JP7572005B2 - Position estimation system, position estimation device, position estimation method, and position estimation program - Google Patents

Description

This disclosure relates to a technology for estimating the location of a wireless terminal whose location is unknown using wireless signals.

Technology is known that uses wireless signals to estimate the position of a wireless terminal whose location is unknown. One example of such technology is disclosed in Patent Document 1. In the method disclosed in Patent Document 1, the position of a wireless terminal is estimated based on the time it takes to send and receive signals between a wireless LAN base station and the wireless terminal.

JP 2019-124597 A

However, in the method disclosed in Patent Document 1, in order to estimate the position of a wireless terminal, the base station antennas must be distributed and installed at locations that are somewhat distant from each other. In other words, the method disclosed in Patent Document 1 has limitations on the placement of base station antennas.

The present disclosure aims to provide a technology that can estimate the location of a wireless device whose location is unknown, without being restricted by the location of the antenna of the wireless device that serves as the base station.

To achieve the above object, the present disclosure provides a position estimation system. The position estimation system of the present disclosure includes a first wireless device having two or more antennas, a plurality of second wireless devices that perform wireless communication with the first wireless device and have known installation positions, and a position estimation device having a wireless capture function, and is configured to estimate the position of a third wireless device that performs wireless communication with the first wireless device and has an unknown location. The first wireless device is configured to transmit known signals from each antenna. The plurality of second wireless devices and the third wireless device are configured to transmit propagation path state information indicating the state of the propagation path to the first wireless device, which is derived from the received known signals.

In the position estimation system of the present disclosure, the position estimation device is configured to execute the following information acquisition process, correlation determination process, and output process. In the information acquisition process, propagation path state information transmitted by a plurality of second wireless devices and a third wireless device is acquired. In the correlation determination process, the correlation between the propagation path state information transmitted by the plurality of second wireless devices and the propagation path state information transmitted by the third wireless device is determined for each second wireless device. Then, in the output process, the installation position or identification information of the second wireless device that transmitted the propagation path state information having the highest correlation with the propagation path state information transmitted by the third wireless device is output.

In order to achieve the above object, the present disclosure provides a position estimation device. The position estimation device of the present disclosure is configured to capture information included in wireless communication between a first wireless device having two or more antennas, a plurality of second wireless devices whose installation positions are known, and a third wireless device whose location is unknown, and to estimate the position of the third wireless device based on the captured information. The measurement device of the present disclosure is configured to execute the following information acquisition process, correlation determination process, and output process. In the information acquisition process, propagation path state information indicating the state of the propagation path to the first wireless device transmitted by the plurality of second wireless devices and the third wireless device is acquired. In the correlation determination process, the correlation between the propagation path state information transmitted by the plurality of second wireless devices and the propagation path state information transmitted by the third wireless device is determined for each second wireless device. Then, in the output process, the installation position or identification information of the second wireless device that transmitted the propagation path state information having the highest correlation with the propagation path state information transmitted by the third wireless device is output.

The present disclosure provides a position estimation method to achieve the above object. The position estimation method of the present disclosure is a method of capturing information included in wireless communication between a first wireless device having two or more antennas, a plurality of second wireless devices whose installation positions are known, and a third wireless device whose location is unknown, and estimating the position of the third wireless device based on the captured information. The position estimation method of the present disclosure includes the following first to fifth steps. In the first step, the first wireless device is caused to transmit known signals from each antenna. In the second step, the plurality of second wireless devices and the third wireless device are caused to transmit propagation path state information indicating the state of the propagation path to the first wireless device derived from the received known signals. In the third step, the propagation path state information transmitted by the plurality of second wireless devices and the third wireless device is acquired. In the third step, the correlation between the propagation path state information transmitted by the plurality of second wireless devices and the propagation path state information transmitted by the third wireless device is determined for each second wireless device. Then, in the fifth step, it is determined that the third wireless device is present near the installation location of the second wireless device that transmitted the propagation path state information that has the highest correlation with the propagation path state information transmitted by the third wireless device.

To achieve the above object, the present disclosure provides a position estimation program. The position estimation program of the present disclosure includes a program for causing a computer to execute the processing performed by the above position estimation device. In other words, the above measurement device can be realized by a computer and a position estimation program. The position estimation program may be recorded on a computer-readable recording medium. The position estimation program may be provided via a network.

The position estimation system, position estimation device, position estimation method, and position estimation program disclosed herein can estimate the position of a wireless device whose location is unknown by using a wireless terminal whose installation location is known, without being restricted by the position of the base station antenna.

