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

Abstract

The present invention relates to a wireless communication system comprising a plurality of wireless devices, a plurality of relay devices having the plurality of wireless devices under the control thereof, and a control device for controlling the plurality of wireless devices via the plurality of relay devices. Each relay device executes: processing for acquiring, from another relay device, position information of the plurality of wireless devices that are under the control of the other relay device; processing for transmitting an inquiry including a desired frequency, received from a target wireless device under the control of the relay device, to the control device; processing for receiving a response including usable frequencies for the target wireless device from the control device; processing for restricting the response on the basis of a previously-received response that was received previously, targeting another wireless device; processing for transmitting a modified response, based on the restriction, to the target wireless device; processing for determining, on the basis of the position information, whether there is an interfering wireless device that may cause mutual interference with the target wireless device, among the plurality of wireless devices under the control of the other relay device; notification processing for notifying the relay device having the interfering wireless device under the control thereof of the modified response; and processing for reflecting a modified response received from the other relay device in the previously-received response.

Description

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

[0001] The present disclosure relates to a wireless communication system, a wireless communication method, a relay device, and a wireless communication program.

[0002] A method for controlling the total amount of interference to an interfered system is known as AFC (Automated Frequency Coordination) for wireless LANs. In AFC, each wireless device transmits an inquiry message about the wireless resources it uses to a control device. The control device responds with the range of wireless resources that each wireless device can use, taking into account the conditions of the interfered device.

[0003] In a wireless communication system using AFC, a relay device may be installed between the control device and the wireless device. The relay device can relay messages between the wireless devices and the control device under its control. The relay device can also concatenate and store the messages it relays, or modify and transmit them as response messages.

[0004] Wi-Fi Alliance, “Wi-Fi Alliance furthers Automated Frequency Coordination specification and compliance development to accelerate Wi-Fi 6E”, June 30, 2021, <URL: https: / / www.wi-fi.org / news-events / newsroom / wi-fi-alliance-furthers-automated-frequency-coordination-specification-and>Wi-Fi Alliance, “DRAFT AFC System to AFC Device Interface Specification”, v0.1.17, P9

[0005] However, when a system such as AFC includes multiple relay devices, the relay devices cannot cooperate with each other, which poses a problem that mutual interference may occur between wireless devices under the control of different relay devices, leading to a decrease in wireless communication throughput.

[0006] In order to solve the above-mentioned problems, the first object of the present disclosure is to provide a wireless communication system that can reduce the amount of interference to an interfered device while avoiding mutual interference between wireless devices under the control of different relay devices.

[0007] A second object of the present disclosure is to provide a wireless communication method that can reduce the amount of interference to an interfered device and at the same time avoid mutual interference between wireless devices under the control of different relay devices.

[0008] A third object of the present disclosure is to provide a relay device that can reduce the amount of interference to an interfered device and at the same time avoid mutual interference between wireless devices under the control of different relay devices.

[0009] A fourth object of the present disclosure is to provide a wireless communication program that can reduce the amount of interference to an interfered device and at the same time avoid mutual interference between wireless devices under the control of different relay devices.

[0010] a process of transmitting a modified response based on the restriction to the target wireless device; a process of determining, based on the location information, whether or not there is an interfering wireless device that may cause mutual interference with the target wireless device among the multiple wireless devices under the control of the other relay devices; a process of notifying a relay device that has the interfering wireless device under its control, if there is an interfering wireless device, of the modified response; and a process of reflecting the modified response received from the other relay devices in the modified response; and

[0011] a control device that controls the plurality of wireless devices via the plurality of relay devices, the control device including: a relay device acquiring location information of the plurality of wireless devices under its control from the other relay devices; transmitting to the control device a query including a desired frequency received from each of the plurality of wireless devices under its control, the query including a desired frequency received from a target wireless device that is one of the plurality of wireless devices under its control; receiving from the control device a response including a usable frequency for the target wireless device; restricting the response to the target wireless device based on a first received response targeted for the other wireless device that was received earlier; transmitting a modified response based on the restriction to the target wireless device; determining, based on the location information, whether there is an interfering wireless device that may cause mutual interference with the target wireless device among the plurality of wireless devices under the control of the other relay devices;

