Device, distance measuring system, and distance measuring method

Abstract

To provide a distance measuring system independent of infrastructure facilities.SOLUTION: (1a) performs two way ranging with other devices (1a) by communication, and autonomously passes a token which is an activation right of the two way ranging to the other devices.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a device, a ranging system, and a ranging method. [Background technology]

[0002] In recent years, ranging methods using ultra-wideband impulse radio (IR-UWB) have been attracting attention. IR-UWB is a communication technology that uses short time pulses on the order of nanoseconds, which provides high time resolution and enables highly accurate ranging (positioning) on ​​the order of centimeters. Ranging methods using IR-UWB include ToA (Time of Arrival) and RToF (Round Trip of Flight) (or ToF).

[0003] RToF is a method in which an anchor device is placed in infrastructure facilities in advance and distances between devices are measured based on the round-trip time of radio waves between the anchor device and tag devices. In RToF, access control based on global scheduling is typically performed on the infrastructure facility (host device) side to avoid contention in ranging communications between multiple tag devices. Such a configuration is disclosed, for example, in Patent Documents 1 and 2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special table number 2022-539782 [Patent Document 2] International Publication No. 2022 / 264509 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional distance measurement methods require access control via infrastructure, making it difficult to apply them in situations where infrastructure is unavailable (such as manufacturing or construction sites) or where infrastructure is not functioning (such as fire sites).

[0006] Furthermore, conventional distance measurement methods require line-of-sight communication to ensure there are no radio wave obstacles between the infrastructure and the tag device, making it difficult to apply these distance measurement methods in situations where line-of-sight communication is expected due to obstacles, such as fire scenes.

[0007] One aspect of the present invention has been made in consideration of the above-mentioned problems, and has as its object to realize a ranging system that does not depend on infrastructure facilities. [Means for solving the problem]

[0008] In order to solve the above problem, a device according to aspect 1 of the present invention is a device that performs two-way ranging with another device via communication, and autonomously hands over a token that is the right to initiate the two-way ranging to the other device.

[0009] The device according to the second aspect of the present invention may be configured in the first aspect to autonomously hand over the token to the other device that has performed the two-way ranging.

[0010] In a device according to aspect 3 of the present invention, in aspect 2 above, the two-way ranging is DS-TWR, and when the device is a responder and receives an end message of the DS-TWR addressed to the device from the other device which is an initiator, the device may transition from a responder to an initiator.

[0011] In a device according to aspect 4 of the present invention, in aspect 2 or 3 above, the two-way ranging is DS-TWR, and when the device is an initiator and sends an end message of the DS-TWR to the other device which is a responder, and then receives a start message of the DS-TWR from the other device, the device may transition from an initiator to a responder.

[0012] A device according to aspect 5 of the present invention may, in aspects 1 to 4 above, autonomously generate the token if the device is a responder and has not received a two-way ranging start message from the other device for a predetermined period of time.

[0013] A device according to a sixth aspect of the present invention may be configured such that, in any of the first to fifth aspects described above, when the device is an initiator and receives a frame other than the response message from another device, the device autonomously discards the token.

[0014] In order to solve the above problem, a ranging system according to aspect 7 of the present invention is a ranging system including a plurality of devices that perform two-way ranging between devices through communication, wherein the plurality of devices include a first device that is an initiator and a second device that is a responder, and the first device autonomously hands over a token that is the right to initiate the two-way ranging to the second device.

