Wireless communication system, relay device, communication method, and non-transitory computer-readable storage medium

Abstract

The relay device of the wireless communication system determines a first number of terminals among the terminals under the control of the first base station that should use the relay device, determines a second number of terminals among the terminals under the control of the second base station that should use the relay device, and based on the ratio between the first number and the second number, determines a first time interval during which the first base station uses the relay device and a second time interval during which the second base station uses the relay device. The relay device includes a control unit and a transmission unit. The transmission unit transmits information indicating the first time interval to the first base station and transmits information indicating the second time interval to the second base station.

Description

[Technical Field]

[0001] The present invention relates to a relay device, a communication method, and a non-transitory computer-readable storage medium in a wireless communication system. [Background technology]

[0002] Reconfigurable Intelligent Surface (RIS) is an effective method for controlling the channel by appropriately adjusting the phase and amplitude of electromagnetic signals. Recent research and experiments have proposed various architectures and multiple access techniques.

[0003] The use of RIS is being considered to extend cell coverage. When direct waves from a base station are blocked, the reception level of a radio signal from a user device located at the edge of a cell becomes lower than the reception level of a radio signal in line-of-sight communication.

[0004] In such cases, by combining the beamformed transmission waves sent from the base station and the reflected waves from the RIS, it is possible to increase the reception level of user equipment located in a location where the direct waves from the base station are blocked by buildings, etc. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] M. Hua, Q. Wu, DWK Ng, J. Zhao and L. Yang, “Intelligent Reflecting Surface-Aided Joint Processing Coordinated Multipoint Transmission,” in IEEE Transactions on Communications, vol. 69, no. 3, pp. 1650-1665, March 2021. [Non-patent document 2] B. Di, “Sharing the Surface: RIS-aided Distributed Mechanism Design for Hybrid Beamforming in Multi-cell Multi-user Networks,” IEEE INFOCOM 2021 - IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS), 2021, pp. 1-2, doi: 10.1109 / INFOCOMWKSHPS51825.2021.9484464. Summary of the Invention [Problem to be solved by the invention]

[0006] In a system consisting of multiple cells and multiple base stations, such as cellular communications, it is expected that multiple radio base stations will share the same RIS (reflector) and each perform beamforming toward user terminals under its own cell.

[0007] In such a system, competition for the same RIS is likely to occur.

[0008] The present invention has been made in view of the above points, and an object of the present invention is to provide a method for resolving conflicts between the same RIS while reducing the overhead of control information. [Means for solving the problem]

[0009] According to one aspect of the present invention,

[0010] a first base station;

[0011] a second base station;

[0012] relay device, and

[0013] A wireless communication system including a plurality of terminals,

[0014] a first communication area formed by the first base station overlaps with a second communication area formed by the second base station;

[0015] The relay device

[0016] a receiving unit that receives, from the first base station, values ​​of reception quality reported from a plurality of terminals under the control of the first base station, and receives, from the second base station, values ​​of reception quality reported from a plurality of terminals under the control of the second base station;

[0017] a control unit that determines, based on the reception quality value, a first number of terminals that should use the relay device among terminals under the first base station, determines a second number of terminals that should use the relay device among terminals under the second base station, determines a first time interval during which the first base station uses the relay device and a second time interval during which the second base station uses the relay device based on a ratio between the first number and the second number, and determines a first time position of the first time interval and a second time position of the second time interval based on a priority between the first base station and the second base station;

[0018] a transmitter that transmits information indicating the first time interval and a first time position of the first time interval to the first base station, and transmits information indicating the second time interval and a second time position of the second time interval to the second base station; Equipped with A wireless communication system is provided. [Effects of the Invention]

[0019] According to an embodiment, a method for resolving conflicts for the same RIS is provided while reducing the overhead of control information. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. [Figure 2] FIG. 2 is a diagram illustrating an example of the functional configuration of a base station. [Figure 3] FIG. 2 is a diagram illustrating an example of a functional configuration of a terminal. [Figure 4] FIG. 1 is a diagram illustrating an example of the functional configuration of a Reconfigurable Intelligent Surface (RIS). [Figure 5] FIG. 1 is a diagram showing an example of a plurality of elements included in a RIS. [Figure 6] FIG. 2 is a diagram illustrating an example of the hardware configuration of a base station, a terminal, and a RIS. [Figure 7] FIG. 10 is a diagram illustrating an example in which multiple base stations share the same RIS. [Figure 8] FIG. 10 is a diagram illustrating an example of time resource allocation when sharing a RIS. [Figure 9] 10 is a flowchart illustrating an example of a processing procedure of a wireless communication system. [Figure 10] 10 is a flowchart illustrating an example of a processing procedure of a terminal in a wireless system. DETAILED DESCRIPTION OF THE INVENTION

[0021] Reconfigurable Intelligent Surface (RIS) is considered to be a method to effectively control the radio wave propagation channel by appropriately controlling the phase and amplitude of electromagnetic waves. Recent research and experiments have revealed various architectures and multiple access techniques.

[0022] As an application of RIS, a system in which multiple base stations share a single RIS is considered to be effective for improving communication efficiency. Since RIS is mainly implemented to improve coverage in blocked areas, it is important to enable multiple base stations to share a single RIS. A system in which RIS is placed at each base station can also be considered, but this system is considered to increase interference and costs.

