Wireless relay system and wireless relay method

Abstract

A wireless relay system according to an embodiment executes processing for estimating a position to which a wireless terminal moves after a lapse of a predetermined time, calculating respective candidates for phase rotation patterns of reflection elements each capable of reflecting a radio wave toward the wireless terminal that has moved to the estimated position, calculating received power at the estimated position of the wireless terminal for each of the calculated candidates for the phase rotation patterns of the reflection elements, calculating the number of reflection elements that need to switch a phase rotation amount if switching from the current respective phase rotation patterns of the reflection elements to the calculated respective candidates for the phase rotation patterns of the reflection elements has been done, selecting the respective phase rotation patterns of the reflection elements in which the calculated received power is equal to or more than a predetermined value and the number of reflection elements that need to switch the calculated phase rotation amount becomes minimum, and switching the respective phase rotation patterns of the reflection elements to the selected phase rotation patterns.

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 in which radio waves emitted by a wireless communication device are reflected by a RIS equipped with a plurality of reflecting elements to relay the radio waves to a moving wireless terminal, the wireless relay system comprising: an estimation unit that estimates a position to which the wireless terminal will move after a predetermined time has elapsed; a candidate calculation unit that calculates candidates for phase rotation patterns of the reflecting elements that can reflect radio waves toward the wireless terminal that has moved to the position estimated by the estimation unit; a received power calculation unit that calculates received power at the position of the wireless terminal estimated by the estimation unit for each of the candidates for phase rotation patterns of the reflecting elements calculated by the candidate calculation unit; a switching number calculation unit that calculates the number of reflecting elements for which the amount of phase rotation needs to be switched when the phase rotation pattern of each reflecting element is switched to the candidate phase rotation pattern of each reflecting element calculated by the candidate calculation unit from the phase rotation pattern of each reflecting element; a selection unit that selects the phase rotation pattern of each reflecting element for which the received power calculated by the received power calculation unit is equal to or greater than a predetermined value and for which the number of reflecting elements for which the amount of phase rotation calculated by the switching number calculation unit needs to be switched is the smallest; and a switching execution unit that executes processing to switch the phase rotation pattern of each reflecting element to the phase rotation pattern selected by the selection unit.

[0009] Furthermore, a wireless relay method according to one aspect of the present invention is a wireless relay method in which a RIS having a plurality of reflecting elements reflects radio waves emitted by a wireless communication device and relays the radio waves to a moving wireless terminal, the method comprising: an estimation step of estimating a position to which the wireless terminal will move after a predetermined time has elapsed; a candidate calculation step of calculating candidates for phase rotation patterns of the reflecting elements that can reflect radio waves toward the wireless terminal that has moved to the position estimated by the estimation step; a received power calculation step of calculating received power at the position of the wireless terminal estimated by the estimation step for each of the candidates for phase rotation patterns of the reflecting elements calculated by the candidate calculation step; a switching number calculation step of calculating the number of reflecting elements for which the amount of phase rotation needs to be switched when the phase rotation pattern of each of the reflecting elements is switched to the candidate phase rotation pattern of each of the reflecting elements calculated in the candidate calculation step from the phase rotation pattern of each of the reflecting elements; a selection step of selecting a phase rotation pattern for each of the reflecting elements for which the received power calculated in the received power calculation step is equal to or greater than a predetermined value and which minimizes the number of reflecting elements for which the amount of phase rotation calculated in the switching number calculation step needs to be switched; and a switching execution step of executing a process of switching the phase rotation pattern of each of the reflecting elements to the phase rotation pattern selected in the selection step.

[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. 2 is a diagram schematically illustrating an operation in which a wireless relay system controls multiple reflecting elements in a RIS of a relay device to shorten the response time of the relay device; FIG. 3 is a diagram illustrating an element phase pattern θt that reflects radio waves at a predetermined reflection angle; FIG. 4 is a diagram illustrating an element phase pattern θt+1 that reflects radio waves in a direction different from the example shown in FIG. 4; FIG. 5 is a graph illustrating a relationship between reception characteristics at a wireless terminal when the response delay of the relay device is long; and FIG. 6 is a graph illustrating a relationship between reception characteristics at a wireless terminal when the response delay of the relay device is short. A functional block diagram illustrating functions of a relay device; A flowchart illustrating a method for acquiring element phase pattern candidates; A flowchart illustrating a process for selecting a pattern for turning on and off each of the reflecting elements of the relay device based on a reflection gain threshold of the relay device; and FIG. 7 is a diagram illustrating an example of a hardware configuration of a relay device according to an embodiment.

