Position determining system, position determining device, and position determining method

Abstract

According to the present invention, a vehicle-mounted key system functions as a position determining system, and comprises a plurality of anchors (30a to 30f) that perform ranging communication for measuring the distance to a portable terminal (110), and a DK-ECU that controls the anchors (30a to 30f). The vehicle-mounted key system determines effective anchors (3E) from among the anchors (30a to 30f) on the basis of information relating to the position of the portable terminal (110), and performs channel sounding ranging using the effective anchors (3E) to acquire ranging data relating to a phase difference or flight time. Furthermore, the vehicle-mounted key system limits channel sounding ranging by unnecessary anchors (3D) other than the effective anchors (3E). The vehicle-mounted key system identifies the position of the portable terminal (110) on the basis of the ranging data of the effective anchors (3E).

Description

Position determination system, position determination device, and position determination method CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Patent Application No. 2023-206918 filed in Japan on December 7, 2023, and the contents of the original application are incorporated by reference in their entirety.

[0002] TECHNICAL FIELD This disclosure relates to techniques for determining the location of a mobile terminal.

[0003] Patent Literature 1 discloses a short-range wireless communication system that performs wireless communication with a user's mobile terminal by short-range wireless communication conforming to standards such as Bluetooth (registered trademark). This short-range wireless communication system estimates the position of the mobile terminal based on the received signal strength indicator (RSSI) of radio waves received from the mobile terminal.

[0004] Japanese Patent Application Laid-Open No. 2016-171401

[0005] As one of the wireless ranging technologies for measuring the distance to a mobile terminal, there is channel sounding ranging using Bluetooth Low Energy communication (hereinafter referred to as LE-CS ranging), in addition to the wireless ranging using RSSI described in Patent Document 1. However, in LE-CS ranging, the signal transmission and reception time is longer than in wireless ranging using RSSI, which can make radio wave interference more likely to occur.

[0006] The present disclosure aims to provide a position determination system, a position determination device, and a position determination method that are capable of suppressing the occurrence of radio wave interference even when LE-CS ranging is adopted.

[0007] In order to achieve the above-mentioned object, one disclosed aspect is a location determination system comprising a plurality of anchors that perform ranging communication to measure the distance to a mobile terminal, and a control device that controls the plurality of anchors, wherein the anchors perform channel sounding ranging via Bluetooth Low Energy communication and acquire ranging data related to phase difference or time of flight, and a processing circuit provided in at least one of the anchors or the control device determines a valid anchor from among the plurality of anchors based on information regarding the location of the mobile terminal, and includes a communication control unit that restricts channel sounding ranging of unnecessary anchors that are anchors other than the valid anchors, and a location determination unit that determines the location of the mobile terminal based on the ranging data of the valid anchors.

[0008] Another disclosed aspect is a position determination device that controls multiple anchors and causes the anchors to perform channel sounding ranging using Bluetooth Low Energy communication as ranging communication to measure the distance to a mobile terminal, and is equipped with a communication control unit that determines a valid anchor from among the multiple anchors based on information regarding the position of the mobile terminal and restricts channel sounding ranging of unnecessary anchors other than the valid anchor, and a position determination unit that determines the position of the mobile terminal based on ranging data related to the phase difference or time of flight obtained at the valid anchor.

[0009] Another disclosed aspect is a position determination method for determining the position of a mobile terminal through ranging communication using multiple anchors, which includes the following steps in processing performed by at least one processing unit: determining a valid anchor from among the multiple anchors based on information regarding the position of the mobile terminal; performing channel sounding ranging using Bluetooth Low Energy communication using the valid anchor; obtaining ranging data related to phase difference or time of flight; restricting channel sounding ranging of unnecessary anchors that are anchors other than the valid anchor; and identifying the position of the mobile terminal based on the ranging data of the valid anchor.

[0010] In these aspects, ranging data is acquired by performing LE-CS ranging using valid anchors, while LE-CS ranging of unnecessary anchors other than valid anchors is restricted. As described above, by restricting the anchors that perform LE-CS ranging, it is possible to suppress radio wave interference.

[0011] Another disclosed aspect is a location determination system comprising a plurality of anchors that perform ranging communication to measure the distance to a mobile terminal, and a control device that controls the plurality of anchors, wherein the anchors have execution modes for channel sounding ranging using Bluetooth Low Energy communication, including at least a first mode in which they transmit and receive RTT packets to calculate the time of flight of a signal, and a second mode in which they transmit and receive CW signals to calculate the phase of the signal, and wherein a processing circuit provided in at least one of the anchors or the control device includes a communication control unit that determines the execution mode to be executed by the anchor from the first mode and the second mode based on information regarding the position of the mobile terminal, and a location determination unit that determines the position of the mobile terminal based on ranging data obtained by the execution mode determined by the communication control unit.

[0012] Another disclosed aspect is a position determination device that controls multiple anchors and causes the anchors to perform channel sounding ranging using Bluetooth Low Energy communication as ranging communication to measure the distance to a mobile terminal, and the position determination device is equipped with a communication control unit that determines an execution mode to be executed by the anchor from among a first mode that transmits and receives RTT packets to calculate the time of flight of a signal and a second mode that transmits and receives CW signals to calculate the phase of the signal, based on information regarding the position of the mobile terminal, and a position determination unit that determines the position of the mobile terminal based on ranging data obtained by the execution mode determined by the communication control unit.

[0013] Another disclosed aspect is a location determination method for determining the location of a mobile terminal through ranging communication by multiple anchors, which includes the steps of determining, based on information regarding the location of the mobile terminal, an execution mode for channel sounding ranging using Bluetooth Low Energy communication to be performed by the anchor from among a first mode in which RTT packets are transmitted and received to calculate the time of flight of the signal, and a second mode in which CW signals are transmitted and received to calculate the phase of the signal, acquiring ranging data by performing channel sounding ranging in the determined execution mode, and identifying the location of the mobile terminal based on the acquired ranging data, in the processing performed by at least one processing unit.

[0014] In these aspects, the mobile terminal can switch between a first mode in which RTT packets are transmitted and received and a second mode in which CW signals are transmitted and received, depending on the location of the mobile terminal. In this way, radio wave interference can be suppressed by performing ranging communication in the first mode using RTT packets, which have a shorter transmission and reception time than CW signals.

[0015] It should be noted that the reference numbers in parentheses in the claims merely indicate an example of the correspondence with the specific configurations in the embodiments described below, and do not limit the technical scope in any way. Furthermore, claims not explicitly stated in the claims may be combined together if no particular problems arise in the combination.

[0016] 1 is a diagram showing an overall view of a vehicle key system according to the present disclosure. FIG. 1 is a block diagram showing the electrical configuration of the vehicle key system and a mobile terminal. FIG. 2 is a block diagram showing the detailed configuration of an anchor and a mobile terminal. FIG. 3 is a diagram showing an example of anchor mounting positions and terminal areas. FIG. 4 is a table showing a comparison of features of a plurality of ranging methods. FIG. 5 is a diagram showing details of signals transmitted in a plurality of execution modes of channel sounding ranging. FIG. 6 is a table showing an example of antenna switching for switching communication paths in phase difference ranging. FIG. 7 is a table showing an example of linking information between terminal areas and valid anchors. FIG. 8 is a block diagram showing the configuration of a processing circuit. FIG. 9 is a flowchart showing details of a ranging communication process according to a first embodiment together with FIG. 11. FIG. 10 is a flowchart showing details of a ranging communication process together with FIG. 12. FIG. 11 is a diagram showing examples of valid anchors and unnecessary anchors in a scene where a mobile terminal is moving in a second embodiment of the present disclosure. FIG. 12 is a diagram showing examples of valid anchors and unnecessary anchors in a scene where a mobile terminal is not moving. FIG. 12 is a flowchart showing details of a ranging communication process together with FIG. 10. FIG. 13 is a diagram showing examples of valid anchors and unnecessary anchors in a scene where a mobile terminal is approaching a vehicle in a third embodiment of the present disclosure. FIG. 14 is a diagram showing examples of valid anchors and unnecessary anchors in a scene where a mobile terminal is moving away from a vehicle. FIG. 11 is a flowchart showing details of the distance measurement communication process together with FIG. 10. FIG. 12 is a diagram showing an example of a terminal area set around a vehicle in an in-vehicle key system according to a fourth embodiment of the present disclosure. FIG. 13 is a diagram showing a distance measurement method performed when a mobile terminal is in a far area. FIG. 14 is a diagram showing a distance measurement method performed when a mobile terminal is in an intermediate area. FIG. 15 is a diagram showing a distance measurement method performed when a mobile terminal is in a nearby area. FIG. 16 is a flowchart showing details of the distance measurement communication process together with FIG. 10. FIG. 17 is a flowchart showing details of the distance measurement communication process according to a fifth embodiment of the present disclosure together with FIG. 10. FIG. 18 is a flowchart showing details of the distance measurement communication process according to a sixth embodiment of the present disclosure together with FIG. 10. FIG. 19 is a flowchart showing details of the distance measurement communication process according to a seventh embodiment of the present disclosure together with FIG. 10. FIG. 19 is a flowchart showing details of the distance measurement communication process when distance measurement communication is performed between multiple mobile terminals. FIG. 20 is a diagram showing details of the distance measurement performed between multiple mobile terminals. FIG. 21 is a diagram showing aspects of the terminal area of ​​variant 1.10 is a table showing an example of linking information according to Modification 1. FIG. 11 is a diagram showing the arrangement of anchors in the vehicle key system according to Modification 2.

[0017] Hereinafter, several embodiments will be described with reference to the drawings. Note that corresponding components in each embodiment are given the same reference numerals, and redundant description may be omitted. When only a portion of the configuration is described in each embodiment, the configuration of another embodiment described previously can be applied to the remaining portion of the configuration. Furthermore, in addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of several embodiments can also be partially combined together even if not explicitly stated, as long as there is no particular problem with the combination.

[0018] First Embodiment As shown in FIG. 1 , a vehicle key system 100 according to a first embodiment of the present disclosure is mounted on a mobile body such as a hybrid vehicle. The vehicle key system 100 is a system for providing security-related benefits to a user of the hybrid vehicle. The vehicle key system 100 can provide the user with functions related to locking and unlocking the vehicle's doors, starting the engine, and preventing theft.

[0019] <Overall Configuration> As shown in Figures 1 and 2, the vehicle key system 100 includes a digital key ECU (hereinafter referred to as DK-ECU) 10 and multiple anchors 30. ECU stands for Electronic Control Unit. DK stands for Digital Key. The vehicle key system 100 is capable of communicating with a mobile terminal 110 carried by the user of the vehicle Hv. The mobile terminal 110 is a key device that functions as a key for the vehicle Hv.

[0020] The DK-ECU 10, anchor 30, and mobile terminal 110 are configured to be capable of short-range communication. Short-range communication is communication conforming to a specific short-range wireless communication standard, with a practical communication distance of 1 m to 30 m, and up to approximately 100 m. Possible short-range communication standards include Bluetooth Low Energy communication / Bluetooth (registered trademark) Low Energy (hereinafter referred to as Bluetooth LE). Communication conforming to the Bluetooth LE standard will be referred to as LE communication hereinafter. Short-range communication may also be referred to as SR (Short Range) communication. In short-range communication, multiple channels in the 2.4 GHz band are used. Wireless signals exchanged between wireless modules (described later) contain codes indicating the sender or destination. The sender and destination of a wireless signal are expressed, for example, by a device ID.

[0021] <Configuration of the Mobile Terminal> As shown in FIGS. 1 to 3, the mobile terminal 110 is a key device equipped with a short-range communication function. Various key devices that can be carried by the user of the vehicle Hv, such as a smartphone, a wearable device, or a key fob, can be used as the mobile terminal 110. The wearable device may have various shapes, such as a wristband, a watch, a ring, glasses, or earphones. The key fob may be a dedicated device (such as a smart key) that serves as an electronic key for the vehicle Hv. The key fob is one of the accessories of the vehicle Hv that is transferred to the owner when the vehicle Hv is purchased. The smart key may have various shapes, such as a flat rectangular parallelepiped, a flat ellipsoid, or a card.

[0022] The mobile terminal 110 includes a terminal control unit 111 and a communication module 113. The terminal control unit 111 is a processing circuit that controls the operation of the mobile terminal 110. The terminal control unit 111 includes a processor 112a, a memory, a storage 112b, an input / output circuit, and the like, and functions as a computer that executes various processes for operating the mobile terminal 110.

[0023] The communication module 113 is a wireless module provided in the mobile terminal 110. The communication module 113 is capable of performing LE communication. The configuration and functions of the communication module 113 may be the same as those of the communication module 33 of the anchor 30, which will be described later. The communication module 113 has two-axis antennas 121 and 122, an RF switch 124, and a communication controller 130 (see FIG. 3 ).

[0024] The antennas 121 and 122 are antenna elements that transmit and receive radio waves in the above-mentioned frequency band (2.4 GHz band) used in LE communication. The antennas 121 and 122 correspond to "terminal antennas." The antennas 121 and 122 are electrically connected to an RF switch 124.

[0025] The RF switch 124 is a signal processing circuit that performs signal processing related to the transmission and reception of radio signals. The RF switch 124 includes components such as a modulation circuit, a demodulation circuit, a frequency conversion circuit, an amplifier circuit, and a local oscillator. The RF switch 124 performs output processing of signals directed to the antennas 121 and 122 and input processing of signals received by the antennas 121 and 122. The RF switch 124 can switch between the two-axis antennas 121 and 122. The RF switch 124 is connected to the communication controller 130 so as to be able to communicate with each other. The RF switch 124 demodulates signals received by the antennas 121 and 122 and provides the demodulated signals to the communication controller 130. The RF switch 124 modulates transmission data input from the communication controller 130 and radiates the data as radio waves from the antennas 121 and 122.

