Wireless communication system

Abstract

The present invention makes it possible to easily introduce a wireless communication system that enables communication using radio waves in a frequency band having large propagation attenuation and high directivity, between a first communication device and a second communication device arranged at positions that are shielded by a shield and cannot be seen from each other.　A communication system S capable of communicating with a first communication device 10, a second communication device A20a, and a second communication device B20b can be introduced by a simple method of installing a radio wave scattering sheet 1 (a radio wave scattering sheet 30 with a protective layer), which is a radio wave scattering body having scattering characteristics of reflecting incident radio waves in a plurality of directions and not requiring a power supply, at an appropriate place on a ceiling, a floor, or a side wall that can be commonly seen from the first communication device 10, the second communication device A20a, and the second communication device B20b arranged so as not to be directly seen from each other by a shield 110 of a room 100.

Description

Wireless communication system

[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.

[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 the 28 GHz band are used for wireless communication in this 5G. In the wireless communication service of 5G, high-speed and large-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 transmission antenna of the first communication device cannot reach the reception antenna of the second communication device, and the communication quality may deteriorate significantly. 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, a method of reflecting the radio waves in a direction that can be received by the second communication device by interposing a radio wave reflection member is known. However, it is complicated to specify what kind of characteristics the radio wave reflection 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 reflection member has been proposed (for example, refer to Patent Document 1).

[0004] Japanese Patent No. 7221333

[0005] However, in order to apply the information processing device for determining the installation position of the radio wave reflection member described in Patent Document 1, it is necessary to use a radio wave reflection member that can adaptively control the reflection beam direction of the radio wave reflector according to changes in the positions of a plurality of second communication devices existing in the blind area of the first communication device. Therefore, an expensive radio wave reflector that requires power, such as a radio wave reflection plate in which a plurality of reflection elements are two-dimensionally arranged in an array, must be used as the radio wave reflection member, and restrictions on the installation location of the radio wave reflector, as well as a significant increase in the introduction cost and operation cost of the radio wave reflector, are assumed.

[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 an expensive radio wave reflector that requires a power supply as a radio wave reflector. 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 is 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 or change the installation location of the radio wave reflector. As a result, even if a wireless communication system is built using inexpensive radio wave reflectors, the costs required for the maintenance and management of the radio wave reflectors 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.

[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 configured 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.

[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.

[0015] Figure 1A is a schematic configuration 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 1B is a schematic configuration diagram of a wireless communication system according to the first embodiment. Figure 2A is a schematic longitudinal cross-sectional view of a radio wave scattering sheet with a protective layer, which is a first example of the configuration of a radio wave scattering body. Figure 2B is a schematic longitudinal cross-sectional view of a radio wave scattering sheet with a protective layer, which is a second example of the configuration of a radio wave scattering body. Figure 3 is a scattering characteristics diagram showing the scattering characteristics of a radio wave scattering sheet with commercially available wallpaper attached as a protective layer. Figure 4 is a schematic configuration diagram of a radio wave scattering body installation area determination device. Figure 5 is a schematic configuration diagram showing the area where a radio wave scattering body can be installed in the wireless communication system of the first embodiment. Figure 6 is a schematic configuration diagram showing the line-of-sight area of ​​the first communication device in the wireless communication system of the first embodiment. Figure 7 is a schematic configuration diagram showing the line-of-sight area of ​​the second communication device A in the wireless communication system of the first embodiment. Figure 8 is a schematic configuration diagram showing the line-of-sight area of ​​the second communication device B in the wireless communication system of the first embodiment. Figure 9 is a schematic configuration diagram showing the radio wave scattering body installation area in the wireless communication system of the first embodiment. Figure 10 is a schematic configuration diagram showing the placement of a radio wave scattering sheet in the radio wave scattering 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 is a schematic configuration diagram showing the radio wave scattering area corresponding to the second communication device A. Figure 12 is a schematic configuration diagram showing the placement of a radio wave scattering sheet in the radio wave scattering area corresponding to the second communication device A in the wireless communication system of the first embodiment. Figure 13 is a schematic configuration diagram showing the radio wave scattering area corresponding to the second communication device B. Figure 14 is a schematic configuration diagram showing the placement of a radio wave scattering sheet in the radio wave scattering area corresponding to the second communication device B in the wireless communication system of the first embodiment. Figure 15 is a schematic configuration diagram showing the placement of a radio wave scattering area corresponding to a mobile second communication device whose movement range is from the position of the second communication device A to the position of the second communication device B. Figure 16 is a schematic configuration diagram showing the placement of a radio wave scattering sheet in the radio wave scattering area corresponding to a mobile second communication device in the wireless communication system of the first embodiment. Figure 17 is a schematic diagram of a wireless communication system according to the second embodiment, which includes an auxiliary radio wave scattering sheet.Figure 18 is a schematic configuration diagram showing the line-of-sight area of ​​the second communication device and the area where the auxiliary radio wave scatterer is installed in the wireless communication system of the second embodiment. Figure 19 is a schematic configuration diagram of the wireless communication system of the third embodiment, which includes a second communication device equipped with a sub-antenna and compatible with multipath reception, and a radio wave scattering sheet for multipath. Figure 20 is a schematic configuration diagram showing the sub-line-of-sight area of ​​the second communication device and the area where the radio wave scattering material for multipath is installed in the wireless communication system of the third embodiment.

