Wireless communication device, wireless communication method, and wireless communication system

Abstract

Provided is a wireless communication device suitable for use in an environment where restrictions on transmission time can be relaxed by utilizing a plurality of channels. A first wireless communication module (NIC-1) is provided for performing wireless communication with a master device belonging to a first communication group by switching between a plurality of channels that do not have overlapping frequency ranges. A second wireless communication module (NIC-2) is provided for switching between the plurality of channels and wirelessly communicating with slave devices belonging to a second communication group. The NIC-1 and the NIC-2 are provided with a control circuit that commands a channel to be used for communication and a switching timing of the channel. The NIC-1 and the NIC-2 relay packets between the master device and the slave devices receive the command and switch channel #1 and channel #2 in synchronization with each other.

Description

[Technical Field]

[0001] The present disclosure relates to a wireless communication device, a wireless communication method, and a wireless communication system, and more particularly to a wireless communication device, a wireless communication method, and a wireless communication system suitable for use in an environment where restrictions on transmission time can be relaxed by utilizing multiple channels. [Background technology]

[0002] For example, in Japan, the use of the 920MHz band is subject to a limit on the total transmission time: specifically, the total transmission time of a wireless communication terminal in this frequency band is limited to 360 seconds per hour, meaning that the upper limit of the duty cycle is 10%.

[0003] In Japan, the above transmission limits are strictly per channel. A single wireless communication terminal is permitted to transmit for up to 720 seconds by utilizing multiple channels. This effectively allows transmission with a duty cycle of 20%. However, the multiple channels used must not overlap, the total length of the multiple channels must be within 720 seconds, and the transmission time on a single channel must not exceed 360 seconds.

[0004] The propagation range of wireless signals using the 920 MHz band is wider than that of signals using the 2.4 GHz or 5 GHz bands. Furthermore, repeaters may be used to expand the communication area due to the presence of obstructions. In such cases, by using multiple wireless communication modules within the repeater and using separate channels for each wireless communication module, interference between the wireless communication modules can be avoided while maintaining the repeater function. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] IEEE Standard for Information Technology--Telecommunications and Information Exchange between Systems - Local and Metropolitan Area Networks--Specific Requirements - Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications Summary of the Invention [Problem to be solved by the invention]

[0006] As IoT devices become more widespread and their uses become more diverse, there are now use cases where the demands of conventional short-term communications alone cannot be met, such as transmitting video from surveillance cameras over a wide area.

[0007] In this situation, a single repeater may be required to collect wireless signals from multiple terminals and forward all of them. In this case, the repeater is required to have a higher communication capacity than other wireless communication terminals.

[0008] Since utilizing multiple channels can alleviate the restrictions on transmission time as described above, it is conceivable to have the multiple wireless communication modules equipped in the repeater switch channels as appropriate in order to expand communication capacity. However, since the number of usable frequency channels is limited, if multiple wireless communication modules were to independently select and use channels, it would be difficult to efficiently use channels with less interference.

[0009] Figure 1 shows how two wireless communication modules, NIC-1 (Network Interface Card or Network Interface Controller) and NIC-2, switch channels as needed. As shown in Figure 1, when wireless communication module NIC-1 uses channels #1 and #2, it is essential that they do not overlap even partially in order to achieve a 20% duty cycle. Similarly, when wireless communication module NIC-2 uses channels #3 and #4, it is also necessary that they do not overlap at all.

[0010] Furthermore, because NIC-1 and NIC-2 are located close to each other within the repeater, it is necessary that channels with overlapping usage periods do not interfere with each other. Furthermore, if the timing of channel transitions on NIC-1 and NIC-2 do not match, all channels used by the other channel must be treated as channels with overlapping usage periods. Therefore, in the example shown in Figure 1, it is necessary for channel #1 to have no overlap with channels #3 and #4, and for channel #2 to have no overlap with channels #3 and #4. Therefore, if multiple wireless communication modules are to perform channel transitions independently, a total of four non-interfering channels must be provided for the two wireless communication modules NIC-1 and NIC-2.

