JP2006266859A - Position measurement system and position measurement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position measurement system and a position measurement method for precisely measuring the position of a human, or the like regardless of position measurement using radio wave strength that has been considered to be unsuitable for indoor position measurement conventionally. <P>SOLUTION: The position measurement system comprises a radio tag 14 that is a object to be measured for position, a plurality of access points AP1-AP9 for measuring the position of the radio tag 14, and a server 16 connected directly or indirectly to the access points AP1-AP9. The access points AP1-AP9 acquire information related to the strength of radio waves from radio waves received from the radio tag 14 and other access points AP1-AP9, and send the acquired information to the server 16. The server 16 measures the position of the radio tag 14 by a triangulation method and upon whether the radio tag 14 is located inside a triangle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a position measurement system and a position measurement method using radio wave intensity, and in particular, a network (sensor network) including a measurement device for recognizing the position and movement of a moving body moving indoors or the like and a wireless The present invention relates to a system and method for recognizing position and movement using the intensity of radio waves emitted from a sensor network.

  Some systems for recognizing position and movement conventionally use radio wave intensity. The radio wave intensity attenuates in inverse proportion to the square of the distance. For example, Patent Literature 1 describes this. There is a technique for estimating the distance to an object using this law.

JP-A-10-213614

  However, when the position is determined using only the radio wave intensity, it is difficult to specify the position because there are multiple propagations due to reflection of radio waves, that is, multipath fading, attenuation of radio waves due to the presence of people, and the like. It is difficult to identify the location, especially indoors. For example, experimental data show that position measurement errors increase around indoor metal installations and near walls, and that the strength of radio waves decreases when a person stands between radio communication terminals. Known from.

  As the distance between the terminals that perform radio wave communication increases, these problems become more serious. When installed every 100 meters, the position is easily affected by obstacles, and the position is measured using the radio wave intensity. Not suitable for. Therefore, products of these standards are not suitable for indoor position measurement.

  The present invention eliminates such disadvantages of the prior art, and the position of a person or the like who moves around indoors can be accurately measured while using conventional radio field strength that is not suitable for indoor position measurement. It is an object of the present invention to provide a position measuring system and method capable of measuring well.

  In order to solve the above-described problems, the present invention provides a wireless device capable of wireless communication, which is an object of position measurement, a plurality of measurement devices capable of wireless communication for position measurement of a wireless device, and a plurality of In a position measurement system that includes a position measurement means connected to a measurement device and measures the position of a wireless device, the plurality of measurement devices receive information on the strength of the radio wave from radio waves received from the wireless device and other measurement devices. And the received reception information is sent to the position measurement means, and the position measurement means measures the position of the wireless device from the reception information.

  At this time, it is preferable that the plurality of measurement devices acquire received information using the output as a trigger when the radio device outputs radio waves. In this case, using a sensor network consisting of multiple measuring devices, using radio waves received from a measuring device (for example, an access point) that is triggered by radio waves from wireless devices that are movable nodes, each receiving point (each access The wireless device is positioned according to the reception strength at the point).

  When the present invention is applied to a wireless network environment, a radio wave transmitted from a wireless device (for example, a radio wave tag) is used as a trigger, and a radio wave intensity of an radio wave from an access point installed around the radio tag is used as a position measuring means (for example, a server). ), The position of the radio wave tag can be calculated with a small error.

  In this system, at least three measurement devices are included, and the position measurement means determines whether there is a wireless device inside the triangle formed by the three measurement devices based on the received information received from the three measurement devices. Can be determined.

  In the position measurement system, the position measurement unit measures the position of the wireless device using the reception information acquired by the measurement device and having a radio wave intensity included in the information of a predetermined magnitude or more. Is preferred. Even if the moving object moves around in the environment where the radio field intensity is measured, there are few errors by using a large number of access points and using only a large number of access points whose radio field intensity is determined to be above the threshold. Position measurement can be performed.

  The wireless communication used in the present invention is preferably short-range wireless communication. When short-range wireless is used, for example, battery operation is possible in the wireless device and the measuring device. For this reason, it is easy to install the wireless device and the measuring device, and it is also easy to reinstall the measuring device for changing the position of the measuring device. In the case of long-distance wireless communication in which battery driving is difficult, a power line is connected to the measuring device, but an outlet for that is required, and the power line is difficult to route. Thus, installation and re-installation become more difficult.

  In the present invention, in order to solve the above-described problem, a wireless device capable of wireless communication, which is a position measurement object, and a plurality of measurement devices capable of wireless communication for position measurement of the wireless device; In a position measuring system that includes a position measuring unit connected to a plurality of measuring devices and measures the position of the wireless device, the plurality of measuring devices are triggered by the output when the wireless device outputs radio waves. The reception information regarding the intensity of the radio wave is acquired from the radio wave received from the mobile station, the acquired reception information is sent to the position measurement unit, and the position measurement unit may measure the position of the wireless device from the reception information.

