Radio control device, radio control method, and radio control program

Abstract

This radio control device includes an acquisition unit, an estimation unit, and an instruction unit. The acquisition unit acquires a reference signal received by a radio communication device and transmitted intermittently from a relay station moving in the sky. The estimation unit estimates, by machine learning using the acquired reference signal, a reference signal during a period when the reference signal is not received. The instruction unit causes the radio communication device to perform channel estimation between the radio communication device and the relay station on the basis of the reference signal transmitted from the relay station and the estimated reference signal, and to perform beamforming of the signal to be transmitted to the relay station on the basis of the result of the channel estimation.

Description

Wireless control device, wireless control method, and wireless control program

[0001] The present invention relates to a wireless control device, a wireless control method, and a wireless control program.

[0002] Patent Document 1 below discloses that a wireless communication device performs channel estimation based on an SRS received from a UE, and controls beamforming to the UE based on the result of the channel estimation.

[0003] Japanese Unexamined Patent Application Publication No. 2019-216366

[0004] The wireless control device disclosed in the present application includes an acquisition unit, an estimation unit, and an instruction unit. The acquisition unit acquires a reference signal that is intermittently transmitted from a relay station moving in the sky and received by the wireless communication device. The estimation unit estimates a reference signal during a period when the acquired reference signal is not received by machine learning using the acquired reference signal. The instruction unit causes the wireless communication device to execute channel estimation with the relay station based on the reference signal transmitted from the relay station and the estimated reference signal, and execute beamforming of a signal transmitted to the relay station based on the result of the channel estimation.

[0005] FIG. 1 is a diagram showing an example of a wireless communication system. FIG. 2 is a diagram showing an example of the structure of a frame in TDD. FIG. 3 is a block diagram showing an example of a base station. FIG. 4 is a flowchart showing an example of the operation of the wireless control device. FIG. 5 is a flowchart showing an example of the operation of the wireless communication device. FIG. 6 is a hardware configuration diagram showing an example of the functional configuration of a computer that realizes the wireless control device.

[0006] Hereinafter, embodiments of the wireless control device, the wireless control method, and the wireless control program disclosed in the present application will be described in detail with reference to the drawings. Note that the disclosed technology is not limited by the following embodiments.

[0007] [Wireless communication system 1] FIG. 1 is a diagram showing an example of a wireless communication system 1. The wireless communication system 1 includes a relay station 2, a base station 3, and a user terminal 4. The wireless communication system 1 includes a plurality of relay stations 2.

[0008] The relay station 2 moves in the air and communicates wirelessly with the base station 3 and the user terminal 4. The relay station 2 relays communication between the base station 3 and the user terminal 4. In this embodiment, the relay station 2 is, for example, a HAPS (High-Altitude Platform Station) which is an aircraft orbiting in the stratosphere. The relay station 2 may also function as a user terminal for the base station 3. The wireless link between the relay station 2 and the base station 3 is called a feeder link, and the wireless link between the relay station 2 and the user terminal 4 is called a service link.

[0009] Furthermore, the relay station 2 is not limited to HAPS, but may be a geostationary satellite or a low-Earth orbit satellite, as long as it is an aircraft that moves in the air and has the function of relaying communication between the base station 3 and the user terminal 4.

[0010] Base station 3 is located on the ground and communicates wirelessly with relay station 2. Note that base station 3 is not limited to being located on the ground surface; it may also be mounted on buildings or on aircraft flying at altitudes of several tens to several hundreds of meters.

[0011] Base station 3 has a directional antenna such as a phased array antenna and performs wireless communication with relay station 2 via the directional antenna. Based on the Sounding Reference Signal (SRS) transmitted from relay station 2, base station 3 performs channel estimation between relay station 2 and base station 3, and uses the channel estimation result to control the direction of the beam 30 from the directional antenna.

[0012] Here, because the base station 3 located on the ground and the relay station 2 moving in the air are far apart, the signal attenuation is large. Therefore, it is necessary to increase the antenna gain by beamforming. In order to perform beamforming, it is necessary to improve the accuracy of channel estimation between the relay station 2 and the ground base station 3. Channel estimation between the relay station 2 and the ground base station 3 is performed based on the Sounding Reference Signal (SRS) transmitted from the relay station 2 to the ground base station 3.