[0012] A third aspect of the present disclosure is preferably a relay device that has multiple wireless devices under its control and is mediated by a control device that controls the multiple wireless devices, and is configured to perform the following processes: acquiring location information of the multiple wireless devices under its control from other relay devices; transmitting to the control device a query including a desired frequency received from a target wireless device that is one of the multiple wireless devices under its control; receiving a response including a usable frequency for the target wireless device received from the control device; restricting the response to the target wireless device based on a first-received response previously received for the other wireless device; transmitting a modified response based on the restriction to the target wireless device; determining, based on the location information, whether there is an interfering wireless device that may cause mutual interference with the target wireless device among the multiple wireless devices under the control of the other relay devices; and, if an interfering wireless device is found, notifying the relay device that has the interfering wireless device under its control of the modified response; and reflecting the modified response received from the other relay devices in the first-received response.

[0013] A fourth aspect of the present disclosure is preferably a wireless communication program to be executed by a relay device that has multiple wireless devices under its control and is mediated by a control device that controls the multiple wireless devices, the wireless communication program including a program that causes a computer to execute the following processes: a process of acquiring location information of the multiple wireless devices under its control from other relay devices; a process of transmitting to the control device a query including a desired frequency received from each of the multiple wireless devices under its control, the query including a desired frequency received from a target wireless device that is one of the multiple wireless devices under its control; a process of receiving a response including a usable frequency for the target wireless device received from the control device; a process of restricting the response to the target wireless device based on a first-received response previously received for the other wireless device; a process of transmitting a modified response based on the restriction to the target wireless device; a process of determining, based on the location information, whether there is an interfering wireless device among the multiple wireless devices under the control of the other relay devices that may cause mutual interference with the target wireless device; and, if an interfering wireless device is found, a notification process of notifying the relay device that has the interfering wireless device under its control of the modified response; and a process of reflecting the modified response received from the other relay devices in the first-received response.

[0014] According to the first to fourth aspects of the present disclosure, it is possible to reduce the amount of interference to an interfered device and, at the same time, to avoid mutual interference between wireless devices under the control of different relay devices.

[0015] FIG. 1 is a diagram showing an AFC system of a comparative example. FIG. 2 is a diagram showing an AFC system according to a first embodiment of the present disclosure. FIG. 3 is a diagram showing an inquiry and a response performed by the AFC system according to the first embodiment of the present disclosure. FIG. 4 is a diagram showing a hardware configuration of a relay device according to the first embodiment of the present disclosure. FIG. 5 is a diagram showing an inquiry and a response performed by an AFC system according to a second embodiment of the present disclosure. FIG. 6 is a flowchart showing a notification process from a relay device to another relay device according to the second embodiment of the present disclosure. FIG. 7 is a diagram showing an inquiry and a response performed by an AFC system according to a third embodiment of the present disclosure.

[0016] First Embodiment [AFC System of Comparative Example] Prior to describing the first embodiment, an AFC system of a comparative example will be described. Fig. 1 is a diagram showing the AFC system of the comparative example. The AFC system 500 includes a control device 2. The control device 2 controls wireless devices 4a to 4e.

[0017] The AFC system 500 also includes a relay device 6. The relay device 6 relays and connects messages between the control device 2 and the wireless devices 4a to 4e.

[0018] The AFC system 500 also includes an interfered device 8. This disclosure deals with a situation in which the interfered device 8 and wireless devices 4a to 4e share the same frequency band. That is, there is a risk of interference 10a to 10e occurring between the wireless devices 4a to 4e and the interfered device 8. The AFC system 500 is a system that reduces this risk.

[0019] The following describes a method for controlling the amount of interference with an interfered system, which is implemented by the AFC system 500. First, the control device 2 receives in advance information related to wireless communication with the interfered device 8. Examples of the information received here include the location information, operating frequency, and allowable amount of interference of the interfered device 8.

