JP2017212649A - Radio communication system, base station, and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately control a communication area without preparing measuring means other than a communication device for performing actual communication even if a propagation environment fluctuates due to change in weather conditions or the like.SOLUTION: A radio communication system includes: a mobile station moving on a route; a plurality of base stations that include a directional antenna, are arranged along the route, and wirelessly communicate with the mobile station; and a measuring unit for measuring propagation attenuation between the base stations and the mobile station. Each of the base stations in the radio communication system changes the direction of the directional antenna of the base station so as to make an angle between the directivity of the directional antenna and the route smaller as the measured propagation attenuation is larger.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a radio communication system, a base station, and a radio communication method.

  There is an increasing demand for communication between a fixed station and a mobile station that moves at high speed along with a vehicle such as a railroad or an automobile. A vehicle that moves at a high speed, for example, has a low movement speed, and the movement route is often limited as compared to a pedestrian who moves on a relatively free route. For this reason, when performing wireless communication between a mobile station that moves with a vehicle and a fixed station, it is possible to improve signal strength by forming a communication area along the movement path using the directivity of radio waves. Interference suppression is possible.

  In general, there is a feature that the directivity is easier to narrow down and the communication area is more easily restricted as the radio wave has a higher frequency. On the other hand, it is known that higher frequency radio waves are subjected to propagation attenuation due to various factors, and for example, millimeter wave radio waves having a frequency of 30 GHz or more are greatly attenuated by weather conditions such as rainfall. For this reason, when using radio waves of a high frequency such as millimeter waves outdoors, control is performed by various methods against changes in attenuation.

  As background art in this technical field, for example, there are JP-A-11-136184 (Patent Document 1) and JP-A-2003-318795 (Patent Document 2). In Patent Document 1, “measurement means 31 for measuring the received electric field strength of the transmission wave 24 in a wireless service system set to perform service in a predetermined service area 20 by a transmission wave from the wireless transmission base station” is disclosed. And at least one field strength monitoring receiver 31 provided near the boundary in the service area 20 and having communication means 33 for transmitting information on the received field strength to the radio transmission base station 21; A radio transmission base station 21 having control means 22 for controlling the output of the transmission wave 24 so that the received electric field intensity received by the electric field intensity monitoring receiver 31 is constant upon receiving the intensity information. Service system "(see summary).

  Further, Patent Document 2 states that “the control unit 106 receives weather information from the sensor 105 that is a weather information acquisition unit. The control unit 106 transmits the radio unit 100 (the radio transmission unit 102 and the radio reception unit 103 according to the weather information). For example, the control unit 106 changes the amplification amount of the amplifier unit 111 included in the wireless transmission unit 102 according to the weather information, or the control unit 106 controls the wireless reception unit 103 according to the weather information. The ON / OFF control of the operation of the waveform equalizer provided in the included digital detection unit 117 is performed, or the control unit 106 determines the antenna directivity of the reception antenna 113 included in the wireless reception unit 103 according to weather information. Control ”(see summary).

JP-A-11-136184 JP 2003-318895 A

  The technique described in Patent Document 1 needs to prepare a measurement unit for measuring the reception intensity and a communication unit for notifying the measurement result separately from a communication device for actually performing communication.

  Also, in wireless communication, the received signal strength varies greatly due to fading caused by the influence of reflected waves, etc., so even if transmission power control is performed based on the received power at a certain measurement location, the received signal at other points The power is not always a desired value, and the communication area cannot be appropriately controlled.

  In addition, the control method based on the received weather information as in the technique described in Patent Document 2 is roughly equivalent to the fact that the amount of attenuation is greater when it rains than when it is sunny, as the association between the weather conditions and the actual propagation environment. It is practically difficult to perform detailed control beyond the relationship.

  In one embodiment of the present invention, in order to solve the above-described problem, even if the propagation environment fluctuates due to a change in weather conditions or the like, it is possible to prepare measurement means other than a communication device for actually performing communication. The purpose is to appropriately control the communication area.