[0026] The communication controller 130 includes a processor 131, a memory 132, a storage 133, an input / output circuit, and the like. The communication controller 130 is a microcomputer or microcontroller that controls the RF switch 124. The storage 112b, 133 of at least one of the terminal control unit 111 and the communication controller 130 stores the device ID of the mobile terminal 110 and a key code (encryption key) used in wireless authentication processing with the DK-ECU 10. In addition, application software (digital key app) for causing the mobile terminal 110 to function as a key for the vehicle hybrid vehicle is installed in at least one of the storages 112b, 133. The digital key app is a program for securely communicating with the DK-ECU 10 and responding to inquiries and requests from the DK-ECU 10.

[0027] When the mobile terminal 110 is not connected to the DK-ECU 10 for communication, the communication module 113 transmits an advertising signal at a predetermined interval. The advertising signal is a wireless signal for notifying other devices of the presence of the mobile terminal 110. The communication module 113 performs a communication connection process with the DK-ECU 10 upon receiving a connection request from the DK-ECU 10. In response to the advertising signal from the mobile terminal 110, the vehicle key system 100 (DK-ECU 10) returns a connection request, thereby establishing a communication connection between the mobile terminal 110 and the DK-ECU 10. The communication module 113 performs authentication processing via short-range communication (hereinafter referred to as wireless authentication processing) upon the establishment of a communication connection with the DK-ECU 10. The wireless authentication processing is performed, for example, using a challenge-response method.

[0028] <Configuration of DK-ECU> The DK-ECU 10 is connected to an in-vehicle network that is established as a communication network within the vehicle Hv. Standards for in-vehicle networks include Controller Area Network (CAN: registered trademark), Ethernet (registered trademark), and FlexRay (registered trademark). The DK-ECU 10 is connected to each of the multiple anchors 30 via the in-vehicle network or via dedicated communication cables.

[0029] The DK-ECU 10 is mounted at any position in the vehicle Hv. As an example, the DK-ECU 10 is attached to the left C-pillar of the vehicle Hv (see FIG. 4). The C-pillar is the third pillar from the front among the pillars provided on the vehicle Hv. The DK-ECU 10 may also be located in the instrument panel, the overhead console, the right C-pillar, under the driver's seat, or the like.

[0030] The DK-ECU 10 controls multiple anchors 30. The DK-ECU 10 functions as a position determination device that determines the position of the mobile terminal 110 (hereinafter referred to as terminal position) in cooperation with the multiple anchors 30. The terminal position means the relative position of the mobile terminal 110 with respect to the vehicle Hv. Because the mobile terminal 110 is linked to the user, determining the terminal position corresponds to determining the user position.

[0031] The DK-ECU 10 includes a gateway module 13 , an in-vehicle connection circuit 15 , and a main controller 20 .

[0032] The gateway module 13 is a wireless module provided in the DK-ECU 10. The gateway module 13 is capable of at least LE communication. The configuration and functions of the gateway module 13 may be the same as those of the communication modules 33 and 113. The gateway module 13 is supplied with power from the vehicle battery even when the driving power supply is set to off. The gateway module 13 is in a standby state constantly or intermittently using the power supplied from the vehicle battery even when the vehicle Hv is parked. The gateway module 13 periodically scans and attempts to connect with the mobile terminal 110.

[0033] The in-vehicle connection circuit 15 is a signal processing circuit that performs signal processing between the main controller 20 and the multiple anchors 30. The in-vehicle connection circuit 15 includes a PHY chip and a cable connector that conform to the communication method of the anchors 30. The in-vehicle connection circuit 15 converts signals input from the anchors 30 into a format that can be received by the main controller 20 and outputs the signals to the main controller 20. The in-vehicle connection circuit 15 performs predetermined signal processing on the data input from the main controller 20 and outputs the data to the anchors 30.

[0034] The main controller 20 is a processing circuit that controls the operation of the DK-ECU 10. The main controller 20 includes a processor 21, a memory 22, a storage 23, an input / output circuit, and the like. The main controller 20 functions as a computer that executes various processes related to determining the terminal position. The main controller 20 remains in a stopped state unless the gateway module 13 receives a signal transmitted from the mobile terminal 110. The main controller 20 is activated when communication between the gateway module 13 and the mobile terminal 110 is established.

[0035] <Configuration of Anchor> The anchor 30 is used to determine the terminal position. The anchor 30 performs LE communication with the mobile terminal 110 based on instructions from the DK-ECU 10. The anchor 30 includes a communication module 33 and an in-vehicle communication circuit 35.

[0036] The communication module 33 is a wireless module provided in the anchor 30. The communication module 33 is capable of performing LE communication. The configuration and functions of the communication module 33 may be the same as those of the communication module 113 and the gateway module 13 described above. The communication module 33 has two-axis antennas 31 and 32, an RF switch 34, and a communication controller 40 (see FIG. 3).

[0037] The antennas 31 and 32, the RF switch 34, and the communication controller 40 are substantially the same as the antennas 121 and 122, the RF switch 124, and the communication controller 130 of the communication module 113. The antennas 31 and 32 correspond to "anchor antennas." The communication controller 40 includes a processor 41, a memory 42, a storage 43, an input / output circuit, and the like. The communication controller 40 is a microcomputer or microcontroller that controls the RF switch 34.

[0038] The in-vehicle communication circuit 35 is a signal processing circuit that processes signals between the anchor 30 and the main controller 20. The in-vehicle communication circuit 35 converts signals input from the DK-ECU 10 into a format that can be received by the communication module 33, and outputs the converted signals to the communication module 33. The in-vehicle communication circuit 35 performs predetermined signal processing on the data input from the communication module 33, and outputs the processed signals to the DK-ECU 10.

[0039] The anchor 30 operates according to instructions received from the DK-ECU 10. The anchor 30 is activated based on instructions from the DK-ECU 10 and performs ranging communication, which will be described later. The anchor 30 is capable of communication in an active state, a wake state, or the like. After performing ranging communication, the anchor 30 stops operation either spontaneously or based on instructions from the DK-ECU 10. The stopped operation state is a state in which power consumption can be reduced, such as a power-saving state, a power-saving mode, a sleep state, or a disabled state. In these states, the power may be turned off, or some functions may be stopped or disabled. Activating the anchor 30 means transitioning from such a power-saving state to a state in which communication is possible.

[0040] <Vehicle Arrangement of Anchors> A plurality of anchors 30a to 30f are mounted on the vehicle Hv (see FIG. 4). The number of anchors 30 mounted on the vehicle Hv and the arrangement of each anchor 30 may be changed as appropriate for each vehicle model. The plurality of anchors 30a to 30f are substantially identical in configuration, function, and performance. Of the plurality of anchors 30, anchors 30a to 30d are outdoor unit or exterior anchors and are attached to the exterior of the vehicle Hv. In contrast, anchors 30e and 30f are indoor unit or interior anchors and are attached to the passenger compartment of the vehicle Hv.

[0041] The anchor 30a (anchor in FIG. 41) is disposed at the left front corner of the vehicle Hv. Specifically, the anchor 30a is disposed near the left front wheel, at the left end of the front bumper, and at the left side mirror. Such an anchor 30a may be referred to as the left front anchor, the first anchor, or the like.

[0042] The anchor 30b (anchor in FIG. 42) is disposed at the right front corner of the vehicle Hv. Specifically, the anchor 30b is disposed near the right front wheel, at the right end of the front bumper, and at the right side mirror. Such an anchor 30b may be referred to as the right front anchor, the second anchor, or the like.

[0043] The anchor 30c (anchor 3 in FIG. 4) is disposed at the right rear corner of the vehicle Hv. Specifically, the anchor 30c is disposed near the right rear wheel and at the right end of the rear bumper. Such an anchor 30c may be referred to as the right rear anchor or the third anchor.

[0044] The anchor 30d (anchor in FIG. 44) is disposed at the left rear corner of the vehicle Hv. Specifically, the anchor 30d is disposed near the left rear wheel and at the left end of the rear bumper. Such an anchor 30d may be referred to as the left rear anchor or the fourth anchor.

[0045] Anchor 30e (anchor in FIG. 45) and anchor 30f (anchor in FIG. 46) are arranged offset in the front-to-rear direction in the vehicle interior. Anchor 30e is mounted forward of anchor 30f. Specifically, anchor 30e is arranged on the instrument panel, the upper edge of the windshield, the center console, etc. Anchor 30e may be referred to as the interior front anchor, the fifth anchor, etc. On the other hand, anchor 30f is mounted rearward of anchor 30e. Specifically, anchor 30f is arranged on the center of the rear seat, the ceiling above the rear seat, the trunk, etc. Anchor 30f may be referred to as the interior rear anchor, the sixth anchor, etc.

[0046] <Registering the Mobile Terminal in the Vehicle Key System> First, an example of an owner device registration process for registering (pairing) the mobile terminal 110 as an owner device in the vehicle key system 100 will be described.

[0047] In the owner device registration process, if the mobile terminal 110 is a communication terminal such as a smartphone, the user performs biometric authentication, inputs a passcode, or the like on the mobile terminal 110. This makes it possible to confirm that the mobile terminal 110 is being operated by the user himself / herself in the owner device registration process.

[0048] The user uses the mobile terminal 110 to request the management server to start the owner device registration process. In response to this request, the management server creates a password. The created password is distributed to the mobile terminal 110 and the vehicle key system 100 via wireless communication.

[0049] In the vehicle key system 100, when the main switch of the vehicle hybrid vehicle is turned on, a button for starting pairing between the owner device and the vehicle key system 100 is displayed, for example, on a multimedia screen provided in the vehicle interior. When the user operates the pairing start button, the pairing process begins. At this time, the vehicle key system 100 preferably authenticates the user by, for example, holding a smart key having a near-field wireless communication function such as NFC near the main switch. Alternatively, the user may be authenticated by entering a passcode identifying the user on the multimedia screen. The pairing start button may also be displayed on the display 95 of the mobile terminal 110, rather than on the multimedia screen provided in the vehicle interior.

[0050] When the pairing start button is operated, an advertising signal is transmitted from the slave (DK-ECU10 or mobile terminal 110) in the LE communication to the central (mobile terminal 110 or DK-ECU10). The central in the LE communication receives the advertising signal from the slave. Then, when the central confirms that the communication partner is legitimate based on the password distributed by the management server, it responds to the advertising signal and returns a connection request. An LE communication connection between the central and the slave is established based on the slave's receipt of the connection request from the central.

[0051] When an LE communication connection between the central and the slave is established, the central and the slave mutually generate encryption keys and exchange them via LE communication. After the authenticity of the exchanged encryption key is verified, the exchanged encryption key is stored in a storage medium such as each storage. After pairing, the data signal of the LE communication is encrypted using the exchanged encryption key. This ensures the security of the LE communication between the DK-ECU 10 and the mobile terminal 110.

[0052] Next, the DK-ECU 10 determines whether the mobile terminal 110 supports LE-CS ranging (described later). If the DK-ECU 10 determines that the mobile terminal 110 supports LE-CS ranging, the DK-ECU 10 associates the device ID of the mobile terminal 110 with the set CS compatibility flag, registers it, and saves it. Note that the confirmation of whether the mobile terminal 110 supports LE-CS ranging may be performed each time the DK-ECU 10 and the mobile terminal 110 start LE communication, rather than when registering the mobile terminal 110 as an owner device.

[0053] The owner device registration process is completed by notifying the management server that the mobile terminal 110 has been registered as an owner device in the vehicle key system 100 of the vehicle Hv. After the owner device registration process is completed, the slave in the LE communication (the DK-ECU 10 or the mobile terminal 110) starts transmitting an advertising signal. The central in the LE communication (the mobile terminal 110 or the DK-ECU 10) starts scanning for the corresponding advertising signal.

[0054] <Details of Distance Measurement Communication> When the mobile terminal 110 is registered as an owner device in the vehicle key system 100, the relative position of the mobile terminal 110 with respect to the vehicle Hv is determined as the mobile terminal 110 approaches the vehicle Hv. In determining the terminal position, the vehicle key system 100 and the mobile terminal 110 perform distance measurement communication to measure the distance between each anchor 30 and the mobile terminal 110. The vehicle key system 100 and the mobile terminal 110 combine multiple distance measurement methods depending on the situation.

[0055] Specifically, the anchor 30 and the mobile terminal 110 perform ranging (RSSI ranging) using received signal strength indicator / indication (hereinafter referred to as RSSI) in LE communication. Furthermore, the anchor 30 and the mobile terminal 110 perform channel sounding ranging (hereinafter referred to as LE-CS ranging) using LE communication. LE-CS ranging includes ranging using round trip time (RTT) packets (hereinafter referred to as RTT ranging) and phase difference ranging using a continuous wave (hereinafter referred to as CW signal) of a predetermined waveform.

[0056] Details of these ranging methods will be explained below in order, based on Figures 3, 5 to 7, and with reference to Figures 1 and 2. In each ranging communication, as an example, the mobile terminal 110 is on the master (central) side of the communication and corresponds to the "Initiator." The anchor 30 is on the slave side of the communication and corresponds to the "Reflector." The relationship between master and slave in each ranging communication may be reversed.

[0057] [RSSI Ranging] As described above, RSSI ranging is a ranging method based on RSSI, which is an intensity value related to the radio wave intensity of LE communication. When the RF switch 34 of the anchor 30 receives an LE communication signal transmitted from the mobile terminal 110, it measures the reception intensity of the received signal. The RF switch 34 calculates the RSSI, which is a measurement value of the reception intensity, and outputs the calculated RSSI value to the communication controller 40.