[0023] The application of RIS is evolving alongside existing technologies. The optimization of base station transmit beamforming and phase shift of each RIS, based on the base station transmit power allocation, has been studied. Furthermore, negotiation between base stations has been proposed to achieve consensus on RIS-based beamforming without disclosing information about the terminals under their control. In other words, different base stations accessing a RIS are expected to provide similar reflection responses to terminals after reaching consensus on RIS-based beamforming.

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system according to the embodiment. As illustrated in FIG. 1, the wireless communication system includes a first base station 10A, a second base station 10B, a terminal 20, a Reconfigurable Intelligent Surface (RIS) 30, and a network 40. The first base station 10A and the second base station 10B are connected to the network 40 by wire or wirelessly. The first base station 10A and the second base station 10B are connected to each other so that they can communicate with each other, for example, via an X2 interface. The first base station 10A and the RIS 30 are connected to each other so that they can communicate with each other, by wire or wirelessly. The second base station 10B and the RIS 30 are connected to each other so that they can communicate with each other, by wire or wirelessly. The RIS 30 may also be connected to the network 40 by wire or wirelessly. The first base station 10A, the second base station 10B, and the terminal 20 are all capable of transmitting and receiving signals by performing beamforming.

[0025] The first base station 10A is equipped with a plurality of antenna ports and is capable of forming beams in the vertical direction as well as the horizontal direction. The first base station 10A can impart directionality to beams transmitted from the plurality of antenna ports by multiplying data supplied to each antenna port by a weighting factor of a precoding vector and adjusting the amount of phase rotation (and / or amplitude) for each antenna port.

[0026] Similarly, the second base station 10B is equipped with multiple antenna ports and is capable of forming beams in the vertical direction in addition to the horizontal direction. The second base station 10B can impart directionality to beams transmitted from the multiple antenna ports by multiplying the data supplied to each antenna port by a weighting factor of a precoding vector and adjusting the phase rotation amount (and / or amplitude) for each antenna port. Note that the terminal 20 may also be equipped with multiple antenna ports and may be capable of forming beams in the vertical direction in addition to the horizontal direction.

[0027] The first base station 10A is a base station that forms a communication area outdoors, etc. The first base station 10A realizes high-speed wireless communication with the terminal 20 by transmitting and receiving radio waves in a frequency band used in a fifth-generation mobile communication system (5G), for example. The second base station 10B is a base station that forms a communication area that overlaps with the communication area formed by the first base station 10A. Here, the overlapping of the two communication areas may mean that the communication areas overlap almost completely, that one communication area is included in the other communication area, or that the two communication areas partially overlap. The second base station 10B realizes high-speed wireless communication with the terminal 20 by transmitting and receiving radio waves in a frequency band used in 5G, for example. The terminal 20 is a communication device such as a smartphone, a tablet terminal, or a PC (Personal Computer).

[0028] The first base station 10A can communicate with the terminal 20 directly or via the RIS 30 serving as a relay device. The second base station 10B can communicate with the terminal 20 directly or via the RIS 30 serving as a relay device.

[0029] The RIS 30 is connected to the first base station 10A by wire or wirelessly. The RIS 30 can relay a signal from the terminal 20 to the first base station 10A by changing the reflection direction of a carrier wave carrying the signal from the terminal 20 in accordance with setting information from the first base station 10A. The RIS 30 can also relay a signal from the first base station 10A to the terminal 20 by changing the reflection direction of a carrier wave carrying the signal from the first base station 10A in accordance with setting information from the first base station 10A.

[0030] The RIS 30 is also connected to the second base station 10B by wire or wirelessly. The RIS 30 can relay signals from the terminal 20 to the second base station 10B by changing the reflection direction of a carrier wave carrying the signal from the terminal 20 in accordance with setting information from the second base station 10B. The RIS 30 can relay signals from the second base station 10B to the terminal 20 by changing the reflection direction of a carrier wave carrying the signal from the second base station 10B in accordance with setting information from the second base station 10B.

[0031] When the RIS 30 is connected to the network 40 by wire or wirelessly, the RIS 30 may relay a signal from the terminal 20 to the first base station 10A and / or the second base station 10B by changing the reflection direction of a carrier wave carrying the signal from the terminal 20 in accordance with setting information from the network 40. The RIS 30 may also relay a signal from the first base station 10A to the terminal 20 by changing the reflection direction of a carrier wave carrying the signal from the first base station 10A in accordance with setting information from the network 40. The RIS 30 may also relay a signal from the second base station 10B to the terminal 20 by changing the reflection direction of a carrier wave carrying the signal from the second base station 10B in accordance with setting information from the network 40.

[0032] In the example of Fig. 1, only one terminal 20 is shown. However, the number of terminals 20 is not limited to that in the example of Fig. 1, and more than one terminal 20 may be included. Also, in the example of Fig. 1, a first base station 10A and a second base station 10B are shown, but the number of base stations 10 is not limited to that in the example of Fig. 1, and more than two base stations 10 may be included. Also, in the example of Fig. 1, only one RIS 30 is shown, but the number of RIS 30 is not limited to that in the example of Fig. 1, and more than one RIS 30 may be included.

[0033] Fig. 2 is a diagram showing an example of the functional configuration of the first base station 10A and the second base station 10B. As shown in Fig. 2, both the first base station 10A and the second base station 10B have a transmitting unit 110, a receiving unit 120, and a control unit 130. The functional configuration shown in Fig. 2 is merely an example. The names of the functional divisions and functional units may be any as long as they can perform the operations according to this embodiment.

