Wireless communication device, wireless communication system, and wireless communication method

Abstract

This wireless communication device for performing wireless communication using MIMO with a reception device 2 comprises: a transmission device 1 for transmitting a radio wave; and a laser beam generator 3 for emitting a laser beam into the atmosphere to form a plasma region, thereby reflecting or refracting the radio wave in the plasma region and propagating the radio wave to the reception device 2.

Description

Wireless communication device, wireless communication system, and wireless communication method

[0001] The technologies described herein relate to wireless communication devices, wireless communication systems, and wireless communication methods.

[0002] The volume of satellite communications (traffic) is increasing, raising concerns about a shortage of radio wave resources. One solution to this problem is to use MIMO (Multiple-Input Multiple-Output) or adaptive modulation / demodulation as technologies to increase the communication capacity per unit of frequency bandwidth (for example, Non-Patent Document 1).

[0003] Japan Patent Office, "FY2017 Standard Technology Collection MIMO (Multiple-Input Multiple-Output) Related Technologies," [Accessed December 24, 2024] Internet, <URL: https: / / www.jpo.go.jp / resources / report / sonota / document / hyohyou_gijutsu / h29_mimo.pdf>, February 2018, Arios Co., Ltd., "Basic Technology of Atmospheric Pressure Plasma," [Accessed January 27, 2025] Internet, <URL: https: / / www.arios.co.jp / library / p10-2.html>Hiroshi Kikuchi, Satoshi Yoshida, Takeshi Morimoto, Tomoo Ushio, Zenichiro Kawasaki, "Evaluation of the influence of the ionosphere on the estimation of lightning discharge location using VHF band electromagnetic waves from an artificial satellite," Transactions of the Institute of Electrical Engineers of Japan, Vol. 133, No. 4, pp. 159-165, 2013. Keiji Nakamura, Takamitsu Suzuki, Chohei Yamacho, Kenji Horii, "Basic study of laser-induced lightning using ultraviolet lasers," Transactions of the Institute of Electrical Engineers of Japan, Vol. 113, No. 11, pp. 1265-1273, 1993.

[0004] Figure 1 is a schematic diagram showing an example of the configuration of a conventional wireless communication system 600.

[0005] In a wireless communication system 600 that performs satellite communication from a radio wave transmitting antenna 6 to a radio wave receiving antenna 7 as shown in Figure 1, a direct wave radio wave propagation path (see symbol A1 in Figure 1) is formed in an environment where there are no radio wave reflectors around the communication path and only line-of-sight objects are present. As a result, spatial multiplexing effects cannot be obtained, and an increase in communication capacity due to MIMO cannot be expected.

[0006] In one respect, the technology described herein aims to achieve increased communication capacity through MIMO.

[0007] In one aspect, the wireless communication device is a wireless communication device that performs wireless communication using MIMO (Multiple-Input Multiple-Output) with a receiving device, comprising a transmitting device that transmits radio waves, and a laser beam generator that emits a laser beam into the atmosphere to form a plasma region, thereby reflecting or refracting the radio waves in the plasma region and propagating them to the receiving device.

[0008] One aspect of this is that MIMO can be used to increase communication capacity.

[0009] This figure schematically shows an example of the configuration of a wireless communication system in the prior art. This figure schematically shows an example of the configuration of a wireless communication system in an embodiment. This figure schematically shows a first example of the configuration of a wireless communication system in the first modified example. This figure schematically shows a second example of the configuration of a wireless communication system in the first modified example. This figure schematically shows an example of the configuration of a radio wave transmitting antenna and a laser beam generator in the first modified example, where (a) is its top view, (b) is its front view, and (c) is its side view. This figure schematically shows a first example of the configuration of a wireless communication system in the second modified example. This figure schematically shows a second example of the configuration of a wireless communication system in the second modified example. This figure schematically shows an example of the configuration of a radio wave transmitting antenna and a laser beam generator in the second modified example, where (a) is its top view, (b) is its front view, and (c) is its side view.

