Wireless communication system, relay device, communication method, and non-transitory computer-readable storage medium
The method addresses RIS resource competition in multi-cell wireless systems by allocating time intervals based on terminal quality values and priority settings, reducing control information overhead and preventing interference, thus enhancing communication efficiency.
Patent Information
- Application Number
- JP2024569221
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-07-28
- Publication Date
- 2025-05-30
- Estimated Expiration
- 2042-07-28
AI Technical Summary
In a multi-cell, multi-base station wireless communication system, the competition for shared Reconfigurable Intelligent Surface (RIS) resources leads to increased overhead in control information and potential interference between base stations.
A method is introduced where the relay device receives quality values from terminals under multiple base stations, determines the number of terminals to use the RIS for each base station, and allocates time intervals based on these determinations and priority settings, thereby reducing control information overhead and avoiding interference.
This approach effectively resolves RIS resource competition while minimizing control information overhead and preventing interference, thereby enhancing communication efficiency in multi-cell wireless systems.
Smart Images
Figure 2025516937000001_ABST
Abstract
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 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. Various architectures and multiple access technologies have been proposed in recent research and experiments.
[0003] Using RIS has been considered for expanding the coverage of a cell. 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 (reflector) and perform beamforming toward 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 the competition of the same RIS while reducing the overhead of control information.
Means for Solving the Problems
[0009] According to one aspect of the present invention,
[0010] a first base station,
[0011] a second base station,
[0012] a relay device, and
[0013] a wireless communication system including a plurality of terminals,
[0014] The first communication area formed by the first base station overlaps with the second communication area formed by the second base station,
[0015] The relay device,
[0016] receives the received quality values reported from a plurality of terminals under the first base station from the first base station, and receives the received quality values reported from a plurality of terminals under the second base station from the second base station; a receiving unit;
[0017] Based on the received quality values, among the terminals under the first base station, determine the first number of terminals that should use the relay device, and among the terminals under the second base station, determine the second number of terminals that should use the relay device. Based on the ratio between the first number and the second number, determine the first time interval during which the first base station uses the relay device and the second time interval during which the second base station uses the relay device. Based on the priority between the first base station and the second base station, determine the first time position of the first time interval and the second time position of the second time interval; a control unit;
[0018] transmits information indicating the first time interval and the first time position of the first time interval to the first base station, and transmits information indicating the second time interval and the second time position of the second time interval to the second base station; a transmitting unit; Comprising, A wireless communication system is provided.
Advantages of the Invention
[0019] 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
[0020]
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Embodiments for Carrying Out the Invention
[0021] Reconfigurable Intelligent Surface (RIS) is considered to be a method of effectively controlling the radio wave propagation channel by appropriately controlling the phase and amplitude of electromagnetic waves. According to recent research and experiments, various architectures and multiple access technologies have been found.
[0022] As an application of the RIS, the method of a plurality of base stations sharing 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.
[0023] The applications of RISs are evolving along with existing technologies. The optimization of the transmission beamforming of the base stations and the phase shifts of each RIS, assuming the allocation of the transmission power of the base stations, is being considered. Also, for RIS-based beamforming, negotiation between base stations to obtain consensus between base stations without revealing information of terminals under the control of a base station has been proposed. That is, it is assumed that different base stations accessing an RIS perform a similar reflection response to a terminal after obtaining consensus between base stations regarding RIS-based beamforming.
[0024] 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.
[0025] 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 the plurality of antenna ports directional 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.
[0026] 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.
[0027] 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).
[0028] 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.
[0029] 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.
[0030] 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.
[0031] Note that 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.
[0032] 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.
[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 transmission unit 110, a reception unit 120, and a control unit 130. The functional configuration shown in FIG. 2 is merely an example. As long as the operations according to this embodiment can be executed, the functional division and the names of the functional units may be anything.
[0034] 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 acquires 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 acquire received power and the like.
[0035] 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.
[0036] 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. As long as the operations according to this embodiment can be executed, the functional division and the names of the functional units may be anything.
[0037] The transmitting 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 receiving 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. Further, the receiving unit 220 includes a measuring unit that measures the received signals to obtain received power and the like.
