JP5604880B2 - Position estimation apparatus and position estimation method - Google Patents

Description

  The present invention relates to a position estimation device and a position estimation method.

  In recent years, wireless IC (Integrated Circuit) tags are incorporated in terminal devices such as mobile phones. The wireless IC tag stores various data and communicates with a device that reads the data by radio waves or electromagnetic waves. In addition, the wireless IC tag is attached not only to the terminal device but also to various things, and identification and management of a person or an object to which the wireless IC tag is attached is performed.

  In addition, estimating the position of the wireless IC tag is important when providing product information, position information, and the like to the user of the terminal device. In particular, in a multipath environment such as an underground shopping center or a crowded station, a more accurate position estimation is required. As one method of position estimation, for example, the position estimation error is suppressed by performing position estimation based on an access point in which the distance to the terminal device is relatively short and the installation position is determined in advance. There is a technique to do.

  In the position estimation based on the access point, in a multipath environment, the line of sight (LOS) environment or the line of sight (NLOS) is not used between the access point and the terminal device. The environment appears dynamically. As a result, it is difficult to use a ranging method using a laser or the like that can be applied only to the LOS environment in a multipath environment.

  Therefore, recently, there is a position estimation method using radio waves that can be applied even in an NLOS environment. For example, in the position estimation method using radio waves, the position is estimated by communicating with the terminal device by the beam type directivity output from the array antenna arranged at the access point.

JP 2008-45953 A JP 2008-199316 A

  However, the conventional technique has a problem that misrecognition of position estimation occurs in position estimation using a beam antenna. The problem of the prior art will be described with reference to FIG. FIG. 11 is a diagram for explaining the problems of the prior art.

  For example, as shown in FIG. 11, the position estimation device 7 as an access point according to the prior art includes an array antenna 8 that outputs beams in predetermined ranges in six directions 1 to 6. This predetermined range refers to the range of the ellipse in FIG. In FIG. 11, the terminal device 40 and the terminal device 50 in which the wireless IC tag is incorporated are arranged in a predetermined range in the direction 3 from the position estimation device 7 and in a predetermined range in the direction 5, respectively. . In FIG. 11, the reflector 30 that is a wall, a moving object, and the like is also illustrated because it is in a multipath environment.

  In the above configuration, the position estimation device 7 according to the conventional technique outputs a beam to the propagation path 20 in the direction 3 using the array antenna 8. A reflector 30 is disposed on the propagation path 20, and the beam output to the propagation path 20 in the direction 3 is reflected by the reflector 30 to become a reflected wave 21.

  That is, the beam output by the position estimation device 7 passes through the terminal device 40 arranged in the direction 3, is reflected by the reflector 30, and reaches the terminal device 50 arranged in the direction 5. As a result, the position estimation device 7 that has output the beam in the direction 3 receives the responses from the terminal device 40 and the terminal device 50, and the position in the direction 3 includes the terminal device 50 that actually exists in the position in the direction 5. Will be misrecognized as existing.

  In addition, another position estimation device according to the related art detects the direction in which the reception sensitivity from the wireless IC tag is maximized, scans the detected direction several times left and right, and minimizes the reception sensitivity. There is a technique for identifying the null direction as the direction of the wireless IC tag. Note that “null” refers to a position where reading / writing is not possible, even though the reader / writer and the wireless IC tag can communicate with each other.

  However, this technique is not practical because it is required to control the direction of the null with very fine resolution when the wireless IC tags are located close to each other. In other words, the position estimation device according to the related art cannot cope with identification of a plurality of terminal devices having a wireless IC tag in a multipath environment.

  Therefore, the technology disclosed in the present application has been made in view of the above, and provides a position estimation device and a position estimation method capable of performing position estimation with high accuracy in position estimation using a beam antenna. The purpose is to do.

  In order to solve the above-described problems and achieve the object, a position estimation device disclosed in the present application controls the direction of a beam output from a directional antenna. In addition, the position estimation device outputs a beam output from the directional antenna in the above direction at the first frequency, and then outputs the beam at a second frequency different from the first frequency. In addition, the position estimation device acquires the identification information from the wireless tag that has reacted to the output of the first frequency beam among the plurality of wireless tags that hold the identification information. In addition, the position estimation device acquires identification information from a wireless tag that reacts to the output of the beam of the second frequency among the plurality of wireless tags that hold the identification information. Further, the position estimation device specifies identification information acquired in common with the first frequency beam and the second frequency beam. In addition, when the commonly acquired identification information is specified, the position estimation device acquires the beam direction and outputs the acquired direction and the specified identification information.

  According to one aspect of the position estimation device and the position estimation method disclosed in the present application, there is an effect of performing position estimation with high accuracy in position estimation using a beam antenna.