[0013] The SRS transmitted from the relay station 2 to the base station 3 is transmitted at the uplink transmission timing within a single frame 5, as shown in Figure 2, for example. Figure 2 is a diagram illustrating an example of the structure of frame 5 in TDD (Time Division Duplex). In the frame 5 illustrated in Figure 2, "D" indicates a subframe assigned to the downlink signal, "U" indicates a subframe assigned to the uplink signal, and "S" indicates a special subframe.

[0014] However, if the number of relay stations 2 increases, it becomes impossible to accommodate SRS from all relay stations 2 within the subframe of a single frame 5 uplink. Therefore, focusing on a single relay station 2, there may be periods when no SRS is included in the subframe, as shown in Figure 2, i.e., periods when no SRS is transmitted. This reduces the frequency of SRS transmission.

[0015] If the frequency of SRS transmission from relay station 2 decreases, the accuracy of channel estimation using SRS for relay station 2 may decrease. When the accuracy of channel estimation decreases, the accuracy of the beam 30 formed from base station 3 to relay station 2 decreases, and the quality of communication between relay station 2 and base station 3 deteriorates.

[0016] Therefore, in this embodiment, as shown in Figure 2 for example, the SRS during periods when SRS is not transmitted is estimated using machine learning. This improves the accuracy of channel estimation between the relay station 2 and the base station 3, and improves the quality of communication between the relay station 2 and the base station 3.

[0017] [Configuration of Base Station 3] Figure 3 is a block diagram showing an example of a base station 3. The base station 3 includes a radio control device 31, a radio communication device 32, and a directional antenna 33. The radio control device 31 may be implemented as part of a function such as an SMO (Service Management and Orchestration) or a RIC (RAN Intelligent Controller).

[0018] The wireless communication device 32 includes a receiving unit 320, a transmitting unit 321, a channel estimation unit 322, and a beam control unit 323. The receiving unit 320 receives a signal from the relay station 2 via the directional antenna 33 at the timing of the subframe assigned to the uplink signal in the frame 5, and extracts the SRS from the received signal. The receiving unit 320 then outputs the extracted SRS to the wireless control device 31 and the channel estimation unit 322.

[0019] The channel estimation unit 322 performs channel estimation for each relay station 2 based on the SRS output from the receiving unit 320 and the wireless control device 31. The channel estimation unit 322 performs channel estimation using methods such as ZF (Zero Forcing) or MMSE (Minimum Mean Square Error).

[0020] The beam control unit 323 generates a control signal for controlling the directivity of the directional antenna 33 for each relay station 2, based on the channel estimation result from the channel estimation unit 322. The beam control unit 323 then outputs the generated control signal to the directional antenna 33.

[0021] The transmitting unit 321 transmits a signal to the relay station 2 via the directional antenna 33 at the timing of the subframe assigned to the downlink signal within frame 5.

[0022] The directional antenna 33 forms a directional beam 30 in response to a control signal output from the beam control unit 323, and transmits and receives radio signals using the formed beam 30.

[0023] The wireless control device 31 includes an acquisition unit 310, a storage unit 311, an estimation unit 312, and an instruction unit 313. The acquisition unit 310 acquires the SRS output from the receiving unit 320 for each relay station 2. The wireless control device 31 also acquires information indicating the status of each relay station 2 from a management device or the like that manages the status of the relay station 2 via a communication line 6 such as the Internet. The acquisition unit 310 then stores the SRS and the information indicating the status of the relay station 2 in the storage unit 311 for each relay station 2, associating them with each other.

[0024] In this embodiment, the information indicating the state of the relay station 2 includes information indicating at least one of the following: the position of the relay station 2, the attitude of the relay station 2, the speed at which the relay station 2 moves, and the direction of movement of the relay station 2.

[0025] The estimation unit 312 estimates the SRS for each relay station 2 during periods when the SRS is not received, using machine learning based on the SRS stored in the memory unit 311. The estimation unit 312 includes a generation unit 3120 and a reference signal estimation unit 3121.