[0038] 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 transmitting unit 210, and the function 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 the RIS 30. As shown in FIG. 4, the RIS 30 includes 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. Any functional division and names of functional units may be used as long as the operations according to the present embodiment can be executed.
[0040] The transmitting 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 receiving 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.
[0041] 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 the 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 the reflection direction) of the reflected wave by controlling the impedance, the element interval, and / or the orientation of the reflection element of each of the plurality of elements 340.
[0042] 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 interval between the plurality of elements 340, it is possible to change the reflection phase of the reflected wave and change the traveling 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 interval, 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 changing the orientation of the reflection element including a reflection element for changing the reflection direction of the incident wave for each of the plurality of elements 340. For example, a configuration may be adopted in which the reflection element includes an actuator using Micro Electro Mechanical Systems (MEMS), and the reflection direction of the reflected wave is controlled by controlling the voltage applied to the piezoelectric material forming the actuator.
[0043] 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 (for example, using wired, wireless, etc.) connected and realized using 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 the processing according to the present embodiment. FIG. 6 is a diagram showing 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 devices of the first base station 10A, the second base station 10B, the terminal 20, and the RIS 30 may physically be 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.
[0045] 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.
[0046] 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.
[0047] 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 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 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.
[0048] In the example of FIG. 7, at 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 within line of sight with the first base station 10A.
[0049] In contrast, the communication between the first base station 10A and the terminal 20_3 is out-of-sight communication. Also, the communication between the first base station 10A and the terminal 20_4 is also out-of-sight communication.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] In contrast, the communication between the second base station 10B and the terminal 20_6 is out-of-line-of-sight communication.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] 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.
[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 transmits the received quality values reported from a plurality of terminals 20 under the first base station 10A to the RIS 30, and the RIS 30 may calculate the total number of terminals 20 to be used by the RIS 30 among the plurality of terminals 20 under the first base station 10A based on the reported received quality values. As the received quality reported from the terminal 20, for example, Signal to Interference plus Noise Ratio (SINR) may be considered. The RIS 30 may determine whether the RIS 30 should be used 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 RIS 30 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.
[0063] Similarly, the second base station 10B transmits the received quality values reported from a plurality of terminals 20 under the second base station 10B to the RIS 30, and the RIS 30 may calculate the total number of terminals 20 to which the RIS 30 should be used among the plurality of terminals 20 under the second base station 10B based on the reported received quality values.
[0064] For example, the RIS 30 may determine the time intervals t1 and t2 by applying the proportional fairness method based on the total number of terminals 20 to which the RIS 30 should be used 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, etc. 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 in the front in the time direction, and the time interval t2 may be arranged behind the time interval t1 in the time direction.
[0065] 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, a more practical method can be considered. Hereinafter, an example of a practical method will be described.
[0066] 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. The RIS 30 determines a first time interval (and the time position of the first time interval) to 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) to which the second base station 10B can access the RIS 30.
[0067] 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, terminal 20_3 and terminal 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, terminal 20_1, terminal 20_2, terminal 20_3, terminal 20_4, terminal 20_5, and terminal 20_6 will also be described as U1, U2, U3, U4, U5, and U6, respectively.
[0068] Since U3 and U4 of the RIS 30 are the terminals 20 that should use the RIS 30, it is determined 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 of the RIS 30 is the terminal 20 that should use the RIS 30, it is determined 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.
[0069] The RIS 30 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, 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 are determined. Specifically, as shown in FIG. 8, the RIS 30 determines the time interval (and time position) during which the RIS 30 is used for U3 and U4. Also, as shown in FIG. 8, the RIS 30 determines the time interval during which the RIS 30 is used for U6.
[0070] As shown in FIG. 8, the first base station 10A may perform scheduling for U1 and U2 during a 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 a time interval when the second base station 10B does not use the RIS 30.
[0071] Note that the example in FIG. 8 may be generalized as follows. Let RIS 30 be represented by r, the base station 10 be represented by j, and the terminal 20 that should use 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 RIS 30(r) to the terminal 20(u). In this case, the time interval actually allocated to the terminal 20(u) may be \(min\{A_{u,j}^r,D_{u,j}^r\}\).
