Position estimation device and position estimation method

Abstract

To provide a position estimation device that can estimate the position of an unknown wave source.SOLUTION: A position estimation device 1 includes: an arrival direction acquisition unit 11 for acquiring the direction of arrival of an electric wave from an unknown wave source 5; a reception position acquisition unit 12 for acquiring the position of reception when an electric wave acquired from the direction of arrival is received; and an estimation unit 13 for optimizing an objective function according to the difference between the estimated direction of arrival at each reception position and the direction of arrival by using a plurality of sets of the direction of arrival and the position of reception and the estimated position of the unknown wave source 5.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a position estimation device that estimates the position of an unknown wave source using the direction of arrival of radio waves. [Background technology]

[0002] With the spread of ICT (Information and Communication Technology) devices that perform wireless communication, various radio waves are flying around in the air. Some of these devices transmit without a license or proper certification. These radio waves can interfere with other devices, causing communication failures.

[0003] In order to understand such situations and take measures, it is necessary to identify the location of the signal source emitting radio waves. The following methods are mainly known as the methods for doing so: A method of measuring the RSSI (Received Signal Strength Indication) of radio waves emitted from a signal source at multiple points and estimating the location of the signal source using triangulation methods based on the results. A method of estimating the location of a signal source by receiving signals from a signal source simultaneously at multiple locations and estimating the location of the signal source from the difference in the delivery time (TDoA: Time Difference of Arrival) A method of estimating the direction of arrival of a signal from a signal source by receiving the signal simultaneously at multiple locations and estimating the direction of arrival from the phase difference (DoA: Direction of Arrival)

[0004] When estimating the location of a signal source using TDoA or DoA, measurements must be taken at multiple locations simultaneously. 8(m / s). Therefore, to measure the propagation time difference or phase difference at multiple points simultaneously, a receiving mechanism with extremely high time resolution is required. In that case, it is difficult to achieve "simultaneity" at multiple distant points. When the points are close together, where it is easy to achieve simultaneous measurement, the propagation time difference and phase difference become small, resulting in a problem of reduced estimation accuracy.

[0005] Although the method using RSSI requires measurements at multiple points, it is not necessary to receive signals at those points simultaneously, so it is possible to estimate the location by moving a single receiver and recording the RSSI. In addition, the method using RSSI has the advantage that it only needs to measure the strength of the received signal and can be implemented with a simple circuit.

[0006] As for position estimation using radio waves, for example, the method described in Patent Document 1 is also known. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6030976 Summary of the Invention [Problem to be solved by the invention]

[0008] In the invention of Patent Document 1, multiple base stations measure the RSSI from the terminal to estimate the location. However, since the base station's location is assumed to be unknown, a process is performed in which the base station's location is also estimated from the mutual received power between base stations in order to determine the location. If the base station's location shifts during this process, the terminal's location cannot be accurately determined. This method also requires multiple base stations.

[0009] Although the method of estimating the location of the signal source using RSSI has the above advantages, there is a problem that if an approximation is made for the propagation loss of the radio wave from the location of the wave source to the location of the receiver, an estimation error occurs according to the approximation.Furthermore, if the output of the signal source changes during the measurement, an estimation error occurs according to the change.

[0010] The present invention has been made to solve the above problems, and its object is to provide a location estimation device and a location estimation method that can estimate the location of an unknown wave source with higher accuracy without using TDoA or DoA. [Means for solving the problem]

[0011] In order to achieve the above object, a position estimation device according to one embodiment of the present invention includes an arrival direction acquisition unit that acquires the arrival direction of radio waves from an unknown wave source, a reception position acquisition unit that acquires the reception position when the radio waves whose arrival direction is acquired are received, and an estimation unit that estimates an estimated position by optimizing an objective function according to the difference between the estimated arrival direction and the arrival direction for each reception position using multiple pairs of arrival directions and reception positions and the estimated position of the unknown wave source. With this configuration, it becomes possible to estimate the position of an unknown wave source using the direction of arrival of radio waves without using TDoA or DoA. In this way, since TDoA or the like is not used, it is possible to estimate the position of the wave source with a simple configuration. In addition, since there is no need to approximate the propagation loss of the radio waves, it is possible to estimate the position with higher accuracy. In addition, even if the output of the signal source changes during the measurement, it is possible to perform more appropriate position estimation. Furthermore, since estimation is performed by optimizing the objective function, it becomes possible to estimate the position of the wave source while reducing the effect of multipath by using a sufficient number of pairs of the direction of arrival and the receiving position.

[0012] In addition, in a position estimation device according to one aspect of the present invention, there may be one or more unknown wave sources, and the estimation unit may also estimate the number of estimated wave sources so that an optimal value per wave source, which is the value of the optimized objective function, is divided by the number of estimated wave sources, is optimized. With this configuration, it is also possible to estimate the number of wave sources.

[0013] In addition, in a position estimation device according to one aspect of the present invention, the estimation unit may optimize an objective function in which a weight is applied to the difference between the estimated arrival direction and the arrival direction according to spatial information regarding the space between the estimated position and the receiving position used in calculating the estimated arrival direction. With this configuration, it is possible to achieve more accurate estimation.