  Embodiments of a position measurement system according to the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 shows the configuration of an embodiment of a position measurement system 10 according to the present invention. Referring to FIG. 1, a position measurement system 10 includes a wireless tag 14 worn by a person 12, access points AP1 to AP9 capable of wirelessly communicating with the wireless tag 14, and a wireless network including access points AP1 to AP9. Server GW that connects the server and the server, a server that determines the position by recording and managing the information of the wireless tag 14 collected by the access points AP1 to AP9 and the information of the access points AP1 to AP9 collected by the wireless tag 14 Has 16.

  The wireless tag 14 is compliant with, for example, the IEEE802.15.4 communication standard, and includes a 2.4 GHz analog wireless circuit, a radio wave intensity measurement circuit, a signal processing circuit, and a storage circuit (not shown). The access points AP1 to AP9 can also have the same configuration as the wireless tag 14.

  In this embodiment, the wireless network is a so-called mesh network. In the mesh network, the access points AP1 to AP9 communicate with each other, and the access points AP1 to AP9 have a function of relaying data one after another and finally relaying data to the server 16. In this embodiment, access points AP5 and AP9 are connected to the server 16 via the gateway GW. An example of a mesh network is the Internet.

  The wireless network may be a star wireless network. In a star-type wireless network, the access points are connected to each other via the gateway GW, with the gateway GW at the center.

  An arbitrary number of wireless tags 14 and access points AP1 to AP9 may be provided. Wireless communication is performed between the access points AP1 to AP9 and between the access points AP1 to AP9 and the wireless tag 14. The wireless tag 14 and the access points AP1 to AP9 have omnidirectional antennas. Both the access points AP1 to AP9 and the wireless tag 14 can change the size of the wireless output, and by changing the size of the wireless output, the range over which the radio wave can reach can be increased or decreased. . These devices may have overlapping radio wave ranges, or one range may include the other range. The connection between the access points AP1 to AP9 and the server 16 is a wireless connection in this embodiment, but may be a wired connection.

  The wireless tag 14 used in this system has a transmission / reception function, a function that periodically transmits radio waves from the wireless tag 14, and a function that receives radio waves output from the access points AP1 to AP9 and measures their radio field strength. Have. Similarly to the wireless tag 14, the access points AP1 to AP9 receive the radio waves output from the wireless tag 14 and other access points AP1 to AP9 and measure the radio field strength, and the obtained strength is stored in the server 16. It has the function to transfer (send) to. The server side gateway GW relays the data to the server 16. The control unit 20 of the server 16 stores the input data in the storage unit 22. The controller 20 uses the stored data to determine the position of the wireless tag 14 by a method described later.

  In the mesh network of the present embodiment, when the position of the access points AP1 to AP9 is changed, the network is automatically reconfigured and isolated so that communication with any of the access points AP1 to AP9 is possible (others It shall have a function to eliminate access points.

  In this system, a person 12 holds a wireless tag 14 as shown in FIG. 2, and the wireless tag 14 transmits radio waves at a certain time interval (for example, 3 seconds). The position when the person 12 walks around the wireless communication range covered by the mesh network as shown by the path 18 can be measured every 3 seconds. In FIG. 2, the access points AP are arranged in a substantially lattice point shape.

  Returning to FIG. 1, in this system, the access points AP1 to AP9 are installed so as to cover an area where the position of the wireless tag 14 is measured. Before starting the measurement of the position of the wireless tag 14, pre-registration is performed for the access points AP1 to AP9 as follows. Identification information (hereinafter referred to as access point ID) for identifying the installed access points AP1 to AP9 and the coordinates of the positions of the access points AP1 to AP9 are registered in the server 16.

  As an example, registration is performed as follows. In order to register the positions where the access points AP1 to AP9 are installed, the coordinates of the location where each access point exists are registered using XY coordinate axes separated by a predetermined interval. Alternatively, the relative distance between the access points AP1 to AP9 may be measured, and the relative coordinates of the access points AP1 to AP9 may be set on the basis of the positions of the predetermined access points AP1 to AP9. When the positions of the installed access points AP1 to AP9 are changed, the coordinates of the positions of the access points AP1 to AP9 are checked and re-registered in the server.

  Here, the distance between the access points AP1 to AP9 may be measured, or the access points AP1 to AP9 estimated from the radio field strength obtained by communicating between the access points AP1 to AP9. It may be the distance between. The radio wave intensity is measured by a radio wave intensity measurement circuit. As the radio wave intensity measurement circuit, for example, a so-called received signal strength display (RSSI (Received Signal Strength Indicator) circuit is used. The amplitude of the square wave detection output of the radio wave is measured, and the measured value is used as the received signal strength.

  Next, a method for measuring the position of the wireless tag will be described. In this system, wireless tags, access points, and server-side gateways operate in cooperation. Each individual operation will be described first.

