JP6684151B2 - Wireless communication system, base station, and wireless communication method - Google Patents

Description

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

  There is an increasing demand for communication between fixed stations and mobile stations that move at high speed along with vehicles such as railways and automobiles. A vehicle moving at a high speed has a slow moving speed, and its moving route is often limited as compared with a pedestrian who moves on a relatively free route. Therefore, when wireless communication is performed between a mobile station that moves with a vehicle and a fixed station, the directivity of radio waves is used to form a communication area along the movement route to improve the signal strength. Interference can be suppressed.

  In general, the higher the frequency of the radio wave, the easier it is to narrow the directivity and the more easily the communication area is limited. On the other hand, it is known that radio waves with a higher frequency undergo propagation attenuation due to various factors, and radio waves in the millimeter wave band with a frequency of 30 GHz or higher, for example, are greatly attenuated due to weather conditions such as rainfall. Therefore, when a radio wave having a high frequency such as a millimeter wave is used outdoors, various methods are used to control the change in the attenuation amount.

  Background arts of the present technical field include, for example, JP-A-11-136184 (Patent Document 1) and JP-A-2003-318795 (Patent Document 2). Japanese Patent Application Laid-Open No. 2004-242242 describes, "In a wireless service system set to perform a service within a predetermined service area 20 by a transmission wave from a wireless transmission base station, a measuring unit 31 for measuring a reception electric field strength of the transmission wave 24. And at least one electric field strength monitor / receiver 31 provided near the boundary in the service area 20 and having communication means 33 for transmitting the information of the received electric field strength to the wireless transmission base station 21, and the received electric field. Upon reception of the transmission of the strength information, the radio transmission base station 21 having a control means 22 for controlling the output of the transmission wave 24 so that the reception electric field strength received by the electric field strength monitoring receiver 31 becomes constant. Service system "(see summary).

  In addition, in Patent Document 2, "the control unit 106 receives weather information from a sensor 105 that is a weather information acquisition unit. The control unit 106 controls the wireless unit 100 (the wireless transmission unit 102 and the wireless reception unit 103 according to the weather information. 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 causes the wireless reception unit 103 to change according to the weather information. The ON / OFF control of the operation of the waveform equalizer included in the included digital detection unit 117 is performed, or the control unit 106 changes the antenna directivity of the reception antenna 113 included in the wireless reception unit 103 according to the weather information. Control is performed. ”(See the summary).

JP-A-11-136184 JP, 2003-318795, A

  The technique described in Patent Document 1 needs to be provided with a measuring device for measuring the reception intensity and a communication device for notifying the measurement result separately from a communication device for actual communication.

  Also, in wireless communication, the received signal strength fluctuates greatly due to fading that occurs due to the influence of reflected waves, so even if the transmission power is controlled based on the reception power at a certain measurement point, the reception signal at other points The power does not always reach a desired value, and the communication area cannot be controlled appropriately.

  Further, the method of controlling based on the received meteorological information as in the technique described in Patent Document 2 is a rough method of associating the meteorological condition with the actual propagation environment such that the amount of attenuation is greater during rain than during fine weather. It is practically difficult to perform detailed control beyond the relationship.

  According to an aspect of the present invention, in order to solve the above problems, even when the propagation environment changes due to changes in weather conditions, etc., without providing a measuring 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 adopts the following configuration. Between a mobile station moving on a path and a directional antenna, arranged along the path, and performing radio communication with the mobile station, between a plurality of base stations, and between the plurality of base stations and the mobile station. A measurement unit for measuring the propagation attenuation of the base station, wherein 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 a flexible antenna and the path is reduced.

  One embodiment of the present invention appropriately controls a communication area without preparing a measurement means other than a communication device for actual communication even when the propagation environment changes due to changes in weather conditions or the like. be able to.

3 is a block diagram showing a configuration example of a wireless communication system in Example 1. FIG. FIG. 6 is a block diagram showing another configuration example of the wireless communication system according to the first embodiment. 3 is a block diagram showing a configuration example of a base station in Embodiment 1. FIG. FIG. 6 is a sequence diagram showing an example of directivity control processing in the first embodiment. FIG. 8 is a sequence diagram showing another example of directivity control processing in the first embodiment. 5 is a graph showing a judgment function for creating directivity control information in Example 1.