[0010] The embodiments will now be described with reference to the drawings. However, the embodiments shown below are merely illustrative, and there is no intention to exclude various modifications or applications of techniques not explicitly shown in the embodiments. In other words, these embodiments can be implemented with various modifications without departing from their spirit.

[0011] Furthermore, each figure is not intended to represent only the components shown in the figure, but may include other components. In the following figures, parts denoted by the same reference numerals indicate the same or similar parts unless otherwise specified.

[0012] [A] Figure 2 of the embodiment is a schematic diagram showing an example of the configuration of the wireless communication system 100 in the embodiment.

[0013] The wireless communication system 100 shown in Figure 2 comprises a radio wave transmitting antenna 1, a radio wave receiving antenna 2, and a laser beam generator 3. The radio wave transmitting antenna 1 is an example of a transmitting device, and the radio wave receiving antenna 2 is an example of a receiving device. The combination of the radio wave transmitting antenna 1 and the laser beam generator 3 is an example of a wireless communication device.

[0014] The radio wave transmitting antenna 1 transmits radio waves to the radio wave receiving antenna 2, and the radio wave receiving antenna 2 receives radio waves from the radio wave transmitting antenna 1. The radio wave receiving antenna 2 may also transmit radio waves towards the radio wave transmitting antenna 1. The laser beam generator 3 outputs a laser beam into the atmosphere in the direction of the radio wave receiving antenna 2, ionizing the atmosphere to form a plasma region, and reflecting and refracting radio waves in this plasma region.

[0015] The wireless communication system 100 shown in Figure 2 generates a plasma region (see reference numeral B1 in Figure 2) by ionizing the upper atmosphere with a high-power laser output by a laser beam generator 3. The wireless communication system 100 uses this plasma region to act like an artificial ionosphere, acting as a reflector for radio waves, thereby creating a reflected radio wave propagation path (see reference numeral B3 in Figure 2) in addition to the direct wave radio wave propagation path (see reference numeral B2 in Figure 2) that is line of sight to the satellite, and thus realizing MIMO. The wireless communication system 100 may also propagate radio waves by refracting them in the plasma region.

[0016] The radio transmission antenna 1 and the laser beam generator 3 may be located in the Earth's atmosphere (on the ground or in the air) or in an ionizable gas layer on a celestial body other than Earth. On the other hand, the radio reception antenna 2 may be located in the atmosphere or gas layer, or in outer space (vacuum).

[0017] In the example shown in Figure 2, the radio wave transmitting antenna 1 and laser beam generator 3 are installed on the ground, while the radio wave receiving antenna 2 is installed on an artificial satellite in outer space.

[0018] In addition, the radio wave transmitting antenna 1 and the laser beam generator 3 may be installed in a vehicle traveling on the ground, or in an aircraft navigating the atmosphere or gas layer, and the radio wave receiving antenna 2 may be installed in another aircraft navigating the atmosphere, gas layer or outer space.

[0019] In the example shown in FIG. 2, the laser beam generator 3 outputs a fan-shaped laser beam, but the shape of the laser beam may be various shapes such as an ellipse or a circle. When the radio wave transmitting antenna 1 and the laser beam generator 3 are installed on the ground and the radio wave receiving antenna 2 is installed on a satellite as shown in FIG. 2, the output distance of the laser beam may be about one-fifth of the altitude of the satellite. The output range of the laser beam preferably is a region where animals such as humans and aircraft do not intrude.

[0020] The angular frequency at which electromagnetic waves can be reflected by electrons generated by ionization is called the plasma angular frequency, ω p 2 =(N×e 2 ) / (m×ω0) is represented by. Here, N is the electron density [m -3 , e is the electric charge of an electron -1.602×10 -19 [C], m is the mass of an electron 9.109×10 -31 [kg], ω0 is the permittivity of vacuum 8.854×10 -12 [F / m]. From this, the plasma frequency is f p ≒9×√N [Hz]. According to Non-Patent Document 3, the charge density in the ionosphere is N = 10 12 approximately, so the plasma frequency is f p ≒9×√(10 12 )≒9 [MHz].

