Communication device, control method, and program

Abstract

To suppress occurrence of interference between networks caused by transition from one network to another in a communication device that communicates over a plurality of networks.SOLUTION: A communication device for communicating wirelessly notifies another communication device that has a function of performing a roaming instruction from a first network to a second network when the communication device is connected to the first network of information on frequency channels used in a third network in which the communication device can communicate in parallel with the first network, as information on frequency channels on which roaming is not possible. When the communication device receives the roaming instruction from the other communication device based on the notification after connecting to the first network, the communication device performs roaming based on the instruction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control technique for suppressing the occurrence of interference in a wireless communication system. [Background technology]

[0002] Wireless local area networks (LANs) are widely used. In wireless LANs, communication devices operate as access points (APs) or stations (STAs), and STAs join a network formed by the APs to perform communication. Technical standards for various communication control of wireless LANs have been formulated by the Wi-Fi Alliance, which is promoting wireless LANs. One such technical standard is the Wi-Fi Agile Multiband (trademark) standard. According to this standard, an AP can collect information about surrounding networks from STAs connected to the AP, and prompt the connected STAs to migrate to another network based on the information. By having the AP migrate the connected STAs to another network, network load can be distributed, enabling efficient use of network resources. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-019366 A Summary of the Invention [Problem to be solved by the invention]

[0004] A wireless LAN communication device can operate as an AP while also operating as an STA (see Patent Document 1). When such a communication device changes the network to which it is connected in response to a network transition instruction from an AP connected as an STA, the communication performance may unintentionally decrease in relation to the network that the device forms as an AP. For example, if the network to which the device transitions as an STA uses the same frequency as the network that the device forms as an AP, the communications performed in these networks may interfere with each other. This is not limited to wireless LANs, but in wireless communication devices that communicate in multiple networks, interference between networks may occur due to transition from one network to another. [Means for solving the problem]

[0005] The present invention provides a technique for suppressing the occurrence of interference between networks caused by transition from one network to another network in a communication device that communicates through a plurality of networks.

[0006] A communication device according to one embodiment of the present invention has a communication means for wirelessly communicating, a notification means for notifying another communication device having a function for instructing roaming from a first network to a second network when the communication device is connected to the first network, of information on a frequency channel used in a third network in which the communication device can communicate in parallel with the first network, as information on a frequency channel on which the communication device cannot roam, and an execution means for, after connecting to the first network, performing roaming based on the instruction when the communication device receives the roaming instruction based on the notification from the other communication device. Effect of the Invention

[0007] According to the present invention, in a communication device that communicates through a plurality of networks, it is possible to suppress the occurrence of interference between networks caused by transition from one network to another network. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 illustrates an example of the configuration of a communication system. [Diagram 2] FIG. 2 illustrates an example of the configuration of a printer. [Diagram 3] FIG. 1 is a diagram illustrating an example of a flow of processing executed in a communication system. [Figure 4] FIG. 11 is a diagram illustrating an example of a flow of processing executed by a printer. [Diagram 5] FIG. 11 is a diagram illustrating an example of a flow of processing executed by a printer. [Figure 6] FIG. 11 is a diagram illustrating another example of the flow of processing executed in the communication system. [Figure 7] FIG. 11 is a diagram illustrating another example of the flow of processing executed in the communication system. [Figure 8] FIG. 2 is a diagram showing an example of the flow of processing executed by the printer 101. [Figure 9] FIG. 2 is a diagram showing an example of the flow of processing executed by the printer 101. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0010] (System Configuration) FIG. 1 shows an example of the configuration of a wireless communication system according to this embodiment. The wireless communication system in FIG. 1 is a system configured using a wireless local area network (LAN) conforming to the IEEE 802.11 series standard. For example, this wireless communication system is configured using a wireless LAN that supports at least one of the IEEE 802.11a / b / g / n / ac / ax / be standards. Note that IEEE is an abbreviation for the Institute of Electrical and Electronics Engineers. Note that the following description focuses on a wireless LAN, but similar discussions can be applied to other wireless networks. For example, the following discussion can be applied to a system using any wireless network by replacing an access point (AP) with a base station and a station (STA) with a terminal.