  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, separate logic circuits, software on one processor, or logic. It may be implemented as a combination of circuits and software. Further, when the same processing block is present in plural, each processing block may be implemented separately, or a single implemented logic circuit or software may be used for time multiplexing to perform a plurality of processes. Good.

  Further, in the sequence diagram described below, each process and notification of a message are merely examples for description, and in a range where order or the like is not particularly necessary, for example, notification of a plurality of messages or processes are unified. They may be collectively performed at the same time, conversely, message notification and processing may be performed multiple times, and the order may be reversed.

  The configuration of the wireless communication system according to the embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a wireless communication system. The wireless communication system has one or a plurality of control stations 110. When the wireless communication system has 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 by an inter-base station control station interface 121 (hereinafter, also simply referred to as an interface 121). The base station 120 wirelessly communicates with one or more mobile stations 130 moving on the route 140. Note that the base station 120 and the mobile station 130 perform wireless communication using, for example, millimeter waves, but may perform wireless communication using any frequency.

  The plurality of base stations 120 are arranged along the route 140, for example. Further, the plurality of base stations 120 may, for example, form a continuous communication area on the route 140, that is, enable the mobile station 130 to communicate with at least one base station 120 at any place on the route 140. Has been placed.

  The control station 110 is, for example, a computer including 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 required for the operation of the base station 120 to each base station 120 via the interface 121. The control station 110 also receives an input of the communication status and the like from the base station 120 via the interface 121. The control station 110 also receives and outputs control information from 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 the reception data received by the base station 120 from the mobile station 130 via the interface 121.

  The base station 120 has a signal processing function and a directional antenna that transmits and receives a radio signal. The directional antenna included in the base station 120 in this embodiment is also simply referred to as an antenna. The base station 120 creates a control signal necessary for performing wireless communication by the signal processing function, and transmits the wireless signal from the antenna. The base station 120 also converts the transmission data input from the control station 110 via the interface 121 into a radio signal by 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 the radio signal into a reception data signal by a signal processing function, and then outputs the reception data signal to the control station 110 via the interface 121. The base station 120 also receives input from the control station 110 via the interface 121, such as parameters required for operation. The base station 120 also outputs information indicating the propagation environment, the communication state, etc. to the control station 110 via the interface 121.

  The mobile station 130 has a signal processing function and an antenna for transmitting and receiving radio signals, and moves on the path 140. The mobile station 130 receives the radio signal transmitted by the base station 120 through an antenna and performs a reception process with 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 installed in, for example, a train.

  Here, the parameter output from the control station 110 to each base station 120 includes, 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 wireless quality such as the received power value or the signal-to-noise power ratio at the base station 120 of the wireless signal transmitted by the mobile station 130. Including 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.

  The base station 120 in the configuration of FIG. 1 can also 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, radio signal transmission / reception, and the like. Is. FIG. 2 is a block diagram showing a configuration example of a 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 by a base station control station interface 121 (hereinafter, also simply referred to as an interface 121). Have. The wireless communication system has, for each base station center unit 122, one or a plurality of base station remote units 124 connected by an interface 123 in the base station. The base station remote unit 124 wirelessly communicates with the mobile station 130 moving on the path 140.

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

  The transmission signal and the reception signal via 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 or the reception signal before DA conversion may be analog-transmitted as a baseband, intermediate frequency, or radio frequency signal.

  FIG. 3 is a block diagram showing 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 is composed of a CPU, a logic circuit, and the like, executes a program stored in the memory 470, and uses information stored in the memory 470 to perform signal processing for communication. The memory 470 includes a ROM which is a non-volatile storage element and a RAM which is a volatile storage element. The ROM stores an immutable program (for example, BIOS) and the like. 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 (Control Channel) 420, one or more user channel units (User Channel) 430, and a channel modem unit (Channel Modem) 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 part or all of the functions of the respective units included in the arithmetic unit 460 may be realized by, for example, a DSP (not shown), a logic circuit, or the like.