[0014] In addition, in a position estimation device according to one aspect of the present invention, the arrival direction acquisition unit may also acquire the received power of the radio waves from which the arrival direction is acquired, and the estimation unit may optimize an objective function in which a weight is applied to the difference between the estimated arrival direction and the arrival direction according to the received power of the radio waves from which the arrival direction is acquired. With this configuration, it is possible to achieve more accurate estimation.

[0015] In addition, in a position estimation device according to one aspect of the present invention, the arrival direction acquisition unit may also acquire the received power of the radio waves from which the arrival direction is acquired, and the estimation unit may estimate the estimated position and estimated transmission power by optimizing an objective function according to the difference between the estimated arrival direction and the arrival direction for each receiving position and the difference between the estimated received power and the received power for each receiving position, using a pair of the arrival direction, the receiving position, and the received power, the estimated position of the unknown wave source, the estimated transmission power of the radio waves from the unknown wave source, and the propagation loss of the radio waves. With this configuration, the position of the wave source is estimated using the received power in addition to the direction of arrival, so that it is possible to realize more accurate estimation. Also, the transmission power of the wave source can be estimated.

[0016] In the position estimation device according to an aspect of the present invention, the estimation unit may optimize the objective function by sequential calculation processing. With this configuration, it becomes possible to optimize the objective function by sequential calculations such as the Newton method.

[0017] In the position estimation device according to an aspect of the present invention, the estimation unit may optimize the objective function by sequential calculation processing using a plurality of initial values. With this configuration, it is possible to prevent the optimum solution from corresponding to a local optimum value, and it is possible to realize more accurate estimation.

[0018] In addition, in a position estimation device according to one aspect of the present invention, the estimation unit may change the step size to a larger value when the objective function converges to a local optimum value in the sequential calculation process, and may change the step size to a smaller value when the objective function converges to a global optimum value. With this configuration, it is possible to prevent the optimum solution from corresponding to a local optimum value, and it is possible to realize more accurate estimation.

[0019] In addition, a position estimation method according to one aspect of the present invention includes a step of acquiring an arrival direction of radio waves from an unknown wave source, a step of acquiring a receiving position when the radio waves whose arrival direction is acquired are received, and a step of estimating an estimated position by optimizing an objective function according to a difference between the estimated arrival direction and the arrival direction for each receiving position using multiple pairs of the arrival direction and the receiving position and the estimated position of the unknown wave source. Effect of the Invention

[0020] According to a position estimation device and the like according to an aspect of the present invention, it becomes possible to estimate the position of an unknown wave source by using the direction of arrival, which is information related to radio waves, without using TDoA or DoA. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a block diagram showing a configuration of a position estimation device according to an embodiment of the present invention; [Diagram 2] A flowchart showing the operation of the position estimation device according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, a location estimation device and a location estimation method according to the present invention will be described using embodiments. The location estimation device and the location estimation method according to the present embodiment estimate the location of an unknown wave source by optimization using the direction of arrival of radio waves.

[0023] FIG. 1 is a block diagram showing the configuration of a position estimation device 1 according to this embodiment. The position estimation device 1 according to this embodiment includes an arrival direction acquisition unit 11, a reception position acquisition unit 12, and an estimation unit 13. As described later, the position estimation device 1 may or may not receive radio waves. In the former case, it is preferable that the position estimation device 1 is a device whose position can be changed (for example, a portable device or a device that can be mounted on a moving body such as an automobile). On the other hand, when radio waves are not received, the position estimation device 1 may be, for example, a server device that receives the arrival direction of radio waves from one or more client devices. In this embodiment, a case in which the position estimation device 1 receives radio waves and is a device whose position can be changed will be mainly described.

[0024] The arrival direction acquisition unit 11 acquires the arrival direction of radio waves from an unknown wave source 5. The number of unknown wave sources 5 may be one or more. In this embodiment, first, a case where the number of unknown wave sources 5 is one will be mainly described, and a case where the number of unknown wave sources 5 may be other than one will be described later. The arrival direction acquisition unit 11 may receive radio waves from the unknown wave source 5 and acquire the arrival direction of the radio waves, or may receive the arrival direction of the radio waves received by another device from another device. In this embodiment, as described above, the former case will be mainly described. That is, in this embodiment, it is assumed that the arrival direction acquisition unit 11 receives radio waves by the antenna 11a and acquires the arrival direction of the radio waves.

[0025] The antenna 11a is preferably a directional antenna. The directional antenna may be one that has directivity due to the structure of the antenna, such as a Yagi antenna or a parabolic antenna, or may be an antenna that has directivity by multiplying the received signals of multiple antennas by weights based on the amplitude and phase, such as an array antenna. In order to properly estimate the arrival direction of the radio wave, it is preferable that the directivity of the antenna 11a is sharp.

