Wireless positioning device, wireless positioning system, wireless positioning method, and program

Abstract

This wireless positioning device comprises: a selection unit that selects a combination of wireless base stations for executing communication with a wireless terminal using a wireless signal; an angle positioning unit that, for the selected combination, measures the position of the wireless terminal on the basis of the arrival angle or departure angle of the wireless signal arriving at each wireless base station from the wireless terminal; a time positioning unit that, for the selected combination, measures the position of the wireless terminal on the basis of the arrival time or arrival time difference of the wireless signal arriving at each wireless base station from the wireless terminal; an estimation unit that estimates the difference between the position measured on the basis of the arrival angle or departure angle and the position measured on the basis of the arrival time or arrival time difference; and a determination unit that, in the case where the difference is less than a threshold value, determines the final position of the wireless terminal on the basis of at least one of the position measured on the basis of the arrival angle or departure angle and the position measured on the basis of the arrival time or arrival time difference.

Description

Wireless positioning device, wireless positioning system, wireless positioning method, and program

[0001] The present invention relates to a wireless positioning device, a wireless positioning system, a wireless positioning method, and a program.

[0002] Technologies in which at least one of the network side and the wireless terminal measures the position of the wireless terminal are useful in many applications. Applications include, for example, navigation of vehicles, people, and robots equipped with wireless terminals, safety confirmation and position confirmation of people carrying wireless terminals, and management of assets equipped with wireless terminals.

[0003] In the positioning of wireless terminals outdoors where the sky can be seen through, GPS (Global Positioning System) that utilizes radio waves (wireless signals) from artificial satellites is used for the positioning of vehicles and smartphones, and high-precision positioning accuracy has been achieved. On the other hand, in the positioning of wireless terminals indoors where the sky cannot be seen through, short-range wireless such as BLE (Bluetooth) (registered trademark) and UWB (Ultra Wide Band), dedicated wireless for positioning, and radio waves from indoor wireless base stations such as wireless LAN (Local area network) are utilized to achieve high-precision positioning accuracy.

[0004] As one of the positioning methods, there is a method that utilizes the characteristic that the reception level of radio waves attenuates according to the propagation distance of the radio waves for positioning. However, since the reception level fluctuates greatly due to factors other than the propagation distance (for example, fading and shadowing), it is difficult to improve the positioning accuracy.

[0005] As other positioning methods, there are AoA (Angle of Arrival) that utilizes the arrival angle of radio waves for positioning, DoA (Deperture of Arrival) that utilizes the departure angle of radio waves for positioning, ToA (Time of Arrival) that utilizes the arrival time of radio waves for positioning, and TDoA (Time Difference of Arrival) that utilizes the time difference of arrival of radio waves between a wireless terminal and multiple base stations for positioning (see Non-Patent Document 1).

[0006] In AoA and DoA, if the arrival or departure angle of the radio waves is acute, it is possible to achieve high positioning accuracy if a line-of-sight environment exists between the wireless terminal and the wireless base station (an environment in which radio waves arrive at the wireless terminal and wireless base station as direct waves without reflection). In ToA and TDoA as well, if a line-of-sight environment exists between the wireless terminal and the wireless base station, it is possible to achieve high positioning accuracy regardless of the arrival or departure angle of the radio waves.

[0007] However, if there is no line-of-sight environment between the wireless terminal and the wireless base station, the radio waves propagating between the wireless terminal and the wireless base station arrive at both the wireless terminal and the wireless base station as reflected waves. Therefore, the arrival angle and departure angle of the radio waves are estimated based on the direction of the reflected waves. In addition, the arrival time and the difference in arrival time are estimated based on the path length (propagation time) of the reflected waves.

[0008] When reflected waves are used for positioning, the estimated direction of the wireless terminal as seen from the wireless base station will differ from the actual direction of the wireless terminal, thus degrading positioning accuracy. Similarly, when reflected waves are used for positioning, the estimated arrival time and arrival time difference will differ from the actual arrival time and arrival time difference, thus degrading positioning accuracy.

[0009] Furthermore, even if a line-of-sight environment exists between the wireless terminal and the wireless base station, if it is not possible to clearly extract the direct and reflected waves arriving at the wireless terminal and the wireless base station, the reflected wave component will be included in the estimated arrival angle, departure angle, arrival time, and arrival time difference, thus degrading the positioning accuracy. Therefore, to improve positioning accuracy, it is necessary to create a line-of-sight environment where only direct waves arrive, for example, as in GPS. Also, in environments where both direct and reflected waves are present, it is necessary to estimate the arrival angle or departure angle, and the arrival time or arrival time difference, based only on the direct waves extracted from the direct and reflected waves.

