Base station, communication system and communication method

Abstract

To provide a base station, a communication system, and a communication method that can suppress reduction in throughput.SOLUTION: A base station includes: a use channel information acquisition unit 114 that acquires first use channel information transmitted from another base station and indicating a first use channel used for transmitting and receiving data frames with the other base station; a use channel determination unit 115 that determines that a channel belonging to any one frequency band W52, W53, or W56, different from the first use channel, among the frequency bands W52, W53, and W56 is a second use channel used for transmitting and receiving data frames with the other base station; and a use channel notification unit 116 that transmits the use channel information indicating the determined use channel to the other base station.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a base station, a communication system, and a communication method. [Background technology]

[0002] A wireless communication system has been proposed that includes multiple wireless base stations that can communicate with each other using WDS (Wireless Distribution System) communication, which transmits and receives data between multiple wireless base stations by wireless communication (see, for example, Patent Document 1).In addition, in this wireless communication system, when communication is performed in Japan using a channel belonging to channel group W56 among channels in the 5 GHz band, for example, if radar waves are detected, the system has a DFS (Dynamic Frequency Selection) function that stops the channel being used and changes it to another channel, and the wireless base station that detects the radar waves notifies other wireless base stations performing WDS communication of the channel to be used for communication. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-200156 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the wireless communication system performing WDS communication described in Patent Document 1, if the timing of frame transmission in multiple wireless base stations overlaps, there is a risk of throughput degradation due to insufficient bandwidth. For example, this is the case when multiple slave units under a wireless base station perform WDS communication at the same transmission timing. In WDS communication, multiple wireless base stations communicate with each other using the same channel (same channel), so that one slave unit's communication uses one bandwidth for multiple slave units, resulting in a degradation of throughput due to insufficient bandwidth in the wireless communication system.

[0005] The present invention has been made in view of the above, and has an object to provide a base station, a communication system, and a communication method that can suppress a decrease in throughput. [Means for solving the problem]

[0006] In order to achieve the above object, a base station according to the present invention comprises: A first frequency band is a frequency band that does not overlap with a frequency band used by a radar wave, and at least one second frequency band that includes the frequency band used by the radar wave. a plurality of wireless modules that wirelessly communicate with a plurality of other base stations through channels that belong to any of a plurality of frequency bands; a usage channel information acquisition unit that acquires first usage channel information indicating a first usage channel used for transmitting and receiving a data frame to and from the first base station, the first usage channel information being transmitted from a preset first base station among the other multiple base stations; a channel-to-be-used determining unit that determines a channel different from the first channel to be a second channel to be used for transmitting and receiving data frames between the second base station and the other base station, the second base station being different from the first base station; a use channel notification unit that transmits second use channel information indicating the determined second use channel to the second base station via any one of the plurality of wireless modules; 、 a usage status detection unit that detects a usage status of each of the plurality of frequency bands; a usage status notifying unit that transmits first usage status information indicating the detected usage status to the first base station via one of the plurality of wireless modules; a usage status acquisition unit that acquires second usage status information indicating a usage status of each of the plurality of frequency bands in the second base station, the second usage status information being transmitted from the second base station, via one of the plurality of wireless modules; Equipped with 、 The use channel determination unit determines the second use channel based on the first use channel information, the first use status information, and the second use status information. .

[0007] A communication system according to another aspect of the present invention comprises: A first base station, a second base station, and a third base station capable of communicating with the first base station and the second base station, The first base station, the second base station, and the third base station each A first frequency band is a frequency band that does not overlap with a frequency band used by a radar wave, and at least one second frequency band that includes the frequency band used by the radar wave. A plurality of wireless modules that wirelessly communicate on channels belonging to any of a plurality of different frequency bands Le Has The third base station, a usage channel information acquisition unit that acquires first usage channel information indicating a first usage channel used for transmitting and receiving a data frame between the first base station and the first base station, the first usage channel information being transmitted from the first base station; a usage channel determination unit that determines a channel different from the first usage channel as a second usage channel to be used for transmitting and receiving data frames to and from the second base station; a use channel notification unit that transmits second use channel information indicating the determined second use channel to the second base station via one of the plurality of wireless modules; a usage status detection unit that detects a usage status of each of the plurality of frequency bands; a usage status notifying unit that transmits first usage status information indicating the detected usage status to the first base station via one of the plurality of wireless modules; a usage status acquisition unit that acquires second usage status information indicating a usage status of each of the plurality of frequency bands in the second base station, the second usage status information being transmitted from the second base station, via one of the plurality of wireless modules; Have death, The use channel determination unit determines the second use channel based on the first use channel information, the first use status information, and the second use status information. .

[0008] A communication method according to another aspect of the present invention comprises: A first frequency band is a frequency band that does not overlap with a frequency band used by a radar wave, and at least one second frequency band that includes the frequency band used by the radar wave. A communication method using a plurality of wireless modules that wirelessly communicates with a plurality of other base stations on a channel that belongs to any of a plurality of frequency bands different from each other, comprising: acquiring first use channel information indicating a first use channel used for transmitting and receiving a data frame to and from the first base station, the first use channel information being transmitted from a preset first base station among the other plurality of base stations; detecting a usage status of each of the plurality of frequency bands; transmitting first usage status information indicating the detected usage status to the first base station via any one of the plurality of wireless modules; acquiring, via one of the plurality of wireless modules, second usage status information indicating usage statuses of the plurality of frequency bands in the second base station, the second usage status information being transmitted from a second base station different from the first base station among the other plurality of base stations; Based on the first used channel information, the first usage status information, and the second usage status information, A channel different from the first channel used , the above determining a second available channel to be used for transmitting and receiving data frames between the first and second base stations; and transmitting second channel-in-use information indicating the determined second channel-in-use to the second base station via any one of the plurality of wireless modules. Effect of the Invention

[0009] According to the base station of the present invention, the channel-in-use determining unit determines a channel belonging to a frequency band different from the first channel-in-use as the second channel-in-use used for transmitting and receiving data frames with the second base station. As a result, the first channel-in-use used for transmitting and receiving data frames with the first base station and the second channel-in-use used for transmitting and receiving data frames with the second base station are different from each other, so that it becomes easier to secure the bandwidth required for wireless communication between the base stations when transmitting data frames from a slave unit under the base station to the first base station and a slave unit under the second base station. Therefore, it is possible to suppress a decrease in throughput in data frame transmission caused by a lack of bandwidth that occurs in conventional WDS communication in which wireless communication between base stations is performed using one channel-in-use. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a configuration of a communication system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating a hardware configuration of a base station according to the first embodiment. [Diagram 3] FIG. 2 is a diagram illustrating a functional configuration of a base station according to the first embodiment. [Figure 4] FIG. 1A is a diagram showing an example of information stored in a usage status memory unit according to embodiment 1, and FIG. 1B is a diagram showing an example of information stored in a used channel memory unit according to embodiment 1. [Diagram 5] FIG. 4 is a sequence diagram showing an operation of the communication system according to the first embodiment. [Figure 6] FIG. 4 is a sequence diagram showing an operation of the communication system according to the first embodiment. [Figure 7] 5 is a flowchart showing an example of the flow of a communication control process executed by an upper base station according to the first embodiment. [Figure 8] 10 is a flowchart showing an example of the flow of a use channel determination process executed by an upper base station according to the first embodiment. [Figure 9] 5 is a flowchart showing an example of the flow of a communication control process executed by a lower base station according to the first embodiment. [Figure 10] FIG. 11 is a diagram illustrating a functional configuration of a base station according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a diagram illustrating an example of information stored in a used channel storage unit according to the second embodiment; [Figure 12] FIG. 11 is a sequence diagram showing an operation of a communication system according to a second embodiment. [Figure 13] 11 is a flowchart showing an example of a flow of a communication control process executed by a base station according to the second embodiment. [Figure 14] FIG. 13 is a diagram showing a configuration of a communication system according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Embodiment 1) A base station according to an embodiment of the present invention will be described in detail below with reference to the drawings. The base station according to this embodiment includes a plurality of wireless modules that perform wireless communication with a plurality of other base stations on a channel belonging to one of a plurality of different frequency bands. The base station determines a channel different from the first usage channel as a second usage channel to be used for transmitting and receiving data frames with the second base station based on first usage status information indicating the usage status of each of the plurality of frequency bands of the base station itself, first usage channel information indicating a first usage channel belonging to one frequency band used for transmitting and receiving data frames with a first base station that is set in advance, and second usage status information indicating the usage status of each of a plurality of frequency bands in a second base station different from the first base station among the plurality of other base stations. This embodiment will be described in detail below.

