Location detection system

Abstract

This invention provides a location detection system that can appropriately avoid signal collisions from tags when detecting the location of a person using tags that are activated by power from a transmitter. [Solution] The position detection system 10 includes a transmitter 300 that transmits power and a carrier signal, and a tag 200 that is activated by power from the transmitter 300, receives the carrier signal, modulates the received carrier signal, and transmits a measurement frame with identification information into space. The position detection system 10 also includes a receiver 400 that is activated by power from the transmitter 300, receives the measurement frame, and calculates distance information indicating the distance to the tag based on the channel state information of the measurement frame. Furthermore, the position detection system 10 includes a position detection device 100 that acquires distance information between the receiver 400 and the tag 200 and detects the position of a person wearing the tag 200.

Description

Technical Field

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[0001] The present invention relates to a position detection system.

Background Art

[0002] Conventionally, techniques for detecting a person's position and behavior using radio waves have been proposed. Patent Document 1 discloses a monitoring device that utilizes a frequency shift caused by the interference synthesis of environmental radio waves and self-transmitted radio waves. The monitoring device disclosed in Patent Document 1 operates the oscillator of a state sensor to generate a frequency shift in the interference radio waves by causing fluctuations in which the reflection and absorption of environmental radio waves are repeated at the oscillation frequency, enabling the recognition of situation changes.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When performing position detection corresponding to a plurality of sensors as in the monitoring device disclosed in Patent Document 1, signal collision avoidance becomes a problem. Therefore, there is a need for a system that can appropriately perform signal collision avoidance in position detection using a plurality of sensors.

[0005] The present invention has been made in view of such problems of the prior art. The object of the present invention is to provide a position detection system capable of appropriately avoiding signal collisions in the position detection of a person using a tag activated by power from a transmitter. <00OO029>

Means for Solving the Problems

[0006] A location detection system according to an aspect of the present invention comprises: a transmitter that transmits power and a carrier signal; a tag that is activated by power from the transmitter, receives the carrier signal, modulates the received carrier signal, and transmits a measurement frame with identification information attached into space; a receiver that is activated by power from the transmitter, receives the measurement frame, and calculates distance information indicating the distance to the tag based on the channel state information of the measurement frame; and a location detection device that acquires distance information between the receiver and the tag and detects the location of a person wearing the tag. [Effects of the Invention]

[0007] According to the present invention, a location detection system is provided that can appropriately avoid signal collisions from tags when detecting the location of a person using tags that are activated by power from a transmitter. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the configuration of the location detection system according to this embodiment. [Figure 2] This diagram illustrates the communication method applied to the location detection system according to this embodiment. [Figure 3] This is a block diagram showing the configuration of the position detection device according to this embodiment. [Figure 4] This is a block diagram showing the functional configuration of the position detection device according to this embodiment. [Figure 5] This diagram illustrates the processing of the position detection system according to this embodiment. [Figure 6] This is a sequence diagram illustrating the processing of the position detection system according to this embodiment. [Modes for carrying out the invention]

[0009] The position detection system 10 according to this embodiment will be described in detail below with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios. In addition, in the following drawings, identical or similar parts are denoted by the same or similar reference numerals.

[0010] (Regarding worker location detection in production plants) In wire harness (W / H) production plants, production processes are being advanced to create a fluid production system by handling a wide variety of part numbers and reducing costs through design changes and inventory reductions. Therefore, there is a need to improve equipment utilization rates and worker efficiency.

[0011] In production process design, the number of workers required for a particular process is determined, and the process is designed to improve work efficiency by minimizing worker movement.

[0012] However, if workers on site are moving in a manner different from the process design, the expected efficiency cannot be achieved, and the process needs to be redesigned. Therefore, improving production efficiency by acquiring worker location information in real time is being considered. One method of acquiring worker location information in real time is to obtain location and movement information from sensors (tags) attached to the workers.