  In order to solve the above problems, one embodiment of the present invention employs the following configuration. A plurality of base stations that have a directional antenna and that are arranged along the route and perform radio communication with the mobile station; and between the plurality of base stations and the mobile station Each of the plurality of base stations, the greater the measured propagation attenuation, the more the direction of the directional antenna of the base station A wireless communication system that changes so that the angle formed by the directivity of the directional antenna and the path is reduced.

  One aspect of the present invention is to appropriately control a communication area without preparing measurement means other than a communication device for actually performing communication even when the propagation environment fluctuates due to changes in weather conditions or the like. be able to.

1 is a block diagram illustrating a configuration example of a wireless communication system according to a first embodiment. FIG. 3 is a block diagram illustrating another configuration example of the wireless communication system according to the first embodiment. 3 is a block diagram illustrating a configuration example of a base station in Embodiment 1. FIG. It is a sequence diagram which shows an example of the directivity control process in Example 1. It is a sequence diagram which shows another example of the directivity control process in Example 1. FIG. 6 is a graph illustrating a determination function for creating directivity control information in the first embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. Note that in the block diagram described below, each processing block is merely an example, and may be implemented as, for example, a separate logic circuit, may be implemented as software on one processor, or may be It may be implemented as a combination of a circuit and software. In addition, when a plurality of the same processing blocks coexist, each processing block may be mounted separately, or a plurality of processes are performed by using one mounted logic circuit or software by time multiplexing. Also good.

  In the sequence diagram described below, each process and message notification are merely examples for explanation, and in a range where there is no need for ordering, for example, notification and processing of a plurality of messages are combined into one. You may perform collectively and simultaneously, conversely, you may perform message notification and processing several times, and the order may be reversed.

  Hereinafter, the configuration of a wireless communication system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration example of a wireless communication system. The wireless communication system has one or more control stations 110. When the wireless communication system includes a plurality of control stations 110, each control station 110 is connected by an inter-control-station interface 111 (hereinafter also simply referred to as an interface 111).

  The wireless communication system further includes a plurality of base stations 120 connected to each control station 110 via base station control station interfaces 121 (hereinafter also simply referred to as interfaces 121). The base station 120 communicates wirelessly with one or more mobile stations 130 moving on the path 140. The base station 120 and the mobile station 130 perform wireless communication using, for example, millimeter waves, but may perform wireless communication using an arbitrary frequency.

  The plurality of base stations 120 are arranged along the path 140, for example. In addition, the plurality of base stations 120 form, for example, a continuous communication area on the path 140, that is, the mobile station 130 can communicate with at least one base station 120 at any place on the path 140. Have been placed.

  The control station 110 is a computer configured by, for example, a processor (CPU), a memory, an auxiliary storage device, a communication interface, and an input / output interface. The control station 110 outputs parameters and the like necessary for the operation of the base station 120 to each base station 120 via the interface 121. The control station 110 also receives input such as a communication status from the base station 120 via the interface 121. The control stations 110 also receive control information from and to each other via the interface 111.

  The control station 110 also inputs transmission data to be transmitted to the mobile station 130 to the base station 120 via the interface 121. The control station 110 also receives input of received data received from the mobile station 130 by the base station 120 via the interface 121.

  The base station 120 has a signal processing function and a directional antenna that transmits and receives radio signals. In the present embodiment, the directional antenna included in the base station 120 is also simply referred to as an antenna. The base station 120 creates a control signal necessary for wireless communication by the signal processing function, and transmits a wireless signal from the antenna. The base station 120 also converts transmission data input from the control station 110 via the interface 121 into a radio signal using a signal processing function, and transmits the radio signal from the antenna.

  The base station 120 also receives the radio signal transmitted by the mobile station 130, converts it to a received data signal by the signal processing function, and outputs it to the control station 110 via the interface 121. The base station 120 also receives input of parameters and the like necessary for operation from the control station 110 via the interface 121. The base station 120 also outputs information indicating a propagation environment, a communication state, and the like to the control station 110 via the interface 121.

