Position estimation device, position estimation system, position estimation method, and program

Abstract

An intensity information acquisition unit (312) acquires intensity information indicating the reception intensity of a wireless signal in a wireless terminal (20), the wireless signal being periodically transmitted from a transmitter. An intensity identification unit (313) identifies a threshold intensity that is a reception intensity at which the cumulative relative frequency of the reception intensity indicated by the intensity information acquired by the intensity information acquisition unit (312) becomes a predetermined threshold. A position estimation unit (314) estimates the position of the wireless terminal (20) on the basis of the threshold intensity identified by the intensity identification unit (313) and the position of the transmitter.

Description

Position estimation device, position estimation system, position estimation method and program

[0001] The present disclosure relates to a position estimation device, a position estimation system, a position estimation method, and a program.

[0002] There are known techniques for estimating the position of a wireless terminal. For example, triangulation is a main method for estimating the position of a wireless terminal. Patent Document 1 (JP-A-2005-102666) discloses a system that, as an alternative to triangulation, estimates the current position of an operating terminal by using the radio wave intensities of two or more beacon signals transmitted from two or more air conditioners and a previous position, which is the last estimated position at which the operating terminal was located.

[0003] International Publication No. 2021 / 192222

[0004] In the technology for estimating the position of a wireless terminal as described above, wireless signal interference may occur due to, for example, multipath caused by reflected waves, the influence of wireless signals from other devices, etc. When such interference occurs, the received strength of the wireless signal at the wireless terminal becomes unstable, which poses a problem of reducing the accuracy of position estimation.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a position estimation device and the like that can estimate the position of a wireless terminal with high accuracy.

[0006] In order to achieve the above-mentioned object, the position estimation device of the present disclosure is a position estimation device that estimates the position of a wireless terminal, and includes: a strength information acquisition means that acquires strength information indicating the reception strength at the wireless terminal of a wireless signal periodically transmitted from a transmitter; a strength identification means that identifies a threshold strength, which is a reception strength at which the cumulative relative frequency of the reception strength indicated in the strength information acquired by the strength information acquisition means becomes a predetermined threshold; and a position estimation means that estimates the position of the wireless terminal based on the threshold strength identified by the strength identification means and the position of the transmitter.

[0007] A location estimation device according to the present disclosure identifies a threshold intensity, which is a reception intensity at a wireless terminal of a wireless signal periodically transmitted from a transmitter, at which a cumulative relative frequency of reception intensity at the wireless terminal reaches a predetermined threshold, and estimates the location of the wireless terminal based on the identified threshold intensity and the location of the transmitter. Thus, according to the present disclosure, the location of the wireless terminal can be estimated with high accuracy.

[0008] FIG. 1 is a diagram showing the overall configuration of a location estimation system according to embodiment 1. FIG. 1 is a diagram showing an example of a building in which a transmitter according to embodiment 1 is installed. Block diagram showing the hardware configuration of a wireless terminal according to embodiment 1. Block diagram showing the hardware configuration of a management device according to embodiment 1. Block diagram showing the functional configuration of a location estimation system according to embodiment 1. FIG. 1 is a diagram showing an example of transmitter information according to embodiment 1. FIG. 1 is a diagram showing an example of intensity information according to embodiment 1. FIG. 1 is a diagram showing an example in which reception intensities included in the intensity information according to embodiment 1 are sorted in ascending order for each transmitter. FIG. 1 is a diagram showing two examples of frequency distribution of reception intensity and cumulative relative frequency according to embodiment 1. FIG. 2 is a diagram showing the relationship between reception intensity and distance according to embodiment 1. FIG. 2 is a diagram showing an example of display of a location estimated by a location estimation system according to embodiment 1. Flowchart showing the flow of intensity information transmission processing executed by a wireless terminal according to embodiment 1. Flowchart showing the flow of location estimation processing executed by a management device according to embodiment 1. Block diagram showing the functional configuration of a location estimation system according to embodiment 2. FIG. 2 is a diagram showing an example in which a room to be estimated is divided into a plurality of areas in embodiment 2. FIG. 2 is a diagram showing an example of a neural network in embodiment 2.

[0009] Hereinafter, embodiments will be described in detail with reference to the drawings, in which the same or corresponding parts are designated by the same reference numerals.

[0010] 1 shows the overall configuration of a position estimation system 1 according to embodiment 1. The position estimation system 1 is a system that estimates the position of a wireless terminal 20 and the position of a user who carries or operates the wireless terminal 20. The position estimation system 1 includes a plurality of transmitters 10, the wireless terminal 20, and a management device 30. The plurality of transmitters 10 and the wireless terminal 20 are installed in a building 5, which is an example of a position estimation area.

[0011] Each of the multiple transmitters 10 is a device that transmits a wireless signal. The wireless signal is a signal for transmitting information between distant devices. As an example, the wireless signal is a Bluetooth (registered trademark) radio wave signal, which is a beacon signal conforming to the BLE (Bluetooth Low Energy (registered trademark)) standard.

[0012] As shown in Fig. 2, each transmitter 10 is installed in a building 5. The building 5 is a structure such as a detached house, an apartment building, an office building, a commercial facility, or a factory. The building 5 has multiple floors, including a first floor and a second floor. Each floor of the building 5 also has multiple rooms. Each transmitter 10 is installed in an appropriate location, such as a wall, ceiling, or floor, in any of the multiple rooms in the building 5.

[0013] For ease of understanding, Fig. 2 shows an example in which one or two transmitters 10 are installed in each of a plurality of rooms in the building 5. However, there may be rooms in the building 5 in which no transmitter 10 is installed, or three or more transmitters 10 may be installed in one room. The building 5 may also have three or more floors. The following description will be given taking as an example a case in which there are multiple rooms on each floor of the building 5, and three or more transmitters 10 are installed in each room.

[0014] Each transmitter 10 may be any device that transmits a wireless signal. For example, each transmitter 10 may be a device that only has the function of transmitting a Bluetooth (registered trademark) radio signal. Alternatively, devices such as air conditioners, lighting, and environmental sensors installed in the building 5 may have the function of transmitting a wireless signal, and these devices may function as transmitters 10.

[0015] It is not necessary for each transmitter 10 to be completely fixed as long as it is installed, but since the position of each transmitter 10 is used to estimate the position of the wireless terminal 20, it is desirable to keep it as still as possible.

[0016] Each transmitter 10 periodically transmits a wireless signal of a predetermined strength. Here, "periodically" refers to repeatedly executing a predetermined process, and the interval at which the processes are executed is not limited to a fixed interval. The interval may be determined arbitrarily by the administrator of the management device 30, or may be determined at the time of shipping the transmitter 10. The interval may be set according to a predetermined rule, or may be set to an irregular value. For example, each transmitter 10 repeatedly transmits a wireless signal once per second. Note that the strength of the wireless signal transmitted from each transmitter 10 is predetermined so that the strength is equal among multiple transmitters 10 installed in the building 5.

[0017] A transmitter ID, which is identification information of the transmitter, is included in the wireless signal transmitted from each transmitter 10. The transmitter ID is, for example, a beacon ID, and is information that is uniquely set for each transmitter 10, which is the transmitter, so that the source of the wireless signal can be identified.

[0018] Returning to Fig. 1 , the wireless terminal 20 is a terminal device such as a smartphone, a PC (Personal Computer), a tablet terminal, etc. As shown in Fig. 2 , the wireless terminal 20 is carried and operated by a user present in the building 5. Because the wireless terminal 20 is a portable terminal, when the user carries the wireless terminal 20 and moves around the building 5, the wireless terminal 20 moves to various locations within the building 5. As shown in Fig. 3 , the wireless terminal 20 includes a control unit 21, a storage unit 22, an operation unit 23, a display unit 24, and a communication unit 25.

[0019] The control unit 21 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU is also called a central processing unit, central arithmetic unit, processor, microprocessor, microcomputer, etc., and functions as a central processing unit that executes processing and calculations related to the control of the wireless terminal 20. In the control unit 21, the CPU reads programs and data stored in the ROM and uses the RAM as a work area to perform overall control of the wireless terminal 20.