[0013] Conventional technologies have proposed methods for determining a worker's location by using Bluetooth® or similar technologies to receive beacon signals from wireless terminals with sensors worn by the worker, and then calculating the location from the signal strength.

[0014] However, since the sensors worn by workers include heavy objects such as batteries, there is a risk of reducing work efficiency. In the case of operating with batteries, battery replacement is required at regular intervals. However, replacement during work leads to a decrease in work efficiency, and pre-work inspection also becomes less efficient. Therefore, it is considered that sensors that do not require batteries for grasping the position information of workers can contribute to improving production efficiency.

[0015] In addition, in the prior art, for the position information of workers, a method is used in which the radio waves of a plurality of beacons whose positions are known are received by a sensor, and the distance is calculated from the difference. However, if the number of beacons is small, the position accuracy is low.

[0016] Therefore, the position detection system 10 according to the present embodiment applies a configuration that supplies power to the sensor by using "Bistatic backscatter" in order to apply a sensor (tag) that does not require a battery. In addition, the position information in the position detection system 10 realizes a means for grasping the position of a worker by WLAN (Wireless LAN) sensing used in IEEE802.11bf.

[0017] (Configuration of the position detection system 10) Next, the position detection system 10 according to the present embodiment will be described. FIG. 1 is a diagram showing the configuration of the position detection system 10 according to the present embodiment. As shown in FIG. 1, the position detection system 10 includes a position detection device 100, a tag 200 provided on a worker 20, a transmitter 300, and a receiver 400.

[0018] The position detection device 10 gets the distance information between the receiver 400 and the tag 200, and detects the position of the person (worker 20) wearing the tag 200. In the position detection system 10 according to the present embodiment, position detection using Bistatic backscatter is applied.

[0019] (Position detection by Bistatic backscatter) Bistatic backscatter is a form of wireless communication, especially used in passive RFID (Radio Frequency Identification) systems and sensor networks. Figure 2 is a diagram for explaining the communication method by bistatic backscatter.

[0020] As shown in Figure 2, the communication system by bistatic backscatter includes a transmitter 300 called a Carrier Emitter that transmits power. Also, the communication system by bistatic backscatter includes a tag 200 that activates a sensor using the power from the Carrier Emitter (transmitter 300) and reflects and transmits its signal. Furthermore, the communication system by bistatic backscatter is composed of a reader, which is a receiver 400 that receives data from the tag 200.

[0021] The transmission procedure of Bistatic Backscatter is as follows. First, the transmitter 300 generates a carrier signal and continuously transmits it at a specific frequency. Next, the tag 200 and the receiver 400 are activated by the power from the transmitter 300. Next, the tag 200 with a sensor mounted receives the carrier signal sent from the transmitter 300, and the tag 200 modulates its own data. In the modulation of data by this tag 200, information for identifying the tag 200 is added to the carrier signal. The modulated signal is reflected and transmitted through space again. Finally, the receiver 400 receives the modulated signal reflected from the tag 200 and analyzes this modulated signal to extract the data from the tag 200.

[0022] (Regarding WLAN sensing) Next, the acquisition of location information by WLAN sensing used in IEEE802.11bf will be explained. In WLAN sensing, a method of calculating location information using CSI (Channel State Information) is applied.

[0023] CSI (Cross-Sensitivity Index) represents the frequency response and time variation of the signal's amplitude and phase, and indicates the spatial quality of communication between the sender and receiver. In addition, some wireless LANs employ OFDM (Orthogonal Frequency Division Multiplexing) transmission, which consists of multiple subcarriers according to the bandwidth.

[0024] WLAN sensing uses several subcarriers and calculates the arrival time SI (Clock Significance) from the transmitter to the receiver. For example, if there is an obstacle, the direct wave and the delayed wave caused by the obstacle are combined, and a frequency spectrum corresponding to the delay time is obtained, making obstacle detection possible.

