Radio station, radio station control method and program

Abstract

To narrow a range of transmitting beams while maintaining a communication state with a communication partner even if the communication partner moves.SOLUTION: A radio station 1A includes: a storage unit 12 which stores an orientation in which a beam receiving unit 111 receives a beam of another station and a time at which the beam of the other station is received, in association with each other; a relative speed specifying unit 132 which specifies, based on relations between the plurality of orientations and the plurality of times stored in the storage unit 12, a speed relative to another radio station 1B at a plurality of points in time; a calculation unit 133 which calculates variability values indicating the magnitude of variability of a plurality of relative speeds corresponding to the plurality of points in time; an estimation unit 134 which estimates an orientation range of the other radio station in the next time, on the basis of the previous orientation of the other station, the relative speed specified by the relative speed specifying unit, and the variability values; and a sweeping control unit 135 which causes the beam receiving unit and a beam transmission unit to sweep the beams in the orientation range.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a radio station used in radio communication, a control method for the radio station, and a program. [Background technology]

[0002] BACKGROUND ART Conventionally, a technique is known in which a base station of a wireless communication network stores the direction of a communication partner and sets the directivity of an antenna based on the stored direction (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-142925 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional base stations detect the direction of a communication partner after it moves. In this case, the base station cannot recognize the direction of the communication partner immediately after the communication partner moves, which causes a problem in that communication with the communication partner becomes impossible.

[0005] Therefore, the present invention has been made in consideration of these points, and aims to provide a radio station that can narrow the transmission range of a beam while maintaining communication with a communication partner even when the communication partner moves. [Means for solving the problem]

[0006] a memory unit that stores the direction in which the beam of the other station was received by the beam receiving unit and the time at which the beam of the other station was received in association with each other; a relative speed determination unit that determines a relative speed with respect to the other radio station at a plurality of time points based on the relationship between the plurality of directions and the plurality of time points stored in the memory unit; a calculation unit that calculates a variation value that indicates the magnitude of variation in the plurality of relative speeds corresponding to the plurality of time points; an estimation unit that estimates the direction range of the other radio station at the next time point based on the direction immediately before the other radio station, the relative speed determined by the relative speed determination unit, and the variation value; and a sweep control unit that causes the beam receiving unit and the beam transmitting unit to sweep the beam in the direction range.

[0007] The sweep control unit may cause the beam transmitting unit to transmit the own station's beam in a range wider than the azimuth range if the beam receiving unit does not receive the other station's beam after a predetermined time has elapsed since transmitting the beam in the azimuth range.

[0008] If the beam receiving unit does not receive the other station's beam when a predetermined time has elapsed since transmitting the beam in the azimuth range, the sweep control unit may cause the beam transmitting unit to transmit the own station's beam in a range including the azimuth in which the beam receiving unit previously received the other station's beam, as stored in the memory unit.

[0009] The sweep control unit may cause the beam transmitting unit to stop transmitting the station's own beam in the azimuth range if the distance to the other radio station estimated based on the intensity of the other station's beam received from the other radio station is greater than the communication distance.

[0010] When the azimuth range estimated by the estimation unit is the range of one of the local station beams, the sweep control unit may cause the beam transmission unit to transmit the one local station beam and transmit the local station beam corresponding to another range.

[0011] When the number of directions of the local station beam included in the direction range is greater than the number of beams that the beam transmitting unit can transmit, the sweep control unit may cause the beam transmitting unit to transmit the local station beam in a range corresponding to multiple directions preferentially selected from directions close to the center of the direction range.

[0012] If the number of azimuths of the local station beam included in the azimuth range is greater than the number of beams that the beam transmitting unit can transmit, the sweep control unit may cause the beam transmitting unit to transmit the local station beam within a range corresponding to multiple azimuths selected preferentially from the azimuths with the largest number stored in the memory unit.

