Wireless communication method and radio station

Abstract

To provide a technology capable of efficiently performing beamforming when wireless communication is performed between a wireless station and an aircraft.SOLUTION: A wireless communication method for performing wireless communication between a wireless station and an aircraft includes beamforming processing for forming a beam directed from a wireless station to an aircraft, and communication processing for by communicating between the wireless station and the aircraft by using beams. The beamforming process includes movement direction acquisition processing for acquiring movement direction information indicating the movement direction of the aircraft, and beam direction determination processing for determining the beam direction of the beam within the range of a subspace intersecting with the movement direction of the aircraft on the basis of the movement direction information.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a technique for performing wireless communication between a wireless station and an aircraft.

Background Art

[0002] Currently, in order to expand the communication area, a wireless communication system using an aircraft such as a drone equipped with a wireless communication function is being studied (Non-Patent Document 1). By using such a wireless communication system, it becomes possible to realize high-quality wireless communication even in an area where radio waves do not reach and wireless communication cannot be used.

[0003] In addition, for further communication speedup, the use of high-frequency bands such as the millimeter wave band is accelerating. Generally, radio waves in the high-frequency band are more likely to attenuate and are less likely to diffract compared to the low-frequency band. In other words, radio waves in the high-frequency band have the characteristics of large propagation loss and strong directivity. Therefore, when the distance between wireless stations is large or there are obstacles between wireless stations, there is a problem that high-quality wireless communication cannot be provided. An aircraft such as a drone is also useful for such problems, and it becomes possible to stably provide wireless communication by utilizing the aircraft.

[0004] In wireless communication using a high-frequency band, beamforming that can compensate for radio wave attenuation and increase the received power is effective. Beamforming includes analog beamforming using analog devices and digital beamforming based on digital signal processing. In order to perform beamforming, information such as the direction of the wireless station of the communication partner and propagation channel information is required. For example, in the case of analog beamforming, in order to know the direction of the wireless station of the communication partner, beams are transmitted in various directions using the beam-variable antenna of the local station, and measurement results (such as received power) of the beams in each direction are obtained. Then, based on the measurement results, the optimal beam direction directed to the wireless station of the communication partner is determined.

Prior Art Documents

Non-Patent Literature

[0005]

Non-Patent Literature 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Consider the case of applying beamforming technology to wireless communication between a wireless station and a flying object such as a drone. In the case of wireless communication between a wireless station and a flying object, since their vertical heights are different, it is necessary to transmit a beam in three-dimensional space. Therefore, compared with the case of a two-dimensional plane, the beam transmission / measurement process for determining an appropriate beam direction increases. This causes a decrease in transmission efficiency. Also, transmitting radio waves in various directions can also cause interference.

[0007] One object of the present disclosure is to provide a technique capable of efficiently performing beamforming when performing wireless communication between a wireless station and a flying object.

Means for Solving the Problems

[0008] The first aspect relates to a wireless communication method for performing wireless communication between a wireless station and a flying object. The wireless communication method includes a beamforming process for forming a beam directed from the wireless station to the flying object, and a communication process for performing communication between the wireless station and the flying object using the beam and includes. The beamforming process is Movement direction acquisition processing for acquiring movement direction information indicating the movement direction of the flying object, beam direction determination processing for determining the beam direction of the beam within the range of the partial space that intersects the movement direction of the flying object based on the movement direction information, and are included.

[0009] The second aspect is related to a radio station that performs wireless communication with the flying object. The radio station includes a controller that forms a beam directed from the radio station to the flying object and communicates with the flying object using the beam. The controller further performs movement direction acquisition processing for acquiring movement direction information indicating the movement direction of the flying object, and beam direction determination processing for determining the beam direction of the beam within the range of the partial space that intersects the movement direction of the flying object based on the movement direction information. It is configured to execute.

Advantages of the Invention

[0010] According to the present disclosure, in beamforming for forming a beam directed from a radio station to a flying object, the movement direction of the flying object is taken into consideration. The beam direction is determined not from all of the three-dimensional space but within the range of the partial space that intersects the movement direction of the flying object. Therefore, the processing load and processing time required for determining the beam direction are reduced. That is, it becomes possible to perform beamforming efficiently.

