 and performs the distance measuring process. However, the distance measuring device 200 may measure the RSSI of the advertisement signal transmitted by the distance measuring device 100 and perform the distance measuring process.

[0170] In addition, the above description has been given of a method in which the distance measuring unit 235 of the distance measuring device 200 performs the distance measuring process in the RTT format if the distance between the distance measuring devices 100 and 200 becomes less than the distance 3. However, the distance measuring unit 235 may perform the distance measuring process in the TOA format only instead of the RTT format. In this case, the frequency of performing the distance measuring process in the TOA format may be changed according to whether the distance between the distance measuring devices 100 and 200 is less than the distance 1. In this case, the distance measuring device 100 may measure the RSSI of the advertisement signal until the distance between the distance measuring devices 100 and 200 becomes the distance 2.

[0171] In addition, the MUC 230 of the distance measuring device 200 may be configured not to include the angle measuring unit 236 and the distance measuring device 200 may not perform the angle measurement process.

[0172] <Modification>

[0173] Figure 5 This is a diagram showing an example of a configuration in which a distance measuring system 300M according to a modification of Embodiment 1 is applied to a speaker system. The distance measuring system 300M includes a distance measuring device 100M and a distance measuring device 200M.

[0174] Figure 5 The state where two speakers A and B constituting the speaker system are arranged is shown. The speakers A and B of the speaker system operate according to the positional relationship with the smartphone 20M. Figure 5 , the smartphone 20M is shown in a state where it moves relative to the two speakers A and B. Therefore, the smartphone 20M is shown at five locations according to the position of the smartphone 20M, but one smartphone 20M is provided for the two speakers A and B.

[0175] Speakers A and B include distance measuring devices 100M1 and 100M2, respectively. Figure 2 The distance measuring device 100 shown in the figure can measure the RSSI of the advertising signal sent by the distance measuring device 200. When there is no particular distinction between the distance measuring devices 100M1 and 100M2, they are simply referred to as the distance measuring device 100M. In addition, any one of the speakers A and B can be provided, and the number of distance measuring devices 100M included in the distance measuring system 300M can also be one.

[0176] In addition, the smartphone 20M includes a distance measuring device 200M. The distance measuring device 200M and Figure 2 The distance measuring device 200 shown is the same as that of the distance measuring device 100M1 and 100M2, and can perform distance measuring processing for measuring the distance between the distance measuring devices 100 and 200, and angle measuring processing for obtaining the angle (azimuth and elevation) of the distance measuring device 100 relative to the distance measuring device 200.

[0177] As an example, if the smartphone 20M moves, the signal strength measuring unit 132 of the ranging device 100M measures the RSSI of the advertising signal sent by the ranging device 200M. When the distance between the ranging devices 100M and 200M is longer than the distance 3, only the RSSI is measured and the ranging device 200M does not perform the ranging process.

[0178] If the distance between the distance measuring devices 100M and 200M becomes less than the distance 3 due to the movement of the smartphone 20M, the distance measuring device 200M performs the distance measuring process in the form of RTT, and if it becomes less than the distance 2, it performs the distance measuring process in the form of TOA. If the distance between the distance measuring devices 100M and 200M becomes less than the distance 1, the distance measuring device 200M notifies the distance measuring device 100M1 or 100M2 that the distance is less than 1, and the speaker A or B outputs a sound. The speaker A or B outputs a sound when the distance between the distance measuring device 100M1 or 100M2 and the distance measuring device 200M is less than the distance 1, and stops the output of the sound if it is longer than the distance 1. In addition, the sound may be a voice guidance, music, etc.

[0179] In this way, the distance measuring system 300M can be used in the speaker system. The frequency of performing the distance measuring process is set according to the distance measured by the distance measuring device 200M in the distance measuring process.

[0180] Therefore, by being able to set the measurement frequency according to the measured distance, it is possible to provide a distance measurement system 300M capable of high-precision distance measurement. In addition, since the measurement frequency is set according to the measured distance, the power consumption of the distance measurement devices 100M and 200M can be reduced according to the measured distance.

[0181] <Implementation Method 2>

[0182] The difference between the second embodiment and the first embodiment is that the distance measuring unit 135 and the angle measuring unit 136 of the distance measuring device 100 on the vehicle 10 side perform distance measuring processing and angle measuring processing, etc., and the distance measuring unit 235 and the angle measuring unit 236 of the distance measuring device 200 on the smartphone 20 side do not perform distance measuring processing and angle measuring processing, etc. In addition, the distance measuring devices 100 and 200 of the second embodiment perform additional processing that is not performed in the first embodiment, and therefore have additional components to the distance measuring devices 100 and 200 of the first embodiment.

[0183] The distance measuring device 100 of the second embodiment is different from the distance measuring device 100 of the first embodiment in that a process of selecting one distance measuring device 200 that performs distance measuring process and angle measuring process simultaneously from a plurality of distance measuring devices 200 is performed. In addition, the distance measuring device 200 of the second embodiment is different from the distance measuring device 200 of the first embodiment in that an advertisement signal including distance measuring information related to the distance measuring process and angle measuring process performed by the distance measuring unit 135 and the angle measuring unit 136 of the distance measuring device 100 is transmitted.

[0184] In Embodiment 2, unlike Embodiment 1, the distance measuring device 100 is an example of the second communication station, and the distance measuring device 200 is an example of the first communication station. Embodiment 2 will be described below with the differences from Embodiment 1 as the center. In addition, for the same components as the distance measuring devices 100 and 200 of Embodiment 1, repeated descriptions are omitted.

[0185] Figure 6 1 is a diagram showing an example of the configuration of the distance measuring devices 100 and 200 according to Embodiment 2. A system including the distance measuring devices 100 and 200 is a distance measuring system 300. Figure 6 The distance measuring devices 100 and 200 according to the second embodiment will be described.

