JP5712548B2 - Base station, communication program, communication method, and communication system - Google Patents

Description

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

  There is an IEEE 802.11A standard as a standard for performing wireless LAN communication. For example, there are W52, W53, and W56 bands as frequency bands in which communication can be performed in accordance with the IEEE 802.11A standard in Japan. Since the W53 and W56 bands overlap with a frequency band to which specific priority radio waves used by weather radars and air traffic control radars are assigned, implementation of DFS (Dynamic Frequency Selection) is obligatory (for example, Patent Document 1 below) , 2).

  The wireless LAN base station confirms the presence / absence of a radar signal for 1 minute before using the channel by DFS and starts operation. In addition, the wireless LAN base station confirms the presence or absence of a radar signal even after starting operation, and if a radar signal is detected, stops using the channel that detected the radar signal, Do not send radio waves.

  Therefore, when a radar signal is detected while using the W53 and W56 band channels and operating as a wireless LAN base station, the wireless LAN base station changes the channel to be used to another channel. Alternatively, when the wireless LAN base station detects a radar signal using the W53 and W56 band channels and operates as a wireless LAN base station, the wireless LAN base station stops the transmission of radio waves for 30 minutes, and then detects the radar signal. Restart the use of the channel that detected

  In an infrastructure mode in which communication is performed between a wireless LAN base station and a terminal, if the channel of the base station is changed, the terminal cannot receive a beacon frame from the base station and is synchronized with the base station. I can't take it. On the other hand, the terminal searches and sets the channel used by the base station when the synchronization with the base station is lost. For this reason, the base station and the terminal can be reconnected to each other on the channel after the change, and communication can be continued.

  By the way, a WDS (Wireless Distribution System) mode for performing wireless communication between base stations is known in order to cover a wide range or reduce places where radio waves are difficult to reach (see, for example, Patent Document 3 below). .)

JP 2007-325041 A JP 2009-100210 A JP 2006-67297 A

  However, in the above-described prior art, when wireless communication is performed between base stations using, for example, the WDS mode, if one base station detects a specific priority radio wave and changes the channel, the base stations use different channels. Become. For this reason, there is a problem that base stations cannot communicate with each other. Further, when the use of the channel is stopped and the same channel is used again, the channel in which the specific priority radio wave is detected cannot be used for a certain period of time. Furthermore, even if the channel is used again after a certain period of time, the specific priority radio wave may be detected again and communication may be disabled again.

  On the other hand, when designing the network, when using the WDS mode in the IEEE802.11A standard, avoid the W53 and W56 bands that require DFS, and design the network with only four channels of the W52 band. May do. That is, when designing in the WDS mode, 15 channels of W53 and W56 bands cannot be effectively used. In addition, when using the WDS mode, there is also a base station apparatus that cannot set the W53 and W56 band channels.

  The disclosed base station, communication program, communication method, and communication system are intended to solve the above-described problems and to suppress a state incapable of communication.

  In order to solve the above-described problems and achieve the object, the disclosed technology provides a first base station and a first base station that perform wireless communication with each other through a channel of a specific frequency band in which a specific radio wave is preferentially allocated over the radio wave of the local station. In a communication system including two base stations, when the first base station detects the specific radio wave and detects the specific radio wave, or the first base station communicates with the second base station. When it is determined that communication is impossible, a change destination channel is selected from a frequency band different from the specific frequency band, and a notification signal indicating the selected change destination channel is selected. Transmitting to the second base station, changing the channel used by the own station for the wireless communication to the channel to be changed, and changing the channel used by the second base station for the wireless communication to the first base station Sent by The change to the newly selected channel indicated by the notification signal.

  According to the disclosed base station, communication program, communication method, and communication system, it is possible to suppress an incommunicable state.

It is a figure which shows the communication system concerning embodiment. It is a figure which shows the specific example of a communication system. It is a figure which shows the specific example of a base station. It is a flowchart which shows an example of the survival confirmation process of a base station. It is a flowchart which shows an example of the radar detection process of a base station. It is a flowchart which shows Example 1 of the channel change process of a base station. It is a flowchart which shows Example 2 of the channel change process of a base station. It is a flowchart which shows Example 3 of the channel change process of a base station. It is a flowchart which shows Example 4 of the channel change process of a base station. It is a figure which shows an example of the change destination channel table of W52 band. It is a figure which shows an example of the memory area which shows the next change destination channel of W52 band. It is a figure which shows an example of the change destination channel table of W53 / W56 band. It is a figure which shows an example of the storage area which shows the next change destination channel of W53 / W56 band. It is a sequence diagram which shows the operation example 1 of the channel change of a communication system. It is a sequence diagram which shows the operation example 2 of the channel change of a communication system.

  Hereinafter, preferred embodiments of the disclosed technology will be described in detail with reference to the accompanying drawings.

(Embodiment)
(Communications system)
FIG. 1 is a diagram illustrating a communication system according to an embodiment. As shown in FIG. 1, the communication system 100 according to the embodiment includes a first base station 110, a second base station 120, and mobile stations 11 and 12. The mobile station 11 is located in the cell of the first base station 110 and performs wireless communication with the first base station 110. The mobile station 12 is located in the cell of the second base station 120 and performs wireless communication with the second base station 120.

  The first base station 110 and the second base station 120 perform wireless communication with each other (WDS mode). In addition, each of the first base station 110 and the second base station 120 is wireless by a channel of a frequency band in which a specific priority radio wave (specific radio wave) is preferentially assigned to the first base station 110 and the second base station 120. Communicate.

  For example, each of the first base station 110 and the second base station 120 performs wireless communication using the W53 and W56 band channels of the IEEE802.11A standard to which specific priority radio waves such as weather radar and air traffic control radar are preferentially assigned. Do. In addition, each of the first base station 110 and the second base station 120 can perform wireless communication through a W52 band channel of the IEEE802.11A standard to which no specific priority radio wave is assigned.