Brief Description of the Drawings

[0011]

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Embodiments for Carrying Out the Invention

[0012] The embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0013] 1. Overview FIG. 1 is a conceptual diagram schematically showing a wireless communication system 1 according to the present embodiment. The wireless communication system 1 includes a wireless station 10 and an aircraft 20. The wireless station 10 exists on the ground. Examples of the wireless station 10 include a wireless base station and a wireless terminal. On the other hand, the aircraft 20 is movable in the air. An example of the aircraft 20 is a drone. The aircraft 20 is equipped with a wireless communication function and can perform wireless communication with the wireless station 10. For example, the aircraft 20 functions as a relay station that relays communication between the wireless stations 10.

[0014] In the present embodiment, beamforming technology is applied to the wireless communication between the wireless station 10 and the aircraft 20. At least the wireless station 10 performs beamforming and communicates with the aircraft 20 using a beam. However, in the case of wireless communication between the wireless station 10 and the aircraft 20, since their heights in the vertical direction are different, it is necessary to transmit a beam with respect to a three-dimensional space. Therefore, there is a possibility that the processing load for determining an appropriate beam direction increases as compared with the case of a two-dimensional plane. Therefore, the present disclosure proposes a technology that can reduce the processing load for determining an appropriate beam direction and perform beamforming efficiently.

[0015] FIG. 2 is a conceptual diagram for explaining beamforming according to the present embodiment. When performing wireless communication with the aircraft 20, the wireless station 10 forms a beam directed at the aircraft 20. In this beamforming, the wireless station 10 determines the beam direction DB in consideration of the moving direction DF of the aircraft 20.

[0016] More specifically, the radio station 10 acquires movement direction information indicating the movement direction DF of the aircraft 20. As will be described in detail later, various examples can be considered as methods for acquiring the movement direction information. Then, based on the movement direction information, the radio station 10 determines the beam direction DB within the range of the partial space PS that intersects the movement direction DF of the aircraft 20. The radio station 10 does not need to search for an appropriate beam direction DB from all of the three-dimensional space, but only needs to search for an appropriate beam direction DB within the range of the partial space PS that intersects the movement direction DF of the aircraft 20. For example, the space existing in the direction opposite to the movement direction DF of the aircraft 20 may be excluded from the search range of the beam direction DB. Therefore, the processing load and processing time required for determining the beam direction DB are reduced.

[0017] Thus, according to the present embodiment, in beamforming for forming a beam directed from the radio station 10 to the aircraft 20, the movement direction DF of the aircraft 20 is considered. The beam direction DB is determined not from all of the three-dimensional space, but within the range of the partial space PS that intersects the movement direction DF of the aircraft 20. Therefore, the processing load and processing time required for determining the beam direction DB are reduced. That is, it becomes possible to perform beamforming efficiently. Further, since the processing load and processing time required for determining the beam direction DB are reduced, a decrease in transmission efficiency is suppressed. Furthermore, since the search range of the beam direction DB is reduced, interference generation is also suppressed.

[0018] Hereinafter, the wireless communication system 1 according to the present embodiment will be described in more detail.

[0019] 2. Configuration example 2-1. Configuration example of radio station FIG. 3 is a block diagram showing a functional configuration example of the radio station 10. Here, in particular, the functional configuration related to beamforming is shown. The radio station 10 includes a signal generation unit 11, a transmission unit 12, a beam variable antenna 13, a reception unit 14, a signal analysis unit 15, and a beam direction determination unit 16.

[0020] The signal generation unit 11 generates a transmission signal to be transmitted by the wireless station 10, and outputs the generated transmission signal to the transmission unit 12. The transmission signal also includes a measurement signal used when determining an appropriate beam direction DB (beam pattern). The transmission unit 12 converts the input transmission signal into a radio signal, and outputs the radio signal to the beam-steerable antenna 13. The beam direction determination unit 16 determines the beam direction DB, and notifies the beam direction DB to the beam-steerable antenna 13. The beam-steerable antenna 13 sets a beam according to the beam direction DB notified from the beam direction determination unit 16, and transmits the radio signal input from the transmission unit 12 into the air.

[0021] Also, the beam-steerable antenna 13 receives a radio signal in the air, and outputs the received radio signal to the reception unit 14. The reception unit 14 converts the input radio signal into a reception signal, and outputs the reception signal to the signal analysis unit 15. The signal analysis unit 15 extracts necessary data from the input reception signal. The extracted data may be used for the determination of the beam direction DB by the beam direction determination unit 16.