  The operation of the wireless tag 14 will be described. The wireless tag 14 transmits the wireless tag information by multicast at a predetermined time interval (for example, 3 seconds). This radio wave that triggers the operation of the system transmitted by the wireless tag 14 at predetermined time intervals is referred to as radio wave 1. The wireless tag information includes a tag ID, which is identification information of the wireless tag 14, and a time ID indicating the transmission time. A detailed example will be described later.

  The access point that has received the radio wave 1 measures the intensity of the received radio wave and then transmits the information to the gateway. The other access point that received the transmission radio wave measures the intensity of the received radio wave, and uses the APID that is identification information of the access point that transmitted the radio wave and the reception radio wave intensity as AP reception information. This AP reception information is called return AP reception information. The return path AP reception information is information generated by the access point receiving the radio wave output by the access point. However, when the information is not obtained from the access point from the first time and the previous transmission to the present time, the AP reception information cannot be generated, so the empty character string is generated as the return path AP reception information and the empty character string is transmitted.

  After the radio wave 1 is transmitted, until the next transmission, the wireless tag 14 stands by in a state waiting for reception of the radio wave from the access point.

  When the wireless tag 14 receives a radio wave (radio wave 2 described below) from the access point, the radio tag 14 measures the radio field intensity. This measurement operation is performed every time the transmitted radio waves are received from a plurality of access points during the next transmission time, that is, after 3 seconds. In this embodiment, the radio wave intensity is not used for position measurement of the wireless tag 14, but may be used for position measurement to improve measurement accuracy. When the next transmission time comes, the wireless tag 14 transmits the wireless tag information.

  An operation sequence of the wireless tag 14 will be described with reference to FIG. When activated, the wireless tag 14 first clears stored data in a built-in memory (not shown) and resets a built-in timer (not shown). After resetting the timer, time measurement is started by the timer (step S1). Next, it is checked by the timer whether or not the transmission time of 3 seconds has elapsed (step S2). If 3 seconds have elapsed, the wireless tag information is transmitted (step S3). After transmission, the accumulated data in the built-in memory is cleared and the built-in timer is reset. The reason for clearing the stored data in the built-in memory is that the capacity of the memory built in the wireless tag is small. After resetting the timer, time measurement is started by the timer (step S4).

  On the other hand, if 3 seconds have not elapsed, it is checked whether or not radio waves from the access point have been received (step S5). When receiving, the electric field strength of the received radio wave is measured (step S6). After the measurement, it is stored in the memory (Step S7). On the other hand, when the radio wave from the access point is not received, the process returns to step S2. The operation of the wireless tag has been described above. Next, the operation of the access point will be described.

  The access point is waiting in a reception waiting state, and starts processing when receiving a radio wave transmitted by the wireless tag 14 by multicast or a radio wave transmitted by an access point other than itself to the server side gateway.

  When the access point receives the radio wave transmitted by the wireless tag 14 (the above-described radio wave 1), the access point measures the reception intensity, and then, the wireless tag information on the radio wave of the wireless tag and the measured reception intensity are Generated as outbound reception information. The access point transmits a radio wave carrying the generated outbound reception information to the server side gateway. This radio wave is defined as radio wave 2. The radio wave 2 is a radio wave that is first output from the access point after the radio wave 1 is transmitted. A radio wave output by another access point after the radio wave 2 is output is a radio wave 3. Outbound reception information is information generated by an access point receiving radio waves output from a wireless tag.

  When the access point receives a radio wave from another access point to the server-side gateway, the access point measures the reception intensity and then records the received AP AP reception information in a built-in memory (not shown). This recording is continued until the next radio wave is received from the wireless tag, and all the radio waves received from other access points and their intensities are recorded.

  Focusing on one access point, the operation sequence of the access point will be described with reference to FIG. All access points perform the same operation. The access point checks whether there is reception from the wireless tag 14 (step S8). When receiving, the electric field strength of the received radio wave is measured (step S9). The forward path reception information obtained by measurement is transmitted (step S10). After transmission, the process returns to step S8.

  On the other hand, if not received, it is checked whether or not radio waves from the access point are received (step S12). When receiving, the electric field strength of the received radio wave is measured (step S13). After the measurement, it is stored in the memory as return AP reception information (step S14). On the other hand, when the radio wave from the access point is not received, the process returns to step S8. The operation of the access point has been described above. Next, the operation of the server side gateway will be described.

  The access point corresponding to the server side gateway is always waiting to receive radio waves. Every time a radio wave of forward path reception information or return path AP reception information arrives from another access point, all information added thereto is sent to the server 16, and the server 16 stores the information. The sequence is shown in FIG. The gateway checks whether it has received radio waves from other access points (step S15). When receiving, the information contained in the received radio wave is transferred to the server 16 (step S16). On the other hand, when the radio wave from the access point is not received, the process returns to step S15.

