Base station device, terminal device, and wireless communication system

Abstract

In the present invention, a communication device comprises: a first transmission unit that transmits a first signal to another communication device; a first reception unit that receives, from said other communication device, a second signal which includes first information pertaining to the reception quality of the first signal; and a control unit that determines whether to transmit a third signal to said other communication device in accordance with the first information, and, if it is determined that the third signal is to be transmitted to said other communication device, controls the transmission power of the third signal in accordance with the first information.

Description

Base station device, terminal device, and wireless communication system

[0001] The present invention relates to a base station device, a terminal device, and a wireless communication system.

[0002] 2. Description of the Related Art A communication system using radio waves (hereinafter also referred to as a wireless communication system) performs wireless communication by transmitting and receiving radio waves between a base station device and a terminal device, for example.

[0003] In the wireless communication system described above, if an obstruction such as a building exists within the communication area of ​​the base station device (hereinafter simply referred to as the communication area), the terminal device may not be able to receive radio waves transmitted from the base station device. In this case, the terminal device may not be able to establish a wireless connection with the base station device even if it is located within the communication area.

[0004] Therefore, in the wireless communication system described above, for example, in an area within the communication area where radio waves do not reach (hereinafter also referred to as a blind area), by using a reflection control device (RIS: Reconfigurable Intelligent Surface) that can reflect radio waves, it may be possible to transmit and receive radio waves between a base station device and a terminal device (see, for example, Patent Documents 1 and 2).

[0005] International Publication No. WO 2023 / 163124 International Publication No. WO 2022 / 018815

[0006] In the wireless communication system described above, it is desirable to further reduce the occurrence of blind areas within the communication area of ​​the base station device, for example.

[0007] Therefore, in one aspect, the present invention aims to provide a base station device, a terminal device, and a wireless communication system that can suppress the occurrence of blind areas within the communication area of ​​the base station device.

[0008] In one aspect of the embodiment, a base station device is a base station device in a wireless communication system having a base station device, a terminal device, and a reflection control device that reflects at least one of a first radio wave transmitted by the base station device and a second radio wave transmitted by the terminal device, and has a transmitting unit that transmits first control information regarding the reflection direction of the first radio wave by the reflection control device, and a receiving unit that receives the second radio wave transmitted from the terminal device and reflected by the reflection control device, and the transmitting unit transmits the first radio wave corresponding to the second radio wave to the terminal device at a timing when the reflection direction of the first radio wave becomes the same reflection direction as the reception timing of the second radio wave.

[0009] According to one aspect, it is possible to prevent blind areas from occurring within the communication area of ​​a base station device.

[0010] FIG. 1 is a diagram illustrating a configuration of a wireless communication system 10 according to a first embodiment. FIG. 2 is a diagram illustrating a specific example of wireless communication between a base station device 1 and a terminal device 2 when a RIS 3 is used. FIG. 3 is a diagram illustrating a specific example of wireless communication between a base station device 1 and a terminal device 2 when a RIS 3 is used. FIG. 4 is a diagram illustrating a specific example of wireless communication between a base station device 1 and a terminal device 2 when a RIS 3 is used. FIG. 5 is a diagram illustrating the hardware configuration of a base station device 1. FIG. 6 is a diagram illustrating the hardware configuration of a terminal device 2. FIG. 7 is a diagram illustrating the hardware configuration of a RIS 3. FIG. 8 is a diagram illustrating functions of a base station device 1. FIG. 9 is a diagram illustrating functions of a terminal device 2. FIG. 10 is a diagram illustrating functions of a RIS 3. FIG. 11 is a sequence chart of communication control processing according to the first embodiment. FIG. 12 is a flowchart illustrating details of the communication control processing according to the first embodiment. FIG. 13 is a flowchart illustrating details of the communication control processing according to the first embodiment. FIG. 14 is a flowchart illustrating details of the communication control processing according to the first embodiment. FIG. 15 is a flowchart illustrating details of the communication control processing in the first embodiment. FIG. 16 is a flowchart illustrating details of the communication control processing in the first embodiment. FIG. 17 is a flowchart illustrating details of the communication control processing in the first embodiment. FIG. 18 is a diagram illustrating a specific example of the control information DT1 in the first embodiment. FIG. 19 is a diagram illustrating a specific example of the control information DT1 in the first embodiment. FIG. 20 is a diagram illustrating a specific example of S32. FIG. 21 is a diagram illustrating another specific example of S32. FIG. 22 is a diagram illustrating a specific example of the communication control processing in the first embodiment. FIG. 23 is a diagram illustrating another specific example of the communication control processing in the first embodiment. FIG. 24 is a diagram illustrating communication control processing in the first modified example. FIG. 25 is a diagram illustrating communication control processing in the first modified example. FIG. 26 is a diagram illustrating communication control processing in the second modified example.FIG. 27 is a diagram illustrating the communication control process in the second modified example.

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, such descriptions should not be interpreted in a limiting sense, and do not limit the subject matter described in the claims. Furthermore, various changes, substitutions, and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, different embodiments can be combined as appropriate.

[0012] [Configuration of Wireless Communication System in First Embodiment] First, a configuration of a wireless communication system 10 in the first embodiment will be described. Fig. 1 is a diagram illustrating the configuration of a wireless communication system 10 in the first embodiment.

[0013] 1 , the wireless communication system 10 includes, for example, a base station device 1 and a terminal device 2. The base station device 1 establishes a wireless connection with, for example, the terminal device 2 located within a communication area A of the base station device 1.

[0014] The wireless communication system 10 may be, for example, a wireless communication system compatible with a communication standard of a 5th generation mobile communication system (5G) or a next-generation communication standard of the 5th generation mobile communication system. The terminal device 2 may be, for example, a terminal device such as a personally owned smartphone, or an IoT device installed outdoors. The following description will be given assuming that the wireless communication system 10 includes one base station device 1, but the wireless communication system 10 may include, for example, two or more base station devices 1. The following description will be given assuming that one terminal device 2 is located within a communication area A of the base station device 1, but the communication area A of the base station device 1 may include, for example, two or more terminal devices 2.

[0015] [Specific example of wireless communication using RIS] Next, a specific example of wireless communication between the base station device 1 and the terminal device 2 when using the RIS 3 will be described. Figures 2 to 4 are diagrams explaining a specific example of wireless communication between the base station device 1 and the terminal device 2 when using the RIS 3.

