Wireless communication system

Abstract

This invention enables the easy introduction of a wireless communication system that allows communication using radio waves in a frequency band with high propagation attenuation and high directivity between a first communication device and a second communication device positioned in locations where they cannot see each other due to obstructions. [Solution] A communication system S that enables communication between the first communication device 10 and the second communication devices A20a and B20b can be introduced by a simple method of installing a radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer), which is a power-free radio wave scattering material with scattering characteristics that reflect incident radio waves in multiple directions, at a suitable location on the ceiling, floor, or side wall that is visible from the first communication device 10 and the second communication devices A20a and B20b, which are arranged so that they cannot see each other directly by the shielding 110 of the room 100.

Description

Technical Field

[0001] The present invention includes a first communication device that communicates using radio waves in a frequency band of GHz or higher with high propagation attenuation and high directivity, and one or more second communication devices, and is arranged at positions where the first communication device and the second communication device are blocked by a shielding object and cannot see each other. The present invention relates to a wireless communication system that performs wireless communication between a first communication device and a second communication device.

Background Art

[0002] Since the service of the fifth-generation mobile communication system (hereinafter referred to as 5G) has been started since 2020, radio waves with frequencies including the millimeter-wave band of 28 GHz are used for wireless communication in this 5G. In the wireless communication service of 5G, high-speed and high-capacity communication is possible. On the other hand, in a frequency band of GHz or higher, since the propagation attenuation of radio waves is large and the directivity is high, when there is a shielding object 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, and the communication quality may be significantly deteriorated. Therefore, in a wireless communication service using radio waves in a frequency band with high propagation attenuation and high directivity, eliminating the dead zone is a major issue.

[0003] When the second communication device cannot directly receive the radio waves from the first communication device, there is a known method of reflecting the radio waves in a direction that can be received by the second communication device by interposing a radio wave reflecting member. However, it is complicated to specify what kind of characteristics the radio wave reflecting member should have, where it should be placed, 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, refer to Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in order to apply the information processing device for determining 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 located in the line-of-sight area of ​​the first communication device. For this reason, it is necessary to use an expensive radio wave reflector that requires a power supply, such as a radio wave reflector plate in which multiple reflecting elements are arranged in a two-dimensional array, as the radio wave reflecting member. This is expected to impose restrictions on 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, it may be possible to avoid the constraints on the installation location of the radio wave reflector and the increase in installation costs, as there is no need to use expensive radio wave reflectors that require a power supply as radio wave reflector members. However, if the deviation due to aging or other factors (for example, the deviation between the reflected beam direction of the radio wave reflector and the position of the second communication device) becomes large after the radio wave reflector member has been installed, the communication performance of the wireless communication system will deteriorate significantly, and it may be necessary to adjust the orientation of the radio wave reflector member or change the installation location of the radio wave reflector member. As a result, even if a wireless communication system is built using inexpensive radio wave reflector members, the costs required for the maintenance and management of the radio wave reflector members will increase, and the operating costs will rise.

[0007] Therefore, the present invention aims to provide a wireless communication system that can be easily and inexpensively introduced, and that also keeps operating costs low, enabling wireless communication using radio waves in a frequency band with high propagation attenuation and high directivity between a first communication device and a second communication device positioned in locations where they cannot see each other due to obstructions. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides 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 high propagation attenuation and high directivity, and the first communication device and the second communication device are positioned in locations where they cannot see each other due to obstructions, and is characterized in that a radio wave scattering device installation area is set as an area where a radio wave scattering device having scattering characteristics that reflect incident radio waves in multiple directions can be installed, a line-of-sight area of ​​the first communication device which is in line of sight from the position of the first communication device, and a line-of-sight area of ​​the second communication device which is in 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 scattering device installed in the radio wave scattering device installation area.

[0009] Furthermore, 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 formed by creating a specific metal pattern on a dielectric.

[0010] Furthermore, in the above configuration, the first communication device may be equipped with 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, if there are one or more unreachable second communication devices that are out of line of sight of the radio wave scatter installed in the radio wave scatter installation area, the radio wave scatter may be considered a radio wave source, and the area where the line-of-sight area of ​​the radio wave scatter (which is in line of sight from the radio wave scatter), the line-of-sight area of ​​the unreachable second communication device (which is in line of sight from the unreachable second communication device), and the area where the radio wave scatter can be installed may overlap may be set as the auxiliary radio wave scatter installation area, and wireless communication between the first communication device and the unreachable second communication device may be performed via the radio wave scatter installed in the radio wave scatter installation area and the auxiliary radio wave scatter installed in the auxiliary radio wave scatter installation area.

