Wireless communication system, base station, communication method, and non-transitory computer-readable storage medium

Abstract

The first base station of the wireless communication system includes: a receiving unit that receives information indicating the number of terminals to communicate via the relay device among the terminals under the control of the second base station; a control unit that calculates the sum of the number indicated by the information and the number of terminals to communicate via the relay device among the terminals under the control of the first base station as the total number of terminals to communicate via the relay device, and based on the total number, determines a first time interval during which the first base station uses the relay device and determines a second time interval during which the second base station uses the relay device; and a transmitting unit that transmits information indicating the second time interval to the second base station.

Description

Technical Field

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

Background Art

[0002] Reconfigurable Intelligent Surface (RIS) is an effective method for controlling a channel by appropriately adjusting the phase and amplitude of an electromagnetic signal. In recent research and experiments, various architectures and multiple access technologies have been proposed.

[0003] For extending the coverage of a cell, using RIS has been considered. The reception level of a radio signal of a user device located at the edge of a cell becomes lower compared to the reception level of a radio signal in line-of-sight communication when the direct wave from a base station is blocked.

[0004] In such a case, it is possible to increase the reception level of a user device placed in a location where the direct wave from a base station is blocked by a building or the like by a combination of a beamformed transmission wave transmitted from the base station and a reflected wave from RIS.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In a system composed of multiple cells and multiple base stations, such as cellular communication, it is assumed that multiple radio base stations share the same RIS (reflecting plate) and perform beamforming towards user terminals under their respective cells.

[0007] In such a system, it is considered that competition of the same RIS occurs.

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

Means for Solving the Problems

[0009] According to one aspect of the present invention, there is provided 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 first base station includes a first receiving unit that receives, from the second base station, information indicating the number of terminals to communicate via the relay device among one or more terminals under the second base station, Calculate the sum of the number indicated by the received information and the number of terminals to communicate via the relay device among one or more terminals under the first base station, and use the sum as the total number of terminals to communicate via the relay device. Based on the total number, determine a first time interval during which the first base station uses the relay device, and determine a second time interval during which the second base station uses the relay device, where the second time interval is other than the first time interval. Based on the priority set for the second base station, determine a first time position of the first time interval and a second time position of the second time interval by a first control unit. A first transmission unit that transmits information indicating the second time interval and the second time position of the second time interval to the second base station. Comprising During the first time interval at the first time position, the first control unit schedules a first communication between each terminal to communicate via the relay device among one or more terminals under the first base station and the first base station, where the first communication is via the relay device. The second base station A second transmission unit that transmits information indicating the number of terminals to communicate via the relay device among one or more terminals under the second base station to the first base station. A second reception unit that receives information indicating the second time interval and the second time position of the second time interval from the first base station. During the second time interval at the second time position, a second control unit schedules a second communication between each terminal to communicate via the relay device among one or more terminals under the second base station and the second base station, where the second communication is via the relay device. Comprising A wireless communication system.

Advantages of the Invention

[0010] According to the embodiment, a method for resolving the conflict of the same RIS while reducing the overhead of control information is provided.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0012] Reconfigurable Intelligent Surface (RIS) is considered to be a method of effectively controlling a radio wave propagation channel by appropriately controlling the phase and amplitude of an electromagnetic wave. According to recent research and experiments, various architectures and multiple access technologies have been found.

[0013] As an application of the RIS, a method in which a plurality of base stations share a single RIS is considered to be effective for improving communication efficiency. Since the RIS is mainly implemented to improve the coverage of blocked areas, it is important to enable a plurality of base stations to share a single RIS. Although a method of arranging the RIS for each base station is also conceivable, in this method, interference and cost are considered to increase.

[0014] The applications of RIS are evolving along with existing technologies. The optimization of the transmission beamforming of the base station and the phase shift of each RIS has been studied on the premise of the allocation of the transmission power of the base station. Also, regarding RIS-based beamforming, negotiation between base stations has been proposed to obtain consensus between base stations without revealing information on terminals under the control of the base station. That is, it is assumed that different base stations accessing the RIS perform a similar reflection response to the terminal after obtaining consensus between the base stations regarding RIS-based beamforming.