[0012] As shown in FIG. 1, the communication system according to the present embodiment includes three base stations 1 (1A, 1B, 1C) and terminal devices 3 (3A, 3B, 3C, 3D, 3E, 3F) under each base station 1. This communication system is for constructing a wireless LAN network using a WDS (Wireless Distribution System) function. The base stations are, for example, access points employed as a home network or an office wireless LAN. A hierarchical relationship is set between the three base stations 1A, 1B, 1C, and, for example, the base station 1A is set to be the highest, the base station 1A is set to be higher than the base station 1B, and the base station 1B is set to be higher than the base station 1C. In this case, the base stations 1A, 1B, 1C correspond to the first base station, the third base station, and the second base station, respectively, as described in the claims. The terminal device 3 is, for example, a general-purpose personal computer equipped with a wireless module.

[0013] As shown in Fig. 2, each base station 1 according to the present embodiment includes a CPU (Central Processing Unit) 101, a main memory 102, an auxiliary memory 103, three wireless modules 105A, 105B, and 105C, and a bus 109 connecting each unit. The main memory 102 is composed of a volatile memory such as a RAM (Random Access Memory) and is used as a working area for the CPU 101. The auxiliary memory 103 is composed of a non-volatile memory such as a ROM (Read Only Memory), or an SSD (Solid State Drive), an HDD (Hard Disk Drive), or the like, and stores a program for controlling the base station 1. The CPU 101 reads the program stored in the auxiliary memory 103 into the main memory 102 and executes it.

[0014] The wireless modules 105A, 105B, and 105C each communicate in a communication method conforming to the wireless LAN standard, for example, IEEE802.11. The wireless modules 105A, 105B, and 105C each have an antenna (not shown), a receiving circuit (not shown), a signal processing unit (not shown), and a transmitting circuit (not shown). The receiving circuit receives a wireless signal via the antenna, demodulates a signal corresponding to the received wireless signal to generate a baseband signal, and outputs the baseband signal to the signal processing unit. The transmitting circuit generates a wireless signal corresponding to a frame to be transmitted by modulating a carrier signal using a baseband signal input from the signal processing unit, and transmits the generated wireless signal via the antenna. The signal processing unit is realized by, for example, a DSP (Digital Signal Processor), and generates a frame corresponding to the wireless signal received by the receiving circuit based on the baseband signal input from the receiving circuit, and sends the frame to the bus 109. The signal processing unit also generates a baseband signal based on various frames transferred from the main memory unit 102 via the bus 109, and outputs the baseband signal to the transmitting circuit. In this embodiment, the base station 1 includes three wireless modules 105A, 105B, and 105C. For example, the wireless module 105A uses 14 channels belonging to the 2.4 GHz frequency band, and the wireless modules 105B and 105C use channels W52, W53, and W56 belonging to the 5 GHz frequency band. The wireless modules 105A, 105B, and 105C may be freely configured with a combination of the 2.4 GHz, 5 GHz (W52, W53, and W56) and 6 GHz frequency bands, respectively. For example, the wireless module 105A may use channels belonging to the 2.4 GHz frequency band, the wireless module 105B may use channels belonging to the 5 GHz frequency bands W52 and W53, and the wireless module 105C may use channels in the 6 GHz frequency band. In the present embodiment, the wireless module 105A corresponds to a first wireless module recited in the claims, and the wireless modules 105B and 105C correspond to a second wireless module recited in the claims.Although each base station 1 according to the present embodiment is described as including three wireless modules 105A, 105B, and 105C, it may include four or more.

[0015] In the base station 1, the CPU 101 loads the program stored in the auxiliary storage unit 103 into the main storage unit 102 and executes it, thereby functioning as a usage status detection unit 111, a usage status notification unit 112, a usage status acquisition unit 113, a usage channel information acquisition unit 114, a usage channel determination unit 115, a usage channel notification unit 116, a frame acquisition unit 117, and a transmission control unit 118, as shown in Fig. 3. The auxiliary storage unit 103 shown in Fig. 2 is realized by a flash memory, a HDD, an SSD, or the like, and has a usage status storage unit 131, a usage channel storage unit 132, and a notification destination storage unit 133, as shown in Fig. 3. The main storage unit 102 shown in Fig. 2 is realized by a RAM, or the like, and has a frame buffer 121 that temporarily stores data frames received by the wireless modules 105B and 105C, as shown in Fig. 3.

[0016] As shown in FIG. 4A, for example, the usage status storage unit 131 stores usage status information for each of the multiple channels belonging to the 5 GHz frequency bands W52, W53, and W56 in association with a combination of channel information indicating each of the multiple channels, frequency band information indicating the frequency band to which each of the multiple channels belongs, and base station identification information. The usage status information stored in the usage status storage unit 131 includes information about the own station as well as usage status information transmitted from lower base stations, as described later. Here, the usage status information includes, for each of the multiple channels belonging to the frequency bands used by the wireless modules 105B and 105C, for example, the 5 GHz frequency bands W52, W53, and W56, information about the number of used base stations indicating the number of base stations using these channels, load factor information indicating the load factor of each of the multiple channels, and noise level information indicating the floor noise level of each of the multiple channels. The usage status information stored in the usage status storage unit 131 includes information about the own station and information about the lower base station transmitted from the lower base station. As the base station identification information, for example, a service set identifier (SSID) given to the wireless module 105A using a channel in the 2.4 GHz frequency band can be adopted. In the example shown in Fig. 4(A), in the base station 1B given the base station identification information SSID[1], the number of base stations using the channel "36ch" belonging to W52 in the 5 GHz band is n[1], the load factor of the channel "36ch" is L[1][%], and the floor noise level of the channel "36cn" is P[1][dBm].

[0017] As shown in FIG. 4B, for example, the channel-in-use storage unit 132 stores channel-in-use information indicating channels to be used when transmitting and receiving data frames to and from other base stations 1 located at higher and lower positions, in association with base station identification information for identifying the other base stations. Here, the base station identification information may be, for example, an SSID. The example shown in FIG. 4B is an example of information stored in the channel-in-use storage unit 132 of the base station 1B to which the base station identification information SSID[1] is assigned, and indicates that the channel "36ch" belonging to the frequency band W52 is used for transmitting and receiving data frames to and from the base station 1A to which the base station identification information SSID[0] is assigned, and the channel "52ch" belonging to the frequency band W53 is used for transmitting and receiving data frames to and from the base station 1C to which the base station identification information SSID[2] is assigned.

[0018] The notification destination storage unit 133 stores information on upper and lower base stations that are predetermined notification destinations. The information includes channel information (notification channel information) indicating a channel to be used when transmitting a later-described use status notification frame to another base station 1, base station identification information for identifying the base station itself, password information indicating a preset password, and MAC address information indicating a MAC (Media Access Control) address of the destination base station 1. Here, when the base station 1A is the top-level, the MAC address indicated by the MAC address information stored in the notification destination storage unit 133 of the base station 1A may be set uniquely. This indicates that there are no more destinations for the transmission of the use status notification frame of the base station 1A (i.e., it is the top level).

