WO2017026571A1

WO2017026571A1 - Positioning method and positioning system for improving location accuracy

Info

Publication number: WO2017026571A1
Application number: PCT/KR2015/009265
Authority: WO
Inventors: 최병호; 조충상
Original assignee: 전자부품연구원
Priority date: 2015-08-12
Filing date: 2015-09-02
Publication date: 2017-02-16
Also published as: KR101599986B1

Abstract

The present invention relates to a positioning technology using a tag, and provides a positioning method comprising the steps of: (a) calculating the location of a first tag on the basis of signals received from three access points which have the first to third greatest signal strengths among a plurality of access points; (b) when the calculated location is out of a predetermined error range, searching for first adjacent tags located around the first tag on the basis of the signals received from the three access points; (c) calculating the locations of the first adjacent tags on the basis of the signals received from the three access points, respectively; (d) extracting second adjacent tags from the first adjacent tags on the basis of the calculated locations; and (e) calculating the location of the first tag on the basis of signals received from the second adjacent tags and the locations of the second adjacent tags.

Description

Position measuring method and position measuring system for improving position accuracy

The present invention relates to a position measuring technique using a tag, and more particularly, a position measuring method and a position capable of accurately tracking a position of a tag-attached object through an inter-tag communication, thereby improving accuracy of measuring a tag. It relates to a measuring system.

Indoor positioning technology is a technology for measuring the position of an object in an indoor environment, and various methods have been developed. Among them, the positioning technique using the RF signal measures the position of the object using an RF signal transmitted and received between a tag attached to the object and an access point (AP).

There are two types of positioning techniques using RF signals, triangulation and fingerprinting. Triangulation technique is a representative position estimation technique that measures the signal strength (RSSI, Received Signal Strength Indication) of signals received from three or more access points (AP), converts them into distances, and solves the equation to calculate the position. .

However, in the triangulation technique, there is a problem in that a large error occurs in a calculated position due to attenuation, reflection, diffraction, etc. of the RF signal generated by walls, obstacles, etc. in an indoor space.

An embodiment of the present invention is to provide a position measuring method and a position measuring system that can use the surrounding tags as an AP and accurately measure the position of a specific tag through inter-tag collaboration.

An embodiment of the present invention provides a position measuring method and a position measuring system capable of accurately measuring a position not only for a tag located in a space where a line of sight (LoS) is secured, but also for a tag located in a space where a LoS is not secured. To provide.

One embodiment of the present invention is to provide a position measuring method and a position measuring system that can improve the accuracy of position measurement while utilizing the existing position measuring system as it is.

Among the embodiments, the method for measuring a position includes (a) calculating a position of a first tag based on a signal received at three access points having the largest signal strength among a plurality of access points, and (b) calculating the position of the first tag. Retrieving first peripheral tags located around the first tag based on signals received at the three access points when the location is out of a predetermined error range, and (c) receiving at the three access points. Calculating positions of the first peripheral tags based on the calculated signals, (d) extracting second peripheral tags from the first peripheral tags based on the calculated position; and (e) the second peripheral tags. Calculating a position of the first tag based on a signal received from the peripheral tags and the position of the second peripheral tags.

In one embodiment, the step (a) includes calculating the position of the first tag according to a triangulation technique based on the signal strength of the signals received at the three access points.

In an embodiment, the step (b) may include requesting the three access points to search for the first neighboring tags, and each tag having a strength greater than or equal to a predetermined value received from the three access points from a specific access point. And receiving identification information on the corresponding signal strength.

In an embodiment, the specific access point may be an access point having the largest signal strength among the three access points based on the strength of the signal received from the first tag. In one embodiment, the step (c) May calculate the positions of the first peripheral tags based on the positions of the three access points and the signal strength received by the first peripheral tags.

In an embodiment, the step (d) may include extracting, as the second peripheral tags, tags in which a calculated position among the first peripheral tags is within a preset error range.

In an embodiment, the step (e) may include requesting a specific one of the three access points to transmit the signal to the first tag by the second peripheral tags and the first tag by the second peripheral tag. Receiving the strength of the signal received in the field and the identification information of the corresponding tag from the specific access point.