[0058] RSSI ranging is a method of ranging that uses signals used in data communication. Therefore, compared to LE-CS ranging, RSSI ranging can keep the communication occupancy rate of LE communication low (see Figure 5). The communication occupancy rate is a value that indicates the proportion of the period during which signals are actually transmitted and received (communication occupancy time) within the communication period. On the other hand, the ranging accuracy of RSSI ranging is lower than that of LE-CS ranging.

[0059] [LE-CS Ranging (Mode 1): RTT Ranging] RTT ranging is mode 1 ranging of LE-CS ranging (see FIG. 6). The mobile terminal 110 and the anchor 30 transmit and receive RTT packets to each other. Each communication controller 40, 130 measures the round trip time from when it transmits the RTT packet to when it receives the response signal, and calculates the distance based on this round trip time.

[0060] In more detail, the mobile terminal 110 (Initiator) transmits an RTT packet to the anchor 30 (Reflector). The anchor 30 records a timestamp when the RTT packet is received. Similarly, the anchor 30 transmits an RTT packet to the mobile terminal 110. The mobile terminal 110 records a timestamp when the RTT packet is received. The propagation time of the radio waves is calculated from the timestamp when the RTT packet is transmitted and received. Then, the distance between the mobile terminal 110 and the anchor 30 is calculated by converting the propagation time into distance. Note that the anchor 30 transmits and receives the RTT packet by changing the frequency used to avoid radio wave interference.

[0061] Because RTT ranging requires the transmission and reception of RTT packets, the communication occupancy rate of LE communication is higher than that of RSSI ranging (see Figure 5). On the other hand, RTT ranging can keep the communication occupancy rate of LE communication lower than that of phase difference ranging, which will be described later. Furthermore, the ranging accuracy of RTT ranging is higher than that of RSSI ranging, but lower than that of phase difference ranging.

[0062] [LE-CS Ranging (Mode 2): Phase Difference Ranging] Phase difference ranging is mode 2 of LE-CS ranging (see Figure 6). The mobile terminal 110 and anchor 30 transmit unmodulated CW signals to each other and measure the phase. The mobile terminal 110 and anchor 30 increase the frequency of the CW signal in 1 MHz or 2 MHz increments from 2400 MHz to 2480 MHz. When the frequency of the CW signal is changed, the phase measured on the receiving side also changes. Based on the difference in the received phase for each frequency, the distance between the mobile terminal 110 and the anchor 30 is calculated.

[0063] The mobile terminal 110 and the anchor 30 measure the phase by switching antenna paths (communication paths) during communication at one frequency. Specifically, the RF switch 124 of the mobile terminal 110 switches the two-axis antennas 121 and 122 on and off in sequence (see FIG. 7). Similarly, the RF switch 34 of the anchor 30 switches the two-axis antennas 31 and 32 on and off in sequence (see FIG. 7). Four antenna paths (see SW1 to SW4 in FIGS. 6 and 7) are used in phase difference ranging.

[0064] Since phase difference ranging requires continuous transmission and reception of CW signals, the communication occupancy rate of LE communication is higher than that of RSSI ranging and RTT ranging (see Figure 5). On the other hand, the ranging accuracy of phase difference ranging can be ensured to be higher than that of RSSI ranging and RTT ranging.

[0065] [LE-CS Ranging (Mode 3): RTT + Phase Difference Ranging] LE-CS ranging can combine phase difference ranging and RTT ranging within a single frequency (see Mode 3 in Figure 6). The mobile terminal 110 and anchor 30 transmit RTT packets and CW signals in sequence. LE-CS ranging in Mode 3 can ensure higher ranging accuracy. However, because it requires the transmission and reception of both RTT packets and CW signals, the communication occupancy rate of LE-CS ranging in Mode 3 is higher than in Modes 1 and 2. The detailed principle of phase difference ranging using LE communication will be explained further below (Details of LE-CS Ranging / Phase Difference Ranging).

[0066] <Start and End Conditions for LE-CS Ranging> Next, the start and end conditions for LE-CS ranging between the mobile terminal 110 and the vehicle key system 100 will be described in detail.

[0067] LE-CS ranging is initiated when the received signal strength in LE communication exceeds a predetermined strength threshold, or when the distance between the positions measured by each GPS receiver falls below a distance threshold. When any of the above-mentioned conditions for starting LE-CS ranging is satisfied, the DK-ECU 10 transmits a request to start LE-CS ranging to the anchor 30. In response to the request for starting LE-CS ranging, the anchor 30 transitions from a sleep state to an active state. This enables the anchor 30 to transmit signals for LE-CS ranging. The anchor 30 is in a sleep state while not performing LE-CS ranging.

[0068] LE-CS ranging is terminated when the mobile terminal 110 is powered off and the LE communication connection is disconnected, or when the received signal strength of the LE signal falls below a predetermined intensity threshold. The intensity threshold used to terminate LE-CS ranging may be the same as or different (lower) from the intensity threshold used to start LE-CS ranging. Furthermore, LE-CS ranging may be terminated if no action is taken on the vehicle for a predetermined time after LE-CS ranging is started. LE-CS ranging may also be terminated when the user gets into the vehicle Hv and turns on the start switch. When any of the above-described LE-CS ranging termination conditions is met, the DK-ECU 10 transmits a request to the anchor 30 to stop LE-CS ranging. If the anchor 30 does not receive a new request to start LE-CS ranging within a predetermined time after terminating LE-CS ranging based on the stop request, it can transition to a sleep state. When the communication connection with the mobile terminal 110 is cut off, the DK-ECU 10 and the anchor 30 return to the same state as before the mobile terminal 110 approached.

[0069] When LE-CS ranging is terminated in response to the user turning on the start switch, LE-CS ranging may be started (restarted) in response to the opening and closing of the door of the vehicle Hv. This makes it possible to detect the position of the mobile terminal 110 through LE-CS ranging when the mobile terminal 110 is taken out of the vehicle while the vehicle Hv is temporarily stopped with the start switch not turned off.

[0070] <Issues with LE-CS Ranging and Solutions> As explained above, by using LE-CS ranging to determine the terminal location, the vehicle key system 100 can identify the terminal location with higher accuracy. However, compared to RSSI ranging, LE-CS ranging requires longer transmission and reception times for radio waves, resulting in a higher communication occupancy rate, which can lead to issues with radio wave interference. In particular, when considering that multiple anchors 30 communicate with the mobile terminal 110 and that the vehicle key system 100 communicates with multiple mobile terminals 110, radio wave interference becomes even more likely to occur.

[0071] To address these issues, the vehicle key system 100 limits the anchors 30 used for LE-CS ranging depending on the area where the mobile terminal 110 (user) is located (hereinafter referred to as the terminal area; see Figures 4 and 8). This allows the radio wave transmission and reception time to be kept to a minimum, preventing deterioration in responsiveness, even when multiple mobile terminals 110 are present.

[0072] [Processing Circuit Configuration for Distance Measurement Communication] In the following description, for convenience, the main controller 20 of the DK-ECU 10 and the communication controller 40 of the anchor 30 are referred to as the processing circuit 50 of the vehicle key system 100 (see FIG. 9 ). The processing circuit 50 executes the position determination method according to the present disclosure. The processing circuit 50 is provided with an information storage unit 51, a communication control unit 52, and a position identification unit 53 as functional units. The functions of the information storage unit 51, the communication control unit 52, and the position identification unit 53 may be realized by either the main controller 20 or the communication controller 40 alone, or may be realized by cooperation between the main controller 20 and the communication controller 40.

[0073] The information storage unit 51 stores linking information (see FIG. 8 ) that links terminal areas with valid anchors 3E, which will be described later. Terminal areas are set around the vehicle Hv. For example, five terminal areas are set around the vehicle Hv (see FIG. 4 ). The driver's side area Aa (see area A in FIG. 4 ) is a terminal area that is defined so as to face the side of the driver's side of the vehicle Hv. The passenger's side area Ac (see area C in FIG. 4 ) is a terminal area that is defined so as to face the side of the passenger's side of the vehicle Hv. The front area Ab (see area B in FIG. 4 ) is a terminal area that is defined so as to face the front part of the vehicle Hv. The front area Ab is adjacent to the front sides of the driver's side area Aa and the passenger's side area Ac. The rear area Ad (see area D in FIG. 4 ) is a terminal area that is defined so as to face the rear part of the vehicle Hv. The rear area Ad is adjacent to the rear of the driver's side area Aa and the passenger's side area Ac. The outer area Ae (see area E in FIG. 4) is a terminal area defined so as to surround the outside of the driver's side area Aa, the front area Ab, the passenger's side area Ac, and the rear area Ad.

[0074] In the linking information, valid anchors 3E are set for these terminal areas. The valid anchors 3E are the anchors 30 that perform LE-CS ranging among the multiple anchors 30. Among the multiple anchors 30, the anchors other than the valid anchors 3E are designated as unnecessary anchors 3D (see FIG. 4). The unnecessary anchors 3D are restricted from performing LE-CS ranging.

[0075] For the driver's seat side area Aa (area A), anchors 30b, 30c, 30e, and 30f (see anchors 2, 3, 5, and 6 in FIG. 4) are defined as effective anchors 3E. On the other hand, anchors 30a and 30d (see anchors 1 and 4 in FIG. 4) are defined as unnecessary anchors 3D.

[0076] For the front area Ab (area B), anchors 30a, 30b, and 30e (see anchors 1, 2, and 5 in FIG. 4) are defined as effective anchors 3E, while anchors 30c, 30d, and 30f (see anchors 3, 4, and 6 in FIG. 4) are defined as unnecessary anchors 3D.

[0077] For the passenger seat side area Ac (area C), anchors 30a, 30f, 30e, and 30f (see anchors 1 and 4 to 6 in FIG. 4) are defined as effective anchors 3E, while anchors 30b and 30c (see anchors 2 and 3 in FIG. 4) are defined as unnecessary anchors 3D.

[0078] For the rear area Ad (area D), anchors 30c, 30d, and 30f (see anchors 3, 4, and 6 in FIG. 4) are defined as effective anchors 3E, while anchors 30a, 30b, and 30e (see anchors 1, 2, and 5 in FIG. 4) are defined as unnecessary anchors 3D.

[0079] For the outer area Ae (area E), anchor 30e (see anchor 5 in FIG. 4) is determined as an effective anchor 3E, while the other anchors 30a to 30d and 30e (see anchors 1 to 4 and 6 in FIG. 4) are determined as unnecessary anchors 3D.

[0080] The communication control unit 52 determines an effective anchor 3E and an unnecessary anchor 3D from among the multiple anchors 30 based on information about the location of the mobile terminal 110. Based on ranging data obtained by RSSI ranging, the communication control unit 52 identifies a terminal area in which the mobile terminal 110 is located from among multiple preset terminal areas. The communication control unit 52 references the linking information and determines an effective anchor 3E and an unnecessary anchor 3D from among the multiple anchors 30 that correspond to the identified terminal area. The effective anchor 3E acquires ranging data related to phase difference or time of flight (RTT) by performing LE-CS ranging in modes 1 to 3. Meanwhile, the communication control unit 52 stops signals for LE-CS ranging by the unnecessary anchor 3D as a process to limit the operation of the unnecessary anchor 3D. This stops the transmission and reception of RTT packets and CW signals by the unnecessary anchor 3D. As a result, the unnecessary anchor 3D no longer acquires ranging data.

[0081] The position specifying unit 53 specifies the position of the mobile terminal 110 based on the ranging data of the valid anchor 3E determined by the communication control unit 52. If ranging communication continues after the position specifying unit 53 specifies the position of the mobile terminal 110, the communication control unit 52 again determines the terminal area and the valid anchor 3E based on the latest ranging data specified by the position specifying unit 53. The position specifying unit 53 again specifies the position of the mobile terminal 110 based on the ranging data of the reset valid anchor 3E.

[0082] [Details of the Distance Measurement Communication Process] The details of the distance measurement communication process performed by the vehicle key system 100 described above will be described below with reference to Figures 1 to 9 and based on Figures 10 and 11. The distance measurement communication process is started by the processing circuit 50 of the vehicle key system 100 upon receiving a signal from the mobile terminal 110. The distance measurement communication process may be started when communication with the mobile terminal 110 is established, or when an advertising signal is received.

[0083] In S11 of the distance measurement communication process (see FIG. 10), pairing between the DK-ECU 10 and the mobile terminal 110 is performed via LE communication. In S12, the pairing process started in S11 is completed, and it is determined whether LE communication between the vehicle key system 100 and the mobile terminal 110 has been established. If LE communication has not been established (NO in S12), the process waits for the establishment of LE communication. If LE communication is not established and a timeout occurs, the distance measurement communication process is terminated.

[0084] If LE communication is established (S12: YES), the processing circuit 50 performs RSSI ranging via LE communication as the first ranging in S13. The processing circuit 50 acquires information on the terminal location of the mobile terminal 110 through RSSI ranging. Based on the terminal location information acquired in S13, the processing circuit 50 determines in S14 whether the mobile terminal 110 is present within a predetermined distance from the vehicle Hv. The predetermined distance used in S14 corresponds to the distance to the outer edge of the outer area Ae. If it is determined that the mobile terminal 110 is not present within the predetermined distance (S14: NO), the processing circuit 50 repeats the processes of S11 to S14 and waits until the mobile terminal 110 is within the predetermined distance.

[0085] If the mobile terminal 110 is present within the predetermined distance (S14: YES), the communication control unit 52 identifies the terminal area in which the mobile terminal 110 is located in S21 to S24 (see FIG. 11 ). As one example, the communication control unit 52 identifies the terminal area in which the mobile terminal 110 is located based on the result of RSSI ranging. As another example, the communication control unit 52 temporarily activates all anchors 30 and starts LE-CS ranging. The communication control unit 52 identifies the area in which the mobile terminal 110 is located by LE-CS ranging using all anchors 30.

