Position estimation system and position estimation method

Abstract

To provide a position estimation system and a position estimation method capable of estimating a position of a mobile station stably even if providing the mobile station in an object that is at a standstill without any movement usually.SOLUTION: A position estimation system 1 includes: four or more fixed stations 3 rotating at a predetermined radius with predetermined position coordinates in an area AR as the center and having a transmission / reception antenna 3a for transmitting and receiving radio waves in respective rotational positions of three or more spots; a mobile station 5 capable of transmitting electric waves arriving at the transmission / reception antenna 3a of the fixed stations 3; an electric wave strength acquisition section 7 for acquiring reference electric wave strength and mobile station electric wave strength from the fixed stations 3; and a mobile station position estimation section (control section) 17 for estimating position coordinates of the mobile station 5 on the basis of the reference electric wave strength and the mobile station electric wave strength. The mobile station position estimation section 17 has: a distance calculation section 17A for calculating a fixed station-to-mobile station distance between each of four or more fixed stations and the mobile station 5; and a position calculation section 17B for calculating position coordinates within the area AR of the mobile station 5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a position estimation system and a position estimation method for estimating the position of a mobile station in an area where fixed stations and mobile stations exist. [Background technology]

[0002] 2. Description of the Related Art A position estimation system and a position estimation method are known in which a plurality of fixed stations are placed within an area, and mobile objects carry mobile stations that transmit radio waves, and the positions of the mobile objects present within the area are estimated.

[0003] For example, the location estimation systems disclosed in Patent Documents 1 and 2 include three or more fixed stations located at predetermined position coordinates within a region and capable of transmitting and receiving radio waves to and from each other, a mobile station capable of transmitting radio waves to the fixed stations, a radio wave strength acquisition unit that acquires reference radio wave strength and mobile station radio wave strength from the fixed stations, and a mobile station location estimation unit that estimates the location coordinates of the mobile station within the region based on the reference radio wave strength and the mobile station radio wave strength. The mobile station location estimation unit calculates fixed station-to-mobile station distances between each of the three or more fixed stations and the mobile station using a distance calculation unit. The location calculation unit calculates the location coordinates of the mobile station within the region based on the three or more fixed station-to-mobile station distances. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-37311 [Patent Document 2] Japanese Patent Application Publication No. 2024-37312 Summary of the Invention [Problem to be solved by the invention]

[0005] When estimating position within an area such as an indoor space, radio waves emitted from a mobile station reflect off walls and floors, causing the reflected waves to collide with the direct wave, or with each other, resulting in wave interference (multipath fading). This multipath fading disrupts the distribution of radio wave strength in the space, resulting in increased positioning errors in position estimation. For this reason, it is necessary to stabilize the estimated position by adding numerical processing such as moving averages to the positioning calculation. However, when installing a mobile station on an object such as equipment at a construction site, the object is usually stationary and does not move, making it difficult to obtain a moving average and perform stable position estimation. [Means for solving the problem]

[0006] The present invention has been made to solve such problems, Three or more or four or more fixed stations that rotate at a predetermined radius around a predetermined position coordinate within the area and have transmitting and receiving antennas that transmit and receive radio waves at each of at least three or more rotational positions, and that can transmit and receive radio waves to and from each other; a mobile station capable of transmitting radio waves that reach a transmitting / receiving antenna provided at each fixed station; a radio wave strength acquisition unit that acquires a reference radio wave strength obtained by averaging the reception strength of radio waves transmitted from each of the transmitting and receiving antennas provided at other fixed stations and received at each point by the transmitting and receiving antennas provided at each of the fixed stations, and a mobile station radio wave strength obtained by averaging the reception strength of radio waves transmitted from mobile stations and received at each point by the transmitting and receiving antennas provided at each of the fixed stations; a mobile station position estimation unit that estimates a position coordinate of the mobile station within the area based on the reference radio wave intensity and the mobile station radio wave intensity acquired from the radio wave intensity acquisition unit; A mobile station position estimation unit a distance calculation unit that calculates fixed-station-to-mobile-station distances between each of three or more or four or more fixed stations and the mobile station based on a ratio between a reference radio wave strength between each of the fixed stations and a mobile station radio wave strength between each of the fixed stations and the mobile station; a position calculation unit that calculates the position coordinates of the mobile station within the area based on three or more or four or more distances between the fixed station and the mobile station; A position estimation system having the following features was constructed.

[0007] The present invention also provides a reference radio wave intensity acquisition step of rotating a transmitting / receiving antenna at each of three or more or four or more fixed stations that rotate at a predetermined radius around a predetermined position coordinate within the area and transmit and receive radio waves at each of at least three or more rotational positions, the transmitting / receiving antenna being rotated while receiving radio waves sequentially transmitted from each rotational position of the transmitting / receiving antenna provided at another fixed station, and acquiring a reference radio wave intensity between each of the fixed stations by averaging the reception intensities of radio waves sequentially received at each rotational position of the transmitting / receiving antenna; a mobile station radio wave intensity acquisition step of rotating a transmitting / receiving antenna provided in a fixed station and having the transmitting / receiving antenna receive radio waves transmitted from a mobile station at each rotational position, and acquiring a mobile station radio wave intensity between each fixed station and the mobile station by averaging the reception intensities of radio waves sequentially received by the transmitting / receiving antenna at each rotational position; a distance calculation step of calculating fixed-station-to-mobile-station distances between each of three or more or four or more fixed stations and the mobile station based on a ratio between a reference radio wave strength between each of the fixed stations and a mobile station radio wave strength between each of the fixed stations and the mobile station; a position calculation step of calculating a position coordinate within the area of ​​the mobile station based on three or more or four or more distances between the fixed station and the mobile station; A location estimation method including the above is constructed.

[0008] With these configurations, the radio wave strength of the mobile station between each fixed station and the mobile station is acquired by rotating the transmitting and receiving antennas installed in each fixed station at a predetermined radius around a predetermined position coordinate within the area and averaging the radio waves received from the mobile station at at least three or more rotational positions. Therefore, even if the mobile station is stationary and not moving, the acquired radio wave strength of the mobile station is a moving average because the transmitting and receiving antennas on the fixed station side rotate and move.

[0009] Furthermore, the reference radio wave strength between each fixed station is obtained by averaging the reception strength of radio waves transmitted sequentially from each point of the transmitting and receiving antennas installed at other fixed stations, which are received sequentially at each point by the transmitting and receiving antennas installed at each fixed station. The transmitting and receiving antennas installed at each fixed station rotate at a predetermined radius around a predetermined position coordinate within the area, and the transmitting side transmits radio waves sequentially to the other fixed stations at each of at least three or more rotational positions, while the receiving side receives radio waves transmitted from the other fixed stations sequentially at each of at least three or more rotational positions. Therefore, the reference radio wave strength between each fixed station is stable and proportional in the logarithmic domain to the distance between the average position of the transmitting and receiving antennas on the receiving side and the average position of the transmitting and receiving antennas on the transmitting side.