[0016] As shown in FIG. 2, the wireless communication system 10 includes, for example, a base station device 1, a terminal device 2, and a RIS 3.

[0017] 2, the RIS 3 reflects, for example, radio waves W1 (downstream radio waves W1) transmitted from the base station device 1. Hereinafter, the radio waves W1 reflected by the RIS 3 will also be referred to as radio waves W2.

[0018] Specifically, the RIS 3 reflects the radio waves W1 (transmits the radio waves W2 to the terminal device 2) while switching the reflection direction of the radio waves W1 (hereinafter, also simply referred to as the reflection direction).

[0019] As a result, in the wireless communication system 10, as shown in Figure 2, even if, for example, there is an obstruction OB between the base station device 1 and the terminal device 2 and the radio waves transmitted from the base station device 1 cannot reach the terminal device 2 directly, the radio waves can be transmitted via RIS3, thereby making it possible to transmit radio waves (radio waves W1 and W2) from the base station device 1 to the terminal device 2.

[0020] More specifically, as shown in FIG. 3, the RIS3 controls the transmission so that, for example, the timing of transmitting radio waves W2 (hereinafter also referred to as radio waves W2a) directed in a first direction by reflecting the radio waves W1, the timing of transmitting radio waves W2 (hereinafter also referred to as radio waves W2b) directed in a second direction different from the first direction by reflecting the radio waves W1, and the timing of transmitting radio waves W2 (hereinafter also referred to as radio waves W2c) directed in a third direction different from the first direction and the second direction by reflecting the radio waves W1 are repeated.

[0021] Here, the reflection direction at each timing by the RIS 3 is shared in advance with, for example, the base station device 1. Therefore, when the base station device 1 transmits radio waves to, for example, the terminal device 2, the base station device 1 transmits the radio waves to the terminal device 2 (RIS 3) at a timing when the reflection direction by the RIS 3 is a direction in which radio waves can be transmitted to the terminal device 2.

[0022] On the other hand, the reflection direction at each timing by the RIS 3 may not be shared in advance with the terminal device 2, for example. Therefore, the terminal device 2 may not be able to identify the timing when the reflection direction of the RIS 3 is in a direction that allows transmission of radio waves to the base station device 1, and may not be able to transmit radio waves to the base station device 1.

[0023] Specifically, as shown in Fig. 4, for example, radio waves W3 transmitted from the terminal device 2 may not reach the base station device 1 even when reflected by the RIS 3. More specifically, as shown in Fig. 4, for example, if the reflection direction by the RIS 3 is such that the radio waves W3 (hereinafter also referred to as radio waves W4) reflected by the RIS 3 cannot be transmitted toward the base station device 1, the radio waves W3 transmitted from the terminal device 2 will not reach the base station device 1 even when the RIS 3 is used.

[0024] Therefore, the terminal device 2 may not be able to make a PRACH (Physical Random Access CHannel) in a random access procedure reach the base station device 1, and may not be able to establish a wireless connection with the base station device 1. Therefore, in the wireless communication system 10, for example, blind areas may occur even when the wireless communication system 10 has a RIS 3.

[0025] Therefore, the base station device 1 included in the wireless communication system 10 in this embodiment transmits, for example, information (hereinafter also referred to as first control information) regarding the reflection direction of a radio wave (hereinafter also referred to as first radio wave) from the RIS 3. The first control information is, for example, broadcast information indicating the reflection direction from the RIS 3 at each timing.

[0026] Then, the base station device 1 included in the wireless communication system 10 in this embodiment receives, for example, radio waves (hereinafter also referred to as second radio waves) transmitted from the terminal device 2 and reflected by the RIS. Thereafter, the base station device 1 included in the wireless communication system 10 in this embodiment transmits a first radio wave corresponding to the second radio wave to the terminal device 2, for example, at a timing when the reflection direction of the first radio wave becomes the same as the reflection direction at the reception timing of the second radio wave. Note that the same reflection direction may be expressed as, for example, the reflection angle of the first radio wave and the reflection angle of the second radio wave being equal, or the difference in angle being within a predetermined difference.

[0027] That is, the base station device 1 included in the wireless communication system 10 in this embodiment notifies the terminal device 2 of the reflection direction at each timing by the RIS 3, for example, by broadcasting first control information. Then, the terminal device 2 included in the wireless communication system 10 in this embodiment, for example, references the first control information transmitted from the base station device 1 and identifies the reflection direction of the RIS 3 at the timing of receiving the first control information transmitted from the base station device 1 (hereinafter also referred to as the first reflection direction) as the reflection direction that allows radio waves to reach the base station device 1 from the terminal device 2. Thereafter, the terminal device 2 included in the wireless communication system 10 in this embodiment, for example, references the first control information transmitted from the base station device 1 and identifies the timing (next or subsequent timing) at which the reflection direction at the RIS 3 becomes the first reflection direction. Then, the terminal device 2 included in the wireless communication system 10 in this embodiment transmits radio waves to the base station device 1, for example, at the identified timing.

[0028] As a result, the wireless communication system 10 in this embodiment can, for example, increase the areas in which radio waves can be transmitted and received between the base station device 1, and can suppress the occurrence of blind areas within the communication area A of the base station device 1.

[0029] [Hardware Configuration of Wireless Communication System] Next, the hardware configuration of the wireless communication system 10 will be described. Fig. 5 is a diagram illustrating the hardware configuration of the base station device 1. Fig. 6 is a diagram illustrating the hardware configuration of the terminal device 2. Fig. 7 is a diagram illustrating the hardware configuration of the RIS 3.

[0030] First, we will explain the hardware configuration of the base station device 1. As shown in Fig. 5, the base station device 1 includes, for example, a CPU (Central Processing Unit) 101, which is a processor, a memory 102, a communication circuit 103, and a storage device 104. These components are connected to each other via a bus 105.

[0031] The storage device 104 has, for example, a program storage area (not shown) that stores a program 110 for performing a process (hereinafter also referred to as a communication control process) that causes radio waves transmitted from the terminal device 2 to reach the base station device 1. The storage device 104 also has, for example, a storage unit 130 (hereinafter also referred to as an information storage area 130) that stores information used when performing the communication control process. The storage device 104 may be, for example, a hard disk drive (HDD) or a solid state drive (SSD).