[0011] The wireless communication system includes a plurality of communication devices. Each communication device has at least one of the functions of an access point (AP) having a function of forming a network and a STA participating in a network formed by the AP. In this embodiment, the printer 101 can function as both an AP and a STA, and can form a wireless LAN network 111 and participate in any of the networks formed by the APs 102 to 104. In the following, the operation mode of the printer 101 as an AP is called an AP mode, and the operation mode of the printer 101 as an STA is called an STA mode. The APs 102 to 104 each form a wireless LAN network. FIG. 1 shows an example in which the AP 102 forms a network 112, the AP 103 forms a network 113, and the AP 104 forms a network 114. In the following, the formed wireless LAN network may be called a BSS (Basic Service Set). In the present embodiment, the printer 101 is considered to participate in, for example, the network 112 as an STA. Also, it is assumed that, for example, the STA 105 participates in the network 111 formed by the printer 101 .

[0012] Here, it is assumed that AP102 to AP104 are configured to be able to communicate with each other via a backbone network (not shown), and the network is configured so that a STA connected to any of these APs can roam between these APs. The backbone network may be configured as a wired network such as a wired LAN, or as a wireless network such as a wireless LAN.

[0013] In addition to the IEEE802.11 series standard, each communication device may be compatible with other communication standards such as Bluetooth (registered trademark), NFC, UWB, ZigBee, MBOA, etc. In addition, UWB is an abbreviation for Ultra Wide Band, MBOA is an abbreviation for Multi Band OFDM Alliance, and NFC is an abbreviation for Near Field Communication. Here, OFDM is an abbreviation for Orthogonal Frequency Division Multiplexing. UWB includes wireless USB, wireless 1394, WiNET, etc. In addition to the IEEE802.11 series standard, the communication device may be compatible with standards such as the Wi-Fi Direct standard established by the Wi-Fi Alliance. In addition, the communication device may be compatible with a communication standard for wired communication such as wired LAN.

[0014] In this embodiment, the printer 101 can use different frequency bands in both the STA mode and the AP mode when operating in both modes. For example, the printer 101 can form a network in the 5 GHz band in the AP mode while participating in a network formed using the 2.4 GHz band in the STA mode. The printer 101 may also use different frequency channels in the same frequency band in the STA mode and the AP mode. For example, the printer 101 may form a network using a channel belonging to W52 in the same 5 GHz band in the AP mode while participating in a network formed using a channel belonging to W53 in the 5 GHz band in the STA mode. That is, the printer 101 can use frequency channels in the STA mode and the AP mode such that the respective communications do not interfere with each other or such interference is sufficiently small. Also, since the interference between adjacent channels in the 5 GHz band is smaller than that in the 2.4 GHz band, the printer 101 may use adjacent channels in the 5 GHz band. The printer 101 may also be capable of operating at 6 GHz in addition to 2.4 GHz and 5 GHz.

[0015] In this embodiment, it is assumed that 1ch in the 2.4 GHz band is used in network 112, and 6ch in the 2.4 GHz band is used in networks 111 and 113. It is assumed that "ch" means "channel." It is also assumed that 11ch is used in network 114. Networks 112 to 114 are roaming-enabled wireless networks that are set, for example, so that the Service Set Identifier (SSID) and passphrases required for encryption and decryption of communications are the same. It is to be noted that this is just an example, and any setting that enables roaming between networks 112 to 114 can be made.

[0016] In this embodiment, in order to efficiently utilize the network, each communication device may exchange network information, and perform dynamic monitoring of the network and balancing of the network load based on the information. In this embodiment, the printer 101, APs 102 to 104, and STA 105 are assumed to be compatible with the Wi-Fi Agile Multiband standard established by the Wi-Fi Alliance. In the Wi-Fi Agile Multiband standard, an AP may collect information on surrounding networks from a STA connected to the device itself, and based on the information, may prompt the connected STA to migrate to another network. For example, the AP 102 may collect information on surrounding networks from the printer 101 connected to the device itself, and may transmit an instruction to the printer 101 to migrate to a network formed by another AP. The AP may determine the migration of the connected STA to another network according to the resource usage (load status) in the surrounding network and the network formed by the device itself. Note that this is just an example, and the AP may determine the migration of the connected STA to another network based on another policy.