[0025] The target frequency range for IEEE 802.11bf is 1 GHz to 7.125 GHz, and above 45 GHz. Below 7 GHz, CSI is measured using the WLAN sensing procedure. IEEE 802.11bf also supports bistatic sensing, where the transmitter and receiver are different, and multistatic sensing, where one transmitter and multiple receivers are used.

[0026] In the position detection system 10 according to this embodiment, a unidirectional measurement method from the tag 200 to the receiver 400 is desirable, as it is a position information acquisition system that utilizes a bistatic backscatter communication method. The measurement method may be a "Trigger-based sensing measurement instance" method that uses a Trigger frame. Alternatively, the measurement method may be a "Non-Trigger-based sensing measurement instance" method that does not use a Trigger frame.

[0027] Next, the configuration of the position detection system 10 according to this embodiment will be described. As shown in Figure 1, the position detection system 10 is equipped with multiple transmitters 300 and receivers 400 at predetermined intervals.

[0028] In the example shown in Figure 1, the system consists of three transmitters 300: transmitter 300a, transmitter 300b, and transmitter 300c. From now on, unless it is necessary to distinguish between transmitters 300a, 300b, and 300c, they will simply be referred to as "transmitter 300".

[0029] Furthermore, the example shown in Figure 1 consists of three receivers 400: receiver 400a, receiver 400b, and receiver 400c. From now on, unless it is necessary to distinguish between receivers 400a, 400b, and 400c, they will simply be referred to as "receiver 400".

[0030] Furthermore, in the example shown in Figure 1, the system consists of five tags 200: tags 200a, 200b, 200c, 200d, and 200e, each worn by multiple workers 20. Hereafter, unless it is necessary to distinguish between tags 200a to 200e, they will simply be referred to as "tag 200." Also, the number of transmitters 300, receivers 400, and tags 200 is not limited to the configuration shown in Figure 1; it may be more or less than the number shown in Figure 1.

[0031] The receiver 400 has pre-configured or stored information regarding the distance measurement order corresponding to the installation location and the installation position within the factory. The transmitter 300 and receiver 400 are installed in a location with a clear line of sight, such as the ceiling of the factory. The position detection device 100 and the multiple transmitters 300 and multiple receivers 400 are connected by wires, and the settings of the transmitters 300 and receivers 400 from the position detection device 100 are performed via the wires. The information collected by the receiver 400 is also aggregated in the position detection device 100 via the wires.

[0032] The transmitter 300, which corresponds to the Carrier Emitter in the Bistatic backscatter communication method, transmits power and a carrier signal. The carrier signal corresponds to CW (Continuous Wave) and includes a certain characteristic frequency component. For example, in the case of Bluetooth®, the carrier signal corresponds to a 2.4 GHz continuous wave. Specifically, in the case of 2441 MHz communication in Bluetooth Classic, the carrier signal corresponds to a 2441 MHz continuous wave.

[0033] The tag 200 is powered by the transmitter 300, receives a carrier signal, modulates the received carrier signal, and transmits a measurement frame with identification information into space.

[0034] Furthermore, tag 200 transmits a Start Of Frame (SOF) to other tags 200 and multiple receivers 400. After transmitting the Start Of Frame, tag 200 transmits measurement frames to multiple receivers 400 in a predetermined order. In addition, after transmitting multiple measurement frames, tag 200 transmits an End Of Frame (EOF) to other tags 200 and multiple receivers 400.

[0035] Furthermore, tag 200 transmits a start frame when it receives an end frame from another tag 200 and it corresponds to a predetermined transmission order, or when it does not receive an end frame but receives power for startup from transmitter 300. The transmission of start frames, measurement frames, and end frames by tag 200 and other tags 200 will be described later.

[0036] The receiver 400 is powered by the transmitter 300, receives a measurement frame, and calculates distance information indicating the distance to the tag 200 based on the channel status information (CSI) of the measurement frame. The receiver 400 identifies the originating tag 200 based on the identification information assigned to the measurement frame.