  The mobile station 130 has a signal processing function and an antenna that transmits and receives radio signals, and moves on the path 140. The mobile station 130 receives the radio signal transmitted from the base station 120 through an antenna and performs reception processing using a signal processing function. The mobile station 130 also transmits the radio signal created by the signal processing function through the antenna. For example, a railroad track is an example of the route 140, and at this time, the mobile station 130 is mounted on, for example, a train.

  Here, the parameters output from the control station 110 to each base station 120 include, for example, information for controlling the directivity of the directional antenna in the base station 120. The information indicating the propagation environment output from the base station 120 to the control station 110 indicates the radio quality such as the received power value of the radio signal transmitted by the mobile station 130 at the base station 120 and the signal-to-noise power ratio. Contains information. Each base station 120 may have the function of the control station 110. That is, each base station 120 may control the directivity of its own directional antenna. At this time, the wireless communication system may not include the control station 110.

  1 can be divided into a base station center unit that performs baseband signal processing and the like, and a base station remote unit that performs radio frequency signal processing and transmission / reception of radio signals. It is. FIG. 2 is a block diagram illustrating a configuration example of the wireless communication system in this case.

  Differences from FIG. 1 will be described. In the configuration example illustrated in FIG. 2, the wireless communication system includes one or a plurality of base station center units 122 that are connected to each control station 110 via an interface 121 between base station control stations (hereinafter also simply referred to as an interface 121). Have. The wireless communication system includes one or a plurality of base station remote units 124 connected to each base station center unit 122 by an interface 123 in the base station. The base station remote unit 124 communicates wirelessly with the mobile station 130 moving on the path 140.

  The operation of each component of the wireless communication system of FIG. 2 is performed by dividing the signal processing function of the base station 120 of the wireless communication system of FIG. 1 into a base station center unit 122 and a base station remote unit 124 coupled by an interface 123. It is the same except that it has a divided signal processing function. Specifically, for example, the base station signal processing is performed by the base station center unit 122, and the radio frequency signal processing is performed by the base station remote unit 124. In addition, another process division may be performed.

  The transmission signal and the reception signal that pass through the interface 123 between the base station center unit 122 and the base station remote unit 124 may be baseband digital signals such as CPRI (Common Public Radio Interface), The transmission signal after AD conversion and the reception signal before DA conversion may be analog-transmitted as baseband, intermediate frequency, or radio frequency signals.

  FIG. 3 is a block diagram illustrating a configuration example of the base station 120 of FIG. The base station 120 includes, for example, a calculation unit 460, a memory 470, an RF unit 450, and a network interface unit 410. The arithmetic unit 460 includes a CPU, a logic circuit, and the like, executes a program stored in the memory 470, and executes signal processing for performing communication using information stored in the memory 470. The memory 470 includes a ROM that is a nonvolatile storage element and a RAM that is a volatile storage element. The ROM stores an immutable program (for example, BIOS). The RAM is a high-speed and volatile storage element such as a DRAM (Dynamic Random Access Memory), and temporarily stores data used when the signal processing executed by the arithmetic unit 460 is executed.

  The calculation unit 460 includes, for example, a controller 400, a control channel unit 420, one or more user channel units 430, and a channel modem unit 440.

  For example, the arithmetic unit 460 functions as the controller 400 by operating according to the controller program loaded in the memory 470 and functions as the control channel unit 420 by operating according to the control channel program loaded in the memory 470. The same applies to other units included in the calculation unit 460. Note that some or all of the functions of the respective units included in the calculation unit 460 may be realized by, for example, a DSP (not shown) or a logic circuit.

  The controller 400 collects information from each part of the base station 120 and controls the overall operation of the base station 120 by setting parameters in each part in the base station. The control channel unit 420 generates a control signal necessary for wireless communication between the base station 120 and the mobile station 130 in accordance with an instruction from the controller 400, performs processing such as encoding, and the like as a transmission control channel signal. The data is output to the modem unit 440. Further, the control channel unit 420 decodes the reception control channel signal input from the channel modem unit 440 in accordance with an instruction from the controller 400 and notifies the controller 400 of the decoding result.

