JP2012074889A - Base station, radio communication system and control method of communication area in base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide technology facilitating connection of a communication terminal in a communication area with a base station, even when the communication terminals are crowded densely in the communication area of the base station.SOLUTION: A density determination unit 141 determines whether a high-density area, in which communication terminals are crowded densely, exists or not in a service area of a base station. When the density determination unit 141 determines that the high-density area exists, an area control unit 150 controls directivity of communication of a plurality of antennas so as to narrow an area in the service area of the base station overlapping with a service area of a peripheral base station and excepting the high-density area.

Description

  The present invention relates to control of a communication area of a base station that performs wireless communication with a communication terminal.

  As described in Patent Documents 1 and 2, various techniques have been proposed for wireless communication.

Japanese Patent No. 3101535 JP 2003-125439 A

  In a service area of a base station in a wireless communication system such as a PHS (Personal Handyphone System), that is, a communication area in which the base station can communicate bidirectionally with a communication terminal, a dense area (hereinafter referred to as “ Sometimes called a “terminal crowded area”).

  For example, when an event such as a fireworks display or a sporting game is held, communication terminals are concentrated on a route connecting the event venue and the station before and after the start of the event. As a result, a terminal dense area occurs in the service area of the base station including the route. During the event, communication terminals are crowded at the event venue. As a result, a terminal crowded area occurs in the service area of the base station including the event venue.

  Since the radio resources that can be used between the base station and the communication terminal are limited and the number of communication terminals that can be connected to one base station is limited, there is a terminal congestion area in the base station service area. When more communication terminals exist in the service area, the communication terminals are difficult to connect (communication) with the base station. That is, a call loss is likely to occur in a communication terminal existing in the service area. Here, “call loss” means that the communication terminal could not connect to the base station due to a lack of available radio resources even though the communication terminal made a connection request to the base station. Say that.

  In order to solve such a problem, it may be possible to arrange more base stations near the event venue.

  However, since the terminal congestion area occurs only temporarily, such as before the start of the event, there are many base stations in the vicinity of the event venue when there is no terminal congestion area. It is not preferable.

  Therefore, the present invention has been made in view of the above points, and even when communication terminals are concentrated in the communication area of the base station, the communication terminals existing in the communication area are connected to the base station. It aims at providing the technology which becomes easy.

  In order to solve the above-described problem, a base station according to the present invention is a base station that performs radio communication with a communication terminal, wherein a radio communication unit that communicates with the communication terminal using a plurality of antennas, and the base station is a communication terminal In a local area that is a communication area capable of two-way communication with a congestion determination unit that determines whether there is a congestion area where communication terminals are dense, and the congestion determination unit determines that the congestion area exists, In the local station area, the portions other than the crowded area, where the peripheral base stations overlap with the peripheral station area that is a communication area capable of bidirectional communication with the communication terminal, are narrowed by the plurality of antennas. An area control unit that controls communication directivity.

  Further, in one aspect of the base station according to the present invention, the area control unit communicates with the communication terminal through the wireless communication unit while controlling the directivity of communication with the plurality of antennas, thereby the local station area. The crowded area at is identified.

  Further, in one aspect of the base station according to the present invention, the base station is notified of a call loss rate with a communication terminal in each of a plurality of neighboring base stations from a server device, and the area control unit The directivity null is set toward the peripheral base station having the smallest call loss rate among the peripheral base stations.

  Further, in one aspect of the base station according to the present invention, the area control unit is a portion excluding the crowded area in the own station area, and after narrowing a portion overlapping with the peripheral station area, the crowded area. When the determination unit determines that the dense area is no longer present, the shape of the local station area is restored.

  In the aspect of the base station according to the present invention, the congestion determination unit also determines whether or not the congestion area exists in the peripheral station area, and the area control unit includes If it is determined that the dense area exists in the area, the local station area is expanded.

  Further, in one aspect of the base station according to the present invention, the area control unit determines that the congestion area no longer exists in the peripheral station area after the area control unit has expanded the local station area. The shape of the local station area is restored.

  In one aspect of the base station according to the present invention, when the server apparatus that determines whether or not the dense area exists in the peripheral station area, the base station determines that the dense area exists in the peripheral station area. When the station is instructed to expand the local station area, and the server apparatus is instructed to expand the local station area to the base station, the area control unit To enlarge.

  In one aspect of the base station according to the present invention, when the server apparatus determines that the congestion area does not exist in the peripheral station area after instructing to expand the own station area, the base station If the server device is instructed to restore the shape of the local station area to the base station, the area control unit The shape of the local station area is restored.

  Moreover, the radio | wireless communications system which concerns on this invention is a radio | wireless communications system provided with the some base station which carries out radio | wireless communication with a communication terminal, Comprising: The 1st base station in the said some base station uses a some antenna. In the first communication area, which is a communication area in which the first base station is capable of two-way communication with a communication terminal, and a wireless communication unit that communicates with the communication terminal, it is determined whether there is a dense area where communication terminals are dense When the congestion determination unit and the congestion determination unit determine that the congestion area exists, a communication area in the first communication area that excludes the congestion area and in which a peripheral base station can bidirectionally communicate with a communication terminal And an area control unit for controlling the directivity of communication with the plurality of antennas so that the overlapping part becomes narrow.

  Moreover, in one aspect of the wireless communication system according to the present invention, a server device that communicates with the plurality of base stations is further provided, and the plurality of base stations include peripheral base stations that are located around the first base station. Each of the plurality of second base stations calculates a call loss rate with the communication terminal and notifies the server device, and the server device sends the plurality of second base stations to the first base station. The call loss rate of each of the stations is notified, and the area control unit of the first base station sets the directivity null toward the second base station having the smallest call loss rate among the plurality of second base stations. To do.

  Moreover, in one aspect of the wireless communication system according to the present invention, a server device that communicates with the plurality of base stations is further provided, and the plurality of base stations include peripheral base stations that are located around the first base station. Each of the plurality of second base stations calculates a call loss rate with the communication terminal and notifies the server device of the call loss rate. If there is a second base station larger than the second base station, the second base station determines that the dense area exists in a communication area in which the second base station can bidirectionally communicate with a communication terminal, and When instructing to expand the first communication area and instructing to expand the first communication area from the server device in the first base station, the area control unit of the first base station Expand first communication area That.

