JP2018201238A - Radio communication equipment, communication method, and program - Google Patents

Abstract

To provide a radio communication technology capable of executing communication by selecting a channel of a better communication environment with high versatility.SOLUTION: A radio communication system is configured to include a RAM 214 and a channel control unit 209 in a radio access point device 102 which stores channel selection order information indicating a priority order according to communication quality of each of a plurality of channels in a frequency band used for radio communication and selects a channel in order of decreasing priority indicating the channel selection order information to execute radio communication with an opposite device making a channel change. The RAM 214 stores the same channel selection order information as the opposite device. The channel control unit 209 determines whether or not a channel change is required according to communication quality of a channel used for radio communication with the opposite device or presence/absence of an interference wave and when it is determined to be required, selects a channel used for radio communication with the opposite device in order of decreasing priority indicating the channel selection order information stored in the RAM 214.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wireless communication device such as a wireless access point device in a wireless local area network (LAN).

  In recent years, the communication speed and usability of this type of wireless communication apparatus have been rapidly improved, and wireless LANs have been widely used in various places such as homes, offices, and schools. In wireless communication, unlike wired communication, communication may be interrupted or communication quality may deteriorate due to the influence of electromagnetic noise or interference waves emitted from other electronic devices. In the worst case, wireless communication may be disconnected. Thus, various techniques for solving such problems of wireless communication have been proposed in the past, and an example thereof is the technique disclosed in Patent Document 1.

  Generally, a frequency band used for wireless communication is divided into a plurality of channels, and one of the channels is used for wireless communication between wireless communication apparatuses. The wireless communication device disclosed in Patent Document 1 monitors the presence or absence of an interference wave in a channel used for wireless communication with a counterpart device, and changes to another channel when an interference wave is detected. When this channel is changed, the wireless communication apparatus notifies the partner apparatus of the channel to be changed prior to the change. Then, the wireless communication device checks the presence / absence of the interference wave in the change destination channel prior to the restart of the wireless communication, and if the interference wave is detected, the channel change is further performed without performing the channel change notification again. Do. On the other hand, the counterpart device grasps the channel to be changed by passive scanning using a beacon. This makes it possible to perform wireless communication while avoiding the influence of interference waves.

Japanese Patent No. 4,856,736

  However, the technique disclosed in Patent Document 1 has a problem that the channel change notification does not always reach the counterpart device. The channel used for wireless communication with the partner device is used for transmission of the channel change notification. However, because this channel contains an interference wave, the transmission of the channel change notification is hindered by the influence of the interference wave. It is because it may be done. When the channel change notification does not reach the counterpart device, the counterpart device needs to detect the channel change by some means. However, Patent Document 1 does not describe providing a configuration for detecting a channel change in the counterpart device. That is, it is considered that the technique disclosed in Patent Document 1 cannot sufficiently reduce the influence of interference waves.

  Furthermore, the technique disclosed in Patent Document 1 has a problem that use is hesitant when the frequency band used for wireless communication is the 5 GHz band. The reason is as follows. In wireless communication using the 5 GHz band, radar waves such as weather radar and air traffic control radar can be considered as interference waves. This is because the W53 and W56 channels included in the 5 GHz band are shared with these radar waves. According to the laws and regulations (Radio Equipment Regulations Article 49-23 No. 3 / No. 2-2 No. 364 of the Ministry of Internal Affairs and Communications), radio transmission within 10 seconds after detecting radar waves It is stipulated that should be stopped. However, depending on the communication quality of the channel used for wireless communication, it is not always possible to notify the channel change in a short time of 10 seconds. In the first place, in view of the gist of the law, it is difficult to transmit a new channel change notification after detecting a radar wave. This is the reason why the use of the technique disclosed in Patent Document 1 is hesitant when the frequency band used for wireless communication is the 5 GHz band.

  In addition, the technique disclosed in Patent Document 1 is based on the fact that an interference wave is detected in a channel to be changed, and when a channel change occurs continuously, the partner device uses a beacon to determine which channel has been changed finally. It is the structure which makes it grasp. That is, the technique disclosed in Patent Document 1 is based on the regular transmission of beacons. Therefore, although the technique of patent document 1 is applicable to infrastructure mode communication, it cannot be applied to ad hoc mode communication when a beacon is not used, and lacks versatility. In addition, in the technique disclosed in Patent Document 1, only the influence of interference waves is considered as a channel change factor, and communication quality deteriorates due to factors other than interference waves (such as the presence of temporary shielding objects and electromagnetic noise). Etc. are not considered.

  The present invention has been made in view of the circumstances as described above, and an object thereof is to provide a wireless communication technique that enables communication using a channel with high versatility and better communication quality.

  In order to solve the above-described problems, the present invention provides a storage device as information representing a priority order according to communication quality for each of a plurality of channels used for wireless communication in a wireless communication device that performs wireless communication with one or a plurality of counterpart devices. The channel selection unit that selects the channels used for wireless communication with the partner device in descending order of the priority indicated by the channel selection order information stored in the channel, and the communication quality of the channel being used for wireless communication or the presence / absence of interference waves The channel selection stored in the storage device is a channel used for wireless communication between the determination unit that determines whether or not channel change is necessary for each partner device, and the partner device that is determined by the determination unit that channel change is necessary. And a channel changing unit for changing to a channel selected in descending order of priority indicated by the rank information. To.

  In the wireless communication apparatus of the present invention, the channel used for wireless communication with the counterpart apparatus is selected and changed according to the priority order indicated by the channel selection order information stored in the storage device. For this reason, if the channel is selected and changed in the partner device in accordance with the priority order indicated by the channel selection order information stored in the storage device, either the wireless communication device or the partner device of the present invention is used. However, even if the channel is changed first, the other side can change the channel by referring to the same channel selection order information when communication is interrupted, and the communication can be resumed. That is, according to the present invention, it is not necessary to notify the partner device of the channel to be changed prior to the channel change, and such notification is not performed. According to the present invention, since there is no notification of the channel to be changed to the partner device, there is no problem in executing the channel change even when there is interference in the channel being used for wireless communication with the partner device. Rather, it is possible to perform wireless communication with a partner apparatus using a channel with better communication quality. Further, according to the present invention, even if the channel change is caused by a radar wave, it does not violate the law and does not violate the purpose of the law. Furthermore, in the present invention, since the use of a beacon is not assumed, it can be applied not only to the ad hoc mode but also to the WDS (Wireless Distribution System) mode and the infrastructure mode. Thus, the present invention can be applied to various communication modes and has high versatility.

  In a more preferred aspect, an interference wave detection unit that detects the presence or absence of an interference wave in a channel in use is provided, and the determination unit monitors the presence or absence of the interference wave according to a detection result of the interference wave detection unit. According to this aspect, since the interference wave detection unit is included as hardware for detecting the presence or absence of the interference wave in the channel in use, the processing performed by the determination unit is small.

  In a more preferred aspect, the channel changing unit monitors the presence / absence of an interference wave for the change destination channel selected according to the channel selection order information, and when the interference wave is detected, the channel change order information is again displayed. Refer to and change the channel. According to this aspect, it is possible to perform wireless communication using a channel with better communication quality while avoiding the influence of interference waves such as radar waves. Even when the channel change occurs continuously as described above, if the partner apparatus also changes the channel in the order of the priority indicated by the channel selection order information, the final change destination channel is determined. The time required until is shortened. In a more preferable aspect, the channel use confirmation unit for confirming the absence of interference waves in the change destination channel for a predetermined period before using the change destination channel selected according to the channel selection order information, The determination unit monitors the presence or absence of an interference wave according to the confirmation result of the channel use confirmation unit. According to this aspect, since the channel use confirmation unit is provided as hardware for confirming the absence of the interference wave in the channel before the change destination channel is used, the processing performed by the determination unit can be reduced.

  In another preferable aspect, the presence notification frame may be periodically transmitted to and received from the partner apparatus. As an example of such an aspect, a timer that starts timing every time a presence notification frame transmitted from the counterpart device is received is provided, and the determination unit includes a predetermined threshold value for the time counted by the timer In the case where the number of channels is exceeded, it can be considered that the channel change is determined to be necessary. According to this aspect, it is possible to evaluate the communication quality of the currently used channel using the presence notification frame, and it is possible to omit the process for evaluating the communication quality of the channel. As a more preferable aspect, a timer that counts down using the threshold value as an initial value is used as the timer, and the timer timing is stopped and reset prior to the channel change. In the case of changing the channel by detection, a mode in which a reset unit for resetting the initial value of the timer to a larger value is further considered. Although details will be described later, according to such an aspect, even when a channel change is performed again when an interference wave is detected in the change destination channel in the channel change on the wireless communication device side of the present invention, It is possible to avoid occurrence of unnecessary reception timeout for the presence notification frame transmitted from the partner apparatus.

