JP7742593B2 - Estimation system, estimation method, and program - Google Patents

Description

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.

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, the wireless terminal transmits multiple positioning signals (radio signals), and the 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.

However, in the positioning system described in Patent Document 1, as the number of times 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.

Japanese Patent Application Laid-Open No. 2005-181255

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

An estimation system according to one aspect of the present disclosure includes a transmitter and an estimation unit. The transmitter outputs a plurality of mutually different wireless signals. The estimation unit estimates a position of the transmitter based on 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 that correspond 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 estimates 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.

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 multiple wireless signals that are different from each other. In the estimating step, a position of the transmitter is estimated using multiple received signals. The multiple received signals are generated by a receiver that receives the multiple wireless signals. The receiver generates multiple signal sets that correspond one-to-one to the multiple wireless signals. Each of the multiple signal sets includes two or more composite signals generated by combining two or more received signals that correspond to corresponding wireless signals among the multiple wireless signals. In the estimating step, the position of the transmitter is estimated using a maximum value of received power of the two or more composite signals included in each of the multiple signal sets, or an average value of received power of the two or more composite signals included in each of the multiple signal sets.

A program according to one aspect of the present disclosure causes one or more processors to execute the estimation method.

FIG. 1 is a functional block diagram showing the configuration of an estimation system according to the first embodiment. FIG. 2 is a sequence diagram showing the operation of the estimation system. 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. FIG. 4 is a functional block diagram showing the configuration of an estimation system according to the second embodiment. FIG. 5 is a functional block diagram showing the configuration of a receiver in the estimation system. FIG. 6 is a sequence diagram showing the operation of the estimation system. FIG. 7 is a functional block diagram showing the configuration of an estimation system according to the third embodiment. FIG. 8 is a functional block diagram showing the configuration of a transmitter in an estimation system according to the fourth embodiment. FIG. 9 is a functional block diagram showing the configuration of a transmitter in an estimation system according to the fifth embodiment. FIG. 10 is a functional block diagram showing the configuration of a transmitter in an estimation system according to the sixth embodiment. FIG. 11 is a schematic diagram showing timing of radio signals in the estimation system. FIG. 12 is a schematic diagram showing the timing of radio signals in the first comparative example. FIG. 13 is a schematic diagram showing timing of radio signals in the second comparative example. FIG. 14 is a schematic diagram showing the timing of radio signals in the third comparative example. FIG. 15 is a functional block diagram illustrating a configuration of an estimation system according to the seventh embodiment. FIG. 16 is a sequence diagram showing the operation of the estimation system.

(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.

(1) Configuration 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 is shown in FIG. 1), and an estimation unit 30.

(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.

The transmitter 11 is a circuit that generates multiple 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 contain information such as the identification information of the transmitter 10. The identification information of the transmitter 10 is, for example, a MAC (Media Access Control) address.

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

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 Figure 2) of the received signal corresponding to the radio signal Tx1 and the signal strength Rx2 (see Figure 2) of the received signal corresponding to the radio signal Tx2.

(1.3) Estimation Unit 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.

The estimation unit 30 comprises a signal processing unit 31 and a position estimation unit 32.

(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.

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.

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.

(1.3.2) Position Estimation Unit 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.

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 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 amount of attenuation into the distance between the receiver 20 and the transmitter 10.

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, for example, includes a memory 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 virtual space with the receiver 20 at its center and a 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.

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

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 the "direct wave") reaches the antenna 21 of each receiver 20 directly. In addition, a portion of the radio signal Tx1 output from the antenna 12 of the transmitter 10 (hereinafter referred to as the "reflected wave") reaches the antenna 21 after being reflected by an object other than the transmitter 10 and the receiver 20.

Next, each receiver 20 performs reception processing of the wireless signal Tx1 (step S2). Each receiver 20 outputs the signal strength Rx1 of the received signal based on the wireless signal Tx1.

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.

Next, each receiver 20 performs reception processing of the wireless signal Tx2 (step S4). Each receiver 20 outputs the signal strength Rx2 of the received signal based on the wireless signal Tx2.

Next, 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 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 signal.

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 radio signal based on, for example, the representative value Rx of the received signal and the power of the radio signal from 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.

(3) Calculation of Representative Value of 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 the 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.