[0032] The CPU 101 executes, for example, a program 110 loaded from the storage device 104 into the memory 102 to perform communication control processing.

[0033] The communication circuit 103 also establishes a wireless connection with the terminal device 2 and the RIS 3 via, for example, an antenna 106 to perform communication.

[0034] Next, we will explain the hardware configuration of the terminal device 2. As shown in Fig. 6, the terminal device 2 has, for example, a CPU 201 which is a processor, a memory 202, a communication circuit 203, and a storage device 204. Each unit is connected to each other via a bus 205.

[0035] The storage device 204 has, for example, a program storage area (not shown) that stores a program 210 for performing communication control processing. The storage device 204 also has, for example, a storage unit 230 (hereinafter also referred to as information storage area 230) that stores information used when performing communication control processing. The storage device 204 may be, for example, an HDD or an SSD.

[0036] The CPU 201 executes, for example, a program 210 loaded from the storage device 204 to the memory 202 to perform communication control processing.

[0037] The communication circuit 203 also establishes a wireless connection with the base station device 1 and the RIS 3 via the antenna 206 to perform communication, for example.

[0038] Next, we will explain the hardware configuration of the RIS 3. As shown in Fig. 7, the RIS 3 includes, for example, a CPU 301 which is a processor, a memory 302, a communication circuit 303, a storage device 304, and a RIS element group 306. Each unit is connected to one another via a bus 305.

[0039] The storage device 304 has, for example, a program storage area (not shown) that stores a program 310 for performing communication control processing. The storage device 304 also has, for example, a storage unit 330 (hereinafter also referred to as information storage area 330) that stores information used when performing communication control processing. The storage device 304 may be, for example, an HDD or an SSD.

[0040] The CPU 301 executes, for example, a program 310 loaded from the storage device 304 to the memory 302 to perform communication control processing.

[0041] The communication circuit 303 performs communication by establishing a wireless connection with, for example, the base station device 1 and the terminal device 2 .

[0042] The RIS element group 306 is, for example, a collection of RIS elements (not shown) each capable of reflecting radio waves transmitted from the base station device 1 and the terminal device 2. Specifically, the RIS element group 306 is arranged, for example, in a position (for example, outside the housing of the RIS 3) where it is capable of reflecting radio waves transmitted from the base station device 1 and the terminal device 2. In the RIS element group 306, the reflection direction is controlled, for example, by appropriately changing the applied voltage.

[0043] [Functions of the Wireless Communication System] Next, functions of the wireless communication system 10 will be described. Fig. 8 is a diagram illustrating functions of the base station device 1. Fig. 9 is a diagram illustrating functions of the terminal device 2. Fig. 10 is a diagram illustrating functions of the RIS 3.

[0044] [Functions in the Base Station Device 1] First, the functions in the base station device 1 will be described.

[0045] As shown in FIG. 8, the base station device 1 realizes various functions including a timing control unit 111, an information generation unit 112, a radio wave transmission unit 113 (hereinafter also referred to simply as the transmission unit), a radio wave reception unit 114 (hereinafter also referred to simply as the reception unit), and a random access execution unit 115 by organically cooperating with hardware such as a CPU 101 and a memory 102 and a program 110.

[0046] The timing control unit 111 determines, for example, the reflection direction at each timing by the RIS 3. In other words, the timing control unit 111 determines, for example, the timing at which to change (switch) the reflection direction by the RIS 3. Note that the reflection direction at each timing by the RIS 3 may be determined in advance by, for example, an administrator of the wireless communication system 10.

[0047] The information generating unit 112 generates control information DT1 including information indicating the reflection direction at each timing by the RIS 3 (the reflection direction determined by the timing control unit 111), for example.

[0048] Specifically, the information generator 112 generates the control information DT1 at predetermined regular intervals, for example, and stores the generated control information DT1 in the information storage area 130, for example.

[0049] The radio wave transmitting unit 113 broadcasts, for example, the control information DT1 stored in the information storage area 130 (the control information DT1 generated by the information generating unit 112).

[0050] The radio wave receiving unit 114 receives, for example, radio waves transmitted from the terminal device 2. Specifically, the radio wave receiving unit 114 receives, for example, radio waves transmitted from the terminal device 2 and reflected by the RIS 3.

[0051] For example, when the information included in the radio waves transmitted from the terminal device 2 is a PRACH, the random access execution unit 115 refers to the control information DT1 stored in the information storage area 130 and identifies the timing at which the reflection direction by the RIS 3 becomes the same reflection direction (first reflection direction) as the reception timing of the radio waves transmitted from the terminal device 2 (the reception timing of the radio waves in the radio wave receiving unit 114). Hereinafter, the PRACH is also referred to as a message 1.

[0052] Specifically, the random access execution unit 115 identifies the next timing when the reflection direction by the RIS 3 becomes the same reflection direction (first reflection direction) as the reception timing of the radio wave transmitted from the terminal device 2, for example.

[0053] Then, the radio wave transmitting unit 113 transmits a Random Access Response in the random access procedure to the terminal device 2, for example, at the timing specified by the random access executing unit 115. Hereinafter, the Random Access Response will also be referred to as a message 2.

[0054] [Functions in RIS3] Next, the functions in RIS3 will be described.

[0055] As shown in FIG. 9, RIS3 realizes various functions including a radio wave receiving unit 311, a timing management unit 312, and a reflection direction control unit 313 by organically cooperating with hardware such as a CPU 301 and a memory 302 and a program 310.

[0056] The radio wave receiving unit 311 receives, for example, radio waves transmitted from the base station device 1. Then, the radio wave receiving unit 311 stores, in the information storage area 330, for example, control information DT1 included in the received radio waves.

[0057] The timing management unit 312, for example, refers to the control information DT1 stored in the information storage area 330 (the control information DT1 contained in the radio waves received by the radio wave receiving unit 311) and identifies the reflection direction at each timing by the RIS3.

[0058] The reflection direction control unit 313 changes (switches) the reflection direction of the RIS 3 according to, for example, the reflection direction at each timing by the RIS 3 (the reflection direction specified by the timing management unit 312).

