JP5016700B2 - Wireless LAN system - Google Patents

Description

  The present invention relates to a technique for reducing the adverse effects of radio wave interference in a wireless LAN.

  With the development of wireless LAN, the number of access points has increased. For this reason, not only radio waves from the access point of the network originally intended to be connected but also radio waves from other networks may be received simultaneously. This state is shown in FIG.

  In FIG. 1, access point devices AP1, AP2, and AP3 are wireless LAN access points for connecting to an in-house network. The client device T1 is a device connected to an in-house network via these access points AP1, AP2, and AP3. The radio wave transmission / reception areas of the access points AP1, AP2, and AP3 are set so as to overlap each other without any breaks. Thereby, even if the client device T1 moves, the connection to the network can be secured without interruption.

  However, if radio waves having the same frequency are used in a portion where radio wave transmission / reception areas of the access points AP1, AP2, and AP3 overlap, interference occurs and communication is hindered. Therefore, the frequencies of radio waves used by the access points AP1, AP2, and AP3 are set to different frequencies so that their bandwidths do not interfere with each other. In the case of IEEE802.11b / g, as shown in FIG. 2, even if the channels are different, there are cases where the bands interfere with each other like channel 1 and channel 2. Therefore, for example, frequency bands are selected so that the bands do not interfere with each other, such as 1 channel, 6 channels, and 11 channels. In the case of IEEE802.11a, since there is no band interference between different channels, any three channels are selected. Although not shown in the figure, many other access point devices for the in-house network are provided.

  When the client device T1 is in the position indicated by α in FIG. 1, the client device T1 communicates with the access point device AP2 via the channel 6 and is connected to the in-house network. When the client apparatus T1 moves to the position β, the radio wave of the channel 6 used by the external network AP11 interferes with the radio wave of the channel 6 used by the in-house access point AP2. For this reason, there has been a problem that the communication speed of the client device T1 to the in-house network decreases.

  In order to solve such a problem, a wireless LAN controller for controlling all access point devices in the in-house network is provided, and when receiving notification that there is interference from the client device T1, each access point is set to avoid the interference. Some systems change the channel of the device. According to this technique, when the client apparatus T1 is at the position β in FIG. 1, the client apparatus T1 avoids interference by requesting switching to the in-house access point AP1 that uses the channel 1. be able to.

  Patent Document 1 discloses a technique for switching connection to another access point device using a different channel when a client device detects radio wave interference.

  Further, in Patent Document 2, when the client device detects radio wave interference, the client device requests the access point device to switch the channel specifying a different channel, and the access point device is specified accordingly. A technique for changing a channel is disclosed.

JP 2007-318501 A Japanese Patent Laid-Open No. 2004-357056

  However, the technique of Patent Document 1 is effective when the client apparatus T1 is at the position of β as shown in FIG. 1, but when it is at the position of γ, it is outside the range of the access point apparatus AP1. As a result, there is no in-house access point to be switched, and as a result, interference cannot be avoided.

  Further, in the technique of Patent Document 2, since the client device designates a channel and does not consider the channel usage status of other access point devices, there is a possibility that new radio wave interference may occur after channel switching.

  If a wireless LAN controller is provided, the above-mentioned problems of Patent Document 1 and Patent Document 2 can be solved, but a wireless LAN controller that controls all access point devices increases the complexity of the system and increases the cost of the system. There was a problem.

  Accordingly, an object of the present invention is to solve the above-described problems and provide a system that can appropriately avoid interference without a wireless LAN controller.

(1) (2) (3) (6) (7) A wireless LAN system according to claim 1 is a wireless LAN system having a plurality of access point devices and at least one client device.
The client device detects whether there is interference with an access point device other than the currently communicating access point device capable of communicating with the client device, and the interference detection unit determines that there is interference. Then, upon receiving a channel switching request transmitting means for transmitting a channel switching request to the currently communicating access point device and a client side switching determination request clearly indicating channel switching from the access point device, the channel switching is performed. Switching determination means for determining whether or not is possible and returning the determination result to the access point device,
When the access point device receives the channel switching request from the client device, at least one of the candidate channels is set by another access point device for a candidate channel that does not interfere with the currently communicating channel. If there is not, the first channel switching determination means for determining that the channel can be switched and the first channel switching determination means for determining that the channel switching is possible, the communication with the client device is performed at the present time. When the first channel switching means for switching from the channel being communicated to the candidate channel and the first channel switching determination means determine that channel switching is not possible, other access point devices belonging to the own system can communicate with each other. On the other hand, whether channel switching is possible based on the changed channel combination Upon receiving an access point side switching determination request means for requesting an access point side switching determination request and an access point side switching determination request from the other access point device, it is determined whether the channel switching is possible. The access point side switching determination means for returning the determination result to the other access point device, and all the determination results returned from the other access point device in response to the access point side switching determination request If switching is possible, the access point side switching determination integration unit that determines that the access point side channel can be switched and the first channel switching determination unit determine that the channel switching is not possible, and then perform communication by themselves. For all existing client devices A client-side switching determination request means for sending a client-side switching determination request clearly indicating its own channel switching, and all the determination results returned from the client device in response to the client-side switching determination request are channel switching. If possible, the determination of the client-side switching determination integration unit that determines that the client-side channel can be switched and the determination of the access point-side switching determination integration unit can be switched, and the determination of the client-side switching determination integration unit is And a second channel switching means for switching the own channel based on the changed channel combination and transmitting the changed channel combination to another access point device. It is a feature.
Therefore, it is possible to appropriately avoid radio wave interference with a simple configuration.