[0086] Specifically, in S21, the communication control unit 52 determines whether or not the mobile terminal 110 is present in the driver's seat side area Aa (area A). If the mobile terminal 110 is not present in the driver's seat side area Aa (S21: NO), the communication control unit 52 determines whether or not the mobile terminal 110 is present in the passenger's seat side area Ac (area C) in S22. If the mobile terminal 110 is not present in the passenger's seat side area Ac (S22: NO), the communication control unit 52 determines whether or not the mobile terminal 110 is present in the rear area Ad (area D) in S23. If the mobile terminal 110 is not present in the rear area Ad (S23: NO), the communication control unit 52 determines whether or not the mobile terminal 110 is present in the forward area Ab (area B) in S24.

[0087] In S25 to S29, the communication control unit 52 determines an effective anchor 3E from among the multiple anchors 30 based on information about the terminal area identified by RSSI ranging or LE-CS ranging. In S25 to S29, the effective anchor 3E corresponding to the terminal area is determined based on the linking information stored in the information storage unit 51. Furthermore, in S30 to S34, the communication control unit 52 sets anchors 30 other than the selected effective anchor 3E as unnecessary anchors 3D, thereby restricting LE-CS ranging by the unnecessary anchors 3D. Once the communication control unit 52 has activated all anchors 30 for LE-CS ranging, it transmits a stop request to the anchors 30 that have been set as unnecessary anchors 3D, thereby terminating the LE-CS ranging.

[0088] Specifically, if the mobile terminal 110 is present in the driver's seat side area Aa (S21: YES), the communication control unit 52 determines an effective anchor 3E corresponding to the driver's seat side area Aa in S25. Furthermore, the communication control unit 52 determines all anchors other than the effective anchor 3E corresponding to the driver's seat side area Aa as unnecessary anchors 3D in S30, and stops transmission and reception of distance measurement signals by these unnecessary anchors 3D.

[0089] If the mobile terminal 110 is present in the passenger-side area Ac (S22: YES), the communication control unit 52 determines in S26 an effective anchor 3E corresponding to the passenger-side area Ac. Furthermore, in S31, the communication control unit 52 designates all anchors other than the effective anchor 3E corresponding to the passenger-side area Ac as unnecessary anchors 3D, and stops transmission and reception of distance measurement signals by these unnecessary anchors 3D.

[0090] If the mobile terminal 110 is present in the rear area Ad (S23: YES), the communication control unit 52 determines an effective anchor 3E corresponding to the rear area Ad in S27. Furthermore, the communication control unit 52 determines all anchors other than the effective anchor 3E corresponding to the rear area Ad as unnecessary anchors 3D in S32, and stops transmission and reception of distance measurement signals by these unnecessary anchors 3D.

[0091] If the mobile terminal 110 is present in the forward area Ab (S24: YES), the communication control unit 52 determines an effective anchor 3E corresponding to the forward area Ab in S28. Furthermore, the communication control unit 52 determines all anchors other than the effective anchor 3E corresponding to the forward area Ab as unnecessary anchors 3D in S33, and stops transmission and reception of distance measurement signals by these unnecessary anchors 3D.

[0092] If the mobile terminal 110 is not present in the forward area Ab (S24: NO), in other words, if the mobile terminal 110 is present in the outer area Ae, the communication control unit 52 determines an effective anchor 3E corresponding to the outer area Ae in S29. Furthermore, in S34, the communication control unit 52 designates all anchors other than the effective anchor 3E corresponding to the outer area Ae as unnecessary anchors 3D, and stops transmission and reception of distance measurement signals by these unnecessary anchors 3D.

[0093] In S35, the position identification unit 53 identifies the terminal position based on the ranging data of the valid anchor 3E. In S36, the processing circuit 50 determines whether to end ranging. As an example, the processing circuit 50 determines to end ranging when there is no longer a signal received from the mobile terminal 110 (S36: YES). In this case, the ranging communication process ends.

[0094] On the other hand, if the signal from the mobile terminal 110 continues to be received, the processing circuit 50 determines to continue ranging (S36: NO). In this case, the communication control unit 52 again executes S21 to S24 and identifies the terminal area in which the mobile terminal 110 is located based on the information on the terminal location identified in S35. Furthermore, when determining to continue ranging and again executing S21 to S24, the communication control unit 52 may determine whether the identified terminal location has moved from the previously identified terminal area. If the communication control unit 52 determines that the user has moved between different terminal areas, it temporarily activates all anchors 30. The communication control unit 52 determines the terminal area in which the user is located by LE-CS ranging using all anchors 30. Although movement between nearby terminal areas can be detected using only LE-CS ranging using the valid anchors 3E, temporarily activating all anchors 30 allows for more accurate detection of user movement across multiple terminal areas.

[0095] (Summary of First Embodiment) In the first embodiment described so far, ranging data is acquired by performing LE-CS ranging using an effective anchor 3E. On the other hand, LE-CS ranging of unnecessary anchors 3D, which are anchors 30 other than the effective anchor 3E, is restricted. As described above, by restricting the anchors 30 that perform LE-CS ranging, it is possible to suppress radio wave interference.

[0096] By limiting the number of anchors, radio wave interference can be suppressed, or in other words, communication occupancy can be reduced, thereby preventing deterioration in the responsiveness of the digital key system even when multiple mobile terminals 110 are present around the vehicle Hv. Furthermore, by minimizing radio wave transmission and reception time, responsiveness can be improved and dark current in the vehicle Hv can be reduced.

[0097] Additionally, in the first embodiment, the terminal area in which the mobile terminal 110 is located is identified based on a strength value related to the radio wave strength of the LE communication, i.e., RSSI. Then, based on information about the terminal area identified using RSSI, an effective anchor 3E is determined from among the multiple anchors 30. As a result, before the start of LE-CS ranging, the approximate location of the mobile terminal 110 can be identified by RSSI ranging. As a result, it becomes possible to set an unnecessary anchor 3D from the first LE-CS ranging and restrict communication by the unnecessary anchor 3D.

[0098] Furthermore, in the first embodiment, the terminal area in which the mobile terminal 110 is located is identified based on the ranging data. Then, based on information about the terminal area identified using the ranging data, an effective anchor 3E is determined from among the multiple anchors 30. In this way, by using the ranging data from the LE-CS ranging, the terminal area in which the mobile terminal 110 is located can be accurately determined. As a result, the effective anchor 3E and the unnecessary anchor 3D are appropriately set, and it becomes possible to restrict communication by the unnecessary anchor 3D while ensuring ranging accuracy.

[0099] Furthermore, in the first embodiment, linking information linking the terminal area with the valid anchor 3E is stored. Then, the valid anchor 3E corresponding to the terminal area can be determined based on the linking information. As described above, by determining the valid anchor 3E for each terminal area, the vehicle key system 100 can accurately determine the terminal location even if communication with the unnecessary anchor 3D is restricted.

[0100] In addition, in the first embodiment, if ranging communication continues even after the terminal position is identified, the effective anchor 3E is determined again based on the latest ranging data. As described above, if the effective anchor 3E is updated based on the latest ranging data, the communication control unit 52 can appropriately switch between the effective anchor 3E and the unnecessary anchor 3D even if the user carrying the mobile terminal 110 moves.

[0101] In the first embodiment, the process of restricting the operation of the unnecessary anchors 3D at least stops the transmission and reception of signals for LE-CS ranging by the unnecessary anchors 3D. In this way, by reducing the number of anchors 30 that perform ranging communication, it is possible to reduce the communication occupancy rate and, in turn, suppress radio wave interference.

[0102] In the first embodiment, the DK-ECU 10 corresponds to the "position determination device" and the "control device," the processors 21 and 41 correspond to the "processing unit," and the vehicle key system 100 corresponds to the "position determination system." Also, the driver's seat area Aa, the front area Ab, the passenger's seat area Ac, the rear area Ad, and the outer area Ae each correspond to the "terminal area."

[0103] Second Embodiment A second embodiment of the present disclosure shown in Figures 12 to 14 is a modification of the first embodiment. In the second embodiment, the number of anchors is controlled using the relative speed of the mobile terminal 110 with respect to the vehicle Hv. When the user carrying the mobile terminal 110 is within a predetermined distance from the vehicle Hv, the communication control unit 52 changes the number of effective anchors 3E depending on whether the mobile terminal 110 is moving at a certain speed.

[0104] Specifically, when the moving speed of the mobile terminal 110 is known (see FIG. 12 ), the communication control unit 52 determines the effective anchors 3E and unnecessary anchors 3D associated with each terminal area, as in the first embodiment (see FIG. 8 ). On the other hand, when the moving speed of the mobile terminal 110 is not known (see FIG. 13 ), in other words, when the user is not moving, the communication control unit 52 reduces the number of effective anchors 3E compared to when the moving speed is known. The communication control unit 52, for example, changes the outer anchor from the effective anchor 3E to the unnecessary anchor 3D.

[0105] The details of the ranging communication process according to the second embodiment will be described below based on Fig. 14, with reference to Figs. 2, 9, 12, and 13. In the ranging communication process of the second embodiment, the processes performed in S11 to S14 (see Fig. 10) and S21 to S36 are substantially the same as those in the first embodiment.

[0106] If the processing circuit 50 determines to continue the distance measurement in S36 of the distance measurement communication process, the communication control unit 52 calculates the moving speed of the mobile terminal 110 based on the distance measurement data from multiple anchors 30 (effective anchors 3E) in S237. The communication control unit 52 determines whether the calculated moving speed of the mobile terminal 110 is equal to or less than a threshold. The threshold is a value used to determine whether the mobile terminal 110 is moving, and is a value close to zero.

[0107] If the moving speed of the mobile terminal 110 exceeds the threshold (S237: NO), the communication control unit 52 executes the processes from S21 onwards again. The communication control unit 52 identifies the current terminal area based on the information on the terminal location identified in the previous S35, and determines the effective anchors 3E and unnecessary anchors 3D. Then, the location identification unit 53 updates the terminal location.

[0108] On the other hand, if the moving speed of the mobile terminal 110 is equal to or less than the threshold and it is estimated that the user is not moving (S237: YES), the communication control unit 52 determines in S238 a valid anchor 3E that corresponds to the time when the user is stopped. In this case, only the in-vehicle anchor is set as a valid anchor 3E. Furthermore, in S239, the communication control unit 52 designates all anchors other than the valid anchor 3E that corresponds to the time when the user is stopped as unnecessary anchors 3D. Then, in the next S35, the position identification unit 53 identifies the terminal position based on the ranging data of the valid anchor 3E determined in S238.

[0109] In S239, the communication control unit 52 stops all anchors 3E other than the effective anchor 3E corresponding to the time of stopping as unnecessary anchors 3D, and then, in S237, which is executed again, if it determines that the moving speed of the mobile terminal 110 exceeds the threshold (S237: NO), it resets the effective anchor 3E. As an example, the communication control unit 52 stores the setting of the effective anchor 3E before the moving speed becomes equal to or less than the threshold, and activates the stored effective anchor 3E when the moving speed again exceeds the threshold. As another example, the communication control unit 52 temporarily activates all anchors 30 when the moving speed again exceeds the threshold. The communication control unit 52 identifies the terminal area and determines the effective anchors 30 by LE-CS ranging using all anchors 30.

[0110] The second embodiment described so far also achieves the same effect as the first embodiment, and by limiting LE-CS ranging by unnecessary anchors 3D, it is possible to reduce communication occupancy rate and thereby suppress radio wave interference.

[0111] Additionally, in the second embodiment, the effective anchors 3E are determined based on the mobile terminal 110's moving speed in addition to the terminal area. Therefore, when the mobile terminal 110 is not moving, the communication control unit 52 can switch some of the effective anchors 3E (e.g., outer anchors) to additional unnecessary anchors 3D. In this way, the number of effective anchors 3E is reduced to a level that allows confirmation that the user is stationary. As described above, reducing the number of anchors performing LE communication can further reduce radio interference. Furthermore, when the user begins to move, the communication control unit 52 again increases the number of effective anchors 3E. Therefore, the vehicle key system 100 can accurately track the location of a user who has resumed moving.

[0112] 15 to 17 are another modified example of the first embodiment. In the third embodiment, the number of anchors is controlled using the direction of movement of the mobile terminal 110 relative to the vehicle Hv. When the user carrying the mobile terminal 110 is within a predetermined distance from the vehicle Hv, the communication control unit 52 changes the number of effective anchors 3E depending on whether the mobile terminal 110 is approaching the vehicle Hv.

[0113] Specifically, when the mobile terminal 110 is approaching the vehicle Hv (see FIG. 15 ), the communication control unit 52 determines valid anchors 3E and unnecessary anchors 3D associated with each terminal area, as in the first embodiment (see FIG. 8 ). On the other hand, when the mobile terminal 110 is moving away from the vehicle Hv (see FIG. 16 ), the communication control unit 52 reduces the number of valid anchors 3E compared to when the mobile terminal 110 is approaching the vehicle Hv. For example, the communication control unit 52 changes the in-vehicle anchor from a valid anchor 3E to an unnecessary anchor 3D.

[0114] The details of the ranging communication process according to the third embodiment will be described below based on Fig. 17, with reference to Figs. 2, 9, 15, and 16. In the ranging communication process of the third embodiment, the processes performed in S11 to S14 (see Fig. 10) and S21 to S36 are substantially the same as those in the first embodiment.

[0115] If the processing circuit 50 determines to continue distance measurement in S36 of the distance measurement communication process, the communication control unit 52 calculates the movement direction of the mobile terminal 110 in S337 based on the distance measurement data from multiple anchors 30 (effective anchors 3E). The communication control unit 52 determines whether the calculated movement direction of the mobile terminal 110 is a direction approaching the vehicle Hv (hereinafter referred to as the approaching direction) or a direction away from the vehicle Hv (hereinafter referred to as the leaving direction).