[0019] The usage status detection unit 111 detects the usage status of each of the three frequency bands W52, W53, and W56, and stores it in the usage status storage unit 131 as shown in FIG. 4(A). Specifically, the usage status detection unit 111 detects the number of used base stations, which is the number of base stations 1 using each channel, the load factor of each channel, and the noise level of floor noise in each channel, for each of the multiple channels belonging to the frequency bands W52, W53, and W56. Specifically, the usage status detection unit 111 specifies the number of used base stations for each of the multiple channels based on the number of types of SSIDs included in frames arriving at the station via the multiple channels belonging to the frequency bands W52, W53, and W56. In addition, the usage status detection unit 111 calculates the load factor of each of the multiple channels based on the frame size and the number of frames arriving at the station via each of the multiple channels belonging to the frequency bands W52, W53, and W56 per unit time set in advance. Furthermore, the usage status detection unit 111 calculates the noise level of the floor noise based on the SNR when a frame is received on each of the multiple channels belonging to the frequency bands W52, W53, and W56. Then, the usage status detection unit 111 stores in the usage status storage unit 131, for the multiple channels, number-of-used base stations information indicating the specified number of used base stations, load factor information indicating the calculated load factor, and noise level information indicating the calculated noise level, in association with a combination of the channel information, frequency band information corresponding to each channel, and base station identification information of the own station.

[0020] The usage status notification unit 112 generates a usage status notification frame including usage status information (i.e., information about the own station stored in the usage status storage unit 131) indicating the usage status of each of the multiple channels detected by the usage status detection unit 111, and transmits the generated usage status notification frame to a preset base station 1 on a notification channel via the wireless module 105A. Here, the preset base station 1 corresponds to the upper base station 1 of the own station, and when the upper base station of the base station 1B is the base station 1A, the usage status notification unit 112 of the base station 1B transmits the usage status notification frame to the base station 1A via the wireless module 105A. Also, when the upper base station of the base station 1C is the base station 1B, the usage status notification unit 112 of the base station 1C transmits the usage status notification frame to the base station 1B via the wireless module 105A. Here, the usage status notification unit 112 generates a usage status notification frame including the corresponding channel information and the base station identification information of the own station in addition to the usage status information stored in the usage status storage unit 131. Here, the usage status information includes the above-mentioned number of used base stations information, load factor information, and noise level information for each of the multiple channels, as described above. Then, the usage status notification unit 112 transmits the generated usage status notification frame based on the MAC address information of the preset base station 1 (e.g., 1A or 1B) stored in the notification destination storage unit 133 to another higher-level base station 1 (e.g., 1A or 1B) via the notification channel (e.g., a preset channel belonging to the 2.4 GHz frequency band) indicated by the notification channel information stored in the notification destination storage unit 133.

[0021] The usage status acquisition unit 113 acquires, via the wireless module 105A, a usage status notification frame including usage status information indicating the usage status of each of a plurality of frequency bands in another lower base station 1 stored in the notification destination storage unit 133 and transmitted from the other lower base station 1. After that, the usage status acquisition unit 113 extracts the usage status information included in the acquired usage status notification frame, the channel information corresponding to each of the information, and the base station identification information of the transmission source. Then, the usage status acquisition unit 113 stores the extracted usage status information, channel information, and base station identification information in the usage status storage unit 131 in association with each other. In addition, the usage status acquisition unit 113 notifies the use channel notification unit 116 of the base station identification information of the transmission source base station 1 (lower base station) of the usage status notification frame included in the usage status notification frame. This is information that will be the transmission destination of the identified usage channel information, as described later.

[0022] The channel-used information acquisition unit 114 acquires, via the wireless module 105A, a channel-used notification frame including channel-used information indicating a channel to be used for transmitting and receiving a data frame to and from the higher-level base station 1, which is transmitted from the higher-level base station 1 identified by the base station identification information stored in the notification destination storage unit 133. The channel-used information acquisition unit 114 extracts the channel-used information included in the acquired channel-used notification frame, and stores the extracted channel-used information in the channel-used storage unit 132 in association with the base station identification information of the higher-level base station 1. For example, when the channel-used information acquisition unit 114 of the base station 1B acquires a channel-used notification frame transmitted from the higher-level base station 1A, it extracts the channel-used information included in the acquired channel-used notification frame and stores it in the channel-used storage unit 132. When the channel-used information acquisition unit 114 of the base station 1C acquires a channel-used notification frame transmitted from the higher-level base station 1B, it extracts the channel-used information included in the acquired channel-used notification frame and stores it in the channel-used storage unit 132.

[0023] The use channel determination unit 115 determines a use channel to be used for transmitting and receiving a data frame to and from another base station 1 (lower base station) that is the source of the use status notification frame, based on the use channel information notified in advance by the higher-level base station and stored in the use channel storage unit 132 and the use status information on the base station itself and the lower-level base station stored in the use status storage unit 131. Here, the use channel determination unit 115 determines, as the above-mentioned use channel, a channel that belongs to one of three frequency bands W52, W53, and W56 in the 5 GHz band that is different from the frequency band to which the use channel set by the higher-level base station belongs. Specifically, the use channel determination unit 115 determines, as the use channel, a channel that is different from the use channel set by the higher-level base station, but more preferably, first, from among the channels that belong to a frequency band different from the frequency band to which the use channel set by the higher-level base station belongs, the use channel determination unit 115 refers to the use base station number information for each of the multiple channels stored in the use status storage unit 131, and identifies a channel with the smallest number of use base stations from among the multiple channels. Here, when there is only one channel with the minimum number of used base stations, the use channel determination unit 115 determines the one channel as the use channel. On the other hand, when there are multiple channels with the minimum number of used base stations, the use channel determination unit 115 refers to the load factor information of each of the multiple channels with the minimum number of used base stations stored in the use status storage unit 131, and identifies the channel with the minimum load factor from among the channels with the minimum number of used base stations. Here, when there is only one channel with the minimum load factor, the use channel determination unit 115 determines the one channel as the use channel. On the other hand, when there are multiple channels with the minimum load factor, the use channel determination unit 115 further refers to the noise level information of each of the multiple channels with the minimum load factor stored in the use status storage unit 131, and identifies the channel with the minimum noise level from among the channels with the minimum load factor. Here, when there is only one channel with the minimum noise level, the use channel determination unit 115 determines the one channel as the use channel.On the other hand, when there are multiple channels with the lowest noise level, the use channel determination unit 115 identifies one of the channels with the lowest noise level and determines the identified channel as the use channel. Here, the use channel determination unit 115 may identify the channel with the smallest channel number indicated by the channel information, for example. In addition, the use channel determination unit 115 stores the use channel information indicating the use channel thus determined in the use channel storage unit 132 in association with the base station identification information of the corresponding lower-level base station 1.

[0024] In the above description, the channel-in-use determination unit 115 identifies a channel belonging to one of the three frequency bands W52, W53, and W56 in the 5 GHz band that is different from the frequency band to which the channel-in-use corresponding to the pre-set base station 1 belongs, but the channel may be another channel belonging to the same frequency band of frequency bands W52, W53, and W56 (for example, identifying 60ch for channel 52ch in W53, which are not adjacent bands).

[0025] The channel in use notification unit 116 transmits a channel in use notification frame including channel in use information indicating the channel in use determined by the channel in use determination unit 115 to another base station 1 (lower base station) that is the source of the usage status notification frame via the wireless module 105A. For example, when the channel in use notification unit 116 of the base station 1A receives a channel in use notification frame from the base station 1B, it transmits the determined channel in use notification frame to the base station 1B. Also, when the channel in use notification unit 116 of the base station 1B receives a channel in use notification frame from the base station 1C, it transmits the determined channel in use notification frame to the base station 1C.

[0026] Frame acquisition unit 117 determines whether or not a connection request frame or a connection permission frame has been received in wireless modules 105A, 105B, and 105C, and notifies the determination result to usage status detection unit 111, usage status acquisition unit 113, or transmission control unit 118. In addition, frame acquisition unit 117 acquires data frames received by wireless modules 105B and 105C, and stores the acquired data frames in frame buffer 121.

[0027] The transmission control unit 118 controls the transmission of the data frames stored in the frame buffer 121 to other base stations 1 based on the used channel information stored in the used channel storage unit 132 .

[0028] Next, the operation of the communication system according to the present embodiment will be described in detail with reference to Fig. 5 and Fig. 6. Here, a case will be described in which the base station 1A is at the top, the base station 1A is at the top of the base station 1B, and the base station 1B is at the top of the base station 1C. Also, a case will be described in which data frames are transmitted and received via the wireless modules 105B and 105C.