[0020] Next, the wireless devices 4a to 4e issue an inquiry 12 to the control device 2. Examples of information included in the inquiry 12 include the location of the wireless device, the desired frequency, and the transmission power of each frequency. If the wireless devices are fixed, their location information may be registered in the control device in advance. In the AFC system 500, the information from the wireless devices 4a to 4c is relayed by the relay device 6.

[0021] The control device 2 receives the inquiry 12. Then, based on the information regarding the wireless communication of the interfered device 8 and the inquiry 12, the control device 2 derives the frequencies and transmission powers that can be used by each wireless device. The control device 2 then transmits the derived information to the wireless devices 4a to 4e as a response 14. Examples of information contained in the response 14 include whether the frequencies are usable, the usable frequencies, the usable transmission powers, and the time limits for which these can be used.

[0022] The wireless devices 4a to 4e receive the response 14 and perform wireless communication based on the response 14. This limits the frequency and power that each wireless device uses for wireless communication, making it possible to control the amount of interference to the interfered system.

[0023] However, when an AFC system includes multiple relay devices, this method does not allow the relay devices to cooperate with each other. As a result, there is a problem that mutual interference may occur between wireless devices under the control of different relay devices, which may lead to a decrease in wireless communication throughput. The present disclosure solves this problem.

[0024] 2 is a diagram illustrating an AFC system according to the first embodiment of the present disclosure. The AFC system 100 differs from the AFC system 500 of the comparative example in that the AFC system 100 includes a plurality of relay devices each of which has a plurality of wireless devices under its control.

[0025] The AFC system 100 includes a control device 2. The control device 2 is connected to relay devices 6a and 6b via a public network 15. The relay device 6a is connected to wireless devices 4a and 4b. The relay device 6b is connected to wireless devices 4c and 4d. The AFC system 100 also includes interfered devices 8a and 8b.

[0026] The wireless devices 4b and 4c are located close to each other, and there is a high possibility of mutual interference. The relay devices 6a and 6b are connected wirelessly or by wire, and are capable of transmitting and receiving information.

[0027] In this embodiment, the relay device 6a and the relay device 6b each notify the wireless devices under their control of the response message they have sent. Then, the relay device 6a and the relay device 6b refer to the notified message in addition to the message from the wireless device that previously inquired or responded, and avoid frequency overlap or reduce transmission power when the same frequency is used. This reduces interference between wireless devices, thereby improving throughput and reducing the amount of interference to the interfered device.

[0028] 3 is a diagram illustrating an inquiry and a response performed by the AFC system according to the first embodiment of the present disclosure. First, in acquisition 11, relay device 6a acquires in advance from relay device 6b the location information of the wireless devices under relay device 6b. This acquisition 11 reveals that wireless device 4c under relay device 6b is located close to wireless device 4b. In other words, relay device 6a can recognize wireless device 4b as a target for checking mutual interference.

[0029] Next, the wireless device 4b transmits an inquiry 12a directed to the control device 2 to the relay device 6a. Examples of information contained in the inquiry 12a include the location information of the wireless device, the desired frequency, and the transmission power of each frequency. In this example, f1, f2, and f3 are being inquired about as the desired frequencies. The relay device 6a relays the inquiry 12a and transmits an inquiry 12b with the same content to the control device 2.

[0030] The control device 2 receives the inquiry 12b. Then, based on the inquiry 12b, the control device 2 derives the frequency and transmission power that can be used by the wireless device 4b. Then, the control device 2 transmits the derived information to the relay device 6 as a response 14. Examples of information contained in the response 14 include the available frequency and power. In this example, the available frequency and power are power 2-2 for frequency f2 and power 2-3 for frequency f3.

[0031] When the relay device 6a receives the response 14, it restricts its content. In doing so, it references messages from other wireless devices that have responded earlier and may interfere with each other, avoids overlapping frequencies, and reduces transmission power if the same frequency is used. Then, it transmits a response 16 modified based on the restrictions to the wireless device 4b. The wireless device 4b then performs wireless communication based on the response 16.