[0010] Therefore, the distance between the fixed station and the mobile station calculated by the distance calculation unit based on the ratio between the reference radio wave strength between the fixed stations and the mobile station radio wave strength between each fixed station and the mobile station, and the position coordinates within the mobile station's area calculated by the position calculation unit based on this distance between the fixed station and the mobile station, become stable, making it possible to perform stable position estimation of the mobile station.

[0011] The present invention also provides Each fixed station is characterized in that, instead of a transmitting / receiving antenna that transmits and receives radio waves at each rotational position, it has three transmitting / receiving antennas provided at each vertex of a triangle that surrounds a predetermined position coordinate within the area, or four transmitting / receiving antennas provided at each vertex of a rectangle that surrounds a predetermined position coordinate within the area, or at least three transmitting / receiving antennas arranged at predetermined intervals on the circumference of a circle centered on a predetermined position coordinate within the area.

[0012] The present invention also provides a reference radio wave intensity acquisition step of averaging the reception intensities of radio waves simultaneously received at each of the transmitting and receiving antennas provided at the other fixed stations by having at least three transmitting and receiving antennas provided at each of three or four or more fixed stations, each of which is arranged at at least three or more points surrounding a predetermined position coordinate within the area and simultaneously transmits and receives radio waves, receive at each of the transmitting and receiving antennas provided at the other fixed stations; a mobile station radio wave intensity acquisition step of receiving radio waves transmitted from the mobile station at a transmitting / receiving antenna provided at each point of the fixed station, and acquiring the mobile station radio wave intensity between each fixed station and the mobile station by averaging the reception intensities of radio waves simultaneously received at each point by the transmitting / receiving antenna; a distance calculation step of calculating fixed-station-to-mobile-station distances between each of three or more or four or more fixed stations and the mobile station based on a ratio between a reference radio wave strength between each of the fixed stations and a mobile station radio wave strength between each of the fixed stations and the mobile station; a position calculation step of calculating a position coordinate within the area of ​​the mobile station based on three or more or four or more distances between the fixed station and the mobile station; A location estimation method including the above is constructed.

[0013] With these configurations, the mobile station radio wave strength between each fixed station and the mobile station is obtained by averaging the radio waves simultaneously received from the mobile station by the transmitting and receiving antennas of each fixed station, which are located at at least three points surrounding a predetermined position coordinate within the area. Therefore, even if the mobile station is stationary and not moving, the obtained mobile station radio wave strength is a moving average because the transmitting and receiving antennas of the fixed stations are located at at least three points surrounding the predetermined position coordinate within the area.

[0014] Furthermore, the reference radio wave strength between each fixed station is obtained by averaging the reception strength of radio waves transmitted from each point of the transmitting and receiving antennas installed at other fixed stations, which are received at each point by the transmitting and receiving antennas installed at each fixed station. The transmitting and receiving antennas installed at each fixed station are respectively located at at least three points surrounding a predetermined position coordinate within an area, and on the transmitting side, radio waves are simultaneously transmitted from each point to the other fixed stations, and on the receiving side, radio waves transmitted from the other fixed stations are simultaneously received by the transmitting and receiving antennas installed at each point. Therefore, the reference radio wave strength between each fixed station is stable and proportional in the logarithmic domain to the distance between the average position of the transmitting and receiving antennas on the receiving side and the average position of the transmitting and receiving antennas on the transmitting side.

[0015] Therefore, the distance between the fixed station and the mobile station calculated by the distance calculation unit based on the ratio between the reference radio wave strength between the fixed stations and the mobile station radio wave strength between each fixed station and the mobile station, and the position coordinates within the mobile station's area calculated by the position calculation unit based on this distance between the fixed station and the mobile station, become stable, making it possible to perform stable position estimation of the mobile station. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a position estimation system and a position estimation method that are capable of stably estimating the position of a mobile station even when the mobile station is installed on an object that is normally stationary and does not move. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a block diagram showing a configuration of a position estimation system according to a first embodiment of the present invention. [Figure 2] 2 is a perspective view showing a schematic configuration of a rotation drive mechanism used in a fixed station that constitutes the position estimation system shown in FIG. 1. [Figure 3] 2 is a flowchart showing the process of a position estimation method performed using the position estimation system shown in FIG. 1. [Figure 4] 2 is a conceptual diagram illustrating a reference radio wave intensity measured by the position estimation system shown in FIG. 1. FIG. [Figure 5] 2 is a conceptual diagram illustrating the radio wave intensity of a mobile station measured by the position estimation system shown in FIG. 1. [Figure 6] 2 is a conceptual diagram illustrating calculation of the distance between the fixed station and the mobile station in the position estimation system shown in FIG. 1. FIG. [Figure 7] 4 is a flowchart showing details of a position calculation step in the flowchart shown in FIG. 3. [Figure 8] 2 is a schematic diagram showing a method for calculating position coordinates in the position estimation system shown in FIG. 1 when there are two intersections between a first circle and a second circle. FIG. [Figure 9] 2 is a schematic diagram showing a method for calculating position coordinates in the position estimation system shown in FIG. 1 when the first circle and the second circle have one or no intersection point. [Figure 10] 2 is a diagram illustrating a position estimation model used in a demonstration experiment for verifying the position estimation performed by the position estimation system shown in FIG. 1. FIG. [Figure 11] 2 is a diagram showing an indoor model for explaining a desirable size of the diameter of rotation of the transmitting and receiving antennas in the position estimation system shown in FIG. 1. FIG. [Figure 12] FIG. 12 is a diagram showing the radio wave intensity distribution of a transmitting antenna in a room measured using the indoor model shown in FIG. [Figure 13] 13(a) is a graph showing the relationship between distance and radio wave intensity in a room obtained from the radio wave intensity distribution shown in FIG. 12, and (b) and (c) are partial enlarged views of the characteristic line shown in (a). [Figure 14] 10. (a) is a diagram showing the result of estimating the position of a mobile station using the instantaneous value of radio waves transmitted from the mobile station and received by the fixed station in the position estimation model shown in FIG. 10. (b) is a diagram showing the result of estimating the position of a mobile station using the average value of radio waves received by the fixed station. [Figure 15] 1. (a), (b), and (c) are diagrams showing modified examples of the transmitting and receiving antennas used in the fixed station of the position estimation system shown in FIG. [Figure 16]FIG. 10 is a conceptual diagram showing the principle of trilateration using the distance between a fixed station and a mobile station in a position estimation system according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, an embodiment of a position estimation system and a position estimation method according to the present invention will be described.