  As a more preferable aspect, channel selection order information is written in the presence notification frame transmitted from the counterpart device, and the channel selection order information stored in the storage device is added to the presence notification frame received from the counterpart device. A mode is further conceivable that further includes a channel selection order update unit that updates the channel selection order information that has been written. In general, the communication quality of each channel in the frequency band used for wireless communication changes from moment to moment. However, in the technique disclosed in Patent Document 1, the channel to be changed is fixed in advance, so this change occurs. It is conceivable that the channel cannot be tracked and the channel must be changed again. If channel changes occur continuously in this way, it takes time to determine the final channel to be changed, and the wireless communication interruption time becomes longer accordingly. On the other hand, if the partner device is a wireless communication device that updates the channel selection order information according to the communication quality, writes it in the presence notification frame, and transmits it, the communication quality of each channel can be improved by adopting this aspect. Even if a change occurs, it is possible to follow the change and always perform wireless communication using a channel with better communication quality. Note that a channel selection order update unit that detects the communication quality of each of the plurality of channels and updates the channel selection order information stored in the storage device according to the detection result of the communication quality is a wireless communication apparatus according to the present invention. The effect can be obtained in the same manner.

  As another specific example of the mode of periodically transmitting / receiving presence notification frames to / from the counterpart device, each of the one or more counterpart devices has a storage device that stores channel selection information, and each storage device While selecting the channel to be used for wireless communication according to the channel selection order information stored in the wireless communication device of the present invention, the wireless communication device of the present invention also has a storage device for storing the channel selection information, A mode in which a channel to be used for wireless communication is selected according to channel selection order information stored in the storage device of the own apparatus, and a mode in which the following channel selection order update unit is provided in the wireless communication apparatus is conceivable. That is, the channel selection order update unit detects the communication quality of each of the plurality of channels, updates the channel selection order information stored in the storage device of the own apparatus according to the detection result of the communication quality, and A process of periodically transmitting the presence notification frame in which the selection order information is written to the partner apparatus is executed. Also according to such an aspect, it becomes possible to perform radio communication using a channel with always better communication quality following the change in communication quality of each channel.

  In yet another preferred embodiment, the present invention provides a channel selection order stored in a storage device as information representing a priority order according to communication quality for each of a plurality of channels in a frequency band used for wireless communication. First processing for selecting a channel to be used for wireless communication with a partner apparatus in descending order of priority indicated by the information, and whether or not to change the channel according to the communication quality of the channel being used for wireless communication or the presence or absence of an interference wave The second process for determining each channel device and the channels used for wireless communication with the partner device determined to require channel change in the second process in the descending order of priority indicated by the channel selection order information. And a third process for changing to the selected channel (that is, the computer selects the channel selection unit, the determination). Providing a program) for causing to function as parts and channel switching unit. According to this aspect, the present invention can be implemented simply by rewriting an existing wireless communication apparatus control program to the program of the present invention, and it is not necessary to newly introduce the wireless communication apparatus of the present invention, leading to cost reduction.

  In still another preferred aspect, the present invention includes one or more first wireless communication devices and a second wireless communication device that wirelessly communicates with the one or more first wireless communication devices, The second wireless communication device is configured in the descending order of priority indicated by channel selection order information stored in a storage device as information indicating priority according to communication quality for each of a plurality of channels used for wireless communication. A channel selection unit that selects a channel to be used for wireless communication with one wireless communication device, and first wireless communication that determines whether or not to change the channel according to the communication quality of the channel being used for wireless communication or the presence or absence of an interference wave Channels stored in the storage device are used for wireless communication with a determination unit for each device and a first wireless communication device determined by the determination unit that a channel change is necessary. To provide a wireless communication system characterized by having a channel changing unit for changing the selected channel in order of priority indicated by the selected order information. According to this aspect, not only the ad hoc mode can be applied to the communication between the wireless communication apparatuses, but also the WDS mode and the infrastructure mode can be applied, and the communication can be applied to various communication modes. Becomes higher.

  In yet another preferred aspect, the present invention provides a wireless communication method in a wireless communication device that wirelessly communicates with one or a plurality of counterpart devices, and sets a priority according to communication quality for each of a plurality of channels used for wireless communication. A first step of selecting a channel to be used for wireless communication with the counterpart device in descending order of priority indicated by channel selection order information stored in the storage device as information to be represented, and communication quality of the channel being used for wireless communication Alternatively, a second step of determining for each partner device whether or not a channel change is necessary according to the presence or absence of an interference wave, and a channel used for wireless communication with the partner device determined in the second step that the channel change is necessary. A third step of changing the channel to a channel selected in descending order of priority indicated by the channel selection order information stored in the storage device; The provides a wireless communication method characterized by executing the wireless communication device. According to this aspect, communication can be performed using a channel with high versatility and better communication quality.

It is a block diagram which shows the structure of the radio | wireless communications system 1 containing the radio | wireless access point apparatuses 102 and 103 which are one Embodiment of the radio | wireless communication apparatus of this invention. 2 is a block diagram showing a hardware configuration of the wireless access point device 102. FIG. It is a flowchart which shows the flow of the main process which CPU205 of the wireless access point apparatus 102 performs according to a control program. It is a flowchart which shows the flow of the channel selection order determination processing which the same CPU205 performs according to a control program. It is a flowchart which shows the flow of the heartbeat transmission process which the same CPU205 performs according to a control program. It is a flowchart which shows the flow of the heart bead reception process which the same CPU205 performs according to a control program. It is a flowchart which shows the flow of the channel change process which the same CPU205 performs according to a control program. 3 is a time chart showing an operation example of wireless access point devices 102 and 103. 3 is a time chart showing an operation example of wireless access point devices 102 and 103. 3 is a time chart showing an operation example of wireless access point devices 102 and 103. It is a figure for demonstrating the modification (2) of this invention. It is a figure for demonstrating the modification (7) of this invention. It is a figure for demonstrating the modification (8) of this invention. It is a figure for demonstrating the modification (9) of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(A: Configuration)
FIG. 1 is a block diagram showing a configuration of a wireless communication system 1 including wireless access point devices 102 and 103 which are an embodiment of the wireless communication device of the present invention. The wireless communication system 1 is a communication system laid in a company or the like. As shown in FIG. 1, the wireless communication system 1 includes personal computers (hereinafter referred to as personal computers) 101 and 104 and wireless access point devices 102 and 103 used by employees of the company. As shown in FIG. 1, the personal computer 101 is connected to the wireless access point device 102 via a wired LAN, and the personal computer 104 is connected to the wireless access point device 103 via another wired LAN. In the present embodiment, data communication between the personal computer 101 and the personal computer 104 is realized via a wireless LAN including the wireless access point devices 102 and 103. That is, the wireless communication system 1 shown in FIG. 1 includes a wireless LAN. When data communication is performed between the personal computer 101 and the personal computer 104, it is of course possible to connect the personal computer 101 and the personal computer 104 to the same wired LAN and realize the data communication by communication via the wired LAN. However, depending on where the personal computers 101 and 104 are installed, it may be difficult to lay a signal line connecting the personal computers 101 and 104. For example, the personal computer 101 and the personal computer 104 are installed with a fire door separated. According to the present embodiment, data communication between the personal computer 101 and the personal computer 104 can be realized via the wireless LAN even when the signal line cannot be laid by a fire door or the like.

  In the wireless LAN of the present embodiment, a frequency band of 5 GHz band is used. The wireless access point devices 102 and 103 perform wireless communication with each other in the WDS mode. In the present embodiment, the wireless access point devices 102 and 103 execute the WDS mode connection procedure (exchange of encryption key, etc.) only at the first connection, and continue to use the encryption key exchanged at the first connection thereafter. . For this reason, in the wireless communication system 1 of the present embodiment, even if the channel used for wireless communication is changed, the wireless communication can be resumed immediately without going through the connection procedure again.

  As is well known, the frequency band of the 5 GHz band is divided into a plurality of channels, and each of the plurality of channels, W53 and W56, is shared with a weather radar or the like. In the present embodiment, for each of the plurality of channels, the priority order (hereinafter referred to as channel selection order) selected as a channel to be used for wireless communication is changed by evaluating the communication quality of each channel according to a certain standard. Determined. The wireless access point devices 102 and 103 store channel selection order information indicating the channel selection order. When a channel change is necessary due to a radio communication interruption or an interference wave, the wireless access point apparatuses 102 and 103 follow the channel selection order. Select the destination channel and execute the channel change.

  What should be noted here is that each of the wireless access point devices 102 and 103 of this embodiment does not notify the other device of the channel to be changed when performing the channel change. There is one of the features of the embodiment. More specifically, in the present embodiment, each of the wireless access point devices 102 and 103 periodically transmits a heartbeat to the partner device. A heartbeat is a signal for notifying other devices that the device is operating normally. Each of the wireless access point devices 102 and 103 detects the occurrence of a channel change on the partner device side due to the interruption of the heartbeat from the partner device, and changes the destination channel according to the channel selection order information stored in the own device. Is determined. For this reason, in this embodiment, it is not necessary to notify the partner device of the channel to be changed prior to the channel change. Hereinafter, the wireless access point apparatuses 102 and 103 that clearly show the features of the present embodiment will be mainly described.