  The controller 400 controls the overall operation of the base station 120 by collecting information from each unit of the base station 120 and setting parameters in each unit 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 according to an instruction from the controller 400, performs a process such as encoding, and performs a channel as a transmission control channel signal. 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 according to the instruction from the controller 400, and notifies the decoding result to the controller 400.

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

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

  The channel modem unit 440 allocates 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, multiplexes them, and digitally modulates them according to an instruction from the controller 400. Perform processing.

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

  Further, the channel modem unit 440 receives the 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 the instruction from the controller 400, and performs the demodulation processing on each channel. It divides and outputs the received control channel signal to control channel section 420 and the received user channel signal to user channel section 430.

  The network interface unit 410 includes a network interface, receives as input information to be transmitted to the mobile station 130 via the base station 120, and outputs it to the user channel unit 430 as transmission user information. The network interface unit 410 also 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 by the base station 120 from the mobile station 130 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 radio frequency 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 of the antenna may be controlled by moving or rotating the whole or a part of the directional antenna physically by using, for example, a turntable, or by controlling the signal phase difference between the plurality of directional antennas. Sex may be controlled.

  The base station remote unit 124 is configured by a part of the RF unit 450 including the directional antenna or the RF unit 450. The base station center unit 122 includes the configuration of the base station 120 of FIG. 3 which is not included in the base station remote unit 124. The hardware configuration of the mobile station 130 is similar to that of the base station 120, for example.

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

  Each control station 110 first notifies each base station 120 connected to the control station 110 of the parameter setting for communication (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 of fixed transmission power and information of transmission power in the base station 120.

  Each mobile station 130 measures the reception power of the downlink signal transmitted from each base station 120 and creates a reception quality value corresponding to the measured reception 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 the propagation environment. Further, the received power value is an example of a value indicating the propagation attenuation in the propagation environment, and 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. Further, the reception quality value may be created directly from the value obtained by one measurement, or may be created from the value obtained by averaging a plurality of measurement results. Further, the reception quality value may be created only from the downlink signal 210 transmitted by one base station 120, or may be created respectively from the downlink signals 210 transmitted by a plurality of base stations 120.

  Next, each mobile station 130 transmits an uplink signal to each base station 120 (S340). The upstream 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 perform a smoothing process on a plurality of reception quality values to create a measurement aggregate value, or may use each reception quality value as a measurement aggregate value. Then, each base station 120 reports as a 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, the directivity control evaluation value corresponding to the arrival state of the 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, for each base station 120, based on the directivity control evaluation value created in step S370 and the antenna directivity control information notified to each base station 120 in step S310. Antenna directivity control information is created (S380). Details of the method of creating the 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 processing 330 (S390). Each base station 120 sets the angle of the antenna to the angle indicated by the received directivity control information.

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

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

  Following step S320, each mobile station 130 transmits an upstream 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 of fixed transmission power and information of transmission power 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 similar to the reception quality value created in step S350, for example.

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

  Hereinafter, in step S370, the control station 110 is based on the measurement aggregate value 230 notified from the base station 120, the larger the reach range of the radio wave on the route 140 from each base station 120 (the smaller the propagation attenuation), the greater the An example of a process of creating a directivity control evaluation value that is smaller as it is narrower (as 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 of the following values (a) to (e) while preserving the magnitude relationship. By doing so, a directivity control evaluation value is created. Further, when the directivity control processing illustrated in FIG. 5 is executed, the control station 110, for example, keeps one or more values among the following values (f) to (g) while keeping the magnitude relationship. By synthesizing, the directivity control evaluation value is created.

  Combining while maintaining the magnitude relation includes simple addition and multiplication after multiplication with a predetermined positive coefficient. Note that, for example, the method of creating the directivity control evaluation value, that is, the value to be combined and the combining method among the following (a) to (g) are predetermined.