  The first base station 110 includes a communication unit 111, a detection unit 112, a selection unit 113, a transmission unit 114, and a change unit 115. The communication unit 111 performs wireless communication between the mobile station 11 and the second base station 120. The detection unit 112 detects specific priority radio waves (for example, radar signals). For example, the detection unit 112 detects a specific priority radio wave by monitoring a signal in a specific frequency band received by the communication unit 111. When detecting the specific priority radio wave, the detection unit 112 notifies the selection unit 113 that the specific priority radio wave has been detected.

  When the detection unit 112 is notified that the specific priority radio wave has been detected, the selection unit 113 selects a channel to be changed from a frequency band different from the specific frequency band to which the specific priority radio wave is assigned. Then, the selection unit 113 notifies the transmission unit 114 and the change unit 115 of the selected change destination channel. The transmission unit 114 transmits a channel change notification signal indicating the change destination channel notified from the selection unit 113 to the second base station 120. Transmission of the channel change notification signal by the transmission unit 114 is performed via wireless communication by the communication unit 111, for example.

  The change unit 115 changes the channel of the wireless communication between the mobile station 11 and the second base station 120 by the communication unit 111 to the change destination channel notified from the selection unit 113. When transmission of the channel change notification signal by the transmission unit 114 is performed via wireless communication by the communication unit 111, the change unit 115 changes the channel after the transmission of the channel change notification signal by the transmission unit 114. Thereby, it can be avoided that the second base station 120 cannot receive the channel change notification signal due to the change of the transmission channel of the channel change notification signal.

  The second base station 120 includes a communication unit 121, a receiving unit 122, and a changing unit 123. The communication unit 121 performs wireless communication between the mobile station 12 and the first base station 110. The receiving unit 122 receives the channel change notification signal transmitted from the first base station 110. The reception unit 122 notifies the change unit 123 of the change destination channel indicated by the received channel change notification signal. The changing unit 123 changes the channel of the wireless communication between the mobile station 12 and the first base station 110 by the communication unit 121 to the change destination channel notified from the receiving unit 122.

  With such a configuration of the first base station 110 and the second base station 120, when the specific priority radio wave is detected in the first base station 110 and the first base station 110 changes the channel, the change destination channel is set to the second channel. The base station 120 can be notified. The second base station 120 can continue wireless communication with the first base station 110 by changing the use channel to the change destination channel notified from the first base station 110. Thereby, the state in which the first base station 110 and the second base station 120 cannot communicate with each other can be suppressed.

  In addition, the detection unit 112, the selection unit 113, the transmission unit 114, and the change unit 115 of the first base station 110 are provided also in the second base station 120, and the reception unit 122 and the change unit 123 of the second base station 120 are provided in the first base station 110. The base station 110 may also be provided. Thereby, it is possible to continue the wireless communication between the first base station 110 and the second base station 120 regardless of whether the specific priority radio wave is detected in either the first base station 110 or the second base station 120. become.

  In addition, when the channel is changed by the changing unit 115, the communication unit 111 of the first base station 110 may transmit a request signal for requesting a response to the second base station 120 through the changed channel. And the communication part 111 starts the data communication by the channel of a change destination between the 2nd base stations 120, when the response signal with respect to the transmitted request signal is received.

  As a result, data communication can be started after confirming that the second base station 120 has changed to the change destination channel. For this reason, it is possible to avoid the start of data communication in a state where the channels of the first base station 110 and the second base station 120 do not match, and to suppress lost data.

  In addition, the changing unit 115 of the first base station 110 specifies the wireless communication channel by the communication unit 111 when a predetermined condition is satisfied after changing the wireless communication channel by the communication unit 111 to the change destination channel. You may change to the frequency band. Thereby, the specific frequency band to which the specific priority radio wave is allocated can be utilized. The predetermined condition is, for example, that the current time is a predetermined time zone. The predetermined time zone is a time zone in which the amount of communication is small, such as at night, and the influence of a temporary communication disabled state for radar detection confirmation is limited.

  In addition, the communication unit 111 of the first base station 110 sends a response to the second base station 120 through the channel used for wireless communication in order to monitor whether communication with the second base station is possible. The requested signal may be repeatedly transmitted. In this case, when the second base station 120 detects the specific priority radio wave and changes the channel, the second base station 120 does not receive the request signal from the first base station 110. When the number of times that the response signal is not received from the second base station 120 within a certain period with respect to the request signal transmitted by the communication unit 111 exceeds the threshold, the changing unit 115 performs a wireless communication channel by the communication unit 111. To change.

  Thereby, when the second base station 120 detects the specific priority radio wave and changes the channel, the channel of the wireless communication by the communication unit 111 is changed. Then, the channel of the wireless communication by the communication unit 111 matches the channel to which the second base station 120 is changed, and a response signal is received from the second base station 120 in response to the request signal from the communication unit 111. Until the wireless communication channel by the communication unit 111 is changed.

  Thereby, even if the second base station 120 does not have a function corresponding to the transmission unit 114, for example, when the second base station 120 detects the specific priority radio wave and changes the channel, the first base station 110 Can also follow and change the channel. Thereby, it becomes possible to continue the wireless communication between the first base station 110 and the second base station 120.

  Even when the second base station 120 has a function corresponding to the transmission unit 114, for example, the channel change notification signal transmitted by the second base station 120 is lost due to the influence of noise or the like, Even if the first base station 110 does not reach the first base station 110 or the second base station 120 cannot transmit the channel change notification signal during the one-minute radar detection period before the channel is used, the first base station 110 The channel can be changed following the channel of the base station. Thereby, it becomes possible to continue the wireless communication between the first base station 110 and the second base station 120.

  For example, each of the first base station 110 and the second base station 120 may be realized by a communication program that causes a computer of the base station to operate as each unit illustrated in FIG. The communication program is stored in each memory of the first base station 110 and the second base station 120. The computers of the first base station 110 and the second base station 120 implement the above functions by reading out the communication program from the memory and executing it.