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a wireless communication system in an embodiment. As shown 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, a network 40, and the like. 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 communicably connected via, for example, an X2 interface. The first base station 10A and the RIS 30 are communicably connected by wire or wirelessly. The second base station 10B and the RIS 30 are communicably connected by wire or wirelessly. Also, the RIS 30 may be connected to the network 40 by wire or wirelessly. The first base station 10A, the second base station 10B, and the terminal 20 can all perform beamforming to transmit and receive signals.

[0016] Note that the first base station 10A is equipped with a plurality of antenna ports and can form beams not only in the horizontal direction but also in the vertical direction. The first base station 10A can make the beam transmitted from a plurality of antenna ports have directivity by multiplying the data supplied to each antenna port by the weight of the precoding vector and adjusting the phase rotation amount (and / or amplitude) for each antenna port.

[0017] Similarly, the second base station 10B is equipped with a plurality of antenna ports and can form beams not only in the horizontal direction but also in the vertical direction. The second base station 10B can impart directivity to the beams transmitted from the plurality of antenna ports by multiplying the data supplied to each antenna port by the weights of the precoding vectors to adjust the phase rotation amount (and / or amplitude) for each antenna port. Note that the terminal 20 may also be equipped with a plurality of antenna ports and may be capable of forming beams not only in the horizontal direction but also in the vertical direction.

[0018] The first base station 10A is a base station that forms a communication area outdoors or the like. 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, for example, the fifth-generation mobile communication system (5G). The second base station 10B is a base station that forms a communication area overlapping 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 almost completely overlap, or that one of the communication areas is included in the other communication area, or that a part of the two communication areas overlaps. 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), for example.

[0019] The first base station 10A can communicate with the terminal 20 directly or via the RIS 30 as a relay device. The second base station 10B can communicate with the terminal 20 directly or via the RIS 30 as a relay device.

[0020] The RIS 30 is connected to the first base station 10A, either by wire or wirelessly. The RIS 30 can relay the signal from the terminal 20 to the first base station 10A by changing the reflection direction of the carrier wave on which the signal from the terminal 20 is carried, according to the configuration information from the first base station 10A. Also, the RIS 30 can relay the signal from the first base station 10A to the terminal 20 by changing the reflection direction of the carrier wave on which the signal from the first base station 10A is carried, according to the configuration information from the first base station 10A.

[0021] Also, the RIS 30 is connected to the second base station 10B, either by wire or wirelessly. The RIS 30 can relay the signal from the terminal 20 to the second base station 10B by changing the reflection direction of the carrier wave on which the signal from the terminal 20 is carried, according to the configuration information from the second base station 10B. Also, the RIS 30 can relay the signal from the second base station 10B to the terminal 20 by changing the reflection direction of the carrier wave on which the signal from the second base station 10B is carried, according to the configuration information from the second base station 10B.

[0022] In addition, when the RIS 30 is connected to the network 40, either by wire or wirelessly, the RIS 30 may relay the signal from the terminal 20 to the first base station 10A and / or the second base station 10B by changing the reflection direction of the carrier wave on which the signal from the terminal 20 is carried, according to the configuration information from the network 40. Also, the RIS 30 may relay the signal from the first base station 10A to the terminal 20 by changing the reflection direction of the carrier wave on which the signal from the first base station 10A is carried, according to the configuration information from the network 40. Also, the RIS 30 may relay the signal from the second base station 10B to the terminal 20 by changing the reflection direction of the carrier wave on which the signal from the second base station 10B is carried, according to the configuration information from the network 40.

[0023] In the example of FIG. 1, only one terminal 20 is shown. However, the number of terminals 20 is not limited to the example of FIG. 1, and more than one terminal 20 may be included. Also, in the example of FIG. 1, the first base station 10A and the second base station 10B are shown, but the number of base stations 10 is not limited to the example of FIG. 1, and more than two base stations 10 may be included. Further, in the example of FIG. 1, only one RIS 30 is shown, but the number of RISs 30 is not limited to the example of FIG. 1, and more than one RIS 30 may be included.