[0013] A radio station control method according to a second aspect of the present invention is executed by a computer and includes the steps of: determining a relative speed with respect to another radio station at multiple time points based on a relationship between multiple directions and multiple times stored in a memory unit that stores the direction in which a radio station receives a beam from another radio station and the time at which the beam from the other radio station is received in association with each other; calculating a variation value indicating the magnitude of variation in the multiple relative speeds corresponding to the multiple time points; estimating a direction range of the other radio station at the next time point based on the previous direction of the other radio station, the determined relative speed, and the variation value; and causing the radio station to sweep its beam in the direction range.

[0014] A third aspect of the program of the present invention causes a computer to execute the following steps: determining a relative speed with respect to another radio station at multiple time points based on a relationship between multiple directions and multiple times stored in a memory unit that stores the direction in which a radio station received a beam from another radio station and the time at which the beam was received in association with each other; calculating a variation value that indicates the magnitude of variation in the multiple relative speeds corresponding to the multiple time points; estimating a direction range of the other radio station at the next time point based on the previous direction of the other radio station, the determined relative speed, and the variation value; and causing the radio station to sweep its beam in the direction range. [Effects of the Invention]

[0015] According to the present invention, it is possible to narrow the transmission range of the beam while maintaining the communication state with the communication partner even when the communication partner moves. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram for explaining an overview of a wireless communication system S. [Figure 2] FIG. 10 is a diagram showing an overview of the range of predicted orientations. [Figure 3] FIG. 2 is a diagram illustrating a configuration of a wireless station 1. [Figure 4] 10 is a diagram for explaining the operation of the sweep control unit 135. FIG. [Figure 5] 4 is a flowchart showing the flow of processing in the wireless station 1. DETAILED DESCRIPTION OF THE INVENTION

[0017] [Overview of Wireless Communication System S] 1 is a diagram illustrating an overview of a wireless communication system S. The wireless communication system S includes a wireless station 1A and a wireless station 1B. The wireless station 1A and the wireless station 1B are wireless stations that communicate by sweeping beams in multiple directions, such as in a fifth-generation (5G) communication system.

[0018] The wireless station 1A is, for example, a base station or relay station of a wireless communication network, and the wireless station 1B is a wireless communication terminal that communicates with the wireless station 1A, but the functions of the devices of the wireless station 1A and the wireless station 1B are arbitrary. In this specification, a case where the position of the wireless station 1A is fixed and the wireless station 1B is mobile is mainly illustrated, but both the wireless station 1A and the wireless station 1B may also be mobile. In the following explanation, when explaining functions common to the wireless station 1A and the wireless station 1B, the wireless station 1A and the wireless station 1B may be referred to as the wireless station 1.

[0019] As shown in Fig. 1(a), each of wireless stations 1A and 1B sweeps a beam while changing its direction at predetermined intervals. Sweeping a beam means transmitting a beam while sequentially changing its direction, and receiving beams transmitted from other wireless stations (sometimes referred to as "other stations") from sequentially different directions. In the example shown in Fig. 1(a), while wireless station 1A sweeps its beam in directions from #1 to #M, wireless station 1B sweeps its beam in directions from #1 to #N.

[0020] When a wireless station sweeps a beam, if it sweeps the beam in a direction where no other wireless stations are present, it will transmit a beam in a direction where it cannot communicate with other wireless stations, or it will wait to receive the beam in that direction. As a result, it will waste time and processing time where communication is not possible, and it will also increase power consumption.

[0021] Therefore, in the wireless communication system S, the wireless station 1A and the wireless station 1B estimate the current direction of the other wireless station and calculate the moving speed of the other wireless station based on the history of the past direction of the other wireless station, thereby estimating the direction of the other wireless station at a future time. Specifically, as shown in FIG. 1(b), the wireless station 1A estimates that the direction of the wireless station 1B is at the coordinate (θ uest ,φ uest ), and the wireless station 1B estimates that the direction of the wireless station 1A is the coordinate (θ rest ,φ rest ) is estimated to be the direction.