[0021] In the ionosphere surrounding the earth, due to the relationship between solar light intensity and atmospheric pressure, the charge density N is about 10 12 as described above. However, on the ground, the atmospheric pressure is high, and in this embodiment, it is possible to locally increase the intensity of light involved in ionization to be higher than the solar light intensity using a plurality of high-intensity laser beam generators 3. From this, by making N 10 15 or more, the plasma frequency f p ≒9×√(10 15) ≈ 285 [MHz] or higher, N = 10 19 By doing the above, f p ≈ 9 × √(10 19 ) ≈ 28.5 [GHz] or higher. The communication frequency between the radio wave transmitting antenna 1 and the radio wave receiving antenna 2 only needs to be lower than the plasma frequency, so it can be set in the UHF (Ultra High Frequency) band or the SHF (Super High Frequency) band.

[0022] For example, Non-Patent Document 2 states that in a plasma generator used under atmospheric pressure, the plasma density (charge density) is 10 19 [m -3 It is stated that ] can be generated.

[0023] The radio wave transmitting antenna 1 and the laser beam generator 3 may be integrated into a single unit.

[0024] According to Non-Patent Document 4, the intensity of the laser beam is 10 15 To achieve the charged particle density, a KrF excimer laser is used to 10 11 W / m 3 This can be achieved if the output is available.

[0025] [B] Figure 3 of the first modified example schematically shows a first configuration example of the wireless communication system 100a in the first modified example.

[0026] In the example shown in Figure 2, the laser beam generator 3 generates a fan-shaped plasma region, but it is not limited to this. In the first modified example shown in Figure 3, multiple (two in the example shown in Figure 3) laser beam generators 3a generate a cylindrical plasma region (see reference numerals C1 and C2 in Figure 3). The combination of the radio wave transmitting antenna 1 and the laser beam generator 3a is an example of a wireless communication device.

[0027] In the example shown in FIG. 3, the wireless communication system 100a generates a plasma pipeline, which is a waveguide-like communication path, by cylindrically surrounding a part of the upper atmosphere with a plasma region. Through this pipeline, electromagnetic waves are propagated from a transmission point to a space at a certain distance in a specific direction. Then, the wireless communication system 100a forms radio wave propagation paths (refer to reference numerals C4 and C5 in FIG. 3) other than the radio wave propagation path of the direct wave (refer to reference numeral C3 in FIG. 3), which is a line-of-sight path, by radiating electromagnetic waves through the communication path of the plasma pipeline, thereby realizing MIMO.

[0028] The laser beam generator 3a forms a cylindrical plasma region by reflecting and scanning the laser beam on the built-in mirror.

[0029] The numbers of the radio wave transmission antenna 1 and the laser beam generator 3a may be variously changed. For example, the wireless communication system 100a may include the same number (for example, 2 to 4 each) of the radio wave transmission antenna 1 and the laser beam generator 3a.

[0030] FIG. 4 is a diagram schematically showing a second configuration example of the wireless communication system 100b in the first modification.

[0031] As another aspect of the present embodiment, FIG. 4 is an example of reducing attenuation in a radio wave propagation path by a plasma pipeline, which is a waveguide-like communication path, and realizing an increase in communication capacity by using adaptive equalization.

[0032] The wireless communication system 100b shown in FIG. 4 includes an integrated radio wave transmission antenna 1 and a laser beam generator 3a, and a radio wave reception antenna 2a installed on a balloon, an unmanned aircraft, a high-altitude base station, etc. that navigate in the atmosphere or gas layer.

[0033] The laser beam generator 3a forms a pipeline-like radio wave propagation path (refer to reference numeral C6 in FIG. 4), and the radio wave transmission antenna 1 transmits electromagnetic waves to the radio wave reception antenna 2a while reflecting the electromagnetic waves within the radio wave propagation path.