  Therefore, it is possible to appropriately avoid radio wave interference with a simple configuration.

(4) In the client program according to the present invention, the switching determination unit sets the same channel as the switching channel specified in the determination request in any of the communicable access point apparatuses other than the access point apparatus that made the determination request. If not, it is determined that switching is possible.

  Therefore, it is possible to prevent new radio wave interference from occurring due to channel switching.

(5) The client program according to the present invention includes a computer, a determination unit that determines whether or not channel switching has been performed in response to detection of interference by the interference detection unit, and channel switching. If it is determined that the access point device is not connected, another access point device capable of communicating with itself is searched, and the access point device functions as an access point changing means for changing the connection.

  Therefore, even when the first channel switching and the second channel switching cannot be performed, the radio wave interference can be eliminated.

(8) In the access point program according to the present invention, the client-side switching determination requesting means only applies to the change channel combination when the access point-side switching determination integration means determines that the change channel combination can be switched. The client side switching determination request is performed.

  Therefore, it is possible to avoid making a useless client-side switching determination request.

(9) In the access point program according to the present invention, the access point side switching determination requesting means only applies to the change channel combination when the client side switching determination integration means determines that the change channel combination can be switched. The access point side switching determination request is made.

  Therefore, it is possible to avoid making a useless access point side switching determination request.

(10) The access point program according to the present invention determines that the access point side switching determination means determines that channel switching is possible when there is no client device communicating with its own access point device. It is a feature.

  Therefore, new radio wave interference after channel switching can be avoided.

(11) In the access point program according to the present invention, when there is a client device that communicates with its own access point device, the access point side switching determination means transmits a switching determination request to the client device. When a reply indicating that the channel can be switched is received from all of the client apparatuses that have transmitted the switching determination request, it is determined that the channel can be switched.

  Therefore, new radio wave interference after channel switching can be avoided.

  In the present embodiment, “interference detection means” in the present invention corresponds to step S1.

  In the embodiment, “switching request transmission means” corresponds to step S3.

  In the embodiment, “switch determination means” corresponds to step S6.

  In the first embodiment, “first channel switching determination unit” corresponds to step S11.

  The “first channel switching means” corresponds to step S13 in the embodiment.

  In the embodiment, “access point side switching determination request means” corresponds to step S152.

  In the embodiment, “access point side switching determination unit” corresponds to steps S211 to S217.

  In the embodiment, “access point side switching determination integration unit” corresponds to step S153.

  In the embodiment, “client side switching determination request unit” corresponds to step S156.

  In the embodiment, “client side switching determination integration unit” corresponds to step S157.

  In the embodiment, “second channel switching means” corresponds to step S16.

  The “program” is a concept that includes not only a program that can be directly executed by the CPU, but also a source format program, a compressed program, an encrypted program, and the like.

It is a figure for demonstrating the condition where electromagnetic interference arises. It is a figure which shows the relationship of the channel currently used in wireless LAN. 1 is a functional block diagram of a wireless LAN system according to an embodiment of the present invention. It is a figure for demonstrating cancellation of radio wave interference. It is a hardware configuration of an access point device. It is a hardware configuration of a client device. It is a flowchart which shows the outline of a radio wave interference cancellation process. It is a flowchart which shows the outline of a radio wave interference cancellation process. It is a flowchart of a radio wave interference detection process. It is a flowchart of a 1st channel switching determination process. It is a flowchart of a 2nd channel switching determination process. It is a flowchart of a 2nd channel switching determination process. It is a flowchart of a 2nd channel switching determination process. It is a table which shows the combination of a change channel. It is a flowchart of the channel switching determination process in a client program.

1. System Overview FIG. 3 shows a functional block diagram of a wireless LAN system according to an embodiment of the present invention.

  The interference detection means 2 of the client device T1 detects that radio wave interference has occurred. When the interference detection unit 2 detects radio wave interference, the switching request transmission unit 4 transmits a channel switching request to the access point device AP1 that is currently communicating.

  The first channel switching determination means 10 of the access point device AP1 that has received the channel switching request determines candidate channels that do not cause radio wave interference with the currently used channel, and these candidate channels are received from other access point devices. Determine whether radio waves can be received. At this time, it is determined whether there is a radio wave of another channel causing interference (for example, radio waves of channels 2, 3, 4, 5, etc. for channel 1 in FIG. 2) as well as the radio wave of the same channel.

  If radio waves from other access point apparatuses cannot be received for any of the candidate channels, this means that there is no other access point apparatus that sets the candidate channel for use. Therefore, in this case, the first channel switching determination unit 10 determines that switching to the candidate channel is “permitted”. On the other hand, if radio waves from other access points can be received for all candidate channels, radio wave interference will occur even when switching to these candidate channels, so switching is determined to be “impossible”.

  When the first channel switching determining unit 10 determines that the switching is “permitted”, the first channel switching unit 12 performs a switching process to the candidate channel with the client device T1. When the first channel switching determination means 10 determines that the switching is “impossible”, the channel switching by the first channel switching means 12 is not performed.