[0019] [First embodiment] Fig. 1 is a block diagram showing the configuration of a position estimation system 1 according to a first embodiment of the present invention. As shown in Fig. 1, the position estimation system 1 is composed of a fixed station 3, a mobile station 5, a radio wave intensity acquisition unit 7, and an information terminal 9, and estimates the position of the mobile station 5 using the principles of multilateral positioning, or in this embodiment, quadrilateral positioning.

[0020] The fixed station 3 is arranged around a predetermined position coordinate within an area (a measurement target area on a floor within a building) AR. Four or more fixed stations 3 must be arranged, and in this embodiment, a total of four fixed stations 3 having identification codes ID1 to ID4 are arranged at position coordinates (x1, y1), (x2, y2), (x3, y3), and (x4, y4) (hereinafter and in the drawings, the identification codes may be added in parentheses after the code of the fixed station 3 to distinguish the fixed stations 3).

[0021] In this embodiment, each base station 3 has a rotation drive mechanism, as shown in the perspective view of FIG. 2, that rotates around each of the position coordinates (x1, y1), (x2, y2), (x3, y3), and (x4, y4) within the area AR. In this rotation drive mechanism, the motor 4b is driven to rotate in accordance with a control signal from the control box 4a, causing the turntable 4c to rotate, causing one transmitting / receiving antenna 3a to continuously rotate with a predetermined radius around each of the position coordinates (x1, y1), (x2, y2), (x3, y3), and (x4, y4). In FIG. 1, dotted circles centered on each position coordinate represent the rotation locus of the transmitting / receiving antenna 3a. The transmitting / receiving antenna 3a transmits and receives radio waves at at least three rotation positions on this rotation locus.

[0022] The transmitting / receiving antenna 3a uses radio waves in the sub-gigahertz band and performs wireless communication using an LPWA (Low-Power Wide Area) module suitable for long-distance communication. More specifically, in this embodiment, radio waves in the 920 MHz band are used. Because the LPWA module has a wide communication range using radio waves in the sub-gigahertz band, it is possible to cover a wide area AR with a small number of fixed stations 3. The transmitting / receiving antenna 3a of each fixed station 3 can transmit and receive radio waves to and from each other over a wide communication range. Because each fixed station 3 is arranged around a predetermined position coordinate, the center-to-center distance [m] between the fixed stations 3 is known.

[0023] The mobile station 5 is a beacon terminal that is held by or attached to a mobile object, and is capable of transmitting radio waves in the same sub-gigahertz band as the fixed station 3, to reach the transmitting / receiving antenna 3a of the fixed station 3. The mobile object may be a living thing such as a person or an animal, a mobile device such as a vehicle or a drone, or an immobile movable property such as materials or equipment. By estimating the position of the mobile station 5, the positions of any mobile objects present together with the mobile station 5 can be estimated.

[0024] The radio wave strength acquisition unit 7 is a gateway that connects the fixed stations 3 and mobile stations 5 with the information terminal 9, and acquires and stores reference radio wave strength and mobile station radio wave strength from the fixed stations 3. The reference radio wave strength is the radio wave strength obtained by averaging the reception strength of radio waves transmitted from the transmission / reception antennas 3a of other fixed stations 3 at each rotational position and received by the transmission / reception antennas 3a of each fixed station 3 at each rotational position. The mobile station radio wave strength is the radio wave strength obtained by averaging the reception strength of radio waves transmitted from the mobile stations 5 and received by the transmission / reception antennas 3a of each fixed station 3 at each rotational position.

[0025] The information terminal 9 is a computer terminal used by a user. Specifically, it may be a mobile phone, a smartphone, a tablet terminal, a personal computer (notebook PC, desktop PC), etc., but is not limited to these. In this embodiment, a computer program for using the position estimation system 1 is installed in the information terminal 9. By starting the computer program, the position estimation system 1 can be used on the information terminal 9. The information terminal 9 has a communication unit 11, an input unit 13, a data storage unit 15, a control unit 17, and a display unit 19.

[0026] The communication unit 11 is for communicating with the radio wave intensity acquisition unit 7. The input unit 13 is for inputting data and performing operations, and various devices can be used depending on the user terminal, such as a keyboard, a mouse, or a touch panel using the display unit 19. The data storage unit 15 stores the reference radio wave intensity and mobile station radio wave intensity acquired from the radio wave intensity acquisition unit 7.

[0027] The control unit 17 functions as a mobile station position estimation unit by an installed computer program, and estimates the position coordinates of the mobile station 5 within the area AR based on the reference radio wave intensity and the mobile station radio wave intensity. The control unit 17 has a distance calculation unit 17A and a position calculation unit 17B.

[0028] Distance calculation unit 17A calculates the fixed-station-mobile-station distance between each of fixed stations 3 and mobile station 5 based on the ratio between the reference radio wave strength between each of fixed stations 3 and the mobile station radio wave strength between each of fixed stations 3 and mobile station 5. Position calculation unit 17B calculates the position coordinates of mobile station 5 within area AR based on the four or more fixed-station-mobile-station distances calculated by distance calculation unit 17A.

[0029] <Location estimation flowchart> FIG. 3 is a flowchart showing the processing of the position estimation system 1.

[0030] [Steps to obtain radio wave strength] The user operates the input unit 13 of the information terminal 9 to issue a command to the radio wave intensity acquisition unit 7 to acquire the reference radio wave intensity and the mobile station radio wave intensity.

[0031] Upon receiving the command, the radio wave intensity acquisition unit 7 first acquires a reference radio wave intensity (reference radio wave intensity acquisition step ST1). As shown in Fig. 4, the reference radio wave intensity is the radio wave intensity obtained by averaging the reception intensities of radio waves transmitted from the transmission / reception antennas 3a provided in other fixed stations 3 at each rotational position, which are received by the transmission / reception antennas 3a provided in each fixed station 3 at each rotational position. In this embodiment, for example, the average radio wave intensity of radio waves received by the transmission / reception antenna 3a of the fixed station 3 (ID1) at each rotational position from the transmission / reception antennas 3a at each position of the fixed station 3 (ID2) is ref_RSSI(1-2) This is expressed as follows.

[0032] The average radio wave strength of radio waves received by the transmitting and receiving antenna 3a of the fixed station 3 (ID2) from the transmitting and receiving antenna 3a at each position of the fixed station 3 (ID1) at each rotational position is the same as the average radio wave strength of radio waves received by the transmitting and receiving antenna 3a of the fixed station 3 (ID1) from the transmitting and receiving antenna 3a at each position of the fixed station 3 (ID2) at each rotational position, and therefore is omitted in this embodiment. Similarly, as shown in Figure 4, the radio wave strength acquisition unit 7 acquires six average radio wave strengths of radio waves received by each transmitting and receiving antenna 3a of the fixed station 3 from the transmitting and receiving antennas 3a at each position of the other fixed stations 3 at each rotational position.