[0029] First, as shown in FIG. 5, the base station 1A detects the usage status of each of the multiple channels belonging to the frequency band used by the wireless module 105B (step S1), and detects the usage status of each of the multiple channels belonging to the frequency band used by the wireless module 105C (step S2). Then, the base station 1A stores usage status information indicating the detected usage status in the usage status storage unit 131 of the base station 1A. Similarly, the base station 1B also detects the usage status of each of the multiple channels belonging to the frequency band used by the wireless module 105B (step S3), and detects the usage status of each of the multiple channels belonging to the frequency band used by the wireless module 105C (step S4). Then, the base station 1B stores the usage status information indicating the detected usage status in the usage status storage unit 131 of the base station 1B. Furthermore, the base station 1C also detects the usage status of each of the multiple channels belonging to the frequency band used by the wireless module 105B (step S5), and detects the usage status of each of the multiple channels belonging to the frequency band used by the wireless module 105C (step S6). Then, the base station 1C stores the usage status information indicating the detected usage status in the usage status storage unit 131 of the base station 1C.

[0030] Next, suppose that the base station 1B transmits an authentication request frame to the base station 1A via the wireless module 105A and then receives an authentication response frame transmitted from the base station 1A at the wireless module 105A (not shown), whereby authentication such as open system authentication is successful. In this case, a connection request frame including SSID information indicating the SSID assigned to the wireless module 105A of the base station 1B is transmitted from the wireless module 105A of the base station 1B to the wireless module 105A of the base station 1A via a notification channel (step S7). On the other hand, when the base station 1A acquires the connection request frame via the wireless module 105A, a connection permission frame corresponding to the connection request frame is transmitted from the wireless module 105A of the base station 1A to the wireless module 105A of the base station 1B via a notification channel (step S8).

[0031] On the other hand, when the base station 1B receives the connection permission frame via the wireless module 105A, it generates a usage status notification frame including the usage status information stored in the usage status storage unit 131 (step S9). Then, the generated usage status notification frame is transmitted from the wireless module 105A of the base station 1B to the wireless module 105A of the base station 1A via a notification channel (step S10). On the other hand, when the base station 1A receives the usage status notification frame via the wireless module 105A, it stores the usage status information included in the received usage status notification frame in the usage status storage unit 131. Then, the base station 1A determines a usage channel to be used when transmitting and receiving a data frame to and from the base station 1B based on the usage status information of the base station 1A and the usage status information of the base station 1B stored in the usage status storage unit 131 (step S11). Thereafter, base station 1A generates a channel-in-use notification frame including channel-in-use information indicating the determined channel-in-use (step S12), and the generated channel-in-use notification frame is transmitted from wireless module 105A of base station 1A to wireless module 105A of base station 1B via a notification channel (step S13).

[0032] On the other hand, when the base station 1B receives the use channel notification frame via the wireless module 105A, it stores the use channel information included in the received use channel notification frame in the use channel storage unit 132. This use channel information indicates a channel belonging to the frequency band used by the wireless module 105B, and data communication between the base station 1A and the base station 1B is performed using the channel (corresponding to the first use channel) stored in the use channel storage unit. It is assumed that the authentication is successful (not shown) when the base station 1B transmits an authentication request frame to the base station 1A via the wireless module 105B and then receives an authentication response frame transmitted from the base station 1A at the wireless module 105B. In this case, a connection request frame including SSID information indicating the SSID assigned to the wireless module 105B of the base station 1B is transmitted from the wireless module 105B of the base station 1B to the wireless module 105B of the base station 1A using the use channel stored in the use channel storage unit 132 (step S14). On the other hand, when the base station 1A receives a connection request frame via the wireless module 105B, a connection permission frame corresponding to the connection request frame is transmitted from the wireless module 105B of the base station 1A to the wireless module 105B of the base station 1B (step S15).

[0033] Thereafter, it is assumed that the base station 1C transmits an authentication request frame to the base station 1B via the wireless module 105A, and then receives an authentication response frame transmitted from the base station 1B at the wireless module 105A, whereby the authentication is successful. In this case, a connection request frame including SSID information indicating the SSID assigned to the wireless module 105A of the base station 1C is transmitted from the wireless module 105A of the base station 1C to the wireless module 105A of the base station 1B (step S16). On the other hand, when the base station 1B receives the connection request frame via the wireless module 105A, a connection permission frame corresponding to the connection request frame is transmitted from the wireless module 105A of the base station 1B to the wireless module 105A of the base station 1C (step S17).

[0034] When the base station 1C receives the connection permission frame via the wireless module 105A, it generates a usage status notification frame including the usage status information stored in the usage status storage unit 131 (step S18). Next, the generated usage status notification frame is transmitted from the wireless module 105A of the base station 1C to the wireless module 105A of the base station 1B via the notification channel (step S19). On the other hand, as shown in FIG. 6 below, when the base station 1B receives the usage status notification frame via the wireless module 105A, it stores the usage status information included in the received usage status notification frame in the usage status storage unit 131. Then, the base station 1B determines a usage channel (corresponding to a second usage channel) to be used when transmitting and receiving a data frame with the base station 1C based on the usage status information of the base station 1B and the usage status information of the base station 1C stored in the usage status storage unit 131 and the usage channel information to be used for data frame communication with the base station 1A stored in the usage channel storage unit 132 (step S20). As the usage channel, a channel different from the usage channel to be used for data communication with the base station 1A is selected. Preferably, the channel to be used is a channel of a different frequency band from the channel to be used for data communication with base station 1A. Next, base station 1B generates a channel-to-be-used notification frame including channel-to-be-used information indicating the determined channel to be used (step S21), and the generated channel-to-be-used notification frame is transmitted from wireless module 105A of base station 1B to wireless module 105A of base station 1C via the notification channel (step S22).

[0035] On the other hand, when the base station 1C receives the used channel notification frame via the wireless module 105A, it stores the used channel information included in the received used channel notification frame in the used channel storage unit 132. This used channel information indicates a channel belonging to the frequency band used by the wireless module 105C, and data communication between the base stations 1B and 1C is performed using the channel stored in the used channel storage unit. It is assumed that the authentication is successful (not shown) when the base station 1B transmits an authentication request frame to the base station 1B via the wireless module 105C and then receives an authentication response frame transmitted from the base station 1B at the wireless module 105C. In this case, a connection request frame including SSID information indicating the SSID assigned to the wireless module 105C of the base station 1C is transmitted from the wireless module 105C of the base station 1C to the wireless module 105C of the base station 1B (step S23). On the other hand, when the base station 1B receives the connection request frame via the wireless module 105C, a connection permission frame corresponding to the connection request frame is transmitted from the wireless module 105C of the base station 1B to the wireless module 105C of the base station 1C (step S24).

[0036] After that, when the base station 1A receives a data frame addressed to the terminal device 3E or 3F under the base station 1C from the terminal device 3A or 3B under the base station itself (step S25), the acquired data frame is transmitted from the wireless module 105B of the base station 1A to the wireless module 105B of the base station 1B (step S26). On the other hand, when the base station 1B receives the data frame via the wireless module 105B, the received data frame is transmitted from the wireless module 105C of the base station 1B to the wireless module 105C of the base station 1C (step S27). Note that the channel used for transmission from the base station 1A to the base station 1B is different from the channel used for transmission from the base station 1B to the base station 1C. This avoids channel interference between reception and transmission in the base station 1B, and can suppress a decrease in throughput in data frame transmission. On the other hand, when the base station 1C receives the data frame via the wireless module 105C, it transmits the received data frame to the terminal devices 3E and 3F (step S28).

[0037] Next, the communication control process executed by the base station 1 according to this embodiment will be described in detail with reference to Figs. 7 to 9. This communication control process is started, for example, when the base station 1 is powered on. Here, the communication control process of the base station 1 will be described separately for the case of a higher-level base station 1 (Figs. 7 and 8) and a lower-level base station 1 (Fig. 9). Here, the detailed description will be given on the assumption that, for example, the base station 1A is the higher-level base station 1 and the base station 1B is the lower-level base station 1.

