Radio communication system and radio communication method

Abstract

The purpose of the present disclosure is to provide a radio communication system and a radio communication method with which it is possible to reduce the overhead when a relay device to be used for relaying is selected from among a plurality of relay devices in radio communication via a relay device. The radio communication system according to the present disclosure comprises a base station, a plurality of relay devices, and a relay device selection device. The relay device selection device has a database. The relay device selection device executes: a process for acquiring position information of a terminal; a process for referring to the database to acquire information of a relay path using one or more relay devices to be used in radio communication between the base station and the terminal; and a process for causing the relay devices included in the acquired relay path to relay the radio communication between the base station and the terminal. In the database, information of the relay route to be used in the radio communication between the base station and the terminal is set according to a position within a radio area of the base station.

Description

Wireless communication system and wireless communication method

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[0001] The present disclosure relates to a wireless communication system and a wireless communication method for selecting a relay device to be used for relaying from among a plurality of relay devices in wireless communication via a relay device.

[0002] Non-Patent Document 1 discloses a relay device capable of dynamically switching the reflection direction of radio waves. By forming a wireless propagation path between a base station and a terminal using the relay device, it is possible to improve the communication quality in an environment with poor visibility where there are obstacles.

[0003] Y. Cao, T. Lv and W. Ni, "Intelligent Reflecting Surface Aided Multi-User mmWave Communications for Coverage Enhancement," 2020 IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications, London, UK, 2020, pp. 1-6, doi: 10.1109 / PIMRC48278.2020.9217160.

[0004] When there are a plurality of relay devices, it is necessary to determine a relay device that relays the wireless communication between the base station and the terminal. Conventionally, as the position information of the terminal is input, a plurality of candidates for the relay path are selected, and the relay device is selected based on the geometric calculation results for each relay path.

[0005] However, conventionally, the relay device has been selected by performing calculations each time for newly input terminal position information. Therefore, even if the input position information is the same as or similar to the already calculated position information, an overhead associated with the calculation each time has occurred.

[0006] An object of the present disclosure is to provide a wireless communication system and a wireless communication method capable of reducing the overhead when selecting a relay device to be used for relaying from among a plurality of relay devices in wireless communication via a relay device, in order to solve the above problems.

[0007] A first aspect of this disclosure is a wireless communication system comprising a base station, a plurality of relay devices capable of relaying wireless communication between the base station and a terminal, and a relay device selection device, wherein the relay device selection device has a database and is configured to perform the following: a process of acquiring location information of the terminal; a process of referring to the database and acquiring information on a relay route using one or more of the relay devices to be used in wireless communication between the base station and the terminal; and a process of causing a relay device included in the acquired relay route to relay the wireless communication between the base station and the terminal, wherein the database preferably has information on relay routes to be used in wireless communication between the base station and the terminal set according to their location within the base station's wireless area.

[0008] A second aspect of the present disclosure is preferably a wireless communication method comprising: virtually dividing at least a portion of the wireless area of ​​a base station into a plurality of grids; designating one of the grids as a virtual terminal installation location; selecting a plurality of candidate relay paths for relaying wireless communication between the base station and the installation location by combining one or more relay devices present in the wireless area; calculating geometric information for the candidate relay paths; selecting a relay path from the candidates based on the geometric information; associating the information of the selected relay paths with the location information of the grids and storing it in a storage device; and selecting and storing relay paths for all of the plurality of grids in the storage device.

[0009] In this disclosure, the base station determines the relay path to be used for wireless communication with the terminal that has notified its location information by referring to a database. In the database, information on the relay path to be used for wireless communication between the base station and the terminal is set according to the location within the base station's wireless area. Since geometric calculations are not performed each time a relay path is selected, the overhead when selecting a relay device can be reduced.

[0010] This is a diagram showing the wireless communication system according to Embodiment 1. This is a flowchart showing the database creation procedure performed by the relay device selection device according to Embodiment 1. This is a flowchart showing the relay control procedure performed by the base station according to Embodiment 1. This is a block diagram showing the configuration of the wireless communication system according to Embodiment 1. This is a modified example of Figure 4. This is a diagram showing the hardware configuration of the relay device selection device according to Embodiment 1.

[0011] Embodiments of this disclosure will be described with reference to the drawings. The same or corresponding components will be denoted by the same reference numerals, and repetition of the description may be omitted.