[0033] That is, in this reference radio wave intensity acquisition step ST1, the radio wave intensity acquisition unit 7 rotates with a predetermined radius around predetermined position coordinates (x1, y1), (x2, y2), (x3, y3), (x4, y4) within the area AR, and transmits and receives radio waves at each of at least three or more rotational positions, by causing each of the transmitting and receiving antennas 3a provided at each of the four fixed stations 3 to receive, at each rotational position, radio waves transmitted sequentially from each rotational position of the transmitting and receiving antennas 3a provided at the other fixed stations 3 while rotating the transmitting and receiving antenna 3a, thereby acquiring a reference radio wave intensity between each of the fixed stations 3 which is the average of the reception strengths of radio waves received sequentially at each rotational position of the transmitting and receiving antenna 3a.

[0034] Next, the radio wave intensity acquisition unit 7 acquires the radio wave intensity of the mobile station (mobile station radio wave intensity acquisition step ST2). As shown in Fig. 5, the radio wave intensity of the mobile station is the radio wave intensity obtained by averaging the reception intensities of radio waves transmitted from the mobile station 5 and received at each rotational position by the transmitting / receiving antenna 3a provided in each of the fixed stations 3. In this embodiment, for example, the average radio wave intensity of radio waves transmitted from the mobile station 5 and received at each rotational position by the transmitting / receiving antenna 3a provided in the fixed station 3 (ID1) is meas_RSSI(1) This is expressed as follows.

[0035] Similarly, the radio wave intensity acquisition unit 7 acquires four radio wave intensities by averaging the reception intensities of radio waves transmitted from the mobile station 5 received at each rotational position by the transmitting / receiving antenna 3a provided in each fixed station 3, as shown in Figure 5.

[0036] That is, in this mobile station radio wave intensity acquisition step ST2, the radio wave intensity acquisition unit 7 rotates the transmitting / receiving antenna 3a provided in the fixed station 3, and causes the transmitting / receiving antenna 3a to receive radio waves transmitted from the mobile station 5 at each rotational position, thereby acquiring the mobile station radio wave intensity between each fixed station 3 and the mobile station 5, which is the average reception strength of the radio waves received sequentially by the transmitting / receiving antenna 3a at each rotational position.

[0037] The information terminal 9 receives the reference radio wave intensity and the mobile station radio wave intensity acquired by the radio wave intensity acquisition unit 7 at the communication unit 11 and stores them in the data storage unit 15.

[0038] [Distance calculation step] Next, the distance calculation unit 17A calculates the fixed-to-mobile distance [m] between each of the four fixed stations 3 and the mobile station 5 based on the ratio between the reference radio wave strength between each of the fixed stations 3 and the mobile station 5 (distance calculation step ST3). The fixed-to-mobile distances between the fixed station 3 (ID1) to the fixed station 3 (ID4) and the mobile station 5 are designated as L1 to L4, respectively.

[0039] In this embodiment, for example, the fixed station-to-mobile station distance L1 between the fixed station 3 (ID1) and the mobile station 5 is calculated by the following (a) to (d).

[0040] (a) As shown in Figure 6, assuming that the fixed station 3 (ID1) is the primary fixed station 3, one of the other fixed stations 3, the fixed station 3 (ID2), is the secondary fixed station 3, and that the mobile station 5 is located on a straight line connecting the primary fixed station 3 and the secondary fixed station 3, the distance between the primary fixed station 3 and the mobile station 5 is calculated from the ratio of the reference radio wave strength (ref_RSSI(1-2)) based on the average radio wave strength of radio waves received from the transmitting and receiving antennas 3a of the secondary fixed station 3 at each rotational position by the transmitting and receiving antennas 3a of the primary fixed station 3, to the mobile station radio wave strength (meas_RSSI(1)) based on the average radio wave strength of radio waves received from the mobile station 5 at each rotational position by the transmitting and receiving antennas 3a of the primary fixed station 3.

[0041] Generally, when the distance between the transmitting antenna and the receiving antenna is r [m], the radio wave strength RSSI [W] of the radio wave with a frequency of 920 [MHz] received by the receiving antenna is calculated using the following equation (1):

number

[0042] By transforming equation (1), we obtain the following equation (2).

number

[0043] Here, if the distance between fixed station 3 (ID1) and fixed station 3 (ID2) is a [m] and the distance between fixed station 3 (ID1) and mobile station 5 is a' [m], the following equations (3) and (4) can be obtained from equation (2).

number

number

[0044] Here, if Gt, Gr, λ, and Pt are the same in calculating the distance a [m] and the distance a′ [m], the following equation (5) is obtained from equations (3) and (4).

number

[0045] When equation (5) is converted to dBm, the following equation (6) is obtained.

number

[0046] Therefore, since the distance a [m] between the fixed station 3 (ID1) and the fixed station 3 (ID2) is known, the distance a' [m] between the fixed station 3 (ID1) and the mobile station 5 can be calculated from equation (6).

[0047] (b) As in (a) above, if the distance between fixed station 3 (ID1) and fixed station 3 (ID3) is b [m] and the distance between fixed station 3 (ID1) and mobile station 5 is b' [m], the following equation (7) is obtained.

number

[0048] Since the distance b [m] between the fixed station 3 (ID1) and the fixed station 3 (ID3) is known, the distance b' [m] between the fixed station 3 (ID1) and the mobile station 5 can be calculated from equation (7).

[0049] (c) Also, similar to (a) above, if the distance between fixed station 3 (ID1) and fixed station 3 (ID4) is c [m] and the distance between fixed station 3 (ID1) and mobile station 5 is c' [m], the following equation (8) is obtained.

number

[0050] Since the distance c [m] between the fixed station 3 (ID1) and the fixed station 3 (ID4) is known, the distance c' [m] between the fixed station 3 (ID1) and the mobile station 5 can be calculated from equation (8).

[0051] (d) The distances a' [m], b' [m], and c' [m] between the base station 3 (ID1) and the mobile station 5 obtained above are theoretically the same value, but since they contain some error, in this embodiment, the average value of these (= (a' + b' + c') / 3) is taken as the fixed-to-mobile distance L1 between the base station 3 (ID1) and the mobile station 5.

[0052] For the fixed station 3 (ID2), the fixed station 3 (ID3), and the fixed station 3 (ID4), the distances L2 to L4 between the fixed station and the mobile station are obtained in the same manner as in (a) to (d) above.

[0053] [Position calculation step] Next, the position calculation unit 17B calculates the position coordinates within the area of ​​the mobile station 5 from the calculated fixed station-to-mobile station distances L1 to L4 (position calculation step ST4).

