Location identification device, location identification method, and program

Abstract

The present invention provides a location identification device capable of detecting a malfunction of a receiver used to identify the location of a terminal device. [Solution] The location determination device 1 comprises first and second receiver sets 11, 12 each including one or more receivers, an identification unit 13 that determines the location of the terminal device 2 based on the difference in strength of radio waves transmitted from the terminal device 2 and received by the first and second receiver sets 11, 12, respectively, and an output unit 15 that provides output related to the determined location.The first and second receiver sets 11, 12 include transmitters 31, 32 that transmit reference radio waves using the receiver antennas, and further comprise a detection unit 14 that detects a malfunction of the receiver that received the reference radio waves based on the reception strength of the reference radio waves received by two or more receivers.

Description

[Technical Field]

[0001] The present invention relates to an information processing device or the like that identifies the location of a terminal device using radio waves transmitted from the terminal device. [Background technology]

[0002] Conventionally, radio waves transmitted from a terminal device are received at a plurality of positions to identify the position of the terminal device (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 080314 Summary of the Invention [Problem to be solved by the invention]

[0004] When a receiver that receives radio waves is used for many years, the antenna, circuits, etc. of the receiver may deteriorate. If such a malfunction such as deterioration occurs in the receiver, it becomes impossible to accurately identify the location in response to receiving radio waves transmitted from a terminal device. Therefore, there has been a demand for a way to detect such malfunctions.

[0005] The present invention has been made to solve the above-mentioned problems, and aims to provide a location identification device etc. that can detect malfunctions in a receiver used to identify the location of a terminal device. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, a location determination device according to one embodiment of the present invention comprises first to Nth receiver sets (N is an integer greater than or equal to 2) each including one or more receivers that receive radio waves transmitted from a terminal device carried by a user using an antenna, an identification unit that determines the location of the terminal device based on the difference in strength of the radio waves transmitted from the terminal device and received by the first to Nth receiver sets, and an output unit that provides output related to the location determined by the identification unit, wherein at least one of the first to Nth receiver sets includes a transmitter that transmits reference radio waves using at least one antenna of the one or more receivers, and the reference radio waves transmitted by the transmitter are received by two or more receivers that use antennas located at positions different from the position of the antenna used to transmit the reference radio waves, and further comprises a detection unit that detects a malfunction of the receiver that received the reference radio waves based on the reception strength of the reference radio waves received by the two or more receivers.

[0007] With this configuration, it is possible to detect a malfunction in a receiver that receives the reference radio wave using the reception results of the reference radio wave by two or more receivers. Then, for example, it is possible to repair or replace a receiver that has a detected malfunction. Furthermore, by transmitting the reference radio wave using the receiver's antenna, there is no need to install an additional antenna for transmitting the reference radio wave, and existing facilities can be used effectively.

[0008] In addition, in a position determination device according to one aspect of the present invention, the detection unit may detect a malfunction by comparing the reception strength of reference radio waves received by two or more receivers using antennas located at the same position.

[0009] With this configuration, it is possible to detect a malfunction by comparing the reception strength of the reference radio wave received by two or more receivers. For example, if the difference in reception strength of the reference radio wave received by two receivers is greater than a threshold, it is possible to detect that there is a malfunction in at least one of the two receivers.

[0010] In addition, in a position determination device according to one aspect of the present invention, the detection unit may detect a malfunction of a receiver corresponding to an identified outlier in the reception strength of a reference radio wave received by three or more receivers using antennas located at the same position.

[0011] Such a configuration makes it possible to detect a specific receiver defect corresponding to an outlier.

[0012] In addition, in a position determination device according to one aspect of the present invention, the detection unit may detect a malfunction based on the reception strength of a reference radio wave received using an antenna at two or more positions different from the position of the antenna used to transmit the reference radio wave by the transmitter.

[0013] With this configuration, the reception strength of the reference radio wave received using antennas at two or more locations is used, so that a malfunction of the receiver can be detected even if, for example, there is only one receiver at each of two or more locations different from the location of the antenna used to transmit the reference radio wave.

[0014] In addition, in a position determination device according to one aspect of the present invention, the detection unit may detect a malfunction of the receiver corresponding to an outlier identified using the reception strength of a reference radio wave received using an antenna at two or more positions different from the position of the antenna used to transmit the reference radio wave by the transmitter, and a reference value of the difference in strength of the radio waves received at the two or more positions.

[0015] With this configuration, for example, a malfunction of the receiver can be detected by converting the reception strength of a reference radio wave received at a certain location into the reception strength of a reference radio wave received at another location using a reference value of the intensity difference.

[0016] In addition, in a position determination device according to one aspect of the present invention, the detection unit may detect a malfunction of the receiver corresponding to an outlier identified in the difference in intensity of reference radio waves received using antennas at two or more positions different from the position of the antenna used to transmit the reference radio waves by the transmitter.

[0017] With this configuration, defects can be detected by comparing two or more intensity differences.

[0018] In addition, in a location determination device according to one aspect of the present invention, when a malfunction is detected in one of two or more receivers that receive radio waves using antennas located at the same position, the determination unit may determine the location of the terminal device using the reception results for a longer reception period from the receiver among the two or more receivers in which no malfunction has been detected.

[0019] With this configuration, the location of the terminal device can be identified using a receiver other than the receiver in which the malfunction has been detected.

[0020] In addition, in a location determination device according to one aspect of the present invention, the determination unit may determine the location of the terminal device using the corrected reception strength obtained by adding a correction value to the reception strength of the radio waves received by the receiver corresponding to the outlier.

[0021] With this configuration, the position of the terminal device can be more accurately identified by correcting the reception strength of the radio waves received by the receiver in which a malfunction has been detected.

[0022] In addition, in a position determination device according to one aspect of the present invention, the transmitter transmits multiple reference radio waves of different intensities, and the determination unit may perform correction using a correction value when the degrees of deviation of multiple outliers corresponding to the multiple reference radio waves of different intensities are the same.

[0023] With this configuration, for example, a receiver for which correction is not effective can be prevented from being used to identify the location of a terminal device.

[0024] In addition, in a position determination device according to one embodiment of the present invention, the first to Nth receiver sets may include two or more transmitters that transmit reference radio waves using antennas located at different positions, and the detection unit may detect malfunctions using the reference radio waves transmitted from each of the two or more transmitters.

[0025] With this configuration, it becomes possible to determine whether or not there is a malfunction in all of the receivers included in the first to Nth receiver sets, for example.

[0026] Furthermore, a location determination method according to one embodiment of the present invention includes the steps of receiving, using an antenna, radio waves transmitted from a terminal device carried by a user by first to Nth receiver sets (N is an integer greater than or equal to 2), each set including one or more receivers; determining, by an identification unit, the location of the terminal device based on the difference in strength of the radio waves transmitted from the terminal device and received by the first to Nth receiver sets; and outputting, by an output unit, information related to the location determined by the identification unit, wherein at least one of the first to Nth receiver sets includes a transmitter that transmits reference radio waves using at least one antenna of the one or more receivers, and the method further includes the steps of transmitting the reference radio waves by the transmitter; receiving the reference radio waves by two or more receivers using antennas located at positions different from the position of the antenna used to transmit the reference radio waves; and detecting, by a detection unit, a malfunction of the receiver that received the reference radio waves based on the reception strength of the reference radio waves received by the two or more receivers. [Effects of the Invention]

[0027] According to the position specifying device and the like according to one aspect of the present invention, it is possible to detect a malfunction in a receiver that receives a reference radio wave by using the reception results of the reference radio wave by two or more receivers. [Brief explanation of the drawings]

[0028] [Figure 1]FIG. 1 is a block diagram showing the configuration of a location specifying device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view showing an example of the placement of receivers in the embodiment. [Figure 3] A flowchart showing the operation of the position specifying device according to the embodiment. [Figure 4] FIG. 2 shows an example of the configuration of a computer system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, a location determination device and a location determination method according to the present invention will be described using embodiments. Note that in the following embodiments, components and steps denoted with the same reference numerals are the same or equivalent, and repeated description may be omitted. The location determination device according to this embodiment determines the location of a terminal device based on the difference in intensity of radio waves transmitted from the terminal device and received by two or more receiver sets, each having one or more receivers, and detects a malfunction of the receiver using the reception result of a reference radio wave transmitted via the antenna of one of the receivers via an antenna located at a different position from the position of that antenna.

[0030] Fig. 1 is a block diagram showing the configuration of a position determining device 1 according to this embodiment, and Fig. 2 is a plan view showing an example of the arrangement of receivers. The position determining device 1 according to this embodiment receives radio waves transmitted from a terminal device 2 carried by a user 3 and determines the position of the terminal device 2, and includes a first receiver set 11, a second receiver set 12, an identification unit 13, a detection unit 14, and an output unit 15.

[0031] 1 illustrates a situation in which the user 3 is holding the terminal device 2 in his / her hand, the user 3 carrying the terminal device 2 may mean, for example, that the terminal device 2 moves in accordance with the movement of the user 3, and the user 3 does not necessarily have to be holding the terminal device 2 in his / her hand. The terminal device 2 may be placed in, for example, a pocket or a bag of the user 3's clothes. Also, while FIG. 1 illustrates a case in which the position identification device 1 receives radio waves from one terminal device 2 carried by one user 3, the position identification device 1 may receive radio waves from, for example, multiple terminal devices 2 carried by multiple users 3.

