Propagation environment estimation method, propagation environment estimation system, and propagation environment estimation device

Abstract

This disclosure relates to a propagation environment estimation method for estimating a propagation environment of radio waves using a scale model. This method comprises the following steps. A scale model is created (Step 1). A light source capable of emitting directional light and scanning in an irradiation direction is installed in the scale model, the light source simulating a radio wave transmitting station (Step 2). The inside of the scale model is scanned by the light source, and, in the process of scanning, a central light generation condition in which central light travelling toward a measurement point set in the scale model is generated is detected. A light-receiving sphere is installed such that the center thereof coincides with the measurement point (Step 3). A direction connecting the position of the center and the position of an irradiation point that appears on the light-receiving sphere under the central light generation condition is estimated as the direction of arrival of the light reaching the measurement point (Step 4).

Description

[Technical Field]

[0001] The present disclosure relates to a propagation environment estimation method, a propagation environment estimation system, and a propagation environment estimation device, and more particularly to a propagation environment estimation method, a propagation environment estimation device, and a propagation environment estimation system that are suitable for estimating the environment of a wireless signal using a scale model. [Background technology]

[0002] In recent years, the explosive spread of wireless communication devices has led to an increasing demand for wireless communication. However, the frequency resources available for wireless communication are limited. This has made it necessary to utilize previously unused frequencies in addition to existing frequencies. When using a new frequency band, it is necessary to investigate in advance the propagation characteristics of wireless signals in the service area and the impact of interference that signals in the new frequency band may have on other systems.

[0003] In response to these demands, the International Telecommunication Union (ITU) Radiocommunication Sector (ITU-R) is attempting to measure the propagation characteristics of wireless signals in real areas and develop propagation models based on various measurement results. However, these types of attempts face challenges, such as insufficient measurement results for unexplored frequencies and insufficient development of propagation models.

[0004] The following Non-Patent Document 1 discloses a method for reproducing propagation loss characteristics in a mobile communication environment using a scale model. Figure 1 is a schematic diagram comparing the process of estimating a propagation model through actual measurements in an actual area with the process of estimating a model through actual measurements using a scale model.

[0005] As shown in Figure 1, in the scale modeling method, a scale model of an actual urban area is created at a scale of, for example, 1 / 100. Radio signals are then generated in the scale model environment, and the propagation characteristics of the radio waves are measured. This method can significantly reduce the cost of collecting the necessary data compared to measuring the propagation environment in an actual urban area. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] "Establishment of scale model method for radio wave propagation," Shinichi Ichitsubo, Grant-in-Aid for Scientific Research (JSPS) Research Report, May 18, 2012. Summary of the Invention [Problem to be solved by the invention]

[0007] In urban areas where various buildings coexist, radio waves emitted from a transmitting station are repeatedly reflected, so the direction from which the radio waves arrive at each point within the area varies. For this reason, when launching a new communication service, it is important to estimate the direction from which radio waves will arrive at each point in the target area.

[0008] As described above, conventional methods using scale models estimate the propagation environment by actually measuring the behavior of radio waves in a scale model environment. In measurements using radio waves, for example, multiple antennas are placed at the measurement point and the arrival direction can be estimated by analyzing the phase difference of the radio waves arriving at them. Alternatively, the arrival direction can be estimated by placing an antenna with sharp directivity at the measurement point and performing omnidirectional scanning with that antenna.

[0009] However, installing multiple antennas at each measurement point on a scale model requires a great deal of cost and effort. Furthermore, antennas with sharp directivity are generally large, making it difficult to fit them into a scale model. Therefore, a key challenge in estimating the radio wave propagation environment using a scale model has been how to easily and inexpensively estimate the direction of arrival of radio waves.

[0010] The present disclosure has been made in consideration of the above-mentioned problems, and has a first object to provide a propagation environment estimation method for easily and inexpensively estimating the direction of arrival of radio waves at any measurement point when estimating the propagation characteristics of radio waves using a scale model.

[0011] A second object of the present disclosure is to provide a propagation environment estimation system that, when estimating radio wave propagation characteristics using a scale model, estimates the direction of arrival of radio waves at any measurement point simply and at low cost.