[0059] Specifically, the reflection direction control unit 313 changes the reflection direction of the RIS 3 by, for example, transmitting information (for example, numerical information) indicating the applied voltage after the change to the RIS element group 306 .

[0060] [Functions of Terminal Device 2] Next, functions of the terminal device 2 will be described.

[0061] As shown in FIG. 10, the terminal device 2 realizes various functions including a radio wave receiving unit 211 (hereinafter also referred to simply as the receiving unit), a random access execution unit 212 (hereinafter also referred to simply as the processing unit), and a radio wave transmitting unit 213 (hereinafter also referred to simply as the transmitting unit) by organically cooperating with hardware such as a CPU 201 and a memory 202 and a program 210.

[0062] The radio wave receiving unit 211 receives, for example, radio waves transmitted from the base station device 1. Specifically, the radio wave receiving unit 211 receives, for example, radio waves transmitted from the base station device 1 at a timing when the reflection direction by the RIS 3 is the first reflection direction. Then, the radio wave receiving unit 211 stores, for example, control information DT1 included in the received radio waves in the information storage area 230.

[0063] The random access execution unit 212, for example, refers to the control information DT1 stored in the information storage area 230 (the control information DT1 contained in the radio waves received by the radio wave receiving unit 211) and determines the timing at which the reflection direction by RIS3 becomes the first reflection direction.

[0064] Specifically, the random access execution unit 212 identifies the next timing when the reflection direction by the RIS 3 will become the first reflection direction, for example.

[0065] The radio wave transmitting unit 213 transmits the PRACH to the base station device 1 at the timing specified by the random access executing unit 212, for example.

[0066] Thereafter, the radio wave receiving unit 211 receives, for example, a Random Access Response transmitted from the base station device 1 .

[0067] [Sequence Chart of Communication Control Processing in First Embodiment] Next, a sequence chart of communication control processing in the first embodiment will be described. Fig. 11 is a sequence chart of communication control processing in the first embodiment.

[0068] As shown in FIG. 11, the base station device 1 broadcasts, for example, control information DT1 relating to the reflection direction of the radio wave (first radio wave) from the RIS 3 (S1).

[0069] Specifically, the base station device 1 broadcasts, for example, the control information DT1 stored in the information storage area 130. In this case, the terminal device 2 receives, for example, the control information DT1 broadcast by the base station device 1. Specifically, the terminal device 2 receives the control information DT1 included in the radio waves reflected by the RIS 3, for example, at the timing when the reflection direction by the RIS 3 is the first reflection direction.

[0070] Next, the terminal device 2, for example, refers to the control information DT1 received in S1 and transmits radio waves (second radio waves) to the base station device 1 (S2).

[0071] Specifically, the terminal device 2, for example, refers to the control information DT1 received in S1, and identifies the timing at which the reflection direction by the RIS 3 becomes the first reflection direction. Then, the terminal device 2 transmits the PRACH to the base station device 1, for example, at the identified timing.

[0072] Thereafter, the base station device 1 transmits, for example, a radio wave (first radio wave) corresponding to the radio wave received in S2 to the terminal device 2 (S3).

[0073] Specifically, the base station device 1, for example, refers to the control information DT1 stored in the information storage area 130, and identifies the timing at which the reflection direction by the RIS 3 becomes the first reflection direction. Then, the base station device 1 transmits a Random Access Response (a Random Access Response corresponding to the PRACH received from the terminal device 2) to the terminal device 2, for example, at the identified timing.

[0074] That is, the base station device 1 included in the wireless communication system 10 in this embodiment notifies the terminal device 2 of the reflection direction at each timing by the RIS3, for example, by broadcasting control information DT1. Then, the terminal device 2 included in the wireless communication system 10 in this embodiment, for example, references the control information DT1 transmitted from the base station device 1 and identifies the first reflection direction of the RIS3 at the timing of receiving the control information DT1 transmitted from the base station device 1 as the reflection direction that allows radio waves to reach the base station device 1 from the terminal device 2. Thereafter, the terminal device 2 included in the wireless communication system 10 in this embodiment, for example, references the control information DT1 transmitted from the base station device 1 and identifies the timing (next or subsequent timing) at which the reflection direction at the RIS3 becomes the first reflection direction. Then, the terminal device 2 included in the wireless communication system 10 in this embodiment transmits radio waves to the base station device 1, for example, at the identified timing.

[0075] As a result, the wireless communication system 10 in this embodiment can, for example, increase the areas in which radio waves can be transmitted and received between the base station device 1, and can suppress the occurrence of blind areas within the communication area A of the base station device 1.

[0076] [Details of communication control processing in the first embodiment] Next, details of the communication control processing in the first embodiment will be described. Figures 12 to 17 are flowcharts illustrating details of the communication control processing in the first embodiment. Figures 18 to 23 are diagrams illustrating details of the communication control processing in the first embodiment.

[0077] [Reflection Control Processing] First, a description will be given of the communication control processing, which is a processing for controlling the reflection direction by the RIS 3 (hereinafter also referred to as reflection control processing). Figures 12 to 14 are flowcharts illustrating the reflection control processing.

[0078] 12, the timing control unit 111 of the base station device 1 waits until, for example, an information reporting timing (NO in S11). The information reporting timing may be, for example, a regular timing such as every 80 ms or 160 ms.

[0079] Then, when it is time to notify information (YES in S11), the timing control unit 111 determines, for example, the reflection direction at each timing by the RIS 3 (S12).

[0080] Next, the information generator 112 of the base station device 1 generates control information DT1 including information indicating the reflection direction determined in S12 (S13). A specific example of the control information DT1 will be described below.

[0081] [Specific Examples of Control Information] FIGS. 18 and 19 are diagrams illustrating specific examples of the control information DT1 in the first embodiment.

[0082] As shown in FIG. 18, the control information DT1 has, for example, items such as a "unit reflection time" that sets the time (hereinafter also referred to as the unit reflection time) for continuously reflecting radio waves in each reflection direction, and a "number of reflection directions" that indicates the number of reflection directions.

[0083] Specifically, in the example shown in FIG. 18, the control information DT1 has, for example, "1 (frame)" set as the "unit reflection time" and "3" set as the "number of reflection directions."