[0034] The transmitter 110 creates a transmission signal from transmission data and transmits the transmission signal wirelessly. The receiver 120 receives various signals wirelessly and acquires higher layer signals from the received physical layer signals. The receiver 120 also includes a measurement unit that measures the received signals and acquires the received power, etc.

[0035] The control unit 130 controls the base station (the first base station 10A or the second base station 10B). Note that the transmission-related functions of the control unit 130 may be included in the transmitting unit 110, and the reception-related functions of the control unit 130 may be included in the receiving unit 120.

[0036] Fig. 3 is a diagram showing an example of the functional configuration of terminal 20. As shown in Fig. 3, terminal 20 has transmitting unit 210, receiving unit 220, and control unit 230. The functional configuration shown in Fig. 3 is merely an example. The names of the functional divisions and functional units may be any names as long as they can execute the operations according to this embodiment.

[0037] The transmitter 210 includes a function of generating a signal to be transmitted to the base station (the first base station 10A and / or the second base station 10B) and transmitting the signal wirelessly. The receiver 220 includes a function of receiving various signals transmitted from the base station (the first base station 10A and / or the second base station 10B) and acquiring, for example, information of a higher layer from the received signal. The receiver 220 also includes a measurement unit that measures the received signal and acquires the received power, etc.

[0038] The control unit 230 controls the terminal 20. Note that the functions of the control unit 230 related to transmission may be included in the transmitting unit 210, and the functions of the control unit 230 related to reception may be included in the receiving unit 220.

[0039] Fig. 4 is a diagram showing an example of the functional configuration of RIS 30. As shown in Fig. 4, RIS 30 has a transmitting unit 310, a receiving unit 320, a control unit 330, and a plurality of elements 340. The functional configuration shown in Fig. 4 is merely an example. The names of the functional divisions and functional units may be any names as long as they can perform the operations according to this embodiment.

[0040] The transmitter 310 has a function of generating a signal to be transmitted to the base station (the first base station 10A and / or the second base station 10B) and transmitting the signal by wire and / or wirelessly. The receiver 320 has a function of receiving various signals transmitted from the base station (the first base station 10A and / or the second base station 10B) and acquiring, for example, information of a higher layer from the received signal.

[0041] The control unit 330 controls the RIS 30. The multiple elements 340 have a function of changing the reflection direction of a carrier wave carrying a signal from the terminal 20 and / or the base station (the first base station 10A and / or the second base station 10B). The control unit 330 has a function of controlling the reflection phase (or reflection direction) of a reflected wave reflected by each element 340 among the multiple elements 340 in response to, for example, an instruction signal from the first base station 10A and / or the second base station 10B. For example, the control unit 330 controls the reflection phase (or reflection direction) of the reflected wave by controlling the impedance, element spacing, and / or orientation of the reflecting element of each element 340 among the multiple elements 340.

[0042] The elements 340 may be configured as a reflectarray, for example. FIG. 5 is a diagram illustrating an example of the elements 340 configured as a reflectarray. When the elements 340 are configured as a reflectarray, for example, the element spacing between the elements 340 can be changed to change the reflection phase of the reflected wave and the traveling direction of the reflected wave. The method for changing the reflection phase of the reflected wave is not limited to changing the element spacing, but may also be performed by changing the impedance of each of the elements 340. Additionally or alternatively, each of the elements 340 may include a reflecting element for changing the reflection direction of the incident wave, and the reflection direction of the reflected wave may be changed by changing the orientation of the reflecting element. For example, the reflecting element may include an actuator using a microelectromechanical system (MEMS), and the reflection direction of the reflected wave may be controlled by controlling the voltage applied to a piezoelectric material forming the actuator.

[0043] 2 to 4 show functional unit blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. There are no particular limitations on how each functional block is realized. That is, each functional block may be realized using one device that is physically or logically coupled, or may be realized using two or more devices that are physically or logically separated and connected directly or indirectly (for example, by wire, wirelessly, etc.) and these multiple devices.

[0044] For example, the first base station 10A, the second base station 10B, the terminal 20, and the RIS 30 may all function as a computer that performs processing according to this embodiment. FIG. 6 is a diagram illustrating an example of the hardware configuration of the first base station 10A, the second base station 10B, the terminal 20, and the RIS 30. Any of the first base station 10A, the second base station 10B, the terminal 20, and the RIS 30 may be physically configured as a computer device having a drive device 100, an auxiliary storage device 102, a memory device 103, a CPU 104, an interface device 105, and the like. The drive device 100, the auxiliary storage device 102, the memory device 103, the CPU 104, the interface device 105, and the like are connected to each other via a bus B.

[0045] In a computer device, a program for realizing processing is provided by a recording medium 101 such as a CD-ROM. When the recording medium 101 storing the program is set in the drive device 100, the program is installed from the recording medium 101 to the auxiliary storage device 102 via the drive device 100. However, the program does not necessarily have to be installed from the recording medium 101, but may be downloaded from another computer via a network. The auxiliary storage device 102 stores the installed program as well as necessary files, data, etc.

[0046] When an instruction to start a program is received, the memory device 103 reads the program from the auxiliary storage device 102 and stores it. The CPU 104 executes functions related to the computer device in accordance with the program stored in the memory device 103. The interface device 105 is used as an interface for connecting to a network.