[0024] 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 transmission unit 110, a reception unit 120, and a control unit 130. The functional configuration shown in FIG. 2 is merely an example. Any functional division and names of functional units may be used as long as the operations according to this embodiment can be executed.

[0025] The transmission unit 110 creates a transmission signal from the transmission data and wirelessly transmits the transmission signal. The reception unit 120 wirelessly receives various signals and obtains signals of a higher layer from the received physical layer signals. Also, the reception unit 120 includes a measurement unit that measures the received signals to obtain received power and the like.

[0026] The control unit 130 controls the base station (the first base station 10A or the second base station 10B). Note that the functions of the control unit 130 related to transmission may be included in the transmission unit 110, and the functions of the control unit 130 related to reception may be included in the reception unit 120.

[0027] FIG. 3 is a diagram showing an example of the functional configuration of the terminal 20. As shown in FIG. 3, the terminal 20 has a transmission unit 210, a reception unit 220, and a control unit 230. The functional configuration shown in FIG. 3 is merely an example. Any functional division and names of functional units may be used as long as the operations according to this embodiment can be executed.

[0028] The transmission unit 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) side and wirelessly transmitting the signal. The reception unit 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 obtaining information of a higher layer, for example, from the received signals. The reception unit 220 also includes a measurement unit that measures the received signal to obtain the received power and the like.

[0029] The control unit 230 controls the terminal 20. Note that the function of the control unit 230 related to transmission may be included in the transmission unit 210, and the function of the control unit 230 related to reception may be included in the reception unit 220.

[0030] FIG. 4 is a diagram showing an example of the functional configuration of the RIS 30. As shown in FIG. 4, the RIS 30 includes a transmission unit 310, a reception unit 320, a control unit 330, and a plurality of elements 340. The functional configuration shown in FIG. 4 is merely an example. Any functional division and names of functional units may be used as long as the operations according to the present embodiment can be executed.

[0031] The transmission unit 310 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) side and transmitting the signal by wire and / or wirelessly. The reception unit 320 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 obtaining information of a higher layer, for example, from the received signals.

[0032] The control unit 330 controls the RIS 30. The plurality of elements 340 have a function of changing the reflection direction of the carrier wave on which the signals from the terminal 20 and / or the base stations (the first base station 10A and / or the second base station 10B) are carried. The control unit 330 has a function of controlling the reflection phase (or reflection direction) of the reflected wave reflected by each of the plurality of 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 the orientation of the reflection elements of each of the plurality of elements 340.

[0033] Note that the plurality of elements 340 may be configured as, for example, a reflectarray. FIG. 5 is a diagram showing an example of the plurality of elements 340 as a reflectarray. When the plurality of elements 340 are configured as a reflectarray, for example, by changing the element spacing between the plurality of elements 340, it is possible to change the reflection phase of the reflected wave and change the propagation direction of the reflected wave. Note that the method of changing the reflection phase of the reflected wave is not limited to changing the element spacing, and may be performed by changing the impedance of each of the plurality of elements 340. Additionally or alternatively, the reflection direction of the reflected wave may be changed by including a reflection element for changing the reflection direction of the incident wave in each of the plurality of elements 340 and changing the orientation of the reflection element. For example, the reflection element may include an actuator using Micro Electro Mechanical Systems (MEMS), and the reflection direction of the reflected wave may be controlled by controlling the voltage applied to the piezoelectric material forming the actuator.

[0034] Figures 2 to 4 show the functional unit blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. The realization method of each functional block is not particularly limited. That is, each functional block may be realized using one physically or logically combined device, or two or more physically or logically separated devices may be directly or indirectly (e.g., using wired, wireless, etc.) connected and realized using these multiple devices.

[0035] 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 the processing according to the present embodiment. FIG. 6 is a diagram showing a hardware configuration example of the first base station 10A, the second base station 10B, the terminal 20, and the RIS 30. Any of the devices 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, and the interface device 105 are mutually connected by a bus B.

