Radio station selection method and radio station selection system

Abstract

This wireless station selection method includes: an acquisition step for acquiring image information indicating a captured image of a space in which radio waves can be propagated in communication between a first wireless station and a second wireless station; an estimation step for estimating a propagation loss of the radio waves in the communication on the basis of the image information acquired in the acquisition step; and a determination step for determining, on the basis of the propagation loss estimated in the estimation step, whether or not the wireless station being connected to communicate with the first wireless station is to be switched from the second wireless station to a third wireless station.

Description

[Technical field]

[0001] The present invention relates to a radio station selection method and a radio station selection system. [Background technology]

[0002] Nowadays, mobile terminals such as smartphones and tablet terminals that can be used outdoors, and terminal devices capable of wireless communication such as IoT (Internet of Things) terminals, are becoming widespread. Wireless base stations (hereinafter referred to as "base stations") to which such terminal devices (hereinafter referred to as "terminal stations") are connected for communication are installed in multiple locations such as utility poles and building walls. In order to transmit and receive stable radio waves in wireless communication between a base station and a terminal station and to achieve higher communication quality, it is basically preferable for the terminal station to connect to a base station that is closer to the base station. However, when the terminal station is a mobile terminal, the distance between the base station and the terminal station changes from moment to moment, and therefore the base station located closer to the terminal station may change over time.

[0003] Furthermore, there may be cases where an object (hereinafter referred to as "obstruction") that blocks radio waves exists between the base station and the terminal station. Obstructions include, for example, buildings such as buildings and houses, elevated roads, signs and traffic signs, trees, and vehicles such as parked automobiles. In this case, in order to achieve higher communication quality, it is necessary to determine the presence or absence of line of sight between the base station and the terminal station while taking into consideration the presence of the obstruction, and to appropriately select a base station with which the terminal station will communicate. In particular, when the obstruction is an object that moves or changes, such as a parked automobile or tree, the base station to be selected may change over time.

[0004] Conventionally, a number of methods have been used to determine the line of sight between a base station and a terminal station. For example, the easiest line of sight determination method is a line of sight determination method based on communication distance. In the line of sight determination method based on communication distance, it is determined that there is line of sight when the distance between a candidate installation position of the base station and a representative point is within a predetermined distance that allows communication, and it is determined that there is no line of sight when the distance is longer than the distance that allows communication. However, this line of sight determination method based only on communication distance has a problem of low determination accuracy.

[0005] The visibility determination method based on map information is also a relatively easy method. The map information includes information showing the outer contours, such as the outer walls, of buildings existing in the evaluation target area. In the visibility determination method based on map information, if a line segment connecting a base station candidate installation position and a representative point on a two-dimensional map does not intersect with the outer contour of a building, it is determined that there is visibility, and if it intersects with the outer contour of the building, it is determined that there is no visibility. However, since the map information does not include information about the presence of objects (e.g., trees, signs, road signs, etc.) that block the view other than the building, this visibility determination method based on map information also has a problem of not being highly accurate.

[0006] As a method for determining the presence or absence of line of sight between a base station and a terminal station with higher accuracy, there is a line of sight determination method that uses three-dimensional point cloud data obtained by imaging the space (see, for example, Patent Document 1). In this line of sight determination method, first, a vehicle equipped with, for example, an MMS (Mobile Mapping System) is driven along roads in an area to be evaluated, such as a residential area. In this way, this line of sight determination method obtains three-dimensional point cloud data indicating the positions of all objects existing in the area to be evaluated. Then, this line of sight determination method performs line of sight determination based on the point cloud data existing in the space between the position of the base station and the position where the terminal station may be located, and determines whether communication between the base station and the terminal station is possible.

[0007] The visibility determination method using the above-mentioned three-dimensional point cloud data assumes that the above-mentioned space is, for example, a Fresnel zone formed in wireless communication between a base station and a terminal station. Specifically, this visibility determination method determines the presence or absence of visibility between the base station and the terminal station according to, for example, the number of point cloud data contained in the space of the Fresnel zone. In this way, in order to perform a more accurate visibility determination based on the three-dimensional point cloud data, it is necessary to obtain a sufficient amount of point cloud data indicating the positions of obstacles existing in the evaluation target area in advance.

[0008] Furthermore, as a method for determining visibility with higher accuracy using three-dimensional point cloud data, there is a visibility determination method that takes the obstruction rate into consideration (for example, see Non-Patent Document 1). The obstruction rate here is an index value that indicates the degree to which visibility between a base station and a terminal station is obstructed. In other words, the obstruction rate can be said to be an index that indicates the degree to which obstructions affect wireless communication between a base station and a terminal station, leading to a decrease in communication quality. The visibility determination method that takes the obstruction rate into consideration, for example, calculates the amount of propagation loss of radio waves from the obstruction rate calculated based on acquired point cloud data, and performs line design for wireless communication between the base station and the terminal station based on the calculated amount of loss, thereby determining visibility.

[0009] However, the visibility assessment method using the above-mentioned three-dimensional point cloud data requires a large amount of calculation and places a high load on the system for calculation processing, so at present it is limited to assessing visibility using only point cloud data on a few cross sections of the Fresnel zone, for example, and has not yet reached the stage of evaluating the cumulative visibility over the entire propagation path of radio waves. As a result, this visibility assessment method using three-dimensional point cloud data also has the problem of not being very accurate.

[0010] In recent years, in order to expand the communication area, artificial satellites such as low earth orbit satellites (LEO: Low Earth Orbit) are also used as base stations. Furthermore, plans and demonstration experiments are being made to build a communication network in the stratosphere by using a high altitude unmanned aerial vehicle (HAPS: High Altitude Platform Station) as a base station (see, for example, Non-Patent Documents 2 and 3). Research on such non-terrestrial networks (NTNs) has been actively conducted in recent years. NTNs are communication networks that expand communication areas not only to the ground but also to all places such as the sky, sea, and space. Research is being conducted to apply such NTNs to wireless communication for various purposes, such as realizing stable wireless communication during disasters and realizing large-capacity wireless communication on aircraft (see, for example, Non-Patent Document 4). [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2020-107955 A [Non-patent literature]

[0012] [Non-Patent Document 1] “TsuKuBa History: Millimeter-Wave Band Station Design Support Tool”, NTT Access Network Service Systems Laboratories, 2019, [Retrieved December 17, 2021], Internet (URL: https: / / www.rd.ntt / as / history / pdf / wireless / wi0212.pdf) [Non-Patent Document 2] “Demonstration experiment of radio wave propagation measurement in the 39 GHz band to expand communication areas from the sky ~Assuming use cases of HAPS in urban areas, forests, and remote islands~”, Press release, NTT DOCOMO, Inc., March 10, 2021 [Non-Patent Document 3] “Continuous non-stop flight in the stratosphere: ‘Flying base station’ becomes a reality”, Nikkei Crosstech, March 19, 2020, [Retrieved December 17, 2021], Internet (URL: https: / / xtech.nikkei.com / atcl / nxt / mag / ne / 18 / 00007 / 00100 / ) [Non-Patent Document 4] Yuki Hokazono, Yoshihisa Kishiyama, Takahiro Asai, "NTN Technology Research for 5G Evolution & 6G", NTT Technical Journal, pp.22-27, September 2021 Summary of the Invention [Problem to be solved by the invention]

[0013] However, as described above, particularly when the obstruction is a moving object such as a vehicle, the obstruction may or may not be present at a position blocking the line of sight between the base station and the terminal station depending on the time. In this case, the impact of the obstruction on communication quality changes with time. Also, when the obstruction is, for example, a tree, the tree may be covered with leaves or may not have leaves depending on the season and weather. In this case, the impact of the obstruction on communication quality changes with the season and weather. Also, the impact on communication quality may differ depending on the position and distribution of the obstruction in the space of the Fresnel zone.

[0014] Therefore, for example, simply counting the number of point cloud data points that exist between a base station and a terminal station at a particular point in time, as in the conventional visibility assessment that uses the aforementioned three-dimensional point cloud data, may not appropriately select the base station with which the terminal station should communicate.

[0015] In view of the above circumstances, an object of the present invention is to provide a technique that enables a terminal station to appropriately select a base station to communicate with. [Means for solving the problem]

[0016] One aspect of the present invention is a wireless station selection method including an acquisition step of acquiring image information showing an image of a space through which radio waves can propagate in communication between a first wireless station and a second wireless station, an estimation step of estimating a propagation loss of radio waves in the communication based on the image information acquired in the acquisition step, and a determination step of determining whether or not to switch the wireless station with which the first wireless station is connected for communication from the second wireless station to a third wireless station based on the propagation loss estimated in the estimation step.

[0017] Another aspect of the present invention is a wireless station selection system including: an acquisition unit that acquires image information indicating an image of a space through which radio waves can propagate in communication between a first wireless station and a second wireless station; an estimation unit that estimates a propagation loss of radio waves in the communication based on the image information acquired by the acquisition unit; and a determination unit that determines whether to switch a wireless station with which the first wireless station is communicatively connected from the second wireless station to a third wireless station based on the propagation loss estimated by the estimation unit. Effect of the Invention

[0018] According to the present invention, it becomes possible for a terminal station to appropriately select a base station to which it will communicate. [Brief description of the drawings]

[0019] [Figure 1] FIG. 13 is a diagram showing how communication availability is determined in consideration of the Fresnel zone fz. [Diagram 2] 1 is a schematic diagram showing how visibility is determined by regarding the Fresnel zone as a cylinder; [Diagram 3] This is a diagram showing a cylindrical Fresnel zone Cz superimposed on a Fresnel zone fz. [Figure 4] FIG. 1 is a schematic diagram showing an example of a communication environment in which a terminal station is a smartphone. [Diagram 5] 1 is a schematic diagram showing an overall configuration of a base station selection system 1 in a first embodiment of the present invention. [Figure 6]FIG. 2 is a diagram showing an example of an image captured by a measurement camera 15 of the base station selection system 1 in the first embodiment of the present invention. [Figure 7] 1 is a block diagram showing a functional configuration of a base station selection system 1 according to a first embodiment of the present invention. [Figure 8] 5 is a flowchart showing an operation of a base station selection unit 100 in the first embodiment of the present invention. [Figure 9] FIG. 1 is a diagram illustrating an example of a communication environment when a blocking object is a moving object. [Figure 10] FIG. 13 illustrates the deviation of lobes rf in the cross section of a cylindrical Fresnel zone Cz. [Figure 11] FIG. 13 illustrates the deviation of lobes rf in the cross section of a cylindrical Fresnel zone Cz. [Figure 12] FIG. 11 is a block diagram showing a functional configuration of a base station selection system 1a in a modified example of the first embodiment of the present invention. [Figure 13] 6 is a flowchart showing an operation of the learning device 30 in a modified example of the first embodiment of the present invention. [Figure 14] 13 is a flowchart showing an operation of the terminal station 10a in a modified example of the first embodiment of the present invention. [Figure 15] FIG. 5 is a diagram showing the communication environment illustrated in FIG. 4 as viewed from above. [Figure 16] FIG. 11 is a schematic diagram showing an overall configuration of a base station selection system 1c according to a third embodiment of the present invention. [Figure 17] FIG. 13 illustrates the deviation of lobes rf in the cross section of a cylindrical Fresnel zone Cz. [Figure 18] FIG. 13 illustrates the deviation of lobes rf in the cross section of a cylindrical Fresnel zone Cz. [Figure 19] FIG. 11 is a schematic diagram showing an overall configuration of a base station selection system 1c according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, a wireless station selection method and a wireless station selection system according to an embodiment will be described with reference to the drawings.

