JP6476526B2 - Wireless base station - Google Patents

Description

  The present invention relates to a radio base station that performs a suitable channel change in a radio communication system.

  In recent years, wireless base stations (hereinafter also referred to as wireless access points) that can perform wireless communication using two or more different frequency bands, such as 2.4 GHz band and 5 GHz band, have become widespread. When there are a plurality of wireless access points in the vicinity, a plurality of users may use channels of the same frequency band. In such a case, in the surrounding wireless communication, traffic quality is affected by a sudden increase in traffic. In particular, the 2.4 GHz band has prevailed earlier, and there is a possibility that there is more traffic than the 5 GHz band.

  However, since some frequency bands in the 5 GHz band are used for various radars and satellite communications, wireless access points that use these frequency bands avoid interference with various radars and satellite communications. Is required. For example, a wireless access point is required to perform DFS (Dynamic Frequency Selection) operation for changing a channel when various radar waves are detected. When using a channel, the wireless access point will determine whether or not "various radars will detect" for at least 1 minute (60 seconds), and if the conditions are bad (such as when the radar is detected again in the channel that moved) I have a problem that communication stops for a long time. Therefore, in using the 5 GHz band, the point is how to process the DFS without making the user aware of it.

  For example, in Patent Document 1, when one of two or more wireless LAN access points operating in a WDS (Wireless Distribution System) mode detects a radar wave in a frequency band, candidates for other frequency bands are listed. A technique is disclosed that notifies the other side, monitors radar waves in other frequency bands, and transmits beacons using other frequency bands if no radar waves are detected.

JP 2010-278825 A

  Here, in Patent Document 1, when DFS operates with one wireless LAN access point, it is urged to change to a channel that can communicate with the other wireless LAN access point communicating in the WDS mode, and between wireless LAN access points. Continue communication with. At this time, the wireless slave device connected to each wireless LAN access point can receive a channel change notification only from the wireless LAN access point to which the slave device is connected (for example, CSA (Channel Switch Announcement)). Such).

  However, the channel change notification in the WDS mode may not be supported. For example, a wireless slave unit communicates with a wireless LAN access point serving as a parent unit (route), and passes through a plurality of wireless LAN access points that operate in a repeater mode of WDS mode (relay data to be communicated as it is). Now consider the case where a network connection is established with the communication terminal of the communication destination. In this case, when a wireless LAN access point in the network operating in the repeater mode detects a radar, the wireless LAN access point that is the root is notified (notification that the wireless LAN access point in the network has detected the radar). After that, the wireless LAN access point serving as the root notifies other wireless LAN access points in the network of channel change or the like. However, if a wireless LAN access point that is newly connectable to the network joins the network, the root wireless LAN access point is not aware of the existence of the wireless LAN access point, so a channel change notification is made. Cannot be transmitted, and wireless communication in the network is interrupted.

  The present invention has been made to solve the above-described problem. In a network using a plurality of wireless access points, a part of the 5 GHz band (for example, W56) is used. It is an object of the present invention to allow wireless communication to continue even when operating, and to change the channel optimal for wireless communication independent of the operation mode of the wireless access point.

  In order to solve the above-described problem, a radio base station according to an aspect of the present invention is a radio base station in a radio communication system having a plurality of radio base stations and at least one radio terminal. A wireless communication unit that performs wireless communication with a wireless base station, and a monitoring unit that monitors whether a radar wave is present on a channel that is being used for wireless communication, and receives a notification of the result, When a notification indicating that a radar wave has been detected is received from the monitoring interface, the alternative channel is monitored by the monitoring interface and predetermined channel information temporarily used for maintaining wireless communication is notified to the channel setting unit. Before receiving the notification that the radar wave has been detected. If it is determined that it has received the notification, and a determination unit that notifies the channel information after change to the channel setting unit.

  According to this, when a wireless communication is performed using a certain frequency band (for example, W56, etc.) in the 5 GHz band in a network using a plurality of wireless base stations, it is wireless even if a radar wave is detected. Communication can be continued, and a channel change optimal for wireless communication independent of the operation mode of the wireless base station (for example, a mode in which radar is monitored) can be performed.

