Wireless communication system

Abstract

To easily introduce a wireless communication system that enables communication between a first communication device and a second communication device that are positioned such that they cannot see each other due to an obstruction, using radio waves in a frequency band that has large propagation attenuation and high directivity. [Solution] A communication system S capable of communication between the first communication device 10 and the second communication device A20a and the second communication device B20b can be introduced by the simple method of installing a radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer), which is a radio wave scatterer that does not require a power source and has scattering properties that reflect incident radio waves in multiple directions, in appropriate locations on the ceiling, floor, and side walls that are commonly visible from the first communication device 10 and the second communication device A20a and the second communication device B20b, which are arranged so that they cannot directly see each other due to obstructions 110 in the room 100.

Description

[Technical field]

[0001] The present invention relates to a wireless communication system that includes a first communication device and one or more second communication devices that communicate using radio waves in the GHz band or higher frequency band, which has large propagation attenuation and high directionality, and that performs wireless communication between the first communication device and the second communication device, which are located in positions where they cannot see each other due to being obstructed by an obstruction. [Background technology]

[0002] Fifth generation mobile communication system (hereinafter referred to as 5G) services will be launched in 2020, and in this 5G, radio waves of frequencies including the millimeter wave band of 28 GHz are used for wireless communication. While 5G wireless communication services enable high-speed and large-capacity communication, in frequency bands of GHz and above, radio waves have large propagation attenuation and high linearity, so that if there is an obstruction between the first communication device and the second communication device, the radio waves from the transmitting antenna of the first communication device may not reach the receiving antenna of the second communication device, resulting in a significant deterioration in communication quality. Therefore, in wireless communication services using radio waves in frequency bands with large propagation attenuation and high linearity, eliminating dead zones is a major challenge.

[0003] When a second communication device cannot directly receive radio waves from a first communication device, a method is known in which a radio wave reflecting member is inserted to reflect the radio waves in a direction that allows the second communication device to receive the radio waves, but it is complicated to specify what characteristics the radio wave reflecting member should have, in what position, and in what direction. Therefore, an information processing device that can determine the installation position of the radio wave reflecting member has been proposed (for example, see Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Patent Document 1] Patent No. 7221333 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in order to apply the information processing device that determines the installation position of the radio wave reflecting member described in Patent Document 1, it is necessary to use a radio wave reflecting member that can adaptively control the direction of the reflected beam of the radio wave reflector in accordance with changes in the positions of multiple second communication devices that exist in the non-line-of-sight area of ​​the first communication device. Therefore, it is necessary to use an expensive radio wave reflector that requires a power source, such as a radio wave reflector in which multiple reflecting elements are arranged two-dimensionally in an array, as the radio wave reflecting member, which is expected to restrict the installation location of the radio wave reflector and significantly increase the introduction and operating costs of the radio wave reflector.

[0006] If the conventional wireless communication system described in Patent Document 1 does not perform adaptive control of the reflected beam direction, there is no need to use an expensive radio wave reflector that requires a power source as a radio wave reflecting member, so restrictions on the installation location of the radio wave reflecting member and increased costs for introduction may be avoided. However, if the deviation due to aging or the like from the time the radio wave reflecting member is installed (for example, the deviation between the reflected beam direction of the radio wave reflecting member and the position of the second communication device) becomes large, the communication performance of the wireless communication system will be significantly reduced, so there is a possibility that it will be necessary to adjust the orientation of the radio wave reflecting member or change the installation position of the radio wave reflecting member. As a result, even if a wireless communication system is constructed using an inexpensive radio wave reflecting member, the cost required for maintaining and managing the radio wave reflecting member will increase, and the operating cost will increase.

[0007] Therefore, the present invention aims to provide a wireless communication system that enables wireless communication using radio waves in a frequency band with large propagation attenuation and high directionality between a first communication device and a second communication device that are located in positions where they cannot see each other due to being blocked by an obstruction, and that can be introduced easily and at low cost, while also keeping operating costs low. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention is a wireless communication system that includes a first communication device and a second communication device that communicate using radio waves in the GHz band or higher frequency band, which have large propagation attenuation and high directionality, and performs wireless communication between the first communication device and the second communication device, which are located in positions where they are blocked by an obstruction and cannot see each other, and is characterized in that a radio wave scatterer installation area is set as an area in which a radio wave scatterer having scattering properties that reflect incident radio waves in multiple directions can be installed, and an area where a first communication device line-of-sight area that is line-of-sight from the position of the first communication device and a second communication device line-of-sight area that is line-of-sight from the position of the second communication device overlap, and wireless communication between the first communication device and the second communication device is performed via the radio wave scatterer installed in the radio wave scatterer installation area.

[0009] In addition, in the above configuration, the radio wave scatterer is a radio wave scattering sheet with a metamaterial structure that scatters electromagnetic waves in multiple directions when it receives electromagnetic waves of a specific frequency band on a radio wave scattering surface having a specific metal pattern formed on a dielectric material.

[0010] In the above configuration, the first communication device may have a multi-device connection function, and the second communication device may be connected to the first communication device on a one-to-one basis.

[0011] Furthermore, in the above configuration, when there are one or more unreachable second communication devices for which the radio wave scatterer installed in the radio wave scatterer installation area is out of line of sight, the radio wave scatterer may be regarded as a radio wave emission source, and an area where the radio wave scatterer line of sight area that is line of sight from the radio wave scatterer, the unreachable second communication device line of sight area that is line of sight from the unreachable second communication device, and the radio wave scatterer installable area overlap may be set as an auxiliary radio wave scatterer installation area, and wireless communication may be performed between the first communication device and the unreachable second communication device via the radio wave scatterer installed in the radio wave scatterer installation area and the auxiliary radio wave scatterer installed in the auxiliary radio wave scatterer installation area.