[0032] The terminal device 2 may be, for example, a mobile information terminal with a communication function, such as a smartphone, a tablet terminal, a PDA (Personal Digital Assistant), a notebook computer, or a transceiver, or may be other devices. The terminal device 2 transmits radio waves. The radio waves transmitted by the terminal device 2 may include, for example, a user identifier that identifies the user 3 carrying the terminal device 2. The user identifier may be, for example, the user's telephone number, an address such as an email address, or a name, or may be a character string unique to the user. Furthermore, a device identifier that identifies the terminal device 2 may be used as the user identifier of the user carrying the terminal device 2. The terminal identifier may be, for example, a device address or a character string unique to the device. The device address may be, for example, a physical address such as a MAC address, or other addresses.

[0033] The first receiver set 11 includes one or more receivers that receive radio waves transmitted from a terminal device 2 carried by a user 3. Each of the one or more receivers may have an antenna and may receive the radio waves transmitted from the terminal device 2 using that antenna. The first receiver set 11 may be located, for example, at a first receiving position. The one or more receivers included in the first receiver set 11 each receive radio waves using a different antenna. The antennas of the one or more receivers included in the first receiver set 11 may be located, for example, in a single location, or may be located in two or more separate locations.

[0034] The second receiver set 12 includes one or more receivers that receive radio waves transmitted from a terminal device 2 carried by a user 3. Each of the one or more receivers may have an antenna and may use that antenna to receive the radio waves transmitted from the terminal device 2. The second receiver set 12 may be located, for example, at a second receiving position different from the first receiving position. The one or more receivers included in the second receiver set 12 each receive radio waves using a different antenna. The antennas of the one or more receivers included in the second receiver set 12 may be located, for example, in a single location, or may be located in two or more separate locations. The second receiver set 12 may be similar to the first receiver set 11 except for the locations at which they are located.

[0035] At least one of the first and second receiver sets 11 and 12 includes a transmitter that transmits a reference radio wave using at least one antenna of one or more receivers. The reference radio wave is a radio wave transmitted to detect malfunctions in the receiver. In other words, the reference radio wave can be considered a radio wave used to test for malfunctions in the receiver. By having the transmitter transmit the reference radio wave using the receiver's antenna, a separate antenna for transmitting the reference radio wave is not required, allowing for effective use of existing facilities. The reference radio wave transmitted by the transmitter is received by an antenna other than the antenna used to transmit the reference radio wave. Note that malfunction detection may use the reception strength of the reference radio wave received by two or more receivers using antennas located at positions different from the antenna used to transmit the reference radio wave. These two or more receivers are the two or more receivers included in the first and second receiver sets 11 and 12. Malfunction detection using the reception strength of the reference radio wave will be described later. Note that the transmitter may transmit, for example, multiple reference radio waves of different intensities.

[0036] From the viewpoint of realizing more accurate location identification of the terminal device 2, it is preferable that the first receiver set 11 includes multiple receivers, and it is preferable that the second receiver set 12 includes multiple receivers. As shown in FIG. 1, for example, the first receiver set 11 may include eight receivers 21a-21h, and the second receiver set 12 may include eight receivers 22a-22h, but the number of receivers included in the first and second receiver sets 11 and 12 may be any number from one to seven, or may be nine or more. Note that when the multiple receivers 21a-21h are not particularly distinguished, they may also be referred to as receivers 21. The same applies to other configurations. It is assumed that each of the receivers 21 and 22 included in the first and second receiver sets 11 and 12 is capable of acquiring the strength of received radio waves.

[0037] 1, the first receiver set 11 may include one transmitter 31, and the second receiver set 12 may include one transmitter 32. In this embodiment, the transmitter 31 transmits the reference radio wave using the antenna of the receiver 21a, and the transmitter 32 transmits the reference radio wave using the antenna of the receiver 22a. In this case, for example, the receiver 21a and the transmitter 31 may constitute one communication device that transmits and receives radio waves via one antenna, and the receiver 22a and the transmitter 32 may constitute one communication device that transmits and receives radio waves via one antenna.

[0038] If the first receiver set 11 includes multiple receivers 21, the first receiving position may be, for example, the position of the center of gravity of multiple antennas for the multiple receivers 21. More specifically, the position of the antenna for each receiver 21 may be identified, and the center of gravity of the identified multiple antenna positions may be set as the first receiving position. The multiple antennas of the multiple receivers 21 may be located close to each other, or may be located far apart. Even in the latter case, it is preferable that the multiple antennas of the multiple receivers 21 are located within a range from the first receiving position to the second receiving position. The same applies to the second receiving position of the second receiver set 12.

[0039] The receivers 21 and 22 may or may not include a wireless receiving device such as an antenna for receiving radio waves. The receivers 21 and 22 may be realized by hardware or software such as a driver that drives the receiving device.

[0040] The transmitters 31 and 32 may or may not include a wireless transmitting device for transmitting radio waves. The transmitters 31 and 32 may be realized by hardware or software such as a driver that drives a receiving device.

[0041] As shown in FIG. 2 , for example, the first receiver set 11 may be arranged upstream of the gate 5 in the direction of movement of the user 3, and the second receiver set 12 may be arranged downstream of the gate 5 in the direction of movement of the user 3. That is, in FIG. 2 , if the user 3 moves from left to right, the first receiver set 11 may be arranged on the left side of the gate 5, and the second receiver set 12 may be arranged on the right side of the gate 5. Note that in FIG. 2 , the direction of movement of the user 3 is assumed to be from left to right, as indicated by the arrow. In FIG. 2 , the gate 5 has partition plates 51 and 52, and the user 3 passes through a passage partitioned by the partition plates 51 and 52. The positions of the receivers 21 and 22 shown in FIG. 2 etc. may be the positions of antennas used by the receivers 21 and 22 to receive radio waves. In Figure 2, the position of the center of gravity of the antennas of receivers 21a to 21h included in the first receiver set 11 is the first receiving position P1, and the position of the center of gravity of the antennas of receivers 22a to 22h included in the second receiver set 12 is the second receiving position P2.

[0042] The position determining device 1 according to this embodiment will be mainly described in terms of determining the position of a terminal device 2 carried by a user 3 passing through a gate 5, for example. However, it goes without saying that the position determining device 1 may also determine the position of a terminal device 2 at a location other than a gate 5. The position determining device 1 may determine the position of the terminal device 2 near, for example, a vending machine, the door of a hotel or a rental conference room, a cash register, etc. The gate 5 may be, for example, an automatic ticket gate at a station or the like, or a security gate through which a user passes when entering or exiting a building, company, event venue, etc. Furthermore, the user 3 passing through the gate 5 may be, for example, a user 3 near the gate 5, such as a user 3 approaching the gate 5, a user 3 passing through the gate 5, or a user 3 exiting the gate 5.

[0043] 2, the following description will be given mainly of a case in which receivers 21a-21d included in first receiver set 11 are arranged at a first position L1, receivers 21e-21h included in first receiver set 11 are arranged at a second position L2, receivers 22a-22d included in second receiver set 12 are arranged at a third position L3, and receivers 22e-22h included in second receiver set 12 are arranged at a fourth position L4. Also, it is assumed that transmitter 31 included in first receiver set 11 is arranged at the first position L1, and transmitter 32 included in second receiver set 12 is arranged at the second position L2. That is, in this embodiment, four receiver antennas are arranged at each of positions L1-L4, and radio waves are received using the antennas arranged at the four positions L1-L4, and reference radio waves are transmitted using antennas arranged at different positions L1 and L3. 2, for the sake of convenience, the receivers 21a to 21d placed at the first position L1 appear to be in different positions, but it is preferable that they are close enough to be considered to be in substantially the same position. The same is true for the receivers 21 and 22 placed at the other positions L2 to L4.

[0044] The radio waves transmitted from the terminal device 2 may be, for example, pulse waves transmitted intermittently or continuous waves transmitted continuously. Furthermore, any wireless communication standard may be used to transmit and receive the radio waves. For example, the radio waves may be communicated using Bluetooth Low Energy (BLE), Bluetooth Basic Rate (BR) / Enhanced Data Rate (EDR), wireless LAN (IEEE802.11), IEEE802.15.4 such as ZigBee (registered trademark), or other wireless communication standards. It is preferable that the radio waves be transmitted and received using short-range wireless communication such as BLE, Bluetooth BR / EDR, or wireless LAN.

[0045] The frequency of the radio waves is not particularly limited, and may be, for example, a frequency in the range of 300 MHz to 300 GHz. Furthermore, the terminal device 2 may transmit radio waves by broadcast or unicast, for example. Broadcast radio waves are preferable because they can be transmitted without specifying a communication partner. In this embodiment, a case where the terminal device 2 transmits radio waves by broadcast will be mainly described. It is preferable that the terminal device 2 transmits radio waves without receiving a transmission instruction from the user 3. The terminal device 2 may transmit radio waves in response to receiving a predetermined beacon, for example. In response to receiving this beacon, the terminal device 2 may transmit radio waves only once, or for a predetermined period of time, or may continuously transmit radio waves while receiving this beacon. This beacon may be transmitted so as to be received by the terminal device 2 of the user 3 approaching the gate 5, for example. As an example, the positioning device 1 may transmit a beacon. In this case, the positioning device 1 may further include a transmitting unit for transmitting the beacon.

[0046] The terminal device 2 may or may not be in line of sight from the position identification device 1. In the latter case, the user 3 may carry the terminal device 2 in, for example, a pocket of clothes or a bag.