[0012] Furthermore, a third object of the present disclosure is to provide a propagation environment estimation device that, when estimating radio wave propagation characteristics using a scale model, estimates the direction of arrival of radio waves at any measurement point easily and at low cost. [Means for solving the problem]

[0013] In order to achieve the above object, a first aspect is a propagation environment estimation method for estimating a radio wave propagation environment using a scale model, comprising: A model making step to make a scale model; a light source installation step of installing a light source that emits directional light and can scan an irradiation direction on the scale model, the light source being likened to a radio wave transmitting station; a scanning step of scanning the light source through the scale model; a central light searching step of detecting a central light generation state in which a central light is generated toward a measurement point set in the scale model during the scanning process; an irradiation point detection step of detecting the position of an irradiation point that appears under the central light generation state on a light receiving sphere that is installed so that its center coincides with the measurement point; It is desirable to include an estimation step of estimating a direction connecting the position of the center and the position of the irradiation point as the direction of arrival of the light that reaches the measurement point.

[0014] A second aspect is a propagation environment estimation system that estimates a radio wave propagation environment using a scale model, comprising: 3D printers to create scale models, an element mounter for mounting a light source that emits directional light and can scan the irradiation direction on the scale model, likening it to a radio wave transmitting station; a control device that controls the 3D printer and the element mounter; The control device scanning the light source through the scale model; a process of detecting a central light generation state in which a central light is generated toward a measurement point set in the scale model during the scanning process; A process of detecting the position of an irradiation point that appears under the central light generation state on a light receiving sphere that is installed so that its center coincides with the measurement point; A process of estimating a direction connecting the position of the center and the position of the irradiation point as the arrival direction of the light reaching the measurement point; It is preferable that the system is further configured to execute the following:

[0015] A third aspect is a propagation environment estimation device that estimates a radio wave propagation environment using a scale model, A 3D printer section for creating scale models, an element mounter unit for mounting a light source that emits directional light and can scan the irradiation direction on the scale model, the light source being likened to a radio wave transmitting station; A control device unit that controls the 3D printer unit and the element mounter unit, The control device unit scanning the light source through the scale model; a process of detecting a central light generation state in which a central light is generated toward a measurement point set in the scale model during the scanning process; A process of detecting the position of an irradiation point that appears under the central light generation state on a light receiving sphere that is installed so that its center coincides with the measurement point; A process of estimating a direction connecting the position of the center and the position of the irradiation point as the arrival direction of the light reaching the measurement point; It is preferable that the system is further configured to execute the following: [Effects of the Invention]

[0016] According to the first to third aspects, when estimating the propagation characteristics of radio waves using a scale model, the direction of arrival of radio waves can be estimated easily and at low cost at any measurement point. [Brief explanation of the drawings]

[0017] [Figure 1] This is a schematic diagram showing a comparison between estimating a propagation model through actual measurements in an actual area and estimating a model through actual measurements using a scale model. [Figure 2] FIG. 1 is a diagram for explaining an overview of a propagation environment estimation method according to a first embodiment of the present disclosure. [Figure 3] FIG. 2 is a diagram for explaining one point to be noted when determining the scale of a scale model in the propagation environment estimation method according to the first embodiment of the present disclosure. [Figure 4] 1A and 1B are diagrams illustrating how the light-receiving sphere used in the first embodiment of the present disclosure is irradiated with light that does not pass through the center of the sphere. [Figure 5] 1 is a diagram illustrating how a light-receiving sphere used in the first embodiment of the present disclosure is irradiated with light passing through the center of the sphere. FIG. [Figure 6] 4 is a flowchart illustrating a processing flow when estimating a propagation environment according to the propagation environment estimation method according to the first embodiment of the present disclosure. [Figure 7]FIG. 7 is a block diagram for explaining the configuration of a propagation environment estimation system that performs the series of processes shown in FIG. 6 continuously and fully automatically. [Figure 8] 10 is a flowchart illustrating a processing flow when estimating a propagation environment according to a propagation environment estimation method according to a second embodiment of the present disclosure. [Figure 9] FIG. 13 is a diagram illustrating learning items for determining whether or not irradiated light is central light passing through the center of a sphere in the third embodiment of the present disclosure. [Figure 10] 11 is a flowchart illustrating a processing flow when estimating a propagation environment according to a propagation environment estimation method according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0018] Embodiment 1 [Outline of the first embodiment] Fig. 2 is a diagram for explaining an overview of the propagation environment estimation method according to the first embodiment of the present disclosure. More specifically, the upper part of Fig. 2 shows a perspective view of a scale model used in the propagation environment estimation method according to this embodiment. Even more specifically, the left side of the upper part of Fig. 2 shows a case where a hollow point on the scale model is set as a measurement point for radio waves. Furthermore, the right side of the upper part of Fig. 2 shows a case where a point on the ground surface on the scale model is set as a measurement point for radio waves.