[0186] exist Figure 6 In the embodiment 2, one distance measuring device 100 and one distance measuring device 200 are respectively represented, but in the embodiment 2, there can be multiple distance measuring devices 100 and 200. In the embodiment 2, the multiple distance measuring devices 100 respectively select one distance measuring device 200 that performs distance measurement processing and angle measurement processing at the same time in an environment where multiple distance measuring devices 200 exist. As an example, the multiple distance measuring devices 100 are arranged to be separated by more than 100m, and each distance measuring device 100 independently performs the processing described below. Therefore, the processing of one distance measuring device 100 is described below.

[0187] The distance measuring device 100 performs distance measuring processing and angle measuring processing together with the selected distance measuring device 200. In Embodiment 2, the distance measuring processing performed by the distance measuring unit 235 of the distance measuring device 200 of Embodiment 1 is performed by the distance measuring unit 135 of the distance measuring device 100 of Embodiment 2. The processing performed by the transceiver processing unit 234 of the distance measuring device 200 of Embodiment 1 is performed by the transceiver processing unit 134 of the distance measuring device 100 of Embodiment 2. In addition, the processing performed by the transceiver processing unit 134 of the distance measuring device 100 of Embodiment 1 is performed by the transceiver processing unit 234 of the distance measuring device 200 of Embodiment 2. In addition, the processing performed by the angle measuring unit 236 of the distance measuring device 200 of Embodiment 1 is performed by the angle measuring unit 136 of the distance measuring device 100 of Embodiment 2. In addition, similarly to the main control unit 231 of the distance measuring device 200 in embodiment 1 that calculates the position of the distance measuring device 100 relative to the distance measuring device 200 based on the distance and the angle (elevation angle and azimuth angle), the main control unit 131 of the distance measuring device 100 in embodiment 1 calculates the position of the distance measuring device 200 relative to the distance measuring device 100 based on the distance and the angle (elevation angle and azimuth angle).

[0188] <Configuration of Distance Measuring Device 200 According to Embodiment 2>

[0189] The distance measuring device 200 includes three antennas 210, a communication unit 220, and an MCU 230. The configurations of the three antennas 210 and the communication unit 220 are the same as those of the first embodiment.

[0190] <mcu230>

[0191] MCU130 includes a main control unit 231, a signal strength measuring unit 232, a permission determination unit 233, a transmission and reception processing unit 234, a distance measuring unit 235, a distance measurement information acquisition unit 235A, an angle measuring unit 236, a frequency setting unit 237, and a memory 238. MCU230 of the second embodiment has a configuration in which a distance measurement information acquisition unit 235A is added to the MCU230 of the first embodiment.

[0192] <Distance Measurement Information Acquisition Unit 235A>

[0193] The distance measurement information acquisition unit 235A acquires distance measurement information related to the distance measurement process performed by the distance measurement unit 135 of the distance measurement device 100. As an example, the distance measurement information includes identification information of the distance measurement device 100 in the distance measurement process that the distance measurement device 200 performed last time together with the distance measurement device 100, the time when the last distance measurement process was performed (distance measurement time), the position of the distance measurement device 200 obtained from the distance obtained in the last distance measurement process and the angle obtained in the last angle measurement process (last position), and the relative speed of the distance measurement device 200 that performed the last distance measurement process together with the distance measurement unit 135 (relative speed of the distance measurement devices 100 and 200).

[0194] The last position is determined by the distance obtained by the distance measuring unit 135 in the last distance measuring process and the elevation angle and azimuth angle obtained by the angle measuring unit 136 in the last angle measuring process. The elevation angle and azimuth angle obtained by the angle measuring unit 136 are the elevation angle and azimuth angle of the position of the distance measuring device 200 relative to the distance measuring device 100 in the polar coordinate system.

[0195] Furthermore, when the transceiver processing unit 134 transmits and receives signals with the transceiver processing unit 234 of the distance measuring device 200 in order to obtain data such as the round-trip time, phase difference, and frequency component of the signal required for the distance measuring unit 135 to perform distance measurement, the transceiver processing unit 134 obtains the relative speed.

[0196] Specifically, the transceiver processing unit 134 transmits and receives signals of multiple frequencies f1 to fm (m is an integer greater than 2) between the transceiver processing unit 234 of the ranging device 200, and for the signal that is sent from the ranging device 100 to the ranging device 200 and sent from the ranging device 200 to the ranging device 100 and back, the round-trip phase (first round-trip phase) of the phase when received by the ranging device 200 and the phase when received by the ranging device 100 is calculated.

[0197] In addition, after obtaining the first round-trip phase, the transceiver processing unit 134 transmits and receives signals of multiple frequencies f1 to fm (m is an integer greater than 2) between the transceiver processing unit 234 of the ranging device 200, and obtains the round-trip phase (second round-trip phase) of the phase when received by the ranging device 200 and the phase when received by the ranging device 100 for the signal that is sent from the ranging device 100 to the ranging device 200 and sent from the ranging device 200 to the ranging device 100.

[0198] Then, the transmission / reception processing unit 134 obtains the relative speed with respect to the distance measuring device 100 based on the difference between the first round-trip phase and the second round-trip phase at the frequencies f1 to fm.

[0199] Furthermore, when the smartphone 20 including the distance measuring device 200 is moving, the distance measuring device 100 with which the distance measuring device 200 performed the last distance measuring process may be different from the distance measuring device 100 with which the distance measuring device 200 performs the next distance measuring process. The next distance measuring process is a distance measuring process performed immediately after the last distance measuring process.