[0017] Here, a procedure that is executed when an AP instructs a STA to transition to another network, that is, when a STA is instructed to roam, according to the Wi-Fi Agile Multiband standard, will be outlined.

[0018] The AP and the STA can execute the function when the connected device is compatible with (supports) the Wi-Fi Agile Multiband standard. The STA can determine whether the AP is compatible with the Wi-Fi Agile Multiband standard based on whether the wireless frame transmitted by the AP includes MBO Capability Indication information. That is, for example, the STA can determine that the AP is compatible with the Wi-Fi Agile Multiband standard when the wireless frame transmitted by the AP includes MBO Capability Indication information. Note that MBO stands for Multiband Operation. The STA may also determine whether the AP is compatible with the Wi-Fi Agile Multiband standard based on other information such as whether the BTM Capability bit is set in the wireless frame transmitted by the AP. For example, the STA can determine that the AP is compatible with the Wi-Fi Agile Multiband standard when the BTM Capability bit is set in the wireless frame transmitted by the AP. Note that BTM stands for BSS Transition Management. The wireless frame transmitted from the AP may be a Beacon, a Probe Response, or an Association Response. These are merely examples, and it may be determined whether the AP supports the Wi-Fi Agile Multiband standard by using other wireless frames.

[0019] In addition, the AP may determine whether the STA supports the Wi-Fi Agile Multiband standard based on whether the BTM Capability bit is set in the wireless frame transmitted by the STA. For example, if the BTM Capability bit is set in the wireless frame transmitted by the STA, the AP may determine that the STA supports the Wi-Fi Agile Multiband standard. The wireless frame here may be, for example, a Probe Request or an Association Request. Note that these are only examples, and whether the STA supports the Wi-Fi Agile Multiband standard may be determined based on other wireless frames.

[0020] In the following, it is assumed that both the AP and the STA are compatible with the Wi-Fi Agile Multiband standard.

[0021] The AP transmits 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, the STA observes the Beacons transmitted from the surrounding APs based on the information in the frame to collect Beacon information. Then, the STA generates a Beacon Report frame including the collected information and transmits the frame to the AP. The AP can determine whether to roam the STA to another network based on the load status of the network formed by the AP itself and information such as the Beacon Report received from the STA. When the AP determines to roam the STA to another network, it instructs the STA to roam using, for example, a BTM Request frame. The BTM Request frame includes a list of BSS candidates for roaming destinations, the time until a disconnection frame is transmitted, the time until roaming can be started, priority information of the BSS candidate list, and the like. When the STA receives the BTM Request frame, it determines whether to perform roaming based on the information included in the frame. The STA then generates a BTM Response frame based on that decision and transmits the frame to the AP. The BTM Response frame contains information on whether or not to accept roaming, and, if roaming is to be performed, the identification information (BSSID) of the roaming destination network.

[0022] The AP and the STA can perform roaming according to the Wi-Fi Agile Multiband standard as described above. When performing roaming, the roaming method conforming to the Wi-Fi Agile Multiband standard may be used as is, or only a part of the functions of the standard may be used. In addition, other standards that realize equivalent functions different from the Wi-Fi Agile Multiband standard may be used.

[0023] In this embodiment, the printer 101, which is a communication device capable of operating as both an AP and a STA, changes the network to which it is connected in STA mode according to the Wi-Fi Agile Multiband standard. In this case, the frequency channel used in AP mode and the frequency channel used in the network to which it is connected after the change in STA mode may strongly interfere with each other. That is, the printer 101 uses 6ch in AP mode, and is connected to a network 112 in which 1ch is used in STA mode. In this case, if the AP 102 instructs the printer 101 to roam to the network 113 and the printer 101 roams according to the instruction, 6ch will be used in both the AP mode and the STA mode. In this case, communication in the AP mode and communication in the STA mode may interfere with each other. In view of such circumstances, this embodiment provides a technology for suppressing the occurrence of a level of interference that affects communication between communication in the AP mode and communication in the STA mode due to roaming.