  A service area control method in a base station according to the present invention is a communication area control method in a base station that performs radio communication with a communication terminal using a plurality of antennas, and (a) the base station A step of determining whether or not there is a dense area where communication terminals are densely located in a local area which is a communication area capable of bidirectional communication with a communication terminal; and (b) the dense area in the step (a). In the local station area, the plurality of the plurality of the base station areas excluding the crowded area, and the overlapping part with the communication area in which the peripheral base station can bidirectionally communicate with the communication terminal is narrowed. And a step of controlling the directivity of communication with the antenna.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where a communication terminal is crowded in the communication area of a base station, the communication terminal which exists in the said communication area becomes easy to connect with a base station.

1 is a diagram showing a configuration of a radio communication system according to Embodiment 1. FIG. 6 is a diagram illustrating an arrangement example of a plurality of base stations according to Embodiment 1. FIG. FIG. 2 is a diagram showing a configuration of a base station according to Embodiment 1. 3 is a diagram illustrating a main configuration of an overall control unit according to Embodiment 1. FIG. 3 is a diagram showing a configuration of a TDMA frame according to Embodiment 1. FIG. It is a figure which shows a mode that the terminal congestion area has generate | occur | produced in the service area of the base station. It is a figure which shows a mode that the service area of a base station is narrowing. It is a figure which shows a mode that the service area of a base station is expanding. 3 is a flowchart showing an operation of the base station according to Embodiment 1. 6 is a diagram for explaining an operation of the base station according to Embodiment 1. FIG. 3 is a flowchart showing an operation of the base station according to Embodiment 1. 3 is a flowchart showing an operation of the base station according to Embodiment 1. It is a figure which shows the main structures of the whole control part which concerns on Embodiment 2. FIG. 6 is a flowchart showing an operation of a base station according to the second embodiment.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a radio communication system 100 according to the first embodiment. The wireless communication system 100 according to the present embodiment is, for example, a PHS, and includes a plurality of base stations 1 that communicate with the communication terminal 2 using a TDMA / TDD (Time Division Multiple Access / Time Division Duplexing) method. . The plurality of base stations 1 are connected through a network 4 to a server device 3 that manages the operation of the entire wireless communication system 100. Each base station 1 can communicate with each other through the network 4 and can communicate with the server apparatus 3 through the network 4. Each base station 1 has an array antenna as a transmission / reception antenna, and can control the directivity of the array antenna using an adaptive array antenna system.

  FIG. 2 is a diagram illustrating an arrangement example of a plurality of base stations 1. As shown in FIG. 2, the service area 10 of each base station 1 is circular and partially overlaps with each of the service areas 10 of a plurality of peripheral base stations 1 located in the vicinity thereof. Here, the “service area” means a communication area where the base station 1 can bidirectionally communicate with the communication terminal 2. Usually, in the base station 1, the reception area is wider than the transmission area, and the transmission area is included in the reception area. Therefore, the service area 10 of the base station 1 matches the transmission area of the base station 1. In the present embodiment, the reception area of each base station 1 includes all service areas 10 of a plurality of peripheral base stations 1 located around the base station 1. Accordingly, each base station 1 can receive a signal transmitted by the communication terminal 2 communicating with the neighboring base station 1.

  FIG. 3 is a diagram showing the configuration of each base station 1. As shown in FIG. 3, each base station 1 controls the wireless communication unit 11 that performs wireless communication, the network communication unit 12 that communicates with the network 4, and the overall control that controls the wireless communication unit 11 and the network communication unit 12. Part 13.

  The wireless communication unit 11 has an array antenna 110 configured with a plurality of antennas 110a. The wireless communication unit 11 performs amplification processing, down-conversion, and the like on each of the plurality of reception signals received by the array antenna 110, and generates and outputs a plurality of baseband reception signals.

  The wireless communication unit 11 also performs up-conversion and amplification processing on each of the plurality of baseband transmission signals generated by the overall control unit 13 to generate a plurality of transmission signals in the carrier band. Then, the wireless communication unit 11 inputs the generated plurality of transmission signals in the carrier band to the plurality of antennas 110a configuring the array antenna 110, respectively. Thereby, a transmission signal is wirelessly transmitted from each antenna 110a.

  The network communication unit 12 is connected to the network 4 by an optical fiber or the like, for example. The network communication unit 12 transmits data input from the overall control unit 13 to the network 4 and outputs data input from the network 4 to the overall control unit 13.

  The overall control unit 13 includes a CPU (Central Processing Unit), a DSP (Digital Signal Processor), a memory, and the like. The overall control unit 13 generates transmission data for the communication terminal 2 based on data from the network communication unit 12 or the like. Then, the overall control unit 13 generates a baseband transmission signal including the generated transmission data. This transmission signal is generated by the number of the plurality of antennas 110a constituting the array antenna 110. The overall control unit 13 sets a plurality of transmission weights for controlling the directivity of transmission at the array antenna 110 for the plurality of generated transmission signals. Then, the overall control unit 13 outputs a plurality of transmission signals in which a plurality of transmission weights are set to the wireless communication unit 11.

  The overall control unit 13 sets a plurality of reception weights for controlling the directivity of reception at the array antenna 110 for the plurality of reception signals input from the wireless communication unit 11. The overall control unit 13 generates a new reception signal by combining a plurality of reception signals each having a plurality of reception weights. The overall control unit 13 performs demodulation processing or the like on the new received signal, and obtains received data included in the received signal. The overall control unit 13 outputs the data for the network 4 included in the acquired reception data to the network communication unit 12.

  FIG. 4 is a diagram illustrating a main configuration of the overall control unit 13. As illustrated in FIG. 4, the overall control unit 13 includes a transmission weight processing unit 131, a reception weight processing unit 132, and a control unit 130 that controls them. In the overall control unit 13, the control unit 130, the transmission weight processing unit 131, and the reception weight processing unit 132 constitute an area control unit 150 that transforms the service area 10 of the base station 1. The area control unit 150 can partially deform the service area 10 or enlarge and deform the entire service area 10. Further, the area control unit 150 can restore the deformed shape of the service area 10.