  The radio wave transmission / reception relationship between the wireless tag 14 and the access point is shown in FIGS. FIG. 6 shows a transmission / reception relationship in this system including the wireless tag 14 and the two access points AP1 and AP2. The radio wave 124 transmitted from the wireless tag 14 held by the person 12 is received by the nearest access points AP1 and AP2 (FIG. 6 (a)). The radio wave 124 includes wireless tag information.

  When receiving the radio wave 124, the access points AP1 and AP2 measure the radio field intensity. When the access points AP1 and AP2 receive the radio wave from the wireless tag 14, they immediately transmit the forward path reception information and the return path AP reception information recorded in their own access points AP1 and AP2 (FIG. 6 (b)).

  In the case of this figure, it is assumed that the access point AP1 outputs the radio wave to the gateway before the access point AP2. This radio wave becomes radio wave 2 26. Assume that the access point AP2 outputs radio waves toward the gateway behind the access point AP1. This radio wave becomes radio wave 328. The radio wave 3 is a radio wave output from another access point after the radio wave 2. The radio wave 226 immediately after the activation of this system does not include return path AP reception information. This is because the access point AP1 has not yet received the radio wave 3 and therefore cannot generate return path AP reception information.

  When the wireless tag 14 receives the radio wave 26 and the radio wave 328, the wireless tag 14 measures the intensity of the radio wave 226 and the radio wave 328, and then, for each radio wave (access point AP1, AP2) in the wireless tag 14 Record and continue waiting for reception until the next transmission.

  When radio wave 226 and radio wave 328 are received by other access points AP1 and AP2 instead of the wireless tag, that is, when radio wave 226 is received by access point AP2 or radio wave 328 is received by access point AP1. In this case, the other access points AP1 and AP2 measure the radio field strength, accumulate the return path AP reception information in the access points AP1 and AP2, and wait until the next time the wireless tag 14 outputs radio waves.

  When the server-side gateway receives the radio wave 226 and the radio wave 328, all the received information is transferred to the server, and the server stores the information in the DB 22 shown in FIG. Thereafter, when 3 seconds elapse, the wireless tag 14 outputs the radio wave 124 (FIG. 6 (c)). The radio wave 124 includes wireless tag information. As shown in FIG. 6A, the radio waves 124 are received by the access points AP1 and AP2.

  In this way, the processes of FIGS. 6A to 6C are repeated. The system repeats the operations described above. That is, the strength of the radio wave 124 transmitted from the wireless tag 14 is measured at each access point, and the radio wave from each access point is triggered by the arrival of the radio wave 124 transmitted from the wireless tag 14 as another access point. , And received by wireless tag. Other access points and wireless tags measure their radio field strength. Each access point includes the received information in the radio wave 226 and the radio wave 328 and sends it to the server side gateway, and the server side gateway collects the information.

  Next, with respect to the details of the stored information, a case of a system including one wireless tag 14 and one access point AP1 will be described with reference to FIG. FIG. 7 shows a radio wave 1 30a, a radio wave 2 30b, a radio wave 1 30c, and a radio wave 2 30d that are sequentially transmitted and received between the wireless tag 14 and the access point AP1. Further, FIG. 7 shows a table format in which the radio tag information 32a when these radio wave 1 30a, radio wave 2 30b, radio wave 1 30c, and radio wave 2 30d include radio tag information, and the transmission partner 32b of these radio waves. The received partner and its radio wave intensity 32c, the access point 32d when the access point transmits, and the transmission information 32e are shown. MC described in the transmission partner 32b column means multicast, and GW means server side gateway.

  When this system is activated, the wireless tag 14 outputs the radio wave 130a by multicast. The radio wave 130a includes a wireless tag ID 34a for identifying a wireless tag and a time ID 34b for identifying time as wireless tag information. In the case of the radio wave 130a, the wireless tag ID 34a is Tag1, and the time ID 34b is 111140000. At this time, it is assumed that the access point AP1 receives the radio wave 130a at the reception strength −45.

  Next, the access point AP1 transmits a radio wave 230b to the server side gateway GW. The radio wave 230b includes Tag1 (11140000, -45) as the forward path reception information 40a. This forward path reception information 40a means that the radio wave 130a has been received at the reception intensity −45 when the time is 11140000 as described above. The wireless tag 14 receives the transmission of the radio wave 230b to the server-side gateway and measures the radio field intensity of -38.

  The wireless tag 14 transmits a radio wave 130c at the next transmission time. The radio wave 130c does not include outbound or inbound AP reception information. This is because the received intensity of the radio wave received by the wireless tag 14 is not used for position measurement in this embodiment. At that time, the access point AP1 receives the radio wave 130c with the reception strength -42.