[0012] Embodiment 1 Figure 1 is a diagram showing a wireless communication system 100 according to Embodiment 1. The wireless communication system 100 comprises a base station 2, a plurality of relay devices 8, and a relay device selection device 4.

[0013] Base station 2 acquires location information and quality information from one or more terminals 6 under its control. Base station 2 refers to the database 10 created by the relay device selection device 4 and determines the relay route to be used for wireless communication with the terminal 6 that notified the location information. Base station 2 transmits control signals for relay control to one or more relay devices 8 included in the determined relay route.

[0014] Each time location information is received from terminal 6, base station 2 refers to database 10 and updates the relay route used for wireless communication with terminal 6. When communicating wirelessly with terminal 6, base station 2 sends and receives wireless signals to and from terminal 6 using the relay route determined based on the latest location information of terminal 6. In this way, base station 2 establishes mobile communication with terminal 6. However, terminal 6 is not limited to a mobile terminal and may be a fixed terminal.

[0015] Terminal 6 transmits its own location information and quality information to base station 2 using a low-frequency band. Quality information refers to information about communication quality, such as the strength of received power (RSSI and RSRQ), noise indices (RSRP and SINR), throughput, and propagation path information. If terminal 6 does not have a function to acquire location information, the location information of terminal 6 may be acquired by another sensing device and transmitted to base station 2.

[0016] In this disclosure, descriptions applicable to terminals 6a, 6b, and 6c, where there is no need to distinguish between them, will simply refer to them as terminal 6. Only when it is necessary to distinguish between them will their respective reference numerals be used.

[0017] The relay device selection device 4 creates a database 10 to be provided to the base station 2. The database 10 contains information on relay routes to be used in wireless communication between the base station 2 and the terminal 6, set according to their location within the base station 2's wireless area. Specifically, in the database 10, the wireless area is divided into multiple grids 9, and relay routes are set for each grid 9. In the example shown in this figure, a relay route using relay device 8a is set in grid 9a where terminal 6a is located. Similarly, relay device 8b is set in grid 9c where terminal 6c is located. However, in the figure, relay device 8a is simply referred to as a, and relay device 8b is simply referred to as b.

[0018] The relay device 8 is a reflector capable of relaying signals transmitted from the base station 2 or terminal 6. Based on control signals received from the base station 2, the relay device 8 can be turned on / off or its relay resources can be changed. For example, the relay device 8 may be an Intelligent reflecting surface (IRS) or a Reconfigurable Intelligent Surface (RIS) that performs dynamic beam control by power-driving multiple reflective elements. However, the relay device 8 may also be an unpowered device that does not have the function of dynamically controlling the beam.

[0019] In this disclosure, descriptions applicable to relay devices 8a and 8b, where there is no need to distinguish between them, will simply refer to them as "relay device 8." Only when it is necessary to distinguish between them will their respective reference numerals be used.

[0020] In this disclosure, the base station 2 determines the relay route to be used for wireless communication with the terminal 6 that has notified its location information by referring to the database 10. In the database 10, information on the relay route to be used for wireless communication between the base station 2 and the terminal 6 is set according to the location within the base station 2's wireless area. Since geometric calculations are not performed each time a relay route is selected, the overhead when selecting the relay device 8 can be reduced.

[0021] <Method for creating database 10> Figure 2 is a flowchart showing the procedure for creating database 10 performed by the relay device selection device 4 according to Embodiment 1. Here, we assume that there is only one relay device 8 included in the relay path.

[0022] First, the location information of the base station 2 and the multiple relay devices 8 is acquired (step S01). In most cases, the location information of the base station 2 and the relay devices 8 does not change because they are fixed stations. Therefore, this step only needs to be performed when the base station 2 or the relay devices 8 are newly installed, or when the relay devices 8 are mobile stations.

[0023] Next, for each relay device 8 present in the wireless area, the distance from the base station 2 to the relay device 8 and the angle of incidence of radio waves at the relay device 8 are calculated geometrically (step S02). This step should only be performed if the base station 2 or the relay device 8 is newly installed, or if the relay device 8 is a mobile station.

[0024] Next, at least a portion of the wireless area of ​​base station 2 is virtually divided into multiple grids 9 (step S03).

[0025] Furthermore, one of the divided grids 9 is designated as the installation location for the virtual terminal 6 (step S04).