In an embodiment, the step (e) is a step of calculating the position of the first tag according to a triangulation technique based on the signal strength of a signal received from three second peripheral tags among the second peripheral tags. It may include.

Among the embodiments, in a tag positioning system comprising a plurality of access points, a plurality of tags and a position measuring device, the position measuring device is (a) the signal strength of the plurality of access points of the 3 Calculating a position of the first tag based on the signals received at the three access points; and (b) when the calculated position is out of a preset error range, the first tag is based on the signals received at the three access points. Search for first peripheral tags located around the tag, and (c) calculate positions of the first peripheral tags based on signals received at the three access points, and (d) based on the calculated positions. Extracting second peripheral tags from the first peripheral tags, and (e) the first tag based on a signal received from the second peripheral tags and the position of the second peripheral tags. Calculate the position of.

In one embodiment, the location measuring device requests the three access points to search for the first peripheral tags, and for a tag whose strength of a signal received at the three access points from a specific access point is greater than or equal to a predetermined value, respectively. The identification information and the corresponding signal strength may be received.

In an embodiment, the position measuring apparatus may extract, as the second peripheral tags, tags in which a calculated position among the first peripheral tags is within a preset error range.

Among the embodiments, the location measuring method comprises the steps of: (a) calculating the location of a particular tag based on a signal received at at least three access points having the greatest signal strength among the plurality of access points, (b) When the calculated position is out of a preset first error range, the second position is within a preset second error range of at least one first neighboring tag around the specific tag based on the signals received from the at least three access points. Determining at least one second neighbor tag and (c) repositioning the location of the particular tag through the at least one second neighbor tag.

The position measuring method and the position measuring system according to an embodiment of the present invention can use the surrounding tags as APs and accurately measure the position of a specific tag through the inter-tag collaboration.

The position measurement method and the position measurement system according to an embodiment of the present invention can accurately measure the position of the tag located in the space where the LoS is not secured as well as the tag located in the space where the line of sight (LoS) is secured. have.

Position measuring method and position measuring system according to an embodiment of the present invention can improve the accuracy of the position measurement while utilizing the existing position measuring system as it is.

1 is a view for explaining a position measuring system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of the position measuring device in FIG. 1.

3 is a diagram illustrating a triangulation technique.

4 is a diagram for explaining a situation where an error occurs due to an obstacle.

5 is a diagram illustrating a process of searching for a first peripheral tag.

FIG. 6 is a diagram illustrating a process of measuring a location of a specific tag through tag-to-tag collaboration using neighboring tags as an access point.

FIG. 7A is a flowchart illustrating a part of a position measuring method performed by the position measuring apparatus in FIG. 1.

FIG. 7B is a flowchart illustrating another part of the position measuring method performed by the position measuring apparatus in FIG. 1.

Description of the present invention is only an embodiment for structural or functional description, the scope of the present invention should not be construed as limited by the embodiments described in the text. That is, since the embodiments may be variously modified and may have various forms, the scope of the present invention should be understood to include equivalents capable of realizing the technical idea. In addition, the objects or effects presented in the present invention does not mean that a specific embodiment should include all or only such effects, the scope of the present invention should not be understood as being limited thereby.

On the other hand, the meaning of the terms described in the present application should be understood as follows.

Terms such as "first" and "second" are intended to distinguish one component from another component, and the scope of rights should not be limited by these terms. For example, the first component may be named a second component, and similarly, the second component may also be named a first component.

When a component is referred to as being "connected" to another component, it should be understood that there may be other components in between, although it may be directly connected to the other component. On the other hand, when a component is referred to as being "directly connected" to another component, it should be understood that there is no other component in between. On the other hand, other expressions describing the relationship between the components, such as "between" and "immediately between" or "neighboring to" and "directly neighboring to", should be interpreted as well.

Singular expressions should be understood to include plural expressions unless the context clearly indicates otherwise, and terms such as "comprise" or "have" refer to a feature, number, step, operation, component, part, or feature thereof. It is to be understood that the combination is intended to be present and does not exclude in advance the possibility of the presence or addition of one or more other features or numbers, steps, operations, components, parts or combinations thereof.