[0012] Furthermore, in the above configuration, the first communication device may be designated as a transmitting station, and one or more of the second communication devices as receiving stations. The received signal strength of the second communication device may be estimated from the operating gain of the antenna of the first communication device in the direction of the radio wave scatterer, the operating 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.

[0013] Furthermore, in the above configuration, the second communication device may be provided with one or more sub-antennas located far enough apart that the signal fluctuations are uncorrelated, in addition to the antenna which is the target of the line-of-sight area of ​​the second communication device, and the area in which the multipath radio wave scatter can be installed, which is in line of sight from the radio wave scatter, the sub-line-of-sight area of ​​the second communication device which is in line of sight from any one of the sub-antennas of the second communication device, and the radio wave scatter can be installed area may be set as the multipath radio wave scatter installation area, and multipath wireless communication between the first communication device and the second communication device may be performed via the radio wave scatter installed in the radio wave scatter installation area and the multipath radio wave scatter installed in the multipath radio wave scatter installation area. [Effects of the Invention]

[0014] According to the wireless communication system of the present invention, by simply installing a radio wave scattering material that does not require a power source in the radio wave scattering sheet installation area, which is the 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, wireless communication between the first communication device and the second communication device, which are positioned in locations where they cannot see each other due to obstructions, becomes possible. Therefore, a wireless communication system can be introduced simply and at low cost, and operating costs can also be kept low. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1(A) is a schematic diagram of a first communication device and two second communication devices positioned in a location where they cannot see each other due to obstructions in the room. Figure 1(B) is a schematic diagram of a wireless communication system according to the first embodiment. [Figure 2]FIG. 2(A) is a schematic longitudinal 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 longitudinal sectional view of a radio wave scattering sheet with a protective layer, which is a second configuration example of a radio wave scatterer. [Figure 3] FIG. 3 is a scattering characteristic diagram showing the scattering characteristics of a radio wave scattering sheet with a commercially available wallpaper pasted as a protective layer. [Figure 4] FIG. 4 is a schematic configuration diagram of a radio wave scatterer installation area determination device. [Figure 5] FIG. 5 is a schematic configuration diagram showing an area where 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 viewable 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 viewable area of a second communication device A in the wireless communication system of the first embodiment. [Figure 8] FIG. 8 is a schematic configuration diagram showing a viewable area of a second communication device B in the wireless communication system of the first embodiment. [Figure 9] FIG. 9 is a schematic configuration diagram showing an area where a radio wave scatterer is installed in the wireless communication system of the first embodiment. [Figure 10] FIG. 10 is a schematic configuration diagram in which a radio wave scattering sheet is arranged in an area where a radio wave scatterer can be installed (a limited area 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 configuration diagram showing an area where a radio wave scatterer can be installed corresponding to the second communication device A. [Figure 12] FIG. 12 is a schematic configuration diagram in which a radio wave scattering sheet is arranged in an area where a radio wave scatterer can be installed corresponding to the second communication device A in the wireless communication system of the first embodiment. [Figure 13] FIG. 13 is a schematic configuration diagram showing an area where a radio wave scatterer can be installed corresponding to the second communication device B. [Figure 14] FIG. 14 is a schematic configuration diagram in which a radio wave scattering sheet is arranged in an area where a radio wave scatterer can be installed corresponding to the second communication device B in the wireless communication system of the first embodiment. [Figure 15] FIG. 15 is a schematic configuration diagram showing a radio wave scatterer installation area corresponding to a moving second communication device having a moving range from the position of the second communication device A to the position of the second communication device B. [Figure 16] FIG. 16 is a schematic configuration diagram in which a radio wave scatter sheet is arranged in a radio wave scatterer installation area corresponding to a moving second communication device in the wireless communication system of the first embodiment. [Figure 17] FIG. 17 is a schematic configuration diagram of a wireless communication system according to a second embodiment including an auxiliary radio wave scatter sheet. [Figure 18] FIG. 18 is a schematic configuration diagram showing a non-reachable second communication device visibility area and an auxiliary radio wave scatterer installation area in the wireless communication system of the second embodiment. [Figure 19] FIG. 19 is a schematic configuration diagram of a wireless communication system according to a third embodiment including a second communication device equipped with a sub-antenna corresponding to multipath reception and a radio wave scatter sheet for multipath. [Figure 20] FIG. 20 is a schematic configuration diagram showing a second communication device sub-visibility area and a radio wave scatterer installation area for multipath in the wireless communication system of the third embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0016] Hereinafter, embodiments of the wireless communication system according to the present invention will be described in detail with reference to the attached drawings. In the present invention, as shown in Figure 1(A), a first communication device 10 and a second communication device 20 (for example, two second communication devices, A20a and B20b) are positioned in a room 100, separated by an obstruction 110, and are unable to see each other. The invention provides wireless communication using radio waves in the GHz band or higher, which have high propagation attenuation and high directivity. The first communication device 10 is equipped with a multi-device connection function, and the two second communication devices 20 (A20a and B20b) are each connected to the first communication device 10 on a one-to-one basis. However, in the 5G service using the 28GHz band frequency, to which this embodiment is applied, the presence of the obstruction 110 prevents direct communication between the first communication device 10 and the second communication devices A20a and B20b.