[0200] When the distance measuring device 200 performs the distance measuring process together with the distance measuring device 100, the distance measuring information acquisition unit 235A stores the identification information of the distance measuring device 100, the distance measuring time at which the distance measuring process is performed, the measured position, and the relative speed in the memory 238 as the distance measuring information. When the distance measuring device 200 performs the angle measuring process and the angle measuring process together with the distance measuring device 100 next, the distance measuring information is acquired by the distance measuring device 100. Therefore, when the angle measuring process and the angle measuring process are performed next, the identification information of the distance measuring information is the identification information of the distance measuring device 100 that performed the angle measuring process and the angle measuring process together last time (hereinafter, the last identification information), the distance measuring time is the last distance measuring time at which the last angle measuring process is performed, the measured position is the last position measured in the last angle measuring process and the angle measuring process, and the relative speed is the relative speed (hereinafter, the last relative speed) obtained in the last angle measuring process.

[0201] The distance measuring device 200 stores the distance measuring information including the last identification information, the last distance measuring time, the last position and the last relative speed in the advertisement signal and transmits the same.

[0202] Here, use Figure 7 To illustrate where the ranging information is stored in the advertising signal. Figure 7 FIG. 1 is a diagram showing an example of a location where distance measurement information is stored in an advertisement signal. Figure 7 An example of the data structure of the advertisement signal is shown in FIG.

[0203] The ranging information (last identification information, last ranging time, last position, and last relative speed) can be stored after the mobile ID in the advertiser data in the protocol data unit between the access address and CRC of the advertisement signal. The mobile ID is the identification information of the ranging device 200 that sends the advertisement signal. In addition, the ranging information is not limited to such a position, and can also be configured at other positions in the advertisement signal.

[0204] <Configuration of Distance Measuring Device 100 According to Embodiment 2>

[0205] The distance measuring device 100 includes three antennas 110, a communication unit 120, and an MCU 130. The configurations of the three antennas 110 and the communication unit 120 are the same as those of the first embodiment.

[0206] <mcu130>

[0207] MCU130 includes a main control unit 131, a signal strength measuring unit 132, a first processing unit 132A, a permission determination unit 133, a transmission and reception processing unit 134, a distance measuring unit 135, an angle measuring unit 136, a frequency setting unit 137, and a memory 138. MCU130 of embodiment 2 has a configuration in which the first processing unit 132A is added to the MCU130 of embodiment 1. The memory 138 is an example of a storage unit.

[0208] The main control unit 131, signal strength measuring unit 132, first processing unit 132A, permission determination unit 133, transmission and reception processing unit 134, distance measuring unit 135, angle measuring unit 136, and frequency setting unit 137 represent the functions of the program executed by MCU 130 as functional blocks. In addition, memory 138 functionally represents the memory of MCU 130.

[0209] <First Processing Unit 132A>

[0210] The first processing unit 132A determines whether the RSSI (signal strength) of the advertisement signal measured by the signal strength measuring unit 132 is greater than or equal to a predetermined strength for each of the plurality of distance measuring devices 200, and extracts a plurality of distance measuring devices 200 whose RSSI is greater than or equal to the predetermined value (predetermined strength). Then, the first processing unit 132A selects one distance measuring device 200 to be subjected to distance measurement processing together from among the plurality of distance measuring devices 200 whose RSSI is greater than or equal to the predetermined value (predetermined strength) extracted.

[0211] For example, the plurality of distance measuring devices 200 whose RSSI measured by the signal strength measuring unit 132 is greater than or equal to a predetermined value are distance measuring devices 200 whose distance from the distance measuring device 100 is less than or equal to 100 m. The RSSI of the advertisement signal received by the distance measuring device 100 from the distance measuring device 200 is approximately proportional to the distance between the distance measuring devices 100 and 200, so by using the RSSI when the distance between the distance measuring devices 100 and 200 is 100 m as the predetermined value (predetermined strength), the distance measuring devices 200 whose distance from the distance measuring device 100 is within about 100 m can be extracted.

[0212] In the case where there are multiple distance measuring devices 200 whose RSSI is greater than or equal to a specified value (specified strength), the first processing unit 132A saves the multiple RSSIs and the multiple distance measuring information contained in the received multiple advertisement signals to the memory 138. The distance measuring information includes the last identification information, the distance measuring time, the last position, and the last relative speed. The last identification information is the identification information of the distance measuring device 100 that performed the last distance measuring process together with the distance measuring device 200 that sent the advertisement signal. The distance measuring time is the last distance measuring time indicating the time when the distance measuring device 200 that sent the advertisement signal performed the last distance measuring process. The last position is the last position obtained based on the distance and angle (elevation angle and azimuth angle) obtained by the distance measuring device 200 that sent the advertisement signal in the last distance measuring process and the last angle measuring process. The last relative speed is the relative speed obtained when the distance measuring device 200 that sent the advertisement signal performed the last distance measuring process.

[0213] Furthermore, the first processing unit 132A selects a distance measuring device 200 whose last identification information indicates a distance measuring device 100 different from its own distance measuring device 100 from among the plurality of distance measuring devices 200 whose RSSI is greater than or equal to a predetermined value (predetermined strength) as a distance measuring device 200 for which distance measuring processing is performed together.

[0214] Furthermore, when there are multiple ranging devices 200 different from the ranging device 100 indicated by the previous identification information, the first processing unit 132A selects the ranging device 200 whose receiving time of the advertisement signal is the earliest among the multiple ranging devices 200 as the ranging device 200 for performing ranging processing together.

[0215] In addition, the first processing unit 132A performs an evaluation based on the last distance measurement time, the last position, and the last relative speed, and selects the distance measurement device 200 with the largest evaluation score as the distance measurement device 200 that performs distance measurement processing together. In addition, the evaluation score is not limited to the method of calculating based on all of the last distance measurement time, the last position, and the last relative speed, and may be calculated based on at least two of the last distance measurement time, the last position, and the last relative speed.