In each step, an identification code (e.g., a, b, c, etc.) is used for convenience of description, and the identification code does not describe the order of the steps, and each step clearly indicates a specific order in context. Unless stated otherwise, they may occur out of the order noted. That is, each step may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

The present invention can be embodied as computer readable code on a computer readable recording medium, and the computer readable recording medium includes all kinds of recording devices in which data can be read by a computer system. . Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage device, and the like, and are also implemented in the form of a carrier wave (for example, transmission over the Internet). It also includes. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

All terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. Generally, the terms defined in the dictionary used are to be interpreted to coincide with the meanings in the context of the related art, and should not be interpreted as having ideal or excessively formal meanings unless clearly defined in the present application.

Referring to FIG. 1, the location measurement system 100 includes an access point (AP) 110, a tag 120, and a location measurement device 130. The access point (AP) 110 is previously arranged in a predetermined area to transmit and receive an RF signal with the tag 120. The access point 110 serves as a kind of beacon, and the position of the tag 120 may be measured and tracked based on the position of the access point 110.

The tag 120 may be attached to a target object to measure the location or track the location. When the position of the object moves, since the tag 120 attached to the object also moves, the position of the object may be tracked through the position tracking of the tag 120. In one embodiment, the tag 120 may correspond to an active tag capable of transmitting and receiving an RF signal with the access point 110. For example, the tag 120 may correspond to an active RFID tag.

The location measuring apparatus 130 may measure the location of the specific tag 120 based on the location of the access point 110 and the received signal strength indication (RSSI) received by the tag 120. For example, the position measuring apparatus 130 may calculate the position of the first tag based on the signals received from the three access points having the largest signal strength among the plurality of access points 110. The first tag measures signal strength of signals received at the plurality of access points 110, and identification information about three access points having the largest signal strength and signal strength values of signals received at the three access points. May be transmitted to the representative access point. The representative access point transmits the identification information for the three received access points and the signal strength values of the signals received at the three access points to the location measuring apparatus 130. In one embodiment, the representative access point may correspond to an access point having the largest signal strength value.

The position measuring device 130 calculates the position of the first tag according to a triangulation technique based on the identification information of the three received access points and the signal strength value of the signal received at the three access points. If the calculated position does not deviate from the preset error range, the position of the first tag is determined as the calculated position. For example, when the calculated position of the first tag is within a preset error range, the position measuring device 130 determines that the first tag is in each access point and a line of sight (LoS) environment, and calculated The position is determined as the position of the first tag.

If the calculated position is out of a preset error range (for example, the first error range), the position measuring device 130 utilizes the peripheral tags of the first tag as an access point and cooperates with each other through the tag to perform the first tag. Accurately measure the position of. For example, when an obstacle or the like is located between the access point and the first tag and is in a non-line of sight (NLoS) environment, the calculated position of the first tag may be outside the preset error range.

When the calculated position is out of a preset error range, the position measuring device 130 may include a first position positioned around the first tag based on signals received at three access points having the largest signal strength with respect to the first tag. The neighbor tags are searched for, and the positions of the first neighbor tags are respectively calculated based on the signals received from the three access points. The position measuring device 130 extracts the second peripheral tags from the first peripheral tags based on the calculated position. For example, the position measuring device 130 may extract, as a second peripheral tag, tags whose positions calculated among the first peripheral tags do not fall within a preset error range (for example, the second error range).

The position measuring device 130 may calculate the position of the first tag based on the signal received from the second peripheral tags and the position of the second peripheral tags.

The access point 110 and the tag 120 may be disposed in various environments, such as indoors as well as outdoors, and may be used for location measurement or location tracking. Hereinafter, for convenience of description, it will be described on the assumption that the access point 110 and the tag 120 are disposed indoors to measure or track the position of an object (eg, logistics).

Referring to FIG. 2, the location measuring device 130 may include a processor 210, a first network interface 220, a second network interface 230, a memory 240, a storage device 250, and an input device interface 260. ) And an output device interface 270.

The processor 210 tracks the location of the identified tag, a tag location measurement procedure that calculates the location of a particular tag (eg, a tag selected by a user or a tag automatically selected by a predefined tag selection procedure). Run the tag location tracking procedure. When the calculated position is out of a preset error range, the processor 210 may accurately measure the position of the specific tag through tag-to-tag collaboration by using the surrounding tags of the specific tag as an access point.