[0026] Furthermore, for each relay device 8, the distance between the relay device 8 and the target grid, and the reflection angle of the radio waves at the relay device 8 are calculated (step S05). Through these steps, geometric information of the relay path is calculated for each relay device 8. The geometric information includes the relay distance and information on the incidence angle and reflection angle of the radio waves at the relay device 8. Note that the geometric information may be calculated for multiple frequencies, taking into account the frequency dependence of the radio waves.

[0027] Furthermore, based on the geometric information calculated for each relay device 8, a relay device 8 is selected to relay wireless communication between the base station 2 and the terminal 6 located in the target grid (step S06).

[0028] In step S06, a relay device 8 is selected based on the relay distance and the angle of incidence of the radio waves at the relay device 8. Specifically, from among multiple relay devices 8, only relay devices 8 whose angle of incidence of radio waves is shallower than a threshold (for example, -60° and 60°) are selected. Furthermore, from the selected relay devices 8, the relay device 8 with the shortest relay distance is selected. Generally, when the angle of incidence is large, power loss occurs because the effective area that can reflect the radio waves incident on the relay device 8 becomes small. By selecting a relay device 8 with a small angle of incidence of radio waves, power loss can be prevented.

[0029] Alternatively, in step S06, a relay device 8 is selected based on the relay distance and the reflection angle of the radio waves at the relay device 8. Specifically, each relay device 8 is weighted such that the closer the reflection direction is to the normal reflection direction, the greater the weight, and the shorter the relay distance. Then, the relay device 8 with the greatest weight is selected. In addition to the weighting described above, a greater weight may be given to a relay device 8 that has a radio wave amplification function, or to a relay device 8 that can dynamically change the reflection angle.

[0030] Alternatively, in step S06, the relay device 8 may be selected based on the incident angle and reflection angle of the radio waves at the relay device 8, and it is sufficient that the relay device 8 is determined based on at least two of the geometric information.

[0031] Furthermore, the information of the selected relay device 8 is associated with the location information of the target grid and saved in the database 10 (step S07). After saving, the process returns to step S04 and the same calculation is performed for the next grid. By performing the calculation for all grids 9, the database 10 is completed.

[0032] Figure 2 illustrates the procedure for creating the database 10 when there is only one relay device 8 included in the relay path. However, the relay path may contain one or more relay devices 8. That is, the relay device selection device 4 selects multiple candidate relay paths for relaying wireless communication between the base station 2 and the terminal 6 located in the target grid by combining one or more relay devices 8. Furthermore, the relay device selection device 4 calculates geometric information for each of the candidate relay paths. Based on the geometric information, the relay device selection device 4 selects a relay path from the candidates and stores the information of the selected relay path in association with the location information of the target grid. By selecting relay paths for all grids 9, the database 10 is completed in the same way as in Figure 2.

[0033] <Relay Control Method> Figure 3 is a flowchart showing the relay control procedure performed by the base station 2 according to Embodiment 1. First, location information is acquired from the terminal 6 (step S11). Next, the relay device selection device 4 refers to the database 10 it has created and acquires information on the relay route set in the grid 9 closest to the acquired location information of the terminal 6 (step S12). The grid 9 closest to the location information of the terminal 6 is the grid 9 with the smallest error between it and the acquired location information of the terminal 6.

[0034] Furthermore, for each relay device 8 within the wireless area, it is determined whether or not it is included in the acquired relay path (step S13). If a relay device 8 is included in the relay path (Yes), a control signal for relay control is transmitted to the relay device 8 (step S14).

[0035] On the other hand, in the case of a relay device 8 that is not included in the relay path (No), a command signal is sent to turn off the power of the relay device 8 (step S15). By turning off the power of the relay devices 8 that are not being used, the power consumption of the wireless communication system 100 can be optimized.

[0036] Note that the process described in the flowchart of Figure 3 does not necessarily have to be performed by base station 2; it may also be performed by relay device selection device 4. In this case, the same effect as described above can be obtained.

[0037] Figure 4 is a block diagram showing the configuration of the wireless communication system 100 according to Embodiment 1. Here, we will first explain the path taken by the relay device selection device 4 when creating the database 10.

[0038] First, at terminal 6, the terminal positioning circuit 62 acquires the location information of terminal 6 and notifies the positioning signal generation circuit 64. The positioning signal generation circuit 64 transmits the notified information to base station 2. Note that the frequency band used for transmission is not limited to the low frequency band; it may also be the high frequency band, licensed band, or unlicensed band.