[0216] In addition, when there are a plurality of distance measuring devices 200 having the largest evaluation score based on the last distance measuring time, the last position, and the last relative speed, the first processing unit 132A predicts the position of the distance measuring device 200 at the time of receiving the signal based on the last position, the last distance measuring time, and the last relative speed for the plurality of distance measuring devices 200. Then, the first processing unit 132A selects the distance measuring device 200 whose predicted position is closest to the distance measuring device 100 as the distance measuring device 200 for which the distance measuring process is performed together.

[0217] <Receiving information and ranging information>

[0218] Figure 8 1 is a diagram showing an example of reception information and distance measurement information received by the distance measurement device 100. The evaluation criteria and evaluation scores are also shown for the last distance measurement time, the last position, and the last relative speed in the distance measurement information. The evaluation scores are shown in parentheses.

[0219] The reception information is the RSSI and the reception time of the advertisement signal when the distance measuring device 100 receives the advertisement signal from the distance measuring device 200. When the distance measuring device 100 receives the advertisement signal from the distance measuring device 200, the distance measuring device 100 obtains the RSSI and the reception time and stores them in the memory 138 as the reception information.

[0220] In addition, the distance measurement information is the last identification information, the last distance measurement time, the last position and the last relative speed, and is included in the advertisement signal received by the distance measurement device 100 from the distance measurement device 200. When the distance measurement device 100 receives the advertisement signal, it reads the distance measurement information and stores the last identification information, the last distance measurement time, the last position and the last relative speed in the memory 138.

[0221] In addition, when the first processing unit 132A of the distance measuring device 100 evaluates the distance measuring device 200 based on the last distance measuring time, the last position, and the last relative speed, as an example, the distance measuring device 200 is evaluated using Figure 8 Rating points shown.

[0222] As an example, the evaluation criterion of the last distance measurement time is whether the time is the earliest (oldest). The first processing unit 132A gives 2 points to the distance measuring device 200 with the earliest last distance measurement time, and gives 1 point to other distance measuring devices 200.

[0223] As an example, the evaluation criterion of the last position is whether the distance from the distance measuring device 100 to the distance measuring device 200 is less than a threshold value. If the distance from the distance measuring device 100 to the last position of the distance measuring device 200 is less than the threshold value, the first processing unit 132A assigns 2 points to the distance measuring device 200, and if the distance from the distance measuring device 100 to the last position of the distance measuring device 200 is longer than the threshold value, the distance measuring device 200 is assigned 1 point.

[0224] For example, the evaluation criterion of the last relative speed is whether the last relative speed is above a threshold value. If the last relative speed is above the threshold value, the first processing unit 132A gives the distance measuring device 200 2 points, and if the last relative speed is below the threshold value, the distance measuring device 200 is given 1 point.

[0225] <Calculation of evaluation points>

[0226] Fig. 9 : is a diagram showing an example of the calculation result of the evaluation score. Here, as an example, an example of the result of the calculation of the evaluation score by the first processing unit 132A of the distance measuring device 100 for eight distance measuring devices 200 A to H will be described.

[0227] As an example, the first processing unit 132A calculates the evaluation score by multiplying the scores assigned to the last distance measurement time, the last position, and the last relative speed. For the distance measuring device 200 of A, the evaluation score obtained by multiplying 2 points of the last distance measurement time, 2 points of the last position, and 2 points of the last relative speed is 8 points. The evaluation scores of the distance measuring devices 200 of B to H can be calculated in the same way.

[0228] <Timeline>

[0229] Fig.10 is a timing chart showing an example of processing performed by the distance measuring devices 100 and 200. Fig.10 In the figure, the processing of the distance measuring device 100 is shown in the left half, and the processing of the four distance measuring devices 200A to 200D is shown in the right half, and the relationship between the processing of the distance measuring devices 100 and 200A to 200D is also explained. Here, in order to distinguish the four distance measuring devices 200, they are marked as distance measuring devices 200A to 200D. In addition, the distance measuring device 100 is an Anchor (fixed station), and the distance measuring devices 200A to 200D are Tags (mobile stations).

[0230] First, the distance measuring devices 200A to 200D transmit advertisement signals in sequence. Here, as an example, the transmission of advertisement signals in the order of the distance measuring devices 200A to 200D will be described.

[0231] The ranging device 100 executes the process 1 each time it receives an advertisement signal. The ranging device 100 sequentially receives advertisement signals from the plurality of ranging devices 200 during a period of 10 ms (milliseconds) set as the advertisement signal reception period. Here, as an example, the ranging device 100 sequentially receives advertisement signals from the ranging devices 200A to 200D during the advertisement signal reception period, and executes the process 1 each time the advertisement signals are received. As an example, the advertisement signal reception period is 10 ms. The contents of the process 1 are described using Fig.11 This will be described later.

[0232] When the advertisement signal reception period ends, the distance measuring device 100 executes process 2. In process 2, the distance measuring device 200 that performs both the distance measuring process and the angle measuring process is selected by the distance measuring device 100. Here, as an example, it is assumed that the distance measuring device 200B is selected.

[0233] After transmitting the advertisement signal, each of the distance measuring devices 200A to 200D waits for 20 ms to elapse before transmitting the positioning start request, for example. The 20 ms is the positioning start request waiting time. If the positioning start request is not received within the positioning start request waiting time, each distance measuring device 200 transmits the advertisement signal periodically.

[0234] The distance measuring device 100 sends a positioning start request to the selected distance measuring device 200B. The distance measuring device 200B that receives the positioning start request sends a reception notification. As a result, the distance measuring device 100 and the distance measuring device 200B perform distance measurement processing and angle measurement processing together. Thereafter, the distance measuring devices 100 and 200B perform the processing used in Embodiment 1. Figure 3A , Figure 3B , Figure 4A as well as Figure 4B Description of the process.

[0235] <Process 1>

[0236] Fig.11 2 is a flowchart showing an example of specific processing contents of the process 1. The process 1 is executed by the distance measuring device 100 .