(A-1: Configuration of wireless access point device 102)
FIG. 2 is a block diagram illustrating a hardware configuration of the wireless access point device 102. As shown in FIG. 2, the wireless access point device 102 includes an antenna 201, an RF (Radio Frequency) unit 202, a modem unit 203, a wireless LAN MAC multiplexing unit 204, a CPU (Central Processing Unit) 205, a heartbeat (HB in the figure). A reception timer unit 206, a heartbeat transmission timer unit 207, a radar wave monitoring unit 208, a channel control unit 209, a basic clock generation unit 210, a wired LAN MAC multiplexing unit 211, a modem unit 212, a wired LAN PHY unit 213, a RAM ( Random Access Memory) 214 and ROM (Read Only Memory) 215 are included.

  The ROM 215 stores in advance a control program (not shown in FIG. 2) that causes the CPU 205 to execute processing that clearly shows the features of the present embodiment. The RAM 214 is used by the CPU 205 as a work area when executing the control program. The RAM 214 stores channel selection order information and various data such as a radar wave detection flag and a CRC error rate, which will be described later. The CPU 205 reads the control program from the ROM 215 to the RAM 214 when the wireless access point device 102 is turned on (not shown), and starts executing it. The CPU 205 operating according to this control program functions as a control unit that plays the role of the control center of the wireless access point device 102. Details of processing executed by the CPU 205 in accordance with the control program will be clarified later.

  The wired LAN PHY unit 213 is connected to the personal computer 101 via a wired LAN. The wired LAN PHY unit 213 receives a signal transmitted from the personal computer 101 (in this embodiment, a signal representing a MAC frame transmitted from the personal computer 101 to the personal computer 104), and provides the modem 212 with the signal. The MAC frame is a data transmission / reception unit in the second layer (data link layer) of the OSI reference model. The modem unit 212 demodulates the signal given from the wired LAN PHY unit according to the standard of the wired LAN, and gives it to the wired LAN MAC multiplexing unit 211.

  The wired LAN MAC multiplexing unit 211 restores the MAC frame from the output signal of the modem unit 212 and supplies it to the CPU 205. The CPU 205 gives the MAC frame to the wireless LAN MAC multiplexing unit 204. The wireless LAN MAC multiplexing unit 204 multiplexes the MAC frame and gives it to the modem unit 203. The modem unit 203 modulates the MAC frame given from the wireless LAN MAC multiplexing unit 204 according to the wireless LAN standard, and gives a circuit signal obtained by this modulation to the RF unit 202. The RF unit 202 converts the output signal of the modulation / demodulation unit 203 into communication power and applies it to the antenna 201, and the antenna 201 radiates the communication power to space. Thereby, transmission of the MAC frame from the wireless access point device 102 to the wireless access point device 103 is realized.

  On the other hand, reception of a MAC frame transmitted from the wireless access point device 103 (for example, a MAC frame transmitted from the personal computer 104 to the personal computer 101) is realized in the following manner. The antenna 201 provides communication power received from the wireless access point device 103 to the RF unit 202. The RF unit 202 converts communication power given from the antenna 201 into a circuit signal and outputs the circuit signal to the modem unit 203. The modem unit 203 demodulates the output signal of the RF unit 202 in accordance with the wireless LAN standard and supplies the demodulated signal to the wireless LAN MAC multiplexing unit 204. The wireless LAN MAC multiplexing unit 204 restores the MAC frame from the output signal of the modem unit 203. The wireless LAN MAC multiplexing unit 204 gives the MAC frame to the CPU 205 only when the destination MAC address of the restored MAC frame is the MAC address of the personal computer 101, and discards it in other cases. The role of selecting MAC frames may be assigned to the RF unit 202, the modem unit 203, or the CPU 205.

  The CPU 205 gives the MAC frame given from the wireless LAN MAC multiplexing unit 204 to the wired LAN MAC multiplexing unit 211. The wired LAN MAC multiplexing unit 211 multiplexes the MAC frame and gives it to the modem unit 212. The modem unit 212 modulates the MAC frame given from the wired LAN MAC multiplexing unit 211 according to the standard of the wired LAN, and gives a signal obtained by this modulation to the wired LAN PHY unit 213. The wired LAN PHY unit 213 transmits the signal given from the modem unit 212 to the personal computer 101 via the wired LAN.

  Further, the CPU 205 determines whether or not there is a CRC error for the MAC frame received from the wireless LAN MAC multiplexing unit 204 and whether or not it is a retransmission frame, calculates a CRC error rate and a frame retransmission rate, and writes them to the RAM 214. . Here, the CRC error means that the checksum calculated from the MAC frame received from the wireless LAN MAC multiplexing unit 204 does not match the checksum written in the header portion of the MAC frame. The CRC error rate is a ratio of the number of MAC frames in which a CRC error has occurred to the number of MAC frames received from the wireless LAN MAC multiplexing unit 204. The frame retransmission rate is the ratio of the number of MAC frames retransmitted by retransmission processing to the number of MAC frames received from the wireless LAN MAC multiplexing unit 204. Whether or not the frame has been retransmitted by the retransmission process can be determined with reference to the header portion of the frame. The CPU 205 calculates the frame retransmission rate for each transmission destination MAC address and writes it to the RAM 214 for each transmission destination MAC address (that is, in association with the transmission destination MAC address). The CRC error rate and the frame retransmission rate may be calculated by the wireless LAN MAC multiplexing unit 204 and the calculation results may be given to the CPU 205.

  The channel control unit 209 changes the transmission / reception frequency of the RF unit 202 under the control of the CPU 205. The radar wave monitoring unit 208 receives a signal output from the RF unit 202, performs spectrum analysis and specific pulse pattern monitoring on the signal, attempts to detect a radar wave, and detects a radar wave. Is notified to the CPU 205 to that effect.

The heartbeat reception timer unit 206 is a timer for measuring a heartbeat non-reception time by down-counting from an initial value. The heartbeat reception timer unit 206 is reset every time a heartbeat is received, and starts counting time. The heartbeat transmission timer unit 207 is a timer for measuring a heartbeat transmission interval. The heartbeat transmission timer unit 207 starts timing when the heartbeat transmission process is completed. The basic clock generation unit 210 generates a basic clock for measuring each time. This basic clock is also referred to in channel selection order determination processing described later.
The hardware configuration of the wireless access point device 102 has been described above.

  Next, processing executed by the CPU 205 of the wireless access point device 102 according to the control program will be described. As described above, the CPU 205 of the wireless access point device 102 reads the control program from the ROM 215 to the RAM 214 when the wireless access point device 102 is turned on, and starts executing the control program. FIG. 3 is a flowchart showing the flow of main processing executed by the CPU 205 of the wireless access point device 102 according to the control program. As shown in FIG. 3, the CPU 205 first executes a channel selection order determination process (see FIG. 4) (step S301). Although details will be described later, in the channel selection order determination process, the CPU 205 determines the channel selection order, and writes the channel selection order information indicating the channel selection order in the RAM 214.

  In step S302 subsequent to step S301, the CPU 205 refers to the timer value of the heartbeat transmission timer unit 207 and determines whether or not a timeout has occurred. However, in step S302 executed immediately after the wireless access point device 102 is turned on, the CPU 205 determines that the timeout has occurred unconditionally. This is because the heartbeat has never been transmitted immediately after the power is turned on. If the determination result in step S302 is “Yes”, the CPU 205 executes a heartbeat transmission process (step S303), and then executes a process in step S304. On the other hand, if the determination result in step S302 is “No”, the CPU 205 does not execute the heartbeat transmission process (step S303) but executes the process in step S304.

  FIG. 5 is a flowchart showing the heartbeat transmission process executed in step S303 of the main process. As shown in FIG. 5, in the heartbeat transmission process, the CPU 205 first assembles a header of a MAC frame (hereinafter referred to as a heartbeat frame) that plays the role of a heartbeat (step S501). Next, the CPU 205 writes the channel selection order information stored in the RAM 214 into the payload of the heartbeat frame (step S502). Then, the CPU 205 transmits the heartbeat frame generated in the above manner to the wireless access point device 103 via the wireless LAN MAC multiplexing unit 204, the modem unit 203, the RF unit 202, and the antenna 201 (step S503), thereby transmitting the heartbeat. Complete the process. When the transmission of the heartbeat is completed as described above, the heartbeat transmission timer unit 207 is reset and starts counting again from that point.