  The reception weight processing unit 132 sets (multiplies) a plurality of reception weights for controlling the directivity of reception at the plurality of antennas 110 a with respect to the plurality of reception signals output from the wireless communication unit 11. Reception weight processing section 132 combines a plurality of reception signals each having a plurality of reception weights, and generates a new reception signal. This new received signal is called a “combined received signal”. The combined received signal is input to the control unit 130.

  In such a reception weight processing unit 132, by adjusting the reception weight to be multiplied with the reception signal, it is possible to set the beam and null of reception directivity at the array antenna 110 in various directions.

  For example, when the base station 1 communicates with the communication terminal 2 to be communicated, the reception weight processing unit 132 receives a known combined received signal such as a pilot signal and a reference signal (ideal for the known combined received signal). Signal), and a reception weight is calculated so that the error becomes small. As a result, the directivity null received at the array antenna 110 is directed to the interference wave (signal from the communication terminal 2 other than the communication terminal 2 to be communicated). As a result, it is possible to direct a directional beam received by the array antenna 110 to a desired wave (a signal from the communication terminal 2 to be communicated).

  The control unit 130 performs demodulation processing or the like on the combined reception signal output from the reception weight processing unit 132, and reproduces reception data included in the combined reception signal. The control unit 130 outputs data for the network 4 included in the acquired reception data to the network communication unit 12.

  The control unit 130 generates transmission data based on data from the network communication unit 12 and the like. The control unit 130 generates a baseband transmission signal including the generated transmission data. This transmission signal is generated by the number of the plurality of antennas 110 a constituting the array antenna 110 and input to the transmission weight processing unit 131.

  Furthermore, the control unit 130 includes a radio resource allocation unit 140, a congestion determination unit 141, and an output control unit 142 as functional blocks.

  The radio resource allocation unit 140 allocates downlink radio resources (transmission frequency and transmission time zone) used for transmission to the communication terminal 2 to each communication terminal 2 to be communicated. The control unit 130 generates a transmission signal for the communication terminal 2 based on the downlink radio resource allocated to the communication terminal 2 by the radio resource allocation unit 140, and transmits the transmission signal at a timing based on the downlink radio resource. Input to the transmission weight processing unit 131. Thereby, a transmission signal directed to the communication terminal 2 is transmitted from the radio communication unit 11 using the downlink radio resource assigned to the communication terminal 2.

  The radio resource allocation unit 140 allocates an uplink radio resource used when the communication terminal 2 transmits to the base station 1 to each communication terminal 2 to be communicated. The control unit 130 generates and outputs a transmission signal for notifying the communication terminal 2 of the uplink radio resource allocated to the communication terminal 2 by the radio resource allocation unit 140. Thereby, the communication terminal 2 can know the uplink radio resource used for transmission to the base station 1, and transmits a signal to the base station 1 using the uplink radio resource.

  Based on the received data acquired by the control unit 130, the congestion determination unit 141 determines whether there is a terminal congestion area in the service area 10 of the base station 1, that is, a congestion area where the communication terminals 2 are dense. judge.

  The output control unit 142 controls the transmission power of the radio communication unit 11 to control the size of the service area 10 of the base station 1. The output control unit 142 controls the transmission power of the wireless communication unit 11 by controlling the amplification factor of the transmission amplifier that the wireless communication unit 11 has to amplify the transmission signal. The output control unit 142 increases the transmission power by increasing the amplification factor of the transmission amplifier, and expands the service area 10. On the other hand, the output control unit 142 reduces the transmission power by reducing the amplification factor of the transmission amplifier, and reduces the service area 10.

  As described above, in the base station 1, since the reception area is larger than the transmission area, the service area 10 can be expanded by increasing the transmission power and expanding only the transmission area.

  The transmission weight processing unit 131 sets (multiplies) a plurality of transmission weights for controlling the directivity of transmission at the plurality of antennas 110a with respect to the plurality of transmission signals from the control unit 130, respectively. The transmission weight processing unit 131 inputs a plurality of transmission signals in which a plurality of transmission weights are respectively set to the wireless communication unit 11.

  Similar to the reception weight processing unit 132, the transmission weight processing unit 131 adjusts the transmission weight multiplied by the transmission signal, thereby setting the beam and null of transmission directivity in the array antenna 110 in various directions. Can do.

  For example, when the base station 1 communicates with the communication terminal 2 to be communicated, the transmission weight is calculated based on the reception weight calculated by the reception weight processing unit 132. Thereby, the directivity null of transmission at the array antenna 110 is directed to the communication terminal 2 (communication terminal 2 that is not a communication target) that transmits the interference wave. As a result, it is possible to direct a directional beam of transmission at the array antenna 110 to the communication terminal 2 to be communicated.

  Next, the configuration of the TDMA frame 200 that the base station 1 uses for communication with the communication terminal 2 will be described. FIG. 5 is a diagram showing the configuration of the TDMA frame 200. As shown in FIG. 5, the TDMA frame 200 includes a downlink frame 200d for the base station 1 to transmit a signal to the communication terminal 2, and an uplink frame 200u for the base station 1 to receive a signal from the communication terminal 2. It consists of and. Each of the downstream frame 200d and the upstream frame 200u includes four slots SL. The radio resource allocation unit 140 of the control unit 130 allocates radio resources to the communication terminal 2 in slot SL units.

  In the wireless communication system 100 as described above, a terminal crowded area may temporarily occur in the service area 10 of the base station 1. FIG. 6 is a diagram showing an example of such a situation. In FIG. 6, two base stations 1 a and 1 b among the plurality of base stations 1 are shown.

  As shown in FIG. 6, in an event venue 300 where an event such as a fireworks display or a sports game is held and a base station 1a arranged in the vicinity of the nearest station 301, before the event starts or after the event ends. The communication terminals 2 are concentrated on the route connecting the event venue 300 and the station 301 included in the service area 10a. As a result, the terminal area 400 is generated in the service area 10a, and a large number of communication terminals 2 are present. Therefore, it becomes difficult for the communication terminal 2 existing in the service area 10a to connect to the base station 1.