[0034] FIG. 5 is a diagram schematically showing a configuration example of the radio wave transmission antenna 1 and the laser beam generator 3a in the first modification, where (a) is a top view thereof, (b) is a front view thereof, and (c) is a side view thereof.

[0035] As shown in FIGS. 5(a) to 5(c), the laser beam generator 3a is installed on the central axis of the radio wave transmitting antenna 1 and is combined with the central mirror 33, the outer peripheral mirror 34, and the turntable 35 on which the central mirror 33 and the outer peripheral mirror 34 are installed. The central mirror 33 is installed on the rotation axis (center point) of the disk-shaped turntable 35, and the outer peripheral mirror 34 is installed near the circumference of the turntable 35.

[0036] In the first modification, the radio wave transmitting antenna 1 and the laser beam generator 3a may be attached to the turntable 35 and rotate together with the mirrors 33 and 34. In that case, the driving power of the laser beam generator 3a and the transmission of the transmission RF signal supplied to the radio wave transmitting antenna 1 are supplied via a slip ring or the like provided on the rotation axis.

[0037] The laser beam generator 3a is configured to irradiate a laser on the side opposite to the radio wave transmission direction of the radio wave transmitting antenna 1. As shown in FIG. 5(b), in the state where the turntable 35 is rotated, the laser beam irradiated from the laser beam generator 3a is reflected 90 degrees in the outer peripheral direction by the central mirror 33 and then reflected by the outer peripheral mirror 34, thereby generating a pipe-shaped radio wave propagation path. Then, the electromagnetic wave irradiated from the radio wave transmitting antenna 1 propagates while being reflected within the generated pipe-shaped radio wave propagation path.

[0038] [C] Second Modification FIG. 6 is a diagram schematically showing a first configuration example of the wireless communication system 100c in the second modification.

[0039] In the second modification shown in FIG. 6, a plurality (two in the example shown in FIG. 6) of laser beam generators 3b generate a plasma pipe that is a pipe-shaped plasma region (see reference numerals D1 and D2 in FIG. 6). The combination of the radio wave transmitting antenna 1 and the laser beam generator 3b is an example of a wireless communication device.

[0040] In the example shown in Figure 6, the wireless communication system 100c generates a plasma conduit, which is a waveguide-like communication path, by surrounding a portion of the upper atmosphere with a plasma region in a conduit-like manner. Electromagnetic waves are propagated through this plasma conduit to a space at a certain distance in a specific direction from the transmission point. The wireless communication system 100c then radiates electromagnetic waves through the plasma conduit, thereby forming radio wave propagation paths other than the direct wave propagation path (see reference numeral D3 in Figure 6) (see reference numeral D4 and D5 in Figure 6), thereby realizing MIMO (Multi-Input / Multi-Output).

[0041] The laser beam generator 3b forms a tubular plasma region by reflecting the laser beam off its built-in mirror and scanning it.

[0042] The number of radio wave transmitting antennas 1 and laser beam generators 3b can be varied. For example, the wireless communication system 100c may be equipped with the same number of radio wave transmitting antennas 1 and laser beam generators 3b (for example, 2 to 4 of each).

[0043] Figure 7 is a schematic diagram showing a second configuration example of the wireless communication system 100d in the second modified example.

[0044] Figure 7, like Figure 4, shows another aspect of this embodiment, which is another example of how to increase communication capacity by reducing attenuation in the radio wave propagation path using a waveguide-shaped communication path called a plasma tube and employing adaptive modulation and demodulation.

[0045] The wireless communication system 100d shown in Figure 7 comprises an integrated radio wave transmitting antenna 1 and laser beam generator 3b, and a radio wave receiving antenna 2a installed on balloons, unmanned aerial vehicles, high-altitude base stations, etc., that navigate through the atmosphere or gas layer.