Figure 3 shows the signal strength values of the received signal versus the distance between the transmitter 10 and the receiver 20. In Figure 3, the dashed line indicates the theoretical value of signal strength when only direct waves reaching the receiver 20 directly from the transmitter 10 reach the receiver 20. Also, in Figure 3, the solid line indicates the theoretical value when both direct waves and reflected waves reaching the receiver 20 after being output from the transmitter 10 are received. The dashed-dotted line in Figure 3 represents the measured 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. Furthermore, the signal strengths Rxa and Rxb in Figure 3 correspond to the wireless signals Tx1 and Tx2, respectively. Furthermore, for 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.

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

Furthermore, because there is not necessarily only one path for the reflected wave between the transmitter 10 and the receiver 20, 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 Figure 3, the power of the radio signals Tx1 and 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.

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 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. As described above, when interference occurs between a direct wave and a reflected wave, a decrease in signal strength often occurs. Therefore, the stronger of the signal strengths Rx1 and Rx2 of the received signal is more likely to be less affected by reflected waves. In other words, by using the signal strength Rx1 or Rx2 of the received signal with the greater signal strength as the representative value Rx of the received signal, the influence of reflected waves can be suppressed in a simple manner.

In embodiment 1, the transmitter 10 transmits different radio signals Tx1 and Tx2, and each receiver 20 outputs signal strengths Rx1 and Rx2 of 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 may be three or more times. In such a case, the receiver 20 outputs the signal strength of the received signal that corresponds one-to-one to the radio signal. 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 that correspond one-to-one to the radio signals as the representative value Rx of the received signal.

(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. This reduces the influence of reflected waves in the estimation system 1 of the first embodiment, thereby improving the accuracy of estimating the position of the transmitter 10.

In addition, in the estimation system 1 according to embodiment 1, 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 the wireless signal is transmitted increases, the amount of calculation can be prevented from increasing.

(Modification)
The signal processing unit 31 according to the first embodiment calculates the maximum value of the signal strengths of a plurality of received signals 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 of the signal strengths Rx1 and Rx2 of the received signals.

In the signal processing unit 31 relating to a modified example of embodiment 1, for example, for each receiver 20, the average value of the signal strengths Rx1 and Rx2 of the received signal is calculated as the representative value Rx of the received signal.

The signal processing unit 31 according to the modified example of embodiment 1 acquires the signal strength of received signals corresponding one-to-one to each wireless signal from each receiver 20. The signal processing unit 31 receives signal strengths Rxi (i is an integer between 1 and n) of n received signals for n wireless signals (n is an integer greater than or equal to 2) from each receiver 20. Here, 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:

The propagation paths of direct waves do not differ significantly between the signal strength Rxi of the received signal corresponding to wireless signal Txi and the signal strength Rxj of the received signal corresponding to wireless signal Txj (j is an integer between 1 and n, and i ≠ j). Therefore, the difference in the 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 wireless signal Txi and the signal strength Rxj of the received signal corresponding to wireless signal Txj. Therefore, the difference in the 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 the components due to direct waves. Therefore, by calculating the average value of the signal strengths Rxi of multiple received signals to calculate the representative value Rx of the received signal, the influence of direct waves in each of the signal strengths Rxi of the received signal can be reinforced and the influence of reflected waves can be mutually canceled out. That is, the representative value Rx of the received signal is less affected by reflected waves than each of the signal strengths Rxi of the received signal.

Therefore, the estimation system 1 relating to the modified example of embodiment 1 can also suppress the influence of reflected waves in a simple manner.

(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.

As shown in Figure 4, the estimation system 1a according to the second embodiment includes multiple receivers 20a and multiple estimation units 30a (only one is shown in Figure 4) instead of multiple receivers 20 and multiple estimation units 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.

(1) Configuration 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.

(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 multiple 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.

The receiver 22a receives the radio signals Tx1 and Tx2 output by the transmitter 10 using the three antennas 21a to 21c. The receiver 22a performs synthesis processing on the three input signals IS1 to IS3 (see Figure 5) input from each of the three antennas 21a to 21c, and outputs four synthesis signals SS1 to SS4 (see Figure 5).