[0017] Therefore, in the wireless communication system S according to the first embodiment, communication between the first communication device 10 and the second communication device 20 is made possible by installing a radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer), which is an example of a radio wave scattering body having scattering characteristics that reflect incident radio waves in multiple directions, in a suitable location on the ceiling of the room 100. The radio wave scattering sheet 1 used as a radio wave scattering body 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 a radio wave scattering surface formed by forming a specific metal pattern on a dielectric.

[0018] Unlike radio reflectors that reflect radio waves only in a specific direction (normal reflection direction) depending on the direction in which the signal is received, power-free radio wave scatterers are known to achieve scattering characteristics that reflect radio waves in multiple directions using various radio wave scattering principles. For example, stealth technology, which uses two types of artificial magnetic conductors with a phase difference of 180° + 37° in their reflection coefficients arranged alternately like a chessboard to produce scattering behavior according to the incident angle of radio waves in 55% of the frequency bandwidth from 28.5 GHz to 50 GHz, can be used as a radio wave scatterer. Furthermore, a metamaterial radio wave reflector, which has a conductive thin film layer formed on the upper surface of a synthetic resin substrate layer with periodically arranged square, rectangular, triangular, or hexagonal radio wave reflectors, and a protective layer provided on the upper surface of the conductive thin film layer via an adhesive layer, can achieve scattering characteristics that reflect incident waves with frequencies between 25 GHz and 30 GHz at an incident angle of 15 to 75 degrees within an angular range of -15 degrees to +15 degrees relative to the normal reflection direction, by designing parameters such as the size and shape of the radio wave reflectors and the spacing between them.

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

[0020] The first example of a radio wave scattering sheet with a protective layer 31 comprises a radio wave scattering sheet 1 formed by providing a back metal plate 1b and a front metal processed layer 1c on both sides of a flat dielectric plate 1a, a dielectric layer 2 as a protective layer that covers the radio wave scattering surface 1d corresponding to the surface of the front metal processed layer 1c of the radio wave scattering sheet 1, and an adhesive layer 3 provided on the outer surface (bottom surface) of the back metal plate 1b for attaching the radio wave scattering sheet 1 to a wall, ceiling, etc. The design of the metamaterial structure of the radio wave scattering sheet 1 (determination of the structural parameters of the metamaterial) can be achieved by combining 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 substrate (grade FR4) with a thickness of approximately 0.68 mm and a relative permittivity of 4.5 as the dielectric 1a, a metal film (e.g., copper foil) of approximately 60 μm formed on one side of the dielectric 1a as the back metal plate 1b, and a metal film (e.g., copper foil) of approximately 60 μm formed on the other side of the dielectric 1a is processed by etching or other means to form a specific metal pattern, which is then used as the surface metal processed layer 1c. 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 over a wide angle by forming a patch structure in the surface metal processed layer 1c that combines regions with reflection phases of 0° and 180° within a unit unit surface (e.g., a 180 mm × 180 mm surface). The radio wave scattering sheet 1 in this example configuration was designed to match electromagnetic waves in the 28 GHz band, which was selected as a specific frequency band. The total thickness of the radio wave scattering sheet 1, which includes the dielectric 1a, the back metal plate 1b, and the front metal processing layer 1c, is approximately 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 to 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 used to form the dielectric layer 2 is opaque, the surface metal processing layer 1c will not be visible, thus improving the appearance of the protective layer-equipped radio wave scattering sheet 31. Furthermore, the surface of the dielectric layer 2 is not limited to a single color, but may be composed of multiple colors. For example, by using multiple types of coating agents with the same relative permittivity but different colors, a multi-colored pattern can be displayed on the surface of the dielectric layer 2.

