Communication apparatus, control method, computer-readable storage medium, and program product

Abstract

The invention provides a communication apparatus, a control method, a computer readable storage medium, and a program product. A communication device that performs wireless communication notifies other communication devices of information of a frequency channel used in a third network in which the communication device is capable of communicating in parallel with a first network, as information of a frequency channel in which roaming cannot be performed, as information of a frequency channel in which roaming cannot be performed. The other communication device has a function of issuing an instruction to roam from a first network to a second network in a case where the communication device is connected to the first network, and issuing a function to roam from the first network to the second network in a case where a roaming instruction based on the notification is received from the other communication device after the communication device is connected to the first network. Roaming is performed based on the instruction.

Description

Technical Field

[0001] The present invention generally relates to a communication device, a control method, a computer-readable storage medium, and a program product, and particularly to a control technology for suppressing the generation of interference in a wireless communication system. Background Art

[0002] Wireless local area networks (LANs) have been widely used. In a wireless LAN, a communication device operates as an access point (AP) or a station (STA), and the STA joins a network formed by the AP to communicate. Technical standards for various communication controls for wireless LANs are being developed by the Wi-Fi Alliance, which has popularized the use of wireless LANs. As one of the technical standards, Wi-FiAgile Standard. According to this standard, the AP can collect information about surrounding networks from STAs connected to the AP, and based on this information, prompt the connected STA to transfer to another network. By transferring the connected STA to another network through the AP, the load of the network can be dispersed to effectively use network resources.

[0003] A communication device in a wireless LAN can operate as a STA in parallel with operating as an AP (see Japanese Patent Laid-Open No. 2018-019366). When a communication device as an STA changes the connection destination network according to a network transfer instruction from the connected AP, it may unintentionally reduce communication performance depending on the relationship with the network formed by the communication device as an AP. For example, when the transfer destination network of the communication device as an STA uses the same frequency as the frequency of the network formed by the communication device as an AP, the communications performed separately in these networks may interfere with each other. This is not limited to wireless LANs, and in wireless communication devices that communicate in multiple networks, interference between networks may occur due to transfer from one network to another. Summary of the invention

[0004] The present invention provides a technology for suppressing interference between networks caused by switching from one network to another in a communication device that communicates in multiple networks.

[0005] According to one aspect of the present invention, there is provided a communication device, comprising: a communication unit for performing wireless communication; a notification unit for notifying other communication devices of information of frequency channels used in a third network as information of frequency channels that cannot roam, wherein the communication device can communicate in parallel with a first network in the third network, wherein the other communication devices have the following functions: when the communication device is connected to the first network, issuing an instruction to roam from the first network to a second network; and an execution unit for executing roaming based on the instruction received from the other communication devices based on the notification after connecting to the first network.

[0006] According to another aspect of the present invention, there is provided a control method performed by a communication device performing wireless communication, the method comprising: notifying other communication devices of information of a frequency channel used in a third network as information of a frequency channel that cannot roam, wherein the communication device is able to communicate in parallel with a first network in the third network, wherein the other communication device has the following functions: when the communication device is connected to the first network, issuing an instruction to roam from the first network to a second network; and when receiving a roaming instruction based on the notification from the other communication device after connecting to the first network, performing roaming based on the instruction.

[0007] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a diagram showing an example of a configuration of a communication system;

[0009] Figure 2 is a block diagram showing an example of the configuration of a printer;

[0010] Figure 3 is a diagram showing an example of a sequence of processes performed in a communication system;

[0011] Figure 4 is a flowchart showing an example of a sequence of processing performed by a printer;

[0012] Figure 5 is a flowchart showing an example of a sequence of processing performed by a printer;

[0013] Figure 6 is a diagram showing another example of the sequence of processing performed in the communication system;

[0014] Figure 7 is a diagram showing still another example of the sequence of processing performed in the communication system;

[0015] Figure 8 is a flowchart showing an example of a sequence of processes executed by the printer 101; and

[0016] Fig. 9 : is a flowchart showing an example of the sequence of processing executed by the printer 101 . DETAILED DESCRIPTION

[0017] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Please note that the following embodiments are not intended to limit the scope of the claimed invention. A plurality of features are described in the embodiments, but are not limited to the invention requiring all of these features, and a plurality of such features may be appropriately combined. In addition, in the accompanying drawings, the same reference numerals are assigned to the same or similar configurations, and redundant descriptions thereof are omitted.

[0018] (System Configuration)

[0019] Figure 1 An example of a configuration of a wireless communication system according to the embodiment is shown. Figure 1 The wireless communication system in is a system composed of a wireless local area network (LAN) that conforms to the IEEE 802.11 series of standards. For example, a wireless communication system is composed of a wireless LAN that conforms to at least any one of the IEEE 802.11a / b / g / n / ac / ax / be standards. Please note that IEEE stands for the Institute of Electrical and Electronics Engineers. Although the focus is on wireless LANs in the following description, similar discussions can be applied to another wireless network. For example, an access point (AP) can also be rewritten as a base station, a station (STA) can be rewritten as a terminal, and the following discussion can be applied to a system using an arbitrary wireless network.

[0020] The wireless communication system includes a plurality of communication devices. Each communication device has the function of at least one of an access point (AP) and a STA, the access point (AP) has the function of forming a network, and the STA joins the network formed by the AP. In the present embodiment, the printer 101 can be used as both an AP and a STA, forming a network 111 of a wireless LAN, and joining any one of the networks formed by the APs 102 to 104. Note that the operation mode of the printer 101 as an AP is referred to as an AP mode, and the operation mode of the printer 101 as a STA is referred to as a STA mode. Each of the APs 102 to 104 forms a network of a wireless LAN. Figure 1An example is shown in which AP 102 forms a network 112, AP 103 forms a network 113, and AP 104 forms a network 114. In the following description, the network of the wireless LAN formed is sometimes referred to as a basic service set (BSS). In this embodiment, the printer 101 joins, for example, the network 112 as an STA. In addition, for example, the STA 105 joins the network 111 formed by the printer 101.

[0021] Here, the network is configured so that APs 102 to 104 can communicate with each other via a backbone network (not shown), and a STA connected to any one of the APs can roam between the APs. For example, the backbone network can be configured as a wired network such as a wired LAN or a wireless network such as a wireless LAN.

[0022] Note that in addition to the IEEE 802.11 series of standards, each communication device may also conform to standards such as Another communication standard of NFC, UWB, ZigBee or MBOA. Please note that UWB stands for Ultra Wideband, MBOA stands for Multi-Band OFDM Alliance, and NFC stands for Near Field Communication. OFDM stands for Orthogonal Frequency Division Multiplexing. UWB includes Wireless USB, Wireless 1394, WiNET, etc. In addition to the IEEE 802.11 series of standards, the communication device may also comply with standards such as the Wi-Fi Direct standard developed by the Wi-Fi Alliance. In addition, the communication device may comply with communication standards for wired communications such as wired LAN.