FIG. 1 is a diagram illustrating a configuration example of the position estimation apparatus according to the first embodiment. FIG. 2 is a diagram illustrating a configuration example of the position estimation apparatus according to the second embodiment. FIG. 3 is a diagram illustrating a direction specifying process according to the second embodiment. FIG. 4 is a diagram illustrating an example of a direction specifying algorithm according to the second embodiment. FIG. 5 is a diagram illustrating an example of an algorithm for determining a frequency difference according to the second embodiment. FIG. 6 is a diagram illustrating a configuration example of the position estimation apparatus according to the third embodiment. FIG. 7 is a diagram illustrating an example of an algorithm for minimizing transmission power according to the third embodiment. FIG. 8 is a diagram illustrating a configuration example of the position estimation apparatus according to the fourth embodiment. FIG. 9 is a diagram illustrating an example of a distance calculation algorithm according to the fourth embodiment. FIG. 10 is a diagram illustrating an example of a computer that executes a position estimation program. FIG. 11 is a diagram for explaining the problems of the prior art.

  Embodiments of a position estimation device and a position estimation method disclosed in the present application will be described below with reference to the accompanying drawings. In addition, this invention is not limited by the following examples.

  A configuration example of the position estimation apparatus according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration example of the position estimation apparatus according to the first embodiment. Further, FIG. 1 illustrates a terminal device 40 and a terminal device 50 in which a wireless IC tag is incorporated, and a reflector 30 that is a wall or a moving object is illustrated in a multipath environment. .

  For example, as illustrated in FIG. 1, the position estimation device 10 includes a directional antenna 11, an antenna control unit 12, an identification information specifying unit 13, and an output unit 14. For example, the position estimation device 10 relays communication related to the terminal device 40 and the terminal device 50 as access points.

  The antenna control unit 12 controls the direction of the beam output from the directional antenna 11 and outputs the beam output from the directional antenna 11 in the controlled direction at the first frequency. The antenna control unit 12 outputs the beam output from the directional antenna 11 at the first frequency, and then outputs the beam at a second frequency different from the first frequency.

  The identification information specifying unit 13 acquires the identification information from the wireless tag that has reacted to the output of the beam of the first frequency by the antenna control unit 12 among the plurality of wireless tags holding the identification information. Moreover, the identification information specific | specification part 13 acquires identification information from the radio | wireless tag which responded to the output of the beam of the 2nd frequency by the antenna control part 12 among the some radio | wireless tags holding identification information. Moreover, the identification information specific | specification part 13 specifies the identification information acquired in common with the beam of the 1st frequency and the 2nd frequency.

  When the identification information acquired in common by the identification information specifying unit 13 is specified, the output unit 14 acquires the direction of the beam from the antenna control unit 12 and outputs the acquired direction and the specified identification information. To do.

  Specifically, the antenna control unit 12 controls the direction of the beam output from the directional antenna 11 to directions 1 to 6. Here, it is assumed that the directional antenna 11 outputs a beam in the direction 3. Then, the antenna control unit 12 outputs the beam output from the directional antenna 11 in the direction 3 at the first frequency “f”. In addition, after outputting at the first frequency “f”, the antenna control unit 12 outputs at the second frequency “f + Δf” different from the first frequency “f” in the same direction 3.

  By these controls, the beam of the first frequency “f” output from the directional antenna 11 in the direction 3 passes through the terminal device 40 through the propagation path 20 with the first frequency “f”, and is reflected by the reflector 30. The reflected wave 21 reaches the terminal device 50. At this time, each of the wireless IC tags incorporated in the terminal device 40 and the terminal device 50 that have received the beam transmits a response signal including identification information to the position estimation device 10.

  The beam of the second frequency “f + Δf” output from the directional antenna 11 in the direction 3 passes through the terminal device 40 through the propagation path 25 of the second frequency “f + Δf”, is reflected by the reflector 30, and is reflected. 26. At this time, the wireless IC tag incorporated in the terminal device 40 that has received the beam transmits a response signal including identification information to the position estimation device 10.

  In other words, when the frequencies of beams output in the same direction are different, the propagation channel of the beam changes, so that the reflected waves are in different directions. Here, the identification information of the wireless IC tag incorporated in the terminal device 40 is “ID1”, and the identification information of the wireless IC tag incorporated in the terminal device 50 is “ID2”.

  On the other hand, the position estimation device 10 that has received the response signal from the wireless IC tag incorporated in the terminal device 40 and the terminal device 50 acquires the identification information “ID1” and the identification information “ID2” in the identification information specifying unit 13. Thereafter, the position estimation device 10 that has received the response signal from the wireless IC tag incorporated in the terminal device 40 acquires the identification information “ID1” in the identification information specifying unit 13.

