Method and apparatus for estimating the position of an object in a wireless communication system

Abstract

A method of operation of an electronic device for position estimation according to one embodiment of the present disclosure comprises: transmitting a first signal to at least one user terminal at a first time point; receiving a second signal corresponding to the first signal from the at least one user terminal at a second time point; identifying a turn-around time corresponding to the at least one user terminal—the turn-around time corresponds to a time interval from a third time point when the at least one user terminal receives the first signal to a fourth time point when the at least one user terminal transmits the second signal—; determining a position for the at least one user terminal based on the first time point, the second time point, and the turn-around time; and performing position correction for the determined position based on at least one of the stride information and group information of the user corresponding to the at least one user terminal.

Description

Technology Field

[0001] The present disclosure relates to a technique for estimating the position of an object in a wireless communication system, and more specifically, to a technique for correcting a time error when estimating the position of an object. Background Technology

[0002] In the case of a typical Fine Timing Measurements (FTM) protocol, the distance is estimated by calculating the protocol's departure and arrival times, as shown in the formula below.

[0003]

[0004] At this time, This is called turnaround time, and it is the time required for a terminal to send a signal back after receiving it. In the case of unidirectional RTT distance estimation, distance estimation is performed without knowing this turnaround time. In WiFi standards, this turnaround time is 10 There exists an older standard document defining it as (IEEE 802.11n 2.4GHz, 802.11g, 802.11b, 802.11-1977 DSSS), and in the latest standard document, 16 It is defined as (IEEE 802.11n, 802.11ac 5GHz, 802.11ax).

[0005] Unlike the definition in standard documents, unidirectional RTT distance estimation has varying processing times depending on the manufacturer and chipset of the terminal and AP, and these errors can range from about 90m to 15000m. In some cases, there may be multiple processing times even within the same terminal-access point (AP) combination, so it is necessary to correct for these time errors. The problem to be solved

[0006] The objective of the present disclosure is to provide a method and apparatus for correcting time errors so that unidirectional RTT distance estimation can be performed and used for location estimation even in older access points that do not support the WiFi Fine Timing Measurements (FTM) protocol. means of solving the problem

[0007] A method of operation of an electronic device for position estimation according to one embodiment of the present disclosure may include: transmitting a first signal to at least one user terminal at a first time point; receiving a second signal corresponding to the first signal from the at least one user terminal at a second time point; identifying a turn-around time corresponding to the at least one user terminal—the turn-around time corresponds to a time interval from a third time point when the at least one user terminal receives the first signal to a fourth time point when the at least one user terminal transmits the second signal—; determining a position for the at least one user terminal based on the first time point, the second time point, and the turn-around time; and performing position correction for the determined position based on at least one of stride information and group information of a user corresponding to the at least one user terminal.

[0008] Additionally, the at least one user terminal includes a first user terminal classified into a first group and a second user terminal classified into a second group, wherein the first user terminal and the second user terminal are located at a predetermined initial position (x, y) with respect to the electronic device, and the first user terminal and the second user terminal can each move a first movement distance and a second movement distance, respectively, in a predetermined direction from the initial position.

[0009] Additionally, when the first user terminal forms a first separation distance with the electronic device and the second user terminal forms a second separation distance with the electronic device, the error information for performing the position correction can be expressed as the solution to a linear equation for the stride information, the first separation distance, and the second separation distance.

[0010] In addition, in the step of performing the position correction, the error information for performing the position correction can be expressed as the solution of a linear equation for the initial position, the first separation distance, and the second separation distance.

[0011] Additionally, the group information includes first group information for the first group and second group information for the second group, wherein the first group information is determined with respect to the second group information, and in the step of performing the position correction, the error information for performing the position correction can be expressed as the solution of a linear equation for the stride information, the first separation distance, and the second separation distance.

[0012] Additionally, the step of performing the position correction is performed based on user stride information and group information corresponding to the at least one user terminal, and the error information for performing the position correction can be expressed as the solution of a linear equation for the initial information and the first separation distance.

[0013] An electronic device for position estimation according to one embodiment of the present disclosure comprises: a transceiver; and at least one control unit operably connected to the transceiver, wherein the at least one control unit transmits a first signal to at least one user terminal at a first time point, receives a second signal corresponding to the first signal from the at least one user terminal at a second time point, identifies a turn-around time corresponding to the at least one user terminal—the turn-around time corresponds to a time interval from a third time point when the at least one user terminal receives the first signal to a fourth time point when the at least one user terminal transmits the second signal—determines a position for the at least one user terminal based on the first time point, the second time point, and the turn-around time, and is configured to perform position correction for the determined position based on at least one of stride information and group information of a user corresponding to the at least one user terminal.