[0023] On the other hand, the protective-layered radio wave scattering sheet 32 ​​of the second configuration example comprises a dielectric layer 2' as a protective layer that covers 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 for attaching the radio wave scattering sheet 1 to a wall or ceiling. The dielectric layer 2' has a two-layer structure with an adhesive layer 2b as a lower protective layer on the lower surface of the surface layer 2a as an upper protective layer, and adheres to the radio wave scattering surface 1d of the radio wave scattering sheet 1 due to 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 will not be visible, thus improving the appearance of the protective-layered radio wave scattering sheet 32. Note that the protective layer is not limited to two layers, but may be a multilayer structure of three or more layers including a printing layer or a surface coating layer.

[0024] Figure 3 shows the scattering characteristics of a protective-layered radio wave scattering sheet 32, in which a commercially available wallpaper, for example, a vinyl chloride resin sheet with a thickness of approximately 0.4 mm (estimated relative permittivity of 3.0), is attached to the radio wave scattering sheet 1 as a protective layer. For comparison, the scattering characteristics of the radio wave scattering sheet 1 alone are shown by a dashed line. The scattering pattern of the protective-layered radio wave scattering sheet 32 ​​does not perfectly match the scattering pattern of the radio wave scattering sheet 1 without the wallpaper, but it achieves a comparable degree of directional diffusion, indicating that the radio wave scattering sheet 1 functions sufficiently even when wallpaper is attached as a protective layer to the radio wave scattering surface 1d. Directional diffusion is a numerical value related to the evaluation of the scattering sheet, indicating the dispersion of energy in each direction of scattered radio waves. A higher degree of directional diffusion indicates that scattering is performed at a wider angle and with a more uniform electric field strength.

[0025] Therefore, as shown in Figure 1(B), if the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) is installed on the walls and ceiling of room 100, the 28 GHz band radio waves transmitted from the first communication device 10 can be delivered over a wide area. Even if the second communication devices A20a and B20b are located behind the first communication device 10, separated by a shielding object 110 such as a screen or partition wall, the 28 GHz band radio waves can reach them, improving communication quality. Moreover, the protective layered radio wave scattering sheets 31 and 32 protect the surface metal processing layer 1c of the radio wave scattering sheet 1 with dielectric layers 2 and 2', thus suppressing increased operating costs due to failure or deterioration.

[0026] Furthermore, 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, making it easy to place on flat surfaces such as the ceiling, floor, and side walls that make up the room 100. As long as the area where the radio wave scattering sheet 1 is to be installed to function as a wireless communication system S is known, no special construction skills or tools are required, thus reducing the introduction cost. Therefore, by using the radio wave scattering material installation area determination device 200 shown in Figure 4, the area where the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) is to be installed as a radio wave scattering material to function as a wireless communication system S can be easily determined. It should be noted that providing the radio wave scattering material installation area determination device 200 as application software that can be installed on a general personal computer, rather than providing it as a dedicated device, would reduce the introduction cost of the radio wave scattering material installation area determination device 200.

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

[0028] The first communication device information input means 201 inputs the position of the first communication device 10 (or the range of movement if the first communication device 10 moves) as information about the first communication device 10. In addition, the power output from the radio unit of the first communication device 10 (antenna power), the operating gain of the radio wave scattering sheet 1 of the antenna connected to the radio unit, or the equivalent isotropically radiated power (EIRP) expressed as the product of the antenna power and the operating gain may also be input as information about the first communication device 10.

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

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

[0031] The environmental information input means 204 inputs information about the environment in which the first communication device 10 and the second communication device 20 are located, including the three-dimensional structure of the room 100, the location and shape of the shielding object 110, and the area where radio wave scatterers can be installed, indicating the range in which radio wave scatterers may be installed.