[0038] First, the communication control process of the upper base station 1 (base station 1A) will be described with reference to FIG. 7. As shown in FIG. 7, the usage status detection unit 111 of the base station 1A detects the usage status of each of the multiple frequency bands W52, W53, and W56 in the 5 GHz band (step S101). Next, the usage status acquisition unit 113 receives an authentication request frame from the lower base station 1 (base station 1B) via the wireless module 105A, transmits a corresponding authentication response frame to the sender of the received authentication request frame via the wireless module 105A, and assumes that the authentication is successful. The frame acquisition unit 117 judges whether or not a connection request frame including SSID information of the wireless module 105A of the lower base station 1 has been received (step S102). If it is judged that the connection request frame has been received, it notifies the usage status acquisition unit 113 to that effect, and the process proceeds to step S103 (step S102: Yes). On the other hand, if it is judged that the connection request frame has not been received, the process of step S102 is repeated (step S102: No). Next, the usage status acquisition unit 113 transmits a connection permission frame to the lower base station 1 (base station 1B) that is the source of the connection request frame via the wireless module 105A (step S103). Next, the usage status acquisition unit 113 judges whether or not the usage status notification frame has been received (step S104). If it is judged that the usage status notification frame has been received, the process proceeds to step 105 (step S104: Yes). On the other hand, if it is judged that the usage status notification frame has not been received, the process of step S104 is repeated (step S104: No). The usage channel determination unit 115 determines a usage channel to be used for transmitting and receiving a data frame to and from the lower base station 1 (base station 1B) that is the source of the usage status notification frame, based on the usage channel information stored in the usage channel storage unit 132 and the usage status information stored in the usage status storage unit 131 (step S105).

[0039] Here, the use channel determination process (step S105 in FIG. 7) executed by the use channel determination unit 115 will be described in detail with reference to FIG. 8. The use channel determination unit 115 first refers to the load factor information of each of the multiple channels stored in the use status storage unit 131, and identifies the channel with the smallest load factor from among the multiple channels (step S201). Next, the use channel determination unit 115 determines whether or not there are multiple channels with the smallest load factor (step S202). Here, if the use channel determination unit 115 determines that there is only one channel with the smallest load factor (step S202: No), it determines the identified one channel as the use channel (step 208). On the other hand, if the use channel determination unit 115 determines that there are multiple channels with the smallest load factor (step S202: Yes), it refers to the number of used base stations information of each of the multiple channels with the smallest load factor stored in the use status storage unit 131, and identifies the channel with the smallest number of used base stations from among the channels with the smallest load factor (step S203).

[0040] Next, the channel-to-be-used determining unit 115 determines whether or not there are multiple channels with the minimum number of base stations used (step S204). If the channel-to-be-used determining unit 115 determines that there is only one channel with the minimum number of base stations used (step S204: No), it determines the identified one channel as the channel to be used (step S208). On the other hand, if the channel-to-be-used determining unit 115 determines that there are multiple channels with the minimum number of base stations used (step S204: Yes), it refers to the noise level information of each of the multiple channels with the minimum load rates stored in the usage status storage unit 131, and identifies the channel with the minimum noise level from among the channels with the minimum load rates (step S205).

[0041] Thereafter, the use channel determination unit 115 judges whether or not there are multiple channels with the lowest noise level (step S206). Here, if the use channel determination unit 115 judges that there is only one channel with the lowest noise level (step S206: No), it determines the identified one channel as the use channel (step S208). On the other hand, if the use channel determination unit 115 judges that there are multiple channels with the lowest noise level (step S206: Yes), it identifies one channel from among the channels with the lowest noise level (step S207) and determines the identified one channel as the use channel (step S208). Here, the use channel determination unit 115 stores use channel information indicating the determined use channel in the use channel storage unit 132 in association with the base station identification information of the corresponding base station 1. Although not shown in Figure 8, if there is a higher-level base station relative to the base station in question, in the process of determining the channel to be used, a process is performed to exclude channels included in the channel to be used information transmitted from the higher-level base station from the candidates.

[0042] Returning to FIG. 7, next, the use channel notification unit 116 generates a use channel notification frame including use channel information indicating the use channel determined by the use channel determination unit 115, and transmits the generated use channel notification frame to the lower base station 1 (base station 1B) (step S106). Next, the frame acquisition unit 117 determines whether or not a connection request frame including SSID information indicating the SSID assigned to the wireless module 105B of the lower base station 1 (base station 1B) has been received (step S107). If it is determined that the connection request frame has been received, it notifies the usage status acquisition unit 113 to that effect, and transitions to step 108 (step S107: Yes). On the other hand, if it is determined that the connection request frame has not been received, the process of step S107 is repeated (step S107: No). Here, it is assumed that the usage status acquisition unit 113 receives an authentication request frame from the lower base station 1 (base station 1B) via the wireless module 105B, transmits a corresponding authentication response frame to the lower base station 1 (base station 1B) that is the source of the received authentication request frame via the wireless module 105B, and the authentication is successful. The usage status acquisition unit 113 transmits a connection permission frame corresponding to the connection request frame to the wireless module 105B of the lower base station 1 (base station 1B) via the wireless module 105B of the base station 1A (step S108). After that, data can be transmitted and received between the wireless module 105B of the base station 1A and the wireless module 105B of the base station 1B (step 109).

[0043] Next, the communication control process of the lower base station 1 (base station 1B) will be described. As shown in FIG. 9, the usage status detection unit 111 of the base station 1B detects the usage status of each of the multiple frequency bands W52, W53, and W56 in the 5 GHz band (step S301). Here, it is assumed that the usage status acquisition unit 113 transmits an authentication request frame to the upper base station 1 (base station 1A) via the wireless module 105A, and receives a corresponding authentication response frame from the reception source of the authentication request frame via the wireless module 105A, and authentication is successful. The usage status notification unit 112 of the base station 1B transmits a connection request frame including SSID information of the wireless module 105A of the upper base station 1 (base station 1A) to the upper base station 1 (base station 1A) via the wireless module 105A (step S302). Next, the frame acquisition unit 117 of the base station 1B determines whether or not a connection permission frame transmitted from the upper base station 1 (base station 1A) via the wireless module 105A has been received (step S303). If it is determined that the connection request frame has been received, it notifies the usage status detection unit 111 to that effect, and the process proceeds to step S304 (step S303: Yes). On the other hand, if it is determined that the connection permission frame has not been received, the process of step S303 is repeated (step S303: No). Next, the usage status notification unit 112 generates a usage status notification frame including usage status information indicating the usage status of each of the multiple channels detected by the usage status detection unit 111, and transmits the generated usage status notification frame to the upper base station 1 (base station 1A) via the wireless module 105A (step S304). Next, the usage channel information acquisition unit 114 determines whether or not the usage channel notification frame has been received from the upper base station 1 (base station 1A) (step S305). If it is determined that the usage channel notification frame has been received, the usage channel information included in the received usage channel notification frame is stored in the usage channel storage unit 132, and the process proceeds to step 306 (step S305: Yes). On the other hand, if it is determined that the used channel notification frame has not been received, the process of step S305 is repeated (step S305: No).Next, a connection request frame including SSID information indicating the SSID assigned to the wireless module 105B of the base station 1B is transmitted from the wireless module 105B of the base station 1B to the wireless module 105B of the base station 1A using the used channel stored in the used channel storage unit 132 (step S306). Next, the frame acquisition unit 117 judges whether or not a connection permission frame, which is a response to the connection request frame, has been received from the wireless module 105B of the upper base station 1 (base station 1A) (step S307). If it is judged that the connection permission frame has been received, it notifies the transmission control unit 118 to that effect, and transitions to step 308 (step S307: Yes). On the other hand, if it is judged that the connection permission frame has not been received, the process of step S307 is repeated (step S307: No). Thereafter, data can be transmitted and received between the wireless module 105B of the base station 1A and the wireless module 105B of the base station 1B (step 308).