[0019] The bottom part of Fig. 2 shows a flowchart for explaining an outline of the propagation environment estimation method of this embodiment. The numbers "1," "2," "3," and "4" shown in the top part of Fig. 2 correspond to the numbers of each step shown in the bottom part of Fig. 2, respectively.

[0020] The propagation environment estimation method of this embodiment is suitable as a technique for investigating in advance the propagation characteristics of wireless signals in a service area when starting a new wireless communication service, etc. A typical service area is assumed to be an urban area with many buildings.

[0021] As shown in FIG. 2, in the propagation environment estimation method of this embodiment, the propagation environment is estimated in the following steps. 1. Create a model of the target area. Hereinafter, this model will be referred to as a "scale model." A scale model is a reproduction of an actual urban space, for example, at a scale of about 1 / 100. Figure 2 shows an example in which an outdoor space is used as the target area, but the interior of a specific building may also be used as the target area.

[0022] 2. A light source is installed to act as a radio wave transmission source. A laser pointer or similar device that emits a laser beam with excellent linearity is used as the light source. The light source is configured so that the direction of the laser beam can be scanned three-dimensionally.

[0023] 3. The receiving sphere is placed so that the measurement point set on the scale model is at its center. The receiving sphere is made of a material that appropriately reflects laser light so that the irradiation point can be identified visually or by an image sensor when irradiated with laser light. The receiving sphere may be coated with, for example, fluorescent paint to make the irradiation point of the laser light clear. If the measurement point is in midair, a perfect sphere is used as the receiving sphere. On the other hand, if the measurement point is on the ground surface, a hemisphere is used as the receiving sphere.

[0024] 4. Next, the direction from which the light reaching the measurement point, i.e. the center of the light-receiving sphere, comes is measured. Hereinafter, this type of light will be referred to as the "center light." The laser light emitted from the light source is reflected by various elements contained in the scale model, so it may arrive at the measurement point from any direction.

[0025] Here, first, the scanning position of the laser light that generates the central light is searched for using a method described below. Then, if a state that generates the central light is found as a result of the search, it is detected which position on the light receiving sphere is irradiated under that state. Since the central light is light that passes through the center of the light receiving sphere, if the irradiated point on the surface of the light receiving sphere is known, the direction connecting that point and the center is the arrival direction of the central light. In this embodiment, the arrival direction of the light reaching the measurement point is estimated according to this principle.

[0026] [Points to note regarding the first embodiment] (1) When creating a scale model of a target area, it is necessary to appropriately determine what scale to adopt. In this embodiment, the following points are typically taken into consideration when determining the scale.

[0027] (1-a) Installation space for elements, etc. As described above, in this embodiment, it is necessary to install a light source in the scale model, which acts as a radio wave transmission source. Furthermore, it is necessary to install a receiving sphere at the measurement point. These are installed on roads or in plazas within the target area. The installation space varies depending on the scale of the scale model, and if an excessive scale is adopted, it may not be possible to install the light source or receiving sphere in the appropriate location on the scale model. For this reason, in this embodiment, the scale of the scale model is determined so that the various elements required for estimating the propagation characteristics do not interfere with buildings, etc.

[0028] (1-b) Reach of the measurement light Figure 3 compares two scale models with different scales. More specifically, the top of Figure 3 shows a large-scale model, and the bottom of Figure 3 shows a small-scale model. Within each scale model, the area where propagation characteristics are to be measured is shown as the "measurement range" 10. Additionally, the circle of light emitted from a light source, which is likened to the radio wave transmission source, is shown as the "irradiation range" 12.

[0029] In the scale model in the upper part of FIG. 3, the scale is too large, resulting in an area in part of the measurement range 10 that is not covered by the illumination range 12 of the light source. In this case, light from the light source cannot reach that part of the measurement range 10. On the other hand, in the scale model in the lower part of FIG. 3, the entire measurement range 10 is covered by the illumination range 12. In this case, light from the light source reaches the entire measurement range 10, so measurement points can be set throughout the entire measurement range 10. In consideration of these circumstances, in this embodiment, the scale of the scale model is determined so that the entire measurement range 10 fits within the illumination range 12 just enough, as shown in the lower part of FIG. 3.

[0030] (2) It is desirable that the behavior of light, which is likened to radio waves, is consistent with the behavior of radio waves in an actual area. In order to meet the above requirement, the propagation characteristics estimation method of this embodiment pays attention to the reflectance of radio waves and light.

