Wireless base station, channel setting method, and program

Abstract

To automatically select a channel to be used for wireless communication.SOLUTION: A radio base station 103 includes: a communication unit 302 that searches for other radio base stations using a search frame and transmits a channel response frame that reports an operating channel in response to a search frame from another radio base station; a determination unit 304 that determines the presence or absence of another radio base station; and a processing unit 305 that determines an operating channel used by its own device to communicate with a wireless terminal. After the processing unit 305 tentatively determines the operating channel, the determination unit 304 determines whether the other radio base station exists.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a radio base station, a channel setting method, and a program therefor. [Background technology]

[0002] Conventionally, wireless base stations conforming to the IEEE802.11 standard have been equipped with an automatic channel selection function called ACS (Automatic Channel Selection), as disclosed in Patent Document 1, and when the wireless base station is started up, it searches for and determines the operating channel with the least interference in the surrounding wireless environment. ACS is used to automatically select the optimal operating channel according to the wireless environment in which the wireless base station is installed, and to suppress interference of wireless waves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-224948 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when multiple wireless base stations equipped with ACS are powered on at the same time, and the start-up timing of the wireless base stations overlap, there is a problem that the channels selected by the ACS may compete with each other among the multiple wireless base stations. In this way, when multiple wireless base stations exist in a communication system, if each wireless base station cannot know the operating channel that the other wireless base stations are going to use, the possibility of competing with each other among the operating channels selected by each wireless base station increases. In order to solve this problem, it is possible to install a central control device to specify the channel of each wireless base station, but this is a complicated system and the increase in cost cannot be ignored. In addition, in the W53 and W56 bands belonging to 5 GHz, the radio laws of each country stipulate that a wireless base station must have a one-minute radar wave monitoring period called CAC (Channel Availability Check) before outputting radio waves, and during this period, it is not permitted to output radio waves, and it becomes necessary to move to another channel where there are no radar waves.

[0005] The present invention has been made in consideration of the above circumstances, and a main object of the present invention is to provide a radio base station that selects an operating channel so as to avoid overlapping of operating channels used for wireless communication when the startup timings of multiple radio base stations overlap in a communication system composed of multiple radio base stations. [Means for solving the problem]

[0006] A wireless base station according to one embodiment of the present invention is a wireless base station in a communication system having a plurality of wireless base stations and a wireless terminal, and comprises: a communication unit that searches for other wireless base stations using a search frame and transmits a channel response frame notifying an operating channel in response to the search frame from the other wireless base station; a determination unit that determines whether or not other wireless base stations exist; and a processing unit that determines an operating channel to be used by the wireless terminal, wherein the processing unit provisionally determines the operating channel, and then the determination unit determines whether or not other frontline base stations exist; (a) if the determination unit determines that no other wireless base station exists, the processing unit selects the provisionally determined operating channel as the operating channel to be used by the wireless terminal, and if the communication unit then receives a search frame from the other wireless base station, it transmits information on the operating channel being used by the wireless terminal to the other wireless base station; and (b) if the determination unit determines that another wireless base station exists, the communication unit receives information on the operating channel being used by the other wireless base station, and the processing unit reselects an operating channel that does not match the operating channel as the operating channel to be used by the wireless terminal.

[0007] According to this, a wireless base station in a communication system selects an operating channel so as to avoid overlapping with channels used by existing wireless base stations. Thus, each of a plurality of wireless base stations in the communication system autonomously selects a separate operating channel, and it is possible to prevent the wireless environment from deteriorating due to channel overlap.

[0008] The wireless base station may further include a timer unit that measures a delay time for startup of the wireless base station, the delay time being determined randomly by a random number.

[0009] According to this, a plurality of wireless base stations are activated at different times and their own channels are determined in accordance with the activation order, making it possible to avoid duplication of operating channels between other wireless base stations.