[0026] The arrival direction acquisition unit 11 may rotate the antenna 11a having directivity such as a Yagi antenna, and may determine the direction of the main lobe of the antenna 11a at the time when the received signal strength (RSSI) of the radio wave from the unknown wave source 5 becomes maximum as the arrival direction of the radio wave. In this case, the arrival direction acquisition unit 11 may have a rotation mechanism for rotating the antenna 11a. The arrival direction acquisition unit 11 may acquire the arrival direction of the radio wave for the antenna 11a by using the phase of the radio wave received by each antenna of the antenna 11a, which is an array antenna, for example. Note that the arrival direction of the radio wave acquired by the arrival direction acquisition unit 11 may be the arrival direction of the radio wave based on a reference direction. The reference direction may be a predetermined direction in a world coordinate system, such as a north direction or an east direction. The arrival direction acquisition unit 11 may have, for example, a geomagnetic sensor for identifying the reference direction. Then, when the arrival direction of the radio waves relative to the antenna 11a has been acquired, the arrival direction acquisition unit 11 may acquire the absolute arrival direction of the radio waves relative to the reference direction by using the relationship between the reference direction and the direction of the antenna 11a.

[0027] The receiving position acquisition unit 12 acquires the receiving position when the radio wave whose arrival direction is to be acquired is received. That is, the position of the antenna or the like when the radio wave from the unknown wave source 5 is received by the antenna or the like is acquired. The receiving position acquisition unit 12 may acquire the receiving position which is the position of the position estimation device 1 at the time when the arrival direction acquisition unit 11 receives the radio wave to acquire the arrival direction, or may receive from another device the receiving position which is the position of the other device at the time when the other device receives the radio wave. In this embodiment, the former case will be mainly described.

[0028] The method by which the reception position acquisition unit 12 acquires the position does not matter. The reception position acquisition unit 12 may acquire the position using, for example, a global positioning system (GPS), or may also acquire the position using a quasi-zenith satellite system. When the position estimation device 1 is mounted on a vehicle or the like, the reception position may be acquired using an autonomous navigation device such as a gyro. When an image of a code or the like (e.g., a QR code (registered trademark) or the like) corresponding to position information indicating the position is placed at a position indicated by the position information, the reception position may be acquired by, for example, photographing an image of the code or the like and reading out the position information, or the reception position may be acquired by other methods. The reception position acquisition unit 12 may accept, for example, a reception position measured manually using a tape measure or the like via an input means such as a keyboard or a touch panel. In this embodiment, a case will be mainly described in which the reception position acquisition unit 12 receives radio waves from a GPS satellite via an antenna 12a and acquires the position using the received radio waves. The position acquired by the reception position acquisition unit 12 may be, for example, coordinates indicating latitude and longitude, or other coordinates.

[0029] It is preferable that the arrival direction acquired by the arrival direction acquisition unit 11 and the reception position acquired by the reception position acquisition unit 12 for the radio wave acquired in the arrival direction are linked and managed. In this embodiment, the linked arrival direction and reception position are referred to as a pair of arrival direction and reception position. The arrival direction is acquired by the arrival direction acquisition unit 11, and the reception position according to the acquisition of the arrival direction is acquired by the reception position acquisition unit 12, so that a plurality of pairs of arrival direction and reception position are acquired. For example, when the position estimation device 1 is movable, a plurality of pairs of arrival direction and reception position may be acquired by receiving radio waves from an unknown wave source 5 at a plurality of positions.

[0030] The estimation unit 13 estimates the estimated position by optimizing an objective function according to the difference between the estimated arrival direction and the arrival direction for each reception position, using multiple pairs of the arrival direction and the reception position, and the estimated position of the unknown wave source 5. That is, using multiple pairs of the arrival direction and the reception position, which are the measurement results, an optimal solution (i.e., the position of the unknown wave source 5) that optimizes the objective function (error function) according to the error between the estimated value of the arrival direction for each reception position and the actual measured value of the arrival direction is obtained so that the error is optimized (i.e., the error is reduced). Note that the estimation unit 13 can estimate the direction of the unknown wave source 5 based on the reception position, i.e., the estimated arrival direction, using the reception position and the estimated position.

[0031] The objective function may be a function whose value increases as the error between the estimated value of the arrival direction for each receiving position and the actual measured value of the arrival direction increases, or may be a function whose value decreases as the error increases. In the former case, optimization is to minimize the objective function, and in the latter case, optimization is to maximize the objective function. In this embodiment, the former case will be mainly described. In addition, various functions can be used as the function whose value decreases as the error between the estimated value of the arrival direction for each receiving position and the actual measured value of the arrival direction increases.

[0032] Hereinafter, a process of obtaining an estimated position of the unknown wave source 5 by optimizing the objective function will be specifically described. First, the estimated position of the unknown wave source 5 is expressed as (x e ,y e ) and the reception position and arrival direction acquired at the i-th position are respectively (x i ,y i ), θ i Therefore, the i-th pair of the arrival direction and the reception position acquired by the arrival direction acquisition unit 11 and the reception position acquisition unit 12 is expressed as, for example, (x i ,y i ,θ i ), where i=1, 2, ..., N. It is preferable that N is an integer that exceeds the unknown number of the estimation target. For example, when there is one wave source 5, the unknown number is 2, so it is preferable that N is 3 or more. If N is the same as the unknown number, it is possible to obtain an estimated position, but the estimation will be performed with substantially the same accuracy as triangulation, making it difficult to reduce the influence of multipath. In addition, the larger N is, the better the influence of multipath can be reduced, so when there is one wave source 5, it is more preferable that N is a value sufficiently larger than 3, such as 10 or more, 20 or more.