[0072] FIG. 9 is a flowchart for explaining an example of a processing procedure executed in the wireless communication system.
[0073] As a premise of the processing procedure in FIG. 9, the plurality of terminals 20 are classified into a normal terminal 20 and a terminal 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 value. RIS 30 determines the resources (time interval and time position of the time interval) for the first base station 10A to use RIS 30 and the resources (time interval and time position of the time interval) for the second base station 10B to use RIS 30. The second base station 10B is a slave base station and uses RIS 30 at the resources (time interval placed at the time position) determined by the first base station 10A. Let u1 be the terminal 20 under the first base station 10A that should use RIS 30. Let u2 be the terminal 20 under 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, when r is not zero, the communication between the base station 10(j) and the terminal 20(u) is relayed by RIS 30(r). When r is zero, the communication between the base station 10(j) and the terminal 20(u) is not relayed by 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 the terminal \(20(u)\) by the RIS \(30(r)\). \(D_{u,j}^r\) is the scheduled time interval involving the use of the base station \(10(j)\). \(D_{u,j}^r\) is calculated by the RIS \(30(r)\).
[0076] Let \(B_{u,j}^r\) be the scheduled time interval for the terminal \(20(u)\) finally calculated by the base station \(10(j)\). \(B_{u,j}^r\) is determined based on \(D_{u,j}^r\) calculated by the RIS \(30(r)\).
[0077] In the example of FIG. 9, in step S110, the first base station \(10A\) transmits, to the RIS \(30\), the received quality values reported from a plurality of terminals \(20\) under the control of the first base station \(10A\), together with the identification information of each terminal. In this case, the first base station \(10A\) may determine the first number of terminals \(20\) that should use the RIS \(30\) among the terminals \(20\) under the control of the first base station \(10A\) by comparing the received quality values reported from the plurality of terminals \(20\) under the control of the first base station \(10A\) with a predetermined threshold value.
[0078] In step S120, the second base station \(10B\) transmits, to the RIS \(30\), the received quality values reported from a plurality of terminals \(20\) under the control of the second base station \(10B\), together with the identification information of each terminal. In this case, the second base station \(10B\) may determine the second number of terminals \(20\) that should use the RIS \(30\) among the terminals \(20\) under the control of the second base station \(10B\) by comparing the received quality values reported from the plurality of terminals \(20\) under the control of the second base station \(10B\) with a predetermined threshold value.
[0079] In step S130, the RIS 30 determines the first number of terminals 20 under the first base station 10A that should use the RIS 30 by comparing the received quality values reported from a plurality of terminals 20 under the first base station 10A with a predetermined threshold value. Also, the RIS 30 determines the second number of terminals 20 under the second base station 10B that should use the RIS 30 by comparing the received quality values reported from a plurality of terminals 20 under the second base station 10B with a predetermined threshold value. 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 number and the second number.
[0080] Next, in step S140, the RIS 30 prioritizes one or more base stations 10 (the first base station 10A and the second base station 10B in the example of FIG. 9) that need to use the RIS 30 (the priority may be set in advance), and based on the priority, 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 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 position of the time interval allocated by the RIS 30 to the first base station 10A and the second base station 10B. In the example of FIG. 9, in step S150, the RIS 30 transmits information indicating a slot during which the first base station 10A can use the RIS 30 (for example, information indicating the length and time position of the slot) to the first base station 10A, and in step S160, transmits information indicating a slot during which the second base station 10B can use the RIS 30 (for example, 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 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 \(min\{A_{u2,2}^r, D_{u2,2}^r\}\).
[0082] In step S180, 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).
[0083] In step S190, 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).
[0084] Next, with reference to FIG. 10, an example of the processing procedure of the terminal 20 under the first base station 10A will be described. In the example of FIG. 10, it is assumed that the terminal 20 is equipped with a plurality of antenna ports and can form beams in a plurality of directions.
[0085] In step S210, the terminal 20 transmits, as a measurement report, information indicating the first received power value of the first signal received from the first base station 10A to the first base station 10A. The first base station 10A receives the measurement report and compares the first received power value with the first threshold.