[0020] The storage unit 22 includes a nonvolatile semiconductor memory such as a flash memory, an EPROM (Erasable Programmable ROM), or an EEPROM (Electrically Erasable Programmable ROM), and serves as a so-called secondary storage device or auxiliary storage device. The storage unit 22 stores programs and data used by the control unit 21 to perform various processes. The storage unit 22 also stores data generated or acquired by the control unit 21 as a result of performing various processes.

[0021] The operation unit 23 includes input devices such as a keyboard, a mouse, buttons, a touchpad, and a touch panel, and receives operations from a user. The user can input various instructions to the wireless terminal 20 by operating the operation unit 23. When the operation unit 23 receives an operation instruction input by the user, it transmits the received operation instruction to the control unit 21.

[0022] The display unit 24 includes a display device such as a liquid crystal display, an organic EL (Electro Luminescence) display, etc. The display unit 24 is driven by a display drive circuit (not shown) and displays various images under the control of the control unit 21.

[0023] The communication unit 25 includes a communication interface for the wireless terminal 20 to communicate with external devices. The communication unit 25 communicates with external devices, including the management device 30, via a communication network, which is a wide-area communication network. The protocol used for communication is not particularly limited, but a protocol with a certain degree of versatility, such as the ECHONET Lite (registered trademark) standard, can be adopted. The communication unit 25 also receives wireless signals transmitted from each of the multiple transmitters 10 using, for example, the BLE (registered trademark) communication standard.

[0024] Returning to Fig. 1 , the management device 30 is a device that manages the position estimation system 1 and is an example of a position estimation device that estimates the position of the wireless terminal 20. The management device 30 is an information processing device such as a PC or a server, and is installed under the management of an administrator of the position estimation system 1. The management device 30 may be a cloud server such as AWS (Amazon Web Services). As shown in Fig. 4 , the management device 30 includes a control unit 31, a storage unit 32, and a communication unit 35.

[0025] The control unit 31 includes a CPU, a ROM, and a RAM. The CPU is also called a central processing unit, a processor, a microprocessor, a microcomputer, etc., and functions as a central processing unit that executes processing and calculations related to the control of the management device 30. In the control unit 31, the CPU reads out programs and data stored in the ROM and uses the RAM as a work area to perform overall control of the management device 30.

[0026] The storage unit 32 includes a nonvolatile semiconductor memory such as a flash memory, an EPROM, or an EEPROM, and serves as a so-called secondary storage device or auxiliary storage device. The storage unit 32 stores programs and data used by the control unit 31 to perform various processes. The storage unit 32 also stores data generated or acquired by the control unit 31 as a result of performing various processes.

[0027] The communication unit 35 includes a communication interface for communication between the management device 30 and external devices. The communication unit 35 communicates with external devices including the wireless terminal 20 via a communication network, which is a wide area communication network.

[0028] Next, the functional configuration of the position estimation system 1 will be described with reference to Fig. 5. The wireless terminal 20 functionally includes, in the control unit 21, a transmitter information acquisition unit 211 which is an example of a transmitter information acquisition means, a signal receiving unit 212 which is an example of a signal receiving means, a strength information transmission unit 213 which is an example of a strength information transmission means, and a notification unit 214 which is an example of a notification means. The management device 30 functionally includes, in the control unit 31, a transmitter information transmission unit 311 which is an example of a transmitter information transmission means, a strength information acquisition unit 312 which is an example of a strength information acquisition means, a strength identification unit 313 which is an example of a strength identification means, a position estimation unit 314 which is an example of a position estimation means, and an output unit 315 which is an example of an output means.

[0029] Each of these functions is realized by software, firmware, or a combination of software and firmware in the control units 21 and 31. The software and firmware are written as programs and stored in the ROM or storage units 22 and 32. In the control units 21 and 31, the CPU executes the programs stored in the ROM or storage units 22 and 32, thereby realizing each of the functions shown in FIG.

[0030] Furthermore, the wireless terminal 20 stores strength information 221 in the storage unit 22. The management device 30 stores transmitter information 321 and property information 322 in the storage unit 32.

[0031] In the management device 30, the storage unit 32 stores transmitter information 321. The transmitter information 321 is information relating to the plurality of transmitters 10 installed in the building 5. Specifically, as shown in Fig. 6 , the transmitter information 321 includes a transmitter ID, which is identification information for each of the plurality of transmitters 10, and location information for each of the plurality of transmitters 10 within the building 5.

[0032] In the transmitter information 321, the transmitter ID is the same as the identification information included in the wireless signal transmitted from each transmitter 10, and is information for uniquely identifying each transmitter 10. The location information is information for specifying the location where each transmitter 10 is installed within the building 5.

[0033] 6 , the location information in the transmitter information 321 indicates the location where each transmitter 10 is installed using three-dimensional coordinates that uniquely indicate the location within the building 5. Alternatively, the location information is not limited to this, and may indicate the location of each transmitter 10 using information that indicates the room in which each transmitter 10 is installed and the detailed location within that room. Such transmitter information 321 is prepared in advance when multiple transmitters 10 are installed in the building 5, which is the location estimation area, and is stored in the memory unit 32 of the management device 30.

[0034] 5 , in wireless terminal 20, transmitter information acquisition unit 211 acquires transmitter information 321 from management device 30. Specifically, transmitter information acquisition unit 211 communicates with management device 30 via communication unit 25 and transmits a request for transmitter information 321 to management device 30. In management device 30, when a request for transmitter information 321 is received from wireless terminal 20, transmitter information transmission unit 311 reads out transmitter information 321 stored in storage unit 32 and transmits it to wireless terminal 20, which is the requestor. Transmitter information acquisition unit 211 acquires transmitter information 321 transmitted from management device 30 in this manner and stores it in storage unit 22.

[0035] Here, the timing at which the transmitter information acquisition unit 211 acquires the transmitter information 321 from the management device 30 is arbitrary. For example, the transmitter information acquisition unit 211 acquires the transmitter information 321 from the management device 30 immediately after the user operates the operation unit 23 of the wireless terminal 20 to start application software that acquires location information of the wireless terminal 20. Alternatively, the transmitter information acquisition unit 211 may acquire the transmitter information 321 from the management device 30 at any timing according to the user's operation.

[0036] In the wireless terminal 20, the signal receiving unit 212 receives wireless signals transmitted from each of the multiple transmitters 10. As described above, each transmitter 10 periodically transmits a wireless signal of a predetermined intensity. When a wireless signal is transmitted from a transmitter 10 that is present within a range in which the wireless terminal 20 can receive the wireless signal, the signal receiving unit 212 receives the wireless signal.

[0037] When the signal receiving unit 212 receives a wireless signal transmitted from any of the transmitters 10, it measures the strength of the received wireless signal. The strength of the wireless signal transmitted from each transmitter 10 is constant at the time of transmission, but attenuates according to the propagation distance of the wireless signal. Therefore, the longer the distance from the transmitting transmitter 10 to the wireless terminal 20, the weaker the strength of the wireless signal received by the wireless terminal 20. When the signal receiving unit 212 receives a wireless signal, it measures the reception strength, which is the strength of the received wireless signal, and stores the measured reception strength value in the memory unit 22.

[0038] More specifically, when the signal receiving unit 212 receives a wireless signal, it updates the strength information 221 stored in the storage unit 22. As shown in Fig. 7 , the strength information 221 is information that associates a transmitter ID, which is identification information of the transmitter 10, with the reception strength of the wireless signal at the wireless terminal 20 in the order of the reception date and time when the wireless terminal 20 received the wireless signal. When the signal receiving unit 212 receives a wireless signal, it measures the reception strength of the received wireless signal. Then, the signal receiving unit 212 stores the measured value of the reception strength in the strength information 221 together with the identification information included in the received wireless signal and the current date and time.

[0039] The signal receiving unit 212 executes a process of updating such intensity information 221 every time it receives a wireless signal transmitted from any one of the multiple transmitters 10. In this way, the signal receiving unit 212 accumulates data on the reception intensity at the wireless terminal 20 of the wireless signals repeatedly transmitted from each of the multiple transmitters 10.

[0040] As described above, each transmitter 10 periodically transmits a wireless signal multiple times. Therefore, the signal receiving unit 212 receives the wireless signal multiple times from each of the multiple transmitters 10 that are present within a range in which the wireless terminal 20 can receive the wireless signal. The strength information 221 is information that indicates the reception strength at the wireless terminal 20 of the wireless signal periodically transmitted from each of the multiple transmitters 10.