The first network interface 220 transmits and receives data with the access point 110. For example, the first network interface 220 may include an adapter for WLAN communication.

The second network interface 230 transmits and receives data with a user terminal (not shown). For example, the second network interface 220 may include an environment for connecting with the location measuring device 130 through a network, and may include, for example, an adapter for local area network (LAN) communication. For example, the position measuring device 130 may perform a command according to a control command or a user input received from a remote user terminal.

The memory 240 is used to store data necessary to execute various procedures of the positioning device. The memory 240 may be implemented as a volatile or nonvolatile memory.

The storage device 250 may be implemented as a nonvolatile memory such as a solid state disk (SSD) or a hard disk drive (HDD), and is used to store data necessary for the location measuring device 130.

The input device interface 260 includes an environment for receiving user input and may include, for example, an adapter such as a mouse, trackball, touch pad, graphics tablet, scanner, touch screen, keyboard or pointing device. Output Device Interface The output device 270 includes an environment for outputting specific information (eg, message thread) to the user, and may include an adapter such as a monitor or touch screen, for example. In one embodiment, input device interface 250 and output device interface 260 may be connected via a remote connection.

3 is a diagram illustrating a triangulation technique.

The location measuring apparatus 130 may measure the location of the specific tag 120 based on the location of the access point 110 and the received signal strength indication (RSSI) received by the tag 120. For example, in FIG. 3, when the position of the first tag 120a is measured, three signals having the highest signal strength among the signals transmitted from the plurality of access points 110 and received by the first tag 120a may be used. It is assumed that is a signal received from the first access point 110a, the second access point 110b, and the third access point 110c.

The position measuring apparatus 130 adjusts the position of the first tag 120a based on the signal strengths of the first access point 110a, the second access point 110b, and the third access point 110c having the largest signal strength. Measure For example, the position measuring device 130 may measure the position of the first tag 120a according to a triangulation technique based on the signal strength from each access point.

For example, the distance range 310 according to the signal strength of the signal received at the first access point 110a, the distance range 320 according to the signal strength of the signal received at the second access point 110b, and the third When the distance range 330 according to the signal strength of the signal received from the access point 110c is the same as that of FIG. 3, the position of the first tag 120a may be estimated as an area 340 in which each distance range overlaps. have.

When the calculated position of the first tag 120a does not deviate from the preset error range, the position measuring device 130 may determine the measured position as the position of the first tag 120a. In an embodiment, when the range of the overlapping area 340 does not deviate from the preset width or the distance from the

specific access point

110a, 110b or 110c to the first tag 210a does not deviate from the preset distance, The position measuring device 130 may determine that the measured position does not deviate from a preset error range.

In another embodiment, the position measuring device 130 may determine whether the error range is out of range using Equation 1 below.

Where D _min is the shortest distance from the access point to the tag, D _max is the longest distance from the access point to the tag, and f (n) is the average from the access point to the tag depending on the number of tags. The distance, n is the number of tags, D _m1 is the minimum distance coefficient, D _m2 is the longest distance coefficient. f (n) represents a value obtained by arranging the average distance from the access point of the tags (for example, tags in the LoS environment) to which the calculated position does not deviate from a preset error range according to the number of tags. . The location measuring apparatus 130 may calculate and DBize the number of tags that do not deviate from the error range and the average distance from the access point to the corresponding tags.

When the condition of Equation 1 is satisfied, the position measuring device 130 may determine that the calculated position of the first tag 120a is out of a preset error range.

If an obstacle 450 or the like is located between the second access point 110b and the first tag 120a and the first tag 120a is in the NLoS environment, the signal strength of the second access point 110b is The first tag 120a may be smaller than in the LoS environment. Accordingly, the distance range according to the signal strength of the received signal of the second access point 110b may be increased from 420 to 422, and the location of the first tag 120a is an area 440 in which 410, 422, and 430 overlap. Can be estimated.

In this case, the calculated position of the first tag 120a may have a large error. When the calculated position of the first tag 120a is out of a preset error range, the position measuring device 130 utilizes the peripheral tags of the first tag 120a as an access point to collaborate between the first tags and the first tag ( The position of 120a) can be measured accurately.

