JP7108473B2 - Wireless communication method and wireless communication system - Google Patents

Description

The present invention relates to a method and system for transmitting radio signals in a frequency hopping manner.

A wireless LAN (Local Area Network) transmits data using a frequency channel designated from among a plurality of frequency channels prepared in advance. Here, for example, when a weather radar signal is detected on a frequency channel in use, the wireless LAN access point stops signal transmission on that frequency channel and selects another frequency channel. That is, the frequency channel is switched by DFS (Dynamic Frequency Selection).

However, depending on the frequency band, in order to use a new frequency channel, it is required that no weather radar signal has been detected on that frequency channel in the past one minute. Therefore, an access point that has detected a weather radar signal performs CAC (Channel Availability Check) for one minute on the frequency channel to which it is switched. That is, this access point cannot perform data communication until CAC ends.

This problem could be solved, for example, if the access points constantly monitored weather radar signals. In this case, the access point can pre-detect frequency channels on which no weather radar signals have been detected in the past minute. Therefore, if DFS selects a frequency channel on which no weather radar signal has been detected in the past minute, the access point can resume data communication on the new frequency channel without waiting for CAC.

As a related technology, a wireless LAN communication device has been proposed that creates a list of channels for which no radar wave has been detected, determines a channel for communication based on the created channel list, and starts communication (for example, , see Patent Document 1).

JP 2017-169028 A

According to the method described above (where the access point constantly monitors weather radar signals), the access point can resume data communication on the new frequency channel without waiting for CAC. However, since the terminal device does not recognize the switching of the frequency channel by the access point, it cannot detect the beacon signal transmitted from the access point. Therefore, when the access point switches the frequency channel, the terminal device disconnects the connection with the access point (for example, IEEE (The Institute of Electrical and Electronics Engineers) 802.11 connection), and then , scans all frequency channels to search for connectable access points. Further, an authentication procedure and a connection procedure are performed between the terminal device and the new access point. Therefore, it may take several seconds to several tens of seconds until the reconnection is completed.

An object of one aspect of the present invention is to provide a wireless network that transmits data using a plurality of frequency channels, and when a frequency channel in use becomes unavailable, another frequency channel can be used without disconnecting communication. is to allow switching to

According to one aspect of the present invention, there is provided a wireless communication method in which a plurality of communication devices communicate in a frequency hopping manner, and based on notifications received from the plurality of communication devices, a plurality of pre-designated available Use candidate frequency channels are determined as use candidates among the frequency channels, a predetermined number of use frequency channels to be used by the plurality of communication devices are determined from the use candidate frequency channels, and the use of the predetermined number of use frequency channels is determined. When the frequency channel is updated, the plurality of communication devices are notified of control information including information representing the updated used frequency channel and information representing timing to start communication using the updated used frequency channel. Each communication device uses the first wireless device to perform communication in a frequency hopping manner according to the control information, and uses the second wireless device to select one of the plurality of available frequency channels specified in advance. At least some of the conditions are measured and the results of the measurements by the second wireless device are communicated to an apparatus for determining the candidate frequency channels for use.

According to the above aspect, in a wireless network that transmits data using a plurality of frequency channels, when a frequency channel in use becomes unavailable, switching to another frequency channel is possible without disconnecting communication. It is possible.

1 is a diagram showing an example of a wireless communication system according to an embodiment of the present invention; FIG. It is a figure which shows an example of the communication control apparatus and central station which concern on embodiment of this invention. 1 is a diagram showing an example of a relay station and terminals according to an embodiment of the present invention; FIG. FIG. 4 is a diagram illustrating an example of a method of managing frequency channels; FIG. 4 is a diagram showing an outline of processing for performing communication using the frequency hopping method; FIG. 4 is a diagram showing an example of interference detected at each access point; FIG. 4 is a diagram showing an example of timing at which basic information (BEACON) is transmitted from a central station to a relay station; 4 is a sequence chart showing an example of CH list update processing performed in a wireless communication system; 8 is a flowchart illustrating an example of DFS list update processing; FIG. 11 is a flowchart showing an example of NF list update processing; FIG. 4 is a flowchart showing an example of communication control processing performed by a communication control device and a central station; FIG. 11 is a flow chart showing an example of RRPT notification processing performed at the central station; FIG. FIG. 11 is a flow chart showing an example of SRPT notification processing performed at the central station; FIG. 4 is a flow chart showing an example of communication control processing performed in a relay station; 4 is a flow chart showing an example of frequency channel update processing performed in a relay station;

FIG. 1 is a diagram showing an example of a wireless communication system according to an embodiment of the invention. As shown in FIG. 1, the wireless communication system 1 of the embodiment includes a communication control device 10, an aggregation station 20, n relay stations 30 (30-1 to 30-n), m terminals 40 (40-1 ~40-m). The central station 20 is installed between the n relay stations 30-1 to 30-n and the communication control device 10, and can operate as a gateway.

The communication control device 10 and the central station 20 are connected so as to be able to communicate with each other. However, the functions of the communication control device 10 may be implemented in the central station 20 . Relay stations 30-1 to 30-n can transmit and receive radio signals to and from other relay stations. That is, relay stations 30-1 to 30-n can operate as respective nodes of a multihop network (hereinafter referred to as "multihop nodes"). Also, the relay stations 30-1 to 30-n can accommodate one or a plurality of terminals 40, and can operate as wireless access points. That is, the relay stations 30-1 to 30-n receive uplink signals output from the terminals 40 and transmit downlink signals to the terminals 40. FIG. Each relay station 30-1 to 30-n is assigned a unique MAC address. Hereinafter, the relay stations 30-1 to 30-n will be referred to as "relay stations 30" unless otherwise distinguished. In addition, the terminals 40-1 to 40-m are referred to as "terminals 40" unless otherwise distinguished. Note that the communication control device 10 and the central station 20 may be wired or wirelessly connected.

The communication control device 10 controls communications of the central station 20 , the relay station 30 and the terminal 40 . Aggregation station 20, relay station 30, and terminal 40 transmit packets while switching frequency channels according to a designated hopping pattern. In frequency hopping, for example, channels are switched at intervals of 100ms.

The central station 20 and the relay station 30 of this embodiment correspond to the communication device of the present invention. Hereinafter, the aggregation station 20 and the relay station 30 will be referred to as "access point AP" unless otherwise distinguished.