[0014] Additionally, the at least one user terminal includes a first user terminal classified into a first group and a second user terminal classified into a second group, wherein the first user terminal and the second user terminal are located at a predetermined initial position (x,y) with respect to the electronic device or access point (AP), and the first user terminal and the second user terminal can each move a first movement distance and a second movement distance, respectively, in a predetermined direction from the initial position.

[0015] Additionally, when the first user terminal forms a first separation distance with the AP and the second user terminal forms a second separation distance with the AP, the error information for performing the position correction can be expressed as the solution to a linear equation for the stride information, the first separation distance, and the second separation distance.

[0016] In addition, error information for performing the above position correction can be expressed as the solution to a linear equation for the initial position, the first separation distance, and the second separation distance.

[0017] Additionally, the group information includes first group information for the first group and second group information for the second group, wherein the first group information is determined with respect to the second group information, and the error information for performing the position correction can be expressed as the solution of a linear equation for the stride information, the first separation distance, and the second separation distance.

[0018] Additionally, the at least one control unit is configured to perform the position correction based on the user's stride information and group information corresponding to the at least one user terminal, and the error information for performing the position correction can be expressed as the solution of a linear equation for the initial information and the first separation distance. Effects of the invention

[0019] The present disclosure has the advantage of more accurately correcting time errors so that unidirectional RTT distance estimation can be performed and used for location estimation even in older access points that do not support the WiFi Fine Timing Measurements (FTM) protocol. Brief explanation of the drawing

[0020] FIG. 1 is a configuration diagram of an electronic device according to one embodiment of the present disclosure. FIG. 2 is a flowchart of an electronic device according to one embodiment of the present disclosure. FIG. 3 illustrates the performance of a unidirectional / bidirectional RTT technique of an electronic device according to one embodiment of the present disclosure. FIGS. 4a to 4c illustrate simulation results regarding the performance of a time error correction technique of an electronic device according to one embodiment of the present disclosure. Specific details for implementing the invention

[0021] Phrases such as "in some embodiments" or "in one embodiment" appearing in various places in this specification do not necessarily refer to the same embodiment.

[0022] Some embodiments of the present disclosure may be represented by functional block configurations and various processing steps. Some or all of these functional blocks may be implemented by various numbers of hardware and / or software configurations that perform specific functions. For example, the functional blocks of the present disclosure may be implemented by one or more microprocessors or by circuit configurations for a specific function. Additionally, for example, the functional blocks of the present disclosure may be implemented in various programming or scripting languages. The functional blocks may be implemented as algorithms executed on one or more processors. Furthermore, the present disclosure may employ prior art for electronic configuration, signal processing, and / or data processing, etc. Terms such as "mechanism," "element," "means," and "configuration" may be used broadly and are not limited to mechanical and physical configurations.

[0023] Furthermore, the connecting lines or connecting members between the components depicted in the drawings are merely illustrative of functional connections and / or physical or circuit connections. In the actual device, connections between components may be represented by various alternative or added functional connections, physical connections, or circuit connections.

[0025] An electronic device according to one embodiment of the present disclosure transmits and receives signals to estimate the location of an object (hereinafter referred to as a 'user terminal') in real time, calculates possible error information based on the acquired information, and provides a technique for obtaining the accurate location of the user terminal.

[0026] The electronic device may be an access point (AP) that transmits and receives signals or data to and from a user terminal via a wireless communication network. Additionally, the user terminal may physically move relative to the AP, and this movement may be performed by the user of the user terminal.

[0027] In an electronic device according to one embodiment of the present disclosure, a new error correction technique is applied to a conventional position estimation method to more accurately estimate the position of a user terminal in an environment where the user terminal, which is the subject of position estimation, moves in real time.

[0028] Specifically, the electronic device may utilize stride information of a user carrying a user terminal, and if there are multiple user terminals, may utilize group information assigned to multiple user terminals. Additionally, the electronic device may adopt an appropriate error correction technique by considering a situation in which at least one of the stride information and group information is given.

[0030] FIG. 1 is a configuration diagram of an electronic device according to one embodiment of the present disclosure.