[0116] If the moving direction of the mobile terminal 110 is the approaching direction (S337: NO), the communication control unit 52 executes the processing from S21 onwards again. The communication control unit 52 identifies the current terminal area based on the information on the terminal location identified in the previous S35, and determines the effective anchor 3E and the unnecessary anchor 3D. The location identification unit 53 then updates the terminal location. Note that even if the moving speed of the mobile terminal 110 is essentially zero, the communication control unit 52 may consider that the mobile terminal 110 is moving in the approaching direction, and may execute the processing from S21 onwards again.

[0117] On the other hand, if the moving direction of the mobile terminal 110 is the leaving direction (S337: YES), the communication control unit 52 determines in S338 an effective anchor 3E that corresponds to the time when the user is leaving. In this case, only the outer anchors are set as effective anchors 3E. Furthermore, in S339, the communication control unit 52 designates all anchors other than the effective anchor 3E that corresponds to the time when the user is leaving as unnecessary anchors 3D. Then, in the next S35, the position specifying unit 53 specifies the terminal position based on the ranging data of the effective anchor 3E determined in S338.

[0118] In S339, the communication control unit 52 stops all valid anchors 3E other than the one corresponding to the user's departure as unnecessary anchors 3D, and then, in S337, which is executed again, if it determines that the mobile terminal 110 is moving in the approaching direction (S337: NO), it resets the valid anchor 3E. As an example, the communication control unit 52 stores the setting of the valid anchor 3E before the mobile terminal 110's movement direction became the departure direction, and activates the stored valid anchor 3E when the mobile terminal 110's movement direction becomes the approaching direction again. As another example, the communication control unit 52 temporarily activates all anchors 30 when the mobile terminal 110's movement direction becomes the approaching direction again. The communication control unit 52 identifies the terminal area and determines the valid anchors 30 by LE-CS ranging using all anchors 30.

[0119] The third embodiment described so far also achieves the same effects as the first and second embodiments, and by limiting LE-CS ranging by unnecessary anchors 3D, it is possible to reduce communication occupancy rates and thereby suppress radio wave interference.

[0120] Additionally, in the third embodiment, the effective anchors 3E are determined based on the direction of movement of the mobile terminal 110 in addition to the terminal area. Therefore, when the mobile terminal 110 is moving away from the vehicle Hv, the communication control unit 52 can switch some of the effective anchors 3E (e.g., in-vehicle anchors) to additional unnecessary anchors 3D. As described above, when the mobile terminal 110 is approaching the vehicle Hv, the number of effective anchors 3E can be increased, thereby improving the accuracy of determining the terminal position. On the other hand, when the mobile terminal 110 is moving away from the vehicle Hv, the number of effective anchors 3E can be reduced, thereby suppressing radio wave interference.

[0121] 18 to 22 are yet another modification of the first embodiment. In the vehicle key system 100 according to the fourth embodiment, instead of the restriction control that sets some of the anchors 30 as unnecessary anchors 3D, a restriction control that switches the execution mode of LE-CS ranging is performed. Details of the processing circuit configuration and ranging communication process of the fourth embodiment are described below.

[0122] [Configuration of Processing Circuit] The processing circuit 50 of the fourth embodiment is provided with functional units such as an information storage unit 51, a communication control unit 52, and a position identification unit 53, as in the first embodiment shown in FIG.

[0123] The information storage unit 51 stores information for setting a terminal area in which the mobile terminal 110 is located. The information storage unit 51 stores three thresholds Th1 to Th3 as information for setting the terminal area. The thresholds Th1 to Th3 are values ​​that are compared with the measured distance from the vehicle Hv to the mobile terminal 110. The threshold Th1 is a value greater than the threshold Th2. The threshold Th2 is a value greater than the threshold Th3.

[0124] A far area A1c, an intermediate area A1b, a nearby area A1a, and the like are set around the vehicle Hv. The far area A1c (see area C in FIG. 18 ) is a terminal area where the measured distance to the mobile terminal 110 is greater than threshold Th1. The intermediate area A1b (see area B in FIG. 18 ) is a terminal area where the measured distance to the mobile terminal 110 is equal to or less than threshold Th1 and greater than threshold Th2. The nearby area A1a (see area A in FIG. 18 ) is a terminal area where the measured distance to the mobile terminal 110 is equal to or less than threshold Th2. Furthermore, the terminal area facing the driver's door within the nearby area A1a is set as an unlocked area A1n. The unlocked area A1n is a terminal area where the measured distance to the mobile terminal 110 is equal to or less than threshold Th3.

[0125] The communication control unit 52 determines the execution mode of the LE-CS ranging to be performed by the anchor 30 based on information about the location of the mobile terminal 110. As described above, the anchor 30 can execute LE-CS ranging in modes 1 to 3 (see FIG. 6). Mode 1 LE-CS ranging is an execution mode in which RTT packets are transmitted and received to calculate the time-of-flight of a signal. Mode 2 LE-CS ranging is an execution mode in which CW signals are transmitted and received to calculate the phase of a signal. Mode 3 LE-CS ranging is an execution mode in which RTT packets are transmitted and received in addition to CW signals. Note that Mode 1 LE-CS ranging corresponds to "Mode 1," and Modes 2 and 3 LE-CS ranging correspond to "Mode 2." In "Mode 1," CW signals are not transmitted and received. In contrast, in "Mode 2," RTT packets may be transmitted and received.

[0126] The communication control unit 52 identifies the terminal area in which the mobile terminal 110 is located from among multiple terminal areas based on the ranging data obtained by RSSI ranging. In addition, if ranging communication continues after the location determination unit 53 determines the location of the mobile terminal 110, the communication control unit 52 again determines the terminal area based on the latest ranging data determined by the location determination unit 53. The communication control unit 52 switches the ranging method between RSSI ranging and LE-CS ranging based on information about the determined terminal area. Furthermore, when performing LE-CS ranging, the communication control unit 52 switches the execution mode of the LE-CS ranging performed by the anchor 30 from modes 1 to 3 based on information about the determined terminal area. As the mobile terminal 110 approaches the vehicle Hv, the communication control unit 52 switches the ranging method so as to improve the accuracy of the ranging information.

[0127] If the distance (measured distance) to the mobile terminal 110 exceeds the threshold Th1, the communication control unit 52 determines that the mobile terminal 110 is located in the far area A1c (area C) (see FIG. 19). If the mobile terminal 110 is located in the far area A1c, the communication control unit 52 performs RSSI ranging.

[0128] If the distance to the mobile terminal 110 is equal to or less than threshold Th1 and exceeds threshold Th2, the communication control unit 52 determines that the mobile terminal 110 is located in intermediate area A1b (area B) (see FIG. 20). If the mobile terminal 110 is located in intermediate area A1b, the communication control unit 52 determines the execution mode of LE-CS ranging to mode 1. This causes the anchor 30 to execute RTT ranging.

[0129] If the distance to the mobile terminal 110 is equal to or less than the threshold Th2, the communication control unit 52 determines that the mobile terminal 110 is present in the nearby area A1a (see FIG. 21). If the mobile terminal 110 is present in the nearby area A1a (see FIG. 18, area A), the communication control unit 52 determines the execution mode of the LE-CS ranging to be mode 2 or mode 3. This causes the anchor 30 to at least execute phase difference ranging.

[0130] Note that RSSI ranging by the gateway module 13 may be performed in parallel with the LE-CS ranging in modes 1 to 3. Additionally, when performing phase difference ranging, the communication control unit 52 may always perform RTT ranging together with phase difference ranging, or may perform RTT ranging together with phase difference ranging for confirmation at the timing of locking and unlocking the vehicle Hv. Specifically, the communication control unit 52 performs LE-CS ranging in mode 3 when the mobile terminal 110 is present in the unlocked area A1n, and performs LE-CS ranging in mode 2 when the mobile terminal 110 is present in the nearby area A1a outside the unlocked area A1n.

[0131] Here, the anchor 30 transmits and receives CW signals on multiple channels in LE-CS ranging in modes 2 and 3. The communication control unit 52 determines whether to transmit and receive CW signals on a specified number of reference channels or on a limited number of channels that is less than the specified number, based on information about the location of the mobile terminal 110. The number of reference channels is, for example, 72 of 80 channels set at 1 MHz intervals from 2400 MHz to 2480 MHz. The limited number of channels may be set at a number less than 72, for example, about half the number of reference channels. The limited channels may be set at 2 MHz intervals in the band from 2400 MHz to 2480 MHz, for example.

[0132] When the communication control unit 52 determines that the distance to the mobile terminal 110 is equal to or less than the threshold value Th3 and that the mobile terminal 110 is in the unlocked area A1n, the communication control unit 52 determines to transmit and receive the CW signal using the standard number of channels. On the other hand, when the mobile terminal 110 is in the nearby area A1a outside the unlocked area A1n, the communication control unit 52 determines to transmit and receive the CW signal using the limited number of channels.

[0133] The position specifying unit 53 specifies the position of the mobile terminal 110 based on the distance measurement data obtained by the distance measurement method determined by the communication control unit 52. As described above, if distance measurement communication continues after the position specifying unit 53 has determined the position of the mobile terminal 110, the communication control unit 52 again determines the distance measurement method and execution mode based on the latest distance measurement data determined by the position specifying unit 53. The position specifying unit 53 again specifies the position of the mobile terminal 110 based on the reset distance measurement method and execution mode.

[0134] [Details of Distance Measurement Communication Processing] Next, details of the distance measurement communication processing of the fourth embodiment will be described below based on FIG. 22 with reference to FIGS. 9, 10, and 18 to 21.

[0135] If the mobile terminal 110 is within the predetermined distance (FIG. 10 S14: YES), the communication control unit 52 determines in S421 whether or not there is location information (ranging data) previously acquired within a predetermined time. For example, if the anchor 30 and the mobile terminal 110 are temporarily in a sleep state when the user approaches the vehicle Hv from a distance, there is location information previously acquired. In this case, the communication control unit 52 determines that there is location information previously acquired.

[0136] If there is no previously acquired location information (S421: NO), the communication control unit 52 determines in S426 to perform RSSI ranging mainly by the gateway module 13. On the other hand, if there is previously acquired location information (S421: YES), the communication control unit 52 determines in S422 and S423 to perform LE-CS ranging and further determines the execution mode of LE-CS ranging.

[0137] In S422, the communication control unit 52 determines whether the distance measurement value is equal to or less than the threshold value Th2 and whether the mobile terminal 110 is present in the nearby area A1a (area A). Furthermore, in S422, the communication control unit 52 determines whether the distance measurement value is equal to or less than the threshold value Th1 and whether the mobile terminal 110 is present in the intermediate area A1b (area B). If the mobile terminal 110 is not present in the nearby area A1a or the intermediate area A1b but is present in the distant area A1c (NO in both S422 and S423), the communication control unit 52 determines in S426 to perform RSSI ranging mainly by the gateway module 13. Then, in S426, ranging data is acquired by performing RSSI ranging.

[0138] On the other hand, if the mobile terminal 110 is present in the intermediate area A1b (S423: YES), the communication control unit 52 determines in S425 that the anchor 30 will perform RTT ranging in mode 1. Also, if the mobile terminal 110 is present in the nearby area A1a (S422: YES), the communication control unit 52 determines in S424 that the anchor 30 will perform phase difference ranging in mode 2 or mode 3. In S424 and S425, ranging data is acquired by performing LE-CS ranging.

[0139] When performing phase difference ranging, the communication control unit 52 further determines in S427 whether the distance (measured distance value) to the mobile terminal 110 exceeds the threshold Th3. If the distance to the mobile terminal 110 exceeds the threshold Th3 (YES in S427) and the mobile terminal 110 is in the nearby area A1a outside the unlocked area A1n, the communication control unit 52 limits the frequency (number of channels) of the CW signal transmitted and received by the anchor 30 in S428. If the user is not in the nearby area A1a, the best ranging accuracy is not required, and therefore the frequency limiting in S428 reduces the communication occupancy rate. On the other hand, if the distance to the mobile terminal 110 is equal to or less than the threshold Th3 (NO in S427) and the mobile terminal 110 is in the unlocked area A1n, the communication control unit 52 determines in S429 to use all frequencies (reference number of channels).

[0140] In S430, the position identification unit 53 identifies the terminal position based on the distance measurement data acquired in S424 to S426. In S431, the processing circuit 50 determines whether to end distance measurement. If the processing circuit 50 no longer receives signals from the portable terminal 110, it determines to end distance measurement (S431: YES) and ends the distance measurement communication process. On the other hand, if the processing circuit 50 continues to receive signals from the portable terminal 110, it determines to continue distance measurement (S431: NO). In this case, the processes of S422 to S431 are executed again.

[0141] (Summary of the Fourth Embodiment) In the fourth embodiment described above, it is possible to switch between LE-CS ranging in Mode 1, which transmits and receives RTT packets, and LE-CS ranging in Modes 2 and 3, which transmit and receive CW signals, depending on the location of the mobile terminal 110. In this way, ranging communication in Mode 1, which uses RTT packets, which have a shorter transmission and reception time than CW signals, makes it possible to suppress radio wave interference. Furthermore, by suppressing radio wave interference by switching between ranging methods in this way, in other words, by reducing the communication occupancy rate, it is possible to suppress deterioration in the responsiveness of the digital key system even in situations where multiple mobile terminals 110 are present around the vehicle Hv.

[0142] Additionally, in the fourth embodiment, the terminal area in which the mobile terminal 110 is located is identified based on a strength value related to the radio wave strength of the LE communication, i.e., RSSI. Then, the communication control unit 52 determines the execution mode of the LE-CS ranging to be performed by the anchor 30 based on the information on the terminal area identified using RSSI. As a result, the approximate location of the mobile terminal 110 can be identified by RSSI ranging before the start of LE-CS ranging. As a result, it becomes possible to select an appropriate execution mode from the first LE-CS ranging and suppress radio wave interference.

