JP2012098071A - Positioning system and positioning method - Google Patents

Abstract

An object of the present invention is to provide a positioning system and a positioning method with reduced installation costs.
A target node that transmits a positioning signal s1, and at least one or more first reference nodes that transmit a reference signal s2 after receiving the positioning signal, and the positioning signal and the reference signal are received. At least two second reference nodes that measure the reception time of the positioning signal and the reception time of the reference signal, and transmit information about the measured positioning signal reception time and the reception time of the reference signal to the positioning server, respectively. (2b, 2c), the reception time of each positioning signal transmitted from the plurality of second reference nodes, the reception time of the reference signal, the position information of each of the first and second reference nodes, And a positioning server 4 that estimates the position of the target node based on the time lag of the first reference node.
[Selection] Figure 1

Description

  The present invention relates to a positioning system and a positioning method.

  Conventionally, as one of positioning techniques, positioning using UWB-IR (Ultra Wide Bande-Impulse Radio) (hereinafter referred to as UWB positioning) is well known (for example, Non-Patent Document 1). reference). In UWB positioning, the arrival time of radio signals, time difference of arrival (TDOA), arrival angle, signal strength, and the like are used as parameters referred to for position estimation. Among them, UWB positioning by TDOA is widely used because a highly accurate positioning result can be obtained with a relatively simple hardware configuration. When performing UWB positioning by this TDOA, it is necessary to synchronize the time of the several base station which receives a UWB signal with high precision.

  In order to realize time synchronization of the base stations, the node transmits a position positioning signal, and the three base stations and one reference station receive the transmitted position positioning signals. After receiving the positioning signal, the reference station transmits the reference signal, and the three base stations receive the transmitted reference signals. Each base station measures the time when the position positioning signal is received and the time when the reference signal is received. Then, the position of the node is calculated using the time when the position positioning signal measured at each base station is received, the time when the reference signal is received, and the position information of each base station (for example, Patent Literature 1).

Japanese Patent Laid-Open No. 2005-140617

Sinan Gezici, H. Vincent, “Position Estimation via Ultra-Wide-Band Signals”, IEEE Proceedings of the IEEE, February 2009, Vol. 97, No. 2, pp. 386-403, 2009

  However, the conventional technique described in Patent Document 1 has a problem that the installation cost increases because it is necessary to newly install a reference station in addition to three base stations in an area where the position of a node is to be measured. Moreover, the prior art described in Patent Document 1 has a problem that it is necessary to secure a place for newly installing a reference station.

  This invention is made | formed in view of said problem, Comprising: It aims at providing the positioning system and positioning method which suppressed installation cost.

  To achieve the above object, a positioning system according to the present invention includes a target node that transmits a positioning signal, and at least one or more first reference nodes that transmit a reference signal after receiving the positioning signal. , Receiving the positioning signal and the reference signal, measuring the reception time of the positioning signal and the reception time of the reference signal, and information on the measured reception time of the positioning signal and the reception time of the reference signal At least two second reference nodes each transmitting to the positioning server, a reception time of each of the positioning signals transmitted from a plurality of the second reference nodes, a reception time of the reference signal, and the first And the position of the target node based on the position information of each of the second reference node and the time lag of the first reference node It is characterized by and a positioning server for estimating.

  In the positioning system according to the present invention, at least two of the second reference nodes that have received the positioning signal and the reference signal may be configured such that a difference between the measured reception time of the positioning signal and the reception time of the reference signal. And transmits information on the difference between the measured reception time of the positioning signal and the reference signal reception time to the positioning server, and the positioning server is transmitted from a plurality of the second reference nodes. In addition, the position of the target node is estimated based on the difference between the reception time of each positioning signal and the reception time of the reference signal, the position information of each of the reference nodes, and each time lag. Also good.

  In the positioning system according to the present invention, the plurality of second reference nodes that have received the positioning signal sequentially transmit the reference signal, and sequentially, the first or second reference other than its own device. The node receives the reference signal transmitted, measures the reception time of the positioning signal and the reception time of the reference signal, and provides information on the measured reception time of the positioning signal and the reception time of the reference signal You may make it each transmit to a server.

  Further, in the positioning system according to the present invention, the plurality of second reference nodes that have received the reference signal transmit the reference signals in a different order from the adjacent first or second reference nodes. The positioning server may estimate the position of the target node using a time lag of each of the second reference nodes.

  In the positioning system according to the present invention, the positioning signal or the reference signal may be a UWB-IR signal.

  In order to achieve the above object, a positioning method according to the present invention includes a transmission step in which a target node transmits a positioning signal, and after at least one first reference node receives the positioning signal, A transmission step of transmitting a reference signal, and at least two second reference nodes receive the positioning signal and the reference signal, measure a reception time of the positioning signal and a reception time of the reference signal, and measure And a transmission step of transmitting information related to the reception time of the positioning signal and the reception time of the reference signal to the positioning server, respectively.

  In the positioning method according to the present invention, at least two second reference nodes that have received the reference signal measure a difference between the measured reception time of the positioning signal and the reception time of the reference signal, A transmission step of transmitting information on a difference between the measured reception time of the positioning signal and the reception time of the reference signal to the positioning server, and the positioning server is transmitted from a plurality of the second reference nodes. The target node based on the difference between the reception time of each positioning signal and the reception time of the reference signal, the position information of each of the first and second reference nodes, and the time lag of the one reference node And a step of estimating the position.