[0011] Figure 2 shows an example of setting channels according to the classification of the 920 MHz band in Japan. More specifically, the upper part of Figure 2 shows an example of setting 1 MHz-wide channels in the 920 MHz band to prevent overlapping areas. The 1 MHz-wide area spanning sub-channels 29 to 33 is designated as a NG area because it straddles the "passive priority" area and the "active priority" area.

[0012] The bottom row of Figure 2 shows an example of setting a 2 MHz wide channel and an example of setting a 4 MHz wide channel in the 920 MHz band. The 2 MHz wide area spanning sub-channels 24 to 33 is also an NG area because it straddles both the "passive priority" and "active priority" areas.

[0013] According to the division shown in Figure 2, a maximum of two 2 MHz wide channels and one 4 MHz wide channel can be provided. In other words, to provide four independent channels in the 920 MHz band without overlapping, each channel must be set to 1 MHz wide. With this configuration, the frequency width in simultaneous use is only 2 MHz, which means that the wide frequency band shown in Figure 2 cannot be fully utilized.

[0014] The present disclosure has been made in consideration of the above-mentioned problems, and has as its first object to provide a wireless communication device that appropriately controls the transition timing of multiple channels so that multiple wireless communication modules arranged in close proximity can fully utilize the frequency band.

[0015] A second object of the present disclosure is to provide a wireless communication method for appropriately controlling the transition timing of multiple channels so that multiple wireless communication modules arranged in close proximity can fully utilize the frequency band.

[0016] A third object of the present disclosure is to provide a wireless communication system that can appropriately control the transition timing of multiple channels so that multiple wireless communication modules arranged in close proximity can fully utilize the frequency band. [Means for solving the problem]

[0017] In order to achieve the above object, a first aspect of the present invention provides a wireless communication system including: a first wireless communication module that switches between a plurality of channels that do not have overlapping frequency bands and wirelessly communicates with a communication device that belongs to a first communication group; a second wireless communication module that switches the plurality of channels to perform wireless communication with a communication device that belongs to a second communication group; a control circuit that issues a command to the first wireless communication module and the second wireless communication module to specify a channel to be used for communication and a channel switching timing; The first wireless communication module and the second wireless communication module executes a process of relaying packets between a communication device belonging to the first communication group and a communication device belonging to the second communication group; Following the above instruction, A process of switching channels in synchronization with each other; selecting channels to be used for communication such that channels used simultaneously do not overlap with each other; Preferably, the system is configured to execute the following:

[0018] A second aspect is a wireless communication method in which a wireless communication device relays communication between a communication device belonging to a first communication group and a communication device belonging to a second communication group, the method comprising: The wireless communication device a first wireless communication module that switches between a plurality of channels that do not have overlapping frequency bands and wirelessly communicates with a communication device that belongs to a first communication group; a second wireless communication module that switches the plurality of channels to perform wireless communication with a communication device that belongs to a second communication group; a control circuit that issues a command to the first wireless communication module and the second wireless communication module to specify a channel to be used for communication and a channel switching timing; the first wireless communication module and the second wireless communication module, relaying packets between a communication device belonging to the first communication group and a communication device belonging to the second communication group; switching channels in synchronization with each other according to the command; selecting channels to be used for communication in accordance with the instruction so that channels used simultaneously do not overlap with each other; It is desirable to include:

[0019] A third aspect is a wireless communication system including a communication device belonging to a first communication group, a communication device belonging to a second communication group, and a wireless communication device that relays communication between the communication devices, The wireless communication device a first wireless communication module that switches between a plurality of channels that do not have overlapping frequency bands and wirelessly communicates with a communication device that belongs to a first communication group; a second wireless communication module that switches the plurality of channels to perform wireless communication with a communication device that belongs to a second communication group; a control circuit that issues a command to the first wireless communication module and the second wireless communication module to specify a channel to be used for communication and a channel switching timing; The first wireless communication module and the second wireless communication module executes a process of relaying packets between a communication device belonging to the first communication group and a communication device belonging to the second communication group; Following the above instruction, A process of switching channels in synchronization with each other; selecting channels to be used for communication such that channels used simultaneously do not overlap with each other; Preferably, the system is configured to execute the following: [Effects of the Invention]