[0237] The distance measuring device 100 receives an advertisement signal (step S251 ).

[0238] The first processing unit 132A acquires the time at which the advertisement signal is received (step S252 ).

[0239] The first processing unit 132A determines whether the distance from the distance measuring device 100 to the distance measuring device 200 is less than the threshold value based on the RSSI (signal strength) of the advertisement signal measured by the signal strength measuring unit 132 (step S253). RSSI is roughly proportional to the distance, so the first processing unit 132A determines whether the distance from the distance measuring device 100 to the distance measuring device 200 is less than the threshold value by determining whether the RSSI is greater than a predetermined strength. In addition, the threshold value used in step S253 is 100m as an example. As an example, the threshold value in step S253 is set to a range of advertisement signals having an RSSI at a level at which the distance measuring device 100 can receive the advertisement signal and read the distance measurement information.

[0240] If the first processing unit 132A determines that the distance from the distance measuring device 100 to the distance measuring device 200 is less than the threshold value (S253: Yes), the RSSI, the reception time, and the distance measuring information are stored in the memory 138 (step S254). The distance measuring information is read out from the received advertisement signal.

[0241] The first processing unit 132A calculates the evaluation score based on the last distance measurement time, the last position, and the last relative speed in the distance measurement information stored in the memory 138 in step S254 (step S255). As described above, the evaluation criterion of the last distance measurement time is whether the time is the earliest (oldest). In addition, the evaluation criterion of the last position is whether the distance from the distance measuring device 100 to the distance measuring device 200 is below a threshold value, and as an example, the threshold value of the distance is 50m. In addition, as an example, the threshold value that serves as the evaluation criterion of the last relative speed is 18km / h.

[0242] First processing unit 132A determines whether the advertisement signal reception period has elapsed (step S256).

[0243] If the first processing unit 132A determines that the advertisement signal reception period has not passed (S256: No), the flow returns to step S251. This is to receive advertisement signals from other distance measuring devices 200 and calculate evaluation points.

[0244] If the first processing unit 132A determines in step S253 that the distance from the distance measuring device 100 to the distance measuring device 200 is not less than the threshold value (S253: No), the process returns to step S251. This is because the distance measuring device 200 is far away from the distance measuring device 100, so that the distance measuring device 100 cannot obtain an advertisement signal having an RSSI at a level at which the advertisement signal can be received and the distance measurement information can be read.

[0245] When first processing unit 132A determines in step S256 that the advertisement signal reception period has elapsed (S256: YES), it ends process 1 and proceeds to process 2.

[0246] The distance measuring device 100 performs the above-described process 1 to extract the distance measuring device 200 having an RSSI of a predetermined value (predetermined strength) or more. When a plurality of distance measuring devices 200 are extracted, process 2 is performed to narrow down the distance measuring device 200 that performs both the distance measuring process and the angle measuring process to one.

[0247] <Process 2>

[0248] Fig.12 2 is a flowchart showing an example of specific processing contents of Process 2. Process 2 is executed by the distance measuring device 100 .

[0249] The first processing unit 132A determines whether there is a distance measuring device 200 (Tag) whose previous identification information is different from the identification information of its own distance measuring device 100 among the plurality of distance measuring devices 200 (Tag) extracted in process 1 (step S261 ).

[0250] If the first processing unit 132A determines that there is a ranging device 200 whose last identification information is different from the identification information of its own ranging device 100 (S261: Yes), then among the multiple ranging devices 200 with different identification information, the ranging device 200 that received the advertising signal the earliest is selected as the ranging device 200 that performs ranging processing and angle measurement processing together (step S262).

[0251] The distance measuring device 200 whose last identification information is different from the identification information of the own distance measuring device 100 is a distance measuring device 200 that performed the last distance measuring process and angle measuring process with another distance measuring device 100 different from the own distance measuring device 100, and is a distance measuring device 200 that moved from the own distance measuring device 100 to within the threshold value (100m) in step S253. Such a distance measuring device 200 performs the distance measuring process and angle measuring process preferentially.

[0252] Furthermore, when there is only one distance measuring device 200 whose last identification information is different from the identification information of the own distance measuring device 100, in step S262, the distance measuring device 200 is selected as the distance measuring device 200 that performs both the distance measurement process and the angle measurement process.

[0253] If the first processing unit 132A determines in step S261 that there is no distance measuring device 200 whose last identification information is different from the identification information of its own distance measuring device 100 (S261: No), it extracts the distance measuring device 200 with the largest evaluation score (step S263). In the case that there is no distance measuring device 200 whose last identification information is different from the identification information of its own distance measuring device 100, all the distance measuring devices 200 extracted in process 1 are distance measuring devices 200 that have performed the last distance measurement process and angle measurement process together with its own distance measuring device 100, so based on the evaluation score, it is determined which distance measuring device 200 is to be prioritized for the distance measurement process and angle measurement process. In addition, the evaluation score of the distance measuring device 200 can be read from the memory 138.

[0254] The first processing unit 132A determines whether there are a plurality of distance measuring devices 200 having the highest evaluation score (step S264).

[0255] When the first processing unit 132A determines that there are not a plurality of distance measuring devices 200 with the highest evaluation scores (S264: No), it selects the distance measuring device 200 with the highest evaluation score as the distance measuring device 200 that performs distance measurement processing and angle measurement processing together (step S265).

[0256] When the first processing unit 132A determines in step S264 that there are a plurality of distance measuring devices 200 having the largest evaluation score (S264: Yes), it calculates the predicted position of each distance measuring device 200 (step S266).

[0257] The predicted position is the position of the distance measuring device 200 predicted at the time of receiving the advertisement signal. The first processing unit 132A calculates the predicted value of the position of the distance measuring device 200 at the time of receiving the advertisement signal by multiplying the time from the last distance measuring time included in the distance measuring information to the time of receiving the advertisement signal by the last relative speed.