  Further, in the positioning method according to the present invention, the plurality of second reference nodes that have received the positioning signal sequentially transmit the reference signal, and sequentially the first or second reference other than its own device. The node receives the reference signal transmitted, measures the reception time of the positioning signal and the reception time of the reference signal, and provides information on the measured reception time of the positioning signal and the reception time of the reference signal You may make it provide the transmission process which each transmits to a server.

  According to the present invention, since the reference node itself that has received the synchronized positioning signal functions as a reference station, it is not necessary to provide a dedicated reference station other than the reference node, and the installation cost of the node can be reduced.

1 is a configuration diagram of a positioning system according to a first embodiment. It is a block diagram which shows the structure of the target node which concerns on the embodiment. It is a block diagram which shows the structure of the reference node 2 (2b, 2c; base station) which concerns on the embodiment. It is a block diagram which shows the structure of the reference node 2a (base station) which concerns on the embodiment. It is a block diagram which shows the structure of the positioning server which concerns on the same embodiment. It is a figure explaining the positioning calculation which concerns on the same embodiment. It is a figure explaining the method of estimating a positioning coordinate by a geometric method using the several TDOA value which concerns on the embodiment. It is a figure explaining the positioning calculation in case the number of reference nodes concerning the embodiment is four. It is a sequence diagram of transmission / reception when the number of reference nodes according to the embodiment is three. It is a flowchart which shows the procedure of the positioning which concerns on the embodiment. It is a figure which shows the positioning field assumed in the simulation which concerns on the same embodiment. It is a figure which shows the simulation result of the maximum value of the positioning error in the evaluated area which concerns on the embodiment. It is a figure which shows the simulation result at the time of putting a target node in the coordinate point (3, 3) which concerns on the same embodiment. It is a figure which shows the simulation result at the time of putting a target node in the coordinate point (5, 5) which concerns on the embodiment. It is a scatter diagram of the positioning result when positioning is performed 11000 times with the target node placed at the coordinate point (3, 3) according to the embodiment. It is a scatter diagram of the positioning result when positioning is performed 11000 times with the target node placed at the coordinate point (5, 5) according to the embodiment. It is a block diagram of the positioning system which concerns on 2nd Embodiment. It is a flowchart which shows the procedure of the positioning which concerns on the embodiment. It is a figure explaining an example of the order of a reference node concerning the embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the embodiment which concerns, A various change is possible within the range of the technical thought.

[First Embodiment]
FIG. 1 is a configuration diagram of a positioning system according to the present embodiment. As shown in FIG. 1, the positioning system 100 includes a target node 1, a reference node 2a, a reference node 2b, a reference node 2c, a network 3, and a positioning server 4.

The target node 1 is a terminal device and has a function of transmitting a radio signal s2 for measuring a position (hereinafter referred to as a positioning signal s2).
The reference node 2a (first reference node) has a function as a reference station that transmits a radio signal s2 (hereinafter referred to as a reference signal s2) for determining a reference time. Note that the reference node 2 a is not connected to the network 3.
The reference nodes 2b and 2c have a function of receiving the positioning signal s1 transmitted from the target node 1 and the reference signal s2 transmitted from the reference node 2a. The reference nodes 2b and 2c (second reference nodes) include a high-accuracy clock (not shown) that can capture an impulse signal having a width of about several hundred picoseconds to several nanoseconds. Each clock of the reference nodes 2b and 2c is, for example, periodically calibrated and synchronized. The reference nodes 2b and 2c measure the time when the positioning signal s1 is received (hereinafter referred to as the reception time of the positioning signal s1) and the time when the reference signal s2 is received (hereinafter referred to as the reception time of the reference signal s2). The reference nodes 2b and 2c have a function of transmitting the measured reception time of the positioning signal s1 and the reception time of the reference signal s2 to the positioning server 4 via the network 3. Note that the positioning signal s1 and the reference signal s2 are, for example, UWB-IR (Ultra Wide Bande-Impulse Radio) signals.
Further, the reference nodes 2a and 2c are arranged at, for example, three different vertices of a square having a side of 20 [m].

The network 3 is constructed by a wired LAN (Local Area Network), a wireless LAN, Bluetooth (registered trademark), or the like.
The positioning server 4 receives the reception time of the positioning signal s1 and the reception time of the reference signal s2 transmitted from the reference nodes 2b and 2c via the network 3. The positioning server 4 determines the target node based on the reception time of the received positioning signal s1, the reception time of the reference signal s2, the position information of the reference nodes 2a, 2b, and 2c, and the time lag of the reference node 2a. 1 position is estimated.

  Next, the target node 1, the reference nodes 2a and 2c, and the positioning server 4 will be described with reference to FIGS. FIG. 2 is a block diagram showing the configuration of the target node according to the present embodiment. FIG. 3 is a block diagram showing the configuration of the reference node 2 (2b, 2c; base station) according to the present embodiment. FIG. 4 is a block diagram showing the configuration of the reference node 2a (reference station) according to the present embodiment. FIG. 5 is a block diagram showing a configuration of the positioning server according to the present embodiment.