  Then, the identification information specifying unit 13 specifies the identification information “ID1” acquired in common with the beams of the first frequency “f” and the second frequency “f + Δf” in the acquired identification information. Further, when the identification information “ID1” acquired in common by the identification information specifying unit 13 is specified, the output unit 14 acquires the beam direction 3 from the antenna control unit 12, and the acquired direction 3 and The identified identification information “ID1” is output. The output by the output unit 14 may be output to a predetermined display unit or an external display device, for example, or may be transmitted to another device via a wired or wireless network.

  As described above, the position estimation device 10 outputs a beam having a different frequency in the same direction, specifies that the identification information included in the response signal from the wireless IC tag that has received the beam is common to the different frequency, and specifies The identification information and the beam direction are output. In other words, the position estimation device 10 specifies identification information only for a wireless IC tag that receives a direct wave, not a reflected wave, and outputs the specified identification information and beam direction.

  As a result, the position estimation apparatus 10 can perform position estimation with high accuracy in position estimation using a beam antenna, as compared with the conventional technique for specifying a wireless IC tag by outputting a single frequency beam. it can. In addition, the position estimation apparatus 10 can perform position estimation with high cost and low cost in position estimation using a beam antenna, as compared with the conventional technique that controls the null direction with fine resolution.

[Configuration of Position Estimation Device According to Second Embodiment]
Next, a configuration example of the position estimation apparatus according to the second embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating a configuration example of the position estimation apparatus according to the second embodiment. In the second embodiment, as in the first embodiment, a case where the position estimation device is an access point will be described.

  For example, as illustrated in FIG. 2, the position estimation apparatus 100 includes an antenna unit 101, an antenna beam direction control unit 102, a switching unit 103, an amplifier 104, a floor area input unit 105, a Δf calculation unit 106, And a voltage controlled oscillator 107. Further, for example, the position estimation apparatus 100 includes a multiplier 108, a demodulation unit 109, an ID recognition unit 110, an AND circuit 111, an ID and direction storage unit 112, a display unit 113, and a modulation unit 114. And an amplifier 116.

  The antenna unit 101 is, for example, a directional antenna such as an array antenna, and outputs a beam in a predetermined direction based on an antenna direction switching signal from the antenna beam direction control unit 102. In addition, the antenna unit 101 outputs a beam at a frequency oscillated from a voltage controlled oscillator (VCO: Voltage Controlled Oscillator) 107 according to a frequency variable signal from the Δf calculation unit 106, for example.

  For example, the antenna beam direction control unit 102 controls the direction of the beam output by the antenna unit 101 and inputs the controlled beam direction to the ID and direction storage unit 112. Note that the ID recognition unit 110 notifies the switching timing of the beam direction of the antenna unit 101 by the antenna beam direction control unit 102.

  For example, the switching unit 103 switches transmission / reception of communication via the antenna unit 101 in accordance with a transmission / reception switching signal from the ID recognition unit 110. For example, the amplifier 104 amplifies a signal input via the switching unit 103 and inputs the amplified signal to the multiplier 108. For example, the floor area input unit 105 inputs the floor area of the place where the position estimation device 100 is arranged to the Δf calculation unit 106. For example, the floor area input unit 105 may hold in advance the floor area of the place where the position estimation device 100 is arranged, or may be an input device having a keyboard, a mouse, or the like.

  For example, the Δf calculation unit 106 obtains a difference “Δf” between the first frequency and the second frequency using the delay spread estimated from the floor area input by the floor area input unit 105, and The difference “Δf” is input to the voltage controlled oscillator 107 as a frequency variable signal. In addition, the Δf calculation unit 106 inputs, for example, the output timings of the first frequency “f” and the second frequency “f + Δf” to the ID recognition unit 110. The trigger for calculating the frequency difference by the Δf calculation unit 106 is notified from the ID recognition unit 110.

  For example, the voltage controlled oscillator 107 oscillates the frequency to the antenna unit 101 via the multiplier 115, the amplifier 116, and the switching unit 103 according to the frequency difference “Δf” as the frequency variable signal input by the Δf calculation unit 106. . Further, the voltage controlled oscillator 107 inputs the oscillation frequency controlled by the voltage to the multiplier 108 and the multiplier 115, for example.

  For example, the multiplier 108 multiplies the signal input by the amplifier 104 and inputs the multiplied signal to the demodulation unit 109. For example, the demodulation unit 109 demodulates the input signal and inputs the demodulated signal to the ID recognition unit 110. Note that information received by the antenna unit 101 and input to the ID recognition unit 110 via the switching unit 103, the amplifier 104, the multiplier 108, and the demodulation unit 109 is, for example, a response to a beam output by the antenna unit 101. Identification information from the wireless IC tag is included.

  For example, the ID recognition unit 110 acquires identification information from a plurality of wireless IC tags for different frequencies, and inputs the acquired identification information to the AND circuit 111. The identification information input to the AND circuit 111 includes, for example, identification information “ID1” and “ID2” acquired when the beam output by the antenna unit 101 is the first frequency “f”, and the second frequency “f + Δf”. "And the identification information" ID1 "acquired at the time.