[0047] FIG. 7 is a diagram showing an example in which multiple base stations share the same RIS. In the example of FIG. 7, the communication area formed by the first base station 10A overlaps with the communication area formed by the second base station 10B. In the example of FIG. 7, the RIS 30 is used by the first base station 10A during time interval t1 (a first time interval at a first time position). Furthermore, the RIS 30 is used by the second base station 10B during time interval t2 (a second time interval at a second time position). Note that a time interval may be configured by one or more radio frames in the time domain. A radio frame may include multiple subframes. A subframe may further be configured by one or more slots in the time domain. A slot may be configured by one or more symbols in the time domain. The time interval may be a time interval in units of one radio frame, one subframe, one slot, or one symbol.

[0048] 7, the RIS 30 is used by the first base station 10A in a time interval t1. Specifically, among the terminals 20_1 to 20_4 under the control of the first base station 10A, the terminals 20_1 and 20_2 communicate with the first base station 10A within line of sight.

[0049] On the other hand, the communication between the first base station 10A and the terminal 20_3 is non-line-of-sight communication. Also, the communication between the first base station 10A and the terminal 20_4 is non-line-of-sight communication.

[0050] In this case, for example, by relaying communication between the first base station 10A and the terminal 20_3 by the RIS 30, it is possible to improve the quality of communication between the first base station 10A and the terminal 20_3. For example, the first base station 10A controls the directivity of a carrier beam to transmit a carrier wave of a signal to be transmitted to the terminal 20_3 toward the RIS 30. The RIS 30 controls the reflection phase (or reflection direction) of the reflected wave from the plurality of elements 340 in accordance with setting information transmitted from the first base station 10A, thereby transmitting the reflected wave toward the terminal 20_3, thereby improving the quality of communication between the first base station 10A and the terminal 20_3.

[0051] As in the example of Figure 7, when the RIS30 is installed in a fixed location, the first base station 10A can direct the carrier beam to the RIS30 by applying a predetermined precoding matrix to multiple antenna ports.

[0052] 7, for example, it is assumed that the RIS 30 can select any one of direction 1, direction 2, ..., direction n as the reflection direction of a reflected wave. The first base station 10A instructs the RIS 30 to reflect a predetermined reference signal from the first base station 10A in the corresponding direction 1, direction 2, ..., direction n at time 1, time 2, ..., time n. The terminal 20_3 transmits reception power values ​​1, 2, ..., and n of the reference signal received at time 1, time 2, ..., and time n as measurement reports to the first base station 10A. The first base station 10A, upon receiving the measurement report from the terminal 20_3, may compare reception power values ​​1, 2, ..., and n of the reference signal received by the terminal 20_3 at time 1, time 2, ..., and time n, and instruct the RIS 30 on the direction corresponding to the largest reception power value among these reception power values.

[0053] Thus, in the example of Figure 7, the first base station 10A can improve the quality of communication between the first base station 10A and the terminal 20_3 by directing the carrier beam from the first base station 10A toward the RIS 30 and further adjusting the reflection direction of the reflected wave from the RIS 30 to a direction that optimizes the received power at the terminal 20_3.

[0054] Similarly, in the example of FIG. 7, by using the RIS 30 to relay communication between the first base station 10A and the terminal 20_4, it is possible to improve the quality of communication between the first base station 10A and the terminal 20_4.

[0055] 7, the RIS 30 is used by the second base station 10B in a time interval t2. Specifically, among the terminals 20_5 to 20_6 under the control of the second base station 10B, the terminal 20_5 communicates with the second base station 10B within line of sight.

[0056] On the other hand, the communication between the second base station 10B and the terminal 20_6 is non-line-of-sight communication.

[0057] In the example of FIG. 7, the RIS 30 relays the communication between the second base station 10B and the terminal 20_6, thereby making it possible to improve the quality of the communication between the second base station 10B and the terminal 20_6.

[0058] In this manner, multiple base stations 10 may share the RIS 30 on a time-division basis, or, for example, in an orthogonal frequency-division multiplexing (OFDM) based communication system, multiple base stations 10 may share the RIS 30 based on scheduling of time and frequency resources.

[0059] By sharing the RIS 30 based on time division or time and frequency resource scheduling, the terminal 20 can receive services without interference from the RIS 30.

[0060] In the example of Fig. 7, the RIS 30 is used by the first base station 10A in time interval t1, and the RIS 30 is used by the second base station 10B in time interval t2. Below, an example of a method for determining the time interval t1, the time position where the time interval t1 is placed, the time interval t2, and the time position where the time interval t2 is placed in the example of Fig. 7 will be described.

[0061] The first base station 10A and the second base station 10B may determine the time interval t1, the time position where the time interval t1 is placed, the time interval t2, and the time position where the time interval t2 is placed based on the total number of terminals 20 using the RIS 30 and the priority between the first base station 10A and the second base station 10B.

[0062] For example, the first base station 10A may transmit reception quality values ​​reported from multiple terminals 20 under the first base station 10A to the RIS 30, and the RIS 30 may calculate the total number of terminals 20 that should use the RIS 30 among the multiple terminals 20 under the first base station 10A based on the reported reception quality values. The reception quality reported from the terminals 20 may be, for example, a signal-to-interference plus noise ratio (SINR). The RIS 30 may determine whether to use the RIS 30 for the terminal 20 by comparing the SINR value reported from the terminal 20 with a predetermined threshold. For example, if the SINR value reported from the terminal 20 is less than a predetermined threshold, the RIS 30 may determine that the RIS 30 should be used for the terminal 20. Note that the reception quality reported from the terminal 20 is not limited to SINR. For example, Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), Received Signal Strength Indicator (RSSI), etc. may also be used.