[0039] The signal generation circuit 66 also generates a signal containing quality information acquired by the terminal 6 and notifies the signal transceiver 68. The signal transceiver 68 transmits the signal containing quality information to the base station 2. This transmission may be via the relay device 8 or may be a direct transmission to the base station 2.

[0040] Next, at base station 2, the information acquisition circuit 24 notifies the relay device selection device 4 of the location information acquired from terminal 6.

[0041] The signal transceiver 25 notifies the quality acquisition circuit 26 of a signal containing quality information acquired from the terminal 6. The quality acquisition circuit 26 acquires the quality information based on the notified signal and notifies the relay device selection device 4.

[0042] The relay device selection device 4 is housed in the base station 2. That is, there are as many relay device selection devices 4 as there are base stations 2. In the relay device selection device 4, the data acquisition circuit 42 stores location information and quality information acquired from one or more terminals 6 in the storage device 44. The storage device 44 stores all the acquired location information and quality information.

[0043] The data processing circuit 46 acquires the position information of the base station 2 and the plurality of relay devices 8 from the storage device 44, and creates the database 10 by the above-described method based on that information. The storage device 44 stores the created database 10.

[0044] Note that the database 10 may be updated at an arbitrary frequency. For example, when updating the database 10 based on the quality information, the data processing circuit 46 estimates the presence of obstacles 5 such as buildings between the base station 2 and the terminal 6 from the propagation path information included in the quality information, and adds the presence of the obstacles 5 and their position information to the created database 10. This enables selection of a relay path considering the presence of the obstacles 5.

[0045] Next, the relay control path by the base station 2 will be described. In the base station 2, each time the control circuit 21 is notified of the position information from the terminal 6, it accesses the storage device 44, refers to the database 10, and determines a relay path to be used for wireless communication with the terminal 6 that is the notification source. The control circuit 21 associates the information on the determined relay path with the position information of the terminal 6 that is the notification source and stores it in a storage device (not shown).

[0046] When receiving a signal addressed to the terminal 6 from above, the control circuit 21 acquires the information on the relay path determined based on the latest position information of the terminal 6 from a storage device (not shown). Alternatively, the control circuit 21 determines a suitable relay path for the latest position information of the terminal 6 by newly referring to the database 10.

[0047] Further, the control circuit 21 calculates reflection control information for controlling the relay device 8 included in the relay path. The reflection control information includes information such as a suitable beam intensity, amplification factor, and number of reflection elements to be used when the relay device 8 relays wireless communication between the base station 2 and the terminal 6. Further, the control circuit 21 notifies the control signal generation circuit 22 of the calculated reflection control information. The control signal generation circuit 22 generates a control signal including the reflection control information and transmits it to the control signal communication device 23.

[0048] The control signal communicator 23 transmits a control signal to the relay device 8 included in the relay path. The line for transmitting the control signal may be wired, wireless, or of any method.

[0049] Note that the control signal does not necessarily have to be transmitted from the base station 2, and may be transmitted from a wireless device or the like (not shown) to the relay device 8.

[0050] Next, in the relay device 8, the control signal communicator 82 transmits the received control signal to the weight setting circuit 84. The weight setting circuit 84 sets parameters for changing the relay resources based on the reflection control information included in the control signal. Then, the weight setting circuit 84 notifies the reflector 86 of the set parameters. The reflector 86 forms an appropriate radio propagation path between the base station 2 and the terminal 6 by changing the resources based on the received parameters.

[0051] FIG. 5 is a modification of FIG. 4. The relay device selection device 4 may be provided outside the base station 2 as a server or a cloud server or the like. In this case, the relay device selection device 4 may have a function of collecting and managing information of a plurality of base stations 2. Further, the relay device selection device 4 may have a function of creating a database 10 considering a plurality of base stations 2.

[0052] FIG. 6 is a diagram showing the hardware configuration of the relay device selection device 4 according to the first embodiment. The processing performed by the relay device selection device 4 may be executed by a program using a computer including a CPU and a memory, with the relay device selection program stored in the memory. Alternatively, it may be executed by a program using an integrated circuit such as an FPGA (Field Programmable Gate Array). Note that the relay device selection program may be provided by being recorded on a storage medium or provided through a network.

