Positioning system and positioning program

Abstract

The system uses signals transmitted from LEO satellites, whose orbital ephemeris is unknown and which are asynchronous, to accurately measure the position of mobile terminals. [Solution] The positioning system (1) includes a first receiving unit (221) mounted on a mobile terminal (2) that receives multiple satellite signals transmitted by multiple satellites (4), a second receiving unit (321) mounted on a base station (3) fixed at a predetermined location that receives multiple satellite signals, and a terminal position estimation unit (222, 322, 622) that calculates a pseudo-distance double difference based on multiple first reception times when the first receiving unit receives multiple satellite signals and multiple second reception times when the second receiving unit receives multiple satellite signals, and estimates the position of the mobile terminal (2) based on the pseudo-distance double difference. The pseudo-distance double difference represents the difference between a first pseudo-distance difference, which is the difference in pseudo-distance from two LEO satellites (4A, 4B) to the mobile terminal, and a second pseudo-distance difference, which is the difference in pseudo-distance from the two LEO satellites (4A, 4B) to the base station.

Description

[Technical Field]

[0001] The present invention relates to a positioning system and a positioning program, and is suitably used, for example, for measuring the position of a mobile terminal using signals from artificial satellites. [Background technology]

[0002] To reduce traffic accidents, there is a need to make it easier for vehicles traveling near pedestrians to detect pedestrians in locations with poor visibility. In this regard, there is a technology that uses GNSS to determine position on a pedestrian's mobile device and transmits the results wirelessly to an in-vehicle terminal. However, in environments such as urban areas where buildings block or reflect GNSS positioning signals, the accuracy of GNSS positioning may not be sufficient.

[0003] In relation to the above, Non-Patent Document 1 (Suhua Tang and Sadao Obana, “Exploiting phase difference of arrival of V2X signals for pedestrian positioning: Key methods and simulation evaluation,” IEEE Access, vol. 11, pp. 88040-88048, Aug. 2023.) discloses a technique for measuring the position of a mobile terminal by having multiple receiving devices, whose timestamps are synchronized and whose respective positions are known, receive OFDM (Orthogonal Frequency Division Multiplexing) signals transmitted from the mobile terminal. This technique makes it possible to measure the position of the mobile terminal by accurately measuring the distance from the mobile terminal to each receiving device using the phase information of the radio signal. However, this technique requires at least four receiving devices that are arranged to receive the same OFDM signal transmitted by the mobile terminal to be positioned simultaneously. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Suhua Tang and Sadao Obana, “Exploiting phase difference of arrival of V2X signals for pedestrian positioning: Key methods and simulation evaluation,” IEEE Access, vol. 11, pp. 88040-88048, Aug. 2023. [Overview of the project] [Problems that the invention aims to solve]

[0005] The inventor considered using LEO (Low Earth Orbit) satellites to measure the position of a mobile terminal, instead of the GNSS satellites and receiving equipment mentioned above. LEO satellites include communication satellites planned for use in 6G (sixth-generation) communication technology. The total number of LEO satellites is far greater than that of GNSS satellites. Also, because LEO satellites orbit lower than GNSS satellites, their signal strength is stronger. On the other hand, unlike GNSS satellites, LEO satellites do not have an orbital ephemeris, their exact position is unknown, and they do not transmit positioning signals. Furthermore, LEO satellites are not time-synchronized with each other. Therefore, a new positioning method is needed to measure the position of a mobile terminal using LEO satellites.

[0006] In light of the above circumstances, one of the objectives of this disclosure is to provide a positioning system and positioning program for accurately determining the position of a mobile terminal using signals transmitted from an asynchronous LEO satellite with an unknown orbital ephemeris. Other challenges and novel features will become apparent from the description herein and the accompanying drawings. [Means for solving the problem]

[0007] The means for solving the problem are described below using the numbers and symbols used in the embodiments for carrying out the invention. These numbers and symbols are added in parentheses for reference to show an example of the correspondence between the claims and the embodiments for carrying out the invention. Therefore, the claims should not be interpreted restrictively because of the parenthetical statements.

[0008] According to one embodiment, the positioning system (1) comprises a first receiving unit (221), a second receiving unit (321), and terminal position estimation units (222, 322, 622). The first receiving unit (221) receives multiple satellite signals transmitted by multiple satellites (4) and is mounted on a mobile terminal (2). The second receiving unit (321) receives multiple satellite signals and is mounted on a reference station (3) fixed at a predetermined location. The terminal position estimation units (222, 322, 622) calculate a pseudo-distance double difference based on multiple first reception times when the first receiving unit (221) receives multiple satellite signals and multiple second reception times when the second receiving unit receives multiple satellite signals, and estimate the position of the mobile terminal (2) based on the pseudo-distance double difference. The pseudo-distance double difference represents the difference between a first pseudo-distance difference and a second pseudo-distance difference. The first pseudo-distance difference represents the difference between the first pseudo-distance from the first satellite (4A) of the multiple satellites (4) to the mobile terminal (2) and the second pseudo-distance from the second satellite (4B) of the multiple satellites (4) to the mobile terminal (2). The second pseudo-distance difference represents the difference between the third pseudo-distance from the first satellite (4A) to the base station (3) and the fourth pseudo-distance from the second satellite (4B) to the base station (3).

