Estimation system, estimation method, and program

Abstract

Provided is an estimation system that can reduce a calculation amount when estimating the position of a target apparatus. An estimation system (1) comprises a transmitter (10) and an estimation unit (30). The transmitter (10) outputs a plurality of mutually different wireless signals. The estimation unit (30) estimates the position of the transmitter (10) on the basis of a plurality of reception signals. A receiver (20) that receives the plurality of wireless signals generates the plurality of reception signals. The estimation unit (30) estimates the position of the transmitter by using the maximum value of the received power for the plurality of reception signals or the average value of the received power for the plurality of reception signals.

Description

[Technical Field]

[0001] The present disclosure relates to an estimation system, an estimation method, and a program, and more particularly to an estimation system, an estimation method, and a program for estimating the position of a transmitter. [Background technology]

[0002] Patent Document 1 describes a positioning system that measures the position of a wireless terminal (transmitter). In the positioning system described in Patent Document 1, a wireless terminal transmits multiple positioning signals (radio signals), and a base station receives the multiple positioning signals by changing the directivity. The positioning system described in Patent Document 1 then calculates the position based on all combinations of the multiple received positioning signals, and selects the combination that results in the least error in the position calculation.

[0003] However, in the positioning system described in Patent Document 1, as the number of times that a wireless terminal transmits a positioning signal and the number of base stations increases, the amount of calculation required for position calculation may become enormous. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-181255 Summary of the Invention

[0005] The present disclosure aims to provide an estimation system, an estimation method, and a program that can reduce the amount of calculation required when estimating the position of a transmitter.

[0006] An estimation system according to one aspect of the present disclosure includes a transmitter and an estimation unit. The transmitter outputs a plurality of different radio signals. The estimation unit estimates a position of the transmitter based on a plurality of received signals. The received signals are generated by a receiver that receives the plurality of radio signals. The receiver generates a plurality of signal sets corresponding to the plurality of wireless signals in one-to-one correspondence, each of the plurality of signal sets including two or more combined signals generated by combining two or more received signals corresponding to a corresponding wireless signal among the plurality of wireless signals. The estimation unit the two or more composite signals included in each of the plurality of signal setsThe maximum value of the received power of the two or more composite signals included in each of the plurality of signal sets The average value of the received power is used to estimate the position of the transmitter.

[0007] An estimation method according to one aspect of the present disclosure includes a transmitting step and an estimating step. In the transmitting step, a transmitter transmits a plurality of different wireless signals. In the estimating step, a position of the transmitter is estimated using a plurality of received signals. The plurality of received signals are generated by a receiver that receives the plurality of wireless signals. The receiver generates a plurality of signal sets corresponding to the plurality of wireless signals in one-to-one correspondence, each of the plurality of signal sets including two or more combined signals generated by combining two or more received signals corresponding to a corresponding wireless signal among the plurality of wireless signals. In the estimation step, the two or more composite signals included in each of the plurality of signal sets The maximum value of the received power of the two or more composite signals included in each of the plurality of signal sets The average value of the received power is used to estimate the position of the transmitter.

[0008] A program according to one aspect of the present disclosure causes one or more processors to execute the estimation method. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a functional block diagram showing the configuration of an estimation system according to the first embodiment. [Figure 2] FIG. 2 is a sequence diagram showing the operation of the estimation system. [Figure 3] FIG. 3 is a graph showing the relationship between the distance between the transmitter and the receiver and the signal strength of the received signal. [Figure 4] FIG. 4 is a functional block diagram showing the configuration of an estimation system according to the second embodiment. [Figure 5] FIG. 5 is a functional block diagram showing a configuration of a receiver in the estimation system. [Figure 6] FIG. 6 is a sequence diagram showing the operation of the estimation system. [Figure 7] FIG. 7 is a functional block diagram showing the configuration of an estimation system according to the third embodiment. [Figure 8] FIG. 8 is a functional block diagram showing the configuration of a transmitter in the estimation system according to the fourth embodiment. [Figure 9]FIG. 9 is a functional block diagram showing the configuration of a transmitter in an estimation system according to the fifth embodiment. [Figure 10] FIG. 10 is a functional block diagram showing the configuration of a transmitter in an estimation system according to the sixth embodiment. [Figure 11] FIG. 11 is a schematic diagram showing timing of radio signals in the estimation system. [Figure 12] FIG. 12 is a schematic diagram showing the timing of radio signals in the first comparative example. [Figure 13] FIG. 13 is a schematic diagram showing the timing of radio signals in the second comparative example. [Figure 14] FIG. 14 is a schematic diagram showing the timing of radio signals in the third comparative example. [Figure 15] FIG. 15 is a functional block diagram showing the configuration of an estimation system according to the seventh embodiment. [Figure 16] FIG. 16 is a sequence diagram showing the operation of the estimation system. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Embodiment 1) Hereinafter, an estimation system 1 according to the present disclosure will be described with reference to the drawings. The estimation system 1 is a local positioning system (LPS) that measures the position of a transmitter 10 that emits a wireless signal using radio waves as a medium.

[0011] (1) Composition As shown in FIG. 1, the estimation system 1 according to the first embodiment includes a transmitter 10, a plurality of receivers 20 (only one of which is shown in FIG. 1), and an estimation unit 30.

[0012] (1.1) Transmitter The transmitter 10 is a beacon device that transmits a plurality of radio signals Tx1 and Tx2 (see FIG. 2). The transmitter 10 includes a transmitting unit 11 and an antenna 12.

[0013] The transmitter 11 is a circuit that generates a plurality of different wireless signals and transmits them from the antenna 12. The wireless signals Tx1 and Tx2 are, for example, beacon signals that comply with the BLE (Bluetooth (registered trademark) Low Energy) standard. The wireless signals include, for example, information such as identification information of the transmitter 10. The identification information of the transmitter 10 is, for example, a MAC (Media Access Control) address.

[0014] (1.2) Receiver The receiver 20 is a receiving device for receiving the radio signals Tx1 and Tx2 transmitted by the transmitter 10. The estimation system 1 includes a plurality of receivers 20, but only one receiver 20 is shown in FIG. 1. The receiver 20 includes an antenna 21 and a receiving unit 22.

[0015] The receiver 22 receives the radio signals Tx1 and Tx2 transmitted by the transmitter 10 using the antenna 21. The receiver 22 outputs the signal strength of the received signal corresponding to each of the radio signals Tx1 and Tx2. The signal strength of the received signal is, for example, a received signal strength indicator (RSSI). Specifically, the receiver 22 outputs the signal strength Rx1 (see FIG. 2) of the received signal corresponding to the radio signal Tx1 and the signal strength Rx2 (see FIG. 2) of the received signal corresponding to the radio signal Tx2.

[0016] (1.3) Estimation part The estimation unit 30 estimates the position of the transmitter 10 based on the signal strengths Rx1 and Rx2 output by the multiple receivers 20 and information relating to the positions of the receivers 20.

[0017] The estimation unit 30 includes a signal processing unit 31 and a position estimation unit 32 .

[0018] (1.3.1) Signal Processing Unit The signal processing unit 31 receives a plurality of signal intensities Rx1, Rx2 from each of the plurality of receivers 20. More specifically, the signal processing unit 31 receives a signal strength Rx1 of a received signal corresponding to a wireless signal Tx1 and a signal strength Rx2 of a received signal corresponding to a wireless signal Tx2 from each of the plurality of receivers 20. Then, the signal processing unit 31 calculates, for each receiver 20, a representative value Rx of the received signal corresponding to the wireless signal transmitted by the transmitter 10.

[0019] The signal processing unit 31 calculates the maximum value of the multiple signal strengths Rx1 and Rx2 as the representative value Rx of the received signal. For example, the signal processing unit 31 calculates the maximum value of the signal strength Rx1 of the received signal corresponding to the wireless signal Tx1 and the signal strength Rx2 of the received signal corresponding to the wireless signal Tx2 as the representative value Rx of the received signal.

[0020] The signal processing unit 31 outputs the representative value Rx of the received signal calculated for each receiver 20 to the position estimation unit 32.

[0021] (1.3.2) Position estimation part The position estimation unit 32 estimates the position of the transmitter 10 using the representative value Rx of the received signals of the multiple receivers 20 and the position information of each of the multiple receivers 20.

[0022] The position estimation unit 32 estimates the distance between the receiver 20 and the transmitter 10 for each receiver 20 based on the representative value Rx of the received signal. The position estimation unit 32 calculates the attenuation of the radio signal Tx1 or Tx2 based on, for example, the representative value Rx of the received signal and the power of the radio signals Tx1 and Tx2 of the transmitter 10, and converts the attenuation amount into the distance between the receiver 20 and the transmitter 10.

[0023] The position estimation unit 32 estimates the distance between the receiver 20 and the transmitter 10 for each receiver 20, and estimates the position of the transmitter 10 using the position information of each receiver 20. The position estimation unit 32 includes, for example, a storage unit (not shown) that stores the position (coordinates) of each receiver 20. For example, for each receiver 20, the position estimation unit 32 draws a sphere in a virtual space with the receiver 20 at its center and the radius equal to the distance between the receiver 20 and the transmitter 10, and calculates the coordinates of the intersection of all the spheres as the position of the transmitter 10.