  Returning to FIG. 3, in step S <b> 304 of the main process, the CPU 205 determines whether or not the wireless access point device 102 has received a heartbeat from the wireless access point device 103. If the decision result in the step S304 is “Yes”, the CPU 205 executes a heartbeat receiving process (step S305). FIG. 6 is a flowchart showing the flow of the heartbeat reception process. In this heartbeat reception process, the CPU 205 first resets the timer value of the heartbeat reception timer unit 206 to the maximum value (that is, the initial value that is the starting point of the downcount, in this embodiment, 15 seconds) (step S601). Next, the CPU 205 determines whether or not channel selection order information is written in the payload of the received heartbeat frame (step S602). If the determination result in step S602 is “Yes”, the CPU 205 reads the channel selection order information from the payload of the heartbeat frame and writes it in a predetermined area of the RAM 214 (step S603), and completes the heartbeat reception process. More specifically, in this embodiment, the CPU 205 writes the received channel selection information in another part of the RAM 214 so that the channel selection order information written in the RAM 214 in the channel selection order determination process is not overwritten. If the result of the determination in step S602 is “No”, the CPU 205 completes the heartbeat reception process without executing the process in step S603. When the heartbeat reception process is completed as described above, the heartbeat reception timer unit 206 starts timing.

  On the other hand, if the determination result in step S304 is “No”, the CPU 205 determines whether or not a timeout of the heartbeat reception timer unit 206 has occurred (step S306). If the determination result in step S306 is “Yes” (that is, if a timeout has occurred), the CPU 205 sets “0” in the radar wave detection flag and executes a channel change process (step S307). Details of this channel change processing will be described later. When the channel change process is completed, the CPU 205 executes the channel selection order determination process (step S301) again. On the other hand, if the determination result of step S306 is “No”, the CPU 205 executes the process of step S308.

In step S308, the CPU 205 determines whether a radar wave has been detected. If the result of determination in step S308 is “Yes”, the CPU 205 sets “1” in the radar wave detection flag and executes channel change processing (step S309). That is, the radar wave detection flag is a flag indicating whether or not the cause of the channel change is radar wave detection. When the channel change process (step S309) is completed, the CPU 205 executes the channel selection order determination process (step S301) again. On the other hand, if the determination result in step S308 is “No”, the CPU 205 executes the channel selection order determination process (step S301) again without executing step S309.
The above is the flow of the main process, the heartbeat transmission process, and the heartbeat reception process.

Next, channel selection order determination processing will be described.
FIG. 4 is a flowchart showing a flow of channel selection order determination processing. First, the CPU 205 refers to the basic clock output from the basic clock generation unit 210 and determines whether or not one second or more has elapsed since the completion of the previous channel selection order determination process (step S401). When the channel selection order determination process is started when the wireless access point device 102 is turned on, the determination result in step S401 is always “Yes”.

  If the determination result in step S401 is “Yes”, the CPU 205 stops outputting the MAC frame to the wireless LAN MAC multiplexing unit 204 (that is, stops transmitting the MAC frame to the wireless LAN) (step S402). The process after step S403 is executed. The MAC frame that was scheduled to be transmitted is buffered in the RAM 214 until the transmission stop is canceled. On the other hand, if the determination result in step S401 is “No”, the CPU 205 completes the channel selection order determination process without executing the processes in and after step S402. When completing the channel selection order determination process, the CPU 205 writes data indicating the time in a predetermined area of the RAM 214. In step S401 described above, the CPU 205 refers to the data stored in the area to determine whether one second or more has elapsed since the completion of the previous channel selection order determination process.

  In step S403 subsequent to step S402, the CPU 205 controls the channel control unit 209 to switch the evaluation target channel (step S403). The channel control unit 209 switches channels received by the RF unit 202 via the antenna 201 one channel at a time in a round robin manner under the control of the CPU 205.

  The CPU 205 switches the wireless LAN MAC multiplexing unit 204 to the promiscuous mode. Thereafter, the wireless LAN MAC multiplexing unit 204 gives all received MAC frames to the CPU 205 regardless of the destination MAC address until the mode is switched again. The CPU 205 selects a frame having a retransmission bit and a beacon frame from the MAC frames received from the wireless LAN MAC multiplexing unit 204. The beacon frame is used to count the number of BSSIDs in the channel, and the CPU 205 cumulatively records the number of BSSIDs newly discovered during the evaluation of each channel in the RAM 214. A frame in which a retransmission bit is set is used for calculating a frame retransmission rate, and the CPU 205 cumulatively records the calculated frame retransmission rate in the RAM 214. In this way, the CPU 205 collects evaluation information regarding the communication quality of each channel (step S404). Note that while the CPU 205 switches the wireless LAN MAC multiplexing unit 204 to the promiscuous mode, even if a notification that the radar wave is detected is given from the radar wave monitoring unit 208, the CPU 205 ignores the notification.

  The CPU 205 refers to the basic clock generated by the basic clock generation unit 210, and determines whether or not 200 ms has elapsed since the start of the process of step S404 (step S405). While the determination result in step S405 is “No”, the CPU 205 continues the process in step S404. When the determination result in step S405 is “Yes”, the CPU 205 cancels the promiscuous mode of the wireless LAN MAC multiplexing unit 204 and switches back to the channel used with the wireless access point device 103 (step S406). The wireless LAN transmission stop is canceled (step S407). Thereafter, the CPU 205 gives the MAC frame received from the wired LAN MAC multiplexing unit 211 to the wireless LAN MAC multiplexing unit 204, and resumes wireless communication.

  The threshold value used in the determination in step S405 (that is, 200 ms) is a time sufficiently long for the CPU 205 to collect evaluation information related to the communication quality of all channels in the 5 GHz band. However, if the evaluation information regarding the communication quality of all the channels cannot be collected within the time due to the convenience of circuit design or the like, the threshold value may be set to a larger value. It needs to be short. Therefore, the threshold value may be set to a suitable value by performing an experiment or the like within a range of 1 second or less.

  In step S408 subsequent to step S407, the CPU 205 calculates the evaluation score of the channel to be evaluated for each channel from the number of BSSIDs stored in the RAM 214, the CRC error rate, and the frame retransmission rate. Here, various aspects can be considered for the algorithm for calculating the evaluation score. The smaller the number of BSSIDs, the higher the evaluation score, the lower the CRC error rate, the higher the evaluation score, and the lower the frame retransmission rate, the higher the evaluation score. Any algorithm can be used. This is because the smaller the number of BSSIDs, the better the communication quality, and the lower the CRC error rate and the frame retransmission rate, the better the communication quality. For example, when a real value in the range of 0 to 1 is used as the CRC error rate (or frame retransmission rate), (predetermined positive integer value−number of BSSSID) + (1−CRC error rate) + (1−frame (Resending rate) is used as an evaluation score. Note that only the number of BSSIDs may be used for calculating the evaluation score, or only the CRC error rate may be used, or only the frame retransmission rate may be used. Further, the evaluation score may be calculated using any two of the number of BSSIDs, the CRC error rate, and the frame retransmission rate.

  The CPU 205 sorts the evaluation scores of the channels calculated in step S408 in descending order, and determines the channel selection order in the order in which the communication quality is expected to be good (that is, the descending order of evaluation scores) (step S409). Then, the CPU 205 writes the channel selection order information indicating the channel selection order determined in step S409 in the RAM 214 (step S410), and the channel selection order determination process (step S301) is completed. A specific example of the channel selection order information is data in a list format in which identifiers uniquely indicating each of a plurality of channels that can be used for wireless communication are arranged in the order of the channel selection order determined in step S409. It is done.

Next, the channel change process will be described.
FIG. 7 is a flowchart showing the flow of channel change processing. In this channel change process, the CPU 205 first stops transmission of the MAC frame to the wireless LAN (step S701). Next, the CPU 205 stops the timing of the heartbeat reception timer unit 206 (step S702).

  In step S <b> 703 subsequent to step S <b> 702, the CPU 205 reads channel selection order information from the RAM 214. Next, the CPU 205 refers to the channel selection order information read in step S703, selects the channel that is expected to have the best communication quality, and changes the channel used for wireless communication to the selected channel (step S704). . If the channel used before the execution of step S703 is expected to have the best communication quality, the CPU 205 changes to the channel that is expected to have the second highest communication quality.

  Next, the CPU 205 refers to the radar wave detection flag to determine whether or not the reason for the channel change is for radar wave detection (step S705). In this embodiment, if the value of the radar wave detection flag is “1”, the determination result in step S705 is “Yes”, and if the value of the radar wave detection flag is “0”, the determination result in step S705 is “No”.

  If “Yes” as a result of the determination in step S705, the CPU 205 resets the timer value of the heartbeat reception timer unit 206 to a value obtained by adding 15 seconds to the current maximum value (that is, the initial value of the down counter). (Step S706). On the other hand, if the result of determination in step S705 is “No”, the CPU 205 resets the timer value of the heartbeat reception timer unit 206 to 15 seconds (step S707). As described above, “0” is set to the radar wave detection flag in step S307, and “1” is set to the radar wave detection flag in step S309. Therefore, in the case of the channel change process in step S307, the process in step S707 is executed, and in the case of the channel change process in step S309, the process in step S706 is executed.