[0015] In order to solve the above problem, a ranging method according to aspect 8 of the present invention is a ranging method in which multiple devices perform two-way ranging through communication, wherein the multiple devices include a first device that is an initiator and a second device that is a responder, and the method includes a ranging step in which the first device and the second device perform two-way ranging, and a handover step in which the first device autonomously hands over a token that is the right to initiate the two-way ranging to the second device. [Effects of the Invention]

[0016] According to one aspect of the present invention, a distance measurement system that does not depend on infrastructure facilities can be realized. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram showing an example of the configuration of a distance measuring system according to a first embodiment. [Figure 2] FIG. 1 is a schematic diagram illustrating a DS-TWR. [Figure 3] FIG. 10 is a schematic diagram illustrating the handover of a token in the distance measurement system. [Figure 4] FIG. 2 is a schematic diagram showing a state in which an obstacle occurs in the distance measuring system. [Figure 5] FIG. 10 is a schematic diagram showing a state in which a token is generated after an obstacle appears in the distance measurement system. [Figure 6] FIG. 6 is a schematic diagram showing a state in which the obstacle is removed from the state of FIG. 5 in the distance measuring system. [Figure 7] 4 is a flowchart showing the flow of processing executed by the device according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] [Embodiment 1] (Outline of distance measurement system) FIG. 1 is a block diagram showing an example of the configuration of a ranging system 100. As shown in FIG. 1, the ranging system 100 includes multiple devices 1 and an upper server 2. The multiple devices 1 communicate wirelessly with each other. The multiple devices 1 may be mobile or immobile media. The multiple devices 1 also communicate wirelessly with the upper server 2. In the example shown in FIG. 1, the main configuration of device 1a is shown as a representative of the multiple devices 1, but the other devices 1A (device 1b, device 1c, etc.) also have the same configuration as device 1a. When there is no need to distinguish between device 1a and the other devices 1A, they will simply be referred to as device 1.

[0019] The device 1a includes a first communication unit 10, a second communication unit 20, a storage unit 30, and a control unit 40. The device 1a performs two-way ranging with another device 1A through communication. Examples of two-way ranging include SS-TWR (Single-Side Two-Way Ranging) and DS-TWR (Double-Side Two-Way Ranging). In this embodiment, an example will be described in which the device 1a performs DS-TWR with the other device 1A. Note that the device 1a may also perform SS-TWR with the other device 1A.

[0020] The first communication unit 10 is a functional unit that enables the device 1a to communicate with the upper server 2. The second communication unit 20 is a functional unit that enables the device 1a to communicate with another device 1A. The first communication unit 10 and the second communication unit communicate using different communication methods. The first communication unit communicates with the upper server 2 using, for example, WiFi (registered trademark). The second communication unit communicates with the other device 1A using, for example, IR-UWB.

[0021] The storage unit 30 stores various data used by the device 1a. For example, the storage unit 30 stores a neighbor list, which is a list of other devices 1A (neighboring devices) that can perform ranging communication with the device 1a. The neighbor list includes IDs or MAC addresses of the neighboring devices. The neighbor list is registered, for example, by receiving a broadcast from the other device 1A before DS-TWR is executed. The storage unit 30 also stores the number of times two-way ranging has been performed (number of pairings) for each other device 1A.

[0022] The control unit 40 includes a communication control unit 41 and a calculation unit 42. The communication control unit 41 controls communication between the first communication unit 10 and the second communication unit 20. The calculation unit 42 calculates the distance between the devices based on DS-TWR. The communication control unit 41 controls the second communication unit 20 to execute DS-TWR and the like. The communication control unit 41 controls the first communication unit 10 to transmit the distance between the devices calculated by the calculation unit 42 to the upper server 2.

[0023] In this embodiment, the device 1a autonomously hands over a token, which is the right to start DS-TWR, to another device 1A. In other words, the device 1a hands over a token as an initiator that starts DS-TWR to another device 1A without instructions from the upper server 2 (upper system). This enables multiple access control without performing global scheduling.

[0024] Furthermore, in this embodiment, the device 1a autonomously hands over the token to the other device 1A that performed the DS-TWR. This allows the token to be autonomously handed over to the other device 1A without increasing the number of sequences in the DS-TWR. An example of the operation of the device 1a that hands over the token in this way will be described below. Note that the device 1a may hand over the token to a device (e.g., device 1c) other than the other device 1A (e.g., device 1b) that performed the two-way ranging.