(A) A larger value as the number of base stations 120 whose received power measured by each mobile station 130 in step S330 is a certain value or more.
(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) In step S330, when each mobile station 130 can measure the received power from N or more base stations 120 (N is a natural number of 2 or more), the received power value of the base station with the Nth largest received power is received. The larger the value, the smaller the value.
(D) In step S340, the downlink signal reception power value from the base station 120 other than the base station 120 (own base station) among the reception power values reported to the base station 120 by the uplink signal from each mobile station 130 About, the larger the received power value, the larger the value. 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 station in (d). It is used as a downlink signal reception power value from the base station 120 other than the station.
(E) In step S340, the received power value reported to the base station 120 by the upstream signal from each mobile station 130, and the larger the number of base stations that 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) Among 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 the signal that is not addressed to the base station 120 (own base station), the larger the value.

  In the control determination process of step S330, the control station 110 derives an increment for the antenna directivity control information being applied by the base station 120 from the directivity control evaluation value created by the evaluation site creation process of 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 route 140, and the smaller the value, the smaller the angle.

  When the path 140 is a straight line, the angle formed by the directional center of the antenna and the path 140 is the angle formed by the vector indicated by the directional center of the antenna and one direction vector indicated by the path 140, and the angle of the antenna. It is the smaller of the angles formed by the vector indicated by the directivity center and the direction vector in the direction opposite to the direction vector.

  When the path 140 is not a straight line, the angle formed by the directivity center of the antenna and the path 140 is a path at a point on the path 140 that connects the vector and the antenna 140 with the shortest distance. The angle formed by one direction vector indicated by the tangent line of 140 and the vector formed by the directivity center of the antenna and the direction vector in the direction opposite to the direction vector is the smaller angle.

  FIG. 6 is an example of a graph showing a conversion function for deriving the increment of the 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 if the directivity control evaluation value is large and takes a negative value if the directivity control evaluation value is small. The conversion function may be, for example, a simple proportional relationship as in the graph a, or may be a step function that selects a specific value by comparing the threshold value and the directivity control evaluation value as in the graph b, It may be a function such as the graph c in which the properties of the graph a and the graph b are combined. Note that, for example, one conversion function is used in advance in the control determination process.

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

  The value obtained by substituting a value obtained by combining the one or more values included in the above (a) to (g) into the conversion function and storing the magnitude relationship as the increment of the directivity control information means that the antenna directivity is controlled. This means that the angle formed between the center of polarization and the path 140 is made smaller, 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. In addition, 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 smaller the angle between the directivity center of the antenna and the path. It means to increase.

  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 an element other than the directivity control evaluation value described above in the control determination processing. The control station 110 increases the antenna directivity control information as the number of mobile stations 130 communicating with the base station 120 increases within a certain time range, and decreases the antenna directivity control information as the number decreases. By performing the correction, the communication area is narrowed when the density of the mobile stations 130 is high and the possibility of interference between communications is high, and the communication area is widened when the possibility of interference is low. Therefore, it is possible to improve the stability of communication.

  As described above, in the wireless communication system of the present embodiment, the smaller the distance attenuation between the base station 120 and the mobile station 130 and the wider the communicable range, the angle formed by the antenna directivity center of the base station 120 and the path 140. The antenna directivity is controlled so as to increase, and the communication range between the base station 120 and the mobile station 130 is controlled so as to be narrowed.

  On the contrary, in the wireless communication system of the present embodiment, as the distance attenuation between the base station 120 and the mobile station 130 is large and the communicable range is narrow, the antenna directivity center of the base station 120 and the path 140 are formed. The antenna directivity is controlled so that the angle becomes small, and the range in which the base station 120 and the mobile station 130 can communicate is expanded.

  As a result, even when the propagation environment changes 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 actual communication. Become. Specifically, the radio waves can cover the path 140 while suppressing the interference of the radio waves on the path 140. This is particularly effective in the millimeter wave having a frequency of 30 GHz or more, which has a large variation in propagation attenuation due to weather conditions.