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 multiple (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 configured, for example, by a 90-degree hybrid unit (hybrid element). The phase combiner 23 in embodiment 2 outputs from the first output terminal O1 and the second output terminal O2 a signal whose power value is 1/√2 times that of the three input signals IS1 to IS3 input to the first input terminal I1 and the second input terminal I2. Furthermore, the phase synthesizer 23 outputs a signal of the same phase from the first output terminal O1 compared to the three input signals IS1 to IS3 input to the first input terminal I1, and outputs a signal whose phase is delayed by 90 degrees from the second output terminal O2.

The phase synthesizer 23a outputs a signal IS4 from the first output terminal O1 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.

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

The phase synthesizer 23c outputs a signal IS7 from the second output terminal O2 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.

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 combined signal SS1 from its first output terminal O1, which is the sum of 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 combined signal SS2 from its second output terminal O2, which is the sum of 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.

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

The output unit 24 outputs four composite signals SS1 to SS4 generated by the phase synthesis unit 25 for each wireless signal to the estimation unit 30. Hereinafter, the combination (signal set) of composite signals SS1, SS2, SS3, and SS4 corresponding to the i-th wireless signal is referred to as the received signal set Rvi. Furthermore, the composite signals SS1, SS2, SS3, and SS4 included in the received signal set Rvi are 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 wireless signal Tx1 are composite signals SS11, SS12, SS13, and SS14, respectively (see Figure 6). Furthermore, the composite signals SS1, SS2, SS3, and SS4 included in the received signal set Rv2 corresponding to the second wireless signal Tx2 are composite signals SS21, SS22, SS23, and SS24, respectively (see FIG. 6).

(1.2) Estimation Unit 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.

The estimation unit 30a comprises a signal processing unit 31a and a position estimation unit 32a.

(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. Then, the signal processing unit 31a calculates a representative signal Rr for each of the receivers 20a.

The signal processing unit 31a performs the following processing for each receiver 20a. That is, the signal processing unit 31a generates a representative signal of all SS1s included in the multiple received signal sets Rvi, and sets this as the representative signal SSr1 of the composite signal SS1. The representative signal SSr1 is, for example, the amplitude value of the composite signal SS1 with the greatest signal strength among the multiple SS1s. For example, if 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.

Similarly, the signal processing unit 31a generates a representative signal of all SSi2 included in the multiple received signal sets Rvi and sets this as the representative signal SSr2 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 multiple SSi2.

Similarly, the signal processing unit 31a generates a representative signal of all SSi3 included in the multiple received signal sets Rvi and sets this as the representative signal SSr3 of the composite signal SS3. The representative signal SSr3 is, for example, the amplitude value of the composite signal with the greatest signal strength among the multiple SSi3.

Similarly, the signal processing unit 31a generates a representative signal of all SSi4 included in the multiple received signal sets Rvi and sets this as the representative signal SSr4 of the composite signal SS4. The representative signal SSr4 is, for example, the amplitude value of the composite signal with the greatest signal strength among the multiple SSi4.

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

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

Let h1 be the complex propagation channel between antenna 21a of receiver 20a and antenna 12 of transmitter 10. Let h2 be the complex propagation channel between antenna 21b of receiver 20a and antenna 12 of transmitter 10. Let h3 be the complex propagation channel between antenna 21c of receiver 20a and antenna 12 of transmitter 10. Let d1 be the distance between antenna 21a and antenna 21b, and the distance between antenna 21b and antenna 21c. Let transmitter 10 be located at an angle θ1 based on the broadside direction of the array antenna composed of antennas 21a, 21b, and 21c.

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

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

Here, the symbol H denotes complex conjugate transpose, and the symbol * denotes complex conjugate. Typically, 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).

|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 gain of the channel on the left side of equations (3) to (6) can be expressed from the signal strength using equations (7) to (10).

If we focus on the gain difference obtained through the phase synthesizer 23d, we obtain equation (11).

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

Furthermore, if we focus on the sum of the gains obtained through the phase combiner 23d, equation (13) is obtained from the arithmetic and geometric mean relationship.

Here, assume 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).

Also, when |h1| and |h2| are approximately equal, equation (15) is obtained.

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

Next, by focusing on the difference in gain obtained through the phase combiner 23e, we obtain equation (17), which allows us to calculate the imaginary parts of R23 and R32. Here, β represents the argument of R23.

Furthermore, if 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.

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

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

Of the correlation matrix R, the correlation matrix for representative signals SSr3 and SSr4 is defined as R2. When correlation matrix R2 is expressed using B and β, equation (21) is obtained, and the correlation matrix is estimated.