[0009] According to one embodiment, the positioning program is used to perform predetermined processing by having the arithmetic unit (22, 32, 62) execute it. This processing includes receiving multiple satellite signals transmitted by multiple satellites (4) with a first receiving unit (221) mounted on a mobile terminal (2) (S2). This processing further includes receiving multiple satellite signals with a second receiving unit mounted on a reference station (3) fixed at a predetermined location (S2). This processing further includes calculating a pseudo-distance double difference (S4) based on multiple mobile reception times when the first receiving unit (221) received multiple satellite signals and multiple second reception times when the second receiving unit (321) received multiple satellite signals. This processing further includes estimating the position of the mobile terminal (2) based on the pseudo-distance double difference (S5). The pseudo-distance double difference represents the difference between a first pseudo-distance difference and a second pseudo-distance difference. The first pseudo-distance difference represents the difference between the first pseudo-distance from the first satellite (4A) of the multiple satellites (4) to the mobile terminal (2) and the second pseudo-distance from the second satellite (4B) of the multiple satellites (4) to the mobile terminal (2). The second pseudo-distance difference represents the difference between the third pseudo-distance from the first satellite (4A) to the base station (3) and the fourth pseudo-distance from the second satellite (4B) to the base station (3). [Effects of the Invention]

[0010] According to one embodiment, the position of a mobile terminal can be accurately measured using signals transmitted from an LEO satellite. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows an example configuration of a positioning system according to one embodiment. [Figure 2] Figure 2 is a block circuit diagram showing an example configuration of a mobile terminal according to one embodiment. [Figure 3] Figure 3 is a block circuit diagram showing one example configuration of a reference station according to one embodiment. [Figure 4] Figure 4 is a block circuit diagram showing an example of a server configuration according to one embodiment. [Figure 5]Figure 5 is a flowchart showing an example of the processing of a positioning program according to one embodiment. [Figure 6] Figure 6 illustrates a method by which a reference station measures the position of an LEO satellite according to one embodiment. [Figure 7] Figure 7 is a diagram illustrating the timing at which a mobile terminal and a reference station receive signals from an LEO satellite according to one embodiment. [Figure 8] Figure 8 is a block circuit diagram showing one example configuration of a mobile terminal according to one embodiment. [Figure 9] Figure 9 is a block circuit diagram showing one example configuration of a reference station according to one embodiment. [Modes for carrying out the invention]

[0012] Referring to the attached drawings, the configurations for implementing the positioning system and positioning program described herein are described below.

[0013] (First embodiment) As shown in Figure 1, a positioning system 1 according to one embodiment includes a mobile terminal 2 and a base station 3. The positioning system 1 may further include a server 6.

[0014] Mobile terminal 2 is the target of positioning by positioning system 1 and may be a mobile device such as a smartphone or tablet owned by a pedestrian or the like, or it may be a terminal mounted on a vehicle. Mobile terminal 2 may be connected to network 5 by wireless communication and communicate with base station 3, server 6, etc. Mobile terminal 2 may receive wireless signals transmitted by LEO satellite 4. Hereafter, various numerical values ​​related to mobile terminal 2 may be represented by symbols with the subscript "r".

[0015] Reference station 3 is fixed on the ground, and its location is known. For example, reference station 3 may be installed on a roadside unit or traffic light located near a road, or on a communication base station located at any location on the ground. The positioning system 1 may include multiple reference stations 3. Reference station 3 may be connected to the network 5 by wired and / or wireless communication and communicate with mobile terminals 2, servers 6, other reference stations 3, etc. Reference station 3 may receive radio signals transmitted by LEO satellites 4. Hereafter, various numerical values ​​related to reference station 3 may be represented by symbols with the subscript "R".

[0016] Server 6 estimates the location of mobile terminal 2 based on various information collected from mobile terminal 2 and base station 3. Server 6 may output information representing the estimated location of mobile terminal 2 to mobile terminal 2, other mobile terminals 2, base station 3, etc. As described later, if mobile terminal 2 and / or base station 3 have some or all of the functions of server 6, the positioning system 1 does not need to include server 6.

[0017] LEO (Low Earth Orbit) satellites 4A, 4B, 4C, and 4D are artificial satellites that orbit the Earth at relatively low altitudes. Hereafter, various numerical values ​​related to the first LEO satellite 4A, the second LEO satellite 4B, the third LEO satellite 4C, and the fourth LEO satellite 4D may be represented by symbols with superscripts "s," "n," "v," and "u," respectively. When LEO satellites 4A, 4B, 4C, and 4D are not distinguished, they may be collectively referred to as LEO satellite 4. For example, the orbit of LEO satellite 4 is less than 2,000 km above the Earth's surface. LEO satellite 4 is mainly used for wireless communication such as 6G (Generation) communication. On the other hand, GNSS (Global Navigation Satellite System) satellites used for positioning orbit in medium orbits at altitudes of 2,000 km to 36,000 km above the Earth's surface. Therefore, the signals received on the ground from LEO satellites 4 are stronger than the signals from GNSS satellites. Also, the total number of LEO satellites 4 that can simultaneously receive signals from the ground is far greater than the total number of GNSS satellites that can simultaneously receive signals from the ground.

[0018] However, the LEO satellite 4, which is for communication, is not intended for positioning. Therefore, the clock circuit on board LEO satellite 4 is less accurate than the atomic clock on board GNSS satellites, and the time between multiple LEO satellites 4 is basically asynchronous. Also, there is basically no orbital ephemeris for LEO satellite 4, and the exact position of LEO satellite 4 at any given moment is unknown. Furthermore, the signals transmitted by LEO satellite 4 are communication signals, not positioning signals. More specifically, LEO satellite 4 transmits synchronization signals using OFDM (Orthogonal Frequency Division Multiplexing) signals for communication. Under these conditions, the inventor considered using LEO satellite 4 for positioning of mobile terminal 2.

[0019] As shown in Figure 2, the mobile terminal 2 according to one embodiment may be configured as a so-called computer. In the example in Figure 2, the mobile terminal 2 comprises a bus 21, an arithmetic unit 22, a storage device 23, a communication device 24, and an input / output device 25. The bus 21 may be configured to enable communication between the arithmetic unit 22, the storage device 23, the communication device 24, and the input / output device 25.

[0020] The arithmetic unit 22 implements the processing of the receiving unit 221 and the transmitting unit 223 by executing at least a part of the work management program according to one embodiment. The receiving unit 221 and the transmitting unit 223 are virtual functional blocks that execute processing realized by the cooperation of the arithmetic unit 22 and the storage device 23. The receiving unit 221 receives the satellite signal transmitted by the LEO satellite 4, associates the signal identification information contained in the satellite signal with the reception time information representing the time the satellite signal was received, and stores it in the data storage unit 232 of the storage device 23. The transmitting unit 223 transmits terminal identification information representing the mobile terminal 2, the signal identification information contained in the satellite signal received from the LEO satellite 4, and the reception time information associated with the signal identification information to the server 6.