[0021] In reality, electromagnetic waves do not propagate only along a straight line connecting two opposing wireless stations, but also along a path within a spheroidal space called the Fresnel zone. Therefore, in order to more accurately determine the line of sight between a base station and a terminal station, it is necessary to determine the line of sight not only along the straight line connecting the base station and the terminal station, but also by taking into account the effects of obstructions that exist within the Fresnel zone.

[0022] The radius of the Fresnel zone in the millimeter wave band is, for example, about 25 cm when transmitting a distance of 50 m using electromagnetic waves in the 60 GHz band. In this way, even if there is no line of sight on the straight line connecting the base station and the terminal station, it is possible to more accurately determine the line of sight by determining the presence or absence of line of sight by further taking into account the shielding rate within the Fresnel zone.

[0023] The term "obstruction" as used herein refers to an object that may block the propagation of radio waves transmitted and received between a base station and a terminal station. Obstructions include all objects that may block the propagation of radio waves, such as buildings (architectures) such as dwellings and buildings, structures such as residential walls and elevated roads, structures such as road signs and billboards, plants such as roadside trees and garden trees, and raised ground.

[0024] In order to make the features of the wireless station selection method and the wireless station selection system in the embodiment easier to understand, an example of a conventional visibility determination method (hereinafter referred to as the "conventional method") based on three-dimensional point cloud data assuming a Fresnel zone will be described below.

[0025] The conventional method performs line of sight determination based on point cloud data, taking into consideration the Fresnel zone formed between the base station and the terminal station. For example, the conventional method determines that there is line of sight (i.e., communication is possible between the base station and the terminal station) if the number of point cloud data included within the range of the Fresnel zone is equal to or less than a predetermined threshold, and determines that there is no line of sight (i.e., communication is impossible between the base station and the terminal station) if the number is greater than the predetermined threshold.

[0026] FIG. 1 is a diagram showing a state of determining whether communication is possible or not taking into consideration the Fresnel zone fz. FIG. 1 shows a base station bs and a terminal station ts installed on a utility pole p. FIG. 1 also shows a Fresnel zone fz formed between the base station bs and the terminal station ts. FIG. 1 also shows three cross sections (cross sections cs1, cs2, and cs3) of the Fresnel zone fz. The cross sections cs1, cs2, and cs3 are planes perpendicular to the straight line connecting the base station bs and the terminal station ts. In this case, as shown in FIG. 1, the shapes of the cross sections cs1, cs2, and cs3 are circular. The radii of the cross sections cs1, cs2, and cs3 are r1, r2, and r3, respectively.

[0027] When an obstruction exists within the range of the Fresnel zone fz, point cloud data exists on the cross section of the Fresnel zone fz. For example, as shown in FIG. 1, the cross section cs1 has an area sh1-1 in which point cloud data exists. The cross section cs2 has an area sh1-2 onto which the above-mentioned area sh1-1 is projected, and an area sh2-2 into which point cloud data exists. The cross section cs3 has an area sh1-3 onto which the above-mentioned area sh1-2 is further projected, an area sh2-3 onto which the above-mentioned area sh2-2 is further projected, and an area sh3-3 into which point cloud data exists.

[0028] In this way, it becomes possible to recognize obstructions that may block radio wave propagation, such as buildings (architectures) such as dwellings and buildings, structures such as residential fences and elevated roads, structures such as road signs and billboards, plants such as roadside trees and garden trees, and raised ground, which exist within the Fresnel zone fz shown in Fig. 1, and the obstruction rate within the entire Fresnel zone fz is calculated. Note that, although the terminal station ts is installed in a building in Fig. 1, the same applies even if the terminal station is a mobile terminal.

[0029] The conventional method, for example, counts the total number of point cloud data included in multiple cross sections of the Fresnel zone fz. That is, the conventional method, for example, counts the total number of point cloud data of the cross section (cross section cs3 in the figure) closest to the terminal station ts side where the above projection is performed. Then, the conventional method compares the calculated total number of point cloud data with a predetermined threshold value to determine whether communication between the base station bs and the terminal station ts is possible.

[0030] Although only three cross sections are shown in Fig. 1, any number of cross sections can be used to count the number of point cloud data. The more cross sections used to calculate the shielding rate, the more accurate the visibility assessment becomes, but the higher the calculation load becomes.

[0031] Alternatively, instead of the number of point cloud data, the ratio of the area of ​​the area where the point cloud data exists to the area of ​​the cross section of the Fresnel zone (hereinafter referred to as "occupancy rate") may be regarded as the blocking rate, and the possibility of communication between the base station bs and the terminal station ts may be determined. For example, the conventional method may determine that there is line of sight (i.e., communication is possible between the base station and the terminal station) if the occupancy rate is equal to or less than a predetermined threshold, and that there is no line of sight (i.e., communication is impossible between the base station and the terminal station) if the occupancy rate is higher than the predetermined threshold.

[0032] Specifically, in the case of the above-mentioned determination method based on the occupancy rate, for example, multiple cross sections of the Fresnel zone fz are superimposed. In this determination method, the ratio of the area of ​​the superimposed cross sections that corresponds to the area of ​​the point cloud data is calculated as the occupancy rate. Then, this determination method regards the calculated occupancy rate as a blocking rate and compares it with a predetermined threshold value to determine whether communication between the base station bs and the terminal station ts is possible.

[0033] In other words, the line of sight determination method based on three-dimensional point cloud data considering the above-mentioned Fresnel zone shielding rate does not simply determine that there is no line of sight even if there are a number of point cloud data exceeding a threshold value between the base station and the terminal station (i.e., even if there are large or many shielding objects), but performs a more detailed line of sight determination taking the shielding rate into consideration. As a result, this line of sight determination method can obtain a more accurate line of sight determination result. This is because shielding objects include not only objects that often have a strong effect on wireless communication, such as buildings, but also objects that have a relatively weak effect on wireless communication, such as sparsely leafed trees.

[0034] Specifically, this line-of-sight determination method calculates the amount of propagation loss of radio waves based on the obtained shielding rate, for example. Then, this line-of-sight determination determines whether or not there is line of sight by designing a line of communication for wireless communication between the base station and the terminal station based on the calculated amount of loss. In the calculation of line-of-sight determination based on the propagation loss of radio waves, for example, the following formula (1) can be used.

[0035] P R =P r +G T -L-S+G R ≧P RS (1)

[0036] The meanings of the parameters in the above formula (1) are as follows: P R : Received power at the terminal station (unit [dBm]) P r: Transmission power at the base station (unit [dBm]) G T : Maximum transmit antenna gain at the base station (unit [dBi]) L: Propagation loss (unit [dB]) S: Loss due to shielding factor (unit [dB]) G R : Receiving antenna gain at the terminal station (unit [dBi]) P RS : Required receiving sensitivity at the terminal station (unit [dBm])

[0037] This line-of-sight determination method is performed when the above formula (1) is satisfied, that is, when the received power P R is the required receiving sensitivity P RS If the above formula (1) is not satisfied, that is, if the received power P R is the required receiving sensitivity P RS If it is lower, it is determined that there is no line of sight between the base station and the terminal station.

[0038] The value of the above propagation loss L can be obtained by the following equation (2).

[0039] L=20log 10 (4πd / λ) (2)

[0040] The meanings of the parameters in the above formula (2) are as follows: d: Distance between transmitter and receiver (unit [m]) λ: Wavelength of radio waves used in wireless communication (unit [m])

[0041] The value of the wavelength λ can be obtained by the following formula (3).

[0042] λ=c / (f×10 9 ) ···(3)

[0043] The meanings of the parameters in the above formula (3) are as follows: c: speed of light (i.e., c≒299,792,458 [m / s]) f: Frequency of radio waves used for wireless communication (unit: GHz)

[0044] The value of the loss S due to the above shielding factor can be obtained by the following equation (4).

[0045] S = α × Sh (4)

[0046] The meanings of the parameters in the above formula (4) are as follows: Sh: Shielding ratio (value range: 0.0000~1.0000) α: Coefficient (can be set to any value depending on frequency f and shielding factor Sh)

[0047] In this way, this visibility determination method can perform visibility determination based on whether or not formula (1) is satisfied by the above-mentioned multiple parameters and the numerical values ​​given by formulas (2) to (4).

[0048] In order to reduce the amount of calculation required for the visibility determination process, the visibility determination may be made easier by regarding the Fresnel zone, which is a spheroid, as a cylinder, which is a simpler shape. Fig. 2 is a schematic diagram showing how the visibility determination is performed by regarding the Fresnel zone as a cylinder. Fig. 2 shows a base station bs, a terminal station ts (corresponding to a representative point), and a Fresnel zone considered to be cylindrical (hereinafter referred to as a "cylindrical Fresnel zone Cz").

[0049] 2, the length of the cylindrical Fresnel zone Cz (i.e., the distance between the base station bs and the terminal station ts) is d, and the radius of the circular cross section, which is the vertical cross section of the cylindrical Fresnel zone Cz, is r. The radius r may be a predetermined value, or may be the maximum radius of the circular cross section of the ellipsoidal Fresnel zone fz that is originally formed between the base station bs and the terminal station ts.