  Further, the ID recognition unit 110 inputs a transmission / reception switching signal to the switching unit 103 when, for example, identification information is acquired or when a frequency output timing is input by the Δf calculation unit 106. For example, when the transmission / reception switching signal is input to the switching unit 103, the ID recognition unit 110 inputs a signal as the antenna direction switching timing to the antenna beam direction control unit 102. For example, when a transmission switching signal is input as a transmission / reception switching signal to the switching unit 103, the ID recognition unit 110 notifies the modulation unit 114 that the transmission switching signal has been input.

  The AND circuit 111, for example, ANDs the identification information “ID1” and “ID2” input by the ID recognition unit 110 and the identification information “ID1”, and stores the identification information “ID1” in the ID and direction storage unit 112. input. For example, when the identification information is input from the AND circuit 111, the ID and direction storage unit 112 acquires the beam direction from the antenna beam direction control unit 102, and stores the acquired direction and the input identification information. To do.

  The display unit 113 is, for example, a display device that acquires identification information and a direction from the ID and direction storage unit 112 and displays the information. For example, the modulation unit 114 modulates a signal and inputs the modulated signal to the multiplier 115. For example, the multiplier 115 multiplies the signal input by the modulator 114 and inputs the product to the amplifier 116. For example, the amplifier 116 amplifies the signal input by the multiplier 115 and inputs the amplified signal to the switching unit 103.

  The antenna beam direction control unit 102, the Δf calculation unit 106, and the voltage control oscillator 107 are examples of the antenna control unit 12 according to the first embodiment. The ID recognition unit 110 and the AND circuit 111 are examples of the identification information specifying unit 13 according to the first embodiment. The display unit 113 is an example of the output unit 14 according to the first embodiment.

[Direction Identification Process According to Example 2]
Next, the direction specifying process according to the second embodiment will be described with reference to FIG. FIG. 3 is a diagram illustrating a direction specifying process according to the second embodiment. In FIG. 3, the vertical axis represents frequency and the horizontal axis represents time. The direction refers to the direction in which the wireless IC tag is located with respect to the position estimation apparatus 100. Further, in FIG. 3, beams # 1 to # 4 are illustrated as beam directions, but the beam directions are not limited to four.

  For example, as illustrated in FIG. 3, the position estimation apparatus 100 acquires wireless IC tag identification information “ID1” and “ID3” obtained when a beam with a frequency “f1” is output in the direction of the beam # 1. . After that, the position estimation apparatus 100 acquires the identification information “ID1” and “ID3” of the wireless IC tag obtained when the beam of the frequency “f1 + Δf” is output in the direction of the beam # 1. Thereby, the position estimation apparatus 100 specifies that the wireless IC tag whose identification information is “ID1” and “ID3” exists in the direction of the beam # 1 by taking AND of the acquired identification information.

  In addition, the position estimation apparatus 100 acquires the identification information “ID2” and “ID4” of the wireless IC tag obtained when the beam with the frequency “f1” is output in the direction of the beam # 2. Thereafter, the position estimation apparatus 100 acquires the identification information “ID1”, “ID2”, and “ID5” of the wireless IC tag obtained when the beam having the frequency “f1 + Δf” is output in the direction of the beam # 2. Thereby, the position estimation apparatus 100 specifies that the wireless IC tag whose identification information is “ID2” is present in the beam # 2 direction by ANDing the acquired identification information.

  Further, when the position estimation apparatus 100 outputs a beam having the frequency “f1” in the direction of the beam # 3, the position estimation apparatus 100 does not acquire identification information because there is no response from the wireless IC tag. After that, the position estimation apparatus 100 acquires the identification information “ID1” of the wireless IC tag obtained when the beam having the frequency “f1 + Δf” is output in the direction of the beam # 3. Thereby, the position estimation apparatus 100 specifies that the wireless IC tag does not exist in the direction of the beam # 3 by taking AND of the acquired identification information.

  Further, the position estimation apparatus 100 acquires the identification information “ID3” and “ID4” of the wireless IC tag obtained when a beam having the frequency “f1” is output in the direction of the beam # 4. Thereafter, the position estimation apparatus 100 acquires the identification information “ID2” and “ID4” of the wireless IC tag obtained when the beam having the frequency “f1 + Δf” is output in the direction of the beam # 4. Thereby, the position estimation apparatus 100 specifies that the wireless IC tag whose identification information is “ID4” exists in the direction of the beam # 4 by taking an AND of the acquired identification information.