[0031] Referring to FIG. 1, an electronic device according to one embodiment of the present disclosure includes a communication unit, a storage unit, and a control unit.

[0032] The communication unit can perform the role of transmitting and receiving data in an electronic device. To this end, it may include a wireless communication module, a wired communication module, an antenna, a filter, etc.

[0033] The communication unit receives wireless signals and analyzes them to extract information that can estimate the location of the user terminal. In this process, the electronic device may use location estimation algorithms such as RSSI (Radio Signal Strength Indicator), TOA (Time of Arrival), TDOA (Time Difference of Arrival), and AOA (Angle of Arrival).

[0034] The storage unit can perform the role of storing and maintaining data in electronic devices. To this end, it may include flash memory, hard disk drives (HDDs), solid-state drives (SSDs), etc.

[0035] The storage unit can store and maintain the estimated location information of the user terminal. In this process, the electronic device may build a location database or use a cache memory for location estimation.

[0036] The control unit can perform the role of controlling the operation of an electronic device. To this end, it may include a microprocessor, memory, sensors, actuators, software, etc. The control unit may also include a device that provides a user interface (UI) and can execute commands stored in a storage unit or an provided memory. Additionally, the control unit is operably connected to at least one of a communication unit and a storage unit to transmit control commands for each component.

[0037] The control unit processes location data collected from the communication unit and can estimate the location of the user terminal using location information stored in the storage unit. In this process, the electronic device can execute a location estimation algorithm and transmit the result to another device. Additionally, the control unit can estimate the location of the user terminal using the location information of the electronic device itself. In this case, the electronic device can estimate its own location using the Global Positioning System (GPS) and estimate the location of the user terminal based on that information.

[0039] FIG. 2 is a flowchart of an electronic device according to one embodiment of the present disclosure.

[0040] In step (S110), the electronic device transmits a first signal to at least one user terminal at a first time.

[0041] The first signal may be referred to as the initial signal transmitted by an electronic device to a user terminal for location estimation. Specifically, the first signal may generally be a beacon frame transmitted by an access point to a user terminal. A beacon frame is one of the basic control messages of a wireless network and may contain information for identifying a specific wireless LAN (WLAN).

[0042] In step (S120), the electronic device receives a second signal corresponding to a first signal from at least one user terminal at a second time.

[0043] The second signal may be a signal transmitted to an electronic device in response to the first signal by a user terminal that has received the first signal. That is, the second signal may be a response signal to the first signal. Specifically, the second signal may be transmitted in the form of an RTS (Request To Send) signal, a CTS (Clear To Send) signal, an ACK (Acknowledgement) signal, etc.

[0044] The electronic device may use a Time Difference of Arrival (TDoA) technique to estimate the location of a user terminal. The first signal and the second signal may be signals used in the TDoA technique.

[0045] In step (S130), the electronic device identifies a turn-around time corresponding to at least one user terminal.

[0046] The processing time of the user terminal can be estimated by an electronic device. For example, an access point, which is an electronic device, can identify time information at the time of receiving a second signal after transmitting a first signal. At this time, the access point can calculate the TDOA value by comparing the time the first signal was transmitted and the time the second signal was received. Here, the access point may consider the processing time of the user terminal to calculate the TDOA value.

[0047] The processing time of a user terminal may be measured differently depending on the model, software version, hardware specifications, etc. The access point can identify the processing time based on information regarding the model, etc. of the user terminal acquired in advance.

[0048] In step (S140), the electronic device determines the location of at least one user terminal based on a first time point, a second time point, and a processing time.

[0049] The electronic device can calculate the distance to the user terminal using the first signal and the second signal, and then estimate the location of the user terminal based on this distance. At this time, the estimated location can be corrected by taking into account the processing time.

[0050] Specifically, the electronic device can calculate the distance to the user terminal as follows, based on the time the first signal was sent, the time the second signal was received, and the processing time.

[0051] For example, the Round Trip Time (RTT) can be calculated as shown in Equation 1 below, with the time t1 being the time the first signal is sent, the time t2 being the time the second signal is received, and the processing time td.

[0052]

[0053] The electronic device can calculate the distance between the user terminal and the electronic device using RTT. In this case, if the propagation speed is c, the distance d can be calculated as shown in Equation 2 below.