[0026] The generation unit 3120 generates a model showing the relationship between the state of relay station 2 and SRS by learning the relationship between the known state of relay station 2 and SRS for each relay station 2. For example, the generation unit 3120 uses the SRS during periods when SRS is not received as the target variable, the state of relay station 2 as the explanatory variable, and the received SRS and the state of relay station 2 at that time as training data to generate a model showing the relationship between the state of relay station 2 and SRS for each relay station 2. The generation unit 3120 then stores the model generated for each relay station 2 in the storage unit 311.

[0027] The reference signal estimation unit 3121 uses the model generated by the generation unit 3120 and information indicating the status of the relay station 2 to estimate the SRS for each relay station 2 during the period when SRS is not received, and outputs the estimated SRS to the instruction unit 313.

[0028] The instruction unit 313 outputs the SRS estimated by the estimation unit 312 to the channel estimation unit 322. That is, the instruction unit 313 causes the channel estimation unit 322 to perform channel estimation between the relay station 2 and the base station 3 based on the SRS transmitted from the relay station 2 and the SRS estimated by the estimation unit 312. Then, the instruction unit 313 causes the beam control unit 323 to perform beamforming of the signal to be transmitted to the relay station 2 based on the channel estimation result by the channel estimation unit 322.

[0029] Here, the relay station 2 is controlled to fly along a predetermined trajectory, and since the relay station 2 is equipped with various sensors, its status, such as position and attitude, can be accurately determined. Therefore, the base station 3 can accurately estimate the SRS during periods when the SRS is not received by using machine learning based on the information indicating the status of the relay station 2. This improves the quality of communication between the relay station 2 and the base station 3.

[0030] [SRS Estimation Procedure] Figure 4 is a flowchart showing an example of the operation of the wireless control device 31. Note that the process illustrated in Figure 4 is performed for each relay station 2. Also, the process illustrated in the flowchart of Figure 4 is an example of a wireless control method.

[0031] First, the acquisition unit 310 acquires the SRS via the wireless communication device 32 (step S10). Step S10 is an example of an acquisition process and acquisition procedure.

[0032] Next, the acquisition unit 310 acquires information indicating the status of the relay station 2 via the communication line 6 (step S11). Then, the acquisition unit 310 stores the SRS acquired in step S10S in the storage unit 311, associating it with the status information acquired in step S11.

[0033] Next, after a certain amount of information pairs indicating the SRS and its state have been accumulated in the memory unit 311, the generation unit 3120 generates a model showing the relationship between the state of the relay station 2 and the SRS by learning the relationship between the known state of the relay station 2 and the SRS (step S12).

[0034] Next, the reference signal estimation unit 3121 uses the model generated by the generation unit 3120 and information indicating the status of the relay station 2 to estimate the SRS for the period during which no SRS is received (step S13). Then, the reference signal estimation unit 3121 outputs the estimated SRS to the instruction unit 313. The instruction unit 313 outputs the SRS estimated by the estimation unit 312 to the channel estimation unit 322 (S14). Steps S13 and S14 are examples of the estimation process and estimation processing. Then, the processing shown in step S10 is executed again.

[0035] [Beamforming Procedure] Figure 5 is a flowchart showing an example of the operation of the wireless communication device 32. Note that the process illustrated in Figure 5 is performed for each relay station 2.

[0036] First, the receiving unit 320 determines whether or not it has received an SRS via the directional antenna 33 at the reception timing of the subframe assigned to the uplink signal (step S20). If an SRS is received (step S20: Yes), the receiving unit 320 outputs the received SRS to the wireless control device 31 and the channel estimation unit 322.

[0037] Next, the channel estimation unit 322 performs channel estimation based on the SRS received by the receiving unit 320 (step S21). Then, the channel estimation unit 322 outputs the channel estimation result to the beam control unit 323.

[0038] Next, the beam control unit 323 controls the directivity of the beam 30 transmitted from the directional antenna 33 based on the channel estimation result (step S23). Then, the process shown in step S20 is executed again.