  Next, the access point AP1 transmits a radio wave 230d to the server side gateway GW. The radio wave 230d includes Tag1 (11140300, -42) as the outbound reception information 40b. This forward path reception information 40b means that the radio wave 130c is received at the reception intensity −42 when the time is 11140300 as described above. The wireless tag 14 receives the transmission of the radio wave 230d to the server side gateway, and measures the radio wave intensity of -35. This is repeated thereafter.

  Next, regarding the details of the stored information, a system including one wireless tag 14 and two access points AP1 and AP2 will be described with reference to FIG. 8 that are the same as those in FIG. 7 are given the same reference numerals, and descriptions thereof are omitted. FIG. 8 shows a radio wave 1 36a, a radio wave 2 36b, a radio wave 3 36c, a radio wave 1 36d, and a radio wave 2 36e that are sequentially transmitted and received between the wireless tag 14 and the access points AP1 and AP2. Further, FIG. 8 is a table format, and for these radio wave 1 36a, radio wave 2 36b, radio wave 3 36c, radio wave 1 36d, and radio wave 2 36e, the RFID tag information 32a, the received partner and its radio wave intensity 32c, and the access point The access point 32d and transmission information 32e when transmitting is shown.

  When there are a plurality of access points AP1 and AP2, the radio waves 1 36a and 1 36d received from the wireless tag 14 are asynchronously transmitted from the access points AP 1 and AP 2 with radio waves 2 36b, 3 36c, and 2 36e. The order of transmission is not specified for radio waves transmitted from the access point, but basically the same operation as in FIG. 7 is performed, and even if transmission is not specified, information is reliably transmitted without causing collisions between transmissions. The following method is used so that can be transmitted.

  When this system is activated, the wireless tag 14 outputs the radio wave 136a by multicast. The radio wave 136a includes a wireless tag ID 34a and a time ID 34b as wireless tag information. In the case of the radio wave 136a, the wireless tag ID 34a is Tag1, and the time ID 34b is 11140000. At this time, it is assumed that the access point AP1 receives the radio wave 136a with the reception strength −45, and the access point AP2 receives the radio wave 136a with the reception strength −28. These are stored in the access point AP1 and the access point AP2 as the forward path reception information 42a and 42b, respectively.

  Next, the access point AP1 transmits a radio wave 236b to the server side gateway GW. The radio wave 236b includes Tag1 (11140000, -45) as the forward path reception information 42a. This outbound reception information 42a means that the access point AP1 has received the radio wave 136a at the reception intensity −45 when the time is 11140000 as described above. The wireless tag 14 receives the transmission of the radio wave 236b to the server side gateway, and measures the radio wave intensity of −28. The access point AP2 receives the transmission of the radio wave 236b to the server side gateway, measures the radio field intensity of -38, and stores it as the return AP reception information 42c in the access point AP2.

  Next, the access point AP2 transmits a radio wave 336c to the server side gateway GW. The radio wave 336c includes Tag1 (11140000, -28) as the forward path reception information 42b. This forward path reception information 42b means that the access point AP2 has received the radio wave 136a at the reception strength −28 when the time is 11140000 as described above. The radio wave 336c includes (Tag1 (11140000), AP2 (AP1, -38)) as the return path AP reception information 42c. The wireless tag 14 receives the transmission of the radio wave 336c to the server side gateway, and measures the radio wave intensity of -25. The access point AP1 receives the transmission of the radio wave 336c to the server side gateway, measures the radio wave intensity of −32, and stores it as the return AP reception information 42d in the access point AP1.

  The wireless tag 14 transmits a radio wave 136d at the next transmission time. The radio wave 136d includes Tag1 (11140300) as wireless tag information. In the case of the radio wave 136d as the wireless tag information, the wireless tag ID 34a is Tag1, and the time ID 34b is 11140300. At that time, the access point AP1 receives the radio wave 136d with a reception strength of -41, and the access point AP2 receives the radio wave 136d with a reception strength of -39. The access point AP1 accumulates as the forward path reception information 42e. The access point AP2 also accumulates as outbound reception information (not shown).

  Next, the access point AP1 transmits a radio wave 236e to the server side gateway GW. The radio wave 236e includes Tag1 (11140300, -41) as the outbound reception information 42e. This forward path reception information 42e means that the access point AP1 has received the radio wave 136d at the reception intensity −41 when the time is 11140300 as described above. The radio wave 236e includes (Tag1 (11140000), AP1 (AP2, -32)) as the return path AP reception information 42f. The wireless tag 14 receives the transmission of the radio wave 236e to the server side gateway, and measures the radio field intensity of -31. The access point AP2 receives the transmission of the radio wave 236e to the server-side gateway, measures the radio field intensity of −32, and stores it as return path AP reception information (not shown) in the access point AP2. This is repeated thereafter.

  In this way, the server 16 collects information, and the server 16 calculates the position of the radio wave tag 14. The server 16 calculates the position of the radio wave tag 14 from the radio wave intensity when another access point receives the radio wave from the access point and the radio wave intensity when the access point receives the radio wave from the wireless tag.