[0032] For example, suppose that the response previously sent by relay device 6a to wireless device 4a includes frequency f3 as a usable frequency. In this case, relay device 6a restricts the content of the subsequently received response 14 from overlapping with the previously received response. That is, relay device 6a revokes permission to use frequency f3, restricting the content of response 14 so that only frequency f2 is usable. Then, relay device 6a transmits a response 16 modified based on the restriction to wireless device 4b. As a result, wireless device 4b can use only frequency f2.

[0033] Furthermore, relay device 6a notifies relay device 6b of the location information of wireless device 4b and response 16 as information 18. From this location information, relay device 6b knows that wireless device 4b, which is under the control of relay device 6a, is located close to wireless device 4c. In other words, relay device 6b can recognize wireless device 4c as a target for checking mutual interference.

[0034] Next, the wireless device 4c transmits an inquiry 20a directed to the control device 2 to the relay device 6b. Examples of information contained in the inquiry 20a include the location information of the wireless device, the desired frequency, and the transmission power of each frequency. In this example, f1, f2, and f3 are being inquired as the desired frequencies. The relay device 6b relays the inquiry 20a and transmits an inquiry 20b with the same content to the control device 2.

[0035] The control device 2 receives the inquiry 20b. Then, based on the inquiry 20b, the control device 2 derives the frequency and transmission power that can be used by the wireless device 4c. Then, the control device 2 transmits the derived information to the relay device 6b as a response 22. Examples of information contained in the response 22 include the available frequency and power. In this example, the available frequency and power are power 3-2 for frequency f2 and power 3-3 for frequency f3.

[0036] When relay device 6b receives response 22, it restricts its content. In doing so, it references messages from other wireless devices that have responded earlier and may interfere with each other, to avoid overlapping frequencies or reduce transmission power if the same frequency is used. The referenced response message reflects a response message notified by another relay device, such as response 16 included in information 18. Then, it transmits a response 24 modified based on the restrictions to wireless device 4c. Wireless device 4c then performs wireless communication based on response 24.

[0037] In this example, the response 16 included in the information 18 notified by the relay device 6a includes f2 as an available frequency. In this case, the relay device 6b restricts the content of the subsequently received response 22 from overlapping with the previously received first-received response. That is, the relay device 6b revokes permission to use the overlapping frequency f2 and restricts the content of the response 22 so that only frequency f3 is available. The relay device 6b then transmits a response 24 modified based on the restriction to the wireless device 4c. As a result, only frequency f3 becomes available to the wireless device 4c.

[0038] As described above, in this embodiment, when a relay device restricts the content of a response from a control device to a wireless device, the relay device refers to a previously received response that includes the content of responses notified from other relay devices. By performing such processing in the AFC system, it is possible to reduce the amount of interference to an interfered device and to avoid mutual interference between wireless devices under the control of different relay devices.

[0039] [Hardware Configuration of Relay Device According to First Embodiment] Fig. 4 is a diagram showing the hardware configuration of a relay device according to the first embodiment of the present disclosure. The relay device 6a includes a CPU 118. The CPU 118 is connected to a bus line 120. Memory devices such as a ROM 122, a RAM 124, and a storage 126 are connected to the bus line 120. A communication program executed by the CPU 118 is stored in the memory device. The relay device 6a can realize functions specific to this embodiment by the CPU 118 executing the communication program.

[0040] A communication interface 128 is also connected to the bus line 120. The relay device 6a communicates with the network via the communication interface 128. An operation unit 130 and a display unit 132 are also connected to the bus line 120. The operation unit 130 and the display unit 132 function as a user interface for operating the relay device 6a.

[0041] As described above, the relay device 6a can realize the functions specific to this embodiment by the CPU 118 executing the communication program. That is, the relay device 6a can also be realized by a computer and the program. The program can also be recorded on a recording medium or provided over a network.

[0042] 5 is a diagram showing an inquiry and a response performed by an AFC system according to a second embodiment of the present disclosure. The configuration of the AFC system according to the second embodiment is the same as that of the first embodiment. However, the second embodiment differs from the first embodiment in the timing at which a relay device notifies another relay device of a response message.