[0036] In the computer device, the program for realizing the 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 installation of the program does not necessarily have to be performed from the recording medium 101, and it may be downloaded from another computer via a network. The auxiliary storage device 102 stores the installed program and also stores necessary files, data, and the like.

[0037] When there is an instruction to start a program, the memory device 103 reads and stores the program from the auxiliary storage device 102. The CPU 104 executes functions related to the computer device according to the program stored in the memory device 103. The interface device 105 is used as an interface for connecting to a network.

[0038] FIG. 7 is a diagram showing an example in which a plurality of 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, at the time interval t1 (the first time interval at the first time position), the RIS 30 is used by the first base station 10A. Also, at the time interval t2 (the second time interval at the second time position), the RIS 30 is used by the second base station 10B. Note that the time interval may be composed of one or a plurality of radio frames in the time domain. The radio frame may include a plurality of sub-frames. The sub-frame may further be composed of one or a plurality of slots in the time domain. The slot may be composed of one or a plurality of symbols in the time domain. The time interval may be a time interval with one radio frame as a unit, a time interval with one sub-frame as a unit, a time interval with one slot as a unit, or a time interval with one symbol as a unit.

[0039] In the example of FIG. 7, at the time interval t1, the RIS 30 is used by the first base station 10A. Specifically, among the terminals 20_1 to 20_4 under the first base station 10A, the terminals 20_1 and 20_2 are communicating in line of sight with the first base station 10A.

[0040] 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 also non-line-of-sight communication.

[0041] In this case, for example, by relaying the communication between the first base station 10A and the terminal 20_3 through the RIS 30, it is possible to improve the communication quality between the first base station 10A and the terminal 20_3. For example, the first base station 10A transmits the carrier wave of the signal transmitted to the terminal 20_3 toward the RIS 30 by controlling the directivity of the beam of the carrier wave. The RIS 30 controls the reflection phase (or reflection direction) of the reflected waves from the plurality of elements 340 according to the setting information transmitted from the first base station 10A, so that the reflected waves are transmitted toward the terminal 20_3, thereby improving the communication quality between the first base station 10A and the terminal 20_3.

[0042] As in the example of FIG. 7, when the RIS 30 is installed at a fixed position, the first base station 10A can direct the beam of the carrier wave toward the RIS 30 by applying a predetermined precoding matrix to a plurality of antenna ports.

[0043] Also, in the example of FIG. 7, for example, it is assumed that the RIS 30 can select any one of directions 1, 2, ..., n as the reflection direction of the 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 directions 1, 2, ..., n at times 1, 2, ..., n. The terminal 20_3 transmits the received power values 1, 2, ..., n of the reference signals received at times 1, 2, ..., n to the first base station 10A as a measurement report. The first base station 10A that has received the measurement report from the terminal 20_3 compares the received power values 1, 2, ..., n of the reference signals received by the terminal 20_3 at times 1, 2, ..., n, and may instruct the RIS 30 to direct the direction corresponding to the maximum received power value among these received power values.

[0044] Thus, in the example of FIG. 7, the first base station 10A can improve the communication quality between the first base station 10A and the terminal 20_3 by directing the beam of the carrier wave from the first base station 10A towards the RIS 30 and further setting the reflection direction of the reflected wave from the RIS 30 to the direction in which the received power at the terminal 20_3 is optimized.

[0045] Similarly, in the example of FIG. 7, by relaying the communication between the first base station 10A and the terminal 20_4 through the RIS 30, it is possible to improve the communication quality between the first base station 10A and the terminal 20_4.

[0046] In the example of FIG. 7, at time interval t2, the RIS 30 is used by the second base station 10B. Specifically, among the terminals 20_5 to 20_6 under the second base station 10B, the terminal 20_5 is communicating in line of sight with the second base station 10B.

[0047] In contrast, the communication between the second base station 10B and the terminal 20_6 is out-of-sight communication.

[0048] In the example of FIG. 7, by relaying the communication between the second base station 10B and the terminal 20_6 through the RIS 30, it is possible to improve the communication quality between the second base station 10B and the terminal 20_6.