[0084] That is, the control information DT1 shown in FIG. 18 indicates that the reflection direction by the RIS 3 is switched every frame, and that there are three reflection directions by the RIS 3, for example.

[0085] In the example shown in FIG. 19, the control information DT1 has, for example, "2 (frames)" set as the "unit reflection time" and "3" set as the "number of reflection directions."

[0086] That is, the control information DT1 shown in FIG. 19 indicates that the reflection direction by the RIS 3 is switched every two frames, and that there are three reflection directions by the RIS 3, for example.

[0087] Returning to FIG. 12, the radio wave transmitting unit 113 of the base station device 1 broadcasts, for example, the control information DT1 generated in S13 (S14).

[0088] On the other hand, as shown in FIG. 13, the radio wave receiving unit 311 of the RIS 3 waits until it receives, for example, the control information DT1 broadcast from the base station device 1 (NO in S21).

[0089] Then, when the control information DT1 broadcast from the base station device 1 is received (YES in S21), the radio wave receiving unit 311 of the RIS 3 stores the received control information DT1 in the information storage area 330, for example (S22).

[0090] Next, as shown in FIG. 14, the timing management unit 312 of the RIS 3 waits until the timing at which the reflection direction of the RIS 3 is switched (hereinafter also referred to as reflection direction switching timing) arrives (NO in S31).

[0091] Specifically, the timing management unit 312, for example, refers to the control information DT1 (the control information DT1 received in S21) stored in the information storage area 330, and specifies the timing at which the reflection direction of the RIS 3 will next be switched. Then, the timing management unit 312 waits, for example, until the specified timing arrives.

[0092] Thereafter, when it is time to switch the reflection direction (YES in S31), the reflection direction control unit 313 switches the reflection direction by the RIS 3, for example (S32).

[0093] Specifically, the reflection direction control unit 313 refers to, for example, the control information DT1 stored in the information storage area 330, and switches the reflection direction by the RIS 3 so that it corresponds to the current timing. A specific example of the process of S32 will be described below.

[0094] [Specific Example (1) of S32] Fig. 20 is a diagram illustrating a specific example of S32. Hereinafter, the first direction (transmission direction of radio waves W2a) described in Fig. 3 will also be simply referred to as "1," the second direction (transmission direction of radio waves W2b) described in Fig. 3 will also be simply referred to as "2," and the third direction (transmission direction of radio waves W2c) described in Fig. 3 will also be simply referred to as "3."

[0095] Specifically, in the control information DT1 described in FIG. 18 , the "unit reflection time" and the "number of reflection directions" are set to "1 (frame)" and "3," respectively. Therefore, when the control information DT1 received in S21 is the control information DT1 described in FIG. 18 , the reflection direction control unit 313 performs control so that, for example, the reflection directions (the reflection directions for uplink radio waves and the reflection directions for downlink radio waves) in the first, fourth, seventh, and tenth frames are set to "1," as shown in FIG. 20 . Furthermore, in this case, the reflection direction control unit 313 performs control so that, for example, the reflection directions (the reflection directions for uplink radio waves and the reflection directions for downlink radio waves) in the second, fifth, eighth, and eleventh frames are set to "2." Furthermore, in this case, the reflection direction control unit 313 performs control so that, for example, the reflection directions (the reflection directions for uplink radio waves and the reflection directions for downlink radio waves) in the third, sixth, ninth, and twelfth frames are set to "3."

[0096] [Specific Example (2) of S32] FIG. 21 is a diagram illustrating another specific example of S32.

[0097] Specifically, in the control information DT1 described in FIG. 19, the "unit reflection time" and the "number of reflection directions" are set to "2 (frames)" and "3," respectively. Therefore, when the control information DT1 received in S21 is the control information DT1 described in FIG. 19, the reflection direction control unit 313 performs control so that, for example, the reflection directions (the reflection directions for uplink radio waves and the reflection directions for downlink radio waves) in the first, second, seventh, eighth, thirteenth, and fourteenth frames are set to "1," as shown in FIG. 21. Furthermore, in this case, the reflection direction control unit 313 performs control so that, for example, the reflection directions (the reflection directions for uplink radio waves and the reflection directions for downlink radio waves) in the third, fourth, ninth, and tenth frames are set to "2." Furthermore, in this case, the reflection direction control unit 313 controls the reflection direction (the reflection direction for the upstream radio waves and the reflection direction for the downstream radio waves) in the 5th, 6th, 11th, and 12th frames to be "3", for example.

[0098] [Main Processing] Next, the main processing of the communication control processing (hereinafter also simply referred to as the main processing) will be described. Figures 15 to 17 are flowcharts illustrating the main processing.

[0099] As shown in FIG. 15, the radio wave receiving unit 211 of the terminal device 2 waits until it receives radio waves transmitted from the base station device 1 (NO in S41).

[0100] Specifically, the radio wave receiving unit 211 waits until it receives the radio wave transmitted from the base station device 1 at a timing when the direction of reflection by the RIS 3 is the first reflection direction, for example.

[0101] Then, when radio waves transmitted from the base station device 1 are received (YES in S41), the radio wave receiving unit 211 stores, for example, the control information DT1 contained in the received radio waves in the information storage area 230 (S42).

[0102] That is, the terminal device 2 stores in the information storage area 230 the same information as the control information DT1 transmitted from the base station device 1 to the RIS 3 (the control information DT1 stored in the information storage area 330), for example.

[0103] 16 , the random access execution unit 212 of the terminal device 2 waits until it is time to transmit radio waves to the base station device 1 (hereinafter also referred to as radio wave transmission timing) (NO in S51). The radio wave transmission timing may be, for example, the timing to establish a wireless connection with the base station device 1.

[0104] Specifically, the random access execution unit 212, for example, references the control information DT1 stored in the information storage area 230, and identifies the next timing at which the reflection direction by the RIS 3 will become the first reflection direction. Then, the random access execution unit 212 waits, for example, until the identified timing arrives.

[0105] Then, when it is time to transmit radio waves (YES in S51), the radio wave transmitting unit 213 of the terminal device 2 transmits a PRACH to the base station device 1, for example, at the timing specified in S51 (S52).

[0106] On the other hand, as shown in FIG. 17, the radio wave receiving unit 114 of the base station device 1 waits until it receives, for example, a PRACH transmitted from the terminal device 2 (NO in S61).