As illustrated in FIG. 2, the target node 1 includes a processor unit 11, a memory 12, a baseband unit 13, a transmission RF unit 14, and an antenna 15.
The processor unit 11 performs switching control of the operation mode of the target node 1 (the transmission mode of the positioning signal s1, the standby mode, etc.). The processor unit 11 generates packet data of the positioning signal s1 based on a program stored in the memory 12, and outputs the generated packet data of the positioning signal s1 to the baseband unit 13. The timing for transmitting the positioning signal s1 is, for example, a predetermined cycle, for example, an interval such as 10 [msec] or “5 [min]”.
The memory 12 stores predetermined program data and operation parameter settings.
The baseband unit 13 performs management of the transmission operation of the positioning signal s1, setting of operation parameters, baseband processing (spreading and encoding) of transmission packet data, and the like. The baseband unit 13 reads the operation parameter settings stored in the memory 12 and performs baseband processing of the packet data of the positioning signal s1 using the read operation parameter settings. The baseband unit 13 outputs the baseband processed positioning signal s1 data to the transmission RF unit 14.
The transmission RF unit 14 converts the data of the positioning signal s1 output from the baseband unit 13 into a high frequency band, and radiates (transmits) the converted data to the space as the positioning signal s1 via the antenna 15.
In FIG. 2, the target node 1 has been described as having a configuration having only a transmission function, but may have a reception function.

As shown in FIG. 3, the reference node 2 (2b, 2c) includes an antenna 21, a reception RF unit 22, a baseband unit 23, a processor unit 24, a memory 25, and a communication unit 26, respectively.
The reception RF unit 22 receives wireless signals (positioning signal s1 and reference signal s2) via the antenna 21. The reception RF unit 22 frequency-converts the received high-frequency positioning signal s1 to the baseband, and outputs the frequency-converted reception signal to the baseband unit 23.
The baseband unit 23 performs management of radio signal reception operations, setting of operation parameters, baseband processing (despreading and decoding) of received packet data, and the like. The baseband unit 23 reads the operation parameter settings stored in the memory 25, and performs baseband processing of the radio signal using the read operation parameter settings. The baseband unit 23 outputs the baseband processed radio signal data to the processor unit 24 and writes and stores the data in the memory 25. The baseband unit 23 measures the reception time of the positioning signal s1 and the reception time of the reference signal s2 based on a clock (not shown). The baseband unit 23 outputs information on the measured reception time of the positioning signal s1 and the reception time of the reference signal s2 to the processor unit 24, and writes and stores the information in the memory 25.
The processor unit 24 outputs information related to the reception time of the positioning signal s1 and the reception time of the reference signal s2 output from the baseband unit 23 to the communication unit 26.
The memory 25 stores predetermined program data and operation parameter settings.
The communication unit 26 converts the information related to the received reception time of the positioning signal s1 and the reception time of the reference signal s2 according to the network 3, and converts the information regarding the reception time of the converted positioning signal s1 and the reception time of the reference signal s2. Is transmitted to the positioning server 4 via the network 3.

As illustrated in FIG. 4, the reference node 2 a includes an antenna 21, a reception RF unit 22, a baseband unit 23 a, a processor unit 24 a, a memory 25 a, an antenna 27, and a transmission RF unit 28.
The reception RF unit 22 receives a radio signal (positioning signal s1) via the antenna 21. The reception RF unit 22 frequency-converts the received high-frequency positioning signal s1 to the baseband, and outputs the frequency-converted reception signal to the baseband unit 23a.
The baseband unit 23a performs radio signal reception operation management, operation parameter setting, baseband processing (despreading and decoding) of received packet data, and the like. The baseband unit 23a reads the operation parameter setting stored in the memory 25a, and performs baseband processing of the positioning signal s1 using the read operation parameter setting. The baseband unit 23a outputs the baseband processed radio signal data to the processor unit 24a, and writes and stores the data in the memory 25a. The baseband unit 23a measures the reception time of the positioning signal s1 based on a clock (not shown). The baseband unit 23a outputs information on the measured reception time of the positioning signal s1 to the processor unit 24a, and writes and stores the information in the memory 25a. After receiving the positioning signal s1, the baseband unit 23a generates data of the reference signal s2, and performs baseband processing (spreading and encoding) of the generated data of the reference signal s2. The baseband unit 23a outputs the baseband-processed reference signal s2 data to the transmission RF unit 28. In FIG. 4, the reception antenna 21 and the transmission antenna 27 are written separately, but the same antenna may be shared by using a transmission / reception switch or the like.
The transmission RF unit 28 converts the data of the input reference signal s2 into a high frequency band, and radiates (transmits) the converted data to the space as the reference signal s2 via the antenna 27.

As shown in FIG. 5, the positioning server 4 includes a communication unit 41, a positioning unit 42, and a database 43.
The communication unit 41 receives information regarding the reception time of the positioning signal s1 and the reception time of the reference signal s2 transmitted from the reference node 2 (2b, 2c) via the network 3. The communication unit 41 converts information regarding the reception time of the received positioning signal s1 and the reception time of the reference signal s2 into a predetermined signal format, and converts the information regarding the reception time of the converted positioning signal s1 and the reception time of the reference signal s2. The data is output to the positioning unit 42.
The positioning unit 42 reads the position information of the reference nodes 1 and 2 (2a, 2b, 2c) and the information related to the time lag of the reference node 1 (2a) from the database 43. As will be described later, the positioning unit 42 uses the information on each read position information and each time lag and the information on the input reception time of the positioning signal s1 and the reception time of the reference signal s2 to detect the position of the target node 1. Is estimated.
The database 43 holds information about each position of the reference nodes 1 and 2 (2a, 2b, 2c) and information about each time lag of the reference node 1 (2a).