[0012] In addition, in the above configuration, the first communication device may be a transmitting station, and one or more of the second communication devices may be receiving stations, and the receiving strength of the second communication device may be estimated from an operational gain in the direction of the radio wave scatterer of an antenna provided in the first communication device, an operational gain in the direction of the radio wave scatterer of an antenna provided in the second communication device, and an amount of attenuation due to scattering by the radio wave scatterer.

[0013] Furthermore, in the above configuration, the second communication device may be provided with, in addition to the antenna that is the target of identifying the second communication device line-of-sight area, one or more sub-antennas that are separated to such an extent that signal fluctuations are uncorrelated, and the radio wave scatterer may be regarded as a radio wave radiation source, and a multipath radio wave scatterer installation area may be set as a region where a multipath radio wave scatterer installation area that is line-of-sight from the radio wave scatterer overlaps with a second communication device sub-line-of-sight area that is line-of-sight from any one of the sub-antennas of the second communication device, and the radio wave scatterer installation area, and multipath wireless communication may be performed between the first communication device and the second communication device via the radio wave scatterer installed in the radio wave scatterer installation area and the multipath radio wave scatterer installed in the multipath radio wave scatterer installation area. Effect of the Invention

[0014] According to the wireless communication system of the present invention, wireless communication between the first communication device and the second communication device that are located in positions where they cannot see each other due to being blocked by an obstruction can be achieved simply by installing a radio wave scatterer that does not require a power source in the radio wave scattering sheet installation area, which is an area where the sheet installation area, the line-of-sight area of ​​the first communication device, and the line-of-sight area of ​​the second communication device overlap. Therefore, the wireless communication system can be introduced easily and at low cost, and the operating costs can be kept low. [Brief description of the drawings]

[0015] [Figure 1] Fig. 1(A) is a schematic diagram of a first communication device and two second communication devices that are arranged in positions where they cannot see each other due to an obstruction in a room. Fig. 1(B) is a schematic diagram of a wireless communication system according to a first embodiment. [Diagram 2]Fig. 2(A) is a schematic vertical cross-sectional view of a radio wave scattering sheet with a protective layer, which is a first configuration example of a radio wave scatterer. Fig. 2(B) is a schematic vertical cross-sectional view of a radio wave scattering sheet with a protective layer, which is a second configuration example of a radio wave scatterer. [Diagram 3] FIG. 3 is a scattering characteristic diagram showing the scattering characteristics of a radio wave scattering sheet to which a commercially available wallpaper is attached as a protective layer. [Figure 4] FIG. 4 is a schematic diagram of a radio wave scatterer installation area determination device. [Diagram 5] FIG. 5 is a schematic configuration diagram showing an area in which a radio wave scatterer can be installed in the wireless communication system of the first embodiment. [Figure 6] FIG. 6 is a schematic configuration diagram showing a line-of-sight area of ​​a first communication device in the wireless communication system of the first embodiment. [Figure 7] FIG. 7 is a schematic configuration diagram showing a line-of-sight area of ​​the second communication device A in the wireless communication system of the first embodiment. [Figure 8] FIG. 8 is a schematic configuration diagram showing a line-of-sight area of ​​the second communication device B in the wireless communication system of the first embodiment. [Figure 9] FIG. 9 is a schematic diagram showing a radio wave scatterer installation area in the wireless communication system of the first embodiment. [Figure 10] FIG. 10 is a schematic diagram showing the configuration in which a radio wave scattering sheet is disposed in a radio wave scatterer installation area (a limited area that can be shared by the second communication device A and the second communication device B) in the wireless communication system of the first embodiment. [Figure 11] FIG. 11 is a schematic diagram showing a radio wave scatterer installation area corresponding to the second communication device A. As shown in FIG. [Figure 12] FIG. 12 is a schematic diagram showing the configuration of the radio wave scattering sheet disposed in the radio wave scatterer installation area corresponding to the second communication device A in the wireless communication system of the first embodiment. [Figure 13] FIG. 13 is a schematic diagram showing a radio wave scatterer installation area corresponding to the second communication device B. As shown in FIG. [Figure 14] FIG. 14 is a schematic diagram showing the configuration of a radio wave scattering sheet disposed in a radio wave scatterer installation area corresponding to a second communication device B in the wireless communication system of the first embodiment. [Figure 15] FIG. 15 is a schematic diagram showing a radio wave scatterer installation area corresponding to a mobile second communication device having a movement range from the position of the second communication device A to the position of the second communication device B. In FIG. [Figure 16] FIG. 16 is a schematic diagram showing the configuration of a radio wave scattering sheet disposed in a radio wave scatterer installation area corresponding to a mobile second communication device in the wireless communication system of the first embodiment. [Figure 17] FIG. 17 is a schematic diagram of a wireless communication system according to the second embodiment, which is provided with an auxiliary radio wave scattering sheet. [Figure 18] FIG. 18 is a schematic diagram showing a line-of-sight area of ​​a second communication device not reached and an installation area of ​​an auxiliary radio wave scatterer in a wireless communication system according to the second embodiment. [Figure 19] FIG. 19 is a schematic diagram of a wireless communication system according to a third embodiment, which includes a second communication device having a sub-antenna and capable of multipath reception, and a radio wave scattering sheet for multipath reception. [Figure 20] FIG. 20 is a schematic configuration diagram showing a second communication device sub-line-of-sight area and an installation area of ​​a radio wave scatterer for multipath in the wireless communication system of the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the wireless communication system according to the present invention will be described in detail with reference to the accompanying drawings. In the present invention, as shown in FIG. 1(A), a first communication device 10 and a second communication device 20 (for example, two devices, a second communication device A20a and a second communication device B20b) are arranged in a position where they cannot see each other because they are blocked by a shield 110 in a room 100, and wireless communication is performed using radio waves in a frequency band of GHz or more, which has large propagation attenuation and high linearity. The first communication device 10 has a multi-device connection function, and the two second communication devices 20 (the second communication device A20a and the second communication device B20b) are connected to the first communication device 10 on a one-to-one basis. However, in a 5G service using a frequency of 28 GHz, which is the application target of this embodiment, the presence of the shield 110 means that the first communication device 10 cannot directly communicate with the second communication device A20a and the second communication device B20b.