[0020] According to the first to third aspects, it is possible to use a wide channel by appropriately controlling the timing at which a plurality of closely arranged wireless communication modules transition channels. Therefore, according to the present aspects, it is possible to efficiently use frequencies and increase communication capacity while appropriately avoiding interference between a plurality of adjacently arranged wireless communication modules. [Brief explanation of the drawings]

[0021] [Figure 1] 10 is a timing chart showing how two wireless communication modules NIC-1 and NIC-2 switch channels as appropriate. [Figure 2] FIG. 10 is a diagram showing an example of setting channels according to the classification of the 920 MHz band in Japan. [Figure 3] 1 is a block diagram showing a basic configuration of a wireless communication system according to a first embodiment of the present disclosure. [Figure 4] FIG. 4 is a block diagram showing a detailed configuration of the wireless communication repeater shown in FIG. 3. [Figure 5] FIG. 4 is a diagram showing a state in which communications between two communication groups are carried out simultaneously in the wireless communication system shown in FIG. [Figure 6] 4 is a timing chart for explaining features of the wireless communication system according to the first embodiment of the present disclosure. [Figure 7] 10 is a timing chart illustrating features of a wireless communication system according to a second embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0022] Embodiment 1 [Configuration of the First Embodiment] Fig. 3 is a block diagram showing a basic configuration of a wireless communication system according to a first embodiment of the present disclosure. As shown in Fig. 3, the wireless communication system according to this embodiment includes a wireless communication repeater 10. The wireless communication repeater 10 includes a repeater SoC (System on Chip) 12. The repeater SoC 12 is an integrated circuit for transferring packets between a first wireless communication module NIC-1 (hereinafter simply referred to as NIC-1) and a second wireless communication module NIC-2 (hereinafter simply referred to as NIC-2). The repeater SoC 12 is equipped with various elements, such as a processor and a memory, required to realize the above functions.

[0023] NIC-1 is a wireless communication module for performing wireless communication with a wireless communication master device 14. On the other hand, NIC-2 is a wireless communication module for performing wireless communication with a wireless communication slave device 16. The wireless communication system of this embodiment includes the master device 14 and the slave device 16, and may include multiple slave devices 16. The master device 14 and the slave device 16 are far enough apart that direct communication is not possible, but they can communicate with each other via the wireless communication repeater 10.

[0024] Fig. 4 is a block diagram for explaining the configuration of the wireless communication repeater 10 in more detail. As shown in Fig. 4, the wireless communication repeater 10 includes a communication bus 18. A control circuit 20 and a memory 22 are connected to the communication bus 18. A control program and management information are stored in the memory 22. The control circuit 20 includes a processor, and is realized by the processor executing processing in accordance with the control program using the management information and the like. The control program can be provided via a computer-readable recording medium, or via a network.

[0025] A wired communication module 24 and a drive circuit 26 are also connected to the communication bus 18. The wireless communication repeater 10 can establish wired communication with an external device via the wired communication module 24. The drive circuit 26 also has a built-in storage medium for storing various data.

[0026] A user interface 28 and a timer 30 are also connected to the communication bus 18. The user interface 28 is used for various input operations to the wireless communication repeater 10. The timer 30 is used for various counts required in carrying out communication.

[0027] 3 are further connected to the communication bus 18. As described above, the NIC-1 is a wireless communication module for establishing wireless communication between the wireless communication repeater 10 and the parent device 14. On the other hand, the NIC-2 is a wireless communication module for establishing wireless communication between the wireless communication repeater 10 and the child device 16.