[0041] 5 , in wireless terminal 20, strength information transmission unit 213 transmits strength information 221 to management device 30. Specifically, strength information transmission unit 213 communicates with management device 30 via communication unit 25 every time a first time period elapses, and transmits the latest strength information 221 stored in storage unit 22 to management device 30.

[0042] Here, the first time period is a predetermined length of time and corresponds to the time interval between estimations when the management device 30 repeatedly estimates the position of the wireless terminal 20. To ensure the accuracy of the position estimation, the first time period is set in advance to a time period that allows for the accumulation of, for example, 100 or more pieces of reception strength data per transmitter 10. As an example, if each transmitter 10 repeatedly transmits a wireless signal once per second, the first time period is set in advance to 5 minutes, 10 minutes, or the like.

[0043] In addition, when transmitting the strength information 221 to the management device 30, the strength information transmission unit 213 transmits the identification information of the wireless terminal 20 together with the strength information 221 to the management device 30 so that the management device 30 can identify the wireless terminal 20 that sent the strength information 221.

[0044] More specifically, when a first time period has elapsed since the last transmission of strength information 221, strength information transmission unit 213 transmits information that has not been transmitted in the previous transmission of strength information 221 stored in storage unit 22 to management device 30. In other words, each time the first time period elapses, strength information transmission unit 213 transmits information that has been updated during the most recent first time period to management device 30.

[0045] In the management device 30, the strength information acquisition unit 312 acquires the strength information 221 transmitted from the wireless terminal 20. Specifically, the strength information acquisition unit 312 communicates with the wireless terminal 20 via the communication unit 35, and receives the strength information 221 transmitted from the wireless terminal 20 every time the first time period elapses, together with the identification information of the wireless terminal 20 that is the sender of the strength information 221.

[0046] As described above, the intensity information 221 is information indicating the reception intensity at the wireless terminal 20 of the wireless signals periodically transmitted from each of the multiple transmitters 10. Upon acquiring the intensity information 221, the intensity information acquisition unit 312 stores the acquired intensity information 221 in the storage unit 32.

[0047] The strength identification unit 313 performs data preprocessing based on the strength information 221 acquired by the strength information acquisition unit 312, so that the management device 30 can estimate the position of the wireless terminal 20. Specifically, the strength identification unit 313 identifies a threshold strength, which is a reception strength at which the cumulative relative frequency of the reception strength indicated in the strength information 221 acquired by the strength information acquisition unit 312 becomes a predetermined threshold T1. Here, the cumulative relative frequency of the reception strength means the cumulative sum of the relative frequencies when the reception strengths are sorted in ascending or descending order. When the strength information acquisition unit 312 acquires the strength information 221, the strength identification unit 313 calculates the cumulative relative frequency of the reception strength indicated in the acquired strength information 221 for each transmitter 10.

[0048] Specifically, the strength information 221 acquired by the strength information acquisition unit 312 includes accumulated data on the reception strength of wireless signals periodically transmitted from each of the multiple transmitters 10 during the most recent first time period. The strength identification unit 313 classifies the multiple reception strengths included in the strength information 221 acquired by the strength information acquisition unit 312 for each transmitter 10 based on the identification information of the transmitter 10 associated with each reception strength. Then, the strength identification unit 313 sorts the multiple reception strengths for each transmitter 10 in ascending order, i.e., from smallest to largest reception strength.

[0049] 8 shows an example in which multiple reception intensities included in the intensity information 221 acquired by the intensity information acquisition unit 312 are sorted in ascending order for each transmitter 10. For example, the intensity identification unit 313 sorts the reception intensities of wireless signals transmitted from the transmitter 10 having the transmitter ID "0001" in the most recent first hour from the minimum value of "-71.2 dBm" to the maximum value of "-46.4 dBm." The intensity identification unit 313 similarly sorts the reception intensities of wireless signals transmitted from other transmitters 10 in ascending order.

[0050] After sorting the reception intensities, the intensity specifying unit 313 calculates the cumulative relative frequency of the multiple reception intensities sorted in ascending order for each transmitter 10. That is, the intensity specifying unit 313 calculates the cumulative sum of the relative frequencies of the multiple reception intensities, starting from the smallest reception intensity, for each transmitter 10. Then, the intensity specifying unit 313 specifies the reception intensity at which the cumulative relative frequency becomes a predetermined threshold T1. The threshold T1 is a first threshold and is set in advance to a value of, for example, about 75%.

[0051] 8, the reception strength for the transmitter ID "0001" at which the cumulative relative frequency is 75% of the threshold value corresponds to "-61.4 dBm." The intensity specifying unit 313 specifies, for each of the multiple transmitters 10 identified by the transmitter ID, the reception strength at which this cumulative relative frequency is the threshold value T1 as the threshold intensity.

[0052] The reason for calculating the cumulative relative frequency of the reception strength in this way and specifying the reception strength at which the calculated cumulative relative frequency reaches the threshold T1 as the threshold strength is to suppress variations in the reception strength of the wireless signals transmitted from each transmitter 10. This will be specifically described with reference to FIG.

[0053] Figure 9 shows an example of the frequency distribution and cumulative relative frequency of the reception strength at a wireless terminal 20 of a wireless signal transmitted from a single transmitter 10 on schedules A and B, which are different days or different time periods. The horizontal axis in Figure 9 represents reception strength as a Received Signal Strength Indicator (RSSI), and the vertical axis represents frequency and cumulative relative frequency. In Figure 9, the frequency distribution is represented by a solid line, and the cumulative relative frequency is represented by a dashed line. Note that the positions of the transmitter 10 and the wireless terminal 20 are fixed on both schedules A and B, and the explanation will be given assuming that all conditions other than the schedule are the same.

[0054] For schedule A shown in the upper part of Fig. 9, the frequency distribution of reception strength has one peak near -60 dBm. In contrast, for schedule B shown in the lower part of Fig. 9, the frequency distribution of reception strength has two peaks, i.e., two maximum values, near -70 dBm and -60 dBm.

[0055] The reason for this difference in frequency distribution between schedules A and B is that the strength of the wireless signal received by wireless terminal 20 fluctuates due to the environment surrounding wireless terminal 20. Specifically, radio waves include direct waves and reflected waves, and multiple radio waves circulate in environments such as homes and offices. Radio wave interference occurs due to various factors, such as the influence of reflected waves from walls, floors, and ceilings, and the influence of radio waves emitted from other devices. Therefore, even if wireless terminal 20 is located in the same place, the level of radio wave interference may vary depending on the environment surrounding wireless terminal 20, such as the number of people and their movement, causing the reception strength of the wireless signal to fluctuate. As an example, the reception strength of the wireless signal may momentarily fluctuate by approximately 10 dBm. Due to this fluctuation, when the influence of radio wave interference is low, such as on schedule A, the frequency distribution forms a single peak, but when the influence of radio wave interference is high, such as on schedule B, the frequency distribution forms two peaks.

[0056] In this way, even if the wireless terminal 20 receives a wireless signal at the same location, the reception strength may fluctuate, and therefore the accuracy of the position estimation may not be stable even if the maximum value, average value, median value, mode value, or the like is used as a representative value of the reception strength used to estimate the position of the wireless terminal 20. Taking such circumstances into consideration, the strength identification unit 313 identifies a value based on the cumulative relative frequency of the reception strength as a representative value of the reception strength of wireless signals repeatedly transmitted from one transmitter 10.

[0057] More specifically, the intensity specifying unit 313 specifies the reception intensity at which the cumulative relative frequency of the reception intensity reaches a predetermined threshold T1 as a representative value, i.e., an index, of the reception intensity to be used for estimating the position of the wireless terminal 20. Here, the threshold T1 is predetermined to an appropriate value so that a value that is likely to be stable regardless of the environment can be used as the representative value of the reception intensity.

[0058] For example, the number of peaks in the frequency distribution differs between schedule A and schedule B shown in Figure 9, but for reception intensities near -60 dBm, as indicated by the dashed line in Figure 9, the cumulative relative frequencies are roughly the same on schedule A and schedule B. The reception intensity within this dashed line range corresponds to the intensity near a single peak in the frequency distribution on schedule A, and corresponds to the intensity near the larger of the two peaks in the frequency distribution on schedule B.