[0010] One method for extracting direct waves from direct and reflected waves is to estimate the received level and arrival time of each multipath based on its delay profile, and then extract the direct wave based on the magnitude of the estimated received level and the shortness of its arrival time (see Non-Patent Document 2).

[0011] This method is effective in environments where both direct and reflected waves arrive from a wireless terminal at multiple wireless base stations, and where direct waves are extracted from the reflected waves for each wireless base station. For example, the path length of a direct wave is shorter than the path length of a reflected wave. Therefore, it is possible to extract a direct wave based on the fact that there is no reflection loss in the direct wave, the received level is high, and the arrival time of the direct wave is shorter than the arrival time of the reflected wave. Thus, if a line-of-sight environment exists between multiple wireless base stations and wireless terminals, and both direct and reflected waves are present, each wireless base station can extract a direct wave. By each wireless base station estimating the arrival angle or departure angle and the arrival time or arrival time difference based solely on this direct wave, it is possible to improve the accuracy of measuring the position of the wireless terminal.

[0012] In an environment where both direct and reflected waves arrive from a wireless terminal at multiple wireless base stations, the received level of the superposition of the direct and reflected waves may be measured in advance for each coordinate defined in that environment. When radio waves transmitted from a wireless terminal arrive at a wireless base station, there is also a method to estimate the most likely location of the wireless terminal based on a table that represents the received level of the radio waves for each coordinate (see Non-Patent Document 3).

[0013] Ministry of Land, Infrastructure, Transport and Tourism, Real Estate and Construction Economics Bureau, Information Utilization Promotion Division, "Draft Guidelines for the Construction of Indoor Maps / Indoor Positioning Environments," [online], March 2021, [Retrieved September 6, 2024], Internet<URL: https: / / www.mlit.go.jp / tochi_fudousan_kensetsugyo / content / 001391459.pdf> Watanabe, Inamura, "Distance Measurement and Positioning Technology Using UWB to Realize Indoor Location Information Services," [online], NTT DOCOMO Technical Journal, vol. 17, No. 1, pp. 41-46, [Retrieved September 6, 2017], Internet. <URL: https: / / www.docomo.ne.jp / binary / pdf / corporate / technology / rd / technical_journal / bn / vol17_1 / vol17_1_040jp.pdf> Hasegawa, Kosaka, "A Study on an Indoor Location Estimation Method Integrating Fingerprint and PDR," [online], 16th Information Science and Technology Forum, 2017, C-007, [Retrieved September 6, 2024], Internet <URL: https: / / www.ieice.org / publications / conference-FIT-DVDs / FIT2017 / data / pdf / C-007.pdf>

[0014] Non-patent document 1 states that if there is no line-of-sight environment between the wireless terminal and the wireless base station, and only reflected waves exist without direct waves, the delay profile will be a delay profile consisting only of reflected waves. However, since it is not possible to determine whether or not direct waves exist based on the delay profile, delay profiles that are inferred to be those of direct waves are extracted from among the delay profiles consisting only of reflected waves. In this case, the position of the wireless terminal is measured based on the arrival angle or departure angle of the reflected wave, and the arrival time or arrival time difference of the reflected wave, which leads to a problem of degraded positioning accuracy.

[0015] Non-Patent Document 2 requires the extensive task of pre-measuring the reception level for each coordinate. Furthermore, measuring the reception level itself is difficult in places that are difficult for people to enter (for example, dangerous areas such as tunnels and factories). In such places, it is difficult to use the method disclosed in Non-Patent Document 2. In addition, after the reception level has been pre-measured for each coordinate, new obstructions may be placed within the communication area. If the radio wave propagation environment changes due to the placement of obstructions, the table needs to be updated, and the reception level needs to be remeasured. In communication areas where communication services are already provided, it may be difficult to perform remeasurements, making it difficult to use the method disclosed in Non-Patent Document 2.

[0016] Thus, there is a problem in that it is not possible to improve the accuracy of positioning using the propagation characteristics of wireless signals.

[0017] In view of the above circumstances, the present invention aims to provide a wireless positioning device, a wireless positioning system, a wireless positioning method, and a program that can improve the accuracy of positioning using the propagation characteristics of wireless signals.

[0018] One aspect of the present invention is a wireless positioning device comprising: a selection unit for selecting a combination of wireless base stations that perform communication with a wireless terminal using a wireless signal; an angle positioning unit for measuring the position of the wireless terminal based on the arrival angle or departure angle of the wireless signal for the selected combination; a time positioning unit for measuring the position of the wireless terminal based on the arrival time or arrival time difference of the wireless signal for the selected combination; an estimation unit for estimating the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference; and a determination unit for determining the final position of the wireless terminal based on at least one of the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference when the difference is less than a threshold.