5 is a diagram illustrating a process of searching for a first peripheral tag.

Referring to FIG. 5, the first access point 110a, the second access point 110b, the third access point 110c, the second tag 510a, and the third tag 510b around the first tag 120a. ), Fourth tag 510c, fifth tag 510d, sixth tag 510e, seventh tag 510f, eighth tag 510g, ninth tag 510h, and tenth tag 510i Assume that is located.

The location measuring device 130 transmits a peripheral tag search request message to three

access points

110a, 110b, and 110c having the greatest strength of the signal received from the first tag 120a, and transmits the three access points 110a,. 110b and 110c transmit a signal to the tags according to the received message.

Second tag 510a, third tag 510b, fourth tag 510c, fifth tag 510d, and sixth tag 510e that receive signals from three

access points

110a, 110b, and 110c. , The seventh tag 510f, the eighth tag 510g, the ninth tag 510h, and the tenth tag 510i have constant signal strengths of signals received from the three

access points

110a, 110b, and 110c, respectively. If it is greater than or equal to the value, it transmits its identification information and the signal strength value of the signal received from the three

access points

110a, 110b, 110c to the

representative access point

110a, 110b or 110c.

For example, a tag whose signal strength of a signal received from three

access points

110a, 110b, and 110c is greater than or equal to a predetermined value may be a second tag 510a, a third tag 510b, a fourth tag 510c, Assuming the fifth tag 510d, the sixth tag 510e, the seventh tag 510f, and the eighth tag 510g, the second tag 510a, the third tag 510b, and the fourth tag The 510c, the fifth tag 510d, the sixth tag 510e, the seventh tag 510f, and the eighth tag 510g receive their own identification information and three

access points

110a, 110b, and 110c. Transmits the signal strength of the acquired signal to a representative access point. Therefore, the second tag 510a, the third tag 510b, the fourth tag 510c, the fifth tag 510d, the sixth tag 510e, the seventh tag 510f, and the eighth tag 510g. May correspond to the first peripheral tags.

The representative access point transmits the identification information and the signal strength value received from the tags (the first peripheral tags) to the position measuring device 130, and the position measuring device 130 has three

access points

110a, 110b, and 110c. The positions of the first peripheral tags are respectively calculated based on the received signal. The process of calculating the positions of the first peripheral tags is as described with reference to FIG. 3.

The position measuring device 130 extracts the second peripheral tags from the first peripheral tags based on the position calculated for the first peripheral tags. In an embodiment, the position measuring device 130 may extract tags as the second peripheral tag in which the position of the calculated tag among the first peripheral tags does not deviate from the preset error range. For example, if the range of the overlapping area does not deviate from the preset range, or if the distance from the

specific access point

110a, 110b, or 110c does not deviate from the preset distance, the position measuring apparatus 130 may measure It may be determined that the position does not deviate from the preset error range.

Assuming that the second tag 510a, the third tag 510b, and the fourth tag 510c are extracted as the second peripheral tag, the position measuring apparatus 130 may determine the second peripheral tags ( The identification information of the 510a, 510b, and 510c and the second peripheral tags may transmit a message to transmit a signal to the first tag 120a.

The representative access point transmits a message for the second

peripheral tags

510a, 510b, and 510c to transmit a signal to the first tag 120a, and the second

peripheral tags

510a, 510b, and 510c send the first tag. Send a signal to 120a.

The first tag 120a stores identification information of the

tags

510a, 510b, and 510c corresponding to the signal strength value and the signal strength value of the signal received from the second

peripheral tags

510a, 510b, and 510c to the representative access point. send. The representative access point transmits identification information of the

tags

510a, 510b, and 510c corresponding to the received signal strength value and the signal strength value to the location measuring apparatus 130. The position measuring device 130 may use the first tag 120a based on the strength value of the signal received from the second

peripheral tags

510a, 510b, and 510c and the position of the second

peripheral tags

510a, 510b, and 510c. Calculate the position of.