[0022] FIG. 4 is a block diagram showing a configuration example of the wireless station 10. The wireless station 10 includes a communication controller 100 that controls wireless communication. The communication controller 100 performs beamforming processing and communicates with the flying object 20 using a beam. The communication controller 100 includes one or more processors 101 (hereinafter simply referred to as "processor 101") and one or more storage devices 102 (hereinafter simply referred to as "storage device 102"). The processor 101 performs various information processes. For example, the processor 101 includes a CPU (Central Processing Unit). The storage device 102 stores various information necessary for the processing by the processor 101. Examples of the storage device 102 include a volatile memory, a non-volatile memory, an HDD (Hard Disk Drive), an SSD (Solid State Drive), and the like.

[0023] The communication control program 103 is a computer program executed by the processor 101. The functions of the communication controller 100 are realized by the cooperation of the processor 101 that executes the communication control program 103 and the storage device 102. The communication control program 103 is stored in the storage device 102. The communication control program 103 may be recorded on a computer-readable recording medium. The communication control program 103 may be provided to the communication controller 100 via a network.

[0024] As another example, the communication controller 100 may be implemented using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array).

[0025] 2-2. Configuration Example of the Aircraft FIG. 5 is a block diagram showing a functional configuration example of the aircraft 20. Here, in particular, the functional configuration related to beamforming is shown. The aircraft 20 includes a notification signal generation unit 21, a transmission unit 22, an antenna 23, a reception unit 24, and a signal analysis unit 25.

[0026] The antenna 23 receives the radio signal transmitted from the radio station 10 and outputs the received radio signal to the reception unit 24. The reception unit 24 converts the input radio signal into a reception signal and outputs the reception signal to the signal analysis unit 25. The signal analysis unit 25 generates reception result information based on the input reception signal. Examples of the reception result information include received power, received signal strength, propagation channel information (CSI: Channel State Information), etc. The signal analysis unit 25 outputs the reception result information to the notification signal generation unit 21.

[0027] The notification signal generation unit 21 generates a notification signal including reception result information and outputs the notification signal to the transmission unit 22. Note that instead of the CSI itself, compressed CSI or conversion information obtained by singular value decomposition may be used. The transmission unit 22 converts the input notification signal into a radio signal and outputs the radio signal to the antenna 23. The antenna 23 transmits the radio signal input from the transmission unit 22 into the air.

[0028] 3. Processing related to beamforming FIG. 6 is a flowchart showing the processing in the wireless communication system 1 according to the present embodiment. In step S100, the radio station 10 (communication controller 100) performs a beamforming process for forming a beam directed from the radio station 10 to the aircraft 20. The beamforming process includes at least analog beamforming. In step S200, the radio station 10 (communication controller 100) performs wireless communication with the aircraft 20 using the formed beam.

[0029] FIG. 7 is a block diagram showing a functional configuration example related to the beamforming process (step S100). The communication controller 100 includes a movement direction acquisition unit 110, a beam direction candidate setting unit 120, a beam direction determination unit 130, and a beamforming unit 140. These movement direction acquisition unit 110, beam direction candidate setting unit 120, beam direction determination unit 130, and beamforming unit 140 correspond to the beam direction determination unit 16 and the beam variable antenna 13 in FIG. 3.

[0030] FIGS. 8 and 9 are a flowchart and a timing chart showing the beamforming process (step S100), respectively. Hereinafter, the beamforming process (step S100) according to the present embodiment will be described with reference to FIGS. 7 to 9.

[0031] 3-1. Movement direction acquisition process (step S110) In step S110, the movement direction acquisition unit 110 acquires movement direction information 210 indicating the movement direction DF of the flying object 20. Various examples of this movement direction acquisition process will be described later. The movement direction acquisition unit 110 outputs the movement direction information 210 to the beam direction candidate setting unit 120.

[0032] 3-2. Beam direction candidate setting process (step S120) In step S120, the beam direction candidate setting unit 120 sets at least one beam direction candidate DC. The beam direction candidate DC is a candidate for the beam direction DB. The beam direction candidate setting unit 120 may set a plurality of beam direction candidates DC.