[0031] The behavior of radio waves is reflected by the reflectance of radio waves at each part of the target area. Similarly, the behavior of light emitted from a light source is affected by the reflectance of light at each part of the scale model. In this embodiment, surface treatment is applied to each part of the scale model so that the radio wave reflectance at each part of the target area matches the light reflectance at each part of the scale model. Surface treatment is performed, for example, by applying paint or texturing the model wall surface.

[0032] [Searching for the scanning position that produces the central light] The left side of Figure 4 shows the appearance of a laser beam irradiation spot 16 on the surface of the light-receiving sphere 14. If the laser beam generating the irradiation spot 16 is a central beam passing through the center 18 of the light-receiving sphere 14 as shown by the dashed line in the figure, then the direction of arrival of the laser beam is the direction connecting the irradiation spot 16 and the center 18.

[0033] The right side of Figure 4 shows how an illuminated point 16 similar to the one shown on the left side of Figure 4 appears on the surface of the light-receiving sphere 14 as a result of non-central light that does not pass through the center 18 illuminating the surface of the light-receiving sphere 14. Because it is difficult to capture the trajectory of light in space, only the illuminated point 16 can be easily detected visually or with an image sensor. As mentioned above, even if the illuminated point 16 is detected, it is not possible to recognize the occurrence of central light based solely on that fact. Therefore, even if the occurrence of the illuminated point 16 is detected, the direction of arrival of the light illuminating the light-receiving sphere 14 cannot be estimated.

[0034] FIG. 5 is a diagram illustrating the principle of detecting the generation of a central beam and estimating the direction of arrival of the central beam in this embodiment. The left side of FIG. 5 shows a state in which a laser beam 22 is irradiated onto a light-receiving target 20. The light-receiving target 20 is installed at a point where the direction of arrival of the radio wave is desired to be known, i.e., a measurement point. The sphere indicated by the dashed line in the figure is imaginary and does not actually exist. When the laser beam 22 is irradiated onto the light-receiving target 20, reflection occurs on the light-receiving target 20, and the occurrence of this state can be easily detected by visual inspection or by capturing an image using an image sensor.

[0035] The right side of Figure 5 shows a state in which a laser beam 22 is generated to illuminate a light-receiving target 20, and the light-receiving sphere 14 is positioned so that its center 18 coincides with the measurement point. In this case, the laser beam 22 is a central beam that passes through the center 18 of the light-receiving sphere 14. Furthermore, when illuminated by the laser beam 22, an irradiation point 16 appears on the surface of the light-receiving sphere 14. In this case, since it is guaranteed that the irradiation point 16 is illuminated by the central beam, the direction connecting the irradiation point 16 and the center 18 can be estimated as the direction of arrival of the laser beam 22.

[0036] [Details of the procedure in the first embodiment] Fig. 6 is a flowchart for explaining in detail the procedure of the propagation environment estimation method of this embodiment. The procedure shown in Fig. 6 starts when information collection for an existing target area, such as the dimensions and locations of buildings and roads, the radio wave reflectivity of key points, and the radio wave frequency to be used, has been completed, and the specifications of the light source to be used for measurement, etc. have been decided.

[0037] As shown in Figure 6, according to this procedure, first the scale of the scale model to be created is determined (step 100). In this step 100, taking into consideration the above points (1-a) and (1-b), a scale that is neither too large nor too small is determined, with the essential conditions that elements such as a light source can be installed and that the illumination range 12 of the light source covers the entire measurement range 10.

[0038] Next, a scale model is created by a 3D printer (step 102). First, the 3D printer is provided with the scale, as well as information on the dimensions and layout of various structures and other structures in the target area. The 3D printer creates a scale model of the target area according to the provided scale.

[0039] Once the 3D printer processing is complete, the created scale model is then subjected to a reflective treatment (step 104). For example, the walls of the building model are painted or surface treated to match the reflectance of light to that of radio waves. The reflective treatment in this step may be performed manually by an operator. Alternatively, the painting process may be performed using a fully automated painting device that can specify the areas to be painted in three dimensions. Furthermore, the surface treatment may be achieved by processing using a 3D printer.

[0040] Next, a light source, which resembles a radio wave transmitting station, specifically a laser pointer capable of three-dimensional scanning, is installed (step 106). The light source is installed at a proposed location for the transmitting station on the scale model. The light source may be installed manually by a worker, or may be installed without human intervention by a fully automated element mounter.