[0037] Channel status information (CSI) includes a frequency spectrum in the frequency domain corresponding to the delay time. This frequency spectrum represents the state of multipath transmission. Channel status information provides detailed information, including amplitude and phase variations of the communication channel, allowing the communication system to operate adaptively according to the channel state.

[0038] Furthermore, the receiver 400 acquires distance information to the tag 200 based on channel status information using either the ToA (Time of Arrival) or Phase Difference method.

[0039] Specifically, in the case of a typical ToA (Time of Arrival), receiver 400 measures the distance to tag 200 by the round-trip arrival time. For example, if the round trip is t seconds, and the speed of light is C, the distance is L = Ct / 2. The difference between this ToA and the Phase Difference varies depending on the radio wave environment.

[0040] For example, while general Phase Difference can accurately measure distance in multipath environments, the processing is complex. Conversely, ToA becomes difficult to handle due to the influence of complex radio wave environments. Therefore, in the position detection system 10 according to this embodiment, ToA is normally used to process and determine the position using three or more measurement points. However, in cases of multipath effects, ToA cannot measure accurately, and it becomes impossible to narrow it down to a single point through calculation. In such cases, the receiver 400 remeasures using Phase Difference to determine the position.

[0041] The switch from ToA to Phase Difference may be configured to be performed by the administrator of the position detection system 10. Alternatively, the switch from ToA to Phase Difference may be performed automatically when the number of measurement points at the receiver 400 falls below three.

[0042] The position detection device 100 acquires multiple distance information from multiple receivers 400 and detects the position of a person (worker 20) wearing a tag 200.

[0043] For example, in the example shown in Figure 1, if distance information of a tag 200e is acquired by receivers 400a, 400b, and 400c, the position of the worker 20 wearing the tag 200e can be detected based on the respective distance information. Next, the details of the position detection device 100 will be described.

[0044] (Configuration of position detection device 100) Figure 3 is a block diagram showing the configuration of the position detection device 100 according to this embodiment. The position detection device 100 is composed of a general-purpose computer comprising a control unit 110, a storage unit 120, an input / output IF 130 (Interface), and a communication IF 140. Details of the control unit 110 and the storage unit 120 will be described later.

[0045] Furthermore, if a general-purpose microprocessor is provided in the tag 200, transmitter 300, and / or receiver 400, the configuration of the microprocessor may be the configuration shown in the block diagram in Figure 3.

[0046] The input / output IF130 is, for example, a component (interface) for a user to exchange data with the position detection device 100. The input / output IF130 comprises, for example, an input IF and an output IF (not shown).

[0047] The input interface in the input / output IF 130 has an interface function for inputting various information by the user, and information is input from outside the position detection device 100. Information is input to the input interface by the user through devices connected to the position detection device 100, such as a keyboard, mouse, touch panel, trackball, and voice recognition device. The input interface can also be used as a data input terminal to input data from an external storage device (not shown), etc.

[0048] The output IF of the input / output IF130 can display, for example, the worker's position detection result on a display device (not shown) connected to the position detection device 100. The display device can be, for example, a display device or a projector device.

[0049] The communication IF140 is an interface that enables communication between the position detection device 100 and the transmitter 300 and receiver 400.

[0050] (Functional configuration of the position detection device 100) Figure 4 is a block diagram showing the functional configuration of the position detection device 100 according to this embodiment. As shown in Figure 4, the control unit 110 of the position detection device 100 includes a carrier emitter control unit 111, a reader information acquisition unit 112, and a position information calculation unit 113 as its functions. Each of these functions of the control unit 110 will be described later.

[0051] Furthermore, the control unit 110 controls the entire position detection device 100, for example, by running an operating system. In addition, the control unit 110 operates based on a program stored in the storage unit 120 and executes the functions described above. Note that the program is not limited to being stored in the storage unit 120, but may also be stored in a ROM (Read Only Memory) or the like (not shown) within the position detection device 100.