[0023] In the present embodiment, when the printer 101 operates in both STA mode and AP mode, it can use different frequency bands between the modes. For example, when the printer 101 joins a network formed using the 2.4GHz frequency band in the STA mode, the printer 101 can form a 5GHz frequency band network in the AP mode. The printer 101 can use different frequency channels of the same frequency band in the STA mode and the AP mode. For example, while the printer 101 joins a network formed using a channel of W53 belonging to the 5GHz frequency band in the STA mode, the printer 101 can form a network using a channel of W52 belonging to the same 5GHz frequency band. That is, the printer 101 can use such frequency channels to prevent mutual interference between communications in the STA mode and the AP mode or to sufficiently reduce interference. Since the interference between adjacent channels in the 5GHz frequency band is less than the interference between adjacent channels in the 2.4GHz frequency band, the printer 101 can use adjacent channels in the 5GHz frequency band. In addition to 2.4GHz and 5GHz, the printer 101 can also operate at 6GHz.

[0024] In the present embodiment, 1ch in the 2.4 GHz band is used in the network 112, and 6ch in the 2.4 GHz band is used in the networks 111 and 113. Note that "ch" means "channel". In the network 114, 11ch is used. The networks 112 to 114 are wireless networks capable of roaming, which are respectively set to have, for example, the same service set identifier (SSID), the same pass phrase, etc. required for encryption and decryption of communications. Note that this is merely an example, and any setting may be made so that roaming can be performed between the network 112 to the network 114.

[0025] According to the present embodiment, in order to effectively use the network, the communication device can exchange network information to perform dynamic monitoring of the network, balance adjustment of the network load based on the information, etc. In the present embodiment, the printer 101, AP 102 to AP 104, and STA 105 comply with the Wi-Fi Agile multi-band standard developed by the Wi-Fi Alliance. According to the Wi-Fi Agile multi-band standard, the AP can collect information about the surrounding network from the STA connected to the AP, and based on the information, prompt the connected STA to transfer to another network. For example, the AP 102 can collect information about the network existing around the AP 102 from the printer 101 connected to the AP 102, and send an instruction to the printer 101 to transfer to a network formed by another AP. The AP can decide the transfer of the connected STA to another network based on the usage status (load status) of the resources in the surrounding network and the network formed by the AP. Please note that this is just an example, and the AP can decide to transfer the STA to another network based on another policy.

[0026] Here, a process performed when an AP instructs a STA to transfer to another network according to the Wi-Fi Agile Multi-Band standard, that is, when the AP instructs the STA to roam will be roughly described.

[0027] When the connection partner device complies with (supports) the Wi-Fi Agile multi-band standard, the AP and STA can perform this function. Based on whether the radio frame sent from the AP includes MBO capability indication information, the STA can determine whether the AP complies with the Wi-Fi Agile multi-band standard. For example, when the radio frame sent from the AP includes MBO capability indication information, the STA can determine that the AP complies with the Wi-Fi Agile multi-band standard. Note that MBO stands for multi-band operation. Alternatively, based on other information such as whether the BTM capability bit is set in the radio frame sent from the AP, the STA can determine whether the AP complies with the Wi-Fi Agile multi-band standard. For example, when the BTM capability bit is set in the radio frame sent from the AP, the STA can determine that the AP complies with the Wi-Fi Agile multi-band standard. Note that BTM stands for BSS transition management. The radio frame sent from the AP can be a beacon, a probe response, or an association response. These are just examples, and it can be determined based on another radio frame whether the AP complies with the Wi-Fi Agile multi-band standard.

[0028] In addition, based on whether the BTM capability bit is set in the radio frame sent from the STA, the AP can determine whether the STA complies with the Wi-Fi Agile multi-band standard. For example, when the BTM capability bit is set in the radio frame sent from the STA, the AP can determine that the STA complies with the Wi-Fi Agile multi-band standard. The radio frame can be, for example, a probe request or an association request. Note that these are just examples, and whether the STA complies with the Wi-Fi Agile multi-band standard can be determined based on another radio frame.

[0029] In the following description, both the AP and the STA comply with the Wi-Fi Agile multi-band standard.

[0030] The AP sends a beacon request frame to the connected STA. The beacon request frame is a frame that instructs the STA to collect beacon information of surrounding APs. When the STA receives the beacon request frame, it observes the beacons sent from the surrounding APs based on the information in the frame and collects the beacon information. The STA generates a beacon report frame including the collected information and sends the frame to the AP. Based on the load status of the network formed by the AP and the information such as beacon reports received from the STA, the AP can decide whether to roam the STA to another network. When the AP decides to roam the STA to another network, it instructs the STA to roam by using, for example, a BTM request frame. The BTM request frame may include a roaming destination BSS candidate list, a time until a disconnection frame is sent, a time until roaming can start, priority information of the BSS candidate list, etc. When the STA receives the BTM request frame, it decides whether to perform roaming based on the information included in the frame. The STA generates a BTM response frame based on the decision and sends the frame to the AP. The BTM response frame may include information on whether to accept roaming, and when roaming is performed, identification information (BSSID) of the roaming destination network.

[0031] In the above manner, the AP and STA can perform roaming in accordance with the Wi-Fi Agile multi-band standard. When roaming, the roaming method in accordance with the Wi-Fi Agile multi-band standard can be directly used, or only some functions of the standard can be used. Another standard different from the Wi-Fi Agile multi-band standard and implementing similar functions can be used.

[0032] In the present embodiment, the printer 101, which is a communication device operable as both an AP and a STA, changes the connection destination network in the STA mode according to the Wi-FiAgile multi-band standard. In this case, the frequency channel used in the AP mode and the frequency channel used in the connection destination network after the change in the STA mode may strongly interfere with each other. More specifically, it is assumed that the printer 101 uses 6ch in the AP mode and is connected to the network 112 using 1ch in the STA mode. In this case, when the AP 102 instructs the printer 101 to roam to the network 113 and the printer 101 roams according to the instruction, 6ch is used in both the AP mode and the STA mode. In this case, the communication in the AP mode and the communication in the STA mode may interfere with each other. In view of this situation, the present embodiment provides a technology for suppressing the interference between the communication in the AP mode and the communication in the STA mode that is generated by roaming to the extent that it affects the communication.

[0033] (Device Structure)

[0034] Figure 2An example of the hardware configuration of the printer 101 according to the present embodiment is shown. As a hardware configuration, the printer 101 includes, for example, a printing unit 201, an image processing unit 202, an operation unit 203, a display unit 204, a communication unit 205, an antenna 206, a storage unit 209, a control unit 210, and a power supply unit 211. The printing unit 201 performs a printing process. The printing unit 201 includes, for example, a sheet conveying mechanism and a printing processing mechanism. The image processing unit 202 performs image processing on an image to be printed before the printing unit 201 performs a printing process. The image processing unit 202 includes, for example, image processing hardware and a memory for converting an input image to be printed into data suitable for printing by the printing unit 201. The operation unit 203 accepts various inputs and the like used by the user to operate the printer 101. The operation unit 203 includes, for example, buttons and keys for accepting various operations. The operation unit 203 may include hardware for accepting inputs other than inputs from buttons and keys (such as audio input). The display unit 204 includes: a display and a light emitting diode that output information in a visually recognizable form, a speaker that outputs information by voice, etc. In the example, the display unit 204 outputs information in a form that is at least visually or auditorily recognizable. Note that this is only an example, and information can be displayed by vibration, etc. When the display unit 204 displays visual information, it has a video random access memory (VRAM) that holds the picture data corresponding to the visual information to be displayed. In the example, the display unit 204 performs display control to continue to display the picture data stored in the VRAM. For example, a touch panel display obtained by integrating the display unit 204 and the operating unit 203 can be used.