  Further, the channel information of the change destination is either information that is held in advance by itself or information included in a notification that a radar wave from another radio base station has been detected.

  As a result, even if a radar wave is detected not only on its own base station but also on a channel being used by another base station in the system, the base station of the entire system can change the channel to the channel to be changed.

  Further, when the channel setting unit receives either the notification that the radar wave is detected from the monitoring unit or the notification that the radar wave is detected from another radio base station, the channel setting unit determines the channel that detected the radar wave. Information including the channel to be changed is stored in a beacon frame, and is notified to the radio communication unit in order to notify other radio base stations.

  According to this, a radio base station that has received information including a channel in which a radar wave is detected and a channel to be changed from the beacon frame notification further notifies the plurality of radio base stations of the information notified in the beacon frame. Information is quickly transmitted to all the wireless base stations in the network.

  In addition, based on the notification that the radar wave is detected from the monitoring unit, a first count that counts the elapsed time after the time when the monitoring unit detects the radar wave on the channel being used, and the wireless communication unit And a second count that counts the time since the channel being used is switched to a predetermined channel.

  According to this, it is possible to determine whether or not the regulations for changing the channel from the time when each radio base station detects the radar wave and continuing the radio communication are satisfied. The specified condition is that when a radar wave is detected in a channel of 5 GHz band, it is necessary to change the channel quickly (for example, 10 seconds), and for a certain period of time, for example, 60 seconds after the channel is changed. For example, no radar wave is detected between the two.

  In addition, the radio base station further includes an information table in which channel information that can be used for a plurality of radio communications is stored with priorities, and the channels used in the system are used according to the priorities.

  According to this, by unifying in all the radio base stations in advance, the radio base station that has detected the radar wave is only informing that the radar wave has been detected, and without reporting the next channel candidate. The radio base stations can start the radar wave detection operation all at once.

  Furthermore, the channels stored in the information table are 5 GHz band channels, and the predetermined channels are channels in a frequency band different from 5 GHz.

  According to this, by using a channel of a frequency band different from 5 GHz for the purpose of maintaining wireless communication, even if each wireless base station is performing a radar wave detection operation, wireless communication between the wireless base stations is performed. Communication can be maintained.

  The wireless base station of the present invention can maintain wireless communication quality by performing appropriate channel change processing even in an environment where DFS operates when performing wireless communication with a plurality of other wireless base stations in the WDS mode. .

FIG. 1 is an overall view of a wireless communication system according to an embodiment. FIG. 2 is a hardware configuration diagram of the radio base station according to the embodiment. FIG. 3 is a functional block diagram of the radio base station according to the embodiment. FIG. 4 is an operation flow of the radio base station according to the embodiment. FIG. 5 is an example of a beacon frame notified by the radio base station according to the embodiment. FIG. 6 is a sequence diagram relating to communication between radio base stations in the radio communication system according to the embodiment.

  Numerical values, constituent elements, arrangement positions of constituent elements, and the like shown in the following embodiments are merely examples, and various modifications and changes can be made within the scope of the invention.

(Embodiment)
FIG. 1 is an overall view of a radio communication system according to an embodiment of the present invention.

  As illustrated in FIG. 1, the radio communication system 100 includes a plurality of radio base stations A1, A2 and A3, a radio terminal S1, and a communication terminal T1. The radio base stations A1, A2 and A3 are arranged such that radio communication is possible in the radio communication possible ranges C1 and C2, respectively, and the radio communication possible ranges partially overlap each other. The communication path R1 is a radio communication path between the radio base station A1 and the radio terminal S1, and the communication path R2 is a radio communication path between the radio base station A3 and the communication terminal T1.

  The wireless base stations A1, A2, and A3 may have both a wired communication interface and a wireless communication interface, or may have only a wireless communication interface.

  Further, since the wireless base stations A1, A2 and A3 overlap with each other in the wireless communicable ranges C1 and C2, communication between the wireless base stations can be performed by using the WDS.