2 and 3 are diagrams showing examples of the communication control device 10, central station 20, relay station 30, and terminal 40 according to the embodiment of the present invention.

The communication control device 10 has an interface (IF) 11 , a channel control section 12 and a memory 17 . The memory 17 stores an available channel list 51, a DFS list 52, an NF list 53, a use candidate channel list 54 and a use channel list 55. FIG. Note that the communication control device 10 may have other functions not shown in FIG. The memory 17 may also store other information not shown in FIG. The usable channel list 51, the DFS list 52, the NF list 53, the use candidate channel list 54, and the use channel list 55 will be described later.

An interface (IF) 11 receives measurement results measured by the central station 20 , relay station 30 and terminal 40 . The measurement results are, for example, a radar detection report (RRPT) transmitted from the central station 20 or the relay station 30, a statistical information report (SRPT), a CAC response (CAC-ACK), a statistical information report (SRPT ) etc. The measurement results transmitted from the central station 20, the relay station 30, and the terminal 40 are stored in the memory 17. FIG.

The channel control unit 12 creates a usable channel list 51 as shown in FIG. A use candidate channel list 54 shown in FIG. Then, from the use candidate channel list 54, a use channel list 55 shown in FIG. A method for determining the use candidate channel list 54 and the use channel list 55 will be described later.

The notification received from the aggregation station 20 or the relay station 30 includes channel measurement results measured by the second wireless devices 22b, 32b of the aggregation station 20 or the relay station 30, which will be described later. The channel measurement results measured at the aggregation station 20 and the relay station 30 include radar detection reports (RRPT), statistical information reports (SRPT), CAC responses (CAC-ACK), and the like.

A radar detection report (RRPT) is information transmitted from the central station 20 or the relay station 30 to the communication control device 10 . A radar detection report (RRPT) contains information on the channel on which radar was detected. A statistical information report (SRPT) is information transmitted from the central station 20 , relay station 30 or terminal 40 to the communication control device 10 . The statistical information report (SRPT) includes information on the noise floor (NF: noise floor) for each channel and information on the channel usage rate for each channel. The CAC response (CAC-ACK) contains information on radar detection results for each channel.

Further, the channel control unit 12 determines a predetermined number of frequency channels to be used by the access point AP from the use candidate channel list 54 shown in FIG. In this case, it is preferable that the channel control unit 12 define frequency channels while avoiding channels that are targets of channel bonding. Moreover, it is preferable that the channel control unit 12 equally determine frequency channels from different frequency bands 5.2 GHz band (W52), 5.3 GHz band (W53), and 5.6 GHz band (W56). For example, the channel control unit 12 selects frequency channels to be used from the candidate channels to be used in the candidate channel list 54 shown in FIG. In this case, the channel control unit 12 determines one frequency channel to be used from one frequency band, avoiding simultaneous selection of channels to be subjected to channel bonding. After determining one frequency channel to be used, the channel control unit 12 similarly determines one frequency channel to be used from other frequency bands. In this manner, the channel control unit 12 selects one use frequency channel from all frequency bands.

Specifically, a case where the channel control unit 12 defines three frequency channels will be described. In this case, the channel control unit 12 determines one frequency channel from each of the 5.2 GHz band (W52), the 5.3 GHz band (W53), and the 5.6 GHz band (W56). This can prevent bias toward a specific frequency band. For example, the channel control unit 12 selects the 36CH frequency channel from the 5.2 GHz frequency band (W52), as shown in the used channel list of FIG. , 52CH frequency channel is selected, and 100CH frequency channel is selected from the frequency band 5.6 GHz band (W56). As shown in FIG. 4A, the selected frequency channels 36CH, 52CH, and 100CH are channels that are not subject to channel bonding and belong to different frequency bands.

The interface (IF) 11 transmits control information (BEACON_SET) to the central station 20 when a predetermined number of frequency channels are updated. The control information (BEACON_SET) transmitted by the interface (IF) 11 includes information on the initial value of an update timer that counts the timing of starting communication using the updated frequency channel. Details of the process of starting communication on the updated frequency channel will be described later. Also, the interface (IF) 11 transmits CAC-IND to the central station 20 at predetermined intervals. CAC-IND is a command that instructs the central station 20 and relay station 30 to implement CAC.

The aggregation station 20 includes an interface (IF) 21, a first wireless device 22a, a second wireless device 22b, a notification unit 24, an update timing setting unit 25, and a use channel setting unit . Note that the central station 20 may have other functions not shown in FIG.

In addition, the interface (IF) 21 is a radar detection report (RRPT) including the DFS detection results detected by the CAC unit 61a and the CAC unit 61b, and the noise for each channel measured by the NF measurement unit 62b and the CH usage rate measurement unit 63b. It notifies the communication control unit 10 of a statistical information report (SRPT) including level and channel usage rate information for each channel.

The first radio device 22a includes a CAC unit 61a, an NF measurement unit 62a, and a CH usage rate measurement unit 63a. Note that the first wireless device 22a may have other functions not shown in FIG.

Upon receiving CAC-IND from the communication control device 10, the CAC unit 61a performs CAC to check whether there is radar in the frequency channel currently being used by the first radio device 22a. The first radio device 22a stops the frequency channel on which the radar is detected by the CAC unit 61a.

The NF measurement unit 62a measures the noise level of the frequency channel currently used by the first radio device 22a. The CH usage rate measurement unit 63a measures the usage rate of the currently used frequency channel. The noise level measurement by the NF measurement unit 62a and the usage rate measurement by the CH usage rate measurement section 63a will be described later.

The second radio device 22b includes a CAC unit 61b, an NF measurement unit 62b, and a CH usage rate measurement unit 63b. Note that the second wireless device 22b may have other functions not shown in FIG.

The CAC section 61b is substantially the same as the CAC section 61a of the first wireless device 22a. However, the CAC unit 61b of the second radio device 22b has a CAC that checks whether radar is detected in a frequency channel to be updated other than the currently used frequency channel, in addition to the currently used frequency channel. implement.

The NF measurement section 62b is substantially the same as the NF measurement section 62a of the first wireless device 22a. However, the NF measurement unit 62b of the second wireless device 22b measures the noise level of the frequency channel to be updated other than the currently used frequency channel, in addition to the currently used frequency channel.

The CH usage rate measurement unit 63b is substantially the same as the CH usage rate measurement unit 63a of the first wireless device 22a. However, the CH usage rate measurement unit 63b of the second wireless device 22b measures the usage rates of frequency channels to be updated other than the currently used frequency channel in addition to the currently used frequency channel.