[0047] The identification unit 13 identifies the location of the terminal device 2 based on the difference in strength of radio waves transmitted from the terminal device 2 and received by the first and second receiver sets 11, 12, respectively. The difference in strength of the radio waves may be, for example, the difference in received signal strength (RSSI: Received Signal Strength Indicator) of the radio waves. Furthermore, when the first and second receiver sets 11, 12 include two or more receivers 21, 22, the difference in strength may be, for example, the difference between representative values ​​of multiple received signal strengths acquired by the two or more receivers 21, 22 in the first and second receiver sets 11, 12, respectively. That is, the difference between the representative value of the received signal strengths acquired by the multiple receivers 21 and the representative value of the received signal strengths acquired by the multiple receivers 22 may be used as the difference in strength of the radio waves. The representative value may be, for example, an average value, a median value, or the like. Furthermore, when the first receiver set 11 includes two or more receivers 21, it is preferable that the two or more receivers 21 have equivalent performance. For example, it is preferable that the antenna gains of the two or more receivers 21 included in the first receiver set 11 are the same. The same applies when the second receiver set includes two or more receivers 22. When identifying the position of the wave source using the difference in intensity of the received radio waves, for example, an Apollonius circle or line corresponding to the difference in reception intensity may be identified using the reception intensity of the radio waves received by the first and second receiver sets 11, 12 and the first and second reception positions, which are the positions of the first and second receiver sets 11, 12, and a position on the Apollonius circle, line, or within the circle may be identified as the position of the terminal device 2, or the position of the terminal device 2 may be identified by other methods.

[0048] Furthermore, the position identified by the identification unit 13 may be, for example, a point-like position, or a linear, planar, or three-dimensional position. In this embodiment, a case where a planar position of the terminal device 2 is identified by the identification unit 13 will be mainly described. The identified position may be, for example, a position on a two-dimensional plane, or a position in three-dimensional space. In this embodiment, the former case will be mainly described.

[0049] Note that identifying the location of a wave source using the difference in reception intensity of radio waves is already known, and detailed description thereof will be omitted. For example, see Patent Document 1 above for a method of identifying the location of such a wave source. Furthermore, when multiple users 3 carrying terminal devices 2 pass through a gate 5, radio waves from the multiple terminal devices 2 are received by the first and second receiver sets 11 and 12. In this case, the identification unit 13 may identify the location of one terminal device 2 using the difference in intensity of radio waves transmitted from the terminal device 2 and received by the first and second receiver sets 11 and 12. Therefore, for example, the identification unit 13 may identify the location of the terminal device 2 carried by a user 3 identified by the user identifier using the difference in intensity of radio waves containing the same user identifier among the radio waves received by the first and second receiver sets 11 and 12.

[0050] The identification unit 13 may determine whether the terminal device 2 is included in a predetermined region R1 of the gate 5 shown in FIG. 2 based on, for example, a comparison result between the difference in strength of the radio waves received by the first and second receiver sets 11 and 12 and a predetermined threshold. In this case, for example, when the difference in strength, which is the result of subtracting the received signal strength of the radio waves received by the second receiver set 12 from the received signal strength of the radio waves received by the first receiver set 11, is greater than the predetermined threshold, the region R1 may be identified as the location of the terminal device 2 that transmitted the radio waves. The region R1 may be an area within the Apollonius circle described above. The predetermined threshold may be a predetermined value, for example, 10 dB.

[0051] The detection unit 14 detects a malfunction of a receiver that received the reference radio wave based on the reception strength of the reference radio wave received by two or more receivers. The two or more receivers are two or more receivers that use antennas located at positions different from the antenna used to transmit the reference radio wave. For example, if the reference radio wave is transmitted from an antenna located at a first position L1, a malfunction of the receiver that received the reference radio wave may be detected based on the reception strength of the reference radio wave received by receivers using antennas located at second to fourth positions L2 to L4. The receiver malfunction may be, for example, a malfunction or deterioration of the receiver, and may be a state in which the correct reception strength of the radio wave cannot be obtained to the extent that the location of the terminal device 2 cannot be accurately determined using the radio wave. The receiver malfunction may be, for example, a malfunction of the receiver circuit or antenna, or other malfunction related to the receiver. The reception strength may be, for example, the received signal strength.

[0052] The reception strength of the reference radio wave received by each receiver may be, for example, a time average of the reception strength. Normally, the reception strength of the reference radio wave fluctuates over time, but by taking the time average, it converges to a constant value. Therefore, it is preferable that the time average of the reception strength of the reference radio wave acquired by each receiver is a time average over a period of time in which the reception strength converges to a constant value. Furthermore, the reception strength of the reference radio wave in the following description may be, for example, a time average of the reception strength of the reference radio wave.

[0053] The detection unit 14 may, for example, detect a malfunction in two or more receivers using antennas located in the same position, or in two or more receivers using antennas located in two or more positions. In this case, it is not necessary to identify which receiver has a malfunction. Note that, since multiple antennas cannot be located in the same position in the strict sense, antennas located in the same position may refer to antennas located close enough to be considered to be in substantially the same position. Alternatively, the detection unit 14 may detect a malfunction in, for example, one receiver. In this case, the receiver in which the malfunction exists will be identified. Next, a specific description will be given of a method for detecting a receiver malfunction by the detection unit 14.

[0054] (1) Detecting malfunctions related to receivers using co-located antennas The detector 14 may detect a malfunction by comparing the reception strength of a reference radio wave received by two or more receivers that receive radio waves using antennas located at the same location. In this case, the first and second receiver sets 11, 12 may include two or more receivers that use antennas located at the same location.

[0055] (1-1) Detecting defects using maximum and minimum reception strength For example, the detection unit 14 may detect a malfunction in two or more receivers using antennas located at the same location if the absolute value of the difference between the maximum and minimum reception intensities of the reference radio wave received by those receivers is greater than a predetermined threshold. Normally, when a reference radio wave is received at the same location, the reception intensities of the reference radio wave are considered to be the same. However, if the absolute value of the difference between the maximum and minimum reception intensities is greater than the threshold, it is considered that a malfunction has occurred in at least one of the two or more receivers. Therefore, the threshold may be set to a positive real number greater than the absolute value of the difference between the maximum and minimum reception intensities when the reference radio wave is received by two or more normal receivers using antennas located at the same location. This malfunction can be detected when there are two or more receivers using antennas located at the same location.

[0056] For example, when a reference radio wave is transmitted from the transmitter 31 from the first position L1 and the reception strength of the reference radio wave is acquired by the receivers 21e-21h at the second position L2, the detector 14 may identify the maximum and minimum reception strengths of the four receivers 21e-21h and determine whether the absolute value of the difference between the maximum and minimum reception strengths is greater than a threshold. If the absolute value of the difference between the maximum and minimum reception strengths is greater than the threshold, the detector 14 may detect a malfunction in the receivers 21e-21h; otherwise, the detector 14 may not detect a malfunction. Similar malfunction detection may be performed for the third and fourth positions L3 and L4.

[0057] (1-2) Detecting defects using outliers in reception strength As another example, the detection unit 14 may detect a malfunction of a receiver corresponding to an outlier identified in the reception strength of a reference radio wave received by three or more receivers that receive radio waves using antennas located in the same position. In this case, the first and second receiver sets 11 and 12 may include three or more receivers using antennas located in the same position. The receiver corresponding to the outlier is the receiver whose reception strength of the reference radio wave is the outlier. The detection unit 14 may, for example, calculate the average value μ and standard deviation σ of the reception strength of the reference radio wave received by three or more receivers, and determine that the reception strength of the reference radio wave of a receiver among the three or more receivers is not an outlier if it is within the range μ±A×σ, and determine that the reception strength of the reference radio wave of a receiver that is not within that range is an outlier, where A is a positive real number. That is, the detection unit 14 may, for example, determine that the reception strength of the reference radio wave that satisfies the following relationship is not an outlier. μ-A×σ≦Reference radio wave reception strength≦μ+A×σ

[0058] On the other hand, the detection unit 14 may determine that the reception strength of the reference radio wave that satisfies any of the following relationships is an outlier. Reference radio wave reception strength < μ-A × σ Reference radio wave reception strength > μ + A × σ

[0059] Note that the reception strength of the reference radio wave that is equal to μ-A×σ or μ+A×σ may be determined to be an outlier, for example. The constant A may be, for example, a value greater than or equal to 1, 2 or 3. Furthermore, the constant A may be, for example, a value less than or equal to 6, 5 or 4. As an example, the constant A may be a real number ranging from 1.5 to 3. When A=3, that is, when the reception strength of the reference radio wave is determined to be not an outlier if it is within the range of μ±3σ, assuming that the reception strength follows a normal distribution, 99.7% of the reception strengths are determined to be not outliers. Therefore, it is considered that the possibility that a value determined to be an outlier by the detection unit 14 is not actually an outlier is significantly low. Note that the same method may be used to identify other outliers.

[0060] For example, when a reference radio wave is transmitted from the transmitter 31 from a first position L1 and the reception strength of the reference radio wave is acquired by the receivers 21e to 21h at a second position L2, the detection unit 14 may calculate the average value μ and standard deviation σ of the reception strengths of the four receivers 21e to 21h. Then, an outlier reception strength may be identified by determining whether each reception strength is within the range μ±A×σ. As an example, assume that the reception strength of the receiver 21e is an outlier. Then, the detection unit 14 detects a malfunction of the receiver 21e corresponding to the outlier. Similar malfunction detection may be performed for the third and fourth positions L3 and L4.

[0061] By detecting a malfunction as in (1-1) or (1-2), it is possible to detect a malfunction regardless of the transmission strength of the reference radio wave. Therefore, even if a malfunction occurs in the transmitter or the antenna used by the transmitter and the transmitter is unable to transmit a reference radio wave of a predetermined strength, the malfunction can be detected.