[0050] Figure 3 shows a diagram in which a cylindrical Fresnel zone Cz is superimposed on the Fresnel zone fz. If the distance from the base station bs to the circular cross section of the Fresnel zone fz and the distance from the terminal station ts to the circular cross section of the Fresnel zone fz are d1 and d2, respectively, then d can be expressed as d=d1+d2. In addition, the n-th Fresnel zone radius r(n) is a function of the wavelength λ of the radio wave used in wireless communication, and is expressed by the following formula (5).

[0051]

number

[0052] Here, the radius r of the cross section at the center (d1=d2) in the first Fresnel zone, that is, the largest circular cross section, can be expressed by a simpler formula, as in the following formula (6).

[0053]

number

[0054] The wavelength λ is expressed as a function of the speed of light c and the frequency f of the radio wave used in wireless communication, as shown in the following equation (7). Therefore, it makes sense to change the radius of the cylindrical Fresnel zone Cz depending on the frequency f, such as the millimeter wave band.

[0055]

number

[0056] Note that a user who performs visibility determination based on this visibility determination method may set the radius r of the circular cross section of the cylindrical Fresnel zone Cz in accordance with the wavelength λ.

[0057] In this way, by regarding the Fresnel zone fz, which is a spheroid, as a cylindrical Fresnel zone Cz as shown in Figure 2, the process of extracting point cloud data that exists within the Fresnel zone (i.e., that is a factor that blocks visibility) from all point cloud data that exists within the evaluation target area is greatly simplified.

[0058] In addition, as shown in FIG. 3, the size of the circular cross section varies depending on the location in the Fresnel zone fz, which is a spheroid, so the process of overlapping the blocked parts of the circular cross sections of different sizes (by projecting them in order as described above) is complicated. On the other hand, by regarding the Fresnel zone fz as a cylindrical Fresnel zone Cz, the above complicated process can be replaced with a simple process of simply counting the number of point cloud data present in the cylinder. In other words, the visibility determination process is much simpler when a method of determining whether the number of point cloud data present in a cylinder exceeds a threshold is used than when a method of determining whether the area of ​​the blocked parts of the overlapped circular cross sections exceeds a predetermined threshold is used.

[0059] <First embodiment> A first embodiment of the present invention will be described below. The base station selection system of the first embodiment described below is a system that appropriately selects a base station to which a terminal station is connected from among a plurality of base stations. The base station selection system selects an appropriate base station in consideration of obstructions present within a Fresnel zone formed in wireless communication between the base station and the terminal station.

[0060] In the first embodiment, the base station is a wireless base station installed on an outdoor facility such as a high-rise building or a utility pole, and the terminal station is, for example, a terminal device installed on a wall of a low-rise house in an FWA (Fixed Wireless Access) system, or a mobile wireless terminal such as a smartphone or a tablet terminal. For example, an unlicensed millimeter wave radio is used for communication between the base station and the terminal station.

[0061] Fig. 4 is a schematic diagram showing an example of a communication environment in which the terminal station is a smartphone. Fig. 4 shows an urban area where, for example, office buildings, a post office, a fire station, and a convenience store are built. In addition, a plurality of utility poles on which base stations of a wireless communication system are attached are installed in this urban area. As shown in Fig. 4, for example, a base station bs1 is attached to a utility pole installed near a fire station, and a base station bs2 is attached to a utility pole installed near an office building.

[0062] Also, a user who holds a terminal station ts that is a smartphone is shown in Fig. 4. Also, Fig. 4 shows a cylindrical Fresnel zone Cz1 that approximates the Fresnel zone formed between the base station bs1 and the terminal station ts, and a cylindrical Fresnel zone Cz2 that approximates the Fresnel zone formed between the base station bs2 and the terminal station ts.

[0063] As shown in Fig. 4, a tree tr is planted between the base station bs1 and the terminal station ts. A part of the tree tr is within the range of the cylindrical Fresnel zone Cz1. Therefore, when the terminal station ts is connected to the base station bs1, there is a possibility that the tree tr will affect the quality of the wireless communication between the terminal station ts and the base station bs1 (i.e., degrade the communication quality). On the other hand, there are no obstructions such as trees within the range of the cylindrical Fresnel zone Cz2.

[0064] In the first embodiment, when an obstruction such as a tree tr shown in FIG. 4 exists between the base station bs1 and the terminal station ts and the obstruction reduces the quality of communication between the base station bs1 and the terminal station ts, the base station selection system 1 controls the terminal station ts to switch the connection to another base station (for example, base station bs2 in FIG. 4).

[0065] [Overall configuration of base station selection system] Fig. 5 is a schematic diagram showing the overall configuration of a base station selection system 1 in the first embodiment of the present invention. Fig. 5 also shows an example of a communication environment in which a terminal station is a terminal device installed on a wall of a low-rise house. In the following description, such a communication environment will be used as an example.

[0066] 5 shows a low-rise house with the terminal station 10 and the measurement camera 15 attached to the wall, a utility pole with the base station 20-1 attached, and a utility pole with the base station 20-2 attached. Also shown in Fig. 5 is a cylindrical Fresnel zone Cz that approximates the Fresnel zone formed between the base station 20-1 and the terminal station 10.

[0067] 5, a tree tr is planted between the base station 20-1 and the terminal station 10. A part of the tree tr is within the range of the cylindrical Fresnel zone Cz. Therefore, when the terminal station 10 is connected to the base station 20-1 for communication, the tree tr may affect the quality of wireless communication between the terminal station 10 and the base station 20-1 to some extent (i.e., may deteriorate the communication quality).

[0068] 5, the measurement camera 15 is attached near the terminal station 10. The measurement camera 15 captures an image in the direction in which the base station 20-1 exists. Therefore, the image captured by the measurement camera 15 shows the state seen from the position of the terminal station 10 in the direction in which the base station 20-1 exists. The measurement camera 15 may be configured to further capture an image in the direction in which other base stations (e.g., base station 20-2, etc.) exist.

[0069] Fig. 6 is a diagram showing an example of an image captured by the measurement camera 15 of the base station selection system 1 in the first embodiment. As shown in Fig. 6, the image captured by the measurement camera 15 shows the utility pole to which the base station 20-1 is attached and a tree tr planted between the terminal station 10 and the base station 20-1. Also, as shown in Fig. 6, when viewed from the position of the measurement camera 15 (i.e., the position of the terminal station 10), the base station 20-1 is not entirely visible, but is partially visible through gaps between the leaves of the tree tr.

[0070] In Fig. 6, the range surrounded by a solid line circle is the range of the cylindrical Fresnel zone Cz. Therefore, in communication between the terminal station 10 and the base station 20-1, radio waves propagate through the space within this circular range. The base station selection system 1 in the first embodiment uses an arbitrary image analysis method to identify an image area within this circular range in which an obstruction (e.g., a tree tr, etc.) is captured. Then, the base station selection system 1 calculates, for example, the ratio of the area of ​​the image area in which the obstruction is captured to the area of ​​the circle as the obstruction rate.

[0071] Then, the base station selection system 1 calculates the amount of propagation loss of radio waves using the calculated value of the shielding rate, and performs line-of-sight determination based on whether the above formula (1) is satisfied. If the base station selection system 1 determines that there is no line of sight between the terminal station 10 and the base station 20-1, it controls the terminal station 10 to switch its connection to another base station (for example, the base station 20-2 in FIG. 5).

[0072] The base station selection system 1 also simultaneously performs line-of-sight determination between the terminal station 10 and another base station (for example, the base station 20-2 in FIG. 5), and, for example, P R The terminal station 10 may be controlled so as to switch the connection destination to the base station that has the highest received power (at the terminal station 10).

[0073] [Functional configuration of the base station selection system] The following describes the functional configuration of the base station selection system 1. Fig. 7 is a block diagram showing the functional configuration of the base station selection system 1 in the first embodiment of the present invention.

[0074] As shown in FIG. 7, the base station selection system 1 includes a terminal station 10, a measurement camera 15, and a plurality of base stations 20 (a base station 20-1 and a base station 20-2).

[0075] The terminal station 10 is, for example, a terminal device installed on a wall of a low-rise house in an FWA (Fixed Wireless Access) system. The terminal station 10 may be a mobile wireless terminal such as a smartphone or a tablet terminal. The terminal station 10 communicates with the base station 20 and transmits and receives information to and from the base station 20. The terminal station 10 appropriately selects an appropriate base station 20 as a connection destination from among multiple connectable base stations 20. The terminal station 10 switches the connection destination so as to communicate with the selected base station 20.

[0076] The measurement camera 15 is, for example, an optical camera installed near the terminal station 10. Since the measurement camera 15 is a camera intended to capture an image in the direction of the base station 20 as seen from the position of the terminal station 10, it is desirable to install the measurement camera 15 in approximately the same position as the terminal station 10. The measurement camera 15 may be built into the terminal station 10. The measurement camera 15 captures an image in the direction in which the base station 20 exists, for example, periodically (for example, once a minute). The measurement camera 15 transmits image information indicating the captured image to the terminal station 10.

[0077] The base station 20 is a wireless base station installed within a communicable distance with the terminal station 10. The base station 20 is installed on outdoor equipment such as a utility pole or a high-rise building. The base station 20 is connected to the terminal station 10 for communication and transmits and receives information to and from the terminal station 10.

[0078] The following provides a more detailed explanation of the functional configuration of the terminal station 10. As shown in FIG.

[0079] Based on the image information acquired from the measurement camera 15, the base station selection unit 100 determines whether or not it is necessary to switch the base station 20 to be connected to, and if it determines that it is necessary to switch the base station 20, outputs information indicating the base station 20 newly selected as the connection destination to the base station switching control unit 110.

[0080] The base station switching control unit 110 acquires information indicating the base station 20 selected as a new connection destination, output from the base station selection unit 100. The base station switching control unit 110 controls the communication unit 120 to switch the connection destination base station 20 based on the acquired information.

[0081] The communication unit 120 is connected to the base station 20 for communication, and transmits and receives information to and from the base station 20. Under the control of the base station switching control unit 110, the communication unit 120 switches the base station 20 to which it is connected.

[0082] The functional configuration of the base station selection unit 100 will be described in more detail below. As shown in Fig. 7, the base station selection unit 100 includes an image information acquisition unit 101, a spatial information extraction unit 102, a propagation loss estimation unit 103, and a base station switching determination unit 104. Note that, in the first embodiment, the base station selection unit 100 is built into the terminal station 10, but is not limited to this configuration, and the base station selection unit 100 may be provided in an external device separately from the terminal station 10.