[0024] (2) Operation The operation of the estimation system 1 of the first embodiment will be described with reference to the sequence diagram of FIG.

[0025] First, the transmitter 10 outputs a radio signal Tx1 (step S1). A portion of the radio signal Tx1 output from the antenna 12 of the transmitter 10 (hereinafter referred to as a "direct wave") directly reaches the antenna 21 of each receiver 20. In addition, a portion of the radio signal Tx1 output from the antenna 12 of the transmitter 10 (hereinafter referred to as a "reflected wave") reaches the antenna 21 after being reflected by an object different from the transmitter 10 and the receiver 20.

[0026] Next, each of the receivers 20 performs a receiving process for the wireless signal Tx1 (step S2). Each of the receivers 20 outputs the signal strength Rx1 of the received signal based on the wireless signal Tx1.

[0027] Next, the transmitter 10 outputs a radio signal Tx2 (step S3). The radio signal Tx2 output from the antenna 12 of the transmitter 10 reaches the antenna 21 of each receiver 20 directly, or reaches the antenna 21 after being reflected by an object different from the transmitter 10 and the receiver 20.

[0028] Next, each of the receivers 20 performs a receiving process for the wireless signal Tx2 (step S4). Each of the receivers 20 outputs the signal strength Rx2 of the received signal based on the wireless signal Tx2.

[0029] Next, the signal processing unit 31 of the estimation unit 30 calculates, for each receiver 20, a representative value Rx of the received signals corresponding to the wireless signals Tx1 and Tx2 transmitted by the transmitter 10 (step S5). For each receiver 20, the signal processing unit 31 calculates the maximum value of the signal strength Rx1 and the signal strength Rx2 as the representative value Rx of the received signals.

[0030] Next, the position estimation unit 32 of the estimation unit 30 estimates the position of the transmitter 10 (step S6). The position estimation unit 32 estimates the distance between the receiver 20 and the transmitter 10 for each receiver 20 based on the representative value Rx of the received signal. The position estimation unit 32 calculates the amount of attenuation of the wireless signal based on, for example, the representative value Rx of the received signal and the power of the wireless signal of the transmitter 10, and converts it into the distance between the receiver 20 and the transmitter 10. The position estimation unit 32 estimates the distance to the transmitter 10 for each receiver 20, and estimates the position of the transmitter 10 using the position information of each receiver 20.

[0031] (3) Calculation of the representative value of the received signal The signal processing unit 31 according to the first embodiment calculates, for each receiver 20, a representative value Rx of a received signal corresponding to a wireless signal transmitted by a transmitter 10. For example, the signal processing unit 31 calculates the maximum value of the signal strength Rx1 of the received signal corresponding to the wireless signal Tx1 and the signal strength Rx2 of the received signal corresponding to the wireless signal Tx2 as the representative value Rx of the received signal.

[0032] FIG. 3 shows the signal strength of a received signal versus the distance between the transmitter 10 and the receiver 20. In FIG. 3, the dashed line indicates the theoretical value of signal strength when only a direct wave that reaches the receiver 20 directly from the transmitter 10 reaches the receiver 20. In FIG. 3, the solid line indicates the theoretical value when both a direct wave and a reflected wave that is output from the transmitter 10 and then reflected to the receiver 20 arrive. The dashed-dotted line in FIG. 3 represents the actual measured value of the signal strength of the received signal at the receiver 20 when the power of the wireless signal is kept constant and the distance between the transmitter 10 and the receiver 20 is changed. In FIG. 3, the signal strengths Rxa and Rxb correspond to the wireless signals Tx1 and Tx2, respectively. In addition, for the signal strengths Rxa and Rxb, the positional relationship between the transmitter 10 and the receiver 20 is the same, and the power of the wireless signals Tx1 and Tx2 is equal.

[0033] As shown in Figure 3, in the theoretical value when only a direct wave reaches receiver 20, the signal strength monotonically decreases as the distance between transmitter 10 and receiver 20 increases. In contrast, in the theoretical value when both a direct wave and a reflected wave reach receiver 20, interference occurs between the direct wave and the reflected wave, so the signal strength does not necessarily correspond one-to-one to the distance between transmitter 10 and receiver 20. Furthermore, since the direct wave and the reflected wave often weaken each other due to interference, as shown in Figure 3, the signal strength when both the direct wave and the reflected wave reach receiver 20 is often smaller than the signal strength when only the direct wave reaches receiver 20.

[0034] Furthermore, because the path of the reflected wave between the transmitter 10 and the receiver 20 is not necessarily one, the influence of the reflected wave may not be constant even if the relative positions of the transmitter 10 and the receiver 20 are the same. For example, in the case of the signal strengths Rxa and Rxb shown in FIG. 3, the power of the wireless signal Tx1 and the wireless signal Tx2 is equal, and the relative positions of the transmitter 10 and the receiver 20 are also the same, but the signal strengths are different. In such a case, if the position of the transmitter 10 is estimated using the signal strength Rxa of the received signal, the estimated distance between the receiver 20 and the transmitter 10 will be greater than the distance between the receiver 20 and the transmitter 10. Therefore, the distance between the transmitter 10 and the receiver 20 will not be predicted correctly, resulting in a large error in the predicted position of the transmitter 10.

[0035] In contrast, the signal processing unit 31 according to the first embodiment calculates, for each receiver 20, the maximum value of the signal strength Rx1 of the received signal corresponding to the radio signal Tx1 and the signal strength Rx2 of the received signal corresponding to the radio signal Tx2 as the representative value Rx of the received signals. As described above, when interference occurs between a direct wave and a reflected wave, a decrease in signal strength often occurs. Therefore, the signal strength Rx1 or the signal strength Rx2 of the received signal, whichever has the stronger signal strength, is more likely to be less affected by reflected waves. In other words, by using the signal strength Rx1 or the signal strength Rx2 of the received signal, whichever has the stronger signal strength, as the representative value Rx of the received signals, the influence of reflected waves can be suppressed in a simple manner.

[0036] In the first embodiment, the transmitter 10 transmits different radio signals Tx1 and Tx2, and the receivers 20 each output signal strengths Rx1 and Rx2 of the received signals corresponding to the radio signals Tx1 and Tx2. However, the number of times a radio signal is transmitted is not limited to two, and it may be transmitted three or more times. In such a case, the receiver 20 outputs the signal strength of the received signal corresponding to the radio signal one-to-one. Then, the signal processing unit 31 of the estimation unit 30 calculates, for each receiver 20, the maximum value of the signal strengths of the multiple received signals corresponding to the radio signals one-to-one as the representative value Rx of the received signal.

[0037] (4) Effects According to the estimation system 1 of the first embodiment, the transmitter 10 transmits a plurality of different radio signals Tx1 and Tx2. Furthermore, the signal processing unit 31 of the estimation unit 30 calculates, for each receiver 20, a representative value Rx of the received signal corresponding to the radio signal transmitted by the transmitter 10. Furthermore, the position estimation unit 32 of the estimation unit 30 estimates the position of the transmitter 10 using the representative value Rx of the received signal that corresponds one-to-one to the receiver 20. Therefore, the estimation unit 30 uses the received signal that is considered to be least affected by reflected waves in signal propagation between the transmitter 10 and the receiver 20 as a representative signal, and estimates the position of the transmitter 10 using the signal strength of the representative signal. As a result, the estimation system 1 of the first embodiment can reduce the influence of reflected waves and improve the accuracy of estimating the position of the transmitter 10.

[0038] Furthermore, in the estimation system 1 according to the first embodiment, a representative value Rx of the received signal is calculated for each receiver 20, and the position of the transmitter 10 is estimated using the representative value Rx of the received signal for each receiver 20. Therefore, even if the number of times of transmitting wireless signals increases, an increase in the amount of calculation can be suppressed.

[0039] (Variation) In the signal processing unit 31 according to the first embodiment, the maximum value among the signal strengths of a plurality of received signals is calculated as the representative value Rx of the received signals for each receiver 20. However, the representative value Rx of the received signals is not limited to the maximum value among the signal strengths Rx1 and Rx2 of the received signals.

[0040] In the signal processing unit 31 according to the modification of the first embodiment, for example, for each receiver 20, the average value of the signal strengths Rx1 and Rx2 of the received signals is calculated as the representative value Rx of the received signals.

[0041] The signal processing unit 31 according to the modification of the first embodiment acquires, from each receiver 20, the signal strengths of received signals that correspond one-to-one to each wireless signal. The signal processing unit 31 receives, from each receiver 20, signal strengths Rxi (i is an integer between 1 and n) of n received signals for n wireless signals (n is an integer between 2 and n) from each receiver 20. Here, the signal strength Rxi is the signal strength of the received signal corresponding to the i-th wireless signal Txi. For each receiver 20, the signal processing unit 31 calculates the average value of the signal strengths Rxi of the received signals as a representative value Rx of the received signals. That is, the representative value Rx of the received signals is expressed by the following formula:

[0042]

number

[0043] The propagation paths of direct waves do not differ significantly between the signal strength Rxi of the received signal corresponding to the wireless signal Txi and the signal strength Rxj of the received signal corresponding to the wireless signal Txj (j is an integer between 1 and n, and i ≠ j). Therefore, the difference in components due to direct waves between the signal strength Rxi of the received signal and the signal strength Rxj of the received signal is small. On the other hand, the propagation paths of reflected waves may differ between the signal strength Rxi of the received signal corresponding to the wireless signal Txi and the signal strength Rxj of the received signal corresponding to the wireless signal Txj. Therefore, the difference in components due to reflected waves between the signal strength Rxi of the received signal and the signal strength Rxj of the received signal is greater than the difference in components due to direct waves. Therefore, by calculating the average value of the signal strengths Rxi of multiple received signals and calculating the representative value Rx of the received signals, the influences of direct waves in each of the signal strengths Rxi of the received signals can be strengthened and the influences of reflected waves can be mutually canceled out. In other words, the representative value Rx of the received signals is less affected by reflected waves than each of the signal strengths Rxi of the received signals.