[0017] Therefore, in the wireless communication system S according to the first embodiment, a radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer), which is an example of a radio wave scatterer having scattering properties that reflect incident radio waves in multiple directions, is installed in an appropriate position on the ceiling of a room 100, thereby enabling communication between the first communication device 10 and the second communication device 20. The radio wave scattering sheet 1 used as the radio wave scatterer in this embodiment does not require a power source, and is a flat sheet body with a metamaterial structure that scatters electromagnetic waves in multiple directions when it receives electromagnetic waves of a specific frequency band on its radio wave scattering surface having a specific metal pattern formed on a dielectric material.

[0018] Unlike radio wave reflectors that reflect radio waves only in a specific direction (regular reflection direction) depending on the direction in which the signal is received, radio wave scatterers that do not require a power source are known to have scattering characteristics that reflect radio waves in multiple directions using various radio wave scattering principles. For example, a stealth technology that generates scattering behavior according to the incidence angle of radio waves in 55% of the frequency bandwidth from 28.5 GHz to 50 GHz by arranging two types of artificial magnetic conductors with a phase difference of 180° + 37° in the reflection coefficient alternately like a chessboard can be used as a radio wave scatterer. In addition, a radio wave reflector with a metamaterial structure in which a conductive thin film layer in which radio wave reflective materials such as squares, rectangles, triangles, and hexagons are arranged in a periodic and uniform pattern is formed on the top surface of a synthetic resin base layer, and a protective layer is provided on the top surface of the conductive thin film layer via an adhesive layer, can be designed using parameters such as the size and shape of the radio wave reflective material and the spacing between the radio wave reflective materials to achieve scattering characteristics that reflect the incident wave with a frequency of 25 GHz or more and 30 GHz or less in angle range of -15 degrees or more and +15 degrees or less with respect to the regular reflection direction when the incident angle is 15 degrees or more and 75 degrees or less.

[0019] The radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) used in this embodiment also has scattering properties like the radio wave scatterer described above. Fig. 2(A) shows a schematic vertical cross-sectional view of a radio wave scattering sheet 31 with protective layer of a first configuration example, and Fig. 2(B) shows a schematic vertical cross-sectional view of a radio wave scattering sheet 12 with protective layer of a second configuration example.

[0020] The radio wave scattering sheet 31 with a protective layer of the first configuration example includes a radio wave scattering sheet 1 consisting of a flat dielectric 1a with a back metal plate 1b and a front metalized layer 1c provided on both sides thereof, a dielectric layer 2 as a protective layer covering a radio wave scattering surface 1d corresponding to the front surface of the front metalized layer 1c of the radio wave scattering sheet 1, and an adhesive layer 3 provided on the outer surface (lower surface) of the back metal plate 1b for attaching the radio wave scattering sheet 1 to a wall surface, a ceiling, etc. The design of the radio wave scattering sheet 1 with a metamaterial structure (determination of the structural parameters of the metamaterial) can be realized by combining the array antenna theory for deriving the scattering pattern and a genetic algorithm for optimizing the structure.

[0021] The radio wave scattering sheet 1 uses a glass epoxy board (grade FR4) with a thickness of about 0.68 [mm] and a relative dielectric constant of 4.5 as the dielectric 1a, a metal film (e.g., copper foil) of about 60 [μm] formed on one side of the dielectric 1a as the back metal plate 1b, and a surface metal processing layer 1c in which a specific metal pattern is formed by processing the metal film (e.g., copper foil) of about 60 [μm] formed on the other side of the dielectric 1a by etching or the like. This radio wave scattering sheet 1 has a metamaterial structure that can scatter radio waves arriving at the radio wave scattering surface 1d from multiple directions in a wide angle by forming a patch structure in the surface metal processing layer 1c that combines areas with reflection phases of 0° and 180° within a unit unit surface (e.g., a surface of 180 [mm] x 180 [mm]). The radio wave scattering sheet 1 of this configuration example was designed to match electromagnetic waves in the 28 [GHz] band selected as a specific frequency band. The total thickness of the radio wave scattering sheet 1, which is made up of the dielectric 1a, the back metal plate 1b, and the front metalized layer 1c, is about 0.8 mm.

[0022] The dielectric layer 2 may be formed by applying a coating agent or the like to the radio wave scattering surface 1d of the radio wave scattering sheet 1 in a uniform thickness, or by attaching a plate-shaped material made of an adhesive material to the radio wave scattering surface 1d of the radio wave scattering sheet 1. However, if the material forming the dielectric layer 2 is opaque, the surface metal processed layer 1c becomes invisible, improving the appearance of the radio wave scattering sheet 31 with protective layer. In addition, the surface of the dielectric layer 2 is not limited to a single color, and may be configured in multiple colors. For example, if multiple types of coating agents with the same relative dielectric constant but different colors are used, a multi-colored pattern can be expressed on the surface of the dielectric layer 2.