  In this embodiment, radio waves from the wireless tag 14 to each access point are used for position measurement of the wireless tag 14 by a so-called triangulation method. The triangulation method is possible if there are two access points. However, in the triangulation method of this embodiment, the position is determined more accurately by using the radio wave intensity at three or more access points. For example, when the measurement result of the position using the radio wave intensity at a certain access point is significantly different from the measurement results of the position by the other two access points, the measurement result by the access point is not adopted.

  The reason for using radio waves from the wireless tag 14 to each access point in the triangulation method is that, according to this radio wave, position information of the wireless tag 14 acquired by each access point at the same time can be obtained. In the following triangular positioning method, since the position cannot be measured only with the radio wave from the wireless tag 14 to each access point, radio waves from the access point to other access points are also used. The triangulation method itself will not be described further.

  On the other hand, radio waves from the access point to the wireless tag and other access points are used to determine the position of the wireless tag 14 by the triangular positioning method. In this case, the three access points determine whether or not there is a wireless tag inside the triangle formed by the three access points, based on the radio wave intensity received from the three access points. The final position is determined from the results of the two positionings of the triangulation method and the triangular positioning method.

  The positioning results by the two methods are combined as follows, for example. The triangle positioning method determines which triangle the wireless tag 14 is inside. And among the positions of the wireless tags obtained by the triangulation method, only those located inside the triangle are adopted.

  In the present invention, the position of the wireless tag 14 may be determined using only one of the triangulation method and the triangulation method.

  Hereinafter, the triangle positioning method will be described. The triangle positioning method is based on the following idea. There is a law that the radio wave intensity attenuates in inverse proportion to the square of the distance. This is a law where there is no influence, such as an anechoic chamber, and it does not hold in a general place. However, according to this law, when radio waves transmitted from an access point (access point AP1) are measured at two locations (location A and location B), the radio field intensity at the two measurement locations is If the relationship of radio wave intensity (location A)> radio wave intensity (location B) is satisfied, it can be considered that the location A is closer to the access point AP1. This measurement is made for a number of access points and this idea is applied. In general, in a range where the radio wave intensity is strong (a range where the distance between the radio wave transmission point and the radio wave reception point is short), this idea can be considered to be valid with a considerable probability. In this system, this measurement is performed at a plurality of access points. A mobile node (wireless tag) can exist with high probability in a triangle having any three access points as vertices. And by increasing the number of access points one by one to these three access points and adopting the method described later, it is possible to obtain a number of triangles in which mobile nodes may exist. it can. By obtaining the common part of these triangles, the range of positions where the mobile node exists can be narrowed.

The triangle positioning method will be described with reference to FIG. First, consider access points Nl, N2, N3 and mobile node M1. It is assumed that the mobile node M1 is in a triangle surrounded by access points N1, N2, and N3. The triangle positioning method is performed according to the following procedure.
(1) The radio field intensity of the radio wave output from the access point N1 is measured at the mobile node M1 and the access points N2 and N3.
(2) The radio field intensity of the radio wave output from the access point N2 is measured at the mobile node M1 and the access points N1 and N3.
(3) The radio field intensity of the radio wave output from the access point N3 is measured at the mobile node M1 and the access points N1 and N2.
(4) For the radio wave transmitted from access point N1, if the radio field intensity measured at mobile node Ml is stronger than the radio field intensity measured at access points N2 and N3, mobile node M1 has access points from access points N2 and N3. You may judge that it is close to N1.
(5) Similarly, for radio waves transmitted from access point N2, if the radio field intensity measured at mobile node M1 is stronger than the radio field intensity measured at access points N1 and N3, mobile node M1 is more than access points N1 and N3. It may be determined that the access point is near the access point N2.
(6) Similarly, for radio waves transmitted from access point N3, if the radio field intensity measured at mobile node M1 is stronger than the radio field intensity measured at access points N1 and N2, mobile node M1 is more than access points N1 and N2. It may be determined that the access point is near the access point N3.
Thus, when the above conditions (4), (5), (6) are satisfied, the mobile node is in the triangle connecting the access points N1, N2, N3 from (4), (5), (6). It can be determined that M1 is present.
(7) Further, as shown in FIG. 10, if the access point N4 is added and the mobile node M1-a is found in the access points N1, N2, N4, the access points N1, N2, N3 are formed. The range can be narrowed down to a common area of the triangle formed by the triangle and the access points N1, N2, and N4.

  Since radio waves are affected by fading, the measurement results of two triangles do not always match (referred to as “singularity generation”) even when measuring with four nodes as described above. Therefore, as shown in FIG. 11, the number of access points can be further increased to determine whether the point is a singular point.