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

From the above, the estimated correlation matrix R can be expressed as equation (23).

The position estimation unit 32 can estimate the direction of the transmitter 10 by using various direction-of-arrival estimation algorithms for the correlation matrix R. Specifically, when using the beamformer method, 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.

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 the correlation matrix R, the evaluation function P(θ) can be expressed as equation (25).

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.

The position estimation unit 32 performs the above-mentioned estimation for each receiver 20a and estimates the range of presence of the transmitter 10 based on the position of the receiver 20a. The range of presence of the transmitter 10 is estimated on a straight line passing through the positions of the antennas 21a to 21c of the receiver 20a. The position estimation unit 32 then draws the range of presence of the transmitter 10 based on the position of the receiver 20a in a virtual space and calculates the position of the transmitter 10 as the intersection of the range of presence of the transmitter 10.

(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.

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 reaches each of the antennas 21a to 21c of each receiver 20a directly. 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.

Next, each receiver 20a performs reception processing of the wireless signal Tx1 (step S12). Each receiver 20a outputs composite signals SS11 to SS14 based on the wireless signal Tx1.

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 receiver 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.

Next, each receiver 20a performs reception processing of the radio signal Tx2 (step S14). Each receiver 20a outputs composite signals SS21 to SS24 based on the radio signal Tx2.

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 designates the amplitude value of the combined signal having the greater signal strength, between combined signals SS11 and SS21, as representative signal SSr1. The signal processing unit 31a also designates the amplitude value of the combined signal having the greater signal strength, between combined signals SS12 and SS22, as representative signal SSr2. The signal processing unit 31a also designates the amplitude value of the combined signal having the greater signal strength, between combined signals SS13 and SS23, as representative signal SSr3. The signal processing unit 31a also designates the amplitude value of the combined signal having the greater signal strength, between combined signals SS14 and SS24, as representative signal SSr4.

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

(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 a high signal strength to estimate the position of the transmitter 10. As a result, the estimation system 1a of the second embodiment can reduce the influence of reflected waves and improve the accuracy of estimating the position of the transmitter 10.

In addition, in the estimation system 1a according to embodiment 2, 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 that wireless signals are transmitted increases, the amount of calculation can be prevented from increasing.

(Modification)
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.

In the signal processing unit 31a relating 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.

The signal processing unit 31a according to a modified example of embodiment 2 acquires composite signals SS1 to SS4 from each of the receivers 20a. The signal processing unit 31a averages the signal strengths of the composite signal SSi1 corresponding to each of the n wireless signals to obtain the signal strength of the representative signal SSr1. That is, the signal processing unit 31a calculates the signal strength of the representative signal SSr1 based on the following formula:

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

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

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

Even for the combined signal SS1 in one receiver 20a, the difference in the component due to direct waves 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 reflected waves is greater than the difference in the component due to direct waves. Therefore, by setting the average amplitude value 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 multiple combined signals SSi1, 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.

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

(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 a radio signal Tx1 from the antenna 12a and a radio signal Tx2 from the antenna 12b.

As shown in Figure 7, in the estimation system 1b of embodiment 3, the transmitter 10b includes a transmitter unit 11b and multiple antennas 12a, 12b.

Antenna 12a and antenna 12b output radio signals with different polarization planes. For example, antenna 12a and antenna 12b output radio signals with polarization planes that are orthogonal to each other. Antenna 12a and antenna 12b are implemented, for example, as a single dual-polarized patch antenna.

Furthermore, in the estimation system 1b according to embodiment 3, the antenna 21 of the receiver 20 receives radio signal components along one polarization plane. Note that the receiver 20 may be equipped with multiple antennas, but all of the antennas commonly receive radio signal components along one polarization plane.

The transmitter 11b of the transmitter 10b according to the third embodiment transmits a radio signal Tx1 using the antenna 12a. The transmitter 11b of the transmitter 10b according to the third embodiment transmits a radio signal Tx2 using the antenna 12b.

In the estimation system 1b according to embodiment 3, the planes of polarization of the radio signals Tx1 and Tx2 are different from each other. 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 before and after 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 polarization components in a plane perpendicular 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.