  Next, positioning calculation according to the present embodiment will be described with reference to FIGS. 1 and 6. FIG. 6 is a diagram for explaining positioning calculation according to the present embodiment. FIG. 6A is a diagram schematically illustrating the radio signal D1 received by the reference node 2b (base station). FIG. 6B is a diagram schematically illustrating the radio signal D3 received by the reference node 2c (base station). FIG. 6C is a diagram schematically showing the radio signal D2 received and transmitted by the reference node 2a (reference station). In FIG. 6, the horizontal axis represents time, and the vertical axis represents the signal level.

The distance from the target node 1 is assumed that the reference node 2b is closest, the reference node 2c is next closest, and the reference node 2a is farthest.
First, the target node 1 transmits a positioning signal s1. Based on the distance to the target node 1, the reference node 2b receives the positioning signal s1 at time T1a (FIG. 6 (a), waveform 201). The reference node 2a receives the positioning signal s1 at time T1b (FIG. 6B, waveform 211). Similarly, the reference node 2c receives the positioning signal s1 (waveform 221) at time T3 (FIG. 6 (c)).

  After receiving the positioning signal s1, the reference node 2a transmits the reference signal s2 (waveform 222) at time T4. A time difference TD3 between the time T3 and the time T4 is a time required for processing of the reference node 2a (hereinafter also referred to as a time lag, a processing time, and a processing time). Here, the time lag is a propagation delay when a signal is transmitted in the circuit of the reference node 2a. This time lag is measured in advance or calculated from a design value, and is stored in the database 43 of the positioning server 4. Alternatively, the time lag is transmitted to the positioning server 4 via the reference node 2b (base station) or 2c (base station) by being written in the payload portion of the reference signal s2 transmitted by the reference node 2a. Also good. The payload portion is a data body to be transferred excluding the header portion of the communication packet.

The reference node 2c receives the reference signal s2 (waveform 212) at time T2b (FIG. 6 (b)). Similarly, the reference node 2b receives the reference signal s2 (waveform 202) at time T2a (FIG. 6 (a)).
That is, the time difference TD1a represents the time difference between the reception time T1a of the positioning signal s1 and the reception time T2a of the reference signal s2 at the reference node 2b. The time difference TD2a is a TDOA (Time Difference Of Arrival) value of each positioning signal s1 measured at the reference node 2a (reference station) and the reference node 2b (base station). The time difference TD3 represents the processing time required for the reference node 2a (reference station) to receive the positioning signal s1 and transmit the reference signal s2. The time difference TD4a represents the time difference of the reference signal s2 from the reference node 2a (reference station) to the reference node 2b (base station). The time difference TD1b represents the propagation time between the reception time T1b of the positioning signal s1 and the reception time T2b of the reference signal s2 at the reference node 2c.

The time difference TD1a is a value measured based on the clock of the reference node 2b. Since the time difference TD4a has known coordinates of the reference node 2a (reference station) and the reference node 2b (base station), the distance L1 between the reference node 2a (reference station) and the reference node 2b (base station) is It can be calculated by dividing by the speed of light c (3 × 10 ⁸ [m / s]) as in the following equation (1).

  TD4a = L1 / c (1)

  That is, the time differences TD1a and TD4a can be calculated, or since the time lag TD3 is known, the arrival time difference TD2a can be calculated using the following equation (2).

  TD2a = TD1a-TD3-TD4a (2)

  Similarly, the arrival time difference TD2b of the positioning signal s1 measured at the reference node 2a (reference station) and the reference node 2c (base station) can also be calculated as the following equation (3).

  TD2b = TD1b-TD3-TD4b (3)

In Equation (3), the time difference TD4b represents the propagation time of the reference signal s2 from the reference node 2a (reference station) to the reference node 2c (base station).
The positioning server 4 estimates the position of the target node 1 by a geometric technique or a statistical technique using the two TDOA values of the expressions (2) and (3). FIG. 7 is a diagram illustrating a method for estimating positioning coordinates by a geometric method using a plurality of TDOA values according to the present embodiment. Here, as shown in FIG. 7, the geometric technique is a technique in which, for example, intersections 271 between a plurality of hyperbolas 251 and a hyperbola 261 determined by a plurality of TDOA values are used as positioning coordinates. In FIG. 7, the horizontal axis is the x direction [m], and the vertical axis is the y direction [m]. In FIG. 7, for example, the hyperbola 251 is an estimated value of the arrival time difference TD2a calculated by the equation (2), and the hyperbola 261 is the arrival time difference TD2b calculated by the equation (3).
The statistical method is a method in which, for example, a positioning coordinate is obtained by having a point at which the value of the likelihood function defined by the error between the measured value of the TDOA value and the theoretical value is minimum.