[0086] When the first received power value is greater than or equal to the first threshold, the first base station 10A determines to continue the communication with the terminal 20 as it is. That is, the first base station 10A determines not to relay the communication between the first base station 10A and the terminal 20 through the RIS 30.
[0087] When 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] When the second received power value is greater than or equal to the first threshold, the first base station 10A may transmit a handover command to the terminal 20 to cause the terminal 20 to hand over to the second base station 10B.
[0089] In step S220, when 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. That is, the first base station 10A determines to relay the communication between the first base station 10A and the terminal 20 through the RIS 30.
[0090] In step S230, the first base station 10A transmits a predetermined reference signal to the RIS 30, and based on the measurement report received from the terminal 20, indicates to the RIS 30 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 directions 1, 2, ..., n at times 1, 2, ..., n. The terminal 20 transmits, as a measurement report, the received power values 1, 2, ..., n of the reference signals received at times 1, 2, ..., n to the first base station 10A. The first base station 10A that has received the measurement report from the terminal 20 compares the received power values 1, 2, ..., n of the reference signals received by the terminal 20 at times 1, 2, ..., n, and may indicate to the RIS 30 the direction corresponding to the maximum 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 reference signal for the uplink (which may be a Sounding Reference Signal (SRS)) in the corresponding directions 1, 2, ..., n at times 1, 2, ..., n. For example, in response to receiving the instruction from the first base station 10A, the terminal 20 may transmit an uplink reference signal by applying the precoding vector V1 corresponding to direction 1 at time 1 (the uplink reference signal may include information indicating the precoding vector V1). Similarly, the terminal 20 may transmit an uplink reference signal by applying the precoding vector V2 corresponding to direction 2 at time 2 (the uplink reference signal may include information indicating the precoding vector V2). Similarly, the terminal 20 may transmit an uplink reference signal by applying the precoding vector Vn corresponding to direction n at time n (the uplink reference signal may include information indicating the precoding vector Vn).
[0092] In step S250, the first base station 10A compares the received power values 1, 2,..., n of a predetermined reference signal of the uplink received at times 1, 2,..., n, and identifies the direction with respect to the maximum 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 the information included in the reference signal of the uplink 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 the information included in the reference signal of the uplink 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 the information included in the reference signal of the uplink received from the terminal 20A at time n. Then, the first base station 10A compares the received power values 1, 2,..., n of the reference signals of the uplink received at times 1, 2,..., n, and may 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 the communication between the first base station 10A and the terminal 20, and determines the time interval (which may be a time slot) used for the 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, the time interval determined in step S260, and information indicating the time position of the time interval. For example, the first base station 10A may include in the scheduling information information indicating a time slot for communication between the first base station 10A and the terminal and the time position of the time slot. Further, as the information indicating the direction determined in step S250, the first base station 10A may notify the terminal 20 of a precoding vector corresponding to the maximum reception power value among a plurality of reception power values of uplink reference signals.
[0095] In step S280, the first base station 10A and the terminal 20 communicate via the RIS 30 based on the scheduling information. For example, the first base station 10A and the terminal 20 may communicate via the RIS 30 in a time slot placed at the notified time position based on the information indicating the time slot and the time position of the time slot notified by the first base station 10A to the terminal 20 in step S270. Further, when transmitting an uplink signal to the first base station 10A via the RIS 30 in a time slot placed at the time position notified by the first base station 10A, the terminal 20 may apply the precoding vector indicated by the scheduling information received from the first base station 10A in step S270 to transmit the uplink signal.
[0096] Note that in the example of FIG. 10, in steps S210 and S220, the first base station 10A determines to relay the communication between the first base station 10A and the terminal 20 via the RIS 30, but the embodiment is not limited to this example. For example, similar to the process of step S130 in FIG. 9, the RIS 30 may determine to relay the communication between the first base station 10A and the terminal 20 via the RIS 30.
[0097] As described above, in the embodiments of the present invention, a resource allocation technique for the utilization time of a Reconfigurable Intelligent Surface (RIS) in a wireless communication technology using the RIS is described.