  The user channel unit 430 encodes transmission user information including communication data received from the network interface unit 410 according to an instruction from the controller 400, and outputs the encoded transmission user information as a transmission user channel signal to the channel modem unit 440.

  Further, the user channel unit 430 decodes the received user channel signal input from the channel modem unit 440 in accordance with an instruction from the controller 400, and outputs received user information obtained as a decoding result to the network interface unit 410. An independent user channel unit 430 may be provided for each mobile station that communicates simultaneously, or for each channel that communicates simultaneously, or a user channel unit 430 that is smaller than the number of mobile stations that communicate simultaneously or the number of channels that communicate simultaneously is provided. The user channel unit 430 may perform time multiplexing processing.

  The channel modem unit 440 assigns and multiplexes each of the transmission control channel signal input from the control channel unit 420 and the transmission user channel signal input from the user channel unit 430 to communication resources according to instructions from the controller 400, and performs digital modulation. Process.

  Further, channel modem section 440 performs precoding processing as necessary on the signal subjected to digital modulation processing, and outputs the result to RF section 450 as a baseband transmission signal corresponding to each transmission antenna. The communication resource is a unit called a resource block, for example, and includes a time range, a frequency range, a code, an antenna, a precoding vector, and the like used for communication.

  Also, the channel modem unit 440 receives a restored baseband received signal corresponding to each receiving antenna from the RF unit 450, performs demodulation processing on the restored baseband received signal according to an instruction from the controller 400, and performs channel-by-channel demodulation. The received control channel signal is output to control channel section 420 and the received user channel signal is output to user channel section 430.

  The network interface unit 410 includes a network interface, receives information to be transmitted to the mobile station 130 via the base station 120 as an input, and outputs the information to the user channel unit 430 as transmission user information. Further, the network interface unit 410 receives a control message for the base station as an input from the control station, and outputs it to the controller 400. Further, the network interface unit 410 receives the received user information received from the mobile station 130 by the base station 120 as an input from the user channel unit 430 and outputs it to the control station 110. Further, the network interface unit 410 receives a control message for the control station 110 as an input from the controller 400 and outputs it to the control station 110.

  The RF unit 450 includes a directional antenna and an amplifier, converts a baseband transmission signal input from the channel modem unit 440 into a radio frequency signal according to an instruction from the controller 400, and transmits the signal as a radio signal through the directional antenna. . The radio frequency signal may be a microwave band signal, a millimeter wave band signal, or a signal of another frequency.

  The RF unit 450 also converts a radio signal received through the directional antenna into a baseband digital signal according to an instruction from the controller 400 and outputs the baseband digital signal to the channel modem unit 440. The RF unit 450 also controls the directivity of the directional antenna according to an instruction from the controller 400. The directivity control of the antenna may be performed by physically moving or rotating the entire directional antenna or a part thereof using a turntable or the like, or by adjusting the signal phase difference between a plurality of directional antennas. Sex may be controlled.

  The base station remote unit 124 includes a part including the directional antenna of the RF unit 450 or the RF unit 450. The base station center unit 122 includes a configuration that is not included in the base station remote unit 124 among the configurations of the base station 120 in FIG. 3. Moreover, the hardware configuration of the mobile station 130 is the same as the hardware configuration of the base station 120, for example.

  FIG. 4 is a sequence diagram illustrating an example of directivity control processing in the wireless communication system. In FIG. 4 and FIG. 5 described later, an example of processing in the wireless communication system in FIG. 1 will be described, but the same applies to processing in the wireless communication system in FIG.