[0052] As shown in Figure 4, the storage unit 120 stores the information contained in the control information DB121 (DB: Database), the acquired information DB122, and the location information DB123 as data. Note that there may be one or more storage units 120 that store each of these data. For example, a single storage unit 120 may be configured to store data in separate areas. Alternatively, the data may be distributed and stored in multiple storage devices located in physically separate locations.

[0053] The carrier emitter control unit 111 sets information such as the startup timing and startup order for the transmitter 300 based on the information stored in the control information DB 121. The transmitter 300 is driven based on the control from the carrier emitter control unit 111.

[0054] The leader information acquisition unit 112 acquires distance information obtained by the receiver 400. The leader information acquisition unit 112 also stores the acquired distance information in the acquisition information DB 122.

[0055] As described above, the location information calculation unit 113 detects the location of the person (worker 20) wearing the tag 200 based on multiple distance information acquired from multiple receivers 400. The location information calculation unit 113 also stores the calculated location information in the location information DB 123.

[0056] (Processing by the position detection system 10) Figure 5 is a diagram illustrating the processing of the position detection system 10 according to this embodiment. As shown in Figure 5, the transmission order from tag 200 to receiver 400 is predetermined. In the example shown in Figure 5, measurement frames are transmitted sequentially from tag a to receiver 400, which are readers A, B, C, and D. Also, in the example shown in Figure 5, the transmission order of tag 200 is tag a, tag b, and tag c.

[0057] As shown in Figure 5, each tag sends an SOF (start frame) at the start of transmission and an EOF (end frame) at the end. All installed Carrier Emitter transmitters 300 transmit periodically at times t1, t2, ..., t19 as shown in Figure 5. This prevents the tags 200 from running out of power.

[0058] Furthermore, the transmitters 300 are connected by wires, and are synchronized with each other through control from the carrier emitter control unit 111, so that power and carrier signals are transmitted simultaneously.

[0059] Furthermore, in the position detection system 10 according to this embodiment, all tags 200 are synchronized with the transmitter 300, so synchronization is also achieved among the tags 200. As a result, it operates using the scheduler shown in Figure 5, and no communication collisions occur.

[0060] Figure 6 is a sequence diagram illustrating the processing of the position detection system 10 according to this embodiment. The series of operations of the position detection system 10 shown in the sequence diagram of Figure 6 begin when the position detection device 100 is activated and end when the work is completed. The processing of the position detection system 10 shown in Figure 6 also ends when the power of the position detection device 100 is turned off or when an interrupt indicating the end of processing occurs. Furthermore, in the following explanation of the sequence diagram, the same content as described in the above-mentioned explanation of the position detection system 10 and position detection device 100 will be omitted or simplified.

[0061] In step S601, the position detection device 100 issues a disclosure instruction to the transmitter 300. Specifically, the carrier emitter control unit 111 of the position detection device 100 sets information such as the startup timing and startup order to the transmitter 300 based on the information stored in the control information DB 121. The transmitter 300 is driven based on the control from the carrier emitter control unit 111. The process then proceeds to step S602.

[0062] In step S602, the transmitter 300 transmits power and carrier signals to the tag 200 and receiver 400. The tag 200 and receiver 400 are powered up by the power from the transmitter 300. The process then proceeds to step S603.

[0063] In step S603, tag 200a receives the carrier signal. Tag 200 also transmits a Start Frame (SOF) to other tags 200 and multiple receivers 400. The process then proceeds to step S604.

[0064] In step S604, the tag 200 modulates the received carrier signal and transmits measurement frames with identification information to multiple receivers 400 in a predetermined order. The process then proceeds to step S605.

[0065] In step S605, after transmitting multiple measurement frames, tag 200 transmits an end frame (EOF) to other tags 200 and multiple receivers 400. Subsequently, the processing from steps S603 to S605 is repeated for tags 200b, ..., and tag 200n. After the processing from steps S603 to S605 is completed for all tags 200, the process proceeds to step S606.