[0059] Thus, actual measurements have shown that when two peaks are formed in a frequency distribution, the reception intensity corresponding to the upper peak tends to be stable and not affected by the environment. The reason for this is that when multiple peaks are formed in a frequency distribution, the peaks at lower intensities often correspond to intensities attenuated by interference and are therefore less stable than the peaks at higher intensities. Taking this phenomenon into consideration, the threshold T1 is set to a value near the upper peak when there are two peaks in the frequency distribution, i.e., a value where the cumulative relative frequency is 50% or more when the reception intensities are sorted in ascending order.

[0060] More specifically, since a value close to 100% is inappropriate, the threshold T1 is set to a value equal to or greater than 50% but less than 100%. For example, a value between 70% and 80% is preferable. The following description will be given using an example in which the threshold T1 is set to 75%. In other words, the reception strength corresponding to the lowest 75% of the reception strengths of wireless signals transmitted multiple times from a single transmitter 10 is used as the threshold strength, which is a representative value of the reception strengths. Since the threshold strength specified for each transmitter 10 serves as an indicator of the distance from each transmitter 10 to the wireless terminal 20, the threshold T1 is set to the same value for all transmitters 10 installed in the building 5.

[0061] In this way, the intensity specifying unit 313 calculates the cumulative relative frequency of the reception strength from the accumulated data of the reception strength of wireless signals received by the wireless terminal 20 in the most recent first time period for each of the multiple transmitters 10, and specifies the reception strength at which the calculated cumulative relative frequency is equal to the threshold value T1 as the threshold intensity. In this way, the intensity specifying unit 313 derives an index of the reception strength for each of the multiple transmitters 10 that is different from general representative values ​​such as the maximum value, average value, median value, mode, etc. and is less likely to vary depending on the surrounding environment.

[0062] 5 , the position estimation unit 314 estimates the position of the wireless terminal 20 based on the threshold strength identified by the strength identification unit 313 and the positions of each of the multiple transmitters 10. To estimate the position of the wireless terminal 20, the position estimation unit 314 first determines whether the threshold strength identified for each of the multiple transmitters 10 by the strength identification unit 313 is smaller than a predetermined threshold T2. The threshold T2 is a second threshold set to improve the accuracy of position estimation.

[0063] Fig. 10 shows how the reception strength of a radio signal at the radio terminal 20 attenuates depending on the distance between the transmitter 10 and the radio terminal 20. In Fig. 10, the solid line represents the reception strength that is actually measured, and the dashed line represents the ideal attenuation curve of the radio signal.

[0064] As shown by the dashed line in Fig. 10, ideally, the reception strength of a wireless signal attenuates smoothly as the distance between the transmitter 10 and the wireless terminal 20 increases. However, the actually measured reception strength varies compared to the ideal attenuation curve due to the effects of multipath, as shown by the solid line in Fig. 10. When such variation occurs, it becomes difficult to calculate the distance from the reception strength value, and the error in position estimation increases.

[0065] Therefore, the position estimation unit 314 nullifies the calculation results of threshold intensities smaller than the threshold T2 among the threshold intensities identified by the intensity identification unit 313 for each of the multiple transmitters 10, and excludes them from the reception intensities used in position estimation. In other words, if the wireless terminal 20 receives a wireless signal but the threshold intensity is smaller than the threshold T2, there is a high possibility that the wireless terminal 20 is not present near the transmitter 10. Such transmitters 10 that are far from the wireless terminal 20 and whose reception intensities are likely to vary are excluded from targets for use in position estimation. In this way, the position estimation unit 314 does not use reception intensities for which the distance is difficult to uniquely determine in position estimation, thereby improving the accuracy of position estimation. In the example of FIG. 10, the threshold T2 is set to a value equivalent to -70 dBm.

[0066] More specifically, if all of the threshold intensities identified by the intensity identification unit 313 for each of the multiple transmitters 10 are smaller than the threshold T2, the location estimation unit 314 estimates that the wireless terminal 20 is not present in the building 5. Specifically, if the threshold intensities from all of the transmitters 10 are smaller than the threshold T2, the wireless terminal 20 is located far from all of the transmitters 10, and therefore is highly likely not to be present inside the building 5 in the first place. Therefore, in this case, the location estimation unit 314 estimates that the location of the wireless terminal 20 is outside the building 5.

[0067] In contrast, when some of the threshold intensities identified for the multiple transmitters 10 are smaller than the threshold T2 and the remaining threshold intensities are larger than the threshold T2, the location estimation unit 314 excludes the remaining threshold intensities smaller than the threshold T2 from the threshold intensities to be used for location estimation. In this case, the location estimation unit 314 determines the remaining threshold intensities larger than the threshold T2 as targets for location estimation, as described below. This allows for the accuracy of location estimation to be improved by excluding transmitters 10 that are far from the wireless terminal 20 and whose reception strength is likely to vary from targets for location estimation. Furthermore, when all of the threshold intensities identified for the multiple transmitters 10 are larger than the threshold T2, the location estimation unit 314 determines all of the threshold intensities as targets for location estimation, as described below.

[0068] When a threshold strength greater than threshold T2 is determined as the target for location estimation in this manner, location estimation unit 314 estimates the floor and room where wireless terminal 20 is located. Among multiple transmitters 10 with threshold strengths greater than threshold T2, location estimation unit 314 identifies the transmitter 10 with the highest threshold strength. Then, location estimation unit 314 references transmitter information 321 to acquire location information for the transmitter 10 with the highest threshold strength, and identifies the floor and room within building 5 that correspond to the acquired location information.

[0069] When identifying the floors and rooms within the building 5, the location estimation unit 314 refers to property information 322 stored in the storage unit 32. The property information 322 is information about the building 5, which is the location estimation area, and includes information about the floors and rooms of the building 5. Specifically, the property information 322 includes information such as the number of floors of the building 5 and a floor map showing the layout of rooms on each floor. From the property information 322 and the location information of each transmitter 10 in the transmitter information 321, it is possible to identify the floor and room within the building 5 on which each transmitter 10 is located.

[0070] The location estimation unit 314 acquires the property information 322 from a property information management device, which is an external device to the management device 30, via the communication unit 35. The property information management device, although not shown, is a device that manages information about properties including the building 5. The property information management device has a communication interface and transmits the latest property information 322 about the building 5 to the management device 30 in response to a request from the management device 30. The timing at which the location estimation unit 314 acquires the property information 322 from the property information management device is an arbitrary design matter. For example, the location estimation unit 314 may acquire the property information 322 from the property information management device immediately after the management program in the management device 30 is started, or may acquire the property information 322 from the property information management device in response to an operation by an operator.

[0071] The location estimation unit 314 refers to the property information 322 and identifies the floor on which the transmitter 10 with the highest threshold strength is located from among the multiple floors of the building 5. The location estimation unit 314 then estimates that the wireless terminal 20 is located on the identified floor, and determines the identified floor as the floor to be estimated.

[0072] This makes it possible to narrow down the floor where the wireless terminal 20 is located when multiple transmitters 10 are installed across multiple floors. In particular, there are cases where a wireless signal is received from a transmitter 10 on a floor other than the floor where the user is located, and by narrowing down the floor to be estimated to the floor of the transmitter 10 with the highest threshold strength, the accuracy of subsequent position estimation can be improved.

[0073] After identifying the floor on which the wireless terminal 20 is located, the location estimation unit 314 further identifies the room in which the transmitter 10 with the highest threshold intensity is located from among the multiple rooms on the identified floor by referring to the property information 322. The location estimation unit 314 then estimates that the wireless terminal 20 is located in the identified room, and determines the identified room as the room to be estimated.

[0074] This allows pinpointing the estimation target to one room when multiple transmitters 10 are installed in multiple rooms. In particular, radio signals from transmitters 10 installed in closed spaces such as conference rooms or apartment rooms are more susceptible to radio wave attenuation by walls, ceilings, etc. than radio signals from transmitters 10 installed in open spaces. When the user is outside a closed space, the accuracy of subsequent position estimation can be improved by not using transmitters 10 in closed spaces where radio waves are more likely to be attenuated.