[0010] In addition, the communication unit may include a wireless communication unit including a first wireless module and a wired communication unit, and the first wireless module may be used for a first communication to perform wireless communication with a wireless terminal connected to the device, and the wired communication unit may be used for a second communication to transmit and receive an exploration frame and operating channel information between other wireless base stations.

[0011] This enables a wireless base station to independently perform wireless data frame communication with subordinate wireless terminals and transmission and reception of operating channel information with other wireless base stations.

[0012] Alternatively, the communication unit may be equipped with a wireless communication unit including a first wireless module and a second wireless module, wherein the first wireless module is used for a first communication for wireless communication with a wireless terminal connected to the device, and the second wireless module is used for a second communication for transmitting and receiving an exploration frame and operating channel information being used by other wireless base stations between the device and the other wireless base stations.

[0013] This configuration also enables the wireless base station to independently perform wireless data frame communication with subordinate wireless terminals and transmission and reception of operating channel information with other wireless base stations.

[0014] Moreover, a channel selection method according to one embodiment of the present invention is a method for selecting an operating channel to be used for communication with a wireless terminal in a communication system having a plurality of wireless base stations and a wireless terminal, the method including the steps of: searching for other wireless base stations using a search frame; tentatively determining an operating channel; and judging whether or not other wireless base stations exist; (a) if it is determined in the judgment step that no other wireless base station exists, determining the tentatively determined operating channel as the operating channel to be used by the own terminal; and if a search frame is subsequently received from the other wireless base station, transmitting operating channel information currently being used by the own terminal to the other wireless base station; and (b) if it is determined in the judgment step that other wireless base stations exist, receiving operating channel information currently being used by the other wireless base station, and re-setting an operating channel that does not match the operating channel included in the received operating channel information as the operating channel to be used by the own terminal.

[0015] This provides the same effects as the above-mentioned wireless base station. Effect of the Invention

[0016] According to the present invention, in a communication system in which a plurality of wireless base stations exist, the plurality of wireless base stations can autonomously select an optimal operating channel without contention between the respective operating channels used for wireless communication. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing an overview of a communication system 100 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing an overview of a communication system 100a according to another embodiment of the present invention. [Diagram 3] FIG. 3 is a block diagram showing a functional configuration of a radio base station according to an embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart showing the operation of the radio base station according to the embodiment of the present invention. [Diagram 5]FIG. 5 is a sequence diagram showing a process in which a wireless base station in a wireless communication system according to an embodiment of the present invention determines an operating channel via a backhaul. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, the embodiment will be specifically described with reference to the drawings. The embodiments described below each show a preferred specific example of the present invention. The numerical values, shapes, components, the arrangement and connection of the components, steps, and the order of steps shown in the following embodiments are merely examples and are not intended to limit the present invention. Furthermore, among the components in the following embodiments, those components that are not described in the independent claims showing the highest concept of the present invention are described as any components that constitute a more preferred embodiment. Note that the same reference numerals are used for the same components, and descriptions thereof may be omitted. [Embodiment Mode]

[0019] In this embodiment, an example will be described in which information on an operating channel is shared among a plurality of wireless base stations in a communication system 100, using a wireless network or a wired network as a backhaul. Hereinafter, the operating channel means a channel used by each wireless base station for communication with a wireless terminal under its control.

[0020] Fig. 1 is a schematic diagram showing an overview of a communication system 100 according to an embodiment of the present invention. As shown in Fig. 1, the communication system 100 includes an L2 switch 101, a wired link 102, a plurality of wireless base stations (hereinafter also referred to as APs) 103a, 103b, and 103c, a wireless link 104, and a wireless terminal (hereinafter also referred to as STA) 105. The communication system 100 is a wireless communication system established, for example, in an office or the like.

[0021] In this embodiment, the communication system 100 includes three wireless base stations 103a, 103b, and 103c, but is not limited to this, and the number of wireless base stations included in the communication system 100 may be two, or four or more. Hereinafter, the multiple wireless base stations in FIG. 1 are collectively referred to as wireless base station 103. In this embodiment, the communication system 100 includes one wireless terminal 105, but is not limited to this, and one or multiple wireless terminals 105 may be connected to each of the wireless base stations 103.