Based on the control information (BEACON_SET) transmitted from the communication control device 10, the update timing setting unit 25 sets the timing for starting communication using the updated frequency channel. Specifically, based on the initial value of the update timer included in the control information (BEACON_SET) transmitted from the communication control device 10, the update timing setting unit 25 sets the timing for starting communication using the updated frequency channel. set.

The used channel setting unit 26 sets the control information (BEACON_SET ) to set the frequency channel to be used for frequency hopping. The first wireless device 22 a communicates with the relay station 30 and/or the terminal 40 at the timing set by the update timing setting section 25 using the frequency channel set by the use channel setting section 26 .

In addition, the notification unit 24 includes information on the timing to start communication using the updated frequency channel set by the update timing setting unit 25 and information on the updated frequency channel transmitted from the communication control device 10. basic information (BEACON) is transmitted to relay station 30 and/or terminal 40 .

The configuration and operation of the relay station 30 are substantially the same as those of the central station 20 . That is, the relay station 30 includes a first wireless device 32a, a second wireless device 32b, a notification section 34, and a use channel setting section . Note that the relay station 30 may have other functions not shown in FIG.

The first radio device 32a includes a CAC unit 71a, an NF measurement unit 72a, and a CH usage rate measurement unit 73a. Note that the first wireless device 32a may have other functions not shown in FIG.

Upon receiving CAC-IND from the aggregation station 20, the CAC unit 71a performs CAC to check whether there is radar in the frequency channel currently being used by the first wireless device 32a. The first radio device 32a stops the frequency channel on which the radar is detected by the CAC unit 71a.

The NF measurement unit 72a measures the noise level of the frequency channel currently used by the first radio device 32a. The CH usage rate measurement unit 73a measures the usage rate of the currently used frequency channel. The noise level measurement by the NF measurement section 72a and the usage rate measurement by the CH usage rate measurement section 73a will be described later.

The second radio device 32b includes a CAC unit 71b, an NF measurement unit 72b, and a CH usage rate measurement unit 73b. Note that the second wireless device 32b may have other functions not shown in FIG.

The CAC section 71b is substantially the same as the CAC section 71a of the first wireless device 32a. However, in addition to the currently used frequency channel, the CAC unit 71b of the second radio device 32b performs a CAC that checks whether radar is detected in a frequency channel to be updated other than the currently used frequency channel. implement.

The NF measurement section 72b is substantially the same as the NF measurement section 72a of the first wireless device 32a. However, the NF measuring unit 72b of the second wireless device 32b measures the noise level of the frequency channels to be updated other than the currently used frequency channel, in addition to the currently used frequency channel.

The CH usage rate measurement unit 73b is substantially the same as the CH usage rate measurement unit 73a of the first wireless device 32a. However, the CH usage rate measurement unit 73b of the second wireless device 32b measures the usage rates of frequency channels to be updated other than the currently used frequency channel in addition to the currently used frequency channel.

The first wireless device 32 a receives the measurements made by the terminal 40 . In addition, the noise level for each channel measured by the radar detection report (RRPT) including the detection result of the DFS detected by the CAC unit 71a and the CAC unit 71b and the NF measurement unit 72b and the CH usage rate measurement unit 73b, and the channel for each channel A statistical information report (SRPT) containing utilization information is communicated to the aggregation station 20 via the first wireless device 32a.

The setting unit 36 sets a frequency channel to be used for frequency hopping based on basic information (BEACON) including updated frequency channel information transmitted from the aggregation station 20 . The first wireless device 32a of the relay station 30 starts communication using the updated frequency channel included in the basic information (BEACON) transmitted from the central station 20 by the frequency channel set by the use channel setting unit 36. It communicates with the central station 20 and/or the terminal 40 at the timing to do so. Also, the relay station 30 may have other functions not shown in FIG.

The terminal 40 includes a first wireless device 42 a , a second wireless device 42 b , a notification section 44 and a channel setting section 46 . Note that the terminal 40 may have other functions not shown in FIG.

The first radio device 42a includes an NF measuring section 82a and a CH usage rate measuring section 83a. Note that the first wireless device 42a may have other functions not shown in FIG.

The NF measurement unit 82a measures the noise level of the frequency channel currently used by the first radio device 42a. The CH usage rate measurement unit 83a measures the usage rate of the currently used frequency channel.

The second radio device 42b includes an NF measuring section 82b and a CH usage rate measuring section 83b. Note that the second wireless device 42b may have other functions not shown in FIG.

The NF measurement section 82b is substantially the same as the NF measurement section 82a of the first wireless device 42a. However, the NF measuring unit 82b of the second wireless device 42b measures the noise level of the frequency channels to be updated other than the currently used frequency channel, in addition to the currently used frequency channel.

The CH usage rate measurement unit 83b is substantially the same as the CH usage rate measurement unit 83a of the first wireless device 42a. However, the CH usage rate measurement unit 83b of the second wireless device 42b measures the usage rates of frequency channels to be updated other than the currently used frequency channel in addition to the currently used frequency channel.

A statistical information report (SRPT) including information on the noise level for each channel and the channel usage rate for each channel measured by the NF measuring unit 82b and the CH usage rate measuring unit 83b is sent to the relay station 30 via the first wireless device 42a. to be notified.

The used channel setting unit 46 sets a frequency channel to be used in frequency hopping based on basic information (BEACON) including updated frequency channel information transmitted from the relay station 30 . The first radio device 42a of the terminal 40 starts communication using the updated frequency channel included in the basic information (BEACON) transmitted from the relay station 30 by the frequency channel set by the use channel setting unit 46. It communicates with the relay station 30 at the timing. Terminal 40 may also have other functions not shown in FIG.

Information on various channels stored in the memory 17 will be described with reference to FIG. FIG. 4 shows an example of information on various channels stored in the memory 17 of the communication control device 10. As shown in FIG. FIG. 4A is a diagram showing an example of a usable channel list 51 of a plurality of wireless LANs designated in advance.

The available channel list 51 stores information on available channels of a plurality of predesignated wireless LANs. A wireless LAN access point AP is connected by a frequency hopping method by switching at least two or more frequencies of a plurality of channels (CH: channels) 36 to 140 belonging to a plurality of frequency bands.