  In step S708 executed subsequent to step S706 or 707, the CPU 205 determines whether or not the change destination channel in step S704 is W53 or W56 (step S708). If the determination result in step S708 is “No”, the CPU 205 cancels the time stop of the heartbeat reception timer unit 206 (step S712), and further cancels the suspension of MAC frame transmission to the wireless LAN (step S713). The channel change process is terminated. On the other hand, if the result of determination in step S708 is “Yes”, the CPU 205 enters a standby state and waits for radar wave detection by the radar wave monitoring unit 208 (step S709). The CPU 205 continues this standby state for one minute regardless of whether or not there is a notification from the radar wave monitoring unit 208 (step S710).

When the standby for 1 minute is completed (step S710: Yes), the CPU 205 determines whether or not a notification indicating that a radar wave has been detected is received from the radar wave monitoring unit 208 during the standby state (step S711). . If the determination result in step S711 is “Yes”, the CPU 205 sets “1” in the radar wave detection flag, and executes the processes in and after step S703 again. On the other hand, if the decision result in the step S711 is “No”, the CPU 205 executes the processes of the steps S712 and S713 described above and ends the channel change process.
The above is the configuration of the wireless access point device 102.

(A-2: Configuration of wireless access point device 103)
Next, the configuration of the wireless access point device 103 will be described.
Since the hardware configuration of the wireless access point device 103 is the same as the hardware configuration of the wireless access point device 102 (see FIG. 2), detailed description thereof is omitted. The processing executed by the CPU 205 of the wireless access point device 103 according to the control program is the same as the processing executed by the CPU 205 of the wireless access point device 102 according to the control program, except for the following two points.

First, the channel selection order determination process (step S301) is executed only when the wireless access point device 103 is powered on. That is, the CPU 205 of the wireless access point device 103 completes the channel change process (FIG. 3: step S307 or S309), or when the determination result in step S308 is “No”, performs the process of step S301. The process of step S302 is executed without executing it. Second, the channel selection order information stored in the RAM 214 of the own apparatus is updated using the channel selection order information read from the heartbeat received from the wireless access point device 102 (more specifically, the former and the latter Overwriting). For this reason, the same channel selection order information is stored in the RAM 214 of the wireless access point device 102 and the RAM 214 of the wireless access point device 103.
The above is the configuration of the wireless access point device 103.

(B: Operation)
Next, an operation in a case where channel switching is performed by detecting a radar wave in a situation where the wireless access point device 102 and the wireless access point device 103 are performing wireless communication using W53 will be described. In the following, W53 is “channel A”, W56 is “channel B”, and other channels in the 5 GHz band are “channel C”. At the start of the operation described below, channel selection order information indicating that channel A has the highest priority, channel B has the highest priority, and channel C has the lowest priority is channel selection order determination. It is generated by processing and stored in the RAM 214 of the wireless access point device 102. The channel selection order information is transmitted to the wireless access point apparatus 103 by transmitting and receiving heartbeats between the wireless access point apparatus 102 and the wireless access point apparatus 103, and the channel selection order information is also stored in the RAM 214 of the wireless access point apparatus 103. Is remembered.

(B-1: Operation when channel B is not used by radar)
First, the operation when channel B is not used by the radar will be described.
FIG. 8 is a time chart showing a flow of operations of the wireless access point devices 102 and 103 when the channel B is not used by the radar. As illustrated in FIG. 8, the wireless access point device 102 and the wireless access point device 103 perform wireless communication using the channel A. Under this situation, it is assumed that a radar wave is detected by the radar wave monitoring unit 208 of the wireless access point device 102 at timing T81 in FIG. In the wireless access point device 102, the radar wave monitoring unit 208 notifies the CPU 205 of the detection of the radar wave. In the main process executed by the CPU 205 of the wireless access point apparatus 102, the determination result in step S308 is “Yes” at this timing T81, and the CPU 205 of the wireless access point apparatus 102 sets “1” to the radar wave detection flag. Channel change processing (step S309) is executed.

  The CPU 205 of the wireless access point device 102 starts the channel change process shown in FIG. 7, and executes the processes from step S701 to step S705. Since the value of the radar wave detection flag is “1”, the determination result of step S705 is “Yes”, and the process of step S706 is executed. At the start of this operation, the maximum value of the timer value of the heartbeat reception timer unit 206 is 15 seconds. For this reason, in the wireless access point device 102, the maximum value of the timer value of the heartbeat reception timer unit 206 is updated to the maximum value +15 seconds, that is, 30 seconds. In this operation example, the channel to be changed determined according to the channel selection order information is channel B (that is, W56). For this reason, the determination result in step S708 is “Yes”, and the CPU 205 of the wireless access point device 102 executes the processing from step S709 to step S711. That is, the CPU 205 of the wireless access point apparatus 102 enters a standby state for detecting radar waves for one minute from the timing T81, but the channel B is not used by the radar. For this reason, no radar wave is detected during the one-minute waiting period, and the determination result in step S711 is “No”. As a result, the CPU 205 of the wireless access point device 102 executes the processes of steps S712 and S713, and resumes heartbeat transmission using the channel (channel B) after switching. This restart timing is timing T82 (timing after 1 minute has elapsed from timing T81) in FIG.

  On the other hand, in the main processing executed by the CPU 205 of the wireless access point device 103, a heartbeat reception timeout occurs at timing T83 in FIG. 8 (timing after 15 seconds from T81) (FIG. 3: Step S306, Yes). The CPU 205 of the wireless access point device 103 sets “0” to the radar wave detection flag and executes channel change processing (step S307). As described above, the CPU 205 of the wireless access point device 102 stops transmission of frames to the wireless LAN at the timing T81, and transmission of heartbeats is also stopped.

  The CPU 205 of the wireless access point device 103 starts the channel change process shown in FIG. 7, and executes the processes from step S701 to step S705. However, since the value of the radar wave detection flag is “0”, the determination result of step S705 is “No”, and the process of step S707 is executed. That is, in the wireless access point device 103, the timer value of the heartbeat reception timer unit 206 is reset to the maximum value (that is, 15 seconds) at that time. Even in the channel change process executed by the CPU 205 of the wireless access point device 103, the change destination channel determined according to the channel selection order information is channel B (ie, W56), so the determination result in step S708 is “Yes”. Processing in steps S709 to S711 (that is, waiting for one minute for radar wave detection) is executed. However, as described above, in this operation example, since channel B is not used by the radar, the determination result of step S711 is “No”, the processing of steps S712 and S713 is executed, and the changed channel (channel B ) Is used to resume heartbeat transmission. This restart timing is timing T84 in FIG.

  At time T82 in FIG. 8, the maximum timer value of the heartbeat reception timer unit 206 of the wireless access point device 102 is 30 seconds, while the timing T84 at which heartbeat transmission from the wireless access point device 103 is resumed is This is the time when 15 seconds have passed since the timing T82. Therefore, in the wireless access point device 102, a reception timeout for the heartbeat transmitted from the wireless access point device 103 does not occur, and a channel change due to the heartbeat reception timeout does not occur. Therefore, the wireless access point devices 102 and 103 can continue the wireless communication using the channel B that is expected to have the best communication quality.

(B-2: Operation when channel B is also used by radar)
Next, the operation when channel B is also used in the radar will be described.
In this case, in both the channel change process executed in the wireless access point apparatus 102 and the channel change process executed in the wireless access point apparatus 103, a radar wave is detected in the channel B, and the determination result in step S711 is “No” Can be. However, the subsequent operation is different between the case where the determination result of step S711 is “Yes” in the wireless access point device 102 and the case where the determination result of step S711 is “Yes” in the wireless access point device 103. It will be a thing. Therefore, hereinafter, the operation will be described separately when the radar wave is detected by the wireless access point device 102 and when the radar wave is detected by the wireless access point device 103. The operation until the CPU 205 of the wireless access point device 102 detects a radar wave on channel A and executes the channel change processing, and the channel change occurs when the CPU 205 of the wireless access point device 103 generates a heartbeat reception timeout. Since the operations until the process is executed are the same as those in the case where the channel B is not used by the radar, the description thereof is omitted.

(B-2-1: Operation when the wireless access point device 102 detects use of the channel B radar)
FIG. 9 is a time chart showing the operations of the wireless access point devices 102 and 103 when the channel B is also used by the radar and the use of the channel B is detected by the wireless access point device 102. Note that timings T91, T92, T93, and T94 in FIG. 9 correspond to timings T81, T82, T83, and T84 in FIG.