[0062] (2) Detection of malfunctions related to receivers using antennas located at two or more positions The detector 14 may detect a malfunction based on the reception strength of a reference radio wave received using an antenna at two or more positions different from the position of the antenna used to transmit the reference radio wave by the transmitter. In this case, the first and second receiver sets 11, 12 may include receivers that receive radio waves using antennas located at three or more positions. More strictly, the reception strength of the reference radio wave received using an antenna may refer to the reception strength of the reference radio wave received by the receiver using that antenna.

[0063] (2-1) Detecting defects using outliers in reception strength For example, the detection unit 14 may detect a malfunction of a receiver corresponding to an outlier identified using the reception strength of a reference radio wave received using antennas at two or more locations different from the location of the antenna used to transmit the reference radio wave by the transmitter and a reference value of the intensity difference between the radio waves received at those two or more locations. In this case, it is preferable that there are three or more receivers that receive radio waves using antennas at two or more locations different from the location of the antenna used to transmit the reference radio wave. The reference value of the intensity difference may be an ideal value for the intensity difference, which is the difference between the reception strength of a reference radio wave received by an antenna at one location and the reception strength of a reference radio wave received by an antenna at another location, i.e., the intensity difference of the reference radio wave received by a malfunction-free receiver. The reference value of the intensity difference may be, for example, a theoretically calculated value or a value obtained by an experiment using a malfunction-free receiver. In the latter case, for example, the intensity difference of the reference radio wave obtained by receiving the reference radio wave transmitted from the transmitter using receivers at two or more locations different from the transmitter at the time of shipping or starting operation of the position determination device 1 may be used as the reference value of the intensity difference. This is because there is a high possibility that no malfunctions will occur in the receivers at the time of shipment or when operation begins. Here, the reference value for the intensity difference can be calculated, for example, using the following formula: D1 is the distance from the transmitter antenna to the antenna of one receiver, and D2 is the distance from the transmitter antenna to the antenna of the other receiver. Reference value of intensity difference = -20log10 (D1 / D2)

[0064] By using the reference value of the intensity difference, the reception strength of the reference radio wave received by an antenna at one location can be converted into the reception strength of the reference radio wave received by an antenna at another location, making it possible to compare the reception strengths of the reference radio wave received by antennas located at different locations. For example, if the reference value of the intensity difference between the first and second locations L1 and L2 is used to convert the reception strength of the reference radio wave received by receiver 21a at first location L1 into the reception strength of the reference radio wave received at second location L2, the reception strength after conversion will be the reception strength of the reference radio wave received by receiver 21a at second location L2 if receiver 21a is located at second location L2.

[0065] The detector 14 may, for example, use a reference value for the intensity difference to convert the reception strength of a reference radio wave received at one location into the reception strength of a reference radio wave received at another location, and then identify an outlier using the result and the reception strength of the reference radio wave received at the converted location, and determine that the receiver corresponding to the outlier has a malfunction. That is, the detector 14 may, for example, use the reception strength of reference radio waves received using antennas at two or more locations different from the antenna used to transmit the reference radio wave by the transmitter, and a reference value for the intensity difference between the radio waves received at those two or more locations, to identify the reception strength of multiple reference radio waves received using an antenna at one location, identify an outlier in the reception strength of the identified multiple reference radio waves, and detect a malfunction of the receiver corresponding to the identified outlier. By identifying outliers in this way, even if there are not many reception results at one location, the reception results from multiple locations can be merged, making it possible to identify outliers using more reception strengths, thereby more appropriately identifying outliers. Furthermore, for example, if there are two receivers located at one location, it is not possible to identify an outlier using only the reception results at that location, but it becomes possible to identify an outlier by merging the reception results from two or more locations. Identification of an outlier may be performed in the same manner as in (1-2), for example.

[0066] For example, when a reference radio wave is transmitted from the first location L1 by the transmitter 31 and the reception strength of the reference radio wave is acquired by the receivers 21e-21h and 22a-22d at the second and third locations L2 and L3, the detection unit 14 may convert the reception strength of the receivers 22a-22d at the third location L3 to the reception strength at the second location L2 using a reference value of the difference in strength between the second and third locations L2 and L3. The detection unit 14 then calculates the average value μ and standard deviation σ of the reception strengths of the receivers 21e-21h and the converted reception strengths of the receivers 22a-22d. The detection unit 14 also determines whether each reception strength is within a range of A×σ from the average value μ. As an example, suppose the reception strength of the receiver 21e is an outlier. The detection unit 14 then detects a malfunction of the receiver 21e corresponding to the outlier. Similarly, for the reception strength of the reference radio waves acquired by the receivers 21e to 21h, 22e to 22h at the second and fourth positions L2, L4, outlier detection may be performed using a reference value of the difference in strength between the second and fourth positions L2, L4.

[0067] (2-2) Detecting defects using outliers in intensity differences As another example, the detection unit 14 may detect a malfunction of a receiver corresponding to an outlier identified in the intensity difference of a reference radio wave received using an antenna at two or more locations different from the location of the antenna used to transmit the reference radio wave by the transmitter. In this case, it is preferable that, for example, two or more receivers are provided for each location of the antenna receiving the reference radio wave. In this case, the detection unit 14 may, for example, calculate the intensity differences corresponding to all combinations of the reception intensity of a reference radio wave received by multiple receivers at one location and the reception intensity of a reference radio wave received by multiple receivers at another location, identify outliers for the multiple intensity differences, and determine that the receiver corresponding to the identified outlier is malfunctioning. For example, if a receiver is malfunctioning, all intensity differences calculated using the reception intensity obtained by the malfunctioning receiver are considered to be outliers. Therefore, multiple outliers are usually identified. Therefore, a malfunction may be detected in the receiver corresponding to the multiple outliers. The receiver corresponding to the multiple outliers may, for example, be the receiver that obtained the reception intensity used to calculate all of the multiple intensity differences that are the multiple outliers.

[0068] For example, when a reference radio wave is transmitted from a first position L1 by the transmitter 31 and the reception intensities of the reference radio wave are acquired by the receivers 21e-21h and 22a-22d at the second and third positions L2 and L3, the detection unit 14 may calculate the intensity differences for all combinations of the receivers 21e-21h and the receivers 22a-22d, i.e., 16 combinations, and identify outliers among the intensity differences. Then, for example, if all the intensity differences related to the receiver 21e are outliers, the detection unit 14 may detect a malfunction of the receiver 21e. The intensity differences related to a certain receiver may be intensity differences calculated using the reception intensities of that receiver. For example, if all the intensity differences related to receiver 21e are outliers, i.e., if the intensity differences of the reference radio waves between receiver 21e and receiver 22a, between receiver 21e and receiver 22b, between receiver 21e and receiver 22c, and between receiver 21e and receiver 22d are all outliers, receiver 21e may be determined to have a malfunction. For example, if the absolute value of the difference between the calculated intensity difference and the reference value of the intensity difference is greater than a threshold, the calculated intensity difference may be determined to be an outlier. The threshold may be a predetermined positive real number. The threshold may be set, for example, to a value obtained by multiplying the standard deviation of the intensity differences calculated based on experimental results by the constant A described above. Furthermore, the outlier of the intensity difference of the reference radio waves may be identified in the same manner as in (1-2), for example, without using the reference value of the intensity difference. In this case, it is preferable, for example, to have three or more receivers for each position of the antenna receiving the reference radio waves. Similarly, for the reception strength of the reference radio waves acquired by the receivers 21e to 21h, 22e to 22h at the second and fourth positions L2, L4, defects may be detected using outliers in the intensity difference between the second and fourth positions L2, L4.

[0069] By detecting a malfunction as in (2-1) or (2-2), it is possible to detect a malfunction regardless of the transmission strength of the reference radio wave. For example, this is because the difference in the strength of the reference radio wave does not depend on the transmission strength of the reference radio wave. Therefore, even if a malfunction occurs in the transmitter or the antenna used by the transmitter and the transmitter is unable to transmit a reference radio wave of the predetermined strength, it is possible to detect the malfunction.

[0070] Furthermore, detection of a malfunction other than (2-1) or (2-2) may also be performed. For example, the detection unit 14 may use the reception strength of a reference radio wave received using an antenna at two or more positions different from the position of the antenna used in transmitting the reference radio wave by the transmitter and a reference value of the difference in strength of the radio waves received at the two or more positions to identify the reception strength of multiple reference radio waves received using an antenna at one position, and perform detection of a malfunction of (1-1) for the reception strength of the multiple reference radio waves. In this case, for example, even if there is only one receiver at each of two or more positions different from the position of the antenna used in transmitting the reference radio wave, it is possible to detect a malfunction of the receiver.

[0071] (3) Detecting defects using representative values ​​of reception strength In the above (1) and (2), we have described the case where a malfunction is detected using the reception strength of the reference radio wave for each receiver, but a receiver malfunction may also be detected using a representative value of the reception strength of the reference radio wave for multiple receivers. In this case, it is determined that one of two or more receivers has a malfunction, but it is not determined which receiver has the malfunction. The representative value may be, for example, an average value or a median value.

[0072] For example, the detection unit 14 may compare a representative value of the reception strength of the reference radio wave received by multiple receivers using antennas located at the same location with a reference value of the reception strength of the reference radio wave at that location, and detect a malfunction in the multiple receivers if the absolute value of the difference between the representative value and the reference value is greater than a threshold. The multiple receivers may, for example, include all receivers using antennas located at the same location. The threshold may be a predetermined positive real number. In this case, a malfunction exists in at least one of the multiple receivers for which a malfunction has been detected. In this case, even if some of the multiple receivers using antennas located at the same location have malfunctioned, such as deterioration, as long as the absolute value of the difference between the representative value of the reception strength of the reference radio wave and the reference value does not exceed the threshold, there is no problem in identifying the location of the terminal device 2, and the multiple receivers can continue to be used.