FIG. 1 is a diagram illustrating a configuration example of a position estimation system common to each embodiment of the present disclosure. FIG. 2 is a diagram showing an example of a sequence in wireless communication between an AP and a STA. FIG. 13 is a diagram illustrating an example of a VHT NDP frame transmitted from an AP. FIG. 2 illustrates an example of compressed CSI. FIG. 13 is a diagram illustrating an example of a method for converting polar coordinates into Cartesian coordinates. FIG. 1 is a diagram illustrating an example of the configuration of a position estimation device common to each embodiment of the present disclosure. FIG. 13 is a diagram showing an example of a table held by a CSI storage unit. 5 is a flowchart showing a correlation determination process according to the first embodiment of the present disclosure. 10 is a flowchart showing a correlation determination process according to a second embodiment of the present disclosure. 13 is a flowchart showing a correlation determination process according to a third embodiment of the present disclosure.

Below, embodiments of the position estimation system, position estimation device, position estimation method, and position estimation program disclosed herein will be described with reference to the drawings.

1. Configuration of a location estimation system common to each embodiment FIG. 1 shows a configuration example of a location estimation system 100 common to each embodiment of the present disclosure. The location estimation system 100 uses a wireless LAN system having a wireless LAN base station (AP: Access Point) 101 having two or more antennas and a plurality of wireless LAN terminals (STA: Station) 102. The installation position of each STA 102 within the communication area is known. In FIG. 1, as an example, six STAs 102 are installed within the communication area. Here, the AP 101 corresponds to a first wireless device, and each STA 102 corresponds to a second wireless device.

In FIG. 1, in addition to STA102, whose installation location is known, there is another STA104. As long as wireless communication with AP101 can be performed, the configuration of STA104 may be the same as or different from STA102. However, the location of STA104 is unknown. An example of such a STA104 is a mobile terminal carried by user 110. Here, STA104 corresponds to a third wireless device.

A measuring device 103 with a wireless capture function is used to estimate the location of a STA 104 whose location is unknown. The installation location of each STA 102 is registered in the measuring device 103. Here, the measuring device 103 corresponds to a location estimation device.

The wireless LAN system shown in FIG. 1 is compatible with the wireless LAN standard 802.11ac, and AP101 performs MIMO communication using two or more antennas. STA102 and STA104 receive wireless signals transmitted from each antenna of AP101. Conversely, STA102 and STA104 transmit wireless signals to each antenna of AP101. In this way, wireless communication compatible with 802.11ac is performed between AP101 and STA102 and STA104. In 802.11ac, STA102 and STA104 measure the state of the wireless propagation path between each antenna and their own device based on measurement data transmitted from each antenna of AP101. STA102 and STA104 transmit propagation path state information indicating the state of the measured wireless propagation path to AP101.

The measuring device 103 captures propagation path state information transmitted to the AP 101 from the STA 104 whose location is unknown, and also captures propagation path state information transmitted to the AP 101 from each STA 102 whose installation location is known. The measuring device 103 then estimates the location of the STA 104 whose location is unknown based on the captured propagation path state information. Details of the method by which the measuring device 103 estimates the location of the STA 104 will be described later.

Note that the position of the measuring device 103 shown in FIG. 1 is an example. The position of the measuring device 103 may be anywhere as long as it can receive a wireless signal transmitted from the STA 102. In addition, in the example of FIG. 1, the measuring device 103 is placed separately from the AP 101 and the STA 102, but the measuring device 103 may be integrated into the AP 101 or one of the STAs 102 without using an independent measuring device 103.

In addition, although only one AP101 is arranged in FIG. 1, multiple AP101 may be arranged. When multiple AP101 are arranged, the remaining AP101 except for one AP101 may function in the same manner as STA102, and wireless communication may be performed between AP101. Furthermore, the antenna of AP101 may be arranged away from the main body by a coaxial cable or the like.

2. Overview of wireless communication between AP and STA Fig. 2 shows an example of a sequence in wireless communication between AP 101 and STA 102. AP 101 broadcasts a VHT NDP Announcement frame as a start signal of a sounding protocol for acquiring propagation path state information, i.e., CSI. Immediately after that, AP 101 transmits a VHT NDP frame including measurement data to the destination STA 102. VHT stands for Very High Throughput, and 802.11ac is based on a VHT frame for ultra-high speed communication. NDP stands for Null Data Packet, and the VHT NDP frame is a frame that does not include communication data. The VHT NDP Announcement frame includes the address of the AP 101 and the destination STA 102, and is a frame for notifying the STA 102 in advance of the transmission of the VHT NDP frame. Note that the VHT NDP Announcement frame is transmitted from one or more specific antennas, but even when transmitted from two or more antennas, the same data signal is transmitted from each antenna.