For example, let's consider the case where antenna 21 of receiver 20 receives vertically polarized waves. For example, when antenna 12a transmits vertically polarized waves, 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, 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.

Therefore, in the receiver 20 and the estimation unit 30, as in embodiment 1, 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.

In the receiver 20 and the estimation unit 30, as in the modified example of embodiment 1, the average 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 may be used as the representative value Rx of the received signal for each receiver 20. Also, as in the modified example of embodiment 2, the receiver 20 may output composite signals SS11 to SS14 corresponding to the wireless signal Tx1 and composite signals SS21 to SS24 corresponding to the wireless signal Tx2, and estimate the position of the transmitter 10b based on these.

Furthermore, the transmitter 10b according to embodiment 3 is equipped with antennas 12a and 12b having different polarization planes. Therefore, when the transmitter 10b is a portable device, regardless of the orientation in which the transmitter 10b is held, it is highly likely that the polarization plane of either the antenna 12a or the antenna 12b will 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, the influence of reflected waves can be suppressed in a simple manner regardless of the orientation of the transmitter 10b.

(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, a transmitter 10c according to the fourth embodiment changes the directivity of the antenna 12 for the radio signals Tx1 and Tx2.

As shown in Figure 8, in the estimation system of embodiment 4, the transmitter 10c includes an antenna 12 and a parasitic antenna 12c. The parasitic antenna 12c is connected to ground via a switch 13.

The transmitter 10c according to embodiment 4 transmits a radio signal Tx1 using the antenna 12 when the switch 13 is open. The transmitter 10c according to embodiment 4 also transmits a radio signal Tx2 using the antenna 12 when the switch 13 is closed.

In the transmitter 10c according to embodiment 4, the radio signal Tx1 is transmitted with the parasitic antenna 12c not connected to ground. In addition, in the transmitter 10c according to embodiment 4, the radio signal Tx2 is transmitted with one end of the parasitic antenna 12c connected to ground. Because the coupling state between the antenna 12 and the parasitic antenna 12c changes depending on whether the switch 13 is open or closed, the directivity of the antenna 12 changes between transmitting the radio signal Tx1 and transmitting the radio signal Tx2.

In the transmitter 10c according to embodiment 4, the directivity of the radio signal Tx1 is different from that of the radio signal Tx2. Therefore, in the receiver 20, the signal propagation paths of the received signal corresponding to the radio signal Tx1 and the received signal corresponding to the radio signal Tx2 are different, and therefore the signal intensity ratio between the direct wave and the reflected wave is different.

Therefore, in the receiver 20 and the estimation unit 30, as in the modified example of embodiment 1, for each receiver 20, the average 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. This makes it possible to suppress the influence of reflected waves in a simple manner and estimate the position of the transmitter 10c.

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.

(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.

As shown in Figure 9, the transmitter 10d according to the fifth embodiment includes a transmitter 11d and multiple antennas 12d and 12e. The antennas 12d and 12e are separated from each other by half the wavelength of the carrier waves of the radio signals Tx1 and Tx2.

The transmitter 11d of the transmitter 10d according to the fifth embodiment outputs a radio signal Tx1 using the antenna 12d. The transmitter 11d of the transmitter 10d according to the fifth embodiment outputs a radio signal Tx2 using the antenna 12e.

In the transmitter 10d according to embodiment 5, the antenna 12d from which the radio signal Tx1 is transmitted and the antenna 12e from which the radio signal Tx2 is transmitted are separated by half the wavelength of the carrier wave. Therefore, the propagation paths between the transmitter 10d and the receiver 20 are not the same for the radio signals Tx1 and Tx2. Therefore, at the receiver 20, the signal intensity ratios of the direct wave and the reflected wave differ between the radio signals Tx1 and Tx2.

Therefore, in the receiver 20 and the estimation unit 30, as in embodiment 1, 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 is set as the representative value Rx of the received signal. 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, the influence of the reflected wave can be suppressed in a simple manner, and the position of the transmitter 10d can be estimated.

In the receiver 20 and the estimation unit 30, as in the modified example of embodiment 1, the average 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 may be used as the representative value Rx of the received signal for each receiver 20. Also, as in the modified example of embodiment 2 or embodiment 2, the receiver 20 may output composite signals SS11 to SS14 corresponding to the wireless signal Tx1 and composite signals SS21 to SS24 corresponding to the wireless signal Tx2, and estimate the position of the transmitter 10d based on these.