As shown in FIG. 4A, when using the 5 GHz band with a bandwidth of 20 MHz, 19 frequency channels set to W52, W53, and W56 are available channels. The frequency band 5.2 GHz band (W52) includes four channels of 36CH, 40CH, 44CH and 48CH. The frequency band 5.3 GHz band (W53) includes four channels of 52CH, 56CH, 60CH and 64CH. The frequency band 5.6 GHz band (W56) includes 11 channels of 100CH, 104CH, 108CH, 112CH, 116CH, 120CH, 124CH, 128CH, 132CH, 136CH and 140CH. In the example of FIG. 4(a), 19 channels from 36CH to 140CH are shown as the previously designated available channel list 51 for a plurality of wireless LANs, but this is not the only option. For example, out of the 19 channels, only predetermined channels may be selected as available channels for a plurality of predesignated wireless LANs.

FIG. 4B is a diagram showing an example of the DFS list 52. As shown in FIG. The DFS list 52 stores information on channels on which radars measured by the central station 20 and the relay station 30 are detected. In the DFS list 52, channel information is represented by bit flags in the logical expression. In the example of FIG. 4B, the DFS list 52 represents a state in which radar is detected in CH60.

FIG. 4C is a diagram showing an example of the NF list 53. As shown in FIG. The NF list 53 stores information on channels with large interference and noise measured by the aggregation station 20 and the relay station 30 . In the NF list 53, channel information is represented by bit flags in the logical expression. In the example of FIG. 4(c), the NF list 53 indicates that the NF measured at the central station 20 or the relay station 30 is higher than a predetermined threshold or the average channel usage rate is higher than a predetermined threshold for 36CH, 60CH, and 64CH. represents a higher state.

FIG. 4(d) is a diagram showing an example of the use candidate channel list 54. As shown in FIG. The use candidate channel list stores information of use candidate frequency channels among the plurality of useable frequency channels specified in the use channel list of FIG. 4(a). The use candidate channel list 54 is obtained by logically negating the DPS list 52 and the NF list 53 and ANDing the usable channel list 51 obtained as the processing result of the channel control unit 12 .

FIG. 4E is a diagram showing an example of the used channel list 55. As shown in FIG. The used channel list 55 stores information on a plurality of used frequency channels used in frequency hopping. The use channel list 55 is obtained by determining a predetermined number of use frequency channels from the use candidate frequency channels defined in the use candidate channel list 54 of FIG. 4(d). In the example of FIG. 4(e), the used channel list 55 represents a state in which CH40, CH52, and CH100 are used in frequency hopping.

The channel control unit 12 selects predetermined channels to be used by the aggregation station 20, the relay station 30, and the terminal 40 by avoiding the channels to be used for channel bonding from the usable channel list 51 shown in FIG. 4(a). Determine the number of frequency channels to be used. In addition, it is preferable that the channel control unit 12 equally selects different frequency channels from the 5.2 GHz band (W52), the 5.3 GHz band (W53), and the 5.6 GHz band (W56).

For example, a case where the channel control unit 12 determines three frequency channels to be used as the predetermined number will be described. In this case, the channel control unit 12 selects one use frequency channel from each of the 5.2 GHz band (W52), the 5.3 GHz band (W53), and the 5.6 GHz band (W56). In the example shown in FIG. 4, the channel control unit 12 selects the frequency channel CH40 from the frequency band 5.2 GHz band (W52), selects the frequency channel CH52 from the frequency band 5.3 GHz band (W53), and selects the frequency channel CH52. A frequency channel CH100 is selected from the 5.6 GHz band (W56). At this time, the selected frequency channels CH40, CH52, and CH100 are not subject to channel bonding with each other and belong to different frequency bands.

Next, with reference to FIG. 5, an outline of processing for performing communication by the frequency hopping method in the radio communication system 1 according to the embodiment of the present invention will be described. In the frequency hopping method, frequency channels for transmission and reception are switched on a frame-by-frame basis. In the example of FIG. 5(a), communication is performed by the frequency hopping method while switching between three frequency channels (ch.A, ch.B, ch.C) on a frame-by-frame basis. In this embodiment, an example in which three frequency channels are switched on a frame-by-frame basis is described, but the number of channels is not particularly limited. Each access point AP cyclically uses the channel described in the control information (BEACON_SET) transmitted from the communication control device 10 . In the example of FIG. 5(a), three frequency channels are switched every 100 ms.

The central station 20 transmits basic network information (BEACON) to the relay station 30 at least once within one frame. The basic information (BEACON) includes updated frequency channel information and information indicating the timing of starting communication using the updated frequency channel. The timing of starting communication using the updated frequency channel is represented by an update timer.

The update timer indicates the timing of updating the frequency channel. The initial value of the update timer is set by the communication control device 10 . For example, when "5" is set as the update timer, the used frequency channel is updated in the entire radio communication system 1 after 5 frames. Therefore, it is preferable to determine the initial value of the update timer according to the scale of the wireless communication system 1 and the communication status.

The update timer is decremented by one each time one frame time elapses. Therefore, if relay station 30 and terminal 40 can receive BEACON even once before the value of the update timer reaches "0", they can recognize the update of the frequency channel used in frequency hopping. Therefore, the larger the initial value of the update timer, the more likely it is that the frequency channel used in the radio communication system 1 will fail to update.

Next, the process of updating the frequency channel when radar is detected will be described with reference to FIG. 5(b). In FIG. 5(b), at time (a), ch. A, ch. B, ch. A case where C is recorded will be described.

For example, when the access point AP detects radar at time (b), the access point AP stops the radar-detected channel. In the example of FIG. 5(b), ch. A, the access point AP detects radar on ch. Stop A. After time (c), the access point AP uses the remaining specified frequency channels ch. B, ch. C is used to continue communication in a frequency hopping manner. That is, channel ch. B, ch. Communication continues by frequency hopping using C.

In the example of FIG. 5(b), the central station 20 and relay station 30 cannot transmit BEACON twice at maximum until communication is resumed in the next frame. IEEE 802.11 connection is maintained because is allowed. The access point AP that has detected the radar notifies the communication control device 10 of the radar detection by a radar detection report (RRPT) when communication is resumed. When the central station 20 of the access point AP detects radar, it immediately notifies the communication control unit 10 of the radar detection by means of a radar detection report (RRPT) by wire.