[0021] The storage device 23 comprises a program storage unit 231 and a data storage unit 232. At least a portion of the positioning program may be read from an external recording medium 230 and stored in the program storage unit 231. The recording medium 230 may be a non-transitory and tangible medium. The data storage unit 232 stores terminal identification information representing the mobile terminal 2. The data storage unit 232 may further store signal identification information representing the satellite signal received from the LEO satellite 4 and reception time information associated with the signal identification information.

[0022] The communication device 24 receives satellite signals from the LEO satellite 4. The communication device 24 also communicates with external devices, including the base station 3 and the server 6, via wireless communication over the network 5. At least a portion of the positioning program may be received from an external source by the communication device 24 and stored in the program storage unit 231.

[0023] The input / output device 25 outputs information to the user of the mobile terminal 2 and accepts operations input by the user. As an example, the input / output device 25 includes a touch panel that integrates a display device that outputs an image and a touch pad that accepts input via touch operation.

[0024] As shown in Figure 3, the reference station 3 in one embodiment may be configured as a so-called computer. In the example in Figure 3, the reference station 3 includes a bus 31, an arithmetic unit 32, a storage device 33, a communication device 34, and an input / output device 35. The bus 31 may be configured to enable communication between the arithmetic unit 32, the storage device 33, the communication device 34, and the input / output device 35.

[0025] The arithmetic unit 32 implements the processing of the receiving unit 321, the transmitting unit 323, and the satellite position estimation unit 324 by executing at least a part of the work management program according to one embodiment. Each of the receiving unit 321, the transmitting unit 323, and the satellite position estimation unit 324 is a virtual functional block that executes processing realized by the cooperation of the arithmetic unit 32 and the storage device 33. The receiving unit 321 receives the satellite signal transmitted by the LEO satellite 4, associates the signal identification information contained in the satellite signal with the reception time information representing the time the satellite signal was received, and stores it in the data storage unit 332 of the storage device 33. The transmitting unit 323 transmits the reference station identification information representing the reference station 3, the signal identification information contained in the satellite signal received from the LEO satellite 4, and the reception time information associated with the signal identification information to the server 6. The transmitting unit 323 may further transmit the reference station identification information, the signal identification information, and the reception time information to other reference stations 3. The receiving unit 321 may also receive base station identification information, signal identification information, and reception time information from other base stations 3. The satellite position estimation unit 324 estimates the position of the LEO satellite 4 based on the satellite signal received from the LEO satellite 4, the base station identification information, signal identification information, and reception time information received from other base stations 3, and stores the estimated satellite position information representing the position of the LEO satellite 4 in the data storage unit 332. The transmitting unit 323 may further transmit the satellite position information to the server 6.

[0026] The storage device 33 comprises a program storage unit 331 and a data storage unit 332. At least a portion of the positioning program may be read from an external recording medium 330 and stored in the program storage unit 331. The recording medium 330 may be a non-temporary, tangible medium. The data storage unit 332 stores base station identification information representing base station 3. The data storage unit 332 may further store signal identification information representing satellite signals received from LEO satellites 4 and reception time information associated with the signal identification information. The data storage unit 332 may further store base station identification information, signal identification information, and reception time information received from other base stations 3.

[0027] The communication device 34 receives satellite signals from the LEO satellite 4. The communication device 34 also communicates with external devices, including mobile terminals 2 and servers 6, via wireless communication over the network 5. At least a portion of the positioning program may be received by the communication device 34 from an external source and stored in the program storage unit 331. The communication device 34 may also receive base station identification information, signal identification information, and reception time information from other base stations 3.

[0028] The input / output device 35 outputs information to the user of the base station 3 and accepts input operations from the user. For example, the input / output device 25 includes a display device that outputs images and buttons that accept input.

[0029] As shown in Figure 4, the server 6 may be configured as a so-called computer. In the example in Figure 4, the base station 3 includes a bus 61, an arithmetic unit 62, a storage device 63, a communication device 64, and an input / output device 65. The bus 61 may be configured to enable communication between the arithmetic unit 62, the storage device 63, the communication device 64, and the input / output device 65.

[0030] The arithmetic unit 62 implements the processing of the receiving unit 621, the terminal position estimation unit 622, and the transmitting unit 623 by executing at least a part of the work management program according to one embodiment. The receiving unit 621, the terminal position estimation unit 622, and the transmitting unit 623 are each virtual functional blocks that execute processing realized by the cooperation of the arithmetic unit 62 and the storage device 63. The receiving unit 621 receives terminal identification information, signal identification information, and reception time information transmitted by the mobile terminal 2, and reference station identification information, signal identification information, reception time information, and satellite position information transmitted by the reference station 3, and stores them in the data storage unit 632. The terminal position estimation unit 622 estimates the position of the mobile terminal 2 based on the terminal identification information, signal identification information, and reception time information received from the mobile terminal 2, and the reference station identification information, signal identification information, reception time information, and satellite position information received from the reference station 3, and stores terminal position information representing the estimated position of the mobile terminal 2 in the data storage unit 632. The transmitting unit 623 transmits terminal location information to the mobile terminal 2 via the network 5 and / or the base station 3. The transmitting unit 623 may also transmit the terminal location information to external terminals other than the mobile terminal 2, such as the base station 3 located near the mobile terminal 2, or an onboard terminal installed in a vehicle.

[0031] The storage device 63 comprises a program storage unit 631 and a data storage unit 632. At least a portion of the positioning program may be read from an external recording medium 630 and stored in the program storage unit 631. The recording medium 630 may be a non-temporary, tangible medium. The data storage unit 632 stores terminal identification information, signal identification information, and reception time information received from the mobile terminal 2, and base station identification information, signal identification information, reception time information, and satellite position information received from the base station 3. The data storage unit 632 may further store terminal position information.

[0032] The communication device 64 receives terminal identification information, signal identification information, and reception time information transmitted by the mobile terminal 2, and receives base station identification information, signal identification information, reception time information, and satellite position information transmitted by the base station 3. The communication device 64 also transmits terminal position information to the mobile terminal 2. The communication device 64 may further transmit terminal position information to the base station 3 and / or an external terminal.