(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.

As shown in Figure 10, the transmitter 10e of embodiment 6 includes multiple (two in the illustrated example) transmitting units 11f, 11g, multiple (two in the illustrated example) antennas 12f, 12g, and a control unit 14.

Transmitting unit 11f outputs radio signal Tx1 using antenna 12f. Transmitting unit 11g outputs radio signal Tx2 using antenna 12g. Control unit 14 controls transmitting units 11f and 11g so that the transmission period of radio signal Tx1 and the transmission period of radio signal Tx2 do not overlap.

The transmitter 10e according to the sixth embodiment alternates between outputting the radio signal Tx1 by the transmitter 11f and outputting 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, 1/2 of the transmission interval T1.

When transmitting wireless signals using one transmitter and one antenna (Comparative Example 1), as shown in Figure 12, the reception interval of the received signal at the receiver depends on the transmission interval T3 of the wireless signal from the transmitter. Note that in Figure 12, solid arrows indicate received signals corresponding to wireless signals, and dashed arrows indicate wireless signals that were unsuccessfully received. However, when transmitting wireless signals using one transmitter and one antenna, the transmission interval of the wireless signal from the transmitter depends on the processing power of the transmitter, so there is a limit to how often the transmission frequency of the wireless signal can be improved. Furthermore, as in Comparative Example 2 shown in Figure 13, shortening the transmission interval T4 of the wireless signal to increase the transmission frequency increases the probability of interference with wireless signals output from other transmitters, increasing the probability of reception failure.

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 embodiment 6, the 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 interval T2.

However, when the transmission interval T5 between radio signals Tx1 and Tx2 is short enough that the transmission periods of radio signals Tx1 and Tx2 overlap (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 radio signal Tx1, and the hollow arrow indicates the received signal corresponding to radio signal Tx2. That is, if the transmitter starts transmitting radio signal Tx2 before completing transmission of radio signal Tx1, the probability of reception failure at the receiver increases. In contrast, in the transmitter 10e of embodiment 6, the control unit 14 controls the transmission periods of radio signals Tx1 and 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. As a result, the transmitter 10e can transmit radio signals frequently, thereby reducing the time lag in estimating the position of the transmitter 10e by the estimation unit 30.

Note that the identification information contained in the radio signals Tx1 and Tx2 is different. For example, in transmitter 10e, transmitter 11f has a MAC address, and transmitter 11g has a MAC address that is different from the MAC address of transmitter 11f. Radio signal Tx1 includes the MAC address of transmitter 11f, and radio signal Tx2 includes the MAC address of transmitter 11g. With the above configuration, receiver 20 can easily distinguish between the received signal for radio signal Tx1 and the received signal for radio signal Tx2. Therefore, receiver 20 can generate, for example, the signal strength Rx1 of the received signal for radio signal Tx1 and the signal strength Rx2 of the received signal for radio signal Tx2 without confusing the radio signals. Furthermore, the estimation unit 30 can, for example, upon receiving the signal strength Rx2 of the received signal for the radio signal Tx2 from each of the receivers 20, 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.

In the receiver 20 and the estimation unit 30, as in the modified example of embodiment 1, the average 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 may be used as the representative value Rx of the received signal for each receiver 20. Also, as in the modified example of embodiment 2 or embodiment 2, the receiver 20 may output composite signals SS11 to SS14 corresponding to the wireless signal Tx1 and composite signals SS21 to SS24 corresponding to the wireless signal Tx2, and estimate the position of the transmitter 10d based on these.

(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.

(1) Configuration 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.

The transmitter 10f according to embodiment 7 includes multiple (two in FIG. 15) transmitters 11h and 11i, multiple (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.

Transmitting unit 11h and transmitting unit 11i can both select one of multiple frequencies as the carrier frequency of the wireless signal. More specifically, transmitting unit 11h and transmitting unit 11i transmit wireless signals using, for example, one of channels 37, 38, and 39 in BLE.

The control unit 14f controls the transmitter 11h and the transmitter 11i to transmit radio signals alternately. As in embodiment 6, the transmission period of the radio signal of the transmitter 11h does not overlap with the transmission period of the radio signal of the transmitter 11i. Furthermore, the transmitter 11i transmits a radio signal at a frequency different from the frequency used immediately before by the transmitter 11h. Similarly, the transmitter 11h transmits a radio signal at a frequency different from the frequency used immediately before by the transmitter 11i.