[0019] One aspect of the present invention is a wireless positioning system comprising a wireless positioning device and a plurality of wireless base stations that perform communication with a wireless terminal using wireless signals, wherein the wireless positioning device includes a selection unit that selects a combination of wireless base stations from the plurality of wireless base stations, an angle positioning unit that measures the position of the wireless terminal based on the arrival angle or departure angle of the wireless signal for the selected combination, a time positioning unit that measures the position of the wireless terminal based on the arrival time or arrival time difference of the wireless signal for the selected combination, an estimation unit that estimates the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference, and a determination unit that determines the final position of the wireless terminal based on at least one of the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference when the difference is less than a threshold.

[0020] One aspect of the present invention is a wireless positioning method performed by a wireless positioning device, comprising the steps of: selecting a combination of wireless base stations that perform communication with a wireless terminal using a wireless signal; an angle positioning unit that measures the position of the wireless terminal based on the arrival angle or departure angle of the wireless signal for the selected combination; measuring the position of the wireless terminal based on the arrival time or arrival time difference of the wireless signal for the selected combination; estimating the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference; and determining the final position of the wireless terminal based on at least one of the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference, when the difference is less than a threshold.

[0021] One aspect of the present invention is a program for causing a computer to perform the following steps: selecting a combination of radio base stations that perform communication with a radio terminal using radio signals; measuring the position of the radio terminal based on the arrival angle or departure angle of the radio signal for the selected combination; measuring the position of the radio terminal based on the arrival time or arrival time difference of the radio signal for the selected combination; estimating the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference; and determining the final position of the radio terminal based on at least one of the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference, when the difference is less than a threshold.

[0022] This invention makes it possible to improve the accuracy of positioning using the propagation characteristics of wireless signals.

[0023] This figure shows an example of the configuration of a wireless positioning system in the first embodiment. This figure shows an example of the propagation path of a radio signal arriving at each of all wireless base stations in the first embodiment. This figure shows an example of positioning based on the arrival angle of a radio signal arriving at each wireless base station in the first embodiment. This figure shows an example of positioning based on the arrival time of a radio signal at each wireless base station in the first embodiment. This figure shows an example of the propagation path of a radio signal to each wireless base station constituting a combination of three selected stations in the first embodiment. This figure shows an example of the propagation path of a radio signal to each wireless base station constituting a combination of two selected stations in the first embodiment. This flowchart shows an example of the operation of a wireless positioning device in the first embodiment. This flowchart shows an example of the operation of a wireless positioning device in the second embodiment. This flowchart shows an example of the operation of a wireless positioning device in the third embodiment.

[0024] Embodiments of the present invention will be described in detail with reference to the drawings. (First Embodiment) Figure 1 is a diagram showing an example of the configuration of a wireless positioning system 1 in the first embodiment. The wireless positioning system 1 is a system that measures the position of a wireless terminal using wireless signals. The wireless positioning system 1 comprises a wireless terminal 2 and N wireless base stations 3 (where N is an integer of 2 or more). The wireless terminal 2 comprises a storage device 21, a memory 22, and a communication unit 24.

[0025] The wireless positioning system 1 includes a wireless positioning device 23. Here, the wireless positioning device 23 may be provided in the wireless terminal 2 or in each wireless base station 3. The wireless positioning device 23 includes a selection unit 231, an angle positioning unit 232, a time positioning unit 233, an estimation unit 234, and a determination unit 235. At least one of the selection unit 231, the angle positioning unit 232, the time positioning unit 233, the estimation unit 234, and the determination unit 235 may be provided in each wireless base station 3. The wireless positioning device 23 may be provided in the wireless positioning system 1 independently of the wireless terminal 2 and each wireless base station 3. For example, in the wireless positioning system 1, the wireless positioning device 23 may be provided in a network-side positioning server (not shown) connected to the wireless base station 3.

[0026] The storage device 21 stores identification information of the wireless base station 3. The wireless positioning device 23 is implemented using software, by a processor such as a CPU (Central Processing Unit) executing a program stored in the storage device 21 and memory 22, which have a non-volatile recording medium (non-temporary recording medium). The program may be recorded on a computer-readable recording medium. A computer-readable recording medium is a non-temporary recording medium such as a portable medium such as a flexible disk, magneto-optical disk, ROM (Read Only Memory), or CD-ROM (Compact Disc Read Only Memory), a hard disk built into a computer system, or a storage device such as a solid-state drive (SSD). The communication unit 24 performs predetermined wireless communication processing.