[0028] Both NIC-1 and NIC-2 can switch between multiple channels in response to commands provided by the control circuit 20. For example, if the wireless communication system of this embodiment uses the 920 MHz band used in Japan, it can switch between multiple channels that can be set according to the classification shown in FIG. 2 as needed. Specifically, when the control circuit 20 requests the use of a 1 MHz band spanning sub-channels 24 to 28, for example, NIC-1 and NIC-2 use that band as a single channel. When the control circuit 20 requests the use of a 4 MHz band spanning sub-channels 34 to 53, NIC-1 and NIC-2 use that band as a single channel. Furthermore, NIC-1 and NIC-2 can transition the channel they use at a timing specified by the control circuit 20.

[0029] 5 shows a state in which a first communication group including NIC-1 and parent device 14 and a second communication group including NIC-2 and child device 16 are simultaneously conducting wireless communication. In FIG. 5, the first communication group uses channel #1, and the second communication group uses channel #2. Channel #1 and channel #2 are independent channels with no overlapping frequency ranges.

[0030] The command provided by the control circuit 20 of the repeater SoC12 to NIC-1 is also given from NIC-1 to the parent device 14 belonging to the same communication group. As a result, NIC-1 and the parent device 14 can perform wireless communication on a channel that conforms to the command from the control circuit 20. Similarly, a command issued from the control circuit 20 to NIC-2 is transmitted to all child devices 16 that belong to the same communication group as NIC-2. As a result, NIC-2 and all child devices 16 can perform wireless communication on a channel that conforms to the command from the control circuit 20.

[0031] [Features of the first embodiment] Fig. 6 is a timing chart for explaining the features of the wireless communication system of this embodiment. Fig. 6 shows how NIC-1 uses channel #1 during usage time a, and NIC-2 uses channel #2 over the same period. Fig. 6 also shows how, after channel switching time c has elapsed, NIC-1 uses channel #2 during usage time b, and NIC-2 uses channel #1 over the same period.

[0032] 6, the control circuit 20 provides commands to NIC-1 and NIC-2, each of which includes a channel (#1, #2), a usage time (a, b), a switching time c, and a start timing of a monitoring time d. In response to these commands, NIC-1 sequentially executes the following processes. (1-1) At the start timing of the monitoring time d, communication using channel #1 is started with the parent device 14. (1-2) Maintain channel #1 until usage time a has elapsed. (1-3) During usage time a, the total transmission time is monitored, and the amount of transmitted packets is limited so that the duty ratio during monitoring time d does not exceed 10%. In other words, when the transmission time of NIC-1 during usage time a reaches "d / 10", subsequent packet transmission is stopped. (1-4) When the usage time a has elapsed, communication on channel #1 is stopped and the channel switching time c is awaited. (1-5) After the switching time c has elapsed, communication with the base unit 14 is resumed on channel #2. (1-6) During the usage time b, the total transmission time is monitored, and the amount of transmission packets is limited so that the duty ratio during the monitoring time d does not exceed 10%. (1-7) When the usage time b has elapsed, communication on channel #2 is stopped and the channel switching time c is waited for to elapse. (1-8) After that, the above processes (1-1) to (1-7) are repeatedly executed.

[0033] Upon receiving the above command from the control circuit 20, the NIC-2 executes the following process. (2-1) At the start timing of the monitoring time d, that is, in synchronization with the start of communication on channel #1 by NIC-1, communication using channel #2 is started with slave device 16. (2-3) Maintain channel #2 until usage time a has elapsed. (2-3) During the usage time a, the total transmission time is monitored, and the amount of transmission packets is limited so that the duty ratio during the monitoring time d does not exceed 10%. (2-4) When the usage time a has elapsed, communication on channel #2 is stopped and the channel switching time c is awaited. (2-5) After the switching time c has elapsed, communication with the slave unit 16 is resumed on channel #1. (2-6) During the usage time b, the total transmission time is monitored, and the amount of transmitted packets is limited so that the duty ratio for the monitoring time d does not exceed 10%. (2-7) When the usage time b has elapsed, communication on channel #1 is stopped and the channel switching time c is waited for to elapse. (2-8) After that, the above processes (2-1) to (2-7) are repeatedly executed.