More specifically, transmitter 11h transmits wireless signal Tx1 from antenna 12h using channel 37. Next, transmitter 11i transmits wireless signal Tx2 from antenna 12i using channel 38. Next, transmitter 11h transmits wireless signal Tx1 from antenna 12h using channel 39. Similarly, transmitter 11i then transmits wireless signal Tx1 using channel 37. Next, transmitter 11h transmits wireless signal Tx2 using channel 38. Next, transmitter 11i transmits wireless signal Tx3 using channel 39. Thereafter, transmitter 10f repeats the same operations.

Receiver 20f includes an antenna 21 and a receiving unit 22f. The receiving unit 22f outputs the signal strength of the received signal received by antenna 21 during the 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 receiver 20f according to embodiment 7, 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 the received signal received during the first reception period. Furthermore, the receiving unit 22f outputs the signal strength Ra2 of the received signal received during the second reception period.

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.

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

Transmitter 10f outputs radio signal Tx1 from transmitter 11h using channel 37 (step S21). Next, transmitter 10f outputs radio signal Tx2 from transmitter 11i using channel 38 after a transmission interval has elapsed since step S21 was completed (step S22). Next, transmitter 10f outputs radio signal Tx3 from transmitter 11h using channel 39 after a transmission interval has elapsed since step S22 was completed (step S23). Next, transmitter 10f outputs radio signal Tx1 from transmitter 11i using channel 37 after a transmission interval has elapsed since step S23 was completed (step S24). Next, transmitter 10f outputs radio signal Tx2 from transmitter 11h using channel 38 after a transmission interval has elapsed since step S24 was completed (step S25). Next, after a transmission interval has elapsed since step S22 was completed, the transmitter 10f outputs a radio signal Tx3 from the transmitter 11i using channel 39 (step S26).

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

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

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

When step S32 is completed, receiver 20f repeats the operations of steps S31 and S32. Therefore, in the next step S31, receiver 20f outputs signal strength Ra1 of the received signal corresponding to wireless signal Tx2 related to step S25 and wireless signal Tx3 related to step S26. Furthermore, in the next step S32, receiver 20f outputs signal strength Ra2 of the received signal corresponding to wireless signal Tx1 related to step S21 and wireless signal Tx2 related to step S22.

The signal processing unit 31f of the estimation unit 30f calculates a representative value Rx of the received signal corresponding to the receiver 20f each time it receives the signal strength Ra1 of the received signal and the signal strength Ra2 of the received signal 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.

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).

(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 the position estimation of the transmitter 10.

Furthermore, in the estimation system 1f according to embodiment 7, the operating period of the transmitter 10f does not necessarily coincide with the operating period 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 radio 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.

In the receiver 20f and estimation unit 30f according to embodiment 7, as in the modified example of embodiment 1, the average value of the signal strength Ra1 of the received signal and the signal strength Ra2 of the received signal may be used as the representative value Rx of the received signal for each receiver 20f. Also, as in embodiment 2 or the modified example of embodiment 2, 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.

(summary)
An estimation system (1; 1a; 1b; 1f) according to a first aspect includes a transmitter (10; 10b-10f) and an estimation unit (30; 30a; 30f). The transmitter (10; 10b-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-10f) based on a plurality of received signals (Rx1, Rx2; SS1-SS4; Ra1-Ra2). The plurality of received signals (Rx1, Rx2; SS1-SS4; Ra1-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).

In the estimation system (1; 1a; 1b; 1f) according to the above aspect, the transmitter (10; 10b-10f) outputs multiple, mutually distinct, 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 multiple received signals (Rx; SSr1, SSr2, SSr3, SSr4) or the average value of the received power of the multiple received signals (Rx; SSr1, SSr2, SSr3, SSr4). Therefore, the accuracy of the position estimation of the transmitter (10; 10b-10f) can be improved by using the received signal with the least influence of reflected waves, or by averaging the received signals to reduce the influence of reflected waves.

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

According to the estimation system (1; 1b; 1f) relating to the above aspect, the transmitters (10b to 10f) can easily output multiple different radio signals (Tx1, Tx2, Tx3).