[0083] The image information acquisition unit 101 acquires image information transmitted from the measurement camera 15. The image information here is information indicating an image captured in the direction in which the base station 20 exists from the position of the measurement camera 15 (i.e., substantially the same position as the terminal station 10). The image information acquisition unit 101 outputs the acquired image information to the spatial information extraction unit 102.

[0084] The spatial information extraction unit 102 acquires the image information output from the image information acquisition unit 101. The spatial information extraction unit 102 performs image analysis on the image based on the acquired image information. The image analysis here refers to analysis for identifying the position of the base station 20 in the image and the state of the space within the range of the cylindrical Fresnel zone Cz from the image. Specifically, the spatial information extraction unit 102 identifies the position of the base station 20 in the image, the range of the cylindrical Fresnel zone Cz, and the blocked area within the range of the cylindrical Fresnel zone Cz. Any conventional method may be used for the image analysis method. The spatial information extraction unit 102 outputs information indicating the state of the space within the range of the cylindrical Fresnel zone Cz identified by the image analysis (hereinafter referred to as "spatial information") to the propagation loss estimation unit 103.

[0085] The propagation loss estimation unit 103 acquires the spatial information output from the spatial information extraction unit 102. The propagation loss estimation unit 103 calculates the shielding ratio within the range of the cylindrical Fresnel zone Cz specified by the spatial information extraction unit 102 based on the acquired spatial information. The propagation loss estimation unit 103 estimates the amount of propagation loss due to the shielding ratio based on the calculated shielding ratio. Specifically, the propagation loss estimation unit 103 estimates the amount of propagation loss due to the shielding ratio based on, for example, the calculated shielding ratio and the above formula (4). The propagation loss estimation unit 103 outputs information indicating the estimated amount of propagation loss due to the shielding ratio to the base station switching determination unit 104.

[0086] The base station switching determination unit 104 acquires information indicating the amount of propagation loss due to the shielding rate output from the propagation loss estimation unit 103. The base station switching determination unit 104 uses the amount of loss based on the acquired information to determine whether or not the above formula (1) is satisfied. In other words, the base station switching determination unit 104 estimates the received power P R Then, the base station switching determination unit 104 calculates the calculated reception power P R and the required receiving sensitivity P RS The received power PR The value of this is the required receiving sensitivity P RS If the value is equal to or greater than this value, it is determined that there is no need to switch the base station 20 to be connected.

[0087] On the other hand, the base station switching determination unit 104 detects the received power P R The value of this is the required receiving sensitivity P RS If the value is equal to or greater than the value of , it is determined that it is necessary to switch the connection destination base station 20. In this case, the base station switching determination unit 104 outputs, to the base station switching control unit 110, information indicating the base station 20 to be switched to as the new connection destination.

[0088] The base station selection unit 100 also performs the same process as above for another base station 20 (for example, the base station 20-2 in this case, assuming that the terminal station 10 is currently connected to the base station 20-1), and calculates the received power P R Based on the value of , it may be determined whether or not it is necessary to switch the base station 20 to be connected.

[0089] The base station selection unit 100 performs the same process as above for all base stations 20 that can be connected to the terminal station 10 to obtain the received power P R Calculate the value of each and select the one with the highest received power P R The base station 20 may be switched so that the base station 20 with the larger value of .function..times ...

[0090] For example, the spatial information extraction unit 102, the propagation loss estimation unit 103, and the base station switching determination unit 104 may be configured as components of one control unit (not shown). In this case, the control unit is realized by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Alternatively, the control unit may be configured to be realized by cooperation between software and hardware. The program read by the CPU may be stored in advance in, for example, a storage medium (not shown) included in the base station selection system 1. Furthermore, not only the spatial information extraction unit 102, the propagation loss estimation unit 103, and the base station switching determination unit 104, but also the base station switching control unit 110 may be configured as components of one control unit (not shown).

[0091] [Terminal station operation] The operation of the terminal station 10 in the first embodiment will be described below. Fig. 8 is a flowchart showing the operation of the base station selection unit 100 in the first embodiment of the present invention. The operation of the terminal station 10 shown in the flowchart of Fig. 8 is started, for example, periodically (for example, every minute).

[0092] First, the image information acquiring unit 101 acquires image information transmitted from the measurement camera 15 (step S001). The image information acquiring unit 101 outputs the acquired image information to the spatial information extracting unit .

[0093] Next, the spatial information extraction unit 102 acquires the image information output from the image information acquisition unit 101. The spatial information extraction unit 102 performs image analysis on the image based on the acquired image information, and extracts spatial information such as the position of the base station 20 in the image, the range of the cylindrical Fresnel zone Cz, and the blocked area within the range of the cylindrical Fresnel zone Cz (step S002). The spatial information extraction unit 102 outputs the extracted spatial information to the propagation loss estimation unit 103.

[0094] The propagation loss estimation unit 103 acquires the spatial information output from the spatial information extraction unit 102. Based on the acquired spatial information, the propagation loss estimation unit 103 calculates the shielding ratio within the range of the cylindrical Fresnel zone Cz specified by the spatial information extraction unit 102. Based on the calculated shielding ratio, the propagation loss estimation unit 103 estimates the amount of propagation loss due to the shielding ratio (step S003). The propagation loss estimation unit 103 outputs information indicating the estimated amount of propagation loss due to the shielding ratio to the base station switching determination unit 104.

[0095] The base station switching determination unit 104 acquires information indicating the amount of propagation loss due to the shielding rate output from the propagation loss estimation unit 103. The base station switching determination unit 104 calculates the received power at the terminal station 10 based on the amount of loss based on the acquired information. Then, the base station switching determination unit 104 determines whether the calculated value of the received power is an allowable value (step S004).

[0096] If the calculated received power value is an allowable value (step S004: YES), the base station switching determination unit 104 determines that there is no need to switch the connection destination to another base station 20. This ends the operation of the terminal station 10 shown in the flowchart of FIG.

[0097] On the other hand, if the calculated received power value is not an allowable value (step S004: NO), the base station switching determination unit 104 determines that it is necessary to switch the connection destination base station 20. In this case, the base station switching determination unit 104 outputs information indicating the base station 20 newly selected as the connection destination to the base station switching control unit 110.

[0098] The base station switching control unit 110 acquires information indicating the base station 20 selected as the new connection destination, output from the base station selection unit 100. The base station switching control unit 110 controls the communication unit 120 so as to switch the connection destination base station 20 based on the acquired information (step S005). This completes the operation of the terminal station 10 shown in the flowchart of FIG. 8.

[0099] As described above, the base station selection system 1 in the first embodiment of the present invention appropriately acquires image information indicating an image captured in the direction of the base station 20 by the measurement camera 15 installed at approximately the same position as the terminal station 10. The base station selection system 1 identifies the position of the base station 20 and an image area of ​​an obstruction existing within the range of the cylindrical Fresnel zone Cz from the acquired image. The base station selection system 1 calculates the obstruction rate of the cylindrical Fresnel zone Cz from the identified image area of ​​the obstruction, and estimates the propagation loss of radio waves in communication between the terminal station 10 and the base station 20 based on the calculated obstruction rate. The base station selection system 1 determines whether or not it is necessary to switch the base station 20 to which the terminal station 10 is connected to another base station 20 based on the estimated propagation loss.

[0100] With such a configuration, the base station selection system 1 in the first embodiment of the present invention can perform visibility determination using spatial information that represents a more immediate situation within the range of the cylindrical Fresnel zone Cz, unlike a conventional visibility determination method that simply counts the number of point cloud data that exist between the base station and the terminal station at a certain point in time. As a result, the base station selection system 1 can more appropriately select the base station 20 with which the terminal station 10 will communicate even if the effect of the obstruction on the communication quality changes over time, for example, when the obstruction is a moving object such as a vehicle.

[0101] Fig. 9 is a diagram showing an example of a communication environment when the obstruction is a moving object (large vehicle). Fig. 9 shows a low-rise house with a terminal station 10 and a measuring camera 15 attached to the wall, a utility pole with a base station 20-1 attached, and a utility pole with a base station 20-2 attached. Fig. 9 also shows a cylindrical Fresnel zone Cz that approximates the Fresnel zone formed between the base station 20-1 and the terminal station 10.

[0102] 9, a large vehicle vh exists between the base station 20-1 and the terminal station 10. A part of the large vehicle vh is within the range of the cylindrical Fresnel zone Cz. Therefore, when the terminal station 10 is communicatively connected to the base station 20-1, there is a possibility that the large vehicle vh may affect the quality of the wireless communication between the terminal station 10 and the base station 20-1 (i.e., may deteriorate the communication quality).

[0103] However, since the large vehicle vh is a moving object, there may be cases where the large vehicle vh is not present between the base station 20-1 and the terminal station 10 depending on the time period due to the movement of the large vehicle vh. Also, the magnitude of the influence of the large vehicle vh on the quality of the wireless communication performed between the terminal station 10 and the base station 20-1 (i.e., the degree to which the communication quality is degraded) differs depending on the position of the large vehicle vh. However, even in such a case where the obstruction is a moving object and the communication environment is constantly changing, the base station selection system 1 in the first embodiment of the present invention can use spatial information that represents a more immediate situation within the range of the cylindrical Fresnel zone Cz, and therefore can more appropriately select the base station 20 with which the terminal station 10 will communicate.

[0104] Although not shown, the terminal station 10 may be a mobile object such as a smartphone. In this case, the measurement camera 15 is provided in the terminal station 10 (smartphone, etc.), for example. In this case, even if the terminal station 10 moves, a mechanism is required that allows the measurement camera 15 to capture an image in the direction of the base station 20-1 as necessary. Furthermore, both the terminal station 10 and the obstruction may be mobile objects. Even in such a case, the base station selection system 1 in the first embodiment of the present invention can use spatial information that represents a more immediate situation within the range of the cylindrical Fresnel zone Cz, and therefore can more appropriately select the base station 20 to which the terminal station 10 will communicate.

[0105] Furthermore, the base station selection system 1 in the first embodiment of the present invention, having the above-mentioned configuration, can perform visibility determination by considering the presence of obstructions in the entire space within the range of the cylindrical Fresnel zone Cz, unlike a conventional visibility determination method that uses point cloud data of only some cross sections of the Fresnel zone. This allows the base station selection system 1 to more appropriately select the base station 20 to which the terminal station 10 will communicate, even if the influence of obstructions on communication quality changes depending on the season or weather, such as when the obstructions are trees.