[0025] (DS-TWR) Before explaining the token handover described above, we will first briefly explain an example of a typical DS-TWR operation. Figure 2 is a schematic diagram explaining DS-TWR. In Figure 2, one device performing DS-TWR is called a first device 1-1 (initiator), and the other device is called a second device 1-2 (responder).

[0026] 2, first, the first device 1-1 transmits a DS-TWR start message (Poll) to the second device 1-2, thereby starting the DS-TWR.

[0027] Next, when the second device 1-2 receives the start message addressed to itself, it transmits a response message (Response) to the first device 1-1. The second device 1-2 also measures the time (responder offset time Db) from when it receives the start message to when it transmits the response message.

[0028] Next, upon receiving the response message addressed to itself, the first device 1-1 transmits a DS-TWR end message (Final) to the second device 1-2. The first device 1-1 also measures the time from transmitting the start message to receiving the response message (initiator round time Ra) and the time from receiving the response message to transmitting the end message (initiator offset time Da). The first device 1-1 transmits the initiator round time Ra and the initiator offset time Da to the second device 1-2 along with the end message.

[0029] Next, when the second device 1-2 receives the end message addressed to itself, it measures the time (responder round time Rb) from when it sends the response message to when it receives the end message.The second device 1-2 then calculates the propagation time ToF of the message based on the following equation 1, and further calculates the inter-device distance by multiplying ToF by the speed of light.This completes DS-TWR.

number

[0030] In the initial state, the first device 1-1 is the initiator, and the second device 1-2 and the third device 1-3 are responders. That is, in the initial state, the first device 1-1 has a token that is the right to start two-way ranging, while the second device 1-2 and the third device 1-3 do not have the token.

[0031] 3, the first device 1-1, which is the initiator, sends a start message to the second device 1-2, which is registered as an adjacent device, and starts a DS-TWR (referred to as a first DS-TWR) between the first device 1-1 and the second device 1-2. When the second device 1-2 receives an end message addressed to itself in the first DS-TWR, it recognizes the end of the first DS-TWR and transitions from a responder to an initiator.

[0032] The second device 1-2, which has transitioned to the initiator, sends a start message to the third device 1-3, which is registered as an adjacent device, and initiates a DS-TWR (referred to as a second DS-TWR) between the second device 1-2 and the third device 1-3. Here, when the first device 1-1 receives the second DS-TWR start message from the second device 1-2, it recognizes the end of the first DS-TWR and transitions from initiator to responder. Note that the start message received from the second device 1-2 is not a start message addressed to itself. Therefore, the first device 1-1 transitions to a mode in which it waits for a start message addressed to itself.

[0033] Therefore, at the end of the first DS-TWR, the first device 1-1 autonomously transitions from an initiator to a responder, and the second device 1-2 autonomously transitions from a responder to an initiator. That is, at the end of the first DS-TWR, the first device 1-1 autonomously hands over the token, which is the right to start two-way ranging, to the second device 1-2. Similarly, at the end of the second DS-TWR, the second device 1-2 autonomously hands over the token, which is the right to start two-way ranging, to the third device 1-3. In this way, the multiple devices 1 in the ranging system 100 according to this embodiment hand over the token to other devices in a chain.

[0034] As described above, the ranging system 100 of this embodiment enables multiple devices 1 to measure distances from each other and can realize distributed multiple access control that can avoid contention in ranging communications without receiving instructions from an upper server 2.

[0035] (Token generation) Next, a case will be described in which an obstacle appears from the initial state and multiple devices 1 are divided into a first region R1 and a second region R2 by the obstacle (i.e., a case in which devices in the first region R1 and devices in the second region R2 cannot communicate with each other). FIG. 4 is a schematic diagram showing a state in which an obstacle has appeared in the ranging system 100. FIG. 5 is a schematic diagram showing a state in which a token has been generated in the ranging system 100 after an obstacle has appeared. In FIGS. 4 and 5, the two devices in the first region R1 are referred to as a first device 1-1 and a third device 1-3, respectively, and the two devices in the second region R2 are referred to as a second device 1-2 and a fourth device 1-4, respectively.