[0024] (Device configuration) FIG. 2 shows an example of the hardware configuration of the printer 101 according to the present embodiment. The printer 101 has, as its hardware configuration, 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 printing processing. The printing unit 201 is configured to include, for example, a paper conveying mechanism and a recording processing mechanism. The image processing unit 202 performs image processing of an image to be printed before the printing processing in the printing unit 201 is performed. The image processing unit 202 is configured to include, for example, hardware and memory for image processing to convert 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 for operating the printer 101 by a user. The operation unit 203 is configured to include, for example, buttons and keys for accepting various operations. The operation unit 203 may include hardware for accepting inputs other than buttons and keys, such as voice input. The display unit 204 includes a display or light-emitting diode that outputs information in a visually recognizable format, a speaker that outputs information by voice, and the like. Thus, in one example, the display unit 204 outputs information in a format that is recognizable by at least one of the senses of sight and hearing. Note that this is one example, and information may be displayed by vibration or the like. When displaying visual information, the display unit 204 has a VRAM (Video Random Access Memory) that holds screen data corresponding to the visual information to be displayed. In one example, the display unit 204 performs display control to keep displaying the screen data stored in the VRAM. Note that, for example, a touch panel display in which the display unit 204 and the operation unit 203 are integrated may be used.

[0025] The communication unit 205 includes a radio frequency (RF) circuit and a baseband circuit (wireless LAN chip) for wireless LAN, which provide a communication interface by wireless LAN. The communication unit 205 is configured to be able to execute wireless LAN communication conforming to the IEEE802.11 series standard via the antenna 206. The antenna 206 is an antenna that operates at a frequency band of 2.4 GHz / 5 GHz for wireless LAN communication. In addition, the antenna 206 may operate at a frequency band of 6 GHz. The communication unit 205 includes an STA function unit 207 and an AP function unit 208 so as to be able to operate in the STA mode and the AP mode in parallel. The STA function unit 207 and the AP function unit 208 may be implemented as different wireless I / Fs, or may share one wireless I / F. When one wireless I / F is shared, for example, the STA function unit 207 and the AP function unit 208 may be configured not to operate simultaneously by time division. Also, for example, the STA functional unit 207 and the AP functional unit 208 may share one wireless I / F by operating in different frequency bands.

[0026] The storage unit 209 stores various information such as a control program to be executed by the control unit 210 and information related to communication. The storage unit 209 includes one or more storage media such as one or more memories such as a hard disk drive (HDD), a flash memory, a removable SD card, a ROM, or a RAM. ROM stands for Read Only Memory, and RAM stands for Random Access Memory. The control unit 210 controls the entire printer 101 by executing a control program stored in the storage unit 209. The control unit 210 includes one or more processors such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 210 may control the entire printer 101 in cooperation with an OS (Operating System). The control unit 210 may also 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 described below are implemented by the control unit 210 executing a control program stored in the storage unit 209. The power supply unit 211 supplies power to each piece of hardware. The power supply 211 can obtain power from, for example, an AC power source such as a commercial power source or a DC power source such as a battery.

[0027] (Processing flow) In the following, an embodiment will be described regarding a procedure for suppressing the occurrence of interference between communication in AP mode and communication in STA mode that affects communication in the printer 101 due to roaming.

[0028] [Embodiment 1] When connecting to an AP, the STA can include channel information on which the STA cannot roam in an Association Request frame transmitted to the AP. For example, the STA can transmit an Association Request frame to the AP in which a channel on which the STA cannot roam is set in a Non-preferred Channel Report attribute. The STA can also perform a similar notification in a Reassociation Request frame. Furthermore, even when connected to the AP, the STA can notify the AP of channel information on which the STA cannot roam. For example, the STA can transmit a WNM-Notification Request frame to the AP in which channel information on which the STA cannot roam is set in the Non-preferred Channel Report field. WNM is an abbreviation for Wireless Network Management. When the AP receives channel information on which the STA cannot roam from the STA, the AP can avoid including a BSS using a channel on which the STA cannot roam in a list of BSS candidates to be roamed when instructing the STA to roam. That is, based on channel information from a STA, the AP includes the BSS using a channel that the STA can roam on in a list of BSS candidates to be roamed and notifies the STA. In this embodiment, by having the printer 101 notify the AP 102 of such information on channels that cannot be roamed, the printer 101 is prevented from being notified of roaming destination candidates that may cause interference that affects communication.

[0029] Fig. 3 shows an example of the flow of processing executed in the system according to this embodiment. Fig. 3 shows an example of the flow of processing when the printer 101 roams to the AP 104 in response to an instruction from the AP 102 in the system of Fig. 1.