  Therefore, each base station 1 according to the present embodiment, when the terminal congestion area 400 occurs in the service area 10 of its own device, as shown in FIG. The service area 10 of the own apparatus is modified so that a portion 401 that overlaps with the service area 10 of the neighboring base station 1 is reduced except for the area 400. In the example of FIG. 7, the base station 1a has its own service area 10a so that the portion 401 that overlaps the service area 10b of the neighboring base station 1b is narrower in the service area 10a of the own apparatus. The area 10a is deformed.

  As a result, the service area 10 in which the terminal congestion area 400 occurs is narrowed, and the number of communication terminals 2 existing in the service area 10 can be reduced. Therefore, the communication terminal 2 existing in the service area 10 can be easily connected to the base station 1.

  Further, in the service area 10 where the terminal dense area 400 occurs, the service area 10 where the terminal dense area 400 occurs is modified so that a portion overlapping with the service area 10 of the neighboring base station 1 is reduced. The communication terminal 2 that has come out of the service area 10 by narrowing the service area 10 in which the crowded area 400 is generated can be connected to the peripheral base station 1.

  On the other hand, each base station 1 according to the present embodiment has its own service area 10 as shown in FIG. Expanding. In the example of FIG. 8, when the terminal crowded area 400 occurs in the service area 10a of the neighboring base station 1a, the base station 1b expands the service area 10b of its own device. Thereby, the overlapping part of the service area 10b of the base station 1b and the service area 10a of the peripheral base station 1a can be expanded. Therefore, the communication terminal 2 existing in the service area 10a of the base station 1a in which the terminal congestion area 400 is generated can be easily connected to the base station 1b.

  Although only two base stations 1 are shown in FIGS. 6 to 8, there are actually a plurality of base stations 1 around each base station 1.

  Below, the deformation | transformation operation | movement of such a service area 10 in the base station 1 is demonstrated in detail. In FIG. 9, the base station 1 detects that the terminal congestion area 400 exists in the service area 10 of the own device (hereinafter, may be referred to as “own station service area 10”), and then the service area 10 It is a flowchart which shows the operation | movement until it deform | transforms.

  As shown in FIG. 9, in step s <b> 1, the congestion determination unit 141 determines whether or not the terminal congestion area 400 exists in the local station service area 10. In step s1, the congestion determination unit 141 refers to the total number of connection request signals addressed to the own device received by the own device during a plurality of TDMA frames 200 (at a predetermined time) (hereinafter referred to as “the number of connection requests addressed to the own station”). ). Here, the connection request signal is a signal transmitted when the communication terminal 2 requests connection to the base station 1. This connection request signal is called a “link channel establishment request message” in the PHS described in Non-Patent Document 1. A transmission signal including a connection request signal transmitted by the communication terminal 2 is received by the wireless communication unit 11 of the base station 1 and then input to the overall control unit 13. In the overall control unit 13, the control unit 130 acquires a connection request signal included in the transmission signal input to the overall control unit 13. Since the connection request signal includes identification information for specifying the transmission destination base station 1, the congestion determination unit 141 determines that the connection request signal acquired by the control unit 130 is addressed to its own device. It can be determined whether or not it is a signal.

  In the control unit 130, when the connection request signal is acquired, the radio resource allocation unit 140 allocates radio resources to the communication terminal 2 that has transmitted the connection request signal. As a result, the communication terminal 2 can be connected to the base station 1. However, when there is no available radio resource, the radio resource cannot be assigned to the communication terminal 2 that has transmitted the connection request signal. In this case, the call is lost and the communication terminal 2 cannot connect to the base station 1.

  Next, the congestion determination unit 141 compares the calculated number of connection requests addressed to the own station with a predetermined threshold value. The congestion determination unit 141 determines that the terminal congestion area 400 exists in the local station service area 10 if the number of connection requests addressed to the local station is larger than the threshold value. On the other hand, the congestion determination unit 141 determines that the terminal congestion area 400 does not exist in the local station service area 10 if the number of connection requests addressed to the local station is equal to or less than the threshold value. When the communication terminals 2 are crowded in the service area 10 of the base station 1 and the terminal crowded area 400 is generated in the service area 10, the connection request signals addressed to the own apparatus increase in the base station 1. Therefore, the congestion determination unit 141 can determine that the terminal congestion area 400 exists in the local station service area 10 when the number of connection requests addressed to the local station is large.

  If it is determined in step s1 that the terminal crowded area 400 does not exist in the own station service area 10, the base station 1 executes step s1 again after a predetermined time, and the terminal crowded area 400 exists in the own station service area 10. It is determined whether or not to do so.

  On the other hand, if it is determined in step s1 that the terminal dense area 400 exists in the local station service area 10, the area control unit 150 controls the directivity of the array antenna 110 through the wireless communication unit 11 in step s2. By communicating with the communication terminal 2, the terminal dense area 400 in the local station service area 10 is specified. FIG. 10 is a diagram for explaining the processing in step s2.

  As shown in FIG. 10, the area control unit 150 adjusts the transmission weight and the reception weight in the transmission weight processing unit 131 and the reception weight processing unit 132, so that the directional beam 500 in transmission / reception of the array antenna 110 is predetermined. Perform beamforming in the direction. Then, the area control unit 150 changes the direction in which the beam 500 is directed little by little to rotate the beam 500 by 360 °. Each time the direction of the beam 500 is slightly changed, the area control unit 150 communicates with the communication terminal 2 through the wireless communication unit 11, so that the communication terminal 2 existing in the direction in which the beam 500 is directed is addressed to its own device. The control unit 130 counts the connection request signal for a plurality of TDMA frames 200 (predetermined time). Then, the control unit 130 compares the counted number with a predetermined threshold value. If the counted number is larger than the threshold value, control unit 130 determines that communication terminals 2 are crowded in the direction of beam 500. By performing this process until the beam 500 rotates 360 °, the control unit 130 can specify the terminal crowded area 400 in the local station service area 10.

  When the terminal crowded area 400 in the own station service area 10 is identified, in step s3, the area control unit 150 excludes the terminal crowded area 400 in the own station service area 10 and overlaps with the surrounding service area 10 401. Toward, null steering is performed by adjusting the reception weight and the transmission weight so that the directivity null of the array antenna 110 is directed. As a result, as shown in FIG. 7 described above, in the local station service area 10, the local station service area 10 is modified so that the portion 401 overlapping the peripheral service area 10 is narrow except for the terminal dense area 400. The The overall control unit 13 stores in advance which portion of the own station service area 10 overlaps with the peripheral service area 10.