[0041] Next, the light-receiving target 20 is placed at the measurement point set within the scale model (step 108). The light-receiving target 20 is preferably spherical or approximating a sphere so that it can reflect light from all directions under substantially uniform conditions. The size of the light-receiving target 20 is preferably set smaller than the scaled size of an area in an actual target area where it is desired to ascertain the direction of arrival of radio waves.

[0042] Once the above process is complete, the scanning position of the laser pointer that generates the central light is searched for (step 110). As the scanning direction of the laser pointer changes, various reflected lights are generated within the scale model in addition to direct light. At a certain scanning position, these lights may become laser light 22 that illuminates the light-receiving target 20. In this step 110, while manually or automatically changing the scanning direction of the laser pointer, a state in which the light-receiving target 20 is illuminated by laser light is searched for visually or by image processing. Then, if the occurrence of such a state is confirmed, it is determined that laser light 22 that satisfies the conditions for central light has been generated.

[0043] Once the generation of laser light 22 that satisfies the conditions for central light is confirmed, the light-receiving sphere 14 is placed within the scale model while maintaining this state (step 112). The light-receiving sphere 14 is placed so that its center 18 coincides with the installation position of the light-receiving target 20. As a result, the light-receiving sphere 14 is illuminated by the central light that passes through its center 18.

[0044] Next, the direction of arrival of the central light is estimated (step 114). Here, first, the position of the illuminated point 16 that appears on the light-receiving sphere 14 is measured. The position of the illuminated point 16 can be measured as three-dimensional information by applying well-known image processing to an image obtained using an imaging device that captures the illuminated point 16 within its angle of view. Next, based on the three-dimensional position of the illuminated point 16 and the known three-dimensional position of the center 18, the direction of arrival of the central light, i.e., the direction of arrival of light at the measurement point, is calculated.

[0045] As described above, the propagation environment estimation method of this embodiment makes it possible to estimate the direction of arrival of light at a measurement point without installing multiple antennas or a large directional antenna in the scale model. The direction of arrival of light estimated in this manner accurately matches the direction of arrival of radio waves in an actual target area. Therefore, the method of this embodiment makes it possible to estimate the direction of arrival of radio waves at any measurement point in a target area simply and at low cost.

[0046] [Propagation environment estimation system according to the first embodiment] Fig. 7 is a block diagram for explaining the configuration of a propagation environment estimation system that can continuously and fully automatically carry out the series of processes shown in Fig. 6. The system shown in Fig. 7 includes a control device 30 and a storage device 32. The control device 30 includes an arithmetic processing unit. The storage device 32 stores a program to be executed by the arithmetic processing unit. The control device 30 controls each part of the system shown in Fig. 7 by the arithmetic processing unit carrying out processing in accordance with the program.

[0047] In addition to the above programs, the storage device 32 stores various information related to the target area. This information includes the dimensions, location, and radio wave reflectivity of buildings, roads, etc. The storage device 32 also stores dimensional data for various elements that can be used in the scale model. Furthermore, the storage device 32 also stores the results of measurements performed using the scale model, i.e., information on the direction of arrival obtained in the processing of step 114 above.

[0048] The system shown in Figure 7 includes a 3D printer 34. The control device 30 reads various information from the storage device 32 and performs the process of step 100 above, that is, the process of determining the scale. The 3D printer reads information about the target area from the storage device 32 and carves out a scale model at the scale determined by the control device 30. If texture processing is required on specific areas to match the reflectance of the radio waves and the measurement light, this processing is also performed by the 3D printer 34.

[0049] The system shown in Fig. 7 includes a painting device 36. The painting device 36 is equipped with a paint nozzle that can move three-dimensionally, and can apply a desired paint to any position on the scale model. In response to commands from the control device 30 and based on information read from the memory device 32, the painting device 36 can apply paint to a specified position on the scale model to obtain a desired reflectance.

[0050] The system shown in Figure 7 includes an element mounter 38. The element mounter 38 has the function of installing various elements, etc., planned for use in the scale model, at any position on the scale model. In this embodiment, a laser pointer, which functions as a light source, and a photoreceptor 14, which is installed at a measurement point, are installed by the element mounter 38 in accordance with commands from the control device 30.

[0051] The system shown in Figure 7 further includes a camera 40. The camera 40 has the function of photographing measurement points set in the scale model from multiple directions. More specifically, the camera 40 is configured to be able to photograph the light-receiving target 20 and the light-receiving sphere 14 from all directions. The search process in step 110 and the estimation process in step 114 are both performed based on the image data photographed by the camera 40.