[0258] The first processing unit 132A selects the distance measuring device 200 with the smallest difference between the predicted position and the previous position as the distance measuring device 200 to perform distance measurement processing and angle measurement processing together (step S267).

[0259] When the first processing unit 132A completes the processing of step S262, S265, or S267, it sends a positioning start request to the selected distance measuring device 200 (see Fig.10 As a result, the distance measuring device 100 performs distance measuring processing and angle measuring processing together with the selected distance measuring device 200.

[0260] The distance measuring device 100 transmits the positioning result (position obtained by distance and angle) to the distance measuring device 200, and transmits the interval data to the distance measuring device 200. When the above processing is completed, the distance measuring device 100 returns the flow to process 1.

[0261] <Calculation example of predicted position>

[0262] Fig.13 is a diagram showing an example of calculation of the predicted position. Fig.13 1 shows a distance measuring device 100 (Anchor) and three distance measuring devices 200 (Tag). Situations (1) to (3) are described in order from the top. In addition, the last position is represented by the distance from the distance measuring device 100 to the distance measuring device 200. In order to simplify the description, the elevation angle is 0 degrees and the azimuth angle is relative to Fig.13 The distance measuring device 100 in represents the angle in the left direction. In addition, the last positioning time and the time of receiving the advertisement signal are represented by the elapsed time (seconds) relative to the reference time.

[0263] In case (1), the user holding distance measuring device 200 approaches distance measuring device 100 by bicycle. The last position is 50 mm, the last relative speed is 18 km / h, the last positioning time is 10.0 seconds, and the advertising signal reception time is 15.0 seconds. In this case, the predicted position is 25 m.

[0264] In case (2), the user holding the distance measuring device 200 approaches the distance measuring device 100 on foot. The last position is 30 mm, the last relative speed is 3 km / h, the last positioning time is 10.1 seconds, and the advertising signal reception time is 15.1 seconds. In this case, the predicted position is 25.8 m.

[0265] In case (3), the user holding the distance measuring device 200 moves away from the distance measuring device 100 by bicycle. The last position is 25 mm, the last relative speed is -18 km / h (relative speed in the direction of moving away), the last positioning time is 10.0 seconds, and the advertising signal reception time is 10.2 seconds. In this case, the predicted position is 27.5 m.

[0266] When the predicted positions of the cases (1) to (3) are calculated in step S266, the first processing unit 132A selects the distance measuring device 200 of case (1) with the smallest difference between the predicted position and the previous position as the distance measuring device 200 for performing distance measurement and angle measurement together in step S267. The nearest distance measuring device 200 can be preferentially selected to perform distance measurement and angle measurement together.

[0267] <Effect>

[0268] The distance measuring system 300 of the second embodiment includes the distance measuring device 100 and the distance measuring device 200, wherein the distance measuring device 200 includes: a distance measuring unit 235 that performs distance measuring processing, the distance measuring processing measuring the distance between the distance measuring device 100 and the distance measuring device 100 based on the result of the distance measuring device 200 bidirectionally transmitting the advertisement signal between the distance measuring device 200 and the distance measuring device 100; and a frequency setting unit 237 that sets the frequency of the distance measuring processing performed by the distance measuring unit 235 according to the distance measured by the distance measuring unit 235. In addition, the distance measuring device 100 (the second communication station) may also include: a signal strength measuring unit 132 that performs signal strength measuring processing measuring the RSSI of the advertisement signal received from the distance measuring device 200 (the first communication station); and a first processing unit 132A that determines whether the RSSI measured by the signal strength measuring unit 132 is greater than a predetermined strength for each of the plurality of distance measuring devices 200, and selects the distance measuring device 200 that performs the distance measuring processing together from the plurality of distance measuring devices 200 whose RSSI is greater than the predetermined strength. Therefore, the frequency of distance measurement by the distance measuring unit 235 can be set according to the distance measured by the distance measuring unit 235. In addition, when there are a plurality of distance measuring devices 200 having RSSIs of a predetermined strength or higher, one distance measuring device 200 can be selected to perform distance measurement together.

[0269] Alternatively, the distance measuring device 200 may transmit an advertisement signal including distance measuring information related to distance measuring processing, and the distance measuring device 100 may receive a plurality of advertisement signals from a plurality of distance measuring devices 200. The distance measuring device 100 may further include a memory 138 (storage unit), and the first processing unit 132A may store a plurality of RSSIs and a plurality of distance measuring information included in the received plurality of advertisement signals for a plurality of distance measuring devices 200 having RSSIs of a predetermined strength or higher in the memory 138. Since the RSSIs and the distance measuring information for a plurality of distance measuring devices 200 having RSSIs of a predetermined strength or higher can be stored in the memory 138 as materials for determining when selecting a distance measuring device 200, it is possible to easily select a distance measuring device 200.

[0270] Alternatively, there may be a plurality of distance measuring devices 100, and the distance measuring information may include last identification information for identifying a distance measuring device 100 that has performed the distance measuring process last time together with a distance measuring device 200 among the plurality of distance measuring devices 100, and the first processing unit 132A may select a distance measuring device 200 that is different from its own distance measuring device 100 and that is represented by the last identification information from among the plurality of distance measuring devices 200 whose RSSI is greater than or equal to a predetermined strength, as a distance measuring device 200 that has performed the distance measuring process together. The distance measuring device 100 that is different from its own distance measuring device 100 and the distance measuring device 200 that has performed the distance measuring process last time are distance measuring devices 200 that have moved to the vicinity of its own distance measuring device 100. Such a distance measuring device 200 may be preferentially selected.