  Each control station 110 first notifies parameter settings for communication to each base station 120 connected to the control station 110 (S310). Here, the parameter setting in step S310 includes predetermined directivity control information of the antenna of each base station 120. The antenna directivity control information includes information indicating the angle of the antenna. Each base station 120 sets the angle of the antenna to the angle indicated by the received directivity control information.

  Next, each base station 120 transmits a downlink signal to each mobile station 130 (S430). The downlink signal may include at least one of a reference signal with fixed transmission power and information on transmission power in the base station 120.

  Each mobile station 130 measures the received power of the downlink signal transmitted from each base station 120 and creates a reception quality value corresponding to the measured received power (S330). Here, the reception quality value may be the reception power value itself, or may be another index having a correlation with the reception power such as a signal-to-noise power value. The reception quality value is an example of information indicating a propagation environment. The received power value is an example of a value indicating propagation attenuation in the propagation environment. The larger the received power value, the smaller the propagation attenuation and the better the propagation environment.

  The reception quality value may be the value itself or an index value obtained by quantizing the value. The reception quality value may be created directly from a value obtained by one measurement, or may be created from a value obtained by averaging a plurality of measurement results. Further, the reception quality value may be created only from the downlink signal 210 transmitted from one base station 120, or may be created from the downlink signals 210 transmitted from a plurality of base stations 120, respectively.

  Next, each mobile station 130 transmits an uplink signal to each base station 120 (S340). The uplink signal in step S340 includes the reception quality value created in the reception power measurement process in step S330.

  Each base station 120 extracts a reception quality value from the uplink signal transmitted by each mobile station 130, and creates a measurement aggregate value according to the reception quality value (S350). In step S350, base station 120 may create a measurement aggregate value by performing smoothing processing on a plurality of reception quality values, or each reception quality value may be a measurement aggregate value. Next, each base station 120 reports the measurement aggregate value to the control station 110 connected to the base station (S360).

  Each control station 110, based on the reported measurement aggregate value, directivity control evaluation value corresponding to the arrival status of each transmission signal from each base station 120 connected to the control station 110 to each mobile station 130 Is created (S370). Details of the method of creating the directivity control evaluation value will be described later.

  Next, each control station 110 determines the directivity control evaluation value created in step S370 and the antenna directivity control information of the base station 120 notified to each base station 120 in step S310. Antenna directivity control information is created (S380). Details of the method of creating directivity control information will be described later.

  Next, each control station 110 notifies each base station 120 connected to the control station of the parameter setting including the antenna directivity control information created in the control determination process 330 (S390). Each base station 120 sets the angle of the antenna to the angle indicated by the received directivity control information.

  With the above sequence, the antenna directivity of each base station 120 is controlled according to the signal reception status in the mobile station 130. In addition, after step S390, a series of processes from step S320 to step S390 may be repeated.

  FIG. 5 is a sequence diagram illustrating another example of the directivity control method in the wireless communication system. Differences from the processing of FIG. 4 will be described. The example of FIG. 5 differs from the example of FIG. 4 in that not the mobile station 130 but the base station 120 performs the received power measurement process.

  Subsequent to step S320, each mobile station 130 transmits an uplink signal 220 to each base station 120 (S410). The uplink signal in step S410 may include, for example, at least one of a reference signal with fixed transmission power and transmission power information in the mobile station 130.

  Each base station 120 measures the reception power of the uplink signal transmitted by each mobile station 130 and creates a reception quality value (S420). The reception quality value created in step S420 is the same as the reception quality value created in step S350, for example.

  Next, in step S310, the base station 120 aggregates the reception quality values created in the reception power measurement process 305. The processing after step S310 is the same as the processing in FIG.

  Hereinafter, based on the measurement aggregate value 230 notified from the base station 120 in Step S370, the control station 110 is larger as the reach of the radio wave on the path 140 from each base station 120 is wider (the propagation attenuation is smaller), An example of a process for creating a directivity control evaluation value that is a smaller value (a propagation attenuation is larger) will be described.