[0054] Fig. 7 is a flowchart showing the details of the position calculation step ST4. Fig. 8 is a schematic diagram showing a method for calculating position coordinates when there are two intersections between the first circle and the second circle, and Fig. 9 is a schematic diagram showing a method for calculating position coordinates when there is one or no intersection between the first circle and the second circle.

[0055] Note that the locations of the fixed stations 3 shown in Figures 8 and 9 are different from the locations of the fixed stations 3 shown in Figures 4 to 6. Also, the dimensions and ratios in Figures 8 and 9 may not be accurate for the sake of convenience when illustrating them.

[0056] The position calculation unit 17B selects three distances, namely the smallest distance, the second smallest distance, and the third smallest distance, from the fixed station-to-mobile station distances L1 to L4 (step ST31), draws a first circle with a radius equal to the fixed station-to-mobile station distance and a first fixed station 3 with the smallest fixed station-to-mobile station distance as its center, and draws a second circle with a radius equal to the fixed station-to-mobile station distance and a second fixed station 3 with the second smallest fixed station-to-mobile station distance as its center (step ST32). Note that in this specification, "drawing" a diagram such as a circle not only means displaying the diagram on the display unit 19 of the information terminal 9, but also includes virtually handling the diagram as an internal process in the calculations of the position calculation unit 17B.

[0057] The example shown in FIG. 8 is a case where the first circle and the second circle intersect at two points. In this example, fixed-station-mobile-station distances L1, L2, and L3 are selected from the fixed-station-mobile-station distances L1 to L4, a first circle is drawn with the fixed station 3 (ID1) (first fixed station) at its center, and a second circle is drawn with the fixed station 3 (ID2) (second fixed station) at its center, and it is determined whether or not there is an intersection IP (step ST33). In the example shown in FIG. 8, there are two intersections, intersection IP1 and intersection IP2. In this case, the position coordinates of the point of intersection IP1 or intersection IP2 that is closer to a third circle having the fixed station-mobile-station distance as its radius and centered on the fixed station 3 (ID3) (third fixed station) are calculated as the position coordinates of the mobile station 5 (step ST34). That is, in this example, intersection IP1 is calculated as the position coordinates of the mobile station 5.

[0058] The example shown in Figure 9 is a case where there is no intersection between the first circle and the second circle (including a case where there is only one intersection). In this example, fixed station-to-mobile station distances L1, L2, and L3 are selected from the fixed station-to-mobile station distances L1 to L4, a first circle is drawn with fixed station 3 (ID1) (first fixed station) at the center, and a second circle is drawn with fixed station 3 (ID2) (second fixed station) at the center, and it is determined whether or not there is an intersection IP (step ST33). In the example shown in Figure 9, there is no intersection. In this case, the position calculation unit 17B determines the position coordinates of a first internal division point DP1 that divides the line segment connecting the fixed station 3 (ID1) (first fixed station) and the fixed station 3 (ID2) (second fixed station) internally at the ratio of the fixed station-to-mobile station distance L1 to L2 (step ST35), determines the position coordinates of a second internal division point DP2 that divides the line segment connecting the fixed station 3 (ID1) (first fixed station) and the fixed station 3 (ID3) (third fixed station) internally at the ratio of the fixed station-to-mobile station distance L1 to L3 (step ST36), and calculates the position coordinates of the midpoint MP of the line segment connecting the first internal division point DP1 and the second internal division point DP2 as the position coordinates of the mobile station 5 (step ST37).

[0059] <Actions and Effects of the Location Estimation System and Location Estimation Method> According to the position estimation system 1 and position estimation method of this embodiment, the radio wave intensity of the mobile station between each fixed station 3 and the mobile station 5 is acquired by rotating the transmitting / receiving antenna 3a provided in each fixed station 3 with a predetermined radius around predetermined position coordinates (x1, y1), (x2, y2), (x3, y3), (x4, y4) within the area AR, and averaging the radio waves received from the mobile station 5 at at least three or more rotational positions. Therefore, even if the mobile station 5 is stationary, the acquired radio wave intensity of the mobile station is a moving average obtained by rotating and moving the transmitting / receiving antenna 3a on the fixed station 3 side, and spatial disturbance (spatial fluctuation) of the radio waves due to multipath fading is suppressed.

[0060] Furthermore, the reference radio wave strength between each of the fixed stations 3 is obtained by averaging the received strength of radio waves sequentially transmitted from each rotational position of the transmitting and receiving antennas 3a provided at the other fixed stations 3, which are sequentially received at each rotational position by the transmitting and receiving antennas 3a provided at each of the fixed stations 3. The transmitting and receiving antennas 3a provided at each of the fixed stations 3 rotate with a predetermined radius around predetermined position coordinates (x1, y1), (x2, y2), (x3, y3), and (x4, y4) within the area AR, and the transmitting side sequentially transmits radio waves toward the other fixed stations 3 at each of at least three rotational positions, while the receiving side sequentially receives radio waves transmitted from the other fixed stations 3 at each of at least three rotational positions. Therefore, the reference radio wave strength between each of the fixed stations 3 is stable and proportional in the logarithmic domain to the distance between the average position of the transmitting and receiving antennas 3a on the receiving side and the average position of the transmitting and receiving antennas 3a on the transmitting side.

[0061] Therefore, the fixed station-to-mobile station distance calculated by the distance calculation unit 17A based on the ratio between the reference radio wave strength between the fixed stations 3 and the mobile station radio wave strength between each fixed station 3 and the mobile station 5, and the position coordinates of the mobile station 5 within the area AR calculated by the position calculation unit 17B based on this fixed station-to-mobile station distance, become stable, making it possible to perform stable position estimation of the mobile station 5.

[0062] <Demonstration experiment> A demonstration experiment was conducted in which one transmitting and receiving antenna 3a was continuously rotated on a circle whose diameter φ was the radio wave wavelength λ and whose center was a predetermined position coordinate of the fixed station 3, to estimate the position coordinate of the mobile station 5.

[0063] In this demonstration experiment, the location estimation model shown in Figure 10 was used, and the centers of each fixed station 3 were located at the four corners of a 9.9 m x 9.9 m square area. The square area was divided into nine equal parts, and mobile stations 5 were placed in the center of each of the nine 3.3 m square areas in order. The transmitting and receiving antennas 3a of the fixed stations 3 were rotated, and radio waves were transmitted from the mobile stations 5 at each position to the fixed stations 3 at the four corners in order. The radio wave strength (RSSI) of the radio waves transmitted from the mobile stations 5 at each position and received by the transmitting and receiving antennas 3a of each of the four corner fixed stations 3 at each rotational position was obtained as the mobile station radio wave strength. Once each fixed station 3 obtained 50 radio wave strength data, the mobile station 5 completed one measurement at that position, and then moved to the next mobile station 5 position, performing a total of nine measurements.