[0044] Therefore, the estimation system 1 according to the modification of the first embodiment can also suppress the influence of reflected waves in a simple manner.

[0045] (Embodiment 2) In the estimation system 1 according to the first embodiment, a representative value Rx of the received signal is calculated for each receiver 20, and the distance between each receiver 20 and the transmitter 10 is estimated to estimate the position of the transmitter 10. However, the method for estimating the position of the transmitter 10 is not limited to the above-described method.

[0046] 4, the estimation system 1a according to the second embodiment includes a plurality of receivers 20a and an estimation unit 30a (only one of which is shown in FIG. 4) instead of the plurality of receivers 20 and the estimation unit 30. The estimation system 1a according to the second embodiment differs from the estimation system 1 according to the first embodiment in that the receiver 20a and the estimation unit 30a estimate the direction of the propagation path between the transmitter 10 and the receiver 20a and estimate the position of the transmitter 10.

[0047] (1) Composition As shown in FIG. 4, an estimation system 1a according to the second embodiment includes a transmitter 10, a plurality of receivers 20a, and an estimation unit 30a.

[0048] (1.1) Receiver The receiver 20a is a receiving device for receiving the radio signals Tx1 and Tx2 output by the transmitter 10. As in the first embodiment, the estimation system 1a includes a plurality of receivers 20a, but only one receiver 20a is shown in Fig. 4. The receiver 20a includes three antennas 21a to 21c and a receiving unit 22a.

[0049] The receiver 22a uses the three antennas 21a to 21c to receive the radio signals Tx1 and Tx2 output from the transmitter 10. The receiver 22a performs a synthesis process on three input signals IS1 to IS3 (see FIG. 5) input from the three antennas 21a to 21c, respectively, and outputs four synthesized signals SS1 to SS4 (see FIG. 5).

[0050] As shown in Fig. 5, the receiving unit 22a includes a phase combining unit 25 and an output unit 24. The phase combining unit 25 includes a plurality of (five in the illustrated example) phase combiners 23a, 23b, 23c, 23d, and 23e. In the following description, when the phase combiners 23a, 23b, 23c, 23d, and 23e are not distinguished from one another, they are referred to as phase combiners 23. The phase combiner 23 is formed, for example, by a 90-degree hybrid unit (hybrid element). The phase combiner 23 according to the second embodiment outputs, from a first output terminal O1 and a second output terminal O2, signals whose power value is 1 / √2 times that of three input signals IS1 to IS3 input to a first input terminal I1 and a second input terminal I2. Furthermore, compared to the three input signals IS1 to IS3 input to the first input terminal I1, the phase synthesizer 23 outputs a signal that is in phase from the first output terminal O1 and outputs a signal that is delayed in phase by 90 degrees from the second output terminal O2.

[0051] The phase combiner 23a outputs from the first output terminal O1 a signal IS4 that has a power value 1 / √2 times that of the input signal IS1 input to the first input terminal I1 and is in phase with the input signal IS4.

[0052] The phase combiner 23b outputs from the second output terminal O2 a signal IS5 whose power value is 1 / √2 times that of the input signal IS2 input to the first input terminal I1 and whose phase is delayed by 90 degrees. The phase combiner 23b also outputs from the first output terminal O1 a signal IS6 whose power value is 1 / √2 times that of the input signal IS2 and whose phase is the same as that of the input signal IS2.

[0053] The phase combiner 23c outputs from the second output terminal O2 a signal IS7 that has a power value 1 / √2 times that of the input signal IS3 input to the second input terminal I2 and is in phase with the input signal IS7.

[0054] Phase combiner 23d receives signal IS4 at its second input terminal I2 and signal IS5 at its first input terminal I1. Phase combiner 23d outputs a combined signal SS1 from its first output terminal O1, obtained by adding together a signal whose power value is 1 / √2 times that of signal IS4 and whose phase is delayed by 90 degrees, and a signal whose power value is 1 / √2 times that of signal IS5 and whose phase is the same. Phase combiner 23d also outputs a combined signal SS2 from its second output terminal O2, obtained by adding together a signal whose power value is 1 / √2 times that of signal IS4 and whose phase is the same, and a signal whose power value is 1 / √2 times that of signal IS5 and whose phase is delayed by 90 degrees.

[0055] The phase combiner 23e receives the signal IS6 at the second input terminal I2 and receives the signal IS7 at the first input terminal I1. The phase combiner 23e outputs a combined signal SS3 from the first output terminal O1, which is obtained by adding together a signal whose power value is 1 / √2 times that of the signal IS6 and whose phase is delayed by 90 degrees, and a signal whose power value is 1 / √2 times that of the signal IS7 and whose phase is the same. The phase combiner 23e also outputs a combined signal SS4 from the second output terminal O2, which is obtained by adding together a signal whose power value is 1 / √2 times that of the signal IS6 and whose phase is delayed by 90 degrees, and a signal whose power value is 1 / √2 times that of the signal IS7 and whose phase is delayed by 90 degrees.

[0056] The output unit 24 outputs four composite signals SS1 to SS4 generated by the phase synthesis unit 25 for each of the radio signals to the estimation unit 30. Hereinafter, a combination (signal set) of composite signals SS1, SS2, SS3, and SS4 corresponding to the i-th radio signal will be referred to as a received signal set Rvi. Furthermore, the composite signals SS1, SS2, SS3, and SS4 included in the received signal set Rvi will be referred to as composite signals SSi1, SSi2, SSi3, and SSi4, respectively. For example, the composite signals SS1, SS2, SS3, and SS4 included in the received signal set Rv1 corresponding to the first radio signal Tx1 are composite signals SS11, SS12, SS13, and SS14, respectively (see FIG. 6). Furthermore, the composite signals SS1, SS2, SS3, and SS4 included in the received signal set Rv2 corresponding to the second radio signal Tx2 are composite signals SS21, SS22, SS23, and SS24, respectively (see FIG. 6).

[0057] (1.2) Estimation part As shown in Fig. 4, the estimation unit 30a receives a received signal set Rvi corresponding to each of a plurality of wireless signals from a plurality of receivers 20a. The estimation unit 30a calculates a representative signal Rr of the received signal set Rvi for each of the receivers 20a. The estimation unit 30a then estimates the position of the transmitter 10 based on the representative signal Rr for each receiver 20a.

[0058] The estimation unit 30a includes a signal processing unit 31a and a position estimation unit 32a.

[0059] (1.2.1) Signal Processing Unit The signal processing unit 31a receives a received signal set Rvi corresponding to each of the plurality of wireless signals from each of the plurality of receivers 20a, and then calculates a representative signal Rr for each of the receivers 20a.

[0060] The signal processing unit 31a performs the following process for each receiver 20a. That is, the signal processing unit 31a generates a representative signal of all SS1 included in the multiple received signal sets Rvi and sets the representative signal SSr1 of the composite signals SS1. The representative signal SSr1 is, for example, the amplitude value of the composite signal SS1 with the greatest signal strength among the multiple SS1. For example, when the transmitter 10 transmits two radio signals Tx1 and Tx2, the amplitude value of the composite signal with the greatest signal strength between the composite signal SS1 (SS11) corresponding to the radio signal Tx1 and the composite signal SS1 (SS21) corresponding to the radio signal Tx2 is set as the representative signal SSr1.

[0061] Similarly, the signal processor 31a generates a representative signal of all SSi2 included in the plurality of received signal sets Rvi, and sets the representative signal SSr2 as the representative signal of the composite signal SS2. The representative signal SSr2 is, for example, the amplitude value of the composite signal with the greatest signal strength among the plurality of SSi2.

[0062] Similarly, the signal processor 31a generates a representative signal of all SSi3 included in the multiple received signal sets Rvi, and sets the representative signal SSr3 as the representative signal of the combined signal SS3. The representative signal SSr3 is, for example, the amplitude value of the combined signal with the greatest signal strength among the multiple SSi3.

[0063] Similarly, the signal processor 31a generates a representative signal of all SSi4 included in the multiple received signal sets Rvi, and sets the representative signal SSr4 as the representative signal of the combined signal SS4. The representative signal SSr4 is, for example, the amplitude value of the combined signal with the greatest signal strength among the multiple SSi4.

[0064] The signal processing unit 31a outputs a combination of the representative signals SSr1, SSr2, SSr3, and SSr4 calculated for each receiver 20a as a representative signal Rr corresponding to the receiver 20a.