[0107] Then, when the PRACH transmitted from the terminal device 2 is received (YES in S61), the random access execution unit 115 of the base station device 1, for example, refers to the control information DT1 stored in the information storage area 130, and identifies the timing at which the reflection direction by the RIS3 becomes the same reflection direction (first reflection direction) as the reception timing of the radio waves transmitted from the terminal device 2 (the reception timing of the radio waves in S61) (S62).

[0108] Specifically, the random access execution unit 115 identifies the next timing when the reflection direction by the RIS 3 becomes the same reflection direction (first reflection direction) as the reception timing of the radio wave transmitted from the terminal device 2, for example.

[0109] Then, the radio wave transmitting unit 113 transmits a Random Access Response to the terminal device 2 at the timing specified in S62 (S63). A specific example of the communication control process will be described below.

[0110] [Specific Example (1) of Communication Control Processing] FIG. 22 is a diagram illustrating a specific example of communication control processing in the first embodiment.

[0111] As shown in Figure 22, for example, if the control information DT1 received in S41 is the control information DT1 described in Figure 18 and the timing at which the control information DT was received in S41 is the second frame, the terminal device 2 determines that the reflection direction by the RIS3 when the control information DT1 transmitted from the base station device 1 was transmitted to the terminal device 2 (when the control information DT1 transmitted from the base station device 1 reached the terminal device 2) was "2".

[0112] Therefore, in this case, the terminal device 2 transmits a PRACH to the base station device 1 at the next or subsequent timing (a timing after the second frame) when the reflection direction by the RIS 3 is "2", for example.

[0113] Specifically, as shown in FIG. 22, the terminal device 2 transmits a PRACH to the base station device 1 in the fifth frame in which the reflection direction by the RIS 3 is "2", for example.

[0114] Meanwhile, in this case, the base station device 1 receives the PRACH transmitted from the terminal device 2 in, for example, the fifth frame.

[0115] In this case, the base station device 1 determines that the reflection direction by the RIS3 was "2" when the PRACH transmitted from the terminal device 2 was transmitted to the base station device 1 (when the PRACH transmitted from the terminal device 2 reached the base station device 1).

[0116] Therefore, the base station device 1 transmits a Random Access Response to the terminal device 2, for example, at the next timing or later (a timing after the fifth frame) when the reflection direction by the RIS 3 is "2".

[0117] Specifically, as shown in FIG. 22, the base station apparatus 1 transmits a Random Access Response to the terminal apparatus 2 in the eighth frame in which the reflection direction by the RIS 3 is "2", for example.

[0118] [Specific Example (2) of Communication Control Processing] Next, another specific example of the communication control processing in the first embodiment will be described. Fig. 23 is a diagram illustrating another specific example of the communication control processing in the first embodiment.

[0119] As shown in Figure 23, for example, if the control information DT1 received in S41 is the control information DT1 described in Figure 20 and the timing at which the control information DT was received in S41 is the first frame, the terminal device 2 determines that the reflection direction by RIS3 when the control information DT1 transmitted from the base station device 1 was transmitted to the terminal device 2 (when the control information DT1 transmitted from the base station device 1 reached the terminal device 2) was "1".

[0120] Therefore, in this case, the terminal device 2 transmits a PRACH to the base station device 1 at the next or subsequent timing (a timing after the first frame) when the reflection direction by the RIS 3 is "1".

[0121] Specifically, as shown in FIG. 23, the terminal device 2 transmits a PRACH to the base station device 1 in the seventh frame in which the reflection direction by the RIS 3 is "1", for example.

[0122] Meanwhile, in this case, the base station device 1 receives the PRACH transmitted from the terminal device 2 in, for example, the seventh frame.

[0123] In this case, the base station device 1 determines that the reflection direction by the RIS3 was "1" when the PRACH transmitted from the terminal device 2 was transmitted to the base station device 1 (when the PRACH transmitted from the terminal device 2 reached the base station device 1).

[0124] Therefore, the base station apparatus 1 transmits a Random Access Response to the terminal apparatus 2, for example, at the next timing or later (a timing after the seventh frame) when the reflection direction by the RIS 3 is "1".

[0125] Specifically, as shown in FIG. 23 , the base station apparatus 1 transmits a Random Access Response to the terminal apparatus 2, for example, in the 13th frame in which the reflection direction by the RIS 3 is “1” (the next timing in which the reflection direction is “1”).

[0126] As described above, in the wireless communication system 10 according to the present embodiment, the base station device 1 transmits, for example, control information DT1 relating to the reflection direction of radio waves (first radio waves) transmitted by the RIS 3. Then, the base station device 1 receives, for example, radio waves (second radio waves) transmitted from the terminal device 2 and reflected by the RIS. Thereafter, the base station device 1 transmits, for example, the first radio waves corresponding to the second radio waves to the terminal device 2 at a timing when the reflection direction of the first radio waves is the same as the reception timing of the second radio waves.

[0127] That is, the base station device 1 included in the wireless communication system 10 in this embodiment notifies the terminal device 2 of the reflection direction at each timing by the RIS3, for example, by broadcasting control information DT1. Then, the terminal device 2 included in the wireless communication system 10 in this embodiment, for example, references the control information DT1 transmitted from the base station device 1 and identifies the first reflection direction of the RIS3 at the timing of receiving the control information DT1 transmitted from the base station device 1 as the reflection direction that allows radio waves to reach the base station device 1 from the terminal device 2. Thereafter, the terminal device 2 included in the wireless communication system 10 in this embodiment, for example, references the control information DT1 transmitted from the base station device 1 and identifies the timing (next or subsequent timing) at which the reflection direction at the RIS3 becomes the first reflection direction. Then, the terminal device 2 included in the wireless communication system 10 in this embodiment transmits radio waves to the base station device 1, for example, at the identified timing.

[0128] As a result, the wireless communication system 10 in this embodiment can, for example, increase the areas in which radio waves can be transmitted and received between the base station device 1, and can suppress the occurrence of blind areas within the communication area A of the base station device 1.

[0129] Furthermore, the wireless communication system 10 in this embodiment is capable of suppressing the occurrence of blind areas within the communication area A of the base station device 1, for example, without having a unique protocol between the base station device 1 and the RIS 3.