Next, positioning calculation performed by the positioning server 4 using a statistical method will be described with reference to FIG. FIG. 8 is a diagram illustrating positioning calculation when the number of reference nodes is four according to the present embodiment. As shown in FIG. 8, around the target node 1, four reference nodes 1 to 4 have coordinates (x ₁ , y ₁ ), (x ₂ , y ₂ ), (x ₃ , y), respectively. ₃ ) and (x ₄ , y ₄ ).
In FIG. 8, when the reference node 1 is a reference station, the likelihood function P (x, y) can be defined as the following equation (4).

In the formula (4), _{v c} is the speed of _{light, t ab} is a reference node a and the reference node b is the TDOA values of time of receiving the positioning signal s1 from the target node. Then, the positioning server 4 sets the position of (x, y) at which the likelihood function P (x, y) is minimum as the estimated value of the coordinates of the target node 1.

Next, transmission / reception and positioning estimation of the positioning system 100 according to the present embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 is a sequence diagram of transmission and reception when the number of reference nodes is three according to the present embodiment. FIG. 10 is a flowchart showing a positioning procedure according to the present embodiment.
First, the target node 1 transmits a positioning signal s1 (step S1).
Next, each reference node 2a, 2b, 2c receives the positioning signal s1 at time T1a, time T1b, and time T3, respectively. Each reference node 2a to 2c measures the reception time of the positioning signal s1 (step S2).

Next, the reference node 2a transmits the reference signal s2 at time T4 (step S3).
Next, the reference node 2b receives the reference signal s2, and measures the reception time T2a of the received reference signal s2. The reference node 2b calculates the time difference TD1a using the measured reception time T1a of the positioning signal s1 and the reception time T2a of the reference signal s2. The reference node 2b transmits information regarding the calculated time difference TD1a to the positioning server 4 via the network 3 (step S4).
Next, the reference node 2c receives the reference signal s2, and measures the reception time T2b of the received reference signal s2. The reference node 2c calculates the arrival time difference TD1b using the measured reception time T1b of the positioning signal s1 and the reception time T2b of the reference signal s2. The reference node 2c transmits information on the calculated arrival time difference TD1b to the positioning server 4 via the network 3 (step S5).

  Next, the positioning server 4 receives information on the arrival time difference TD1a and information on the arrival time difference TD1b from the reference nodes 2b and 2c via the network 3. The positioning server 4 reads the position information of the reference nodes 2a, 2b and 2c and the information of the time lag TD3 stored in the database 43. The positioning server 4 uses the expressions (2) and (3) based on the read position information of the reference node 2a, information on the time lag TD3, and the received information on the arrival time difference TD1a and the arrival time difference TD1b. Estimation is performed by calculating the position of the target node 1 (step S6).

  In the present embodiment, an example has been described in which the reference node 2b calculates the arrival time difference TD1a and transmits the calculated arrival time difference TD1a to the positioning server 4. However, the information regarding the reception time T1a of the measured positioning signal s1 Information related to the reception time T2a of the reference signal s2 may be transmitted to the positioning server 4. Similarly, the reference node 2c may transmit information relating to the measured reception time T1b of the positioning signal s1 and information relating to the reception time T2b of the reference signal s2 to the positioning server 4.

In the present embodiment, the reference node 2a has the function of the reference station. However, the reference node 2b or 2c may be the reference station. In this case, the reference node 2a is a base station.
Further, the number of reference nodes may be three or more, for example, four. In this case, the number of reference nodes having the function of a reference station that transmits the reference signal s2 is not limited to one, and at least one reference node is sufficient.

Next, in order to evaluate the performance of the positioning method according to the present embodiment, results of simulation of the positioning system will be described with reference to FIGS.
FIG. 11 is a diagram showing positioning fields assumed in the simulation according to the present embodiment. In FIG. 11, the horizontal axis represents the distance [m] in the x direction, and the vertical axis represents the distance [m] in the y direction. As shown in FIG. 11, the reference station 2a, the base station 2b, and the base station 2c are arranged at coordinates (0, 0), (0, 6), (6, 0), respectively, and 1 ≦ x ≦ 5 and 1 ≦ y The positioning accuracy in the area of ≦ 5 (region 301 indicated by hatching in FIG. 11) was evaluated. In this simulation, the width of the measurement error of the time difference between the positioning signal s1 received by the base stations 2b and 2c and the reference signal s2 is assumed to be ± 2 ns.

  FIG. 12 is a diagram showing a simulation result of the maximum value of the positioning error in the evaluated area according to the present embodiment. As shown in FIG. 12, the maximum value of the positioning error is the smallest at the center of gravity 311 of the triangle formed by the three reference nodes 2a to 2c, and is 0.3 m or less. As the distance from the center of gravity 311 increases, the maximum value of the positioning error gradually increases.

FIG. 13 is a diagram showing a simulation result when the target node is placed at the coordinate point (3, 3) according to the present embodiment. FIG. 14 is a diagram showing a simulation result when the target node is placed at the coordinate point (5, 5) according to the present embodiment. In FIG. 13 and FIG. 14, the reference nodes 2a to 2c are arranged at the same positions as in FIG.
A range 321 indicated by a circle in FIG. 13 is a range of the positioning error, and a point 322 indicates a positioning when the measurement error of the time difference between the positioning signal s1 and the reference signal s2 is 0 (zero). It is a result. In FIG. 14, the ellipse 331 indicates the range of positioning error, and the point 332 indicates that the time difference measurement error between the positioning signal s1 and the reference signal s2 is 0 (zero). This is the positioning result. In both FIG. 13 and FIG. 14, when the measurement error of the time difference between the positioning signal s1 and the reference signal s2 is 0, the positioning result accurately indicates true coordinates.
As shown in FIG. 13, when the target node is placed near the center of gravity of the triangle formed by the three reference nodes, the positioning error range 321 is a perfect circle and its radius is about 0.3 [m]. . On the other hand, as shown in FIG. 14, when the target node is placed outside the triangle formed by the three reference nodes, the positioning error range 331 is an ellipse, and the maximum radius is about 1 [m]. is there.