[0073] As another example, the detection unit 14 may detect a malfunction in multiple receivers related to the intensity difference when the absolute value of the difference between the intensity difference of reference radio waves received using antennas at two or more locations different from the antenna location used to transmit the reference radio wave by the transmitter and the reference value of the intensity difference is greater than a threshold. The intensity difference of the reference radio waves may be, for example, the difference between a representative value of the reception intensity of the reference radio wave received by multiple receivers using an antenna at one location and a representative value of the reception intensity of the reference radio wave received by multiple receivers using an antenna at another location. Furthermore, the multiple receivers related to the intensity difference may be multiple receivers that acquired the reception intensity of the reference radio wave used to calculate the intensity difference. In this case, a malfunction is detected in at least one of the multiple receivers for which a malfunction has been detected. The multiple receivers using an antenna at one location may be, for example, all receivers using antennas located at that location. Furthermore, when detecting a malfunction by comparing the intensity difference between the representative value of the reception strength of the reference radio wave with the reference value of the intensity difference in this way, even if a malfunction such as deterioration occurs in some of multiple receivers using antennas located at the same location, as long as the absolute value of the difference between the intensity difference between the representative value of the reception strength of the reference radio wave and the reference value of the intensity difference does not exceed a threshold, there will be no problem in identifying the location of the terminal device 2, and the multiple receivers can be continued to be used. Also, even if a malfunction such as deterioration occurs in all of multiple receivers using antennas at one location and multiple receivers using antennas at another location, there will be no problem in identifying the location of the terminal device 2, and the multiple receivers using antennas at those two locations can be continued to be used.

[0074] To calculate the time average of the reception strength of the reference radio wave received by one receiver, it is necessary to calculate the time average over a predetermined period. On the other hand, when the reception strength of the reference radio wave is received by multiple receivers using multiple antennas placed in the same location, the representative value of the reception strength of the reference radio wave received by the multiple receivers usually converges in a period shorter than the predetermined period. Therefore, it is thought that by detecting a malfunction using the representative value of the reception strength of the reference radio wave as in (3), it will be possible to detect a malfunction in a shorter time.

[0075] If the first and second receiver sets 11 and 12 each include two or more transmitters, the detector 14 may detect a malfunction using a reference radio wave transmitted from each of the two or more transmitters. The two or more transmitters may transmit reference radio waves using antennas located at different positions. For example, if the first receiver set 11 includes a transmitter 31 and the second receiver set 12 includes a transmitter 32, the detector 14 may detect a malfunction using the reference radio wave transmitted from the transmitter 31 and also using the reference radio wave transmitted from the transmitter 32. As an example, the reference radio wave transmitted from the transmitter 31 may be used to detect a malfunction in the receivers using antennas located at the second to fourth positions L2 to L4, and the reference radio wave transmitted from the transmitter 32 may be used to detect a malfunction in the receivers using antennas located at the first, second, and fourth positions L1, L2, and L4.

[0076] The output unit 15 may perform output related to the position identified by the identification unit 13. The output unit 15 may, for example, output information indicating the position identified by the identification unit 13, or may perform other output related to the position identified by the identification unit 13. In the latter case, for example, when the identification unit 13 identifies a predetermined area, for example, area R1, as the position of the terminal device 2, the output unit 15 may output an instruction to perform processing to a device that performs processing accordingly.

[0077] The output unit 15 may also output, for example, the detection results obtained by the detection unit 14. For example, if a malfunction is detected in one or more receivers, a message to that effect may be output. In this case, the output information may include information identifying the receiver in which the malfunction was detected.

[0078] Here, this output may be, for example, a display on a display device (e.g., a liquid crystal display or an organic EL display), transmission to a predetermined device via a communication line, audio output by a speaker, storage in a recording medium, or delivery to another component. Note that output unit 15 may or may not include a device that performs output (e.g., a display device or a communication device). Also, output unit 15 may be realized by hardware, or may be realized by software such as a driver that drives such a device.

[0079] Next, a response when a malfunction is detected in a receiver will be described. As an example, when a malfunction is detected in one of two or more receivers that receive radio waves using antennas located at the same position, the identification unit 13 may identify the location of the terminal device 2 using the reception results of a receiver in which a malfunction is not detected among the two or more receivers. That is, the identification unit 13 may identify the location of the terminal device 2 using multiple receivers excluding the receiver in which a malfunction is detected. Note that, as the number of receivers using antennas located at a certain position decreases, the time until the reception strength of the reference radio waves converges increases accordingly. Therefore, when the location of the terminal device 2 is identified using the reception results of a receiver in which a malfunction is not detected, the location of the terminal device 2 may be identified using the reception results of a longer reception period by the receiver in which a malfunction is not detected. The longer reception period may be longer than when no malfunction is detected. In this way, when a receiver in which a malfunction is detected is not used for location identification, for example, information including information identifying the receiver in which a malfunction is detected may be output by the output unit 15. Then, for example, the receiver in which a malfunction is detected may be repaired or replaced depending on the output.

[0080] As another example, the identification unit 13 may identify the location of the terminal device 2 using the corrected reception strength obtained by adding a correction value to the reception strength of radio waves received by a receiver corresponding to an outlier. The receiver corresponding to the outlier may be a receiver identified as having a malfunction based on the outlier. The correction value is added to the reception strength of the receiver in which the malfunction was detected to adjust the reception strength of the radio waves received by the receiver in which the malfunction was detected to the reception strength of radio waves received by a normal receiver. For example, the correction value may be a value obtained by subtracting the reception strength of the outlier from an average value or a reference value. This correction value may be a positive or negative real number. Note that a correction value for the intensity difference can also be identified in a similar manner when an outlier is identified for the intensity difference. Furthermore, when the intensity difference is calculated by subtracting the reception strength B2 of another reference radio wave from the reception strength B1 of a reference radio wave acquired by the receiver in which the malfunction was detected, i.e., when the intensity difference = B1 - B2, the correction value for the intensity difference may be used as the correction value to be added directly to the reception strength of the radio waves received by the receiver in which the malfunction was detected. On the other hand, when the intensity difference is calculated by subtracting the reception strength B1 of the reference radio wave acquired by the receiver in which the malfunction has been detected from the reception strength B2 of another reference radio wave, i.e., when the intensity difference = B2 - B1, the value with the positive and negative signs of the correction value for the intensity difference reversed, i.e., the value obtained by multiplying the correction value for the intensity difference by (-1), may be used as the correction value to be added to the reception strength of the radio wave received by the receiver in which the malfunction has been detected.

[0081] Even if the transmission strength of the reference radio wave changes, if the degree of outlier deviation remains the same, the correction using the correction value described above can be performed. On the other hand, if the degree of outlier deviation changes depending on the change in the transmission strength of the reference radio wave, the correction using the correction value described above cannot be performed. Therefore, the identification unit 13 performs correction using the correction value when the degree of outlier deviations corresponding to multiple reference radio waves of different intensities are the same. Otherwise, if the degree of outlier deviations corresponding to multiple reference radio waves of different intensities are not the same, the identification unit 13 may not perform correction using the correction value. In the latter case, as described above, the receiver in which a malfunction is detected may not be used for location identification. Note that the multiple reference radio waves of different intensities may or may not include, for example, the reference radio wave used to detect the malfunction. Whether the degree of outlier deviations is the same may be determined, for example, by whether the variance or standard deviation calculated for the multiple outliers is smaller than a threshold, or by whether the absolute value of the difference between the maximum and minimum values ​​of the multiple outliers is smaller than a threshold. For example, if the absolute value of the variance, standard deviation, or difference between the maximum and minimum values ​​is smaller than a threshold, it may be determined that the degree of deviation of the outliers is the same, and if not, it may be determined that the degree of deviation of the outliers is not the same.

[0082] Furthermore, whether the degrees of outliers corresponding to multiple reference radio waves of different intensities are the same may be determined, for example, before or after the correction of the reception strength. If the determination is performed after the correction of the reception strength, for example, when no outliers exist for multiple reference radio waves of different intensities, it may be determined that the degrees of outliers corresponding to multiple reference radio waves of different intensities are the same, and when an outlier exists, it may be determined that the degrees of outliers corresponding to multiple reference radio waves of different intensities are not the same. In this embodiment, a case will be mainly described in which it is determined whether the degrees of outliers corresponding to multiple reference radio waves of different intensities are the same before the correction of the reception strength.

[0083] Next, the operation of the position identifying device 1 will be described with reference to the flowchart of Fig. 3. In the flowchart of Fig. 3, a case will be described in which the detecting unit 14 identifies an outlier and thereby detects a malfunction of the receiver.

[0084] (Step S101) The first and second receiver sets 11, 12 determine whether or not they have received radio waves transmitted from the terminal device 2. If they have received radio waves, the process proceeds to step S102; if not, the process proceeds to step S104.

[0085] (Step S102) The identification unit 13 identifies the location of the terminal device 2 using the radio waves received by the first and second receiver sets 11 and 12.

[0086] (Step S103) The output unit 15 outputs information relating to the identified position, and then the process returns to step S101.

[0087] (Step S104) The detection unit 14 determines whether or not to perform malfunction detection processing. If malfunction detection processing is to be performed, the process proceeds to step S105; if not, the process returns to step S101. The detection unit 14 may determine to perform malfunction detection processing, for example, when a predetermined time arrives. This time may be, for example, a time when the location of the terminal device 2 is not to be specified. As an example, if the gate 5 is an automatic ticket gate, the time when the location is not to be specified may be a time during the night when the automatic ticket gate is not in use.