  The CPU 205 of the wireless access point device 102 starts executing the channel change process at timing T91. In this channel change process, the process of step S706 is executed subsequent to the process of steps S701 to S705, which is the same as the case where channel B is not used by the radar. Similarly, the processing from step S708 to step S711 is also executed. In this embodiment, channel B is used by the radar, and the wireless access point device 102 detects its use. For this reason, in this operation example, the determination result of step S711 is “Yes”, and the processing after step S703 is executed again. That is, the channel used for wireless communication is switched to channel C according to the channel selection order information (step S704), and the maximum value of the heartbeat reception timer is obtained by adding 15 seconds to the maximum value (30 seconds) at that time. The value is updated (ie, 45 seconds) (step S706). Thereafter, the CPU 205 of the wireless access point device 102 performs the determination in step S708, but the determination result in step S708 is “No” because the channel C is not W53 or W56. For this reason, the CPU 205 of the wireless access point device 102 executes the processing of steps S712 and S713 without executing the processing of steps S709 to S711, and transmits the heartbeat using the channel (channel C) after switching. Resume. This restart timing is timing T92 in FIG.

  On the other hand, the CPU 205 of the wireless access point device 103 detects a heartbeat reception timeout at timing T93 (timing after 15 seconds from T91) in FIG. 9, sets the radar wave detection flag to “0”, and changes the channel. The process (step S307) is executed. However, since the use of channel B in the radar is not detected in the wireless access point device 103, the CPU 205 of the wireless access point device 103 detects the heartbeat from timing T94 as in the case where the channel B is not used in the radar. Start sending. However, in this operation example, the wireless communication channel of the wireless access point device 102 is further changed to the channel C at the timing T94, and the wireless access point device 103 transmits the heartbeat transmitted from the wireless access point device 102 to the channel. It will not receive via B. Therefore, in wireless access point apparatus 103, a heartbeat reception timeout occurs at timing T95 after 15 seconds have elapsed from timing T94, and the channel change process (step S307) is executed again.

  In the channel change process executed again in this way, the channel used for wireless communication is switched to channel C according to the channel selection order information (step S704), and the maximum value of the heartbeat reception timer is reset to 15 seconds. (Step S706). Thereafter, the CPU 205 of the wireless access point device 103 makes the determination in step S708, but the determination result in step S708 is “No” because the channel C is not W53 and not W56. For this reason, the CPU 205 of the wireless access point device 103 executes the processing of steps S712 and S713 without executing the processing of steps S709 to S711, and resumes transmission of the heartbeat using the channel C. Since the processing in steps S709 to S711 is not executed, the heartbeat transmission resumption timing substantially coincides with the timing T95 in FIG.

  At time T92 in FIG. 9, the maximum value of the timer of the heartbeat reception timer unit 206 of the wireless access point device 102 is 45 seconds, while the heartbeat transmission from the wireless access point device 103 to the channel C is resumed. Timing T95 is a time when 15 seconds have elapsed from timing T94 (timing T94 is a time when 15 seconds have elapsed since timing T92, and therefore, time when 30 seconds have elapsed since timing T92). The wireless access point device 102 receives the heartbeat transmitted from the wireless access point device 103 to the channel C before the timing T96 when 45 seconds have elapsed from the timing T92. No receive timeout occurs for the heartbeat. Therefore, channel change due to heartbeat reception timeout does not occur. Therefore, the wireless access point devices 102 and 103 can continue the wireless communication using the channel C that is expected to have the best communication quality among channels without interference such as radar waves.

(B-2-2: Operation when wireless access point device 103 detects use of channel B in radar)
FIG. 10 is a time chart showing the operation flow of the wireless access point devices 102 and 103 when the channel B is also used by the radar and the use of the channel B is detected by the wireless access point device 103. Note that timings T101, T102, T103, and T104 in FIG. 9 correspond to timings T81, T82, T83, and T84 in FIG.

  The CPU 205 of the wireless access point device 102 starts executing the channel change process at timing T101. In this channel change process, the process of step S706 is executed subsequent to the process of steps S701 to S705, which is the same as the case where channel B is not used by the radar. Similarly, the processing from step S708 to step S711 is also executed. In this operation example, although channel B is used by the radar, since the use is detected by the wireless access point device 102, the determination result of step S711 is “No”, and the processing of steps S712 and S713 is executed. The Therefore, the CPU 205 of the wireless access point device 102 resumes the transmission of the heartbeat to the channel B at the timing T102 in FIG.

  The CPU 205 of the wireless access point device 103 detects a heartbeat reception timeout at timing T103 (timing 15 seconds after T101) in FIG. 10, sets “0” to the radar wave detection flag, and changes the channel ( Step S307) is executed. That is, the CPU 205 of the wireless access point device 103 switches the channel used for wireless communication to channel B according to the channel selection order information (step S704), and resets the maximum value of the heartbeat reception timer to 15 seconds (step S707). Then, the processes of steps S709 to S711 are executed. In this operation example, since the wireless access point device 103 detects the use of channel B in the radar, the determination result in step S711 is “Yes”, and the processing from step S703 is executed again. That is, the channel used for wireless communication is switched to channel C according to the channel selection order information (step S704), and the maximum value of the heartbeat reception timer is a value obtained by adding 15 seconds to the maximum value (15 seconds) at that time. (That is, 30 seconds) (step S706). Thereafter, the CPU 205 of the wireless access point device 103 makes the determination in step S708, but the determination result in step S708 is “No” because the channel C is neither W53 nor W56. For this reason, the CPU 205 of the wireless access point device 103 executes the processing of steps S712 and S713 without executing the processing of steps S709 to S711, and resumes transmission of the heartbeat using the channel C. This restart timing is timing T104 in FIG.

  As described above, at time T104 in FIG. 10, the wireless access point device 102 transmits a heartbeat to channel B, and the wireless access point device 103 transmits a heartbeat to channel C. For this reason, the wireless access point device 102 does not receive the heartbeat transmitted from the wireless access point device 103 until the timing T105 when 30 seconds have elapsed from the timing T102. Receive timeout occurs. The CPU 205 of the wireless access point device 102 sets “0” to the radar wave detection flag when the reception timeout occurs, and executes channel change processing (S307). In this channel change process, the channel used for wireless communication is switched to channel C according to the channel selection order information (step S704), and the maximum value of the heartbeat reception timer is reset to 15 seconds (step S706). Thereafter, the CPU 205 of the wireless access point device 102 makes the determination in step S708, but the determination result in step S708 is “No” because the channel C is neither W53 nor W56. For this reason, the CPU 205 of the wireless access point device 102 executes the processes of steps S712 and S713 without executing the processes of steps S709 to S711, and resumes transmission of the heartbeat using the channel C. Since the processing of steps S709 to S711 is not executed, the heartbeat transmission restart timing substantially coincides with the timing T105 in FIG.

  At time T104 in FIG. 10, the maximum value of the timer of the heartbeat reception timer unit 206 of the wireless access point device 103 is 30 seconds, while the heartbeat transmission from the wireless access point device 102 to the channel C is started. Timing T105 is a time point when 30 seconds have elapsed from timing T102 (since timing T102 is a time point 15 seconds before timing T104, 15 seconds have passed since timing T104). The wireless access point device 103 receives the heartbeat transmitted from the wireless access point device 102 to the channel C before the timing T106 when 30 seconds have elapsed from the timing T104. No receive timeout occurs for the heartbeat. Therefore, channel change due to heartbeat reception timeout does not occur. Therefore, the wireless access point devices 102 and 103 can continue the wireless communication using the channel C that is expected to have the best communication quality among channels without interference such as radar waves.

  As described above, in the wireless communication devices (wireless access point devices 102 and 103) of the present embodiment, the channel is changed according to the channel selection order indicated by the channel selection order information stored in the RAM 214 of the wireless communication device. Therefore, it is not necessary to notify the partner device of the channel to be changed prior to the channel change, and no problem occurs in the channel change even if an interference wave exists in the channel being used. Since the channel selection order information is periodically updated, the channel can be changed to the channel having the best communication quality when the channel needs to be changed. That is, according to the present embodiment, even when an interference wave is present in a channel used for wireless communication, switching to a channel with better communication quality can be performed reliably. Furthermore, even if the interference is caused by a radar wave, it does not violate the law and does not violate the purpose of the law. Further, since the channel change is performed according to the channel selection order, the time required until the final change destination channel is shortened even if the channel change needs to be performed continuously many times.