[0012] An overview of a wireless relay system 1 according to one embodiment will be described. Fig. 1 is a diagram illustrating an overview of the wireless relay system 1 according to one embodiment. As shown in Fig. 1, in the wireless relay system 1, a relay device 3 reflects radio waves emitted by a base station 2, which is a wireless communication device, and relays the radio waves to a moving wireless terminal 4.

[0013] The relay device 3 has a RIS with a plurality of reflecting elements 30 and has a function of switching the reflection direction of radio waves. The wireless relay system 1 relays radio waves using the RIS, improving the communication quality from the base station 2 to the wireless terminal 4.

[0014] 2 is a diagram illustrating an operation in which the wireless relay system 1 controls a plurality of reflecting elements 30 in the RIS of the relay device 3 to reduce the response time of the relay device 3. The control of the plurality of reflecting elements 30 may be performed by the base station 2 or by the relay device 3 itself.

[0015] The white or black color of each reflective element 30 indicates whether the phase switching is on or off. The amount of phase rotation that each reflective element 30 can take may be multi-valued.

[0016] For example, when the base station 2 controls a plurality of reflecting elements 30, the base station 2 prepares candidate element phase patterns for the plurality of reflecting elements 30 and selects the candidate with the smallest number of reflecting elements that need to switch the element phase.

[0017] In the example shown in Figure 2, the base station 2 selects, from among multiple pattern candidates, pattern candidate #2, which has an improvement characteristic for the received power of the wireless terminal 4 that is equal to or greater than a predetermined value and has the smallest number of reflecting elements that need to switch the element phase.

[0018] As a result, the wireless relay system 1 can reduce the number of reflecting elements that switch the element phase of the relay device 3, and can shorten the response delay in the RIS of the relay device 3, thereby improving the tracking performance for the wireless terminal 4.

[0019] 3A and 3B are diagrams schematically illustrating an example of control of a plurality of reflecting elements in a RIS of a comparative example. Fig. 3A is a diagram illustrating an element phase pattern θt that reflects radio waves at a predetermined reflection angle. Fig. 3B is a diagram illustrating an element phase pattern θt+1 that reflects radio waves in a direction different from the example shown in Fig. 3A.

[0020] In the example shown in Fig. 3, the phases of all the reflecting elements in the RIS are adjusted, which increases the response time for switching the reflection direction of the radio waves. In this case, the tracking performance of the RIS for the wireless terminal deteriorates, and communication quality may not be ensured.

[0021] 4A and 4B 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. 4A is a graph showing the relationship between the response delay of the relay device and the reception characteristics of a wireless terminal when the response delay of the relay device is long. Fig. 4B is a graph showing the relationship between the response delay of the relay device and the reception characteristics of a wireless terminal when the response delay of the relay device is short.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] Therefore, the wireless relay system 1 prevents degradation of the reception characteristics of wireless terminals due to response delays of the relay devices by limiting the number of reflecting elements that switch the element phase of the relay device 3.

[0026] Next, a specific configuration example of the relay device 3 will be described when the relay device 3 itself controls the reflection direction of the radio waves by the relay device 3. Fig. 5 is a functional block diagram illustrating the functions of the relay device 3. As shown in Fig. 5, the relay device 3 includes, for example, a RIS 31 and a control unit 32.

[0027] The RIS 31 has a plurality of reflecting elements 30 and switches the direction of reflection of radio waves under the control of a control unit 32 .

[0028] The control unit 32 includes, for example, an estimation unit 321 , a candidate calculation unit 322 , a received power calculation unit 323 , a switching number calculation unit 324 , a selection unit 325 , and a switching execution unit 326 , and controls the RIS 31 .

[0029] The estimation unit 321 estimates the position to which the wireless terminal 4 will move after a predetermined time has elapsed, and outputs the estimation result to the candidate calculation unit 322 .

[0030] The candidate calculation unit 322 calculates candidates for the phase rotation pattern of each reflecting element 30 that can reflect radio waves toward the wireless terminal 4 that has moved to the position estimated by the estimation unit 321, and outputs the calculated results to the received power calculation unit 323.