[0022] An L2 switch 101 is connected to a wireless base station 103 via a wired link 102. The L2 switch complies with wired network standards such as IEEE802.3, and is connected to, for example, network devices and an in-house LAN, the Internet, or the like.

[0023] The wired link 102 is a wired network that complies with the IEEE 802.3 standard or the like. Wired links 102 connect each of the multiple wireless base stations 103 in the communication system 100 to the L2 switch 101, forming a mutual communication path.

[0024] The wireless base station 103 conforms to standards such as IEEE802.11ac and performs wireless communication by forming a wireless network with a wireless terminal 105 connected thereto. It also has a function of transferring a data frame received via the wired link 102 to another wireless network, and transferring a data frame received from a wireless terminal to the wired network to which the wired link 102 is connected.

[0025] The wireless link 104 is a communication path when wireless communication is performed between the wireless base station 103 and the wireless terminal 105. The wireless base station 103 and the wireless terminal 105 perform wireless communication (corresponding to a first communication) conforming to a standard such as IEEE802.11ac via the wireless link 104. In the first communication, the wireless communication is performed between the wireless base station 103 and the wireless terminal 105 using a frequency band of, for example, 5 GHz (corresponding to a first frequency band).

[0026] The wireless terminal 105 connects to the wireless base station 103 and performs wireless communication conforming to standards such as IEEE802.11ac. The wireless terminal 105 is a personal computer, a smartphone, or the like.

[0027] Fig. 2 is a schematic diagram showing an overview of a communication system 100a having another configuration according to the present invention, which differs from the communication system 100 shown in Fig. 1 in that communication between wireless base stations 103 is performed by wireless links 201 instead of wired links 102.

[0028] The wireless link 201 is a communication path for performing wireless communication between the multiple wireless base stations 103, and may use a frequency band (corresponding to a second frequency band) different from that of the wireless link 104. The multiple wireless base stations 103 are configured to perform WDS (Wireless Distribution System) communication via the wireless link 201, and perform wireless communication conforming to a standard such as IEEE802.11ac (corresponding to a second communication). The second communication is performed by using a frequency band of, for example, 2.4 GHz for wireless communication between the multiple wireless base stations 103. The wireless link 201 is configured to use a frequency band different from that used by the wireless link 104 for communication, thereby avoiding radio wave interference when communication is performed simultaneously through the wireless link 201 and the wireless link 104.

[0029] 3 is a block diagram showing a functional configuration of wireless base station 103 according to the embodiment of the present invention. Wireless base station 103 is a type of computer, and functions as communication unit 302, determination unit 304, processing unit 305, storage unit 306, and timing unit 307 by a CPU reading a program stored in an auxiliary storage unit into a main storage unit and executing the program in cooperation with each piece of hardware. In addition, communication unit 302 includes wireless communication unit 301 and wired communication unit 303.

[0030] The wireless communication unit 301 includes a first wireless module 301a that performs wireless communication with the wireless terminal 105 using a first frequency band. The wireless base station in the communication system 100a includes a second wireless module 301b that performs wireless communication between the base stations using a frequency band (second frequency band) different from that of the first wireless module 301a. The second wireless module 301b transmits and receives an exploration frame with another wireless base station 103, and transmits and receives a channel response frame including operating channel information with another wireless base station as a response frame. The wireless communication unit 301 monitors a provisionally determined operating channel for a certain period of time in order to detect radar waves as defined by the Radio Law and the like. The wireless communication unit 301 is realized by a wireless module, an antenna (not shown), a driver program for the wireless module, and the like, and performs wireless communication with other wireless base stations 103 and the wireless terminal 105 in accordance with a standard such as IEEE802.11ac.

