Wireless relay system and wireless relay method

Abstract

A wireless relay system according to one embodiment comprises: a plurality of radio wave direction changing units that each change the direction of travel of radio waves incident from a wireless communication device so as to emit the radio waves in different directions; and a control unit that controls the direction of the radio waves emitted by each of the radio wave direction changing units. The control unit includes: an estimation unit that estimates the position to which a wireless terminal will move after a predetermined time elapses; an angle calculation unit that calculates, for each of the radio wave direction changing units, the angle between the direction in which the radio wave is currently being emitted and the direction in which the radio wave will be emitted when emitted toward the wireless terminal that has moved after the predetermined time has elapsed, the angle being calculated on the basis of the estimated position of the wireless terminal; a selection unit that selects, from among the plurality of radio wave direction changing units, the radio wave direction changing unit for which the angle calculated by the angle calculation unit is smallest; and an assignment unit that assigns the selected radio wave direction changing unit to emit radio waves toward the wireless terminal after the predetermined time has elapsed.

Description

Wireless relay system and wireless relay method

[0001] The present invention relates to a wireless relay system and a wireless relay method.

[0002] In order to achieve high speed and large capacity wireless access, attention is being paid to utilizing high frequency bands that can secure wide bandwidth. For example, the 28 GHz band is used in the 5th generation mobile communication system, and the 60 GHz band is used in the wireless LAN standard IEEE802.11ad (millimeter wave wireless LAN system).

[0003] For example, if a Reconfigurable Intelligent Surface (RIS) that can dynamically switch the reflection direction is applied as a wireless relay node, the RIS needs to switch the reflection direction of the radio waves and direct them toward the radio wireless terminal when the target wireless terminal moves.

[0004] One method for controlling a dynamic reflector is to change the characteristics of radio waves by controlling the phase of the radio waves when the dynamic reflector reflects them. For example, one method is to change the phase of the radio waves reflected by a dynamic reflector made up of array elements based on channel state information (CSI) between the transmitting and receiving stations.

[0005] E. Baser, MD Renzo, JD Rosny, M. Debbah, MS Alouini, and R. Zhang, "Wireless communications through reconfigurable intelligent surfaces," IEEE Access, Vol.7, Aug. 2019.

[0006] However, in the RIS, a response delay occurs when switching the reflection direction due to device constraints such as response speed, etc. As a result, in the RIS, a state occurs in which the wireless terminal is no longer in the reflection direction when the switching is completed, and the expected improvement in received power by the RIS cannot be obtained.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a wireless relay system and a wireless relay method that can prevent a decrease in communication quality even when wireless communication is relayed by switching the direction in which radio waves travel.

[0008] A wireless relay system according to one aspect of the present invention is a wireless relay system that relays radio waves emitted by a wireless communication device to a moving wireless terminal, and includes a plurality of radio wave direction change units that each change the direction in which the radio waves incident from the wireless communication device travel so that the radio waves are emitted in another direction, and a control unit that controls the direction of the radio waves emitted by each of the radio wave direction change units, wherein the control unit includes an estimation unit that estimates the position to which the wireless terminal will move after a predetermined time has elapsed, an angle calculation unit that calculates, for each of the radio wave direction change units, the angle between the direction in which the radio waves are currently being emitted and the direction in which the radio waves will be emitted toward the wireless terminal that has moved after the predetermined time has elapsed based on the position of the wireless terminal estimated by the estimation unit, a selection unit that selects from the plurality of radio wave direction change units the radio wave direction change unit for which the angle calculated by the angle calculation unit is smallest, and an assignment unit that assigns the radio wave direction change unit selected by the selection unit to emit radio waves toward the wireless terminal after the predetermined time has elapsed.

[0009] In addition, a wireless relay method according to one aspect of the present invention is a wireless relay method for relaying radio waves to a moving wireless terminal, the wireless relay method comprising a plurality of radio wave direction change units each changing the direction in which radio waves incident from a wireless communication device travel so as to be emitted in another direction, and a control unit controlling the direction of the radio waves emitted by each of the radio wave direction change units, the method including the steps of: an estimation step of estimating the position to which the wireless terminal will move after a predetermined time has elapsed; an angle calculation step of calculating, for each of the radio wave direction change units, the angle between the direction in which the radio waves are currently being emitted and the direction in which radio waves will be emitted toward the wireless terminal that has moved after the predetermined time has elapsed, based on the position of the wireless terminal estimated by the estimation step; a selection step of selecting from the plurality of radio wave direction change units the radio wave direction change unit for which the angle calculated by the angle calculation step is smallest; and an assignment step of assigning the radio wave direction change unit selected by the selection step to emit radio waves toward the wireless terminal after the predetermined time has elapsed.