[0053] The relay device selection device 4 has an input unit 200, an output unit 201, a communication unit 202, a CPU (Central Processing Unit, also called a processor) 203, a memory 204, and an HDD (Hard Disk Drive) 205 connected via a bus 206, and functions as a computer. The relay device selection device 4 is also configured to input and output data to and from a storage medium 207 that can be read by a computer.

[0054] The input unit 200 is, for example, a keyboard and mouse. The output unit 201 is, for example, a display device such as a display.

[0055] The communication unit 202 is, for example, a communication interface that communicates with the base station 2.

[0056] Memory 204 refers to volatile or non-volatile semiconductor memory such as RAM, ROM, and flash memory, or magnetic disks, flexible disks, optical disks, and DVDs.

[0057] The CPU 203 controls each component of the relay device selection device 4 and performs the processes shown in the flowcharts of Figures 2 and 3 by reading the relay device selection program. The memory 204 and HDD 205 are storage devices 44 that store data such as the relay device selection program and the created database 10.

[0058] The storage medium 207 is capable of storing a relay device selection program, etc., which executes the functions of the relay device selection device 4. The storage medium 207 is a USB (Universal Serial Bus) memory, a CD-ROM (Compact Disc Read Only Memory), etc.

[0059] Note that the architecture of the relay device selection device 4 is not limited to the example shown in the figure.

[0060] As explained above, in this disclosure, the base station 2 determines the relay route to be used for wireless communication with the terminal 6 that has notified its location information by referring to the database 10. In the database 10, information on the relay route to be used for wireless communication between the base station 2 and the terminal 6 is set according to the location within the base station 2's wireless area. Since geometric calculations are not performed each time a relay route is selected, the overhead when selecting the relay device 8 can be reduced.

[0061] This disclosure is not limited to the embodiments described above, and various modifications can be made during implementation without departing from its essence. Furthermore, each embodiment and its modifications may be combined as appropriate, and in that case, the combined effects can be obtained.

[0062] 2: Base station, 4: Relay device selection device, 5: Obstacle, 6: Terminal, 6a: Terminal, 6b: Terminal, 6c: Terminal, 8: Relay device, 8a: Relay device, 8b: Relay device, 9: Grid, 9a: Grid, 9c: Grid, 10: Database, 21: Control circuit, 22: Control signal generation circuit, 23: Control signal communication device, 24: Information acquisition circuit, 25: Signal transceiver, 26: Quality acquisition circuit, 42: Data acquisition circuit, 44: Storage device, 46: Data processing circuit, 62: Terminal positioning circuit, 64: Positioning signal generation circuit, 66: Signal generation circuit, 68: Signal transceiver, 82: Control signal communication device, 84: Wait setting circuit, 86: Reflector, 100: Wireless communication system, 200: Input unit, 201: Output unit, 202: Communication unit, 203: CPU, 204: Memory, 205: HDD, 206: Bus

Claims

1. A wireless communication system comprising a base station, a plurality of relay devices capable of relaying wireless communication between the base station and a terminal, and a relay device selection device, wherein the relay device selection device has a database and is configured to perform the following: a process of acquiring location information of the terminal; a process of referring to the database and acquiring information on a relay route using one or more of the relay devices to be used in wireless communication between the base station and the terminal; and a process of causing a relay device included in the acquired relay route to relay the wireless communication between the base station and the terminal, wherein the database is configured to have information on a relay route to be used in wireless communication between the base station and the terminal, according to its location within the base station's wireless area.

2. The wireless communication system according to claim 1, wherein the database sets the relay path to be used based on at least two of the following: relay distance, incident angle of radio waves at relay devices included in the relay path, and reflection angle.

3. A wireless communication method comprising: virtually dividing at least a portion of the wireless area of ​​a base station into multiple grids; designating one of the grids as a virtual terminal installation location; selecting multiple candidate relay paths for relaying wireless communication between the base station and the installation location by combining one or more relay devices present in the wireless area; calculating geometric information for the candidate relay paths; selecting a relay path from the candidates based on the geometric information; associating the information of the selected relay paths with the location information of the grids and storing it in a storage device; and selecting and storing relay paths for all of the multiple grids in the storage device.

4. The wireless communication method according to claim 3, wherein the geometric information includes the relay distance and at least two of the incident angle and reflection angle of radio waves at relay devices included in the relay path.

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