[0049] Thus, the plurality of base stations 10 may share the RIS 30 in a time-division manner. Also, for example, in the case of an orthogonal frequency-division multiplexing (OFDM)-based communication system, the plurality of base stations 10 may share the RIS 30 based on the scheduling of time and frequency resources.

[0050] By sharing the RIS 30 based on time-division or the scheduling of time and frequency resources, the terminal 20 can receive services without being affected by interference from the RIS 30.

[0051] In the example of FIG. 7, at time interval t1, the RIS 30 is used by the first base station 10A, and at time interval t2, the RIS 30 is used by the second base station 10B. Hereinafter, in the example of FIG. 7, 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 will be described.

[0052] 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.

[0053] For example, the first base station 10A may calculate the total number of terminals 20 to use the RIS 30 among the plurality of terminals 20 under the first base station 10A based on the received quality values reported from the plurality of terminals 20 under the first base station 10A. As the received quality reported from the terminal 20, for example, Signal to Interference plus Noise Ratio (SINR) may be considered. The first base station 10A may determine whether to use the RIS 30 for the terminal 20 by comparing a predetermined threshold value with the SINR value reported from the terminal 20. For example, when the SINR value reported from the terminal 20 is less than the predetermined threshold value, the first base station 10A may determine that the RIS 30 should be used for the terminal 20. Note that the received 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 be used.

[0054] Similarly, the second base station 10B may calculate the total number of terminals 20 under the second base station 10B that should use the RIS 30 based on the received quality values reported by a plurality of terminals 20 under the second base station 10B.

[0055] For example, the first base station 10A and the second base station 10B may apply the 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 to determine the time intervals t1 and t2. 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. Then, based on the priority between the first base station 10A and the second base station 10B, the time position where the time interval t1 is placed and the time position where the time interval t2 is placed may be determined. For example, when the priority set for the first base station 10A is higher than the priority set for the second base station 10B, in a predetermined time region, the time interval t1 may be arranged forward in the time direction, and the time interval t2 may be arranged behind the time interval t1 in the time direction.

[0056] 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. Hereinafter, examples of practical methods will be described.

[0057] FIG. 8 is a diagram showing an example of time resource allocation for the first base station 10A and the second base station 10B when sharing the RIS 30 in the example of FIG. 7. In the example of FIG. 7, the first base station 10A is the master base station. The first base station 10A determines 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. The second base station 10B is a slave base station, and the second time interval during which the second base station 10B can access the RIS 30 is determined by the first base station 10A.

[0058] In the example of FIG. 7, among the plurality of terminals 20 (terminal 20_1, terminal 20_2, terminal 20_3, terminal 20_4) under the jurisdiction of the first base station 10A, terminals 20_3 and 20_4 are the terminals 20 that should use the RIS 30. Also, among the plurality of terminals (terminal 20_5, terminal 20_6) under the jurisdiction of the second base station 10B, terminal 20_6 is the terminal 20 that should use the RIS 30. Hereinafter, for convenience of explanation, terminals 20_1, 20_2, 20_3, 20_4, 20_5, and 20_6 are also described as U1, U2, U3, U4, U5, and U6, respectively.

[0059] Since U3 and U4 are the terminals 20 that should use the RIS 30, the first base station 10A determines that the total number of terminals 20 that should use the RIS 30 among the plurality of terminals 20 under the jurisdiction of the first base station 10A is 2. Since U6 is the terminal 20 that should use the RIS 30, the second base station 10B determines that the total number of terminals 20 that should use the RIS 30 among the plurality of terminals 20 under the jurisdiction of the second base station 10B is 1. The second base station 10B notifies the first base station 10A of information indicating that the total number of terminals 20 that should use the RIS 30 among the plurality of terminals 20 under the jurisdiction of the second base station 10B is 1.