[0106] <Modification of the first embodiment> In the above-described first embodiment, an example is shown in Fig. 6 where the leaves of the tree tr are sparsely distributed over the entire cross section of the cylindrical Fresnel zone Cz as viewed from the terminal station 10. However, as shown in Figs. 10 and 11, for example, the leaves rf may be concentrated in a portion of the cross section of the cylindrical Fresnel zone Cz.

[0107] In the cross section of the cylindrical Fresnel zone Cz shown in FIG. 10, the leaves rf are biased toward the upper left. On the other hand, in the cross section of the cylindrical Fresnel zone Cz shown in FIG. 11, the leaves rf are biased toward the center. In this case, the shielding ratios in both FIG. 10 and FIG. 11 are equivalent. However, in the case of FIG. 10, the entire base station 20-1 can be seen directly from the position of the terminal station 10, but in the case of FIG. 11, only a part of the base station 20 can be seen directly from the position of the terminal station 10 because it is in the shadow of the leaves rf. In such a case, even if the shielding ratios are equivalent, it is considered that a large difference occurs in the value of the propagation loss based on the shielding ratio. Specifically, it is expected that the value of the propagation loss will be larger in the case of FIG. 11.

[0108] A base station selection system 1a in a modification of the first embodiment described below estimates propagation loss from spatial information using a trained model by machine learning, instead of calculating a shielding ratio based on spatial information and estimating propagation loss as in the base station selection system 1 in the above-described first embodiment. This allows the base station selection system 1a in the modification of the first embodiment to estimate a more accurate propagation loss even if the shielding ratios are the same value.

[0109] [Functional configuration of the base station selection system] The functional configuration of the base station selection system 1a will be described below. Fig. 12 is a block diagram showing the functional configuration of the base station selection system 1a in a modified example of the first embodiment of the present invention.

[0110] As shown in FIG. 12, the base station selection system 1a includes a terminal station 10a, a measurement camera 15, a plurality of base stations 20 (a base station 20-1 and a base station 20-2), and a learning device 30.

[0111] The terminal station 10a is, for example, a terminal device installed on the wall of a low-rise house in an FWA system. The terminal station 10a may be a mobile wireless terminal such as a smartphone or a tablet terminal. The terminal station 10a is connected to the base station 20 for communication and transmits and receives information to and from the base station 20. The terminal station 10a appropriately selects an appropriate base station 20 as a connection destination from among a plurality of connectable base stations 20. The terminal station 10a switches the connection destination so as to connect to and communicate with the selected base station 20.

[0112] The measurement camera 15 is, for example, an optical camera installed near the terminal station 10a. The measurement camera 15 is a camera intended to capture an image in the direction of the base station 20 as seen from the position of the terminal station 10a, so it is desirable to install it in approximately the same position as the terminal station 10a. The measurement camera 15 may be built into the terminal station 10a. The measurement camera 15 captures an image in the direction in which the base station 20 exists, for example, periodically (for example, once a minute). The measurement camera 15 transmits image information indicating the captured image to the terminal station 10a.

[0113] The base station 20 is a wireless base station installed within a communicable distance with the terminal station 10a. The base station 20 is installed on outdoor equipment such as a utility pole or a high-rise building. The base station 20 is connected to the terminal station 10a for communication and transmits and receives information to and from the terminal station 10a.

[0114] The base station 20 may output information indicating the propagation loss of radio waves actually generated in communication with the terminal station 10a to a learning device 30 described later. In this case, the information indicating the propagation loss is used as one of the teacher data for machine learning performed by the learning device 30, for example.

[0115] The functional configuration of the terminal station 10a will be described in more detail below. As shown in FIG. 12, the terminal station 10a includes a base station selection unit 100a, a base station switching control unit 110, and a communication unit 120.

[0116] The base station selection unit 100a judges whether or not it is necessary to switch the base station 20 to be connected based on the image information acquired from the measurement camera 15, and when it judges that it is necessary to switch the base station 20, outputs information indicating the base station 20 newly selected as the connection destination to the base station switching control unit 110. Note that the configurations of the base station switching control unit 110 and the communication unit 120 are the same as those of the first embodiment described above, and therefore the description thereof will be omitted.

[0117] The functional configuration of the base station selection unit 100a will be described in more detail below. As shown in Fig. 12, the base station selection unit 100a includes an image information acquisition unit 101, a spatial information extraction unit 102a, a propagation loss estimation unit 103a, and a base station switching determination unit 104. In the modification of the first embodiment, the base station selection unit 100a is built in the terminal station 10a, but the present invention is not limited to this configuration, and the base station selection unit 100a may be provided in an external device separately from the terminal station 10a.

[0118] The image information acquisition unit 101 acquires image information transmitted from the measurement camera 15. The image information here is information indicating an image captured in the direction in which the base station 20 exists from the position of the measurement camera 15 (i.e., substantially the same position as the terminal station 10). The image information acquisition unit 101 outputs the acquired image information to the spatial information extraction unit 102a.

[0119] The spatial information extraction unit 102a acquires the image information output from the image information acquisition unit 101. The spatial information extraction unit 102a performs image analysis on the image based on the acquired image information. The image analysis here refers to analysis for identifying the position of the base station 20 in the image and the state of the space within the range of the cylindrical Fresnel zone Cz from the image. Specifically, the spatial information extraction unit 102a identifies the position of the base station 20 in the image, the range of the cylindrical Fresnel zone Cz, and the like. Any conventional method may be used for the image analysis method. The spatial information extraction unit 102a outputs information including information indicating the state of the space within the range of the cylindrical Fresnel zone Cz identified by the image analysis and image information as spatial information to the propagation loss estimation unit 103.

[0120] 12, the spatial information extraction unit 102a may output the spatial information to a learning device 30 described later. In this case, the spatial information is used as one of the teacher data for machine learning performed by the learning device 30, for example.

[0121] The propagation loss estimation unit 103a acquires spatial information output from the spatial information extraction unit 102a. The propagation loss estimation unit 103a also acquires a learning model (hereinafter referred to as a "trained model") that has been trained by machine learning and is transmitted from a learning device 30 described later. This trained model receives spatial information as an input and outputs an estimated value of the amount of propagation loss due to the shielding rate. The propagation loss estimation unit 103a inputs the spatial information acquired from the spatial information extraction unit 102a to the trained model, thereby obtaining an estimated value of the amount of propagation loss due to the shielding rate. The propagation loss estimation unit 103a outputs information indicating the estimated amount of propagation loss due to the shielding rate to the base station switching determination unit 104.

[0122] The base station switching determination unit 104 acquires information indicating the amount of propagation loss due to the shielding rate output from the propagation loss estimation unit 103a. The base station switching determination unit 104 uses the amount of loss based on the acquired information to determine whether or not the above formula (1) is satisfied. In other words, the base station switching determination unit 104 estimates the received power P R Then, the base station switching determination unit 104 calculates the calculated reception power P R and the required receiving sensitivity P RS The received power P R The value of this is the required receiving sensitivity P RS If the value is equal to or greater than this value, it is determined that there is no need to switch the base station 20 to be connected.

[0123] On the other hand, the base station switching determination unit 104 detects the received power P R The value of this is the required receiving sensitivity P RS If the value is equal to or greater than the value of , it is determined that it is necessary to switch the connection destination base station 20. In this case, the base station switching determination unit 104 outputs, to the base station switching control unit 110, information indicating the base station 20 to be switched to as the new connection destination.

[0124] The base station selection unit 100a also performs the same process as above for another base station 20 (for example, the base station 20-2 in this case, assuming that the terminal station 10a is currently connected to the base station 20-1), and calculates the received power P R Based on the value of , it may be determined whether or not it is necessary to switch the base station 20 to be connected.

[0125] The base station selection unit 100a performs the same process as above for all base stations 20 with which the terminal station 10a can communicate, and obtains the received power P R Calculate the value of each and select the one with the highest received power P R The base station 20 may be switched so that the base station 20 with the larger value of .function..times ...

[0126] For example, the spatial information extraction unit 102a, the propagation loss estimation unit 103a, and the base station switching determination unit 104 may be configured as components of one control unit (not shown). In this case, the control unit is realized by, for example, a hardware processor such as a CPU executing a program (software). Alternatively, the control unit may be configured to be realized by cooperation between software and hardware. The program read by the CPU may be stored in advance in, for example, a storage medium (not shown) included in the base station selection system 1a. Furthermore, not only the spatial information extraction unit 102a, the propagation loss estimation unit 103a, and the base station switching determination unit 104, but also the base station switching control unit 110 may be configured as components of one control unit (not shown).

[0127] The learning device 30 is an information processing device such as a general-purpose computer. The learning device 30 includes a teacher data acquisition unit 301, a learning unit 302, and a trained model transmission unit 303. The learning device 30 may be built into the terminal station 10a.

[0128] The teacher data acquisition unit 301 acquires a large amount of teacher data from an external device. The teacher data here is a set of space information indicating the actual spatial situation within the range of the cylindrical Fresnel zone Cz and information indicating the propagation loss of radio waves actually occurring in the communication between the terminal station 10a and the base station 20 in the corresponding situation. The teacher data acquisition unit 301 outputs the teacher data to the learning unit 302.

[0129] In addition, the teacher data acquisition unit 301 may further use, as teacher data, information that is a pair of the actual spatial information output from the spatial information extraction unit 102a and information indicating the actual propagation loss output from the base station 20.

[0130] The learning unit 302 acquires the teacher data output from the teacher data acquisition unit 301. The learning unit 302 performs machine learning using the spatial information included in the teacher data and information indicating the propagation loss as input. As described above, in the modification of the first embodiment, the spatial information includes, for example, spatial information including information such as the position of the base station 20 and the range of the cylindrical Fresnel zone Cz, and image information. The learning unit 302 outputs the trained model generated by the machine learning to the trained model transmission unit 303.

[0131] The trained model transmission unit 303 acquires the trained model output from the training unit 302. The trained model transmission unit 303 transmits the acquired trained model to the propagation loss estimation unit 103a.

[0132] [Learning device operation] The following describes the operation of the learning device 30 in the modified example of the first embodiment. Fig. 13 is a flowchart showing the operation of the learning device 30 in the modified example of the first embodiment of the present invention.