  When the base station 1 operates as described above and the terminal congestion area 400 is generated in the local station service area 10, the local station service area 10 becomes narrow and the communication terminals existing in the local station service area 10 are present. The number of 2 can be reduced. As a result, the communication terminal 2 existing in the local station service area 10 in which the terminal congestion area 400 is generated can be easily connected to the base station 1.

  Further, in the local station service area 10, the local station service area 10 is modified so that a portion overlapping with the peripheral service area 10 is narrowed. Therefore, the local station service area 10 is reduced by narrowing the local station service area 10. The communication terminal 2 that has come out of the range can be connected to the peripheral base station 1 having the peripheral service area 10.

  Next, the base station 1 detects that there is a terminal crowded area 400 in the service area 10 of the neighboring base station 1 (hereinafter sometimes referred to as “peripheral service area 10”). The operation until the deformation is performed will be described. FIG. 11 is a flowchart showing the operation.

  As shown in FIG. 11, in step s11, the congestion determination unit 141 determines the peripheral base station that the local apparatus receives between the plurality of TDMA frames 200 for each of the plurality of peripheral base stations 1 present in the vicinity of the local apparatus. The total number of connection request signals addressed to the station 1 (hereinafter referred to as “number of connection requests addressed to peripheral stations”) is counted. Then, the congestion determination unit 141 compares, for each peripheral base station 1, the calculated number of connection requests addressed to the peripheral station and a predetermined threshold value. The congestion determination unit 141 determines that the terminal congestion area 400 exists in the service area 10 of the peripheral base station 1 if the number of connection requests addressed to the peripheral station for a certain peripheral base station 1 is larger than the threshold value. On the other hand, the congestion determination unit 141 determines that there is no terminal congestion area 400 in the service area 10 of the peripheral base station 1 if the number of connection requests addressed to the peripheral station for a certain peripheral base station 1 is equal to or less than the threshold value. To do. Hereinafter, the peripheral base station 1 in which the terminal dense area 400 is generated in the service area 10 is referred to as “terminal dense peripheral base station 1”.

  If it is determined in step s11 that the terminal dense area 400 does not exist in all the service areas 10 of the plurality of neighboring base stations 1, the base station 1 executes step s11 again after a predetermined time, and each neighboring service area 10 It is determined whether or not the terminal dense area 400 exists.

  On the other hand, when it is determined in step s11 that the terminal congestion area 400 is present in at least one service area 10 of the plurality of neighboring base stations 1, the output control unit 142 determines that the current state of the wireless communication unit 11 is present in step s12. It is determined whether or not the transmission power is maximum. If it is determined in step s12 that the current transmission power of the wireless communication unit 11 is maximum, the base station 1 ends the process. On the other hand, when it is determined in step s12 that the current transmission power of the wireless communication unit 11 is not the maximum, the output control unit 142 increases the amplification factor of the transmission amplifier included in the wireless communication unit 11 in step s13. Thus, the transmission power of the wireless communication unit 11 is maximized. Accordingly, as shown in FIG. 8 described above, the local station service area 10 is expanded, and the local station service area 10 includes the peripheral service area 10 where the terminal congestion area 400 is generated. Thereby, the overlapping part of the local station service area 10 and the peripheral service area 10 in which the terminal crowded area 400 occurs increases. As a result, the communication terminal 2 existing in the peripheral service area 10 can be easily connected to the base station 1.

  In the above example, the transmission power of the base station 1 is suddenly set to the maximum when the terminal dense area 400 exists in the peripheral service area 10, but the transmission power may be gradually increased. The operation of the base station 1 in this case will be described below.

  If it is determined in step s12 that the transmission power of the wireless communication unit 11 is not the maximum, the output control unit 142 increases the transmission power of the wireless communication unit 11 by a predetermined amount. Thereafter, the overall control unit 13 causes the control unit 130 to again count the number of connection requests addressed to the peripheral station for the terminal crowded peripheral base station 1. The overall control unit 13 determines that the newly determined number of connection requests addressed to the peripheral station is not decreased by a predetermined amount or more than the number of connection requests addressed to the peripheral station for the terminal crowded peripheral base station 1 determined in step s11. Therefore, it is determined that the ease of connection between the terminal crowded peripheral base station 1 and the communication terminal 2 has not been improved. Thereafter, the output control unit 142 further increases the transmission power of the wireless communication unit 11 by a predetermined amount.

  On the other hand, the overall control unit 13 reduces the newly obtained number of connection requests addressed to peripheral stations by a predetermined amount or more than the number of connection requests addressed to peripheral stations for the terminal crowded peripheral base station 1 obtained in step s11. If it is determined, the ease of connection between the terminal crowded peripheral base station 1 and the communication terminal 2 is determined to be improved. Thereafter, the output control unit 142 stops increasing the transmission power of the wireless communication unit 11 and maintains the transmission power.

  Thereafter, the overall control unit 13 operates in the same manner, and whenever the output control unit 142 increases the transmission power of the wireless communication unit 11, it is easy to establish a connection between the terminal crowded peripheral base station 1 and the communication terminal 2. Judge whether the situation has improved. When the ease of connection between the terminal crowded peripheral base station 1 and the communication terminal 2 is improved, the overall control unit 13 maintains the transmission power of the wireless communication unit 11 at that time. Note that if the transmission power of the wireless communication unit 11 is maximized, the maximum transmission power is maintained.

  Thus, by gradually increasing the transmission power of the base station 1, it is possible to suppress the transmission power of the base station 1 from becoming larger than necessary.

  Next, the operation of the base station 1 when the shape of the modified service area 10 is restored will be described. FIG. 12 is a flowchart showing an operation when the base station 1 in which the terminal dense area 400 is generated in the local station service area 10 and the local station service area 10 is transformed returns the shape of the local station service area 10 to the original state. .