[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 1A, 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 28 GHz band, 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 radio wave reflectors such as squares, rectangles, triangles, and hexagons, 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 degrees 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 2A shows a schematic longitudinal cross-sectional view of the radio wave scattering sheet 31 with protective layer of the first configuration example, and Figure 2B 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 processing 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 processing 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 surface 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 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 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 is possible to obtain a similar degree of directional diffusion, indicating that even when wallpaper is attached as a protective layer to the radio wave scattering surface 1d, the radio wave scattering sheet 1 still functions sufficiently. Directional diffusion is a numerical value related to the evaluation of the scattering sheet, indicating the dispersion value 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 1B, if the radio wave scattering sheet 1 (radio wave scattering sheet 30 with protective layer) is installed on the walls or ceiling of the 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 line-of-sight area of ​​the first communication device, which is the first communication device, and the line-of-sight area of ​​the second communication device, which is the second communication device, which is the second communication device, which overlaps with 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 the 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 there is a possibility of forming 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 a nearly flat surface such as the side wall or ceiling of the room 100, so these planes are entered as areas where the radio wave scattering body can be installed. From the structure of the 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 the radio wave scattering body can be installed 301.

[0034] Next, as shown in Figure 6, the first communication device line-of-sight area 302 is identified, which is the range of positions that are in line of sight (LOS: Line Of Sight) from the position of the first communication device 10. The first communication device line-of-sight area 302 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, by considering that the Fresnel radius of the Fresnel zone is maximized at half the communication distance, and setting the position of the virtual receiving antenna in the air gap G such that the Fresnel radius is maximized, the first Fresnel zone can be determined, thereby obtaining the line-of-sight area 302 of the first communication device that spans from the ceiling 140 to the side wall 130.

[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] After identifying the first communication device line-of-sight area 302, the second communication device A line-of-sight area 303a, and the second communication device B line-of-sight area 303b as described above, the area where the radio wave scattering body installation area 301 (radio wave scattering sheet with protective layer 30) can be installed, the first communication device line-of-sight area 302 (which is in line of sight from the position of the first communication device 10), the second communication device A line-of-sight area 303a (which is in line of sight from the position of the second communication device A 20a), and the second communication device B line-of-sight area 303b (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 body installation 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 device A20a and the second communication device 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 the minimum size (for example, 180 [mm] x 180 [mm]) radio wave scattering sheet 1 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 determines 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 device A 20a and the second communication device B 20b 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 amount of attenuation due to scattering by the radio wave scattering sheet 1. Furthermore, if the received signal strength at the second communication device 20 has not reached 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 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 with protective layer 30) 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 with protective layer 30) in radio wave scattering area 304a, 304b which is 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 with protective layer 30) 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 device A20a and the second communication device 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] Also, in the wireless communication system S of the first embodiment, all the second communication devices 20 (second communication device A20a and second communication device B20b) were in positions where they could see through the radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer). However, as shown in FIG. 17, it is assumed that there may be a second communication device 20 that cannot see through the radio wave scattering sheet 1 due to a shielding object 120 with a complex shape. In addition to the second communication device 21 (hereinafter referred to as the reachable second communication device 21) that can communicate by the radio wave from the first communication device 10 reaching it by providing the radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer), there may be a second communication device 22 (hereinafter referred to as the unreachable second communication device 22) where the radio wave from the first communication device 10 remains 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 enabled. That is, when there is one or more unreachable second communication devices 22 where the radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) installed in the radio wave scatterer installation area 304 is out of sight, regarding the main radio wave scattering sheet 1 as a radio wave radiation source, if an auxiliary radio wave scattering sheet 1' (auxiliary radio wave scattering sheet 30' with a protective layer) is provided at a location where the range visible from the main radio wave scattering sheet 1 overlaps with the range visible 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 a protective layer) has the same structure as the main radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) and has the same function.