Here, an example of a VHT NDP frame transmitted from AP101 is shown in FIG. 3. In FIG. 3, the VHT NDP frame is composed of a header 151 (storing frame type, etc.), measurement data 250, and a tailor 156 (storing error detection, etc.). The header 151 and tailor 156 are transmitted in the same way as the VHT NDP Announcement, but the measurement data 250 is transmitted individually from each antenna (ANT). In the example shown in FIG. 3, there are four antennas, and measurement data 152, measurement data 153, measurement data 154, and measurement data 155 are transmitted from the four antennas in a time-division manner. The measurement data 152, measurement data 153, measurement data 154, and measurement data 155 transmitted from each antenna are received by STA102 as one VHT NDP frame.

Returning to FIG. 2, the sequence of wireless communication between AP 101 and STA 102 will be described. STA 102 receives a VHT NDP frame from AP 101 and derives a compressed CSI value using the method specified in IEEE 802.11ac (see H. Yu and T. Kim, “Beamforming transmission in IEEE 802.11ac under time-varying channels,” The Scientific World J., vol. 2014, pp. 1-11, Jul. 2014, article ID 920937.).

Here, an example of compressed CSI is shown in FIG. 4. In FIG. 4, the number of transmitting antennas × the number of receiving antennas, the number of compressed CSI, and an example of compressed CSI are listed in order from the left column. φij indicates the phase difference at the antenna of STA102 of the signal transmitted from the i-th antenna and the j-th antenna. Here, φij ∈ [0, 2π). Also, ψij indicates a value (tan ⁻¹ value of the ratio of the absolute values of the amplitudes) representing the amplitude ratio at the antenna of STA102 of the signal transmitted from the i-th antenna and the j-th antenna in angle. Here, ψij ∈ [0, π/2).

According to the example of FIG. 4, for example, when the number of transmitting antennas is two and the number of receiving antennas is one (described as 2×1), the number of compressed CSIs is two, and the compressed CSIs are φ11 and ψ21. Similarly, when it is 2×2, the number of compressed CSIs is two, and the compressed CSIs are φ11 and ψ21. Also, when it is 3×1, the number of compressed CSIs is four, and the compressed CSIs are φ11, φ21, ψ21, and ψ31. Similarly, compressed CSIs are obtained according to the combination of the number of transmitting antennas and the number of receiving antennas.

Returning to FIG. 2, the sequence of wireless communication between AP101 and STA102 will be described. STA102 stores the derived compressed CSI in a VHT Compressed Beamforming Report frame and transmits it. As described above, measurement data for the VHT NDP frame is transmitted individually from each antenna of AP101, so STA102 can obtain CSI for each antenna of AP101. As the number of antennas increases, the amount of CSI information fed back from STA102 to AP101 increases. For this reason, CSI (compressed CSI) selected from all CSI according to predetermined conditions is fed back to AP101.

AP101 acquires the state of the wireless propagation path between each antenna of AP101 and STA102 based on the compressed CSI information fed back from STA102. Based on the acquired state of the wireless propagation path, MIMO communication is performed between AP101 and STA102.

Wireless communication according to the sequence shown in FIG. 2 is also performed between AP101 and STA104. Compressed CSI is fed back from STA104 to AP101, and MIMO communication is performed between AP101 and STA104 based on the state of the wireless propagation path obtained from the fed back information.

The measuring device 103 monitors and captures the VHT Compressed Beamforming Report frame transmitted by each STA 102 to the AP 101. The measuring device 103 also monitors and captures the VHT Compressed Beamforming Report frame transmitted by STA 104 to the AP 101. The measuring device 103 then extracts the compressed CSI stored in the captured VHT Compressed Beamforming Report and performs pre-processing on the extracted data. In the pre-processing, for example, a conversion from polar coordinates to Cartesian coordinates is performed.

Here, an example of a method for converting from polar coordinates to Cartesian coordinates is shown in FIG. 5. In FIG. 5, the angle φij from the x-axis can be converted to the corresponding x and y coordinates on a circumference of a radius of 1. Although the angles 0 and 2π have the same value, they are not suitable as inputs to machine learning because they are discontinuous numerically. Therefore, as shown in the following formula, the angle φij is converted to numerical values of the x and y coordinates, thereby maintaining the continuity of the numerical values. Similarly, the angle ψij is also converted to numerical values of the x and y coordinates.
xij = cosφij
yij = sinφij

In this manner, preprocessed data (compressed CSI) is obtained for each STA102 and STA104, and the position of STA104 is estimated by the measuring device 103 using this data.