[0022] Here, (θ,φ) are coordinates in a spherical coordinate system with each wireless station as the origin. θ is the argument based on a first axis of the spherical coordinate system, and φ is the argument based on a second axis that is perpendicular to the first axis. Each of wireless stations 1A and 1B stores direction history data in which coordinates indicating estimated directions are associated with time.

[0023] Next, each of the wireless stations 1A and 1B calculates its relative speed with respect to the other wireless station based on the stored direction history data. When the wireless stations 1A and 1B are moving, the relative speed is the difference between the moving speed of the wireless station 1A and the moving speed of the wireless station 1B. When either the wireless station 1A or the wireless station 1B is not moving, the relative speed is the moving speed of the other wireless station.

[0024] The time interval between the recording of the directions of other radio stations is Δt, the number of directions included in the direction history data is N, and the direction at the i-th time is θ i Then, the relative velocity is calculated by the following equation (1).

number

number

[0025] However, if the predicted direction at the next time is incorrect, wireless station 1A and wireless station 1B will no longer be able to communicate. Therefore, in the wireless communication system S, at least one of wireless station 1A and wireless station 1B estimates the range of prediction error and sweeps its beam within a range that predicts the direction of the other wireless station while taking the range of error into account. For example, wireless station 1B sweeps its beam within a narrower range than the range shown in FIG. 1(a), as shown in FIG. 1(c). By operating in this manner, wireless station 1 can narrow the transmission range of its beam while maintaining communication with the other wireless station even if the other wireless station moves.

[0026] Figure 2 shows an overview of the range of predicted azimuths. Figure 2(a) shows how the coordinates of other wireless stations change over time. The squares corresponding to times T[-4], T[-3], T[-2], and T[-1] indicate the coordinates of past azimuths stored as azimuth history data. The square corresponding to time T[0] indicates the coordinates of the next azimuth predicted using, for example, equation (2) based on the history of past azimuths. The dashed circle around the square corresponding to T[0] indicates the predicted azimuth range R, which is the range of azimuths predicted taking into account errors.

[0027] Figure 2(b) shows the range in which a wireless station sweeps its beam. Each of the solid-line circles arranged at equal intervals in the θ-axis and φ-axis directions indicates the beam's irradiation range in one direction. The dashed-line circle indicates the predicted azimuth range R shown in Figure 2(a). The minimum number of beams that cover the dashed circle among the irradiation ranges of multiple beams are the beams to be swept and are shown in gray.

[0028] In this way, the wireless station according to this embodiment sweeps its beam in a range of multiple directions where it is predicted that other wireless stations will be present, thereby narrowing the beam sweep range. Since prediction errors are taken into consideration when determining this sweep range, the probability that other wireless stations will be present outside the sweep range is low, and the wireless communication system S can achieve both improved reliability and efficiency of communication.

[0029] [Configuration of Radio Station 1] 3 is a diagram showing the configuration of the wireless station 1. The wireless station 1 has a communication unit 11, a storage unit 12, and a control unit 13. The communication unit 11 has a beam receiving unit 111 and a beam transmitting unit 112. The control unit 13 has an orientation estimating unit 131, a relative speed identifying unit 132, a calculating unit 133, an estimating unit 134, and a sweep control unit 135.

[0030] The communication unit 11 functions as a sweep control unit that sweeps a range specified by the sweep control unit 135. The beam receiving unit 111 receives other-station beams transmitted by other wireless stations. The beam receiving unit 111 receives other-station beams arriving from the range specified by the sweep control unit 135. When the beam receiving unit 111 receives other-station beams, it inputs an electrical signal based on the received other-station beam to the direction estimation unit 131.

[0031] The beam transmitting unit 112 transmits a beam of the local station to other radio stations. The beam transmitting unit 112 transmits the beam of the local station to the range specified by the sweep control unit 135.

[0032] The storage unit 12 includes storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The storage unit 12 stores programs executed by the control unit 13. The storage unit 12 also stores data used by the control unit 13 to predict the directions of other wireless stations and sweep beams. The storage unit 12 stores, for example, direction history data that associates the directions in which the beam receiving unit 111 received the beam of another station with the times at which the beam of the other station was received.