  The wireless terminal S1 has a wireless communication interface, and is, for example, a notebook PC, a tablet, a smartphone, or the like. The wireless terminal S1 performs wireless communication with the wireless base station A1 through the communication path R1. Note that the wireless communication is realized by a wireless LAN conforming to, for example, the IEEE 802.11 standard.

  The communication terminal T1 has a wireless communication interface and is, for example, a notebook PC, a tablet, a smartphone, or the like. The communication terminal T1 performs wireless communication with the wireless base station A3 through the communication path R2. Note that the wireless communication is realized by a wireless LAN conforming to, for example, the IEEE 802.11 standard.

  With the above configuration, the wireless terminal S1 communicates directly with the wireless base station A1, and further performs wireless communication with the communication terminal T1 via the wireless base station A1 via W2 and A2 and A3. Is possible.

  FIG. 2 is a hardware configuration diagram of the radio base stations A1, A2 and A3 according to the embodiment of the present invention.

  As shown in FIG. 2, these devices include a CPU (Central Processing Unit) 20, a ROM (Read Only Memory) 21, a RAM (Random Access Memory) 22, a storage device 23, a WNIC (Wireless Network Interface IC) 24, and the like. A wireless network interface card (NIC) 25, a network interface card (NIC) 26, and an internal bus 27 that connects each component are provided. The NIC 26 is not an essential component.

  The CPU 20 is a processor that executes a control program stored in the ROM 21.

  The ROM 21 is a read-only storage area that holds a control program and the like.

  The RAM 22 is a storage area used as a work area used when the CPU 20 executes a control program.

  The storage device 23 is a storage area that holds a control program, control information, device information, authentication information, or the like.

  The WNIC 24 includes a wireless communication interface that performs wireless communication. For example, a wireless LAN communication interface conforming to the IEEE802.11a, b, g, n, and ac standards. As will be described later, the WNIC 24 is used as a communication interface for wireless communication or a monitoring interface for acquiring radio wave conditions around the wireless base stations A1, A2, and A3. The WNIC 24 operates independently of the WNIC 25.

  The WNIC 25 is a wireless communication interface having a hardware configuration similar to that of the WNIC 24, and is used for the same application as the WNIC 24. The WNIC 25 operates independently of the WNIC 24. It is a feature of the hardware of the present invention that a plurality of wireless communication interfaces are provided in one apparatus.

  The NIC 26 includes a wired communication interface that performs wired communication. For example, a wired LAN communication interface conforming to the IEEE 802.3 standard or the like.

  The internal bus 27 is a bus that electrically connects the CPU 20, ROM 21, RAM 22, storage device 23, WNIC 24, WNIC 25, and NIC 26 to exchange signals.

  FIG. 3 is a block diagram showing a functional configuration of the radio base stations A1 to A3 according to the embodiment of the present invention. In addition, although each function of radio base station A1 which concerns on embodiment of this invention is demonstrated below using FIG. 3, since other radio base stations A2 and A3 also have the same function, these details The detailed explanation is omitted.

  As shown in FIG. 3, the radio base station A1 includes a radio communication unit 30, a radio communication interface 31, a monitoring interface 32, a monitoring unit 33, an information table 34, a determination unit 35, a counting unit 36, and a channel setting unit 37. Etc.

  The wireless communication unit 30 is a processing unit that performs wireless communication with the wireless terminal S1 and other wireless base stations. Specifically, the wireless communication unit 30 establishes a wireless connection with the wireless terminal S1 and the wireless base station A2 through the wireless communication interface 31, and communicates between the communication terminal T1 and the wireless terminal S1 through the established wireless connection. Send and receive communication frames. The wireless communication unit 30 is realized by the CPU 20, RAM 21, ROM 22, storage device 23, and the like.

  The radio communication interface 31 is a radio interface that establishes and maintains communication with the radio terminal S1 and other radio base stations. The wireless communication interface 31 is realized by one or both of the WNIC 24 and the WNIC 25, and operates according to control by the wireless communication unit 30.

  The monitoring interface 32 is a processing unit that acquires the radio wave condition around the base station and notifies the monitoring unit 33 of the acquired radio wave condition. The monitoring interface 32 is realized by one or both of the WNIC 24 and the WNIC 25, and operates according to control by the monitoring unit 33.