[0035] The communication unit 205 includes: a radio frequency (RF) circuit and a baseband circuit (wireless LAN chip) for wireless LAN, which provides a communication interface through the wireless LAN. The communication unit 205 is configured so that it can perform wireless LAN communication that complies with the IEEE802.11 series standards via the antenna 206. The antenna 206 uses the 2.4 GHz band / 5 GHz band for wireless LAN communication as an operating band. In addition, the antenna 206 can use the 6 GHz band as an operating band. Note that the communication unit 205 includes a STA function unit 207 and an AP function unit 208 so that it can perform operations in the STA mode and operations in the AP mode in parallel. The STA function unit 207 and the AP function unit 208 can be implemented as different radio I / Fs, or can share one radio I / F. For example, when sharing one radio I / F, the STA function unit 207 and the AP function unit 208 can be controlled by time division not to operate simultaneously. Alternatively, for example, one radio I / F may be shared by operating the STA function unit 207 and the AP function unit 208 in different frequency bands.

[0036] The storage unit 209 stores various information such as a control program to be executed by the control unit 210 and information about communication. The storage unit 209 includes, for example, one or more storage media such as a hard disk drive (HDD), a flash memory, a removable SD card, and at least one or more memories such as a ROM and a RAM. Note that ROM stands for read-only memory and RAM stands for random access memory. The control unit 210 controls the entire printer 101 by executing the control program stored in the storage unit 209. The control unit 210 includes at least one or more processors such as a central processing unit (CPU) and a microprocessing unit (MPU). Note that the control unit 210 can control the entire printer 101 in cooperation with an operating system (OS). The control unit 210 can control the entire printer 101 using information input via the operation unit 203. Information input via the operation unit 203 and to be stored in the printer 101 is stored in the storage unit 209. Various operations to be described later are realized by executing the control program stored in the storage unit 209 by the control unit 210. The power supply unit 211 supplies power to each hardware unit. The power supply unit 211 may obtain power from an AC power source such as a commercial power source or a DC power source such as a battery.

[0037] (Processing order)

[0038] An embodiment will be described regarding a process of suppressing the generation of interference between communication in the AP mode and communication in the STA mode accompanying roaming to such an extent that the communication is affected in the printer 101 .

[0039] [First embodiment]

[0040] When the STA is connected to the AP, it can send an association request frame including information about channels that the STA cannot roam to the AP. For example, the STA can send an association request frame to the AP, in which the channels that the STA cannot roam are set in the non-preferred channel report attribute. The STA can even make a similar notification in the reassociation request frame. In addition, even when the STA is connected to the AP, the STA can notify the AP of information about channels that cannot roam. For example, the STA can send a WNM-notification request frame to the AP, in which the information about channels that the STA cannot roam is set in the non-preferred channel report field. Please note that WNM stands for Wireless Network Management. When the AP receives information about channels that cannot roam from the STA, it can prevent the BSS using the channels that cannot roam from being included in the roaming target BSS candidate list. That is, based on the channel information from the STA, the AP notifies the STA of a roaming target BSS candidate list, which includes BSSs using channels that the STA can roam. In the present embodiment, the printer 101 notifies the AP 102 of information on channels that cannot be roamed, and thus the printer 101 is not notified of roaming destination candidates that may cause interference to affect communication.

[0041] Figure 3 An example of the sequence of processes performed in the system according to this embodiment is shown. Figure 3 Shown in Figure 1 An example of a sequence of processing when the printer 101 performs roaming to the AP 104 according to an instruction from the AP 102 in the system.

[0042] exist Figure 3In the process, first, the printer 101 accepts, for example, an AP mode start instruction operation from a user, and activates the AP mode (F301). Then, the printer 101 forms a network 111. It is assumed that 6ch of the 2.4GHz band is used in the network 111. After that, the STA 105 accepts, for example, an instruction to connect to the printer 101 from the user, and the printer 101 performs a process of connecting to the network 111 formed in the AP mode (F302). When the connection process is completed, data communication can be performed between the printer 101 and the STA 105 (F303). Here, the printer 101 accepts an infrastructure connection (hereinafter also referred to as "Infra connection") instruction. In this case, the printer 101 performs a process of connecting to the surrounding APs using the function of the STA mode. The printer 101 establishes a connection with the AP 102 that forms the network 112. It is assumed that 1ch of the 2.4GHz band is used in the network 112. In the STA mode, the printer 101 receives a beacon frame from the surrounding APs. Here, the printer 101 receives a beacon frame sent from the AP 102 (F304). The printer 101 checks the MBO capability indication information included in the received beacon frame. Thus, the printer 101 can identify whether the AP 102 is an AP compliant with the Wi-Fi Agile multi-band standard. Here, the AP 102 is an AP compliant with the Wi-Fi Agile multi-band standard, and the printer 101 recognizes this.

[0043] Subsequently, the printer 101 performs a determination process when connected to the AP (F305). The details of the determination process will be described later. In the determination process, the printer 101 determines whether to send an association request frame when connected to the AP, the association request frame including information of a channel used in the AP mode as a non-preferred channel. In the present embodiment, the printer 101 determines to send an association request frame including information of the channel used in the AP mode. In this case, the printer 101 sends an association request frame to the AP 102, the association request frame including information indicating 6ch (which is a channel used in the AP mode) as a non-preferred channel (F306). Note that the printer 101 can set the BTM capability bit in the association request frame and send the BTM capability bit. Thereby, the AP 102 can recognize that the printer 101 complies with the Wi-Fi Agile Multi-band standard. Note that the processing required for the authentication process such as the authentication frame is performed before the association request frame, but in Figure 3 Its description is omitted.

[0044] When the AP 102 receives the association request frame in F306, the AP 102 stores the setting information (6ch) as a non-preferred channel of the printer 101. The AP 102 sends an association response frame to the printer 101 (F307). The printer 101, upon receiving the association response frame, performs a key setting process with the AP 102 (F308). The key setting process is a process of setting a cryptographic key or the like used for encryption and decryption in wireless LAN communication between the printer 101 and the AP 102 in STA mode. In the key setting process, for example, a 4-way handshake process or the like is performed. When the key setting process is completed, data communication is performed between the printer 101 and the AP 102 (F309).

[0045] Then, it is assumed that AP 102 detects that network 112 is congested due to an increase in traffic of network 112 formed by AP 102 and an increase in the number of connected STAs. For example, when the amount of allocated resources exceeds a predetermined value or the number of connected STAs exceeds a predetermined value, AP 102 may determine that network 112 is congested. When AP 102 determines that network 112 is congested, it determines whether to transfer the STA connected to AP 102 to another network capable of roaming. In the present embodiment, AP 102 determines to transfer printer 101 to another network. As described above, roaming is possible from network 112 formed by AP 102 to network 113 formed by AP 103 and network 114 formed by AP 104. In addition, as described above, 6ch is used in network 113, and 11ch is used in network 114.

[0046] When AP 102 decides to transfer printer 101 to another network, it selects a roaming destination network for printer 101. AP 102 stores in F306 that the non-preferred channel of printer 101 is 6ch. Therefore, AP 102 excludes network 113 using 6ch from the roaming destination candidates for printer 101. Since network 114 uses 11ch different from 6ch, AP 102 selects network 114 as a roaming destination candidate for printer 101. Then, AP 102 sends a BTM request frame (F310) including information of network 114 as a roaming destination candidate to printer 101. Although only network 113 and network 114 are regarded as roaming destinations from network 112 in the embodiment, there may be other networks capable of roaming. In this case, AP 102 may notify printer 101 of a plurality of networks capable of roaming that do not use 6ch as roaming destination candidates.