[0044] As described above, according to the base station 1 according to the present embodiment, the use channel determination unit 115 determines the use channel to be used for transmitting and receiving data frames with the other lower base station 1, based on the use status information indicating the use status of each of the three frequency bands W52, W53, and W56 of the base station itself and the second use status information indicating the use status of each of the three frequency bands W52, W53, and W56 in the other lower base station 1, while avoiding the use channel notified as the use channel to be used for transmitting and receiving data frames with the other upper base station 1. As a result, the use channel to be used for transmitting and receiving data frames with the higher base station 1 and the use channel to be used for transmitting and receiving data frames with the lower base station 1 are different, and it becomes easier to secure the band required for wireless communication between the base stations when transmitting and receiving data frames from a slave unit under the base station itself to a slave unit under the higher base station 1 and a slave unit under the lower base station 1. Therefore, it is possible to suppress the decrease in throughput in data frame transmission caused by the band shortage that occurred in the conventional WDS communication in which wireless communication between base stations is performed using one use channel.

[0045] (Embodiment 2) The base station according to the present embodiment differs from the first embodiment in that it includes a detection and discrimination unit that discriminates whether or not radar waves are detected in any of the channels belonging to the second frequency band to which the channel used for transmitting and receiving data frames to and from other base stations belongs. In the base station according to the present embodiment, when the detection and discrimination unit discriminates that radar waves are detected in the channel used, the transmission control unit temporarily changes the channel used to a channel belonging to the first frequency band, and transmits the data frame to the other base station via the first wireless module. The first frequency band means a band that does not overlap with a frequency band used by radar waves, for example, the W52 band in the 2.4 GHz band or the 5 GHz band. On the other hand, the second frequency band is the 5 GHz and 6 GHz frequency bands that are suitable for transmitting data frames, and more specifically, it is a band including the W53 and W56 bands used by radar waves in the 5 GHz band.

[0046] The hardware configuration of the base station according to this embodiment is the same as the hardware configuration of the base station 1 described in the first embodiment. Hereinafter, the same components as those in the first embodiment will be described using the same reference numerals as those in FIG. 1 and FIG. 2 as appropriate. In the base station 2001 according to this embodiment, the CPU 101 shown in FIG. 2 loads a program stored in the auxiliary storage unit 103 into the main storage unit 102 and executes it, thereby functioning as a usage status detection unit 111, a usage status notification unit 112, a usage status acquisition unit 113, a usage channel information acquisition unit 114, a usage channel determination unit 115, a usage channel notification unit 2116, a frame acquisition unit 117, a transmission control unit 2118, and a detection discrimination unit 2119, as shown in FIG. 10. In FIG. 10, the same components as those in the first embodiment are denoted by the same reference numerals as those in FIG. 3. In addition, the auxiliary storage unit 103 shown in FIG. 2 has a usage status storage unit 131, a usage channel storage unit 2132, and a notification destination storage unit 133, as shown in FIG. 10. Furthermore, the main storage unit 102 shown in Fig. 2 has a frame buffer 121 that temporarily stores frames received by the wireless modules 105A and 105B, as shown in Fig. 10. The channel-in-use storage unit 2132 stores channel-in-use information indicating a channel normally used when transmitting a data frame to each of the other base stations and a channel used when a radar wave is detected, in association with base station identification information that identifies the other base stations, as shown in Fig. 11. In the example shown in Fig. 11, the channels normally used for transmitting and receiving data frames are set to channels belonging to the 5 GHz frequency bands W53 and W56, and the channels used when a radar wave is detected (corresponding to channels of the first frequency band) are set to channels (1ch and 11ch) belonging to the 2.4 GHz frequency band.

[0047] 10, detection discrimination unit 2119 discriminates whether or not a used channel used for transmitting and receiving data frames to and from other base stations 1 (upper and lower base stations) is a channel belonging to frequency band W53 or W56 in a preset monitoring cycle and whether radar waves have been detected in either of them. If detection discrimination unit 2119 discriminates that the used channel is a channel belonging to frequency band W53 or W56 and that radar waves have been detected in either of them, it notifies used channel notification unit 2116 and transmission control unit 2118 that radar waves have been detected in the used channel.

[0048] When the detection and discrimination unit 2119 determines that the used channel has detected radar waves and the used channel belongs to a frequency band (e.g., W53 and W56 of the 5 GHz band) that needs to be changed to a different channel when radar waves are detected in the second frequency band, the transmission control unit 2118 stops communication in the used channel determined to have detected radar waves, changes the used channel to a channel belonging to the first frequency band, e.g., the 2.4 GHz frequency band, and transmits the data frame to another base station 1 via the wireless module 105A. Specifically, when the transmission control unit 2118 is notified by the detection and discrimination unit 2119 that the radar waves have been detected, the transmission control unit 2118 changes the used channel to the 2.4 GHz band channel stored in the used channel storage unit 2132 when the radar waves were detected, and transmits the data frame to another base station 1 via the wireless module 105A. The transmission control unit 2118 may also change the used channel to a channel in the second frequency band where radar waves are not detected (a channel belonging to the 5 GHz frequency band W53 and W56). When a preset carrier sense time has elapsed, the transmission control unit 2118 may change the changed usage channel back to the channel determined by the usage channel determination unit 115. Here, the carrier sense time is set to, for example, 30 minutes.

[0049] When the detection discrimination unit 2119 notifies the use channel that radar waves have been detected in the use channel, the use channel notification unit 2116 identifies the use channel (e.g., a channel in the 2.4 GHz band) stored in the use channel storage unit 2132 when the radar waves corresponding to the notified frequency band information are detected. Then, the use channel notification unit 2116 generates a temporary use channel notification frame including use channel information indicating the identified use channel, and transmits the generated temporary use channel notification frame via the wireless module 105A to other base stations 1 using the channels belonging to the frequency bands W53 and W56 in which the radar waves were detected. In addition, when the above-mentioned carrier sense time has elapsed after the transmission control unit 2118 changes the use channel, the use channel notification unit 2116 generates a use channel return notification frame including use channel information indicating the use channel determined by the use channel determination unit 115, and transmits the generated use channel return notification frame via the wireless module 105A to other base stations 1 using the changed use channel.

[0050] Next, the operation of the communication system according to the present embodiment will be described in detail with reference to FIG. 12. In FIG. 12, the same processes as those in the first embodiment are denoted by the same reference numerals as those in FIG. 5 and FIG. 6. As in the description of FIG. 5 and FIG. 6, a case will be described in which the upper base station of the base station 2001B is the base station 2001A, the upper base station of the base station 2001C is the base station 2001B, and data frames are transmitted and received via the wireless modules 105B and 105C. First, after a series of processes up to step S28 described in the first embodiment are performed, it is assumed that the base station 2001B detects a radar wave in the frequency band to which the channel used by the wireless module 105B belongs (step S2001). Specifically, it is assumed that it is determined that the base station 2001B detects a radar wave in the channel used by the wireless module 105B. In this case, the base station 2001B identifies the channel to be used when radar waves are detected, which is stored in the channel to be used storage unit 2132, and generates a temporary channel to be used notification frame including channel to be used information indicating the identified channel to be used (step S2002). Next, the generated temporary channel to be used notification frame is transmitted from the wireless module 105A of the base station 2001B to the wireless module 105A of the base station 2001A (step S2003). Next, the base station 2001B changes the channel to be used when radar waves are detected, for transmitting and receiving data frames to and from the base station 2001A (step S2004).

[0051] On the other hand, when the base station 2001A receives the temporary use channel notification frame, it changes the use channel to the channel indicated by the use channel information included in the received temporary use notification frame (step S2005). After that, the data frame is transmitted from the wireless module 105A of the base station 2001A to the wireless module 105A of the base station 2001B through the changed use channel (step S2006).

[0052] Next, it is assumed that the base station 2001B determines that the above-mentioned carrier sense time has elapsed after changing the channel in use (step S2007). In this case, the base station 2001B generates an in-use channel return notification frame including in-use channel information indicating the channel in use determined by the channel in use determination unit 115 (step S2008). Then, the generated in-use channel return notification frame is transmitted from the wireless module 105A of the base station 2001B to the wireless module 105A of the base station 2001A (step S2009). Thereafter, the base station 2001B changes the channel in use for transmitting and receiving data frames to the base station 2001A back to the channel in use determined by the channel in use determination unit 115 (step S2010).