3. Configuration of the Measuring Device Common to Each of the Embodiments FIG. 6 shows an example of the configuration of the measuring device 103 common to each of the embodiments. In FIG. 6, the measuring device 103 includes an antenna 201, a wireless interface unit 202, a capture unit 203, a filtering unit 204, a CSI extraction unit 205, a preprocessing unit 206, a CSI storage unit 207, and a numerical processing and judgment unit 208. The measuring device 103 can be configured with an integrated circuit such as a computer or an FPGA (Field Programmable Gate Array), and each function from the wireless interface unit 202 to the numerical processing and judgment unit 208 can be realized by a program executable by a computer. The program includes a position estimation program that causes the measuring device 103 to function as a position estimation device. The program may be provided by recording it on a storage medium, or may be provided through a network.

The antenna 201 receives radio waves communicated between the AP 101 and the STA 102 and between the AP 101 and the STA 104, converts each received radio wave into a received signal, and outputs it to the wireless interface unit 202.

The wireless interface unit 202 demodulates the wireless LAN frame from the received signal input from the antenna 201 and outputs it to the capture unit 203. Note that the processing of each unit described below is performed each time a wireless LAN frame is received.

The capture unit 203 captures the wireless LAN frames output by the wireless interface unit 202. This allows the acquisition of propagation path status information transmitted by each STA102 and STA104.

The filtering unit 204 selects only frames that meet preset conditions from among the wireless LAN frames captured by the capture unit 203, and outputs them to the CSI extraction unit 205. Here, the preset conditions are that the source and destination of the frame are the target AP 101 and STA 102, or AP 101 and STA 104, and that the type of the frame is a VHT Compressed Beamforming Report frame.

The CSI extraction unit 205 extracts the compressed CSI information from the VHT Compressed Beamforming Report frame selected by the filtering unit 204, and records this together with the time information of reception. Here, the process in which the AP 101 transmits a VHT NDP frame and the STAs 102 and 104 return VHT Compressed Beamforming Report frames is repeated. Note that the repetition time interval may be a regular interval, or may not be a regular interval.

The preprocessing unit 206 performs coordinate transformation on the compressed CSI extracted by the CSI extraction unit 205. Specifically, the preprocessing unit 206 transforms φij, which indicates the phase difference of the compressed CSI, and ψij, which indicates the amplitude ratio of the compressed CSI, from polar coordinates to Cartesian coordinates. In the following description, unless otherwise specified, CSI refers to the compressed CSI preprocessed by the preprocessing unit 206.

The CSI storage unit 207 stores the CSI input from the pre-processing unit 206 in chronological order. FIG. 7 is a diagram showing an example of a table held by the CSI storage unit 207. As shown in this table, the CSI storage unit 207 stores CSI in chronological order at regular time intervals for each combination of an AP address and a terminal address. Here, the AP address is the MAC address of AP101. The terminal addresses are the MAC addresses of STA102 and STA104.

In the CSI storage unit 207, CSI is stored for each CSI component. The CSI components are the x and y coordinate values obtained by converting the phase difference from the angle φij to x and y coordinate values, and the x and y coordinate values obtained by converting the amplitude ratio from the angle ψij to x and y coordinate values, and each value exists for each OFDM subcarrier. Data from the present to a specified time in the past is stored in the table, and the table is updated every time new data is acquired.

The numerical processing and determination unit 208 performs a correlation determination process to determine the correlation between the CSI obtained from each STA102 and the CSI obtained from the STA104 for each STA102. This correlation represents the correlation for each STA102 between the propagation path state information transmitted by each STA102 and the propagation path state information transmitted by the STA104.

The numerical processing and determination unit 208 determines that the STA104 is located near the STA102 that transmits the propagation path state information that has the highest correlation with the propagation path state information transmitted by the STA104, and outputs the determination result. This process is called output processing. In the output process by the numerical processing and determination unit 208, the installation position (installation position registered in advance in the measuring device 103) of the STA102 determined to be closest to the location of the STA104 is output as the determination result. Alternatively, identification information (e.g., MAC address) that identifies the STA102 determined to be closest to the location of the STA104 may be output as the determination result. In the example shown in FIG. 1, the STA102 numbered 6 is determined to be closest to the location of the STA104.

The processing performed by the numerical processing and determination unit 208, particularly the correlation determination processing, will be described in more detail below for each embodiment.

4. Correlation Determination Processing According to the First Embodiment In the first embodiment, the correlation determination processing by the numerical processing and determination unit 208 includes statistical processing and comparison processing. In the statistical processing, a statistical value indicating a CSI fluctuation at a predetermined time is calculated for the CSI obtained from each STA 102 and the CSI obtained from the STA 104. As described above, data from the present to a predetermined past time is accumulated in the table of the CSI accumulation unit 207. The statistical processing is performed on the accumulated data for each CSI component.