[0031] The wireless base station in the communication system 100 includes a wired communication unit 103. The wired communication unit 303 transmits and receives an exploration frame to and from other wireless base stations 103, and also transmits and receives a channel response frame including operating channel information to and from other wireless base stations as a response frame. The wired communication unit 303 is realized by a wired interface (not shown) or the like, and performs wired communication between a wired network device such as the L2 switch 101 and the wireless base station 103 in accordance with, for example, the IEEE802.3 standard or the like.

[0032] The determination unit 304 determines whether or not there is another wireless base station. The determination unit 304 may be in the form of a computer realized by a CPU (Central Processing Unit), a RAM (Random Access Memory), or the like, or may be realized in the form of a program that has a similar determination effect.

[0033] The processing unit 305 performs communication control processing based on information from the determination unit 304, the storage unit 306, and the timer unit 307. Specifically, in order to tentatively determine an operating channel, set the operating channel, and find out whether or not there is another wireless base station, the processing unit 305 causes the wired communication unit 303 or the second wireless module 301b to transmit an independently determined search frame, and notifies the determination unit 304 of the response result. Specific processing content will be described later. The processing unit 305 may be realized by a CPU, a RAM, etc.

[0034] The storage unit 306 stores the tentatively determined operating channel, information on operating channels being used by other radio base stations, connection information, etc. The storage unit 306 may be realized by a volatile storage device such as a RAM, or may be realized by a non-volatile storage device such as an embedded multimedia card (eMMC), a solid state drive (SSD), or a hard disk drive (HDD).

[0035] The timer 307 measures the delay time for delaying the startup of the wireless base station 103, and notifies the processing unit 305. Specifically, the timer 307 counts down the delay time determined by itself, and notifies the processing unit 305 when a predetermined delay time has elapsed. The timer 307 randomly determines the delay time using random numbers or the like. The timer 307 may be realized by hardware such as an RTC (Real Time Clock), or may be realized by software having a similar function. [Explanation of flow according to embodiment]

[0036] FIG. 4 is a flowchart showing the operation of the radio base station 103 according to the embodiment of the present invention. Step S401 is a step of delaying the timing at which the wireless base station 103 starts operation for an arbitrary time. By randomly delaying the timing at which the wireless base station 103 starts operation, it is possible to prevent multiple wireless base stations 103 in the communication system from completing startup processing at the same time. In this step, the timer unit 307 notifies the processing unit 305 that a randomly determined delay time has elapsed, and the processing unit 305 starts up its own device based on the notification. The processing unit 305 also provisionally determines the operating channel that its own device is to use at this timing.

[0037] Step S402 is a step in which the wireless base station 103 searches the surroundings using the provisionally determined operating channel. This search step is performed for the purpose of confirming the absence of specific radio waves (radar waves) defined by the radio wave laws of each country. The search period (monitoring period) is specifically, for example, one minute (60 seconds). The search is performed by the wireless communication unit 301, and when the search period ends, the wireless communication unit 301 notifies the processing unit 305 of the result. Should radar waves be detected in the search, the processing unit 305 changes the provisionally determined operating channel and performs step S402 again.

[0038] Step S403 is a step in which the wireless base station 103 searches for other wireless base stations 103 that may exist in the communication system. For example, in FIG. 1, this is a step in which the wireless base station 103a searches for wireless base stations 103b and 103c. This step is realized by mutual communication between the multiple wireless base stations 103 existing in the communication system, via the wired communication unit 303 or the second wireless module 301b, respectively, via the wired link 102 or the wireless link 201. Specifically, the processing unit 305 controls the wired communication unit 303 or the second wireless module 301b of its own device to transmit a search frame that it determines independently to the wired communication unit 303 or the second wireless module 301b of the other wireless base station 103.