[0053] On the other hand, when the base station 2001A receives the used channel return notification frame, it changes the used channel to the channel indicated by the used channel information included in the received used channel return notification frame (step S2011). Next, the data frame is again transmitted from the wireless module 105A of the base station 2001A to the wireless module 105A of the base station 2001B via the used channel determined by the used channel determination unit 115 (step S2012).

[0054] Next, the communication control process executed by the base station 1 according to this embodiment will be described in detail with reference to Fig. 13. Here, it is assumed that transmission and reception of data frames has already started. Also, the base station 1 is performing wireless communication with a plurality of other base stations 1 on different channels. First, the channel in use notification unit 2116 determines whether or not the detection and determination unit 2119 has detected radar waves on any of the channels in use used for transmitting and receiving data frames with the other base stations 1 (step S2101). Here, as long as it is determined that the channel in use notification unit 2116 has not detected radar waves on any of the channels in use used for transmitting and receiving data frames (step S2101: No), the process of step S2101 is repeated again.

[0055] On the other hand, suppose that the channel in use notification unit 2116 determines that radar waves have been detected in a channel in use used for transmitting and receiving data frames with another base station 1 (step S2101: Yes). In this case, when the detection and determination unit 2119 notifies the channel in use notification unit 2116 that radar waves have been detected in the channel in use, the channel in use notification unit 2116 identifies the channel in use when the radar waves were detected that is stored in the channel in use storage unit 2132. Then, the channel in use notification unit 2116 generates a temporary channel in use notification frame including channel in use information indicating the identified channel in use, and transmits the generated temporary channel in use notification frame via the wireless module 105A to the other base station 1 of the communication using that channel (step S2102).

[0056] Next, when the transmission control unit 2118 is notified by the detection discrimination unit 2119 that radar waves have been detected on the channel in use, the transmission control unit 2118 changes the channel in use to the channel in use when radar waves are detected, which is stored in the channel in use memory unit 2132 (step S2103).

[0057] Thereafter, the channel in use notification unit 2116 judges whether the above-mentioned carrier sense time has elapsed after the transmission control unit 2118 has changed the channel in use (step S2104). Here, if the channel in use notification unit 2116 judges that the carrier sense time has not yet elapsed (step S2104: No), it repeats the process of step S2104 again. On the other hand, it is assumed that the channel in use notification unit 2116 judges that the carrier sense time has elapsed (step S2104: Yes). In this case, the channel in use notification unit 2116 generates a channel in use return notification frame including the channel in use information indicating the channel in use determined by the channel in use determination unit 115, and transmits the generated channel in use return notification frame to another base station 1 using the changed channel in use via the wireless module 105A (step S2105). Next, the transmission control unit 2118 changes the changed channel in use to the channel determined by the channel in use determination unit 115 again (step S2106). Then, the process of step S2101 is executed again.

[0058] As described above, in base station 2001 according to the present embodiment, detection and discrimination unit 2119 discriminates whether or not radar waves are detected on any of the channels used for transmitting and receiving data frames to and from other base stations 2001. Then, transmission control unit 2118 changes the channel used in which radar waves are detected to the channel used when detection and discrimination unit 2119 discriminates that radar waves are detected, and transmits the data frame to other base stations via the first wireless module. This allows transmission of data frames to other base stations 1 to be continued even within the carrier sense time when radar waves are detected on the channel used determined by channel used determination unit 115. This makes it possible to suppress a decrease in throughput in data frame transmission caused by interference with radar waves.

[0059] (Modification) Although each embodiment of the present invention has been described above, the present invention is not limited to the configuration of each of the above-mentioned embodiments. For example, a base station 1 (e.g., 1B, 1C) may transmit use status notification information to a higher-level base station 1 (e.g., 1A, 1B) using TCP / IP. In this case, the notification destination storage unit 133 may store IP address information indicating the IP address of the base station 1 to which the use status notification frame is to be transmitted. Then, the use status notification unit 112 may generate a use status notification frame including TCP header information and IP header information and transmit the frame to the higher-level base station 1.

[0060] In each embodiment, the frequency band used by the wireless module 105A is not limited to the 2.4 GHz frequency band, and for example, the wireless module 105A may use frequency band W52, and the wireless modules 105B and 105C may use any channel belonging to frequency bands W53 and W56. In this case, even when radar waves are detected, there is no need to change the wireless module for transmitting and receiving data frames to the 2.4 GHz wireless module 105A.

[0061] In each embodiment, the base station 1, 2001 may be capable of communicating with other base stations 1, 2001 in the 6 GHz frequency band in addition to the 2.4 GHz frequency band and the 5 GHz frequency bands W52, W53, and W56. Here, the 6 GHz frequency band has a bandwidth of 20 MHz and 60 channels. In this case, the base station 1, 2001 may be provided with five wireless modules corresponding to the five frequency bands, respectively, or may be realized as one wireless module for both the 2.4 GHz frequency band and the 5 GHz frequency band, or may be realized as one wireless module for both the 5 GHz frequency band and the 6 GHz frequency band, and any combination of wireless modules corresponding to each of the five frequency bands may be used. In this case, as shown in Fig. 14, for example, eight base stations 1A, 1B, 1C, 1D, 1E, 1F, 1G, and 1H can be configured to communicate with adjacent base stations via a channel in use belonging to one of four frequency bands (W53, W54, W56 in the 5 GHz frequency band, and the 6 GHz band) suitable for transmitting and receiving data frames, and to use channels in different frequency bands for adjacent wireless communication links. In this case, it is preferable that the usage status notification frame and the usage channel notification frame are transmitted and received via a channel in the 2.4 GHz frequency band, which is less likely to be interrupted.

[0062] In each embodiment, the base station 1, 2001 may include only one wireless module 105, and the single wireless module 105 may function as three virtual wireless modules 105A, 105B, and 105C.

[0063] In each embodiment, an example has been described in which the use channel determination unit 115 determines a use channel based on all of the number of base stations in use, the load factor, and the noise level for each of the channels belonging to the three frequency bands W52, W53, and W56. However, this is not limited to this, and the use channel determination unit 115 may determine a use channel based on only one or two of the number of base stations in use, the load factor, and the noise level for each of the channels belonging to the three frequency bands W52, W53, and W56. Also, in each embodiment, an example has been described in which the use channel determination unit 115 determines the magnitude in the order of the load factor, the number of base stations in use, and the noise level to determine a use channel, but this order is not particularly limited.

[0064] The various functions of the base station 1, 2001 according to the present invention can be realized by using a computer system equipped with a wireless communication module, without using a dedicated system. For example, a program for executing the above operations may be stored in a non-transitory recording medium (such as a CD-ROM) that can be read by the computer system and distributed to a computer connected to the network, and the base station 1, 2001 that executes the above-mentioned processes may be configured by installing the program in the computer system.

[0065] The method of providing the program to the computer is arbitrary. For example, the program may be uploaded to a server on a communication line and distributed to the computer via the communication line. The computer then starts the program and executes it under the control of the OS in the same way as other applications. In this way, the computer functions as the base station 1, 2001 that executes the above-mentioned processing.