[0033] For the wave from unknown source 5, the estimated position (x e ,y e ), receiving position (x i ,y i ) is used to calculate the receiving position (x i ,y i ) Estimated direction of arrival θ i e In this case, the estimated arrival direction θ i e is the angle with the x-axis direction as the reference direction.

number

[0034] As described above, when the arrival direction and reception position are acquired at N locations, the objective function (evaluation function) f according to the difference between the estimated arrival direction and the arrival direction for each reception position is, for example, as follows:

number

[0035] Although the objective function is shown here as the sum of squares of the difference between the estimated direction of arrival and the direction of arrival, it goes without saying that the objective function may be, for example, the sum of the absolute value of the difference between the estimated direction of arrival and the direction of arrival for each receiving position, or the sum of the fourth or sixth power of the difference between the estimated direction of arrival and the direction of arrival for each receiving position. In addition, in the sum (total sum), the difference between the estimated direction of arrival and the direction of arrival may be weighted, as in the formula of the objective function f above.

[0036] Weighting the difference between the estimated arrival direction and the arrival direction may be a value corresponding to the difference between the estimated arrival direction and the arrival direction, such as the square of the difference, the absolute value of the difference, the fourth power of the difference, or the sixth power of the difference. i is a weight for the measurement result at the i-th receiving position, and is usually a positive real number. For example, the estimated arrival direction θ i e and the arrival direction θ i The difference between the estimated arrival direction θ i e The estimated position (x e ,y e ) and receiving position (x i ,y i ) weighting w according to spatial information about the space between i Specifically, a weight w corresponding to the spatial information indicating the line of sight may be added. i is set to a large value, e.g., "1", and the weight w imay be set to a value smaller than the weight corresponding to the spatial information of visibility, for example, "0.3" or "0.5". The weight may also be changed according to the degree of obstruction. In this case, the more obstructions indicated by the spatial information, the smaller the weight may be used. For example, the weight corresponding to the spatial information indicating the presence of a small number of high-rise buildings may be set to a larger value such as "0.5", and the weight corresponding to the spatial information indicating the presence of a large number of high-rise buildings may be set to a smaller value such as "0.2". In this way, the weight w i For example, when the spatial information indicates that there is a lot of multipath, the weight w may be set to a smaller value, and when the spatial information indicates that there is a little multipath, the weight w may be set to a larger value. The estimation unit 13 may acquire the spatial information by using map information, for example. A method of acquiring the spatial information will be described later. In addition, the weight w i may be changed according to, for example, the magnitude or accuracy of the received signal. In that case, for example, the closer to ideal reception, the larger the weighting may be used. Furthermore, the estimation unit 13 may optimize an objective function in which the difference between the estimated arrival direction and the arrival direction is weighted according to the received power of the radio wave acquired in that arrival direction. In this case, the larger the received power, the larger the weighting may be used. This is because it is considered that the higher the received power, the more appropriately the radio wave is received, and therefore it is preferable to use a larger weighting for the arrival direction. Note that the weighting w i may be a constant. In this way, the objective function may not use weights for each receiving position. In this case, the above w i may be, for example, 1 or 1 / N.

[0037] x that minimizes the objective function f above e ,y e is the position of the wave source 5 to be estimated. The solution that minimizes the objective function f, i.e., the optimal solution, corresponds to a local minimum, so the partial differential of each variable of the objective function f becomes 0. Therefore, the estimated position can be calculated by the following equation (x e ,y e ) is required.

number

[0038] Such (x e ,y e As a method for calculating (x), i.e., a method for optimizing the objective function, various algorithms can be considered, and examples thereof include the Newton method and the steepest descent method, but are not limited thereto. For example, optimization may be performed using a parameter estimation method such as a Kalman filter. For example, when performing sequential calculations using the steepest descent method, the initial value (x 0 e ,y 0 e ) and set an appropriate step size α k By setting and repeating the iterative calculation of the following equation, the objective function f can be optimized. Note that k = 0, 1, 2, .... In addition, the iterative calculation requires ∇f(x e ,y e ) may be calculated in advance and the calculation result may be used in the sequential calculation. k The number of calculations may be reduced by initially setting a large value and then setting a small value according to the convergence state. Note that a constant may be used as the step size.

number

[0039] Here, ∇f(x e k ,y e k ) is calculated from the above equations as follows:

number

[0040] In this way, the estimation unit 13 may optimize the objective function f by sequential calculation processing. In this case, the optimization processing may be terminated when a predetermined termination condition is satisfied. The termination condition may be, for example, that a convergence condition is satisfied, that k has exceeded a predetermined maximum number of sequential calculations, or another condition. The estimation unit 13 may, for example, estimate the absolute value |f(x k+1 e ,y k+1 e )-f(x k e ,y k e The estimation unit 13 may determine that the convergence condition is satisfied when the objective function f| becomes smaller than a predetermined threshold value. The threshold value is a positive real number and is usually set to a small value. The estimation unit 13 may also determine that the convergence condition is satisfied when the value of the objective function f becomes smaller than a predetermined value. The predetermined value is a positive real number and is usually set to a small value.