Next, in order to evaluate the performance of the positioning method according to the present embodiment, the positioning system of the present embodiment was evaluated by experiments.
FIG. 15 is a scatter diagram of positioning results when positioning is performed 1000 times with the target node placed at the coordinate point (3, 3) according to the present embodiment. FIG. 16 is a scatter diagram of positioning results when positioning is performed 1000 times with the target node placed at the coordinate point (5, 5) according to the present embodiment.
15 and 16, the positioning error distributions in FIGS. 13 and 14 are in good agreement with the experimental results and the simulation results. For this reason, the positioning error of the positioning method according to the present embodiment is as simulated, and it was confirmed that high positioning accuracy was obtained.

  As described above, in the present embodiment, one of the three reference nodes is a reference station that transmits the reference signal s2, and the other reference node is a base station. Then, the positioning server estimates the position of the target node using the time difference between the reception time of the positioning signal s1 measured by each base station and the reception time of the reference signal s2, the position of each base station, and the time lag. Therefore, since the reference node itself functions as a reference station, it is not necessary to provide a dedicated reference station other than the reference node, and the installation cost of the node can be reduced.

[Second Embodiment]
FIG. 17 is a configuration diagram of a positioning system according to the second embodiment. As shown in FIG. 17, the positioning system 100a includes a target node 1, a reference node 2a ′, a reference node 2b ′, a reference node 2c ′, a network 3, and a positioning server 4 ′. The configuration of the target node 1 is the same as that of the first embodiment (FIG. 2), the configurations of the reference nodes 2a ′, 2b ′, and 2c ′ are the same as those of FIG. 4, and the configuration of the positioning server 4 ′ is This is the same as FIG.

Next, transmission / reception and positioning estimation of the positioning system 100a according to the present embodiment will be described with reference to FIG. FIG. 18 is a flowchart showing a positioning procedure according to this embodiment.
First, the target node 1 transmits a positioning signal s1 (step S101).
Next, each reference node 2a ′, 2b ′, 2c ′ receives the positioning signal s1, and measures the reception time of the positioning signal s1 (step S102).

Next, after receiving the positioning signal s1, the reference node 2b ′ transmits the reference signal s2b (step S103).
The reference node 2b ′ receives the reference signal s2a transmitted from the reference node 2a ′, and measures the reception time of the reference signal s2a. The reference node 2b ′ calculates the arrival time difference TDOA _2bs1s2a between the reception time of the positioning signal s1 and the reception time of the reference signal s2a, and transmits information on the calculated arrival time difference TDOA _2bs1s2a to the positioning server 4 ′ via the network 3. (Step S104).
The reference node 2b ′ receives the reference signal s2c transmitted from the reference node 2c ′, and measures the reception time of the reference signal s2c. The reference node 2b ′ calculates the arrival time difference TDOA _2bs1s2c between the reception time of the positioning signal s1 and the reception time of the reference signal s2c, and transmits information related to the calculated arrival time difference TDOA _2bs1s2c to the positioning server 4 ′ via the network 3. (Step S105).

In parallel with step S103, the reference node 2c ′ transmits the reference signal s2c after receiving the positioning signal s1 (step S106).
The reference node 2c ′ receives the reference signal s2b transmitted from the reference node 2b ′, and measures the reception time of the reference signal s2b. The reference node 2c ′ calculates the arrival time difference TDOA _2cs1s2b between the reception time of the positioning signal s1 and the reception time of the reference signal s2b, and transmits information on the calculated arrival time difference TDOA _2cs1s2b to the positioning server 4 ′ via the network 3. (Step S107).
The reference node 2c ′ receives the reference signal s2a transmitted from the reference node 2a ′, and measures the reception time of the reference signal s2a. The reference node 2c ′ calculates the arrival time difference TDOA _2cs1s2a between the reception time of the positioning signal s1 and the reception time of the reference signal s2a, and transmits information on the calculated arrival time difference TDOA _2cs1s2a to the positioning server 4 ′ via the network 3. (Step S108).

In parallel with step S103, the reference node 2a ′ transmits the reference signal s2a after receiving the positioning signal s1 (step S109).
The reference node 2a ′ receives the reference signal s2b transmitted from the reference node 2b ′ and measures the reception time of the reference signal s2b. The reference node 2a ′ calculates the arrival time difference TDOA _2as1s2b between the reception time of the positioning signal s1 and the reception time of the reference signal s2b, and transmits information on the calculated arrival time difference TDOA _2as1s2b to the positioning server 4 ′ via the network 3. (Step S110).
The reference node 2a ′ receives the reference signal s2c transmitted from the reference node 2c ′, and measures the reception time of the reference signal s2c. The reference node 2a ′ calculates the arrival time difference TDOA _2as1s2c between the reception time of the positioning signal s1 and the reception time of the reference signal s2c, and transmits information on the calculated arrival time difference TDOA _2as1s2c to the positioning server 4 ′ via the network 3. (Step S111).