  The above process will be described with reference to FIG. 4A. The client device T1 communicates with the access point device AP1 through the channel 1. Since the client apparatus T1 also receives the channel 1 radio wave from the external access point AP11, radio wave interference occurs. The client device T1 that has detected the radio wave interference transmits a channel switching request to the access point AP1.

  Receiving this, the access point AP1 uses channel 6 and channel 11 that do not cause radio wave interference with channel 1 as candidate channels. Furthermore, the access point AP1 receives radio waves (beacons) from all nearby access points within the radio wave reception range. Here, only radio waves from the access point device AP2 are received.

  Then, it is determined whether there is a candidate channel that has not been set by another access point device. Here, although another access point device AP2 has set channel 6, no access point device set to channel 11 is found. That is, it can be determined that channel switching is “permitted”.

  Therefore, the access point AP1 switches the radio wave used for communication with the client device T1 from the channel 1 to the channel 11 found above. As described above, the client device T1 can communicate with the access point device AP1 using the channel 11, and can avoid radio wave interference with the channel 1 emitted by the access point AP11.

  As shown in FIG. 4B, when the access point device AP3 set for the channel 11 exists in the radio wave area, all of the candidate channels are set by other access point devices, and the above channel There is no switching.

  The above processing is performed by the interference detection unit 2, the switching request transmission unit 4, the first channel switching determination unit 10, and the first channel switching unit 12 of FIG.

  When the first channel switching determination unit 10 determines that the switching is “impossible”, the channel switching by the first channel switching unit 12 is not performed. In this case, the access point side switching determination request unit 14 makes a switching determination request to another access point device, and the client side switching determination request unit 18 makes a switching determination request to the client device.

  The access point side switching determination requesting means 14 generates a combination of changed channels that does not cause interference, including other nearby access point devices within the radio wave range. Further, based on each combination, an inquiry is made as to whether or not channel switching is possible to other neighboring access point devices (switching determination request).

  Receiving this, the access point side switching determination means 24 of the other access point device determines whether or not the channel switching requested by the switching determination is possible. The access point side switching determination integration means 16 determines whether or not all the determination results from each access point device can be switched for each combination of changed channels.

  The client-side switching determination requesting unit 18 requests all client devices with which the access point device is communicating to determine whether or not channel switching based on the combination of the changed channels is possible.

  Upon receiving this, the switching determination means 6 of the client device determines whether the channel switching that has received the determination request is possible, and returns the determination result to the access point device. Receiving the determination result from the switching determination unit 6 of each client device, the client-side switching determination integration unit 20 of the access point device determines that channel switching is possible if all of them are switchable.

  The second channel switching means 22 switches its own channel based on the changed channel combination if both the access point side switching determination integration means 16 and the client side switching determination integration means 20 determine that switching is possible. A switching instruction is issued to other access point devices.

  The above process will be described with reference to FIG. 4B. As described above, since the access point devices AP2 and AP3 are both set to channels 6 and 11, channel switching by the first channel switching means 12 is not performed. In this case, the access point device AP1 generates a combination of change channels including other access point devices AP2 and AP3 so as not to cause radio wave interference. In the case of FIG. 4B, for example, if the access point device AP1 uses channel 6, the access point device AP2 uses channel 11, and the access point device AP3 uses channel 1, radio wave interference can be prevented. The access point device AP1 generates all combinations of changed channels that do not cause such radio wave interference.

  The access point device AP1 inquires of the other access point devices AP2 and AP3 whether or not channel switching based on the generated combination of changed channels is possible (switching determination request). For example, if the access point device AP1 is a combination of changed channels where the access point device AP2 is channel 6, the access point device AP2 is channel 11, and the access point device AP3 is channel 1, whether or not the access point device AP2 can switch to the channel 11 is determined. Therefore, the access point device AP3 is inquired of whether or not switching to channel 1 is possible.

  The access point AP3 that has received the inquiry determines that switching is possible because there is no client device to which the access point AP3 is connected (communication), and returns switching “permitted”.

  The access point AP2 that has received the inquiry further asks the client device T2 whether or not it is possible to switch to the channel 11, since there is a client device T2 connected to itself. Upon receiving this inquiry, the client apparatus T2 determines whether there is another access point apparatus set for the channel 11 within the radio wave range. For example, as shown in FIG. 5, when the client apparatus T2 is within the radio wave range of the access point AP4 set for the channel 11, it is determined that switching to the channel 11 is “impossible”, and the access point apparatus Reply to AP2. This is because, when switching is performed, radio wave interference occurs in the client device T2. The access point device AP1 receives a reply “impossible” from the access point device AP2.

  Therefore, the access point device AP1 can know that the channel switching by the combination of the changed channels cannot be executed. Next, the access point device AP1 repeats the above processing for the other changed channel combinations generated.

  For example, when the access point device AP1 is the channel 6, the access point device AP2 is the channel 1, and the access point device AP3 is the channel 11, there is a reply of “enable” switching from both the access point devices AP2 and AP3. . Accordingly, the access point device AP1 inquires of the client device T1 with which it is communicating whether switching to the channel 6 is possible. Since the client device T1 does not receive the channel 6 radio wave from another access point device after the channel switching, the client device T1 returns a response indicating that the switching is possible to the access point device AP1.