[0054]

[0055] Based on the distance d, the electronic device can estimate that the user terminal is located on a circle centered on the location where the first signal was sent and the location where the second signal was received. In the case of multiple electronic devices, a more accurate location estimate can be obtained by using the location estimate calculated at each access point.

[0056] In step (S150), the electronic device performs position correction for a determined position based on at least one of the user's stride information and group information corresponding to at least one user terminal.

[0057] The user corresponding to the user terminal may be a user who possesses or carries the user terminal and moves. Additionally, the user may move with a certain stride. The movement distance of the user terminal may be determined based on the user's stride information and the number of steps taken by the user.

[0058] There may be multiple user terminals, and each of the multiple user terminals may correspond to multiple users. The multiple user terminals may be classified into multiple groups. For example, the multiple groups may be referred to as a first group and a second group. Additionally, a user corresponding to a user terminal included in the first group (the first user terminal) may be referred to as the first user, and a user corresponding to a user terminal included in the second group (the second user terminal) may be referred to as the second user.

[0059] Here, the first user terminal and the second user terminal may be located at a predetermined initial position (x, y) with respect to the electronic device.

[0060] Additionally, the first user terminal and the second user terminal can move by a first movement distance and a second movement distance, respectively, in a preset direction from an initial position. For example, the first user and the second user can move with a constant stride in the x-axis direction.

[0061] In this case, the electronic device may perform the method of correcting the time error differently depending on whether it has acquired the user's stride information.

[0062] First, when a user moves in a straight line and takes n-1 steps from an initial position (x, y), the position of the user terminal can be expressed as Equation 3 below.

[0063]

[0064] In this case, even if there are multiple time errors, the difference between each time error is greater than 100m, so it is possible to determine which time error occurred. For example, assuming there are two time error groups, the above formula can be changed to Equation 4 and Equation 5 as follows.

[0065]

[0066]

[0067] At this time, , And, each group can have the same time error.

[0069] 1) When stride length is not given

[0070] first, person If you select and substitute it into Equations 4 and 5 and then subtract it from the original formula, you can obtain results such as Equations 6 and 7 below, respectively.

[0071]

[0072]

[0073] In the above formula person Select and re-assign If we rearrange it so that the slashes disappear, the following mathematical formulas 8 and 9 appear, respectively.

[0074]

[0075]

[0076] The above expression If each is organized and expressed as a matrix, it can be calculated as shown in mathematical formula 10 below.

[0077]

[0078] If so, the above formula can be used to obtain the solution to the linear equation as shown in Equation 11 below.

[0079]

[0081] Specifically, when a first user terminal forms a first separation distance with an electronic device and a second user terminal forms a second separation distance with an electronic device, the error information for the electronic device to perform position correction can be expressed as the solution of a linear equation for stride information (d), the first separation distance (b1), and the second separation distance (b2).

[0083] 2) When stride length is given

[0084] If the stride length is given, Equations 6 and 7 It can be organized and expressed as a matrix like Equation 12 below.

[0085]

[0086] The above mathematical formula 12 degrees If so, a solution to the linear equation as shown in Equation 13 below can be obtained.

[0087]

[0088] Specifically, the error information for the electronic device to perform position correction can be expressed as the solution to a linear equation for the initial position (x), the first separation distance (b1), and the second separation distance (b2).

[0090] 3) When relationships between groups are given

[0091] if, Given the relationship, in Equations 4 and 5 instead Substitute, second By substituting and simplifying, the following mathematical formula 14 can be obtained.

[0092]

[0093] At this time, And, is, silver when substituted It means the value of. In the above formula By substituting If we rearrange it so that disappears, we can obtain the following mathematical formula 15.

[0094]

[0095] When the above mathematical formula 15 is expressed as a matrix, It can be expressed as such, and similarly, the solution to the linear equation can be found.

[0096] Specifically, the group information used by the electronic device to perform position correction includes first group information for a first group and second group information for a second group, the first group information is determined with respect to the second group information, and the error information for performing position correction can be expressed as the solution of a linear equation for stride information (d), a first separation distance (b1), and a second separation distance (b2).

[0098] 4) When both inter-group relationships and strides are given

[0099] If we organize mathematical equation 14 into a matrix, Since it can be arranged in the form of, the solution to the linear equation can be found.

[0100] The electronic device may use both the user's stride information and group information corresponding to the user terminal to perform the above position correction, and the error information for performing the position correction may be expressed as the solution of a linear equation for the initial information (x) and the first separation distance (b1).