  In FIG. 11, when viewed from the access point N1, the mobile node M1 is measured to be at the position M1 (N1), and similarly, when viewed from the access point N2, N3, N4, N5, N6. , And M1 (N2), M1 (N3), M1 (N4), M1 (N5), and M1 (N6). In this case, considering the triangle of the access points N1, N2, N3, the mobile node M1 is outside the triangle. On the other hand, considering the triangles of the access points N2, N3, and N4, the mobile node M1 is inside the triangle.

  If an access point (access point N5 or N6 in FIG. 11) ahead of mobile node M1 (N1), which is a singular point, is used, it can be determined whether the singular point is due to fading. In the case of FIG. 11, the mobile node M1 is calculated to be farther than the access points N2 and N3 when viewed from the access point N1, but is closer to the access points N2 and N3 when viewed from the access points N5 and N6. Since the conclusion was obtained, it is deleted as a singular point. Thus, when it is judged that it is an influence by fading (shadowing etc.), a final positioning is performed from the surveying point except a singular point.

  In this system that emits radio waves for positioning from all access points using radio waves from wireless tags as triggers, radio waves are likely to collide. Therefore, it is assumed that radio waves for positioning are not transmitted from an access point determined that radio waves from the wireless tag are weak. Further, radio wave collision may be prevented by CSMA / CD (Carrier Sense Multiple Access with Collision Detection).

  According to this embodiment, the following effects can be obtained. If you use a network (sensor network) that uses a short-range wireless (for example, a short-range wireless using a device that conforms to the ZigBee communication standard as a sensor) that is capable of two-way communication at low speed, you can Many access points can be installed where the view from the mobile node works. By using such a large number of access points, it is possible to determine whether the radio field intensity measured at the mobile node is due to a singular point or not, so that effective positioning is possible even with positioning using the radio field intensity.

  Positioning using radio field strength contributes to making wireless tags thin, small and cheap. This is because a circuit for measuring the radio wave intensity is usually provided in a device. However, methods that use other than radio field strength use the difference in arrival time of radio waves and the direction of arrival of radio waves, but in order to realize these methods, it is necessary to add dedicated hardware. The wireless tag is thicker, larger and more expensive.

  Furthermore, even if there is a person between the access point and the wireless tag and there is a situation where the radio wave is dynamically disturbed or there are many access points that the radio wave from the wireless tag is determined to be weak, the radio field strength is above the threshold value. If there are three or more access points determined to be, positioning can be performed.

  When the position of the access point is changed, it is only necessary to change the position of the access point registered on the server side, and the application area of this system is wide. In addition, for locations that are intricate and where visibility is not effective, high location accuracy can be obtained by installing a large number of access points. It is more advantageous than positioning by devices that have received WiFi certification according to the IEEE 802.11 communication standard, which is expensive and cannot install many access points.

  Several application examples of the present invention will be described below. The first application example uses the present invention in a showroom using one large space, and will be described with reference to FIG. The showroom allows visitors to freely see the products, but there is a two-point that they want to know how much interest the viewers were looking at. By positioning with this system, it is possible to grasp how long it was before which product.

  First, an access point AP indicated by a black circle in FIG. 12 is installed. It is mainly installed on the wall 44, but if there is no wall to install, it is installed on the ceiling. After installation, register the coordinates of the access point AP in the server. Installation is completed after confirming that each access point AP is wirelessly connected to the sensor network.

  Hand over the wireless tag to receptionist at reception 46. Visitors can hang a wireless tag from their necks and freely tour the showroom. An example of the route 48 visited by the visitor is shown in FIG. During the tour, for example, a radio wave is emitted from the visitor's wireless tag at intervals of 3 seconds, and the radio wave is transmitted from the access point AP close to the visitor using the transmission of the radio wave as a trigger. The radio field intensity can be measured and positioning can be performed.

  At this time, the access point AP that has determined that the radio wave from the wireless tag is weak can prevent radio wave collision by not transmitting the radio wave for positioning. As a result of this positioning, if it is known that the user stays for 5 minutes in front of a certain product, it can be determined that the product has been watched carefully.

  Even if there is a device that disturbs the radio wave, there is something that disturbs the radio wave due to the indoor shape, and even if a person is between the access point AP and the wireless tag, a large number of access point APs are installed where visibility is possible Therefore, those influences can be avoided. After the tour, the visitor returns the wireless tag to the reception 46. Thus, even if there is an obstacle or the like, the position and movement of a person can be specified with considerable accuracy.

  Next, another application example will be described. In this application example, the location of visitors who come to seminars and the like is confirmed. Those who come to seminar are usually free to choose their seats. Even if the person is identified at the reception desk at the entrance, once you enter the venue, you do not know where you are. In this situation, the system can be used to find out who is sitting where.

  Position measurement is performed as follows. If there is a desk, put one access point per desk. If there is no desk, install each chair. After installation, register the access point location. Since chairs and desks are assumed to move, chair numbers and desk numbers are set on the chairs and desks. The chair number and desk number should be recognized from a distance, considering the convenience of the staff looking for a specific person. Confirm that each access point is connected to the network, and preparations are complete.