  FIG. 2 is a diagram illustrating a specific example of a communication system. A communication system 200 shown in FIG. 2 is a specific example of the communication system 100 shown in FIG. The communication system 200 includes wireless LANs 210 and 220. The wireless LAN 210 includes a base station 211 and mobile stations 212 to 214 (STA). The base station 211 corresponds to the first base station 110 shown in FIG. Each of the mobile stations 212 to 214 corresponds to the mobile station 11 shown in FIG. The base station 211 performs wireless communication with the mobile stations 212 to 214 and wireless communication with the base station 221 (WDS mode).

  The wireless LAN 220 includes a base station 221 and mobile stations 222 to 224. The base station 221 corresponds to the second base station 120 shown in FIG. Each of the mobile stations 222 to 224 corresponds to the mobile station 12 shown in FIG. The base station 221 performs wireless communication with the mobile stations 222 to 224 and wireless communication with the base station 211 (WDS mode).

  Each of the base stations 211 and 221 facing each other periodically transmits a survival confirmation request signal to the opposite base station in order to confirm the existence of the opposite base station when the WDS mode is valid. Each of the base stations 211 and 221 returns a survival confirmation response signal in response to the survival confirmation request signal from the opposite base station. Each of the base stations 211 and 221 is alive if the survival confirmation response signal from the opposite base station is returned within a certain time in response to the transmission of the survival confirmation request signal from the own station. The operation is continued.

  Further, each of the base stations 211 and 221 determines a change destination channel in the W52 band that does not require DFS when a radar signal is detected, and sends a channel change notification signal indicating the determined change destination channel to the opposite base station. Change the channel after sending to. By determining the change destination channel in the W52 band that does not require DFS, wireless communication can be reliably performed after the channel change.

  Each of the base stations 211 and 221 also changes the channel when the existence of the opposing base station cannot be confirmed by the existence confirmation. Further, each of the base stations 211 and 221 changes the channel based on the channel change notification signal when receiving the channel change notification signal from the opposite base station. After the channel change, each of the base stations 211 and 221 resumes the operation as an access point when the existence of the opposite base station is confirmed by the existence confirmation.

(Specific examples of base stations)
FIG. 3 is a diagram illustrating a specific example of a base station. A base station 300 illustrated in FIG. 3 is a specific example of the base station 211 and the base station 221 illustrated in FIG. 2, for example. The base station 300 includes an arithmetic processing unit 310, a memory control unit 320, a nonvolatile memory 321, a memory 322, an antenna 330, a wireless LAN control unit 340, a connector 350 (CN), and a wired LAN control unit 360. And.

  The arithmetic processing unit 310 is a processing unit that controls the entire base station 300. The memory control unit 320 controls the nonvolatile memory 321 and the memory 322 in accordance with instructions from the arithmetic processing unit 310. The nonvolatile memory 321 stores a startup program for the base station 300, a basic software program, a wireless LAN control program for the wireless LAN control unit 340, a variable area, and the like. The memory 322 stores a basic software program, a wireless LAN control program, a variable area, and the like loaded from the nonvolatile memory at the time of activation, and is also used as a work area for the program.

  The startup program stored in the nonvolatile memory 321 performs initialization processing of the arithmetic processing unit 310 and the memory control unit 320, and when the memory 322 becomes usable, the program and variable area of the nonvolatile memory 321 are stored. A program to be loaded into the memory 322. The base station 300 operates as a wireless LAN access point by executing a basic software program and a wireless LAN control program in the memory 322. The arithmetic processing unit 310 stores various settings such as a wireless LAN channel and mode in the variable area of the nonvolatile memory 321 and can start the operation with the settings stored at the time of activation.

  The antenna 330 is an antenna that transmits and receives radio signals to and from other base stations and mobile stations. The wireless LAN control unit 340 is provided between the antenna 330 and the arithmetic processing unit 310. The wireless LAN control unit 340 controls the wireless LAN wireless communication via the antenna 330 in accordance with an instruction from the arithmetic processing unit 310.

  Specifically, the wireless LAN control unit 340 includes an RF unit 341 (Radio Frequency), a BB processing unit 342 (Base Band), and a MAC unit 344 (Media Access Control). The RF unit 341 is provided between the antenna 330 and the BB processing unit 342. The RF unit 341 performs high-frequency signal processing.

  The BB processing unit 342 is provided between the RF unit 341 and the MAC unit 344. The BB processing unit 342 performs baseband processing including signal modulation processing and demodulation processing such as OFDM / CCK (Orthogonal Frequency Division Multiplexing / Complementary Code Keying).

  The BB processing unit 342 includes a radar detection unit 343. The radar detection unit 343 detects a radar signal (specific priority radio wave) by monitoring each signal subjected to baseband processing by the radar detection unit 343. For example, the BB processing unit 342 detects a radar signal using a wireless LAN control program stored in the memory 322. The MAC unit 344 is provided between the BB processing unit 342 and the arithmetic processing unit 310. The MAC unit 344 performs MAC layer protocol control.

  The connector 350 is a connector connected to a wired LAN. The wired LAN control unit 360 controls wired LAN communication via the connector 350 in accordance with an instruction from the arithmetic processing unit 310. Specifically, the wired LAN control unit 360 includes a PHY unit 361 (Physical Layer) and a MAC unit 362. The PHY unit 361 is provided between the connector 350 and the MAC unit 362. The PHY unit 361 performs protocol control of the physical layer. The MAC unit 362 is provided between the PHY unit 361 and the arithmetic processing unit 310. The MAC unit 362 performs MAC layer protocol control.

  The communication unit 111 and the transmission unit 114 illustrated in FIG. 1 can be realized by a program stored in the arithmetic processing unit 310, the antenna 330, the wireless LAN control unit 340, and the memory 322, for example. The detection unit 112 illustrated in FIG. 1 can be realized by a program stored in the radar detection unit 343, the arithmetic processing unit 310, and the memory 322, for example. The selection unit 113 and the change unit 115 illustrated in FIG. 1 can be realized by a program stored in the arithmetic processing unit 310 and the memory 322, for example. The communication unit 121 and the reception unit 122 illustrated in FIG. 1 can be realized by, for example, the arithmetic processing unit 310, the antenna 330, the wireless LAN control unit 340, and a program stored in the memory 322. The changing unit 123 illustrated in FIG. 1 can be realized by a program stored in the arithmetic processing unit 310 and the memory 322, for example.