In the comparison process, the difference between the statistical value obtained by statistical processing of the CSI obtained from each STA102 and the statistical value obtained by statistical processing of the CSI obtained from STA102 is calculated for each STA102. The difference in the statistical values indicates the difference in the most recent CSI fluctuation conditions. Therefore, the smaller the difference in the statistical values, the less the difference in the CSI fluctuation conditions, and it can be determined that there is a high correlation between the propagation path state information transmitted by STA102 and the propagation path state information transmitted by STA104.

In the first embodiment, the number of CSI components whose variance value exceeds a predetermined threshold value at a predetermined time is used as a statistical value indicating the fluctuation of CSI over a predetermined time. In this case, the numerical processing and determination unit 208 calculates the variance value for each CSI component stored in the CSI storage unit 207 for each STA102 and STA104, and calculates the number of CSI components whose variance value exceeds the threshold value. CSI components whose variance value exceeds the threshold value are referred to as fluctuation components because they are components whose fluctuation is large over a predetermined time. Note that the threshold value may be common to the CSI components, or a value may be set for each CSI component.

If the difference in the number of fluctuation components between the two CSIs is small, the fluctuation conditions of the CSIs can be considered to be similar. In this case, the numerical processing and determination unit 208 calculates the difference between the number of fluctuation components contained in the CSI obtained from the STA102 and the number of fluctuation components contained in the CSI obtained from the STA104 for each STA102. The numerical processing and determination unit 208 then identifies the STA102 that provides the CSI with the smallest difference in the number of fluctuation components in comparison with the CSI obtained from the STA104. The STA102 identified in this way is the STA102 located closest to the STA104. The numerical processing and determination unit 208 outputs the installation location or identification information of the STA102 determined to be located closest to the STA104.

The numerical processing and determination unit 208 executes the above-mentioned correlation determination process in response to the CSI obtained from the STA 104 fluctuating beyond a predetermined level. Specifically, the execution condition of the correlation determination process is that the number of fluctuating components included in the CSI obtained from the STA 104 is equal to or greater than a reference number. The variance value of the CSI components at a predetermined time exceeds a threshold value, which means that the CSI value fluctuates greatly over time. Therefore, the increase in components with large variance suggests the presence of an element that fluctuates the CSI, that is, some moving object. However, the CSI may fluctuate greatly even when there is no moving object due to the influence of noise or disturbance. The above reference number is a criterion for distinguishing between the fluctuation of the CSI due to a moving object and the fluctuation of the CSI due to noise, etc. In this embodiment, in order to prevent erroneous determination due to the influence of noise or disturbance, if the number of fluctuating components included in the CSI obtained from the STA 104 is less than the reference number, it is considered that the CSI fluctuates due to the influence of noise or disturbance, and the correlation determination process is not executed.

Figure 8 is a flowchart showing the flow of the above-mentioned processing by the numerical processing and determination unit 208. In step S101, the number Nx of fluctuation components whose variance value exceeds a threshold value among the components of the CSI of the STA 104, which is the terminal to be detected, is counted. Then, in step S102, it is determined whether the number Nx of fluctuation components is equal to or greater than a reference number. If the number Nx of fluctuation components is less than the reference number, it is highly likely that the fluctuation in CSI is due to the influence of noise or disturbance, and the subsequent processing is skipped.

When the number Nx of fluctuation components becomes equal to or greater than the reference number, the processes of steps S103 and S104 are executed. In step S103, the number Ni (i = 1, ..., 6) of fluctuation components whose variance value exceeds a threshold value among the components of the CSI of the STA102, which is a known terminal, is counted for each STA102. In step S104, the difference |Nx-Ni| between the numbers of fluctuation components counted in steps S101 and S103 is calculated for each STA102. Then, it is determined that STA104 exists in the vicinity of the STA102 that has the smallest difference |Nx-Ni| in the number of fluctuation components.

In the first embodiment, the above-described processing is performed by the measuring device 103 as a position estimation device. This makes it possible to estimate the position of the STA 104, whose location is unknown, by using the STA 102, whose installation location is known, without being restricted by the position of the antenna of the AP 101.

5. Correlation determination process according to the second embodiment The correlation determination process according to the second embodiment includes statistical processing and comparison processing, as in the first embodiment. However, in the second embodiment, the number of components of the CSI whose autocorrelation value corresponding to the time difference of the predetermined time is below a predetermined threshold is used as a statistical value indicating the fluctuation of the CSI at a predetermined time. In this case, the numerical processing and determination unit 208 calculates the autocorrelation value for each CSI component stored in the CSI storage unit 207 for each STA 102 and STA 104, and calculates the number of CSI components whose autocorrelation value is below the threshold. The CSI components whose autocorrelation value is below the threshold are called fluctuation components because they are components that fluctuate greatly over a predetermined time. The threshold may be common to the CSI components, or a value may be set for each CSI component.