[0133] First, the teacher data acquisition unit 301 acquires a large amount of teacher data from an external device (step S101). The teacher data acquisition unit 301 outputs the teacher data to the learning unit 302.

[0134] Next, the learning unit 302 acquires the teacher data output from the teacher data acquisition unit 301. The learning unit 302 performs machine learning using the spatial information included in the teacher data and the information indicating the propagation loss as input (step S102). The learning unit 302 outputs the trained model generated by the machine learning to the trained model transmission unit 303.

[0135] Next, the trained model transmission unit 303 acquires the trained model output from the training unit 302. The trained model transmission unit 303 transmits the acquired trained model to the propagation loss estimation unit 103a (step S103). This completes the operation of the training device 30 shown in the flowchart of FIG.

[0136] [Terminal station operation] The operation of the terminal station 10a in the modified example of the first embodiment of the present invention will be described below. Fig. 14 is a flowchart showing the operation of the terminal station 10a in the modified example of the first embodiment of the present invention. The operation of the terminal station 10 shown in the flowchart of Fig. 14 is started, for example, periodically (for example, every minute).

[0137] First, the propagation loss estimation unit 103a acquires the trained model transmitted from the training device 30 (step S201).

[0138] Next, the image information acquiring unit 101 acquires the image information transmitted from the measurement camera 15 (step S202). The image information acquiring unit 101 outputs the acquired image information to the spatial information extracting unit 102a.

[0139] Next, the spatial information extraction unit 102a acquires the image information output from the image information acquisition unit 101. The spatial information extraction unit 102a performs image analysis on the image based on the acquired image information, and extracts information such as the position of the base station 20 in the image and the range of the cylindrical Fresnel zone Cz (step S203). The spatial information extraction unit 102a outputs information including the extracted information and the image information as spatial information to the propagation loss estimation unit 103a.

[0140] The propagation loss estimation unit 103a acquires the spatial information output from the spatial information extraction unit 102a. The propagation loss estimation unit 103a inputs the spatial information acquired from the spatial information extraction unit 102a to the learned model to obtain an estimated value of the amount of propagation loss due to the shielding ratio (step S204). The propagation loss estimation unit 103a outputs information indicating the estimated amount of propagation loss due to the shielding ratio to the base station switching determination unit 104.

[0141] The base station switching determination unit 104 acquires information indicating the amount of propagation loss due to the shielding rate output from the propagation loss estimation unit 103a. The base station switching determination unit 104 calculates the received power at the terminal station 10a based on the amount of loss based on the acquired information. Then, the base station switching determination unit 104 determines whether the calculated value of the received power is an allowable value (step S205).

[0142] If the calculated received power value is an allowable value (step S205: YES), the base station switching determination unit 104 determines that there is no need to switch the connection destination to another base station 20. This ends the operation of the terminal station 10 shown in the flowchart of FIG.

[0143] On the other hand, if the calculated received power value is not an allowable value (step S205: NO), the base station switching determination unit 104 determines that it is necessary to switch the connection destination base station 20. In this case, the base station switching determination unit 104 outputs information indicating the base station 20 newly selected as the connection destination to the base station switching control unit 110.

[0144] The base station switching control unit 110 acquires information indicating the base station 20 selected as the new connection destination, output from the base station selection unit 100a. The base station switching control unit 110 controls the communication unit 120 so as to switch the connection destination base station 20 based on the acquired information (step S206). This ends the operation of the terminal station 10 shown in the flowchart of FIG. 14.

[0145] As described above, the base station selection system 1a in the modified example of the first embodiment of the present invention appropriately acquires image information indicating an image captured in the direction of the base station 20 by the measurement camera 15 installed at approximately the same position as the terminal station 10a. The base station selection system 1a identifies the position of the base station 20 and an image area of ​​an obstruction existing within the range of the cylindrical Fresnel zone Cz from the acquired image. The base station selection system 1a estimates the propagation loss of radio waves in communication between the terminal station 10a and the base station 20 by inputting information indicating the identified image area and spatial information including the image information into the trained model. The base station selection system 1 determines whether or not it is necessary to switch the base station 20 to which the terminal station 10a is connected to another base station 20 based on the estimated propagation loss.

[0146] With such a configuration, the base station selection system 1a in the modified example of the first embodiment of the present invention can perform visibility determination using spatial information that represents a more immediate situation within the range of the cylindrical Fresnel zone Cz, unlike a conventional visibility determination method that simply counts the number of point cloud data that exist between the base station and the terminal station at a certain point in time. As a result, the base station selection system 1a can more appropriately select the base station 20 with which the terminal station 10a will communicate even if the influence of an obstruction on communication quality changes over time, for example, when the obstruction is a moving object such as a vehicle.

[0147] Furthermore, by being provided with such a configuration, the base station selection system 1a in the modified example of the first embodiment of the present invention can perform visibility determination by considering the presence of obstructions in the entire space within the range of the cylindrical Fresnel zone Cz, unlike a conventional visibility determination method that uses point cloud data of only some cross sections of the Fresnel zone. As a result, the base station selection system 1a can more appropriately select the base station 20 to which the terminal station 10a will communicate even if the influence of obstructions on communication quality changes depending on the season or weather, such as when the obstructions are trees.

[0148] Furthermore, by being provided with such a configuration, the base station selection system 1a in the modification of the first embodiment of the present invention estimates the propagation loss from spatial information using a trained model by machine learning, instead of calculating the shielding ratio based on spatial information and estimating the propagation loss as in the base station selection system 1 in the above-mentioned first embodiment. As a result, even in cases where the shielding ratios are the same, such as in the cylindrical Fresnel zones Cz shown in Figs. 10 and 11, the base station selection system 1a in the modification of the first embodiment can estimate the propagation loss more accurately without simply estimating the same propagation loss.

[0149] <Second embodiment> Recently, in order to expand the communication area, it has been realized or considered to use artificial satellites such as low earth orbit satellites (LEO) and high altitude unmanned aerial vehicles (HAPS) as base stations. A base station selection system 1b in a second embodiment described below uses an imaging device (measurement camera) mounted on such a device flying in the sky (hereinafter referred to as an "aircraft") to determine whether or not it is necessary to switch the base station with which a terminal station is connected for communication.

[0150] In the first embodiment and the modified example of the first embodiment described above, the propagation loss is estimated based on an image captured in the direction of the base station 20 by the measurement camera 15 installed at approximately the same position as the terminal station 10, and whether or not it is necessary to switch the base station 20 with which the terminal station 10 is connected for communication is determined. In contrast, the base station selection system 1b in the second embodiment described below captures an image of an area including a Fresnel zone formed between the terminal station and the base station from the sky by a measurement camera installed on an aircraft. The base station selection system 1b estimates the propagation loss based on the image captured from the sky, and determines whether or not it is necessary to switch the base station with which the terminal station is connected for communication.

[0151] Fig. 15 is a diagram showing the communication environment shown in Fig. 4 as viewed from above. As shown in Fig. 15, by looking down from the sky onto the ground, it becomes possible to view the cylindrical Fresnel zone Cz1 and the cylindrical Fresnel zone Cz2 from the direction of the side of the cylinder. In this way, when viewed from the direction of the side of the cylinder, it becomes possible to confirm where an obstruction (for example, a tree tr, etc.) exists between the terminal station ts and the base station bs1 (or between the terminal station ts and the base station bs2).

[0152] That is, for example, it becomes possible to grasp a situation in which within the cylindrical Fresnel zone Cz1, obstructions are concentrated at positions closer to the terminal station ts, obstructions are concentrated at positions closer to the base station bs, obstructions are concentrated at a position near the center between the terminal station ts and the base station bs, obstructions are concentrated at both positions closer to the terminal station ts and closer to the base station bs, or obstructions are distributed throughout the entire cylindrical Fresnel zone Cz1.

[0153] [Overall configuration of base station selection system] Fig. 16 is a schematic diagram showing the overall configuration of a base station selection system 1b in the second embodiment of the present invention. Fig. 16 shows a low-rise house with a terminal station 10 attached to the wall, a utility pole with a base station 20-1 attached, a utility pole with a base station 20-2 attached, and a low-earth orbit satellite 50 (LEO) and a high-altitude unmanned aerial vehicle 51 (HAPS) that are aircraft flying in the sky. A measurement camera 15 (not shown) is attached to each of the low-earth orbit satellite 50 and the high-altitude unmanned aerial vehicle 51. Fig. 16 also shows a cylindrical Fresnel zone Cz that approximates the Fresnel zone formed between the base station 20-1 and the terminal station 10.

[0154] 16 shows a low-orbit satellite 50 and a high-altitude drone 51, but in the base station selection system 1b in the second embodiment, the low-orbit satellite 50 and the high-altitude drone 51 have the same role, so at least one of them is sufficient. In the following description, a case where a low-orbit satellite 50 is used will be described as an example, but a high-altitude drone 51 may be used instead. Unlike the first embodiment and the modified example of the first embodiment described above, a measurement camera is not installed near the terminal station 10.

[0155] 16, a tree tr is planted between the base station 20-1 and the terminal station 10. A part of the tree tr is within the range of the cylindrical Fresnel zone Cz. Therefore, when the terminal station 10 is connected to the base station 20-1 for communication, the tree tr may affect the quality of wireless communication between the terminal station 10 and the base station 20-1 to some extent (i.e., may deteriorate the communication quality).

[0156] As described above, the low-orbit satellite 50 is fitted with a measurement camera 15 (not shown). The measurement camera 15 captures an image, for example, every time the low-orbit satellite 50 passes above the Fresnel zone. If the high-altitude unmanned aerial vehicle 51 described above is used, the measurement camera 15 may capture an image periodically (for example, once a minute). The measurement camera 15 transmits image information indicating the captured image to the terminal station 10.

[0157] [Functional configuration of the base station selection system] The functional configuration of the base station selection system 1b in the second embodiment is basically the same as the functional configuration of the base station selection system 1 in the first embodiment shown in the block diagram of Fig. 7. The functional configuration of the base station selection system 1b differs from the functional configuration of the base station selection system 1 in that the measurement camera 15 is not installed near the terminal station 10 but is provided on a low-orbit satellite 50 (or a high-altitude unmanned vehicle 51) flying in the sky.