[0088] (Step S105) The transmitter transmits a reference radio wave. The transmission of this reference radio wave may be performed under the control of the detection unit 14, for example.

[0089] (Step S106) Three or more receivers using antennas located at positions different from the position of the antenna used to transmit the reference radio wave receive the reference radio wave.

[0090] (Step S107) The detection unit 14 identifies outliers related to the reception strength of the reference radio wave received by three or more receivers. Note that the outliers may be, for example, outliers of the reception strength of the reference radio wave itself, or outliers of the intensity difference of the reception strength of the reference radio wave.

[0091] (Step S108) If an outlier is identified in step S107, the process proceeds to step S109, otherwise, that is, if there is no malfunction in the receiver, the process returns to step S101.

[0092] (Step S109) The detection unit 14 detects a malfunction of the receiver corresponding to the outlier. As an example, the detection unit 14 may store information identifying the receiver corresponding to the outlier in a recording medium (not shown). Furthermore, the output unit 15 may output information related to the malfunction of the receiver detected by the detection unit 14. As an example, information identifying the receiver in which the malfunction was detected may be output. Then, in response to the output, the receiver in which the malfunction was detected may be repaired or replaced.

[0093] (Step S110) The transmitter transmits a plurality of reference radio waves with different intensities. The transmission of these reference radio waves may also be performed under the control of the detection unit 14, for example.

[0094] (Step S111) Two or more receivers using antennas placed at positions different from the position of the antenna used to transmit the reference radio wave receive a plurality of reference radio waves with different intensities.

[0095] In the flowchart shown in FIG. 3, multiple reference radio waves are transmitted in step S110 and received in step S111, but strictly speaking, in steps S110 and S111, one reference radio wave is transmitted and the process of receiving that reference radio wave is repeated the same number of times as the number of reference radio waves.

[0096] (Step S112) The detection unit 14 identifies an outlier for each of the plurality of reference radio waves. That is, a plurality of outliers are identified.

[0097] (Step S113) The detection unit 14 determines whether the multiple outliers are similar, that is, whether the degree of outlier is the same. If the degree of outlier is the same, the process proceeds to step S114; if not, the process proceeds to step S115.

[0098] (Step S114) The detection unit 14 sets a correction value for the receiver in which a malfunction was detected in step S109. After setting this correction value, the identification unit 13 adds the correction value to the reception strength acquired by the receiver in which a malfunction was detected, and uses the result as the reception strength of that receiver. Then, the process returns to step S101.

[0099] (Step S115) The detection unit 14 sets the receiver in which a malfunction was detected in step S109 as a receiver that will not be used to identify the location of the terminal device 2. After this setting, the identification unit 13 identifies the location of the terminal device 2 without using the receiver in which a malfunction was detected. At that time, it is preferable that the identification unit 13 identifies the location of the terminal device 2 using reception results for a longer reception period for a receiver that uses an antenna in the same position as the antenna used by the receiver in which a malfunction was detected. Then, the process returns to step S101.

[0100] In the flowchart of FIG. 3, for example, if the first and second receiver sets 11 and 12 each include two or more transmitters, the processes of steps S105 to S115 may be repeated for each transmitter. For example, if the detection of a malfunction in (1-2) is performed for each antenna position, the processes of steps S107 to S109 may be repeated for each antenna position. For example, if the identification of a malfunction using the reception strength at the positions of two antennas is performed for each of two or more pairs of two antennas, as in (2-1) or (2-2), the processes of steps S107 to S109 may be repeated for each pair of two antennas. In the flowchart of FIG. 3, if malfunctions in multiple receivers are detected, the process of step S112 may be performed for each of the multiple receivers, and the processes of steps S113 to S115 may be performed for each receiver in which a malfunction is detected. Although the flowchart of FIG. 3 illustrates a case in which a receiver malfunction is detected by identifying an outlier, it goes without saying that receiver malfunctions may be detected by other methods. 3 is an example, and the order of the steps may be changed as long as the same results are obtained. In addition, in the flowchart of FIG. 3, the processing may be terminated by power-off or an interrupt to terminate the processing.

[0101] Next, the operation of the position identification device 1 according to this embodiment will be described using a specific example. In this specific example, the receivers 21 and 22 of the first and second receiver sets 11 and 12 and the transmitters 31 and 32 are respectively arranged at the gate 5 as shown in FIG.

[0102] First, assume that a user 3 carrying a terminal device 2 enters area R1 of the gate 5. Then, radio waves transmitted from the terminal device 2 are received by the receivers 21 and 22 of the first and second receiver sets 11 and 12, and the reception strength of the radio waves and the user identifier contained in the radio waves are passed to the identification unit 13 (step S101). Upon receiving the reception strengths, the identification unit 13 calculates a representative value of the reception strengths of the receivers 21 of the first receiver set 11 and a representative value of the reception strengths of the receivers 22 of the second receiver set 12, and calculates an intensity difference, which is the difference between the representative values ​​of the reception strengths. The identification unit 13 then compares the intensity difference with a predetermined threshold to determine whether the terminal device 2 is present in area R1, and passes the determination result and the user identifier received from the receiver to the output unit 15 (step S102). In this case, it is determined that the terminal device 2 is present in area R1. The output unit 15 then transmits the received user identifier and information indicating that the user 3 identified by the user identifier is present in the area R1 to the management device that manages the gate 5 (step S103). The management device references information associated with the received user identifier and determines whether the user 3 identified by the user identifier can pass through the gate 5. If the user 3 can pass through the gate 5, the management device allows the user 3 to pass through the gate 5. If the user 3 cannot pass through the gate 5, the management device may control the gate 5, for example, to close the door, to prevent the user 3 from passing through the gate 5.

[0103] Furthermore, when it is nighttime and gate 5 is not in use, the detection unit 14 determines to detect a malfunction and first transmits an instruction to the transmitter 31 to transmit a reference radio wave (step S104). Upon receiving the instruction, the transmitter 31 transmits the reference radio wave (step S105). The reference radio wave is received by each of the receivers 21 and 22 at the second to fourth positions L2 to L4, and the reception strengths thereof are acquired and transmitted to the detection unit 14 (step S106). Upon receiving the reception strengths, the detection unit 14 identifies outliers. Here, it is assumed that the outliers are identified by the above (1-2). Specifically, the detection unit 14 calculates the average value μ and the standard deviation σ using the reception strengths of the reference radio waves transmitted from the transmitter 31 and received by the receivers 21e to 21h at the second position L2. The detection unit 14 then determines whether each reception strength is within the range μ±A×σ. In this specific example, it is assumed that the reception strength of receiver 21e is an outlier (step S107). Then, detection unit 14 detects a defect in receiver 21e corresponding to the outlier (steps S108 and S109). Detection unit 14 may also perform similar defect detection for third and fourth positions L3 and L4, respectively (steps S107 to S109).

[0104] The detector 14 then sends an instruction to the transmitter 31 to transmit multiple reference radio waves of different intensities. Upon receiving this instruction, the transmitter 31 transmits multiple reference radio waves of different intensities, and the multiple reference radio waves are received by the receivers 21, 22 at the second to fourth positions L2 to L4, respectively, and the reception intensities are acquired and passed to the detector 14 (steps S110 and S111). Upon receiving the reception intensities, the detector 14 identifies an outlier for each reference radio wave for the receiver 21e in which a malfunction has been detected (step S112). In other words, multiple outliers are identified. Note that if malfunctions have been detected in other receivers besides the receiver 21e, outliers for each reference radio wave for those receivers may also be identified.

[0105] Furthermore, if the outliers for the receiver 21e in which a malfunction has been detected are determined to have the same degree of outlier, the detection unit 14 calculates a correction value, which is a value obtained by subtracting the outlier for the receiver 21e from the average value, and passes the correction value and information identifying the receiver 21e to the identification unit 13 (steps S113 and S114). The identification unit 13 may store the received set of the correction value and the information identifying the receiver 21e in a recording medium (not shown). Thereafter, when performing location identification, the identification unit 13 adds the correction value to the reception strength acquired by the receiver 21e and uses the result as the reception strength of the receiver 21e. Note that similar processing may be performed for other receivers in which a malfunction has been detected. Furthermore, for example, if the outliers for a certain receiver in which a malfunction has been detected are not the same degree of outlier, the detection unit 14 may pass information identifying the receiver and a message to the identification unit 13 that the receiver will not be used for location identification (step S115). The identification unit 13 may store the received information identifying the receiver in a recording medium (not shown). Thereafter, the identification unit 13 may identify the location without using the reception strength of the receiver identified by the information identifying that receiver. Note that, if the receiver not used to identify the location is, for example, the receiver 22a at the third position L3, the identification unit 13 may not use the reception strength of the receiver 22a to identify the location, and may acquire the reception strength at the third position L3 by lengthening the reception period of the radio waves transmitted from the terminal device 2 by the receivers 22b to 22d at the third position L3 longer than usual.

[0106] Similarly, detection of a malfunction in a receiver may be performed using the reference radio wave transmitted from the transmitter 32. Note that by using the transmitter 31, it is possible to detect malfunctions in each of the receivers 21, 22 at the second to fourth positions L2 to L4. Therefore, for example, detection of a malfunction in a receiver using the reference radio wave transmitted from the transmitter 32 may be performed only for the first position L1. As another example, detection of a malfunction in the receivers at the third and fourth positions L3, L4 may be performed using the reference radio wave transmitted from the transmitter 31, and detection of a malfunction in the receivers at the first and second positions L1, L2 may be performed using the reference radio wave transmitted from the transmitter 32.