Figure 9 is a flowchart showing the flow of correlation determination processing according to the second embodiment. In step S201, the number Nx of fluctuation components whose autocorrelation values are below a threshold value among the components of the CSI of STA104, which is the terminal to be detected, is counted. Then, in step S202, it is determined whether the number Nx of fluctuation components is equal to or greater than a reference number. If the number Nx of fluctuation components is less than the reference number, it is highly likely that the fluctuation in CSI is due to the effects of noise or disturbance, and the subsequent processing is skipped.

When the number Nx of fluctuation components becomes equal to or greater than the reference number, the processes of steps S203 and S204 are executed. In step S203, the number Ni (i = 1, ..., 6) of fluctuation components whose autocorrelation values are below a threshold value among the components of the CSI of the STA102, which is a known terminal, is counted for each STA102. In step S204, the difference |Nx-Ni| between the numbers of fluctuation components counted in steps S201 and S203 is calculated for each STA102. Then, it is determined that STA104 exists in the vicinity of the STA102 that has the smallest difference |Nx-Ni| in the number of fluctuation components.

In the second embodiment, the above-mentioned processing is performed by the measuring device 103 as a position estimation device. This makes it possible to estimate the position of the STA 104, whose location is unknown, by using the STA 102, whose installation location is known, without being restricted by the position of the antenna of the AP 101.

6. Correlation Determination Processing According to the Third Embodiment In the third embodiment, the correlation determination processing by the numerical processing and determination unit 208 includes a discrimination process and a matching process. In the discrimination process, a fluctuation component whose fluctuation amount in a predetermined time exceeds a threshold is discriminated among the components of the CSI obtained from the STA 102, and a fluctuation component whose fluctuation amount in a predetermined time exceeds a threshold is discriminated among the components of the CSI obtained from the STA 104. As described above, data from the present to a predetermined time in the past is accumulated in the table of the CSI accumulation unit 207. The discrimination process is performed on the accumulated data for each CSI component.

In the matching process, the CSI fluctuation components obtained from each STA102 are matched with the CSI fluctuation components obtained from STA104 for each STA102. The more the number of matching fluctuation components between the two, the less difference there is in the CSI fluctuation conditions, and it can be determined that there is a high correlation between the propagation path state information transmitted by STA102 and the propagation path state information transmitted by STA104.

In the third embodiment, the variance value of each CSI component at a specified time is used as the amount of fluctuation of each CSI component at a specified time. In this case, the numerical processing and determination unit 208 calculates the variance value for each CSI component stored in the CSI storage unit 207 for each STA102 and STA104, and determines the components whose variance value exceeds the threshold. A CSI component whose variance value exceeds the threshold is a component that fluctuates greatly over a specified time, and is therefore referred to as a fluctuating component. Note that the threshold value may be common to the CSI components, or a value may be set for each CSI component.

The numerical processing and determination unit 208 identifies the STA 102 that provides the CSI that has the largest number of common fluctuation components with the CSI obtained from the STA 104. The STA 102 identified in this way is the STA 102 that is located closest to the STA 104. The numerical processing and determination unit 208 outputs the installation location or identification information of the STA 102 that is determined to be located closest to the STA 104.

Figure 10 is a flowchart showing the flow of correlation determination processing according to the third embodiment. In step S301, the number Nx of fluctuation components whose variance value exceeds a threshold value among the components of the CSI of STA104, which is the terminal to be detected, is counted. Then, in step S302, it is determined whether the number Nx of fluctuation components is equal to or greater than a reference number. If the number Nx of fluctuation components is less than the reference number, it is highly likely that the fluctuation in CSI is due to the influence of noise or disturbance, and the subsequent processing is skipped.

When the number Nx of fluctuation components is equal to or greater than the reference number, the processes of steps S303 to S306 are executed. In step S303, fluctuation components whose variance values exceed a threshold are identified among the components of the CSI of STA104, which is the terminal to be detected. In step S304, fluctuation components whose variance values exceed a threshold are identified among the components of the CSI of STA102, which is a known terminal. The discrimination of fluctuation components is performed for each STA102.