[0065] (1.2.2) Position estimation part The position estimation unit 32a estimates the position of the transmitter 10 using the representative signal Rr for each of the multiple receivers 20a and the position information of each of the multiple receivers 20.

[0066] The complex propagation channel between antenna 21a of receiver 20a and antenna 12 of transmitter 10 is defined as h1. The complex propagation channel between antenna 21b of receiver 20a and antenna 12 of transmitter 10 is defined as h2. The complex propagation channel between antenna 21c of receiver 20a and antenna 12 of transmitter 10 is defined as h3. The distance between antenna 21a and antenna 21b, and the distance between antenna 21b and antenna 21c are defined as d1. The transmitter 10 is located at an angle θ1 with respect to the broadside direction of the array antenna formed by antennas 21a, 21b, and 21c.

[0067] The propagation channels can be collectively expressed as equation (1).

[0068]

number

[0069] The correlation matrix R of this propagation channel can be expressed as equation (2).

[0070]

number

[0071] Here, the symbol H denotes complex conjugate transpose, and the symbol * denotes complex conjugate. Usually, the diagonal terms of the correlation matrix R are real numbers, and the off-diagonal terms are complex numbers. By calculating the correlation matrix R, the position estimation unit 32a can estimate the direction of arrival of the wireless signal to the receiver 20. The position estimation unit 32a calculates the correlation matrix R based on information related to signal strength. Using the propagation channel of equation (1), the amplitude values ​​SSr1 to SSr4 of the four representative signals input to the position estimation unit 32 can be expressed by equations (3) to (6).

[0072]

number

[0073]

number

[0074]

number

[0075]

number

[0076] |y1| indicates the value of the representative signal SSr1 of the combined signal SS1 output from the first output terminal O1 of the phase combiner 23d. |y2| indicates the value of the representative signal SSr2 of the combined signal SS2 output from the second output terminal O2 of the phase combiner 23d. |y3| indicates the value of the representative signal SSr3 of the combined signal SS3 output from the first output terminal O1 of the phase combiner 23e. |y4| indicates the value of the representative signal SSr4 of the combined signal SS4 output from the second output terminal O2 of the phase combiner 23e. Furthermore, the gains of the channels on the left-hand sides of equations (3) to (6) can be expressed from the signal strengths using equations (7) to (10).

[0077]

number

[0078]

number

[0079]

number

[0080]

number

[0081] When the difference in gain obtained through phase combiner 23d is taken into consideration, equation (11) is obtained.

[0082]

number

[0083] Furthermore, from the relationship in equation (11), equation (12) is obtained, and the real parts of R12 and R21 can be calculated. Here, α represents the argument of R12.

[0084]

number

[0085] Furthermore, when attention is paid to the sum of the gains obtained through the phase combiner 23d, the following equation (13) is obtained from the arithmetic and geometric mean relationship.

[0086]

number

[0087] Here, it is assumed that the propagation loss from antenna 12 of transmitter 10 to antenna 21a is equal to the propagation loss from antenna 12 to antenna 21b, and that |h1| and |h2| are approximately equal. When |h1| and |h2| are approximately equal, α, the argument of R12, can be expressed by equation (14).

[0088]

number

[0089] Furthermore, when |h1| and |h2| are approximately equal, equation (15) is obtained.

[0090]

number

[0091] Here, A is a real constant. Of the correlation matrix R shown in equation (2), the correlation matrix relating to the representative signals SSr1 and SSr2 is defined as R1. When the correlation matrix R1 is expressed using A and α, equation (16) is obtained.

[0092]

number

[0093] Next, by focusing on the difference in gain obtained through the phase combiner 23e, equation (17) is obtained, and the imaginary parts of R23 and R32 can be calculated: where β represents the argument of R23.

[0094]

number

[0095] Furthermore, when we focus on the sum of the gains obtained through phase combiner 23e, we obtain equation (18) from the arithmetic and geometric mean relationship. Here, we assume that the propagation loss from antenna 12 of transmitter 10 to antenna 21b is equal to the propagation loss from antenna 12 to antenna 21c, and that |h2| and |h3| are approximately equal.

[0096]

number

[0097] When |h2| and |h3| are approximately equal, β, the argument of R23, can be expressed by equation (19).

[0098]

number

[0099] Similarly, when |h2| and |h3| are approximately equal, we obtain Equation (20), where B is a real constant.

[0100]

number

[0101] Of the correlation matrix R, the correlation matrix relating to the representative signals SSr3 and SSr4 is defined as R2. When the correlation matrix R2 is expressed using B and β, equation (21) is obtained, and the correlation matrix is ​​estimated.

[0102]

number

[0103] Furthermore, R13 represents the correlation of the radio signals between the antennas 21a and 21c. R13 can be expressed by equation (22) using the calculated |R23|.

[0104]

number

[0105] From the above, the estimated correlation matrix R can be expressed by equation (23).

[0106]

number

[0107] The position estimation unit 32 can estimate the direction of the transmitter 10 by applying various direction-of-arrival estimation algorithms to the correlation matrix R. Specifically, when the beamformer method is used, the position estimation unit 32 can estimate the direction of the transmitter 10 by calculating the correlation between the correlation matrix R and the steering vector (theoretical value) shown in equation (24) from the product of the correlation matrix R and the steering vector.

[0108]

number

[0109] Here, d is the antenna spacing and k is the wave number. The wave number k is k = 2π / λ, where λ is the wavelength. Using this steering vector and correlation matrix R, the evaluation function P(θ) can be expressed by equation (25).

[0110]

number

[0111] The position estimation unit 32 substitutes various values ​​for θ in equation (25) and determines that the direction in which the evaluation function P(θ) is maximized is the direction of the transmitter 10 relative to the receiver 20a.

[0112] The position estimation unit 32 performs the above estimation for each receiver 20a and estimates the presence range of the transmitter 10 based on the position of the receiver 20a. The presence range of the transmitter 10 is estimated on a straight line that passes through the positions of the antennas 21a to 21c of the receiver 20a. The position estimation unit 32 then draws the presence range of the transmitter 10 based on the position of the receiver 20a in a virtual space, and calculates the position where the presence range of the transmitter 10 intersects as the position of the transmitter 10.

[0113] (2) Operation The operation of the estimation system 1a according to the second embodiment will be described with reference to the sequence diagram of FIG.

[0114] First, the transmitter 10 outputs a radio signal Tx1 (step S1). A portion of the radio signal Tx1 output from the antenna 12 of the transmitter 10 directly reaches each of the antennas 21a to 21c of each receiver 20a. Furthermore, a portion of the radio signal Tx1 output from the antenna 12 of the transmitter 10 reaches each of the antennas 21a to 21c after being reflected by an object other than the transmitter 10 and the receiver 20a.

[0115] Next, each of the receivers 20a performs a receiving process on the wireless signal Tx1 (step S12). Each of the receivers 20a outputs composite signals SS11 to SS14 based on the wireless signal Tx1.

[0116] Next, the transmitter 10 outputs a radio signal Tx2 (step S3). The radio signal Tx2 output from the antenna 12 of the transmitter 10 reaches the antennas 21a to 21c of each of the receivers 20a directly, or reaches each of the antennas 21a to 21c after being reflected by an object other than the transmitter 10 and the receiver 20a.

[0117] Next, each of the receivers 20a performs a receiving process for the wireless signal Tx2 (step S14). Each of the receivers 20a outputs composite signals SS21 to SS24 based on the wireless signal Tx2.

[0118] Next, the signal processing unit 31a of the estimation unit 30a outputs, for each receiver 20a, a representative signal Rr corresponding to the radio signals Tx1 and Tx2 transmitted by the transmitter 10 (step S15). The signal processing unit 31a performs the following processing for each receiver 20a. The signal processing unit 31a determines the amplitude value of the composite signal having the greater signal strength, between the composite signals SS11 and SS21, as a representative signal SSr1. The signal processing unit 31a also determines the amplitude value of the composite signal having the greater signal strength, between the composite signals SS12 and SS22, as a representative signal SSr2. The signal processing unit 31a also determines the amplitude value of the composite signal having the greater signal strength, between the composite signals SS13 and SS23, as a representative signal SSr3. The signal processing unit 31a also determines the amplitude value of the composite signal having the greater signal strength, between the composite signals SS14 and SS24, as a representative signal SSr4.

[0119] Next, the position estimation unit 32a of the estimation unit 30a estimates the position of the transmitter 10 (step S16). The position estimation unit 32a estimates the direction of the transmitter 10 relative to the receiver 20a based on the representative signal Rr for each receiver 20a. The position estimation unit 32a estimates the direction of the transmitter 10 for each receiver 20a, and estimates the position of the transmitter 10 using the position information of each receiver 20a.

[0120] (3) Effects According to the estimation system 1a of the second embodiment, the transmitter 10 transmits a plurality of different radio signals Tx1 and Tx2. Furthermore, the signal processing unit 31a of the estimation unit 30a calculates, for each receiver 20a, a representative signal Rr corresponding to the radio signal transmitted by the transmitter 10. Furthermore, the position estimation unit 32a of the estimation unit 30a estimates the position of the transmitter 10 using the representative signal Rr that corresponds one-to-one to the receiver 20a. That is, for each of the composite signals SS1 to SS4 for each receiver 20a, the estimation unit 30a uses the amplitude values ​​SSr1, SSr2, SSr3, and SSr4 of the composite signal that is less affected by reflected waves and has high signal strength, for estimating the position of the transmitter 10. This reduces the influence of reflected waves in the estimation system 1a of the second embodiment, thereby improving the accuracy of estimating the position of the transmitter 10.