[0023] On the other hand, the radio wave scattering sheet 32 ​​with a protective layer of the second configuration example includes a dielectric layer 2' as a protective layer covering the radio wave scattering surface 1d corresponding to the surface of the surface metal processing layer 1c of the radio wave scattering sheet 1, and an adhesive layer 3 provided on the outer surface of the back metal plate 1b in order to attach the radio wave scattering sheet 1 to a wall surface, a ceiling, or the like. The dielectric layer 2' has a two-layer structure in which an adhesive layer 2b as a lower protective layer is provided on the lower surface of the surface layer 2a as an upper protective layer, and is attached to the radio wave scattering surface 1d of the radio wave scattering sheet 1 by the viscosity of the adhesive layer 2b. Here, if the material forming the surface layer 2a of the dielectric layer 2' is opaque, the surface metal processing layer 1c becomes invisible, so that the appearance of the radio wave scattering sheet 32 ​​with a protective layer can be improved. The protective layer is not limited to two layers, and may be a multi-layer structure of three or more layers including a printing layer, a surface coating layer, or the like.

[0024] FIG. 3 shows the scattering characteristics of a radio wave scattering sheet 32 ​​with a protective layer, which is made by attaching a commercially available wallpaper, for example, a vinyl chloride resin sheet with a thickness of about 0.4 [mm] (estimated relative dielectric constant: 3.0), as a protective layer to the radio wave scattering sheet 1. For comparison, the scattering characteristics of the radio wave scattering sheet 1 alone are shown by a dashed line. Although the scattering pattern of the radio wave scattering sheet 32 ​​with a protective layer does not completely match the scattering pattern of the radio wave scattering sheet 1 without wallpaper, it is possible to obtain the same degree of directional diffusion, and it is found that the radio wave scattering sheet 1 can fully function as a radio wave scattering sheet 1 even if wallpaper is attached as a protective layer to the radio wave scattering surface 1d. The degree of directional diffusion is a numerical value related to the evaluation of the scattering sheet, which indicates the dispersion value of the energy of the scattered radio waves in each direction, and the higher the degree of directional diffusion, the wider the angle and the more uniform the electric field strength of the scattered radio waves.

[0025] 1(B), if the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) is installed on the wall or ceiling in the room 100, radio waves in the 28 [GHz] band transmitted from the first communication device 10 can reach a wide area, so that even if the second communication device A20a and the second communication device B20b are located at the back side separated from the first communication device 10 by a shielding object 110 such as a screen or a partition wall, radio waves in the 28 [GHz] band can reach them, improving communication quality. Moreover, the radio wave scattering sheets 31, 32 with protective layer protect the surface metal processing layer 1c of the radio wave scattering sheet 1 with the dielectric layers 2, 2', so that it is possible to suppress an increase in operating costs associated with breakdowns and deterioration.

[0026] Moreover, since the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) does not require a power source and is thin and light, it can be easily arranged on flat surfaces such as the ceiling, floor, and side walls that constitute the room 100. As long as the area in which the radio wave scattering sheet 1 is to be installed so that it functions as the wireless communication system S is known, no special construction skills or tools are required, so that the introduction cost can be reduced. Therefore, by using the radio wave scatterer installation area determination device 200 shown in FIG. 4, the area in which the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) as a radio wave scatterer is to be installed so that it functions as the wireless communication system S can be easily determined. Note that the introduction cost of the radio wave scatterer installation area determination device 200 can be reduced by providing it as application software that is installed and used on a general personal computer, etc., rather than providing it as a dedicated device.

[0027] The radio wave scatterer installation area determination device 200 includes a first communication device information input means 201 for inputting information about the first communication device 10, a second communication device information input means 202 for inputting information about the second communication device 20, a radio wave scatterer information input means 203 for inputting information about the radio wave scatterer (radio wave scattering sheet 30 with protective layer), an environment information input means 204 for inputting information about the environment (for example, the room 100 and the shield 110) in which the first communication device 10 and the second communication device 20 are placed, a storage means 205 for storing the input information, and a radio wave scatterer installation area determination means 206 for retrieving the information stored in the storage means 205 and determining the area in which the radio wave scatterer is to be installed. The radio wave scatterer installation area determined by the radio wave scatterer installation area determination means 206 is output as visible information from a display or a printer.

[0028] The position of the first communication device 10 (the range of movement if the first communication device 10 moves) is input from the first communication device information input means 201 as information related to the first communication device 10. In addition, the power (antenna power) output from the wireless device main body of the first communication device 10, or the operating gain in the installation direction of the radio wave scattering sheet 1 of the antenna connected to the wireless device main body, or the equivalent isotropically radiated power (EIRP) expressed as the product of the antenna power and the operating gain, etc. may be input as information related to the first communication device 10.

[0029] The position of the second communication device 20 (the range of movement if the second communication device 20 moves) is input from the second communication device information input means 202 as information relating to the second communication device 20. In addition, the operating gain of the antenna connected to the wireless device main body of the second communication device 20 in the direction of the radio wave scattering sheet 1 may be input as information relating to the second communication device 20.

[0030] From the radio wave scatterer information input means 203, information relating to the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) designed for the frequency band used in the wireless communication system S, such as the radiation pattern and the amount of attenuation due to scattering, is input.

[0031] The environmental information input means 204 inputs information regarding the environment in which the first communication device 10 and the second communication device 20 are located, such as the three-dimensional structure of the room 100, the position and shape of the obstruction 110, and the radio wave scatterer installation area indicating the area within which radio wave scatterers may be installed.