[0052] The propagation environment estimation system shown in Fig. 7 can perform the series of steps shown in Fig. 6 in a seamless and fully automated manner. Therefore, this system can significantly improve the efficiency of the task of estimating the direction of arrival of radio waves in a target area using a scale model.

[0053] [Modification of the first embodiment] In the first embodiment described above, the occurrence of central light is detected by visually checking or by using an image sensor whether the light-receiving target 20 is reflecting laser light. However, the present disclosure is not limited to this. A light-receiving element that reacts to light irradiation may be disposed as the light-receiving target 20, and the occurrence of central light may be detected based on whether the light-receiving element detects light irradiation.

[0054] In the first embodiment described above, the position of the irradiation point 16 is detected by an image sensor when the light-receiving sphere 14 is irradiated with the central light. However, the present disclosure is not limited to this. For example, a plurality of light-receiving elements may be arranged on the surface of the light-receiving sphere 14 so that the irradiated light can be detected in all directions, and the position of the light-receiving element irradiated with the central light may be recognized as the position of the irradiation point 16.

[0055] In addition, in the above-described first embodiment, the configuration shown in Fig. 7 is described as a system consisting of multiple devices, but the present disclosure is not limited to this. That is, the configuration shown in Fig. 7 may be a single device in which the illustrated elements are housed in a single housing.

[0056] The above-mentioned modifications are also possible in the second and third embodiments described below.

[0057] Embodiment 2 [Features of the second embodiment] Next, a second embodiment of the present disclosure will be described with reference to Figures 2 to 5, 7, and 8. In the first embodiment described above, the process of detecting the generation of central light using light-receiving target 20 and the process of placing light-receiving sphere 14 while the central light is being generated are carried out in chronological order. The propagation environment estimation method of this embodiment is characterized in that two scale models are used and these processes are carried out simultaneously in parallel.

[0058] [Details of the procedure in the second embodiment] Fig. 8 is a flowchart for explaining in detail the procedure of the propagation environment estimation method of this embodiment. Similar to the procedure shown in Fig. 6, the procedure shown in Fig. 8 is started when information collection about an existing target area is completed and the specifications of the light source to be used for measurement, etc., are determined. In the following explanation, among the steps shown in Fig. 8, steps that are the same as those shown in Fig. 6 are assigned the same reference numerals, and their explanations will be omitted or simplified.

[0059] According to the flowchart shown in Figure 8, following the processing of step 100, processing is performed using a 3D printer (step 122), where two overlapping scale models that reproduce the target area at a desired scale are created.

[0060] Next, the two scale models are similarly processed to match the reflectance of radio waves and light (step 124). Next, light sources, specifically laser pointers, which act as radio wave transmitters, are placed on each of the two scale models (step 126).

[0061] Next, a light-receiving target 20 is placed at the measurement point on one of the scale models (step 128). Also, a light-receiving sphere 14 is placed on the other scale model so that its center 18 coincides with the measurement point (step 130).

[0062] Once the above process is complete, a search for the central light is performed using the two scale models (step 132). First, scanning with the laser pointer is performed in the same way on both scale models. As a result, various reflected lights are generated in the same way on the two scale models. When the light-receiving target 20 placed on one scale model is illuminated by the laser light 22, the light-receiving sphere 14 on the other scale model should be illuminated by the central light. Therefore, if this state is detected, it is determined that the scanning position that generates the central light has been found.

[0063] Thereafter, the direction of arrival of the light is estimated by the processing of step 114, as in the case of embodiment 1. That is, the direction connecting the position of the illuminated point 16 on the light-receiving sphere 14 placed on the other scale model and the center 18 of that light-receiving sphere 14 is estimated as the direction of arrival of the light.

[0064] As described above, the propagation environment estimation method of this embodiment also makes it possible to estimate the direction from which light arrives at a measurement point on a scale model without using multiple antennas or a large directional antenna, as in Embodiment 1. Therefore, the method of this embodiment also makes it possible to estimate the direction of arrival of radio waves at any measurement point in a target area simply and at low cost, as in Embodiment 1.

[0065] As in the first embodiment, the series of procedures performed in this embodiment can be performed in a continuous and fully automatic manner by a propagation environment estimation system or a propagation environment estimation device having the configuration shown in FIG. 7.