[0039] On the other hand, if the SRS is not received at the reception timing of the subframe assigned to the uplink signal (step S20: No), the channel estimation unit 322 performs channel estimation based on the SRS estimated by the estimation unit 312 (step S22). The channel estimation unit 322 then outputs the channel estimation result to the beam control unit 323. Then, the process shown in step S23 is executed.

[0040] [Hardware] The wireless control device 31 described above is implemented by a computer 100 having a configuration such as that shown in Figure 6. Figure 6 is a hardware configuration diagram showing an example of the functional configuration of the computer 100 that implements the wireless control device 31. The computer 100 includes a CPU 101, RAM (Random Access Memory) 102, ROM (Read Only Memory) 103, and auxiliary storage device 104. The computer 100 also includes a communication interface (I / F) 105, an input / output interface (I / F) 106, and a media interface (I / F) 107.

[0041] The CPU 101 operates based on programs stored in the ROM 103 or auxiliary storage device 104, and controls each part. The ROM 103 stores boot programs executed by the CPU 101 when the computer 100 starts up, as well as programs that depend on the computer 100's hardware.

[0042] The auxiliary storage device 104 is, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive), and stores the program executed by the CPU 101 and the data used by that program. The CPU 101 reads the program from the auxiliary storage device 104, loads it onto the RAM 102, and executes the loaded program.

[0043] The communication interface 105 receives signals and data from the wireless communication device 32 via a communication line such as a LAN (Local Area Network), and receives signals and data from an external server via the communication line 6, and sends the received signals and data to the CPU 101. The communication interface 105 also transmits signals and data generated by the CPU 101 to the wireless communication device 32 via the communication line.

[0044] The CPU 101 controls an input device and an output device via the input / output I / F 106. The CPU 101 acquires a signal input from the input device via the input / output I / F 106 and sends it to the CPU 101. Also, the CPU 101 outputs the generated data to the output device via the input / output I / F 106.

[0045] The media I / F 107 reads a program or data stored in the storage medium 108 and stores it in the auxiliary storage device 104. The storage medium 108 is, for example, an optical recording medium such as a DVD (Digital Versatile Disc), a PD (Phase change rewritable Disk), a magneto-optical recording medium such as a MO (Magneto-Optical disk), a tape medium, a magnetic recording medium, or a semiconductor memory.

[0046] The CPU 101 of the computer 100 realizes each process illustrated in the flowchart of FIG. 4 by executing a program loaded on the RAM 102. A wireless control program for realizing each process illustrated in the flowchart of FIG. 4 is stored in the storage medium 108. The CPU 101 of the computer 100 reads the wireless control program loaded on the RAM 102 from the storage medium 108 and stores it in the auxiliary storage device 104. As another example, the CPU 101 of the computer 100 may acquire a wireless control program from another device via a communication line and store it in the auxiliary storage device 104.

[0047] As described above, the embodiments of the present disclosure have been described. According to the wireless control device 31 of this embodiment, the communication quality between the relay station 2 and the base station 3 can be improved. Thereby, it is possible to contribute to the achievement of Goal 9, "Build the infrastructure for industry and innovation," of the Sustainable Development Goals (SDGs).

[0048] [Others] Note that the disclosed technology is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist.

[0049] For example, in the embodiment described above, the acquisition unit 310 acquires information indicating the state of the relay station 2 and the SRS and stores them in the storage unit 311, and the generation unit 3120 generates a model by learning the relationship between the information indicating the state of the relay station 2 and the SRS. Then, the reference signal estimation unit 3121 uses the generated model and the information indicating the state of the relay station 2 to estimate the SRS during the period when the SRS is not received. However, the disclosed technology is not limited to this.

[0050] Alternatively, the acquisition unit 310 may further acquire information indicating the state of the area around the relay station 2 and store it in the storage unit 311, and the generation unit 3120 may generate a model by learning the relationship between the information indicating the state of the relay station 2, the SRS, and the information indicating the state of the area around the relay station 2. The reference signal estimation unit 3121 may then use the generated model, the information indicating the state of the relay station 2, and the information indicating the state of the area around the relay station 2 to estimate the SRS during periods when the SRS is not received.