The communication control device 10 updates the DFS list 52 based on the radar detection report (RRPT) received from the access point AP. Then, the communication control device 10 updates the used frequency channels in the used channel list 55 based on the updated DFS list 52 . After that, the communication control device 10 transmits the information of the used frequency channels in the used channel list 55 as control information (BEACON_SET) to the central station 20 to instruct the used frequency channels to be used for frequency hopping. Upon receiving the control information (BEACON_SET), the central station 20 transmits the information of the used frequency channels in the used channel list 55 as the network basic information (BEACON) to the relay station 30 to indicate the used frequency channels to be used for frequency hopping. . Similarly, the relay station 30 that has received the network basic information (BEACON) transmits the received basic information (BEACON) to the terminal to indicate the frequency channel to be used for frequency hopping. Therefore, the central station 20, the relay station 30, and the terminal 40 control to perform communication on the used frequency channel included in the control information (BEACON_SET) transmitted from the communication control device 10. FIG.

In this way, the frequency channels used in the radio communication system 1 are synchronized and controlled so that IEEE 802.11 connection disconnection does not occur. If the radar is not detected for 30 minutes, the information stored in the DFS list 52 is cleared.

Here, an example of changing the frequency channel will be described with reference to FIG. 5(b). In the following description, before time (a), frequency channel ch. It is assumed that A, B, and C are used for frequency hopping communication.

At time (b), frequency channel ch. When radar is detected at A, the communication control device 10 is notified of the detection result. Then, the communication control device 10 updates the frequency channel used in frequency hopping communication. Specifically, "ch. A, B, C" is updated to "ch. D, B, C".

Subsequently, at time (c), BEACON is transmitted to notify the updated frequency channel. This BEACON contains the following information:
(1) Frequency channels used: D, B, C
(2) Prohibited channel: A
(3) Update timer: 5

A new frequency channel ch. D is selected from among the available frequency channels. That is, a new frequency channel is selected for which the noise is below the threshold level, the average utilization is below the threshold, and no radar has been detected within the last 30 minutes. Usable frequency channels are managed using an available channel list 51 , a DFS list 52 , and an NF list 53 in the communication control device 10 .

This BEACON is transmitted to each relay station 30 and each terminal 40 . However, at this point the update timer is not zero. This update timer is decremented by one each time a frame is transmitted. Thus, the update timer expires at the time five frames have been transmitted from time (c) (ie, time (d)).

Each relay station 30 and each terminal 40 performs frequency hopping communication on the pre-update frequency (excluding frequency channel ch.A) until the update timer expires. That is, from time (c) to time (d), frequency channel ch. Communication is performed on B and C.

After time (d), that is, at the timing when the update timer expires (zero) and at the beginning of the frame, each relay station 30 and each terminal 40 perform frequency hopping communication using the updated frequency channel. I do. That is, the frequency channel ch. Communication is performed on D, B, and C.

In this way, when some of the frequency channels in use become unavailable in frequency hopping, a new frequency channel is selected. Here, the new frequency channel has previously been verified to have noise below the threshold level, average utilization below the threshold, and no radar detected within the last 30 minutes. Therefore, frequency hopping communication can be continued.

Moreover, the updated frequency channel is notified to each relay station 30 and each terminal 40 in advance by BEACON. That is, since relay station 30 and terminal 40 can recognize the updated frequency channel in advance, they can wait for BEACON transmitted on the updated frequency channel. Therefore, the relay station 30 and the terminal 40 can maintain the 802.11 connection and do not need to reestablish the IEEE 802.11 connection.

Next, interference detected by each access point AP when another wireless communication system 100 exists around the wireless communication system 1 will be described with reference to FIG. FIG. 6 is a diagram showing an example of interference detected by each access point AP. When another wireless communication system 100 exists around the wireless communication system 1, the packets transmitted and received by the external access point 110 in the wireless communication system 100 and the external terminals 120-1 to 120-4 are aggregated. It is measured as interference at the station 20 and the relay station 30 .

The central station 20 and the relay station 30 notify the communication control apparatus 10 of the measured result as the NF and the channel usage rate of the statistical information report (SRPT). The communication control apparatus 10 stores the channels with large interference in the NF list 53, thereby excluding the information on the channels with large interference from the frequency channels selected by the channel control unit 12. FIG.

The conditions for storing channel information in the NF list are not particularly limited. Determination by a method of determining the maximum value of the channel usage rate notified from the relay station 30 using a predetermined threshold (determination condition 2), a method of determining by a logical sum of determination conditions 1 and 2 (determination condition 3), and the like. can do. When interference is determined in the used frequency channel, the aggregation station 20 and the relay station 30 notify the communication control device 10 of the detection of interference by statistical information report (SRPT), as in radar detection.

The communication control device 10 updates the NF list 53 based on statistical information reports (SRPT) received from the central station 20 and relay station 30 . Then, the communication control device 10 updates the used frequency channels in the used channel list 55 based on the updated NF list 53 . After that, the communication control device 10 transmits the information of the used frequency channels in the used channel list 55 as control information (BEACON_SET) to the central station 20 to instruct the used frequency channels to be used for frequency hopping. The central station 20 that has received the control information (BEACON_SET) controls communication to be performed using the frequency channel included in the control information (BEACON_SET).

Further, the central station 20 transmits the information of the frequency channel to be used included in the control information (BEACON_SET) as the basic information (BEACON) to the relay station 30 to indicate the frequency channel to be used for frequency hopping. Similarly, the relay station 30 transmits the basic information (BEACON) transmitted from the central station 20 to the terminal to indicate the frequency channel to be used for frequency hopping. Upon receiving the basic information (BEACON), the relay station 30 and the terminal 40 control to perform communication using the frequency channel included in the basic information (BEACON). Thereby, the communication control device 10, the central station 20, the relay station 30 and the terminal 40 are synchronized with each other. It should be noted that the channel information stored in the NF list 53 is held until the interference determination is no longer true.

Next, the timing at which the central station 20 transmits basic information (BEACON) to the relay station 30 will be described. FIG. 7 is a diagram showing an example of timing at which basic information (BEACON) is transmitted from the central station 20 to the relay station 30. As shown in FIG.

The BEACON packet broadcasted from the central station 20 contains update timer information indicating the timing of starting communication using the updated frequency channel. Aggregation station 20, relay station 30, and terminal 40, which constitute each node in radio communication system 1, synchronize the used frequency channel based on the information of the update timer included in the basic information (BEACON).