[0043] In the first embodiment, a relay device notifies another relay device of a response message every time a response is made to a wireless device under its control. However, if the content of the notified response message remains unchanged, the response message is not necessary for controlling wireless communication, which may result in a waste of wireless resources.

[0044] Therefore, in this embodiment, the timing at which a relay device notifies another relay device of a response message is limited to two cases. The first case is when the content of the response to be notified changes. That is, when a change in the wireless resource to be used causes a change in the content of the response message to be notified to another relay device that may interfere with the relevant wireless device. Figure 5 shows the inquiry and response performed by the AFC system in this first case.

[0045] The second case is when a notification is received from another relay device. For example, consider the case where relay device 6a receives a response message from relay device 6b in AFC system 100. Suppose relay device 6b receives an inquiry from a wireless device newly installed under its control and transmits it to control device 2. In this case, relay device 6b restricts the response received from control device 2 and transmits it as a response to the newly installed wireless device under its control, while simultaneously notifying relay device 6a of a response message with the same content. This response message includes location information of the wireless device newly installed under relay device 6b.

[0046] The relay device 6a that has received the response message including the location information determines whether the wireless device having the notified location information is located in close proximity to a wireless device under its control. If it determines that the wireless device is located in close proximity, it notifies the relay device that sent the notification of a response message to the wireless device that may interfere with the wireless device. The relay device that sent the notification can refer to the notified message when restricting the content of the response to a wireless device that newly joins its control next time.

[0047] The contents of Fig. 5 will now be described. First, in acquisition 11, relay device 6a acquires in advance from relay device 6b the location information of the wireless devices under relay device 6b. This acquisition 11 reveals that wireless device 4c under relay device 6b is located close to wireless device 4b. In other words, relay device 6a can recognize wireless device 4b as a target for checking mutual interference.

[0048] Next, the relay device 6a performs processing for the wireless device 4a. First, the wireless device 4a transmits a query 26a directed to the control device 2 to the relay device 6a. Examples of information contained in the query 26a include the location information of the wireless device, the desired frequencies, and the transmission power of each frequency. In this example, f1, f2, and f3 are being queried as the desired frequencies. The relay device 6a relays the query 26a and transmits a query 26b with the same content to the control device 2.

[0049] The control device 2 receives the inquiry 26b. Then, based on the inquiry 26b, the control device 2 derives the frequencies and transmission powers that can be used by the wireless device 4b. The control device 2 then transmits the derived information to the relay device 6 as a response 28. Examples of information contained in the response 28 include the available frequencies and powers. In this example, the available frequencies and powers are power 1-2 for frequency f2 and power 1-3 for frequency f3.

[0050] When the relay device 6a receives the response 28, it restricts its content. In doing so, it refers to messages from other wireless devices that have responded earlier and may interfere with each other, to avoid overlapping frequencies, or to reduce transmission power if the same frequency is used. In this case, since it is determined that there is no need to restrict the content of the response 28, it transmits a response 30, which has the same content as the response 28, to the wireless device 4a. The wireless device 4a performs wireless communication based on the response 30.

[0051] Here, it is known that wireless device 4a is not a wireless device that may interfere with wireless devices under the control of relay device 6b, based on the location information previously acquired in acquisition 11. Therefore, relay device 6a completes the process for wireless device 4a without notifying relay device 6b of response 30.

[0052] Next, the relay device 6a performs processing for the wireless device 4b. The inquiry 12a, inquiry 12b, response 14, and response 16 included in the processing for the wireless device 4b are as described above, and therefore will not be described here.

[0053] Here, it is known from the location information previously acquired in acquisition 11 that wireless device 4b may be subject to mutual interference with wireless device 4c under the control of relay device 6b. Therefore, relay device 6a determines whether the content of response 16 is the same as the previous response 16. If it determines that the content is the same, it does not notify relay device 6b and completes the processing for wireless device 4b. If it determines that the content is not the same, relay device 6a notifies relay device 6b of the location information of wireless device 4b and response 16 as information 18.