[0010] According to the present invention, even if wireless communication is relayed by switching the direction in which radio waves travel, it is possible to prevent a decrease in communication quality.

[0011] 1 is a diagram illustrating an overview of a wireless relay system according to an embodiment; FIG. 1(a) is a graph illustrating the relationship between reception characteristics at a wireless terminal when the response delay of a relay device is long; FIG. 1(b) is a graph illustrating the relationship between reception characteristics at a wireless terminal when the response delay of a relay device is short; FIG. 1(a) is a graph illustrating the relationship between reception characteristics at a wireless terminal when the angular velocity of the wireless terminal is fast; FIG. 1(b) is a graph illustrating the relationship between reception characteristics at a wireless terminal when the angular velocity of the wireless terminal is slow; FIG. 1(b) is a functional block diagram illustrating functions of a relay device; FIG. 1 is a diagram schematically illustrating an operation example of a wireless relay system; FIG. 1 is a diagram schematically illustrating an operation example of a modified wireless relay system; FIG. 1 is a diagram illustrating an operation example of a modified wireless relay system;

[0012] 9 is a diagram showing a configuration example of a wireless repeating system 10 of a comparative example equipped with a RIS (dynamic reflector).

[0013] In the wireless relay system 10, a base station (wireless communication device) 12 emits radio waves, which are reflected by a relay device 14 equipped with a RIS and relayed to a moving wireless terminal 16. The wireless terminal 16 moves at the same speed as an automobile, for example.

[0014] The relay device 14 receives the signal from the wireless terminal 16 at time t ０ From time t ０ If the mobile station moves between the time +T and the time +T, the direction of reflection of the RIS is controlled so that the direction of reflection of the radio wave is directed toward the wireless terminal 16.

[0015] However, due to constraints such as the response speed of the devices that make up the relay device 14, a response delay may occur when switching the characteristics of the multiple reflecting elements provided in the RIS to change the reflection direction, which may degrade the reception characteristics of the wireless terminal 16 for the radio waves emitted by the base station 12.

[0016] For example, the base station 12 receives the ０ If the relay device 14 controls the direction of reflection of radio waves based on the position of the wireless terminal 16 in the area, a response delay Tc occurs in the relay device 14, causing the direction of reflection of the radio waves to deviate from the wireless terminal 16. In this case, the RIS will not be sufficiently effective in improving communication quality.

[0017] Therefore, a wireless relay system according to one embodiment is configured to be able to prevent a decrease in communication quality even when wireless communication is relayed by switching the direction in which radio waves travel.

[0018] 1 is a diagram illustrating an overview of a wireless relay system 1 according to one embodiment. As shown in FIG. 1, in the wireless relay system 1, a radio wave emitted by a base station 2, which is a wireless communication device, is reflected by a relay device 3-1 or 3-2 and relayed to a moving wireless terminal 4.

[0019] Each of the relay devices 3-1 and 3-2 has a RIS equipped with a plurality of reflecting elements 30, and has the function of switching the direction of reflection of radio waves. When there is no need to specify which of the multiple configurations is used, such as the relay devices 3-1 and 3-2, they will be simply referred to as the relay device 3.

[0020] The wireless relay system 1 relays radio waves using a RIS, improving the quality of communication from a base station 2 to a wireless terminal 4 .

[0021] For example, the base station 2 (or the relay device 3-1 or the relay device 3-2) first detects that the wireless terminal 4 has ０ From time t ０ +T (predetermined time).

[0022] Then, based on the estimated position of the wireless terminal 4, the base station 2 calculates the angle (A, B in Figure 1) between the direction in which the radio waves are currently being emitted to the relay devices 3-1 and 3-2 and the direction in which the radio waves will be emitted to the wireless terminal 4 that has moved after a predetermined time has passed.

