Radio relay system, radio relay method, and control device

Abstract

A radio relay system according to one embodiment of the present invention relays a radio wave radiated by a radio communication device to a moving radio terminal, and includes: a plurality of radio wave direction change units that each change the direction of travel of a radio wave incident from the radio communication device so that the radio wave is emitted in another direction; and a control unit that controls the direction of the radio wave emitted by each of the radio wave direction change units. The control unit includes: an estimation unit that estimates a position to which the radio terminal is to move after elapse of a predetermined period of time; and a sequential allocation unit that uses the position of the radio terminal estimated by the estimation unit to determine an allocation in which each of the radio wave direction change units sequentially emits a radio wave toward the radio terminal each time the predetermined period of time elapses.

Description

Wireless relay system, wireless relay method, and control device

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

[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, a wireless relay method, and a control device 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, and a sequential allocation unit that assigns each of the radio wave direction change units to emit radio waves sequentially toward the wireless terminal every time a predetermined time has elapsed based on the position of the wireless terminal estimated by the estimation unit.

[0009] In addition, a wireless relay method according to one aspect of the present invention is a wireless relay method in which a wireless relay system having a plurality of radio wave direction change units, each of which changes the direction in which radio waves incident from a wireless communication device travel so as to emit the radio waves in another direction, and a control unit which controls the direction of the radio waves emitted by each of the radio wave direction change units, relays radio waves to a moving wireless terminal, and is characterized in that it includes an estimation step of estimating the position to which the wireless terminal will move after a predetermined time has elapsed, and a sequential assignment step of assigning each of the radio wave direction change units to emit radio waves sequentially toward the wireless terminal every time a predetermined time has elapsed, based on the position of the wireless terminal estimated by the estimation step.

[0010] In addition, a control device according to one aspect of the present invention is a control device that controls a plurality of relay devices that switch and emit incident radio waves in a plurality of directions and relay the radio waves to a moving wireless terminal, and is characterized in that it has an estimation unit that estimates the position to which the wireless terminal will move after a predetermined time has elapsed, and a sequential allocation unit that assigns each of the relay devices to emit radio waves toward the wireless terminal in sequence every time a predetermined time has elapsed, based on the position of the wireless terminal estimated by the estimation unit.

[0011] 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.

[0012] 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 block diagram illustrating an example of the configuration of a wireless relay system; FIG. 1(b) is a diagram illustrating an example of the operation of a wireless relay system according to an embodiment; FIG. 1(b) is a diagram illustrating reception characteristics when a wireless terminal receives radio waves via each relay device in sequence; FIG. 1(c) is a flowchart illustrating a method by which a base station determines a control offset ΔT; FIG. 1(d) is a flowchart illustrating a method by which the number of divisions of a RIS is determined; FIG. 1(a) is a diagram illustrating an example of the configuration of a wireless relay system according to an embodiment;

[0013] 9 is a diagram showing a configuration example of a wireless repeating system 10 of a comparative example equipped with a RIS (dynamic reflector).

[0014] 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.

[0015] 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 to +Tc, the reflection direction of the RIS is controlled so that the radio wave is reflected toward the wireless terminal 16 .

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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, radio waves emitted from a base station 2, which is a wireless communication device with a control device function, are sequentially reflected by relay devices 3-1 to 3-3 and relayed to a moving wireless terminal 4.

[0020] Each of the relay devices 3-1 to 3-3 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, such as the relay devices 3-1 to 3-3, they will be simply referred to as the relay device 3.

[0021] 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 .

[0022] For example, the base station 2 (or any of the relay devices 3-1 to 3-3) first estimates the positions to which the wireless terminal 4 has moved at the control timings Tc, Tc+ΔT, and Tc+2ΔT for each of the relay devices 3-1 to 3-3.

[0023] Then, based on the estimated positions of the wireless terminals 4, the base station 2 assigns each of the relay devices 3-1 to 3-3 to emit radio waves sequentially toward the wireless terminals 4 at predetermined intervals (T).