[0066] In step S606, the receiver 400 receives a measurement frame and calculates distance information indicating the distance to the tag 200 based on the channel status information (CSI) of the measurement frame. The receiver 400 also identifies the sending tag 200 based on the identification information attached to the measurement frame. The receiver 400 then transmits the measurement result to the position detection device 100, which detects the position of the person (worker 20) wearing the tag 200 based on the multiple distance information obtained from the multiple receivers 400.

[0067] As described above, the position detection system 10 according to this embodiment includes a transmitter 300 that transmits power and a carrier signal. The position detection system 10 also includes a tag 200 that is activated by power from the transmitter 300, receives a carrier signal, modulates the received carrier signal, and transmits a measurement frame with identification information attached into space. The position detection system 10 also includes a receiver 400 that is activated by power from the transmitter 300, receives a measurement frame, and calculates distance information indicating the distance to the tag based on the channel state information of the measurement frame. Furthermore, the position detection system 10 includes a position detection device 100 that acquires distance information between the receiver 400 and the tag 200 and detects the position of a person wearing the tag 200.

[0068] As a result, the position detection system 10 identifies the tag 200 based on the identification information assigned to the measurement frame by the receiver 400 and calculates distance information indicating the distance to the tag 200. Therefore, the position detection system 10 can appropriately avoid signal collisions from the tag 200 when detecting the position of a person using the tag 200 which is activated by power from the transmitter 300.

[0069] Furthermore, the transmitter 300 and receiver 400 of the position detection system 10 may be provided in multiple units at predetermined intervals. The position detection device 100 may also acquire multiple distance information from multiple receivers 400 and detect the position of a person wearing the tag 200. This makes it possible for the position detection system 10 to more accurately detect the position information of workers in an area of ​​a predetermined size, such as a factory.

[0070] Furthermore, tag 200 may transmit a start frame to other tags 200 and multiple receivers 400. Also, after transmitting the start frame, tag 200 may transmit measurement frames to multiple receivers 400 in a predetermined order. Furthermore, after transmitting multiple measurement frames, tag 200 may transmit a end frame to other tags 200 and multiple receivers 400.

[0071] As a result, the tag 200 of the position detection system 10 can recognize the timing of transmission of measurement frames, and can more effectively avoid signal collisions from the tag 200 when detecting the position of a person.

[0072] Furthermore, tag 200 may transmit a start frame if it receives an end frame from another tag 200 and it corresponds to a predetermined transmission order, or if it does not receive an end frame but receives power for startup from transmitter 300.

[0073] This enables the location detection system 10 to transmit start frames from the tag 200 in the appropriate order, making it possible to more effectively avoid signal collisions from the tag 200 when detecting the location of a person.

[0074] Furthermore, the receiver 400 may acquire distance information to the tag based on channel status information using the ToA (Time of Arrival) or Phase Difference method. This enables the position detection system 10 to accurately calculate distance information indicating the distance between the tag 200 and the receiver 400.

[0075] (Other embodiments) While embodiments have been described in detail with reference to the drawings, these embodiments are not limited to those described above. Furthermore, the components described above include those easily conceivable by those skilled in the art, and those that are substantially the same. Moreover, the configurations described above can be combined as appropriate. In addition, various omissions, substitutions, or modifications of the configurations can be made without departing from the spirit of the embodiments.

[0076] The features of the location detection system 10 are described below.

[0077] The first embodiment of the position detection system 10 includes a transmitter 300 that transmits power and a carrier signal. The position detection system 10 also includes a tag 200 that is activated by power from the transmitter 300, receives a carrier signal, modulates the received carrier signal, and transmits a measurement frame with identification information into space. The position detection system 10 also includes a receiver 400 that is activated by power from the transmitter 300, receives a measurement frame, and calculates distance information indicating the distance to the tag based on the channel state information of the measurement frame. Furthermore, the position detection system 10 includes a position detection device 100 that acquires distance information between the receiver 400 and the tag 200 and detects the position of a person wearing the tag 200.