In the estimation system (1b) relating to the third aspect, in the second aspect, the multiple antennas (12a, 12b) output multiple signals having different polarization planes as multiple radio signals (Tx1, Tx2).

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

In the estimation system (1) relating to the fourth aspect, in the second aspect, the multiple antennas (12, 12c) output multiple radio signals (Tx1, Tx2) having different directivities from each other as multiple radio signals.

According to the estimation system (1) relating to 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 with the least influence of reflected waves or by reducing the influence of reflected waves by averaging the received signals.

In the estimation system (1) relating to the fifth aspect, in the second aspect, the spacing between the multiple antennas (12d, 12e) is half the wavelength of the radio signal (Tx1, Tx2).

In the estimation system (1) according to 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 received signal (Rx1, Rx2; SS1-SS4; Ra1-Ra2). Therefore, the accuracy of position estimation of the transmitter (10d) can be improved by using the received signal with the least influence of reflected waves, or by averaging the received signals to reduce the influence of reflected waves.

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 the multiple wireless signals. The second antenna (12g) outputs a second wireless signal (Tx2) from 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 the transmission period of the first wireless signal (Tx1) and the transmission period of the second wireless signal (Tx2) do not overlap.

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

In the estimation system (1f) according to the seventh aspect, in the second aspect, the multiple antennas include 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 multiple radio signals (Tx1, Tx2, Tx3).

In the estimation system (1f) according to the above aspect, the multiple wireless signals (Tx1, Tx2, Tx3) do not have the same frequency, and therefore the degree of influence of reflected waves varies for each received signal (Rx1, Rx2; SS1-SS4; Ra1-Ra2). Therefore, the accuracy of position estimation of the transmitter (10d) can be improved by using the received signal with the least influence of reflected waves, or by averaging the received signals to reduce the influence of reflected waves.

In the estimation system (1; 1b; 1f) relating to the eighth aspect, in any of the first to seventh aspects, multiple received signals (Rx1, Rx2) correspond one-to-one to multiple radio signals (Tx1, Tx2).

The estimation system (1; 1b; 1f) relating to the above aspect makes it possible to estimate the position of the transmitter (10; 10b to 10f) in a simple manner.

In the estimation system (1a) according to the ninth aspect, in any of the first to seventh aspects, the plurality of received signals includes a plurality of signal sets. Each of the plurality of signal sets includes a plurality of received signals (SS1, SS2, SS3, SS4). The plurality of signal sets correspond one-to-one to the plurality of radio signals (Tx1, Tx2).

The estimation system (1a) relating to the above aspect makes it possible to estimate the position of the transmitter (10) in a highly accurate manner.

The estimation method according to the tenth aspect includes a transmission step and an estimation step. In the transmission step, a transmitter (10; 10b to 10f) transmits multiple different radio signals (Tx1, Tx2, Tx3). In the estimation step, the position of the transmitter (10; 10b to 10f) is estimated using multiple received signals (Rx1, Rx2; SS1 to SS4; Ra1 to Ra2). The multiple received signals (Rx1, Rx2; SS1 to SS4; Ra1 to Ra2) are generated by a receiver (20; 20a; 20f) that receives the multiple radio signals (Tx1, Tx2). In the estimation step, the position of the transmitter is estimated 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).

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 reflected waves, or by reducing the influence of reflected waves by averaging the received signal.

The estimation program of the eleventh aspect is a program for causing one or more processors to execute the estimation method of the tenth aspect.

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 reflected waves, or by reducing the influence of reflected waves by averaging the received signal.

1, 1a, 1b, 1f Estimation system 10, 10b, 10c, 10d, 10e, 10f Transmitter 12a, 12b, 12d, 12e Antenna 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 unit Tx1 Radio signal (first radio signal)
Tx2 wireless signal (second wireless signal)
Tx3: Radio signal Rx1, Rx2: Signal strength of received signal (received signal)
Rx Representative value of received signal (maximum received power, average received power)
SS1, SS2, SS3, SS4 composite 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 (10)

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. the transmitter includes a plurality of antennas that output the plurality of radio signals;
The estimation system of claim 1 . 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 . 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 . The intervals between the plurality of antennas are equal to half the wavelength of the radio signal.
The estimation system according to claim 2 . 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 . 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 . 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. 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. A program for causing one or more processors to execute the estimation method according to claim 9.