[0039] Step S404 is a step in which the wireless base station 103 determines whether or not the presence of another wireless base station 103 has been detected as a result of the search in step S403. The presence of another wireless base station 103 can be confirmed by receiving a channel response frame in response to the search frame, in which another base station that is already active notifies the operating channel. If the determination unit 304 determines that another wireless base station 103 has been detected (Yes in step S404), it notifies the storage unit 306 of this effect and transitions to step S406. If the determination unit 304 determines that the other wireless base station 103 has not been detected (No in step S404), it notifies the processing unit 305 of this effect and transitions to step S405.

[0040] Step S405 is a step in which the wireless base station 103 sets an operating channel to be used when wirelessly communicating with the wireless terminal 105 and the like using the wireless link 104. Specifically, when the processing unit 305 determines the operating channel, it notifies the wireless communication unit 301 of the determined operating channel. Thereafter, the first wireless module uses the notified channel as the operating channel to wirelessly communicate data frames and the like with the wireless terminal.

[0041] Step S406 is a step of storing channels already being used by other wireless base stations 103 detected as a result of the search in step S403. When the wireless base station 103 receives a channel response frame including at least information of an operating channel transmitted by the other wireless base station 103 in response to the search frame transmitted by the wireless base station 103 in step S403, the wireless base station 103 stores in the storage unit 306 of the wireless base station 103 the channel information being used by the other wireless base station 103 included in the received channel response frame.

[0042] Step S407 is a step in which the radio base station 103 switches to the next channel of the channel tentatively determined when executing step S401, if the channel stored in step S406 overlaps with the channel being used by the other radio base station. This switching refers to an operation in which, for example, as described later in FIG. 5, if the channel tentatively determined by the radio base station 103b is 100ch, when it is found in the channel response frame received from the radio base station 103a that 100ch overlaps as an operating channel, the radio base station 103b switches to a channel (e.g., 116ch) that is next suitable for communication. After completing the execution of this step, step S403 may be executed again, and repeated until the operating channel tentatively determined by the radio base station 103 does not match the operating channel used by the other radio base station 103. In other words, the radio base station 103 reselects a channel that does not match the operating channel of the other radio base station as the operating channel to be used by the radio base station 103. As a result, the channels used by each radio base station 103 in the communication radio links 104 between the radio terminals 105 and the like are different from each other, and deterioration of the radio environment due to radio interference caused by the same channel (i.e., the same frequency) can be suppressed. [Sequence Description]

[0043] Next, a series of behaviors of the communication system 100 or 100a according to the present embodiment will be described with reference to the sequence diagram of Fig. 5. In the description of Fig. 5, an example will be described in which, in the communication system 100a, the radio base stations 103a to 103c are started up after random times have elapsed, and as a result, the radio base stations 103a, 103b, and 103c are started up in this order, and the subsequent sequence is performed.

[0044] First, in the communication system 100 (or 100a), the power is turned on in each wireless base station 103 (wireless base stations 103a, b and c), and after a certain period of time has elapsed, the processing unit 305 starts up the wireless base station 103 based on a notification from the timing unit 307 (steps S401a, b and c).

[0045] Next, the wireless base station 103a performs a channel search to confirm that radar waves are not detected for a certain period of time on the operating channel tentatively determined for use by the wireless base station 103a, and determines the tentative operating channel to be used by the wireless base station 103a (step S402a).

[0046] Next, the wireless base station 103a performs an AP search to search for whether or not there is an AP other than the wireless base station itself (step S403a). For example, the wireless base station 103a transmits a search frame using the wired communication unit 303 or the second wireless module 301b (step S501a).

[0047] On the other hand, the wireless base station 103b also starts to start up later, but since the start-up has not been completed at the time of transmitting the probe frame in the previous step S501a, it cannot respond to the probe frame in step S501a (the same is true for the wireless base station 103c). After that, the wireless base station 103b completes the start-up and performs a channel search in the same manner as the wireless base station 103a in the above description (step S402b).