[0034] The wireless communication system of this embodiment is assumed to be used in a frequency band subject to transmission restrictions, such as Japan's 920 MHz band. In this embodiment, all communication devices included in this system are required to limit the duty ratio of the total transmission time on a single channel to 10% or less. Furthermore, the duty ratio is permitted to be capped at a maximum of 20%, provided that the channel is switched to one that does not have overlapping areas. The monitoring time d is a unit of time for monitoring the transmission duty ratio, e.g., one hour.

[0035] If channel #1 and channel #2 do not have overlapping areas, then the above processes (1-1) to (1-8) can be used to assign a 10% duty ratio to NIC-1 on each channel. In other words, a maximum 20% duty ratio can be assigned to NIC-1. Similarly, if channel #1 and channel #2 do not have overlapping areas, then the above processes (2-1) to (2-8) can be used to assign a maximum 20% duty ratio to NIC-2.

[0036] In the example shown in Figure 6, NIC-1 and NIC-2 switch channels at the same time. Therefore, the period in which NIC-1 uses channel #1 and the period in which NIC-2 uses channel #1 do not overlap. The same is true for channel #2. Therefore, according to the operation example shown in Figure 6, if only two independent channels with no overlapping areas can be prepared, signal interference between the first communication group and the second communication group can be avoided throughout the entire period.

[0037] Taking the 920 MHz band in Japan as an example, as explained with reference to Figure 2, in order to provide four independent channels, each channel width must be set to 1 MHz. On the other hand, if two independent channels are sufficient, each channel width can be set to 2 MHz. Therefore, in this embodiment, control circuit 20 provides NIC-1 and NIC-2 with commands allocating a width of 2 MHz to channel #1 and channel #2, respectively.

[0038] As a result, the wireless communication system of this embodiment can utilize a wide frequency range of 4 MHz in total during utilization times a and b. When NIC-1 and NIC-2 each independently switch channels, the width of the range that can be utilized simultaneously is 2 MHz, so the system of this embodiment significantly improves frequency utilization efficiency. Improved frequency utilization efficiency also increases communication capacity. Therefore, according to this embodiment, the communication capacity of the entire system can be significantly increased.

[0039] Embodiment 2 [Configuration of the second embodiment] Next, a second embodiment of the present disclosure will be described with reference to FIG. 7 as well as FIGS. 2 to 5. The wireless communication system of this embodiment can be realized by the hardware configuration shown in Figures 3 and 4, as in the case of embodiment 1. Also in this embodiment, as shown in Figure 5, a first communication group including NIC-1 and parent device 14 and a second communication group including NIC-2 and child device 16 simultaneously communicate using channels that do not interfere with each other.

[0040] In the first embodiment described above, the first communication group and the second communication group communicate using channel #1 and channel #2, each 2 MHz wide. In Japan's 920 MHz band, only one 4 MHz wide channel can be prepared without creating overlapping areas. Therefore, if multiple 4 MHz wide channels are used by switching between them, overlapping areas will inevitably occur, and the maximum transmission duty will be 10%. Furthermore, interference will occur between the two communication groups, which will result in retransmission requests and make it difficult to ensure sufficient capacity. For these reasons, switching between two independent 2 MHz wide channels is useful for increasing frequency utilization efficiency.

[0041] However, in the division shown in Figure 2, if a 4 MHz wide channel and a 1 MHz wide channel are combined, two channels with no overlapping areas can be prepared. If NIC-1 and NIC-2 are requested to switch between them, a total of 5 MHz of area can be used simultaneously, enabling a wider range of frequency utilization than in the first embodiment.

[0042] [Features of the second embodiment] Fig. 7 shows an example of a timing chart when NIC-1 and NIC-2 each switch between 4 MHz wide channel #1 and 1 MHz wide channel #2. In this embodiment, the wireless communication repeater 10 causes each of NIC-1 and NIC-2 to switch between channel #1 and channel #2 so as to realize the state shown in Fig. 7. As a result, in this embodiment, the efficiency of frequency utilization is further improved compared to the first embodiment.