[0030] In the process of FIG. 3, first, the printer 101 accepts, for example, an instruction operation by a user to start the AP mode and starts the AP mode (F301). Then, the printer 101 forms a network 111. Note that it is assumed that 6ch in the 2.4 GHz band is used in the network 111. After that, the STA 105 accepts, for example, an instruction to connect to the printer 101 by the user, and executes a process to connect to the network 111 formed by the printer 101 in the AP mode (F302). When this connection process is completed, data communication can be performed between the printer 101 and the STA 105 (F303). Here, it is assumed that the printer 101 accepts an instruction for infrastructure connection (hereinafter, sometimes referred to as "Infra connection"). In this case, the printer 101 executes a process to connect to a surrounding AP using a function of the STA mode. Here, it is assumed that the printer 101 establishes a connection to the AP 102 forming the network 112. It is assumed that 1ch in the 2.4 GHz band is used in the network 112. In the STA mode, the printer 101 receives a Beacon frame from a surrounding AP. Here, it is assumed that the printer 101 has received a Beacon frame sent from the AP 102 (F304). Here, the printer 101 checks the MBO Capability Indication information included in the received Beacon frame. This allows the printer 101 to identify whether or not the AP 102 is an AP that supports the Wi-Fi Agile Multiband standard. Here, it is assumed that the AP 102 is an AP that supports the Wi-Fi Agile Multiband standard, and the printer 101 has identified this fact.

[0031] Next, the printer 101 performs a determination process when connecting to an AP (F305). Details of this determination process will be described later. In this determination process, the printer 101 determines whether to include information on the channel used in AP mode as a non-preferred channel in the Association Request frame when connecting to the AP. In this embodiment, it is assumed that the printer 101 has determined to transmit an Association Request frame including information on the channel used in AP mode. In this case, the printer 101 transmits to the AP 102 an Association Request frame including information indicating 6ch, which is the channel used in AP mode, as a non-preferred channel (F306). Note that the printer 101 can set a BTM Capability bit in the Association Request frame and transmit it. This enables the AP 102 to identify that the printer 101 is compatible with the Wi-Fi Agile Multiband standard. Note that a process required for authentication, such as an Authentication frame, is also executed before the Association Request frame, but its description is omitted in FIG. 3.

[0032] When the AP 102 receives the Association Request frame in F306, it stores the information (6ch) that is set as the non-preferred channel of the printer 101. Then, the AP 102 transmits an Association Response frame to the printer 101 (F307). When the printer 101 receives the Association Response frame, it subsequently performs key setting processing with the AP 102 (F308). This key setting processing is processing for setting an encryption key and the like used for encryption and decryption in wireless LAN communication between the STA mode of the printer 101 and the AP 102. In the key setting processing, for example, a 4-way handshake process and the like are executed. After the completion of this key exchange processing, data communication is performed between the printer 101 and the AP 102 (F309).

[0033] Thereafter, for example, the AP 102 detects that the network 112 formed by the AP 102 is congested due to an increase in traffic of the network 112 formed by the AP 102 itself or an increase in the number of connected STAs. The AP 102 may determine that the network 112 is congested, for example, when the amount of allocated resources exceeds a predetermined value or when the number of connected STAs exceeds a predetermined number. When the AP 102 determines that the network 112 is congested, the AP 102 determines whether or not to migrate the STAs connected to the AP 102 itself to another network that allows roaming. In this embodiment, the AP 102 determines that the printer 101 is to be migrated to another network. Here, as described above, the network 113 formed by the AP 103 and the network 114 formed by the AP 104 are capable of roaming from the network 112 formed by the AP 102. Also, as described above, the 6ch is used in the network 113, and the 11ch is used in the network 114.

[0034] When the AP 102 determines to move the printer 101 to another network, the AP 102 selects a network to which the printer 101 will roam. The AP 102 stores in F306 that the non-preferred channel of the printer 101 is 6ch. Therefore, the AP 102 excludes the network 113, which uses 6ch, from the candidates for the roaming destination of the printer 101. On the other hand, the network 114 uses 11ch, which is different from 6ch, so the AP 102 selects the network 114 as a candidate for the roaming destination of the printer 101. Then, the AP 102 transmits a BTM Request frame including information on the network 114 as a candidate for the roaming destination to the printer 101 (F310). Note that in this embodiment, only the networks 113 and 114 are considered as roaming destinations from the network 112, but there may be other networks that can be roamed to. In this case, the AP 102 may notify the printer 101 of a plurality of networks that can be roamed to and do not use 6ch, as candidates for the roaming destination.