The relay station 30 acquires update timer information from the basic information (BEACON) transmitted from the central station 20 . Therefore, it is necessary to control the transmission timing of the basic information (BEACON) so that the number of hops from the central station 20 to the terminal relay station 30 or terminal 40 is the shortest. Therefore, in the present embodiment, the communication control device 10 allocates beacon transmission slots in ascending order of hop count from the central station 20 . Then, the communication control device 10 includes information on the allocated beacon transmission slot and route information to each node in the control information (BEACON_SET) and transmits the information to the central station 20 .

The central station 20 includes the beacon transmission slot information transmitted from the communication control device 10 and the route information to each node in the basic information (BEACON) and notifies each relay station 30 constituting each multihop node. . If there are multiple relay stations 30 with the same number of hops, the communication control device 10 assigns update timers to transmission slots in BEACON packets so that each relay station 30 does not overlap. Upon receiving the BEACON, the relay station 30 can synchronize the used frequency channel based on the update timer information included in the BEACON.

In the above-described embodiment, the relay station 30 synchronizes the used frequency channel based on the update timer information included in BEACON, but the present invention is not limited to this. For example, by including a common time stamp in BEACON in the entire radio communication system 1 , time synchronization can be achieved among the communication control device 10 , central station 20 , relay station 30 and terminal 40 .

FIG. 8 is a sequence chart showing an example of CH list update processing performed in the wireless communication system.

The communication control device 10 notifies the central station 20 of the CAC instruction (CAC-IND) (step S11). The central station 20 that has received the CAC instruction notifies the relay station 30-1 of the CAC instruction (CAC-IND) (step S12). The relay station 30-1 that has received the CAC instruction (CAC-IND) notifies the relay station 30-2 of the CAC instruction (CAC-IND) if there is a relay station 30-2 below it. (step S13).

When the relay station 30-1 detects radar during CAC (step S14), it notifies the central station 20 of a radar detection report (RRPT) (step S15). Upon receiving the radar detection report (RRPT), the central station 20 notifies the received radar detection report (RRPT) to the communication control device 10 (step S16). Note that the central station 20 itself may detect the radar. In this case, the central station 20 notifies the communication control device 10 of a radar detection report (RRPT) in the same manner as the detection result notified from the relay station 30 . Upon receiving a radar detection report (RRPT) from relay station 30 or aggregation station 20 , communication control device 10 updates DFS list 52 , use candidate channel list 54 and use channel list 55 . Then, the communication control device 10 selects a channel to be used for communication based on the updated used channel list 55 (step S17).

The communication control device 10 notifies the central station 20 of control information (BEACON_SET) including information on the channel to be used for communication selected in step S17 (step S18). The central station 20, which has received the notification of the channel to be used, notifies the relay station 30-1 of the basic information (BEACON) including the information on the channel to be used notified in step S18 (step S19). Similarly, relay station 30-1, which has received the notification of the channel to be used, notifies relay station 30-2 and terminal 40 of basic information (BEACON) including the information on the channel to be used notified in step S19 (step S20).

The relay station 30-2, which has received the CAC instruction (CAC-IND) in step S13, performs CAC and notifies the relay station 30-1 of the CAC response to the notification (CAC-ACK) (step S21). . The relay station 30-1 notifies the central station 20 of the CAC response (CAC-ACK) received from the relay station 30-2 (step S22). The central station 20 notifies the communication control device 10 of the CAC response (CAC-ACK) received from the relay station 30 (step S23).

Similarly, the relay station 30-1 that has received the CAC instruction (CAC-IND) notification in step S12 performs CAC and notifies the central station 20 of the CAC response to the notification (CAC-ACK) (step S24). ). The central station 20 notifies the communication control device 10 of the CAC response (CAC-ACK) received from the relay station 30 (step S25).

Similarly, the central station 20 that receives the CAC instruction (CAC-IND) notification in step S11 performs CAC and notifies the communication control device 10 of the CAC response to the notification (CAC-ACK) (step S26). .

Next, the DFS list update process performed by the communication control device 10 will be described. FIG. 9 is a flowchart illustrating an example of DFS list update processing. First, the channel control unit 12 of the communication control device 10 determines whether or not a radar detection report (RRPT) notified from the central station 20 or the relay station 30 has been received (step S31). If the radar detection report (RRPT) has not been received (NO in step S31), the process waits until the radar detection report (RRPT) is received. When the radar detection report (RRPT) is received (YES in step S31), the channel control unit 12 updates the DFS list 52 based on the received radar detection report (RRPT) (step S32). The channel control unit 12 updates the used channel list 55 based on the updated DFS list 52 (step S33).

The channel control unit 12 determines whether or not an instruction to terminate the radio communication system 1 has been received (step S34). If the termination instruction for the wireless communication system 1 has not been received (NO in step S34), the process returns to step S31, and the processes of steps S31 to S34 are repeatedly executed. If the end instruction for the wireless communication system 1 is received (YES in step S34), the DFS list update process ends.

Next, NF list update processing performed by the communication control device 10 will be described. FIG. 10 is a flowchart illustrating an example of NF list update processing.

First, the channel control unit 12 of the communication control device 10 determines whether or not a statistical information report (SRPT) notified from the central station 20, the relay station 30, or the terminal 40 has been received (step S41). If the statistical information report (SRPT) has not been received (NO in step S41), the process waits until the statistical information report (SRPT) is received. When the statistical information report (SRPT) is received (YES in step S41), the channel control unit 12 updates the NF list 53 based on the received statistical information report (SRPT) (step S42). The channel control unit 12 updates the used channel list 55 based on the updated NF list 53 (step S43).

The channel control unit 12 determines whether or not an instruction to terminate the radio communication system 1 has been received (step S44). If the instruction to end the wireless communication system 1 has not been received (NO in step S44), the process returns to step S41, and the processes of steps S41 to S44 are repeatedly executed. If the end instruction for the wireless communication system 1 is accepted (YES in step S44), the NF list update process ends.

Next, communication control processing performed by the communication control device 10 and the central station 20 will be described. FIG. 11 is a flowchart showing an example of communication control processing performed by the communication control device 10 and the central station 20. As shown in FIG. First, the central station 20, the relay station 30, and the terminal 40 communicate in frequency hopping based on a predetermined number of frequency channels selected from available frequency channels.