[0032] The radio wave scatterer installation area determination means 206 reads out various information stored in the storage means 205, and determines an appropriate radio wave scatterer installation area as an area where a radio wave scatterer is to be installed, according to a predetermined radio wave scattering sheet installation position determination method. In summary, this determination method determines, as the radio wave scatterer installation area, an area where a radio wave scatterer installable area set as an area where a radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) can be installed overlaps with a first communication device line-of-sight area that is line-of-sight from the position of the first communication device 10 which is the first communication device, and a second communication device line-of-sight area that is line-of-sight from the position of the second communication device 20 (second communication device A 20a and second communication device B 20b). The determination process will be described below with reference to Figs. 5 to 9. For simplicity of explanation, it is assumed here that the first communication device 10 and the second communication device 20 are fixed or parked in their positions and do not move during communication. However, as described below, if the first communication device 10 and the second communication device 20 move, it is possible to set up an appropriate wireless communication system S corresponding to the range of movement by determining the radio wave scatterer installation area taking into account the range of movement.

[0033] As shown in FIG. 5, the environment in which the first communication device 10 and the second communication device 20 are arranged is divided into spaces separated by a shielding object 110 in a room 100. However, since there is a gap G above the shielding object 110 that connects the space in which the first communication device 10 is arranged and the space in which the second communication device 20 is arranged, it can be seen that there is a possibility that a communication propagation path for the first communication device 10 and the second communication device 20 can be formed through this gap G. Since the radio wave scattering sheet 1 can be installed on a substantially flat surface such as a side wall or ceiling of the room 100, these planes are input as the radio wave scatterer installable area. From the structure of the room 100 and the position of the gap G, for example, the entire surface of the side wall 130 and the entire surface of the ceiling 140 in the vicinity of the second communication device 20 are interpreted as the radio wave scatterer installable area 301.

[0034] Next, as shown in FIG. 6, a first communication device line-of-sight area 302 is specified, which is a range of positions that are line-of-sight (LOS) from the position of the first communication device 10. The first communication device line-of-sight area 302 may be set as an optically visible range that can be seen from the first communication device 10 through the gap G, or may be a range where a first Fresnel zone starting from the first communication device 10 intersects with the inner surface of the room 100 through the gap G. The Fresnel zone quantitatively represents a guide to ensuring line-of-sight between a transmitting antenna and a receiving antenna, and is an elliptical radio wave path from a transmitting antenna to a space until a radio wave radiated from the transmitting antenna arrives at the receiving antenna. Since most of the radio wave energy exists in the first Fresnel zone, which is the innermost area, if the first Fresnel zone is set so that it is not blocked by a shield 110, reliable and stable wireless communication can be performed. In the room 100, the first communication device 10 and the second communication device 20 cannot directly communicate with each other through the gap G, so the position of the receiving antenna of the second communication device 20 relative to the transmitting antenna of the first communication device 10 is indefinite, but the shape of the first Fresnel zone can be specified by assuming that a virtual receiving antenna is located beyond the ceiling 140. For example, taking into consideration that the Fresnel radius of the Fresnel zone is maximum at 1 / 2 the communication distance, the position of the virtual receiving antenna is set so that the Fresnel radius is maximum in the gap G, and the first Fresnel zone is specified, and a first communication device line-of-sight area 302 spanning from the ceiling 140 to the side wall 130 is obtained.

[0035] Next, as shown in Fig. 7, a line-of-sight area 303a of the second communication device A, which is a range of positions that are line-of-sight (LOS) from the position of the second communication device A20a, is specified. Similarly, as shown in Fig. 8, a line-of-sight area 303b of the second communication device B, which is a range of positions that are line-of-sight (LOS) from the position of the second communication device B20b, is specified. Note that the line-of-sight area 303a of the second communication device A and the line-of-sight area 303b of the second communication device B may be set as an optically visible range that can be seen from the second communication device A20a and the second communication device B20b without being blocked by the obstruction 110, but may also be a range where a first Fresnel zone in which the second communication device A20a and the second communication device B20b are set as transmitting antennas intersects with the inner surface of the room 100.

[0036] After identifying the line-of-sight area 302 of the first communication device, the line-of-sight area 303a of the second communication device A, and the line-of-sight area 303b of the second communication device B as described above, as shown in FIG. 9, the area where the radio wave scatterer installation area 301, which is set as an area where the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) can be installed, overlaps with the line-of-sight area 302 of the first communication device which is line-of-sight from the position of the first communication device 10, the line-of-sight area 303a of the second communication device A which is line-of-sight from the position of the second communication device A20a, and the line-of-sight area 303b of the second communication device B which is line-of-sight from the position of the second communication device B20b, is determined to be the radio wave scatterer installation area 304.

[0037] 10, if the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) is installed so as to cover the entire radio wave scatterer installation area 304, a radio communication system S is obtained that enables radio communication between the first communication device 10 and the second communication device A20a and the second communication device B20b via the radio wave scattering sheet 1. Since the radio wave scatterer installation area 304 is an area where all the radio waves from the first communication device 10, the second communication device A20a, and the second communication device B20b can reach, the radio communication system S can be established even if a radio wave scattering sheet 1 of a minimum size (for example, 180 [mm] x 180 [mm]) is provided somewhere within the range of the radio wave scatterer installation area 304. However, considering the amount of attenuation due to the scattering characteristics of the radio wave scattering sheet 1, by arranging the radio wave scattering sheet 1 so as to cover the entire radio wave scatterer installation area 304, non-delivery due to attenuation can be reduced.