[0033] The input / output device 65 outputs information to the user of the server 6 and accepts input operations from the user. For example, the input / output device 25 includes a display device that outputs images and a keyboard or mouse that accepts input.

[0034] Referring to the flowchart in Figure 5, an example of the processing of a positioning program according to one embodiment will be described. The positioning program includes multiple parts, which are executed by the arithmetic unit 22 of the mobile terminal 2 in Figure 2, the arithmetic unit 32 of the reference station 3 in Figure 3, and the arithmetic unit 62 of the server 6 in Figure 4. Each of the multiple parts included in the positioning program may be started when the mobile terminal 2 in Figure 2, the reference station 3 in Figure 3, and the server 6 in Figure 4 are started up.

[0035] When the positioning program starts, step S1 in Figure 5 is executed. In step S1, the satellite position estimation unit 324 of the reference station 3 in Figure 3 estimates the position of the LEO satellite 4. For example, the satellite position estimation unit 324 may estimate the position of the LEO satellite 4 using the method described in Non-Patent Document 1 (Suhua Tang and Sadao Obana, “Exploiting phase difference of arrival of V2X signals for pedestrian positioning: Key methods and simulation evaluation,” IEEE Access, vol. 11, pp. 88040-88048, Aug. 2023.).

[0036] More specifically, as shown in Figure 6, in each of the multiple reference stations 3 (3A, 3B, 3C, 3D), the receiving unit 321 in Figure 3 receives the satellite signal transmitted by the LEO satellite 4 at the same time. Here, the satellite signal may be an OFDM-type communication synchronization signal. Also, the times of the multiple reference stations 3 (3A, 3B, 3C, 3D) are synchronized with sufficient precision. The receiving unit 321 associates the signal identification information contained in the received satellite signal with the reception time information representing the time the satellite signal was received and the phase information representing the phase at the time the satellite signal was received, and stores this information in the data storage unit 332 of the reference station 3 equipped with the receiving unit 321.

[0037] Subsequently, at least one of the reference stations 3 (3A, 3B, 3C, 3D) in Figure 6, reference station 3 (3A), receives and aggregates signal identification information, reception time information, and phase information, as well as reference station position information representing the location of each of the other reference stations 3 (3B, 3C, 3D), respectively. Hereafter, for distinction, the at least one reference station 3 that aggregates the various information will be called the main reference station 3A, and the other reference stations 3 will be called sub-reference stations 3B, 3C, 3D. The transmitting unit 323 of each sub-reference station 3B, 3C, 3D transmits the signal identification information, reception time information, phase information, and reference station position information stored in the data storage unit 332 of the sub-reference station 3B, 3C, 3D to the main reference station 3A. The receiving unit 321 of the main reference station 3A receives signal identification information, reception time information, phase information, and reference station position information transmitted by each of the sub-reference stations 3B, 3C, and 3D, and stores them in the data storage unit 332 of the main reference station 3A. At this time, the receiving unit 321 of the main reference station 3A confirms that the signal identification information and reception time information received from the sub-reference stations 3B, 3C, and 3D match the signal identification information and reception time information stored in the data storage unit 332 of the main reference station 3A, respectively.

[0038] After that, the satellite position estimator 324 of the main reference station 3A estimates the position of the LEO satellite 4 based on the signal identification information, reception time information, phase information, and reference station position information aggregated from the secondary reference stations 3B, 3C, and 3D, and the signal identification information, reception time information, phase information, and reference station position information stored in the data storage unit 332 of the main reference station 3A. The position of the LEO satellite 4 is represented as (x, y, z) in a rectangular coordinate system, and the positions of the reference stations 3A, 3B, 3C, and 3D are (x B , y A , z A ), (x B , y B , z B ), (x C , y C , z C ), (x D , y D , z D ), respectively. When represented in this way, the position of the LEO satellite 4 is calculated based on the system of simultaneous equations shown in the following "Equation 1".

[0039]

Equation

[0040] In the above equation "Equation 1," the pseudo-distance is the actual distance plus various errors due to actual measurement. For example, these errors may include ionospheric errors caused by the electromagnetic waves of the signal transmitted by LEO satellite 4 passing through the ionosphere, tropospheric errors caused by the electromagnetic waves passing through the troposphere, time difference errors caused by time errors between LEO satellite 4 and base station 3, and thermal noise errors caused by thermal noise of base station 3. The pseudo-distance ρ from LEO satellite 4 to main base station 3A. A And the pseudo-distance ρ from LEO satellite 4 to each of the sub-reference stations 3B, 3C, and 3D. B ρ C ρ D The difference is calculated based on phase information. Furthermore, the coordinates (x) representing the respective positions of base station 3 (3A, 3B, 3C, 3D) are used. A ,y A ,z A ), (x B ,y B ,z B ), (x C ,y C ,z C ), (x D ,y D ,z D ) is known. Therefore, the system of equations in "Equation 1" above contains three mutually independent equations, so the three unknowns representing the coordinates of the position of LEO satellite 4 can be calculated. For this reason, in the positioning system 1 according to one embodiment, as shown in Figure 6, at least four reference stations 3 (3A, 3B, 3C, 3D) are used to estimate the position of one LEO satellite 4. The transmitter 323 of the main reference station 3A in Figure 3 transmits satellite position information representing the estimated position of LEO satellite 4 to the server 6.

[0041] In one embodiment of the positioning system 1, as shown in Figure 1, the position of the mobile terminal 2 is estimated using satellite signals transmitted by at least four LEO satellites 4A, 4B, 4C, and 4D. Therefore, in one embodiment of the positioning system 1, the positions of at least four LEO satellites 4A, 4B, 4C, and 4D are estimated using the method described above. Some or all of the four reference stations 3 used to estimate the position of the first LEO satellite 4A may be used to estimate the positions of the second LEO satellite 4B, the third LEO satellite 4C, and the fourth LEO satellite 4D.