The interface (IF) 11 of the communication control device 10 transmits a CAC instruction (CAC-IND) to the central station 20 at predetermined intervals. Similarly, the central station 20 transmits a CAC instruction (CAC-IND) to the relay station 30 at predetermined intervals (step S51). The interface (IF) 11 receives the CAC response (CAC-ACK) notified from the central station 20 and relay station 30 in response to the CAC instruction (CAC-IND) transmitted in step S51 (step S52). The channel control unit 12 determines whether or not the content of the received CAC response (CAC-ACK) is NG (step S53). If the content of the CAC response (CAC-ACK) is not NG (NO in step S53), the process returns to step S51, and the processes of steps S51 to S53 are repeatedly executed.

On the other hand, if the CAC response (CAC-ACK) is NG (NO in step S53), the channel control unit 12 selects a predetermined number of frequency channels based on the used channel list 55 (step S54). For example, the channel control unit 12 selects three frequency channels, CH40, CH52, and CH100, based on the used channel list 55 of FIG. 4(e). The interface (IF) 11 transmits control information (BEACON_SET) including information on the frequency channel selected by the channel control unit 12 and information on the initial value of the update timer to the central station 20 .

The update timing setting unit 25 of the central station 20 determines whether or not the predetermined number of selected frequency channels have been updated based on the control information (BEACON_SET) transmitted from the communication control device 10 (step S55). If the frequency channel has not been updated (NO in step S56), the process returns to step S51, and the processes of steps S51 to S55 are repeatedly executed until the frequency channel is updated.

If the frequency channel has been updated (YES in step S56), the update timing setting unit 25 starts communication using the updated frequency channel based on the control information (BEACON_SET) transmitted from the communication control device 10. An update timer for timing to be set is set (step S57). Then, the update timing setting unit 25 sets the information representing the updated frequency channel and the basic information of the set update timer in BEACON (step S58).

The central station 20 transmits the set basic information (BEACON) to the relay station 30 . Similarly, the relay station 30 that has received the basic information (BEACON) transmits the basic information (BEACON) to another relay station 30 or terminal 40 (step S59). The update timing setting unit 25 determines whether or not the update timer set in step S57 has expired (step S60). If the set update timer has not expired (NO in step S60), the process waits until the update timer expires. When the set update timer expires (YES in step S60), the first wireless device 22a of the central station 20 starts communication with the relay station 30 and the terminal 40 using the frequency hopping method on the updated frequency channel ( step S61). When this process ends, the communication control process performed in the wireless communication system 1 ends.

Next, the RRPT notification process performed by the central station 20 will be described. FIG. 12 is a flowchart showing an example of RRPT notification processing performed by the central station 20. As shown in FIG. Note that the RRPT notification process performed by the relay station 30 is substantially the same as the RRPT notification process performed by the central station 20, so the description thereof will be omitted.

First, the CAC unit 61b of the second wireless device 22b determines whether or not the CAC instruction (CAC-IND) transmitted from the communication control unit 10 in step S51 of FIG. 11 has been received (step S71). If the CAC instruction (CAC-IND) has not been received (NO in step S71), the process waits until the CAC instruction (CAC-IND) is received. When the CAC instruction (CAC-IND) is received (YES in step S71), the CAC unit 61b of the second wireless device 22b executes CAC (step S72). The notification unit 24 notifies the communication control device 10 of a radar detection report (RRPT) including the detection result of the radar detected in step S72 (step S73).

The CAC unit 61b notifies the communication control device 10 of a CAC response (CAC-ACK) to the CAC instruction (CAC-IND) received in step S71 (step S74). The first wireless device 22a determines whether or not it has received an instruction to end the wireless communication system 1 (step S75). If the instruction to end the wireless communication system 1 has not been received (NO in step S75), the process returns to step S71, and the processes of steps S71 to S75 are repeatedly executed. If the instruction to end the wireless communication system 1 is received (YES in step S75), the RRPT notification process performed by the central station 20 ends. In the central station 20, the CAC unit 61b notifies the communication control device 10 of a CAC response (CAC-ACK) to the CAC instruction (CAC-IND). In this regard, in the relay station 30, the CAC unit 71b notifies the communication control device 10 of the CAC response (CAC-ACK) in response to the CAC instruction (CAC-IND) via the central station 20. differ. Note that the central station 20 and the relay station 30 may voluntarily perform radar detection and notify the communication control device 10 of the result.

Next, SRPT notification processing performed by the central station 20 will be described. FIG. 13 is a flowchart showing an example of SRPT notification processing performed by the central station 20. As shown in FIG. Note that the SRPT notification process performed by the relay station 30 is substantially the same as the SRPT notification process performed by the central station 20, so the description thereof will be omitted.

First, the NF measurement unit 62b of the second radio device 22b measures NF at predetermined time intervals. In addition, the CH usage rate measuring unit 63a measures the average channel usage rate every predetermined time (step S81). The notification unit 24 notifies the communication control device 10 of the statistical information report (SRPT) including the NF and the average channel usage rate measured in step S81 (step S82).

The first wireless device 22a determines whether or not it has received an instruction to end the wireless communication system 1 (step S83). If the termination instruction for the wireless communication system 1 has not been received (NO in step S83), the process returns to step S81, and the processes of steps S81 to S83 are repeatedly executed. If the instruction to end the wireless communication system 1 is received (YES in step S83), the SRPT notification process performed by the central station 20 ends. In addition, in the central station 20, the notification unit 24 notifies the communication control device 10 of the statistical information report (SRPT) including the measured NF and average channel usage rate. In this respect, in the relay station 30, the notification unit 34 notifies the communication control device 10 via the central station 20 of the statistical information report (SRPT) including the measured NF and average channel usage rate. differ.

Next, communication control processing performed in the relay station 30 will be described. FIG. 14 is a flowchart showing an example of communication control processing performed by the relay station 30. As shown in FIG.

The use channel setting unit 36 determines whether or not the basic information (BEACON) transmitted by the central station 20 in step S59 of FIG. 11 has been received (step S91). If the basic information (BEACON) has not been received (NO in step S91), the process waits until the basic information (BEACON) is received. When the basic information (BEACON) is received (YES in step S91), the use channel setting unit 36 stops the use prohibited channel based on the information included in the basic information (BEACON) (step S92). In this process, for example, the used channel setting unit 36 stops the frequency channel on which the radar is detected.

The used channel setting unit 36 determines whether or not a value is set in the update timer included in the basic information (BEACON) (step S93). If no value is set in the update timer included in the basic information (BEACON) (NO in step S93), the process proceeds to step S95. If a value is set in the update timer included in the basic information (BEACON) (YES in step S93), the used channel setting unit 36 sets the update timer (step S94). In this process, the used channel setting unit 36 decrements the value of the update timer by 1 each time one frame time elapses, and performs the frequency channel update process, which will be described later.