[0027] The wireless positioning device 23 may be implemented using hardware that includes electronic circuits (electronic circuits or circuits) such as LSI (Large Scale Integrated Circuit), ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), or FPGA (Field Programmable Gate Array).

[0028] The radio base station 3 performs wireless communication with the radio terminal 2. Hereinafter, wireless communication between the radio base station 3 and the radio terminal 2 includes the communication of radio signals used for positioning and radio signals used for purposes other than positioning. Radio signals used for purposes other than positioning may be actual data communication, communication of control signals for establishing a wireless connection between the radio terminal 2 and the radio base station 3, communication of control signals for maintaining a wireless connection, communication of beacon signals from the radio base station 3 for the radio terminal 2 to search for nearby radio base stations 3, or communication of active beacon signals transmitted from the radio terminal 2. The radio base station 3 estimates the arrival angle or departure angle of the radio signal for radio signals arriving at it from the radio terminal 2. An example of a positioning method based on the arrival angle is AoA. An example of a positioning method based on the departure angle is DoA. If the radio terminal 2 is equipped with a radio positioning device 23, the radio base station 3 transmits a signal representing the arrival angle or departure angle of the radio signal to the radio terminal 2. The radio base station 3 estimates the arrival time or arrival time difference of the radio signal that has arrived at its station from the radio terminal 2. A positioning method based on arrival time is, for example, Time of Arrival (TA). A positioning method based on arrival time difference is, for example, TDoA. The radio base station 3 transmits a signal representing the arrival time or arrival time difference of the radio signal to the radio terminal 2.

[0029] The communication unit 24 performs wireless communication with the radio base stations 3. For example, the communication unit 24 transmits radio signals to each radio base station 3. For example, the communication unit 24 obtains signals from each radio base station 3 that represent the arrival angle or departure angle of radio signals that have arrived at each radio base station 3 from the radio terminal 2. For example, the communication unit 24 obtains signals from each radio base station 3 that represent the arrival time or arrival time difference of radio signals that have arrived at each radio base station 3 from the radio terminal 2. The communication unit 24 may record the data represented by each obtained signal in the storage device 21.

[0030] The selection unit 231 selects a combination of radio base stations 3 that will communicate with the radio terminal 2 using radio signals used for positioning. The angle positioning unit 232 measures the position of the radio terminal 2 for the selected combination based on the arrival angle or departure angle of the radio signals that arrive at each radio base station 3 from the radio terminal 2. The time positioning unit 233 measures the position of the radio terminal 2 for the selected combination based on the arrival time or arrival time difference of the radio signals that arrive at each radio base station 3 from the radio terminal 2. The communication unit 24 may also perform wireless communication with a combination of radio base stations 3 not selected by the selection unit 231 using radio signals used for purposes other than positioning.

[0031] The estimation unit 234 estimates the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference. The determination unit 235 determines the final position of the wireless terminal 2 based on at least one of the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference, provided that the difference is less than a threshold.

[0032] Next, the details of the wireless positioning system 1 will be explained. Figure 2 is a diagram showing an example of the propagation path of radio signals arriving at each of the radio base stations 3 in the first embodiment. In the following, as an example, a radio terminal 2, four radio base stations 3, and two shielding objects 4 are arranged in the communication area. The shielding objects 4 block the radio signals (radio waves) that arrive at the shielding objects 4 from the radio signals transmitted from the radio terminal 2. In addition, reflectors 5 are arranged on the outer perimeter of the communication area. The reflectors 5 reflect the radio signals that arrive at the reflectors 5 from the radio signals transmitted from the radio terminal 2.

[0033] In the following example, at base station 3-1, a radio signal (reflected wave) reflected by the reflector 5 arrives from the radio terminal 2. At base station 3-2, a radio signal (direct wave) transmitted from the radio terminal 2 arrives. At base station 3-3, a radio signal (reflected wave) reflected by the reflector 5 arrives from the radio terminal 2. At base station 3-4, a radio signal (direct wave) transmitted from the radio terminal 2 arrives.

[0034] Figure 3 shows an example of positioning based on the arrival angle of radio signals arriving at each radio base station 3 in the first embodiment. In Figure 3, the selection unit 231 selects all radio base stations 3.

[0035] Each radio base station 3 estimates the arrival angle of the radio signal that has arrived at its radio base station from the radio terminal 2. Each radio base station 3 may also estimate the arrival angle of the radio signal by receiving the radio signal using an adaptive array antenna. Each radio base station 3 may also estimate the arrival angle of the radio signal using a method such as MUSIC (Multiple Signal Classification) or ESPRIT (Estimation of Signal Parameters via Rotational Invariance Technique). Each radio base station 3 may also estimate the arrival angle of the radio signal as the beam direction selected in analog beamforming or digital beamforming. Each radio base station 3 transmits each estimated arrival angle result to the radio terminal 2.