  The monitoring unit 33 causes the monitoring interface 32 to detect whether or not a radar wave is present in the wireless communication range (C1) in order for the channels that can be used for wireless communication stored in the information table 34. Specifically, the monitoring interface 32 sequentially scans each channel (channel stored in a white list described later) that can be used for wireless communication stored in the information table 34 as time passes, To monitor. For example, if the monitoring interface 32 detects a radar wave in one of the channels (for example, 100 ch) that can be used for wireless communication, the monitoring interface 32 notifies the information table 34 that the radar wave has been detected. The radar wave is monitored in the same manner in the stored channel (for example, 104 ch) that can be used for the next order wireless communication. If a radar wave is not detected after a lapse of a predetermined time, the system changes the channel to be used from the evacuation communication channel to this channel (104ch), but if a radar wave is detected, it is stored in the information table 34 thereafter. It is monitored whether or not radar waves are detected in order for channels that can be used for wireless communication. The monitoring unit 33 is realized by the CPU 20, RAM 21, ROM 22, storage device 23, and the like.

  The information table 34 is a table (hereinafter also referred to as a white list) in which 5 GHz band channels that can be used for wireless communication are stored in advance. The plurality of channels in the table are stored in order. The order may be determined based on the magnitude of the frequency, or may be determined based on experience of the traffic congestion degree of the channel. Further, the information table 34 also holds a channel (hereinafter also referred to as an evacuation communication channel) that is temporarily used for maintaining wireless communication with WDS without interruption. The information table 34 is realized by the ROM 22, the storage device 23, and the like.

  The determination unit 35 determines whether a channel change notification (specifically, a beacon frame) is received from another wireless base station via the wireless communication interface 31.

Further, the determination unit 35 acquires the channel information and the evacuation communication channel from which the other radio base station has detected the radar wave from the received beacon frame, and notifies the channel setting unit 37 of the channel information.
Further, the determination unit 35 determines whether or not the numerical value counted by the counting unit 36 exceeds a predetermined numerical value (for example, 5 seconds). The determination unit 35 is realized by the CPU 20, RAM 21, ROM 22, storage device 23, and the like.

  The counting unit 36 counts the time from when the notification is received based on the notification that the monitoring unit 33 detects the radar wave. Specifically, the count unit 36 uses a first count (details will be described later) that starts counting from when a radar wave is detected on the channel (first channel) that was used first, and an evacuation communication channel. Switching is performed, and a second count (details will be described later) for starting the radar wave monitoring in the next channel candidate is executed. The count unit 36 is realized by the CPU 20, the RAM 21, the ROM 22, the storage device 23, and the like.

  The channel setting unit 37 stores the communication channel for evacuation (for example, 11ch) and the channel for detecting the radar wave (for example, 100ch) in a beacon frame, triggered by the notification from the monitoring unit 33 that the radar wave has been detected. The wireless communication unit 30 is notified. Further, the channel setting unit 37 stores a new 5 GHz band channel (for example, 104 ch) selected and determined as a next channel candidate from the white list and a channel (for example, 100 ch) detected by the radar wave in a beacon frame, and stores the radio communication unit 30. Notify The channel setting unit 37 is realized by the CPU 20, RAM 21, ROM 22, storage device 23, and the like.

  Next, the operation flow of the radio base station according to the embodiment of the present invention will be described in order with reference to FIG.

  FIG. 4 illustrates an operation in the embodiment of the present invention. As an example, the radio base station A2 detects a radar wave while the radio terminal S1 is communicating with the communication terminal T1 via the radio base stations A1 to A3. FIG. 5 is a flowchart until wireless communication is continued using a new channel capable of wireless communication in the network.

  In step S401, the monitoring interface 32 of the radio base station A2 monitors the first channel stored in advance in the information table 34 and notifies the monitoring unit 33 of the monitoring status. The monitoring unit 33 determines whether a radar wave is detected based on the notification from the monitoring interface 32. If detected, the process proceeds to step S404 (Yes in step S401). If not detected, the process proceeds to step S402 (No in step S401).