[0043] In the wireless communication system of this embodiment, NIC-2 may communicate with multiple slave devices 16. Each of the multiple slave devices 16 can transmit at a duty cycle of 10%. The same restriction is imposed on transmissions from NIC-1 to the master device 14. Therefore, if the transmission rates of the two communication groups are the same, the amount of packets received by NIC-2 will be greater than the amount of packets sent by NIC-1. For this reason, packet congestion is likely to occur in NIC-1 in this system.

[0044] In this embodiment, during the usage time a, NIC-1 uses a 4 MHz bandwidth, and NIC-2 uses channel #1 with 1 MHz, as described above. In this case, since the bandwidth used is four times larger, the transmission rate r1_1 of NIC-1 is sufficiently larger than the transmission rate r2_2 of NIC-2. In other words, during the usage time a, multiple slave devices 16 upload packets to NIC-2 at a small transmission rate r2_2, while NIC-1 uploads packets to the master device 14 at a large transmission rate r1_1. In this case, packet congestion is unlikely to occur in the wireless communication repeater 10.

[0045] In this embodiment, as shown in Fig. 7, usage time a, in which 4 MHz is allocated to NIC-1, is set to be longer than usage time b, in which 1 MHz is allocated to NIC-1. With this setting, it is possible to maintain a state in which congestion is unlikely to occur for a long period of time during monitoring time d for the reasons described above.

[0046] During usage time b, the opposite phenomenon occurs, making packet congestion more likely to occur in the wireless communication repeater 10. However, regardless of the length of usage time b, NIC-1 is allowed to transmit on a single channel up to an upper limit of 10% of monitoring time d. If usage time b is d / 10, after the channel is switched, NIC-1 can continue transmitting on channel #2 throughout usage time b. In other words, if usage time b is set shorter than usage time a, the (NIC-1 transmission ratio) = (NIC-1 transmission time) / (usage time b) during usage time b can be set to a high value.

[0047] During the usage time b, uploading from the slave device 16 to the NIC-2 is performed using a wide bandwidth of 4 MHz, but the transmission is not continuous. Therefore, if the (transmission ratio of NIC-1) is a high value, it is possible to suppress packet congestion in the wireless communication repeater 10 even during the usage time b.

[0048] In this way, in this embodiment, by combining 4 MHz channel #1 and 1 MHz channel #2, the simultaneously usable bandwidth is set to 5 MHz, and the frequency utilization efficiency can be further improved compared to embodiment 1. Furthermore, by setting the utilization time a longer than the utilization time b, it is possible to effectively avoid congestion in the wireless communication repeater 10 in an environment where the loads of the two wireless communication modules NIC-1 and NIC-2 are unbalanced.

[0049] [Setting usage time a and b] However, if the 4 MHz channel #1 and the 1 MHz channel #2 are switched between as described above, a situation may arise in which the user feels a change in communication quality as the channel is switched. In this embodiment, in order to suppress such a change in the user's feeling, the usage times a and b are specifically set by the following calculation so that the upper limit or average value of the transmission rate is constant for both channel #1 and channel #2.

[0050] Here, the parameters used to calculate the usage times a and b are defined again. - The transmission rate that NIC-1 can transmit on channel #1 (4MHz): r1_1 - The transmission rate that NIC-1 can transmit on channel #2 (1MHz): r1_2 Amount of data that can be transmitted on channel #1 with a 10% duty cycle: d1 [byte] Amount of data that can be transmitted on channel #2 with a duty cycle of 10%: d2 [bytes]

[0051] To obtain the maximum rate on NIC-1, it is necessary to transmit d1 amount of data during usage time a and d2 amount of data during usage time b. In this case, the transmission rates r1_1 and r1_2 that should be secured on each channel are as follows: r1_1=d1 / a (1) r1_2=d2 / b (2)

[0052] In order to keep the transmission rate of NIC-1 constant before and after switching channels, the following relationship must be established: r1_1 = r1_2 (3)

[0053] When the relationship in the above formula (3) is applied to the above formulas (1) and (2), the following relationship is established. d1 / a=d2 / b (4)

[0054] From the above equation (4), the relationship between a and b is as follows: a=d1 / d2*b (5)