[0023] Next, the base station 2 selects the relay device 3-1 or relay device 3-2 that has the smallest calculated angle, and assigns either the selected relay device 3-1 or relay device 3-2 to emit radio waves toward the wireless terminal 4 after a predetermined time has elapsed.

[0024] In addition, the base station 2 may estimate the angular velocity of the wireless terminal 4 centered on each of the relay devices 3-1 and 3-2, and assign the relay device 3-1 or 3-2 that slows the angular velocity of the wireless terminal 4 as the relay device that reflects radio waves to the wireless terminal 4.

[0025] This is because, when the angular velocity of the wireless terminal 4 is greater than that of the relay device 3-2, as in the case of the relay device 3-1, the reflection angle after the time T has elapsed becomes larger, and high-speed control of the relay device 3-1 becomes necessary.

[0026] Also, when the angular velocity of the wireless terminal 4 is smaller than that of the relay device 3-1, as in the case of the relay device 3-2, the change in the reflection angle after the time T has elapsed is small, and high-speed control of the relay device 3-2 is not necessary.

[0027] 2A and 2B are graphs showing a comparison of the relationship between the response delay and the reception characteristics of a wireless terminal when a relay device equipped with a RIS switches the reflection direction of radio waves. Fig. 2A is a graph showing the relationship between the response delay of the relay device and the reception characteristics of the wireless terminal when the response delay of the relay device is long. Fig. 2B is a graph showing the relationship between the response delay of the relay device and the reception characteristics of the wireless terminal when the response delay of the relay device is short.

[0028] 3A and 3B are graphs showing a comparison of the relationship between the response delay and the reception characteristics of a wireless terminal when a relay device equipped with a RIS switches the reflection direction of radio waves, based on the angular velocity of the wireless terminal. Fig. 3A is a graph showing the relationship between the response delay and the reception characteristics of a wireless terminal when the angular velocity of the wireless terminal is fast. Fig. 3B is a graph showing the relationship between the response delay and the reception characteristics of a wireless terminal when the angular velocity of the wireless terminal is slow.

[0029] For example, when a wireless terminal moves, the reception characteristics of the wireless terminal will deteriorate unless the direction of reflection by the relay device is appropriately controlled.

[0030] If the time required to set the appropriate phase for each reflecting element of the RIS (the response delay Tc) is long, the reception characteristics of the wireless terminal may be degraded due to the response delay. If the response delay is large, the reception characteristics of the wireless terminal may be degraded, and communication may be interrupted.

[0031] On the other hand, if the response delay of the RIS is short, the setting values ​​of each reflecting element can be updated before the reception characteristics of the wireless terminal deteriorate significantly, so the reception characteristics of the wireless terminal do not deteriorate due to the response delay. In other words, even if the response delay of the RIS is large, the time during which the reception characteristics of the wireless terminal can be improved is long.

[0032] Therefore, the wireless relay system 1 assigns a relay device that slows down the angular velocity of the wireless terminal to a relay device that reflects radio waves toward the wireless terminal, thereby preventing deterioration of the reception characteristics of the wireless terminal due to response delays of the relay device.

[0033] Next, a specific configuration example of the relay device 3 will be described. Fig. 4 is a functional block diagram illustrating the functions of the relay device 3. As shown in Fig. 4, the relay device 3 includes, for example, a radio wave direction change unit 31 and a control unit 32.

[0034] The radio wave direction changer 31 is, for example, a RIS including a plurality of reflecting elements 30, and switches the reflection direction of the radio waves by switching the phase of the radio waves reflected by each of the reflecting elements 30 under the control of the control unit 32. For example, the radio wave direction changer 31 changes the traveling direction of the radio waves so that the radio waves incident from a wireless communication device such as the base station 2 (FIG. 1) are emitted in a different direction.

[0035] The radio wave direction changer 31 may also constitute a repeater that amplifies radio waves received from the base station 2 and outputs them in a different direction.

[0036] The control unit 32 includes, for example, an estimation unit 321, an angle calculation unit 322, a selection unit 323, and an allocation unit 324, and controls the direction of the radio waves emitted (reflected) by the radio wave direction change unit 31 of each of the multiple relay devices 3.

[0037] The estimation unit 321 estimates the position to which the wireless terminal 4 (FIG. 1) will move after a predetermined time has elapsed, and outputs the estimation result to the angle calculation unit 322 .