[0036] When an obstacle occurs, the first device 1-1 is the initiator, and the second device 1-2, the third device 1-3, and the fourth device 1-4 are responders. That is, when an obstacle occurs, the first device 1-1 has a token that is the right to start two-way ranging, while the second device 1-2, the third device 1-3, and the fourth device 1-4 do not have the token.

[0037] As shown in FIG. 4, the first device 1-1, which is the initiator, sends a start message to the second device 1-2, which is registered as a neighboring device. However, due to an obstacle, the start message does not reach the second device 1-2. Therefore, DS-TWR is not initiated between the first device 1-1 and the second device 1-2. If the first device 1-1 does not receive a response message from the second device 1-2 within a predetermined waiting time (initiator-response waiting time), it deletes the second device 1-2 from its neighbor list. The first device 1-1 then performs DS-TWR with the third device 1-3, which is a neighboring device in the first region R1. In this way, when an obstacle occurs, DS-TWR is not performed between the two regions separated by the obstacle, and ranging communication is performed only in the first region R1 where the token exists.

[0038] Therefore, in this embodiment, if device 1a is a responder and does not receive a start message for any destination from the initiator for a predetermined period of time, it autonomously generates a token. Specifically, since devices in an area where no initiator exists do not receive a start message for any destination from the initiator for a predetermined period of time (responder-poll waiting time), one of the devices in that area (the device with the smallest set timeout value) autonomously generates a token.

[0039] 5, the second device 1-2 generates a token and transitions from a responder to an initiator. Then, the second device 1-2 performs DS-TWR with the fourth device 1-4, which is an adjacent device in the second region R2.

[0040] As described above, in the ranging system 100 according to this embodiment, even if multiple devices 1 are separated by an obstacle, devices in an area where no initiator is present autonomously generate tokens. Therefore, multiple devices 1 in two areas separated by the obstacle can appropriately perform ranging communication.

[0041] (Token Revocation) Next, a case will be described in which the obstacle is removed from the state of Fig. 5 and the first device 1-1, which is the initiator, and the second device 1-2, which is also the initiator, join together. Fig. 6 is a schematic diagram showing a state in which the obstacle is removed from the state of Fig. 5 in the ranging system 100.

[0042] When the obstacle is removed, the first device 1-1 and the second device 1-2 are initiators, and the third device 1-3 and the fourth device 1-4 are responders. In other words, since both the first device 1-1 and the second device 1-2 have the token, there is a possibility that a contention in ranging communication will occur as shown in FIG.

[0043] Therefore, in this embodiment, when device 1a is an initiator and receives a frame other than a response message from another device, it autonomously discards the token. Specifically, when an initiator receives a start message or end message not addressed to itself from another initiator, it recognizes an over-token state (a state in which another initiator exists in the area in which the initiator exists). Each of the multiple initiators in the area performs a process to resolve the over-token state. That is, each of the multiple initiators stops its own ranging communication, discards the token, and transitions to a responder state. Note that if multiple initiators simultaneously transition to a responder state, there will be no initiator, and one of the devices (the device with the smallest set timeout value) will autonomously generate a token.

[0044] In the example shown in Figure 6, the first device 1-1 receives a start message addressed to the fourth device 1-4 from the second device 1-2, so it discards the token and transitions to a responder. Similarly, the second device 1-2 receives a start message addressed to the third device 1-3 from the first device 1-1, so it discards the token and transitions to a responder. This resolves the over-token situation. Thereafter, one of the first device 1-1 to the fourth device 1-4 autonomously generates a token and transitions to an initiator.

[0045] As described above, in the ranging system 100 according to this embodiment, when there are multiple initiators, each initiator recognizes the excess token and performs a process to resolve the excess token. This makes it possible to avoid contention in ranging communications that may occur when removing an obstacle, for example.

[0046] (Device operation example) 7 is a flowchart showing the flow of processing executed by the device 1a. An example of the operation of the device 1a that executes the above-mentioned DS-TWR will be described below with reference to FIG.