[0041] In addition, in order to prevent the optimization of the objective function f from becoming a local optimum, the estimation unit 13 may optimize the objective function f by, for example, sequential calculation processing using a plurality of initial values. For example, the estimation unit 13 may obtain an optimal solution for each initial value and an optimal value obtained by substituting the optimal solution into the objective function by setting a plurality of initial values ​​and performing optimization using each initial value. Thereafter, the estimation unit 13 may set the optimal solution corresponding to the most appropriate optimal value among the plurality of optimal values ​​as the final estimated position. The optimal solution is a solution (here, the estimated position) obtained by optimizing the objective function. In addition, the most appropriate optimal value means that the optimal value is the smallest when the optimization is minimization, and that the optimal value is the largest when the optimization is maximization. In addition, the initial value is, strictly speaking, the initial value of the estimated position. The initial value of the estimated position may be randomly specified, for example, in an area including N receiving positions (for example, it may be the smallest area including N receiving positions).

[0042] In addition, in order to prevent the optimization of the objective function f from becoming a local optimum, for example, in the sequential calculation process, when the objective function f converges to a local optimum value, the estimation unit 13 increases the step size α k If the objective function f converges to the global optimum, the step size α k may be changed to a smaller value. Whether the objective function f is converging to a local optimum value or a global optimum value may be determined, for example, by whether the value of the objective function f is close to an ideal optimum value. When the value of the objective function f is close to the ideal optimum value, it may be determined that the objective function f is converging to a global optimum value, and when the value of the objective function f is far from the ideal optimum value, it may be determined that the objective function f is converging to a local optimum value. More specifically, when the optimization is minimization, for example, it may be determined that the objective function f is converging to a value larger than a first threshold value, and it may be determined that the objective function f is converging to a global optimum value when the objective function f is converging to a value smaller than the first threshold value. When the optimization is maximization, for example, it may be determined that the objective function f is converging to a local optimum value when the value of the objective function f is converging to a value smaller than a second threshold value, and it may be determined that the objective function f is converging to a global optimum value when the objective function f is converging to a value larger than the second threshold value. The first and second threshold values ​​may be the same value or may be different values. Both threshold values ​​are usually positive real numbers. The step size α used when the objective function f has converged to a local optimum. k , and the step size α used when the objective function f has converged to the global optimum. k may or may not be predetermined. In the latter case, for example, when the objective function f is converging to a local optimum, a step size α that gradually increases with each update of k may be used. k is used, and when the objective function f has converged to the global optimum, a step size α k Even in this case, upper and lower limits of the step size may be set.

[0043] The estimated position of the wave source 5 acquired by the estimation unit 13 may be output by, for example, an output unit (not shown). The output may be, for example, displayed on a display device (for example, a liquid crystal display or an organic EL display), transmitted to a predetermined device via a communication line, printed by a printer, or stored in a recording medium.

[0044] Next, the operation of the position estimation device 1 will be described with reference to the flowchart in Fig. 2. Here, a case will be described in which the objective function f is optimized by sequential calculation.

[0045] (Step S101) The arrival direction acquisition unit 11 and the reception position acquisition unit 12 acquire a plurality of pairs of the arrival direction and reception position of a radio wave from an unknown wave source 5. The plurality of pairs may be stored, for example, in a recording medium (not shown).

[0046] (Step S102) The estimation unit 13 sets an initial value of the estimated position. The setting of this initial value may be, for example, reading out a predetermined value.

[0047] (Step S103) The estimation unit 13 sets a counter k to 1. The value of the counter k indicates the number of sequential calculations.

[0048] (Step S104) The estimation unit 13 calculates a provisional estimated position. The calculation of this provisional estimated value may be performed, for example, by updating the estimated position so as to approach an optimal solution, as in the above formula.

[0049] (Step S105) The estimation unit 13 calculates the value of the objective function f according to the estimated position acquired in step S104.

[0050] (Step S106) The estimation unit 13 judges whether or not the convergence condition is satisfied. If the convergence condition is satisfied, the series of processes for estimating the estimated position ends, and if not, the process proceeds to step S107.

[0051] (Step S107) The estimation unit 13 increments the counter k by one.

[0052] (Step S108) The estimation unit 13 judges whether the counter k has exceeded the maximum number of sequential calculations. If k has exceeded the maximum number of sequential calculations, the series of processes for estimating the estimated position ends. If not, the process returns to step S104.

[0053] When the series of processes for estimating the estimated position is completed, the estimated position finally calculated in step S104 becomes the final estimation result.

[0054] In the flowchart of FIG. 2, sequential calculations using multiple initial values ​​may be performed. In that case, the processes of steps S102 to S108 are repeated for each initial value, and after each process is completed, an optimal solution corresponding to the optimal value may be set as the estimated position of the wave source 5. In addition, the flowchart of FIG. 2 shows a case in which the arrival direction and reception position are first acquired, and then the position of the wave source 5 is estimated by optimizing the objective function, but this is not necessary. For example, when the arrival direction and reception position acquisition at a predetermined number of points is completed, the estimated position may be estimated, and the estimation process may be repeated each time the number of arrival directions and reception positions acquired increases. Then, when an estimated position with sufficient accuracy is acquired, the acquisition of the arrival direction, etc. and the process of estimating the estimated position may be terminated. In addition, the order of the processes in the flowchart of FIG. 2 is an example, and the order of each step may be changed as long as the same result can be obtained.