[Direction Identification Algorithm According to Second Embodiment]
Next, an example of a direction specifying algorithm according to the second embodiment will be described with reference to FIG. FIG. 4 is a diagram illustrating an example of a direction specifying algorithm according to the second embodiment. In FIG. 4, the beam direction is “dir (direction)”, the identification information (ID) acquired when the frequency is “f1” is “n1, n2,...”, And the frequency is “f1 + Δf”. The identification information (ID) acquired at the time is shown as “m1, m2,. In the following description, a case where there are six beam directions to be output will be described.

  For example, as shown in FIG. 4, the position estimation apparatus 100 controls the beam direction to “dir = 1” (step S101). Then, the position estimation apparatus 100 controls the frequency of the output beam to “f1” (step S102). At this time, the position estimation apparatus 100 outputs a beam having a controlled direction and frequency.

  Subsequently, the position estimation apparatus 100 stores the identification information “n1, n2,...” Acquired from the wireless IC tag that has responded to the output of the beam with the frequency “f1” (step S103). Thereafter, the position estimation apparatus 100 controls the frequency of the output beam to “f1 + Δf” (step S104). Then, the position estimation apparatus 100 stores the identification information “m1, m2,...” Acquired from the wireless IC tag that has responded to the output of the beam with the frequency “f1 + Δf” (step S105).

  Subsequently, the position estimation apparatus 100 specifies common identification information by performing AND of the acquired identification information “n1, n2,...” And the identification information “m1, m2,. (Step S106). Thereafter, when the common identification information is specified, the position estimation apparatus 100 acquires the current beam direction, and stores the acquired direction and the specified identification information (step S107).

  Then, the position estimation apparatus 100 determines whether or not the beam direction is “max”, that is, the direction “dir = 6” (step S108). At this time, if the beam direction is not “max” (No at Step S108), the position estimating apparatus 100 counts up the direction “dir = dir + 1” (Step S109), and executes the process of Step S102. The position estimating apparatus 100 ends the direction specifying algorithm when the beam direction is “max” (Yes in step S108).

[Frequency Difference Determination Algorithm According to Second Embodiment]
Next, the example of the algorithm which determines the frequency difference which concerns on Example 2 is demonstrated using FIG. FIG. 5 is a diagram illustrating an example of an algorithm for determining a frequency difference according to the second embodiment. The frequency difference means a difference “Δf” between the frequency “f1” and the frequency “f1 + Δf” obtained by the Δf calculation unit 106.

For example, as illustrated in FIG. 5, the position estimation device 100 determines whether or not the floor area of the place where the position estimation device 100 is disposed is larger than 100 m ² (step S201). Then, when the floor area is larger than 100 m ² (Yes at Step S201), the position estimating apparatus 100 obtains a frequency difference “Δf = 3 MHz” (Step S202). Further, when the floor area is smaller than 100 m ² (No at Step S201), the position estimating apparatus 100 obtains the frequency difference “Δf = 5 MHz” (Step S203).

The frequency difference Δf is calculated from the following (Equation 1) as a frequency difference (correlation bandwidth) at which the power correlation coefficient becomes “0.5”. The delay spread value is “σ _τ ”.
Δf = 1 / (2πσ _τ ) (Formula 1)
The delay spread value “σ _τ ” is highly dependent on the surrounding environment where position estimation is performed, and the floor area can be defined in a closed space such as an underground shopping center or a station premises.

In addition, the relationship between the floor area and the delay spread value is as follows. From <Reference> shown below, the delay spread value when the floor area is 10 to 100 m ² is “σ _τ = 30 ns”, and the floor area is 100 to 100 The delay spread value at 1000 m ² is “σ _τ = 50 ns”.

<References>
“Indoor propagation delay identification and model for delay simulator”, Shinichi Ichitsubo, Ikuo Furuno, Hideaki Okamoto, Ryoji Kawasaki, IEICE Transactions B, Vol. J79-B2 No. 12 pp. 1048-1050, December 20, 1996

[Effects of Example 2]
As described above, the position estimation apparatus 100 uses the delay spread estimated from the floor area of the place where the position estimation apparatus 100 is arranged to obtain the difference in the frequency of the beams to be output, and the obtained frequency difference. To output a beam. As a result, the position estimation apparatus 100 outputs the beam by changing the frequency in the same direction with a suitable difference in the frequency of the beam that varies depending on the floor area, so that the position estimation can be performed with higher accuracy.

  In the first and second embodiments, the case where the wireless IC tag existing in the predetermined direction is specified has been described. However, the influence of the reflected wave in a multipath environment can be further reduced. Therefore, in the third embodiment, a case where the influence of reflected waves in a multipath environment is further reduced will be described.

[Configuration of Position Estimation Device According to Third Embodiment]
A configuration example of the position estimation apparatus according to the third embodiment will be described with reference to FIG. FIG. 6 is a diagram illustrating a configuration example of the position estimation apparatus according to the third embodiment. In FIG. 6, the same components as those of the position estimation apparatus 100 according to the second embodiment are denoted by the same reference numerals, and the description of the same processes as those of the position estimation apparatus 100 according to the second embodiment is omitted.