[0035] When the printer 101 receives the BTM Request frame, the printer 101 determines whether or not to perform roaming based on the information included in the frame. For example, the printer 101 may obtain information on a network that is a candidate for a roaming destination and a frequency channel used in the network from the information included in the BTM Request frame, and determine whether or not roaming is possible. Here, the printer 101 specifies from the BTM Request frame that the candidate for a roaming destination is network 114, and that 11ch is used in network 114. The printer 101 may determine that roaming is possible because the mutual interference between the frequency channel (6ch) used in the AP mode and the channel (11ch) used in the network 114 that is a candidate for a roaming destination is small enough not to affect communication. Note that the printer 101 may always determine to perform roaming when roaming is possible, or may determine whether or not to perform roaming depending on the wireless quality of the signal of the network that is a candidate for a roaming destination.

[0036] Here, it is assumed that the printer 101 has decided to roam to the network 114. In this case, the printer 101 transmits a BTM Response frame including information indicating that the printer 101 will roam to the network 114 to the AP 102 (F311). Then, the printer 101 disconnects from the AP 102 (F312). After that, the printer 101 performs a process of connecting to the AP 104 that provides the network 114, which is the roaming destination (F313). Note that this connection process is the same as the processes of F304 to F308 described above. Note that, as described in relation to F306, the printer 101 also transmits an Association Request frame including a Non-preferred Channel to the AP 104. When the printer 101 connects to the AP 104 and completes roaming, the printer 101 performs data communication with the AP 104 (F314).

[0037] 3, information about the channel used by the printer 101 in AP mode is notified in advance to the connection destination AP as a non-preferred channel. This makes it possible to select roaming destination candidates excluding networks using the channel used by the printer 101 in AP mode in response to a roaming instruction from the AP. This makes it possible to prevent strong interference between communication in STA mode and communication in AP mode when the printer 101 roams in STA mode.

[0038] Next, an example of the flow of the determination process when the above-mentioned F305 is connected to an AP will be described with reference to Fig. 4. The printer 101 can execute the process in Fig. 4 by, for example, reading and executing a computer program stored in the storage unit 209 by the control unit 210. Note that this is just one example, and dedicated hardware for executing at least a part of the process in Fig. 4 may be provided.

[0039] When the determination process at the time of AP connection is started, the printer 101 determines whether or not an interference pre-avoidance setting for avoiding interference during roaming in advance is enabled (ON) (S401). If the interference pre-avoidance setting is enabled (YES in S401), the printer 101 advances the process to S402. On the other hand, if the interference pre-avoidance setting is not enabled (NO in S401), the printer 101 advances the process to S409. The interference pre-avoidance setting can be enabled or disabled by a user operation accepted via the operation unit 203. Also, for example, in a computer program executed by the control unit 210, control may be performed so that the interference pre-avoidance setting is autonomously enabled or disabled when a predetermined condition is satisfied. For example, the printer 101 may be configured so that the interference pre-avoidance setting is automatically enabled or disabled based on the network load (congestion level) in either the STA mode or the AP mode of the printer 101 or in both modes.

[0040] In S402, the printer 101 acquires information on the AP to which the printer 101 is to be connected. For example, as described in relation to F304, the printer 101 may receive a Beacon frame arriving from the AP and acquire information on the AP from the frame. Also, in the STA mode of the printer 101, the printer 101 may transmit a Probe Request frame, receive a Probe Response frame as a response to the frame, and acquire information on the AP from the Probe Response frame. Note that the printer 101 may transmit a Probe Request frame including information related to the Wi-Fi Agile Multiband standard. For example, the printer 101 transmits a Probe Request frame with a BTM Capability bit set. Also, the printer 101 may transmit a predetermined Action frame defined in the IEEE802.11 series standard, and acquire information on the AP by receiving a response frame to the frame. Thereafter, the printer 101 determines whether the AP to which the printer 101 is to be connected complies with the Wi-Fi Agile Multiband standard based on the information on the AP acquired in S402 (S403). If the printer 101 determines that the connection destination AP supports the Wi-Fi Agile Multiband standard (YES in S403), the process proceeds to S404. On the other hand, if the printer 101 determines that the connection destination AP does not support the Wi-Fi Agile Multiband standard (NO in S403), the process proceeds to S409.