[0036] The angle positioning unit 232 measures the position of the wireless terminal 2 based on the estimated results of the incoming angles. Here, the angle positioning unit 232 draws a straight line in the direction of arrival of the wireless signal, starting from the position of each wireless base station 3. For example, the angle positioning unit 232 estimates the position of the wireless terminal 2 to be the position 6 that is closest and most likely to each straight line. For example, the angle positioning unit 232 may estimate the position of the wireless terminal 2 to be the position 6 where the sum of distances from each straight line is minimized. For example, the angle positioning unit 232 may weight each straight line according to the reception level of each wireless base station 3, and estimate the position of the wireless terminal 2 to be the position 6 where the sum of distances with these weights added is minimized. If the positioning of the wireless terminal 2 is performed at predetermined intervals, the angle positioning unit 232 may perform time-direction filtering on the positioning results by AoA so as to absorb errors in the positioning results by AoA for each interval.

[0037] The angle positioning unit 232 may also estimate the arrival angle of the radio signals that arrive at the wireless terminal 2 from each radio base station 3. The angle positioning unit 232 may also measure the position of the wireless terminal 2 based on the arrival angle of the radio signals that arrive at the wireless terminal 2 from each radio base station 3.

[0038] Figure 4 shows an example of positioning based on the arrival time of radio signals at each radio base station 3 in the first embodiment. In Figure 4, the selection unit 231 selects all radio base stations 3 for positioning.

[0039] Each radio base station 3 estimates the arrival time of a radio signal received from a radio terminal 2. For example, each radio base station 3 estimates the arrival time of a radio signal and estimates the distance between the radio base station 3 and the radio terminal 2 by multiplying the estimated arrival time by the propagation speed of radio waves (speed of light). If the time of each radio base station 3 and the time of the radio terminal 2 are synchronized using GPS or the like, and each radio base station 3 knows in advance the transmission time of the radio signal at the radio terminal 2, each radio base station 3 may estimate the distance between the radio base station 3 and the radio terminal 2 based on the transmission time and reception time of the radio signal. If control signals are exchanged between the radio base station 3 and the radio terminal 2, each radio base station 3 may estimate the distance between the radio base station 3 and the radio terminal 2 based on the round-trip time of the control signals. Each radio base station 3 transmits each estimated arrival time result to the radio terminal 2. Each radio base station 3 may also transmit each estimated distance between the radio base station 3 and the radio terminal 2 to the radio terminal 2.

[0040] The time positioning unit 233 measures the position of the wireless terminal 2 based on the estimated arrival time. Here, if the time positioning unit 233 has not obtained the estimated distance between the wireless base station 3 and the wireless terminal 2 from each wireless base station 3, it may estimate the distance between the wireless base station 3 and the wireless terminal 2 based on the estimated arrival time. The time positioning unit 233 draws a perfect circle 7 for each wireless base station 3, with the estimated distance as its radius and the position of the wireless base station 3 as its center. For example, the time positioning unit 233 estimates the position of the wireless terminal 2 to be the closest and most likely position 8 from each perfect circle 7. The time positioning unit 233 may also estimate the position of the wireless terminal 2 to be the position 8 where the sum of distances from each perfect circle 7 is minimized. For example, the time positioning unit 233 may weight each perfect circle 7 according to the reception level of each wireless base station 3, and estimate the position of the wireless terminal 2 to be the position 8 where the sum of distances with these weights added is minimized. If positioning of the wireless terminal 2 is performed at predetermined intervals, the time positioning unit 233 may perform time-direction filtering on the positioning results by ToA so as to absorb errors in the positioning results by ToA for each period.

[0041] The time positioning unit 233 may also estimate the arrival time of radio signals that have arrived at the wireless terminal 2 from each radio base station 3. The time positioning unit 233 may also measure the position of the wireless terminal 2 based on the arrival time of radio signals that have arrived at the wireless terminal 2 from each radio base station 3.

[0042] As described above, when reflected waves are used for positioning, the accuracy of both AoA-based and ToA-based positioning results deteriorates significantly. Moreover, this deterioration is due to a discrepancy in the estimated arrival angle in AoA and a discrepancy in the estimated arrival time (distance) in ToA. Therefore, the positioning results using AoA and ToA differ significantly. In contrast, when only direct waves are used for positioning, the accuracy of both AoA-based and ToA-based positioning results improves significantly. In this case, the positioning results using AoA and ToA almost coincide. That is, the difference between the positioning results using AoA and ToA is below a threshold.