(Base station processing)
FIG. 4 is a flowchart showing an example of a base station survival confirmation process. The base station 300 executes the steps shown in FIG. 4 at, for example, periodically set confirmation timings. First, the base station 300 sets a “survival check failure count”, which is a variable assigned to the memory 322, to 0 (step S401). Next, the base station 300 transmits a survival confirmation request signal to the opposite base station of the WDS (step S402). Next, the base station 300 waits for a predetermined time (step S403).

  Next, the base station 300 determines whether or not a survival confirmation response signal from the opposite base station with respect to the survival confirmation request signal transmitted in step S402 has been received (step S404). When the survival confirmation response signal is received (step S404: Yes), the base station 300 determines whether or not the access point by itself is in operation (step S405).

  In step S405, when the access point is not in the operating state (step S405: No), the base station 300 sets the access point in the operating state (step S406), and proceeds to step S407. If the access point is in operation (step S405: Yes), the base station 300 waits until the next confirmation timing (step S407) and returns to step S401.

  In step S404, when the survival confirmation response signal has not been received (step S404: No), the base station 300 determines whether or not the “survival confirmation failure count” is equal to or greater than the threshold (step S408). If the “survival confirmation failure count” is not equal to or greater than the threshold (step S408: No), the base station 300 increments (+1) the “survival verification failure count” (step S409). Next, the base station 300 waits until the next confirmation timing (step S410), and returns to step S402.

  In step S408, when the “survival confirmation failure count” is equal to or greater than the threshold (step S408: Yes), the base station 300 sets the access point to the non-operating state (step S411). Next, the base station 300 performs a channel change process (step S412), and proceeds to step S407. The channel change process will be described later.

  FIG. 5 is a flowchart showing an example of radar detection processing of the base station. For example, the base station 300 repeatedly executes the steps shown in FIG. First, the base station 300 determines whether or not a radar signal is detected (step S501), and waits until a radar signal is detected (step S501: No loop). When the radar signal is detected (step S501: Yes), the base station 300 executes a channel change process (step S502) and ends a series of processes. The channel change process will be described later.

  FIG. 6 is a flowchart illustrating Example 1 of channel change processing of the base station. FIG. 6 shows an example of the channel change process based on the judgment of the own station. The base station 300 executes, for example, each step shown in FIG. 6 when the survival confirmation has failed (for example, step S412 in FIG. 3) or when the radar is detected (for example, step S502 in FIG. 4). First, the base station 300 acquires the change destination channel table from the nonvolatile memory 321 (step S601).

  Next, base station 300 determines a change destination channel based on the change destination channel table acquired by step S601 (step S602). Next, the base station 300 transmits a channel change notification signal indicating the change destination channel determined in step S602 to the opposite base station of the WDS (step S603). Next, the base station 300 changes the wireless communication channel to the change destination channel determined in step S602 (step S604), and ends the series of processes.

  FIG. 7 is a flowchart illustrating Example 2 of channel change processing of the base station. FIG. 7 shows an example of channel change processing by receiving a channel change notification signal. The base station 300 executes, for example, each step shown in FIG. 7 when receiving a channel change notification signal from the opposite base station of the WDS. First, the base station 300 acquires a change destination channel indicated by the received channel change notification signal (step S701).

  Next, the base station 300 transmits a channel change notification signal indicating the change destination channel acquired in step S701 to the opposite base station of the WDS (step S702). Next, the base station 300 changes the wireless communication channel to the change destination channel acquired in step S701 (step S703), and ends the series of processes.

  However, when the base station 300 receives the channel change notification signal transmitted from the opposite base station in response to the channel change notification signal transmitted from the own station, the base station 300 does not execute the steps illustrated in FIG. Thereby, it can be avoided that the opposing base stations transmit and receive channel change notification signals to each other and repeat the channel change.

  FIG. 8 is a flowchart illustrating Example 3 of channel change processing of the base station. FIG. 8 shows an example of channel change processing from the W52 band to the W53 / W56 band based on the judgment of the own station. For example, when the base station 300 changes the channel to the W53 band or the W56 band while operating on the W52 band channel, the base station 300 executes the steps shown in FIG. First, the base station 300 acquires the change destination channel table from the memory 322 (step S801). Next, the base station 300 determines a change destination channel based on the change destination channel table acquired in step S801 (step S802).

  Next, the base station 300 determines a channel change time (step S803). Next, the base station 300 transmits a channel change notification signal indicating the change destination channel determined in step S802 to the opposite base station of the WDS (step S804). The channel change notification signal transmitted in step S804 includes the channel change time determined in step S803.

  Next, the base station 300 waits for a certain time (step S805). Next, the base station 300 determines whether or not an ACK has been received from the opposite base station for the channel change notification signal transmitted in step S804 (step S806). When ACK is not received (step S806: No), the base station 300 returns to step S804.

  When ACK is received in step S806 (step S806: Yes), the base station 300 waits for a certain time (step S807). Next, the base station 300 determines whether or not a channel change OK signal from the opposite base station has been received (step S808). When the channel change OK signal has not been received (step S808: No), the base station 300 returns to step S801.

  If the channel change OK signal is received in step S808 (step S808: Yes), the base station 300 waits until the channel change time determined in step S803 (step S809). Next, the base station 300 puts the access point by the own station into a non-operation state (step S810).

  Next, the base station 300 changes the channel for wireless communication to the change destination channel determined in step S802 (step S811). Next, the base station 300 performs radar detection processing for 1 minute (step S812). Next, the base station 300 determines whether or not a radar signal is detected in step S812 (step S813).