  In step S402, the determination unit 35 determines whether a channel change notification (specifically, a beacon frame) is received from another wireless base station via the wireless communication interface 31. If received, the process proceeds to step S403 (Yes in step S402). If not received, step S401 is repeated (No in step S402).

  In step S403, the determination unit 35 acquires channel information (for example, 100ch) and a evacuation communication channel (for example, 11ch) from which other radio base stations have detected radar waves from the received beacon frame, and a channel setting unit 37. Notify The channel setting unit 37 notifies the wireless communication unit 30 that the wireless communication is continued using the evacuation communication channel.

  In step S404, the monitoring unit 33 notifies the channel setting unit 37 of the evacuation communication channel (for example, 11ch) and the channel (for example, 100ch) from which the radar wave is detected based on the detection of the radar wave. The count unit 36 is also notified that a radar wave has been detected. In addition, the channel setting unit 37 stores the channel information for detecting the evacuation communication channel and the radar wave in a beacon frame and notifies the wireless communication unit 30 of the information. Further, the wireless communication unit 30 notifies the other wireless base stations of this via the wireless communication interface 31, and then proceeds to step S405.

  In step S405, the count unit 36 starts the first count based on the notification that the monitoring unit 33 detects the radar wave. Here, the first count is a time when the monitoring unit 33 sets a detection time when the radar wave is detected on the first channel, and counts an elapsed time thereafter.

  In step S406, the determination unit 35 determines whether or not the numerical value of the first count in the counting unit 36 exceeds a predetermined numerical value (for example, 5 seconds). If the numerical value is exceeded, the process proceeds to step S407 (Yes in step S406). If the numerical value is not exceeded, step S406 is repeated (No in step S406). Here, waiting for the elapse of a predetermined time is sent to all wireless base stations in the network that the communication channel for evacuation is changed, and is also evacuated to the wireless slave devices connected to the wireless base stations. By setting a sufficient time for the notification of the communication channel change to pass through, the wireless slave devices connected to all the wireless base stations in the network use the evacuation communication channel at the same time and perform wireless communication. To be able to do that.

  In step S407, based on the notification from the determination unit 35, the wireless communication unit 30 switches the use channel to the evacuation communication channel and continues wireless communication via the wireless communication interface 31. (By step S404, the other radio base stations are switched to the evacuation communication channel almost simultaneously.)

  In step S408, based on the notification from the monitoring unit 33 in step 407, the count unit 36 starts the second count. Here, the second count is a time counted after the wireless communication unit 30 switches the use channel to the save communication channel.

  In step S409, the monitoring interface 32 of the radio base station A2 monitors the next channel (second channel) stored in advance in the information table 34, and notifies the monitoring unit 33 of the monitoring status. This is a preparatory operation from the evacuation communication channel to switching to a new channel (second channel) stored as a white list. The monitoring unit 33 determines whether a radar wave is detected based on the notification from the monitoring interface 32. If detected, the process proceeds to step S411 (Yes in step S409). If not detected, the process proceeds to step S410 (No in step S409).

  In step S410, the determination unit 35 determines whether a channel change notification (specifically, a beacon frame) is received from another wireless base station via the wireless communication interface 31. If received, step S408 is repeated (Yes in step S410). If not received, the process proceeds to step S412 (No in step S410).

  In step S411, the monitoring unit 33 notifies the channel setting unit 37 of the evacuation communication channel (for example, 11ch) and the channel (for example, 104ch) from which the radar wave is detected based on the detection of the radar wave. The count unit 36 is also notified that a radar wave has been detected. In addition, the channel setting unit 37 stores the channel information for detecting the evacuation communication channel and the radar wave in a beacon frame and notifies the wireless communication unit 30 of the information. Furthermore, after notifying this to other radio base stations via the radio communication interface 31, the radio communication unit 30 proceeds to step S408 and repeats the process.