[0158] The shape of the range of the cylindrical Fresnel zone Cz extracted from the image by the spatial information extraction unit 102 varies depending on the position of the measurement camera 15 as described above. That is, in the first embodiment, the shape of the cylindrical Fresnel zone Cz in the planar image is circular, for example, as shown in Figures 6, 10, and 11. On the other hand, in the second embodiment, since imaging is performed from the direction of the side of the cylindrical Fresnel zone Cz, the shape of the cylindrical Fresnel zone Cz in the planar image is square (for example, rectangular), as described later.

[0159] The propagation loss estimation unit 103 calculates, for example, the ratio of the area of ​​an image region in which the obstruction appears to the area of ​​a square that is the range of a cylindrical Fresnel zone Cz in a planar image as the obstruction ratio.

[0160] The functional configuration of the base station selection system 1b in the second embodiment may be basically the same as the functional configuration of the base station selection system 1a in the modified example of the first embodiment shown in the block diagram of Fig. 12. In this case, the functional configuration of the base station selection system 1b differs from the functional configuration of the base station selection system 1a in that the measurement camera 15 is not installed near the terminal station 10 but is provided on a low-orbit satellite 50 (or a high-altitude unmanned vehicle 51) flying in the sky.

[0161] 17 and 18, the cylindrical Fresnel zone Cz has a rectangular shape in the planar image captured by the measurement camera 15. Within the range of this rectangle, even if the blocking rate is the same, there are various possible positions where a blocking object may exist.

[0162] For example, in the cylindrical Fresnel zone Cz illustrated in Fig. 17, the leaves rf are concentrated in a part of the rectangular range of the cylindrical Fresnel zone Cz. Specifically, in the cylindrical Fresnel zone Cz illustrated in Fig. 17, the leaves rf are densely present in a position closer to the base station 20-1 than to the terminal station 10, and in an upper position in the figure.

[0163] On the other hand, for example, in the cylindrical Fresnel zone Cz illustrated in FIG. 18, the leaves rf are biased toward the upper position in the figure, but unlike the cylindrical Fresnel zone Cz illustrated in FIG. 17, there is relatively no bias between the terminal station 10 and the base station 20-1, and the leaves rf are evenly distributed.

[0164] Thus, the position of the obstruction within the cylindrical Fresnel zone Cz shown in Fig. 17 is different from the position of the obstruction within the cylindrical Fresnel zone Cz shown in Fig. 18. However, if the measurement camera 15 is installed at approximately the same position as the terminal station 10 as in the first embodiment and the modified example of the first embodiment described above, the position of the obstruction in the captured image will be approximately the same in both cases. Specifically, in both cases, the position of the obstruction will be similar to the position of the leaf rf within the cylindrical Fresnel zone Cz shown in Fig. 10 described above.

[0165] It is considered that the shielding ratio within the range of the cylindrical Fresnel zone Cz shown in Fig. 17 and the shielding ratio within the range of the cylindrical Fresnel zone Cz shown in Fig. 18 will be substantially the same, but it is also considered that a large difference will occur in the value of the propagation loss based on the shielding ratio. Specifically, in the case of Fig. 17, the leaves rf are more densely present, so it is expected that the value of the propagation loss will be larger.

[0166] In this way, since it is expected that the propagation loss value may differ even if the shielding rate has the same value, it is considered that it is possible to more accurately determine whether or not it is necessary to switch the base station 20 with which the terminal station 10 is connected to communicate by estimating the propagation loss from spatial information using a trained model through machine learning, as in the base station selection system 1a in the modified example of the first embodiment described above, rather than calculating the shielding rate based on spatial information and estimating the propagation loss, as in the base station selection system 1 in the first embodiment described above.

[0167] [Operation of terminal station and learning device] The operation of the terminal station 10 in the second embodiment is basically similar to the operation of the terminal station 10 in the first embodiment shown in the flowchart of Fig. 8, or the operation of the terminal station 10 in the modified example of the first embodiment shown in the flowchart of Fig. 14. Moreover, the operation of the learning device 30 in the second embodiment is basically similar to the operation of the learning device 30 in the modified example of the first embodiment shown in the flowchart of Fig. 13.

[0168] As described above, the base station selection system 1b in the second embodiment of the present invention appropriately acquires image information indicating an image captured by the measurement camera 15 installed on a low-orbit satellite 50 (or a high-altitude unmanned vehicle 51) flying in the sky, the image information indicating at least the range of a cylindrical Fresnel zone Cz formed in communication between the terminal station 10 and the base station 20. From the acquired image, the base station selection system 1b identifies the position of the terminal station 10, the position of the base station 20, and the image area of ​​an obstruction existing within the range of the cylindrical Fresnel zone Cz.

[0169] The base station selection system 1b calculates the shielding rate of the cylindrical Fresnel zone Cz from the identified image area of ​​the shielding object, and estimates the propagation loss of radio waves in communication between the terminal station 10 and the base station 20 based on the calculated shielding rate. The base station selection system 1 determines whether or not it is necessary to switch the base station 20 to which the terminal station 10 is connected to another base station 20 based on the estimated propagation loss.

[0170] Alternatively, the base station selection system 1b estimates a propagation loss of radio waves in communication between the terminal station 10 and the base station 20 by inputting information indicating the identified image area and spatial information including the image information into a trained model. The base station selection system 1 determines whether or not it is necessary to switch the base station 20 to which the terminal station 10 is connected to another base station 20, based on the estimated propagation loss.

[0171] With such a configuration, the base station selection system 1b in the second embodiment of the present invention can perform visibility determination using spatial information that represents a more immediate situation within the range of the cylindrical Fresnel zone Cz, unlike a conventional visibility determination method that simply counts the number of point cloud data that exist between the base station and the terminal station at a certain point in time. As a result, the base station selection system 1b can more appropriately select the base station 20 with which the terminal station 10 will communicate even if the influence of an obstruction on communication quality changes over time, for example, when the obstruction is a moving object such as a vehicle.

[0172] Furthermore, by being provided with such a configuration, the base station selection system 1b in the second embodiment of the present invention can perform visibility determination by considering the presence of obstructions in the entire space within the range of the cylindrical Fresnel zone Cz, unlike a conventional visibility determination method that uses point cloud data of only some cross sections of the Fresnel zone. As a result, the base station selection system 1b can more appropriately select the base station 20 to which the terminal station 10 will communicate even if the influence of obstructions on communication quality changes depending on the season or weather, such as when the obstructions are trees.

[0173] Furthermore, since the base station selection system 1b in the second embodiment of the present invention is configured to estimate propagation loss from spatial information using a trained model based on machine learning, even in cases where the shielding rates are equivalent, such as the cylindrical Fresnel zone Cz shown in Figures 17 and 18, it is possible to estimate the propagation loss more accurately without simply estimating the same propagation loss.

[0174] Moreover, the base station selection system 1b in the second embodiment of the present invention does not use an image captured by a measurement camera 15 installed in a position near the terminal station 10 as in the above-mentioned first embodiment and the modified example of the first embodiment, but uses an image captured by a measurement camera 15 installed in a low-orbit satellite 50 (or a high-altitude unmanned vehicle 51) flying in the sky. This allows the base station selection system 1b in the second embodiment to obtain more information about the position of an obstruction within the cylindrical Fresnel zone Cz, and therefore can estimate the propagation loss more accurately, and can more accurately determine whether or not it is necessary to switch the base station 20 to which the terminal station 10 is connected to another base station 20.

[0175] <Third embodiment> In the first embodiment and the modified example of the first embodiment described above, a configuration is used in which it is determined whether or not it is necessary to switch the base station 20 to which the terminal station 10 is connected to another base station 20 based on an image captured by a measurement camera 15 installed in a position near the terminal station 10. On the other hand, in the second embodiment described above, a configuration is used in which it is determined whether or not it is necessary to switch the base station 20 to which the terminal station 10 is connected to another base station 20 based on an image captured by a measurement camera 15 installed in a low-orbit satellite 50 (or a high-altitude unmanned vehicle 51) flying in the sky.

[0176] If both of the above images can be used, it is possible to identify the three-dimensional position of each obstruction within the cylindrical Fresnel zone Cz. In this way, if both of the images can be used, it is considered that the accuracy of estimating the propagation loss of radio waves in the communication between the terminal station 10 and the base station 20 will be improved.

[0177] [Overall configuration of base station selection system] Fig. 19 is a schematic diagram showing the overall configuration of a base station selection system 1c in the third embodiment of the present invention. Fig. 19 shows a low-rise house with a terminal station 10 and a measurement camera 15 attached to the wall, a utility pole with a base station 20-1 attached, a utility pole with a base station 20-2 attached, and a low-earth orbit satellite 50 (LEO) and a high-altitude unmanned aerial vehicle 51 (HAPS) that are aircraft flying in the sky. The low-earth orbit satellite 50 and the high-altitude unmanned aerial vehicle 51 are each equipped with a measurement camera 15 (not shown). Fig. 19 also shows a cylindrical Fresnel zone Cz that approximates the Fresnel zone formed between the base station 20-1 and the terminal station 10.

[0178] 19 shows a low-orbit satellite 50 and a high-altitude drone 51, but in the base station selection system 1c in the third embodiment, the low-orbit satellite 50 and the high-altitude drone 51 have the same role, so at least one of them is sufficient. As in the first embodiment and the modified example of the first embodiment described above, a measurement camera 15 is also installed near the terminal station 10.

[0179] 16, a tree tr is planted between the base station 20-1 and the terminal station 10. A part of the tree tr is within the range of the cylindrical Fresnel zone Cz. Therefore, when the terminal station 10 is connected to the base station 20-1 for communication, the tree tr may affect the quality of wireless communication between the terminal station 10 and the base station 20-1 to some extent (i.e., may deteriorate the communication quality).

[0180] As described above, the low-orbit satellite 50 is fitted with a measurement camera 15 (not shown). The measurement camera 15 captures an image, for example, every time the low-orbit satellite 50 passes above the Fresnel zone. If the high-altitude unmanned aerial vehicle 51 described above is used, the measurement camera 15 may capture an image periodically (for example, once a minute). The measurement camera 15 transmits image information indicating the captured image to the terminal station 10.

[0181] The terminal station 10 determines whether or not it is necessary to switch the base station 20 to which the terminal station 10 is connected to another base station 20 based on both an image captured by a measurement camera 15 installed in a position near the terminal station 10 itself and an image captured by a measurement camera 15 installed on a low-orbit satellite 50 (or a high-altitude unmanned aerial vehicle 51) flying above.