[0031] The received power calculation unit 323 calculates the received power at the position of the wireless terminal 4 estimated by the estimation unit 321 for each candidate phase rotation pattern of each reflecting element 30 calculated by the candidate calculation unit 322, and outputs the calculation result to the switching number calculation unit 324.

[0032] The switching number calculation unit 324 calculates the number of reflecting elements 30 whose phase rotation amount needs to be switched when switching from the current phase rotation pattern of each reflecting element 30 to the candidate phase rotation pattern of each reflecting element 30 calculated by the candidate calculation unit 322, and outputs the calculation result to the selection unit 325.

[0033] The selection unit 325 selects a phase rotation pattern for each reflecting element 30 such that the received power calculated by the received power calculation unit 323 is equal to or greater than a predetermined value and the number of reflecting elements 30 that need to switch the phase rotation amount calculated by the switching number calculation unit 324 is the smallest, and outputs the selected result to the switching execution unit 326.

[0034] The switching execution unit 326 executes a process of switching the phase rotation pattern of each reflecting element 30 to the phase rotation pattern selected by the selection unit 325 , and controls the RIS 31 .

[0035] The estimation unit 321, the candidate calculation unit 322, the received power calculation unit 323, the switching number calculation unit 324, the selection unit 325, and the switching execution unit 326 may be provided in the base station 2 or in the relay device 3.

[0036] In addition, the information necessary to calculate the incident angle and reflection angle of the radio wave used to switch the phase rotation amount of each reflecting element 30, and the element phase pattern, may be acquired by the relay device 3 from a network (such as the base station 2), or the relay device 3 may have the functions necessary to acquire the information and acquire it itself.

[0037] In this way, the wireless relay system 1 can prevent a decrease in communication quality even when relaying wireless communications by switching the direction in which radio waves travel, by reducing the number of reflecting elements that switch the element phase of the relay device 3.

[0038] Next, a description will be given of the processing executed by the wireless relay system 1. Fig. 6 is a flowchart showing a method for acquiring element phase pattern candidates. Here, a pattern is used that turns on and off all reflecting elements that can reflect in a desired direction.

[0039] First, for example, the base station 2 acquires information on the incident angle and reflection angle of the radio wave (S100), and calculates all element phase patterns that can reflect in the desired direction (S102).

[0040] Next, the base station 2 calculates the reflection gain for all the calculated patterns (S104), and calculates the number of reflecting elements that need to be switched for all the calculated patterns (S106).

[0041] Then, the base station 2 calculates the maximum reflection gain G ０ is calculated (S108), and G ０ A pattern that satisfies -Gn<ΔG and minimizes the number of reflecting elements that need to be switched is selected (S110), where ΔG indicates the threshold value of the allowable reflection gain.

[0042] FIG. 7 is a flowchart showing a process for selecting a pattern for turning on and off each of the reflecting elements 30 of the repeater 3 based on, for example, the reflection gain threshold of the repeater 3.

[0043] For example, the base station 2 acquires information on the radio wave incident angle and reflection angle (S200), and calculates the element phase pattern (pattern #0) that is likely to provide the best improvement characteristics (S202).

[0044] Next, the base station 2 calculates the reflection gain G ０ is calculated (S204), the number of reflecting elements that need to be switched is calculated (S206), and this is set as a candidate pattern (S208).

[0045] Then, base station 2 ０ It is determined whether an element phase pattern that satisfies -Gn<ΔG can be calculated (S210), and if it can be calculated (S210: Yes), proceed to processing S212, and if it cannot be calculated (S210: No), proceed to processing S220.

[0046] Next, the base station 2 calculates a different element phase pattern in S212, and calculates the reflection gain Gn for that pattern in S214.

[0047] Then, the base station 2 calculates the number of reflecting elements that need to be switched (S216), and sets the number as a candidate pattern (S218). This process is repeated.

[0048] In S220, the base station 2 selects the pattern that has the fewest number of reflecting elements that need to be switched.

[0049] In this way, the wireless relay system 1 selects the pattern with the fewest number of reflecting elements that require switching, so that even if the direction of radio waves is switched to relay wireless communication, a decrease in communication quality can be prevented.