[0063] Similarly, the second base station 10B may transmit to the RIS30 the reception quality values ​​reported from the multiple terminals 20 under the second base station 10B, and the RIS30 may calculate the total number of terminals 20 that should use the RIS30 among the multiple terminals 20 under the second base station 10B based on the reported reception quality values.

[0064] For example, the RIS 30 may determine the time intervals t1 and t2 by applying a proportional fairness method based on the total number of terminals 20 that should use the RIS 30 obtained as described above and the reported SINR values. For example, instead of the proportional fairness method, a max-min fairness method, a method based on α-fairness, or the like may be used. Furthermore, the time positions at which the time intervals t1 and t2 are placed may be determined based on the priorities between the first base station 10A and the second base station 10B. For example, if the priority set for the first base station 10A is higher than the priority set for the second base station 10B, the time interval t1 may be placed earlier in the time direction and the time interval t2 may be placed later in the time direction than the time interval t1 in a predetermined time region.

[0065] A more practical method can be considered as a method for determining the time interval t1, the time position where the time interval t1 is placed, the time interval t2, and the time position where the time interval t2 is placed. An example of a practical method will be described below.

[0066] Fig. 8 is a diagram showing an example of allocation of time resources to the first base station 10A and the second base station 10B when sharing the RIS 30 in the example of Fig. 7. The RIS 30 defines a first time interval (and the time position of the first time interval) during which the first base station 10A can access the RIS 30, and a second time interval (and the time position of the second time interval) during which the second base station 10B can access the RIS 30.

[0067] 7, among a plurality of terminals 20 (terminal 20_1, terminal 20_2, terminal 20_3, terminal 20_4) under the first base station 10A, terminal 20_3 and terminal 20_4 are the terminals 20 that should use RIS 30. Also, among a plurality of terminals (terminal 20_5, terminal 20_6) under the second base station 10B, terminal 20_6 is the terminal 20 that should use RIS 30. For convenience of explanation, hereinafter, terminal 20_1, terminal 20_2, terminal 20_3, terminal 20_4, terminal 20_5, and terminal 20_6 will also be referred to as U1, U2, U3, U4, U5, and U6, respectively.

[0068] Since U3 and U4 are terminals 20 that should use RIS30, RIS30 determines that the total number of terminals 20 that should use RIS30 among the multiple terminals 20 under the control of the first base station 10A is 2. Since U6 is terminal 20 that should use RIS30, RIS30 determines that the total number of terminals 20 that should use RIS30 among the multiple terminals 20 under the control of the second base station 10B is 1.

[0069] The RIS 30 determines that the total number of terminals 20 that should use the RIS 30 is three. Based on the total number of terminals 20 that should use the RIS 30 and the priorities of the first base station 10A and the second base station 10B, the RIS 30 determines the time interval (and time position) in which the first base station 10A uses the RIS 30 and the time interval (and time position) in which the second base station 10B uses the RIS 30 during the predetermined time interval shown in Fig. 8. Specifically, the RIS 30 determines the time interval (and time position) in which the RIS 30 is used for U3 and U4 as shown in Fig. 8. The RIS 30 also determines the time interval in which the RIS 30 is used for U6 as shown in Fig. 8.

[0070] 8, the first base station 10A may schedule U1 and U2 in a time interval in which the first base station 10A does not use the RIS 30. The second base station 10B may schedule U5 in a time interval in which the second base station 10B does not use the RIS 30.

[0071] The example in FIG. 8 may be generalized as follows. Let RIS 30 be represented as r, base station 10 as j, and terminal 20 that should use RIS 30 as u. Let A_{u, j}^r be the time interval that can be allocated to terminal 20(u) by base station 10(j). Let D_{u, j}^r be the time interval that can be allocated to terminal 20(u) by RIS 30(r). In this case, the time interval actually allocated to terminal 20(u) may be min{A_{u, j}^r, D_{u, j}^r}.

[0072] FIG. 9 is a flowchart illustrating an example of a processing procedure executed in the wireless communication system.

[0073] As a premise of the processing procedure of FIG. 9, multiple terminals 20 are classified into normal terminals 20 and terminals 20 that should use RIS 30. The classification may be performed by comparing the SINR value reported from each terminal 20 with a predetermined threshold. RIS 30 determines resources (time intervals and time positions of the time intervals) for the first base station 10A to use RIS 30 and resources (time intervals and time positions of the time intervals) for the second base station 10B to use RIS 30. The second base station 10B is a slave base station and uses RIS 30 in the resources (time intervals placed at the time positions) determined by the first base station 10A. Let u1 be a terminal 20 under the control of the first base station 10A that should use RIS 30. Let u2 be a terminal 20 under the control of the second base station 10B that should use RIS 30.

[0074] Let A_{u,j}^r be the time interval scheduled by the base station 10(j) for the terminal 20(u). Here, if r is not zero, the communication between the base station 10(j) and the terminal 20(u) is relayed by the RIS 30(r). If r is zero, the communication between the base station 10(j) and the terminal 20(u) is not relayed by the RIS 30(r). A_{u,j}^r is calculated by the base station 10(j).