  In step S412, the determination unit 35 determines whether or not the numerical value (second count) counted by the counting unit 36 exceeds a predetermined numerical value (for example, 60 seconds). When the numerical value is not exceeded, it returns to step S409 and repeats (No of step S412). If the numerical value is exceeded, the process proceeds to step S413 (Yes in step S412). That is, since no radio base station has detected a radar wave within a predetermined count value, the channel used is switched from the evacuation communication channel to a new channel in the white list.

  In step S413, based on the notification from the determination unit 35, the wireless communication unit 30 switches the use channel from the evacuation communication channel to the second channel, and continues wireless communication via the wireless communication interface 31.

  According to the above flow, when a radar signal is detected on the communication channel (first channel) that was used first, the communication is temporarily switched to the evacuation communication channel, but then stored in the whitelist from the evacuation communication channel. The channel is switched to a new communication channel (second channel) in which no radar signal is detected. The switching of these channels is notified from the radio base station that has detected the radar wave to other radio base stations that are communicating with each other by WDS, and the WDS communication is maintained by switching the channels at substantially the same time. .

  When the radar signal is detected also in the second channel thus switched, the channel is switched to a new channel in the same manner as the flow described above.

  Next, a beacon frame according to an embodiment of the present invention will be described with reference to FIG.

  The beacon frame shown in FIG. 5 stores necessary unique information so that the configuration of the beacon frame conventionally used in wireless communication can be applied to the wireless communication system according to the embodiment of the present invention. .

  A conventional beacon frame is one in which a radio base station periodically broadcasts (for example, every 100 milliseconds) to surrounding radio base stations and terminals (in infrastructure mode), and a normal beacon frame arrives. It can be said that the range is a radio communicable range of the radio base station. Therefore, in the radio communication system (see FIG. 1) according to the embodiment of the present invention, the beacon frame according to the embodiment of the present invention can be transmitted and received between the radio base stations A1, A2 and A3.

  Here, information necessary for wireless communication is stored in the conventional beacon frame. For example, device information (such as an address) of a wireless base station, SSID (Service Set Identifier), a transmission rate supported by the wireless base station, a security method, and the like are stored. In addition to such information, various information can be optionally stored.

  The unique information stored in the beacon frame according to the embodiment of the present invention will be described below in order with reference to FIG.

  FIG. 5 shows a beacon frame 500 according to an embodiment of the present invention.

An area 501 is an area that can be uniquely set by an apparatus manufacturer as an option.
For example, “information indicating the manufacturer”, “evacuation communication channel”, “first channel information”, and the like are stored. The evacuation communication channel is a communication channel temporarily used so that wireless communication can be continuously performed in the wireless communication system according to the embodiment of the present invention. Further, the first channel information and the like are information on a channel for which a radar wave is detected by the monitoring unit 33, and the detected channel information is sequentially stored in a beacon frame.

  An area 502 is an area that can be set independently by an equipment manufacturer or the like as an option, as in the case of the area 501. A frame in region 502 is a frame that is transmitted only when a radar wave is detected by itself or a notification that a radar wave is detected is received from another base station.

  An area 503 shows details such as the first channel information. Specifically, the area 503 stores the channel number in which the radar wave is detected and the remaining time until the detected channel becomes usable.

  An area 504 is a channel number (second channel number) scheduled to be used next to the first channel based on the priority order stored in the white list of the information table 34 after the monitoring unit 33 detects the radar wave on the first channel. Candidate).

  The area 505 stores the remaining time until the wireless base station that transmitted the beacon frame uses the second channel and wireless communication becomes possible.

  Area 506 stores the identifier of the radio base station that has detected the radar wave in the first channel (the radio base station that is transmitting this beacon frame). The identifier is, for example, a MAC address.

  With reference to FIG. 6, the sequence diagram of each radio base station in the radio communication system according to the embodiment of the present invention will be described in order.

  FIG. 6 shows a network after the radio base station A2 (repeater) detects a radar wave during radio communication with the communication terminal T1 using the first channel via the radio base stations A1 to A3. Devices (wireless base stations A1 to A3, wireless terminal S1, and communication terminal T1) in the wireless communication system are optimal using new channels (second channel to third channel) that can be wirelessly communicated FIG. 6 is a sequence diagram for changing all at once in a channel and continuing wireless communication.