[0038] As described above, in the wireless communication system S of the first embodiment, the first communication device 10 and the second communication device 20 are in an environment where they cannot see each other because of the obstruction 110, but when communication is to be performed using radio waves in the GHz band or higher frequency band, which have large propagation attenuation and high linearity, the radio wave scattering sheet 1, which does not require a power source, can be installed in the radio wave scatterer installation area 304 simply and at low cost, and the operating costs can be kept low. For example, even if the first communication device 10, which is a radio base station for 5G communication services, and the second communication device 20, which is a mobile terminal, cannot directly communicate with each other because of the presence of the obstruction 110, the dead zone area can be eliminated simply by installing a radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) of an appropriate size in an appropriate position.

[0039] The radio wave scatterer installation area determination device 200 described above determines the radio wave scatterer installation area 304 in which the first communication device 10 and the second communication device 20 are included in the scattering direction by the radio wave scattering sheet 1, but may have a function of setting comprehensive communication conditions so that communication between the first communication device 10 and the second communication device 20 can be more reliably performed. For example, the first communication device 10 is a transmitting station, and the second communication device A20a and the second communication device B20b are receiving stations, respectively, and the reception strength of the second communication device 20 is estimated from the operating gain of the antenna provided in the first communication device 10, which is the transmitting station, in the installation direction of the radio wave scattering sheet 1, the operating gain of the antenna provided in the second communication device 20, which is the receiving station, in the installation direction of the radio wave scattering sheet 1, and the amount of attenuation due to scattering by the radio wave scattering sheet 1. Then, when the reception strength at the second communication device 20 does not reach a sufficient level, information is presented as to how much the operating gain of the first communication device 10 or the second communication device 20 needs to be increased, so that downstream communication from the first communication device 10 to the second communication device 20 can be adjusted to a good state. Conversely, in order to improve upstream communication from the second communication device 20 to the first communication device 10, the second communication device A20a and the second communication device B20b are each a transmitting station, and the first communication device 10 is a receiving station, and the reception strength of the first communication device 10 is estimated, and information for making the reception strength at the first communication device 10 a sufficient level is presented.

[0040] 9 is set to a limited area that can be shared by the second communication device A20a and the second communication device B20b, and a case has been shown in which the wireless communication system S is configured with a relatively small radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) as in FIG 10, but a wider area may be set as the radio wave scatterer installation area, and the radio wave scattering sheet 1 may be provided over a wider area. For example, as shown in FIG 11, a radio wave scatterer installation area (area where the radio wave scatterer installable area, the line-of-sight area of ​​the first communication device, and the line-of-sight area of ​​the second communication device A overlap) 304a corresponding to the second communication device A20a may be set, and as shown in FIG 12, a radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) may be placed in the radio wave scatterer installation area 304a corresponding to the second communication device A20a to form the wireless communication system S. Alternatively, as shown in Fig. 13, a radio wave scatterer installation area (area where the radio wave scatterer installable area, the line-of-sight area of ​​the first communication device, and the line-of-sight area of ​​the second communication device B overlap) 304b corresponding to the second communication device B20b may be set, and as shown in Fig. 14, a radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) may be arranged in the radio wave scatterer installation area 304b corresponding to the second communication device B20b to form a wireless communication system S. In this way, by providing the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) in the radio wave scatterer installation areas 304a, 304b that are wider than the limited area that can be shared by the second communication device A20a and the second communication device B20b, the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) can be arranged including the radio wave scatterer installation area effective only for the second communication device A20a or the radio wave scatterer installation area effective only for the second communication device B20b, which can contribute to increasing the reception strength in the communication between the first communication device 10 and the second communication device A20a and the second communication device B20b. Of course, the entire area which is the union (304a∪304b) of the radio wave scatterer installation area 304a corresponding to the second communication device A20a and the radio wave scatterer installation area 304b corresponding to the second communication device B20b may be defined as the radio wave scatterer installation area 304', and a radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) may be provided so as to cover the entire radio wave scatterer installation area 304' (see Figures 15 and 16).

[0041] From a different perspective, the radio wave scatterer installation area 304' can be regarded as including all of the radio wave scatterer installation areas into which a mobile second communication device 20', such as a portable terminal, moves as it moves from the position of the second communication device A20a to the position of the second communication device B20b, since the radio wave scatterer installation area 304a corresponding to the second communication device A20a and the radio wave scatterer installation area 304b corresponding to the second communication device B20b are continuous without any breaks, as shown in Fig. 15. Therefore, as shown in Fig. 16, if the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) is provided so as to cover the entire radio wave scatterer installation area 304' corresponding to the mobile second communication device 20', good communication between the first communication device 10 and the mobile second communication device 20' can be maintained even if the mobile second communication device 20' moves within the movement range corresponding to the radio wave scatterer installation area 304'.

[0042] In this manner, when the second communication device 20 or the first communication device 10 is a moving body, characteristic points such as the outer edge of the moving range are extracted, and the radio wave scatterer installation area when the second communication device 20 or the first communication device 10 is placed at each characteristic point is individually determined, and a radio wave scatterer installation area for the moving range is set so as to include all of the individually determined radio wave scatterer installation areas, and a radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) is provided so as to cover the entire radio wave scatterer installation area for the moving range.

[0043] The radio wave scatterer installation area determination means 206 of the radio wave scatterer installation area determination device 200 may be provided with a movement restricted area determination function for determining that there is a movement restricted area in which the radio wave scatterer installation area cannot be set when the first communication device 10 or the second communication device 20 is placed within the movement range of the first communication device 10 or the second communication device 20. When the movement restricted area determination function of the radio wave scatterer installation area determination means 206 determines that there is a movement restricted area in which wireless communication via the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) cannot be realized, this is notified to the user, thereby encouraging the user not to place the first communication device 10 or the second communication device 20 in the movement restricted area or not to move with the first communication device 10 or the second communication device 20 in the movement restricted area.