[0075] After estimating the floor and room to be subjected to location estimation, the location estimation unit 314 estimates the location of the wireless terminal 20 in more detail on the estimated floor and room. Specifically, the location estimation unit 314 estimates the location of the wireless terminal 20 based on the threshold strength of at least one transmitter 10 installed in the room to be estimated on the floor to be estimated, among the multiple transmitters 10 installed in the building 5, and the location of the at least one transmitter 10.

[0076] More specifically, the location estimation unit 314 uses one of the following estimation methods (1) to (3) or a combination of multiple estimation methods to estimate the location of the wireless terminal 20. Which estimation method to use from the following estimation methods (1) to (3) may be set in advance by, for example, an operator of the management device 30, or may be selectable by the user of the wireless terminal 20.

[0077] (1) In a first estimation method, the position estimation unit 314 estimates that the wireless terminal 20 is located at the position of the transmitter 10 with the highest threshold strength among the multiple transmitters 10 installed on the floor and room to be estimated. For example, if the transmitter 10 with the highest threshold strength is installed on the wall of the room, the position estimation unit 314 estimates that the wireless terminal 20 is located at the position of that wall. Note that if there is only one transmitter 10 installed on the floor and room to be estimated, the position estimation unit 314 estimates that the wireless terminal 20 is located at the position of that transmitter 10. The accuracy of position estimation in the first estimation method is limited by the installation interval of the transmitters 10. Therefore, the first estimation method has the lowest position estimation accuracy of the three estimation methods, but is the simplest method to process.

[0078] (2) As a second estimation method, the position estimation unit 314 estimates the position of the wireless terminal 20 using the principles of so-called triangulation or triangulation. Specifically, the position estimation unit 314 uses the position of one transmitter 10 as a reference and sets a range based on the threshold strength specified for that one transmitter 10 for each of the multiple transmitters 10 installed on the floor and room to be estimated. The position estimation unit 314 then estimates that the wireless terminal 20 is located at a position where the ranges set for each of the multiple transmitters 10 overlap. Here, the range based on the threshold strength is represented by a circle that becomes larger as the value of the threshold strength becomes smaller, based on an attenuation curve of the wireless signal according to the distance. The position estimation unit 314 sets such a circle for each transmitter 10 and estimates that the wireless terminal 20 is located at a position where the multiple circles overlap.

[0079] (3) As a third estimation method, the position estimation unit 314 sets a plurality of candidate positions and estimates the position of the wireless terminal 20 from among the plurality of candidate positions. Specifically, the position estimation unit 314 sets a plurality of candidate positions for the floor and room to be estimated. For example, the position estimation unit 314 sets a plurality of candidate positions within a predetermined range based on the previous position, which is the position of the wireless terminal 20 most recently estimated by the position estimation unit 314.

[0080] When multiple candidate positions are set, the position estimation unit 314 compares the distance order, in which the distance between one of the multiple candidate positions and each of the multiple transmitters 10 installed on the floor and room to be estimated is arranged in ascending order, with the intensity order, in which the threshold intensities identified for each of the multiple transmitters 10 are arranged in descending order.

[0081] The location estimation unit 314 performs a comparison process for each of the multiple candidate locations, comparing the distance order with the intensity order. Since the closer the distance, the stronger the reception strength, so when the wireless terminal 20 is located at a candidate location, the distance order and intensity order at that candidate location ideally match perfectly. Therefore, the location estimation unit 314 estimates that the wireless terminal 20 is located at the candidate location among the multiple candidate locations whose distance order and intensity order most closely match.

[0082] Regardless of which of the estimation methods (1) to (3) is used, the threshold strength specified based on the cumulative relative frequency of the reception strength is used, so the position estimation unit 314 can estimate the position of the wireless terminal 20 using a stable index. Therefore, the position of the wireless terminal 20 can be estimated with high accuracy.

[0083] 5 , the output unit 315 outputs output information based on the position of the wireless terminal 20 estimated by the position estimation unit 314. Specifically, when the position of the wireless terminal 20 is estimated by the position estimation unit 314, the output unit 315 communicates with the wireless terminal 20 via the communication unit 35 and transmits output information indicating the estimated position to the wireless terminal 20. As a result, the output unit 315 causes the position of the wireless terminal 20 estimated by the position estimation unit 314 to be displayed on the display unit 24 of the wireless terminal 20.

[0084] In the wireless terminal 20, the notification unit 214 notifies the user of the position of the wireless terminal 20 estimated by the position estimation unit 314. When output information is transmitted from the management device 30, the notification unit 214 receives the transmitted output information and displays the received output information on the display unit 24 of the wireless terminal 20.

[0085] The notification unit 214 displays, for example, a notification screen shown in Fig. 11 on the display unit 24. Specifically, the notification unit 214 displays a floor map centered on the room to be estimated on the floor to be estimated in the building 5. The notification unit 214 then displays a mark indicating the current location of the wireless terminal 20 on the floor map at a position indicated in the output information received from the management device 30. This allows the user of the wireless terminal 20 to easily confirm their own current location within the building 5.

[0086] Next, a flow of processing executed in the position estimation system 1 will be described with reference to Fig. 12 and Fig. 13. The processing shown in Fig. 12 and Fig. 13 is an example of a position estimation method.

[0087] First, Fig. 12 shows the flow of the strength information transmission process executed by the wireless terminal 20. The strength information transmission process shown in Fig. 12 starts when application software that acquires the location information of the wireless terminal 20 is started in the wireless terminal 20.

[0088] When the intensity information transmission process is started, the control unit 21 in the wireless terminal 20 acquires, from the management device 30, transmitter information 321 including identification information and location information of the multiple transmitters 10 present in the building 5, and stores the acquired information in the storage unit 22 (step S1). In step S1, the control unit 21 functions as the transmitter information acquisition unit 211.

[0089] When the transmitter information 321 is acquired, the control unit 21 determines whether or not a wireless signal has been received from any of the transmitters 10 (step S2). If a wireless signal has been received (step S2; YES), the control unit 21 measures the reception strength of the received wireless signal (step S3).

[0090] After measuring the reception strength, the control unit 21 updates the strength information 221 (step S4). Specifically, the control unit 21 associates the measured reception strength value with the identification information of the transmitter 10 that is the sender and is included in the received wireless signal and the current date and time, and stores the result in the strength information 221 stored in the storage unit 22.

[0091] On the other hand, if no wireless signal is received (step S2; NO), the control unit 21 skips steps S3 and S4. In steps S2 to S4, the control unit 21 functions as the signal receiving unit 212.

[0092] Next, the control unit 21 determines whether a first time has elapsed since the most recent transmission of the strength information 221 (step S5). If the first time has elapsed (step S5; YES), the control unit 21 transmits the strength information 221 to the management device 30 (step S6).

[0093] On the other hand, if the first time period has not elapsed since the most recent transmission of the intensity information 221 (step S5; NO), the control unit 21 skips step S6. In steps S5 and S6, the control unit 21 functions as the intensity information transmission unit 213.

[0094] Thereafter, the control unit 21 returns the process to step S2 and executes the processes of steps S2 to S6 again, whereby the control unit 21 repeats the process of updating the intensity information 221 every time a wireless signal is received from any of the transmitters 10 and the process of transmitting the intensity information 221 to the management device 30 every time the first time period elapses.

[0095] Secondly, Fig. 13 shows the flow of the position estimation process executed by the management device 30. The position estimation process shown in Fig. 13 is executed when the strength information 221 is transmitted from the wireless terminal 20 while the management device 30 is in a state where it can operate normally.

[0096] When the position estimation process is started, the control unit 31 in the management device 30 determines whether or not the strength information 221 transmitted from the wireless terminal 20 has been acquired (step S11). If the strength information 221 has not been acquired (step S11; NO), the control unit 31 does not execute the processes from step S12 onwards and ends the position estimation process shown in Fig. 13. In step S11, the control unit 31 functions as the strength information acquisition unit 312.

[0097] When the intensity information 221 is acquired (step S11; YES), the control unit 31 sorts the reception intensities included in the acquired intensity information 221 in ascending order for each transmitter 10, and calculates the cumulative relative frequency of the reception intensities (step S12). Then, the control unit 31 identifies, for each transmitter 10, a threshold intensity that is the reception intensity at which the cumulative relative frequency becomes a threshold T1 (step S13). In steps S12 to S13, the control unit 31 functions as the intensity identification unit 313.