[0046] The laser beam generator 3b forms a tubular radio wave propagation path (see reference numeral D6 in Figure 7), and the radio wave transmitting antenna 1 transmits electromagnetic waves to the radio wave receiving antenna 2a while reflecting the electromagnetic waves within this radio wave propagation path.

[0047] Figure 8 schematically shows an example of the configuration of the radio wave transmitting antenna 1 and the laser beam generator 3b in the second modified example, where (a) is a top view, (b) is a front view, and (c) is a side view.

[0048] As shown in Figure 8(a), the laser beam generator 3b is combined with a polygon mirror 31 and a concave mirror 32. In one example, four sets of laser beam generators 3b, polygon mirrors 31, and concave mirrors 32 are installed to surround, for example, a horn antenna, which is a radio wave transmitting antenna 1. Note that there are two or more sets, not limited to four. Furthermore, the number of laser beam generators 3b may be reduced by devising the arrangement of the polygon mirrors 31 and concave mirrors 32.

[0049] As shown in Figures 8(b) and 8(c), the laser beam emitted from the laser beam generator 3b is reflected by a rotatable polygon mirror 31 positioned diagonally above it, towards a concave mirror 32 positioned diagonally behind it, and then reflected by the concave mirror 32 in a direction parallel to the direction of radio wave generation from the radio wave transmitting antenna 1, thereby generating a conduit-like radio wave propagation path around the radio wave transmitting antenna 1. The electromagnetic waves emitted from the radio wave transmitting antenna 1 then propagate through the generated conduit-like radio wave propagation path while being reflected.

[0050] According to the embodiments and modifications described above, it is possible to increase communication capacity by using MIMO or adaptive modulation / demodulation methods.

[0051] [D] The other disclosed technologies are not limited to the embodiments described above and can be implemented in various ways without departing from the spirit of each embodiment. Each configuration and each process of each embodiment can be selected or combined as needed.

[0052] 100, 100a-100d, 600: Wireless communication system 1, 6: Radio wave transmitting antenna 2, 2a, 7: Radio wave receiving antenna 3, 3a, 3b: Laser beam generator 31: Polygon mirror 32: Concave mirror 33: Center mirror 34: Outer edge mirror 35: Rotating platform

Claims

1. A wireless communication device that performs wireless communication using MIMO (Multiple-Input Multiple-Output) with a receiving device, comprising: a transmitting device that transmits radio waves; and a laser beam generator that emits a laser beam into the atmosphere to form a plasma region, thereby reflecting or refracting the radio waves in the plasma region and propagating them to the receiving device.

2. The wireless communication device according to claim 1, wherein the laser beam generator propagates the radio waves by reflecting or refracting them in the fan-shaped plasma region, thereby forming the fan-shaped plasma region.

3. The wireless communication device according to claim 1, wherein the laser beam generator propagates the radio waves by reflecting them through a waveguide formed inside the tubular plasma region.

4. A wireless communication system that performs wireless communication using MIMO (Multiple-Input Multiple-Output), comprising: a transmitting device that transmits radio waves; a laser beam generator that emits a laser beam into the atmosphere to form a plasma region, thereby reflecting or refracting the radio waves in the plasma region; and a receiving device that receives the radio waves that have been reflected or refracted in the plasma region.

5. A wireless communication method using MIMO (Multiple-Input Multiple-Output), comprising: transmitting radio waves using a transmitting device; emitting a laser beam into the atmosphere using a laser beam generator to form a plasma region, thereby reflecting or refracting the radio waves in the plasma region; and receiving the radio waves reflected or refracted in the plasma region using a receiving device.

6. A wireless communication method using a conduit made of plasma artificially generated by a laser beam generator, comprising: transmitting radio waves by a transmitting device; emitting a laser beam into the atmosphere by the laser beam generator to form a conduit-shaped plasma region, thereby reflecting or refracting the radio waves within the plasma conduit; and receiving the radio waves in the conduit that have been reflected or refracted by the plasma region by a receiving device.

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