[0050] 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.

[0051] 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.

[0052] 8 is a diagram illustrating an example of the hardware configuration of the relay device 3 according to one embodiment. As illustrated in FIG. 8, 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.

[0053] The input unit 600 is, for example, a keyboard and a mouse. The output unit 610 is, for example, a display device. The communication unit 620 is, for example, a wired or wireless network interface.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 1...wireless relay system, 2...base station, 3...relay device, 4...wireless terminal, 30...reflection element, 31...RIS, 32...control unit, 321...estimation unit, 322...candidate calculation unit, 323...received power calculation unit, 324...switching number calculation unit, 325...selection unit, 326...switching execution 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 reflects radio waves radiated by a wireless communication device using a RIS having a plurality of reflection elements and relays the radio waves to a moving wireless terminal, an estimation unit that estimates the position where the wireless terminal will move after a predetermined time has elapsed; a candidate calculation unit that calculates candidates for the phase rotation pattern of each of the reflection elements that can reflect radio waves toward the wireless terminal that has moved to the position estimated by the estimation unit; a received power calculation unit that calculates the received power at the position of the wireless terminal estimated by the estimation unit for each of the candidates for the phase rotation pattern of each of the reflection elements calculated by the candidate calculation unit; a switching number calculation unit that calculates, for each of the reflection elements, the number of reflection elements that need to switch the phase rotation amount when switching from the current phase rotation pattern of each of the reflection elements to the candidate for the phase rotation pattern of each of the reflection elements calculated by the candidate calculation unit; a selection unit that selects the phase rotation pattern of each of the reflection elements in which the received power calculated by the received power calculation unit is equal to or greater than a predetermined value and the number of reflection elements that need to switch the phase rotation amount calculated by the switching number calculation unit is minimized; and a switching execution unit that executes a process of switching the phase rotation pattern of each of the reflection elements to the phase rotation pattern selected by the selection unit. A wireless relay system characterized by having the above components.

2. The wireless relay system according to claim 1, characterized in that the estimation unit, the candidate calculation unit, the received power calculation unit, the switching number calculation unit, the selection unit, and the switching execution unit are provided in the wireless communication device.

3. The wireless relay system according to claim 1, characterized in that the estimation unit, the candidate calculation unit, the received power calculation unit, the switching number calculation unit, the selection unit, and the switching execution unit are provided in the RIS.

4. The wireless relay system according to any one of claims 1 to 3, characterized in that the phase rotation amount that each of the reflection elements can take is multi-valued.

5. In a wireless relay method in which radio waves radiated by a wireless communication device are reflected by a RIS having a plurality of reflection elements and relayed to a moving wireless terminal, an estimation step of estimating a position to which the wireless terminal moves after a lapse of a predetermined time, a candidate calculation step of calculating a candidate of a phase rotation pattern of each of the reflection elements capable of reflecting radio waves toward the wireless terminal that has moved to the position estimated in the estimation step, a received power calculation step of calculating received power at the position of the wireless terminal estimated in the estimation step for each of the candidates of the phase rotation patterns of the respective reflection elements calculated in the candidate calculation step, a switching number calculation step of calculating, for each of the reflection elements, the number of reflection elements that need to switch the phase rotation amount when switching from the current phase rotation pattern of each of the reflection elements to the candidate of the phase rotation pattern of each of the reflection elements calculated in the candidate calculation step, a selection step of selecting a phase rotation pattern of each of the reflection elements in which the received power calculated in the received power calculation step is equal to or greater than a predetermined value and the number of the reflection elements that need to switch the phase rotation amount calculated in the switching number calculation step is minimized, and a switching execution step of executing a process of switching the phase rotation pattern of each of the reflection elements to the phase rotation pattern selected in the selection step. The wireless relay method is characterized by including these steps.

6. The wireless relay method according to claim 5, wherein the estimation step, the candidate calculation step, the received power calculation step, the switching number calculation step, the selection step, and the switching execution step are performed by the wireless communication device.

7. The wireless relay method according to claim 5, wherein the estimation step, the candidate calculation step, the received power calculation step, the switching number calculation step, the selection step, and the switching execution step are performed by the RIS.

8. The wireless relay method according to any one of claims 5 to 7, wherein the phase rotation amount that each of the reflection elements can take is a multi-value.

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