  In FIG. 6 (1), when a radar wave is detected on the first channel by the monitoring unit 33 of the radio base station A2, the radar wave channel (first channel) detected by the radio base station A1 and the radio base station A3 is preliminarily determined. The set communication channel for evacuation (for example, 11ch) is stored in a beacon frame and notified, and after a predetermined time has elapsed (for example, 5 seconds), the process proceeds to FIG. Here, the reason for making the transition to FIG. 6 (2) after a predetermined time elapses is that all devices in the wireless communication system (wireless base stations A1 to A3, wireless terminal S1, communication terminal T1, etc.) are notified of beacons. This is to obtain a preparation period for receiving the frame and transitioning to the operation of FIG.

  In FIG. 6 (2), the radio base station A1 and the radio base station A3 use the evacuation communication channel stored in the beacon frame from the radio base station A2 via the radio communication interface 31 to Continue wireless communication. That is, in order to continue the wireless communication, the wireless communication unit 30 of the wireless base stations A1 to A3 wirelessly changes from the first channel (for example, 100ch) used for the wireless communication to the evacuation communication channel. Communication can be continued. Here, the evacuation communication channel is, for example, 11ch used in the 2.4 GHz band not affected by DFS. In this way, wireless communication can be continued even while the DFS is operating.

  In FIG. 6 (2), the monitoring unit 33 of the radio base stations A 1 to A 3 receives the channel that is prioritized next to the first channel stored in the white list of the information table 34 via the monitoring interface 32 ( Radar wave monitoring is started on the second channel (for example, 104 ch). Here, the determination unit 35 determines whether or not a CAC (Channel Availability Check) period required in the DFS operation has elapsed. This CAC period is a period required by the wireless standard (IEEE802.11h) to pre-check whether or not a radar wave exists in the channel to be used.

  In FIG. 6 (3), when the monitoring unit 33 of the radio base station A3 detects a radar wave within a predetermined time (CAC period) (for example, 60 seconds) on the second channel, the channel of the detected radar wave (First channel and second channel candidate) and a preset communication channel for evacuation (for example, 11ch) are stored in a beacon frame and notified to the radio base station A1 and the radio base station A2, and a predetermined time has elapsed. After (for example, 5 seconds), the process proceeds to FIG. In this way, the radio base station A1 and the radio base station A2 cannot use these (first channel and second channel candidates) during the DFS operation because the radar wave is detected by the first channel and the second channel candidate. Recognize that.

  In FIG. 6 (3), as in FIG. 6 (2), the radio base stations A 1 to A 3 use the save communication channel stored in the beacon frame from the radio base station A 2 via the radio communication interface 31. Use to continue wireless communication within the wireless communication system.

  In FIG. 6 (4), the monitoring unit 33 of the radio base stations A1 to A3 receives the third channel candidate prioritized next to the second channel stored in the white list of the information table 34 via the monitoring interface 32. The radar wave monitoring is started at (for example, 108 ch). Then, when the monitoring unit 33 of the radio base stations A1 to A3 does not detect a radar wave within a predetermined time (for example, 60 seconds) on the third channel candidate, the process transits to FIG. 6 (5). Here, as in FIG. 6B, the determination unit 35 determines whether or not a CAC (Channel Availability Check) period obtained by the DFS operation has elapsed.

  In FIG. 6 (5), since the monitoring unit 33 of the radio base stations A1 to A3 did not detect the radar wave on the third channel candidate in the CAC period in FIG. 6 (4), the radio base stations A1 to A3. The wireless communication unit 30 changes the channel used for wireless communication in the wireless communication system from the evacuation communication channel (11ch) to the third channel candidate 108ch, and continues the wireless communication. In this way, the channels stored in the white list of the information table 34 of the radio base stations A1 to A3 are changed in order of preset priority, and the radar operation is not detected by the monitoring unit 33 and the DFS operation occurs. Select a channel while repeating monitoring until a wireless environment is established.