[0047] When the printer 101 receives the BTM request frame, it determines whether to perform roaming based on the information included in the frame. For example, the printer 101 can obtain information of the roaming destination candidate network and the frequency channel used in the network from the information included in the BTM request frame, and determine whether roaming can be performed. Here, the printer 101 specifies the network 114 as the roaming destination candidate and the 11ch used in the network 114 from the BTM request frame. The printer 101 can determine that the mutual interference between the frequency channel (6ch) being used in the AP mode and the channel (11ch) used in the network 114 as the roaming destination candidate is small enough not to affect the communication, and roaming can be performed. When roaming can be performed, the printer 101 can always determine to perform roaming, or decide whether to perform roaming based on the radio quality of the signal of the roaming destination candidate network, etc.

[0048] Here, the printer 101 decides to perform roaming to the network 114. In this case, the printer 101 sends a BTM response frame including information indicating that roaming to the network 114 is performed to the AP 102 (F311). The printer 101 cancels the connection with the AP 102 (F312). Thereafter, the printer 101 performs a process of connecting to the AP 104 that provides the network 114 as a roaming destination (F313). This connection process is similar to the processes in F304 to F308 described above. As described with respect to F306, the printer 101 sends an association request frame including a non-preferred channel to the AP 104. The printer 101 connects to the AP 104, and when the roaming is completed, performs data communication with the AP 104 (F314).

[0049] As mentioned above, in Figure 3 In the process of , the printer 101 notifies the connection destination AP of information of the channel used in the AP mode as a non-preferred channel. The roaming instruction from the AP can cause selection of a roaming destination candidate from which a network using the channel used by the printer 101 in the AP mode is excluded. This can prevent strong mutual interference between communication in the STA mode and communication in the AP mode when the printer 101 performs roaming in the STA mode.

[0050] Next, we will refer to Figure 4 An example of the sequence of the determination processing at the time of AP connection in F305 described above is described. The printer 101 can execute the determination processing by, for example, reading out a computer program stored in the storage unit 209 and executing the computer program by the control unit 210. Figure 4 Note that this is just an example, and a dedicated Figure 4 Hardware that processes at least a portion of the process.

[0051] When the determination processing at the time of AP connection starts, the printer 101 determines whether the interference avoidance setting for avoiding interference during roaming is enabled (ON) (step S401). If the interference avoidance setting is enabled ("Yes" in step S401), the printer 101 causes the processing to enter step S402. If the interference avoidance setting is not enabled ("No" in step S401), the printer 101 causes the processing to enter step S409. The interference avoidance setting can be enabled or disabled by a user operation accepted via the operation unit 203. For example, when a predetermined condition is met, the computer program executed by the control unit 210 can control to autonomously enable or disable the interference avoidance setting. For example, the printer 101 can be configured to automatically enable or disable the interference avoidance setting based on the network load (congestion level) in either or both of the STA mode and the AP mode of the printer 101.

[0052] In step S402, the printer 101 obtains the information of the connection destination AP. For example, as described with respect to F304, the printer 101 can receive an incoming beacon frame from the AP and obtain the information of the AP from the frame. In the STA mode of the printer 101, the printer 101 can send a probe request frame, receive a probe response frame as a response, and obtain the information of the AP from the probe response frame. Note that the printer 101 can send a probe request frame including information associated with the Wi-Fi Agile multi-band standard. The printer 101 sends, for example, a probe request frame with the BTM capability bit set. The printer 101 can send a predetermined action frame defined in the IEEE 802.11 series of standards, receive a response frame to the frame, and obtain the information of the AP. Then, the printer 101 determines whether the connection destination AP complies with the Wi-Fi Agile multi-band standard based on the AP information obtained in step S402 (step S403). If the printer 101 determines that the connection destination AP conforms to the Wi-Fi Agile Multi-Band standard (YES in step S403), the printer 101 advances the process to step S404. If the printer 101 determines that the connection destination AP does not conform to the Wi-Fi Agile Multi-Band standard (NO in step S403), the printer 101 advances the process to step S409.

[0053] In step S404, the printer 101 determines whether the AP mode is active. If the AP mode is active (YES in step S404), the printer 101 advances the process to step S405. If the AP mode is not active (NO in step S404), the printer 101 advances the process to step S408.

[0054] In step S405, the printer 101 executes processing to execute the connection state in the AP mode. Figure 5 This process will be described.

[0055] exist Figure 5 In step S501, the printer 101 determines whether the channel being used in the AP mode is congested. For example, if the value of the signal-to-noise ratio (SNR) of the received signal is equal to or greater than a predetermined value, the printer 101 may determine that the channel being used in the AP mode is congested, and if the SNR value is less than the predetermined value, the channel is determined to be not congested. Note that this is merely an example, and the congested state may be determined by another criterion. For example, another criterion may be used such that if the time until the transmission of a predetermined amount of data is completed after the start is equal to or longer than a predetermined duration, the channel is determined to be congested. If the printer 101 determines that the channel being used in the AP mode is congested ("Yes" in step S501), the printer 101 advances the process to step S502. If the printer 101 determines that the channel being used in the AP mode is not congested ("No" in step S501), the printer 101 advances the process to step S504. In step S502, the printer 101 determines whether the STA is connected to the network 111 formed in the AP mode. That is, the printer 101 determines whether there is a communication partner device in AP mode. If the STA is connected to the network 111 ("Yes" in step S502), the printer 101 advances the process to step S503. If no STA is connected to the network 111 ("No" in step S502), the printer 101 advances the process to step S504.

[0056] In step S503, the printer 101 sets the channel being used in the AP mode as a channel that cannot be roamed in the STA mode. That is, the printer 101 sets the channel being used in the AP mode as a non-preferred channel. When the channel being used in the AP mode is congested and the STA is connected, the processing in step S503 is performed. In this case, if the same channel as in the AP mode is used by roaming in the STA mode, the influence of interference is predicted to be large. Therefore, in step S503, the channel being used in the AP mode is set to a non-preferred channel to limit the roaming destination in the STA mode. On the contrary, when the channel being used in the AP mode is not congested or no STA is connected, the processing in step S504 is performed. In this case, even if the same channel as in the AP mode is used by roaming in the STA mode, the influence of interference is predicted to be small. Therefore, the printer 101 can determine in step S504 that it is not necessary to set the channel being used in the AP mode as a channel that cannot be roamed in the STA mode. The printer 101 does not include the channel being used in the AP mode in the non-preferred channels.

[0057] Notice, Figure 5The examples in are only examples and can be replaced by Figure 5 Whether to include the channels being used in AP mode in the non-preferred channels may be determined by a different process from the process in step S501. For example, whether to include the channels being used in AP mode in the non-preferred channels may be determined only based on whether there is a connected STA, without performing the process in step S501. In the example, the process in step S502 may be omitted. Alternatively, when the AP mode is activated, the printer 101 may always include the channels being used in AP mode in the non-preferred channels without performing the determination process.