  For example, after the identification information is acquired from all the wireless IC tags by the ID recognition unit 110, the transmission power control unit 217 increases or decreases the transmission power for the wireless IC tag. The transmission power whose increase / decrease is controlled is output from the antenna unit 101 to the wireless IC tag via the amplifier 116 and the switching unit 103. At this time, the wireless IC tag that has received the transmission power whose increase / decrease is controlled transmits a response signal to the reception of the transmission power to the position estimation apparatus 200.

  Then, based on reception of the response signal from the wireless IC tag, the transmission power control unit 217 determines a lower limit value of transmission power that allows communication with the wireless IC tag, and sets the transmission power near the determined lower limit value. Control. The trigger for increasing or decreasing the transmission power by the transmission power control unit 217 may be after the display unit 113 displays the identification information and the direction.

[Transmission power minimization algorithm according to Embodiment 3]
Next, an example of the transmission power minimization algorithm according to the third embodiment will be described with reference to FIG. FIG. 7 is a diagram illustrating an example of an algorithm for minimizing transmission power according to the third embodiment. The following algorithm is executed for the wireless IC tag whose direction has been specified so far.

For example, as illustrated in FIG. 7, the position estimation device 200 obtains a new transmission power “P = P ₀ −ΔP” by subtracting “ΔP” from the transmission power “P ₀ ” (step S301). The determined transmission power “P” is output to the wireless IC tag. Then, the position estimation apparatus 200 determines whether or not a response signal from the wireless IC tag has been received (step S302).

Subsequently, when the response signal is received (Yes at Step S302), the position estimation apparatus 200 further reduces the transmission power by the process at Step S301. Further, when the response signal is not received (No at Step S302), the position estimation apparatus 200 adds “ΔP ′” to the transmission power “P ₀ ” to obtain a new transmission power “P ′ = P ₀ + ΔP ′ (however, , ΔP ′ <ΔP) ”is obtained (step S303). The determined transmission power “P ′” is output to the wireless IC tag.

  Then, the position estimation device 200 determines whether or not a response signal from the wireless IC tag has been received (step S304). Subsequently, when the response signal is not received (No at Step S304), the position estimation apparatus 200 further adds transmission power by the process of Step S303 in order to recover the communication with the wireless IC tag. Moreover, the position estimation apparatus 200 complete | finishes an algorithm, when a response signal is received (step S304 affirmation).

  By the way, although the applied transmission power “ΔP ′” is set to be “ΔP ′ <ΔP”, in order to execute the transmission power control process more quickly, “ΔP ′” is relatively set to “ΔP”. A close value is preferable. For example, the applied transmission power “ΔP ′” is set to “ΔP ′ = 0.5ΔP” or the like. On the other hand, in order to execute the transmission power control process with higher accuracy, it is preferable to set “ΔP ′” to a smaller value than “ΔP”. For example, the applied transmission power “ΔP ′” is set to “ΔP ′ = 0.1ΔP” or the like.

[Effects of Example 3]
As described above, since the position estimation apparatus 200 controls the transmission power near the lower limit value that can reach the wireless IC tag, it is possible to realize power saving and to erroneously recognize the wireless IC tag due to the generation of reflected waves. And interference can be suppressed.

  In the third embodiment, the case where the influence of the reflected wave under the multipath environment is reduced has been described. However, from the position estimation device to the wireless IC tag in a state where the influence of the reflected wave under the multipath environment is reduced. Can also be estimated. Therefore, hereinafter, a case where the distance from the position estimation device to the wireless IC tag is estimated will be described.

[Configuration of Position Estimation Device According to Fourth Embodiment]
A configuration example of the position estimation apparatus according to the fourth embodiment will be described with reference to FIG. FIG. 8 is a diagram illustrating a configuration example of the position estimation apparatus according to the fourth embodiment. In FIG. 8, the same components as those of the position estimation device 100 according to the second embodiment and the position estimation device 200 according to the third embodiment are denoted by the same reference numerals, and the same processing as that of the second and third embodiments is performed. The description of is omitted.

For example, after the transmission power control unit 217 controls the transmission power, the reception power notification request unit 318 transmits a reception power notification request signal to the wireless IC tag so as to notify the reception power in the wireless IC tag. The reception power notification request signal transmitted to the wireless IC tag includes the current transmission power “P _t ”. The wireless IC tag that has received the received power notification request signal measures the received power “P _r ” of itself and transmits the measured received power “P _r ” to the position estimation apparatus 300.

For example, the position estimation apparatus 300 acquires a response to the received power notification request from the received wireless IC tag in the distance calculation unit 319. The distance calculation unit 319, for example, acquires the received power “P _r ”, the current transmission power “P _t ”, the transmission power “P _t0 ”, the reception power “ The distance “d” to the wireless IC tag is estimated based on “P _r0 ” and the distance “d ₀ ”. The distance from the wireless IC tag estimated by the distance calculation unit 319 is displayed and output along with the direction and identification information by the display unit 313.