[0121] Furthermore, in the estimation system 1a according to the second embodiment, a representative signal Rr is calculated for each receiver 20a, and the representative signal Rr for each receiver 20a is used to estimate the position of the transmitter 10. Therefore, even if the number of times of transmitting wireless signals increases, an increase in the amount of calculation can be suppressed.

[0122] (Variation) In the signal processing unit 31a according to the second embodiment, the signal with the greatest signal strength among the composite signals SS1, SS2, SS3, and SS4 is defined as the representative signal Rr. However, each component of the representative signal Rr is not limited to the signal with the greatest signal strength.

[0123] In a signal processing unit 31a according to a modified example of embodiment 2, for example, for each receiver 20a, the average signal strength of the composite signal SS1, the average signal strength of the composite signal SS2, the average signal strength of the composite signal SS3, and the average signal strength of the composite signal SS4 are set as the representative signal Rr.

[0124] A signal processing unit 31a according to a modification of the second embodiment acquires composite signals SS1 to SS4 from each of the receivers 20a. The signal processing unit 31a averages the signal strengths of composite signal SSi1 corresponding to each of n wireless signals to obtain the signal strength of representative signal SSr1. That is, the signal processing unit 31a calculates the signal strength of representative signal SSr1 based on the following formula:

[0125]

number

[0126] Similarly, the signal processing unit 31a calculates the representative signal SSr2 based on the following formula.

[0127]

number

[0128] Similarly, the signal processing unit 31a calculates the representative signal SSr3 based on the following formula.

[0129]

number

[0130] Similarly, the signal processing unit 31a calculates the representative signal SSr4 based on the following formula.

[0131]

number

[0132] Even for the combined signal SS1 in one receiver 20a, the difference in the component due to the direct wave between combined signal SSi1 corresponding to wireless signal Txi and combined signal SSj1 corresponding to wireless signal Txj is small, but the difference in the component due to the reflected wave is larger than the difference in the component due to the direct wave. Therefore, by setting the average value of the amplitude values ​​of combined signal SSi1 corresponding to multiple wireless signals as the amplitude value SSr1 of the representative signal, the effects of reflected waves can be mutually canceled out between the amplitude values ​​of the multiple combined signals SSi1, thereby generating a representative signal SSr1 that is less affected by reflected waves. The same applies to the amplitude values ​​of combined signals SSi2 to SSi4.

[0133] Therefore, the estimation system 1a according to the modified example can also suppress the influence of reflected waves in a simple manner.

[0134] (Embodiment 3) In the first embodiment, the transmitter 10 outputs multiple radio signals Tx1 and Tx2 from a single antenna 12. In contrast, a transmitter 10b according to a third embodiment includes a transmitting unit 11b and antennas 12a and 12b having different planes of polarization, as shown in Fig. 7. The transmitting unit 11b of the transmitter 10b outputs the radio signal Tx1 from the antenna 12a and the radio signal Tx2 from the antenna 12b.

[0135] As shown in FIG. 7, in an estimation system 1b according to the third embodiment, a transmitter 10b includes a transmission unit 11b and a plurality of antennas 12a and 12b.

[0136] The antennas 12a and 12b output radio signals with different planes of polarization. The antennas 12a and 12b output radio signals with planes of polarization that are orthogonal to each other. The antennas 12a and 12b are implemented, for example, as a single dual-polarized patch antenna.

[0137] In the estimation system 1b according to the third embodiment, the antenna 21 of the receiver 20 receives radio signal components along one polarization plane. The receiver 20 may include multiple antennas, but all of the antennas receive radio signal components along one common polarization plane.

[0138] The transmitter 10b according to the third embodiment transmits a radio signal Tx1 using an antenna 12a, and the transmitter 11b according to the third embodiment transmits a radio signal Tx2 using an antenna 12b.

[0139] In the estimation system 1b according to the third embodiment, the radio signals Tx1 and Tx2 have different planes of polarization. The plane of polarization of the direct wave does not change along the propagation path, but the plane of polarization of the reflected wave may differ from that before reflection. Therefore, the plane of polarization of the direct wave is the same as the plane of polarization of the radio signal output from the transmitter 10b, but the reflected wave may contain a polarization component orthogonal to the plane of polarization of the radio signal output from the transmitter 10b. In other words, when the antenna 21 of the receiver 20 receives radio signal components along one plane of polarization, the signal intensity ratio between the direct wave and the reflected wave differs between the received signal corresponding to the radio signal Tx1 and the received signal corresponding to the radio signal Tx2.

[0140] For example, let us consider a case where antenna 21 of receiver 20 receives vertically polarized waves. For example, when antenna 12a transmits vertically polarized waves, the radio signal Tx1 is vertically polarized, so the direct wave is vertically polarized, and the reflected wave may contain a horizontally polarized component. Therefore, the received signal corresponding to radio signal Tx1 has a strong direct wave component. In contrast, when antenna 12b transmits horizontally polarized waves, the radio signal Tx2 is horizontally polarized, so the direct wave is horizontally polarized, and the reflected wave may contain a vertically polarized component. Therefore, the received signal corresponding to radio signal Tx2 has a strong reflected wave component. However, because the power of the reflected wave is smaller than the power of the direct wave, the signal strength of the received signal corresponding to radio signal Tx1 is greater than the signal strength of the received signal corresponding to radio signal Tx2. In other words, the stronger the influence of the direct wave and the smaller the influence of the reflected wave, the greater the signal strength of the received signal.

[0141] Therefore, in the receiver 20 and the estimation unit 30, as in the first embodiment, the maximum value of the signal strength Rx1 of the received signal corresponding to the radio signal Tx1 and the signal strength Rx2 of the received signal corresponding to the radio signal Tx2 is set as the representative value Rx of the received signal for each receiver 20. This makes it possible to suppress the influence of reflected waves in a simple manner and estimate the position of the transmitter 10b.

[0142] In the receiver 20 and the estimation unit 30, similar to the modification of embodiment 1, the average value of the signal strength Rx1 of the received signal corresponding to the radio signal Tx1 and the signal strength Rx2 of the received signal corresponding to the radio signal Tx2 may be set as the representative value Rx of the received signal for each receiver 20. Also, similar to embodiment 2 or the modification of embodiment 2, the receiver 20 may output composite signals SS11 to SS14 corresponding to the radio signal Tx1 and composite signals SS21 to SS24 corresponding to the radio signal Tx2, and estimate the position of the transmitter 10b based on these signals.

[0143] Furthermore, the transmitter 10b according to the third embodiment includes antennas 12a and 12b with different polarization planes. Therefore, when the transmitter 10b is a portable device, regardless of the orientation of the transmitter 10b, the polarization plane of either the antenna 12a or the antenna 12b is likely to be close to the polarization plane of the antenna of the receiver 20. In other words, the influence of reflected waves on the received signal corresponding to the radio signal Tx1 or the received signal corresponding to the radio signal Tx2, whichever has the greater signal strength, is smaller than the influence of reflected waves on the received signal corresponding to the weaker signal strength. Therefore, regardless of the orientation of the transmitter 10b, the influence of reflected waves can be suppressed using a simple method.

[0144] (Embodiment 4) In the first embodiment, the transmitter 10 outputs multiple radio signals Tx1 and Tx2 with the same directivity from a single antenna 12. In contrast, the transmitter 10c according to the fourth embodiment changes the directivity of the antenna 12 for the radio signals Tx1 and Tx2.

[0145] 8, in the estimation system according to the fourth embodiment, a transmitter 10c includes an antenna 12 and a parasitic antenna 12c. The parasitic antenna 12c is connected to the ground via a switch 13.

[0146] The transmitter 10c according to the fourth embodiment transmits a radio signal Tx1 using the antenna 12 when the switch 13 is open. The transmitter 10c according to the fourth embodiment transmits a radio signal Tx2 using the antenna 12 when the switch 13 is closed.

[0147] The transmitter 10c according to the fourth embodiment transmits a radio signal Tx1 with the parasitic antenna 12c not connected to the ground. The transmitter 10c according to the fourth embodiment transmits a radio signal Tx2 with one end of the parasitic antenna 12c connected to the ground. The coupling state between the antenna 12 and the parasitic antenna 12c changes depending on whether the switch 13 is open or closed, and therefore the directivity of the antenna 12 changes between transmitting the radio signal Tx1 and transmitting the radio signal Tx2.

[0148] In the transmitter 10c according to the fourth embodiment, the radio signals Tx1 and Tx2 have different directivities. Therefore, in the receiver 20, the received signals corresponding to the radio signals Tx1 and Tx2 have different signal propagation paths, and therefore have different signal intensity ratios between the direct wave and the reflected wave.