[0078] According to the above configuration, the position detection system 10 identifies the tag 200 based on the identification information attached to the measurement frame by the receiver 400 and calculates distance information indicating the distance to the tag 200. Therefore, the position detection system 10 can appropriately avoid signal collisions from the tag 200 when detecting the position of a person using the tag 200 which is activated by power from the transmitter 300.

[0079] The transmitter 300 and receiver 400 of the position detection system 10 according to the second embodiment may be provided in multiple units at predetermined intervals. The position detection device 100 may also acquire multiple distance information from multiple receivers 400 and detect the position of a person wearing the tag 200.

[0080] According to the above configuration, it becomes possible to more accurately detect the location information of workers in an area of ​​a predetermined size, such as a factory.

[0081] In the third embodiment of the position detection system 10, the tag 200 may transmit a start frame to other tags 200 and multiple receivers 400. Furthermore, after transmitting the start frame, the tag 200 may transmit measurement frames to multiple receivers 400 in a predetermined order. Additionally, after transmitting multiple measurement frames, the tag 200 may transmit a finish frame to other tags 200 and multiple receivers 400.

[0082] With the above configuration, the tag 200 of the position detection system 10 becomes able to recognize the timing of transmission of measurement frames, and in person position detection, it becomes possible to more appropriately avoid signal collisions from the tag 200.

[0083] In the fourth embodiment, the tag 200 of the position detection system 10 may transmit a start frame if it receives a termination frame from another tag 200 and it corresponds to a predetermined transmission order. Alternatively, the tag 200 may transmit a start frame if it does not receive a termination frame but receives power for startup from the transmitter 300.

[0084] With the above configuration, the position detection system 10 can transmit start frames from the tag 200 in the appropriate order, making it possible to more effectively avoid signal collisions from the tag 200 when detecting the position of a person.

[0085] The receiver 400 of the position detection system 10 according to the fifth embodiment may acquire distance information to the tag based on channel status information using the ToA (Time of Arrival) or Phase Difference method.

[0086] With the above configuration, the position detection system 10 can accurately calculate distance information indicating the distance between the tag 200 and the receiver 400. [Explanation of Symbols]

[0087] 10. Location detection system 20 workers 100 Position detection device 110 Control Unit 111 Carrier emitter control unit 112 Leader Information Acquisition Unit 113 Location information calculation unit 120 Storage section 121 Control Information Database 122 Acquisition information DB 123 Location information DB 130 Input / Output Interfaces 140 Communication IF 200, 200a~200e tags 300, 300a, 300b, 300c Transmitters 400, 400a, 400b, 400c receivers

Claims

1. A transmitter that transmits power and carrier signals, A tag that is activated by power from the aforementioned transmitter, receives the carrier signal, modulates the received carrier signal, and transmits a measurement frame with identification information attached into space, A receiver that is powered by the transmitter, receives the measurement frame, and calculates distance information indicating the distance to the tag based on the channel state information of the measurement frame, A location detection device that acquires the distance information between the receiver and the tag and detects the location of the person wearing the tag, A location detection system equipped with the following features.

2. Multiple transmitters and receivers are provided at predetermined intervals. The position detection system according to claim 1, wherein the position detection device acquires a plurality of distance pieces of information from a plurality of receivers and detects the position of a person wearing the tag.

3. The position detection system according to claim 2, wherein the tag transmits a start frame to other tags and a plurality of receivers, transmits the measurement frames to a plurality of receivers in a predetermined order after transmitting the start frames, and transmits a end frame to other tags and a plurality of receivers after transmitting the plurality of measurement frames.

4. The position detection system according to claim 3, wherein the tag transmits the start frame when it receives the end frame from another tag and it corresponds to a predetermined transmission order, or when it does not receive the end frame but receives power for activation from the transmitter.

5. The location detection system according to any one of claims 1 to 4, wherein the receiver acquires the distance information to the tag based on the channel state information using a Time of Arrival (ToA) or Phase Difference method.

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