[0051] Information indicating the conditions around relay station 2 includes at least one of the following: wind direction around relay station 2, wind speed around relay station 2, and weather information between relay station 2 and base station 3. Information indicating the weather between relay station 2 and base station 3 may include information such as temperature, humidity, atmospheric pressure, and cloud thickness.

[0052] Furthermore, among the processes described in the above embodiments, all or part of the processes described as being performed automatically can be performed manually, or all or part of the processes described as being performed manually can be performed automatically by known methods. In addition, the processing procedures, specific names, and various data and parameters shown in the above documents and drawings can be changed at will unless otherwise specified. For example, the various information shown in each figure is not limited to the information shown.

[0053] Furthermore, the components of each illustrated device are functionally conceptual and do not necessarily need to be physically configured as shown. In other words, the specific forms of distribution and integration of each device are not limited to those shown, and all or part of them can be functionally or physically distributed and integrated in any unit according to various loads and usage conditions.

[0054] Furthermore, the wireless control device 31 described above may be implemented using multiple server computers, and depending on the function, it may be implemented by calling external platforms via API (Application Programming Interface) or network computing, allowing for flexible configuration changes.

[0055] 1 Wireless communication system 2 Relay station 3 Base station 30 Beam 31 Wireless control device 310 Acquisition unit 311 Storage unit 312 Estimation unit 3120 Generation unit 3121 Reference signal estimation unit 313 Instruction unit 32 Wireless communication device 320 Receiving unit 321 Transmitting unit 322 Channel estimation unit 323 Beam control unit 33 Directional antenna 4 User terminal 5 Frame 6 Communication line 100 Computer 101 CPU 102 RAM 103 ROM 104 Auxiliary storage device 105 Communication interface 106 Input / output interface 107 Media interface 108 Storage medium

Claims

1. A wireless control device comprising: an acquisition unit that acquires a reference signal intermittently transmitted from a relay station moving in the air, which is received by a wireless communication device; an estimation unit that estimates the reference signal during periods when the reference signal is not received by machine learning using the acquired reference signal; and an instruction unit that causes the wireless communication device to perform channel estimation between itself and the relay station based on the reference signal transmitted from the relay station and the estimated reference signal, and to perform beamforming of the signal transmitted to the relay station based on the channel estimation result.

2. The wireless control device according to claim 1, wherein the estimation unit comprises a generation unit that generates a model showing the relationship between the state of the relay station and the reference signal by learning the relationship between the known state of the relay station and the reference signal, and a reference signal estimation unit that estimates the reference signal during periods when the reference signal is not received using the model.

3. The radio control device according to claim 2, wherein the state of the relay station includes at least one of the position of the relay station, the orientation of the relay station, the speed of movement of the relay station, and the direction of movement of the relay station.

4. The wireless control device according to claim 2 or 3, wherein the generation unit generates the model by further learning the relationship between the known state of the relay station, the reference signal, and the known state of the surroundings of the relay station.

5. The radio control device according to claim 4, wherein the conditions surrounding the relay station include at least one of the wind direction around the relay station, the wind speed around the relay station, and the weather between the relay station and the radio communication device.

6. The radio control device according to claim 1, wherein the relay station is a HAPS (High Altitude Platform Station) flying in the stratosphere.

7. A wireless control method comprising: an acquisition step of acquiring a reference signal intermittently transmitted from a relay station moving in the air, which is received by a wireless communication device; an estimation step of estimating a reference signal for periods when the reference signal is not received by machine learning using the acquired reference signal; and an instruction step of causing the wireless communication device to perform channel estimation between itself and the relay station based on the reference signal transmitted from the relay station and the estimated reference signal, and to perform beamforming of the signal to be transmitted to the relay station based on the results of the channel estimation.

8. A wireless control program that causes a computer to execute an acquisition procedure for acquiring a reference signal intermittently transmitted from a relay station moving in the air, which is received by a wireless communication device; an estimation procedure for estimating the reference signal during periods when the reference signal is not received by machine learning using the acquired reference signal; and an instruction procedure for causing the wireless communication device to perform channel estimation between itself and the relay station based on the reference signal transmitted from the relay station and the estimated reference signal, and to perform beamforming of the signal transmitted to the relay station based on the channel estimation result.

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