[0102] Test results obtained by performing a simulation through an electronic device according to one embodiment of the present disclosure can be classified into the performance of unidirectional RTT distance estimation and the performance of time error correction technology.

[0103] 1) Performance of Unidirectional RTT Distance Estimation

[0104] According to one embodiment of the present disclosure, the extent of the time error of the unidirectional RTT can be obtained by estimating the distance between 4 and 20 m using three user terminals and three access points (electronic devices). At this time, values ​​with a standard deviation of 15 m or more among the estimated results were removed, and the degree of bias due to the time error was estimated through the difference between the measured value and the actual distance. Here, the time error table regarding the time error of the unidirectional RTT is as shown in Table 1 below.

[0105] Chipsets Offset values [m] (std. dev. threshold 15m) Flip3 Pixel 3a Pixel 3a XL 2.4 GHz 5.0 GHz 2.4 GHz 5.0 GHz 2.4 GHz 5.0 GHz BroadcomBCM6755 14706.0 10372.5 316.3 176.3 316.5 179.7 QualcommQCN5502 14528.6,10882.5 10196.4,11944.1,15579.1 90.7 8.0 83.7 1.0 QualcommQCA9886 12331.7,10510.7 10518.6,12337.5,15933.0 912.1 935.1 80.2 939.8

[0106] Table 1 is a table showing the time error between each access point and terminal. Multiple time errors may occur in a specific combination of AP and terminal. Looking at the results, the time error range is about 1 m between the Pixel 3a XL and the Qualcomm QCN5502, showing almost no time error, whereas the combination of the Flip3 and the Qualcomm chipset shows multiple large errors ranging from 10,000 m to 15,500 m.

[0108] FIG. 3 illustrates the performance of a unidirectional / bidirectional RTT technique of an electronic device according to one embodiment of the present disclosure.

[0109] Specifically, the performance of unidirectional RTT distance estimation between the Broadcom BCM6755 of Table 1 and each terminal can be expressed as shown in Figure 3 and Table 2 below.

[0110] Chipset Devices Distance Type 4m 8m 12m 16m 20m BroadcomBCM6755(5.0GHz) Filp3 RMSE 3.53 3.54 4.22 3.82 4.30 Std 17.33 17.53 21.32 20.36 20.87 # of data 25 36 45 61 40 Pixel 3a RMSE 3.90 5.65 4.72 4.80 4.14 Std 22.92 63.43 31.06 43.91 26.70 # of data 58 76 40 89 72 Pixel 3a XL RMSE 8.29 4.91 2.71 4.15 3.73 Std 193.70 41.02 10.11 31.14 15.73 # of data 22 41 2 52 44

[0111] Table 2 is a table regarding the performance of the unidirectional RTT distance estimation method. Referring to Table 2 and Figure 3, it can be seen that the average RMSE of the unidirectional RTT distance estimation method is about 4m, which is more than 10 times greater than the RMSE of the bidirectional RTT distance estimation method, which is 0.3m or less. It can be seen that the unidirectional RTT distance estimation method not only has a very large time error, but even if the time error is resolved well, the error in the estimation performance is very large.

[0113] FIGS. 4a to 4c illustrate simulation results regarding the performance of a time error correction technique of an electronic device according to one embodiment of the present disclosure.

[0114] To verify the performance of the time error correction technology of an electronic device according to one embodiment of the present disclosure, a simulation using an electronic device (hereinafter referred to as an 'access point') can be performed.

[0115] Specifically, in the simulation, the location of the access point is set at the origin (0,0), and the location of the user terminal starts at (-10,-5) and moves to (10, -5), and the distance to the user terminal can be estimated by dividing it into 41 equal points. At this time, the distance estimation error is Zero mean Gaussian, and the error Std. can be set to 3m. At this time, the time error can be set to three values: -500m, 500m, and 1500m, and for each distance estimation result, one of the three time errors can be randomly selected and added to the estimation result.

[0116] FIGS. 4a to 4c illustrate result information obtained by measuring the performance of the time error correction technique and the initial position estimation performance of an electronic device according to one embodiment of the present disclosure while changing simulation values.

[0117] Referring to Figure 4a, it can be seen that the initial position estimation performance is best when the stride length is given, and the initial position estimation performance is lowest when no information is given. Regarding the time error correction performance, it can be seen that the performance of the time error correction technique is best when the relationship between groups is given in all simulations.