In step S305, the CSI fluctuation components of STA104 determined in step S303 are compared with the CSI fluctuation components of each STA104 determined in step S304. In this comparison, the number Nxi (i = 1, ..., 6) of matching CSI fluctuation components between STA102 and STA104 is counted for each STA102. Then, in step S306, it is determined that STA104 exists in the vicinity of the STA102 with the largest number Nxi of matching CSI fluctuation components.

In the third embodiment, the above-mentioned processing is performed by the measuring device 103 as a position estimation device. As a result, the position of the STA 104, whose location is unknown, can be estimated using the STA 102, whose installation location is known, without being restricted by the position of the antenna of the AP 101.

7. Others The above embodiments can be modified in various ways without departing from the scope of the present disclosure. In other words, when the number, quantity, amount, range, etc. of each element is mentioned in the above embodiments, the technology according to the present disclosure is not limited to the mentioned number, unless otherwise specified or clearly specified in principle. In addition, the structures, etc. described in the above embodiments are not necessarily essential to the technology according to the present disclosure, unless otherwise specified or clearly specified in principle.

For example, in the third embodiment, instead of the variance value of each CSI component at a predetermined time, an autocorrelation value corresponding to the time difference of each CSI component at a predetermined time may be used as the amount of fluctuation of each CSI component at a predetermined time. Even with this modified example, the location of STA104, whose location is unknown, can be estimated by using STA102, whose installation location is known.

100 Location Estimation System 101 AP (First Wireless Device)
102 STA (second wireless device)
103 Measuring device (position estimation device)
104 STA (third wireless device)
201 Antenna 202 Wireless interface unit 203 Capture unit 204 Filtering unit 205 CSI extraction unit 206 Preprocessing unit 207 CSI storage unit 208 Numerical processing and determination unit

Claims (8)