[0143] Furthermore, in the fourth embodiment, the terminal area in which the mobile terminal 110 is located is identified based on the ranging data from the LE-CS ranging. Then, the communication control unit 52 determines the execution mode of the LE-CS ranging to be performed by the anchor 30 based on the information on the terminal area identified using the ranging data. In this way, by using the ranging data from the LE-CS ranging, the terminal area in which the mobile terminal 110 is located can be accurately determined. As a result, it is possible to appropriately select the execution mode of the LE-CS ranging, ensure the required ranging accuracy, and suppress radio wave interference.

[0144] Furthermore, in the fourth embodiment, the anchor 30 transmits and receives CW signals on multiple channels in LE-CS ranging in modes 2 and 3. The communication control unit 52 then determines whether to transmit and receive CW signals on a specified number of reference channels or on a limited number of channels that is less than the specified number, based on information about the location of the mobile terminal 110. In this way, by controlling to transmit and receive CW signals on a limited number of channels that is less than the specified number of reference channels, the communication occupancy rate can be reduced even in ranging communications in modes 2 and 3. As a result, radio wave interference can be further suppressed.

[0145] Additionally, in the fourth embodiment, when ranging communication is continued after the location specifying unit 53 specifies the location of the mobile terminal 110, the communication control unit 52 again determines the execution mode of the LE-CS ranging to be performed by the anchor 30 based on the latest ranging data. As described above, if the execution mode of the LE-CS ranging is updated based on the latest ranging data, the communication control unit 52 can appropriately switch the execution mode of the LE-CS ranging even if the user carrying the mobile terminal 110 moves. Note that in the fourth embodiment, the near area A1a, the intermediate area A1b, and the far area A1c each correspond to a "terminal area."

[0146] Fifth Embodiment A fifth embodiment of the present disclosure shown in FIG. 23 is a modification of the fourth embodiment. In the ranging communication process of the fifth embodiment, instead of limiting the number of channels for transmitting and receiving CW signals, a process for limiting the number of antennas for transmitting and receiving CW signals is performed. Details of the ranging communication process of the fifth embodiment will be described below based on FIG. 23 and with reference to FIGS. 3, 9, and 18. Note that the processes performed in S521 to S526, S530, and S531 are substantially the same as S421 to S426, S430, and S431 of the fourth embodiment (see FIG. 22).

[0147] When performing phase difference ranging in modes 2 and 3, the communication control unit 52 determines in S527 whether the portable terminal 110 is present within the unlocked area A1n based on a comparison between the distance (measured distance) to the portable terminal 110 and a threshold Th3. If the distance to the portable terminal 110 is equal to or less than the threshold Th3 (S527: NO) and the portable terminal 110 is present in the unlocked area A1n, the communication control unit 52 determines in S529 to transmit and receive CW signals using the specified number of reference antennas (two). In this case, the anchor 30 performs phase difference ranging using all of the antennas 31 and 32.

[0148] On the other hand, if the distance to the mobile terminal 110 exceeds the threshold Th3 (S527: YES) and the mobile terminal 110 is in the nearby area A1a outside the unlocked area A1n, the communication control unit 52 determines in S528 a limit on the number of antennas that transmit and receive CW signals. In this case, the anchor 30 transmits and receives CW signals using a limited number of antennas (one) that is fewer than the specified reference number of antennas, and performs phase difference ranging using only one anchor antenna.

[0149] In the fifth embodiment described above, ranging communication in mode 1 using RTT packets is executed at an appropriate timing instead of ranging communication in modes 2 and 3 using CW signals, thereby achieving the same effect as the fourth embodiment, reducing the communication occupancy rate and thereby suppressing radio wave interference.

[0150] Additionally, in the fifth embodiment, the anchor 30 has multiple antennas 31 and 32 for transmitting and receiving CW signals. The communication control unit 52 determines whether to transmit and receive CW signals using a specified number of standard antennas or a limited number of antennas that is smaller than the specified number, based on information about the location of the mobile terminal 110. As described above, by limiting the number of anchor antennas that transmit and receive CW signals, it is possible to further reduce the communication occupancy rate.

[0151] Sixth Embodiment The sixth embodiment of the present disclosure shown in FIG. 24 is another modified example of the fourth embodiment. In the ranging communication process of the sixth embodiment, instead of limiting the number of channels for transmitting and receiving CW signals, a process for limiting the number of combinations of communication paths between the anchor 30 and the mobile terminal 110 is performed. As described above, four communication paths (antenna paths) are available between the anchor 30 and the mobile terminal 110 by combining two anchor antennas 31 and 32 and two terminal antennas 121 and 122 (see FIG. 7). In other words, four communication paths constitute the specified reference number of combinations. The communication control unit 52 determines to transmit and receive CW signals using a limited number of combinations that is smaller than the reference number of combinations. As a result, the use of some of the four communication paths is discontinued.

[0152] Details of the ranging communication process of the sixth embodiment will be described below based on Fig. 24, with reference to Fig. 3, Fig. 9, and Fig. 18. Note that the processes performed in S621 to S626, S630, and S631 are substantially the same as S421 to S426, S430, and S431 of the fourth embodiment (see Fig. 22).

[0153] When performing phase difference ranging in modes 2 and 3, the communication control unit 52 determines in S627 whether the portable terminal 110 is present within the unlocked area A1n based on a comparison between the distance (measured distance) to the portable terminal 110 and a threshold Th3. If the distance to the portable terminal 110 is equal to or less than the threshold Th3 (S627: NO) and the portable terminal 110 is present in the unlocked area A1n, the communication control unit 52 determines in S629 to transmit and receive CW signals with the standard number of combinations. In this case, the anchor 30 and the portable terminal 110 use all four antenna paths to perform phase difference ranging.

[0154] On the other hand, if the distance to the mobile terminal 110 exceeds the threshold Th3 (S627: YES) and the mobile terminal 110 is in the nearby area A1a outside the unlocked area A1n, the communication control unit 52 determines in S628 to limit the number of antenna combinations. In this case, the anchor 30 and the mobile terminal 110 perform phase difference ranging using only some of the antenna paths.

[0155] The sixth embodiment described so far also has the same effects as the fourth embodiment, making it possible to reduce the communication occupation rate and, in turn, suppress radio wave interference.

[0156] Additionally, in the sixth embodiment, CW signals are transmitted and received between the anchor antennas 31 and 32 and the terminal antennas 121 and 122. A plurality of combinations of communication paths are set between the anchor antennas 31 and 32 and the terminal antennas 121 and 122. Then, based on information about the location of the mobile terminal 110, the communication control unit 52 determines whether to transmit and receive CW signals using a specified number of standard combinations or a limited number of combinations that is smaller than the specified number. As described above, by limiting the combinations of antennas that transmit and receive CW signals, in other words, the number of antenna paths, it is possible to further reduce the communication occupancy rate.

[0157] 25 is yet another modified example of the first embodiment. In the seventh embodiment, as a process for restricting the operation of the unnecessary anchor 3D, the communication control unit 52 restricts the frequency (number of channels) used by the unnecessary anchor 3D in phase difference ranging. The communication control unit 52 sets the number of channels (e.g., 72 channels) used by the unnecessary anchor 3D in phase difference ranging to be less than the number of channels used by the effective anchor 3E in phase difference ranging.

[0158] Details of the ranging communication process of the seventh embodiment will be described below based on Fig. 25 with reference to Fig. 3, Fig. 4, and Fig. 8. Note that the processes performed in S721 to S729, S735, and S736 are substantially the same as S21 to S29, S35, and S36 in the first embodiment (see Fig. 11).

[0159] If the mobile terminal 110 is present within a predetermined distance (S14: YES), the communication control unit 52 identifies the terminal area in which the mobile terminal 110 is located based on the results of RSSI ranging or the previous LE-CS ranging in S721 to S724. Furthermore, in S725 to S729, the communication control unit 52 determines an effective anchor 3E from among the multiple anchors 30 based on the information on the identified terminal area and the linking information stored in the information storage unit 51.

[0160] Specifically, if the mobile terminal 110 is located in the driver's seat area Aa (area A) (S721: YES), the communication control unit 52 determines the valid anchor 3E and unnecessary anchor 3D corresponding to the driver's seat area Aa in S725 and S730. Furthermore, in S730, the frequency used by the unnecessary anchor 3D corresponding to the driver's seat area Aa is limited.

[0161] If the mobile terminal 110 is located in the passenger-side area Ac (area C) (S722: YES), the communication control unit 52 determines the valid anchor 3E and the unnecessary anchor 3D corresponding to the passenger-side area Ac in S726 and S731. Furthermore, in S731, the frequency used by the unnecessary anchor 3D corresponding to the passenger-side area Ac is limited.

[0162] If the mobile terminal 110 is located in the rear area Ad (area D) (S723: YES), the communication control unit 52 determines the valid anchor 3E and unnecessary anchor 3D corresponding to the rear area Ad in S727 and S732. Furthermore, in S732, the frequency used by the unnecessary anchor 3D corresponding to the rear area Ad is limited.

[0163] If the mobile terminal 110 is located in the forward area Ab (area B) (S724: YES), the communication control unit 52 determines the valid anchor 3E and the unnecessary anchor 3D corresponding to the forward area Ab in S728 and S733. Furthermore, in S733, the frequency used by the unnecessary anchor 3D corresponding to the forward area Ab is limited.

[0164] If the mobile terminal 110 is not present in the forward area Ab (S724: NO), in other words, if the mobile terminal 110 is present in the outer area Ae, the communication control unit 52 determines the valid anchor 3E and the unnecessary anchor 3D corresponding to the outer area Ae in S729. Furthermore, in S734, the frequency used by the unnecessary anchor 3D corresponding to the outer area Ae is restricted.

[0165] The seventh embodiment described so far also achieves the same effect as the first embodiment, and by limiting LE-CS ranging by unnecessary anchors 3D, it is possible to reduce communication occupancy rate and thereby suppress radio wave interference.

[0166] Additionally, in the seventh embodiment, the frequency used by the unnecessary anchor 3D in LE-CS ranging is limited as a process for limiting the operation of the unnecessary anchor 3D. In this way, by reducing the frequency used by the unnecessary anchor 3D, it is possible to reduce the communication occupancy rate and, in turn, suppress radio wave interference.

[0167] (Details of LE-CS Ranging / Phase Difference Ranging) The communication controller 40 of the anchor 30 (see FIG. 3) is provided with a CS ranging unit as a functional unit for LE-CS ranging. The CS ranging unit may be provided in the communication controller of the gateway module 13. The CS ranging unit provided in the anchor 30 or the DK-ECU 10 acquires the reception phase for each frequency using, for example, a one-way method. The one-way method is a method in which, assuming that the initial phase of the CW signal for each frequency transmitted from the mobile terminal 110 is constant, the reception phase of the CW signal transmitted from the mobile terminal 110 is used as the basis for calculating the inter-frequency phase difference. The reception phase (in other words, the single-frequency phase difference) used as the basis for calculating the inter-frequency phase difference can also be acquired using a passive two-way method, an active two-way method, or the like. Details of the passive two-way method and the active two-way method will be described later.

[0168] Once the CS ranging unit has completed collection of the reception phase for each frequency, it calculates a phase change coefficient (α). The phase change coefficient is a parameter that indicates the degree to which the reception phase changes in response to changes in frequency. The phase change coefficient can also be called the phase change degree, phase shift amount, or correlation coefficient between phase and frequency.

[0169] The phase change coefficient is calculated based on the reception phase observed at two arbitrary frequencies, for example, a first frequency and a second frequency. If the difference frequency, which is the difference between the first frequency and the second frequency, is Δf, the inter-frequency phase difference, which is the difference between the reception phases observed at the first frequency and the second frequency, is Δφ, and the phase change coefficient is α, then the relationship is α = Δφ / Δf. The inter-frequency phase difference (Δφ) is the difference between the reception phases observed at two different frequencies. The inter-frequency phase difference can also be called a two-frequency phase difference or a quadratic phase difference. The inter-frequency phase difference corresponds to the amount of phase angle displacement due to a change in the frequency used.

[0170] The CS ranging unit calculates a regression line L indicating the relationship between frequency and reception phase based on the reception phase for each frequency, and uses the slope of the regression line L as the phase change coefficient. This is because the slope of the regression line L indicates the amount of change in reception phase relative to the amount of frequency change. The regression line L and its slope can be calculated using various methods, such as the least squares method. If the regression line is expressed as y = ax + b, the coefficient a of x corresponds to the slope of the regression line L. In other words, the CS ranging unit can calculate the coefficient (a) as the phase change coefficient (α). This configuration makes it possible to calculate a phase change coefficient based on the inter-frequency phase difference and differential frequency for each combination of multiple frequencies. Note that in the above equation, "x" is a variable corresponding to the frequency, and "y" is a variable corresponding to the reception phase. The regression line L can also be called an approximate line.

[0171] The CS ranging unit may provisionally calculate a regression line L1 based on all observed reception phase data, and then recalculate the regression line L after excluding values ​​(so-called outliers) whose distance from the provisionally calculated regression line L1 is equal to or greater than a predetermined value. The phase change coefficient used in distance calculation may be determined based on a regression line whose population is data excluding the outliers. This configuration can improve the accuracy of the inter-frequency phase difference, and ultimately the ranging accuracy.

[0172] The CS ranging unit may calculate the inter-frequency phase difference (Δφ), the differential frequency (Δf), and the phase change coefficient for each combination of frequencies for which the reception phase can be observed. The CS ranging unit may use the average or median of the phase difference change coefficients for each combination of frequencies as the phase difference change coefficient for use in distance calculation.