  If a radar signal is detected in step S813 (step S813: Yes), the base station 300 performs the channel change process shown in FIG. 6 (step S814), and ends the series of processes. When the radar signal is not detected (step S813: No), the base station 300 performs the survival confirmation process shown in FIG. 4 (step S815) and ends the series of processes.

  For example, the nonvolatile memory 321 of the base station 300 stores the change time to the W53 / W56 band channel and is loaded onto the memory 322 at the time of activation. When the base station 300 uses the W52 band channel and the change time recorded in the memory 322 is reached, the base station 300 changes the W52 band channel to the W53 / W56 band channel according to the steps shown in FIG. Do. For example, the influence of communication interruption during channel change can be reduced by setting in the non-volatile memory 321 as a change time, such as a midnight time zone with a small amount of communication.

  Alternatively, the base station 300 counts the number of communication packets per predetermined time of wireless communication by the wireless LAN control unit 340, and when the communication amount falls below a predetermined value, the channel from the W52 band to the W53 / W56 band channel You may make it change. Thereby, the influence of the communication interruption during the channel change can be reduced. Further, after changing from the W53 / W56 band channel to the W52 band channel, the W52 band channel may not be changed to the W53 / W56 band channel.

  FIG. 9 is a flowchart illustrating Example 4 of channel change processing of the base station. FIG. 9 shows an example of channel change processing from the W52 band to the W53 / W56 band by receiving the channel change notification signal. For example, when the base station 300 receives a channel change notification signal indicating a channel change to the W53 band or the W56 band while operating on the W52 band channel, the base station 300 executes the steps shown in FIG.

  First, base station 300 transmits ACK for the received channel change notification signal to the opposite base station that is the transmission source of the channel change notification signal (step S901). Next, the base station 300 determines whether or not the own station can use the change destination channel indicated by the received channel change notification signal (step S902). When the change destination channel can be used (step S902: Yes), the base station 300 transmits a channel change OK signal to the opposite base station that is the transmission source of the channel change notification signal (step S903).

  Next, the base station 300 waits for a predetermined time (step S904). Next, the base station 300 determines whether or not an ACK for the channel change OK signal transmitted in step S903 has been received (step S905). When ACK is not received (step S905: No), the base station 300 returns to step S903. When ACK is received (step S905: Yes), the base station 300 waits until the channel change time indicated by the received channel change notification signal (step S906).

  Next, the base station 300 sets the access point by the own station to a non-operation state (step S907). Next, the base station 300 changes the channel of wireless communication to the change destination channel indicated by the received channel change notification signal (step S908). Next, the base station 300 performs radar detection processing for 1 minute (step S909). Next, the base station 300 determines whether or not a radar signal has been detected in step S909 (step S910).

  If a radar signal is detected in step S910 (step S910: Yes), the base station 300 performs the channel change process shown in FIG. 6 (step S911) and ends the series of processes. When the radar signal is not detected (step S910: No), the base station 300 performs the survival confirmation process shown in FIG. 4 (step S912) and ends the series of processes.

  In step S902, when the own station cannot use the change destination channel (step S902: No), the base station 300 transmits a channel change NG signal to the opposite base station that is the transmission source of the channel change notification signal (step S913). ). Next, the base station 300 waits for a predetermined time (step S914). Next, the base station 300 determines whether or not an ACK for the channel change NG signal transmitted in step S913 has been received (step S915). When ACK is not received (step S915: No), the base station 300 returns to step S913. When ACK is received (step S915: Yes), the base station 300 ends a series of processes.

(Information stored by the base station)
FIG. 10 is a diagram illustrating an example of the change destination channel table of the W52 band. The nonvolatile memory 321 stores, for example, a change destination channel table 1000 shown in FIG. 10 as a change destination channel table of the W52 band. The change destination channel table 1000 is copied from the nonvolatile memory 321 to the memory 322 when the base station 300 is activated. In the change destination channel table 1000, table numbers (0, 1, 2,...) And W52 band channel numbers (36CH, 40CH, 44CH,...) Are associated with each other.

  FIG. 11 is a diagram illustrating an example of a storage area indicating the next change destination channel of the W52 band. For example, a storage area 1100 shown in FIG. 11 is set in the memory 322. The storage area 1100 stores the table number of the next channel to be changed in the W52 band. For example, in step S602 shown in FIG. 6, the base station 300 searches the change destination channel table 1000 for a channel number corresponding to the table number stored in the storage area 1100, and sets the channel number obtained by the search to the change destination channel. Determine as.

  Further, when determining the change destination channel, the base station 300 updates the storage area 1100 with a value obtained by adding 1 to the table number of the storage area 1100. However, if the table number upper limit has been reached, the base station 300 returns the table number of the storage area 1100 to zero. In the example shown in FIG. 10 and FIG. 11, the base station 300 first changes to 36 CH, and if the survival confirmation fails even in 36 CH, it changes to 40 CH, next 44 CH, and next 48 CH.

  FIG. 12 is a diagram illustrating an example of the W53 / W56 band change destination channel table. For example, a change destination channel table 1200 shown in FIG. 12 is stored in the nonvolatile memory 321 as a change destination channel table of the W53 band or W56 band. The change destination channel table 1200 is copied from the nonvolatile memory 321 to the memory 322 when the base station 300 is activated. In the change destination channel table 1200, a table number (0, 1, 2,...), A W53 or W56 band channel number (52CH, 56CH, 60CH,...), And a radar detection flag are associated with each other. Yes.

  The radar detection flag in the change destination channel table 1200 is a flag indicating whether or not the radar signal in the corresponding channel number has been detected within the last 30 minutes. When the base station 300 detects the radar signal, the base station 300 sets the radar detection flag of the channel number in which the radar signal is detected to “Yes”. Also, the base station 300 sets the radar detection flag after 30 minutes from setting “Yes” to “No”.