[0048] Returning to the sequence of the wireless base station 103a, the wireless base station 103a confirms that there is no response from any AP in the communication system, and confirms the setting of the operating channel tentatively determined when step S402a was performed (100ch in the example of step S407 in FIG. 4) (step S502a). Here, the operating channel is set to 100ch. At this stage, the wireless base station 103a completes a series of flows after startup, and while communicating with subordinate wireless terminals on that channel, it is in a state of waiting to receive an exploration frame from another AP.

[0049] Next, when the wireless base station 103b completes the channel search and provisionally determines the operating channel, it performs an AP search (step S403b). Here, the provisionally determined channel is 100ch. The wireless base station 103b, like the wireless base station 103a, transmits a search frame onto the wireless network using its own wired communication unit 303 or second wireless module 301b to search for other wireless base stations (step S501b).

[0050] Next, since the wireless base station 103a has already started operating at this point, when it receives the probe frame transmitted by the wireless base station 103b in the previous step S501b, the wireless base station 103a replies with operating channel information (indicating that the operating channel being used by the wireless base station 103a is 100ch) by a channel response frame (step S503a). The information of the operating channel to which the wireless base station 103a replies is obtained using the wired communication unit 303 or the second wireless module 301b, as in the case of the probe frame (step S504a). Note that the wireless base station 103c is still in the process of starting up and cannot respond to the probe frame transmitted by the wireless base station 103b.

[0051] Next, when the wireless base station 103b receives the operating channel information of the wireless base station 103a in the channel response frame transmitted from the wireless base station 103a in the previous step S504a, the wireless base station 103b memorizes that the tentatively determined operating channel (100ch) is already in use by the wireless base station 103a, and changes the operating channel (100ch) that it had tentatively determined (to 116ch in the example of Figure 4) (step S502b).

[0052] On the other hand, when the wireless base station 103c also completes the startup process, in step S402b, it performs a channel search in the same manner as the wireless base stations 103a and 103b, tentatively determines an operating channel, and then performs an AP search (step S403c).

[0053] Next, when the wireless base station 103c transmits an exploration frame using the wired communication unit 303 or the second wireless module 301b (step S501c), the wireless base station 103a and the wireless base station 103b receive the exploration frame. Since the wireless base station 103a and the wireless base station 103b are already using 100ch and 116ch, respectively, the wireless base station 103a and the wireless base station 103b each include their own operating channel information in the channel response frame (step S503a1, step S504a1, step S503b, and step S504b).

[0054] When the wireless base station 103c receives information from the wireless base station 103a and the wireless base station 103b that 100ch and 116ch are in use, respectively, if the information overlaps with the operating channel tentatively determined by the wireless base station 103c, the wireless base station 103c changes the channel (to 136ch in the example of FIG. 4) and sets it as the operating channel of the wireless base station (step S502c).

[0055] As a result, the wireless base stations 103 in the communication system 100a select operating channels in order of the base stations that have completed activation, and the wireless base stations that are activated later select operating channels so as to avoid channel overlap. This allows each of the wireless base stations in the communication system to automatically select an operating channel while suppressing deterioration of the wireless environment.

[0056] In this embodiment, it has been described that the multiple wireless base stations 103 mutually transmit and receive AP searches, search frame transmissions, and channels in use by the multiple wireless base stations 103 via the wireless communication unit 301 or the wired communication unit 303. However, in the communication system 100, the processing may be appropriately shared and assigned to each of the wireless communication unit 301 and the wired communication unit 303. Furthermore, in this embodiment, nothing is mentioned about the tentatively determined channel and the finally determined operating channel other than avoiding radar waves in the channel search step immediately after operation. However, in the channel search step, the operating channel candidates may be ranked and stored with reference to the surrounding wireless environment (e.g., the load factor for each channel, the floor noise level, etc.), and the highest ranked (preferred) channel may be set as the tentatively determined channel. If the channel overlaps with the operating channel of the AP that was started earlier, the next highest ranked channel may be selected as the operating channel.