[0038] Based on the position of the wireless terminal 4 estimated by the estimation unit 321, the angle calculation unit 322 calculates the angle between the direction in which the radio waves are currently being emitted and the direction in which the radio waves will be emitted toward the moved wireless terminal 4 after a predetermined time has elapsed, for the radio wave direction change unit 31 of each of the multiple relay devices 3, and outputs the angle to the selection unit 323.

[0039] The selection unit 323 selects, from the plurality of radio wave direction change units 31 , the radio wave direction change unit 31 that minimizes the angle calculated by the angle calculation unit 322 , and outputs the selection result to the allocation unit 324 .

[0040] In addition, if the response speed for switching the direction in which radio waves are emitted differs for each radio wave direction change unit 31, the selection unit 323 may select a radio wave direction change unit 31 to be assigned to the wireless terminal 4 from among the multiple radio wave direction change units 31 based on the sum of the distance from the base station 2 to the radio wave direction change unit 31 and the distance from the radio wave direction change unit 31 to the wireless terminal 4, and the response speed of each radio wave direction change unit 31.

[0041] For example, the selection unit 323 may select the relay device 3 for which the sum of the distance between the base station 2 and the relay device 3 and the distance between the relay device 3 and the wireless terminal 4 is the smallest from among the relay devices 3 for which the angular velocity of the wireless terminal 4 is below a predetermined threshold.

[0042] The allocation unit 324 allocates the radio wave direction change unit 31 selected by the selection unit 323 to emit radio waves toward the wireless terminal 4 after a predetermined time has elapsed.

[0043] Here, the relay device 3 is described as having the control unit 32 that controls the radio wave direction change unit 31, but the control unit 32 may be provided in any of the devices that make up the wireless relay system 1. For example, the control unit 32 may be provided in the base station 2, a network control device (not shown), or the like.

[0044] In this way, the wireless relay system 1 is equipped with multiple relay devices, and by spatially distributing the nodes that change the reflection direction of radio waves, it is possible to expect improvement in the characteristics of the entire system. In other words, the wireless relay system 1 is configured to tolerate a response delay of the relay devices when switching the reflection direction of radio waves.

[0045] On the other hand, in order to create a RIS with a short response delay, high performance components may be required, which may increase the cost of the RIS device.

[0046] Next, a description will be given of an example of operation of the wireless relay system 1. Fig. 5 is a diagram schematically showing an example of operation of the wireless relay system 1. Here, it is assumed that the above-mentioned control unit 32 is provided in the base station 2.

[0047] 5, for example, the wireless terminal 4 periodically notifies the base station 2 of location information indicating its own location. The base station 2 may also periodically estimate the location of the wireless terminal 4.

[0048] For example, the base station 2 calculates the angular velocity of the wireless terminal 4 as seen from the relay devices 3-1 and 3-2 using the position information of the wireless terminal 4. It is assumed that the positions of the base station 2, the relay devices 3-1 and 3-2 are known.

[0049] Then, the base station 2 selects the relay device 3-1 or 3-2 with the smallest angular velocity and assigns it as the relay device that reflects radio waves to the wireless terminal 4. In this example, for example, the relay device 3-2 is assigned as the relay device that reflects radio waves to the wireless terminal 4.

[0050] 6 is a diagram schematically illustrating an example of operation of a modified example (wireless relay system 1a) of the wireless relay system 1. In this example, the base station 2 is provided with the control unit 32.

[0051] 6, a relay device 3-1 and a repeater 5 are provided as relay devices. The repeater 5 has a radio wave direction change unit 50. The radio wave direction change unit 50 has a function of amplifying radio waves received from the base station 2 and outputting the amplified radio waves in another direction.

[0052] The wireless terminal 4 periodically notifies the base station 2 of location information indicating its own location. The base station 2 may also periodically estimate the location of the wireless terminal 4.

[0053] For example, the base station 2 uses the position information of the wireless terminal 4 to calculate the angular velocity of the wireless terminal 4 as seen from the relay device 3-1 and the repeater 5. It is assumed that the positions of the base station 2, the relay device 3-1, and the repeater 5 are known.