  FIG. 13 is a diagram illustrating an example of a storage area indicating the next change destination channel of the W53 / W56 band. For example, a storage area 1300 shown in FIG. 13 is set in the memory 322. The storage area 1300 stores the table number of the next channel to be changed in the W53 band or W56 band. For example, in step S602 shown in FIG. 6, the base station 300 searches the change destination channel table 1200 for the channel number corresponding to the table number stored in the storage area 1300, and uses the channel number obtained by the search as the change destination channel. Determine as.

  Further, when determining the change destination channel, the base station 300 updates the storage area 1300 with a value obtained by adding 1 to the table number of the storage area 1300. However, if the table number upper limit has been reached, the base station 300 returns the table number of the storage area 1300 to zero. In the example illustrated in FIGS. 12 and 13, the base station 300 first changes to 52 CH, and if the survival confirmation fails in 52 CH, the base station 300 changes to 56 CH, next to 60 CH, and then to 64 CH.

  However, if the radar detection flag corresponding to the table number stored in the storage area 1300 is “Yes”, the base station 300 updates the storage area 1300 with a value obtained by adding 1 to the number in the storage area 1300. . Then, the base station 300 searches the change destination channel table 1200 for the channel number again.

  For example, when the table number stored in the storage area 1300 is “4”, the base station 300 sets the table number in the storage area 1300 to “5” because the corresponding radar detection flag is “Yes”. Update. Then, the base station 300 determines “104CH”, which is the channel number corresponding to “5” of the table number, as the change destination channel. As a result, a channel within 30 minutes after the radar signal is detected can be prevented from being selected as a change destination channel.

(Operation of communication system)
FIG. 14 is a sequence diagram illustrating a first operation example of channel change in the communication system. FIG. 14 shows a channel change operation from the W53 / W56 band to the W52 band of the communication system 200. First, it is assumed that the base station 211 operates an access point on 100CH (step S1401). Further, it is assumed that the base station 221 operates an access point on 100CH (step S1402).

  Next, the base station 211 performs a survival confirmation process for the base station 221. Specifically, the base station 211 transmits a survival confirmation request signal to the base station 221 (step S1403). Next, the base station 221 transmits a survival confirmation response signal to the base station 211 (step S1404). The survival confirmation process in steps S1403 and S1404 is repeatedly executed.

  Next, the base station 221 performs a survival confirmation process for the base station 211. Specifically, the base station 221 transmits a survival confirmation request signal to the base station 211 (step S1405). Next, the base station 211 transmits a survival confirmation response signal to the base station 221 (step S1406). The survival confirmation process in steps S1405 and S1406 is repeatedly executed.

  Next, it is assumed that the base station 211 detects a radar signal (step S1407). Next, it is assumed that the base station 211 acquires the change destination channel table 1000 from the memory 322, and determines the change destination channel to 36CH based on the acquired change destination channel table 1000 (step S1408). Next, the base station 211 transmits a channel change notification signal indicating 36CH determined in step S1408 to the base station 221 (step S1409). Next, the base station 211 puts the access point into a non-operating state and changes the channel to 36CH (step S1410).

  The base station 211 transmits a survival confirmation request signal to the base station 221 after transmitting the channel change notification signal in step S1409 (step S1411). At this time, the channel of the base station 211 has been changed to 36CH, and the channel of the base station 221 remains 100CH. Therefore, the survival confirmation request signal transmitted in step S1411 is not received by the base station 221, and the survival confirmation response signal from the base station 221 to the base station 211 is not transmitted.

  Next, the base station 211 transmits the survival confirmation request signal to the base station 221 again (step S1412). The retransmission of the survival confirmation request signal in step S1412 is repeatedly performed until the survival confirmation response signal is transmitted from the base station 221. On the other hand, the base station 221 determines 36CH indicated by the channel change notification signal transmitted in step S1409 as a change destination channel (step S1413).

  Next, the base station 221 transmits a channel change notification signal indicating 36CH determined in step S1413 to the base station 211 (step S1414). At this time, the channel of the base station 211 has been changed to 36CH, and the channel of the base station 221 remains 100CH. Accordingly, the channel change notification signal transmitted in step S1414 is not received by the base station 211.

  Next, the base station 221 sets the access point to a non-operating state and changes the channel to 36CH (step S1415). Next, it is assumed that the base station 211 retransmits the survival confirmation request signal to the base station 221 for the nth time (step S1416). At this time, the channel of the base station 211 is changed to 36CH, and the channel of the base station 221 is also changed to 36CH. Accordingly, the channel change notification signal transmitted in step S1416 is received by the base station 221. In response to this, the base station 221 transmits a survival confirmation response signal to the base station 211 (step S1417).

  Next, since the survival confirmation response signal is transmitted from the base station 221, the base station 211 puts the access point into an operating state (step S <b> 1418). Next, the base station 221 transmits a survival confirmation request signal to the base station 211 (step S1419). Next, the base station 211 transmits a survival confirmation response signal to the base station 221 (step S1420). Next, since the survival confirmation response signal is transmitted from the base station 211, the base station 221 sets the access point in an operating state (step S1421), and ends a series of processing.

  Thereby, both the base stations 211 and 221 are in a state of using 36CH, and can resume mutual wireless communication. A period T11 in FIG. 14 indicates a period in which the channel of the base station 211 is set to 100CH. A period T12 in FIG. 14 indicates a period in which the channel of the base station 211 is set to 36CH. A period T21 in FIG. 14 indicates a period in which the channel of the base station 221 is set to 100CH. A period T22 in FIG. 14 indicates a period in which the channel of the base station 221 is set to 36CH.

  FIG. 15 is a sequence diagram illustrating an operation example 2 of channel change in the communication system. FIG. 15 shows a channel change operation from the W52 band to the W53 / W56 band of the communication system 200. First, it is assumed that the base station 211 operates an access point on 36CH (step S1501). Further, it is assumed that the base station 221 operates an access point on 36CH (step S1502).