[0058] Return to reference Figure 4 , after the determination process in step S405, the printer 101 determines whether the channel being used in the AP mode is included in the non-preferred channels based on the determination result in step S405 (step S406). If the channel being used in the AP mode is included in the non-preferred channels ("Yes" in step S406), the printer 101 advances the process to step S407. If the channel being used in the AP mode is not included in the non-preferred channels ("No" in step S406), the printer 101 advances the process to step S409.

[0059] In step S407, the printer 101 sets the channel being used in the AP mode as a non-preferred channel. Sometimes a channel that can be used differently in the AP mode is predetermined in a channel different from the channel being used in the AP mode. In this case, the printer 101 may even set the channel as a non-preferred channel. Then, the printer 101 advances the process to step S409.

[0060] Step S408 is the processing when the printer 101 does not activate the AP mode. In this case, if there is a channel to be used when the AP mode is activated, the printer 101 sets the channel to a non-preferred channel. When there are multiple channels to be used in the AP mode, the printer 101 may set these channels as non-preferred channels. Alternatively, when there are multiple channels to be used in the AP mode, the printer 101 may set not all channels but only some (for example, one) channels as non-preferred channels. When the AP mode is not activated, the printer 101 does not need to do anything. In this case, for example, when the AP mode is activated, the printer 101 may activate the AP mode using a channel different from the channel used in the network connected in the STA mode. After that, the printer 101 advances the processing to step S409.

[0061] In step S409, the printer 101 transmits an association request frame to the AP connected in the STA mode. When non-preferred channel information exists, an association request frame including the non-preferred channel information and information on the Wi-Fi Agile Multi-Band standard is transmitted.

[0062] As described above, according to the present embodiment, the printer 101 can notify the connection destination AP in advance of information indicating the channel being used in the AP mode as information of the channel that should be excluded from the roaming destination candidates. The AP can exclude the network using the notified channel from the roaming destination candidates in the roaming instruction. The printer 101 can receive a roaming instruction to exclude the network using the channel used in the AP mode from the roaming destination candidates. As a result, the printer 101 can prevent the same channel from being used in the STA mode and in the AP mode after roaming in the STA mode. In other words, after roaming in the STA mode, strong mutual interference between the communication in the STA mode and the communication in the AP mode can be prevented.

[0063] In the present embodiment, an example of restrictively performing each determination process on the channel being used in the AP mode has been described. However, the present invention is not limited thereto. For example, each determination process may be performed not only based on the channel being used in the AP mode, but also based on surrounding channels such as channels adjacent to the channel. For example, interference is likely to occur between adjacent channels in the 2.4 GHz band. For all surrounding channels predicted to generate strong mutual interference, these channels may be included in the non-preferred channels to exclude networks using these channels from the roaming target. Note that only the channels used in the AP mode may be notified to the AP 102, and the AP 102 determines to exclude networks using surrounding channels predicted to generate strong mutual interference with the notified channels from the roaming target. When the printer 101 complies with multiple frequency bands such as 2.4 GHz / 5 GHz / 6 GHz, the printer 101 may include in the non-preferred channels: all channels of the frequency band including the channel used in the AP mode. This can suppress the generation of roaming in the STA mode to the frequency band to which the channel being used in the AP mode belongs, and more reliably prevent the generation of interference between the two modes.

[0064] In the above embodiment, the printer 101 determines whether to include information on the channel being used in the AP mode in the association request frame when connected to the AP in the STA mode. However, the present invention is not limited to this. For example, in a state where the printer 101 is connected to the AP, the printer 101 may notify the connection destination AP of non-preferred channel information. For example, after the printer 101 establishes a connection with the AP, it may send a WNM notification request frame including a non-preferred channel to the AP. For example, after the printer 101 activates the AP mode, it may send the WNM notification request frame to the AP. Alternatively, the printer 101 may send the frame to the AP before activating the AP mode. For example, when the printer 101 activates the AP mode after being connected to the AP in the STA mode, or when the AP mode is reactivated using another channel during connection to the AP in the STA mode, the printer 101 may send the frame.

[0065] [Second embodiment]

[0066] In the above-described first embodiment, the printer 101 notifies the AP 102 connected in the STA mode of information indicating the channel used in the AP mode, and the AP 102 excludes a network using the channel from roaming destination candidates. In the second embodiment, a process of preventing mutual interference between communication in the AP mode and communication in the STA mode by roaming in the printer 101 when the printer 101 does not notify the AP 102 of information indicating the channel used in the AP mode will be described.

[0067] Figure 6 An example of the sequence of processing performed in the system according to this embodiment is shown. Figure 6 In, assuming that Figure 1In the system, the printer 101 activates the AP mode and forms the network 111, the STA 105 is connected to the network 111, and data communication is performed between the printer 101 and the STA 105 (F601). When the printer 101 accepts the Infra connection instruction in this state, it searches for surrounding APs for connection in the STA mode. The printer 101 receives a beacon frame from the AP 102 (F602), and performs connection processing with the AP 102 based on the beacon frame (F603). Note that the beacon frame includes the information described in the first embodiment. Note that in the second embodiment, the printer 101 sends an association request frame when connected to the AP, which does not include information on the channel used in the AP mode as a non-preferred channel. In the example, when the interference avoidance setting during roaming as described in step S401 is disabled, the printer 101 sends such an association request frame. However, this is merely an example, and the association request frame that does not include information on the channel used in the AP mode may be sent as a non-preferred channel due to other reasons. Note that the connection processing in F603 is similar to the processing described with reference to F306 to F308 in the first embodiment except that the association request frame does not include information of the channel used in AP mode. The printer 101, after establishing connection with the AP 102, performs data communication with the AP 102 (F604).

[0068] Then, it is assumed that AP 102 detects that network 112 formed by AP 102 is congested, and decides to transfer the connected STA to another network. Note that the detection of congestion can be performed by the method described in the first embodiment. Here, AP 102 decides to transfer printer 101 to another network based on the detection of congestion of network 112. As described above, there are network 113 formed by AP 103 and network 114 formed by AP 104 as roaming destination candidates from network 112. It is assumed that AP 102 selects network 113 formed by AP 103 from these networks. For example, the selection can be made based on information on the congestion levels of network 113 and network 114. For example, when network 114 is congested, AP 102 can exclude network 114 from the roaming destination candidates and select network 113 as the roaming destination candidate. According to the selection, AP 102 sends a BTM request frame (F605) including information on network 113 to printer 101. Note that the BTM request frame may be used to notify the printer 101 of only information capable of specifying a network (such as the BSSID of the network 113), or to notify the printer 101 of the information together with information of channels used in the network. When the AP 102 notifies the printer 101 of only the BSSID of the roaming candidate network, the printer 101 needs to separately specify the channels used in the respective networks. The printer 101 may specify the channels used in the roaming candidate networks by, for example, receiving a beacon frame in each available frequency channel. The printer 101 may separately receive information indicating the channels used in the roaming candidate networks from the AP 102 or the like.

[0069] The printer 101, upon receiving the BTM request frame, performs a roaming instruction reception determination process based on the information included in the frame (F606). In this case, the roaming destination candidate is only the network 113 using the same channel as the channel (6ch) used in the AP mode of the printer 101. In order to perform roaming to the network 113, the printer 101 may decide to change the channel used in the AP mode. Note that the details of the roaming instruction reception determination process will be described later.