[0066] Embodiment 3 [Features of the third embodiment] Next, a third embodiment of the present disclosure will be described with reference to Figures 2 to 5, 7, and 9 and 10. In order to estimate the direction of light arrival using photoreceptor sphere 14, it is necessary to irradiate photoreceptor sphere 14 with central light and then measure the position of irradiation point 16 that appears on its surface. In the first and second embodiments described above, the above requirement is met by searching for a state in which central light is generated and irradiating photoreceptor sphere 14 with that central light.

[0067] Incidentally, the irradiation point 16 that appears on the surface of the light receiving sphere 14 exhibits characteristics that depend on the angle at which the irradiation light reaches the light receiving sphere 14. The left side of Figure 9 shows the appearance of the irradiation point 16 that occurs when the irradiation light is irradiated perpendicularly to the light receiving sphere 14, that is, when the light receiving sphere 14 is irradiated with central light. The right side of Figure 9 shows the appearance of the irradiation point 16 that occurs when the irradiation light is irradiated obliquely to the light receiving sphere 14, that is, when the light receiving sphere 14 is irradiated with non-central light.

[0068] When the light-receiving sphere 14 is irradiated with central light, the irradiation point 16 has a clear circular shape, as shown on the left side of Fig. 9. On the other hand, when the light-receiving sphere is irradiated with non-central light, the irradiation point 16 does not have a clear circular shape but is blurred, as shown on the right side of Fig. 9. Therefore, by learning the characteristics of the irradiation point 16 caused by central light, such as the size of the circle that can be considered to be the irradiation point 16, the brightness difference between the circle and the surrounding area, and the presence of blurring around the circle, it is possible to determine whether the irradiation point 16 is caused by the central light based on the shape of the irradiation point 16 that appears.

[0069] Therefore, in this embodiment, the relationship between the angle of the laser light 22 reaching the light receiving sphere 14 and the characteristics of the irradiation point 16 appearing on the light receiving sphere 14 is learned in advance, and during the scanning process with the laser pointer, the occurrence of central light is determined based on the shape of the irradiation point 16, etc., in light of the results of that learning. Note that the learning of the characteristics of the irradiation point 16 may be done by simple sample acquisition or may utilize machine learning.

[0070] [Details of the procedure in the third embodiment] Fig. 10 is a flowchart for explaining in detail the procedure of the propagation environment estimation method of this embodiment. Similar to the procedure shown in Fig. 6, the procedure shown in Fig. 10 is started when information collection for an existing target area is completed and the specifications of the light source to be used for measurement, etc., are determined. In the following explanation, among the steps shown in Fig. 10, steps that are the same as those shown in Fig. 6 are assigned the same reference numerals, and their explanations will be omitted or simplified.

[0071] According to the flowchart shown in Fig. 10, first, the characteristics of the irradiation point 16 caused by the central light are learned (step 140). This learning may be performed by generating a central light using the same method as in the first embodiment and learning the characteristics of the irradiation point 16 caused by that central light. Alternatively, a laser pointer may be positioned so that the irradiation light is directed toward the center 18 of the light-receiving sphere 14, and the characteristics of the resulting irradiation point 16 may be learned.

[0072] Once learning of the illumination point 16 caused by the central light is completed, the processes of steps 100 to 106 and step 112 are carried out as in the first embodiment. This creates a scale model in which the light source and light-receiving sphere 14 are placed.

[0073] Next, using the method of this embodiment, the scanning position of the laser pointer that generates the central light is searched for (step 142). Specifically, the image sensor monitors the light receiving sphere 14 in all directions while the laser pointer scans. During the scanning process, it is determined successively whether an illuminated point 16 has appeared on the light receiving sphere 14. Furthermore, if the appearance of the illuminated point 16 is confirmed, it is determined whether the characteristics of the illuminated point 16 that has appeared match the characteristics caused by the central light. Then, if a match is determined, the occurrence of the central light is recognized.

[0074] Once the occurrence of central light is confirmed, the direction of arrival of the light is estimated by the processing in step 114 in the same manner as in the first embodiment.

[0075] As described above, the propagation environment estimation method of this embodiment also makes it possible to estimate the direction from which light arrives at a measurement point on a scale model without using multiple antennas or a large directional antenna, as in Embodiment 1. Therefore, the method of this embodiment also makes it possible to estimate the direction of arrival of radio waves at any measurement point in a target area simply and at low cost, as in Embodiment 1.