[0271] Alternatively, when there are multiple distance measuring devices 200 whose distance measuring devices 100 indicated by the last identification information are different from the first processing unit 132A, the first processing unit 132A may select the distance measuring device 200 at which the advertisement signal is received earliest among the multiple distance measuring devices 200 as the distance measuring device 200 for which the distance measuring device 100 performs the distance measuring process together. When there are multiple distance measuring devices 200 that move to the vicinity of the first processing unit 132A, by selecting the distance measuring device 200 at which the advertisement signal is received earliest, the distance measuring device 200 at which the advertisement signal is received longest among the multiple distance measuring devices 200 that move to the vicinity of the first processing unit 132A can be preferentially selected.

[0272] In addition, the distance measuring device 100 may further include: a plurality of antennas 110; and an angle measuring unit 136, which performs an angle measurement process for measuring an angle indicating a position of the distance measuring device 200 relative to the distance measuring device 100 based on a phase difference when the plurality of antennas of the distance measuring device 100 receive signals from the distance measuring device 200 when the distance measuring device 200 and the distance measuring device 100 transmit signals of a plurality of frequencies in both directions, wherein the distance measuring information includes a last distance measuring time when the last distance measuring process was performed, a last position obtained based on a distance measured in the last distance measuring process and an angle measured in the last angle measuring process, and a last relative speed obtained in the last distance measuring process, and the first processing unit 132A selects a distance measuring device 200 having a maximum evaluation score based on at least two or more of the information of the last distance measuring time, the last position, and the last relative speed as the distance measuring device 200 to be performed together with the distance measuring process. The distance measuring device 200 for which the distance measuring process should be performed preferentially can be easily determined by using the evaluation score as a determination index.

[0273] Alternatively, the ranging information may include the last ranging time, the last position, and the last relative speed, and when there are multiple ranging devices 200 having the largest evaluation scores based on the last ranging time, the last position, and the last relative speed, the first processing unit 132A predicts the positions of the ranging devices 200 at the time when the advertisement signal is received based on the last positions, the last ranging time, and the last relative speed for the multiple ranging devices 200, and selects the ranging device 200 whose predicted position is closest to the ranging device 100 as the ranging device 200 for which ranging processing is performed together. The closest ranging device 200 may be preferentially selected and ranging processing may be performed together.

[0274] The distance measuring system 300 of the second embodiment includes a distance measuring device 100 and a distance measuring device 200, wherein the distance measuring device 100 (second communication station) includes: a signal strength measuring unit 132 that performs a signal strength measuring process of measuring the RSSI of the advertisement signal received from the distance measuring device 200 (first communication station); and a first processing unit 132A that determines whether the RSSI measured by the signal strength measuring unit 132 is greater than or equal to a predetermined strength for each of a plurality of distance measuring devices 200, and selects a distance measuring device 200 that performs distance measuring process together from a plurality of distance measuring devices 200 whose RSSI is greater than or equal to the predetermined strength. Therefore, in the case where there are a plurality of distance measuring devices 200 whose RSSI is greater than or equal to the predetermined strength, one distance measuring device 200 that performs distance measuring process together can be selected.

[0275] The distance measurement system, communication station, and distance measurement method according to exemplary embodiments of the present disclosure have been described above, but the present disclosure is not limited to the specific disclosed embodiments, and various modifications and changes can be made without departing from the scope of the claims.

[0276] In addition, the present international application claims priority based on Japanese patent application No. 2022-164644 filed on October 13, 2022, the entire contents of which are incorporated herein by reference.

[0277] Marking Description

[0278] 10 Vehicles

[0279] 20, 20M Smartphone

[0280] 100, 100M, 100M1, 100M2 distance measuring device (an example of the first communication station in the first embodiment and an example of the second communication station in the second embodiment)

[0281] 110 Antenna

[0282] 120 Ministry of Communications

[0283] 131 Main control unit

[0284] 132 Signal strength measurement unit

[0285] 132A First Processing Unit

[0286] 133 Permit Assessment Department

[0287] 134 Transceiver Processing Department

[0288] 135 Distance Measurement Department

[0289] 136 Angle measurement unit

[0290] 137 Frequency setting unit

[0291] 138 Memory

[0292] 200, 200M distance measuring device (an example of the second communication station in Embodiment 1, an example of the first communication station in Embodiment 2)

[0293] 210 Antenna

[0294] 220 Ministry of Communications

[0295] 231 Main Control Unit

[0296] 232 Signal strength measurement unit

[0297] 233 Permission Judgment Department

[0298] 234 Transceiver Processing Department

[0299] 235 Distance Measurement Department

[0300] 235A Distance Measurement Information Acquisition Unit

[0301] 236 Angle measurement department

[0302] 237 Frequency setting unit

[0303] 238 Memory

[0304] 300, 300M ranging system

Claims

1. A ranging system, comprising: First communication station; as well as The second communication station, The second communication station has: a distance measuring unit for performing distance measuring processing, the distance measuring processing measuring the distance between the second communication station and the first communication station based on the result of bidirectional signal transmission between the second communication station and the first communication station; as well as The frequency setting unit sets a frequency of the distance measurement process performed by the distance measurement unit according to the distance measured by the distance measurement unit.

2. The distance measurement system according to claim 1, wherein: The second communication station is movable relative to the first communication station.

3. The ranging system according to claim 1 or 2, wherein: The frequency setting unit increases the frequency as the distance measured by the distance measuring unit is shorter.

4. The distance measurement system according to any one of claims 1 to 3, wherein: The first communication station has: a signal strength measuring unit for performing a signal strength measuring process for measuring the signal strength of a signal received from the second communication station; as well as The permission determination unit permits the ranging unit of the second communication station to perform the ranging process when the signal strength measured by the signal strength measurement unit is equal to or greater than a predetermined strength.