[0047] In S1, device 1a determines whether it has a token. If device 1a does not have a token (No in S1), the process proceeds to S2. That is, device 1a recognizes that it is a responder and performs the responder processing shown in S2 to S6. If device 1a has a token (Yes in S1), the process proceeds to S7. That is, device 1a recognizes that it is an initiator and performs the initiator processing shown in S7 to S13.

[0048] In S2, device 1a determines whether it has received a start message addressed to itself. Specifically, device 1a determines whether it has received a start message during a predetermined responder-poll waiting time after transitioning to responder mode. Default values ​​for the responder waiting time are, for example, a minimum of 10 ms and a maximum of 20 ms. If device 1a has not received a start message (No in S2), it proceeds to S3. If device 1a has received a start message (Yes in S2), it proceeds to S4. Note that in S2, if device 1a receives a frame other than a start message and the source device of the frame is not included in the neighbor list, it adds this source device to the neighbor list.

[0049] In S3, device 1a recognizes that there is no initiator in the area where device 1a exists and generates a token. That is, device 1a transitions from responder to initiator. Then, the process returns to S1.

[0050] In S4, device 1a transmits a response message to the device that sent the start message after a responder offset time Db has elapsed since receiving the start message. Then, the process proceeds to S5. The default value of responder offset time Db is, for example, 900 μs.

[0051] In S5, device 1a determines whether it has received a Finish message addressed to itself. Specifically, device 1a determines whether it has received a Finish message within a predetermined Responder-Final waiting time after sending the response message. The default value of the Responder-Final waiting time is, for example, 3 ms. If device 1a has not received a Finish message (No in S5), it returns to S2. If device 1a has received a Finish message (Yes in S5), it proceeds to S6. Note that in S5, if device 1a receives a frame other than a Finish message and the source device of the frame is not included in the neighbor list, it adds this source device to the neighbor list.

[0052] In S6, device 1a calculates the inter-device distance based on the responder offset time Db and responder round time Rb measured by itself and the initiator round time Ra and initiator offset time Da transmitted from the initiator (distance measurement step). The method for calculating the inter-device distance is as described above. After calculating the inter-device distance, device 1a transitions from responder to initiator. That is, device 1a receives a token from the transmission source device. Then, the process proceeds to S7.

[0053] In S7, device 1a selects a neighboring device that satisfies a predetermined condition and transmits a start message to the neighboring device. Then, the process proceeds to S8. The neighboring device that satisfies the predetermined condition is, for example, the neighboring device that has been paired with device 1a the fewest times, or the neighboring device that has not measured the distance to device 1a for the longest period of time.

[0054] In S8, device 1a determines whether it has received a frame other than a response message (e.g., an initiation message) before receiving a response message addressed to itself from the device to which the initiation message was sent. If it has received a frame other than a response message (Yes in S8), it proceeds to S9. If it has not received a frame other than a response message (No in S8), it proceeds to S10.

[0055] In S9, the device 1a recognizes the over-token and performs processing to resolve the over-token. Specifically, the device 1a stops its own ranging communication, discards the token, and transitions to a responder. Then, the process proceeds to S1.

[0056] In S10, device 1a determines whether it has received a response message addressed to itself from the device to which the start message was sent. Specifically, device 1a determines whether it has received a response message within a predetermined initiator-response waiting time after sending the start message. The default value for the initiator-response waiting time is, for example, 3 ms. If device 1a has not received a response message (No in S10), it proceeds to S11. If device 1a has received a response message (Yes in S10), it proceeds to S12.

[0057] In S11, the device 1a recognizes that the neighboring device selected in S7 is not within communication distance, and deletes the neighboring device from the neighbor list.

[0058] In S12, device 1a transmits a completion message to the device that sent the response message after an initiator offset time Da has elapsed since receiving the response message. Then, the process proceeds to S13. The default value of initiator offset time Da is, for example, 1300 μs.