  In response to this, the access point device AP1 performs channel switching according to the combination of the changed channels. That is, the communication with the client device T1 is switched to the channel 6, and the access point device AP2 is instructed to switch to the channel 1. Note that the access point device AP3 is originally the channel 11 and therefore does not switch.

With the above processing, the access point device AP1 is switched to the channel 6 and the access point device AP2 is switched to the channel 1, so that radio wave interference in the client device T1 is eliminated.

2. Hardware Configuration FIG. 5 shows a hardware configuration of the access point device AP1 according to one embodiment of the present invention. The other access point devices AP2, AP3,... Have the same configuration.

  A non-volatile memory 32, a wireless communication circuit 34, and a communication circuit 36 are connected to the CPU 30.

  The wireless communication circuit 34 is a circuit for performing wireless communication with the client devices T1, T2,. In this embodiment, the wireless communication circuit 34 can switch and set any one of the channels 1 to 13 compliant with IEEE802.11b / g. Switching is performed according to an instruction from the CPU 30.

  The communication circuit 36 is a communication circuit for connecting to an in-house LAN hub or the like, and may be either wireless or wired.

  In the nonvolatile memory 32, an operating system (such as WINDOWS (trademark) of Microsoft Corporation) 44 and an access point program 46 are recorded. The access point program 46 functions in cooperation with the operating system 44. Note that the access point program 46 may perform its function alone.

  FIG. 6 shows a hardware configuration of the client device according to the embodiment of the present invention.

  A memory 52, a wireless communication circuit 54, a hard disk 58, a CD-ROM drive 60, a keyboard / mouse 62, and a display 70 are connected to the CPU 50.

  The wireless communication circuit 54 is a circuit for performing wireless communication with the access point devices AP1, AP2,.

The hard disk 58 stores an operating system (such as WINDOWS (trademark) of Microsoft Corporation) 64 and a client program 66. These programs are those recorded in the CD-ROM 68 and installed in the hard disk 58 via the CD-ROM drive 60. The client program 66 functions in cooperation with the operating system 64. Note that the client program 66 alone may exert its function.

3. Radio interference avoidance processing
(1) Outline of Processing FIGS. 7 and 8 show schematic flowcharts of the access point program 46 and the client program 66 in the radio wave interference avoidance processing.

  Based on the client program 66, the client device (referred to as T1) determines the presence or absence of radio wave interference (step S1). If there is no interference (step S2), the process is terminated and step S1 is executed again.

  If there is interference (step S2), the client device T1 transmits a channel switching request to the connected access point device (assumed to be AP1) (step S3).

  Receiving this, the access point device AP1 performs the first channel switching determination by the processing of the access point program 46 (step S11). Among candidate channels that do not cause interference, there is a channel that is not set by other peripheral access point devices, and it is determined whether or not switching is possible.

  If it is determined that switching is possible (step S12), a channel switching command is transmitted to the client device T1 together with a determination result indicating that switching is possible (step S11A). Receiving this, the client device T1 switches to the candidate channel in cooperation with the access point device AP1 (steps S4, S5, S13).

  In this way, when the first channel switching is performed, both the client program 66 and the access point program 46 are terminated, and the process returns to the first process. That is, the radio interference is detected by the client program 66.

  If the access point device AP1 determines in step S12 that channel switching is not possible, a determination result indicating that switching is not possible is sent (step S11A), and the first channel switching is not performed. Proceed to the process.

  The access point device AP1 generates a combination of changed channels including other access point devices, and determines whether or not switching is possible with the combination of each changed channel, and other access point devices and access point devices in the vicinity. Is transmitted to all the client devices that are communicating with the client (step S14).

  The access point apparatus that has received the determination request determines whether or not the channel switching is possible, and returns it to the access point apparatus AP1 (step S21). Similarly, the client device that has received the determination request also determines whether or not the channel switching is possible and returns it to the access point device AP1 (step S6).

  If the switching “permitted” is returned from all of the other access point devices and client devices that have transmitted the determination request, the access point device AP1 transmits to the other access point devices and client devices that switching is possible. At the same time, a channel switching command is transmitted (step S14A). That is, a channel switching instruction is transmitted to other access point devices and client devices so as to perform channel switching with the combination of the changed channels.

  Receiving this (step S7), the client device cooperates with the access point device AP1 to perform channel switching (steps S8 and S16). The other access point device that has received the channel switching instruction (step S22) performs channel switching in cooperation with the access point device AP1 (steps S23 and S16).

As described above, switching to a channel without radio wave interference is performed. If switching “impossible” is returned from any one of the other access point devices and client devices that transmitted the determination request, the fact that switching is impossible is transmitted to the other access point devices and client devices. The channel switching command is not transmitted (step S14A). Therefore, in this case, channel switching is not performed.

(2) Radio Interference Detection Processing FIG. 9 shows a detailed flowchart of the radio interference detection processing shown in step S1 of FIG.

  The CPU 50 of the client device T1 determines whether or not the communication speed with the access point device has become lower than a predetermined threshold value. When the communication speed becomes lower than a predetermined threshold value, the process of FIG. 9 is executed.