5. The distance measurement system according to any one of claims 1 to 4, wherein: When the distance between the first communication station and the distance measuring unit becomes less than a first specified distance, the distance measuring unit measures the distance between the first communication station and the second communication station based on the relationship between the round-trip phase difference and the multiple frequencies obtained by bidirectionally sending signals of multiple frequencies by the first communication station and the second communication station.

6. The distance measurement system according to claim 5, wherein: When the distance to the first communication station is not less than the first predetermined distance, the distance measuring unit measures the distance to the first communication station based on a round trip time when the first communication station and the second communication station make a round trip signal.

7. The distance measurement system according to claim 6, wherein: When the distance to the first communication station is equal to or smaller than the first predetermined distance, the frequency setting unit sets the frequency at which the distance measuring unit performs the distance measuring process to be higher than the frequency when the distance to the first communication station is not equal to or smaller than the first predetermined distance.

8. The distance measurement system according to claim 5, wherein: When the distance to the first communication station becomes less than a second specified distance shorter than the first specified distance, the frequency setting unit sets the frequency of the ranging process performed by the ranging unit to be higher than the frequency when the distance to the first communication station is not less than the second specified distance.

9. The distance measurement system according to claim 5, wherein: The second communication station also includes: multiple antennas; and An angle measurement unit performs angle measurement processing for determining an angle representing a position of the first communication station relative to the second communication station based on a phase difference when the multiple antennas of the second communication station receive signals from the first communication station when the first communication station and the second communication station transmit signals of multiple frequencies in both directions.

10. The distance measurement system according to claim 1, wherein: The second communication station has: a signal strength measuring unit for performing a signal strength measuring process for measuring the signal strength of a signal received from the first communication station; as well as The first processing unit determines, for each of the plurality of first communication stations, whether the signal strength measured by the signal strength measuring unit is greater than a predetermined strength, and selects a first communication station for performing the ranging process together from the plurality of first communication stations whose signal strength is greater than the predetermined strength.

11. The distance measurement system according to claim 10, wherein: The first communication station transmits the signal including ranging information related to the ranging process, The second communication station receives a plurality of the signals from a plurality of the first communication stations, The second communication station further comprises a storage unit. The first processing unit stores, for the plurality of first communication stations whose signal strengths are equal to or greater than the predetermined strength, the plurality of signal strengths and the plurality of ranging information included in the plurality of received signals in the storage unit.

12. The distance measurement system according to claim 11, wherein: There are multiple second communication stations. The ranging information includes last identification information for identifying the second communication station that performed the last ranging process together with the first communication station among the plurality of second communication stations. The first processing unit selects, from among the plurality of first communication stations having the signal strengths greater than or equal to the predetermined strength, the first communication station whose second communication station indicated by the previous identification information is different from its own second communication station, as the first communication station to perform the ranging process together.

13. The distance measurement system according to claim 12, wherein: The ranging information includes a reception time when the second communication station receives the signal from the first communication station, When there are multiple first communication stations whose second communication station indicated by the previous identification information is different from the first communication station itself, the first processing unit selects the first communication station with the earliest reception time among the multiple first communication stations as the first communication station for performing the ranging process together.

14. The distance measurement system according to claim 12 or 13, wherein: The second communication station also includes: multiple antennas; and an angle measuring unit for performing an angle measuring process for measuring an angle indicating a position of the first communication station relative to the second communication station based on a phase difference when the plurality of antennas of the second communication station receive signals from the first communication station when the first communication station and the second communication station bidirectionally transmit signals of a plurality of frequencies; The distance measurement information includes the last distance measurement time when the last distance measurement process was performed, the last position obtained based on the distance measured in the last distance measurement process and the angle measured in the last angle measurement process, and the last relative speed obtained in the last distance measurement process. The first processing unit selects the first communication station having the highest evaluation score based on at least two or more of the last distance measurement time, the last position, and the last relative speed as the first communication station to perform the distance measurement process together.

15. The distance measurement system according to claim 14, wherein: The ranging information includes the last ranging time, the last position and the last relative speed, When there are multiple first communication stations having the largest evaluation score based on the last distance measurement time, the last position, and the last relative speed, the first processing unit predicts the position of the first communication station at the time when the signal is received based on the last position, the last distance measurement time, and the last relative speed for the multiple first communication stations. The first communication station whose predicted position is closest to the second communication station is selected as the first communication station for performing the ranging process together.

16. A distance measurement system, comprising: First communication station; as well as The second communication station, The second communication station has: a signal strength measuring unit for performing a signal strength measuring process for measuring the signal strength of a signal received from the first communication station; as well as The first processing unit determines, for each of the plurality of first communication stations, whether the signal strength measured by the signal strength measuring unit is greater than a predetermined strength, and selects a first communication station for performing ranging processing together from the plurality of first communication stations whose signal strength is greater than the predetermined strength.

17. A distance measurement system, comprising: First communication station; as well as The second communication station, The first communication station or the second communication station has: a distance measuring unit for performing distance measuring processing for measuring the distance between the first communication station and the second communication station based on the result of bidirectional signal transmission between the first communication station and the second communication station; as well as The frequency setting unit sets a frequency at which the distance measuring unit performs the distance measuring process, based on the distance measured by the distance measuring process.

18. A communication station, as a second communication station capable of communicating with a first communication station, wherein: The second communication station has: a distance measuring unit for performing distance measuring processing, the distance measuring processing measuring the distance between the second communication station and the first communication station based on the result of bidirectional signal transmission between the second communication station and the first communication station; as well as The frequency setting unit sets a frequency of the distance measurement process performed by the distance measurement unit according to the distance measured by the distance measurement unit.

19. A ranging method, comprising a ranging method in a ranging system including a first communication station and a second communication station, wherein: A distance measurement process is performed to measure the distance between the first communication station and the second communication station based on the result of bidirectional signal transmission between the first communication station and the second communication station, and a frequency of performing the distance measurement process is set according to the distance measured by the distance measurement process.

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