[0070] The printer 101 sends a BTM response frame (F607) including information indicating that roaming is performed and information of the network 113 as the roaming destination to the AP 102. Then, the printer 101 performs a process for changing the channel used in the AP mode. In this process, the printer 101 performs a process of changing the channel used and reactivating the AP mode. That is, the printer 101 performs an AP mode reactivation process to use a channel different from the channel used in the roaming destination network in the AP mode. When the STA 105 connected to the network 111 complies with the Wi-Fi Agile multi-band standard, the printer 101 performs roaming of the STA 105 to the network formed in the AP mode after reactivation. For this process, first, the printer 101 sends a BTM request message to the STA 105 (F608). The BTM request message may include information of the AP mode after reactivation, and information until the time when roaming starts. The information until the time when roaming starts can be specified based on, for example, the time required to reactivate the AP mode in the printer 101. STA105, upon receiving the BTM request message from the printer 101, determines whether roaming can be performed, and sends a BTM response message to the printer 101 (F609). It is assumed that STA105 determines that roaming can be performed, and sends a BTM response message including information indicating that roaming is performed to the printer 101. The printer 101 and STA105 perform a disconnection process in which STA105 disconnects from the network 111 (F610). Thereafter, the printer 101 performs an AP mode reactivation process to change the channel used in the AP mode from the currently used channel (F611). It is assumed that the printer 101 changes the used channel from 6ch to 8ch.

[0071] After the AP mode is reactivated, the printer 101 cancels the connection with the AP 102 in the STA mode (F612). Subsequently, the printer 101 performs processing for establishing the connection with the STA 105 again in the AP mode based on the information of the BTM request frame and the BTM response frame transmitted / received in advance (F613). In the AP mode, the printer 101 performs data communication with the STA 105 when the connection processing is completed (F614). In the STA mode, the printer 101 performs connection processing with the AP 103 serving as the roaming destination based on the information of the BTM request frame from the AP 102 (F615). This connection processing is similar to the processing in the above-mentioned F603. In the STA mode, the printer 101 performs data communication with the AP 103 (F616).

[0072] In the above example, only the BSS formed by AP 103 (network 113) is included in the BSS candidate list in the BTM request frame from AP 102 in F605. Network 113 uses 6ch, which is the same channel as that used in the AP mode in the printer 101. Therefore, the printer 101 performs a process of changing the channel used in the AP mode to roam to the network 113 in the STA mode. However, both the BSSs (network 113 and network 114) formed by AP 103 and AP 104, respectively, may be included in the BTM request frame from AP 102. The channel used in the network 114 is different from the channel being used in the AP mode in the printer 101. If the printer 101 decides to roam to the network 114 in the STA mode, it does not need to change the channel used in the AP mode. Figure 7 An example of this processing is shown in FIG. Figure 7 In the drawings, the same reference numerals denote Figure 6 Those processes in are similar to those in , and their description will not be repeated.

[0073] exist Figure 7 In the example of FIG. 1 , it is assumed that AP 102 selects both network 113 formed by AP 103 and network 114 formed by AP 104 as roaming destination candidates. In this case, AP 102 transmits a BTM request frame including information of both network 113 and network 114 to printer 101 according to the selection (F701). When printer 101 receives the BTM request frame, it performs roaming instruction reception determination processing based on the information included in the frame (F702). In this case, the roaming destination candidates include network 114 using a channel different from the channel (6ch) used in the AP mode of printer 101. Therefore, printer 101 decides to perform roaming to network 114. Printer 101 transmits a BTM response frame including information indicating that roaming to network 114 is performed to AP 102 (F703). Printer 101 cancels connection with AP 102 (F704). Thereafter, printer 101 performs connection processing with AP 104 that provides network 114 as a roaming destination (F705). The printer 101 is connected to the AP 104, and when the roaming is completed, data communication with the AP 104 is performed (F706). Note that the processing in F703 to F706 is similar to Figure 3 Processing in F311 to F314.

[0074] Next, we will refer to Figure 8An example of the sequence of the roaming instruction reception determination processing executed in the printer 101 in the above-mentioned F606 and F702 is described. The printer 101 can execute the roaming instruction reception determination processing by, for example, reading out a computer program stored in the storage unit 209 and executing the computer program by the control unit 210. Figure 8 Note that this is just an example, and a dedicated Figure 8 At least part of the processing is done by hardware.

[0075] If the printer 101 receives a roaming instruction from the connected AP ("Yes" in step S801), the printer 101 determines whether the AP mode is activated (step S802). Although the BTM request frame is used as the roaming instruction from the AP, another frame may be used. If the AP mode is activated ("Yes" in step S802), the printer 101 advances the process to step S803. If the AP mode is not activated ("No" in step S802), the printer 101 advances the process to step S809. In step S809, the printer 101 sends a BTM response frame including information indicating that roaming is performed to the AP.

[0076] In step S803, the printer 101 checks the roaming destination BSS candidate list included in the BTM request frame, and determines whether the candidates include a BSS using a channel different from the channel being used in the AP mode. Note that the roaming destination BSS candidate list is notified to the printer 101 by using, for example, the BSS transition candidate list included in the BTM request frame. If the candidates include a BSS using a channel different from the channel being used in the AP mode ("Yes" in step S803), the printer 101 advances the process to step S804. If the candidates do not include a BSS using a channel different from the channel being used in the AP mode ("No" in step S803), the printer 101 advances the process to step S805. When the candidates include only BSSs using channels that are predicted to strongly interfere with communication in the AP mode (such as channels adjacent to the channels being used in the AP mode), the printer 101 may advance the process to step S805.

[0077] In step S804, the printer 101 selects a BSS using a channel different from the channel being used in the AP mode as a roaming destination. In step S809, the printer 101 sends a BTM response frame including information indicating that roaming is to be performed to the AP. Then, the printer 101 performs roaming according to the roaming instruction of the BTM request frame from the AP (step S810).

[0078] In step S805, the printer 101 determines whether roaming can be performed. The printer 101 may select only BSSs that use the same channel as the channel used in the AP mode as roaming destination candidates. Therefore, for example, when reactivation of the AP mode cannot be performed, the printer 101 determines that roaming cannot be performed ("No" in step S805). In this case, for example, during a print process, in which interruption of data communication due to reactivation of the AP mode is not allowed between the printer 101 and the STA connected using the AP mode, the printer 101 may determine that the AP mode cannot be reactivated and roaming cannot be performed. For example, the printer 101 may accept a user setting of whether to allow the same channel to be used in the AP mode and the STA mode via a user interface. When the candidates include only BSSs that use the same channel as the channel being used in the AP mode, and the use of the same channel between the AP mode and the STA mode is not allowed, the printer 101 may determine that roaming cannot be performed. If the printer 101 determines that roaming cannot be performed ("No" in step S805), the printer 101 advances the process to step S806. If the printer 101 determines that roaming can be performed (YES in step S805 ), the printer 101 advances the process to step S807 .

[0079] In step S806, the printer 101 sends a BTM response frame including information indicating that roaming is not to be performed to the AP. In step S807, the printer 101 sends a BTM response frame including information indicating that roaming is to be performed to the AP, and then performs a process for changing the channel used in the AP mode (step S808). Note that the process for changing the channel used in the AP mode will be described later. After changing the channel used in the AP mode, the printer 101 performs roaming according to the roaming instruction (step S810).