[0182] By being provided with the above-mentioned configuration, the base station selection system 1c in the third embodiment can estimate the propagation loss of radio waves in the communication between the terminal station 10 and the base station 20 more accurately than the base station selection system 1 in the above-mentioned first embodiment, the base station selection system 1a in the modified example of the above-mentioned first embodiment, and the base station selection system 1b in the above-mentioned second embodiment. As a result, the base station selection system 1c in the third embodiment can more accurately determine whether or not it is necessary to switch the base station 20 to which the terminal station 10 is connected to another base station 20.

[0183] In each of the above-described embodiments, for example, three-dimensional point cloud data obtained by MMS may be further used to determine whether or not it is necessary to switch the base station 20 to which the terminal station 10 is connected to another base station 20.

[0184] For example, the propagation loss estimation unit 103 shown in FIG. 7 may estimate the propagation loss by taking into consideration both the shielding ratio calculated based on an image captured by the measurement camera 15 (hereinafter referred to as the "shielding ratio based on an image") and the shielding ratio calculated based on point cloud data (hereinafter referred to as the "shielding ratio based on point cloud data").

[0185] In this case, in order to obtain a coverage rate based on point cloud data, the base station selection systems 1, 1a to 1c are provided with, in addition to (or instead of) the measurement camera 15, for example, a laser radar (also called "LiDAR (Light Detection And Ranging)") that measures the position of an object and generates point cloud data. Also, in this case, the base station selection units 100, 100a of the base station selection systems 1, 1a to 1c are provided with, in addition to (or instead of) the image information acquisition unit 101, for example, a point cloud data acquisition unit that acquires the generated point cloud data.

[0186] Specifically, for example, the propagation loss estimation unit 103 may estimate the propagation loss based on an average value of the shielding ratio based on the image and the shielding ratio based on the point cloud data. Alternatively, for example, the propagation loss estimation unit 103 may estimate the propagation loss based on the larger value of the shielding ratio based on the image and the shielding ratio based on the point cloud data. Alternatively, for example, the propagation loss estimation unit 103 may estimate the propagation loss based on the smaller value of the shielding ratio based on the image and the shielding ratio based on the point cloud data.

[0187] In addition, for example, the propagation loss estimation unit 103a shown in the above-mentioned FIG. 12 may further input, in addition to the spatial information acquired from the spatial information extraction unit 102a, three-dimensional point cloud data obtained by MMS (or information based on the point cloud data) to the learned model, thereby obtaining an estimate of the amount of propagation loss due to the shielding rate.

[0188] In this case, the teacher data acquiring unit 301 acquires a large amount of teacher data further including three-dimensional point cloud data (or information based on the point cloud data) from an external device. The teacher data here is a set of spatial information indicating the actual spatial situation within the range of the cylindrical Fresnel zone Cz, three-dimensional point cloud data (or information based on the point cloud data), and information indicating the propagation loss of radio waves actually occurring in the communication between the terminal station 10a and the base station 20 in the actual situation. The teacher data acquiring unit 301 outputs the teacher data to the learning unit 302.

[0189] In addition, the teacher data acquisition unit 301 may further use, as teacher data, information that is a pair of the actual spatial information output from the spatial information extraction unit 102a and information indicating the actual propagation loss output from the base station 20.

[0190] The learning unit 302 acquires the teacher data output from the teacher data acquisition unit 301. The learning unit 302 performs machine learning using as input the spatial information included in the teacher data, the point cloud data (or information based on the point cloud data), and information indicating the propagation loss. As described above, the spatial information includes, for example, spatial information including information such as the position of the base station 20 and the range of the cylindrical Fresnel zone Cz, and image information. The learning unit 302 outputs the learned model generated by the machine learning to the learned model transmission unit 303.

[0191] The trained model transmission unit 303 acquires the trained model output from the training unit 302. The trained model transmission unit 303 transmits the acquired trained model to the propagation loss estimation unit 103a.

[0192] In this way, it is considered that the propagation loss estimation unit 103a can more accurately calculate the amount of propagation loss due to the shielding rate by configuring the propagation loss estimation unit 103a to input, in addition to spatial information, three-dimensional point cloud data (or information based on the point cloud data) to the trained model. This makes it possible to more accurately determine whether or not it is necessary to switch the base station 20 to which the terminal station 10 is connected to another base station 20.

[0193] According to the above-described embodiment, the wireless station selection system includes an acquisition unit, an estimation unit, and a determination unit. For example, the wireless station selection system is the base station selection system 1 in the embodiment, the acquisition unit is the image information acquisition unit 101 in the embodiment, the estimation unit is the propagation loss estimation unit 103 in the embodiment, and the determination unit is the base station switching determination unit 104 in the embodiment.

[0194] The acquisition unit acquires image information showing an image of a space in which radio waves can propagate in communication between a first wireless station and a second wireless station. For example, the first wireless station is the terminal station 10 in the embodiment, the second wireless station is the base station 20-1 in the embodiment, and the space in which radio waves can propagate is the Fresnel zone in the embodiment. The estimation unit estimates a propagation loss of radio waves in the communication based on the image information acquired by the acquisition unit. The determination unit determines whether or not to switch the wireless station with which the first wireless station is connected for communication from the second wireless station to the third wireless station based on the propagation loss estimated by the estimation unit. For example, the third wireless station is the base station 20-1 in the embodiment.

[0195] The wireless station selection system may further include a learning unit. For example, the wireless station selection system is the base station selection system 1a in the embodiment, and the learning unit is the learning unit 302 in the embodiment. The learning unit performs machine learning using teacher data including image information and propagation loss to generate a trained model. In this case, the estimation unit estimates the propagation loss by inputting the image information acquired by the acquisition unit into the trained model generated by the learning unit.

[0196] In the above wireless station selection system, the space is a Fresnel zone formed in communication between a first wireless station and a second wireless station, or a cylindrical space approximating a Fresnel zone. For example, the Fresnel zone is Fresnel zone fz in the embodiment, and the cylindrical space approximating a Fresnel zone is cylindrical Fresnel zone Cz in the embodiment.

[0197] In the above wireless station selection system, the image may be an image captured from the position of the first wireless station toward the second wireless station. For example, the image captured from the position of the first wireless station toward the second wireless station is an image captured by the measurement camera 15 installed near the terminal station 10 in the embodiment.

[0198] In the above wireless station selection system, the image may be an image captured from above the space. For example, the wireless station selection system is the base station selection system 1b in the embodiment.

[0199] In addition, in the above wireless station selection system, the image may be an image consisting of both an image captured from the position of the first wireless station in the direction of the second wireless station, and an image captured from above the space.

[0200] In the above-mentioned wireless station selection system, the image may be an image captured by an imaging device mounted on a low-orbit satellite or a high-altitude unmanned aerial vehicle. For example, the low-orbit satellite is the low-orbit satellite 50 in the embodiment, the high-altitude unmanned aerial vehicle is the high-altitude unmanned aerial vehicle 51 in the embodiment, and the imaging device is a measurement camera 15 (not shown) installed on the low-orbit satellite 50 or the high-altitude unmanned aerial vehicle 51 in the embodiment.

[0201] A part of the base station selection system 1 and 1a to 1c in each of the above-mentioned embodiments may be realized by a computer. In that case, a program for realizing this function may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read into a computer system and executed to realize the function. The term "computer system" here includes hardware such as an OS and peripheral devices. The term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into a computer system. The term "computer-readable recording medium" may also include a medium that dynamically holds a program for a short period of time, such as a communication line when a program is transmitted via a network such as the Internet or a communication line such as a telephone line, and a medium that holds a program for a certain period of time, such as a volatile memory inside a computer system that is a server or client in that case. The above-mentioned program may be a program for realizing a part of the above-mentioned function, or may be a program that can realize the above-mentioned function in combination with a program already recorded in the computer system, or may be a program that is realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0202] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of the present invention are also included. [Explanation of symbols]

[0203] 1, 1a, 1b, 1c... base station selection system, 10, 10a... terminal station, 15... measurement camera, 20, 20-1, 20-2... base station, 30... learning device, 50... low-orbit satellite, 51... high-altitude unmanned aerial vehicle, 100, 100a... base station selection unit, 101... image information acquisition unit, 102, 102a... spatial information extraction unit, 103, 103a... propagation loss estimation unit, 104... base station switching determination unit, 110... base station switching control unit, 120... communication unit, 301... teacher data acquisition unit, 302... learning unit, 303... trained model transmission unit

Claims

1. an acquisition step of acquiring image information indicating an image of a space through which radio waves may propagate in communication between a first wireless station and a second wireless station; an estimation step of estimating a propagation loss of radio waves in the communication, taking into consideration a bias in distribution of positions of objects present within the range of the space based on the image information acquired in the acquisition step; a determination step of determining whether or not to switch a wireless station connected to the first wireless station from the second wireless station to a third wireless station based on the propagation loss estimated in the estimation step; A radio station selection method comprising:

2. A learning step of performing machine learning using training data including the image information and the propagation loss to generate a learned model. and In the estimation step, the propagation loss is estimated by inputting the image information acquired in the acquisition step into the trained model generated in the training step. The method of claim 1 .

3. The space is a Fresnel zone formed in communication between the first wireless station and the second wireless station, or a cylindrical space approximating the Fresnel zone. The method for selecting a wireless station according to claim 1 or 2.

4. The image is an image captured in a direction from the position of the first wireless station to the position of the second wireless station. A method for selecting a wireless station according to any one of claims 1 to 3.

5. The image is an image captured from above the space. A method for selecting a wireless station according to any one of claims 1 to 3.

6. The image includes both an image captured from the position of the first wireless station in the direction of the second wireless station and an image captured from above the space. A method for selecting a wireless station according to any one of claims 1 to 3.

7. The image is captured by an imaging device mounted on a low-orbit satellite or a high-altitude unmanned aerial vehicle. The method of selecting a wireless station according to claim 5.

8. an acquisition unit that acquires image information indicating an image captured of a space through which radio waves may propagate during communication between a first wireless station and a second wireless station; an estimation unit that estimates a propagation loss of radio waves in the communication, taking into consideration a bias in distribution of positions of objects present within the range of the space based on the image information acquired by the acquisition unit; a determination unit that determines whether or not to switch a wireless station to be communicatively connected by the first wireless station from the second wireless station to a third wireless station based on the propagation loss estimated by the estimation unit; A radio station selection system comprising:

Images