[0044] In the wireless communication system S of the first embodiment, all the second communication devices 20 (second communication devices A 20a and second communication devices B 20b) were located in positions where they could see the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer), but as shown in Fig. 17, a case is assumed in which a second communication device 20 exists that cannot see the radio wave scattering sheet 1 due to a complexly shaped obstruction 120. In this case, in addition to a second communication device 21 (hereinafter referred to as reached second communication device 21) that can be reached by radio waves from the first communication device 10 and communicated with by providing the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer), there exists a second communication device 22 (hereinafter referred to as unreachable second communication device 22) to which radio waves from the first communication device 10 remain unreachable.

[0045] In such a case, by applying the wireless communication system S' of the second embodiment, wireless communication between the first communication device 10 and the unreachable second communication device 22 can be made possible. That is, when there are one or more unreachable second communication devices 22 that are out of line of sight of the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) installed in the radio wave scatterer installation area 304, the main radio wave scattering sheet 1 is regarded as a radio wave radiation source, and an auxiliary radio wave scattering sheet 1' (auxiliary radio wave scattering sheet 30' with protective layer) is provided at a location where the range of line of sight from the main radio wave scattering sheet 1 overlaps with the range of line of sight from the unreachable second communication device 22, thereby making it possible to make wireless communication between the first communication device 10 and the unreachable second communication device 22 via the main radio wave scattering sheet 1 and the auxiliary radio wave scattering sheet 1'. Note that the auxiliary radio wave scattering sheet 1' (auxiliary radio wave scattering sheet 30' with protective layer) has the same structure and function as the main radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer).

[0046] First, the line-of-sight area of ​​the radio wave scatterer, which is the line of sight from the main radio wave scattering sheet 1, is set to be from the scattering range (wide area of ​​about 180°) of the radio wave scattering sheet 1 installed on the ceiling 140 to almost the entire side wall 130 of the room 100, as shown in Fig. 18. Since this side wall 130 is the radio wave scatterer installable area 301 as in the first embodiment, it is also possible to install an auxiliary radio wave scattering sheet 1' (auxiliary radio wave scattering sheet 30' with protective layer). Furthermore, the unreachable second communication device 22, which is out of the line of sight of the main radio wave scattering sheet 1 due to the presence of the shield 120, can see through a part of the side wall 130 of the room 100 without being blocked by the shield 120, so that an unreachable second communication device line-of-sight area 305 is formed on the side wall 130. Since this unreachable second communication device line-of-sight area 305 is on the side wall 130, which is the radio wave scatterer line-of-sight area and the auxiliary radio wave scatterer installable area, it coincides with the auxiliary radio wave scatterer installation area 306 where the three areas overlap. Therefore, if the auxiliary radio wave scattering sheet 1' (auxiliary radio wave scattering sheet 30' with protective layer) is provided so as to cover the entire area of ​​the auxiliary radio wave scatterer installation region 306, a wireless communication system S' is obtained.

[0047] The wireless communication system S' of the second embodiment described above uses a multipath by the auxiliary radio wave scattering sheet 1' (auxiliary radio wave scattering sheet 30' with protective layer) to allow radio waves from the first communication device 10 to reach the unreachable second communication device 22, but a multipath may be used to improve communication quality and communication speed. The wireless communication system S'' of the third embodiment shown in FIG. 19 includes a second communication device 23 functioning as a receiving station of spatial diversity, which is one of the multipath communication techniques, and can improve communication quality by, for example, synthesizing signals received by the first antenna 231 and the second antenna 232 via different paths from the first communication device 10 functioning as a transmitting station. For this reason, the wireless communication system S'' of the third embodiment is provided with a multipath radio wave scattering sheet 1'' (multipath radio wave scattering sheet 30'' with protective layer) in addition to the main radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer). The multipath radio wave scattering sheet 1'' (multipath radio wave scattering sheet 30'' with protective layer) has the same structure and function as the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer).

[0048] The first antenna 231 as a main antenna provided in the second communication device 23 is a specified target of the second communication device line-of-sight area 303, and a radio wave scatterer installation area 304 is set as an area overlapping the first communication device line-of-sight area 302 and the radio wave scatterer installable area 301. In FIG. 20, for ease of explanation, it is assumed that the first communication device line-of-sight area 302 and the radio wave scatterer installable area 301 both include the second communication device line-of-sight area 303, and the radio wave scatterer installation area 304 coincides with the second communication device line-of-sight area 303. On the other hand, the second antenna 232 as a sub-antenna provided in the second communication device 23 is provided at a position away from the first antenna 231 to such an extent that signal fluctuations are uncorrelated, and mainly receives radio waves from the first communication device 10 as scattered waves from the multipath radio wave scattering sheet 1″ (multipath radio wave scattering sheet 30″ with protective layer).

[0049] In order to efficiently receive scattered waves from the multipath radio wave scattering sheet 1″ (multipath radio wave scattering sheet 30″ with protective layer) by the second antenna 232 of the second communication device 23, a second communication device sub-line-of-sight area 307 line-of-sight from the second antenna 232 of the second communication device 23, a line-of-sight area from the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) considered as a radio wave radiation source, and an area where the multipath radio wave scatterer installable area 301 and the radio wave scatterer installable area 301 overlap are set as a multipath radio wave scatterer installation area 308, and the multipath radio wave scattering sheet 1″ (multipath radio wave scattering sheet 30″ with protective layer) is provided so as to cover the entire area of ​​the multipath radio wave scatterer installation area 308. Note that the second communication device sub-line-of-sight area 307 is on the side wall 130 which is the radio wave scatterer installable area 301 and the multipath radio wave scatterer installable area, and therefore coincides with the multipath radio wave scatterer installation area 308 where the three areas overlap.