For example, the distance range 610 according to the signal strength of the signal received from the second tag 510a, the distance range 620 according to the signal strength of the signal received from the third tag 510b, and the fourth tag ( When the distance ranges 630 according to the signal strength of the signal received at 510c are respectively shown in FIG. 6, the position of the first tag 120a may be estimated as an area 640 in which each distance range overlaps. Accordingly, the position measuring device 130 may more accurately measure the position of the first tag 120a through inter-tag cooperation by using the peripheral tags of the first tag 120a as an access point.

In another embodiment, when the number of the second peripheral tags is less than three, the positioning device 130 may transmit the first tag to the three access points and the second peripheral tags having the largest signal with respect to the first tag 120a. A message may be transmitted to transmit a signal to 120a. When the representative access point receives the message from the location measuring device 130, the representative access point may transmit a message to the second peripheral tags to transmit a signal to the first tag 120a. The first tag 120a measures each signal strength based on the signals received from the three access points and the second peripheral tags, and among the three access points and the second peripheral tags, the three having the largest signal strength. Select the sender (access point or second peripheral tag). The first tag 120a transmits identification information of three callers and signal strength values measured from the callers to the representative access point. The representative access point transmits the received identification information and the measured signal strength value to the location measuring device 130, and based on the received identification information and the measured signal strength value of the first tag 120a. Calculate the location.

Referring to FIG. 7A, when the location measurement target tag (eg, the first tag 120a) is determined, the location measurement device 130 may determine a plurality of

access points

110a, 110b,. 110n) and transmits a location check request message (step S710). The location confirmation request message may include identification information of the location measurement target tag (first tag 120a). In one embodiment, the location measurement target tag may be selected by a user or automatically selected by a predefined tag selection procedure.

The plurality of

access points

110a, 110b, ..., 110n receiving the location request message transmit a signal to the

tags

120a, 120b, ..., 120n (step S712). For example, the

access points

110a, 110b,..., 110n may transmit a location request message. In one embodiment, the location request message may include identification information of the location measurement target tag (first tag 120a) and identification information of the access point transmitting the message.

The first tag 120a measures the strength of the signal received from each of the

access points

110a, 110b, ..., 110n (step S714). The first tag 120a selects three

access points

110a, 110b, and 110c having the largest signal strength of the received signal (step S716), and identifies three selected

access points

110a, 110b, and 110c. The information and the signal strength value of the signal received at the corresponding access point are transmitted to the representative access point (step S718). In one embodiment, the identification information for the access point may correspond to a media access control (MAC) address of the access point. In one embodiment, the representative access point may correspond to an access point having the largest signal strength among the three

access points

110a, 110b, and 110c.

Assuming that the representative access point is the first access point 110a, the first access point 110a may identify identification information of the three received

access points

110a, 110b, and 110c and a signal received at the corresponding access point. The signal strength value of the signal is transmitted to the position measuring device 130 (step S720).

The position measuring apparatus 130 calculates the position of the first tag 120a based on the identification information of the three

access points

110a, 110b, and 110c received and the signal strength value of the signal received at the access point. (Step S722). If the calculated position is within a preset error range, the position measuring device 130 determines the calculated position as the position of the first tag 120a (step S724).

If the calculated position is out of a preset error range, the position measuring device 130 may set the first position to three

access points

110a, 110b, and 110c having the largest signal strength of the signal received from the first tag 120a. The neighbor tag search request message is transmitted (step S730). The first neighbor tag search request message may include identification information of three

access points

110a, 110b, and 110c.

The three

access points

110a, 110b, and 110c that have received the first neighbor tag search request message transmit signals to the

tags

120a, 120b, ..., 120n (step S732). For example, three

access points

110a, 110b, and 110c may transmit a first neighbor tag search request message. In an embodiment, the first neighbor tag search request message may include identification information of the location measurement target tag (first tag 120a) and identification information of an access point transmitting the message.

The remaining tags except for the first tag 120a measure the strength of the signal received from the three

access points

110a, 110b, and 110c (step S734). A tag whose strength of the signal received from the three

access points

110a, 110b, and 110c is greater than or equal to a predetermined value, respectively, indicates a signal strength value of the signal received from the three

access points

110a, 110b, and 110c. The data is transmitted to the representative access point 110a (step S736, step S738).

The representative access point 110a transmits the identification information of the received tag and the signal strength values of the signals received from the three

access points

110a, 110b, and 110c to the position measuring device 130 (step S740).