  The CPU 50 of the client device T1 receives the beacon radio wave from the receivable access point device via the wireless communication circuit 54 (step S101). For example, if the client device T1 is in the position shown in FIG. 4A, it receives beacon radio waves from the access point devices AP1, AP2, and AP11. The beacon radio wave is transmitted by each access point device AP1, AP2, AP11, and includes data such as the ID of the access point device, the set channel, information on encryption, and the maximum transmission power.

  Among the received access point devices AP1, AP2, and AP11, the CPU 50 of the client device T1 has the same channel as the access point device AP2 and AP11 other than the access point device AP1 with which it is communicating (here, the channel 1 is assumed to be set (step S102).

  If there is an access point device set to the same channel 1 as that of itself (step S103), it is determined that radio wave interference has occurred (step S104).

  If there is no access point device set to the same channel 1 as itself, the CPU 50 transmits a probe request to each access point device via the wireless communication circuit 54 (step S105). This is because the beacon radio wave may not be received even though the access point device exists due to processing timing.

  Here, the probe request is a request issued by the client device in order to search for a communicable access point device. In response to this, the access point apparatus that has received the probe request returns a probe response. The probe response includes data such as an ID of the access point device, a set channel, information on encryption, and maximum transmission power.

  The CPU 50 of the client device T1 receives this probe response (step S106). Based on the probe response received in this way, it is determined whether or not the access point devices AP2 and AP11 other than the access point device AP1 with which they are communicating are set to the same channel 1 as that of itself (step S107).

  If there is an access point device set in the same channel 1 as that of itself (step S108), it is determined that radio wave interference has occurred (step S104). If there is no access point device set in the same channel 1 as that of itself (step S108), it is determined that no radio wave interference has occurred (step S109).

If it is determined that there is radio wave interference (step S2 in FIG. 7), the CPU 50 transmits a channel switching request to the access point device AP1 performing communication (step S3). Note that the channel switching request includes a request to execute channel switching in order to eliminate radio wave interference and the ID of its own client device.

(3) First Channel Switching Process The access point device AP1 that has received a channel switching request from the client apparatus T1 executes a first channel switching determination process (FIG. 7, step S11). FIG. 10 shows a flowchart of the access point program 46 in the first channel switching determination process.

  First, the CPU 30 of the access point device AP1 generates candidate channel information that can avoid radio wave interference by changing its own channel (step S111). For example, in the situation shown in FIG. 4A, if radio wave interference occurs in the client apparatus T1, channels 6 and 11 that do not interfere with the channel 1 of the external access point AP11 are determined as candidate channels.

  In FIG. 4A, when the external access point AP 11 is set to channel 2, candidate channels are determined as channels 7 and 12.

  Next, the CPU 30 of the access point device AP1 determines whether or not it causes interference with channels set in all access point devices within the radio wave range when its own channel is the candidate channel 6. Step S112). For example, in the state shown in FIG. 4A, when the access point apparatus AP1 switches to the channel 6, it interferes with the channel 6 of the access point apparatus AP2. Therefore, switching to the candidate channel 6 is not possible.

  Next, when the CPU 30 sets the channel as the candidate channel 11, the CPU 30 determines whether or not interference occurs with channels set in all access point devices within the radio wave range (step S <b> 112). For example, in the state shown in FIG. 4A, when the access point device AP1 switches to the channel 11, no interference occurs with any of the access point devices AP2 and AP11 within the radio wave range.

  Therefore, since at least one of the candidate channels does not interfere with the channels set by all access point devices within the radio wave range (step S112), it is determined that the first channel switching is “permitted” (step S113).

  When the CPU 30 of the access point device AP1 determines that the first channel switching is “permitted” (step S12 in FIG. 7), it performs a channel switching process to the candidate channel 11 (step S13 in FIG. 7).

  The channel switching process in step S13 is the same as the channel switching process performed conventionally. That is, when the access point device AP1 switches the channel from 1 to 11, the client device T1 follows this.

  In this way, the channel of the access point device AP1 is switched to 11, and the client device T1 follows this, so that radio wave interference from the external access point device AP11 can be eliminated.

In the state as shown in FIG. 4B, any of the candidate channels 6 and 11 interferes with any of the other access point devices AP2 and AP3. Therefore, in step S114 of FIG. 10, it is determined that the first channel switching is “impossible”. Therefore, the first channel switching process (step S13 in FIG. 7) is not executed.

(4) Second Channel Switching Process When the first channel switching determination is “impossible”, the CPU 30 of the access point device AP1 performs the second channel switching determination (FIG. 8, step S14).

  Here, in the situation shown in FIG. 4B, the access point device T1 tried to execute the first channel switching process shown in FIG. 7, but the access point devices T2 and T3 are set to channels 6 and 11. Therefore, a case where the first channel switching process cannot be performed will be described as an example.

  First, the access point device AP1 generates a combination of channels that does not cause radio wave interference, including other access point devices within the radio wave range (step S141). For example, in the state shown in FIG. 4B, the access point device AP1 generates a combination of channels of the access point devices AP1, AP2, and AP3 that can eliminate the radio wave interference of the client device T1. That is, a combination of channels including other access point devices AP2 and AP3 within the radio wave range (that is, capable of receiving beacon radio waves) is generated.