[0033] The control unit 13 has, for example, a CPU (Central Processing Unit). The control unit 13 executes the programs stored in the storage unit 12 to function as an orientation estimation unit 131, a relative speed identification unit 132, a calculation unit 133, an estimation unit 134, and a sweep control unit 135.

[0034] The direction estimation unit 131 analyzes the other station beam notified by the beam receiving unit 111 to create direction history data including the results of estimating the direction of the other radio station that transmitted the other station beam, and stores the created direction history data in the storage unit 12. Specifically, the direction estimation unit 131 creates direction history data in which the time at which the beam receiving unit 111 received the other station beam is associated with coordinates indicating the estimated direction. For example, every time the direction estimation unit 131 receives a direction notification from the beam receiving unit 111, it adds the new direction coordinates and time to the direction history data stored in the storage unit 12.

[0035] The direction estimation unit 131 may estimate the direction of another wireless station by any method, but the direction estimation unit 131 estimates the direction, for example, by the following equation (3).

number

[0036] The direction estimation unit 131 may further calculate the distance between the wireless station 1 and another wireless station using the following equation (4).

number

[0037] The relative speed identification unit 132 identifies the relative speed with respect to other wireless stations at multiple points in time based on the relationship between multiple directions and multiple times stored in the storage unit 12. Specifically, the relative speed identification unit 132 calculates the relative speed with respect to other wireless stations using the above formula (1). The relative speed identification unit 132 notifies the calculation unit 133 of the calculated relative speed.

[0038] The calculation unit 133 calculates a variation value indicating the magnitude of variation in a plurality of relative velocities corresponding to a plurality of time points. The variation value is expressed by a statistical value such as the variance or standard deviation of the relative velocities, for example.

[0039] The calculation unit 133 calculates the standard deviation as a variation value, for example, by the following formula (5).

number

[0040] The estimation unit 134 estimates the predicted direction range of the other wireless station at the next time based on the previous direction of the other wireless station, the relative speed identified by the relative speed identification unit 132, and the dispersion value. The estimation unit 134 estimates the position of the other wireless station at the next time based on, for example, the previous direction of the other wireless station and the latest relative speed identified by the relative speed identification unit 132, and calculates the predicted direction range based on the position to be estimated and the dispersion value. In this way, the predicted direction range, which is the direction range estimated by the estimation unit 134, is a direction range that takes error into consideration.

[0041] Specifically, the estimation unit 134 estimates the error range of the direction of another wireless station at the next time, for example, using the following equation (6).

number

[0042] The sweep control unit 135 causes the beam receiving unit 111 and the beam transmitting unit 112 to sweep the beam in the predicted direction range notified by the estimation unit 134. There is a high probability that other wireless stations are present in the predicted direction range notified by the estimation unit 134, so the sweep control unit 135 causes the beam receiving unit 111 and the beam transmitting unit 112 to sweep the beam in the predicted direction range, thereby enabling the wireless station 1 to communicate with other wireless stations efficiently and reliably.

[0043] Incidentally, the direction range notified by the estimation unit 134 is determined taking error into consideration, but if the other wireless station behaves in an unexpected way, it may not be possible to communicate with the other wireless station even if the beam is swept in that direction range. Therefore, if the beam receiving unit 111 does not receive the other station's beam when a predetermined time has elapsed since the beam transmitting unit 112 transmitted a beam in the predicted direction range notified by the estimation unit 134, the sweep control unit 135 may cause the beam transmitting unit 112 to transmit the own station's beam in a range wider than the predicted direction range.

[0044] The predetermined time is set as the time required for the beam receiving unit 111 to receive the other station's beam after the beam transmitting unit 112 transmits the local station's beam. When the wireless station 1 operates based on, for example, a 5G communication protocol, the beam transmitting unit 112 transmits an SSB as the local station's beam at 20 ms intervals, and the beam receiving unit 111 receives the other station's beam in response to the transmitted SSB. In this case, the predetermined time is 20 ms.