[0064] The diameter φ of rotation of the transmitting / receiving antenna 3a around a predetermined position coordinate is preferably larger than half the radio wave wavelength λ, which is the theoretical period of a standing wave under multipath fading. Therefore, the position estimation system 1 according to this embodiment and the position estimation model used in this demonstration experiment use a rotation drive mechanism that causes the transmitting / receiving antenna 3a to continuously move on a circle with a diameter φ of 1λ and a radius of λ / 2.

[0065] To confirm that the diameter φ of the circumference is preferably greater than λ / 2, radio waves were output from a transmitting antenna 22 placed at one location in an indoor model 21 shown in Fig. 11, and the radio wave intensity throughout the room was measured to determine the repetition period of the standing wave. The indoor model 21 is surrounded by a concrete wall 22a measuring 16 m in length, 20 m in width, and 3 m in height, and is divided into four rooms by concrete walls 22b of the same height. The dielectric constant of the concrete walls 22a and 22b is 7.0. The transmitting antenna 23 has a gain Gt of 0 dBi, an output power of 20 mW, and a transmission frequency f of 920 MHz, and is placed in one of the four rooms as shown.

[0066] Fig. 12 is a diagram showing the distribution intensity throughout the room of the radio waves output from the transmitting antenna 23. The radio wave intensity (power) is expressed in units of dBW, with darker areas indicating higher intensity. This diagram shows that the intensity of the radio waves emitted from the transmitting antenna 23 weakens when separated by the concrete wall 22b due to shielding attenuation caused by the concrete wall 22b. It also shows that interference fringes occur as the radio waves are repeatedly reflected within the room.

[0067] Figure 13(a) is a graph showing the characteristic lines of radio wave strength at each distance on the line segment indicated by the arrow in Figure 12. The horizontal axis of the graph represents distance [m], and the vertical axis represents radio wave strength (RSSI) [dBm]. Figures 13(b) and 13(c) are enlarged views of a portion of the characteristic line in the graph of Figure 13(a).

[0068] 10(b) and 10(c) show that standing waves occur with a period approximately equal to the length of 0.16 m, which corresponds to λ / 2, half the wavelength of the transmission frequency (=920 MHz) of the radio waves output from the transmitting antenna 23. On the other hand, it was confirmed that there are sections where standing waves occur periodically and sections where they do not occur, and this tendency is thought to change depending on the shape of the room and the installation position of the transmitting antenna 23 within the room.

[0069] From this measurement result, it can be said that it is desirable to set the diameter φ of rotation of the transmitting / receiving antenna 3a around a predetermined position coordinate as the center to be larger than 1 / 2 of the radio wave wavelength λ.

[0070] Fig. 14(a) is a diagram showing the result of position estimation of the mobile station 5 estimated based on the instantaneous value of radio wave intensity measured using the position estimation model shown in Fig. 10. The estimated position of the mobile station 5 was obtained in the same manner as in the above-described embodiment from the mobile station radio wave intensity, which is the instantaneous radio wave intensity of the radio waves transmitted from the mobile station 5 at each position and received by the transmitting and receiving antennas 3a of each of the four fixed stations 3 at each rotational position, and the reference radio wave intensity, which is the instantaneous radio wave intensity of the radio waves transmitted and received between the transmitting and receiving antennas 3a of each of the fixed stations 3 at each rotational position.

[0071] In addition, in the same figure, the plots marked with white squares indicate the estimated positions of mobile station 5 measured in the first divided area, the plots marked with crosses indicate the second divided area, the plots marked with black circles indicate the third divided area, the plots marked with white triangles indicate the fourth divided area, the plots marked with black squares indicate the fifth divided area, the plots marked with white circles indicate the sixth divided area, the plots marked with diamonds indicate the seventh divided area, the plots marked with black triangles indicate the eighth divided area, and the plots marked with stars indicate the estimated positions of mobile station 5 measured in the ninth divided area.

[0072] Fig. 14(b) is a diagram showing the result of position estimation of the mobile station 5 estimated based on the average value of 50 radio wave intensities measured using the position estimation model shown in Fig. 10. The estimated position of the mobile station 5 was obtained in the same manner as in the above-described embodiment from the mobile station radio wave intensity, which is the average radio wave intensity of 50 radio waves transmitted from the mobile station 5 at each position and received at each rotational position by the transmitting and receiving antennas 3a of each of the four fixed stations 3, and the reference radio wave intensity, which is the average radio wave intensity of radio waves transmitted and received between the transmitting and receiving antennas 3a at each rotational position of each fixed station 3. The types of plots in each divided area are the same as those in Fig. 14(a).

[0073] 14(b), it can be confirmed that the estimated position of the mobile station 5 falls within one of the nine divided areas by using the average value of radio wave intensity obtained when the transmitting and receiving antenna 3a is continuously moved around the circumference, as in the above-described embodiment. Therefore, by continuously moving the transmitting and receiving antenna 3a of the fixed station 3 around the circumference, and having the transmitting and receiving antenna 3a of each fixed station 3 sequentially receive radio waves transmitted from the mobile station 5, and taking the average of the received signals, it is possible to determine which of the nine divided areas the mobile station 5 is currently located in.

[0074] Therefore, even at construction sites, particularly in large spaces such as logistics facilities and factories, by placing a small number of fixed stations 3, it is possible to grasp the divided areas where materials and equipment with mobile stations 5 are located, and also to grasp the quantity of materials and equipment present in each divided area. Furthermore, it is possible to manage the operating hours of heavy equipment with mobile stations 5 and record its location, thereby reducing the number of unnecessary rentals of heavy equipment and automatically managing things that could not be done manually until now, such as preventing theft.

[0075] [Variations] In the above embodiment, each fixed station 3 has one transmitting / receiving antenna 3a that rotates around a predetermined position coordinate within the area AR and transmits and receives radio waves at each of at least three or more rotational positions.

[0076] However, each fixed station 3 may be configured to rotate around a predetermined position coordinate within the area AR and have a plurality of transmitting and receiving antennas 3a that transmit and receive radio waves at each of at least three or more rotational positions.

[0077] In addition, each fixed station 3 may be configured to have three or more transmitting and receiving antennas fixedly arranged at three or more points surrounding a predetermined position coordinate within the area, instead of a transmitting and receiving antenna that transmits and receives radio waves at each rotational position.

[0078] For example, as shown in Fig. 15(a), each fixed station 3 may be configured to have at least three or more fixed transmitting and receiving antennas 3b arranged at predetermined intervals on a circumference centered on a predetermined position coordinate within the area. In this case, the distance between opposing transmitting and receiving antennas 3b is set to at least half the wavelength λ of the radio wave transmitted by the mobile station 5, for example, 1λ, similar to the rotation diameter φ of the transmitting and receiving antenna 3a in the above-mentioned embodiment. Furthermore, the arrangement intervals of the transmitting and receiving antennas 3b on the circumference centered on the predetermined position coordinate are set to, for example, 10° intervals.