[0060] The first base station 10A determines that the total number of terminals 20 that should use the RIS 30 is 3. 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 first base station 10A determines, at a predetermined time interval shown in FIG. 8, the time interval (and time position) during which the first base station 10A uses the RIS 30, and the time interval (and time position) during which the second base station 10B uses the RIS 30. Specifically, as shown in FIG. 8, the first base station 10A determines the time interval (and time position) during which it uses the RIS 30 for U3 and U4. Thereafter, the first base station 10A notifies the second base station 10B of information indicating the time interval t2 during which the second base station 10B can use the RIS 30 and the time position of the time interval t2. As shown in FIG. 8, the second base station 10B determines the time interval during which it uses the RIS 30 for U6.

[0061] As shown in FIG. 8, the first base station 10A may perform scheduling for U1 and U2 during the time interval when the first base station 10A does not use the RIS 30. Also, the second base station 10B may perform scheduling for U5 during the time interval when the second base station 10B does not use the RIS 30.

[0062] Note that the example in FIG. 8 may be generalized as follows. Let the RIS 30 be represented by r, the base station 10 be represented by j, and the terminal 20 that should use the RIS 30 be represented by u. Let \(A_{u,j}^r\) be the time interval that can be allocated by the base station 10 (j) to the terminal 20 (u). Also, let \(D_{u,j}^r\) be the time interval that can be allocated by the RIS 30 (r) to the terminal 20 (u). In this case, the time interval actually allocated to the terminal 20 (u) may be \(min\{A_{u,j}^r,D_{u,j}^r\}\).

[0063] FIG. 9 is a flowchart for explaining an example of a processing procedure executed in the wireless communication system.

[0064] As a prerequisite for the processing procedure of FIG. 9, the plurality of terminals 20 are classified into a normal terminal 20 and a terminal 20 that should use the RIS 30. The classification may be performed by comparing the SINR value reported from each terminal 20 with a predetermined threshold value. The first base station 10A is a master base station, and determines resources (time interval and time position of the time interval) for the first base station 10A to use the RIS 30 and resources (time interval and time position of the time interval) for the second base station 10B to use the RIS 30. The second base station 10B is a slave base station, and uses the RIS 30 at 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 the RIS 30. Let u2 be a terminal 20 under the control of the second base station 10B that should use the RIS 30.

[0065] Let \(A_{u,j}^r\) be the time interval scheduled for the terminal 20(u) by the base station 10(j). Here, when r is not zero, the communication between the base station 10(j) and the terminal 20(u) is relayed by the RIS 30(r). When 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).

[0066] Let \(D_{u,j}^r\) be the time interval scheduled for the terminal 20(u) by the RIS 30(r). \(D_{u,j}^r\) is a time interval scheduled with the use of the base station 10(j). \(D_{u,j}^r\) is calculated by the RIS 30(r).

[0067] Let \(B_{u,j}^r\) be the time interval finally calculated by the base station 10(j) for the terminal 20(u). \(B_{u,j}^r\) is determined based on \(D_{u,j}^r\) calculated by the RIS 30(r).

[0068] In step S110, the base station 10 (the first base station 10A and the second base station 10B) calculates the time intervals scheduled for the terminals 20 under the base station 10.

[0069] In step S120, the first base station 10A receives, from the second base station 10B, information indicating the number of terminals 20 among the terminals 20 under the second base station 10B that should use the RIS 30. The first base station 10A calculates the number of terminals 20 under the first base station 10A that should use the RIS 30. The first base station 10A calculates the sum of the number of terminals 20 among the terminals 20 under the second base station 10B that should use the RIS 30 and the number of terminals 20 under the first base station 10A that should use the RIS 30 as the total number of terminals 20 that should use the RIS 30. The first base station 10A calculates the time intervals scheduled for each terminal 20 that should use the RIS 30 based on the calculated total number. For example, the first base station 10A calculates A_{u1,1}^r for the terminal u1, which is a terminal 20 under the first base station 10A and should use the RIS 30.

[0070] In step S130, the first base station 10A performs prioritization for one or more base stations 10 that need to use the RIS 30 (in the example of FIG. 9, one second base station 10B) (the priorities may be set in advance), and based on the priorities, determines timing information (for example, the first time position of the first time interval during which the first base station 10A uses the RIS 30 and the second time position of the second time interval during which the second base station 10B uses the RIS 30). The first base station 10A transmits the determined timing information to the one or more base stations 10. Here, the timing information may be information indicating the time position of the time interval assigned by the first base station 10A to the second base station 10B. In the example of FIG. 9, the first base station 10A transmits information indicating the slots during which the second base station 10B can use the RIS 30 (for example, information indicating the length and time position of the slots) to the second base station 10B.