[0057] The present invention can be realized not only as an apparatus, but also as a method in which the processing means constituting the apparatus are steps, as a program for causing a computer to execute those steps, as a computer-readable storage medium such as a CD-ROM on which the program is recorded, or as information, data or signals indicating the program.These programs, information, data and signals may be distributed via a communication network such as the Internet. [Industrial Applicability]

[0058] The present invention can be applied to a wireless base station that improves user convenience, specifically, to a wireless base station of a communication system that is intended to automatically select an operating channel to be used for wireless communication without a user's instruction while avoiding contention of channels to be used for wireless communication. [Explanation of symbols]

[0059] 100 Communication Systems 101 L2 Switch 102 Wired Link 103 Radio Base Station 104 Wireless Link 105 Wireless terminal 200 Communication Systems 201 Wireless Link 301 Wireless Communication Department 301a First wireless module 301b Second wireless module 302 Communications Department 303 Wired Communications Department 304 Judgment section 305 Processing section 306 Storage section 307 Timing section

Claims

1. A radio base station in a communication system including a plurality of radio base stations and a radio terminal, a communication unit that searches for another wireless base station by using an exploration frame, and transmits a channel response frame in response to the exploration frame from the other wireless base station, the channel response frame notifying the wireless terminal of an operating channel that the wireless terminal uses to communicate with the wireless terminal; a determination unit that determines whether or not the other wireless base station exists based on whether or not the communication unit has received the channel response frame; a processing unit for determining an operating channel to be used by the wireless device for communication with the wireless terminal; Equipped with After the processing unit tentatively determines the operating channel, the determination unit determines whether or not the other radio base station exists; (a) when the determination unit determines that the other radio base station is not present, The processing unit selects the provisionally determined operating channel as an operating channel to be used by the own device, Thereafter, when the communication unit receives the search frame from the other wireless base station, the communication unit transmits the channel response frame to the other wireless base station; (b) when the determination unit determines that the other radio base station is present, the communication unit receives an operating channel being used by the other radio base station from the channel response frame; the processing unit reselects an operation channel that does not match the operation channel as an operation channel to be used by the own device; Radio base station.

2. A timer unit is further provided for timing a delay time for starting the own device, The delay time is determined randomly by a random number. The radio base station according to claim 1.

3. the communication unit includes a wireless communication unit including a first wireless module and a wired communication unit; The wireless communication unit includes: The wireless communication device is used for a first communication for wirelessly communicating data frames with the wireless terminal connected to the wireless communication device; The wired communication unit is A second communication is used for transmitting and receiving the search frame and the operating channel in use between the other radio base station and the second radio base station. The radio base station according to claim 1 or 2.

4. The communication unit includes a wireless communication unit including a first wireless module and a second wireless module, and the first wireless module includes: The wireless communication device is used for a first communication for wirelessly communicating data frames with the wireless terminal connected to the wireless communication device; The second wireless module is The search frame and the operating channel in use between the other radio base station are used for a second communication for transmitting and receiving the search frame and the operating channel in use between the other radio base station and the other radio base station. The radio base station according to claim 1 or 2.

5. 1. A method for selecting an operating channel to be used for communication with a wireless terminal in a communication system including a plurality of wireless base stations and a wireless terminal, comprising: searching for other wireless base stations using a search frame; determining the operating channel; determining whether or not the other wireless base station is present; (a) when it is determined that the other radio base station is not present in the determining step, determining the provisionally determined operation channel as an operation channel to be used by the own device; a step of transmitting information of an operating channel being used by the own device to the other wireless base station when the own device subsequently receives the search frame from the other wireless base station; (b) when it is determined in the determining step that the other radio base station is present, receiving information of operating channels in use by the other radio base stations; resetting the operating channel not matching the received operating channel in use as the operating channel to be used by the own device; Including, Channel selection method.

6. A program for causing a computer to execute the channel selection method according to claim 5.

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