[0098] After identifying the threshold intensities, the control unit 31 determines whether the threshold intensities of all transmitters 10 are less than the threshold T2 (step S14). If the threshold intensities of at least one transmitter 10 are equal to or greater than the threshold T2 (step S14; NO), the control unit 31 identifies the floor to be estimated (step S15). Specifically, the control unit 31 identifies the floor on which the transmitter 10 with the largest threshold intensities identified for each transmitter 10 in step S13 is installed, among the multiple floors of the building 5, as the floor to be estimated.

[0099] After identifying the floor to be estimated, the control unit 31 identifies the room to be estimated (step S16). Specifically, the control unit 31 identifies, among the multiple floors included in the floor to be estimated identified in step S15, the room in which the transmitter 10 with the maximum threshold intensity identified for each transmitter 10 in step S13 is installed as the room to be estimated.

[0100] Once the floor and room to be estimated have been identified, the control unit 31 estimates the position of the wireless terminal 20 (step S17). Specifically, the control unit 31 estimates the position of the wireless terminal 20 in the floor and room to be estimated, using any one or a combination of the estimation methods (1) to (3) described above, based on the threshold intensity of at least one transmitter 10 installed in the floor and room to be estimated identified in steps S15 and S16, and the position of at least one transmitter 10. In steps S14 to S17 and S19, the control unit 31 functions as a position estimation unit 314.

[0101] After estimating the position of the wireless terminal 20, the control unit 31 outputs the estimation result (step S18). For example, the control unit 31 transmits output information indicating the position of the wireless terminal 20 estimated in step S17 to the wireless terminal 20, and causes the display unit 24 of the wireless terminal 20 to display the output information. In step S18, the control unit 31 functions as the output unit 315.

[0102] On the other hand, if the threshold intensities of all transmitters 10 are smaller than threshold T2 (step S14; YES), the control unit 31 estimates that the wireless terminal 20 is not in the building 5 (step S19). Then, the control unit 31 proceeds to step S18, and transmits output information indicating that the wireless terminal 20 is not in the building 5 to the wireless terminal 20, and causes the display unit 24 of the wireless terminal 20 to display this. This completes the position estimation process shown in FIG. 13.

[0103] As described above, the position estimation system 1 according to the first embodiment identifies a threshold intensity, which is the reception intensity at which the cumulative relative frequency of the reception intensity at the wireless terminal 20 of the wireless signal periodically transmitted from the transmitter 10 becomes a predetermined threshold T1, and estimates the position of the wireless terminal 20 based on the identified threshold intensity and the position of the transmitter 10. By using the cumulative relative frequency of the reception intensity in this manner, it is possible to suppress variations in reception intensity due to the influence of wireless signal interference, and therefore a stable index can be used as an index for estimating the position of the wireless terminal 20. As a result, the position of the wireless terminal 20 can be estimated with high accuracy.

[0104] In particular, when the wireless terminal 20 is located inside a building 5 where interference is likely to occur due to various factors such as reflected waves and signals from other devices, the reception strength is likely to vary. Even in such a situation, the position estimation system 1 according to the first embodiment can estimate the position of the wireless terminal 20 with high accuracy.

[0105] (Embodiment 2) Next, a description will be given of embodiment 2. Descriptions of the same configurations and functions as those of embodiment 1 will be omitted where appropriate.

[0106] 14 shows the functional configuration of a position estimation system 1 according to embodiment 2. A management device 30 according to embodiment 2 functionally includes a control unit 31 including a transmitter information transmission unit 311, a strength information acquisition unit 312, a strength identification unit 313, a position estimation unit 314, an output unit 315, and a learning unit 316. Each of these functions is realized in the control unit 31 by software, firmware, or a combination of software and firmware.

[0107] Furthermore, the management device 30 stores transmitter information 321, property information 322, and a trained model 323 in the storage unit 32. Note that the configuration of the management device 30 other than the learning unit 316 and the trained model 323, and the configuration of the wireless terminal 20 are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0108] The position estimation unit 314 estimates the floor and room of the estimation target using the same method as in embodiment 1. After estimating the floor and room of the estimation target, the position estimation unit 314 estimates the position of the wireless terminal 20 using an estimation method that uses the trained model 323 instead of the estimation methods (1) to (3) described in embodiment 1.

[0109] First, the position estimation unit 314 divides the room to be estimated into a plurality of areas. As an example, as shown in FIG. 15 , the position estimation unit 314 divides the room to be estimated into 16 areas with area numbers 1 to 16. In this way, the position estimation unit 314 sets a plurality of areas within the room to be estimated as candidates for where the wireless terminal 20 is located. The position estimation unit 314 uses the trained model 323 to estimate the area where the wireless terminal 20 is located from among the 16 areas.

[0110] The trained model 323 is a model for estimating the position of the wireless terminal 20 from the threshold intensity identified for each of the multiple transmitters 10 by the intensity identification unit 313. The trained model 323 receives input of the threshold intensity values ​​identified for each of the multiple transmitters 10 installed in the room to be estimated, and outputs a value indicating a presence probability, which is the likelihood that the wireless terminal 20 is present in each of the multiple areas.

[0111] 15, as an example, four transmitters a to d are installed in the room to be estimated, each at the boundary of the area. The trained model 323 receives the threshold strength values ​​identified for each of the four transmitters a to d and outputs a value indicating the presence probability of the wireless terminal 20 in each of the 16 areas 1 to 16.

[0112] Specifically, as shown in FIG. 16 , the trained model 323 is configured by a neural network. The neural network has an input layer to which input data is input, an output layer to which output data is output, and at least one intermediate layer (hidden layer). The number of nodes in the input layer corresponds to the number of input data, and the number of nodes in the output layer corresponds to the number of output data. The number of intermediate layers may be arbitrary. The straight lines between the nodes represent the parameter connections between the input layer and the output layer. Each node in the input layer accepts input of a threshold strength value specified for each of the four transmitters a to d. In response to this input, each node in the output layer outputs the presence probability of the wireless terminal 20 in each of the 16 areas 1 to 16.

[0113] 14 , the learning unit 316 uses machine learning to generate such a trained model 323. The learning unit 316 is an example of a learning means.

[0114] As an example, the learning unit 316 calculates the distance D1 between each transmitter 10 and the wireless terminal 20 by converting the threshold strength identified for each of the transmitters a to d into a distance according to the formula for the wireless signal attenuation curve. For example, in the ideal attenuation curve shown in FIG. 10 , if the threshold strength of the transmitter a is −55 dBm, the distance between the transmitter a and the wireless terminal 20 is converted to approximately 3 m. Next, the learning unit 316 calculates the distance D2 from each transmitter 10 for each area based on the position coordinates of the transmitters a to d and the coordinates of areas 1 to 16. The learning unit 316 calculates such distances D1 and D2 for each of the four transmitters a to d. Then, the learning unit 316 calculates the sum of the differences between the distances D1 and D2 for each of the four transmitters a to d for each area. The learning unit 316 adjusts the connection weights of each layer in the neural network so that the smaller the calculated sum, the higher the probability of the wireless terminal 20 being present in the area. The learning unit 316 generates a trained model 323 by repeatedly performing such learning.

[0115] Alternatively, actual location information of the wireless terminal 20 may be used as training data. The actual location information of the wireless terminal 20 can be obtained, for example, by a user entering their current location coordinates into the wireless terminal 20 using a questionnaire. By using the location information of the wireless terminal 20, the distance D1 can be calculated from the location coordinates of the wireless terminal 20 and the location coordinates of transmitters a to d. Therefore, by combining the calculated distance D1 with the threshold intensity of transmitters a to d, it is possible to derive a correlation between the distance D1 and the threshold intensity. As a result, the threshold intensity can be converted to the distance D1 without using the attenuation curve formula.

[0116] In addition, the learning unit 316 may generate the learned model 323 by performing supervised learning using multiple data sets as training data, each of which is a combination of the threshold strength values ​​of transmitters a to d and the position coordinates of the wireless terminal 20.

[0117] The position estimation unit 314 estimates the position of the wireless terminal 20 based on the trained model 323 generated by the learning unit 316. Specifically, the position estimation unit 314 inputs the threshold strengths identified for each of the multiple transmitters 10 by the strength identification unit 313 as input data to the trained model 323. Then, the position estimation unit 314 compares the presence probability of the wireless terminal 20 in each area output from the trained model 323 in response to such input, and estimates that the wireless terminal 20 is present in the area with the highest presence probability.