  As shown in FIG. 12, in step s <b> 21, the congestion determination unit 141 determines whether the terminal congestion area 400 no longer exists in the local station service area 10. Specifically, the congestion determination unit 141 counts the number of connection requests addressed to the local station in the same manner as in step s1 described above. Then, the congestion determination unit 141 compares the acquired number of connection requests addressed to the own station with a predetermined threshold value. The congestion determination unit 141 determines that the terminal congestion area 400 no longer exists in the local station service area 10 if the number of connection requests addressed to the local station is equal to or less than the threshold value. On the other hand, if the number of connection requests addressed to the own station is larger than the fourth threshold value, the congestion determination unit 141 determines that the terminal congestion area 400 still exists in the own station service area 10.

  If it is determined in step s21 that the terminal dense area 400 still exists in the local station service area 10, the base station 1 executes step s21 again after a predetermined time, and the local station service area 10 It is determined whether 400 no longer exists.

  On the other hand, if it is determined in step s21 that the terminal crowded area 400 no longer exists in the local station service area 10, the area control unit 150 adjusts the reception weight and the transmission weight to change the modified local station service area 10 Restore the original shape. Thereby, the local station service area 10 (10a) modified as shown in FIG. 7 has a shape as shown in FIG. Thereafter, the base station 1 executes step s1 described above.

  In the base station 1 in which the terminal dense area 400 is generated in the peripheral service area 10 and the own station service area 10 is modified, the own station service area 10 is restored to the original. In such a base station 1, the congestion determination unit 141 first determines whether the terminal congestion area 400 no longer exists in the peripheral service area 10. Specifically, the congestion determination unit 141 counts the number of connection requests addressed to the peripheral stations for the terminal dense peripheral base station 1, and compares the acquired number of connection requests addressed to the peripheral stations with a predetermined threshold value. The congestion determination unit 141 determines that the terminal congestion area 400 no longer exists in the service area 10 of the terminal congestion peripheral base station 1 if the number of connection requests addressed to the peripheral stations of the terminal congestion peripheral base station 1 is equal to or less than the threshold value. . On the other hand, the congestion determination unit 141 indicates that the terminal congestion area 400 still exists in the service area 10 of the terminal congestion peripheral base station 1 if the number of connection requests addressed to the peripheral stations of the terminal congestion peripheral base station 1 is larger than the threshold value. It is determined that

  If it is determined that the terminal crowded area 400 still exists in the service area 10 of the terminal crowded peripheral base station 1, the base station 1 again returns the terminal to the service area 10 of the terminal crowded neighboring base station 1 after a predetermined time. It is determined whether the dense area 400 no longer exists.

  On the other hand, when it is determined that the terminal dense area 400 no longer exists in the service area 10 of the terminal dense peripheral base station 1, the output control unit 142 restores the transmission power of the wireless communication unit 11 to the original state, and changes its own power. The shape of the station service area 10 is restored. Thereby, the local station service area 10 (10a) modified as shown in FIG. 8 has the shape as shown in FIG. Thereafter, the base station 1 executes step s11 described above.

Embodiment 2. FIG.
In the first embodiment described above, the base station 1 determines whether the terminal dense area 400 exists in the local station service area 10 or the peripheral service area 10 based on the number of connection request signals from the communication terminal 2. It was. On the other hand, in the present embodiment, the base station 1 has a terminal congestion area 400 in the local station service area 10 or the peripheral service area 10 based on the call loss rate indicating the probability that the communication terminal cannot connect to the base station. Determine whether or not. Below, the base station 1 which concerns on this Embodiment is demonstrated centering on difference with the base station 1 which concerns on Embodiment 1. FIG.

  FIG. 13 is a diagram showing a main configuration of overall control unit 13 of base station 1 according to the present embodiment. As shown in FIG. 13, in the overall control unit 13, the control unit 130 includes a call loss rate calculation unit 143 that calculates a call loss rate in its own device. The call loss rate calculation unit 143 counts the total number N1 of connection request signals addressed to the own device received by the wireless communication unit 11 between the plurality of TDMA frames 200. Then, the call loss rate calculation unit 143 determines the number N2 of connection request signals that the base station 1 could not connect to the communication terminal 2 out of the N1 connection request signals. N2 indicates the number of call losses that occur between the base station 1 and the communication terminal 2 between the plurality of TDMA frames 200. Then, the call loss rate calculation unit 143 sets a value obtained by dividing N2 by N1 as the call loss rate of the own device. Thus, in the present embodiment, the call loss rate indicates the ratio of the number of call losses to the number of calls (number of connection requests) within a predetermined time. The call loss rate calculation unit 143 periodically calculates the call loss rate.

  When the call loss rate calculation unit 143 obtains the call loss rate, the control unit 130 generates and outputs a transmission signal for the server device 3 including information indicating the call loss rate. Thereby, the server apparatus 3 is notified of the call loss rate calculated by each base station 1. The server device 3 notifies each base station 1 of the call loss rate at each of the plurality of peripheral base stations 1 located in the vicinity thereof. In the base station 1, the call loss rate in the neighboring base station 1 notified from the server device 3 is input to the control unit 130 through the network communication unit 12.

  Next, a service area modification operation in base station 1 according to the present embodiment will be described. FIG. 14 is a flowchart showing operations until the base station 1 according to the present embodiment detects that the terminal dense area 400 exists in the local station service area 10 and then deforms the service area 10.

  As shown in FIG. 14, in step s <b> 31, the congestion determination unit 141 determines whether the terminal congestion area 400 exists in the local station service area 10. In step s31, the congestion determination unit 141 compares the call loss rate calculated by the call loss rate calculation unit 143 with a predetermined threshold value. If the call loss rate is larger than the threshold value, the congestion determination unit 141 determines that the terminal congestion area 400 exists in the local station service area 10. On the other hand, the congestion determination unit 141 determines that the terminal congestion area 400 does not exist in the local station service area 10 if the call loss rate is equal to or less than the threshold value. When the communication terminals 2 are densely packed in the service area 10 of the base station 1 and the terminal crowded area 400 is generated in the service area 10, the call loss rate in the base station 1 increases. Therefore, the congestion determination unit 141 can determine that the terminal congestion area 400 exists in the local station service area 10 when the call loss rate at the local apparatus is large.

  If it is determined in step s31 that the terminal crowded area 400 does not exist in the local station service area 10, the base station 1 executes step s31 again after a predetermined time, and the terminal crowded area 400 exists in the local station service area 10. It is determined whether or not to do so.