Note that the distance calculation unit 319 estimates the distance from the wireless IC tag, for example, using the following (Expression 2).
d = d ₀ * ((P _t * P _r0 ) / (P _r * P _t0 )) ^1/2 (Formula 2)

[Distance Calculation Algorithm According to Embodiment 4]
Next, an example of a distance calculation algorithm according to the fourth embodiment will be described with reference to FIG. FIG. 9 is a diagram illustrating an example of a distance calculation algorithm according to the fourth embodiment.

For example, as illustrated in FIG. 9, the position estimation device 300 transmits a power notification request signal including the current transmission power “P _t ” to the wireless IC tag so as to notify the reception power of the wireless IC tag. (Step S401). The wireless IC tag that has received the received power notification request signal measures the received power “P _r ” of itself and transmits the measured received power “P _r ” to the position estimation apparatus 300.

Then, the position estimation apparatus 300 receives a reception power notification signal that is a response signal to the reception power notification request signal transmitted by the wireless IC tag, and obtains reception power “P _r ” (step S402). Subsequently, the position estimation apparatus 300 receives the received power “P _r ”, the current transmission power “P _t ”, the transmission power “P _t0 ” for the predetermined wireless IC tag held in advance, and the received power “P _r0 ”. ”And the distance“ d ₀ ”, the distance“ d ”to the wireless IC tag is obtained (step S 403).

[Effects of Example 4]
As described above, the position estimation device 300 estimates the distance to the wireless IC tag in a state where the transmission power for the wireless IC tag is near the lower limit value, so that the position estimation can be performed with higher accuracy.

  Now, the embodiments of the position estimation device disclosed in the present application have been described above. However, the present invention may be implemented in various different forms other than the embodiments described above. Therefore, different embodiments in (1) beam frequency, (2) device configuration, and (3) program will be described.

(1) Beam frequency In the above-described embodiment, the case of outputting a beam changed at two frequencies, the first frequency and the second frequency, has been described. However, the number of frequencies to be changed is not limited to two. Alternatively, it is possible to output a beam changed at three or more frequencies.

(2) Device configuration Information including processing procedures, control procedures, specific names, various data, parameters, and the like shown in the document and drawings (for example, specific names of the ID recognition unit 110) About can be changed arbitrarily unless otherwise specified.

  Each component of the illustrated position estimation apparatus is functionally conceptual and does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each device is not limited to the one shown in the figure, and all or a part thereof may be functionally or physically distributed or arbitrarily distributed in arbitrary units according to various burdens or usage conditions. Can be integrated. For example, the antenna control unit 12 is dispersed into an “antenna beam direction control unit” that controls the direction of the beam output from the antenna and a “frequency control unit” that controls the frequency of the beam output from the antenna. Also good.

(3) Program In the above embodiment, the case where various types of processing are realized by hardware logic has been described. However, it may be realized by executing a program prepared in advance by a computer. Therefore, in the following, an example of a computer that executes a position estimation program having the same function as the position estimation apparatus 10 described in the above embodiment will be described with reference to FIG. FIG. 10 is a diagram illustrating an example of a computer that executes a position estimation program.

  As shown in FIG. 10, the computer 60 includes a directional antenna 61, an HDD 63, a CPU 64, a ROM 65, a RAM 66, and the like connected by a bus 68.

  The ROM 65 has a position estimation program that exhibits the same function as the position estimation apparatus 10 shown in the above embodiment, that is, as shown in FIG. 10, an antenna control program 65a, an identification information specifying program 65b, and an output program 65c. Are stored in advance. Note that these programs 65a to 65c may be integrated or distributed as appropriate, similarly to each component of the position estimation apparatus 10 shown in FIG.

  Then, the CPU 64 reads out these programs 65a to 65c from the ROM 65 and executes them. Thereby, as shown in FIG. 10, the programs 65a to 65c function as an antenna control process 64a, an identification information specifying process 64b, and an output process 64c. The processes 64a to 64d correspond to the antenna control unit 12, the identification information specifying unit 13, and the output unit 14 illustrated in FIG. Then, the CPU 64 executes a position estimation program based on the data recorded in the RAM 66.

  Note that the programs 65a to 65c are not necessarily stored in the ROM 65 from the beginning. For example, each program may be stored in a “portable physical medium” such as a flexible disk (FD), a CD-ROM, a DVD disk, a magneto-optical disk, and an IC card inserted into the computer 60. Further, for example, each program may be stored in a “fixed physical medium” such as an HDD provided inside or outside the computer 60. Furthermore, each program may be stored in “another computer (or server)” connected to the computer 60 via a public line, the Internet, a LAN, a WAN, or the like. Then, the computer 60 may read out and execute each program from these.