  When the directivity control process illustrated in FIG. 4 is executed, the control station 110 combines, for example, one or more values of the following values (a) to (e) while maintaining the magnitude relationship: Thus, a directivity control evaluation value is created. Further, when the directivity control process illustrated in FIG. 5 is executed, the control station 110 stores, for example, one or more values of the following values (f) to (g) while maintaining the magnitude relationship: A directivity control evaluation value is created by combining.

  Combining with the magnitude relationship preserved includes simple addition and addition after multiplication by a predetermined positive coefficient. Note that, for example, a method for creating a directivity control evaluation value, that is, a value to be combined and a combining method among the following (a) to (g), are determined in advance.

(A) The value increases as the number of base stations 120 whose received power measured by each mobile station 130 in step S330 is equal to or greater than a certain value.
(B) Among the received power values of the base station 120 measured by each mobile station 130 in step S330, the larger the maximum received power value, the larger the value.
(C) When each mobile station 130 can measure the received power from the N or more base stations 120 in Step S330 (N is a natural number of 2 or more), the received power value of the base station having the Nth largest received power The larger the value, the smaller the value.
(D) Out of the received power values reported to the base station 120 by the uplink signal from each mobile station 130 in step S340, the downlink signal received power value from the base station 120 other than the base station 120 (own base station). The larger the received power value, the larger the value. In addition, when the uplink signal includes downlink signal reception power values of a plurality of base stations 120 other than the own base station, for example, the total value or maximum value of the plurality of downlink reception signal power values is the own base in (d). It is used as the received power value of the downlink signal from the base station 120 other than the station.
(E) The received power value reported to the base station 120 by the uplink signal from each mobile station 130 in step S340, and the larger the number of base stations that have measured the received power value equal to or greater than a certain value, the larger the value.

(F) The larger the received power value measured in the received power measurement process in step S420, the larger the value.
(G) Of the received power values measured by the base station 120 in the received power measurement process in step S420, the larger the signal received power value of a signal not addressed to the base station 120 (own base station), the larger the value.

  In the control determination process in step S330, the control station 110 derives an increment for the antenna directivity control information applied in the base station 120 from the directivity control evaluation value created in the evaluation place creation process in step S320. Here, the antenna directivity control information indicates a value that means that the larger the value, the larger the angle formed between the antenna directivity center in the base station 120 and the path 140, and the smaller the value, the smaller the angle.

  When the path 140 is a straight line, the angle formed between the antenna directivity center and the path 140 is the angle formed between the vector indicated by the antenna directivity center and one direction vector indicated by the path 140, and the antenna This is the smaller angle among the angles formed by the vector indicated by the directivity center and the direction vector opposite to the direction vector.

  When the path 140 is not a straight line, the angle formed between the antenna directivity center and the path 140 is a path at a point on the path 140 connecting the antenna and the path 140 with the shortest distance from the vector indicated by the antenna directivity center. The angle formed by one direction vector indicated by 140 tangent lines and the angle formed by the vector indicated by the antenna directivity center and the direction vector opposite to the direction vector are smaller angles.

  FIG. 6 is an example of a graph showing a conversion function for deriving an increment of directivity control information from the directivity control evaluation value in the control determination process of step S330.

  The conversion function is preferably a broad-sense monotonically increasing function that takes a positive value when the directivity control evaluation value is large and takes a negative value when the directivity control evaluation value is small. The conversion function may be a simple proportional relationship such as graph a, for example, or may be a step function that selects a specific value by comparing the threshold value with the directivity control evaluation value as graph b, A function such as a graph c combining the properties of the graph a and the graph b may be used. For example, one conversion function used for the control determination process is determined in advance.

  In the control determination process in step S330, the control station 110 derives the increment of directivity control information using the conversion function and the preference control evaluation value as described above, and the antenna being applied to each base station 120 to this. A result of adding the directivity control information is created as new antenna directivity control information in each base station 120.