[0042] After step S1 in Figure 5, step S2 is executed. In step S2, the receiving unit 221 of the mobile terminal 2 in Figure 2 and the receiving unit 321 of the reference station 3 in Figure 3 each receive satellite signals from the LEO satellite 4. Hereafter, the symbols s, n, v, u, r, and R in the formulas corresponding to the LEO satellites 4A, 4B, 4C, 4D, the mobile terminal 2, and the reference station 3 may be enclosed in parentheses after their respective notations.

[0043] More specifically, as shown in Figure 7, the first LEO satellite 4A(n) transmits at time t n and transmission time t' n Then, two satellite signals are transmitted. Subsequently, the first LEO satellite 4A(n) transmits at time t n The satellite signal transmitted at t' is called the first forward signal, and the first LEO satellite 4A transmitted at t' n The satellite signal transmitted is called the first post-transmission signal.

[0044] Subsequently, the receiving unit 221 of the mobile terminal 2(r) in Figure 2 receives the reception time t in Figure 7. r n and reception time t' r n The first forward signal and the first backward signal are received, respectively. The receiving unit 221 in Figure 2 receives the identification information contained in the first forward signal and the reception time t when the first forward signal was received. r n The received time information representing the first after signal, the identification information contained in the first after signal, and the received time t' when the first after signal was received. r nThe reception time information representing the reception time in Figure 7 is stored in the data storage unit 232. Also, the receiving unit 321 of the reference station 3(R) in Figure 3 stores the reception time t in Figure 7. R n and reception time t' R n The first forward signal and the first backward signal are received, respectively. The receiving unit 321 in Figure 3 receives the identification information contained in the first forward signal and the reception time t when the first forward signal was received. R n The received time information representing the first after signal, the identification information contained in the first after signal, and the received time t' when the first after signal was received. R n The reception time information representing this is stored in the data storage unit 332.

[0045] Similarly, the second LEO satellite 4B(s) transmitted at time t s and transmission time t' s Then, two satellite signals are transmitted. Subsequently, the second LEO satellite 4B(s) transmits at time t s The satellite signal transmitted at time t' is called the second forward signal, and the second LEO satellite 4B(s) transmitted at time t' s The satellite signal transmitted is called the second post-transmission signal.

[0046] Subsequently, the receiving unit 221 of the mobile terminal 2 in Figure 2 receives the reception time t in Figure 7. r s and reception time t' r s The second forward signal and the second backward signal are received, respectively. The receiving unit 221 in Figure 2 receives the identification information contained in the second forward signal and the reception time t when the second forward signal was received. r s The received time information representing the second follow signal, the identification information contained in the second follow signal, and the received time t' when the second follow signal was received. r s The reception time information representing the reception time t in Figure 7 is stored in the data storage unit 232. Also, the receiving unit 321 of the reference station 3 in Figure 3 stores the reception time t in Figure 7. R s and reception time t' R s The second forward signal and the second backward signal are received, respectively. The receiving unit 321 in Figure 3 receives the identification information contained in the second forward signal and the reception time t when the second forward signal was received.R s The reception time information indicating R , the identification information included in the second subsequent signal, and the reception time t' when the second subsequent signal is received R s The reception time information indicating R and s are stored in the data storage unit 332.

[0047] Thereafter, the transmission unit 223 of the mobile terminal 2 in FIG. 2 transmits the identification information included in the first destination signal, the reception time t when the first destination signal is received r n The reception time information indicating r and n , the identification information included in the first subsequent signal, and the reception time t' when the first subsequent signal is received r n The reception time information indicating r and n , the identification information included in the second destination signal, and the reception time t when the second destination signal is received r s The reception time information indicating r and s , the identification information included in the second subsequent signal, and the reception time t' when the second subsequent signal is received r s The reception time information indicating r and s are transmitted to the server 6 in FIG. 4. Similarly, the transmission unit 323 of the reference station 3 in FIG. 3 transmits the identification information included in the first destination signal, the reception time t when the first destination signal is received R n The reception time information indicating R and n , the identification information included in the first subsequent signal, and the reception time t' when the first subsequent signal is received R n The reception time information indicating R and n , the identification information included in the second destination signal, and the reception time t when the second destination signal is received R s The reception time information indicating R and s , the identification information included in the second subsequent signal, and the reception time t' when the second subsequent signal is received R s The reception time information indicating R and s are transmitted to the server 6 in FIG. 4. The reception unit 621 of the server 6 stores the received various information in the data storage unit 632. The reception unit 621 confirms that the first destination signal, the first subsequent signal, the second destination signal, and the second subsequent signal received by the mobile terminal 2 and the reference station 3 are the same based on the received identification information.

[0048] After step S2 in Figure 5, step S3 is executed. In step S3, the terminal location estimation unit 622 of server 6 in Figure 4 calculates the double difference of reception times. Here, the double difference of reception times is defined as shown in equation "Equation 2" below.

[0049]

number

[0050] This section explains how to correct the reception time of mobile terminal 2. Generally speaking, the clock circuit installed in mobile terminal 2 is smaller and less expensive than the clock circuit installed in base station 3, and therefore has lower accuracy. However, the clock circuits of mobile terminal 2 and base station 3 may have a function to periodically synchronize their time by communicating with an external base station or the like. In this case, the relationship shown in equation "Equation 3" below holds true.

[0051]

number

[0052] Furthermore, in one embodiment, it is assumed that the clocks of the mobile terminal 2 and the reference station 3 stabilize within a short period of time. In this case, when measuring the same time interval, the ratio of the values ​​is constant and is the reciprocal of the ratio of the clock frequencies. In this case, the following relationship, "Equation 4," holds true.

[0053]

number

[0054] When using the time of base station 3 as the reference, the time difference between the two reception times when mobile terminal 2 receives the two satellite signals is corrected by the proportionality coefficient k obtained by equation "Equation 4" above. This correction model then corrects the double difference t of the reception times obtained by equation "Equation 2" above. r,R n,s This can improve accuracy.

[0055] After step S3 in Figure 5, step S4 is executed. In step S4, the terminal position estimation unit 622 of server 6 in Figure 4 calculates the double difference of the pseudo-distance. Here, the double difference of the pseudo-distance is defined as shown in equation "Equation 5" below.