  Next, it is assumed that the base station 211 acquires the change destination channel table 1200 from the nonvolatile memory 321 and determines the change destination channel to 104CH based on the acquired change destination channel table 1200 (step S1503). Next, the base station 211 transmits a channel change notification signal indicating 104CH determined in step S1503 to the base station 221 (step S1504). The channel change notification signal transmitted in step S1504 includes the change time to 104CH.

  Next, the base station 221 transmits ACK to the channel change notification signal transmitted in step S1504 to the base station 211 (step S1505). Next, the base station 221 determines whether or not the own station can use the 104CH indicated by the channel change notification signal transmitted in step S1504 (step S1506). Here, it is assumed that the base station 221 is determined to be able to use 104CH.

  Next, the base station 221 transmits a channel change OK signal to the base station 211 (step S1507). Next, the base station 211 transmits ACK to the channel change OK signal transmitted in step S1507 to the base station 221 (step S1508). Next, the base station 211 waits until the change time to 104CH (step S1509). Further, the base station 221 waits until the change time to 104CH (step S1510).

  Next, the base station 211 changes the access point to a non-operating state and changes the channel to 104CH (step S1511). In addition, the base station 221 sets the access point in a non-operating state and changes the channel to 104CH (step S1512). Next, the base station 211 performs a 1-minute radar detection process (step S1513). Further, the base station 221 performs a radar detection process for one minute (step S1514). Here, it is assumed that no radar signal is detected in steps S1513 and S1514.

  Next, the base station 211 transmits a survival confirmation request signal to the base station 221 (step S1515). At this time, the channels of the base stations 211 and 211 are both changed to 104CH. Therefore, the base stations 211 and 221 can transmit and receive signals to each other. Next, the base station 221 transmits a survival confirmation response signal to the base station 211 (step S1516). Next, since the survival confirmation response signal is transmitted from the base station 221, the base station 211 puts the access point into an operating state (step S 1517).

  Next, the base station 221 transmits a survival confirmation request signal to the base station 211 (step S1518). At this time, the channels of the base stations 211 and 221 are both changed to 104CH. Therefore, the base stations 211 and 221 can transmit and receive signals to each other. Next, the base station 211 transmits a survival confirmation response signal to the base station 221 (step S1519). Next, since the survival confirmation response signal is transmitted from the base station 211, the base station 221 sets the access point in an operating state (step S1520), and ends a series of processing.

  Thereby, both the base stations 211 and 221 are in a state of using the 104CH, and can resume mutual wireless communication. A period T11 in FIG. 15 indicates a period in which the channel of the base station 211 is set to 36CH. A period T12 in FIG. 15 indicates a period in which the channel of the base station 211 is set to 104CH. A period T21 in FIG. 15 indicates a period in which the channel of the base station 221 is set to 36CH. A period T22 in FIG. 15 indicates a period in which the channel of the base station 221 is set to 104CH.

  As described above, according to the communication system 100 according to the embodiment, when the specific priority radio wave is detected and the channel is changed, the opposite base station is notified by notifying the opposite base station in the WDS mode of the change destination channel. It is possible to change the following channels.

  In addition, by monitoring the existence of the opposite base station, whether it can communicate with the opposite base station is monitored, and if the communication becomes impossible, the channel is changed, so that even if the channel notification signal from the opposite base station cannot be received. It can be changed following the channel of the opposite base station. For this reason, the state in which base stations cannot communicate can be suppressed.

  For example, in the IEEE 802.11A standard, when communication is performed in the W53 and W56 bands in the WDS mode, even if radar is detected by DFS, a communication impossible state of 30 minutes does not occur, and the opposite base in the WDS mode. Wireless communication with the station can be continued. Also, considering the influence of 30 minutes of communication interruption, it is not necessary to design the network with only 4 channels of W52 band and avoid using W53 and W56 bands. It can be used effectively.

  As described above, according to the base station, the communication program, the communication method, and the communication system, it is possible to suppress a state incapable of communication. The following additional notes are disclosed with respect to the embodiment described above.

(Appendix 1) A communication unit that performs wireless communication with another base station through a channel of a specific frequency band in which a specific radio wave is preferentially assigned over the radio wave of the own station;
A detection unit for detecting the specific radio wave;
When the specific radio wave is detected by the detection unit, a selection unit that selects a channel to be changed from a frequency band different from the specific frequency band;
A transmission unit that transmits a notification signal indicating the channel to be changed selected by the selection unit to the other base station;
A change unit for changing a channel of wireless communication by the communication unit to the change destination channel;
A base station comprising:

(Supplementary Note 2) When the channel is changed by the changing unit, the communication unit transmits a request signal for requesting a response to the other base station through the change destination channel, and a response signal for the transmitted request signal The base station according to appendix 1, wherein data communication is started with the other base station via the channel of the change destination when the base station is received.

(Supplementary note 3) The base station according to Supplementary note 1 or 2, wherein the change unit changes the channel after the notification signal is transmitted by the transmission unit.

(Supplementary Note 4) The change unit changes the wireless communication channel to the specific frequency band when a predetermined condition is satisfied after changing the wireless communication channel to the change destination channel. The base station according to any one of Supplementary notes 1 to 3, which is characterized.

(Supplementary note 5) The base station according to supplementary note 4, wherein the changing unit changes the channel of the wireless communication to the specific frequency band when a predetermined time period comes.

(Additional remark 6) The said change part changes the channel of the said radio | wireless communication to the said specific frequency band, when the communication volume per fixed time of the said radio | wireless communication falls below predetermined value, The additional note 4 characterized by the above-mentioned. Base station.

(Supplementary note 7) The communication unit transmits a request signal for requesting a response to the other base station through a channel used for the wireless communication,
Any one of Supplementary notes 1 to 6, wherein the changing unit changes the channel of the wireless communication based on a reception result of a response signal from the other base station with respect to the request signal transmitted by the communication unit. The base station according to one.

(Appendix 8) The communication unit repeatedly transmits the request signal,
The change unit changes the wireless communication channel when the number of times the response signal is not received from the other base station within a certain period with respect to the request signal exceeds a threshold value. The base station according to 7.