[0054] 6 is a flowchart illustrating a notification process from a relay device to another relay device according to the second embodiment of the present disclosure. Here, the process is illustrated in a first case of timing when a relay device notifies another relay device of a response message.

[0055] First, in step 100, the initial state is set as a steady state. Next, in step 102, it is confirmed whether there has been a response from the control device 2. For example, it is confirmed whether the relay device 6a has received a response 14. If there has been a response, the process proceeds to step 104. If there has not been a response, the process returns to step 100, and the current state is set as a new steady state.

[0056] Next, in step 104, it is confirmed whether there has been a resource change. That is, it is determined whether the content of the response to be transmitted to the wireless device based on the received response is the same as the content of the previously transmitted response. For example, it is determined whether the content of the response 16 that relay device 6a transmits to wireless device 4b based on response 14 is the same as the content of the previously transmitted response 16. If it is determined that there has been a change, it proceeds to step 106. If it is determined that there has not been a change, it returns to step 100 and sets the current state as the new steady state.

[0057] Next, in step 106, it is confirmed whether there is any wireless device under the control of another relay device that may cause interference with the wireless device in question. For example, relay device 6a confirms whether there is any wireless device under the control of relay device 6b that may cause interference with the wireless device in question 4b. If there is, the process proceeds to step 108. If there is not, the process returns to step 100, and the current state is set as the new steady state.

[0058] Next, in step 108, a response message is sent. For example, the relay device 6a sends the response 16 together with the location information of the wireless device 4b to the relay device 6b. Then, the process returns to step 100, and the current state is set as a new steady state.

[0059] As described above, in this embodiment, a relay device sends a response message to another relay device only when necessary, thereby preventing wireless resources from being wasted.

[0060] 7 is a diagram showing inquiries and responses performed by an AFC system according to a third embodiment of the present disclosure. The configuration of the AFC system according to the third embodiment is the same as that of the first and second embodiments. However, the third embodiment differs from the second embodiment in that the frequency of notifying a response message from a relay device to another relay device is uniformly reduced.

[0061] First, relay device 6a acquires in advance from relay device 6b the location information of the wireless devices subordinate to relay device 6b in acquisition 11. Next, relay device 6a performs processing for wireless device 4a. The inquiry 26a, inquiry 26b, response 28, and response 30 included in the processing for wireless device 4a are as described above, and therefore will not be described here.

[0062] Next, the relay device 6a performs processing for the wireless device 4b. The inquiry 12a, inquiry 12b, response 14, and response 16 included in the processing for the wireless device 4b are as described above, and therefore will not be described here.

[0063] Here, it is known from the location information previously acquired in acquisition 11 that wireless device 4b may be subject to mutual interference with wireless device 4c under the control of relay device 6b. Therefore, relay device 6a, like in embodiment 2, performs the process shown in FIG. 6 to determine whether to notify relay device 6b of the location information of wireless device 4b and response 16 as information 18a. However, in this embodiment, the frequency of actual notification processing is reduced. FIG. 7 shows an example in which information 18a is notified after the process for wireless devices 4a and 4b is performed twice each.

[0064] One possible method for reducing the frequency is to notify all at once when a predetermined number of notifications have accumulated. This is effective when there are multiple wireless devices that may interfere with each other, and notifying every time there is a resource change would put a strain on the wireless resources. Alternatively, one possible method is to notify the latest notification when a predetermined number of notifications have accumulated. This is effective when there is little need to avoid mutual interference, that is, when there is little need to change the allowable resources every time there is a resource change, and when it is desired to further increase the margin of wireless resources.

[0065] As described above, in this embodiment, the frequency at which a relay device notifies other relay devices of a response message is uniformly reduced, which makes it possible to avoid wasting wireless resources and further increase the margin of wireless resources.