[0033] More specifically, the beam direction candidate setting unit 120 sets a partial space PS (see FIG. 2) that intersects the movement direction DF of the flying object 20 based on the movement direction information 210. Then, the beam direction candidate setting unit 120 sets at least one beam direction candidate DC within the range of the partial space PS. Note that the beam direction candidates DC that can be set may be determined in advance over the entire space. In that case, the beam direction candidate setting unit 120 may extract only those that exist in the partial space PS from all the beam direction candidates DC.

[0034] The beam direction candidate setting unit 120 generates beam direction candidate information 220 indicating the set beam direction candidate DC, and outputs the beam direction candidate information 220 to the beam direction determination unit 130.

[0035] 3-3. Beam direction determination process (step S130) In step S130, the beam direction determination unit 130 determines an appropriate beam direction DB. Specifically, the beam direction determination unit 130 selects an appropriate one from the beam direction candidates DC indicated by the beam direction candidate information 220 as the beam direction DB. FIG. 10 is a flowchart for explaining the beam direction determination process (step S130).

[0036] In step S131, the beam direction determination unit 130 notifies each beam direction candidate DC to the beam forming unit 140. The beam forming unit 140 forms the beams of each beam direction candidate DC. The communication controller 100 transmits a measurement signal to the flying object 20 by using the beams of each beam direction candidate DC.

[0037] In step S132, the flying object 20 receives the measurement signal transmitted from the radio station 10 and generates reception result information indicating the reception result. Examples of the reception result information include received power, received signal strength, propagation channel information (CSI), etc. The flying object 20 transmits the reception result information to the radio station 10, that is, feeds back the reception result information to the radio station 10. Note that the reception result information may be transmitted one by one for each beam direction candidate DC, or the reception result information regarding all the beam direction candidates DC may be transmitted collectively. The beam direction determination unit 130 of the radio station 10 acquires the reception result information fed back from the flying object 20.

[0038] In step S133, the beam direction determination unit 130 selects, as the beam direction DB, a beam direction candidate DC whose communication quality satisfies the condition based on the reception result information. For example, the beam direction determination unit 130 selects, as the beam direction DB, the one with the highest received power among the plurality of beam direction candidates DC. When there is only one beam direction candidate DC, the beam direction determination unit 130 may select that beam direction candidate DC as the beam direction DB when the received power exceeds a predetermined power threshold.

[0039] As another example, the beam direction candidate DC with the highest received power may be selected as the beam direction DB under the condition that the interference to other flying objects 20 that are not the beam forming targets is suppressed below a predetermined threshold. Thereby, the interference power to other flying objects can be suppressed. As still another example, when a plurality of beam directions DB are selected, the beam direction with the maximum MIMO transmission capacity may be selected.

[0040] The beam direction determination unit 130 generates beam direction information 230 that specifies the determined beam direction DB, and outputs the beam direction information 230 to the beam forming unit 140.

[0041] 3-4. Beam Forming (Step S140) The beam forming unit 140 receives the beam direction information 230, and forms a beam in the beam direction DB specified by the beam direction information 230. Wireless communication between the radio station 10 and the aircraft 20 is performed based on the formed beam.

[0042] 4. Various Examples of Moving Direction Acquisition Processing Hereinafter, various examples of the moving direction acquisition processing (Step S110) according to the present embodiment will be described.

[0043] 4-1. First Example FIG. 11 is a block diagram for explaining a first example of the moving direction acquisition processing. In the first example, the moving direction acquisition unit 110 includes a camera 111. The moving direction acquisition unit 110 images the aircraft 20 using the camera 111. Then, the moving direction acquisition unit 110 acquires the moving direction DF of the aircraft 20 based on the imaging result by the camera 111. For example, the moving direction acquisition unit 110 analyzes the image captured by the camera 111 to detect (recognize) the aircraft 20. Image analysis methods such as pattern matching are well known. Then, the moving direction acquisition unit 110 acquires the moving direction DF of the aircraft 20 by tracing the detection position of the aircraft 20.

[0044] 4-2. Second Example FIG. 12 is a block diagram for explaining a second example of the moving direction acquisition process. In the second example, the moving direction acquisition unit 110 includes a distance measurement sensor 112. Examples of the distance measurement sensor 112 include LIDAR (Laser Imaging Detection and Ranging), millimeter-wave radar, and the like. The moving direction acquisition unit 110 detects the position of the aircraft 20 using the distance measurement sensor 112. The detected position of the aircraft 20 is the relative position with respect to the distance measurement sensor 112, and is defined by the distance and direction seen from the distance measurement sensor 112. Then, the moving direction acquisition unit 110 acquires the moving direction DF of the aircraft 20 by tracing the detected position of the aircraft 20.