The position measuring apparatus 130 calculates the positions of the first peripheral tags based on the identification information of the received tag and the signal strength values of the signals received from the three

access points

110a, 110b, and 110c with respect to the corresponding tag. (Step S742). The position measuring apparatus 130 extracts, as the second peripheral tag, tags in which the calculated position is within a preset error range based on the calculated position of the first peripheral tags (step S744).

The location measuring apparatus 130 transmits identification information of the second peripheral tags and a message for allowing the second peripheral tags to transmit a signal to the first tag 120a (step S746). The representative access point 110a transmits a message to the second peripheral tags requesting to transmit the message to the first tag (step S748). In one embodiment, the message requesting the message to be transmitted to the first tag may include identification information of the second peripheral tags.

The second peripheral tags receiving the message transmit a signal to the first tag 120a (step S750). According to an embodiment, the second peripheral tags may transmit a signal including identification information of the corresponding tag to the first tag 120a.

The first tag 120a transmits the strength values of the signals received from the second peripheral tags and identification information of the tag corresponding to the strength values to the representative access point 110a (step S752). The representative access point 110a transmits the strength value of the signals received from the second peripheral tags and the identification information of the tag corresponding to the strength value to the location measuring apparatus 130 (step S754).

The position measuring apparatus 130 calculates the position of the first tag 120a based on the positions of the second peripheral tags calculated in operation S742 and the signal strength received from the corresponding tags in the first tag 120a (step S742). S756).

Although described above with reference to the preferred embodiment of the present application, those skilled in the art various modifications and changes to the present application without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims

In the method of measuring the position of the tag,

(a) calculating a position of a first tag based on a signal received at three access points having the largest signal strength among the plurality of access points;

searching for first peripheral tags located around the first tag based on signals received at the three access points when the calculated position is out of a preset error range;

(c) calculating positions of the first peripheral tags based on the signals received at the three access points, respectively;

(d) extracting second peripheral tags from the first peripheral tags based on the calculated position; And

(e) calculating a position of the first tag based on a signal received from the second peripheral tags and the position of the second peripheral tags.
The method of claim 1, wherein step (b)

Requesting the three access points to retrieve the first peripheral tags; And

And receiving identification information and a corresponding signal strength of a tag in which the strengths of the signals received at the three access points are above a predetermined value from a specific access point.
The method of claim 1, wherein step (c)

And calculating the positions of the first peripheral tags based on the positions of the three access points and the signal strength received at each of the first peripheral tags.
The method of claim 1, wherein step (d)

And extracting, as the second peripheral tags, tags having a calculated position among the first peripheral tags within a preset error range.
The method of claim 1, wherein step (e)

Requesting a specific one of the three access points for the second peripheral tags to transmit a signal to the first tag; And

And receiving, by the first tag, the strength of a signal received from the second peripheral tags and identification information of the corresponding tag from the specific access point.
A plurality of access points;

A plurality of tags; And

A tag position measurement system comprising a position measurement device,

The position measuring device

(a) calculating the position of the first tag based on the signals received at the three access points having the largest signal strength among the plurality of access points,

(b) searching for first peripheral tags located around the first tag based on signals received from the three access points when the calculated position is out of a predetermined error range,

(c) calculating positions of the first peripheral tags based on the signals received at the three access points, respectively;

(d) extracting second peripheral tags from the first peripheral tags based on the calculated position;

(e) calculating a position of the first tag based on a signal received from the second peripheral tags and the position of the second peripheral tags.
The apparatus of claim 6, wherein the position measuring device is

Requesting the three access points to search for the first neighbor tags,

The tag position measurement system, characterized in that for receiving the identification information and the corresponding signal strength for the tag, the strength of the signal received at the three access points from each of the three access point or more than a predetermined value.
(a) calculating a position of a specific tag based on a signal received at at least three access points having the largest signal strength among the plurality of access points;

(b) when the calculated position is out of a preset first error range, a preset second of at least one first neighboring tag around the specific tag based on signals received from the at least three access points; Determining at least one second neighbor tag that is within an error range; And

(c) recalculating the position of the specific tag via the at least one second neighbor tag.