[0024] In this way, the wireless relay system 1 controls relay devices 3-1 to 3-3 installed in multiple different locations so that they reflect radio waves at different timings toward the same wireless terminal 4. The wireless relay system 1 controls so that the wireless terminal 4 is located in the reflection direction of one of the relay devices by switching the reflection direction at different control timings for each relay device.

[0025] In other words, the wireless relay system 1 can virtually speed up the control of the reflection direction of radio waves, and can set an appropriate reflection direction for each of the relay devices 3-1 to 3-3 with respect to the moving wireless terminal 4.

[0026] The relay devices 3-1 to 3-3 may be configured by dividing one large-scale RIS.

[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] 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.

[0029] 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.

[0030] 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.

[0031] Therefore, the wireless relay system 1 predicts the position of the moving wireless terminal 4, and based on the position of the wireless terminal 4, assigns each of the relay devices 3-1 to 3-3 to emit radio waves sequentially toward the wireless terminal 4 at predetermined intervals (T), thereby preventing deterioration of the reception characteristics of the wireless terminal due to response delays of the relay devices.

[0032] Next, a description will be given of a specific configuration example of the wireless relay system 1. Fig. 3 is a block diagram showing a configuration example of the wireless relay system 1. Note that although Fig. 3 shows only one relay device 3, the wireless relay system 1 includes multiple relay devices 3.

[0033] The base station 2 has a control unit 20 and a communication unit 22. The control unit 20 controls each unit constituting the base station 2. The communication unit 22 transmits and receives control signals between the relay device 3 and the wireless terminal 4, and also emits radio waves to the relay device 3 for data transmission.

[0034] The relay device 3 includes a communication unit 31, a control unit 32, and a radio wave direction change unit 34. The communication unit 31 transmits and receives control signals to and from the base station 2 and the wireless terminal 4.

[0035] The control unit 32 has an estimation unit 320 and a sequential allocation unit 322, and controls each unit constituting the relay device 3. For example, the control unit 32 controls the direction of radio waves emitted by each of the radio wave direction change units 34 of the multiple relay devices 3.

[0036] The estimation unit 320 estimates the position to which the wireless terminal 4 will move after a predetermined time has elapsed, and outputs the estimation results to the allocation unit 322 in sequence.

[0037] The sequential allocation unit 322 allocates the radio wave direction change units 34 of the multiple relay devices 3 to emit radio waves sequentially toward the wireless terminal 4 at predetermined time intervals based on the position of the wireless terminal 4 estimated by the estimation unit 320.

[0038] The radio wave direction changer 34 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 34 changes the traveling direction of the radio waves so that the radio waves incident from a wireless communication device (or control device) such as the base station 2 are emitted in another direction.

[0039] The radio wave direction changer 34 may also constitute a repeater that amplifies radio waves received from the base station 2 and outputs them in a different direction.

[0040] The wireless terminal 4 has an information acquisition unit 40 and a communication unit 42. The information acquisition unit 40 acquires information necessary for the wireless terminal 4 to estimate its own position and acquire and estimate its own moving speed. The communication unit 42 transmits and receives control signals between the base station 2 and the relay device 3, and emits radio waves to the relay device 3 for data transmission.

[0041] Here, the relay device 3 is provided with the control unit 32 that controls the radio wave direction change unit 34, 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. In other words, the base station 2, the relay device 3, and a network control device (not shown) may be configured as control devices that control multiple radio wave direction change units 34.

[0042] 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.

[0043] 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.

[0044] Next, an operation example of the wireless relay system 1 will be described. Fig. 4 is a diagram schematically showing an operation example of the wireless relay system 1 together with a comparative example. Fig. 4(a) is a diagram showing an operation example of the wireless relay system of the comparative example. Fig. 4(b) is a diagram showing an operation example of the wireless relay system 1 according to one embodiment. Here, the base station 2 is provided with a control unit 32 and performs control to switch the reflection direction of each relay device 3.

[0045] In the example shown in Figure 4(a), for example, the base station acquires terminal information necessary for controlling the reflection direction of radio waves by the relay device, such as location information of the wireless terminal, channel information between the base station and the wireless terminal, channel information between the base station and the relay device (RIS), and channel information between the relay device and the wireless terminal.