[0118] As described above, the position estimation system 1 according to the second embodiment uses the trained model 323 generated by machine learning to estimate the position of the wireless terminal 20. Because the threshold strength specified based on the cumulative relative frequency of the reception strength is used as input to the trained model 323, it is possible to estimate the position of the wireless terminal 20 using a stable index. Therefore, it is possible to estimate the position of the wireless terminal 20 with high accuracy.

[0119] Third Embodiment Next, a third embodiment will be described. Descriptions of the same configurations and functions as those of the first and second embodiments will be omitted where appropriate.

[0120] If any of the multiple transmitters 10 installed in the building 5 is installed in the ceiling, behind a pillar, inside a piece of equipment, or the like, the reception strength of the wireless signal transmitted from that transmitter 10 at the wireless terminal 20 will always be attenuated by a certain value compared to the reception strength from the other transmitters 10. In order to correct for such attenuation of reception strength, in the third embodiment, the position estimation unit 314 corrects the threshold strength identified for at least one transmitter 10 installed behind an obstruction before estimating the position.

[0121] Specifically, the position estimation unit 314 corrects the threshold strength identified by the strength identification unit 313 for at least one transmitter 10 among the multiple transmitters 10 present within a range in which the wireless terminal 20 can receive wireless signals, in accordance with the location where the at least one transmitter 10 is installed. Then, the position estimation unit 314 estimates the position of the wireless terminal 20 based on the corrected threshold strength.

[0122] More specifically, the position estimation unit 314 does not correct the threshold strength for the remaining transmitters 10 other than at least one of the multiple transmitters 10, as in the first embodiment, and instead uses the threshold strength identified by the strength identification unit 313 as is. Therefore, the position estimation unit 314 estimates the position of the wireless terminal 20 based on the corrected threshold strength for at least one of the multiple transmitters 10, the uncorrected threshold strength for the remaining transmitters 10, and the positions of the multiple transmitters 10. Details of the position estimation process are the same as in the first embodiment.

[0123] When correcting the threshold strength, the location estimation unit 314 adds a larger offset value to the threshold strength for transmitters 10 installed in locations where the degree of attenuation of reception strength is greater. Here, the degree of attenuation of reception strength differs depending on the location where each transmitter 10 is installed. The offset value used to correct the threshold strength may be set manually or may be derived by machine learning from past measurement data.

[0124] By correcting the threshold strength in this way, the threshold strength of a transmitter 10 installed in a location where wireless signals are likely to attenuate is converted into a value that can be compared with the threshold strengths of other transmitters 10. This allows the threshold strength of each transmitter 10 to be appropriately used as an index of distance, thereby improving the accuracy of estimating the position of the wireless terminal 20.

[0125] (Modifications) Although the embodiments have been described above, it is possible to combine the embodiments, or to modify or omit the embodiments as appropriate.

[0126] For example, in the above embodiment, the intensity identification unit 313 calculates the cumulative relative frequency by sorting the multiple reception intensities included in the intensity information 221 in ascending order. However, the intensity identification unit 313 may calculate the cumulative relative frequency by sorting the multiple reception intensities included in the intensity information 221 in descending order. The threshold value T1=75% when the reception intensities are sorted in ascending order is the same as the threshold value T1=25% when the reception intensities are sorted in descending order.

[0127] Furthermore, the threshold value T1 is not limited to 75%. The threshold value T1 may be set to, for example, 65%, 70%, 80%, 85%, etc. Furthermore, when there are two peaks, i.e., maximum values, in the frequency distribution of the reception intensity, the threshold value T1 may be any value as long as it is possible to identify the reception intensity at the peak with the greater reception intensity of the two peaks as the threshold intensity.

[0128] The threshold value T1, the threshold value T2, and the first time period for determining the threshold intensity may be set manually or may be derived by machine learning from past measurement data. For example, the threshold value T1 may be derived using measurement data in which two peaks exist in the frequency distribution of the reception intensity of wireless signals transmitted from each transmitter 10 over multiple past measurement periods.

[0129] In the second embodiment, the management device 30 has the functionality of the learning unit 316. However, the management device 30 does not need to have the functionality of the learning unit 316. In this case, a device external to the management device 30 performs machine learning to generate the trained model 323, and the management device 30 acquires the generated trained model 323 via the communication unit 35. The position estimation unit 314 estimates the position of the wireless terminal 20 using the trained model 323 acquired from the external device. Furthermore, the learning unit 316 is not limited to the method using the neural network described above, and may use other machine learning methods.

[0130] In the above embodiment, the position estimation system 1 includes multiple transmitters 10. However, the position estimation system 1 may include only one transmitter 10. When the number of transmitters 10 is one, the position estimation unit 314 estimates that the wireless terminal 20 is located within a range based on the position of the single transmitter 10, with the smaller the threshold strength, the larger the range. In this way, the accuracy of position estimation can be improved by using multiple transmitters 10, but even when the number of transmitters 10 is only one, the position of the wireless terminal 20 can be estimated with a minimum level of accuracy.

[0131] More specifically, in the above embodiment, the position estimation unit 314 estimates that the wireless terminal 20 is not present in the building 5 when all of the threshold intensities identified by the intensity identification unit 313 for each of the multiple transmitters 10 are smaller than the threshold T2. In contrast, when there is one transmitter 10, the position estimation unit 314 estimates that the wireless terminal 20 is not present in the building 5 when the threshold intensity identified by the intensity identification unit 313 for one transmitter 10 is smaller than the threshold T2. Also, in the above second embodiment, the trained model 323 is a model that estimates the position of the wireless terminal 20 from the threshold intensity identified by the intensity identification unit 313 for each of the multiple transmitters 10. In contrast, when there is one transmitter 10, the trained model 323 is a model that estimates the position of the wireless terminal 20 from the threshold intensity identified by the intensity identification unit 313 for one transmitter 10. The learning unit 316 generates such a trained model 323 using machine learning.

[0132] In the above embodiment, the number of wireless terminals 20 whose positions are to be estimated in the position estimation system 1 is one. However, multiple wireless terminals 20 may be present in the building 5. The management device 30 may then execute the process described in the above embodiment for each of the multiple wireless terminals 20 to estimate the positions of each of the multiple wireless terminals 20.

[0133] In the above embodiment, the output unit 315 transmitted output information indicating the position of the wireless terminal 20 estimated by the position estimation unit 314 to the wireless terminal 20, and displayed the output information on the display unit 24 of the wireless terminal 20. However, the output unit 315 is not limited to displaying the output information on the display unit 24, and may be used for other purposes. For example, the output unit 315 may control equipment such as air conditioners and lighting installed in the building 5, based on the position of the wireless terminal 20 estimated by the position estimation unit 314.

[0134] Specifically, the output unit 315 may transmit, as output information, a control command to the air conditioner or the lighting to turn on the air conditioner or the lighting at the position of the wireless terminal 20 estimated by the position estimation unit 314. Alternatively, the position estimation unit 314 may estimate the positions of multiple wireless terminals 20 and, based on the estimated positions of the multiple wireless terminals 20, estimate areas in the building 5 where people are present and areas in the building 5 where no people are present. Then, the output unit 315 may transmit, as output information, a control command to the air conditioner or the lighting to turn on the air conditioner or the lighting in areas in the building 5 where no people are present and to turn off the air conditioner or the lighting in areas in the building 5 where no people are present.

[0135] In the above embodiment, the wireless terminal 20 is an operation terminal that includes the operation unit 23 and the display unit 24 and is operated by a user. However, the wireless terminal 20 does not need to include the operation unit 23 or the display unit 24 as long as it has the function of receiving a wireless signal transmitted from the transmitter 10 and transmitting information related to the reception to the management device 30. For example, the wireless terminal 20 may be a device such as an IC (Integrated Circuit) tag that only has the function of transmitting and receiving radio waves. If the wireless terminal 20 does not have the display unit 24, the wireless terminal 20 may transmit information transmitted from the management device 30 to an external device such as a PC or digital signage, and display the information.