[0055] As described above, according to the position estimation device 1 of this embodiment, the position of the unknown wave source 5 can be estimated without using TDoA or DoA. Moreover, since there is no need to perform approximation of the propagation loss of the radio wave, more accurate position estimation is possible compared to the case where the approximation is inappropriate. Moreover, even if the output of the signal source changes during the measurement, the position of the wave source 5 can be more appropriately estimated. In this way, since TDoA or the like is not used, the position of the wave source 5 can be estimated with a simple configuration. Furthermore, since the estimation is performed by optimizing the objective function, by using a sufficient number of pairs of the arrival direction and the reception position, it is possible to perform position estimation with reduced influence of errors due to multipath or the like. Moreover, when the position estimation device 1 is moved to multiple positions, receives radio waves from the unknown wave source 5, and obtains multiple pairs of the arrival direction and the reception position, it becomes possible to estimate the position of the wave source 5 without using multiple receiving devices. Moreover, even if there is an unreliable value, the weight w i By adjusting the , it is possible to reduce the influence of the ,estimation accuracy can be improved.

[0056] Next, a modification of the position estimation device 1 according to the present embodiment will be described. [Estimation of the locations of multiple wave sources and estimation of the number of wave sources] In the above embodiment, the case where the number of wave sources 5 is one has been mainly described, but this is not essential. The number of wave sources 5 may be multiple or may be indefinite. When the number of wave sources 5 is indefinite, the number of wave sources 5 may also be estimated.

[0057] When the number of unknown wave sources 5 is two, the estimated position of the wave source 5 is expressed as (x (1)e ,y (1)e ), (x (2)e ,y (2)e ) can be used. The objective function is expressed as follows. In this case, the i-th pair of the arrival direction and the reception position acquired by the arrival direction acquisition unit 11 and the reception position acquisition unit 12 can be expressed as, for example, (x i ,y i ,θ (1)i ,θ (2) i ) Two directions of arrival θ (1) i ,θ (2) i For example, the estimated arrival direction θ of the first wave source 5 may be the direction with the strongest and second strongest received signal strength for the radio wave from the unknown wave source 5. (1)e i is the estimated position of the first wave source 5 (x (1)e ,y (1)e ) is used for the calculation. The same applies to the estimated arrival direction of the second wave source 5. Note that when the two wave sources 5 can be distinguished (for example, when the two wave sources 5 can be distinguished by the characteristics of the radio waves such as frequency), the objective function may be the sum of two objective functions for one wave source 5. In this case, the weights may be different for each wave source 5. Also, when the two wave sources 5 can be distinguished, the position may be estimated for each wave source 5.

number

[0058] Even when the number of unknown wave sources 5 is two, it is possible to perform sequential calculations using the steepest descent method as shown in the following equation, for example.

number

[0059] In addition, when the number of wave sources 5 is two, ∇f(x (1)e k ,y (1)e k ,x (2)e k ,y (2)e k ) is expressed as follows:

number

[0060] In this way, even when there are two wave sources 5, the position of each of the wave sources 5 can be estimated by optimizing the objective function in the same manner as for one wave source 5. Also, even when the number of unknown wave sources 5 is three or more, the position of each of the wave sources 5 can be estimated by similarly extending the equation.

[0061] Next, when the number of wave sources 5 is indefinite, the estimation unit 13 may estimate the position of each wave source 5 by optimization for each estimated number of wave sources from the minimum number of wave sources to the maximum number of wave sources. Then, the estimation unit 13 may also estimate the estimated number of wave sources so that an optimal value per wave source, which is obtained by dividing an optimal value, which is the value of the optimized objective function, by the estimated number of wave sources, is optimized. In other words, the number of wave sources may be estimated so that the objective function for estimating the number of wave sources is set as the optimal value per wave source and the objective function is optimized. Note that, for example, when there is one or more unknown wave sources 5, the minimum number of wave sources is 1. The minimum number of wave sources may be 2 or more.

[0062] In addition, estimating the estimated number of wave sources so that the optimal value per wave source is optimized may mean, for example, finding the estimated number of wave sources that results in the smallest optimal value per wave source when the optimization of the objective function f is minimization, or may mean finding the estimated number of wave sources that results in the largest optimal value per wave source when the optimization of the objective function f is maximization.

[0063] In this way, even if the number of wave sources 5 is unknown, it is possible to estimate the number of wave sources 5. Although the case where the processing is performed until the number of wave sources 5 becomes the maximum number of wave sources has been described here, this is not essential. A convergence condition may be set for the optimization of the optimal value per wave source, and the processing may be terminated when the convergence condition is satisfied. For example, it may be determined that the convergence condition is satisfied when the optimal value per wave source becomes more appropriate than a predetermined threshold value (for example, if the optimization is minimization, this may be when the optimal value becomes smaller than the threshold value, and if the optimization is maximization, this may be when the optimal value becomes larger than the threshold value).

[0064] [Optimization of objective function using received power] The estimation unit 13 may estimate the estimated position and the estimated transmission power by optimizing an objective function according to the difference between the estimated arrival direction and the arrival direction for each receiving position and the difference between the estimated reception power and the reception power for each receiving position, using a pair of the arrival direction, the reception position, and the reception power, the estimated position of the unknown wave source 5, the estimated transmission power of the radio waves from the unknown wave source 5, and the propagation loss of the radio waves.