  As described above, when radio communication is performed between the radio base stations A1 to A3 using each channel (for example, 100ch) stored in the white list, a radar wave is detected, and the radio base station A1 Even when A3 is in the DFS operation, the wireless communication can be continued using the evacuation communication channel for the wireless communication. That is, as shown in FIG. 6, from the time when the radar wave is detected on the first channel in FIG. 6 (2) until the wireless communication of the wireless base stations A1 to A3 is performed on the third channel in FIG. 6 (5). By setting the communication channel as the communication channel and continuing the wireless communication in the network, the wireless communication between the wireless terminal S1 and the communication terminal T1 can be continued without interruption (minimum no communication period).

(Other embodiments)
In the embodiment of the present invention, the evacuation communication channel is set to one channel in advance, and all the base stations in the system may recognize this, or a plurality of evacuation channels are provided in advance. In this case, each time a radar wave is detected, the detected base station may decide the evacuation communication channel and notify the other base station. In the former case, communication between base stations can be simplified. On the other hand, if a plurality of evacuation communication channels are provided as in the latter case, it is possible to select a channel with a lower congestion level and perform higher quality communication.

  Also, the order of the 5 GHz band channels in the white list is made uniform for all base stations in advance, so that the base station that has detected the radar wave can report the next channel candidate only by reporting that the radar wave has been detected. Each base station can start the radar wave detection operation all at once without notifying of the above.

  In wireless communication performed using a plurality of wireless base stations, it is useful when it is desired to continue wireless communication even if a prescribed operation that requires a wireless base station defined by a wireless communication standard occurs.

100 wireless communication system A1, A2, A3 wireless base station S1 wireless terminal T1 communication terminal C1, C2, C3 wireless communication possible range 20 CPU
21 ROM
22 RAM
23 Storage device 24, 25 WINC
26 NIC
27 Internal Bus 30 Wireless Communication Unit 31 Wireless Communication Interface 32 Monitoring Interface 33 Monitoring Unit 34 Information Table 35 Judgment Unit 36 Count Unit 37 Channel Setting Unit

Claims (6)

A radio base station in a radio communication system having a plurality of radio base stations and at least one radio terminal,
A wireless communication unit for performing wireless communication with the wireless terminal and other wireless base stations;
An information table storing channel information that can be used for a plurality of wireless communications; and
A monitoring unit that monitors a monitoring interface whether a radar wave is present on a channel that is being used for wireless communication, and receives a result notification;
When a notification that a radar wave has been detected is received from the monitoring interface, the monitoring interface is used to monitor a channel that can be used for wireless communication in the information table and is temporarily used for maintaining wireless communication. A monitoring unit for notifying the channel setting unit of a predetermined channel;
The notification of the detected radar wave on the channel in said use from the other radio base station for a predetermined time to determine whether it has received through the channel in the use, that detects a radar wave A determination unit that notifies the channel setting unit of the channel that has detected the radar wave and a predetermined channel that is temporarily used for maintaining wireless communication ,
A wireless base station comprising:
The predetermined channel that is temporarily used for maintaining the wireless communication is either information held in advance by itself or information included in a notification that a radar wave from the other wireless base station has been detected. The radio base station according to claim 1.
The channel setting unit, when receiving either the effect that detects radar waves notification or the other notification that detects radar waves from the radio base station from the monitoring unit, the channel having detected the radar wave And information including a predetermined channel temporarily used for maintaining the wireless communication is stored in a beacon frame and notified to the wireless communication unit to notify other wireless base stations,
The radio base station according to claim 1.
Based on the notification that radar waves are detected from the monitoring unit,
A first count for counting an elapsed time after the time when the monitoring unit detects a radar wave on the channel in use;
A second count that counts the time since the channel that the wireless communication unit is using is switched to a predetermined channel that is temporarily used to maintain the wireless communication ;
The radio base station according to claim 1, further comprising a counting unit that executes
Said information table, the wireless communications to the available channels are stored are designated in advance priorities,
The channel used in the wireless communication system is used according to the priority.
The radio base station according to claim 1.
The channel that can be used for the wireless communication stored in the information table is a channel of 5 GHz band, and the predetermined channel that is temporarily used for maintaining the wireless communication is a channel of a frequency band different from 5 GHz.
The radio base station according to claim 1.