[0032] The radio wave scattering device installation area determination means 206 reads various information stored in the storage means 205 and determines an appropriate radio wave scattering device installation area according to a predetermined radio wave scattering sheet installation position determination method. In outline, this determination method determines the radio wave scattering device installation area to be the area where the radio wave scattering device installation area, which is set as the area where the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) can be installed, overlaps with the first communication device line-of-sight area, which is the area in line of sight from the position of the first communication device 10, and the second communication device line-of-sight area, which is the area in line of sight from the position of the second communication device 20 (second communication device A20a and second communication device B20b). The determination process will be explained below with reference to Figures 5 to 9. For the sake of simplicity, the first communication device 10 and the second communication device 20 are assumed to be fixed or stationary in their respective positions and not move during communication. However, as will be described later, if the first communication device 10 and the second communication device 20 do move, the radio wave scattering area can be determined by taking the movement range into account, thereby enabling the setting of an appropriate wireless communication system S corresponding to the movement range.

[0033] As shown in Figure 5, the environment in which the first communication device 10 and the second communication device 20 are located is divided into spaces separated by a shield 110 within room 100. However, above the shield 110, there is an air gap G that connects the space in which the first communication device 10 is located and the space in which the second communication device 20 is located, so it can be seen that it is possible to form a communication propagation path between the first communication device 10 and the second communication device 20 through this air gap G. The radio wave scattering sheet 1 can be installed on almost flat surfaces such as the side walls and ceiling of room 100, so these planes are entered as areas where radio wave scattering can be installed. From the structure of room 100 and the location of the air gap G, for example, the entire surface of the side wall 130 and the entire surface of the ceiling 140 near the second communication device 20 can be seen as areas where radio wave scattering can be installed 301.

[0034] Next, as shown in Figure 6, the line-of-sight area 302 of the first communication device is identified, which is the range of positions that are in line of sight (LOS) from the position of the first communication device 10. The line-of-sight area 302 of the first communication device may be set as the optically visible range that can be seen from the first communication device 10 through the air gap G, or it may be the range in which the first Fresnel zone, starting from the first communication device 10, intersects with the inner surface of the room 100 through the air gap G. The Fresnel zone is a quantitative representation of the guideline for ensuring a line of sight between the transmitting antenna and the receiving antenna, and is an elliptical radio wave path from the transmitting antenna to the receiving antenna where the radio waves radiated into space arrive. Since the majority of the radio wave energy resides in the first Fresnel zone, which is the innermost region, reliable and stable wireless communication can be performed if the first Fresnel zone is set so that it is not obstructed by the shielding object 110. In room 100, the first communication device 10 and the second communication device 20 cannot communicate directly through the air gap G. Therefore, the position of the receiving antenna of the second communication device 20 relative to the transmitting antenna of the first communication device 10 is undefined. However, the shape of the first Fresnel zone can be determined by assuming that a virtual receiving antenna is located beyond the ceiling 140. For example, considering that the Fresnel radius of the Fresnel zone is maximum at half the communication distance, the position of the virtual receiving antenna is set so that the Fresnel radius is maximum in the air gap G. By determining the first Fresnel zone, a line-of-sight area 302 for the first communication device, spanning from the ceiling 140 to the side wall 130, can be obtained.

[0035] Next, as shown in Figure 7, the line-of-sight area 303a of the second communication device A is identified, which is the range of locations that are in line of sight (LOS) from the position of the second communication device A20a. Similarly, as shown in Figure 8, the line-of-sight area 303b of the second communication device B is identified, which is the range of locations that are in line of sight (LOS) from the position of the second communication device B20b. 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 the optically visible range that can be seen from the second communication device A20a and the second communication device B20b without being obstructed by the shielding object 110, or it may be the range in which the first Fresnel zone, set with the second communication device A20a and the second communication device B20b as transmitting antennas, intersects with the inner surface of the room 100.

[0036] As described above, after identifying the line-of-sight area 302 for the first communication device, the line-of-sight area 303a for the second communication device A, and the line-of-sight area 303b for the second communication device B, the area where the radio wave scattering sheet 1 (radio wave scattering sheet with protective layer 30) can be installed (the radio wave scattering area 301) is set as the area where the radio wave scattering sheet 1 can be installed (the radio wave scattering sheet 30 with protective layer) can be installed (the radio wave scattering area 301), the line-of-sight area 302 for the first communication device which is in line of sight from the position of the first communication device 10, the line-of-sight area 303a for the second communication device A which is in line of sight from the position of the second communication device A 20a, and the line-of-sight area 303b for the second communication device B which is in line of sight from the position of the second communication device B 20b overlap is determined to be the radio wave scattering area 304.