[0050] According to the wireless communication system S" of the third embodiment configured as described above, scattered waves by the main radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) installed in the radio wave scatterer installation area 304 are received by the first antenna 231 of the second communication device 23, and scattered waves by the multipath radio wave scattering sheet 1" (multipath radio wave scattering sheet 30" with protective layer) installed in the multipath radio wave scatterer installation area 308 are received by the second antenna 232 of the second communication device 23. Therefore, multipath wireless communication between the first communication device 10 and the second communication device 23 can be performed, and signal attenuation caused by the scattering characteristics of the radio wave scattering sheet 1 and the multipath radio wave scattering sheet 1" can be compensated for, thereby improving communication quality. Furthermore, when a sufficient reception level can be obtained from the first and second antennas 231, 232 of the second communication device 23, the communication speed can be increased by simultaneously transmitting two types of signals (a signal directed to the first antenna 231 and a signal directed to the second antenna 232) from the first communication device 10, as in MIMO communication, and simultaneously receiving the two types of signals at the second communication device 23.

[0051] The above describes embodiments of the wireless communication system according to the present invention based on the attached drawings. However, the present invention is not limited to these embodiments, and may be implemented by reusing publicly known, existing equivalent technical means as long as the configuration described in the claims is not changed. [Explanation of symbols]

[0052] S Wireless communication system 100 rooms 110 Shield 10 First communication device 20a 2nd communication device A 20b 2nd communication device B 30 Radio wave scattering sheet with protective layer 1 Radio wave scattering sheet

Claims

1. A wireless communication system includes a first communication device and a second communication device that communicate using radio waves in a frequency band of GHz or higher, which have large propagation attenuation and high linearity, and performs wireless communication between the first communication device and the second communication device, the first communication device and the second communication device being located in a position where they cannot see each other because they are blocked by an obstacle, a radio wave scatterer installation area is set as an area where a radio wave scatterer having scattering properties that reflect incident radio waves in a plurality of directions can be installed, and an area where a first communication device line-of-sight area that is line-of-sight from the position of the first communication device and a second communication device line-of-sight area that is line-of-sight from the position of the second communication device overlap; wireless communication between the first communication device and the second communication device is performed via the radio wave scatterer installed in the radio wave scatterer installation area; The first communication device has a multi-device connection function; the second communication device is connected to the first communication device in a one-to-one relationship; The first communication device is a transmitting station, and one or more of the second communication devices are receiving stations; A wireless communication system characterized in that the receiving strength of the second communication device is estimated from the operational gain of the antenna of the first communication device in the direction of the radio wave scatterer, the operational gain of the antenna of the second communication device in the direction of the radio wave scatterer, and the amount of attenuation due to scattering by the radio wave scatterer.

2. The wireless communication system according to claim 1, characterized in that the radio wave scatterer is a radio wave scattering sheet having a metamaterial structure that scatters electromagnetic waves in multiple directions when it receives electromagnetic waves of a specific frequency band on a radio wave scattering surface formed with a specific metal pattern on a dielectric.

3. When there is one or more unreachable second communication devices where the radio wave scatterer installed in the radio wave scatterer installation area is out of line of sight, the radio wave scatterer is regarded as a radio wave emission source, and an area where the radio wave scatterer line of sight area which is line of sight from the radio wave scatterer, the unreachable second communication device line of sight area which is line of sight from the unreachable second communication device, and the area where the radio wave scatterer can be installed overlap is set as the auxiliary radio wave scatterer installation area; The wireless communication system according to claim 1, characterized in that wireless communication is performed between the first communication device and the unreachable second communication device via the radio wave scatterer installed in the radio wave scatterer installation area and an auxiliary radio wave scatterer installed in the auxiliary radio wave scatterer installation area.

4. when there is one or more unreachable second communication devices that are out of line of sight with the radio wave scatterer installed in the radio wave scatterer installation area, the radio wave scatterer is regarded as a radio wave emission source, and an area where a radio wave scatterer line of sight area that is line of sight from the radio wave scatterer, a non-reachable second communication device line of sight area that is line of sight from the unreachable second communication device, and a radio wave scatterer installable area are set as an auxiliary radio wave scatterer installation area; The wireless communication system according to claim 2, characterized in that wireless communication is performed between the first communication device and the unreachable second communication device via the radio wave scatterer installed in the radio wave scatterer installation area and an auxiliary radio wave scatterer installed in the auxiliary radio wave scatterer installation area.

5. The second communication device includes, in addition to an antenna that is a specific target in the line-of-sight area of ​​the second communication device, one or more sub-antennas that are spaced apart to such an extent that signal fluctuations are uncorrelated; regarding the radio wave scatterer as a radio wave radiation source, a region where a radio wave scatterer for multipath can be installed that is line of sight from the radio wave scatterer, a second communication device sub line of sight region that is line of sight from any one of the sub-antennas of the second communication device, and the radio wave scatterer installable region overlap is set as a radio wave scatterer for multipath installation region; The wireless communication system according to any one of claims 1 to 4, characterized in that multipath wireless communication is performed between the first communication device and the second communication device via the radio wave scatterer installed in the radio wave scatterer installation area and a multipath radio wave scatterer installed in the multipath radio wave scatterer installation area.

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