[0149] Therefore, in the receiver 20 and the estimation unit 30, as in the modified example of the first embodiment, the average of the signal strength Rx1 of the received signal corresponding to the wireless signal Tx1 and the signal strength Rx2 of the received signal corresponding to the wireless signal Tx2 is set as the representative value Rx of the received signal for each receiver 20. This makes it possible to suppress the influence of reflected waves in a simple manner and estimate the position of the transmitter 10c.

[0150] In addition, in the receiver 20 and the estimation unit 30, as in the modified example of embodiment 2, the receiver 20 may output composite signals SS11 to SS14 corresponding to the radio signal Tx1 and composite signals SS21 to SS24 corresponding to the radio signal Tx2, and estimate the position of the transmitter 10c based on these.

[0151] (Embodiment 5) In the first embodiment, the transmitter 10 transmits multiple radio signals Tx1 and Tx2 from a single antenna 12. In contrast, a transmitter 10d according to a fifth embodiment includes antennas 12d and 12e that are spaced apart by half the wavelength of the carrier wave, and the radio signal Tx1 is transmitted from the antenna 12d, and the radio signal Tx2 is transmitted from the antenna 12e.

[0152] 9, a transmitter 10d according to the fifth embodiment includes a transmitter 11d and multiple antennas 12d and 12e. The antennas 12d and 12e are spaced apart from each other by half the wavelength of the carrier waves of the radio signals Tx1 and Tx2.

[0153] A transmitter 10d according to the fifth embodiment has a transmitter unit 11d that outputs a radio signal Tx1 using an antenna 12d, and a transmitter unit 11d according to the fifth embodiment has an antenna 12e that outputs a radio signal Tx2.

[0154] In the transmitter 10d according to the fifth embodiment, the antenna 12d that transmits the radio signal Tx1 and the antenna 12e that transmits the radio signal Tx2 are separated by half the wavelength of the carrier wave. Therefore, the radio signals Tx1 and Tx2 do not propagate along the same path between the transmitter 10d and the receiver 20. Therefore, the radio signals Tx1 and Tx2 have different signal intensity ratios between the direct wave and the reflected wave at the receiver 20.

[0155] Therefore, in the receiver 20 and the estimation unit 30, as in the first embodiment, the maximum value of the signal strength Rx1 of the received signal corresponding to the radio signal Tx1 and the signal strength Rx2 of the received signal corresponding to the radio signal Tx2 is set as the representative value Rx of the received signal for each receiver 20. This makes it possible to estimate the position of the transmitter 10d using either the signal strength Rx1 or the signal strength Rx2, whichever is less affected by the reflected wave. Therefore, it is possible to estimate the position of the transmitter 10d while suppressing the influence of the reflected wave in a simple manner.

[0156] In the receiver 20 and the estimation unit 30, similar to the modification of embodiment 1, the average value of the signal strength Rx1 of the received signal corresponding to the radio signal Tx1 and the signal strength Rx2 of the received signal corresponding to the radio signal Tx2 may be set as the representative value Rx of the received signal for each receiver 20. Also, similar to embodiment 2 or the modification of embodiment 2, the receiver 20 may output composite signals SS11 to SS14 corresponding to the radio signal Tx1 and composite signals SS21 to SS24 corresponding to the radio signal Tx2, and estimate the position of the transmitter 10d based on these signals.

[0157] (Embodiment 6) In the first embodiment, the transmitter 10 transmits multiple radio signals Tx1 and Tx2 from a single transmitting unit 11. In contrast, the transmitter 10e according to the sixth embodiment includes multiple transmitting units connected to an antenna, and transmits a radio signal from each of the multiple transmitting units.

[0158] As shown in FIG. 10, the transmitter 10e according to the sixth embodiment includes a plurality of (two in the illustrated example) transmitting units 11f and 11g, a plurality of (two in the illustrated example) antennas 12f and 12g, and a control unit 14.

[0159] The transmitter 11f outputs a radio signal Tx1 using the antenna 12f. The transmitter 11g outputs a radio signal Tx2 using the antenna 12g. The controller 14 controls the transmitters 11f and 11g so that the transmission period of the radio signal Tx1 and the transmission period of the radio signal Tx2 do not overlap.

[0160] The transmitter 10e according to the sixth embodiment alternately outputs the radio signal Tx1 by the transmitter 11f and the radio signal Tx2 by the transmitter 11g so that the transmission period of the radio signal Tx1 and the transmission period of the radio signal Tx2 do not overlap. The transmitter 10e according to the sixth embodiment outputs the radio signals Tx1 and Tx2, for example, as follows. That is, as shown in FIG. 11, the transmitter 11f outputs the radio signal Tx1 at every transmission interval T1. The transmitter 11g outputs the radio signal Tx2 at every transmission interval T1. The output of the radio signal Tx2 by the transmitter 11g is delayed by an interval T2 from the output of the radio signal Tx1 by the transmitter 11f. The interval T2 is, for example, ½ of the transmission interval T1.

[0161] In the case of transmitting wireless signals using one transmitter and one antenna (Comparative Example 1), as shown in Fig. 12, the reception interval of the received signal at the receiver depends on the transmission interval T3 of the wireless signal from the transmitter. In Fig. 12, the solid arrows indicate received signals corresponding to wireless signals, and the dashed arrows indicate wireless signals that failed to be received. However, in the case of transmitting wireless signals using one transmitter and one antenna, the transmission interval of the wireless signal from the transmitter depends on the processing capacity of the transmitter, so there is a limit to how often the wireless signal can be transmitted. Furthermore, as in Comparative Example 2 shown in Fig. 13, if the transmission interval T4 of the wireless signal is shortened to increase the transmission frequency, the probability of interference with wireless signals output from other transmitters increases, and the probability of reception failure increases.

[0162] In contrast, by including transmitter 10e in transmitter unit 11f and transmitter unit 11g, transmitter 10e can transmit wireless signals at intervals shorter than the transmission intervals of transmitter units 11f and 11g. In transmitter 10e according to the sixth embodiment, interval T2 between the output of wireless signal Tx1 by transmitter unit 11f and the output of wireless signal Tx2 by transmitter unit 11g is set to half the transmission interval T1 of each of wireless signals Tx1 and Tx2. Therefore, wireless signals are output from transmitter 10e at intervals T2.

[0163] However, when the transmission interval T5 between the radio signals Tx1 and Tx2 is short enough to overlap the transmission period of the radio signal Tx1 and the transmission period of the radio signal Tx2 (as in Comparative Example 3), the probability of reception failure increases, as shown in FIG. 14. In FIG. 14, the solid arrow indicates the received signal corresponding to the radio signal Tx1, and the hollow arrow indicates the received signal corresponding to the radio signal Tx2. That is, if the transmitter starts transmitting the radio signal Tx2 before completing the transmission of the radio signal Tx1, the probability of reception failure at the receiver increases. In contrast, in the transmitter 10e according to the sixth embodiment, the control unit 14 controls the transmission period of the radio signal Tx1 and the transmission period of the radio signal Tx2 so that they do not overlap. Therefore, as shown in FIG. 11, the reception interval of the radio signals at the receiver 20 is short, and the frequency of reception failure can be reduced. Therefore, the transmitter 10e can transmit radio signals frequently, and the time lag in the estimation unit 30's estimation of the position of the transmitter 10e can be reduced.

[0164] The wireless signals Tx1 and Tx2 contain different identification information. For example, in the transmitter 10e, the transmitter 11f has a MAC address, and the transmitter 11g has a MAC address different from the MAC address of the transmitter 11f. The wireless signal Tx1 includes the MAC address of the transmitter 11f, and the wireless signal Tx2 includes the MAC address of the transmitter 11g. With the above configuration, the receiver 20 can easily distinguish between the received signal for the wireless signal Tx1 and the received signal for the wireless signal Tx2. Therefore, the receiver 20 can generate, for example, the signal strength Rx1 of the received signal for the wireless signal Tx1 and the signal strength Rx2 of the received signal for the wireless signal Tx2 without mistaking the wireless signals. Furthermore, the estimation unit 30 can generate a representative value Rx of the received signal and estimate the position of the transmitter 10e based on the representative value Rx of the received signal, for example, upon receiving the signal strength Rx2 of the received signal for the wireless signal Tx2 from each of the receivers 20.

[0165] In the receiver 20 and the estimation unit 30, as in the modification of embodiment 1, the average value of the signal strength Rx1 of the received signal corresponding to the radio signal Tx1 and the signal strength Rx2 of the received signal corresponding to the radio signal Tx2 may be set as the representative value Rx of the received signal for each receiver 20. Also, as in embodiment 2 or the modification of embodiment 2, the receiver 20 may output composite signals SS11 to SS14 corresponding to the radio signal Tx1 and composite signals SS21 to SS24 corresponding to the radio signal Tx2, and estimate the position of the transmitter 10d based on these signals.

[0166] (Embodiment 7) In the first embodiment, the transmitter 10 outputs multiple radio signals Tx1 and Tx2 from a single transmitting unit 11. In contrast, in the estimation system 1f according to the seventh embodiment, the transmitter 10f includes multiple transmitting units each equipped with an antenna, and each transmitting unit outputs a radio signal by changing the carrier frequency.

[0167] (1) Composition As shown in FIG. 15, an estimation system 1f according to the seventh embodiment includes a transmitter 10f, a plurality of receivers 20f (only one is shown in FIG. 15), and an estimation unit 30f.