[0071] In step S140, the first base station 10A calculates the actual scheduled time interval for the terminal 20 that should use the RIS 30 under the first base station 10A. Also, the second base station 10B calculates the actual scheduled time interval for the terminal 20 that should use the RIS 30 under the second base station 10B. In the example of FIG. 9, the first base station 10A calculates B_{u1,1}^r by calculating min{A_{u1,1}^r, D_{u1,1}^r}. Also, the second base station 10B calculates B_{u2,2}^r by calculating min{A_{u2,2}^r, D_{u2,2}^r}.

[0072] In step S150, the first base station 10A transmits the setting information regarding the phase and amplitude required for communication via the RIS 30 between the first base station 10A and the terminal 20 that should use the RIS 30 under the first base station 10A, together with the scheduling information (information indicating B_{u1,1}^r in the example of FIG. 9), to the RIS 30. The first base station 10A communicates with the terminal 20 that should use the RIS 30 under the first base station 10A using the RIS 30 at the time interval t1 (B_{u1,1}^r in the example of FIG. 9).

[0073] In step S160, the second base station 10B transmits the setting information regarding the phase and amplitude required for communication via the RIS 30 between the second base station 10B and the terminal 20 that should use the RIS 30 under the second base station 10B, together with the scheduling information (information indicating B_{u2,2}^r in the example of FIG. 9), to the RIS 30. The second base station 10B communicates with the terminal 20 that should use the RIS 30 under the second base station 10B using the RIS 30 at the time interval t2 (B_{u2,2}^r in the example of FIG. 9).

[0074] As described above, in the embodiment of the present invention, a resource allocation technique for the utilization time of the RIS in a wireless communication technology using a Reconfigurable Intelligent Surface (RIS) is described.

[0075] In an embodiment of the present invention, a system composed of a plurality of cells and a plurality of base stations, such as cellular communication, is assumed. It is also assumed that a plurality of radio base stations share the same RIS and perform beamforming for user terminals under their respective cells.

[0076] In such a system, it is considered that competition in the use of RIS may occur. In the conventional method, for all RISs in the system, it is necessary to exchange the weight matrix corresponding to the beam formed by the RIS (corresponding to all terminals communicating) between base stations and perform coordination. This method has problems that the processing is complicated and interference between reflectors cannot be completely avoided.

[0077] Therefore, in an embodiment of the present invention, only information regarding terminals using RIS is shared between radio base stations, and at each radio base station, based on the shared information, the time when the station uses RIS is calculated, thereby reducing the control information to be transmitted and received. Also, it is possible to completely avoid interference without causing competition in the use of RIS.

Explanation of Signs

[0078] 10A First base station 10B Second base station 20 Terminal 30 RIS 40 Network 110 Transmitter 120 Receiver 130 Controller 210 Transmitter 220 Receiver 230 Controller 310 Transmitter 320 Receiver 330 Controller 340 Element 100 Drive device 101 Recording medium 102 Auxiliary storage device 103 Memory device 104 CPU 105 Interface device B bus

Claims

1. A wireless communication system comprising 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 first base station includes: a first receiving unit that receives, from the second base station, information indicating the number of terminals to communicate via the relay device among one or more terminals under the second base station; a first control unit that calculates, as the total number of terminals to communicate via the relay device, the sum of the number indicated by the received information and the number of terminals to communicate via the relay device among one or more terminals under the first base station, determines, based on the total number, a first time interval during which the first base station uses the relay device, determines a second time interval during which the second base station uses the relay device and that is other than the first time interval, 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 level set for the second base station; a first transmitting unit that transmits to the second base station information indicating the second time interval and the second time position of the second time interval; and includes During the first time interval at the first time position, the first control unit schedules a first communication between each terminal to communicate via the relay device among one or more terminals under the first base station and the first base station, which is a first communication via the relay device. The second base station includes: a second transmitting unit that transmits to the first base station information indicating the number of terminals to communicate via the relay device among one or more terminals under the second base station; a second receiving unit that receives from the first base station information indicating the second time interval and the second time position of the second time interval; a second control unit that schedules a second communication between each terminal to communicate via the relay device among one or more terminals under the second base station and the second base station, which is a second communication via the relay device, during the second time interval at the second time position; and includes A wireless communication system.