[0107] As described above, the positioning device 1 according to this embodiment can use the reception result of the reference radio wave to detect a malfunction in the receiver that received the reference radio wave. Then, for example, a receiver in which a malfunction is detected can be repaired or replaced. Furthermore, by identifying outliers related to the reception strength of the reference radio wave or the difference in the strength of the reference radio wave, a malfunction in the receiver can be properly detected. Furthermore, by transmitting the reference radio wave using the antenna of the receiver, there is no need to install an additional antenna for transmitting the reference radio wave, and existing facilities can be effectively utilized. Furthermore, by using two or more transmitters to transmit the reference radio wave using antennas located in different positions, it becomes possible to determine, for example, whether there is a malfunction in all receivers.

[0108] Furthermore, by excluding receivers in which malfunctions have been detected and specifying the location of the terminal device 2, highly accurate location can be achieved. Furthermore, by performing correction using a correction value on a receiver in which malfunctions have been detected and specifying the location using the corrected reception strength, highly accurate location can also be achieved. Furthermore, when the degree of deviation of multiple outliers corresponding to multiple reference radio waves of different intensities is the same, correction using a correction value can be performed so that correction can be performed only on receivers in which reception strength correction is possible, and receivers in which correction is not effective can be prevented from being used for location determination without correction.

[0109] In this embodiment, as shown in FIG. 2, the first and second receiver sets 11 and 12 each include a transmitter 31, 32, but this is not necessarily the case. Only one of the first and second receiver sets 11 and 12 may include one or more transmitters. For example, only the first receiver set 11 may include one transmitter, or may include two transmitters. In the latter case, for example, the two transmitters may transmit reference radio waves via antennas at different positions, i.e., first and second positions L1 and L2.

[0110] In addition, in this embodiment, the detection unit 14 may detect a malfunction, for example, when the reception strength of the reference radio wave does not fall within a predetermined range for one receiver or for multiple receivers using antennas located in the same position.

[0111] Furthermore, in the present embodiment, when a malfunctioning receiver is detected, the malfunctioning receiver is not used to identify the location, or the location of the terminal device 2 is identified using the corrected reception strength obtained by adding a correction value to the reception strength of the radio waves received by the receiver corresponding to the outlier, but this is not necessarily the case. A malfunctioning receiver may be repaired or replaced without undergoing such processing.

[0112] Furthermore, in this embodiment, the location determination device 1 has been mainly described as having two receiver sets, i.e., first and second receiver sets 11 and 12. However, the location determination device 1 may have three or more receiver sets. That is, the location determination device 1 may have first to Nth receiver sets. The first to Nth receiver sets may be arranged at first to Nth receiving positions, respectively. N may be an integer greater than or equal to two. The first to Nth receiver sets may also be similar to the first and second receiver sets 11 and 12. For example, the Kth receiver set may include one or more receivers. K is an integer from 1 to N. It is preferable that the first to Nth receiving positions are different from each other. Furthermore, when N is three or more and location is determined by, for example, triangulation, it is preferable that the first to Nth positions do not lie on a single straight line. However, if this is not the case, the first to Nth positions may lie on a single straight line. Furthermore, when N is 4, for example, when the position is identified by triangular surveying or the like, it is preferable that the first to fourth positions do not become the vertices of a parallelogram. However, if this is not the case, the first to fourth positions may become the vertices of a parallelogram. In this way, when the position identification device 1 has first to N receiver sets, the identification unit 13 may identify the position of the terminal device 2 based on the intensity difference of the radio waves received by the first to N receiver sets. Note that this position identification may be performed, for example, by repeatedly identifying an Apollonius circle or line based on the intensity difference of the radio waves received by each of the two receiver sets for different combinations of two receiver sets among the first to N receiver sets, thereby identifying multiple Apollonius circles or lines, and identifying a position on the identified Apollonius circle, line, or within the circle as the position of the terminal device 2, or by other methods.

[0113] Furthermore, in the above embodiments, each process or function may be realized by centralized processing by a single device or a single system, or may be realized by distributed processing by multiple devices or multiple systems.

[0114] Furthermore, in the above embodiments, the transfer of information between components may be performed, for example, by one component outputting information and the other component receiving information if the two components transferring the information are physically different, or by moving from a processing phase corresponding to one component to a processing phase corresponding to the other component if the two components transferring the information are physically the same.

[0115] Furthermore, in the above-described embodiments, information related to the processing performed by each component, such as information accepted, acquired, selected, generated, transmitted, or received by each component, and information such as thresholds, formulas, and addresses used in processing by each component, may be temporarily or long-term stored in a recording medium (not shown), even if not explicitly stated in the above description. Furthermore, the storage of information in the recording medium (not shown) may be performed by each component or a storage unit (not shown). Furthermore, the reading of information from the recording medium (not shown) may be performed by each component or a reading unit (not shown).

[0116] Furthermore, in the above-described embodiments, if the information used by each component, such as thresholds, addresses, and various setting values ​​used by each component in processing, may be changed by the user, the user may or may not be able to change the information as appropriate, even if not explicitly stated in the above description. If the information is changeable by the user, the change may be realized, for example, by a receiving unit (not shown) that receives a change instruction from the user and a changing unit (not shown) that changes the information in accordance with the change instruction. The change instruction may be received by the receiving unit (not shown), for example, from an input device, by receiving information transmitted via a communication line, or by receiving information read from a predetermined recording medium.

[0117] Furthermore, in the above embodiment, when two or more components included in the position determination device 1 have a communication device, an input device, etc., the two or more components may physically have a single device, or may have separate devices.

[0118] Furthermore, in the above-described embodiments, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program. For example, each component may be realized by a program execution unit such as a CPU reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory. During execution, the program execution unit may execute the program while accessing a storage unit or recording medium. The software that realizes the position identification device 1 in the above-described embodiments is the following program. In other words, this program may cause a computer to execute the steps of receiving radio waves transmitted from a terminal device carried by a user using an antenna by first to Nth receiver sets (N is an integer greater than or equal to 2), each of which includes one or more receivers; determining the location of the terminal device based on the difference in strength of the radio waves transmitted from the terminal device and received by the first to Nth receiver sets; and providing output related to the determined location, wherein at least one of the first to Nth receiver sets includes a transmitter that transmits reference radio waves using at least one antenna of the one or more receivers, and the program may further cause the computer to execute the steps of transmitting the reference radio waves by the transmitter; receiving the reference radio waves by two or more receivers that use antennas located at positions different from the position of the antenna used to transmit the reference radio waves; and detecting a malfunction of the receiver that received the reference radio waves based on the reception strength of the reference radio waves received by the two or more receivers.

[0119] In the above program, the steps of receiving radio waves, transmitting radio waves, and outputting information do not include processing that is performed only by hardware, such as processing performed by a modem or interface card in the steps of receiving radio waves and transmitting radio waves. The steps of receiving radio waves by a receiver and transmitting radio waves by a transmitter may be steps of receiving radio waves and transmitting radio waves by controlling the receiver and transmitter, for example.

[0120] This program may be executed by being downloaded from a server or the like, or by being read from a predetermined recording medium (for example, an optical disk such as a CD-ROM, a magnetic disk, or a semiconductor memory). This program may also be used as a program constituting a program product.

[0121] Furthermore, the computer that executes this program may be a single computer or multiple computers, and may perform centralized processing or distributed processing.

[0122] 4 is a diagram showing an example of a computer system 900 that executes the above program to realize the position identification device 1 according to the above embodiment. The above embodiment can be realized by computer hardware and a computer program executed thereon.

[0123] 4, the computer system 900 includes an MPU (Micro Processing Unit) 911, a ROM 912 such as a flash memory that stores programs such as a boot-up program, application programs, system programs, and data, a RAM 913 connected to the MPU 911 and that temporarily stores instructions for the application program and provides temporary storage space, a touch panel 914, a wireless communication module 915, and a bus 916 that interconnects the MPU 911, the ROM 912, and the like. Note that the computer system 900 may include, for example, a plurality of wireless communication modules 915 corresponding to the first and second receiver sets 11 and 12, or may be connected to a plurality of wireless communication modules corresponding to the first and second receiver sets 11 and 12, and the like. The computer system 900 may also include a display and input devices such as a mouse and a keyboard instead of the touch panel 914. The computer system 900 may also include other recording media such as a hard disk.

[0124] A program that causes the computer system 900 to execute the functions of the position identification device 1 according to the above embodiment may be stored in the ROM 912 via the wireless communication module 915. The program is loaded into the RAM 913 when executed. The program may also be loaded directly from the network.

[0125] The program does not necessarily include an operating system (OS) or a third-party program that causes the computer system 900 to execute the functions of the position determination device 1 according to the above embodiment. The program may include only a portion of instructions that call appropriate functions or modules in a controlled manner to achieve a desired result. How the computer system 900 operates is well known, and a detailed description thereof will be omitted.