[0075] Let D_{u,j}^r be the scheduled time interval for terminal 20(u) by RIS 30(r). D_{u,j}^r is the scheduled time interval involving the use of base station 10(j). D_{u,j}^r is calculated by RIS 30(r).

[0076] Let B_{u,j}^r be the scheduled time interval for terminal 20(u) finally calculated by base station 10(j). B_{u,j}^r is determined based on D_{u,j}^r calculated by RIS 30(r).

[0077] 9, in step S110, the first base station 10A transmits the reception quality values ​​reported from the plurality of terminals 20 under the first base station 10A together with the identification information of each terminal to the RIS 30. In this case, the first base station 10A may determine a first number of terminals 20 that should use the RIS 30, among the terminals 20 under the first base station 10A, by comparing the reception quality values ​​reported from the plurality of terminals 20 under the first base station 10A with a predetermined threshold.

[0078] In step S120, the second base station 10B transmits the reception quality values ​​reported from the plurality of terminals 20 under the second base station 10B together with the identification information of each terminal to the RIS 30. In this case, the second base station 10B may determine a second number of terminals 20 that should use the RIS 30, among the terminals 20 under the second base station 10B, by comparing the reception quality values ​​reported from the plurality of terminals 20 under the second base station 10B with a predetermined threshold.

[0079] In step S130, the RIS 30 compares the reception quality values ​​reported from the plurality of terminals 20 under the first base station 10A with a predetermined threshold to determine a first number of terminals 20 that should use the RIS 30 among the terminals 20 under the first base station 10A. The RIS 30 also compares the reception quality values ​​reported from the plurality of terminals 20 under the second base station 10B with a predetermined threshold to determine a second number of terminals 20 that should use the RIS 30 among the terminals 20 under the second base station 10B. The RIS 30 determines a first time interval during which the first base station 10A can access the RIS 30 and a second time interval during which the second base station 10B can access the RIS 30 based on the first and second numbers.

[0080] Next, in step S140, the RIS 30 prioritizes one or more base stations 10 (in the example of FIG. 9, the first base station 10A and the second base station 10B) that need to use the RIS 30 (the priorities may be set in advance), and determines timing information (for example, a first time position of a first time interval at which the first base station 10A uses the RIS 30 and a second time position of a second time interval at which the second base station 10B uses the RIS 30) based on the priorities. The RIS 30 transmits the determined timing information to the one or more base stations 10. Here, the timing information may be information indicating the time positions of the time intervals that the RIS 30 assigns to the first base station 10A and the second base station 10B. In the example of FIG. 9, in step S150, the RIS30 transmits information indicating the slots in which the first base station 10A can use the RIS30 (e.g., information indicating the length and time position of the slot) to the first base station 10A, and in step S160, transmits information indicating the slots in which the second base station 10B can use the RIS30 (e.g., information indicating the length and time position of the slot) to the second base station 10B.

[0081] In step S170, the first base station 10A calculates an actual scheduled time interval for the terminal 20 that should use the RIS 30 under the control of the first base station 10A. Also, the second base station 10B calculates an actual scheduled time interval for the terminal 20 that should use the RIS 30 under the control of the second base station 10B. In the example of FIG. 9, the first base station 10A calculates min{A_{u1,1}^r, D_{u1,1}^r} to calculate B_{u1,1}^r. Also, the second base station 10B calculates min{A_{u2,2}^r, D_{u2,2}^r} to calculate B_{u2,2}^r.

[0082] In step S180, the first base station 10A transmits setting information related to the phase and amplitude required for communication via the RIS 30 with the terminal 20 that should use the RIS 30 under the first base station 10A, together with scheduling information (information indicating B_{u1, 1}^r in the example of FIG. 9), to the RIS 30. The first base station 10A uses the RIS 30 to communicate with the terminal 20 that should use the RIS 30 under the first base station 10A during time interval t1 (B_{u1, 1}^r in the example of FIG. 9).

[0083] In step S190, the second base station 10B transmits to the RIS 30 setting information related to the phase and amplitude required for communication via the RIS 30 with the terminal 20 that should use the RIS 30 under the second base station 10B, together with scheduling information (information indicating B_{u2, 2}^r in the example of FIG. 9). The second base station 10B uses the RIS 30 to communicate with the terminal 20 that should use the RIS 30 under the second base station 10B, during time interval t2 (B_{u2, 2}^r in the example of FIG. 9).

[0084] Next, an example of a processing procedure of the terminal 20 under the control of the first base station 10A will be described with reference to Fig. 10. Note that the example of Fig. 10 is based on the premise that the terminal 20 is equipped with multiple antenna ports and is capable of forming beams in multiple directions.

[0085] In step S210, the terminal 20 transmits information indicating a first reception power value of the first signal received from the first base station 10A as a measurement report to the first base station 10A. The first base station 10A receives the measurement report and compares the first reception power value with a first threshold.

[0086] If the first received power value is equal to or greater than the first threshold, the first base station 10A determines to continue communication with the terminal 20. In other words, the first base station 10A determines not to have the RIS 30 relay the communication between the first base station 10A and the terminal 20.

[0087] If the first received power value is less than the first threshold, the first base station 10A causes the terminal 20 to report information indicating the second received power value of the second signal from the second base station 10B.