[0037] As shown in Figure 10, if the radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) is installed to cover the entire radio wave scattering area 304, a wireless communication system S is created that enables wireless communication between the first communication device 10 and the second communication devices A20a and B20b via the radio wave scattering sheet 1. Since the radio wave scattering area 304 is an area to which all radio waves from the first communication device 10, the second communication device A20a, and the second communication device B20b can reach, the wireless communication system S can be established even if a radio wave scattering sheet 1 of the minimum size (for example, 180 [mm] × 180 [mm]) is installed somewhere within the radio wave scattering area 304. However, considering the attenuation due to the scattering characteristics of the radio wave scattering sheet 1, the failure to reach the signal due to attenuation can be reduced by arranging the radio wave scattering sheet 1 to cover the entire radio wave scattering area 304.

[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 due to the shield 110. However, when it is desired to communicate using radio waves in the GHz band or higher frequency band, which have high propagation attenuation and high directivity, the system can be introduced simply and at low cost by installing a power-free radio wave scattering sheet 1 in the radio wave scattering installation area 304, and operating costs can also be kept low. For example, even if the first communication device 10, which is a wireless base station for 5G communication services, and the second communication device 20, which is a mobile terminal, cannot communicate directly due to the presence of the shield 110, the dead zone can be eliminated simply by installing a radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) of the appropriate size in the appropriate location.

[0039] The aforementioned radio wave scattering area determination device 200 was designed to determine a radio wave scattering 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. However, it may also be provided with a function to set comprehensive communication conditions to ensure more reliable communication between the first communication device 10 and the second communication device 20. For example, the first communication device 10 is designated as the transmitting station, and the second communication devices A20a and B20b are designated as receiving stations. The received signal strength of the second communication device 20 is estimated from the operating gain of the antenna of the first communication device 10 (the transmitting station) in the direction in which the radio wave scattering sheet 1 is installed, the operating gain of the antenna of the second communication device 20 (the receiving station) in the direction in which the radio wave scattering sheet 1 is installed, and the attenuation due to scattering by the radio wave scattering sheet 1. Furthermore, if the received signal strength at the second communication device 20 is not at a sufficient level, information is provided indicating how much the operating gain of the first communication device 10 or the second communication device 20 needs to be increased, thereby enabling adjustment of the downlink communication from the first communication device 10 to the second communication device 20 to a good state. Conversely, to improve the uplink 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 designated as transmitting stations, and the first communication device 10 is designated as a receiving station. The received signal strength at the first communication device 10 is estimated, and information is provided to bring the received signal strength at the first communication device 10 to a sufficient level.

[0040] Furthermore, while Figure 9 shows a radio wave scattering area 304 that can be shared by the second communication device A20a and the second communication device B20b, and Figure 10 shows a case where a relatively small radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) is used to configure the wireless communication system S, a wider area can also be designated as the radio wave scattering area, and the radio wave scattering sheet 1 can be provided over a wider area. For example, as shown in Figure 11, a radio wave scattering area 304a corresponding to the second communication device A20a (an area where the area where the radio wave scattering can be installed, the line-of-sight area of ​​the first communication device, and the line-of-sight area of ​​the second communication device A overlap) can be set, and as shown in Figure 12, the radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) can be placed in the radio wave scattering area 304a corresponding to the second communication device A20a to form the wireless communication system S. Alternatively, as shown in Figure 13, a radio wave scattering area 304b corresponding to the second communication device B20b (an area where the area where the radio wave scattering can be installed overlaps with the line-of-sight area of ​​the first communication device and the line-of-sight area of ​​the second communication device B20b) may be set, and as shown in Figure 14, a radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) may be placed in the radio wave scattering 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 a protective layer) in radio wave scattering areas 304a and 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 a protective layer) can be placed including a radio wave scattering area that is effective only for the second communication device A20a or a radio wave scattering area that is effective only for the second communication device B20b, thereby contributing to increasing the received signal strength in communication between the first communication device 10 and the second communication devices A20a and B20b. Of course, the entire region that is the union (304a∪304b) of the radio wave scattering area 304a corresponding to the second communication device A20a and the radio wave scattering area 304b corresponding to the second communication device B20b may be defined as the radio wave scattering area 304′, and a radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) may be provided to cover the entire area of ​​this radio wave scattering area 304′ (see Figures 15 and 16).