(C: Modification)
Although one embodiment of the present invention has been described above, this embodiment may be modified as follows.
(1) In the above embodiment, the occurrence of a channel change is also detected on the partner device side due to the interruption of the heartbeat from the partner device. However, each of the wireless access point devices 102 and 103 is caused to execute a process of periodically transmitting a frame for notifying the communication partner of the existence of the own device (hereinafter referred to as presence notification frame) to the communication partner. The frame may play the role of the heartbeat. In this case, the wireless access point device 102 is caused to execute a process of writing channel selection order information indicating the channel selection order determined by the own device into the payload of the presence notification frame and transmitting it, and the wireless access point device 103 Processing for updating the channel selection order information of the own apparatus may be executed using the channel selection order information written in the payload of the presence notification frame received from the apparatus. Moreover, you may make a beacon frame play the role of a presence notification frame. In this case, the wireless access point device 102 may write the channel selection order information in a general information element in the beacon frame, for example, a field in which vendor-specific information is written, and transmit it to the partner device. 102 and 103 may change the channel when the beacon transmitted from the partner apparatus disappears. In the above embodiment, an interference wave detection unit (in the above embodiment, radar wave monitoring unit 208) for detecting the presence or absence of an interference wave (in the above embodiment, a radar wave) in a channel being used for wireless communication is provided. Although implemented as hardware separate from the CPU 205, detection of interference waves may be realized by software processing by the CPU 205.

(2) The wireless communication system 1 of the above embodiment has two wireless communication devices, wireless access point devices 102 and 103. However, the present invention may be applied to a wireless communication system having three or more wireless communication devices. That is, there may be a plurality of counterpart devices that are communication counterparts of the wireless communication device of the present invention. In this case, channel selection order information may be stored in the RAM 214 for each counterpart device.

  For example, when wirelessly communicating with three partner devices, partner device 1, partner device 2, and partner device 3, the channel selection order information shown in FIG. 11B is stored in the RAM 214 in association with the apparatus 2, and the channel selection order information in FIG. 11C is stored in the RAM 214 in association with the counterpart apparatus 3. When changing the channel used for wireless communication with the counterpart apparatus 1, the channel to be changed is selected with reference to the channel selection order information shown in FIG. 11A and used for radio communication with the counterpart apparatus 2. When changing the channel to be selected, refer to the channel selection order information shown in FIG. 11B, select the channel to be changed, and when changing the channel used for wireless communication with the counterpart device 3, The change destination channel may be selected with reference to the channel selection order information shown in FIG.

  In the channel selection order information shown in FIGS. 11A to 11C, in addition to the channel selection order of each channel (abbreviated as “selection order” in FIG. 11), the basis for calculating the channel selection order (score) Various information (communication quality evaluation items (in this example, CRC error rate and frame retransmission rate), signal strength (minimum signal strength: the smallest among multiple terminals), and presence of interference wave) Is stored. These pieces of information are periodically updated, and the channel selection order (score) of each channel is also updated according to a predetermined algorithm using these pieces of information. The channel selection order information of the above embodiment includes only the channel selection order (score) of each channel, but various information (or a part of the information) that is the basis for calculating the channel selection order as in this modification example. Information) may be included. If there is only one counterpart device of the wireless communication device of the present invention, it is only necessary to store only one of the channel selection order information shown in FIGS. good.

  In addition, when there are a plurality of counterpart devices of the wireless communication device of the present invention, various modes are conceivable as arrangement modes of the plurality of counterpart devices of the radio communication device. For example, in the case of a wireless communication system in which three or more wireless communication devices are connected in a line, the wireless access point device 102-1, the wireless access point device 103-1, the wireless access point device 102-2, and the wireless access point device 103 are used. The wireless access point devices 120 and 103 may be alternately arranged, such as −2. In this wireless communication system, the wireless access point device 102-1 executes channel selection order determination processing (step S301) for the wireless communication channel between the wireless access point device 102-1 and the wireless access point device 103-1. It is determined according to the channel selection order determined by this. Similarly, the channel of wireless communication between the wireless access point device 103-1 and the wireless access point device 102-2 is determined according to the channel selection order determined by the wireless access point device 102-2, and the wireless access point device 102-2 is determined. The channel of the wireless communication between 102-2 and the wireless access point device 103-2 is also determined according to the channel selection order determined by the wireless access point device 102-2. That is, the wireless access point 102-2 communicates with each other according to the channel selection order represented by the channel selection order information stored in association with each of the wireless access point 103-1 and the wireless access point 103-2. For each partner device. Therefore, the channel for wireless communication between the wireless access point 102-2 and the wireless access point 103-1 is the same as the channel for wireless communication between the wireless access point 102-2 and the wireless access point 103-2. Not necessarily.

  When the present invention is applied to a wireless communication system having a star network topology in which a plurality of wireless communication devices are arranged radially with a single wireless communication device as a center, the wireless access point 102 is connected to the star network. It suffices to arrange at the center of the topology and to arrange each of the plurality of wireless access points 103 radially from the center. Then, the wireless access point 102 stores channel selection order information indicating the channel selection order for the channels used for wireless communication with each of the plurality of wireless access point apparatuses 103 in association with the wireless access point apparatus 103. The wireless access point device 103 performs a process of changing the channel used for wireless communication with the wireless access point device 103 according to the channel selection order indicated by the channel selection order information corresponding to the wireless access point device 103 for each wireless access point device 103. 102 may be executed.

(3) In the above embodiment, the application example of the present invention to the wireless access point devices (wireless access point device 102 and wireless access point device 103) that perform wireless communication in the WDS mode has been described. However, since the present invention does not use a beacon, it can be applied to wireless communication in ad hoc mode, and can also be applied to wireless communication in infrastructure mode between a wireless access point device and a wireless communication terminal. That is, the wireless communication device of the present invention is not limited to the wireless access point device, and may be a wireless communication terminal.

(4) In the above-described embodiment, a mode has been described in which channel change is triggered by radar wave detection or heartbeat reception timeout. However, the channel change score may be changed when the channel evaluation score calculated in step S408 of the channel selection order determination process in FIG. 4 falls below a predetermined threshold, or a combination of both. Also good. In short, any mode may be used as long as it is necessary to change the channel according to the communication quality of the channel being used for wireless communication with the counterpart device. In the above embodiment, the channel is changed when a reception timeout occurs for the heartbeat transmitted from the partner device (that is, when the communication quality of the channel being used is deteriorated) or when an interference wave is detected. However, it may be determined whether it is necessary to change the channel by monitoring only one of them.

(5) In the above embodiment, the initial value of the timer value of the heartbeat reception timer unit 206 is 15 seconds. However, the initial value is not necessarily 15 seconds. The same applies to the increment of the initial value at the time of radar wave detection. However, if the initial value (or increment) is too long, the time during which wireless transmission / reception is stopped becomes longer and wireless communication cannot be performed smoothly. On the other hand, if it is too short, channel change due to the heartbeat reception timeout is frequently performed, and smooth wireless communication cannot be performed. The initial value and the increment of the initial value may be determined appropriately by appropriately measuring. The initial value and the increment of the initial value may be variable depending on the channel evaluation score calculated in step S408 of the channel selection order determination process in FIG. The higher the channel evaluation score, the smoother the heartbeat can be transmitted / received, so the higher the score, the smaller the initial value and the initial value increment. If the initial value is sufficiently large, it is not necessary to provide the above increment. Alternatively, the heartbeat reception timer unit 206 may be realized by a timer that counts up, and it may be determined that channel change is necessary when the value of the timer reaches the initial value or the like.

(6) In the above embodiment, the channel selection order determination process shown in FIG. However, the channel selection order determination process of FIG. 4 may be divided into a channel evaluation information collection process and a channel evaluation score calculation process, and each process may be distributed to each of the wireless access point devices 102 and 103. More specifically, the channel selection order determination process shown in FIG. 4 can be divided into a channel evaluation score calculation process from step S408 to step S410 and a channel evaluation information collection process other than that. Since each process does not necessarily have to be performed by the same wireless communication device, a mode may be adopted in which each process is performed by a different wireless communication device as long as information is exchanged between the wireless communication devices. Since the wireless access point devices 102 and 103 periodically transmit and receive heartbeats to each other, for example, the wireless access point device 102 performs channel evaluation score calculation processing, and the wireless access point device 103 performs channel evaluation information collection processing. May be. In this case, channel selection order information, which is the result of the channel evaluation score calculation process, is written in the heartbeat payload transmitted from the wireless access point device 102, and the channel is included in the heartbeat payload transmitted from the wireless access point device 103. Evaluation information (number of BSSIDs, CRC error rate, frame retransmission rate, etc.) may be written. According to such an aspect, it becomes possible to distribute each processing load of a channel evaluation information collection process and a channel evaluation score calculation process to two radio | wireless communication apparatuses.

(7) The channel selection order determination processing (channel evaluation information collection processing and channel evaluation score calculation processing), heartbeat transmission processing, and heartbeat reception processing may also be distributed and executed by a plurality of wireless communication devices. . FIG. 12 is a table showing combinations of the dispersion modes. The embodiment described above corresponds to the pattern 1 in FIG.