[0046] Then, when the base station notifies the relay device (RIS) of its control information, the relay device controls each of the reflecting elements and repeats the operation of setting (RIS element control and setting). However, in the example shown in Figure 4(a), the RIS control interval is long, so it is not possible to ensure sufficient communication quality for moving wireless terminals.

[0047] On the other hand, in the wireless relay system 1 according to one embodiment shown in FIG. 4(b), the base station 2 acquires terminal information necessary for controlling the reflection direction of radio waves by the relay device, such as location information of the wireless terminal 4, channel information between the base station 2 and the wireless terminal 4, channel information between the base station 2 and the relay device 3 (RIS), and channel information between the relay device 3 and the wireless terminal 4.

[0048] The base station 2 notifies the first relay device (RIS1) and the second relay device (RIS2) of the RIS control information. When the base station 2 notifies the first relay device (RIS1) and the second relay device (RIS2) of the RIS control information simultaneously, the base station 2 also notifies the first relay device (RIS1) and the second relay device (RIS2) of the control offset ΔT.

[0049] The base station 2 then repeats transmission to the wireless terminal 4 via the first relay (RIS1) and then via the second relay (RIS2). At this time, the control interval for the first relay (RIS1) and the second relay (RIS2) for transmitting data to the wireless terminal 4 is virtually shortened, making it possible to ensure communication quality for the wireless terminal 4. This is because the response delay time Tc of the first relay (RIS1) and the response delay time Tc of the second relay (RIS2) overlap.

[0050] The operation shown in FIG. 4B can be applied not only to the downlink but also to the uplink.

[0051] 5 is a diagram showing the reception characteristics when radio waves are received by the wireless terminal 4 after passing through each of the relay devices 3-1 to 3-3 in sequence. By passing through each of the relay devices 3-1 to 3-3 in sequence, where the radio waves are effectively reflected, the wireless terminal 4 can ensure communication quality even when moving.

[0052] Next, a method for determining the control offset ΔT by the base station 2 will be described. Fig. 6 is a flowchart showing the method for determining the control offset ΔT by the base station 2. Here, it is assumed that the base station 2 includes a control unit 32 and controls switching of the reflection direction of each relay device 3.

[0053] The base station 2 acquires in advance the response delay Tc of each relay device 3 (S100). The response delay Tc differs depending on each relay device 3.

[0054] Next, the base station 2 acquires the moving speed v of the wireless terminal 4 (S102). Note that the base station 2 may acquire the moving speed by receiving it from the wireless terminal 4. Alternatively, the base station 2 may estimate the moving speed v of the wireless terminal 4 based on the position information of the wireless terminal 4 notified by the wireless terminal 4.

[0055] Next, the base station 2 calculates the control offset ΔT (S104). At this time, the reflected beam width of the RIS of the relay device 3 is set to θ Ｂ, where v is the moving speed of the wireless terminal 4 and d is the distance between the relay device 3 and the wireless terminal 4, the desired offset value when v>0 is calculated using the following equations (1) and (2).

[0056]

[0057] If v=0, then ΔT=0.

[0058] Then, the base station 2 determines the desired number of relay devices 3 (desired number of RIS: N ＲＩＳ ) is calculated by the following equation (3) using a ceiling function (S106).

[0059]

[0060] When ΔT=0, N ＲＩＳ =1.

[0061] Next, a method for determining the number of divisions of a RIS will be described. Multiple relay devices 3 may be configured by dividing one large-scale RIS. Fig. 7 is a flowchart showing a method for determining the number of divisions of a RIS. In this example, the base station 2 is provided with a control unit 32 that controls switching of the reflection direction of each relay device 3.

[0062] The base station 2 determines the number of RISes M available to the wireless terminal 4. ＲＩＳ N ＲＩＳ If the RIS falls below 1, the RIS may be divided and control may be executed (S200).

[0063] The base station 2 has M RISs. ＲＩＳ N ＲＩＳ If it exceeds this, there is no need to divide it (S202).

[0064] In S204, the base station 2 sets the initial value of the division number n to 0.