[0054] Then, the base station 2 selects the relay device 3-1 or the repeater 5 that has the smallest angular velocity, and assigns it as the relay device that reflects radio waves to the wireless terminal 4. In this case, for example, the response delay of the repeater 5 is smaller than the response delay of the repeater 3-1, and the repeater 5 is assigned as the relay device that reflects radio waves to the wireless terminal 4.

[0055] 7 is a diagram schematically illustrating an example of operation of a modified example (wireless relay system 1b) of the wireless relay system 1. In this example, the base station 2 is provided with the control unit 32.

[0056] If the wireless relay system 1 selects a relay device based only on the angular velocity of the wireless terminal 4, there is a possibility that a relay device that provides little improvement in the reception characteristics of the wireless terminal 4 will be assigned. Therefore, the wireless relay system 1b calculates, for each relay device 3, the sum of the distance between the base station 2 and the relay device 3 and the distance between the relay device 3 and the wireless terminal 4, and assigns a relay device 3 that can mitigate the effect of response delay while ensuring that the wireless terminal 4 has reception characteristics at or above a predetermined value.

[0057] 7, for example, the wireless terminal 4 periodically notifies the base station 2 of location information indicating its own location. The base station 2 may also periodically estimate the location of the wireless terminal 4.

[0058] For example, the base station 2 calculates the angular velocity of the wireless terminal 4 as seen from each of the relay devices 3-1 to 3-3 using the position information of the wireless terminal 4. It is assumed that the positions of the base station 2 and the relay devices 3-1 to 3-3 are known.

[0059] Furthermore, the base station 2 calculates the sum of the distance between the base station 2 and the relay device 3 and the distance between the relay device 3 and the wireless terminal 4 for each relay device 3 .

[0060] The base station 2 then selects relays 3-2 and 3-3, for example, whose angular velocities are equal to or less than a predetermined threshold. Furthermore, if the sum of the distances for relay 3-3 is smaller than the sum of the distances for relay 3-2, the base station 2 assigns relay 3-3 as the relay that will reflect radio waves to the wireless terminal 4.

[0061] In this way, the wireless relay system 1 can reduce the effect of the response speed when the relay device switches the reflection direction of the radio wave, and prevent the communication quality from deteriorating.

[0062] In addition, each function possessed by the base station 2, relay device 3, wireless terminal 4, and repeater 5 may be partially or completely configured by hardware such as a PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array), or may be configured as a program executed by a processor such as a CPU.

[0063] For example, the base station 2, relay device 3, wireless terminal 4, and repeater 5 can be realized using a computer and a program, and the program can be recorded on a storage medium or provided via a network.

[0064] 8 is a diagram illustrating an example of the hardware configuration of the relay device 3 according to one embodiment. As illustrated in the figure, the relay device 3 has, for example, an input unit 600, an output unit 610, a communication unit 620, a CPU 680, a memory 682, and an HDD 650 connected via a bus 660, and functions as a computer. The relay device 3 is also configured to be able to input and output data to and from a computer-readable storage medium 670.

[0065] The input unit 600 is, for example, a keyboard and a mouse, etc. The output unit 610 is, for example, a display device, etc. The communication unit 620 is, for example, a wired or wireless network interface.

[0066] As described above, the CPU 680 controls each component of the relay device 3 and performs predetermined processing, etc. The memory 682 and the HDD 650 are storage units that store data, etc.

[0067] The storage medium 670 is capable of storing programs and the like that cause the relay device 3 to execute the functions of the relay device 3. The architecture constituting the relay device 3 is not limited to the example shown in Fig. 8. Furthermore, other components constituting the wireless relay system, such as the base station 2, the wireless terminal 4, and the repeater 5, may also have the same hardware configuration as the relay device 3.

[0068] Although the embodiments of the present invention have been described above with reference to the drawings, it is clear that the above-described embodiments are merely examples of the present invention and that the present invention is not limited to the above-described embodiments. Therefore, addition, omission, substitution, and other modifications of components may be made without departing from the technical spirit and scope of the present invention.

[0069] The functions performed by the components described herein may be implemented in circuitry or processing circuitry, including general purpose processors, application specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to perform the described functions.

[0070] A processor includes transistors and other circuits and is considered to be circuitry or processing circuitry. A processor may be a programmed processor that executes programs stored in memory.

[0071] In this specification, a circuitry, unit, or means is hardware that is programmed to realize or performs the described functions, which may be any hardware disclosed herein or any hardware known to be programmed to realize or perform the described functions.