  In pattern 2 of FIG. 12, the channel selection order determination process and the heartbeat transmission process are performed by the wireless access point apparatus 102, and the heartbeat reception process is performed by the wireless access point apparatus 103. Specifically, steps S304, S305, S306, and S307 are deleted from the main process in the wireless access point device 102, and steps S301, S302, and S303 are deleted from the main process in the wireless access point device 103. It is. In this pattern 2, since the wireless access point device 103 does not transmit a heartbeat, the wireless access point device 102 does not need to be provided with the heartbeat reception timer unit 206, and the wireless access point device 103 has a heartbeat transmission timer. There is no need to provide the portion 207.

  In pattern 3 of FIG. 12, channel evaluation information collection processing is executed by the wireless access point device 102, channel evaluation score calculation processing is executed by the wireless access point device 103, and heartbeat transmission processing and heartbeat reception processing are performed by the wireless access point. Both devices 102 and 103 execute.

  The patterns 4 to 6 in FIG. 12 are merely the roles of the wireless access point device 102 and the wireless access point device 103 of the patterns 1 to 3 are exchanged, and thus detailed description thereof is omitted.

  In the pattern 7 of FIG. 12, both the wireless access point devices 102 and 103 perform all processing. Independently determined channel selection order information is written in the heartbeat payloads transmitted by the wireless access point devices 102 and 103, respectively. Since the wireless access point devices 102 and 103 are installed adjacent to each other, it is considered that the determined channel selection order information is the same. However, depending on the channel evaluation information collection processing method, the channel selection order information determined independently by the wireless access point devices 102 and 103 may differ. In such a case, the channel selection order information of one of the wireless access point apparatuses determined in advance may be used preferentially, or the channel selection order information determined by the wireless access point apparatuses 102 and 103 may be compared. If they are different, a mode may be adopted in which the situation is transmitted to the user of the wireless communication system 1 using an alarm or the like.

  Pattern 8 in FIG. 12 is a mode in which only the channel evaluation score calculation process is executed by the wireless access point apparatus 102 and the remaining processes are executed by both the wireless access point apparatuses 102 and 103. In this pattern 8, channel selection order information, which is the result of the channel evaluation score calculation process, is written in the heartbeat payload transmitted by the wireless access point device 102, and the heartbeat payload transmitted by the wireless access point device 103. Channel evaluation information is written in. In pattern 8, since the final channel selection order determination process is performed by the wireless access point apparatus 102, the channel selection order information shared by the wireless access point apparatuses 102 and 103 is not different. May be different. In such a case, a mode in which channel evaluation information collected by one of the wireless access point devices is preferentially used as in pattern 7 may be used, or a mode in which the situation is transmitted to the user by an alarm or the like may be used.

  Pattern 9 in FIG. 12 is merely a replacement of pattern 8 wireless access point devices 102 and 103. In pattern 9, the wireless access point device 103 performs channel evaluation score calculation processing. Therefore, detailed description is omitted.

(8) In the above embodiment, a control program for causing the CPU 205 to execute processing that clearly shows the features of this embodiment is stored in advance in the ROM 215 of the wireless access point device 102 (or 103). However, the control program may be distributed by being written on a computer-readable recording medium such as a CD-ROM (Compact Disk-Read Only Memory), and the control program is distributed by downloading via a telecommunication line such as the Internet. May be. By operating a control unit (computer such as a CPU) of a general wireless communication device in accordance with the control program distributed in this way, the wireless communication device can function as the wireless communication device of the present invention. Because. In the above-described embodiment, the channel selection unit that selects a channel to be used for wireless communication with the partner apparatus in descending order of the priority indicated by the channel selection order information, and the communication quality or interference wave of the channel being used for wireless communication A channel that is stored in a storage device for a wireless communication between a determination unit that determines whether a channel change is necessary for each partner device according to presence or absence, and the partner device that is determined by the determination unit that a channel change is necessary Although the channel change unit for changing to the channel selected in descending order of priority indicated by the selection order information is realized by a software module, these units may be realized by a hardware module such as an electronic circuit. Similarly, the reset of the heartbeat reception timer unit 206 may not be realized by a software module, but may be realized by dedicated hardware (reset unit), and dedicated hardware (channel It may be realized by a selection order update unit). For example, as shown in FIG. 13, a combination of a channel selection unit, a determination unit, a channel change unit, and a channel selection order update unit each realized by hardware and a storage unit (storage device) that stores channel selection order information are combined. Thus, the wireless access point devices 102 and 103 may be configured.

(9) In the above embodiment, the channel selection order information is stored in the storage device (that is, the RAM 214) built in the wireless access point device 102 (or 103). However, as shown in FIG. The channel selection order information is stored in an external storage device accessible by the devices 102 and 103 (for example, a storage device accessible by the wireless access point device 102 via a telecommunication line such as the Internet, such as a network-compatible hard disk device). It may be. FIG. 14 illustrates a case where each of wireless access point apparatuses 102 and 103 is configured by a combination of the channel selection unit, determination unit, and channel change unit. As described above, according to the aspect in which the channel selection order information is stored in the external storage device accessible by the wireless access point apparatuses 102 and 103, the channel selection order information is shared by the wireless access point apparatuses 102 and 103 naturally. Can be realized.

(10) In the above-described embodiment, the channel change confirmation process for confirming the absence of interference waves in the change destination channel over a predetermined period before using the change destination channel selected according to the channel selection order information (see FIG. 7, the CPU 205 is caused to execute the processing of steps S708 to S711 in FIG. However, a channel use confirmation unit that executes the channel change confirmation process may be implemented as hardware different from the CPU 205, and the CPU 205 may be configured to monitor the presence or absence of interference waves according to the confirmation result by the channel use confirmation unit. . In the above embodiment, the wireless access point devices 102 and 103 are allowed to perform 5 GHz band wireless communication, but may be configured to perform 2.4 GHz band wireless communication. Since the 2.4 GHz band is not used by the radar, the channel change confirmation process may be omitted when the wireless access point apparatuses 102 and 103 perform 2.4 GHz band wireless communication.

DESCRIPTION OF SYMBOLS 1, 2 ... Wireless communication system, 101, 104 ... Personal computer, 102, 103 ... Wireless access point apparatus, 201 ... Antenna, 202 ... RF part, 203, 212 ... Modulation / demodulation part, 204 ... Wireless LAN MAC multiplexing part, 205 ... CPU, 206 ... Heartbeat reception timer unit, 207 ... Heartbeat transmission timer unit, 208 ... Radar wave monitoring unit, 209 ... Channel control unit, 210 ... Basic clock generation unit, 211 ... Wired LAN MAC multiplexing unit, 213 ... Wired LANPHY unit, 214 ... RAM, 215 ... ROM.

Claims (8)

In a wireless communication device that wirelessly communicates with one or more counterpart devices,
A transmission unit that transmits in advance channel selection order information stored in a storage device as information representing a priority order according to communication quality for each of a plurality of channels used for wireless communication to one or more partner devices;
A wireless communication apparatus comprising: Channel selection order information is written in the presence notification frame transmitted from the partner device,
Selecting a channel to be used for wireless communication with the counterpart device according to the channel selection order information determined in advance among the channel selection order information received from the counterpart device and the channel selection information stored in the storage device. The wireless communication apparatus according to claim 1, wherein:   The radio communication apparatus according to claim 2, wherein notification is performed when channel selection order information received from a partner apparatus is different from channel selection order information stored in the storage device. In the presence notification frame transmitted from the counterpart device, evaluation information indicating the communication quality of each of the plurality of channels is written,
A channel for updating channel selection order information stored in the storage device according to a predetermined one of the communication quality of each of the plurality of channels detected by the own device and the communication quality indicated by the evaluation information The wireless communication apparatus according to claim 1, further comprising a selection order update unit.   5. The wireless communication apparatus according to claim 4, wherein notification is performed when the communication quality of each channel indicated by the evaluation information received from the counterpart apparatus is different from the communication quality of each channel detected by the own apparatus. A channel selection unit that selects a channel to be used for wireless communication with a partner apparatus in descending order of priority indicated by the channel selection order information;
A determination unit that determines for each partner device whether or not the channel needs to be changed according to the communication quality of the channel being used for wireless communication or the presence or absence of interference waves;
A channel changing unit that changes a channel used for wireless communication with the counterpart device determined by the determining unit to be changed to a channel selected in descending order of priority indicated by channel selection order information stored in the storage device When,
The wireless communication apparatus according to claim 1, further comprising:   A communication method executed by a wireless communication device that wirelessly communicates with one or a plurality of counterpart devices, and stored in a storage device as information indicating a priority order according to communication quality for each of a plurality of channels used for wireless communication A communication method comprising the step of transmitting the selected channel selection order information to one or more counterpart devices in advance. Computer
Channel selection order information stored in the storage device as information indicating the priority order according to the communication quality of each of the plurality of channels used for wireless communication, functioning as a wireless communication device that wirelessly communicates with one or a plurality of counterpart devices Is transmitted to the computer in advance to one or more counterpart devices.

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