[0045] If the beam receiving unit 111 does not receive a beam from another station when a predetermined time has elapsed since the beam transmitting unit 112 transmitted a beam in the predicted direction range notified by the estimation unit 134, the sweep control unit 135 may cause the beam transmitting unit 112 to transmit a beam from its own station in a range including directions in which the beam receiving unit 111 previously received a beam from another station, which directions are stored in the memory unit 12. In this case, the sweep control unit 135 may cause the beam transmitting unit 112 to transmit a beam from its own station in directions in which the beam receiving unit 111 previously received a beam from another station, but not in other directions. By operating the sweep control unit 135 in this manner, the beam transmitting unit 112 can transmit a beam from its own station in a range where there is a relatively high probability that other wireless stations exist.

[0046] The sweep control unit 135 may refer to the direction history data stored in the memory unit 12, identify a past movement pattern similar to the previous movement pattern of another radio station, and cause the beam transmitting unit 112 to transmit a beam of its own station within a range that includes the position where the other radio station was located at the next time in the identified movement pattern.

[0047] The sweep control unit 135, for example, performs pattern matching between a combination of multiple line segments connecting multiple positions where other wireless stations existed in the immediately preceding period and a combination of multiple line segments connecting multiple positions included in the direction history data, to identify the combination of multiple positions with the highest similarity.The sweep control unit 135 then identifies the position next to the last position (position at past time T[-1]) among the multiple positions included in the identified combination as the position where there is a high probability that other wireless stations will exist at the next past time T[0].

[0048] The sweep control unit 135 specifies the position at the time following the current time by adding a vector from the last position (the position at past time T[-1]) to the next position (the position at past time T[0]) to the last position of the multiple positions corresponding to the immediately previous period. By operating the sweep control unit 135 in this manner, the beam transmitting unit 112 can transmit its own station beam to an area where there is a relatively high probability that other wireless stations are present when other wireless stations move in a similar pattern.

[0049] The sweep control unit 135 may cause the beam transmission unit 112 to stop transmitting the beam of the own station in the azimuth range when the distance to the other wireless station estimated by the azimuth estimation unit 131 based on the intensity of the other wireless station beam received from the other wireless station is longer than the communicable distance. The sweep control unit 135 determines whether the other wireless station is in a position where communication is possible, for example, by comparing the distance to the other wireless station estimated by the azimuth estimation unit 131 with the communicable distance stored in the memory unit 12. When it is determined that the other wireless station is not in a position where communication is possible, the sweep control unit 135 excludes the azimuth of the other wireless station from the range where the beam is swept, thereby preventing the beam from being swept in unnecessary azimuths.

[0050] Incidentally, when other wireless stations are not moving, there is no variation in the relative speeds of the other wireless stations, and the predicted direction range estimated by the estimation unit 134 becomes the range of one home station beam. In this way, when the direction range estimated by the estimation unit 134 is the range of one home station beam, the sweep control unit 135 may cause the beam transmission unit 112 to transmit one home station beam corresponding to that range, and not transmit home station beams corresponding to other ranges. By operating the sweep control unit 135 in this way, it is possible to minimize the beam sweep range while reliably enabling communication with other wireless stations.

[0051] If the number of directions of the station's own beam included in the predicted direction range estimated by the estimation unit 134 is greater than the number of beams that the beam transmitting unit 112 can transmit, the sweep control unit 135 may cause the beam transmitting unit 112 to transmit the station's own beam in a range corresponding to multiple directions preferentially selected from directions close to the center of the predicted direction range.

[0052] 4 is a diagram for explaining the operation of the sweep control unit 135. The dashed line in FIG. 4(a) indicates the predicted direction range R, and the multiple solid-line circles indicate the range in which the beam transmission unit 112 can transmit its own station beam. The predicted direction range R is a range in which the ranges of 36 beams partially overlap. If the number of beams that the beam transmission unit 112 can transmit during a predetermined period (for example, a period in which the beam transmission unit 112 should transmit its own station beam) is 16, the sweep control unit 135 causes the beam transmission unit 112 to transmit its own station beams corresponding to the 16 directions shown in gray in FIG. 4(b).