2. The relay device according to claim 1 is a Reconfigurable Intelligent Surface (RIS) including a plurality of reflecting elements and capable of changing the traveling direction of reflected waves, in the wireless communication system.

3. The first control unit determines whether or not the terminal should communicate via the relay device by comparing a value indicating the communication quality between each terminal under the first base station and the first base station with a predetermined threshold value. The second control unit determines whether or not the terminal should communicate via the relay device by comparing a value indicating the communication quality between each terminal under the second base station and the second base station with the predetermined threshold value. The wireless communication system according to claim 1.

4. The second base station includes a plurality of base stations, and the first control unit determines the second time position of the second time interval to be assigned to each base station among the plurality of base stations based on the priority order set for the plurality of base stations. The wireless communication system according to claim 1.

5. The first base station 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, and the first base station includes: a receiving unit that receives, from the second base station, information indicating the number of terminals among one or more terminals under the second base station that should communicate via the relay device; a control unit that calculates, as the total number of terminals to communicate via the relay device, the sum of the number indicated by the received information and the number of terminals among one or more terminals under the first base station that should communicate via the relay device, determines a first time interval during which the first base station uses the relay device based on the total number, determines a second time interval during which the second base station uses the relay device, which is other than the first time interval, and determines the first time position of the first time interval and the second time position of the second time interval based on the priority order set for the second base station; a transmitting unit that transmits information indicating the second time interval and the second time position of the second time interval to the second base station; and includes. In the first time interval at the first time position, the control unit performs scheduling of communication between each terminal to communicate via the relay device among one or more terminals under the first base station and the first base station, the communication being communication via the relay device. Base station.

6. A communication method executed by a first base station 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, and the communication method includes: Receiving, from the second base station, information indicating the number of terminals to communicate via the relay device among one or more terminals under the second base station; Calculating, as the total number of terminals to communicate via the relay device, the sum of the number indicated by the received information and the number of terminals to communicate via the relay device among one or more terminals under the first base station, determining, based on the total number, a first time interval during which the first base station uses the relay device, determining a second time interval during which the second base station uses the relay device, the second time interval being other than the first time interval, 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 order set for the second base station; Transmitting, to the second base station, information indicating the second time interval and the second time position of the second time interval; In the first time interval at the first time position, performing scheduling of communication between each terminal to communicate via the relay device among one or more terminals under the first base station and the first base station, the communication being communication via the relay device; A communication method comprising:

7. A non-transitory computer-readable storage medium storing a program, wherein when the program is executed by a first base station in a wireless communication system including a first base station, a second base station, a relay device, and a plurality of terminals, and a first communication area formed by the first base station overlaps with a second communication area formed by the second base station, the first base station is caused to: Receiving, from the second base station, information indicating the number of terminals among one or more terminals under the second base station that should communicate via the relay device; Calculating, as the total number of terminals that should communicate via the relay device, the sum of the number indicated by the received information and the number of terminals among one or more terminals under the first base station that should communicate via the relay device, determining, based on the total number, a first time interval during which the first base station uses the relay device, determining a second time interval during which the second base station uses the relay device, the second time interval being other than the first time interval, and determining a first time position of the first time interval and a second time position of the second time interval based on the priority level set for the second base station; Transmitting, to the second base station, information indicating the second time interval and the second time position of the second time interval; Scheduling a first communication, via the relay device, between each terminal among one or more terminals under the first base station that should communicate via the relay device and the first base station during the first time interval at the first time position; A non-transitory computer-readable storage medium for causing the above to be executed.

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