[0041] In S404, the printer 101 determines whether the AP mode is active. If the AP mode is active (YES in S404), the printer 101 proceeds to S405. On the other hand, if the AP mode is not active (NO in S404), the printer 101 proceeds to S408.

[0042] In S405, the printer 101 executes a process for determining the connection status in the AP mode. This process will be described with reference to FIG.

[0043] In FIG. 5, the printer 101 determines whether the channel being used in the AP mode is congested (S501). For example, the printer 101 may determine that the channel is congested if the signal-to-noise ratio (SNR) value of the received signal is equal to or greater than a predetermined threshold, and may determine that the channel is not congested if the SNR value is below the predetermined threshold. However, this is only an example, and the congestion status may be determined by other criteria. For example, another criterion may be used, such as determining that the channel is congested if the time from the start to the completion of the transmission of a predetermined amount of data is equal to or greater than a predetermined length. If the printer 101 determines that the channel being used in the AP mode is congested (YES in S501), the printer 101 advances the process to S502. On the other hand, if the printer 101 determines that the channel being used in the AP mode is not congested (NO in S501), the printer 101 advances the process to S504. In S502, the printer 101 determines whether a STA is connected to the network 111 formed in the AP mode. That is, the printer 101 determines whether a communication partner device exists in the AP mode. If the STA is connected to the network 111 (YES in S502), the printer 101 advances the process to S503. On the other hand, if the STA is not connected to the network 111 (NO in S502), the printer 101 advances the process to S504.

[0044] In S503, the printer 101 sets the channel in use in AP mode as a channel that cannot be used for roaming in STA mode. That is, the printer 101 sets the channel in use in AP mode as a non-preferred channel. The process of S503 is performed when the channel in use in AP mode is congested and the STA is connected. In this case, if the same channel as in AP mode is used in STA mode due to roaming, it is assumed that the influence of interference is large. For this reason, in S503, the channel in use in AP mode is set as a non-preferred channel so that the roaming destination in STA mode is limited. On the other hand, the process of S504 is performed when the channel in use in AP mode is not congested or the STA is not connected. In this case, even if the same channel as in AP mode is used in STA mode due to roaming, it is assumed that the influence of interference is small. For this reason, in S504, the printer 101 may determine that it is not necessary to set the channel in use in AP mode as a channel that cannot be used for roaming in STA mode. For this reason, the printer 101 does not include the channel being used in AP mode in the non-preferred channels.

[0045] Note that the example in FIG. 5 is just one example, and whether or not to include the channel in use in AP mode in the Non-preferred Channel may be determined by a process different from that in FIG. 5. For example, the process of S501 may not be performed, and whether or not to include the channel in use in AP mode in the Non-preferred Channel may be determined only depending on whether or not a connected STA exists in AP mode. Also, in one example, the process of S502 may be omitted. Also, the printer 101 may not perform this determination process, and may always include the channel in use in AP mode in the Non-preferred Channel when the AP mode is activated.

[0046] 4, after the determination process of S405, the printer 101 determines whether or not to include the channel in use in AP mode in the Non-preferred Channel based on the result of the determination of S405 (S406). If the printer 101 determines that the channel in use in AP mode is to be included in the Non-preferred Channel (YES in S406), the process proceeds to S407. On the other hand, if the printer 101 determines that the channel in use in AP mode is not to be included in the Non-preferred Channel (NO in S406), the process proceeds to S409.

[0047] In S407, the printer 101 sets the channel being used in AP mode to the Non-preferred Channel. Note that, among the channels different from the channel being used in AP mode, a channel that may be used in AP mode may be determined in advance. In that case, the printer 101 may also set that channel to the Non-preferred Channel. After that, the printer 101 proceeds to the process at S409.