[0130] In addition, in S13, the information generation unit 112 may change the number set in the ``number of reflection directions'' in the control information DT1, for example, depending on the number of terminal devices 2 within the communication area A of the base station device 1.

[0131] Specifically, the information generator 112 may, for example, set a larger number in the "number of reflection directions" in the control information DT1 the greater the number of terminal devices 2 within the communication area A of the base station device 1. Furthermore, the information generator 112 may, for example, set a smaller number in the "number of reflection directions" in the control information DT1 the fewer the number of terminal devices 2 within the communication area A of the base station device 1.

[0132] More specifically, the information generation unit 112 may, for example, estimate that the greater the number of PRACH receptions (number of receptions per unit time) at the radio wave receiving unit 114, the greater the number of terminal devices 2 within the communication area A of the base station device 1, and may estimate that the fewer the number of PRACH receptions (number of receptions per unit time) at the radio wave receiving unit 114, the fewer the number of terminal devices 2 within the communication area A of the base station device 1.

[0133] Furthermore, the information generation unit 112 may, for example, estimate that the greater the time average of the radio wave reception level at the radio wave receiving unit 114, the greater the number of terminal devices 2 within the communication area A of the base station device 1, and that the smaller the time average of the radio wave reception level at the radio wave receiving unit 114, the fewer the number of terminal devices 2 within the communication area A of the base station device 1.

[0134] This allows the wireless communication system 10 in this embodiment to perform control according to the congestion state within the communication area A, for example.

[0135] [First Modification] Next, a modification of the first embodiment (hereinafter also referred to as the first modification) will be described. Figures 24 and 25 are diagrams illustrating the communication control process in the first modification.

[0136] [Specific Example of Control Information] FIG. 24 is a diagram illustrating a specific example of control information DT1 in the first modified example.

[0137] As shown in Fig. 24, the control information DT1 includes, for example, an "offset" item that sets an offset between the reflection direction for downlink radio waves and the reflection direction for uplink radio waves, in addition to the "unit reflection time" and "number of reflection directions." Hereinafter, of the information included in the control information DT1, information regarding the reflection direction for uplink radio waves (for example, information regarding the offset between the reflection direction for downlink radio waves and the reflection direction for uplink radio waves) will also be referred to as second control information.

[0138] Specifically, as shown in FIG. 24, the control information DT1 is set, for example, to "1 (frame)" as the "unit reflection time," to "8" as the "number of reflection directions," and to "3" as the "offset."

[0139] That is, for example, if RIS3 is capable of separately controlling the reflection direction for downlink radio waves and the reflection direction for uplink radio waves, in other words, if RIS3 has both a RIS element group 306 that reflects downlink radio waves and a RIS element group 306 that reflects uplink radio waves, the base station device 1 may, for example, broadcast control information DT1 that includes "offset" as an item.

[0140] As a result, the wireless communication system 10 in this modification can, for example, determine the transmission timing of radio waves (uplink radio waves) from the terminal device 2 to the base station device 1 according to the reflection direction of the uplink radio waves. Therefore, the wireless communication system 10 in this modification can, for example, vary the time from when the terminal device 2 receives the control information DT1 to when it transmits a PRACH to the base station device 1, or the time from when the base station device 1 receives the PRACH to when it transmits a Random Access Response to the terminal device 2. Therefore, even if the value (time) set for the "unit reflection time" in the control information DT1 is large, the wireless communication system 10 in this modification can shorten the time from when the terminal device 2 receives the control information DT1 to when it transmits a PRACH to the base station device 1, or the time from when the base station device 1 receives the PRACH to when it transmits a Random Access Response to the terminal device 2.

[0141] [Specific Example of Communication Control Processing (3)] FIG. 25 is a diagram illustrating a specific example of communication control processing in the first modified example.

[0142] As shown in Figure 25, for example, if the control information DT1 received in S41 is the control information DT1 described in Figure 18 and the timing at which the control information DT was received in S41 is the second frame, the terminal device 2 determines that the reflection direction by RIS3 when the control information DT1 transmitted from the base station device 1 was transmitted to the terminal device 2 (when the control information DT1 transmitted from the base station device 1 reached the terminal device 2) was "2".

[0143] Therefore, in this case, the terminal device 2 transmits a PRACH to the base station device 1 at the next or subsequent timing (a timing after the second frame) when the reflection direction by RIS3 (the reflection direction for the uplink radio waves) is "2".

[0144] Specifically, as shown in FIG. 25, the terminal device 2 transmits a PRACH to the base station device 1, for example, in the fifth frame (the next timing when the reflection direction for the uplink radio waves is "2") when the reflection direction by the RIS 3 (the reflection direction for the uplink radio waves) is "2".

[0145] Meanwhile, in this case, the base station device receives the PRACH transmitted from the terminal device 2 in, for example, the fifth frame.

[0146] In this case, the base station device 1 determines that the reflection direction by the RIS 3 when the PRACH transmitted from the terminal device 2 reaches the base station device 1 is "2".

[0147] Therefore, the base station device 1 transmits a Random Access Response to the terminal device 2, for example, at the next timing or later (a timing after the fifth frame) when the reflection direction by the RIS 3 is "2".

[0148] Specifically, as shown in FIG. 25 , the base station device 1 transmits a Random Access Response to the terminal device 2, for example, in the 10th frame in which the reflection direction by the RIS 3 is “2” (the next timing in which the reflection direction for the downlink radio wave is “2”).

[0149] [Second Modification] Next, a modification of the second embodiment (hereinafter also referred to as the second modification) will be described. Figures 26 and 27 are diagrams illustrating the communication control process in the second modification.

[0150] [Configuration of wireless communication system in second variant] As shown in FIG. 26 , the wireless communication system 10 includes, for example, a base station device 1 and a terminal device 2, as well as a RIS 3 (hereinafter also referred to as RIS 3a) and another RIS 3 (hereinafter also referred to as RIS 3b).

[0151] 26, for example, the RIS 3a reflects the radio wave W1 (hereinafter also referred to as the radio wave W1a) transmitted from the base station device 1. Also, as shown in FIG. 26, for example, the RIS 3b reflects the radio wave W1 (hereinafter also referred to as the radio wave W1b) transmitted from the base station device 1.