Next, the positioning server 4 ′ receives arrival time differences TDOA _2bs1s2a , TDOA _2bs1s2c , TDOA _2cs1s2b , TDOA _2cs1s2a , TDOA _2as1s2b , and TDOA _2as1s2 from the reference nodes 2b ′ and 2c ′ via the network 3. The positioning server 4 ′ reads the position information of the reference nodes 2a ′ to 2c ′ stored in the database 43 and the information of the time lag TD3. Here, when the time lag TD3 has a different value at each reference node, the time lag TD3 is managed as independent. The positioning server 4 ′ calculates the position of the target node 1 based on the read position information of the reference nodes 2a ′ to 2c ′, the information on the time lag TD3, and the received information on the arrival time difference. Estimate (step S112).

  Next, an example of positioning calculation performed by the positioning server 4 'will be described. The target node and the four reference nodes are arranged as shown in FIG. Therefore, the likelihood function P (x, y) when each reference node simultaneously becomes a reference station can be defined as in the following equation (5).

In the formula (5), _{v c} is the speed of _{light, t ab} is a reference node a and the reference node b is the TDOA values of time of receiving the positioning signal s1 from the target node. Then, the positioning server 4 ′ sets the position of (x, y) at which the likelihood function P (x, y) is minimum as the estimated value of the coordinates of the target node 1.

FIG. 19 is a diagram illustrating an example of the order of reference nodes according to the present embodiment. An example of determining the order of reference nodes when four reference nodes are arranged at each vertex of a square area surrounding the target node 1 to be measured will be described.
As shown in FIG. 19, the target node 511 is first located at the coordinates (x ₁₁ , y ₁₁ ) in the region 501. Further, the reference node 521 is arranged at the position of the coordinates (x ₁ , y ₁ ), the reference node 522 is arranged at the position of the coordinates (x ₂ , y ₂ ), and the reference node 523 is arranged at the coordinates (x ₃ , y ₂ ). is disposed at a position of y _3), the reference node 524 is arranged at a position of the coordinate _{(x 4, y} 4). In this case, the contractor of the positioning system 100a, for each reference node 521-524, the ranking of the reference node 521 is 1, the ranking of the reference node 522 is 2, the ranking of the reference node 523 is 3, and the reference The order of the node 524 is set to 4 in advance. Then, the installer of the positioning system 100a stores the order of each reference node in each memory 25a of each reference node 521-524.

When the target node 511 transmits the positioning signal s1 with the coordinates (x ₁₁ , y ₁₁ ), each reference node 521 to 524 sequentially transmits a reference signal based on a predetermined order. In this way, by determining the order in which the reference signals are generated in advance, it is possible to prevent the signals of the reference nodes 521 to 524 from being transmitted simultaneously.

Next, the target node 511 moves to the position of the coordinates (x ₁₂ , y ₁₂ ) in the region 502. Reference nodes 523 to 526 are arranged at the positions of the vertices (x ₃ , y ₃ ), (x ₄ , y ₄ ), (x ₅ , y ₅ ), and (x ₆ , y ₆ ) in the region 502. Has been. In this case, the rank inherits the rank of the area 501, the reference node 523 is set to rank 3, and the reference node 524 is set to rank 4. For this reason, the ranks of coordinates (x ₅ , y ₅ ) and (x ₆ , y ₆ ) are set to ranks 1 and 2 other than ranks 3 and 4 by the installer. That is, a rank that does not overlap with the rank set for the adjacent reference node is set and stored in each memory 25a of each reference node. That is, as shown in FIG. 19, each rank is set to rank 1 for the reference node 525 and rank 2 for the reference node 526.
In this way, by determining the order in which the reference signals are generated in advance, even when the target node moves to another area, it is possible to prevent the signals of the reference nodes 521 to 524 from being transmitted simultaneously. Can do.

  In this embodiment, the example in which the order in which a plurality of reference nodes serve as reference stations is set in advance has been described. However, the order in which the reference nodes become reference stations may be random. In this case, by not fixing the reference node serving as the reference station, there is an effect of reducing the possibility of occurrence of a location that becomes a blind spot in communication within the positioning field. For example, when the target node 511 is moving at a speed of 100 [m / sec], only a specific base station cannot receive the positioning signal s1 due to an obstacle in the field, that is, a blind spot of communication. A condition may occur. In such a case, if the reference station that transmits the reference signal is fixed, it becomes a blind spot for communication, and positioning cannot be performed. For this reason, the reference node can reduce the blind spot of communication by switching between the role of the reference station and the role of the base station, for example, every 100 [msec].

  Further, the time lag of each reference node required for positioning calculation may be measured in advance and stored in the database 43 of the positioning server 4 'or a storage unit (not shown). Further, the time lag of each reference node can be obtained by a calibration process performed before or during positioning. The calibration process is, for example, by transmitting / receiving a signal between two reference nodes and subtracting the time required for the signal to propagate the known distance between the reference nodes from the time required for the round trip of the signal. The time lag at a certain reference node can be estimated. Each reference node may measure these time lags and transmit each measured time lag to the positioning server 4 '.