[0053] The closer to the center of the predicted direction range R, the higher the probability that other wireless stations exist. Therefore, by operating the sweep control unit 135 in this manner, the beam transmission unit 112 can transmit its own station beam to a range where there is a high probability that other wireless stations exist.

[0054] When the number of azimuths of the beam of the own station included in the predicted azimuth range is greater than the number of beams that the beam transmission unit 112 can transmit, the sweep control unit 135 may refer to the azimuth history data stored in the memory unit 12 and cause the beam transmission unit 112 to transmit the beam of the own station in a range corresponding to a plurality of azimuths selected preferentially from the azimuths with the greatest number stored in the memory unit 12. The probability that other wireless stations exist in the azimuths included in the azimuth history data is considered to be higher than the probability that other wireless stations exist in other azimuths. Therefore, by operating the sweep control unit 135 in this manner, the beam transmission unit 112 can transmit the beam of the own station in a range where there is a high probability that other wireless stations exist.

[0055] [Processing flow at radio station 1] Fig. 5 is a flowchart showing the flow of processing in the wireless station 1. The flowchart shown in Fig. 5 starts from the point when the wireless station 1 starts sweeping the beam.

[0056] The sweep control unit 135 causes the communication unit 11 to sweep the beam in an initial range previously stored in the storage unit 12 (S1). The initial range is, for example, the maximum range that the communication unit 11 can sweep.

[0057] Next, the direction estimation unit 131 estimates the directions of other wireless stations based on the power received from the other wireless stations while sweeping in multiple different directions, for example, using equation (3) (S2). The direction estimation unit 131 stores the estimated directions of the other wireless stations in the storage unit 12 (S3).

[0058] Next, if the direction history data is stored in the memory unit 12 (YES in S4), the relative speed determination unit 132 determines the relative speed of the other wireless station with respect to the wireless station 1 based on the multiple directions included in the direction history data and the times corresponding to each direction (S5).

[0059] When the relative speed identification unit 132 identifies the relative speeds at multiple times, the calculation unit 133 calculates a dispersion value (S6). The calculation unit 133 calculates the standard deviation of the relative speeds, for example, using equation (5). Then, the estimation unit 134 determines a predicted direction range for the direction of other wireless stations at the next time, using equation (6) (S7). The sweep control unit 135 causes the communication unit 11 to sweep the beam in the determined predicted direction range (S8).

[0060] [Effects of Radio Station 1] As described above, the wireless station 1 includes the estimation unit 134 that estimates the direction range of the other wireless station at the next time based on the variation value indicating the magnitude of variation in the relative speed of the other wireless station corresponding to multiple points in time, the previous direction of the other wireless station, and the relative speed identified by the relative speed identification unit 132. Then, the sweep control unit 135 causes the beam receiving unit 111 and the beam transmitting unit 112 to sweep the beam in the estimated predicted direction range. With the wireless station 1 configured in this way, the wireless station 1 can narrow the transmission range of the beam while maintaining communication with the communication partner even when the communication partner moves.

[0061] Furthermore, this invention will make it possible to contribute to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is "Build resilient infrastructure, promote inclusive and sustainable industrialization, and promote innovation and resilience."