[0065] In S206, the base station 2 adds 1 to the division number n.

[0066] In S208, the base station 2 determines whether the division number n is equal to the maximum division number n of the RIS. ｍａｘ If it is equal to or less than this, it is determined that division is possible.

[0067] In S210, the base station 2 divides the RIS into n parts.

[0068] In S212, the base station 2 calculates the number of RISs M' available for use by the wireless terminal after dividing the RIS. ＲＩＳ N ＲＩＳ The base station 2 determines whether the number of RISs available to the wireless terminal after the division of the RIS, M', exceeds the number of RISs available to the wireless terminal. ＲＩＳ N ＲＩＳ If it exceeds the limit, the division is terminated, and if it does not exceed the limit, the process returns to S206.

[0069] 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.

[0070] In addition, each function possessed by the base station 2, the relay device 3, and the wireless terminal 4 may be configured in part or in whole by hardware such as a PLD (Programmable Logic Device) or an FPGA (Field Programmable Gate Array), or may be configured as a program executed by a processor such as a CPU.

[0071] For example, the base station 2, the relay device 3, and the wireless terminal 4 can be realized using a computer and a program, and the program can be recorded on a storage medium or provided via a network.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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 and the wireless terminal 4, may also have the same hardware configuration as the relay device 3.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 1...wireless relay system, 2...base station, 3-1 to 3-3...relay device, 4...wireless terminal, 20...control unit, 22...communication unit, 30...reflection element, 31...communication unit, 32...control unit, 34...radio wave direction change unit, 40...information acquisition unit, 42...communication unit, 320...estimation unit, 322...sequential 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 changers that change the direction of travel 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 changers. The control unit includes an estimation unit that estimates the position where the wireless terminal will move after a predetermined time has elapsed, and a sequential assignment unit that, based on the position of the wireless terminal estimated by the estimation unit, assigns each of the radio wave direction changers to sequentially emit radio waves toward the wireless terminal every time a predetermined time has elapsed. A wireless relay system characterized by having the above.

2. The wireless relay system according to claim 1, wherein each of the plurality of radio wave direction changers includes a plurality of reflection elements, and is a plurality of RISs in which the phase of the radio waves reflected by each of the plurality of reflection elements can be controlled.

3. The wireless relay system according to claim 1, wherein each of the plurality of radio wave direction changers includes a plurality of reflection elements, and the plurality of reflection elements together constitute one RIS in which the phase of the radio waves reflected by each of the plurality of reflection elements can be controlled.

4. The wireless relay system according to claim 1, wherein the plurality of radio wave direction changers constitute a plurality of repeaters that amplify the radio waves incident from the wireless communication device and emit them in other directions.

5. In a wireless relay method in which a wireless relay system including a plurality of radio wave direction changers that change the direction of travel of the radio waves so as to emit the radio waves incident from a 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 changers relays radio waves to a moving wireless terminal, an estimation step of estimating the position where the wireless terminal will move after a predetermined time has elapsed, and a sequential assignment step of, based on the position of the wireless terminal estimated in the estimation step, assigning each of the radio wave direction changers to sequentially emit radio waves toward the wireless terminal every time a predetermined time has elapsed. A wireless relay method characterized by including the above.

6. The wireless relay method according to claim 5, wherein each of the plurality of radio wave direction changers includes a plurality of reflection elements, and is a plurality of RISs in which the phase of the radio waves reflected by each of the plurality of reflection elements can be controlled.

7. The method for wireless relaying according to claim 5, characterized in that each of the plurality of radio wave direction changing units includes a plurality of reflecting elements, and the phases of radio waves reflected by each of the plurality of reflecting elements can be controlled to constitute one RIS.

8. A control device for controlling a plurality of relay devices that switch an incident radio wave to a plurality of directions and emit it, and relay the radio wave to a moving wireless terminal, comprising: an estimating unit that estimates a position where the wireless terminal moves after a lapse of a predetermined time; and a sequential assignment unit that assigns, based on the position of the wireless terminal estimated by the estimating unit, each of the relay devices to sequentially emit radio waves toward the wireless terminal every time a predetermined time elapses.

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