[0056]

number

[0057] When measurement errors can be ignored, in equation "5" above, the pseudo-distance ρ r n ρ r s ρ R n ρ R s Each of them satisfies the following relationship, "Equation 6".

[0058]

number

[0059] The double difference ρ of the pseudo-distance defined as in equation "Equation 5" above r,R n,s Using the relationship in equation "Equation 6" above, the transmission time t n ,t s These cancel each other out, and the double difference t of the reception time can be obtained as shown in equation "Equation 2" above. r,R n,s Based on this, it can be calculated as shown in the following equation "Equation 7".

[0060]

number

[0061] The double difference ρ of the pseudo-distance difference r,R n,sHowever, it will be explained that this method has sufficient accuracy as an approximation of the double difference of the actual distance. As described above, the pseudo-distance is calculated by integrating the measured transmission time from when the LEO satellite 4 transmits the satellite signal until when the mobile terminal 2 or reference station 3 receives the satellite signal with the speed of light c in a vacuum. However, since the satellite signal passes through the ionosphere and troposphere, the pseudo-distance calculated based on the measured transmission time of the satellite signal will have errors compared to the actual distance calculated if the generated signal propagated in a vacuum. Furthermore, other errors will occur in the pseudo-distance compared to the actual distance due to the fact that the first LEO satellite 4A and the second LEO satellite 4B are not synchronized in time with the mobile terminal 2 and reference station 3, and due to thermal noise occurring in the mobile terminal 2 and reference station 3. In one embodiment, the relationship between the pseudo-distance, the actual distance, and various errors is approximated as shown in the following equation "Equation 8".

[0062]

number

[0063] In the above equation "Equation 8", when the distance between the mobile terminal 2 and the reference station 3 is sufficiently short, the error ε occurs because the satellite signal transmitted by the first LEO satellite 4A passes through the ionosphere. ion nThe difference between when the mobile terminal 2 and the reference station 3 receive the satellite signal is negligible. Similarly, when the distance between the mobile terminal 2 and the reference station 3 is sufficiently short, the error ε caused by the satellite signal transmitted by the first LEO satellite 4A passing through the troposphere is negligible. trop n The difference in reception between the mobile terminal 2 and the reference station 3 when the satellite signal is received is negligible. Also, when the distance between the mobile terminal 2 and the reference station 3 is sufficiently short, the error ε occurs when the satellite signal transmitted by the second LEO satellite 4B passes through the ionosphere. ion s The difference between when the mobile terminal 2 and the reference station 3 receive the satellite signal is negligible. Similarly, when the distance between the mobile terminal 2 and the reference station 3 is sufficiently short, the error ε occurs as the satellite signal transmitted by the second LEO satellite 4B passes through the troposphere. trop s The difference in reception between the satellite signal received by the mobile terminal 2 and the reference station 3 is negligible.

[0064] As a result, the double difference ρ of the pseudo-distance r,R n,s When calculating the error ε related to the ionosphere, ion n ,ε ion s And the error ε related to the troposphere trop n ,ε trop s This means they all cancel each other out. Substituting equation "Equation 8" above into equation "Equation 5" above, we obtain equation "Equation 9" below.

[0065]

number

[0066] Other error double difference ε r,R n,s At most, other errors ε r n ,ε r s ,ε R n ,ε R s It is less than or equal to the maximum value among them. Therefore, the double difference ρ of the pseudo-distance between mobile terminal 2(r), base station 3(R), first LEO satellite 4A(n), and second LEO satellite 4B(s) r,R n,s The double difference d of the actual distance between mobile terminal 2(r), base station 3(R), first LEO satellite 4A(n), and second LEO satellite 4B(s). r,R n,s The error for is the other error ε r n ,ε r s ,ε R n ,ε R s It is less than or equal to the maximum value among them.

[0067] After step S4 in Figure 5, step S5 is executed. In step S5, the terminal location estimation unit 622 of the server 6 in Figure 4 estimates the location of the mobile terminal 2.

[0068] As described above, the position of reference station 3 is known. Also, as explained in step S1 of Figure 5, the pseudo-position of any LEO satellite 4 at the time it transmits a satellite signal can be estimated. Therefore, the distance from reference station 3 to any LEO satellite 4 at the time of transmission can be calculated based on reference station position information representing the position of reference station 3 and satellite pseudo-position information representing the pseudo-position of the LEO satellite 4. Thus, in step S5, the position of the mobile terminal 2 is estimated based on the pseudo-positions of the four LEO satellites 4 using a calculation method similar to that of GNSS.

[0069] First, in addition to the first LEO satellite 4A and the second LEO satellite 4B, the third LEO satellite 4C and the fourth LEO satellite 4D are introduced. Hereafter, various values ​​related to the third LEO satellite 4C and the fourth LEO satellite 4D may be represented by symbols with superscript subscripts "v" and "u," respectively. In step S3, for each of the third LEO satellite 4C and the fourth LEO satellite 4D, the time t from the transmission of the satellite signal to its reception by the mobile terminal 2 is determined, similar to the case of the second LEO satellite 4B. r v ,t r u t, the time from when the satellite signal is transmitted until it is received by base station 3 R v ,t R u , double difference t of reception time r,R n,v ,t r,R n,u You may also calculate the following. In step S4, for each of the third LEO satellite 4C and the fourth LEO satellite 4D, the pseudo-distance ρ to the mobile terminal 2 is calculated. r v ρ r u , pseudo-distance ρ to base station 3 R v ρ R u , the double difference ρ of pseudo-distance r,R n,v ρ r,R n,u You may also request things like the following.

[0070] Subsequently, these values ​​are used to calculate the position of mobile terminal 2 based on the simultaneous equations shown in equation 10 below.