  In addition, for example, wireless communication mainly using direct waves is assumed. Since the direct wave has a gradual attenuation of distance, even if the output power of the transmitted wave of each base station is weakened to the limit that it is possible to communicate with any base station at a certain point on the route, multiple base stations will be present at that point. The radio waves from may interfere. On the other hand, in the wireless communication system of the present embodiment, by controlling the direction of the directional antenna, it is possible to increase the distance attenuation on the path 140 for the transmission waves of each base station. That is, the wireless communication system according to the present embodiment can appropriately control the communication area particularly in the wireless communication mainly using the direct wave.

  The present invention is not limited to the above-described embodiments, but includes various modifications and equivalent configurations within the spirit of the appended claims. For example, the above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to those having all the configurations described. Further, part of the configuration of one embodiment may be replaced with the configuration of another embodiment. Further, the configuration of another embodiment may be added to the configuration of one embodiment. Further, a part of the configuration of each embodiment may be added / deleted / replaced with another configuration.

  Further, 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 in an integrated circuit, for example, and a processor realizes each function. It may be realized by software by interpreting and executing the program.

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

  Further, the control lines and information lines are shown to be necessary for explanation, and not all the control lines and information lines necessary for mounting are shown. In reality, it can be considered that almost all configurations 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 calculation Part, 470 memory

Claims (12)

A mobile station moving along the path,
A plurality of base stations having a directional antenna, 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 such that the angle formed between the directional center of the directional antenna and the path becomes smaller as the measured propagation attenuation increases. , Wireless communication systems. The wireless communication system according to claim 1, wherein
The measuring unit measures the received signal strength between each of the plurality of base stations and the mobile station,
Each of the plurality of base stations, of the measured received signal strength, the stronger the maximum received signal strength, the direction of the directional antenna of the base station, the directivity center of the directional antenna and the path A wireless communication system in which the angle is changed to be larger. The wireless communication system according to claim 1, wherein
The measuring unit measures the 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 signal strength included in the measured received signal strength. A wireless communication system that changes the orientation of the directional antenna of the base station such that the smaller the angle, the larger the angle formed by the directional center of the directional antenna and the path. The wireless communication system according to claim 1, wherein
The measuring unit measures the received signal strength between each of the plurality of base stations and the mobile station,
In each of the plurality of base stations, the larger the number of the base stations whose measured received signal strength is equal to or more than a predetermined value, the more the direction of the directional antenna of the base station is, A wireless communication system that changes so that the angle formed by The wireless communication system according to claim 1, wherein
The mobile station is a wireless communication system in which millimeter waves are used to perform wireless communication with the plurality of base stations. The wireless communication system according to claim 1, wherein
The route is a railroad track,
The wireless communication system, wherein the plurality of base stations form a continuous communication area on the path. A base station, which performs wireless communication with a mobile station moving on a path, is arranged along the path, and has a directional antenna,
The mobile station is in wireless communication with one or more other base stations,
The base station is
It gets a plurality of base stations consisting of the one or more other base stations and the base station, before Symbol mobile station, the propagation loss between,
A base station that changes the direction of the directional antenna such that the angle formed by the directional center of the directional antenna and the path decreases as the acquired propagation attenuation increases. The base station according to claim 7,
Obtaining received signal strength between each of the plurality of base stations and the mobile station,
Among 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 path becomes larger. Station. The base station according to claim 7,
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 smaller the directional antenna's A base station for changing the orientation so that an angle formed by the directivity center of the directional antenna and the path is increased. The base station according to claim 7,
Obtaining received signal strength between each of the plurality of base stations and the mobile station,
The orientation of the directional antenna is changed so that the angle formed by the directional center of the directional antenna and the path becomes larger as the number of base stations having the acquired received signal strength of a predetermined value or more increases. ,base station. The base station according to claim 7,
A base station that wirelessly communicates with the mobile station using millimeter waves. A method in which a base station having a directional antenna wirelessly communicates with a mobile station moving on a path,
The mobile station is in wireless communication with one or more other base stations,
In the method, the base station
A plurality of base stations consisting of the base station and the one or more other base stations, and the propagation attenuation between the previous period mobile station,
The method of changing the direction of the directional antenna such that the angle formed between the directional center of the directional antenna and the path becomes smaller as the obtained propagation attenuation is larger.

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