[0136] In the above embodiment, the wireless terminal 20 and the management device 30 have the functional configuration shown in FIG. 5 . However, the configuration shown in FIG. 5 is merely an example, and the functions of each unit may be provided in any device in the position estimation system 1. For example, the function of the intensity identification unit 313 may be provided in the wireless terminal 20. In this case, the wireless terminal 20 identifies a threshold intensity, which is a reception intensity at which the cumulative relative frequency of the reception intensity of a wireless signal becomes a predetermined threshold, and transmits information on the identified threshold intensity to the management device 30 via the communication unit 25. Then, in the management device 30, the position estimation unit 314 estimates the position of the wireless terminal 20 based on the threshold intensity identified in the wireless terminal 20 and the position of the transmitter 10. Alternatively, the wireless terminal 20 may be provided with the functions of the position estimation unit 314 in addition to the intensity identification unit 313.

[0137] In the above-described embodiment, the control units 21 and 31 function as the units shown in FIG. 5 by the CPU executing a program stored in the ROM or the storage units 22 and 32. However, the control units 21 and 31 may be dedicated hardware. Examples of dedicated hardware include a single circuit, a composite circuit, a programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. When the control units 21 and 31 are dedicated hardware, the functions of each unit may be realized by individual hardware, or the functions of each unit may be realized together by a single piece of hardware.

[0138] In addition, some of the functions of each unit may be realized by dedicated hardware, and other functions may be realized by software or firmware. In this way, the control units 21 and 31 can realize each of the above-mentioned functions by hardware, software, firmware, or a combination of these.

[0139] By applying a program that defines the operation of the control units 21 and 31 to an existing computer such as a personal computer or an information terminal device, the computer can be made to function as an air conditioning control device.

[0140] Furthermore, the method of distribution of such a program is arbitrary, and for example, it may be stored on a computer-readable recording medium such as a CD-ROM (Compact Disk ROM), a DVD (Digital Versatile Disk), an MO (Magneto Optical Disk), or a memory card and distributed, or it may be distributed via a communication network such as the Internet.

[0141] The present disclosure allows various embodiments and modifications without departing from the broad spirit and scope of the present disclosure. Furthermore, the above-described embodiments are intended to illustrate the present disclosure and do not limit the scope of the present disclosure. That is, the scope of the present disclosure is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of equivalent disclosures are considered to be within the scope of the present disclosure.

[0142] The present disclosure is applicable to systems that estimate position.

[0143] 1 Position estimation system, 5 Building, 10 Transmitter, 20 Wireless terminal 21 Control unit, 22 Memory unit, 23 Operation unit, 24 Display unit, 25 Communication unit, 30 Management device, 31 Control unit, 32 Memory unit, 35 Communication unit, 211 Transmitter information acquisition unit, 212 Signal receiving unit, 213 Intensity information transmission unit, 214 Notification unit, 221 Intensity information, 311 Transmitter information transmission unit, 312 Intensity information acquisition unit, 313 Intensity identification unit, 314 Position estimation unit, 315 Output unit, 316 Learning unit, 321 Transmitter information, 322 Property information, 323 Learned model

Claims

1. A position estimation device for estimating the position of a wireless terminal, comprising: intensity information acquisition means for acquiring intensity information indicating the reception intensity of a wireless signal periodically transmitted from a transmitter at the wireless terminal; intensity identification means for identifying a threshold intensity, which is a reception intensity at which the cumulative relative frequency of the reception intensity indicated by the intensity information acquired by the intensity information acquisition means becomes a predetermined threshold; and position estimation means for estimating the position of the wireless terminal based on the threshold intensity identified by the intensity identification means and the position of the transmitter.

2. The intensity information acquisition means acquires the intensity information indicating the reception intensity of the wireless signal periodically transmitted from each of a plurality of transmitters at the wireless terminal, the intensity identification means identifies the threshold intensity for each of the plurality of transmitters based on the intensity information acquired by the intensity information acquisition means, and the position estimation means estimates the position of the wireless terminal based on the threshold intensity identified by the intensity identification means for each of the plurality of transmitters and the positions of the plurality of transmitters. The position estimation device according to claim 1.

3. The plurality of transmitters are installed in a building, and when all of the threshold intensities identified by the intensity identification means for each of the plurality of transmitters are smaller than a second threshold, the position estimation means estimates that the wireless terminal does not exist in the building. The position estimation device according to claim 2.

4. The plurality of transmitters are installed in a building having a plurality of floors, and the position estimation means estimates that the wireless terminal exists on the floor where the transmitter having the largest threshold intensity among the plurality of transmitters is located among the plurality of floors. The position estimation device according to claim 2 or 3.

5. The plurality of transmitters are installed in a building having a plurality of rooms, and the position estimation means estimates that the wireless terminal exists in the room where the transmitter having the largest threshold intensity among the plurality of transmitters is located among the plurality of rooms. The position estimation device according to any one of claims 2 to 4.

6. The position estimation means estimates that the wireless terminal exists at the position where the transmitter having the largest threshold intensity among the plurality of transmitters is located. The position estimation device according to any one of claims 2 to 5.

7. The position estimation means sets, for each of the plurality of transmitters, a range based on the threshold intensity specified for one transmitter among the plurality of transmitters, with the position of the one transmitter as a reference, and estimates that the wireless terminal exists at a position where the ranges set for each of the plurality of transmitters overlap. The position estimation device according to any one of claims 2 to 6.

8. The position estimation means executes, for each of the plurality of candidate positions, a process of comparing the distance order in which the distances between one candidate position among the plurality of candidate positions and each of the plurality of transmitters are arranged in ascending order of distance, and the intensity order in which the threshold intensities specified for each of the plurality of transmitters are arranged in descending order of intensity, and estimates that the wireless terminal exists at a candidate position among the plurality of candidate positions where the distance order and the intensity order match the most. The position estimation device according to any one of claims 2 to 7.

9. The plurality of candidate positions are set with reference to the position of the wireless terminal finally estimated by the position estimation means. The position estimation device according to claim 8.

10. The position estimation means estimates the position of the wireless terminal using a learned model for estimating the position of the wireless terminal from the threshold intensities specified for each of the plurality of transmitters by the intensity specifying means. The position estimation device according to any one of claims 2 to 9.

11. The position estimation device according to claim 10, further comprising a learning unit that generates the learned model using machine learning.

12. The position estimation means corrects the threshold intensity specified for at least one transmitter among the plurality of transmitters by the intensity specifying means according to the location where the at least one transmitter is installed, and estimates the position of the wireless terminal based on the corrected threshold intensity. The position estimation device according to any one of claims 2 to 11.

13. The transmitter is installed in a building, and when the threshold intensity specified by the intensity specifying means is smaller than a second threshold, the position estimation means estimates that the wireless terminal does not exist in the building. The position estimation device according to claim 1.

14. The position estimation device according to claim 1 or 13, wherein the position estimation means estimates the position of the wireless terminal using a learned model for estimating the position of the wireless terminal from the threshold intensity specified by the intensity specifying means.

15. The position estimation device according to claim 14, further comprising a learning unit that generates the learned model using machine learning.

16. A position estimation system for estimating the position of a wireless terminal, comprising: a transmitter that periodically transmits a wireless signal; intensity specifying means for specifying a threshold intensity, which is a reception intensity at which a cumulative relative frequency of reception intensities of the wireless signal periodically transmitted from the transmitter at the wireless terminal becomes a predetermined threshold; and position estimation means for estimating the position of the wireless terminal based on the threshold intensity specified by the intensity specifying means and the position of the transmitter.

17. A position estimation method for estimating the position of a wireless terminal, comprising: calculating a cumulative relative frequency of reception intensities of a wireless signal periodically transmitted from a transmitter at the wireless terminal; specifying a threshold intensity, which is a reception intensity at which the cumulative relative frequency becomes a predetermined threshold; and estimating the position of the wireless terminal based on the specified threshold intensity and the position of the transmitter.

18. A program that causes a computer to function as intensity information acquisition means for acquiring intensity information indicating a reception intensity of a wireless signal periodically transmitted from a transmitter at a wireless terminal, intensity specifying means for specifying a threshold intensity, which is a reception intensity at which a cumulative relative frequency of the reception intensities indicated by the intensity information acquired by the intensity information acquisition means becomes a predetermined threshold, and position estimation means for estimating the position of the wireless terminal based on the threshold intensity specified by the intensity specifying means and the position of the transmitter.

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