  On the other hand, if it is determined in step s31 that the terminal crowded area 400 exists in the local station service area 10, in step s32, the area control unit 150 determines the call loss rate of each peripheral base station 1 notified from the server device 3. Based on this, the peripheral base station 1 having the smallest call loss rate among the plurality of peripheral base stations 1 is specified.

  Next, in step s33, the area control unit 150 performs null steering by adjusting the reception weight and transmission weight so that the directivity null of the array antenna 110 is directed toward the peripheral base station 1 with the smallest call loss rate.

  As in the example of FIG. 6, when the terminal congestion area 400 generated in the service area 10a of the base station 1a is not included in the service area 10b of the peripheral base station 1b, the call loss rate in the peripheral base station 1b is The call loss rate at other peripheral base stations 1 having the service area 10 including the terminal crowded area 400 becomes smaller. Therefore, the base station 1 sets the directivity null of the array antenna 110 toward the peripheral base station 1 with the smallest call loss rate, thereby setting the terminal congestion area 400 in the local station service area 10 as shown in FIG. The portion 401 that is excluded and overlaps with the peripheral service area 10 can be narrowed. Therefore, the same effect as in the first embodiment can be obtained.

  The operation until the base station 1 according to the present embodiment detects that the terminal dense area 400 exists in the peripheral service area 10 and then transforms the own station service area 10 is described above in the first embodiment. Compared with the base station 1 which concerns on this, the process which determines whether the terminal dense area 400 exists in the periphery service area 10 only differs.

  In the present embodiment, the congestion determination unit 141, for each of a plurality of peripheral base stations 1 existing in the vicinity of the own device, the call loss rate and the predetermined threshold value in the peripheral base station 1 notified from the server device 3 And compare. The congestion determination unit 141 determines that the terminal congestion area 400 exists in the service area 10 of the peripheral base station 1 if the call loss rate for a certain peripheral base station 1 is larger than the threshold value. On the other hand, the congestion determination unit 141 determines that the terminal congestion area 400 does not exist in the service area 10 of the peripheral base station 1 if the call loss rate for a certain peripheral base station 1 is smaller than the threshold value.

  If the congestion determination unit 141 determines that the terminal congestion area 400 does not exist in all the service areas 10 of the plurality of neighboring base stations 1, the base station 1 includes the terminal congestion area 400 in each peripheral service area 10 after a predetermined time. It is determined again whether or not to do so.

  On the other hand, when the congestion determination unit 141 determines that the terminal congestion area 400 exists in at least one service area 10 of the plurality of neighboring base stations 1, the output control unit 142 determines that the current transmission power of the wireless communication unit 11 is the maximum. It is determined whether or not. Thereafter, the base station 1 according to the present embodiment performs the same operation as the base station according to the first embodiment. As a result, the local station service area 10 is expanded, and the local station service area 10 includes the peripheral service area 10 where the terminal congestion area 400 is generated. Therefore, the same effect as in the first embodiment can be obtained. As in the first embodiment, the transmission power of the base station 1 may be suppressed from increasing more than necessary by gradually increasing the transmission power of the base station 1.

  Next, an operation for restoring the shape of the service area 10 deformed by the base station 1 will be described. In the base station 1 in which the terminal congestion area 400 is generated in the own station service area 10 and the own station service area 10 is modified, the congestion determination unit 141 determines whether the terminal congestion area 400 does not exist in the own station service area 10. To do. Specifically, the congestion determination unit 141 compares the call loss rate obtained by the call loss rate calculation unit 143 with a predetermined threshold value. The congestion determination unit 141 determines that the terminal congestion area 400 does not exist in the local station service area 10 if the call loss rate is equal to or less than the threshold value. It is determined that the terminal dense area 400 still exists in the service area 10.

  If the congestion determination unit 141 determines that the terminal congestion area 400 still exists in the local station service area 10, the base station 1 includes the terminal congestion area 400 in the local station service area 10 after a predetermined time. It is determined again whether it is gone.

  On the other hand, if the congestion determination unit 141 determines that the terminal congestion area 400 no longer exists in the own station service area 10, the area control unit 150 adjusts the reception weight and the transmission weight to change the modified own station service. Restore the shape of area 10 to its original shape. Thereby, the local station service area 10 (10a) modified as shown in FIG. 7 has a shape as shown in FIG. Thereafter, the base station 1 executes step s31 described above.

  In the base station 1 in which the terminal dense area 400 is generated in the peripheral service area 10 and the own station service area 10 is modified, the shape of the own station service area 10 is similarly restored. In such a base station 1, first, the congestion determination unit 141 determines whether the terminal congestion area 400 no longer exists in the service area 10 of the terminal congestion peripheral base station 1. Specifically, the congestion determination unit 141 compares the call loss rate in the terminal congestion peripheral base station 1 notified from the server device 3 with a predetermined threshold value. The congestion determination unit 141 determines that the terminal congestion area 400 does not exist in the service area 10 of the terminal congestion peripheral base station 1 if the call loss ratio of the terminal congestion peripheral base station 1 is equal to or less than the threshold value, Is larger than the threshold value, it is determined that the terminal dense area 400 still exists in the service area 10 of the terminal dense peripheral base station 1.

  If it is determined that the terminal crowded area 400 still exists in the service area 10 of the terminal crowded peripheral base station 1, the base station 1 again returns the terminal to the service area 10 of the terminal crowded neighboring base station 1 after a predetermined time. It is determined whether the dense area 400 no longer exists.

  On the other hand, when it is determined that the terminal dense area 400 no longer exists in the service area 10 of the terminal dense peripheral base station 1, the output control unit 142 restores the transmission power of the wireless communication unit 11 to the original state, and changes its own power. The shape of the station service area 10 is restored. Thereby, the local station service area 10 (10a) modified as shown in FIG. 8 has the shape as shown in FIG. Thereafter, in the base station 1, as described above, it is determined whether the terminal dense area 400 exists in each peripheral service area 10.

  When each base station 1 notifies the server device 3 of the call loss rate of its own device as in the present embodiment, it is determined whether or not there is a terminal congestion area 400 in the service area 10 of a certain base station 1. The server device 3 may make a determination, and based on the determination result, the server device 3 may instruct the neighboring base station 1 located around the certain base station 1 to expand the service area 10.