10, 100, 200, 300 Position estimation device 11 Directional antenna 12 Antenna control unit 13 Identification information specifying unit 14 Output unit 101 Antenna unit 102 Antenna beam direction control unit 103 Switching unit 104, 116 Amplifier 105 Floor area input unit 106 Δf calculation Unit 107 voltage controlled oscillator 108, 115 multiplier 109 demodulation unit 110 ID recognition unit 111 AND circuit 112 ID and direction storage unit 113, 313 display unit 114 modulation unit 217 transmission power control unit 318 reception power notification request unit 319 distance calculation unit

Claims (6)

The direction of the beam output from the directional antenna is controlled, and the beam output from the directional antenna in the direction is output at the first frequency, and then output at the second frequency different from the first frequency. An antenna control unit;
Among a plurality of wireless tags holding identification information, the wireless communication device acquires identification information from a wireless tag that has responded to the output of the beam of the first frequency by the antenna control unit and responds to the output of the beam of the second frequency An identification information specifying unit that acquires identification information from a tag and specifies identification information acquired from a radio tag that has reacted to either of the outputs of the beams of the first frequency and the second frequency;
When the identification information acquired from the RFID tag that has reacted to any of the above is specified by the identification information specifying unit, the direction of the beam is acquired from the antenna control unit, and the acquired direction and the specified identification information are And a position estimation device. The direction of the beam output from the directional antenna is controlled, and the beam output from the directional antenna in the direction is output at the first frequency, and then output at the second frequency different from the first frequency. An antenna control unit;
Among a plurality of wireless tags holding identification information, the wireless communication device acquires identification information from a wireless tag that has responded to the output of the beam of the first frequency by the antenna control unit and responds to the output of the beam of the second frequency An identification information specifying unit that acquires identification information from a tag and specifies identification information acquired in common with the beams of the first frequency and the second frequency;
When the identification information acquired in common by the identification information specifying unit is specified, an output unit that acquires a beam direction from the antenna control unit and outputs the acquired direction and the specified identification information;
Using a delay spread the position estimation device is estimated from the floor area of the location to be disposed, it obtains a difference between the first frequency second frequency, enter the difference between the frequency determined in the antenna control unit and the frequency difference calculation unit that
Position estimator you, comprising a.   After the direction and the identification information are output by the output unit, the transmission power for the wireless tag is increased / decreased to determine the lower limit value of the transmission power capable of communication with the wireless tag, and near the determined lower limit value The position estimation apparatus according to claim 1, further comprising a transmission power control unit that controls transmission power. A reception power notification requesting unit that requests the wireless tag to notify the reception power in the wireless tag after the transmission power is controlled by the transmission power control unit;
When a response to the reception power notification request by the reception power notification request unit is received, the received reception power, the transmission power controlled by the transmission power control unit, and transmission to a predetermined wireless tag held in advance A distance estimation unit that estimates a distance from the wireless tag based on power, received power, and distance;
The position estimation apparatus according to claim 3, wherein the output unit outputs the direction, the identified identification information, and the distance estimated by the distance estimation unit. The direction of the beam output from the directional antenna is controlled, and the beam output from the directional antenna in the direction is output at the first frequency, and then output at the second frequency different from the first frequency. An antenna control step;
Among a plurality of wireless tags holding identification information, the wireless communication device acquires identification information from a wireless tag that has responded to the output of the first frequency beam in the antenna control step and responds to the output of the second frequency beam. An identification information specifying step for acquiring identification information from a tag and specifying identification information acquired from a radio tag that has reacted to either of the outputs of the beams of the first frequency and the second frequency;
When the identification information acquired from the RFID tag that has reacted to any of the above is specified by the identification information specifying step, the direction of the beam in the antenna control step is acquired, and the acquired direction and the specified identification information are A position estimating method comprising: an output step for outputting. In the position estimation method executed by the position estimation device,
The direction of the beam output from the directional antenna is controlled, and the beam output from the directional antenna in the direction is output at the first frequency, and then output at the second frequency different from the first frequency. An antenna control step;
Among a plurality of wireless tags holding identification information, the wireless communication device acquires identification information from a wireless tag that has responded to the output of the first frequency beam in the antenna control step and responds to the output of the second frequency beam. An identification information specifying step of acquiring identification information from a tag and specifying identification information acquired in common with the beams of the first frequency and the second frequency;
An output step of acquiring the direction of the beam in the antenna control step when the identification information acquired in common by the identification information specifying step is specified, and outputting the acquired direction and the specified identification information;
A difference between the first frequency and the second frequency is obtained using a delay spread estimated from a floor area where the position estimation device is disposed, and the obtained frequency difference is input to the antenna control step. Frequency difference calculation step to
The position estimation method characterized by performing.

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