[0088] If the second received power value is equal to or greater than the first threshold, the first base station 10A may transmit a handover command to the terminal 20 to hand over the terminal 20 to the second base station 10B.

[0089] In step S220, if the second received power value is less than the first threshold, the first base station 10A determines to communicate with the terminal 20 via the RIS 30. In other words, the first base station 10A determines to have the RIS 30 relay the communication between the first base station 10A and the terminal 20.

[0090] In step S230, the first base station 10A transmits a predetermined reference signal to the RIS 30 and, based on a measurement report received from the terminal 20, instructs the RIS 30 on the direction in which the received power at the terminal 20 is maximized. For example, the first base station 10A instructs the RIS 30 to reflect a predetermined reference signal from the first base station 10A in the corresponding direction 1, direction 2, ..., direction n at time 1, time 2, ..., time n. The terminal 20 transmits received power values ​​1, 2, ..., and n of the reference signal received at time 1, time 2, ..., time n to the first base station 10A as measurement reports. The first base station 10A, having received the measurement report from the terminal 20, may compare received power values ​​1, 2, ..., and n of the reference signal received by the terminal 20 at time 1, time 2, ..., time n, and instruct the RIS 30 on the direction corresponding to the largest received power value among these received power values.

[0091] In step S240, the first base station 10A instructs the terminal 20 to transmit a predetermined uplink reference signal (which may be a Sounding Reference Signal (SRS)) in corresponding directions 1, 2, ..., and n at times 1, 2, ..., and n. For example, in response to receiving the instruction from the first base station 10A, the terminal 20 may transmit an uplink reference signal at time 1 by applying a precoding vector V1 corresponding to direction 1 (the uplink reference signal may include information indicating the precoding vector V1). Similarly, the terminal 20 may transmit an uplink reference signal at time 2 by applying a precoding vector V2 corresponding to direction 2 (the uplink reference signal may include information indicating the precoding vector V2). Similarly, the terminal 20 may transmit an uplink reference signal at time n by applying a precoding vector Vn corresponding to direction n (the uplink reference signal may include information indicating the precoding vector Vn).

[0092] In step S250, the first base station 10A compares received power value 1, received power value 2, ..., received power value n of predetermined uplink reference signals received at time 1, time 2, ..., time n, and identifies the direction corresponding to the largest received power value among these received power values. For example, the first base station 10A may identify the precoding vector V1 applied by the terminal 20A at time 1 based on information included in the uplink reference signal received from the terminal 20A at time 1. Similarly, the first base station 10A may identify the precoding vector V2 applied by the terminal 20A at time 2 based on information included in the uplink reference signal received from the terminal 20A at time 2. Similarly, the first base station 10A may identify the precoding vector Vn applied by the terminal 20A at time n based on information included in the uplink reference signal received from the terminal 20A at time n. Then, the first base station 10A may compare received power value 1, received power value 2, ..., received power value n of the uplink reference signal received at time 1, time 2, ..., time n, and identify the precoding vector corresponding to the maximum received power value among these received power values.

[0093] In step S260, the first base station 10A schedules communication between the first base station 10A and the terminal 20, and determines a time interval (which may be a time slot) to be used for communication between the first base station 10A and the terminal 20 and the time position of the time interval (which may be the time position of the time slot).

[0094] In step S270, the first base station 10A notifies the terminal 20 of scheduling information including information indicating the direction determined in step S250 and information indicating the time intervals and time positions of the time intervals determined in step S260. For example, the first base station 10A may include information indicating time slots and time positions of the time slots for communication between the first base station 10A and the terminal in the scheduling information. Furthermore, the first base station 10A may notify the terminal 20 of a precoding vector corresponding to the maximum received power value among multiple received power values ​​of the uplink reference signal, as information indicating the direction determined in step S250.

[0095] In step S280, the first base station 10A and the terminal 20 communicate with each other via the RIS 30 based on the scheduling information. For example, the first base station 10A and the terminal 20 may communicate with each other via the RIS 30 in a time slot located at the notified time position based on information indicating the time slot and the time position of the time slot notified to the terminal 20 by the first base station 10A in step S270. Furthermore, when transmitting an uplink signal to the first base station 10A via the RIS 30 in a time slot located at the time position notified by the first base station 10A, the terminal 20 may transmit the uplink signal by applying the precoding vector indicated in the scheduling information received from the first base station 10A in step S270.

[0096] 10, in steps S210 and S220, the first base station 10A determines that the RIS 30 should relay the communication between the first base station 10A and the terminal 20, but the embodiment is not limited to this example. For example, the RIS 30 may determine that the RIS 30 should relay the communication between the first base station 10A and the terminal 20 by the same process as in step S130 in FIG.

[0097] As described above, in the embodiment of the present invention, a resource allocation technique, ie, the utilization time of a Reconfigurable Intelligent Surface (RIS), in a wireless communication technique using the RIS is described.

[0098] In the embodiment of the present invention, a system consisting of multiple cells and multiple base stations, such as cellular communications, is assumed, and it is also assumed that multiple radio base stations share the same RIS and perform beamforming for user terminals within their own cell.

[0099] In such a system, it is possible that conflicts in the use of RIS may occur. In conventional methods, for all RISs in the system, the weight matrices (corresponding to all terminals communicating) corresponding to the beams formed by the RIS must be exchanged between base stations for coordination. This method has the problem that the processing is complicated and it is not possible to completely avoid interference between reflectors.