[0041] From a different perspective, the radio wave scattering area 304' is continuous without a break between the radio wave scattering area 304a corresponding to the second communication device A20a and the radio wave scattering area 304b corresponding to the second communication device B20b. As shown in Figure 15, it can be considered to encompass the entire radio wave scattering area as the mobile second communication device 20', such as a portable terminal, moves from the position of the second communication device A20a to the position of the second communication device B20b. Therefore, as shown in Figure 16, if the radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) is provided to cover the entire area of ​​the radio wave scattering area 304' corresponding to the mobile second communication device 20', communication between the first communication device 10 and the mobile second communication device 20' can be maintained in good condition even when the mobile second communication device 20' moves within the range of movement corresponding to the radio wave scattering area 304'.

[0042] Thus, when the second communication device 20 or the first communication device 10 is a moving object, feature points such as the outer edge of the moving range are extracted, and the radio wave scattering area when the second communication device 20 or the first communication device 10 is placed at each feature point is individually determined, and the radio wave scattering area for the moving range is set to encompass all of the individually determined radio wave scattering area, and the radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) is provided to cover the entire area of ​​the radio wave scattering area for the moving range.

[0043] Furthermore, the radio wave scattering area determination means 206 of the radio wave scattering area determination device 200 may be provided with a movement restriction area determination function that determines whether there is a movement restriction area where a radio wave scattering area cannot be set if 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. If the movement restriction area determination function of the radio wave scattering area determination means 206 determines that there is a movement restriction area where wireless communication via the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) cannot be realized, this can be notified to the user, thereby encouraging them not to place the first communication device 10 or the second communication device 20 within the movement restriction area, or not to move the first communication device 10 or the second communication device 20 into the movement restriction area.

[0044] Furthermore, in the wireless communication system S of the first embodiment, all second communication devices 20 (second communication devices A20a and B20b) were in a position where they could see the radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer). However, as shown in Figure 17, it is conceivable that there may be second communication devices 20 that cannot see the radio wave scattering sheet 1 due to a complexly shaped shielding object 120. In addition to second communication devices 21 (hereinafter referred to as "reachable second communication devices 21") that can receive radio waves from the first communication device 10 and communicate with by providing the radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer), there may also be second communication devices 22 (hereinafter referred to as "non-reachable second communication devices 22") that cannot receive radio waves from the first communication device 10.

[0045] In such cases, 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, if 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 scattering area 304, by considering the main radio wave scattering sheet 1 as the radio wave radiation source, and providing an auxiliary radio wave scattering sheet 1' (auxiliary radio wave scattering sheet 30' with protective layer) at the location where the line of sight from the main radio wave scattering sheet 1 overlaps with the line of sight from the unreachable second communication device 22, wireless communication between the first communication device 10 and the unreachable second communication device 22 becomes possible 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 functions 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 in line of sight from the main radio wave scattering sheet 1, is set to almost the entire area of ​​the side wall 130 of the room 100, as shown in Figure 18, from the scattering range (a wide area of ​​approximately 180°) of the radio wave scattering sheet 1 installed on the ceiling 140. Since this side wall 130 is a radio wave scatterer installation 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 a protective layer). Furthermore, the second communication device 22, which is out of line of sight of the main radio wave scattering sheet 1 due to the presence of the shielding object 120, can see a part of the side wall 130 of the room 100 without being obstructed by the shielding object 120, so a line-of-sight area 305 for the second communication device is formed on the side wall 130. Since this line-of-sight area 305 for the second communication device is on the side wall 130, which is both a line-of-sight area for the radio wave scatterer and an area where an auxiliary radio wave scatterer can be installed, it coincides with the auxiliary radio wave scatterer installation area 306 where the three areas overlap. Therefore, if an auxiliary radio wave scattering sheet 1' (auxiliary radio wave scattering sheet 30' with a protective layer) is provided to cover the entire area of ​​the auxiliary radio wave scattering device installation area 306, a wireless communication system S' is formed.