[0065] The received power may be, for example, received signal strength indicator (RSSI). In this case, the arrival direction acquisition unit 11 may also acquire the received power of the radio wave from which the arrival direction is acquired. The arrival direction acquisition unit 11 may acquire the received signal strength of the radio wave by, for example, a spectrum analyzer, or may acquire the received signal strength of the radio wave by other configurations.

[0066] As the propagation loss of radio waves, for example, a propagation loss according to a model according to the propagation path from the estimated position to the receiving position (for example, a free space model, a model considering the effect of multipath, etc.) may be used. For simplicity of explanation, the case where the propagation loss of the free space model is used will be mainly explained here. The propagation loss may be considered as a function with transmission power and distance as arguments.

[0067] The estimation unit 13 may optimize the objective function using a propagation loss according to spatial information regarding the space between the estimated position and the receiving position. The spatial information may indicate the type of propagation path from the estimated position to the receiving position. Therefore, the spatial information may be, for example, line of sight, urban area, mountain area, etc. The estimation unit 13 may, for example, use map information to identify the receiving position and the estimated position at that time, and if there is an urban area or a mountain between the two positions, determine that the spatial information between the two positions is an urban area or a mountain area, and if there is no obstacle such as an urban area or a mountain between the two positions, determine that the spatial information between the two positions is line of sight. If the spatial information is line of sight, for example, a propagation loss corresponding to a free space model may be used, and if the spatial information indicates that there is an obstacle such as an urban area or a mountain area, for example, a propagation loss corresponding to a model considering the effect of multipath may be used. Note that the spatial information may be obtained by the estimation unit 13 accessing map information held in the position estimation device 1, or by accessing a server or the like holding the map information.

[0068] First, the estimated position of the unknown source 5 is (x e ,y e ) and the estimated transmission power of the wave from the unknown wave source 5 is p e The received power obtained at the i-th position is denoted by r i Therefore, the i-th set of the arrival direction, reception power, and reception position acquired by the arrival direction acquisition unit 11 and the reception position acquisition unit 12 is expressed as, for example, (x i ,y i ,θ i ,r i )

[0069] For the radio waves from unknown source 5, the estimated transmission power p e , propagation loss, estimated position (x e ,y e ), receiving position (x i ,y i ) is used to calculate the receiving position (x i ,y i ) Estimated received power r ie is expressed as follows. Note that G r is the gain of the antenna 11a, which is a known value.

number

[0070] In the above formula, d i is the estimated position of the unknown source 5 (x e ,y e ) to the receiving position (x i ,y i ) and is given by:

number

[0071] Also, λ is the wavelength of the received wave, and may be acquired by the arrival direction acquisition unit 11, for example, when the arrival direction acquisition unit 11 acquires the received power by a spectrum analyzer. Also, the received wave may be Fourier transformed to acquire the wavelength λ of the peak in the frequency band. Note that the wave source 5 is unintentional and therefore omnidirectional. Therefore, the value equivalent to the antenna gain is calculated as the effective radiated power, which is the estimated transmission power p e will be included in.

[0072] In addition, the above formula shows the estimated received power using the formula for the propagation loss of radio waves in free space, but as mentioned above, other formulas for propagation loss may be used depending on the spatial information from the position of the wave source 5 to the receiving position. For example, if the spatial information from the estimated position of the wave source 5 to the receiving position indicates the presence of obstacles such as mountainous areas or urban areas, the estimated received power r can be calculated as follows using the propagation loss that takes into account the effects of multipath. i e Also, d in the following formula may be calculated. i 2 Instead of d i 3 / 2 d etc. i mmay be used, where m is a real number between 1 and 2.

number

[0073] As described above, when the arrival direction, reception power, and reception position are acquired at N points, the objective function (evaluation function) f according to the difference between the estimated arrival direction and the arrival direction for each reception position and the difference between the estimated reception power and the reception power for each reception position is, for example, as follows. Note that β is an arbitrary real number from 0 to 1, and is a weight related to the function according to the difference between the estimated arrival direction and the arrival direction for each reception position and the function according to the difference between the estimated reception power and the reception power for each reception position. For example, if the function according to the difference between the estimated arrival direction and the arrival direction for each reception position is more accurate, a value close to 1 may be used as β. If the accuracy of both functions is about the same, 0.5 may be used as β. In addition, the weight w used in both functions here is i It goes without saying that it is possible to use different weights in both functions.

number

[0074] In this case, we also minimize the objective function f. e ,y e ,p e are the position and transmission power of the wave source 5 to be estimated. The solution that minimizes the objective function f, i.e., the optimal solution, corresponds to a local minimum, so the partial differential of each variable of the objective function f becomes 0. Therefore, the estimated position and estimated transmission power can be obtained by the following equation (x e ,y e ,p e ) is required.

number

[0075] The method of estimating the estimated position and the estimated transmission power for optimizing the objective function is the same as that described above, and a detailed description thereof will be omitted.