(Supplementary note 9) The base station computer
A communication unit that performs wireless communication with other base stations through a channel of a specific frequency band in which a specific radio wave is preferentially assigned over the radio wave of its own station,
A detection unit for detecting the specific radio wave;
When the specific radio wave is detected by the detection unit, a selection unit that selects a change destination channel from a frequency band different from the specific frequency band,
A transmission unit that transmits a notification signal indicating the channel to be changed selected by the selection unit to the other base station;
A changing unit for changing a channel of wireless communication by the communication unit to the channel to be changed;
A communication program characterized by being operated as

(Supplementary Note 10) In the communication method by the first base station and the second base station that perform radio communication with each other through a channel of a specific frequency band in which a specific radio wave is preferentially assigned over the radio wave of the local station,
The first base station detecting the specific radio wave;
When the first base station detects the specific radio wave, selecting a change destination channel from a frequency band different from the specific frequency band;
The first base station transmitting a notification signal indicating the selected channel to be changed to the second base station;
The first base station changing the channel used by the local station for the wireless communication to the channel to be changed;
The second base station changes the channel used by the own station for the wireless communication to the channel to be changed indicated by the notification signal transmitted by the first base station;
A communication method comprising:

(Supplementary Note 11) In a communication system including a first base station and a second base station that perform radio communication with each other through a channel of a specific frequency band in which a specific radio wave is preferentially assigned over the radio wave of the local station,
When the specific radio wave is detected, a notification signal indicating a channel to be changed selected from a frequency band different from the specific frequency band is transmitted to the second base station, and the local station uses it for the wireless communication. A first base station that changes a channel to the change destination channel;
A second base station that changes the channel used by the own station for the wireless communication to the channel to be changed indicated by the notification signal transmitted by the first base station;
A communication system comprising:

11, 12, 212 to 214, 222 to 224 Mobile station 100, 200 Communication system 210, 220 Wireless LAN
211,221,300 Base station 1000,1200 Change destination channel table 1100,1300 Storage area

Claims (7)

A communication unit that performs wireless communication with another base station through a channel of a specific frequency band in which a specific radio wave is preferentially allocated over the radio wave of the local station;
A detection unit for detecting the specific radio wave;
When the specific radio wave is detected by the detection unit, a selection unit that selects a channel to be changed from a frequency band different from the specific frequency band;
A transmission unit that transmits a notification signal indicating the channel to be changed selected by the selection unit to the other base station;
A change unit for changing a channel of wireless communication by the communication unit to the change destination channel;
With
After the start of wireless communication with the other base station, the communication unit repeatedly transmits a request signal for requesting a response to the other base station through the channel used for the wireless communication, and the transmitted request signal When the number of times that the response signal is not received from the other base station within a certain period exceeds a threshold value, the processing for changing the channel used by the communication unit for the wireless communication is performed. A base station that repeats until it is received.   When the channel is changed by the changing unit, the communication unit transmits a request signal for requesting a response to the other base station through the channel to be changed, and receives a response signal for the transmitted request signal 2. The base station according to claim 1, wherein the base station starts data communication with the other base station via the channel to be changed.   The base station according to claim 1, wherein the changing unit changes the channel after the notification signal is transmitted by the transmitting unit.   The change unit changes the wireless communication channel to the specific frequency band when a predetermined condition is satisfied after changing the wireless communication channel to the change destination channel. Item 4. The base station according to any one of Items 1 to 3. In the base station computer,
Wireless communication is performed with other base stations via a channel of a specific frequency band in which a specific radio wave is preferentially assigned over the radio wave of your station.
Detecting the specific radio wave,
When the specific radio wave is detected, a channel to be changed is selected from a frequency band different from the specific frequency band,
Send a notification signal indicating the selected channel to be changed to the other base station,
Changing the channel of the wireless communication to the channel to be changed;
After the start of wireless communication with the other base station, a request signal for requesting a response to the other base station is repeatedly transmitted using the channel used for the wireless communication, and the request signal transmitted The process of changing the channel used by the base station for the wireless communication when the number of times the response signal is not received from another base station within a certain period exceeds a threshold value until the response signal is received. A communication program characterized by executing a repeated process. In the communication method by the first base station and the second base station that perform wireless communication with each other through a channel of a specific frequency band in which a specific radio wave is preferentially assigned over the radio wave of the local station,
The first base station detects the specific radio wave,
When the first base station detects the specific radio wave, the channel to be changed is selected from a frequency band different from the specific frequency band,
The first base station transmits a notification signal indicating the selected channel to be changed to the second base station,
The first base station changes the channel used by the own station for the wireless communication to the channel to be changed,
The second base station changes the channel used by the own station for the wireless communication to the channel to be changed indicated by the notification signal transmitted by the first base station,
After the first base station starts wireless communication with the second base station , the first base station repeatedly transmits a request signal requesting a response to the second base station through the channel used for the wireless communication, and transmits A process of changing the channel used by the base station for the wireless communication when the number of times the response signal is not received from the second base station within a certain period of time exceeds a threshold with respect to the request signal It repeats until it receives the said response signal, The communication method characterized by the above-mentioned. In a communication system including a first base station and a second base station that perform wireless communication with each other through a channel of a specific frequency band in which a specific radio wave is preferentially assigned over the radio wave of the local station,
When the specific radio wave is detected, a notification signal indicating a channel to be changed selected from a frequency band different from the specific frequency band is transmitted to the second base station, and the local station uses it for the wireless communication. A first base station that changes a channel to the change destination channel;
A second base station that changes the channel used by the own station for the wireless communication to the channel to be changed indicated by the notification signal transmitted by the first base station;
Including
The first base station repeatedly transmits a request signal for requesting a response to the second base station through a channel used for the wireless communication after the start of wireless communication with the second base station. A process of changing the channel used by the base station for the wireless communication when the number of times the response signal is not received from the second base station within a certain period of time exceeds a threshold with respect to the request signal A communication system, which repeats until the response signal is received.

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