[0045] LIDAR has the characteristic of high spatial resolution. However, in the case of LIDAR, the measurement accuracy may decrease in bad weather or backlight environments. When millimeter-wave radar is used, the influence of weather and backlight is suppressed. Both LIDAR and millimeter-wave radar may be used to integrate (fuse) the measurement results of both.

[0046] In addition, the distance measurement sensor 112 may also detect an object different from the aircraft 20 together. The moving direction acquisition unit 110 may perform pattern matching based on the shape of the detected object to identify the aircraft 20 and other objects. The moving direction acquisition unit 110 may combine the camera 111 and the distance measurement sensor 112 to acquire the moving direction DF of the aircraft 20.

[0047] 4-3. Third Example FIG. 13 is a block diagram for explaining a third example of the moving direction acquisition process. In the third example, the moving direction acquisition unit 110 includes a transceiver 113. The transceiver 113 transmits a wireless signal to another wireless station 10 and also receives a wireless signal from another wireless station 10. Examples of the wireless signal include wireless LAN (Local Area Network) signals.

[0048] FIG. 14 is a conceptual diagram for explaining an example of a method for estimating the moving direction of an object based on a wireless LAN signal. A transmission device Tx transmits a wireless LAN signal toward a reception device Rx. There are multipaths between the transmission device Tx and the reception device Rx. The reception device Rx receives the wireless LAN signal via each path. The reception device Rx monitors the feature amounts of the wireless LAN signal for each path. Examples of the feature amounts include received power, received signal strength, phase, etc. As shown in FIG. 14, when an object crosses paths A, B, and C in order, the feature amounts related to paths A, B, and C change in order. Therefore, it is possible to estimate the moving direction of the object based on the temporal change of the feature amount for each path.

[0049] FIG. 15 is a conceptual diagram for explaining another example of a method for estimating the moving direction of an object based on a wireless LAN signal. The transmission device Tx includes a plurality of antennas. The transmission device Tx transmits wireless LAN signals from each of the plurality of antennas. The reception device Rx receives the wireless LAN signals transmitted from the plurality of antennas. The reception device Rx monitors the feature amounts of the wireless LAN signal for each antenna. Examples of the feature amounts include received power, received signal strength, phase, etc. As shown in FIG. 15, when an object crosses between the transmission device Tx and the reception device Rx, the feature amounts related to each antenna change in order. Therefore, it is possible to estimate the moving direction of the object based on the temporal change of the feature amount for each path. The method shown in FIG. 15 is also applicable to an outdoor environment with few multipaths.

[0050] The moving direction acquisition unit 110 estimates the moving direction DF of the flying object 20 based on the above method. That is, the moving direction acquisition unit 110 receives a wireless signal (e.g., a wireless LAN signal) transmitted from another wireless station 10 via the transceiver 113. Then, the moving direction acquisition unit 110 estimates the moving direction DF of the flying object 20 based on the temporal change of the feature amount of the received wireless signal. As described above, the estimation accuracy is improved by using a plurality of antennas.

[0051] 4-4. The Fourth Example FIG. 16 is a block diagram for explaining a fourth example of the moving direction acquisition process. In the fourth example, the moving direction acquisition unit 110 includes a communication device 114 that communicates with the flying object 20. The flying object 20 is equipped with a position sensor that detects its own position. As the position sensor, a GPS (Global Positioning System) sensor is exemplified. The flying object 20 transmits flying object position information 200 indicating its own position detected by the position sensor to the radio station 10. The moving direction acquisition unit 110 acquires the flying object position information 200 from the flying object 20 via the communication device 114. Then, the moving direction acquisition unit 110 acquires the moving direction DF of the flying object 20 by tracing the position indicated by the flying object position information 200.