[0079] 15(b), each base station 3 may be configured to have three transmitting and receiving antennas 3b at each vertex of a triangle surrounding a predetermined position coordinate within the area AR. In this case, the distance between each vertex of the triangle is set to at least half the wavelength λ of the radio wave transmitted by the mobile station 5, for example, 1λ. Furthermore, it is desirable that the triangle be an equilateral triangle with the predetermined position coordinate as its circumcenter.

[0080] 15(c), each base station 3 may be configured to have four transmitting and receiving antennas 3b provided at each vertex of a rectangle surrounding a predetermined position coordinate within the area AR. In this case, the distance between each vertex of the rectangle is set to at least half the wavelength λ of the radio wave transmitted by the mobile station 5, for example, 1λ. Furthermore, it is desirable that the rectangle be a square in which the predetermined position coordinate is equidistant from each vertex.

[0081] In this way, when the fixed station 3 is configured to have three or more transmitting / receiving antennas 3b fixedly arranged at three or more points surrounding a predetermined position coordinate within the area, the reference radio wave intensity acquisition step ST1 and the mobile station radio wave intensity acquisition step ST2 in the location estimation method for the mobile station 5 shown in the flowchart of Figure 3 are performed as follows.

[0082] In other words, in the reference radio wave intensity acquisition step ST1, the transmitting / receiving antennas 3b installed at four or more fixed stations, which are placed at at least three points surrounding a predetermined position coordinate within the area and which transmit and receive radio waves simultaneously, are each made to receive at each point the radio waves simultaneously transmitted from the transmitting / receiving antennas 3b installed at the other fixed stations 3, and a reference radio wave intensity is acquired between each fixed station 3, which is the average of the reception intensities of the radio waves simultaneously received at each point of the transmitting / receiving antennas 3b.

[0083] In the mobile station radio wave intensity acquisition step ST2, the radio waves transmitted from the mobile station 5 are received by the transmitting / receiving antennas 3b installed at each point of the fixed station 3, and the mobile station radio wave intensity, which is the average of the reception intensities of the radio waves simultaneously received at each point by the transmitting / receiving antennas 3b, is acquired for each of the fixed stations 3 and the mobile station 5.

[0084] Based on the reference radio wave intensity and mobile station radio wave intensity thus acquired, distance calculation step ST3 and position calculation step ST4 shown in FIG. 3 are performed in the same manner as in the above embodiment, and the position of the mobile station 5 is estimated in the same manner as in the above embodiment.

[0085] According to the location estimation system and location estimation method according to the modified example of the above embodiment, the mobile station radio wave strength between each fixed station 3 and the mobile station 5 is obtained by averaging radio waves simultaneously received from the mobile station 5 by the transmitting and receiving antennas 3b of each fixed station 3, which are arranged at at least three points surrounding a predetermined position coordinate within the area AR. Therefore, even if the mobile station 5 is stationary and not moving, the obtained mobile station radio wave strength is a moving average, since the transmitting and receiving antennas 3b on the fixed station 3 side are arranged at at least three points surrounding the predetermined position coordinate within the area AR.

[0086] Furthermore, the reference radio wave strength between each of the fixed stations 3 is obtained by averaging the reception strength of radio waves transmitted from each of the transmitting and receiving antennas 3b installed at the other fixed stations 3, which are received at each point by the transmitting and receiving antennas 3b installed at each of the fixed stations 3. The transmitting and receiving antennas 3b installed at each of the fixed stations 3 are respectively arranged at at least three points surrounding a predetermined position coordinate within the area AR, and on the transmitting side, radio waves are simultaneously transmitted from each point to the other fixed stations 3, and on the receiving side, radio waves transmitted from the other fixed stations 3 are simultaneously received by the transmitting and receiving antennas 3b installed at each point. Therefore, the reference radio wave strength between each of the fixed stations 3 is stable and proportional in the logarithmic domain to the distance between the average position of the transmitting and receiving antennas 3b on the receiving side and the average position of the transmitting and receiving antennas 3b on the transmitting side.

[0087] Therefore, in the position estimation system and position estimation method according to this modified example, the fixed station-to-mobile station distance calculated by the distance calculation unit 17A based on the ratio between the reference radio wave strength between the fixed stations 3 and the mobile station radio wave strength between each fixed station 3 and the mobile station 5, and the position coordinates of the mobile station 5 within the area AR calculated by the position calculation unit 17B based on this fixed station-to-mobile station distance, become stable, making it possible to perform stable position estimation of the mobile station 5.

[0088] [Second Embodiment] Next, a location estimation system and a location estimation method according to a second embodiment of the present invention will be described.

[0089] The position estimation system and method according to the second embodiment differ from those according to the first embodiment in that the position of the mobile station 5 is estimated by a position calculation unit 17B based on the principle of trilateration. In other respects, the position estimation system and method are the same as those according to the first embodiment.

[0090] For this reason, the position estimation system according to the second embodiment requires three or more fixed stations 3, distance calculation unit 17A calculates the fixed-station-mobile-station distances between each of the three or more fixed stations and mobile station 5, and position calculation unit 17B needs to calculate the position coordinates of mobile station 5 within area AR based on the three or more fixed-station-mobile-station distances. In this second embodiment, as in the first embodiment, four fixed stations are deployed, distance calculation unit 17A calculates the fixed-station-mobile-station distances between each of the four fixed stations and mobile station 5, and position calculation unit 17B calculates the position coordinates of mobile station 5 within area AR based on the four fixed-station-mobile-station distances.

[0091] The position calculation method in the second embodiment differs from that in the first embodiment in that the position calculation step ST4 in FIG. 3 is performed as follows.

[0092] [Position calculation step] The position calculation unit 17B calculates the position coordinates within the area of ​​the mobile station 5 from the fixed station-to-mobile station distances L1 to L4 calculated by the distance calculation unit 17A in the distance calculation step ST3 as described above. This position calculation is performed based on the principle of trilateration using the fixed station-to-mobile station distances L1 to L4, as shown in Fig. 16. That is, the location of the mobile station 5 is determined by the intersection IP of a circle C1 centered at the fixed station 3 (ID1) and having a radius of the fixed station-to-mobile station distance L1, a circle C2 centered at the fixed station 3 (ID2) and having a radius of the fixed station-to-mobile station distance L2, a circle C3 centered at the fixed station 3 (ID3) and having a radius of the fixed station-to-mobile station distance L3, and a circle C4 centered at the fixed station 3 (ID4) and having a radius of the fixed station-to-mobile station distance L4. The position calculation unit 17B calculates the position coordinates of the mobile station 5.