[0126] Furthermore, the above-described embodiments are merely examples for specifically implementing the present invention, and are not intended to limit the technical scope of the present invention. The technical scope of the present invention is defined by the claims, not by the description of the embodiments, and is intended to include modifications within the literal scope of the claims and within the scope of equivalent meanings. [Explanation of symbols]

[0127] 1 Locating device 11 First receiver set 12 Second receiver set 13 Specific section 14 Detector 15 Output section 21, 21a-21h, 22, 22a-22h receiver 31, 32 Transmitters

Claims

1. First to Nth receiver sets (N is an integer of 2 or more) each including one or more receivers that receive radio waves transmitted from a terminal device carried by a user using an antenna; an identification unit that identifies a location of the terminal device based on a difference in strength of radio waves transmitted from the terminal device and received by the first to Nth receiver sets, respectively; an output unit that outputs information about the position identified by the identification unit, At least one of the first to Nth receiver sets includes a transmitter that transmits a reference radio wave using at least one antenna of one or more receivers; The reference radio wave transmitted by the transmitter is received by two or more receivers using antennas located at positions different from the positions of the antennas used to transmit the reference radio wave, A location identification device further comprising a detection unit that detects a malfunction of a receiver that receives a reference radio wave by comparing the reception strength of the reference radio wave received by two or more receivers using antennas located in the same position.

2. The position determination device according to claim 1 , wherein the detection unit detects a malfunction of a receiver corresponding to an outlier identified in the reception strength of a reference radio wave received by three or more receivers using antennas arranged at the same location.

3. A first to Nth receiver set (N is an integer of 2 or more) including one or more receivers each receiving radio waves transmitted from a terminal device carried by a user using an antenna; an identification unit that identifies a location of the terminal device based on a difference in strength of radio waves transmitted from the terminal device and received by the first to Nth receiver sets, respectively; an output unit that outputs information about the position identified by the identification unit, At least one of the first to Nth receiver sets includes a transmitter that transmits a reference radio wave using at least one antenna of one or more receivers; The reference radio wave transmitted by the transmitter is received by two or more receivers using antennas located at positions different from the positions of the antennas used to transmit the reference radio wave, A location identification device that detects a malfunction of a receiver that receives the reference radio wave based on the reception strength of the same reference radio wave received by two or more receivers using antennas at two or more positions different from the position of the antenna used to transmit the reference radio wave by the transmitter.

4. 4. The position determination device according to claim 3, wherein the detection unit detects a malfunction of the receiver corresponding to an outlier identified using the reception strength of a reference radio wave received using an antenna at two or more positions different from the position of the antenna used to transmit the reference radio wave by the transmitter, and a reference value of the difference in strength of the radio waves received at the two or more positions.

5. The position determination device according to claim 3, wherein the detection unit detects a malfunction of the receiver corresponding to an outlier identified in the difference in intensity of the reference radio wave received using an antenna at two or more positions different from the position of the antenna used to transmit the reference radio wave by the transmitter.

6. A first to Nth receiver set (N is an integer of 2 or more) including one or more receivers each receiving radio waves transmitted from a terminal device carried by a user using an antenna; an identification unit that identifies a location of the terminal device based on a difference in strength of radio waves transmitted from the terminal device and received by the first to Nth receiver sets, respectively; an output unit that outputs information about the position identified by the identification unit, At least one of the first to Nth receiver sets includes a transmitter that transmits a reference radio wave using at least one antenna of one or more receivers; The reference radio wave transmitted by the transmitter is received by two or more receivers using antennas located at positions different from the positions of the antennas used to transmit the reference radio wave, a detection unit that detects a malfunction of a receiver that receives the reference radio wave based on the reception strength of the reference radio wave received by the two or more receivers, A location identification device in which, when a malfunction is detected in one of two or more receivers that receive radio waves using antennas located at the same position, the identification unit identifies the location of the terminal device using reception results from a longer reception period by one of the two or more receivers in which a malfunction is not detected, compared to a situation in which no malfunction is detected.

7. The location identification device according to claim 2, claim 4, or claim 5, wherein the identification unit identifies the location of the terminal device using a corrected reception strength obtained by adding a correction value to the reception strength of radio waves received by a receiver corresponding to an outlier.

8. The transmitter transmits a plurality of reference radio waves of different intensities, The position specifying device according to claim 7 , wherein the specifying unit performs correction using the correction value when the degrees of deviation of the plurality of outliers corresponding to the plurality of reference radio waves of different intensities are the same.

9. the first to Nth receiver sets each include two or more transmitters that transmit reference radio waves using antennas located at different positions; The position specifying device according to claim 1 , wherein the detection unit detects a malfunction using reference radio waves transmitted from the two or more transmitters.

10. receiving, by first to N-th receiver sets (N being an integer of 2 or more) each including one or more receivers, radio waves transmitted from a terminal device carried by a user using an antenna; a step of identifying, by an identification unit, a location of the terminal device based on a difference in strength of radio waves transmitted from the terminal device and received by the first to Nth receiver sets, respectively; and performing, by an output unit, an output relating to the position identified by the identification unit; At least one of the first to Nth receiver sets includes a transmitter that transmits a reference radio wave using at least one antenna of one or more receivers; transmitting a reference radio wave by the transmitter; receiving the reference radio wave by two or more receivers using antennas located at positions different from the positions of the antennas used to transmit the reference radio wave; The location method further includes a step of detecting, by a detection unit, a malfunction of a receiver that receives the reference radio wave by comparing the reception strength of the reference radio wave received by two or more receivers using antennas located at the same position.

11. A method of receiving radio waves transmitted from a terminal device carried by a user using an antenna of first to Nth receiver sets (N is an integer of 2 or more) each including one or more receivers; a step of identifying, by an identification unit, a location of the terminal device based on a difference in strength of radio waves transmitted from the terminal device and received by the first to Nth receiver sets, respectively; and performing, by an output unit, an output relating to the position identified by the identification unit; At least one of the first to Nth receiver sets includes a transmitter that transmits a reference radio wave using at least one antenna of one or more receivers; transmitting a reference radio wave by the transmitter; receiving the reference radio wave by two or more receivers using antennas located at positions different from the positions of the antennas used to transmit the reference radio wave; The location identification method further includes a step of detecting, by a detection unit, a malfunction of a receiver that received the reference radio wave based on the reception strength of the same reference radio wave received by two or more receivers using antennas at two or more positions different from the position of the antenna used in transmitting the reference radio wave by the transmitter.

12. A method of receiving radio waves transmitted from a terminal device carried by a user using an antenna of first to Nth receiver sets (N is an integer of 2 or more), each set including one or more receivers; a step of identifying, by an identification unit, a location of the terminal device based on a difference in strength of radio waves transmitted from the terminal device and received by the first to Nth receiver sets, respectively; and performing, by an output unit, an output relating to the position identified by the identification unit; At least one of the first to Nth receiver sets includes a transmitter that transmits a reference radio wave using at least one antenna of one or more receivers; transmitting a reference radio wave by the transmitter; receiving the reference radio wave by two or more receivers using antennas located at positions different from the positions of the antennas used to transmit the reference radio wave; and detecting, by a detection unit, a malfunction of a receiver that receives the reference radio wave based on the reception strength of the reference radio wave received by the two or more receivers, In the step of determining the location of the terminal device, when a malfunction is detected in one of two or more receivers that receive radio waves using antennas located at the same position, the location of the terminal device is determined using reception results from a longer reception period by one of the two or more receivers in which no malfunction is detected, compared to a situation in which no malfunction is detected.

13. On the computer, receiving, by first to N-th receiver sets (N being an integer of 2 or more) each including one or more receivers, radio waves transmitted from a terminal device carried by a user using an antenna; determining a location of the terminal device based on a difference in strength of radio waves transmitted from the terminal device and received by the first to Nth receiver sets, respectively; and providing an output relating to the identified location; At least one of the first to Nth receiver sets includes a transmitter that transmits a reference radio wave using at least one antenna of one or more receivers; transmitting a reference radio wave by the transmitter; receiving the reference radio wave by two or more receivers using antennas located at positions different from the positions of the antennas used to transmit the reference radio wave; A program for further executing a step of detecting a malfunction of a receiver that receives a reference radio wave by comparing the reception strength of the reference radio wave received by two or more receivers using antennas located in the same position.

14. A computer comprising: receiving, by first to N-th receiver sets (N being an integer of 2 or more) each including one or more receivers, radio waves transmitted from a terminal device carried by a user using an antenna; determining a location of the terminal device based on a difference in strength of radio waves transmitted from the terminal device and received by the first to Nth receiver sets, respectively; and providing an output relating to the identified location; At least one of the first to Nth receiver sets includes a transmitter that transmits a reference radio wave using at least one antenna of one or more receivers; transmitting a reference radio wave by the transmitter; receiving the reference radio wave by two or more receivers using antennas located at positions different from the positions of the antennas used to transmit the reference radio wave; A program for further executing a step of detecting a malfunction of a receiver that received the reference radio wave based on the reception strength of the same reference radio wave received by two or more receivers using antennas at two or more positions different from the position of the antenna used to transmit the reference radio wave by the transmitter.

15. A computer comprising: receiving, by first to N-th receiver sets (N being an integer of 2 or more) each including one or more receivers, radio waves transmitted from a terminal device carried by a user using an antenna; determining a location of the terminal device based on a difference in strength of radio waves transmitted from the terminal device and received by the first to Nth receiver sets, respectively; and providing an output relating to the identified location; At least one of the first to Nth receiver sets includes a transmitter that transmits a reference radio wave using at least one antenna of one or more receivers; transmitting a reference radio wave by the transmitter; receiving the reference radio wave by two or more receivers using antennas located at positions different from the positions of the antennas used to transmit the reference radio wave; and detecting a malfunction of a receiver that receives the reference radio wave based on the reception strength of the reference radio wave received by the two or more receivers, In the step of determining the location of the terminal device, if a malfunction is detected in one of two or more receivers that receive radio waves using an antenna located in the same position, the program determines the location of the terminal device using reception results from a longer reception period by one of the two or more receivers in which no malfunction is detected, compared to a situation in which no malfunction is detected.

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