[0052] 4-5. Fifth Example FIG. 17 is a block diagram for explaining a fifth example of the moving direction acquisition process. In the fifth example, the moving direction acquisition unit 110 includes a communication device 115 that communicates with a flying object management device 50 outside the radio station 10. The flying object management device (management server) 50 manages the positions, moving directions, states, etc. of the respective flying objects 20. For example, the flying object management device 50 grasps the moving direction of each flying object 20 by any of the methods described in the above first to fourth examples, and provides moving direction information 210 regarding each flying object 20. The moving direction acquisition unit 110 communicates with the flying object management device 50 via the communication device 115, and acquires the moving direction information 210 from the flying object management device 50.

Explanation of Reference Numerals

[0053] 1…Wireless communication system, 10…Wireless station, 11…Signal generation unit, 12…Transmission unit, 13…Beam variable antenna, 14…Reception unit, 15…Signal analysis unit, 16…Beam direction determination unit, 20…Aircraft, 21…Notification signal generation unit, 22…Transmission unit, 23…Antenna, 24…Reception unit, 25…Signal analysis unit, 50…Aircraft management device, 100…Communication controller, 101…Processor, 102…Storage device, 103…Communication control program, 110…Moving direction acquisition unit, 120…Beam direction candidate setting unit, 130…Beam direction determination unit, 140…Beamforming unit, 200…Aircraft position information, 210…Moving direction information, 220…Beam direction candidate information, 230…Beam direction information, DB…Beam direction, DF…Moving direction, PS…Subspace

Claims

1. A wireless communication method for performing wireless communication between a wireless station and an aircraft, comprising: beamforming processing for forming a beam directed from the wireless station to the aircraft; communication processing for performing communication between the wireless station and the aircraft using the beam; wherein the beamforming processing includes: movement direction acquisition processing for acquiring movement direction information indicating the movement direction of the aircraft; processing for setting a partial space obtained by excluding, from the entire three-dimensional space, at least the space existing in the direction opposite to the movement direction as viewed from the aircraft, based on the movement direction information; beam direction determination processing for determining the beam direction of the beam within the range of the partial space. A wireless communication method.

2. The wireless communication method according to claim 1, [[ID=eleven]]wherein the movement direction acquisition processing includes: processing for imaging the aircraft using a camera; processing for acquiring the movement direction of the aircraft based on the imaging result by the camera. A wireless communication method.

3. The wireless communication method according to claim 1, wherein the movement direction acquisition processing includes: processing for detecting the position of the aircraft using a distance measuring sensor; processing for acquiring the movement direction of the aircraft based on the detected position of the aircraft. A wireless communication method.

4. The wireless communication method according to claim 1, wherein the movement direction acquisition processing includes: processing for receiving, at the wireless station, a wireless signal transmitted from another wireless station; processing for estimating the movement direction of the aircraft based on the temporal change of the feature amount of the received wireless signal. A wireless communication method.

5. The wireless communication method according to claim 1, wherein the movement direction acquisition processing includes: processing for acquiring aircraft position information indicating the position of the aircraft detected by the aircraft; processing for acquiring the movement direction of the aircraft based on the aircraft position information. A wireless communication method.

6. The wireless communication method according to any one of claims 1 to 5, wherein the beamforming processing further includes processing for setting at least one beam direction candidate within the range of the partial space, and the beam direction determination processing includes: ​ ​ ​ ​ ​ ​ ​ ​ A process of selecting, as the beam direction, one that satisfies the condition of communication quality among the at least one beam direction candidate based on the reception result information including a wireless communication method.

7. A wireless station that performs wireless communication with an aircraft, comprising a controller that forms a beam directed from the wireless station to the aircraft and communicates with the aircraft using the beam, wherein the controller further performs a moving direction acquisition process of acquiring moving direction information indicating the moving direction of the aircraft, performs a process of setting a partial space obtained by excluding, from the entire three-dimensional space, at least the space existing in the direction opposite to the moving direction as viewed from the aircraft based on the moving direction information, and performs a beam direction determination process of determining the beam direction of the beam within the range of the partial space configured to execute a wireless station.

8. The wireless station according to claim 7, wherein the controller further sets at least one beam direction candidate within the range of the partial space, and the beam direction determination process includes a process of transmitting a measurement signal from the wireless station to the aircraft using the beam of the at least one beam direction candidate, a process of receiving, from the aircraft, reception result information indicating the reception result of the measurement signal at the aircraft, and a process of selecting, as the beam direction, one that satisfies the condition of communication quality among the at least one beam direction candidate based on the reception result information including a wireless station.

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