[0173] The CS ranging unit calculates the device distance (D) using a phase difference change coefficient generated based on received phase information at multiple frequencies. If the device distance is D, there is a relationship between the differential frequency Δf and the inter-frequency phase difference (Δφ): D∝C・Δφ / (2π・Δf)=C・α / 2π. The parameter "C" in the above equation indicates the propagation speed of radio waves (3×10^8 m / sec). The CS ranging unit calculates the device distance based on this relationship.

[0174] For example, the CS ranging unit calculates the device distance using Equation 1: D = k C α / 2π. The parameter k in Equation 1 is a design value and is set to 1.0 or 0.5. The value of k can be determined depending on whether the transmission and reception phase difference is calculated as a phase change coefficient for one way or a round trip. The CS ranging unit stores the calculated device distance data in a memory (such as memory 42) in the controller. In the present disclosure, the communication distance calculated by the communication module 33 or gateway module 13 (hereinafter referred to as the in-vehicle wireless module) in the CS ranging process is referred to as the first distance. The first distance can also be referred to as a CS ranging value.

[0175] Alternatively, the CS ranging unit may calculate a tentative device distance (d) using Δf and Δφ for each frequency combination, and use the average or median of the calculated values ​​as the device distance for the antenna in use. The tentative device distance (d) for a certain frequency combination can be calculated using d = k C Δφ / (2π Δf), etc.

[0176] Next, the passive two-way system and the active two-way system will be further outlined. The in-vehicle wireless module can acquire single-frequency phase differences for each frequency using the active two-way system or the passive two-way system and calculate the inter-frequency phase difference using the acquired single-frequency phase differences. The active two-way system is a system in which an initiator and a reflector transmit and receive CW signals to each other, each detecting the phase difference between the transmitted signal and the received signal, and determining the single-frequency phase difference using these two phase differences. The active two-way system includes a process in which the initiator and the reflector transmit and receive CW signals to each other, and a process in which the reflector transmits the observed received phase (θr) to the initiator.

[0177] The initiator is a device that starts communication, in other words, a device that requests a response. The reflector is a device that returns a response. As an example, the anchor 30 or the in-vehicle wireless module of the DK-ECU 10 corresponds to the initiator, and the mobile terminal 110 corresponds to the reflector. The correspondence between the initiator and the reflector may be reversed.

[0178] If the initial phase of the initiator is δi, the initial phase of the reflector is δr, the single-frequency phase difference that should be observed depending on the one-way distance between the initiator and the reflector is φ, and the target frequency is f, then these have the relationships θr = φ + δi - δr and θi = φ - δi + δr. Based on this relationship, the average value of θi and θr is the single-frequency phase difference (φ) in which the initial phase components of the initiator and the reflector are canceled out. The active two-way system corresponds to a system in which the average value of the reception phase at the initiator and the reception phase at the reflector is calculated as the single-frequency phase difference. Note that, since the phase difference due to one-way propagation is assumed here, the average value of θi and θr is taken as the single-frequency phase difference. As another aspect, if the phase difference due to round-trip propagation is assumed as the single-frequency phase difference, the single-frequency phase difference can be calculated as θi + θr.

[0179] The passive two-way system also involves an initiator and a reflector transmitting and receiving CW signals to and from each other. The difference between the passive two-way system and the active two-way system is that the reflector reflects the received phase of the CW signal transmitted from the initiator in the initial phase of the transmitted signal. For example, if the received phase at the reflector is θr, the reflector transmits a CW signal expressed as z(t) = A·exp{-i(ωt + θr + 2πn)}. A represents amplitude. ω is the angular frequency corresponding to the target frequency (f), and has the relationship ω = 2πf. n is a natural number corresponding to the interval between when the reflector receives the CW signal and when it transmits the CW signal. In this system, the received phase observed by the initiator does not include the reflector's initial phase component. The received phase observed by the initiator is the same value as when the CW signal is received after being reflected by a reflective object such as a wall. As a result, the initiator can calculate the single-frequency phase difference without acquiring the reception phase from the reflector. The passive two-way system has the advantage over the active two-way system that the reflector does not need to transmit a reception phase message. As described above, the single-frequency phase difference and, therefore, the inter-frequency phase difference can be calculated using various methods.

[0180] (Other Embodiments) Although multiple embodiments of the present disclosure have been described above, the present disclosure should not be construed as being limited to the above-described embodiments, and can be applied to various embodiments and combinations within the scope that does not deviate from the gist of the present disclosure.

[0181] In the above embodiment, the distance measurement process for determining the position of one mobile terminal 110 has been described. Meanwhile, the vehicle key system 100 can sequentially perform distance measurement processes with multiple mobile terminals 110, as shown in FIGS. 26 and 27 . Specifically, the communication control unit 52 starts communication with the i-th (first) mobile terminal 110 in S101. Furthermore, the communication control unit 52 transmits and receives a CW signal at one frequency in S102. For one frequency, the communication control unit 52 transmits and receives the CW signal by sequentially switching between multiple antenna paths (see the upper part of FIG. 27 ).

[0182] In S103, the communication control unit 52 determines whether communication on all channels (e.g., 72 channels) has been completed. If communication on all channels has not been completed (S103: NO), the communication control unit 52 increases the frequency by 1 MHz in S104 and performs communication using the CW signal again in S102 (see the middle part of FIG. 27).

[0183] On the other hand, if communication on all channels has been completed (S103: YES), the communication control unit 52 determines in S105 whether communication has been completed with all mobile terminals 110. If there are any mobile terminals 110 with which communication has not been completed (S105: NO), the communication control unit 52 performs processing to switch to communication with the (i+1)th mobile terminal 110 in S106, and starts communication with the next mobile terminal 110 in S101 (see the lower part of FIG. 27 ). On the other hand, if communication with all mobile terminals 110 has been completed (S105: YES), the communication control unit 52 ends the distance measurement processing.

[0184] In Modification 1 of the first embodiment, the method of setting the terminal areas differs from that of the first embodiment. In Modification 1, as shown in FIG. 28, a right front area A2a (area A-1), a right rear area A2b (area A-2), a left front area A2d (area C-1), and a left rear area A2e (area C-2) are set. Furthermore, as in the first embodiment, a forward area A2c (area B), a rear area A2f (area D), and an outer area A2g (area E) are set. In Modification 1, as well, as shown in FIG. 29, linking information linking each terminal area with a valid anchor 3E is stored in the information storage unit 51.

[0185] The number and arrangement of the anchors 30 mounted on the vehicle Hv may be changed as appropriate. For example, in Modification 2 of the above embodiment, as shown in Fig. 30, three anchors 30 are provided as outer anchors on the left, right, and rear of the vehicle Hv. In addition, two anchors 30 are provided as interior anchors, lined up front and rear.

[0186] The vehicle key system 100 of the above embodiment performs only LE communication with the mobile terminal 110. However, the vehicle key system 100 according to a third modification of the above embodiment can also perform ultra-wide band (UWB) communication with the mobile terminal 110 as data communication. In this third modification, the gateway module 13 of the DK-ECU 10 performs RSSI ranging via UWB communication. As in this third modification, information about the location of the mobile terminal 110 may be obtained by RSSI ranging via UWB communication.

[0187] In a configuration in which UWB ranging communication is performed between the vehicle key system 100 and the mobile terminal 110, as in the above-described third modification, a URSK (UWB Ranging Secret Key) is shared. The URSK is a key used in UWB ranging communication. The URSK can be used to create information that proves that the communication partner in the UWB ranging communication is a valid communication partner. After the security of the LE communication is ensured in the owner device registration process, the DK-ECU 10 or the mobile terminal 110 generates a URSK and shares it via the LE communication. The DK-ECU 10 stores the URSK in association with the device ID of the mobile terminal 110. By the DK-ECU 10 and the mobile terminal 110 sharing the URSK, the DK-ECU 10 can perform UWB ranging communication with the mobile terminal 110 as the communication partner. It is preferable that the DK-ECU 10 confirms that UWB ranging communication with the mobile terminal 110 is possible by performing UWB ranging using the generated URSK.

[0188] In addition, the start and end conditions of UWB ranging communication may be set in the same manner as for LE-CS ranging communication. When the start condition of UWB ranging communication is satisfied, the DK-ECU 10 transmits a request to start UWB ranging to the anchor 30. Furthermore, when the end condition of UWB ranging communication is satisfied, the DK-ECU 10 transmits a request to end UWB ranging to the anchor 30.

[0189] In the above embodiment, four antenna paths are set by combining two terminal antennas and two anchor antennas. The antenna configuration of the mobile terminal 110 and the anchor 30 may be changed as appropriate. For example, at least one of the terminal antenna and the anchor antenna may be one. Furthermore, three or more terminal antennas and anchor antennas may be provided.

[0190] A sniffer system is applied to the vehicle key system 100 according to Modification 4 of the above embodiment. In Modification 4, the DK-ECU 10 (gateway module 13) acquires identification information (terminal ID) for identifying the mobile terminal 110 during a process for establishing communication with the mobile terminal 110. The DK-ECU 10 provides the anchor 30 with the ID information and other information acquired through communication with the mobile terminal 110. The anchor 30 acquires the terminal ID from the DK-ECU 10 by eavesdropping on the communication between the DK-ECU 10 and the mobile terminal 110. This allows the anchor 30 to perform RTT ranging and phase difference ranging without directly communicating with the mobile terminal 110. This process may be particularly performed when the frequency of the CW signal is limited (see S428 in FIG. 22 ).

[0191] In Modification 5 of the first and seventh embodiments, the communication control unit 52 limits the number of anchor antennas 31, 32 that the unnecessary anchor 3D uses in LE-CS ranging as a process for limiting the operation of the unnecessary anchor 3D. Also, in Modification 6, the communication control unit 52 stops the activation of the unnecessary anchor 3D itself as a process for limiting the operation of the unnecessary anchor 3D. These Modifications 5 and 6 also limit the operation of the unnecessary anchor 3D, making it possible to reduce the communication occupancy rate and, in turn, suppress radio wave interference.

[0192] In the ranging communication process of the seventh modification of the fourth embodiment, the step of determining whether or not there is pre-acquired location information (see S421 in FIG. 22 ) is omitted. As in the seventh modification, the RSSI ranging may be always performed first.

[0193] In the vehicle key system 100 of the above embodiment, the DK-ECU 10 is configured as an independent electronic control unit. In contrast, in Modification 8 of the above embodiment, the digital key-related functions implemented in the DK-ECU 10 are integrated with another ECU configured to realize other functions. For example, the other ECU may be a central control unit (integrated ECU) equipped with a high-performance processor that plays a central role in the electronic platform of the vehicle hybrid vehicle by integrating and controlling multiple vehicle ECUs. In Modification 8, the central control unit corresponds to the "position determination device" and "controller," and the vehicle key system including the central control unit corresponds to the "position determination system."

[0194] In the above embodiment, each function provided by the processing circuitry 50 can be provided by software and hardware that executes the software, software alone, hardware alone, or a combination of these. Furthermore, when such functions are provided by electronic circuits as hardware, each function can also be provided by digital circuits including a large number of logic circuits, or analog circuits.

[0195] Each processor in the above embodiments is hardware for arithmetic processing coupled to a RAM. The processing unit includes at least one arithmetic core, such as a central processing unit (CPU) and a graphics processing unit (GPU). The processing unit including such a processor may further include a field-programmable gate array (FPGA), a neural network processing unit (NPU), and an IP core with other dedicated functions. The processing unit may be individually mounted on a printed circuit board, or may be mounted on an application-specific integrated circuit (ASIC), an FPGA, or the like.

[0196] In the above-described embodiments, the form of the storage medium (non-transitory tangible storage medium) that stores various programs (position determination programs) and the like may be changed as appropriate. Furthermore, the storage medium is not limited to being provided on a circuit board, but may be provided in the form of a memory card or the like, inserted into a slot, and electrically connected to a processing circuit. Furthermore, the storage medium may be an optical disk, hard disk drive, solid state drive, or the like that is used as a source from which programs are copied or distributed to a processing circuit or the like.

[0197] Vehicles equipped with the above-described onboard key system are not limited to general private passenger cars (Personally Owned Vehicles, POVs). Vehicles equipped with the onboard key system may also be rental cars, manned taxis, ride-sharing vehicles, freight vehicles, buses, etc. Furthermore, vehicles equipped with the onboard key system 100 may be right-hand drive vehicles or left-hand drive vehicles. The configuration of the terminal area may be changed as appropriate depending on the position of the steering wheel of the vehicle hybrid. Furthermore, the onboard key system is not limited to four-wheeled vehicles, and may be installed in various moving objects such as two-wheeled vehicles (motorcycles), ships, airplanes, railroad vehicles, and construction machinery.

[0198] The controller and methods described herein may be implemented by a special-purpose computer comprising a processor programmed to perform one or more functions embodied in a computer program. Alternatively, the apparatus and methods described herein may be implemented by special-purpose hardware logic circuitry. Alternatively, the apparatus and methods described herein may be implemented by one or more special-purpose computers comprising a processor executing a computer program in combination with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory storage medium.

[0199] (Disclosure of Technical Ideas) This specification discloses multiple technical ideas described in the following multiple clauses. Some clauses may be described in a multiple dependent form, with the subsequent clause alternatively referring to the preceding clause. Furthermore, some clauses may be described in a multiple dependent form, with the subsequent clause referring to another multiple dependent clause. These multiple dependent clauses define multiple technical ideas.