[0043] Figure 5 shows an example of the propagation path of radio signals to each radio base station 3 that constitutes a combination of three selected stations in the first embodiment. In Figure 5, the selection unit 231 sequentially selects three radio base stations 3 from among four radio base stations 3 for positioning purposes. The angle positioning unit 232 measures the position of the radio terminal 2 for each combination of three selected stations based on the arrival angle of the radio signal that arrived at each radio base station 3 from the radio terminal 2. The time positioning unit 233 measures the position of the radio terminal 2 for each combination of three selected stations based on the arrival time of the radio signal that arrived at each radio base station 3 from the radio terminal 2.

[0044] FIG. 6 is a diagram showing an example of a propagation path of a radio signal to each radio base station 3 constituting a combination of two selected stations in the first embodiment. In FIG. 6, the selection unit 231 sequentially selects two radio base stations 3 from among the four radio base stations 3 for positioning. The angle positioning unit 232 measures the position of the radio terminal 2 based on the arrival angle of the radio signal arriving from the radio terminal 2 at each radio base station 3 for each combination of two selected stations. The time positioning unit 233 measures the position of the radio terminal 2 based on the arrival time of the radio signal arriving from the radio terminal 2 at each radio base station 3 for each combination of two selected stations.

[0045] Next, an operation example of the radio positioning device 23 will be described. FIG. 7 is a flowchart showing an operation example of the radio positioning device 23 in the first embodiment. Hereinafter, the operations illustrated in the flowchart may be repeatedly executed at a predetermined cycle. The selection unit 231 selects one combination of radio base stations 3 for positioning. Here, the selection unit 231 selects a combination that has not been selected so far (a combination that has not been determined) (step S101).

[0046] The angle positioning unit 232 measures the position of the radio terminal 2 based on the arrival angle or departure angle of the radio signal arriving from the radio terminal 2 at each radio base station 3 for the selected combination (step S102). The angle positioning unit 232 measures the position of the radio terminal 2 based on the arrival time or arrival time difference of the radio signal arriving from the radio terminal 2 at each radio base station 3 for the selected combination (step S103). The estimation unit 234 estimates the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference (step S104).

[0047] The difference (distance) between the measured positions (x - coordinate and y - coordinate) may be expressed, for example, by the difference between the x - coordinate and the y - coordinate, or by the sum of the differences between the x - coordinate and the y - coordinate, or by the sum of the squares of the differences between the x - coordinate and the y - coordinate. The difference in position may be expressed by the Euclidean distance or by the inner - product value of the position vectors of the coordinates. Also, the difference in position may be estimated based on the results of repeated positioning (for example, the average distance). The difference in position may be expressed, for example, by the ratio of the measurement result based on AoA and the measurement result based on ToA.

[0048] The determination unit 235 determines whether the estimated difference is less than the threshold value. For example, when the difference is estimated multiple times, the determination unit 235 may determine whether the difference is less than the threshold value for a predetermined number of times out of those multiple times (step S105). When it is determined that the estimated difference is less than the threshold value (step S105: YES), the determination unit 235 records the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference in the storage device 21 (step S106). The determination unit 235 proceeds to the process in step S107.

[0049] When it is determined that the estimated difference is greater than or equal to the threshold value (step S105: NO), the determination unit 235 determines whether all combinations have been determined (step S107). When it is determined that there is an undetermined combination (step S107: NO), the wireless positioning device 23 returns the process to step S101.

[0050] When it is determined that all combinations have been determined (step S107: YES), the determination unit 235 determines the final position of the wireless terminal 2 based on the recorded positions. For example, the determination unit 235 may determine any one of the recorded positions as the final position. For example, the determination unit 235 may determine the position with the minimum difference in position among the recorded positions as the final position. Here, in ToA, the positioning accuracy can be improved without depending on the arrival direction of the wireless signal. Therefore, the determination unit 235 may determine the positioning result based on ToA as the final position.

[0051] For example, the determination unit 235 may determine the final position as the average of a plurality of recorded positions (positions measured based on the arrival angle or departure angle, and positions measured based on the arrival time or arrival time difference). Here, the determination unit 235 may determine the final position as simply the average of the AoA positioning result and the ToA positioning result. The determination unit 235 may also weight the AoA positioning result and the ToA positioning result and determine the final position as the average value that takes these weights into account (step S108).