[0076] As in the first embodiment, the series of procedures performed in this embodiment can be performed in a continuous and fully automatic manner by a propagation environment estimation system or a propagation environment estimation device having the configuration shown in FIG. 7. [Explanation of symbols]

[0077] 10 Measurement range 12 Irradiation range 14 Photoreceptor sphere 16 irradiation points 18 center 20 Light receiving target 22 Laser light 30 Control device 32 Storage device 34 3D printer 36 Painting equipment 38 Element mounter 40 Imaging equipment

Claims

1. A propagation environment estimation method for estimating a radio wave propagation environment using a scale model, comprising: A model making step to make a scale model; a light source installation step of installing a light source on the scale model that emits directional light and can scan the irradiation direction, the light source being likened to a radio wave transmitting station; a scanning step of scanning the light source through the scale model; a central light searching step of detecting a central light generation state in which a central light is generated toward a measurement point set in the scale model during the scanning process; an irradiation point detection step of detecting the position of an irradiation point that appears under the central light generation state on a light receiving sphere that is installed so that its center coincides with the measurement point; an estimation step of estimating a direction connecting the position of the center and the position of the irradiation point as the arrival direction of the light reaching the measurement point; A propagation environment estimation method including:

2. The center light searching step includes: placing a light-receiving target at the measurement point; detecting a state in which the light receiving target is illuminated by the light as the central light generating state; The irradiation point detection step includes: After detecting the central light generation state, placing the light receiving sphere in the scale model so that the measurement point and the center coincide with each other; The propagation environment estimation method according to claim 1 , further comprising the step of detecting a position of an illumination point that appears on the installed light receiving sphere under the central light generation state.

3. the model creation step includes creating two identical scale models; the light source installation step includes a step of installing the light source on each of the two scale models; the scanning step includes the step of scanning two of the scale models in the same manner with each of the light sources; The center light searching step includes: placing a light-receiving target at the measurement point on one of the scale models; detecting a state in which the light receiving target is illuminated by the light as the central light generating state; The irradiation point detection step includes: placing the light-receiving sphere so that its center coincides with the measurement point of the other scale model; a step of detecting, in a state in which the central light generation state is detected in the one scale model, a position of an irradiation point that appears on the light-receiving sphere installed on the other scale model.

4. The method further includes a scale setting step of setting a scale of the scale model prior to creating the scale model, The scale setting step includes: obtaining information about the installation space of the transmitting station in a target area; obtaining dimensions of the light source; setting the scale so that the light source fits into a corresponding location in the installation space in the scale model; 4. The propagation environment estimation method according to claim 1, further comprising:

5. 5. The propagation environment estimation method according to claim 1, further comprising the step of performing a reflection process on at least a part of the scale model so that the light reflectance of the scale model matches the radio wave reflectance of a target area.

6. 6. The propagation environment estimation method according to claim 1, further comprising the step of setting a wavelength of light emitted by the light source based on a frequency of radio waves expected to be used in the target area, so that behavior of light in the scale model matches behavior of radio waves in the target area.

7. A propagation environment estimation system that estimates a radio wave propagation environment using a scale model, A 3D printer to create scale models, an element mounter for mounting a light source that emits directional light and can scan the irradiation direction on the scale model, likening it to a radio wave transmitting station; a control device that controls the 3D printer and the element mounter, The control device scanning the light source through the scale model; a process of detecting a central light generation state in which a central light is generated toward a measurement point set in the scale model during the scanning process; A process of detecting the position of an irradiation point that appears under the central light generation state on a light receiving sphere that is installed so that its center coincides with the measurement point; A process of estimating a direction connecting the position of the center and the position of the irradiation point as the arrival direction of the light reaching the measurement point; A propagation environment estimation system configured to further execute the above.

8. A propagation environment estimation device that estimates a radio wave propagation environment using a scale model, A 3D printer section for creating scale models, an element mounter unit for mounting a light source that emits directional light and can scan the irradiation direction on the scale model, the light source being likened to a radio wave transmitting station; A control device unit that controls the 3D printer unit and the element mounter unit, The control device unit scanning the light source through the scale model; a process of detecting a central light generation state in which a central light is generated toward a measurement point set in the scale model during the scanning process; A process of detecting the position of an irradiation point that appears under the central light generation state on a light receiving sphere that is installed so that its center coincides with the measurement point; A process of estimating a direction connecting the position of the center and the position of the irradiation point as the arrival direction of the light reaching the measurement point; The propagation environment estimation device is configured to further execute the above.

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