[0066] Although the embodiment and the modified examples of the present invention have been described above, the present invention is not limited to these. The present invention includes appropriate combinations of the embodiment and the modified examples, and appropriate modifications thereto. [Industrial Applicability]

[0067] The present invention is suitable as a base station for constructing a wireless LAN network using the WDS function. [Explanation of symbols]

[0068] 1, 1A, 1B, 1C, 2001, 2001A, 2001B, 2001C: base station, 3, 3A, 3B, 3C, 3D, 3E, 3F: terminal device, 101: CPU, 102: main memory, 103: auxiliary memory, 105A, 105B, 105C: wireless module, 109: bus, 111: usage status detection unit, 112: usage status notification unit, 113: usage status acquisition unit, 114: usage channel information acquisition unit, 115: usage channel determination unit, 116, 2116: usage channel notification unit, 117: frame acquisition unit, 118, 2118: transmission control unit, 121: frame buffer, 131: usage status storage unit, 132, 2132: usage channel storage unit, 133: notification destination storage unit, 2119: detection and discrimination unit

Claims

1. A plurality of wireless modules that wirelessly communicate with a plurality of other base stations on channels belonging to a plurality of frequency bands, the channels including a first frequency band that is a frequency band that does not overlap with a frequency band used by radar waves, and at least one second frequency band that includes a frequency band used by radar waves; a usage channel information acquisition unit that acquires first usage channel information indicating a first usage channel used for transmitting and receiving a data frame to and from the first base station, the first usage channel information being transmitted from a preset first base station among the other plurality of base stations; a usage channel determination unit that determines a channel different from the first usage channel as a second usage channel to be used for transmitting and receiving a data frame between the second base station and the other plurality of base stations, the second base station being different from the first base station; a use channel notification unit that transmits second use channel information indicating the determined second use channel to the second base station via one of the plurality of wireless modules; a usage status detection unit that detects a usage status of each of the plurality of frequency bands; a usage status notifying unit that transmits first usage status information indicating the detected usage status to the first base station via one of the plurality of wireless modules; a usage status acquisition unit that acquires second usage status information indicating a usage status of each of the plurality of frequency bands in the second base station, the second usage status information being transmitted from the second base station, via any one of the plurality of wireless modules; The use channel determination unit determines the second use channel based on the first use channel information, the first use status information, and the second use status information. Base station.

2. A plurality of wireless modules that wirelessly communicate with a plurality of other base stations on channels belonging to a plurality of frequency bands, the channels including a first frequency band that is a frequency band that does not overlap with a frequency band used by radar waves, and at least one second frequency band that includes a frequency band used by radar waves; a usage channel information acquisition unit that acquires first usage channel information indicating a first usage channel used for transmitting and receiving a data frame to and from the first base station, the first usage channel information being transmitted from a preset first base station among the other plurality of base stations; a usage channel determination unit that determines a channel belonging to any one of the plurality of frequency bands, which is different from the first usage channel, as a second usage channel to be used for transmitting and receiving a data frame between the plurality of other base stations and a second base station, which is different from the first base station; a use channel notification unit that transmits second use channel information indicating the determined second use channel to the second base station via one of the plurality of wireless modules; a usage status detection unit that detects a usage status of each of the plurality of frequency bands; a usage status notifying unit that transmits first usage status information indicating the detected usage status to the first base station via one of the plurality of wireless modules; a usage status acquisition unit that acquires second usage status information indicating a usage status of each of the plurality of frequency bands in the second base station, the second usage status information being transmitted from the second base station, via any one of the plurality of wireless modules; The use channel determination unit determines the second use channel based on the first use channel information, the first use status information, and the second use status information. Base station.

3. The plurality of wireless modules include a first wireless module that communicates with the other plurality of base stations on a channel that belongs to the first frequency band; a plurality of second wireless modules configured to wirelessly communicate with other base stations on channels belonging to the second frequency band; the first channel of use and the second channel of use belong to the at least one second frequency band; the first usage status information, the first usage channel information, the second usage status information, and the second usage channel information are transmitted and received by the first wireless module; The base station according to claim 1 or 2.

4. There are a plurality of the second frequency bands, the use channel determination unit determines, as the second use channel, any one of channels belonging to another second frequency band different from a second frequency band to which the first use channel belongs among the plurality of second frequency bands, based on the first use status information and the second use status information; A base station according to any one of claims 1 to 3.

5. the first usage status information and the second usage status information indicate at least one of a number of used base stations indicating a number of other base stations using at least one channel belonging to the second frequency band, a load factor of the channel, and a noise level of the channel; the use channel determination unit determines, as the second use channel, a channel that is different from the first use channel and has at least one of the number of use base stations, the load factor, and the noise level that is the smallest. A base station according to any one of claims 1 to 4.

6. the usage channel determination unit identifies a channel with the minimum load rate, and if there is only one channel with the minimum load rate, determines the identified one channel as the second usage channel; if there are multiple channels with the minimum load rate, identifies a channel with the minimum number of using base stations from among the multiple channels with the minimum load rate, and if there is only one channel with the minimum number of using base stations, determines the identified one channel as the second usage channel; if there are multiple channels with the minimum number of using base stations, identifies a channel with a minimum noise level from the multiple channels with the minimum number of using base stations, and if there is only one channel with the minimum noise level, determines the identified one channel as the second usage channel; if there are multiple channels with the minimum noise level, determines the one channel selected from the identified channels with the minimum noise level as the second usage channel. The base station according to claim 5.

7. a detection determination unit that determines whether or not a radar wave is detected in either the first channel or the second channel; A transmission control unit that controls transmission of the data frame to the first base station or the second base station based on the first usage channel information and the second usage channel information, when it is determined that radar waves have been detected on either the first usage channel or the second usage channel, the transmission control unit changes the channel on which it has been determined that radar waves have been detected to a different channel, and controls to transmit the data frame to the first base station or the second base station. A base station according to any one of claims 1 to 6.

8. the transmission control unit changes at least one of the first channel in use and the second channel in use to a channel belonging to the first frequency band, and then when a preset carrier sense time has elapsed, changes at least one of the first channel in use and the second channel in use back to the channel determined by the channel in use determination unit; The base station according to claim 7.

9. The first frequency band is 2.4 GHz or 5 GHz W52 band; The second frequency band is a 5 GHz W52 band, a 5 GHz W53 band, a 5 GHz W56 band, or a 6 GHz band; A base station according to any one of claims 1 to 8.

10. a first base station, a second base station, and a third base station capable of communicating with the first base station and the second base station; The first base station, the second base station, and the third base station each The wireless communication system includes a plurality of wireless modules that perform wireless communication on a channel that belongs to any of a plurality of mutually different frequency bands, the first frequency band being a frequency band that does not overlap with a frequency band used by radar waves, and at least one second frequency band that includes the frequency band used by radar waves; The third base station, a usage channel information acquisition unit that acquires first usage channel information indicating a first usage channel used for transmitting and receiving a data frame between the first base station and the first base station, the first usage channel information being transmitted from the first base station; a usage channel determination unit that determines a channel different from the first usage channel as a second usage channel to be used for transmitting and receiving data frames with the second base station; a use channel notification unit that transmits second use channel information indicating the determined second use channel to the second base station via one of the plurality of wireless modules; a usage status detection unit that detects a usage status of each of the plurality of frequency bands; a usage status notifying unit that transmits first usage status information indicating the detected usage status to the first base station via one of the plurality of wireless modules; a usage status acquisition unit that acquires second usage status information indicating a usage status of each of the plurality of frequency bands in the second base station, the second usage status information being transmitted from the second base station, via one of the plurality of wireless modules; The use channel determination unit determines the second use channel based on the first use channel information, the first use status information, and the second use status information. Communication systems.

11. A communication method using a plurality of wireless modules that wirelessly communicates with a plurality of other base stations on channels belonging to a plurality of different frequency bands, the channels including a first frequency band that is a frequency band that does not overlap with a frequency band used by radar waves, and at least one second frequency band that includes a frequency band used by radar waves, the method comprising: acquiring first usage channel information indicating a first usage channel used for transmitting and receiving a data frame to and from the first base station, the first usage channel information being transmitted from a preset first base station among the other plurality of base stations; detecting a usage status of each of the plurality of frequency bands; transmitting first usage status information indicating the detected usage status to the first base station via any one of the plurality of wireless modules; acquiring, via one of the plurality of wireless modules, second usage status information indicating usage statuses of the plurality of frequency bands in the second base station, the second usage status information being transmitted from a second base station different from the first base station among the other plurality of base stations; determining a channel different from the first usage channel as a second usage channel to be used for transmitting and receiving data frames with the second base station based on the first usage channel information, the first usage status information, and the second usage status information; and transmitting second use channel information indicating the determined second use channel to the second base station via any one of the plurality of wireless modules. Communication methods.

Images