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

[0048] The first antenna 231, which serves as the main antenna of the second communication device 23, is a designated target within the line-of-sight area 303 of the second communication device. The radio wave scattering area 304 is set as the area overlapping with the line-of-sight area 302 of the first communication device and the area where radio wave scattering can be installed 301. In Figure 20, for the sake of simplicity, both the line-of-sight area 302 of the first communication device and the area where radio wave scattering can be installed 301 are assumed to encompass the line-of-sight area 303 of the second communication device, and the radio wave scattering area 304 is assumed to coincide with the line-of-sight area 303 of the second communication device. On the other hand, the second antenna 232, which serves as a sub-antenna of the second communication device 23, is positioned at a distance from the first antenna 231 such that the signal fluctuations are uncorrelated, and primarily 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 a protective layer) with the second antenna 232 of the second communication device 23, the area where the second communication device sub-line-of-sight area 307, which is in line of sight from the second antenna 232 of the second communication device 23, the area where the multipath radio wave scattering body can be installed, which is in line of sight from the radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) is considered as a radio wave radiation source, and the area where the radio wave scattering body can be installed area 301 overlap is set as the multipath radio wave scattering body installation area 308, and the multipath radio wave scattering sheet 1'' (multipath radio wave scattering sheet 30'' with a protective layer) is installed to cover the entire area of ​​this multipath radio wave scattering body installation area 308. Note that the second communication device sub-line-of-sight area 307 is located on the side wall 130, which is the area where the radio wave scattering body can be installed area 301 and the area where the multipath radio wave scattering body can be installed, so it coincides with the multipath radio wave scattering body 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 from the main radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) installed in the radio wave scattering area 304 are received by the first antenna 231 of the second communication device 23, and scattered waves from the multipath radio wave scattering sheet 1″ (multipath radio wave scattering sheet 30″ with a protective layer) installed in the multipath radio wave scattering area 308 are received by the second antenna 232 of the second communication device 23. As a result, multipath wireless communication can be performed between the first communication device 10 and the second communication device 23, 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, if sufficient reception levels can be obtained with the first and second antennas 231 and 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 both types of signals with the second communication device 23.

[0051] Although embodiments of the wireless communication system according to the present invention have been described above with reference to the attached drawings, the present invention is not limited to these embodiments and may also be implemented by adapting known and existing equivalent technical means without changing the configuration described in the claims. [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. Protective layered radio wave scattering sheet 1. Radio wave scattering sheet

Claims

1. A wireless communication system comprising a first communication device and a second communication device that communicate using radio waves in the GHz band or higher frequency band which have high propagation attenuation and high directivity, wherein the first communication device and the second communication device are positioned in a location where they cannot see each other due to obstructions, and wireless communication is performed between them, The area where the radio wave scatterer installation area, which is defined as an area where a radio wave scatterer having scattering characteristics that reflect incident radio waves in multiple directions can be installed, overlaps with the first communication device line-of-sight area, which is a line of sight from the position of the first communication device, and the second communication device line-of-sight area, which is a line of sight from the position of the second communication device, is defined as the radio wave scatterer installation area. A wireless communication system characterized in that 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.

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 by forming a specific metal pattern on a dielectric.

3. The first communication device is equipped with a multi-device connection function, The second communication device is connected to the first communication device on a one-to-one basis. The wireless communication system according to claim 1 or 2, characterized by the features described above.

4. If there are one or more unreachable second communication devices that are out of line of sight of the radio wave scatterer installed in the radio wave scatterer installation area, the radio wave scatterer is considered a radio wave source, and the area where the line-of-sight area of ​​the radio wave scatterer (which is in line of sight from the radio wave scatterer), the line-of-sight area of ​​the unreachable second communication device (which is in 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 3, characterized in that wireless communication between the first communication device and the second communication device that fails to receive signals is performed via the radio wave scatter installed in the radio wave scatter installation area and the auxiliary radio wave scatter installed in the auxiliary radio wave scatter installation area.

5. The first communication device is designated as a transmitting station, and one or more of the second communication devices are designated as receiving stations. The wireless communication system according to claim 3, characterized in that the received signal strength of the second communication device is estimated from the operating gain of the antenna of the first communication device in the direction of the radio wave scatterer, the operating 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.

6. The second communication device includes, in addition to the antenna which is the target of the line-of-sight area of ​​the second communication device, one or more sub-antennas that are separated to such an extent that the signal fluctuations become uncorrelated. The area in which the multipath radio wave scattering device can be installed, which is in line of sight from the radio wave scattering device, the area in line of sight from any one of the sub-antennas of the second communication device, and the radio wave scattering device can be installed area overlaps is set as the multipath radio wave scattering device installation area. The wireless communication system according to claim 5, characterized in that multipath wireless communication between the first communication device and the second communication device is performed via the radio wave scatter installed in the radio wave scatter installation area and the multipath radio wave scatter installed in the multipath radio wave scatter installation area.

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