[0071]

number

[0072] As mentioned above, in the above "Equation 10", the position X of the LEO satellites 4A(n), 4B(s), 4C(v), and 4D(u) n ,X s ,X v ,X u The distance d from base station 3(R) to LEO satellites 4A(n), 4B(s), 4C(v), and 4D(u) is also calculated. R n d R s d R v d R u The double difference d of the distance from the mobile terminal 2(r) and base station 3(R) to the first LEO satellite 4A(n) and the second LEO satellite 4B(s) r,R n,s The double difference d of the distance from the mobile terminal 2(r) and base station 3(R) to the first LEO satellite 4A(n) and the third LEO satellite 4C(v) r,R n,v The double difference d of the distance from the mobile terminal 2(r) and base station 3(R) to the first LEO satellite 4A(n) and the fourth LEO satellite 4D(u) r,R n,u All of these can be calculated. Furthermore, the system of equations shown in "Equation 10" above contains three independent equations. Therefore, from "Equation 10" above, the position vector X of the mobile terminal 2(r) can be calculated. r The three coordinates included are calculable, and the order of their errors is the double difference ε of the other errors. r,R n,u It is below the order of [order].

[0073] The terminal location estimation unit 622 of the server 6 shown in Figure 4 transmits terminal location information representing the location of the mobile terminal 2 to the mobile terminal 2. The terminal location estimation unit 622 may also transmit the terminal location information to the base station 3 or to external terminals such as onboard terminals installed in vehicles located near the mobile terminal 2 or the base station 3.

[0074] After step S5 in Figure 5, the processing of the positioning program according to one embodiment may return to step S1.

[0075] As described above, the positioning system 1 and positioning program according to one embodiment can accurately estimate the position of a mobile terminal 2 by utilizing multiple LEO satellites 4 that have no orbital ephemeris, whose exact positions are unknown, do not transmit positioning signals, and are not synchronized with each other's time, and multiple reference stations 3 that are fixed on the ground and receive communication synchronization signals transmitted by the multiple LEO satellites 4.

[0076] (modified version) In the above embodiment, a configuration was described in which the main base station 3A aggregates the base station location information of sub-base stations 3B, 3C, and 3D in step S1 of Figure 5. As a modification of this configuration, the base station location information of sub-base stations 3B, 3C, and 3D may be stored in advance in the data storage unit 332 of the main base station 3A. Here, the data storage unit 332 of the main base station 3A stores base station identification information that identifies the sub-base stations 3B, 3C, and 3D along with the base station location information of the sub-base stations 3B, 3C, and 3D, associated with the base station location information. In this modification, the main base station 3A may obtain the base station location information of sub-base stations 3B, 3C, and 3D by receiving the base station identification information of the sub-base stations 3B, 3C, and 3D instead of the base station location information of the sub-base stations 3B, 3C, and 3D, and by extracting the base station location information associated with the received base station identification information from the data storage unit 332.

[0077] (Second embodiment) In this embodiment, the mobile terminal 2 performs the operations that the server 6 performs in the first embodiment described above. As shown in Figure 8, the mobile terminal 2 in this embodiment may be the same as the mobile terminal 2 in the first embodiment shown in Figure 2, with the addition of a terminal position estimation unit 222. The other configurations of the positioning system 1 and positioning program in this embodiment may be the same as those of the positioning system 1 and positioning program in the first embodiment. However, in this embodiment, the server 6 shown in Figure 1 can be omitted.

[0078] More specifically, the terminal location estimation unit 222 of the mobile terminal 2 shown in Figure 8 is configured and operates similarly to the terminal location estimation unit 622 of the server 6 shown in Figure 4. Furthermore, in the flowchart shown in Figure 5, steps S3, S4, and S5, which are performed by the terminal location estimation unit 622 of the server 6 shown in Figure 4 in the first embodiment, are performed by the terminal location estimation unit 222 of the mobile terminal 2 shown in Figure 8 in this embodiment.

[0079] In addition, the receiving unit 221 and transmitting unit 223 in Figure 8 perform the operations of the receiving unit 621 and transmitting unit 623 in Figure 4, respectively; the program storage unit 231 and data storage unit 232 in Figure 8 further store the data stored by the program storage unit 631 and data storage unit 632 in Figure 4, respectively; the communication device 24 in Figure 8 further performs the communication performed by the communication device 64 in Figure 4; and the input / output device 25 in Figure 8 further performs the operations of the input / output device 25 in Figure 4.

[0080] In this embodiment, the mobile terminal 2 performs the operations of the server 6 according to the first embodiment. As a result, some of the communication performed by the server 6 according to the first embodiment can be omitted, and depending on the performance of the mobile terminal 2, the position of the mobile terminal 2 can be measured more efficiently compared to the first embodiment.

[0081] (Third embodiment) In this embodiment, the base station 3 performs the operations that the server 6 performs in the first embodiment described above. As shown in Figure 9, the base station 3 in this embodiment may be the same as the arithmetic unit 32 of the base station 3 in the first embodiment shown in Figure 3, with the addition of a terminal position estimation unit 322. The other configurations of the positioning system 1 and positioning program in this embodiment may be the same as those of the positioning system 1 and positioning program in the first embodiment. However, in this embodiment, the server 6 shown in Figure 1 is optional.

[0082] More specifically, the terminal location estimation unit 322 of the reference station 3 shown in Figure 9 is configured and operates similarly to the terminal location estimation unit 622 of the server 6 shown in Figure 4. Furthermore, in the flowchart shown in Figure 5, steps S3, S4, and S5, which are performed by the terminal location estimation unit 622 of the server 6 shown in Figure 4 in the first embodiment, are performed by the terminal location estimation unit 322 of the reference station 3 shown in Figure 9 in this embodiment.

[0083] In addition, the receiving unit 321 and transmitting unit 323 in Figure 9 perform the operations of the receiving unit 621 and transmitting unit 623 in Figure 4, respectively; the program storage unit 331 and data storage unit 332 in Figure 9 further store the data stored by the program storage unit 631 and data storage unit 632 in Figure 4, respectively; the communication device 34 in Figure 9 further performs the communication performed by the communication device 64 in Figure 4; and the input / output device 35 in Figure 9 further performs the operations of the input / output device 65 in Figure 4.

[0084] In this embodiment, the base station 3 performs the operations of the server 6 according to the first embodiment, so some of the communication performed by the server 6 according to the first embodiment can be omitted, and depending on the performance of the base station 3, the measurement of the location of the mobile terminal 2 can be achieved more efficiently compared to the first embodiment.