[0062] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments. [Explanation of symbols]

[0063] 1 Radio station 11 Communications Department 12 Storage section 13 Control Unit 111 Beam receiving unit 112 Beam transmitter 131 Direction estimation part 132 Relative velocity identification unit 133 Calculation Unit 134 Estimation Department 135 Sweep control section

Claims

1. a beam receiving unit for receiving other-station beams transmitted by other radio stations; a beam transmitting unit that transmits a beam of its own station to the other radio stations; a storage unit that stores the direction in which the beam receiving unit receives the beam from another station and the time at which the beam from the other station is received in association with each other; a relative speed determination unit that determines a relative speed with respect to the other wireless station at a plurality of points in time based on the relationship between a plurality of directions and a plurality of times stored in the storage unit; a calculation unit that calculates a variation value indicating a magnitude of variation of the plurality of relative velocities corresponding to the plurality of time points; an estimation unit that estimates a first direction range of the other wireless station at a next time based on the previous direction of the other wireless station, the relative speed identified by the relative speed identification unit, and the variation value; a sweep control unit that causes the beam transmitting unit to transmit the local station beam in a second azimuth range that is wider than the first azimuth range, when the beam receiving unit does not receive the other station beam after a predetermined time has elapsed since the beam transmitting unit caused the local station beam to be transmitted in the first azimuth range; A radio station having

2. a beam receiving unit for receiving beams transmitted from other radio stations; a beam transmitting unit that transmits a beam of its own station to the other radio stations; a storage unit that stores the direction in which the beam receiving unit receives the beam from another station and the time at which the beam from the other station is received in association with each other; a relative speed determination unit that determines a relative speed with respect to the other wireless station at a plurality of points in time based on the relationship between a plurality of directions and a plurality of times stored in the storage unit; a calculation unit that calculates a variation value indicating a magnitude of variation of the plurality of relative velocities corresponding to the plurality of time points; an estimation unit that estimates a first direction range of the other wireless station at a next time based on the previous direction of the other wireless station, the relative speed identified by the relative speed identification unit, and the variation value; a sweep control unit that, when the beam receiving unit does not receive the other station beam after a predetermined time has elapsed since the beam transmitting unit was made to transmit the own station beam in the first azimuth range, causes the beam transmitting unit to transmit the own station beam in a second azimuth range that includes azimuths in which the beam receiving unit previously received the other station beam, which are stored in the storage unit; A radio station having

3. A beam receiving unit that receives a beam from another station transmitted by another radio station; a beam transmitting unit that transmits a beam of its own station to the other radio stations; a storage unit that stores the direction in which the beam receiving unit receives the beam from another station and the time at which the beam from the other station is received in association with each other; a relative speed determination unit that determines a relative speed with respect to the other wireless station at a plurality of points in time based on the relationship between a plurality of directions and a plurality of times stored in the storage unit; a calculation unit that calculates a variation value indicating a magnitude of variation of the plurality of relative velocities corresponding to the plurality of time points; an estimation unit that estimates a direction range of the other wireless station at a next time based on the previous direction of the other wireless station, the relative speed identified by the relative speed identification unit, and the variation value; a sweep control unit that causes the beam receiving unit to sweep the other station's beam in the azimuth range, causes the beam transmitting unit to sweep the local station's beam in the azimuth range when the distance to the other radio station estimated based on the intensity of the other station's beam received from the other radio station is equal to or shorter than the communicable distance, and causes the beam transmitting unit to stop transmission of the local station's beam in the azimuth range when the distance to the other radio station estimated based on the intensity of the other station's beam received from the other radio station is longer than the communicable distance; A radio station having

4. A beam receiving unit that receives a beam from another station transmitted by another radio station; a beam transmitting unit that transmits a beam of its own station to the other radio stations; a storage unit that stores the direction in which the beam receiving unit receives the beam from another station and the time at which the beam from the other station is received in association with each other; a relative speed determination unit that determines a relative speed with respect to the other wireless station at a plurality of points in time based on the relationship between a plurality of directions and a plurality of times stored in the storage unit; a calculation unit that calculates a variation value indicating a magnitude of variation of the plurality of relative velocities corresponding to the plurality of time points; an estimation unit that estimates a direction range of the other wireless station at a next time based on the previous direction of the other wireless station, the relative speed identified by the relative speed identification unit, and the variation value; a sweep control unit that causes the beam receiving unit to sweep the other station's beam in the azimuth range, and when the azimuth range estimated by the estimation unit is not the range of one of the own station's beams, causes the beam transmitting unit not to transmit the one own station's beam but to transmit the own station's beam corresponding to another range, and when the azimuth range estimated by the estimation unit is the range of one of the own station's beams, causes the beam transmitting unit to transmit the one own station's beam but not to transmit the own station's beam corresponding to another range; A radio station having