  FIG. 14 shows a combination of changed channels generated by the access point device AP1. The process in which the CPU 30 of the access point device AP1 generates this change channel combination is as follows.

  First, channel 6 or channel 11 that does not cause interference with channel 1 of external access point device AP11 causing radio wave interference is set as its own channel. Next, the channels of the other access point devices AP2 and AP3 when the channel 6 is used are determined. There are cases where the access point devices AP2 and AP3 are channel 11 and channel 1 (first line in FIG. 14) and channel 1 and channel 11 (second line in FIG. 14). Describe.

  Next, even when the channel 11 is set as the channel 11, it is described in the table in the same manner as described above (the third and fourth lines in FIG. 14).

  It is assumed that the access point devices AP1, AP2, and AP3 are using channels 3, 8, and 13, respectively (even in this case, the client device T1 causes radio wave interference between channels 1 and 3). However, the combination of change channels is the same as in FIG.

  When the change channel combination table of FIG. 14 is completed, the CPU 30 records this in the memory 32. Next, the CPU 30 reads the first row of the change channel combination table and sets this combination as the target combination (step S151). Subsequently, the CPU 30 transmits a channel switching determination request to the other access point devices AP2 and AP3 based on the target combination (step S152). That is, the access point apparatus AP2 is inquired whether switching to the channel 11 is possible. Also, the access point device AP3 is inquired whether switching to channel 1 is possible.

  Receiving this, each of the access point devices AP2 and AP3 performs the following processing.

  The CPU 30 of the access point device AP3 that has received the request for switching to channel 1 determines whether there is a client device connected to itself (step S211). If there is no connected client device, it is possible to switch to the channel 11, so it is determined that the switching is “permitted” (FIG. 12, step S216).

  Here, as shown in FIG. 4B, since the access point device AP3 does not have a connected client device, it is determined that switching is possible. Then, the CPU 30 of the access point AP3 returns this determination result to the access point device AP1 (step S217).

  On the other hand, the CPU 30 of the access point device AP2 that has received the request for switching to the channel 11 determines whether there is a client device connected to itself (step S211).

  Here, as shown in FIG. 4B, the access point apparatus AP2 includes a connected client apparatus T2. Therefore, it cannot be immediately determined that the channel can be switched. Therefore, an inquiry is made to the connected client device as to whether or not switching to the channel 11 has any effect (step S212). That is, a channel switching determination request is transmitted to all connected client devices.

  Here, since only the client device T2 is connected to the access point device AP2, the client device T2 is inquired whether switching to the channel 11 is possible.

  FIG. 15 shows a flowchart of the channel switching determination process performed by the CPU 50 of the client device T2 that has received the channel switching determination request. The CPU 50 determines whether or not another access point device AP4 within the radio wave range has set the same channel 11 for the channel 11 designated to be switched (step S501).

  Here, since the same channel as the switching channel 11 is set by the access point device AP4, the CPU 50 determines that switching is not possible (step S502). This is because when the switching is performed, new radio wave interference occurs in the client device T2. The CPU 50 of the client device T2 returns this determination result to the requesting access point device AP2 (step S504).

  The access point device AP2 receives the determination result from the client device T2 (step S213). The access point device AP2 determines whether switching “permitted” has been returned from all the connected client devices (step S214). Here, since the switching “impossible” is returned from the client device T2, it is determined that the switching to the channel 11 requested by the access point device AP1 is “impossible” (step S215). The CPU 50 returns this determination result to the access point device AP1 (step S217).

  As described above, the access point device AP1 determines whether or not the switch from the access point device AP3 is “possible” and the switch from the access point device AP2 is “impossible” for the combination of changed channels in the first row of FIG. The determination result is received.

  The CPU 50 of the access point device AP1 that has received the determination result determines whether or not switching “permitted” has been returned from all the access point devices that have made the determination requests (step S153). Here, since the switching “impossible” is returned from the access point device AP2, switching by this combination is not performed, and if an unprocessed combination remains in FIG. 14 (step S154), the next line in FIG. The combination of changed channels is set as the target combination (step S155), and step S152 and subsequent steps are repeatedly executed.

  Here, the CPU 30 of the access point device AP1 performs again the processing from step S152 onward with the change channel combination in the second row of FIG. 14 as the target combination. That is, the CPU 30 transmits a switch determination request to channel 1 to the access point device AP2. Since the access point device AP3 is not changed from the current channel 11, a switching determination request to the access point device AP3 is not transmitted.

  The CPU 30 of the access point device AP2 that has received the request for switching to channel 1 determines whether there is a client device connected to itself (step S211).

  Here, as shown in FIG. 4B, the access point apparatus AP2 includes a connected client apparatus T2. Therefore, it cannot be immediately determined that the channel can be switched. Therefore, an inquiry is made to the connected client device as to whether there is no influence even if switching to channel 1 is performed (step S212). That is, a channel switching determination request is transmitted to all connected client devices.

  Here, since only the client device T2 is connected to the access point device AP2, the client device T2 is inquired whether switching to the channel 1 is possible.

  FIG. 15 shows a flowchart of the channel switching determination process performed by the CPU 50 of the client device T2 that has received the channel switching determination request. The CPU 50 determines whether or not another access point device AP4 within the radio wave range has set the same channel 1 for the channel 1 designated for switching (step S501).