[0093] When the error in the distances L1 to L4 between the fixed station and the mobile station is small, the intersection point IP is obtained. When the error is large, in this embodiment, an error function is calculated, and a solution that minimizes the squared error value (evaluation function value) of the error function is found by the least squares method (linear least squares method), and the position coordinates within the area of ​​the mobile station 5 are calculated. This calculation is similar to general trilateration, so details are omitted.

[0094] The position estimation system and position estimation method according to the second embodiment also achieve the same effects as the position estimation system and position estimation method according to the first embodiment, and it becomes possible to perform stable position estimation of the mobile station 5 even when the mobile station 5 is installed on an object that is normally stationary and does not move, such as equipment and materials at a construction site.

[0095] In each of the above embodiments and variations, the reference radio wave intensity acquired in the reference radio wave intensity acquisition step ST1 may be acquired at regular intervals or at predetermined time intervals (for example, once a day or once an hour).

[0096] Furthermore, in the mobile station radio wave intensity acquisition step ST2, in the above example, the radio waves transmitted from the mobile station 5 are received by the transmitting / receiving antennas 3a and 3b of the fixed station 3, and the radio wave intensity acquisition unit 7 acquires the mobile station radio wave intensity from the fixed station 3. However, conversely, the mobile station 5 may receive the radio waves transmitted from the transmitting / receiving antennas 3a and 3b of the fixed station 3, and the radio wave intensity acquisition unit may acquire the mobile station radio wave intensity from the mobile station 5. [Explanation of symbols]

[0097] 1. Location estimation system 3…Fixed station 3a, 3b...Transmitting and receiving antennas 5...Mobile station 7...Radio wave intensity acquisition unit 9...Information terminal 11. Communications Department 13...Input section 15...Data storage unit 17...Control unit (mobile station position estimation unit) 17A…Distance calculation section 17B…Position calculation unit 19...Display section

Claims

1. three or more or four or more fixed stations that rotate at a predetermined radius around a predetermined position coordinate within the area and have transmitting and receiving antennas that transmit and receive radio waves at each of at least three or more rotational positions, and that can transmit and receive radio waves to and from each other; a mobile station capable of transmitting radio waves that reach the transmitting / receiving antenna provided in each of the fixed stations; a radio wave strength acquisition unit that acquires a reference radio wave strength obtained by averaging the reception strength of radio waves transmitted from the respective points of the transmitting and receiving antennas provided in the other fixed stations and received at the respective points by the transmitting and receiving antennas provided in the respective fixed stations, and a mobile station radio wave strength obtained by averaging the reception strength of radio waves transmitted from the mobile stations and received at the respective points by the transmitting and receiving antennas provided in the respective fixed stations; a mobile station position estimation unit that estimates position coordinates of the mobile station within the area based on the reference radio wave intensity and the mobile station radio wave intensity acquired from the radio wave intensity acquisition unit, The mobile station position estimation unit a distance calculation unit that calculates a fixed-station-to-mobile-station distance between each of the three or more or four or more fixed stations and the mobile station based on a ratio between the reference radio wave strength between each of the fixed stations and the mobile station radio wave strength between each of the fixed stations and the mobile station; a position calculation unit that calculates a position coordinate of the mobile station within its area based on three or more or four or more distances between the fixed station and the mobile station; A location estimation system having:

2. 2. The position estimation system according to claim 1, wherein each of the fixed stations has, instead of the transmitting and receiving antennas that transmit and receive radio waves at each rotational position, three transmitting and receiving antennas that are provided at each vertex of a triangle that surrounds a predetermined position coordinate within the area.

3. The position estimation system according to claim 1, characterized in that each of the fixed stations has four transmitting and receiving antennas provided at each vertex of a rectangle surrounding a predetermined position coordinate within the area, instead of the transmitting and receiving antennas that transmit and receive radio waves at each rotational position.

4. 2. The position estimation system according to claim 1, wherein each of the fixed stations has at least three or more transmitting and receiving antennas arranged at predetermined intervals on a circumference centered on a predetermined position coordinate within the area, instead of the transmitting and receiving antennas that transmit and receive radio waves at each rotational position.

5. a reference radio wave intensity acquisition step of rotating a transmitting / receiving antenna at each of three or more or four or more fixed stations that rotate at a predetermined radius around a predetermined position coordinate within an area and transmit and receive radio waves at each of at least three or more rotational positions, the transmitting / receiving antenna being rotated while receiving radio waves sequentially transmitted from each of the rotational positions of the transmitting / receiving antennas provided at other fixed stations, and acquiring a reference radio wave intensity between the fixed stations by averaging the reception intensities of radio waves sequentially received at each of the rotational positions of the transmitting / receiving antennas; a mobile station radio wave intensity acquisition step of rotating the transmitting / receiving antenna provided in the fixed station and having the transmitting / receiving antenna receive radio waves transmitted from mobile stations at each of the rotational positions, and acquiring a mobile station radio wave intensity between each of the fixed stations and the mobile station by averaging the reception intensities of radio waves sequentially received by the transmitting / receiving antenna at each of the rotational positions; a distance calculation step of calculating a fixed station-to-mobile station distance between each of the three or more or four or more fixed stations and the mobile station based on a ratio between the reference radio wave strength between each of the fixed stations and the mobile station radio wave strength between each of the fixed stations and the mobile station; a position calculation step of calculating a position coordinate of the mobile station within the area based on three or more or four or more distances between the fixed station and the mobile station; A location estimation method comprising:

6. a reference radio wave intensity acquisition step of averaging the reception intensities of radio waves simultaneously received at each of the transmitting and receiving antennas at the respective points by causing at least three or more transmitting and receiving antennas provided at each of three or four or more fixed stations, the transmitting and receiving antennas being arranged at at least three or more points surrounding a predetermined position coordinate within the area and simultaneously transmitting and receiving radio waves, to be received at each of the points by the transmitting and receiving antennas provided at the other fixed stations; a mobile station radio wave intensity acquisition step of receiving radio waves transmitted from a mobile station at the transmitting / receiving antenna provided at each of the locations of the fixed station, and acquiring a mobile station radio wave intensity between each of the fixed stations and the mobile station, the mobile station radio wave intensity being an average of reception intensities of radio waves simultaneously received at each of the locations by the transmitting / receiving antenna; a distance calculation step of calculating a fixed station-to-mobile station distance between each of the three or more or four or more fixed stations and the mobile station based on a ratio between the reference radio wave strength between each of the fixed stations and the mobile station radio wave strength between each of the fixed stations and the mobile station; a position calculation step of calculating a position coordinate of the mobile station within the area based on three or more or four or more distances between the fixed station and the mobile station; A location estimation method comprising:

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