[0059] In S13, device 1a determines whether it has received a start message from the destination device of the end message. Specifically, device 1a determines whether it has received a start message within a predetermined initiator-poll waiting time after sending the end message. The default value of the initiator-poll waiting time is, for example, 3 ms. If device 1a has received a start message from the destination device of the end message (No in S13), device 1a recognizes that the handover of the token to the destination device of the end message has been completed, and transitions from initiator to responder (handover step). Also, device 1a adds 1 to the number of pairings for the destination device of the end message. Then, proceed to S14.

[0060] In S14, device 1a determines whether the initiation message is addressed to itself. If the initiation message is addressed to itself (Yes in S14), the process proceeds to S4. If the initiation message is not addressed to itself (No in S14), the process proceeds to S2.

[0061] (Action and effect) According to the above configuration, the device 1a can autonomously hand over the token to the other device 1A. Therefore, the device 1a can avoid contention in the ranging communication without receiving an instruction from the upper server 2.

[0062] Similarly, the ranging system 100 according to this embodiment enables multiple devices 1 to measure distances to one another and can implement distributed multiple access control that can avoid contention in ranging communications without receiving instructions from the host server 2. Therefore, the ranging system 100 can be applied to situations where there is no infrastructure (such as manufacturing sites or construction sites) or where infrastructure is not functioning (such as the scene of a fire). Such an effect also contributes to the achievement of, for example, Goal 11 of the Sustainable Development Goals (SDGs) advocated by the United Nations, "Make cities and human settlements inclusive, safe, resilient and sustainable."

[0063] [Software implementation example] The functions of device 1 (hereinafter referred to as "device") can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (particularly the communication control unit 41 and calculation unit 42 included in the control unit 40).

[0064] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program, thereby realizing the functions described in each of the above embodiments.

[0065] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0066] Furthermore, some or all of the functions of the control blocks can be realized by logic circuits. For example, an integrated circuit in which a logic circuit that functions as each of the control blocks is formed is also included in the scope of the present invention. In addition, the functions of the control blocks can also be realized by, for example, a quantum computer.

[0067] Furthermore, each process described in each of the above embodiments may be executed by AI (Artificial Intelligence). In this case, the AI ​​may run on the control device or on another device (for example, an edge computer or a cloud server).

[0068] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0069] 1a~1c devices 1A Other Devices 10. First Communications Department 20 Second Communications Department 30 Storage section 40 Control Unit 41 Communication control unit 42 Calculation section 100 Ranging System

Claims

1. A device that performs two-way ranging with another device through communication, The device autonomously hands over a token, which is the right to activate the two-way ranging, to the other device.

2. The device of claim 1 , which autonomously hands over the token to the other device that performed the two-way ranging.

3. The two-way ranging is DS-TWR, 3. The device according to claim 2, wherein the device transitions from a responder to an initiator when the device is a responder and receives an end message of the DS-TWR addressed to the device from the other device that is an initiator.

4. The two-way ranging is DS-TWR, The device of claim 2, wherein the device transitions from an initiator to a responder when the device is an initiator and receives a DS-TWR start message from the other device after sending the DS-TWR end message to the other device that is a responder.

5. The device of claim 1 , wherein the device autonomously generates the token if the device is a responder and does not receive the initiation message of the two-way ranging from the other device for a predetermined period of time.

6. The device according to claim 1 , wherein the device is an initiator and autonomously discards the token when the device receives a frame other than the response message from another device.

7. A ranging system including a plurality of devices that perform two-way ranging between the devices through communication, the plurality of devices includes a first device that is an initiator and a second device that is a responder; The first device autonomously hands over a token, which is an activation right for the two-way ranging, to the second device.

8. A ranging method in which a plurality of devices perform two-way ranging through communication, the plurality of devices includes a first device that is an initiator and a second device that is a responder; a ranging step in which the first device and the second device perform two-way ranging; a handover step in which the first device autonomously hands over a token, which is an activation right for the two-way ranging, to the second device.

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