[0052] As described above, the selection unit 231 selects a combination of radio base stations 3 that will communicate with the radio terminal 2 using radio signals used for positioning. The angle positioning unit 232 measures the position of the radio terminal 2 for the selected combination based on the arrival angle or departure angle of the radio signal that arrives at each radio base station 3 from the radio terminal 2. The angle positioning unit 232 may also measure the position of the radio terminal 2 for the selected combination based on the arrival angle or departure angle of the radio signal that arrives at each radio base station 3 from the radio terminal 2. The time positioning unit 233 measures the position of the radio terminal 2 for the selected combination based on the arrival time or arrival time difference of the radio signal that arrives at each radio base station 3 from the radio terminal 2. The time positioning unit 233 may also measure the position of the radio terminal 2 for the selected combination based on the arrival time or arrival time difference of the radio signal that arrives at each radio base station 3 from the radio terminal 2. The estimation unit 234 estimates the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference. The determination unit 235 determines the final position of the wireless terminal 2 based on at least one of the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference, when the difference is less than a threshold.

[0053] This makes it possible to improve the accuracy of positioning using the propagation characteristics of wireless signals.

[0054] It is possible to prevent the use of radio signals from a radio base station 3, where only reflected radio signals arrive at the radio terminal 2, for positioning. Even in environments where the propagation characteristics of radio signals change, prior measurement and remeasurement of propagation characteristics are unnecessary.

[0055] (Second Embodiment) In the first embodiment, the focus was on improving positioning accuracy by utilizing the positioning results for all combinations of wireless base stations in which the AoA positioning result and the ToA positioning result were close. In contrast, the second embodiment focuses on reducing the amount of processing load by considering the positioning accuracy to be sufficient if even one combination of wireless base stations is found in which the AoA positioning result and the ToA positioning result are close (combinations in which the difference in position is less than a threshold). The second embodiment will be explained in detail, focusing on the differences from the first embodiment.

[0056] Figure 8 is a flowchart showing an example of the operation of the wireless positioning device 23 in the second embodiment. The selection unit 231 determines the initial value of the number of wireless base stations 3 that constitute the combination (variable) to be the total number of wireless base stations 3 (4 stations) (step S201).

[0057] The selection unit 231 selects one combination of the number of radio base stations 3 that has been determined or updated for positioning. Here, the selection unit 231 selects a combination that has not been selected so far (a combination that has not been determined) (step S202). Each step from step S203 to step S206 is the same as each step from step S102 to step S105.

[0058] The determination unit 235 determines whether the estimated difference is less than a threshold (step S206). If it is determined that the estimated difference is less than a threshold (step S206: YES), the determination unit 235 determines the final position of the wireless terminal 2 based on each of the measured positions. For example, the determination unit 235 may determine any of the measured positions as the final position. For example, the determination unit 235 may determine the average of a plurality of measured positions (positions measured based on arrival angle or departure angle, and positions measured based on arrival time or arrival time difference) as the final position (step S207).

[0059] If it is determined that the estimated difference is greater than or equal to a threshold (step S206: NO), the determination unit 235 determines whether or not all combinations have been determined (step S208). If it is determined that all combinations have been determined (step S208: YES), the wireless positioning device 23 returns to step S202.

[0060] If it is determined that there are combinations that have not yet been determined (step S208: NO), the selection unit 231 subtracts 1 from the number of radio base stations 3 that constitute the combination (variable) (step S209). The radio positioning device 23 returns to step S202.

[0061] As described above, if it is determined that for at least one combination of wireless base stations 3, the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference is less than a threshold, the determination unit 235 determines the final position of the wireless terminal 2 based on the measured position.

[0062] This makes it possible to improve the accuracy of positioning using the propagation characteristics of radio signals. It is possible to find in the shortest time the combination of radio base stations 3 in which the difference between the positioning result based on the arrival angle or departure angle and the positioning result based on the arrival time or arrival time difference is below a threshold, and which has the largest number of radio base stations 3. In other words, it is possible to reduce the amount of processing compared to the first embodiment while maintaining a certain level of positioning accuracy.

[0063] (Third Embodiment) In the third embodiment, the main difference from the second embodiment is that the determination is performed until the number of wireless base stations 3 reaches a predetermined lower limit. The third embodiment will be explained focusing on the differences from the second embodiment.

[0064] Figure 9 is a flowchart showing an example of the operation of the wireless positioning device 23 in the third embodiment. Each step from step S301 to step S305 is the same as each step from step S201 to step S205.

[0065] The determination unit 235 determines whether the estimated difference is less than a threshold (step S306). If it is determined that the estimated difference is less than a threshold (step S306: YES), the determination unit 235 records the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference in the storage device 21 (step S307). The determination unit 235 proceeds to step S308.

[0066] If it is determined that the estimated difference is greater than or equal to a threshold (step S306: NO), the determination unit 235 determines whether or not all combinations have been determined (step S308). If it is determined that there are combinations that have not been determined (step S308: NO), the wireless positioning device 23 returns to step S302.