[0085] (modified version) In each of the embodiments described above, a configuration was described in which the reference station 3 used to estimate the position of the LEO satellite 4 in step S1 of Figure 5 and the reference station 3 used to estimate the position of the mobile terminal 2 from step S2 to step S5 are the same reference station 3. As a variation of this configuration, the reference station 3 used to estimate the position of the LEO satellite 4 and the reference station 3 used to estimate the position of the mobile terminal 2 do not have to be the same reference station 3. Hereafter, for distinction, the reference station 3 used to estimate the position of the LEO satellite 4 will be referred to as a ground station. As an example, in the third embodiment described above, the reference station 3 in Figure 3 may be used as a ground station for estimating the position of the LEO satellite 4, and the reference station 3 in Figure 9 may be used for estimating the position of the mobile terminal 2. As another example, the satellite position estimation unit 324 may be omitted from the reference station 3 in Figure 3 or Figure 9 that is not used to estimate the position of the LEO satellite 4.

[0086] The invention made by the inventor has been described in detail based on embodiments above, but it goes without saying that the present invention is not limited to these embodiments and can be modified in various ways without departing from its essence. Furthermore, the features described in the embodiments can be freely combined within a range that does not contradict the technical aspects. [Explanation of symbols]

[0087] 1. Positioning system 2 Mobile terminals 21 Bus 22 Arithmetic unit 221 Receiving Unit 222 Terminal location estimation unit 223 Transmitter 23 Storage device 230 recording media 231 Program Storage Unit 232 Data Storage Unit 24 Communication equipment 25 Input / Output Devices 3,3A,3B,3C,3D reference station 31 Bus 32 Arithmetic unit 321 Trusteeship Department 322 End-position prediction section 323 Correspondence Department 324 Satellite Position Inference Department 33 Memory devices 330 Recording Media 331 プログラムMemory Department 332 Data Memory Department 34 Communication devices 35 Input and output device 4,4A,4B,4C,4D LEO satellites 5 ネットワーク 6 サーバ 61 バス 62 Calculation Device 621 Trusteeship Department 622 End-point position estimation section 623 Correspondence Department 63 Memory device 630 Recording Media 631 プログラムMemory Department 632 Data Memory Department 64 Communication devices 65 Input and output device t n ,t' n ,t s ,t' s Delivery time t r n ,t' r n ,t R n ,t' R n ,t r s ,t' r s ,t R s ,t' R s The moment of receiving faith

Claims

1. A first receiving unit mounted on a mobile terminal receives multiple satellite signals transmitted by multiple satellites, A second receiving unit mounted on a base station fixed at a predetermined location, which receives the aforementioned plurality of satellite signals, A terminal position estimation unit calculates a pseudo-distance double difference based on a plurality of first reception times when the first receiving unit receives the plurality of satellite signals and a plurality of second reception times when the second receiving unit receives the plurality of satellite signals, and estimates the position of the mobile terminal based on the pseudo-distance double difference. Equipped with, The aforementioned pseudo-distance double difference is, A first pseudo-distance difference is defined as the difference between a first pseudo-distance from one of the plurality of satellites to the mobile terminal and a second pseudo-distance from one of the plurality of satellites to the mobile terminal. A second pseudo-distance difference is shown as the difference between the third pseudo-distance from the first satellite to the reference station and the fourth pseudo-distance from the second satellite to the reference station, Showing the difference Positioning system.

2. In the positioning system according to claim 1, The aforementioned multiple satellite signals are The first forward signal transmitted by the first satellite, The first satellite transmitted a first follow signal after the first forward signal, The second forward signal transmitted by the second satellite, The second satellite transmitted a second follow signal after the second forward signal, Includes, The plurality of first reception times include the reception times when the first receiving unit receives the first preceding signal, the first succeeding signal, the second preceding signal, and the second succeeding signal, respectively. The plurality of second reception times include the reception times when the second receiving unit receives the first preceding signal, the first succeeding signal, the second preceding signal, and the second succeeding signal, respectively. The terminal position estimation unit corrects the time difference between the two first reception times, where the first receiving unit receives two signals included in the plurality of satellite signals, based on the time difference between the two second reception times, where the second receiving unit receives two signals, among the plurality of second reception times. Positioning system.

3. In the positioning system according to claim 2, The terminal location estimation unit, The time difference between the two first reception times is corrected based on a correction model that corrects the clock of the mobile terminal based on the clock of the reference station. The correction model approximates the time difference between the two first reception times and the time difference between the two second reception times as a linear relationship. Positioning system.

4. In the positioning system according to claim 1, A satellite position estimation unit estimates the position of the first satellite based on multiple reception times, each of which is received by multiple ground stations fixed at multiple locations far apart from each other, from the first satellite signal transmitted by the first satellite. Furthermore, The terminal position estimation unit estimates the position of the mobile terminal based on the position of the first satellite. Positioning system.

5. In the positioning system according to claim 4, The aforementioned multiple ground stations include the aforementioned reference station. Positioning system.

6. In the positioning system according to claim 1, The aforementioned multiple satellite signals include a communication synchronization signal. Positioning system.

7. A positioning program for achieving predetermined processing by having a computing device execute it, The aforementioned process is, The first receiving unit mounted on the mobile terminal receives multiple satellite signals transmitted by multiple satellites, The aforementioned multiple satellite signals are received by a second receiving unit mounted on a base station fixed at a predetermined location, Based on the multiple first reception times at which the first receiving unit receives the multiple satellite signals and the multiple second reception times at which the second receiving unit receives the multiple satellite signals, the pseudo-distance double difference is calculated. Inferring the position of the mobile terminal based on the aforementioned pseudo-distance double difference, Includes, The aforementioned pseudo-distance double difference is, A first pseudo-distance difference is defined as the difference between a first pseudo-distance from one of the plurality of satellites to the mobile terminal and a second pseudo-distance from one of the plurality of satellites to the mobile terminal. A second pseudo-distance difference is shown as the difference between the third pseudo-distance from the first satellite to the reference station and the fourth pseudo-distance from the second satellite to the reference station, Showing the difference Positioning program.

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