  Saving the magnitude relation and substituting a value obtained by synthesizing one or more values included in (a) to (g) into the conversion function as an increment of the directivity control information means that the antenna directivity This means that the angle formed by the center of the sexuality and the path 140 is reduced, that is, the greater the propagation attenuation between the base station 120 and the mobile station 130, the closer the directivity of the directional antenna becomes parallel to the path 140. Also, the fact that (b) and (c) are included in the above synthesis targets means that the smaller the difference between the maximum received power value and the Nth received power value, the more the angle between the antenna directivity center and the path becomes. It means to enlarge.

  The control station 110 selects the maximum value instead of the addition result when the addition result is larger than the predetermined maximum value, and selects the maximum value instead of the addition result when the addition result is smaller than the predetermined minimum value. Clip processing for selecting the minimum value may be performed.

  Further, the control station 110 may correct the antenna directivity control information based on factors other than the directivity control evaluation value described above in the control determination process. For example, the control station 110 increases the antenna directivity control information as the number of mobile stations 130 communicating with the base station 120 within a certain time range increases, and decreases the antenna directivity control information as the number decreases. By performing correction, the communication area is narrowed when the density of the mobile station 130 is large and the possibility of interference between communications is high, and the communication area is widened when the possibility of interference is low. As a result, the stability of communication can be improved.

  As described above, in the wireless communication system according to the present embodiment, the angle formed between the center of the antenna directivity of the base station 120 and the path 140 becomes larger as the range of communication between the base station 120 and the mobile station 130 is smaller and the communication range is wider. The antenna directivity is controlled so as to increase, and control is performed so that the communicable range between the base station 120 and the mobile station 130 is narrowed.

  Conversely, in the wireless communication system according to the present embodiment, the distance between the base station 120 and the mobile station 130 is large and the communication range is narrow, so that the antenna directivity center of the base station 120 and the path 140 are formed. The antenna directivity is controlled so as to reduce the angle, and control is performed so that the communicable range between the base station 120 and the mobile station 130 is expanded.

  As a result, even if the propagation environment fluctuates due to changes in weather conditions, etc., it is possible to appropriately control the communication area without having to prepare a measuring means other than a communication device for actually communicating. Become. Specifically, the radio wave can cover the path 140 while suppressing interference of the radio wave on the path 140. This is particularly effective for millimeter waves with a frequency of 30 GHz or more, in which propagation attenuation varies greatly due to weather conditions.

  Further, for example, wireless communication using a direct wave as a main is assumed. Since the direct wave has a slow distance attenuation, even if the transmission wave output of each base station is weakened to the limit where communication with any base station is possible at a certain point on the route, a plurality of base stations There is a possibility that radio waves from will interfere. On the other hand, the radio communication system of the present embodiment can increase the distance attenuation on the path 140 for each transmission wave of the base station by controlling the direction of the directional antenna. That is, the wireless communication system of the present embodiment can appropriately control the communication area particularly in wireless communication mainly using direct waves.

  The present invention is not limited to the above-described embodiments, and includes various modifications and equivalent configurations within the scope of the appended claims. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and the present invention is not necessarily limited to those having all the configurations described. A part of the configuration of one embodiment may be replaced with the configuration of another embodiment. Moreover, you may add the structure of another Example to the structure of a certain Example. In addition, for a part of the configuration of each embodiment, another configuration may be added, deleted, or replaced.

  In addition, each of the above-described configurations, functions, processing units, processing means, etc. may be realized in hardware by designing a part or all of them, for example, with an integrated circuit, and the processor realizes each function. It may be realized by software by interpreting and executing the program to be executed.

  Information such as programs, tables, and files that realize each function can be stored in a storage device such as a memory, a hard disk, and an SSD (Solid State Drive), or a recording medium such as an IC card, an SD card, and a DVD.

  Further, the control lines and the information lines are those that are considered necessary for the explanation, and not all the control lines and the information lines that are necessary for the mounting are shown. In practice, it can be considered that almost all the components are connected to each other.