  Specifically, when the call loss rate notified from a certain base station 1 is larger than a predetermined threshold, the server device 3 determines that the terminal congestion area 400 exists in the service area 10 of the certain base station 1. To do. Then, the server device 3 instructs the peripheral base station 1 with the smallest call loss rate to expand the service area 10 among the plurality of peripheral base stations 1 located around the certain base station 1. In the base station 1 that has received an instruction to expand the service area 10 from the server device 3, the output control unit 142 increases the transmission power of the wireless communication unit 11 and expands the service area 10. Thereby, the overlapping part of the service area 10 of a certain base station 1 and the service area 10 of the surrounding base station 1 where the terminal crowded area 400 occurs increases. Therefore, the communication terminal 2 existing in the service area 10 of the certain base station 1 can be easily connected to the peripheral base station 1.

  In addition, when the call loss rate notified from the base station 1 determined that the terminal congestion area 400 exists in the service area 10 is equal to or less than a predetermined threshold, the server device 3 adds the terminal congestion area to the service area 10 of the base station 1. It is determined that 400 no longer exists. Then, the server device 3 instructs the neighboring base station 1 that has instructed expansion of the service area 10 to restore the shape of the service area. In the base station 1 instructed by the server device 3 to restore the shape of the service area 10, the output control unit 142 restores the transmission power of the wireless communication unit 11 to restore the shape of the service area 10. .

  As described above, when the terminal congestion area 400 occurs in the service area 10 of the peripheral base station 1 located in the vicinity of a certain base station 1, the server device 3 transmits the service area 10 to the certain base station 1. The same effect as described above can be obtained by instructing enlargement.

1, 1a, 1b Base station 2 Communication terminal 3 Server device 10, 10a, 10b Service area 11 Wireless communication unit 141 Congestion determination unit 150 Area control unit 400 Terminal congested area

Claims (12)

A base station that performs wireless communication with a communication terminal,
A wireless communication unit that communicates with a communication terminal using a plurality of antennas;
In the own station area where the base station is a communication area capable of bidirectional communication with a communication terminal, a congestion determination unit that determines whether there is a crowded area where communication terminals are crowded,
When the congestion determination unit determines that the congestion area exists, the local station area is a portion excluding the congestion area, and the peripheral station area is a communication area in which the peripheral base station can bidirectionally communicate with a communication terminal; A base station comprising: an area control unit that controls the directivity of communication with the plurality of antennas so that overlapping portions are narrowed. The base station according to claim 1, wherein
The area control unit is a base station that specifies the dense area in the local station area by communicating with a communication terminal through the wireless communication unit while controlling the directivity of communication with the plurality of antennas. The base station according to claim 1, wherein
The base station is notified from the server device of a call loss rate with a communication terminal in each of a plurality of neighboring base stations,
The area control unit is a base station that sets the directivity null toward a peripheral base station having the smallest call loss rate among the plurality of peripheral base stations. A base station according to any one of claims 1 to 3,
When the area control unit narrows a portion of the own station area excluding the crowded area that overlaps with the peripheral station area, the congestion determination unit determines that the crowded area no longer exists. A base station that restores the shape of the local station area. The base station according to claim 1, wherein
The congestion determination unit also determines whether the congestion area exists in the peripheral station area,
The area control unit expands the local station area when the congestion determination unit determines that the congestion area exists in the peripheral station area. The base station according to claim 5, wherein
If the area control unit determines that the congestion area no longer exists in the peripheral station area after expanding the local station area, the area control unit restores the shape of the local station area to the original. Bureau. The base station according to claim 1, wherein
When determining that the dense area exists in the peripheral station area, the server device that determines whether the dense area exists in the peripheral station area expands the local station area with respect to the base station. Direct,
When the server device instructs the base station to expand the own station area, the area control unit expands the own station area. The base station according to claim 7, wherein
The server device, after instructing the base station to expand the local station area, determines that the congestion area no longer exists in the peripheral station area, the base station to the base station Instructing to restore the shape of the
When the server device instructs the base station to restore the shape of the own station area, the area control unit restores the shape of the own station area. A wireless communication system comprising a plurality of base stations that wirelessly communicate with a communication terminal,
The first base station in the plurality of base stations is:
A wireless communication unit that communicates with a communication terminal using a plurality of antennas;
In the first communication area, which is a communication area in which the first base station is capable of bidirectional communication with a communication terminal, a congestion determination unit that determines whether there is a crowded area where communication terminals are crowded,
When the congestion determination unit determines that the congestion area exists, a portion of the first communication area excluding the congestion area that overlaps with a communication area in which a peripheral base station can bidirectionally communicate with a communication terminal. A wireless communication system comprising: an area control unit that controls directivity of communication with the plurality of antennas so as to be narrow. The wireless communication system according to claim 9, wherein
A server device for communicating with the plurality of base stations;
In the plurality of base stations, each of a plurality of second base stations that are peripheral base stations located around the first base station calculates a call loss rate with a communication terminal and notifies the server device,
The server device notifies the first base station of the call loss rate of each of the plurality of second base stations,
The wireless communication system, wherein the area control unit of the first base station sets the directivity null toward a second base station having the smallest call loss rate among the plurality of second base stations. The wireless communication system according to claim 9, wherein
A server device for communicating with the plurality of base stations;
In the plurality of base stations, each of a plurality of second base stations that are peripheral base stations located around the first base station calculates a call loss rate with a communication terminal and notifies the server device,
In the plurality of second base stations, when there is a second base station whose call loss rate is larger than a threshold value, the server device is a communication area in which the second base station can perform two-way communication with a communication terminal. And instructing the first base station to expand the first communication area,
When the first base station is instructed by the server device to expand the first communication area, the area control unit of the first base station expands the first communication area. A method of controlling a communication area in a base station that performs wireless communication with a communication terminal using a plurality of antennas,
(A) determining whether or not there is a dense area in which communication terminals are densely located in a local area where the base station is capable of bidirectional communication with a communication terminal;
(B) If it is determined in step (a) that the crowded area exists, the communication station is a part of the own station area excluding the crowded area, in which the peripheral base station can perform two-way communication with a communication terminal. And a step of controlling the directivity of communication with the plurality of antennas so that the overlapping part becomes narrower.

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