[0055] The use time a and the use time b have the following relationship with the monitoring time d and the channel switching time c. d=a+b+c (6)

[0056] In this embodiment, the use times a and b are set so as to satisfy the above formulas (5) and (6). Therefore, according to the wireless communication system of this embodiment, it is possible to efficiently utilize a wide frequency band and suppress congestion in the wireless communication repeater 10, and also to sufficiently suppress changes in communication quality that the user experiences. [Explanation of symbols]

[0057] 10 Wireless communication repeater 12 Repeater SoC (System on Chip) 14 Base unit 16 Handsets 20 Control circuit 22 Memory NIC-1, NIC-2 Wireless communication module (Network Interface Card or Network Interface Controller)

Claims

1. a first wireless communication module that switches between a plurality of channels that do not have overlapping frequency bands and wirelessly communicates with a communication device that belongs to a first communication group; a second wireless communication module that switches the plurality of channels to perform wireless communication with a communication device that belongs to a second communication group; a control circuit that issues a command to the first wireless communication module and the second wireless communication module to specify a channel to be used for communication and a channel switching timing; The first wireless communication module and the second wireless communication module executes a process of relaying packets between a communication device belonging to the first communication group and a communication device belonging to the second communication group; Following the above instruction, A process of switching channels in synchronization with each other; selecting channels to be used for communication such that channels used simultaneously do not overlap with each other; 10. A wireless communication device configured to:

2. The first wireless communication module and the second wireless communication module A process of monitoring a transmission time for each channel used for communication; a process of stopping further transmission on a single channel when the transmission time reaches a time limit for that channel; The wireless communication device of claim 1 further configured to:

3. A wireless communication device as described in claim 2, used in an environment in which the first wireless communication module and the second wireless communication module are limited in the time they transmit data on a single channel, and when the channel is switched, transmission is again permitted up to the new limit.

4. the plurality of channels are a first channel and a second channel; 2. The wireless communication device according to claim 1, wherein the first channel and the second channel each have a frequency band with the same width.

5. the plurality of channels are a first channel and a second channel; 2. The wireless communication device according to claim 1, wherein the first channel has a wider frequency band than the second channel.

6. packet congestion is more likely to occur in the first wireless communication module than in the second wireless communication module; 6. The wireless communication device according to claim 5, wherein a first usage time during which the first wireless communication module uses the first channel is set to be longer than a second usage time during which the first wireless communication module uses the second channel.

7. A wireless communication method in which a wireless communication device relays communication between a communication device belonging to a first communication group and a communication device belonging to a second communication group, comprising: The wireless communication device a first wireless communication module that switches between a plurality of channels that do not have overlapping frequency bands and wirelessly communicates with a communication device that belongs to a first communication group; a second wireless communication module that switches the plurality of channels to perform wireless communication with a communication device that belongs to a second communication group; a control circuit that issues a command to the first wireless communication module and the second wireless communication module to specify a channel to be used for communication and a channel switching timing; the first wireless communication module and the second wireless communication module, relaying packets between a communication device belonging to the first communication group and a communication device belonging to the second communication group; switching channels in synchronization with each other according to the command; selecting channels to be used for communication in accordance with the instruction so that channels used simultaneously do not overlap with each other; A wireless communication method comprising:

8. A wireless communication system including a communication device belonging to a first communication group, a communication device belonging to a second communication group, and a wireless communication device that relays communication between the communication devices, The wireless communication device a first wireless communication module that switches between a plurality of channels that do not have overlapping frequency bands and wirelessly communicates with a communication device that belongs to a first communication group; a second wireless communication module that switches the plurality of channels to perform wireless communication with a communication device that belongs to a second communication group; a control circuit that issues a command to the first wireless communication module and the second wireless communication module to specify a channel to be used for communication and a channel switching timing; The first wireless communication module and the second wireless communication module executes a process of relaying packets between a communication device belonging to the first communication group and a communication device belonging to the second communication group; Following the above instruction, A process of switching channels in synchronization with each other; selecting channels to be used for communication such that channels used simultaneously do not overlap with each other; 1. A wireless communication system configured to:

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