  The seminar participants will receive the wireless tag at the reception. The work of linking the tag ID and the person is performed using a personal computer placed at the reception desk at the time of receipt. Participants hang wireless tags from their necks and enter the seminar venue. In the case of seminar, since it does not move very much, it grasps the position of the visitor at intervals of 30 seconds. This reduces the collision of radio waves and can track many people at once. Since the access point is installed on the desk, the position of the access point and the wireless tag is very close, so the influence of the reflected wave is low, so the position accuracy is expected to increase considerably. Since the access point can be manufactured at a low price if it is manufactured exclusively for the access point of the sensor network, the cost of this system is not so high. In the case of this application example, the position and movement of a person can be specified with considerable accuracy even if there are obstacles.

It is explanatory drawing which shows the Example of the position measuring system of this invention. It is explanatory drawing which shows the Example of the position measurement of the moving body by the position measurement system of this invention. It is a flowchart which shows operation | movement of a wireless tag. It is a flowchart which shows operation | movement of an access point. It is a flowchart which shows operation | movement of a gateway. It is explanatory drawing which shows the transmission / reception state of the electromagnetic wave in an Example. It is explanatory drawing which shows the information put on an electromagnetic wave. It is explanatory drawing which shows the information put on an electromagnetic wave. It is explanatory drawing of a triangle positioning method. It is explanatory drawing of a triangle positioning method. It is explanatory drawing of the exclusion method of a singular point. It is explanatory drawing which shows the example which used this invention in the showroom.

Explanation of symbols

10 Position measurement system
12 people
14 Wireless tag
16 servers
20 Control unit
22 Memory unit
AP, AP1 to AP9 access point

Claims (12)

A wireless device capable of wireless communication, which is an object of position measurement;
A plurality of measuring devices for measuring the position of the wireless device capable of wireless communication;
A position measuring system including a position measuring means connected to the plurality of measuring devices and measuring the position of the wireless device,
The plurality of measurement devices acquire reception information regarding the strength of the radio waves from radio waves received from the wireless device and other measurement devices, and send the acquired reception information to the position measurement unit,
The position measuring unit measures the position of the wireless device from the received information.   The position measurement system according to claim 1, wherein when the wireless device outputs radio waves, the plurality of measurement devices acquire the reception information using the output as a trigger. The position measurement system according to claim 1 or 2, wherein the system includes at least three of the measurement devices,
The position measuring means determines from the received information received from the three measuring devices whether or not the wireless device is within a triangle formed by the three measuring devices. system. In the position measurement system in any one of Claim 1 to 3,
The measuring device sends the received information to the position measuring means by wireless communication,
The position measurement system characterized in that, during the wireless communication, the other measurement device receives radio waves sent from the measurement device to the position measurement means, and acquires the received information. A wireless device capable of wireless communication, which is an object of position measurement;
A plurality of measuring devices for measuring the position of the wireless device capable of wireless communication;
A position measuring system including a position measuring means connected to the plurality of measuring devices and measuring the position of the wireless device,
The plurality of measurement devices, when the wireless device outputs radio waves, use the output as a trigger to acquire reception information regarding the intensity of the radio waves from the radio waves received from the wireless device, and the acquired reception information To the position measuring means,
The position measuring unit measures the position of the wireless device from the received information.   6. The position measurement system according to claim 1, wherein the position measurement unit includes a radio wave intensity included in the received information acquired by the measurement device that is greater than or equal to a predetermined magnitude. A position measurement system that measures the position of the wireless device using received information.   The position measurement system according to claim 1, wherein the wireless device is held by a moving body.   8. The position measuring system according to claim 1, wherein the wireless communication is short-range wireless communication. Position measurement for measuring the position of the wireless device using a wireless device capable of wireless communication, which is an object of position measurement, and a plurality of measurement devices capable of wireless communication for measuring the position of the wireless device A method comprising the steps of:
The plurality of measurement devices obtain reception information related to the strength of the radio waves from radio waves received from the wireless device and other measurement devices;
Measuring the position of the wireless device from the received information.   10. The position measuring method according to claim 9, wherein the plurality of measuring devices acquire the received information using the output as a trigger when the wireless device outputs radio waves.   11. The position measurement method according to claim 9, wherein the three measurement devices are formed from the received information received from the three measurement devices by using at least three measurement devices. And determining whether or not the wireless device is inside a triangle. Position measurement for measuring the position of the wireless device using a wireless device capable of wireless communication, which is an object of position measurement, and a plurality of measurement devices capable of wireless communication for measuring the position of the wireless device A method comprising the steps of:
The plurality of measurement devices, when the radio device outputs radio waves, using the output as a trigger, from the radio waves received from the radio device, obtaining reception information relating to the strength of the radio waves;
Measuring the position of the wireless device from the received information.

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