[0066] 2 Control device 4, 4a, 4b, 4c, 4d, 4e Wireless device 6, 6a, 6b Relay device 10a, 10b, 10c, 10d, 10e Interference 11 Acquisition 12, 12a, 12b Inquiry 14 Response 16 Response 18, 18a Information 20a, 20b Inquiry 22 Response 24 Response 26a, 26b Inquiry 28 Response 30 Response

Claims

1. A wireless communication system comprising a plurality of wireless devices, a plurality of relay devices having the plurality of wireless devices under its control, and a control device that controls the plurality of wireless devices via the plurality of relay devices, wherein the relay devices are configured to perform the following operations: a process of acquiring location information of the plurality of wireless devices under its control from the other relay devices; a process of transmitting to the control device a query including a desired frequency received from each of the plurality of wireless devices under its control, which is a target wireless device that is one of the plurality of wireless devices under its control; a process of receiving a response including a usable frequency for the target wireless device received from the control device; a process of restricting the response to the target wireless device based on a first received response that was received earlier for the other wireless device; a process of transmitting a modified response based on the restriction to the target wireless device; a process of determining whether or not there is an interfering wireless device that may cause mutual interference with the target wireless device among the plurality of wireless devices under the control of the other relay devices based on the location information; The wireless communication system is configured to perform a process for performing wireless communication based on the correction response received from the relay device.

2. The wireless communication system according to claim 1, wherein the notification process is performed only when there is a change in the content of the response to be notified.

3. The wireless communication system according to claim 1, wherein the notification process is also performed when a notification is received from another relay device.

4. The wireless communication system according to claim 1, wherein the notification process is a process that is carried out collectively when a predetermined number of the notifications have been accumulated.

5. The wireless communication system according to claim 4, wherein the notification process is a process of notifying the latest notification.

6. A wireless communication method implemented by a wireless communication system including a plurality of wireless devices, a plurality of relay devices having the plurality of wireless devices under its control, and a control device that controls the plurality of wireless devices via the plurality of relay devices, comprising: a relay device: acquiring location information of the plurality of wireless devices under its control from the other relay devices; transmitting to the control device a query including a desired frequency received from each of the plurality of wireless devices under its control, which is a target wireless device that is one of the plurality of wireless devices under its control; receiving a response including a usable frequency for the target wireless device received from the control device; restricting the response to the target wireless device based on a first reception response that was received earlier for the other wireless device; transmitting a modified response based on the restriction to the target wireless device; determining whether or not there is an interfering wireless device that may cause mutual interference with the target wireless device among the plurality of wireless devices under the control of the other relay devices based on the location information; if there is an interfering wireless device, notifying the relay device having the interfering wireless device under its control of the modified response; and reflecting the modified response received from the other relay devices in the first reception response; and the target wireless device performing wireless communication based on the modified response received from the relay device. A wireless communication method.

7. A relay device having multiple wireless devices under its control and connected via a control device that controls the multiple wireless devices, the relay device being configured to perform the following operations: acquiring location information of the multiple wireless devices under its control from other relay devices; transmitting to said control device an inquiry including a desired frequency received from a target wireless device that is one of the multiple wireless devices under its control; receiving a response including a usable frequency for the target wireless device received from the control device; restricting the response to the target wireless device based on a first received response targeted at the other wireless device that was received earlier; transmitting a modified response based on the restriction to the target wireless device; determining based on the location information whether there is an interfering wireless device that may cause mutual interference with the target wireless device among the multiple wireless devices under the control of the other relay devices; 8. A wireless communication program to be executed by a relay device via a control device that has multiple wireless devices under its control and controls the multiple wireless devices, the wireless communication program including a program for causing a computer to execute the following processes: acquiring location information of the multiple wireless devices under its control from other relay devices; transmitting to said control devices inquiries including a desired frequency received from a target wireless device that is one of the multiple wireless devices under its control; receiving a response including a usable frequency for the target wireless device received from the control device; restricting the response to the target wireless device based on a first received response targeted at the other wireless device that was received earlier; transmitting a modified response based on the restriction to the target wireless device; determining based on the location information whether there is an interfering wireless device that may cause mutual interference with the target wireless device among the multiple wireless devices under the control of the other relay devices;