[0200] (Technical Idea 1) A position determination system comprising: a plurality of anchors (30) that perform ranging communication to measure the distance to a mobile terminal (110); and a control device (10) that controls the plurality of anchors, wherein the anchors perform channel sounding ranging via Bluetooth Low Energy communication to acquire ranging data related to phase difference or time of flight, a processing circuit (50) provided in at least one of the anchors or the control device including: a communication control unit (52) that determines a valid anchor from among the plurality of anchors based on information about the position of the mobile terminal and limits the channel sounding ranging of unnecessary anchors that are anchors other than the valid anchors, and a position determination unit (53) that determines the position of the mobile terminal based on the ranging data of the valid anchors. (Technical Idea 2) The position determination system according to Technical Idea 1, wherein the control device identifies a terminal area in which the mobile terminal is located based on an intensity value related to the radio wave intensity of the Bluetooth Low Energy communication, and the communication control unit determines the valid anchor from among the plurality of anchors based on information about the terminal area identified using the intensity value. (Technical Idea 3) The position determination system according to Technical Idea 1 or 2, wherein the communication control unit identifies a terminal area in which the mobile terminal is located based on the ranging data, and determines the effective anchor from among the multiple anchors based on information about the terminal area identified using the ranging data. (Technical Idea 4) The position determination system according to Technical Idea 2 or 3, wherein the processing circuit further includes an information storage unit (51) that stores linking information linking the terminal area with the effective anchor, and the communication control unit determines the effective anchor corresponding to the terminal area based on the linking information. (Technical Idea 5) The position determination system according to any one of Technical Ideas 2 to 4, wherein the communication control unit calculates a moving speed of the mobile terminal based on the ranging data from the multiple anchors, and determines the effective anchor based on the moving speed in addition to the terminal area.(Technical Idea 6) The position determination system according to any one of Technical Ideas 2 to 5, wherein the communication control unit calculates the moving direction of the mobile terminal based on the ranging data from the multiple anchors, and determines the effective anchor based on the moving direction in addition to the terminal area. (Technical Idea 7) The position determination system according to any one of Technical Ideas 1 to 6, wherein the communication control unit, when continuing the ranging communication after the location identification unit has identified the location of the mobile terminal, re-determines the effective anchor based on the latest ranging data. (Technical Idea 8) The position determination system according to any one of Technical Ideas 1 to 7, wherein the communication control unit, as the process of limiting the operation of the unnecessary anchor, at least stops the unnecessary anchor from transmitting and receiving signals for the channel sounding ranging. (Technical Idea 9) The position determination system according to any one of Technical Ideas 1 to 7, wherein the communication control unit, as the process of limiting the operation of the unnecessary anchor, limits the frequency used by the unnecessary anchor in the channel sounding ranging or limits the number of antennas (31, 32) used by the unnecessary anchor in the channel sounding ranging. (Technical Idea 10) A location determination program for determining the location of a mobile terminal (110) through ranging communication using a plurality of anchors, the location determination program causing at least one processing unit (21, 41) to execute processes including: determining a valid anchor from among the plurality of anchors based on information relating to the location of the mobile terminal (S21 to S24, S721 to S724); performing channel sounding ranging through Bluetooth Low Energy communication using the valid anchor and acquiring ranging data related to phase difference or time of flight (S25 to S29, S725 to S729); restricting the channel sounding ranging of unnecessary anchors that become anchors other than the valid anchor (S30 to S34, S730 to S734); and identifying the location of the mobile terminal based on the ranging data of the valid anchor (S35, S735).

[0201] (Technical Idea 12) A location determination system comprising a plurality of anchors (30) that perform ranging communication to measure the distance to a mobile terminal (110), and a control device (10) that controls the plurality of anchors, wherein the anchors include at least a first mode in which they transmit and receive RTT packets to calculate the time of flight of a signal, and a second mode in which they transmit and receive CW signals to calculate the phase of a signal, in an execution mode of channel sounding ranging using Bluetooth Low Energy communication, and a processing circuit (50) provided in at least one of the anchors or the control device includes: a communication control unit (52) that determines the execution mode to be executed by the anchor from the first mode and the second mode based on information regarding the position of the mobile terminal, and a location determination unit (53) that determines the position of the mobile terminal based on ranging data acquired by the execution mode determined by the communication control unit. (Technical Idea 13) The location determination system according to Technical Idea 12, wherein the control device identifies a terminal area in which the portable terminal is located based on a strength value related to radio wave strength of the Bluetooth Low Energy communication, and the communication control unit determines the execution mode to be executed by the anchor from the first mode and the second mode based on information about the terminal area identified using the strength value. (Technical Idea 14) The location determination system according to Technical Idea 12 or 13, wherein the communication control unit identifies a terminal area in which the portable terminal is located based on the ranging data, and determines the execution mode to be executed by the anchor from the first mode and the second mode based on information about the terminal area identified using the ranging data. (Technical Idea 15) The location determination system according to any one of Technical Ideas 12 to 14, wherein the anchor transmits and receives the CW signal on a plurality of channels in the second mode, and the communication control unit determines, based on information about the location of the portable terminal, whether to transmit and receive the CW signal on a specified reference channel number or on a limited channel number that is less than the specified number.(Technical Idea 16) A location determination system according to any one of Technical Ideas 12 to 15, wherein the anchor has a plurality of antennas (31, 32) for transmitting and receiving the CW signal, and the communication control unit determines, based on information relating to the location of the mobile terminal, whether to transmit and receive the CW signal using a specified reference number of antennas, or using a limited number of antennas that is less than the specified number. (Technical Idea 17) A location determination system according to Technical Idea 16, wherein the antenna, an anchor antenna, transmits and receives the CW signal between at least one terminal antenna (121, 122) provided on the mobile terminal, and the communication control unit determines, based on information relating to the location of the mobile terminal, whether to transmit and receive the CW signal using a specified reference number of combinations of communication paths between the anchor antenna and the terminal antenna, or using a limited number of combinations that is less than the specified number. (Technical Idea 18) A position determination system according to any one of Technical Ideas 12 to 17, wherein the communication control unit, when continuing the ranging communication after the location identification unit has identified the location of the mobile terminal, re-determines the execution mode to be executed by the anchor based on the latest ranging data. (Technical Idea 19) A location determination program for determining the location of a mobile terminal (110) through ranging communication by a plurality of anchors (30), the location determination program causing at least one processing unit (21, 41) to execute processes including: determining, based on information regarding the location of the mobile terminal, an execution mode of channel sounding ranging by Bluetooth Low Energy communication to be executed by the anchor from a first mode of transmitting and receiving an RTT packet for calculating the time of flight of a signal, and a second mode of transmitting and receiving a CW signal for calculating the phase of the signal (S422, S423, S522, S523, S622, S623); acquiring ranging data by executing the channel sounding ranging in the determined execution mode (S424, S425, S524, S525, S624, S625); and identifying the location of the mobile terminal based on the acquired ranging data (S430, S530, S630).

Claims

1. A location determination system comprising a plurality of anchors (30) that perform ranging communication to measure the distance to a mobile terminal (110), and a control device (10) that controls the plurality of anchors, wherein the anchors perform channel sounding ranging via Bluetooth Low Energy communication and acquire ranging data related to phase difference or time of flight, and a processing circuit (50) provided in at least one of the anchors or the control device comprises: a communication control unit (52) that determines a valid anchor from among the plurality of anchors based on information regarding the position of the mobile terminal, and limits the channel sounding ranging of unnecessary anchors that are anchors other than the valid anchors, and a location determination unit (53) that determines the position of the mobile terminal based on the ranging data of the valid anchors.

2. The position determination system of claim 1, wherein the control device identifies a terminal area in which the mobile terminal is located based on a strength value related to the radio wave strength of the Bluetooth Low Energy communication, and the communication control unit determines the valid anchor from among the multiple anchors based on information about the terminal area identified using the strength value.

3. The position determination system of claim 1, wherein the communication control unit identifies a terminal area in which the mobile terminal is located based on the ranging data, and determines the valid anchor from among the multiple anchors based on information about the terminal area identified using the ranging data.

4. The position determination system of claim 2, wherein the processing circuit further includes an information memory unit (51) for storing linking information linking the terminal area with the valid anchor, and the communication control unit determines the valid anchor corresponding to the terminal area based on the linking information.

5. The position determination system of claim 2, wherein the communication control unit calculates the moving speed of the mobile terminal based on the ranging data from multiple anchors, and determines the valid anchors based on the moving speed in addition to the terminal area.

6. The position determination system of claim 2, wherein the communication control unit calculates the moving direction of the mobile terminal based on the ranging data from multiple anchors, and determines the valid anchors based on the moving direction in addition to the terminal area.

7. A position determination system as described in claim 1, wherein the communication control unit, when continuing the ranging communication after the position determination unit has determined the position of the mobile terminal, determines again the valid anchors based on the latest ranging data.

8. A position determination system as described in claim 1, wherein the communication control unit at least stops the transmission and reception of signals for the channel sounding distance measurement by the unnecessary anchor as a process for restricting the operation of the unnecessary anchor.

9. The position determination system of claim 1, wherein the communication control unit, as a process for restricting the operation of the unnecessary anchor, restricts the frequency used by the unnecessary anchor in the channel sounding ranging, or restricts the number of antennas (31, 32) used by the unnecessary anchor in the channel sounding ranging.

10. A position determination device that controls multiple anchors and causes the anchors to perform channel sounding ranging using Bluetooth Low Energy communication as ranging communication to measure the distance to a mobile terminal (110), comprising: a communication control unit (52) that determines a valid anchor from among the multiple anchors based on information regarding the position of the mobile terminal, and limits the channel sounding ranging of unnecessary anchors other than the valid anchor; and a position determination unit (53) that determines the position of the mobile terminal based on ranging data related to phase difference or time of flight obtained at the valid anchor.

11. A location determination method for determining the location of a mobile terminal (110) through ranging communication with a plurality of anchors, the location determination method including the steps of: determining a valid anchor from among the plurality of anchors based on information regarding the location of the mobile terminal (S21-S24, S721-S724); performing channel sounding ranging through Bluetooth Low Energy communication using the valid anchor and acquiring ranging data related to phase difference or time of flight (S25-S29, S725-S729); restricting the channel sounding ranging of unnecessary anchors that are anchors other than the valid anchors (S30-S34, S730-S734); and identifying the location of the mobile terminal based on the ranging data of the valid anchors (S35, S735), in processing performed by at least one processing unit (21, 41).

12. A location determination system comprising a plurality of anchors (30) that perform ranging communication to measure the distance to a mobile terminal (110), and a control device (10) that controls the plurality of anchors, wherein the anchors have execution modes for channel sounding ranging using Bluetooth Low Energy communication, including at least a first mode for transmitting and receiving an RTT packet for calculating the flight time of a signal, and a second mode for transmitting and receiving a CW signal for calculating the phase of a signal, and a processing circuit (50) provided in at least one of the anchors or the control device, comprising: a communication control unit (52) that determines the execution mode to be executed by the anchor from the first mode or the second mode based on information regarding the position of the mobile terminal, and a location determination unit (53) that determines the position of the mobile terminal based on ranging data obtained by the execution mode determined by the communication control unit.

13. The position determination system of claim 12, wherein the control device identifies a terminal area in which the mobile terminal is located based on a strength value related to the radio wave strength of the Bluetooth Low Energy communication, and the communication control unit determines the execution mode to be executed by the anchor from the first mode and the second mode based on information about the terminal area identified using the strength value.

14. The position determination system of claim 12, wherein the communication control unit identifies a terminal area in which the mobile terminal is located based on the ranging data, and determines the execution mode to be executed by the anchor from the first mode and the second mode based on information about the terminal area identified using the ranging data.

15. The position determination system of claim 12, wherein the anchor transmits and receives the CW signal on a plurality of channels in the second mode, and the communication control unit determines, based on information regarding the location of the mobile terminal, whether to transmit and receive the CW signal on a specified reference number of channels or to transmit and receive the CW signal on a limited number of channels that is less than the specified number.

16. A location determination system as described in claim 12, wherein the anchor has a plurality of antennas (31, 32) for transmitting and receiving the CW signal, and the communication control unit determines, based on information regarding the location of the mobile terminal, whether to transmit and receive the CW signal using a specified number of reference antennas or to transmit and receive the CW signal using a limited number of antennas that is less than the specified number.

17. A position determination system as described in claim 16, wherein the antenna, an anchor antenna, transmits and receives the CW signal between at least one terminal antenna (121, 122) provided on the mobile terminal, and the communication control unit determines, based on information regarding the location of the mobile terminal, whether to transmit and receive the CW signal with a specified standard number of combinations of communication paths between the anchor antenna and the terminal antenna, or to transmit and receive the CW signal with a limited number of combinations that is less than the specified number.

18. A position determination system as described in claim 12, wherein the communication control unit, when continuing the ranging communication after the location determination unit has determined the location of the mobile terminal, again determines the execution mode to be executed by the anchor based on the latest ranging data.

19. A location determination device that controls a plurality of anchors (30) and causes the anchors to perform channel sounding ranging using Bluetooth Low Energy communication as ranging communication for measuring the distance to a mobile terminal (110), comprising: a communication control unit (52) that determines an execution mode to be executed by the anchor from among a first mode for transmitting and receiving an RTT packet for calculating the flight time of a signal and a second mode for transmitting and receiving a CW signal for calculating the phase of a signal, based on information regarding the position of the mobile terminal; and a location determination unit (53) that determines the position of the mobile terminal based on ranging data acquired by the execution mode determined by the communication control unit.

20. A location determination method for determining the location of a mobile terminal (110) through ranging communication by a plurality of anchors (30), comprising the steps of: determining an execution mode of channel sounding ranging by Bluetooth Low Energy communication to be executed by the anchor from a first mode of transmitting and receiving an RTT packet for calculating the time of flight of a signal and a second mode of transmitting and receiving a CW signal for calculating the phase of a signal based on information regarding the location of the mobile terminal (S422, S423, S522, S523, S622, S623); acquiring ranging data by executing the channel sounding ranging in the determined execution mode (S424, S425, S524, S525, S624, S625); and identifying the location of the mobile terminal based on the acquired ranging data (S430, S530, S630), in a process performed by at least one processing unit (21, 41).

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