[0067] If it is determined that all combinations have been determined (step S308: YES), the determination unit 235 determines whether the number of radio base stations 3 constituting the combination (variable) has reached a lower limit (for example, 2 stations) (step S309). The lower limit is predetermined based on the required positioning accuracy.

[0068] If it is determined that the number of wireless base stations 3 constituting the combination has reached the lower limit (step S309: YES), the determination unit 235 determines the final position of the wireless terminal 2 based on the recorded positions (step S310).

[0069] If it is determined that the number of radio base stations 3 constituting the combination has not reached the lower limit (step S309: NO), the selection unit 231 subtracts 1 from the number of radio base stations 3 constituting the combination (variable) (step S311). The radio positioning device 23 returns to step S302.

[0070] As described above, the determination unit 235 determines whether the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference is greater than or equal to a threshold for a predetermined number of combinations of radio base stations 3, until the number of radio base stations 3 reaches a predetermined lower limit.

[0071] This makes it possible to improve the accuracy of positioning using the propagation characteristics of wireless signals. In this case, it is possible to reduce the amount of processing required compared to the first embodiment.

[0072] Furthermore, for all combinations of wireless base stations 3 consisting of a number of stations greater than or equal to a predetermined lower limit, where the difference between the positioning result based on the arrival angle or departure angle and the positioning result based on the arrival time or arrival time difference is less than or equal to a threshold, all positioning results can be used to determine the final position, making it possible to improve the accuracy of positioning compared to the second embodiment.

[0073] In other words, it is possible to determine the final position of the wireless terminal 2 based on positioning results based on arrival angle or departure angle and positioning results based on arrival time or arrival time difference for combinations of wireless base stations 3 that are equal to or greater than a predetermined number (lower limit) from all wireless base stations 3. For example, if the lower limit for the number of wireless base stations 3 used for positioning that meets the required accuracy is 3, the final position of the wireless terminal 2 will be determined for all combinations of 3 and 4 wireless base stations 3 based on positioning results based on arrival angle or departure angle and positioning results based on arrival time or arrival time difference.

[0074] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention.

[0075] The present invention is applicable to wireless positioning systems.

[0076] 1... Wireless positioning system, 2... Wireless terminal, 3... Wireless base station, 4... Shielding object, 5... Reflecting object, 6... Position, 7... Perfect circle, 8... Position, 21... Storage device, 22... Memory, 23... Wireless positioning device, 24... Communication unit, 231... Selection unit, 232... Angle positioning unit, 233... Time positioning unit, 234... Estimation unit, 235... Determination unit

Claims

1. A wireless positioning device comprising: a selection unit for selecting a combination of wireless base stations that perform communication with a wireless terminal using wireless signals; an angle positioning unit for measuring the position of the wireless terminal based on the arrival angle or departure angle of the wireless signal for the selected combination; a time positioning unit for measuring the position of the wireless terminal based on the arrival time or arrival time difference of the wireless signal for the selected combination; an estimation unit for estimating the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference; and a determination unit for determining the final position of the wireless terminal based on at least one of the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference when the difference is less than a threshold.

2. A wireless positioning system comprising a wireless positioning device and a plurality of wireless base stations that perform communication with a wireless terminal using wireless signals, wherein the wireless positioning device includes: a selection unit that selects a combination of wireless base stations in the plurality of wireless base stations; an angle positioning unit that measures the position of the wireless terminal based on the arrival angle or departure angle of the wireless signal for the selected combination; a time positioning unit that measures the position of the wireless terminal based on the arrival time or arrival time difference of the wireless signal for the selected combination; an estimation unit that estimates the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference; and a determination unit that determines the final position of the wireless terminal based on at least one of the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference when the difference is less than a threshold.

3. A wireless positioning method performed by a wireless positioning device, comprising: selecting a combination of wireless base stations that communicate with a wireless terminal using a wireless signal; an angle positioning unit that measures the position of the wireless terminal based on the arrival angle or departure angle of the wireless signal for the selected combination; measuring the position of the wireless terminal based on the arrival time or arrival time difference of the wireless signal for the selected combination; estimating the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference; and determining the final position of the wireless terminal based on at least one of the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference, when the difference is less than a threshold.

4. A program for causing a computer to perform the following steps: selecting a combination of radio base stations that communicate with a radio terminal using radio signals; measuring the position of the radio terminal based on the arrival angle or departure angle of the radio signal for the selected combination; measuring the position of the radio terminal based on the arrival time or arrival time difference of the radio signal for the selected combination; estimating the difference between the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference; and determining the final position of the radio terminal based on at least one of the position measured based on the arrival angle or departure angle and the position measured based on the arrival time or arrival time difference, when the difference is less than a threshold.

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