[0119] A person skilled in the art related to the embodiments will understand that the embodiments may be implemented in modified forms without departing from the essential characteristics of the description above. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of rights is defined in the claims, not in the foregoing description, and all variations within the scope of equivalence should be interpreted as being included in the embodiments.

Claims

Claim 1 A method of operation of an electronic device for position estimation comprises: transmitting a first signal to at least one user terminal at a first time point; receiving a second signal corresponding to the first signal from the at least one user terminal at a second time point; identifying a turn-around time corresponding to the at least one user terminal, wherein the turn-around time corresponds to a time interval from a third time point when the at least one user terminal receives the first signal to a fourth time point when the at least one user terminal transmits the second signal; determining a position for the at least one user terminal based on the first time point, the second time point, and the turn-around time; and performing position correction for the determined position based on user stride information and group information corresponding to the at least one user terminal, wherein the at least one user terminal includes a first user terminal classified into a first group and a second user terminal classified into a second group, wherein the group information includes first group information for the first group and second group information for the second group, wherein the first group information is determined for the second group information, and the first user terminal is at a different time from the second user terminal A method having an error. Claim 2 A method according to claim 1, wherein the first user terminal and the second user terminal are located at a predetermined initial position (x, y) with respect to the electronic device, and the first user terminal and the second user terminal each move a first movement distance and a second movement distance, respectively, in a predetermined direction from the initial position. Claim 3 A method according to claim 2, wherein when the first user terminal forms a first separation distance with the electronic device and the second user terminal forms a second separation distance with the electronic device, the error information for performing the position correction is expressed as the solution of a linear equation for the stride information, the first separation distance, and the second separation distance. Claim 4 A method according to claim 2, wherein, in the step of performing the position correction, the error information for performing the position correction is expressed as the solution of a linear equation for the initial position, the first separation distance, and the second separation distance. Claim 5 A method according to claim 2, wherein, in the step of performing the position correction, the error information for performing the position correction is expressed as the solution of a linear equation for the stride information, the first separation distance, and the second separation distance. Claim 6 A method according to claim 5, wherein the step of performing the position correction is performed based on user stride information and group information corresponding to at least one user terminal, and the error information for performing the position correction is expressed as the solution of a linear equation for the initial position and the first separation distance. Claim 7 In an electronic device for position estimation, a transmitter / receiver; and includes at least one control unit operably connected to the above transceiver, wherein the at least one control unit transmits a first signal to at least one user terminal at a first time point, receives a second signal corresponding to the first signal from the at least one user terminal at a second time point, identifies a turn-around time corresponding to the at least one user terminal—the turn-around time corresponds to a time interval from a third time point when the at least one user terminal receives the first signal to a fourth time point when the at least one user terminal transmits the second signal—determines a position for the at least one user terminal based on the first time point, the second time point, and the turn-around time, and is configured to perform position correction for the determined position based on at least one of user stride information and group information corresponding to the at least one user terminal, wherein the at least one user terminal includes a first user terminal classified into a first group and a second user terminal classified into a second group, wherein the group information includes first group information for the first group and second group information for the second group, wherein the first group information is determined for the second group information, and A device in which the first user terminal has a different time error from the second user terminal. Claim 8 A device according to claim 7, wherein the first user terminal and the second user terminal are located at a predetermined initial position (x,y) with respect to the electronic device or access point (AP), and the first user terminal and the second user terminal each move a first movement distance and a second movement distance, respectively, in a predetermined direction from the initial position. Claim 9 A device according to claim 8, wherein when the first user terminal forms a first separation distance with the AP and the second user terminal forms a second separation distance with the AP, the error information for performing the position correction is expressed as the solution of a linear equation for the stride information, the first separation distance, and the second separation distance. Claim 10 In claim 8, the device, wherein the error information for performing the position correction is expressed as the solution of a linear equation for the initial position, the first separation distance, and the second separation distance. Claim 11 In claim 8, the device, wherein the error information for performing the position correction is expressed as the solution of a linear equation for the stride information, the first separation distance, and the second separation distance. Claim 12 In claim 11, the device is configured such that the at least one control unit performs the position correction based on the user's stride information and group information corresponding to the at least one user terminal, and the error information for performing the position correction is expressed as the solution of a linear equation for the initial position and the first separation distance.

Images