[0076] [3D position estimation] In the above description, the case of estimating the position of the unknown wave source 5 on a two-dimensional plane has been described, but the position of the unknown wave source 5 can also be estimated in a three-dimensional space in a similar manner. When estimating the position of the wave source 5 in a three-dimensional space, the arrival direction of the radio wave is determined by the azimuth angle θ i and the elevation angle φ i The objective function according to the difference between the estimated direction of arrival and the direction of arrival for each reception position may be, for example, an objective function according to the difference between the estimated azimuth angle and the measured azimuth angle and the difference between the estimated elevation angle and the measured elevation angle for each reception position. It is also clear that the two-dimensional position described above can be easily extended to a three-dimensional position when the objective function includes a function according to the difference between the estimated reception power and the reception power for each reception position.

[0077] In addition, in the above embodiments, each process or function may be realized by centralized processing in a single device or a single system, or may be realized by distributed processing in multiple devices or multiple systems.

[0078] In addition, in the above embodiments, the transfer of information between each component may be performed, for example, by one component outputting information and the other component receiving information if the two components transferring the information are physically different, or, if the two components transferring the information are physically the same, by shifting from a processing phase corresponding to one component to a processing phase corresponding to the other component.

[0079] In the above embodiment, information related to the processing performed by each component, such as information accepted, acquired, selected, generated, transmitted, or received by each component, and information such as thresholds, formulas, and addresses used by each component in processing, may be temporarily or long-term stored in a recording medium (not shown) even if not specified in the above description. Furthermore, each component or a storage unit (not shown) may store information in the recording medium (not shown). Furthermore, each component or a reading unit (not shown) may read information from the recording medium (not shown).

[0080] In the above embodiment, if the information used by each component, such as the thresholds, addresses, and various setting values ​​used by each component in processing, may be changed by the user, the user may be able to change the information as appropriate, even if not specified in the above description. If the information is changeable by the user, the change may be realized, for example, by a reception unit (not shown) that receives a change instruction from the user, and a change unit (not shown) that changes the information in response to the change instruction. The reception unit (not shown) may receive the change instruction from an input device, may receive information transmitted via a communication line, or may receive information read from a predetermined recording medium.

[0081] In addition, in the above embodiment, when two or more components included in the position estimation device 1 have a communication device, an input device, etc., the two or more components may have a physically single device, or may have separate devices.

[0082] In each of the above embodiments, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program. For example, each component may be realized by a program execution unit such as a CPU reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory. During execution, the program execution unit may execute the program while accessing a storage unit or a recording medium. The program may be executed by being downloaded from a server or the like, or may be executed by reading a program recorded on a predetermined recording medium (for example, an optical disk, a magnetic disk, a semiconductor memory, etc.). The program may be used as a program constituting a program product. The computer that executes the program may be a single computer or a plurality of computers. That is, centralized processing may be performed, or distributed processing may be performed. [Industrial Applicability]

[0083] As described above, according to the position estimation device etc. of one aspect of the present invention, it is possible to obtain the effect of being able to estimate the position of an unknown wave source, and it is useful, for example, as a device for identifying the source of illegal radio waves. [Explanation of symbols]

[0084] 1 Position estimation device 5. Source 11 Arrival direction acquisition unit 12 Reception position acquisition unit 13 Estimation part

Claims

1. an arrival direction acquisition unit that acquires arrival directions of radio waves from a plurality of unknown wave sources; a reception position acquisition unit that acquires a reception position when the radio wave whose arrival direction is acquired is received; and an estimation unit that estimates a plurality of estimated positions by optimizing an objective function having as an argument a sum of differences between the estimated directions of arrival and directions of arrival for the plurality of wave sources for each receiving position, using a plurality of pairs of directions of arrival and receiving positions and the estimated positions of the unknown wave sources.

2. The position estimation device according to claim 1 , wherein the estimation unit optimizes an objective function in which the sum is weighted according to spatial information relating to a space between the estimated position used in calculating the estimated direction of arrival and the receiving position.

3. The arrival direction acquisition unit also acquires a received power of a radio wave for acquiring the arrival direction, 3. The position estimation device according to claim 1, wherein the estimation unit optimizes an objective function in which the sum is weighted according to a received power of the radio wave acquired in the arrival direction.

4. The arrival direction acquisition unit also acquires a received power of a radio wave for acquiring the arrival direction, 3. The position estimation device according to claim 1, wherein the estimation unit estimates the estimated position and the estimated transmission power by optimizing an objective function according to the sum for each reception position and the difference between the estimated reception power and the received power for each reception position, using a set of the direction of arrival, the reception position, and the received power, the estimated position of the unknown wave source, the estimated transmission power of the radio waves from the unknown wave source, and a propagation loss of the radio waves.

5. The position estimation device according to claim 1 , wherein the estimation unit optimizes the objective function by sequential calculation processing.

6. The position estimation device according to claim 5 , wherein the estimation unit optimizes the objective function by the sequential calculation process using a plurality of initial values.

7. 7. The position estimation device according to claim 5, wherein the estimation unit changes a step size to a larger value when the objective function converges to a local optimum value in the sequential calculation process, and changes the step size to a smaller value when the objective function converges to a global optimum value.

8. obtaining directions of arrival of radio waves from a plurality of unknown sources; acquiring a reception position when the radio wave whose arrival direction is acquired is received; and estimating a plurality of estimated positions by optimizing an objective function having an argument of a sum of differences between the estimated directions of arrival and directions of arrival for the plurality of wave sources for each receiving position, using a plurality of pairs of directions of arrival and receiving positions and the estimated positions of the unknown wave sources.

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