[0168] A transmitter 10f according to the seventh embodiment includes a plurality of (two in FIG. 15) transmitters 11h and 11i, a plurality of (two in FIG. 15) antennas 12h and 12i, and a control unit 14f. The transmitter 11h transmits a wireless signal using the antenna 12h. The transmitter 11i transmits a wireless signal using the antenna 12i.

[0169] The transmitter 11h and the transmitter 11i can each select one of a plurality of frequencies as the carrier frequency of the wireless signal. More specifically, the transmitter 11h and the transmitter 11i transmit the wireless signal using, for example, any one of channels 37, 38, and 39 in BLE.

[0170] The control unit 14f controls the transmitter 11h and the transmitter 11i to alternately transmit wireless signals. As in the sixth embodiment, the transmission period of the wireless signal of the transmitter 11h does not overlap with the transmission period of the wireless signal of the transmitter 11i. Furthermore, the transmitter 11i transmits a wireless signal at a frequency different from the frequency used by the transmitter 11h immediately before. Similarly, the transmitter 11h transmits a wireless signal at a frequency different from the frequency used by the transmitter 11i immediately before.

[0171] More specifically, the transmitter 11h transmits a radio signal Tx1 from the antenna 12h using channel 37. Next, the transmitter 11i transmits a radio signal Tx2 from the antenna 12i using channel 38. Next, the transmitter 11h transmits a radio signal Tx1 from the antenna 12h using channel 39. Similarly, the transmitter 11i then transmits the radio signal Tx1 using channel 37. Next, the transmitter 11h transmits the radio signal Tx2 using channel 38. Next, the transmitter 11i transmits the radio signal Tx3 using channel 39. Thereafter, the transmitter 10f repeats the same operation.

[0172] The receiver 20f includes an antenna 21 and a receiving unit 22f. The receiving unit 22f outputs the signal strength of a received signal received by the antenna 21 during a reception period. The reception period alternates between a first reception period and a second reception period. Each of the first reception period and the second reception period includes a transmission period of at least two wireless signals. In the receiver 20f according to the seventh embodiment, the first reception period and the second reception period include a transmission period of two wireless signals. The receiving unit 22f outputs the signal strength Ra1 of a received signal received during the first reception period. The receiving unit 22f also outputs the signal strength Ra2 of a received signal received during the second reception period.

[0173] The estimation unit 30f includes a signal processing unit 31f and a position estimation unit 32. The signal processing unit 31f calculates, for each receiver 20f, a representative value Rx of the received signal from the signal strength Ra1 of the received signal and the signal strength Ra2 of the received signal.

[0174] (2) Operation The operation of the estimation system 1f of the seventh embodiment will be described with reference to the sequence diagram of FIG.

[0175] The transmitter 10f outputs a wireless signal Tx1 from the transmitter 11h using ch 37 (step S21). Next, after a transmission interval has elapsed since the completion of step S21, the transmitter 10f outputs a wireless signal Tx2 from the transmitter 11i using ch 38 (step S22). Next, after a transmission interval has elapsed since the completion of step S22, the transmitter 10f outputs a wireless signal Tx3 from the transmitter 11h using ch 39 (step S23). Next, after a transmission interval has elapsed since the completion of step S23, the transmitter 10f outputs a wireless signal Tx1 from the transmitter 11i using ch 37 (step S24). Next, after a transmission interval has elapsed since the completion of step S24, the transmitter 10f outputs a wireless signal Tx2 from the transmitter 11h using ch 38 (step S25). Next, after a transmission interval has elapsed since step S22 is completed, the transmitter 10f outputs a radio signal Tx3 from the transmitter 11i using channel 39 (step S26).

[0176] After the transmission interval has elapsed since step S26 was completed, the transmitter 10f repeats the operations from step S21 to step S26.

[0177] Meanwhile, the receiver 20f outputs the signal strength Ra1 of the received signal received by the antenna 21 in the first reception period (step S31). The receiving unit 22f of the receiver 20f receives the wireless signal Tx1 in step S21 and the wireless signal Tx2 in step S22 in the first reception period. Therefore, the receiver 20f outputs the signal strength Ra1 of the received signal corresponding to the wireless signal Tx1 in step S21 and the wireless signal Tx2 in step S22.

[0178] Next, the receiver 20f outputs the signal strength Ra2 of the received signal received by the antenna 21 in the second reception period (step S32). The receiving unit 22f of the receiver 20f receives the wireless signal Tx3 in step S23 and the wireless signal Tx1 in step S24 in the second reception period. Therefore, the receiver 20f outputs the signal strength Ra2 of the received signal corresponding to the wireless signal Tx3 in step S23 and the wireless signal Tx1 in step S24.

[0179] After completing step S32, the receiver 20f repeats the operations of steps S31 and S32. Therefore, in the next step S31, the receiver 20f outputs the signal strength Ra1 of the received signals corresponding to the wireless signal Tx2 related to step S25 and the wireless signal Tx3 related to step S26. Furthermore, in the next step S32, the receiver 20f outputs the signal strength Ra2 of the received signals corresponding to the wireless signal Tx1 related to step S21 and the wireless signal Tx2 related to step S22.

[0180] The signal processing unit 31f of the estimation unit 30f calculates a representative value Rx of the received signal corresponding to the receiver 20f every time the signal strength Ra1 of the received signal and the signal strength Ra2 of the received signal are received from the receiver 20f (step S5). The signal processing unit 31f calculates the maximum value of the signal strength Ra1 of the received signal and the signal strength Ra2 of the received signal as the representative value Rx of the received signal.

[0181] The position estimation unit 32 of the estimation unit 30 estimates the position of the transmitter 10f using the representative value Rx of the received signal for each receiver 20f (step S6).

[0182] (3) Effects According to the estimation system 1f of the seventh embodiment, the multiple wireless signals corresponding to the signal strength Ra1 of the received signal have different frequencies from the multiple wireless signals corresponding to the signal strength Ra2 of the received signal. Therefore, by calculating the representative value Rx of the received signal from the signal strength Ra1 and the signal strength Ra2 of the received signal, the estimation system 1f can reduce the influence of reflected waves and improve the accuracy of estimating the position of the transmitter 10.

[0183] Furthermore, in the estimation system 1f according to the seventh embodiment, the operating cycle of the transmitter 10f does not necessarily coincide with the operating cycle of the receiver 20f. That is, the transmitter 10f switches between three types of carrier frequencies, while the receiver 20f performs reception processing based on the reception of two types of wireless signals. This allows the estimation system 1f to improve the frequency of position estimation. Furthermore, since the operation of the receiver 20f and the operation of the transmitter 10f do not necessarily have to be synchronized, the operation of the receiver 20f is simplified.

[0184] In the receiver 20f and the estimation unit 30f according to the seventh embodiment, the average value of the signal strength Ra1 and the signal strength Ra2 of the received signal may be set as the representative value Rx of the received signal for each receiver 20f, as in the modification of the first embodiment. Also, as in the second embodiment or the modification of the second embodiment, the receiver 20f may output composite signals SS11 to SS14 corresponding to the first reception period and composite signals SS21 to SS24 corresponding to the second reception period, and estimate the position of the transmitter 10f based on these signals.

[0185] (summary) An estimation system (1; 1a; 1b; 1f) according to a first aspect includes a transmitter (10; 10b to 10f) and an estimation unit (30; 30a; 30f). The transmitter (10; 10b to 10f) outputs a plurality of mutually different radio signals (Tx1, Tx2, Tx3). The estimation unit (30; 30a; 30f) estimates the position of the transmitter (10; 10b to 10f) based on a plurality of received signals (Rx1, Rx2; SS1 to SS4; Ra1 to Ra2). The plurality of received signals (Rx1, Rx2; SS1 to SS4; Ra1 to Ra2) are generated by a receiver (20; 20a; 20f) that receives the plurality of radio signals (Tx1, Tx2, Tx3). The estimation unit (30; 30a; 30f) estimates the position of the transmitter using the maximum value of the received power of the plurality of received signals (Rx; SSr1, SSr2, SSr3, SSr4) or the average value of the received power of the plurality of received signals (Rx; SSr1, SSr2, SSr3, SSr4).

[0186] According to the estimation system (1; 1a; 1b; 1f) of the above aspect, the transmitter (10; 10b to 10f) outputs a plurality of mutually different wireless signals (Tx1, Tx2, Tx3). The estimation unit (30; 30a; 30f) estimates the position of the transmitter using the maximum value of the received power of the plurality of received signals (Rx; SSr1, SSr2, SSr3, SSr4) or the average value of the received power of the plurality of received signals (Rx; SSr1, SSr2, SSr3, SSr4). Therefore, the accuracy of the position estimation of the transmitter (10; 10b to 10f) can be improved by using the received signal that is least affected by reflected waves or by averaging the received signals to reduce the effect of reflected waves.

[0187] In the estimation system (1; 1b; 1f) according to the second aspect, in the first aspect, the transmitter (10b to 10f) is equipped with a plurality of antennas (12a, 12b; 12d, 12e; 12f, 12g; 12h, 12i) that output a plurality of radio signals (Tx1, Tx2, Tx3).