  Here, since the same channel as the switching channel 1 is not set by the access point device AP4, the CPU 50 determines that switching is possible (step S503). The CPU 50 of the client device T2 returns this determination result to the requesting access point device AP2 (step S504).

  The access point device AP2 receives the determination result from the client device T2 (step S213). The access point device AP2 determines whether switching “permitted” has been returned from all the connected client devices (step S214). Here, since the switch “permitted” is returned from the client apparatus T2, it is determined that the switch to the channel 1 requested to be determined by the access point apparatus AP1 is “permitted” (step S216). The CPU 50 returns this determination result to the access point device AP1 (step S217).

  As described above, the access point device AP1 receives the determination result of switching “permitted” from the access point device AP2 for the combination of changed channels in the second row of FIG. The CPU 30 of the access point device AP1 determines whether or not switching “permitted” has been sent from all of the access point devices that have requested switching determination (step S153).

  Here, since AP2 is the only access point device to which the access point device AP1 has made a switching determination request, switching “permitted” has been sent from all the access point devices that have made the determination request. As a result, it is found that channel switching based on the combination of changed channels in the second row in FIG. 14 is possible for the other access point devices AP2 and AP3.

  Subsequently, the CPU 30 of the access point device AP1 makes a switching determination request to the client device connected to itself for switching its channel based on the combination of the changed channels. That is, the CPU 30 of the access point device AP1 transmits a channel switching determination request to all the client devices connected to the CPU 30 based on the combination of the changed channels determined to be “enable”. S156).

  Here, since only the client device T1 is connected to the access point device AP1, the change determination to the channel 6 (refer to the change channel of the access point AP1 in the second row in FIG. 14) is performed with respect to the client device T1. Send a request.

  Receiving this, the CPU 50 of the client device T1 executes channel switching determination processing (step S61). Details of the channel switching determination process are shown in FIG. The CPU 50 of the client device T1 determines whether or not other access point devices AP2 and AP11 within the radio wave range have set the same channel 6 for the channel 6 designated to be switched (step S501).

  Here, after switching, the access point device AP2 is set to channel 1, and the access point device AP11 is set to channel 1, so it is not the same as the switching channel 6. Therefore, the CPU 50 determines that the switching is “permitted” (step S503). The CPU 50 of the client device T2 returns this determination result to the requesting access point device AP1 (step S504).

  The access point device AP1 determines whether or not all replies from all connected client devices are “switchable” (step S157). Here, the client device connected to the access point device AP1 is only T1, and the reply from the client device T1 is “permitted”, so that “permitted” replies are sent from all the connected client devices. It can be said that there was.

  Therefore, the CPU 30 of the access point device AP1 determines that the switching is “permitted” (step S159).

  Note that if switching “permitted” is not returned from all client devices, the CPU 30 determines that switching is “impossible” and determines whether switching is possible for other combinations in FIG. 14 (step S154, S155, S152 and below).

  When it is determined that the switching is “impossible” for all the combinations, the CPU 30 of the access point device AP1 finally determines that the switching is “impossible”. In any combination, when it is determined that the switching is “permitted”, it is finally determined that the switching is “permitted”.

  The CPU 30 of the access point device AP1 determines whether or not it is finally determined that switching is “permitted” or “impossible” (step S15 in FIG. 8). If the switch is “permitted”, the CPU 30 switches its own channel based on the combination determined as “permitted”. Here, its own channel is switched from channel 1 to channel 6 (step S16). The channel switching process is the same as the conventional process. As a result, the client apparatus T1 also follows the channel 6 (step S8).

Further, the CPU 30 of the access point device AP1 sends a command to switch from the channel 6 to the channel 1 to the other access point device AP2 based on the above combination. In response to this, the access point device AP2 performs channel switching (step S23). Therefore, the client device connected to the access point device AP2 also follows the channel 1.

4). Other embodiments
(1) In the above embodiment, in the second channel switching process, for the combination of changed channels, first, a switching determination request is made to another access point device. A switching determination request is made to the connected client device. However, for the combination of changed channels, first, a switching determination request is made to the client device to which it is connected, and when this is “permitted”, a switching determination request is made to another access point device. May be.

(2) In the above-described embodiment, if it is determined in the second switching determination process that all the combinations of changed channels are “switching impossible”, the channel change is given up. However, in this case, the access point device notifies the client device that switching is not possible (or if channel switching is not performed even if a predetermined time has elapsed since the client device transmitted a channel switching request). The client device may execute roaming for switching to a connection with another access point device. Note that roaming can be performed based on a conventional method.