In step S95, the first wireless device 32a determines whether or not an instruction to terminate the wireless communication system 1 has been received. If the instruction to end the wireless communication system 1 has not been received (NO in step S95), the process returns to step S91, and the processes of steps S91 to S95 are repeatedly executed. If the instruction to end the wireless communication system 1 is received (YES in step S95), the communication control process performed by the relay station 30 ends.

Next, frequency channel update processing performed in the relay station 30 will be described. FIG. 15 is a flowchart showing an example of frequency channel update processing performed by the relay station 30. As shown in FIG.

The use channel setting unit 36 determines whether or not it is time to update the frequency channel (step S101). In this process, the used channel setting unit 36 determines whether or not it is time for the update timer to expire (zero) and to come to the beginning of the frame. If it is not the frequency channel update timing (NO in step S101), the process waits until the frequency channel update timing. If it is the frequency channel update timing (YES in step S101), the used channel setting unit 36 updates and sets the used frequency channel to the used frequency channel included in the basic information (BEACON) (step S102).

As described above, according to the wireless communication system 1 of the present embodiment, when a frequency channel in use for frequency hopping communication becomes unusable and a predetermined number of frequency channels for frequency hopping are updated, the central station 20 transmits to relay station 30 and terminal 40 control information including information representing the updated frequency channel and information representing the timing of starting communication using the updated frequency channel. This enables the relay station 30 and the terminal 40 to switch to another frequency channel without disconnecting communication.

It should be noted that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the present invention at the implementation stage. Also, various inventions can be formed by appropriate combinations of the plurality of constituent elements disclosed in the above embodiments. For example, all the components shown in the embodiments may be combined as appropriate. Furthermore, components across different embodiments may be combined as appropriate. It goes without saying that various modifications and applications are possible without departing from the spirit of the invention.

In the above-described embodiment, the channel control unit 12 determines usable frequency channels from among a plurality of frequency channels based on the notification received from the access point AP, but it is not limited to this. For example, the channel control unit 12 can determine unavailable channels based on a notification received from the access point AP.

Also, in the above-described embodiment, the initial value of the update timer is transmitted from the communication control device 10 to the central station 20, but this is not the only option. For example, the central station 20 itself may set the initial value of the update timer.

In addition, in the above-described embodiment, the update timing setting unit 25 of the central station 20 sets the timing to start communication using the updated frequency channel, but this is not the only option. For example, the communication control device 10 may set the timing for starting communication using the updated frequency channel. In this case, the communication control device 10 transmits to the central station 20 control information (BEACON_SET) including information on the timing of starting communication using the updated frequency channel. Thereby, the used frequency channel in the radio communication system 1 can be synchronized.

1 Wireless communication system 10 Communication control device 12 Channel control unit 20 Aggregation station 22a First wireless device 22b Second wireless device 24 Notification unit 25 Update timing setting unit 26 Use channel setting unit 30 Relay station 32a First wireless device 32b Second wireless Device 34 Notification unit 36 Use channel setting unit 40 Terminal 42a First wireless device 42b Second wireless device 44 Notification unit 46 Use channel setting unit 51 Available channel list 52 DFS list 53 NF list 54 Use candidate channel list 55 Use channel list 61a , 61b CAC units 62a, 62b NF measurement units 63a, 63b CH usage rate measurement units 71a, 71b CAC units 72a, 72b NF measurement units 73a, 73b CH usage rate measurement units 82a, 82b NF measurement units 83a, 83b CH usage rate measurement Department

Claims (6)

A wireless communication method in which a plurality of communication devices communicate by frequency hopping,
determining use candidate frequency channels as use candidates from among a plurality of pre-designated usable frequency channels based on notifications received from the plurality of communication devices;
determining a predetermined number of use frequency channels to be used by the plurality of communication devices from among the use candidate frequency channels,
When the predetermined number of used frequency channels are updated, control information including information representing updated used frequency channels and information representing timing to start communication using the updated used frequency channels is transmitted to the plurality of communications. notify the device,
Each communication device
communicating in a frequency hopping manner according to the control information using the first wireless device;
using a second wireless device to measure the condition of at least a portion of the plurality of pre-designated usable frequency channels;
A radio communication method, characterized in that a measurement result by the second radio device is notified to a device that determines the use candidate frequency channel. Each communication device
using the second wireless device to detect a frequency channel that is subject to radar signal interference among the plurality of pre-designated frequency channels;
2. The radio communication method according to claim 1, further comprising notifying said device of a frequency channel that is subject to interference by said radar signal. Each communication device
measuring the noise state of each of the plurality of pre-designated frequency channels using the second wireless device;
2. The wireless communication method according to claim 1, further comprising notifying said device of the measurement result of said noise. Each communication device
using the second wireless device to measure a channel utilization rate for each of the plurality of pre-designated frequency channels;
2. The wireless communication method according to claim 1, further comprising notifying said device of the measurement result of said channel usage rate. Each communication device
setting a frequency channel to be used for communication based on information representing an updated frequency channel included in the control information;
frequency hopping communication is started using the set frequency channel based on information indicating timing for starting communication using the updated frequency channel included in the control information. The wireless communication method according to any one of claims 1-4. A wireless communication system comprising a communication device that communicates in a frequency hopping method, a communication control device that controls the communication device, and an aggregation station device provided between the communication device and the communication control device,
The communication control device is
Based on a notification received from the communication device, a use candidate frequency channel is determined as a use candidate among a plurality of pre-specified useable frequency channels, and the use candidate frequency channel is selected from the use candidate frequency channels for the communication. a channel control unit that determines a predetermined number of frequency channels to be used by the device;
a transmission unit configured to transmit first control information including information representing updated frequency channels in use to the aggregation station apparatus when the predetermined number of frequency channels in use are updated;
Based on the first control information, the central station apparatus generates second control information including information representing the updated frequency channel in use and information representing timing to start communication using the updated frequency channel in use. to the communication device; and
The communication device
a first wireless device that performs frequency hopping communication according to the second control information;
a second wireless device that measures the state of at least a portion of the plurality of pre-designated usable frequency channels;
and a notification unit that notifies the communication control apparatus of a measurement result obtained by the second wireless device.

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