  110 control station, 120 base station, 122 base station CU, 124 base station RU, 130 mobile station, 400 controller, 410 network interface, 420 control channel unit, 430 user channel unit, 440 channel modem unit, 450 RF unit, 460 operation Part, 470 memory

Claims (12)

A mobile station moving on the route,
A plurality of base stations having directional antennas, arranged along the path, and performing radio communication with the mobile station;
A wireless communication system including a measurement unit that measures propagation attenuation of radio waves between the plurality of base stations and the mobile station,
Each of the plurality of base stations changes the direction of the directional antenna of the base station so that the angle formed by the directional center of the directional antenna and the path becomes smaller as the measured propagation attenuation increases. Wireless communication system. The wireless communication system according to claim 1,
The measurement unit measures received signal strength between each of the plurality of base stations and the mobile station,
Each of the plurality of base stations determines the direction of the directional antenna of the base station between the directional center of the directional antenna and the path as the maximum received signal strength of the measured received signal strength is stronger. A wireless communication system that changes so that the angle formed becomes large. The wireless communication system according to claim 1,
The measurement unit measures received signal strength between each of the plurality of base stations and the mobile station,
Each of the plurality of base stations has a difference between a maximum received signal strength included in the measured received signal strength and a first received signal strength other than the maximum received strength included in the measured received signal strength. A wireless communication system that changes the direction of the directional antenna of the base station so that the angle formed by the directional center of the directional antenna and the path becomes larger as the value is smaller. The wireless communication system according to claim 1,
The measurement unit measures received signal strength between each of the plurality of base stations and the mobile station,
For each of the plurality of base stations, the more the number of base stations whose measured received signal strength is equal to or greater than a predetermined value, the more the direction of the directional antenna of the base station, the directional center of the directional antenna and the path The wireless communication system is changed so that the angle formed between and becomes larger. The wireless communication system according to claim 1,
The wireless communication system in which the mobile station performs wireless communication with the plurality of base stations using millimeter waves. The wireless communication system according to claim 1,
The route is a railroad track,
The wireless communication system, wherein the plurality of base stations form a continuous communication area on the route. A base station that performs radio communication with a mobile station that moves on a path, is arranged along the path, and has a directional antenna,
The mobile station performs wireless communication with one or more other base stations,
The base station
Obtaining a propagation attenuation between a plurality of base stations consisting of the base station and the one or more other base stations, and a mobile station in the previous period;
The base station that changes the direction of the directional antenna so that the angle formed by the directional center of the directional antenna and the path becomes smaller as the acquired propagation attenuation is larger. The base station according to claim 7, wherein
Obtaining received signal strength between each of the plurality of base stations and the mobile station;
Of the acquired received signal strengths, the stronger the maximum received signal strength is, the more the direction of the directional antenna is changed so that the angle formed by the directional center of the directional antenna and the route becomes larger. Bureau. The base station according to claim 7, wherein
Obtaining received signal strength between each of the plurality of base stations and the mobile station;
The smaller the difference between the maximum received signal strength included in the acquired received signal strength and the first received signal strength other than the maximum received strength included in the acquired received signal strength, the more the directional antenna A base station that changes a direction so that an angle formed by a directional center of the directional antenna and the route is increased. The base station according to claim 7, wherein
Obtaining received signal strength between each of the plurality of base stations and the mobile station;
The more the number of base stations whose acquired received signal strength is equal to or greater than a predetermined value, the more the direction of the directional antenna is changed so that the angle formed by the directional center of the directional antenna and the path becomes smaller. ,base station. The base station according to claim 7, wherein
A base station that performs wireless communication with the mobile station using millimeter waves. A method in which a base station having a directional antenna performs radio communication with a mobile station moving on a route,
The mobile station performs wireless communication with one or more other base stations,
In the method, the base station
Obtaining a propagation attenuation between a plurality of base stations consisting of the base station and the one or more other base stations, and a mobile station in the previous period;
The method of changing the direction of the directional antenna so that the angle formed by the directional center of the directional antenna and the path becomes smaller as the acquired propagation attenuation is larger.

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