[0080] exist Figure 6 In , an example has been described in which the BSS candidate list in the BTM request frame from AP 102 includes only the BSS (network 113) formed by AP 103. Network 113 uses 6ch, which is the same channel as that used in the AP mode in printer 101. In this case, printer 101 determines that the candidates do not include a BSS using a channel different from the channel being used in the AP mode ("No" in step S803). If printer 101 determines to perform roaming ("Yes" in step S805), it changes the channel used in the AP mode (step S808), and performs roaming in the STA mode (step S810). Figure 7, the BTM request frame from AP 102 includes both BSSs (network 113 and network 114) formed by AP 103 and AP 104, respectively. Network 114 uses 11ch which is different from the channel used in AP mode in printer 101. In this case, printer 101 determines that the candidates include a BSS which uses a channel which is different from the channel being used in AP mode ("Yes" in step S803). In this case, printer 101 selects network 114 as the roaming destination (step S804), and performs roaming (step S810).

[0081] In the above example, a method of deciding a roaming destination network based only on whether the channel used in the AP mode is the same as the channel used in the roaming destination candidate has been described. However, this is only an example, and the roaming destination network selection method is not limited thereto. For example, priority information may be included in the BTM request frame, and the roaming destination network may be selected based on the priority information or the communication status. For example, the printer 101 may determine whether to use the same channel as the channel in the AP mode in order starting from the BSS with a higher priority in the BSS candidate list, and determine whether to select the BSS as the roaming destination. Note that depending on the priority, the roaming capability / non-roaming determination criteria according to the communication status in the AP mode and the STA mode may be changed. In the example, when the priority is the first value, if the channel used in the AP mode can be changed, it may be determined that roaming is possible. On the contrary, when the priority is the second value less than the first value, if the channel used in the AP mode needs to be changed, it may be determined that roaming is not possible. In addition, when the priority is the first value, even if the channel used in the AP mode cannot be changed quickly, it may be determined that roaming is possible. When the priority is the second value, it may be determined that roaming is possible under the condition that the channel used in the AP mode changes quickly.

[0082] Then, refer to Fig. 9An example of a sequence of processing for changing a channel used in AP mode performed in step S808 is described. First, the printer 101 determines whether there is an STA connected to the network 111 formed in the AP mode (step S901). If there is an STA connected to the network 111 ("Yes" in step S901), the printer 101 causes the processing to enter step S902. If there is no STA connected to the network 111 ("No" in step S901), the printer 101 causes the processing to enter step S907. In step S902, the printer 101 determines whether the connected STA complies with the Wi-Fi Agile multi-band standard. The printer 101 can make this determination based on information included in an association request frame or a probe request frame received, for example, during a connection process with the STA. For example, when any of these frames includes information indicating compliance with the Wi-Fi Agile multi-band standard, the printer 101 can determine that the STA complies with the Wi-Fi Agile multi-band standard. If the printer 101 determines that the connected STA does not conform to the Wi-Fi Agile Multi-Band standard (No in step S902), the printer 101 advances the process to step S903. If the printer 101 determines that the connected STA conforms to the Wi-Fi Agile Multi-Band standard (Yes in step S902), the printer 101 advances the process to step S905.

[0083] In step S903, the connected STA does not comply with the Wi-Fi Agile multi-band standard, so the printer 101 needs to change the channel used in the AP mode by another method. In the present embodiment, the printer 101 sends a channel switching announcement frame including information of the changed channel to the STA, and notifies the STA of the change of the channel used (step S903). However, this is only an example, and the channel used in the AP mode can be changed by another method. When the channel switching announcement frame is used, the AP mode does not need to be reactivated. Then, the printer 101 changes the setting to use a channel different from the channel used in the roaming destination network in the AP mode in the STA mode (step S904). At this time, the printer 101 can select a channel different from the channels in the connected network and the roaming destination network in the STA mode as the channel used in the AP mode. Alternatively, the printer 101 can select a channel different from the channel used in the BSS included in the BSS candidate list included in the BTM request frame received from the connection destination AP in the STA mode. Therefore, the printer 101 can reduce the possibility that the channel used in the AP mode becomes the same as the channel that may undergo roaming in the STA mode.

[0084] In step S905, the printer 101 sends a BTM request frame including an instruction to roam to a network formed in the AP mode after reactivation to the STA that complies with the Wi-Fi Agile multi-band standard. The sent BTM request includes information about the network formed in the AP mode after reactivation. The information includes information about the channel used in the network, etc. In this case, the printer 101 may change the BSSID to a second BSSID different from the current first BSSID, and reactivate the AP mode, and the BTM request frame may include the second BSSID after reactivation. Considering the reactivation time of the AP mode, the BTM request frame may include information until the time when the connection processing by roaming can be started. When the STA receives the BTM request frame, it performs roaming based on the information of the time until the connection processing by roaming can be started included in the frame. According to the time required to reactivate the AP mode in the printer 101, the connection processing by roaming of the STA is started. This can shorten the period during which the printer 101 is disconnected from the STA in the AP mode.

[0085] After transmitting the BTM request frame, the printer 101 waits for the arrival of a BTM response frame from the STA that is the destination of the BTM request frame (step S906). If the printer 101 receives the BTM response frame ("Yes" in step S906), the printer 101 advances the process to step S907. When the printer 101 receives the BTM response frame including information indicating that the STA cannot perform roaming, the printer 101 may determine that roaming cannot be performed in, for example, step S805. Note that in this case, the printer 101 may perform the process in step S807 after performing the process in step S808. Even when the printer 101 receives the BTM response frame including information indicating that the STA cannot perform roaming, it may forcibly reactivate the AP mode.

[0086] In step S907, the printer 101 reactivates the AP mode in a channel different from the channel used in the roaming destination network in the STA mode. Note that the printer 101 can decide the channel used in the AP mode after reactivation by using a criterion similar to that described with respect to step S904.

[0087] As described above, when there is a network using a channel different from the channel used in the AP mode as a roaming destination candidate in the STA mode, the printer 101 decides the network as the roaming destination. When the channel at the roaming destination in the STA mode is the same as the channel used in the AP mode, the printer 101 can change the channel used in the AP mode to another channel. This can prevent the same channel from being used in the AP mode and the STA mode after roaming is performed in the STA mode. Therefore, mutual interference between the communication in the AP mode and the communication in the STA mode due to roaming can be prevented. In the above example, the process of changing the channel used in the AP mode when the channel at the roaming destination in the STA mode coincides with the channel used in the AP mode has been described. However, the present invention is not limited to this. For example, even if the channel at the roaming destination in the STA mode is inconsistent with the channel used in the AP mode, if these channels have a mutual interference relationship, the channel used in the AP mode can be changed. For example, when the channel at the roaming destination in the STA mode is a peripheral channel such as a channel adjacent to the channel used in the AP mode, the channel used in the AP mode can be changed. Similarly, the printer 101 can select a network using a channel having no mutual interference relationship with the channel used in the AP mode as a roaming destination candidate in the STA mode.