  As described above, in the present embodiment, one of the three reference nodes sequentially becomes a reference station that transmits a reference signal, and the other reference node becomes a base station. The positioning server estimates the position of the target node using the time difference between the reception time of the positioning signal s1 measured by each base station and the reception time of the reference signal, the position of each base station, and the time lag. Since the reference node itself acts as a reference station, it is not necessary to provide a dedicated reference station other than the reference node, and the installation cost of the node can be reduced.

  In this embodiment, an example has been described in which one of the three reference nodes sequentially becomes a reference station that transmits a reference signal and another reference node becomes a base station. For example, a target node that cannot be connected to the network 3 may be used. In FIG. 17, it is assumed that the target nodes 2a 'to 2c' are connected to the network 3 in the initial state. When the positioning signal is received from the target node 1 and the reference node 2a ′ is disconnected from the network 3, the reference node 2a ′ becomes a reference station, and the other reference nodes 2b ′ and 2c ′ It may be a base station.

It should be noted that a program for realizing the functions of the respective units in FIGS. 2 to 5 of the embodiment is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed. You may process each part by. Here, the “computer system” includes an OS and hardware such as peripheral devices.
Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” is a portable medium such as a flexible disk, a magneto-optical disk, a ROM (Read Only Memory), a CD-ROM, or a USB (Universal Serial Bus) I / F (interface). A storage device such as a USB memory or a hard disk built in a computer system. Further, the “computer-readable recording medium” includes a medium that holds a program for a certain period of time, such as a volatile memory inside a computer system serving as a server or a client. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

100, 100a ... positioning system
1,511 ... target nodes 2a-2c, 2a'-2c '... reference nodes (reference station, base station)
3 ... Network 4, 4 '... Positioning server 11, 24, 24a ... Processor unit 12, 25, 25a ... Memory 13, 23a ... Baseband unit 14 ... Transmission RF unit 15 , 21, 27 ... Antenna 22 ... Reception RF unit 23 ... Baseband unit 26, 41 ... Communication unit 28 ... Transmission RF unit 42 ... Positioning unit 43 ... Database s1, ..Positioning signal s2 ... reference signal

Claims (8)

A target node that transmits a positioning signal;
After receiving the positioning signal, at least one first reference node transmitting a reference signal;
Receiving the positioning signal and the reference signal, measuring the reception time of the positioning signal and the reception time of the reference signal, and measuring the information regarding the measured reception time of the positioning signal and the reception time of the reference signal At least two second reference nodes each transmitting to the server;
A reception time of each positioning signal transmitted from a plurality of the second reference nodes, a reception time of the reference signal, position information of each of the first and second reference nodes, and the first A positioning server that estimates the position of the target node based on the time lag of the reference node of
A positioning system comprising: The at least two second reference nodes that have received the reference signal are:
The difference between the measured reception time of the positioning signal and the reception time of the reference signal is measured, and information on the difference between the measured reception time of the positioning signal and the reception time of the reference signal is transmitted to the positioning server. ,
The positioning server
A target based on a difference between a reception time of each positioning signal transmitted from a plurality of the second reference nodes and a reception time of the reference signal, the position information of each of the reference nodes, and a time lag -The position of a node is estimated. The positioning system of Claim 1 characterized by the above-mentioned. The plurality of second reference nodes that have received the positioning signal are:
The reference signal is sequentially transmitted, the reference signal transmitted by the first or second reference node other than its own device is sequentially received, and the reception time of the positioning signal and the reception time of the reference signal are measured. The positioning system according to claim 1, wherein information relating to the measured reception time of the positioning signal and the reception time of the reference signal is transmitted to the positioning server. The plurality of second reference nodes that have received the positioning signal are:
The adjacent first or second reference nodes transmit the reference signals in different orders,
The positioning server
The position information of each of the first and second reference nodes and the time lag of each of the first and second reference nodes are used to estimate the position of the target node. 3. The positioning system according to 3. The positioning system according to any one of claims 1 to 4, wherein the positioning signal or the reference signal is a UWB-IR signal. A transmission process in which the target node transmits a positioning signal;
A transmitting step in which at least one or more first reference nodes transmit a reference signal after receiving the positioning signal;
At least two second reference nodes receive the positioning signal and the reference signal, measure the reception time of the positioning signal and the reception time of the reference signal, and measure the received reception time of the positioning signal and the A transmission step of transmitting information on the reception time of a reference signal to the positioning server,
A positioning method characterized by comprising: At least two second reference nodes that have received the reference signal measure a difference between the measured reception time of the positioning signal and the reception time of the reference signal, and the measured reception time of the positioning signal and the A transmission step of transmitting information on a difference from a reception time of a reference signal to each of the positioning servers;
The positioning server includes a difference between a reception time of each of the positioning signals transmitted from a plurality of the second reference nodes and a reception time of the reference signal, and each of the first and second reference nodes. Estimating the position of the target node based on the position information and the time lag of the one reference node;
The positioning method according to claim 6, further comprising: The plurality of second reference nodes that have received the positioning signal sequentially transmit the reference signal, and sequentially receive the reference signals transmitted by the first or second reference node other than its own device. A transmission step of measuring the reception time of the positioning signal and the reception time of the reference signal, and transmitting information about the measured reception time of the positioning signal and the reception time of the reference signal to the positioning server, respectively. The positioning method according to claim 6 or 7, wherein:

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