5. A beam receiving unit that receives a beam from another station transmitted by another radio station; a beam transmitting unit that transmits a beam of its own station to the other radio stations; a storage unit that stores the direction in which the beam receiving unit receives the beam from another station and the time at which the beam from the other station is received in association with each other; a relative speed determination unit that determines a relative speed with respect to the other wireless station at a plurality of points in time based on the relationship between a plurality of directions and a plurality of times stored in the storage unit; a calculation unit that calculates a variation value indicating a magnitude of variation of the plurality of relative velocities corresponding to the plurality of time points; an estimation unit that estimates a direction range of the other wireless station at a next time based on the previous direction of the other wireless station, the relative speed identified by the relative speed identification unit, and the variation value; a sweep control unit that causes the beam receiving unit to sweep the other station's beam in the azimuth range, and when the number of azimuths of the own station's beam included in the azimuth range is greater than the number of beams that the beam transmitting unit can transmit, causes the beam transmitting unit to transmit the own station's beam in a range corresponding to a plurality of azimuths preferentially selected from azimuths closest to the center of the azimuth range; A radio station having

6. A beam receiving unit for receiving a beam transmitted from another radio station; a beam transmitting unit that transmits a beam of its own station to the other radio stations; a storage unit that stores the direction in which the beam receiving unit receives the beam from another station and the time at which the beam from the other station is received in association with each other; a relative speed determination unit that determines a relative speed with respect to the other wireless station at a plurality of points in time based on the relationship between a plurality of directions and a plurality of times stored in the storage unit; a calculation unit that calculates a variation value indicating a magnitude of variation of the plurality of relative velocities corresponding to the plurality of time points; an estimation unit that estimates a direction range of the other wireless station at a next time based on the previous direction of the other wireless station, the relative speed identified by the relative speed identification unit, and the variation value; a sweep control unit that, when the number of azimuths of the local station beam included in the azimuth range is greater than the number of beams that the beam transmission unit can transmit, causes the beam transmission unit to transmit the local station beam in a range corresponding to a plurality of azimuths that are preferentially selected from the azimuths that have a greater number stored in the storage unit; A radio station having

7. The computer executes determining a relative speed with respect to the other radio station at a plurality of points in time based on a relationship between a plurality of directions and a plurality of times stored in a storage unit that stores the directions in which the radio station received a beam from the other radio station and the times at which the radio station received the beam from the other radio station in association with each other; calculating a variation value indicating a magnitude of variation in the plurality of relative velocities corresponding to the plurality of time points; estimating a first azimuth range of the other wireless station at a next time based on the previous azimuth of the other wireless station, the determined relative velocity, and the dispersion value; a step of causing the radio station to transmit the own station beam in a second azimuth range that is wider than the first azimuth range, when the radio station does not receive the other station beam after a predetermined time has elapsed since the radio station caused the radio station to transmit the own station beam in the first azimuth range; A radio station control method comprising:

8. On the computer, determining a relative speed with respect to the other radio station at a plurality of points in time based on a relationship between a plurality of directions and a plurality of times stored in a storage unit that stores the directions in which the radio station received a beam from the other radio station and the times at which the radio station received the beam from the other radio station in association with each other; calculating a variation value indicating a magnitude of variation in the plurality of relative velocities corresponding to the plurality of time points; estimating a first azimuth range of the other wireless station at a next time based on the previous azimuth of the other wireless station, the determined relative velocity, and the dispersion value; a step of causing the radio station to transmit the own station beam in a second azimuth range that is wider than the first azimuth range, when the radio station does not receive the other station beam after a predetermined time has elapsed since the radio station caused the radio station to transmit the own station beam in the first azimuth range; A program to execute.

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