[0098] In the embodiments of the present invention, a system composed of multiple cells and multiple base stations, such as cellular communication, is assumed. It is also assumed that multiple radio base stations share the same RIS and perform beamforming toward user terminals under their respective cells.
[0099] In such a system, it is conceivable that competition for RIS utilization may occur. In the conventional method, for all RISs in the system, it is necessary to exchange weight matrices (corresponding to all terminals communicating) corresponding to the beams formed by the RISs between base stations and perform coordination. This method has problems that the processing is complicated and interference between reflectors cannot be completely avoided.
[0100] Therefore, in the embodiments of the present invention, between radio base stations, only information regarding terminals using the RIS is shared, and at each radio base station, based on the shared information, the time when the station uses the RIS is calculated, thereby reducing the control information to be transmitted and received. In addition, it is possible to completely avoid interference without causing competition for RIS utilization.
Explanation of Reference Numerals
[0101] 10A First base station 10B Second base station 20 Terminal 30 RIS 40 Network 110 Transmission unit 120 Reception unit 130 Control unit 210 Transmission unit 220 Reception unit 230 Control unit 310 Transmission unit 320 Reception unit 330 Control unit 340 elements 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 relay device, a receiving unit that receives, from the first base station, values of reception quality reported by a plurality of terminals under the control of the first base station, and receives, from the second base station, values of reception quality reported by a plurality of terminals under the control of the second base station; a control unit that determines, based on the values of reception quality, 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, 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 order between the first base station and the second base station; a transmitting unit that transmits information indicating the first time interval and the first time position of the first time interval to the first base station, and transmits information indicating the second time interval and the second time position of the second time interval to the second base station; Comprising, Wireless communication system.
2. The relay device is a Reconfigurable Intelligent Surface (RIS) including a plurality of reflection elements and capable of changing the traveling direction of reflected waves, The wireless communication system according to claim 1.
3. The control unit determines whether each terminal under the control of the first base station should communicate via the relay device by comparing a value indicating the quality of communication between the terminal and the first base station with a predetermined threshold value, and determines whether each terminal under the control of the second base station should communicate via the relay device by comparing a value indicating the quality of communication between the terminal and the second base station with the predetermined threshold value, The wireless communication system according to claim 1.
4. A relay device in 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 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; Based on the values of reception quality, determine a first number of terminals among the terminals under the control of the first base station that should use the relay device, and determine a second number of terminals among the terminals under the control of the second base station that should use the relay device. Based on the ratio between the first number and the second number, determine 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 the priority order between the first base station and the second base station, determine a first time position of the first time interval and a second time position of the second time interval; a control unit; A transmitting unit that transmits information indicating the first time interval and the first time position of the first time interval to the first base station, and transmits information indicating the second time interval and the second time position of the second time interval to the second base station; Comprising; Relay device.
5. A communication method by 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 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; Based on the values of reception quality, determine a first number of terminals among the terminals under the control of the first base station that should use the relay device, and determine a second number of terminals among the terminals under the control of the second base station that should use the relay device. Based on the ratio between the first number and the second number, determine 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 the priority order between the first base station and the second base station, determine a first time position of the first time interval and a second time position of the second time interval; A transmitting unit that transmits information indicating the first time interval and the first time position of the first time interval to the first base station, and transmits information indicating the second time interval and the second time position of the second time interval to the second base station. Comprising A communication method.
6. A non-transitory computer-readable storage medium storing a program, wherein the program is 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. When executed by the relay device in the wireless communication system, the relay device Receiving, from the first base station, values of reception quality reported by a plurality of terminals under the control of the first base station, and receiving, from the second base station, values of reception quality reported by a plurality of terminals under the control of the second base station. Based on the values of the reception quality, determining a first number of terminals among the terminals under the control of the first base station that should use the relay device, determining a second number of terminals among the terminals under the control of the second base station that should use the relay device, 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 based on a ratio between the first number and the second number, 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 between the first base station and the second base station. A transmitting unit that transmits information indicating the first time interval and the first time position of the first time interval to the first base station, and transmits information indicating the second time interval and the second time position of the second time interval to the second base station. Causing to execute A non-transitory computer-readable storage medium.