[0100] Therefore, in the embodiment of the present invention, only information about terminals using the RIS is shared between wireless base stations, and each wireless base station calculates the time for which it will use the RIS based on the shared information, thereby reducing the amount of control information sent and received.In addition, it is possible to completely avoid interference without causing contention for using the RIS. [Explanation of symbols]

[0101] 10A First base station 10B Second base station 20 terminals 30 RIS 40 Network 110 Transmitter 120 Receiver 130 Control Unit 210 Transmitter 220 Receiving unit 230 Control Unit 310 Transmitter 320 Receiving Unit 330 Control Unit 340 Elements 100 Drive device 101 Recording media 102 Auxiliary storage 103 Memory Device 104 CPU 105 Interface Device B Bus

Claims

1. A wireless communication system including a first base station, a second base station, a relay device, and a plurality of terminals, wherein a first communication area formed by the first base station overlaps with a second communication area formed by the second base station; The relay device a receiving unit that receives, from the first base station, values ​​of reception quality reported from a plurality of terminals under the control of the first base station, and receives, from the second base station, values ​​of reception quality reported from a plurality of terminals under the control of the second base station; a control unit that determines, based on the reception quality value, a first number of terminals that should use the relay device among terminals under the first base station, determines a second number of terminals that should use the relay device among terminals under the second base station, determines a first time interval during which the first base station uses the relay device and a second time interval during which the second base station uses the relay device based on a ratio between the first number and the second number, and determines a first time position of the first time interval and a second time position of the second time interval based on a priority between the first base station and the second base station; a transmitter that transmits information indicating the first time interval and a first time position of the first time interval to the first base station, and transmits information indicating the second time interval and a second time position of the second time interval to the second base station; Equipped with Wireless communication system.

2. The relay device is a Reconfigurable Intelligent Surface (RIS) that includes a plurality of reflecting elements and is capable of changing the direction of propagation of reflected waves.

10. The wireless communication system of claim 1.

3. the control unit compares a value indicating a quality of communication between each terminal under the control of the first base station and the first base station with a predetermined threshold to determine whether the terminal should communicate via the relay device, and compares a value indicating a quality of communication between each terminal under the control of the second base station and the second base station with the predetermined threshold to determine whether the terminal should communicate via the relay device.

10. The wireless communication system of claim 1.

4. A relay device in a wireless communication system including a first base station, a second base station, a relay device, and a plurality of terminals, wherein a first communication area formed by the first base station overlaps with a second communication area formed by the second base station; The relay device a receiving unit that receives, from the first base station, values ​​of reception quality reported from a plurality of terminals under the control of the first base station, and receives, from the second base station, values ​​of reception quality reported from a plurality of terminals under the control of the second base station; a control unit that determines, based on the reception quality value, a first number of terminals that should use the relay device among terminals under the first base station, determines a second number of terminals that should use the relay device among terminals under the second base station, determines a first time interval during which the first base station uses the relay device and a second time interval during which the second base station uses the relay device based on a ratio between the first number and the second number, and determines a first time position of the first time interval and a second time position of the second time interval based on a priority between the first base station and the second base station; a transmitter that transmits information indicating the first time interval and a first time position of the first time interval to the first base station, and transmits information indicating the second time interval and a second time position of the second time interval to the second base station; Equipped with Relay device.

5. A communication method using a relay device in a wireless communication system including a first base station, a second base station, a relay device, and a plurality of terminals, the method comprising: forming a first communication area of ​​the first base station overlapping with a second communication area of ​​the second base station; The communication method includes: receiving, from the first base station, values ​​of reception quality reported from a plurality of terminals under the control of the first base station, and receiving, from the second base station, values ​​of reception quality reported from a plurality of terminals under the control of the second base station; determining a first number of terminals that should use the relay device among terminals under the first base station based on the reception quality value, determining a second number of terminals that should use the relay device among terminals under the second base station based on the ratio between the first number and the second number, determining a first time interval during which the first base station uses the relay device and a second time interval during which the second base station uses the relay device, and determining a first time position of the first time interval and a second time position of the second time interval based on a priority between the first base station and the second base station; a transmitter that transmits information indicating the first time interval and a first time position of the first time interval to the first base station, and transmits information indicating the second time interval and a second time position of the second time interval to the second base station; Equipped with Communication method.

6. A non-transitory computer-readable storage medium storing a program, the program being a wireless communication system including a first base station, a second base station, a relay device, and a plurality of terminals, the wireless communication system including a first communication area formed by the first base station overlapping with a second communication area formed by the second base station, when the program is executed by the relay device, the program causing the relay device to: receiving, from the first base station, values ​​of reception quality reported from a plurality of terminals under the control of the first base station, and receiving, from the second base station, values ​​of reception quality reported from a plurality of terminals under the control of the second base station; determining a first number of terminals that should use the relay device among terminals under the first base station based on the reception quality value, determining a second number of terminals that should use the relay device among terminals under the second base station based on the ratio between the first number and the second number, determining a first time interval during which the first base station uses the relay device and a second time interval during which the second base station uses the relay device, and determining a first time position of the first time interval and a second time position of the second time interval based on a priority between the first base station and the second base station; a transmitter that transmits information indicating the first time interval and a first time position of the first time interval to the first base station, and transmits information indicating the second time interval and a second time position of the second time interval to the second base station; Execute A non-transitory computer-readable storage medium.

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