A position estimation system including a first wireless device having two or more antennas, a plurality of second wireless devices that perform wireless communication with the first wireless device and whose installation positions are known, and a position estimation device having a wireless capture function, the system being configured to estimate a position of a third wireless device that performs wireless communication with the first wireless device and whose location is unknown,
the first radio device is configured to transmit a known signal from each antenna;
the plurality of second radio devices and the third radio device are configured to transmit propagation path state information indicating a state of a propagation path to the first radio device derived from the received known signal;
The position estimation device includes:
an information acquisition process for acquiring propagation path state information transmitted by the plurality of second radio devices and the third radio device;
a correlation determination process for determining a correlation between propagation path state information transmitted by the plurality of second radio devices and propagation path state information transmitted by the third radio device for each second radio device;
an output process for outputting the installation location or identification information of the second wireless device that has transmitted the propagation path state information having the highest correlation with the propagation path state information transmitted by the third wireless device ;
In the correlation determination process,
a statistical process for calculating a statistical value indicating a fluctuation of propagation path state information over a predetermined time period for the propagation path state information transmitted by the plurality of second radio devices and the third radio device;
a comparison process for calculating, for each second radio device, a difference between a statistical value obtained by a statistical process on the propagation path state information transmitted by the plurality of second radio devices and a statistical value obtained by a statistical process on the propagation path state information transmitted by the third radio device;
The output process is configured to output the installation location or identification information of the second wireless device that has transmitted the propagation path condition information with the smallest difference.
A position estimation system comprising: 2. The position estimation system according to claim 1 ,
The position estimation device includes:
In the statistical processing, a number of fluctuation components whose variance values exceed a predetermined threshold value in the predetermined time period are counted among the components of propagation path state information for each of the plurality of second radio devices and the third radio device;
A location estimation system characterized in that the comparison process is configured to calculate, for each second wireless device, a difference between the number of fluctuation components contained in the propagation path state information transmitted by the multiple second wireless devices and the number of fluctuation components contained in the propagation path state information transmitted by the third wireless device. 2. The position estimation system according to claim 1 ,
The position estimation device includes:
In the statistical processing, for each of the plurality of second radio devices and the third radio device, the number of fluctuation components whose autocorrelation values corresponding to the time difference of the predetermined time are below a predetermined threshold among the components of the propagation path state information is counted;
A location estimation system characterized in that the comparison process is configured to calculate, for each second wireless device, a difference between the number of fluctuation components contained in the propagation path state information transmitted by the multiple second wireless devices and the number of fluctuation components contained in the propagation path state information transmitted by the third wireless device. A position estimation system including a first wireless device having two or more antennas, a plurality of second wireless devices that perform wireless communication with the first wireless device and whose installation positions are known, and a position estimation device having a wireless capture function, the system being configured to estimate the position of a third wireless device that performs wireless communication with the first wireless device and whose location is unknown,
the first radio device is configured to transmit a known signal from each antenna;
the plurality of second radio devices and the third radio device are configured to transmit propagation path state information indicating a state of a propagation path to the first radio device derived from the received known signal;
The position estimation device includes:
an information acquisition process for acquiring propagation path state information transmitted by the plurality of second radio devices and the third radio device;
a correlation determination process for determining a correlation between propagation path state information transmitted by the plurality of second radio devices and propagation path state information transmitted by the third radio device for each second radio device;
an output process for outputting the installation location or identification information of the second wireless device that has transmitted the propagation path state information having the highest correlation with the propagation path state information transmitted by the third wireless device ;
In the correlation determination process,
a discrimination process for discriminating a fluctuation component whose fluctuation amount in a predetermined time exceeds a threshold value among each component of propagation path state information for each of the plurality of second radio devices and the third radio device;
a comparison process for comparing, for each second radio device, a fluctuation component of the propagation path state information transmitted by the plurality of second radio devices with a fluctuation component of the propagation path state information transmitted by the third radio device;
The output process is configured to output the installation location or identification information of the second wireless device that has transmitted the propagation path state information having the largest number of common fluctuation components with the propagation path state information transmitted by the third wireless device.
A position estimation system comprising: A location estimation device configured to capture information included in wireless communication between a first wireless device having two or more antennas, a plurality of second wireless devices whose installation positions are known, and a third wireless device whose location is unknown, and to estimate a location of the third wireless device based on the captured information,
an information acquisition process for acquiring propagation path state information indicating a state of a propagation path to the first radio device, the propagation path state information being transmitted from the plurality of second radio devices and the third radio device;
a correlation determination process for determining a correlation between propagation path state information transmitted by the plurality of second radio devices and propagation path state information transmitted by the third radio device for each second radio device;
an output process for outputting the installation location or identification information of the second wireless device that has transmitted the propagation path state information having the highest correlation with the propagation path state information transmitted by the third wireless device ;
In the correlation determination process,
a statistical process for calculating a statistical value indicating a fluctuation of propagation path state information over a predetermined time period for the propagation path state information transmitted by the plurality of second radio devices and the third radio device;
a comparison process for calculating, for each second radio device, a difference between a statistical value obtained by a statistical process on the propagation path state information transmitted by the plurality of second radio devices and a statistical value obtained by a statistical process on the propagation path state information transmitted by the third radio device;
The output process is configured to output the installation location or identification information of the second wireless device that has transmitted the propagation path condition information with the smallest difference.
A position estimation device comprising: A location estimation method for capturing information included in wireless communication between a first wireless device having two or more antennas, a plurality of second wireless devices whose installation positions are known, and a third wireless device whose location is unknown, and estimating a location of the third wireless device based on the captured information, comprising:
causing the first radio device to transmit a known signal from each antenna;
causing the plurality of second radio devices and the third radio device to transmit propagation path state information indicating a state of a propagation path to the first radio device derived from the received known signal;
acquiring propagation path state information transmitted by the plurality of second radio devices and the third radio device;
performing statistical processing for calculating a statistical value indicating a fluctuation of the propagation path state information over a predetermined time period for the propagation path state information transmitted by the plurality of second radio devices and the third radio device;
calculating, for each second radio device, a difference between a statistical value obtained by statistical processing of the propagation path state information transmitted by the plurality of second radio devices and a statistical value obtained by statistical processing of the propagation path state information transmitted by the third radio device;
a second wireless device that transmits propagation path condition information having the smallest difference therebetween and that determines that the third wireless device is located near an installation position of the second wireless device that transmits propagation path condition information having the smallest difference therebetween . A location estimation method for capturing information included in wireless communication between a first wireless device having two or more antennas, a plurality of second wireless devices whose installation positions are known, and a third wireless device whose location is unknown, and estimating a location of the third wireless device based on the captured information, comprising:
causing the first radio device to transmit a known signal from each antenna;
causing the plurality of second radio devices and the third radio device to transmit propagation path state information indicating a state of a propagation path to the first radio device derived from the received known signal;
acquiring propagation path state information transmitted by the plurality of second radio devices and the third radio device;
determining, for each of the plurality of second radio devices and the third radio device, a fluctuation component whose fluctuation amount in a predetermined time exceeds a threshold value among each component of propagation path state information;
comparing, for each of the second radio devices, a fluctuation component of the propagation path state information transmitted by the plurality of second radio devices with a fluctuation component of the propagation path state information transmitted by the third radio device;
A location estimation method, comprising: determining that the third wireless device is located near an installation location of a second wireless device that has transmitted propagation path state information having the largest number of common fluctuation components with the propagation path state information transmitted by the third wireless device. A position estimation program, comprising a program for causing a computer to execute the process performed by the position estimation device according to claim 5 .

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