Claims (7)

In a wireless LAN system having a plurality of access point devices and at least one client device,
The client device is
Interference detecting means for detecting whether or not there is interference with an access point device other than the currently communicating access point device capable of communicating with the client device;
When the interference detection unit determines that there is interference, a channel switching request transmission unit that transmits a channel switching request to the access point device currently in communication;
When receiving a client-side switching determination request clearly indicating channel switching from the access point device, it is determined whether or not the channel switching can be performed, and a switching determination unit that returns a determination result to the access point device;
With
The access point device is
When receiving the channel switching request from the client device, if at least one of the candidate channels is not set by another access point device for a candidate channel that does not interfere with the currently communicating channel, the channel First channel switching determination means for determining that switching is possible;
If the first channel switching determination means determines that channel switching is possible, first channel switching means for switching communication with the client device from the currently communicating channel to the candidate channel;
If the first channel switching determination means determines that channel switching is not possible, requests other access point devices belonging to its own system to determine whether channel switching is possible based on the changed channel combination. An access point side switching determination request means for transmitting an access point side switching determination request to be performed;
Upon receiving an access point side switching determination request from the other access point device, it is determined whether the channel switching is possible, and an access point side switching determination unit that returns a determination result to the other access point device;
In response to the access point side switching determination request, if all the determination results returned from the other access point devices are capable of channel switching, the access point side switching determination determines that the access point side channel can be switched. Integration means,
If the first channel switching determination means determines that channel switching is not possible, the client-side switching determination that clearly indicates its own channel switching caused by the changed channel combination to all client devices with which it is communicating. A client-side switching determination requesting means for sending a request; and
In response to the client-side switching determination request, if all the determination results returned from the client device are channel-switchable, a client-side switching determination integration unit that determines that the client-side channel can be switched;
If the determination of the access point side switching determination integration means is channel switchable, and the determination of the client side switching determination integration means is channel switchable, based on the change channel combination, switches its own channel, Second channel switching means for transmitting the changed channel combination to another access point device;
A wireless LAN system comprising: An access point device used in a wireless LAN system,
When a channel switching request is received from a client device, channel switching is possible if at least one of the candidate channels is not set by another access point device for a candidate channel that does not interfere with the currently communicating channel. First channel switching determination means for determining that
If the first channel switching determination means determines that channel switching is possible, first channel switching means for switching communication with the client device from the currently communicating channel to the candidate channel;
If the first channel switching determination means determines that channel switching is not possible, requests other access point devices belonging to its own system to determine whether channel switching is possible based on the changed channel combination. An access point side switching determination request means for transmitting an access point side switching determination request to be performed;
Upon receiving an access point side switching determination request from the other access point device, it is determined whether the channel switching is possible, and an access point side switching determination unit that returns a determination result to the other access point device;
In response to the access point side switching determination request, if all the determination results returned from the other access point devices are capable of channel switching, the access point side switching determination determines that the access point side channel can be switched. Integration means,
If the first channel switching determination means determines that channel switching is not possible, the client-side switching determination that clearly indicates its own channel switching caused by the changed channel combination to all client devices with which it is communicating. A client-side switching determination requesting means for sending a request; and
In response to the client-side switching determination request, if all the determination results returned from the client device are channel-switchable, a client-side switching determination integration unit that determines that the client-side channel can be switched;
If the determination of the access point side switching determination integration means is channel switchable, and the determination of the client side switching determination integration means is channel switchable, based on the change channel combination, switches its own channel, Second channel switching means for transmitting the changed channel combination to another access point device;
An access point device comprising: An access point program for realizing an access point device used in a wireless LAN system by a computer,
The computer,
When a channel switching request is received from a client device, channel switching is possible if at least one of the candidate channels is not set by another access point device for a candidate channel that does not interfere with the currently communicating channel. First channel switching determination means for determining that
If the first channel switching determination means determines that channel switching is possible, first channel switching means for switching communication with the client device from the currently communicating channel to the candidate channel;
If the first channel switching determination means determines that channel switching is not possible, requests other access point devices belonging to its own system to determine whether channel switching is possible based on the changed channel combination. An access point side switching determination request means for transmitting an access point side switching determination request to be performed;
Upon receiving an access point side switching determination request from the other access point device, it is determined whether the channel switching is possible, and an access point side switching determination unit that returns a determination result to the other access point device;
In response to the access point side switching determination request, if all the determination results returned from the other access point devices are capable of channel switching, the access point side switching determination determines that the access point side channel can be switched. Integration means,
If the first channel switching determination means determines that channel switching is not possible, the client-side switching determination that clearly indicates its own channel switching caused by the changed channel combination to all client devices with which it is communicating. A client-side switching determination requesting means for sending a request; and
In response to the client-side switching determination request, if all the determination results returned from the client device are channel-switchable, a client-side switching determination integration unit that determines that the client-side channel can be switched;
If the determination of the access point side switching determination integration means is channel switchable, and the determination of the client side switching determination integration means is channel switchable, based on the change channel combination, switches its own channel, Second channel switching means for transmitting the changed channel combination to another access point device;
Access point program to make it function. In the access point program of claim 3,
The client side switching determination requesting unit issues a client side switching determination request for the changed channel combination only when the access point side switching determination integrating unit determines that switching is possible for the changed channel combination. And access point program. In the access point program of claim 3,
The access point side switching determination requesting unit issues an access point side switching determination request for the changed channel combination only when the client side switching determination integrating unit determines that switching is possible for the changed channel combination. A featured access point program. In the access point program according to any one of claims 3 to 5,
The access point side switching determination means determines that channel switching is possible when there is no client device communicating with its own access point device. In the access point program according to any one of claims 3 to 6,
When there is a client device communicating with its own access point device, the access point side switching determination means transmits a switching determination request to the client device, and all clients that have transmitted the switching determination request An access point program that determines that channel switching is possible when a reply that allows channel switching is received from all of the devices.

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