[0188] According to the estimation system (1; 1b; 1f) of the above aspect, the transmitters (10b to 10f) can easily output a plurality of different radio signals (Tx1, Tx2, Tx3).

[0189] In the estimation system (1b) according to the third aspect, in the second aspect, the plurality of antennas (12a, 12b) outputs a plurality of signals having different planes of polarization as a plurality of radio signals (Tx1, Tx2).

[0190] According to the estimation system (1b) of the above aspect, the receiver (20) can easily reduce the influence of reflected waves on the received signal based on the plane of polarization.

[0191] In the estimation system (1) according to the fourth aspect, in the second aspect, the plurality of antennas (12, 12c) output a plurality of radio signals having different directivities as the plurality of radio signals (Tx1, Tx2).

[0192] According to the estimation system (1) of the above aspect, since the degree of influence of reflected waves differs for each received signal (Rx1, Rx2; SS1 to SS4; Ra1 to Ra2), the accuracy of position estimation of the transmitter (10c) can be improved by using the received signal that is least influenced by reflected waves or by averaging the received signals to reduce the influence of reflected waves.

[0193] In the estimation system (1) according to the fifth aspect, in the second aspect, the interval between the plurality of antennas (12d, 12e) is 1 / 2 the wavelength of the radio signals (Tx1, Tx2).

[0194] According to the estimation system (1) of the above aspect, the radio signal (Tx1) output from the antenna (12d) and the radio signal (Tx2) output from the antenna (12e) do not have the same propagation path in space. Therefore, the degree of influence of reflected waves varies for each of the received signals (Rx1, Rx2; SS1 to SS4; Ra1 to Ra2). Therefore, the accuracy of estimating the position of the transmitter (10d) can be improved by using the received signal that is least influenced by reflected waves or by averaging the received signals to reduce the influence of reflected waves.

[0195] In the estimation system (1) according to the sixth aspect, in the second aspect, the transmitter (10e) further includes a control unit (14). The multiple antennas include a first antenna (12f) and a second antenna (12g). The first antenna (12f) outputs a first wireless signal (Tx1) from among the multiple wireless signals. The second antenna (12g) outputs a second wireless signal (Tx2) from among the multiple wireless signals, the second wireless signal (Tx2) being different from the first wireless signal (Tx1). The control unit (14) controls the first antenna (12f) and the second antenna (12g) so that a transmission period of the first wireless signal (Tx1) and a transmission period of the second wireless signal (Tx2) do not overlap.

[0196] According to the estimation system (1) of the above aspect, it is possible to shorten the transmission intervals of the multiple wireless signals, thereby reducing the time lag in estimating the position of the transmitter (10e). Also, it is possible to prevent degradation in the quality of the received signals (Rx1, Rx2; SS1 to SS4; Ra1 to Ra2) due to interference between the signal corresponding to the first wireless signal (Tx1) and the signal corresponding to the second wireless signal (Tx2).

[0197] In an estimation system (1f) according to a seventh aspect, in the second aspect, the plurality of antennas includes a first antenna (12h) and a second antenna (12i). The first antenna (12h) and the second antenna (12i) output radio signals of different frequencies as the plurality of radio signals (Tx1, Tx2, Tx3).

[0198] According to the estimation system (1f) of the above aspect, since the multiple wireless signals (Tx1, Tx2, Tx3) do not have the same frequency, the degree of influence of reflected waves varies for each received signal (Rx1, Rx2; SS1 to SS4; Ra1 to Ra2). Therefore, the accuracy of estimating the position of the transmitter (10d) can be improved by using the received signal that is least influenced by reflected waves or by averaging the received signals to reduce the influence of reflected waves.

[0199] In an estimation system (1; 1b; 1f) according to an eighth aspect, in any of the first to seventh aspects, the plurality of received signals (Rx1, Rx2) correspond one-to-one to the plurality of radio signals (Tx1, Tx2).

[0200] According to the estimation system (1; 1b; 1f) of the above aspect, the position of the transmitter (10; 10b to 10f) can be estimated by a simple method.

[0201] In an estimation system (1a) according to a ninth aspect, in any one of the first to seventh aspects, the plurality of received signals includes a plurality of signal sets, each of which includes a plurality of received signals (SS1, SS2, SS3, SS4), and the plurality of signal sets correspond one-to-one to the plurality of wireless signals (Tx1, Tx2).

[0202] According to the estimation system (1a) of the above aspect, the position of the transmitter (10) can be estimated with a highly accurate method.

[0203] An estimation method according to a tenth aspect includes a transmitting step and an estimating step. In the transmitting step, a transmitter (10; 10b to 10f) transmits a plurality of mutually different wireless signals (Tx1, Tx2, Tx3). In the estimating step, a plurality of received signals (Rx1, Rx2; SS1 to SS4; Ra1 to Ra2) are used to estimate the position of the transmitter (10; 10b to 10f). The plurality of received signals (Rx1, Rx2; SS1 to SS4; Ra1 to Ra2) are generated by a receiver (20; 20a; 20f) that receives the plurality of wireless signals (Tx1, Tx2). In the estimating step, the position of the transmitter is estimated using a maximum value (Rx; SSr1, SSr2, SSr3, SSr4) of received power of the plurality of received signals or an average value (Rx; SSr1, SSr2, SSr3, SSr4) of received power of the plurality of received signals.

[0204] According to the estimation method of the above aspect, the accuracy of position estimation of the transmitter (10; 10b to 10f) can be improved by using the received signal that is least affected by the reflected wave or by reducing the influence of the reflected wave by averaging the received signal.

[0205] An estimation program according to an eleventh aspect is a program for causing one or more processors to execute the estimation method according to the tenth aspect.

[0206] According to the estimation program of the above aspect, the accuracy of position estimation of the transmitter (10; 10b to 10f) can be improved by using the received signal that is least affected by the reflected wave, or by reducing the influence of the reflected wave by averaging the received signal. [Explanation of symbols]

[0207] 1, 1a, 1b, 1f Estimation System 10, 10b, 10c, 10d, 10e, 10f transmitter 12a, 12b, 12d, 12e antennas 12f, 12h antenna (first antenna) 12g, 12i antenna (second antenna) 12c Parasitic Antenna (Antenna) 14 Control Unit 20, 20a, 20f receiver 30, 30a, 30f estimation part Tx1 radio signal (first radio signal) Tx2 wireless signal (second wireless signal) Tx3 wireless signal Rx1, Rx2 Received signal strength (received signal) Rx: Representative value of received signal (maximum received power, average received power) SS1, SS2, SS3, SS4 combined signal (received signal) SSr1, SSr2, SSr3, SSr4 representative signals (maximum received power, average received power) Ra1, Ra2 Signal strength of received signal (received signal)

Claims

1. a transmitter that outputs a plurality of mutually different wireless signals; an estimation unit that estimates a position of the transmitter based on a plurality of received signals generated by a receiver that receives the plurality of wireless signals; Equipped with the receiver generates a plurality of sets of signals corresponding one-to-one to the plurality of wireless signals; each of the plurality of signal sets includes two or more composite signals generated by combining two or more received signals corresponding to a corresponding wireless signal among the plurality of wireless signals; The estimation unit estimating the position of the transmitter using a maximum value of received power of the two or more composite signals included in each of the plurality of signal sets or an average value of received power of the two or more composite signals included in each of the plurality of signal sets; Estimation system.

2. the transmitter includes a plurality of antennas that output the plurality of radio signals; The estimation system of claim 1 .

3. the plurality of antennas output, as the plurality of radio signals, a plurality of radio signals having different planes of polarization from each other; The estimation system according to claim 2 .

4. the plurality of antennas output, as the plurality of radio signals, a plurality of radio signals having different directivities from each other; The estimation system according to claim 2 .

5. The intervals between the plurality of antennas are equal to half the wavelength of the radio signal. The estimation system according to claim 2 .

6. The transmitter is a control unit, The plurality of antennas a first antenna that outputs a first wireless signal among the plurality of wireless signals; a second antenna that outputs a second radio signal different from the first radio signal among the plurality of radio signals, the control unit controls the first antenna and the second antenna so that a transmission period of the first radio signal and a transmission period of the second radio signal do not overlap. The estimation system according to claim 2 .

7. The plurality of antennas A first antenna; a second antenna; the first antenna and the second antenna output radio signals of different frequencies as the plurality of radio signals; The estimation system according to claim 2 .

8. the plurality of received signals correspond one-to-one to the plurality of wireless signals; The estimation system according to any one of claims 1 to 7.

9. A transmitting step in which a transmitter transmits a plurality of different wireless signals; an estimation step of estimating a position of the transmitter using a plurality of received signals generated by a receiver that receives the plurality of wireless signals; Including, the receiver generates a plurality of sets of signals corresponding one-to-one to the plurality of wireless signals; each of the plurality of signal sets includes two or more composite signals generated by combining two or more received signals corresponding to a corresponding wireless signal among the plurality of wireless signals; In the estimation step, estimating the position of the transmitter using a maximum value of received power of the two or more composite signals included in each of the plurality of signal sets or an average value of received power of the two or more composite signals included in each of the plurality of signal sets; Estimation method.

10. A program for causing one or more processors to execute the estimation method described in claim 9.

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