[0072] If the hardware is a processor considered to be a type of circuitry, the circuitry, means, or unit is a combination of the hardware and software used to configure the hardware and / or processor.

[0073] 1, 1a, 1b...wireless relay system, 2...base station, 3-1 to 3-3...relay device, 4...wireless terminal, 5...repeater, 30...reflecting element, 31...radio wave direction change unit, 32...control unit, 50...radio wave direction change unit, 321...estimation unit, 322...angle calculation unit, 323...selection unit, 324...allocation unit, 600...input unit, 610...output unit, 620...communication unit, 650...HDD, 660...bus, 670...storage medium, 680...CPU, 682...memory

Claims

1. In a wireless relay system that relays radio waves radiated by a wireless communication device to a wireless terminal that moves the radio waves, a plurality of radio wave direction changing units that change the direction of the radio waves so as to emit the radio waves incident from the wireless communication device in other directions, and a control unit that controls the direction of the radio waves emitted by each of the radio wave direction changing units. The control unit includes an estimation unit that estimates the position where the wireless terminal will move after a predetermined time has elapsed, and based on the position of the wireless terminal estimated by the estimation unit, for each of the radio wave direction changing units, an angle between the direction in which the current radio wave is being emitted and the direction in which the radio wave is to be emitted toward the wireless terminal that has moved after a predetermined time has elapsed is calculated by an angle calculation unit. A selection unit that selects the radio wave direction changing unit for which the angle calculated by the angle calculation unit is the smallest from among the plurality of radio wave direction changing units, and an assignment unit that assigns the radio wave direction changing unit selected by the selection unit to emit the radio wave toward the wireless terminal after a predetermined time has elapsed. A wireless relay system characterized by having these components.

2. The selection unit, when the response speed for switching the direction of radio wave emission is different for each of the radio wave direction changing units, selects the radio wave direction changing unit from among the plurality of radio wave direction changing units based on the sum of the distance from the wireless communication device to the radio wave direction changing unit and the distance from the radio wave direction changing unit to the wireless terminal, and the response speed. The wireless relay system according to claim 1, characterized by this.

3. The radio wave direction changing unit is a RIS (Reconfigurable Intelligent Surface) that includes a plurality of reflection elements and is capable of controlling the phase of the radio waves reflected by each of the plurality of reflection elements. The wireless relay system according to claim 1 or 2, characterized by this.

4. The radio wave direction changing unit constitutes a repeater that amplifies the radio waves incident from the wireless communication device and emits them in other directions. The wireless relay system according to claim 1 or 2, characterized by this.

5. In a wireless relay method for relaying radio waves to a moving wireless terminal, the wireless relay system includes a plurality of radio wave direction changing units that change the direction of radio waves so as to emit the radio waves incident from the wireless communication device in other directions, and a control unit that controls the direction of the radio waves emitted by each of the radio wave direction changing units. The method includes: an estimating step of estimating the position where the wireless terminal moves after a lapse of a predetermined time; an angle calculating step of calculating, for each of the radio wave direction changing units, an angle between the direction in which the current radio wave is being emitted and the direction in which the radio wave is to be emitted toward the wireless terminal that has moved after a lapse of the predetermined time, based on the position of the wireless terminal estimated in the estimating step; a selecting step of selecting, from among the plurality of radio wave direction changing units, the radio wave direction changing unit for which the angle calculated in the angle calculating step is the minimum; and an assigning step of assigning, to the radio wave direction changing unit selected in the selecting step, to emit the radio wave toward the wireless terminal after a lapse of the predetermined time.

6. In the selecting step, when the response speed for switching the direction in which the radio wave is emitted is different for each of the radio wave direction changing units, the radio wave direction changing unit is selected from among the plurality of radio wave direction changing units based on the sum of the distance from the wireless communication device to the radio wave direction changing unit and the distance from the radio wave direction changing unit to the wireless terminal, and the response speed.

7. The radio wave direction changing unit according to claim 5 or 6 is a RIS including a plurality of reflecting elements, and the phase of the radio wave reflected by each of the plurality of reflecting elements is controllable.

8. The radio wave direction changing unit according to claim 5 or 6 constitutes a repeater that amplifies the radio wave incident from the wireless communication device and emits it in another direction.

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