[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 of the radio wave scattering sheet 1 installed on the ceiling 140 (a wide area of ​​approximately 180°). 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 the line-of-sight area of ​​the radio wave scatterer and the area where the 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 is the main antenna included in the second communication device 23, is a specific target in the second communication device's line-of-sight area 303. An area where the radio wave scattering body installation area 304 is set as an area that overlaps with the first communication device's line-of-sight area 302 and the radio wave scattering body installable area 301. In Fig. 20, for simplicity of explanation, the first communication device's line-of-sight area 302 and the radio wave scattering body installable area 301 both include the second communication device's line-of-sight area 303, and it is assumed that the radio wave scattering body installation area 304 coincides with the second communication device's line-of-sight area 303. On the other hand, the second antenna 232, which is the sub-antenna included in the second communication device 23, is provided at a position far from the first antenna 231 such that the fluctuations of the signals are uncorrelated, and mainly receives the radio waves from the first communication device 10 as scattered waves from the multi-path radio wave scattering sheet 1″ (multi-path radio wave scattering sheet 30″ with a protective layer).

[0049] In order to efficiently receive the scattered waves from the multi-path radio wave scattering sheet 1″ (multi-path radio wave scattering sheet 30″ with a protective layer) by the second antenna 232 of the second communication device 23, the second communication device sub-line-of-sight area 307, which is in the line-of-sight from the second antenna 232 of the second communication device 23, the multi-path radio wave scattering body installable area, which is in the line-of-sight from this radio wave scattering sheet 1 when considering the radio wave scattering sheet 1 (radio wave scattering sheet 30 with a protective layer) as a radio wave radiation source, and the area where the radio wave scattering body installable area 301 overlaps are set as the multi-path radio wave scattering body installation area 308, and the multi-path radio wave scattering sheet 1″ (multi-path radio wave scattering sheet 30″ with a protective layer) is provided so as to cover the entire area of this multi-path radio wave scattering body installation area 308. Since the second communication device sub-line-of-sight area 307 is in the side wall 130, which is the radio wave scattering body installable area 301 and the multi-path radio wave scattering body installable area, it coincides with the multi-path 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.

[0052] S Wireless communication system 100 Room 110 Shielding 10 First communication device 20a Second communication device A 20b Second communication device B 30 Radio wave scattering sheet with protective layer 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 locations where they cannot see each other due to obstructions, and the wireless communication system 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.

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 wireless communication system according to claim 1 or 2, characterized in that the first communication device has a multi-device connection function, and the second communication device is connected to the first communication device on a one-to-one basis.

4. The wireless communication system according to claim 3, characterized in that, if there is 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 is considered a radio wave source, and the area in which the line-of-sight area of ​​the radio wave scatter, the line-of-sight area of ​​the unreachable second communication device, and the area in which the radio wave scatter can be installed overlap is set as an auxiliary radio wave scatter installation area, and wireless communication between the first communication device and the unreachable second communication device 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 wireless communication system according to claim 3, characterized in that the first communication device is a transmitting station, one or more second communication devices are receiving stations, and 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 wireless communication system according to claim 5, characterized in that 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 fluctuations of the signals are uncorrelated, and 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 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 scattering device can be installed overlaps, and multipath 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 and the multipath radio wave scattering device installed in the multipath radio wave scattering device installation area.

Images