[0088] In the scope of this specification and claims, "mutual interference relationship" refers to a relationship in which the interference level exceeds a predetermined value when a signal of predetermined power is transmitted. For example, when the power value of the component leaking to the second channel among the signals of the first channel among multiple channels is attenuated by a predetermined amount or more compared to the peak power in the first channel, it is possible to specify that these channels have a relationship in which they do not interfere with each other. That is, when the signal transmitted in the first channel is sufficiently attenuated within the frequency range of the second channel and the influence becomes satisfactorily small, it is possible to specify that these channels have a relationship in which they do not interfere with each other. On the contrary, when the attenuation amount of the power of the signal component leaking from the peak power in the first channel to the second channel becomes less than a predetermined amount and a large power leaks to the second channel, it is possible to specify that these channels have a relationship in which they interfere with each other. This relationship can be pre-specified by, for example, theoretical calculations.

[0089] In the above two embodiments, the printer 101 operates as both a STA and an AP. Here, AP can be rewritten as Wi-Fi Group Owner (GO). The above process may be applied when the printer 101 is not operating in the AP mode but in the second STA mode, that is, when the printer 101 joins multiple networks as a STA. The second STA mode may be a mode in which the printer 101 operates as a Wi-Fi Direct P2P client. More generally, the above process may be performed when a communication device connectable to multiple networks should perform roaming from a first network to a second network among the multiple networks.

[0090] More specifically, in the first embodiment, the communication device may notify another communication device having a function of issuing an instruction to roam from the first wireless network to the second network of information on frequency channels used in a third network among the multiple networks. Note that, in the case where there are multiple third networks, the communication device is able to notify other communication devices of information on frequency channels used in each third network. Each third network may be prioritized, and the communication device may notify other communication devices of information on frequency channels used in each of a predetermined number of networks in descending order of priority among the third networks. That is, the communication device may notify other communication devices of all frequency channels used in each third network, or only some frequency channels. When the communication device receives a roaming instruction based on the notification from the other communication device, it may perform roaming based on the instruction. Note that the other communication device may generally be a base station (AP) of the first network, but may be a control device other than the base station. For example, a control device that adjusts the load of the entire network may be prepared, and the control device may instruct the communication device to roam from a connection to one network to a connection to another network via any network to which the communication device is connected.

[0091] In a second embodiment, when a communication device receives an instruction to roam from a first network to a second network from another communication device, it determines whether the second network and the third network among the multiple networks use the same frequency. When the first frequency channel used in the second network and the second frequency channel used in the third channel coincide with each other, the communication device changes the frequency channel used in the third network to the third frequency channel. Note that when the first frequency channel and the second frequency channel have the above-mentioned mutual interference relationship, the communication device can change the second frequency channel to the third frequency channel. Note that the communication device can receive one or more second networks as roaming destination candidates. When there is a roaming destination candidate network that uses a frequency channel that has no mutual interference relationship with the second frequency channel, the communication device can roam to the candidate network. Note that the communication device can receive information on the frequency channel used in the second network in the roaming instruction, or obtain the information separately from the roaming instruction.

[0092] As described above, the process described in the two embodiments can be applied to any communication device that can connect to multiple networks. That is, the communication device does not always need to comply with the IEEE 802.11 series standards, and can suppress the generation of interference with another network accompanying roaming of one network by using the above process.

[0093] According to the present invention, in a communication device that communicates in a plurality of networks, it is possible to suppress interference between networks caused by transition from one network to another.

[0094] Other embodiments

[0095] The (multiple) embodiments of the present invention may also be implemented as follows: a computer of a system or device, the system or device reads and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be more completely referred to as a "non-transitory computer-readable storage medium") to perform one or more functions of the above (multiple) embodiments, and / or the system or device includes one or more circuits (e.g., application-specific integrated circuits (ASICs)) for performing one or more functions of the above (multiple) embodiments; and a method performed by a computer of the system or device, for example, reading and executing computer executable instructions from a storage medium to perform one or more functions of the above (multiple) embodiments, and / or controlling the one or more circuits to perform one or more functions of the above (multiple) embodiments. The computer may include one or more processors (e.g., a central processing unit (CPU), a microprocessing unit (MPU)), and may include a network of separate computers or separate processors to read and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or a storage medium. The storage medium may include, for example, a hard disk, a random access memory (RAM), a read-only memory (ROM), a memory of a distributed computing system, an optical disk (such as a compact disc (CD), a digital versatile disc (DVD), or a Blu-ray disc (BD) TM ), one or more of a flash memory device and a memory card, etc.

[0096] The embodiments of the present invention may also be implemented by providing software (program) for performing the functions of the above-described embodiments to a system or device via a network or various storage media, and a computer or a central processing unit (CPU) or a microprocessing unit (MPU) of the system or device reads and executes the program.

[0097] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A communication device, comprising: A communication unit, which is used for wireless communication; a notification unit configured to notify other communication devices of information of a frequency channel used in a third network as information of a frequency channel that cannot be roamed, wherein the communication device can communicate in parallel with the first network in the third network, wherein the other communication device has the following function: in a case where the communication device is connected to the first network, issuing an instruction to roam from the first network to a second network; as well as An execution unit is configured to execute roaming based on the instruction when receiving a roaming instruction based on the notification from the other communication device after connecting to the first network.

2. The communication device according to claim 1, wherein: The communication device is a communication device of a wireless LAN conforming to the IEEE 802.11 series standards, and notifies the other communication device of information on a frequency channel used as a non-preferred channel in the third network in a frame communicated by the wireless LAN.

3. The communication device according to claim 2, wherein: The communication unit joins the first network as a station and forms the third network as an access point.

4. The communication device according to claim 2, wherein: The communication unit uses Wi-Fi The communication is carried out using the third network of the group owner.

5. The communication device according to claim 3, wherein: The other communication device is an access point forming the first network.

6. The communication device according to claim 5, wherein: The notification unit notifies the other communication device by transmitting an association request frame including the non-preferred channel to the other communication device.

7. The communication device according to claim 5, wherein: The notification unit notifies the other communication device by transmitting a WNM notification request frame including the non-preferred channel to the other communication device.

8. The communication device according to claim 1, wherein: The notification unit notifies the other communication device of information of a frequency channel predicted to be used when connecting to the third network in a state where the third network is not used, as information of a frequency channel that cannot be roamed.

9. The communication device according to claim 1, wherein: When notifying the other communication device of information on a frequency channel used in the third network, the notification unit further notifies the other communication device of information on a frequency channel adjacent to the frequency channel.

10. The communication device according to claim 1, wherein: The notification unit notifies the other communication device of information including the frequency band of the frequency channel as information on the frequency channel used in the third network.

11. The communication device according to claim 1, wherein: The notification unit notifies the other communication device of the information of the frequency channel used in the third network based on the presence of a device connected to the communication device in the third network.

12. The communication device according to claim 1, wherein: The notification unit determines whether to notify the other communication device of information on the frequency channel used in the third network based on a congestion state of the frequency channel used in the third network.

13. The communication device according to claim 2, wherein: The communication unit participates in the first network as a station, and also participates in the third network as a station. 14 . A computer-readable storage medium storing a program for causing a computer to function as each unit included in the communication device according to claim 1 .

15. A program product for causing a computer to function as each unit included in the communication device according to any one of claims 1 to 13.

16. A control method performed by a communication device performing wireless communication, the method comprising: Notifying other communication devices of information of a frequency channel used in a third network in which the communication device can communicate in parallel with the first network as information of a frequency channel that cannot roam, wherein the other communication devices have the following function: in a case where the communication device is connected to the first network, issuing an instruction to roam from the first network to a second network; and When a roaming instruction based on the notification is received from the other communication device after connecting to the first network, roaming is performed based on the instruction.

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