[0152] Specifically, as shown in FIG. 26, the RIS3a performs control so that, for example, the timing of transmitting radio waves W2a in a first direction by reflecting radio waves W1a, the timing of transmitting radio waves W2b in a second direction different from the first direction by reflecting radio waves W1, and the timing of transmitting radio waves W2c in a third direction different from the first direction and the second direction by reflecting radio waves W1 are repeated.

[0153] Furthermore, as shown in FIG. 26, RIS3b performs control so that, for example, the timing of transmitting radio wave W2 (hereinafter also referred to as radio wave W2d) directed in a fourth direction by reflecting radio wave W1b and the timing of transmitting radio wave W2 (hereinafter also referred to as radio wave W2e) directed in a fifth direction different from the fourth direction by reflecting radio wave W1 are repeated.

[0154] [Specific Example of Control Information] FIG. 27 is a diagram illustrating a specific example of control information DT1 in the second modified example.

[0155] 27, the control information DT1 has, for example, items of "unit reflection time" and "number of reflection directions," as well as "identification information" in which identification information is set to identify each RIS 3. Furthermore, as shown in FIG. 27, the control information DT1 has, for example, items of "unit reflection time," "number of reflection directions," and "identification information" for each RIS 3.

[0156] 27, for example, in the control information DT1, "3a" indicating RIS3a is set as the "identification information," "1 (frame)" is set as the "unit reflection time" corresponding to RIS3a, and "3" is set as the "number of reflection directions" corresponding to RIS3a. Also, in the control information DT1, for example, "3b" indicating RIS3b is set as the "identification information," "2 (frame)" is set as the "unit reflection time" corresponding to RIS3b, and "2" is set as the "number of reflection directions" corresponding to RIS3b.

[0157] That is, when the wireless communication system 10 has a plurality of RISs 3, the base station device 1 may broadcast, for example, control information DT1 including information about each of the plurality of RISs 3.

[0158] As a result, the wireless communication system 10 in this modified example can, for example, further increase the areas in which radio waves can be transmitted and received between the base station device 1, and can further reduce the occurrence of blind areas within the communication area A of the base station device 1.

[0159] Furthermore, the wireless communication system 10 in this modification can select, for example, from a plurality of RISs 3, the RIS 3 to be used for transmitting radio waves to the base station device 1. Therefore, the wireless communication system 10 in this modification can further shorten, for example, the time from when the terminal device 2 receives the control information DT1 until when it transmits the PRACH to the base station device 1, and the time from when the base station device 1 receives the PRACH until it transmits the Random Access Response to the terminal device 2.

[0160] 1: Base station device 2: Terminal device 3: RIS 10: Wireless communication system 101: CPU 102: Memory 103: Communication circuit 104: Storage device 105: Bus 106: Antenna 110: Program 130: Information storage area 201: CPU 202: Memory 203: Communication circuit 204: Storage device 205: Bus 206: Antenna 210: Program 230: Information storage area 301: CPU 302: Memory 303: Communication circuit 304: Storage device 305: Bus 306: RIS element group 310: Program 330: Information storage area

Claims

1. A base station device in a wireless communication system having a base station device, a terminal device, and a reflection control device that reflects at least one of a first radio wave transmitted by the base station device and a second radio wave transmitted by the terminal device, the base station device having: a transmitting unit that transmits first control information regarding the reflection direction of the first radio wave by the reflection control device; and a receiving unit that receives the second radio wave transmitted from the terminal device and reflected by the reflection control device, wherein the transmitting unit transmits the first radio wave corresponding to the second radio wave to the terminal device at a timing when the reflection direction of the first radio wave becomes the same reflection direction as the reception timing of the second radio wave.

2. The base station device according to claim 1, wherein the first control information is information indicating the timing at which the reflection direction of the first radio wave becomes one of a plurality of reflection directions.

3. The base station device described in claim 2, wherein the multiple reflection directions include a first reflection direction in which the reflection control device reflects the first radio wave, thereby enabling the first radio wave to be transmitted from the base station device to the terminal device, and the second radio wave received by the receiving unit is the second radio wave transmitted from the terminal device at the timing when the reflection direction of the first radio wave becomes the first reflection direction.

4. The base station device according to claim 1, wherein the transmitting unit transmits the first radio wave including message 2 in the random access procedure to the terminal device when message 1 in the random access procedure is included in the second radio wave.

5. The base station device according to claim 1, wherein the transmitting unit transmits second control information relating to the direction of reflection of the second radio wave by the reflection control device.

6. The base station device described in claim 5, wherein the second control information is information indicating the timing at which each of the reflection directions of the second radio waves transmitted from multiple directions becomes a second reflection direction toward the base station device.

7. The base station device according to claim 6, wherein the second radio wave received by the receiving unit is the second radio wave transmitted from the terminal device at a timing when the reflection direction of the second radio wave becomes the second reflection direction.

8. A terminal device in a wireless communication system having a base station device, a terminal device, and a reflection control device that reflects at least one of a first radio wave transmitted by the base station device and a second radio wave transmitted by the terminal device, the terminal device having: a receiving unit that receives first control information transmitted from the base station device and reflected by the reflection control device, the first control information being information regarding the reflection direction of the first radio wave by the reflection control device; a processing unit that references the first control information received by the receiving unit and identifies the timing at which the reflection direction of the first radio wave will be the same as the reception timing of the first control information; and a transmitting unit that transmits the second radio wave to the terminal device at the timing identified by the processing unit.

9. The terminal device according to claim 8, wherein the receiving unit receives the first radio wave corresponding to the second radio wave from the base station device.

10. A wireless communication system having a base station device, a terminal device, and a reflection control device that reflects at least one of a first radio wave transmitted by the base station device and a second radio wave transmitted by the terminal device, wherein the base station device transmits first control information regarding the reflection direction of the first radio wave by the reflection control device, the terminal device refers to the first control information and identifies the timing at which the reflection direction of the first radio wave will be the same as the reflection direction at the reception timing of the first control information, and transmits the second radio wave to the terminal device at the identified timing, and the base station device transmits the first radio wave corresponding to the second radio wave to the terminal device at the timing at which the reflection direction of the first radio wave will be the same as the reflection direction at the reception timing of the second radio wave.

Images