[0048] S408 is a process when the printer 101 has not started the AP mode. In this case, if there is a channel to be used when the AP mode is started, the printer 101 sets the channel to the Non-preferred Channel. Note that, if there are multiple channels to be used in the AP mode, the printer 101 may set the multiple channels to the Non-preferred Channel. Also, if there are multiple channels to be used in the AP mode, the printer 101 may set only a part (for example, one) of the channels, not all of them, as the Non-preferred Channel. Also, if the AP mode is not started, the printer 101 may not do anything in particular. In this case, for example, when starting the AP mode, the printer 101 may start 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 process to S409.

[0049] In S409, the printer 101 transmits an Association Request frame to the AP connected in the STA mode. If there is non-preferred channel information, an Association Request frame including the non-preferred channel information and information related to the Wi-Fi Agile Multiband standard is transmitted.

[0050] As described above, in this embodiment, the printer 101 can notify the AP of the connection destination in advance of information indicating the channel being used in AP mode as information on the channel to be excluded from the candidates for roaming destinations. This allows the AP to exclude the network using the notified channel from the candidates for roaming destinations in the roaming instruction. Then, the printer 101 can receive a roaming instruction in which the network using the channel being used in AP mode is excluded from the candidates for roaming destinations. As a result, the printer 101 can prevent the channels used in STA mode and AP mode from becoming the same channel after roaming in STA mode. In other words, it is possible to prevent strong interference between the communication in STA mode and the communication in AP mode after roaming in STA mode.

[0051] In the present embodiment, an example in which each determination process is performed only on the channel in use in the AP mode has been described, but the present invention is not limited to this. For example, each determination process may be performed based on not only the channel in use in the AP mode, but also on surrounding channels such as adjacent channels of the channel. For example, in the 2.4 GHz band, interference between adjacent channels is likely to occur. For this reason, all surrounding channels that are expected to cause strong interference with each other may be included in the Non-preferred Channel so that networks using those channels are excluded from roaming targets. Note that only the channel used in the AP mode may be notified to the AP 102, and the AP 102 may determine to exclude networks using surrounding channels that are expected to cause strong interference with the notified channel from roaming targets. In addition, when the printer 101 supports multiple frequency bands such as 2.4 GHz / 5 GHz / 6 GHz, all channels in the frequency band including the channel used in the AP mode may be included in the Non-preferred Channel. This makes it possible to suppress the occurrence of roaming in the STA mode to the frequency band to which the channel in use in the AP mode belongs, and to more reliably suppress the occurrence of interference between both modes.

[0052] In the above embodiment, the printer 101 determines whether to include information on the channel being used in AP mode in the Association Request frame when connecting to an AP in STA mode, but this is not limited to the above. For example, when the printer 101 is connected to an AP, the printer 101 may notify the AP to which the printer 101 is connected of Non-preferred Channel information. For example, after establishing a connection with the AP, the printer 101 may transmit a WNM-Notification Request frame including a Non-preferred Channel to the AP. For example, the printer 101 may transmit a WNM-Notification Request frame to the AP after starting the AP mode. Also, the printer 101 may transmit this frame to the AP before starting the AP mode. For example, the printer 101 may transmit this frame when starting the AP mode after connecting to an AP in STA mode, or when restarting the AP mode on a different channel while connected to an AP in STA mode.

[0053] [Embodiment 2] In the above-described first embodiment, the printer 101 notifies the AP 102 to which it is connected in STA mode of information indicating the channel used in AP mode, and the AP 102 excludes the network using that channel from candidates for roaming destinations. In this embodiment, a process will be described for preventing AP mode communication and STA mode communication in the printer 101 from interfering with each other due to roaming when the printer 101 does not notify the AP 102 of information indicating the channel used in AP mode.

[0054] FIG. 6 shows an example of the flow of processing executed in the system according to this embodiment. In FIG. 6, in the system of FIG. 1, the printer 101 activates the AP mode to form a network 111, the STA 105 connects to the network 111, and data communication is performed between the printer 101 and the STA 105 (F601). When the printer 101 receives an instruction for an Infra connection in this state, it searches for a surrounding AP for connection in the STA mode. Here, the printer 101 receives a Beacon frame from the AP 102 (F602), and executes a connection process with the AP 102 based on the Beacon frame (F603). Note that the Beacon frame includes the information described in the above-mentioned embodiment 1. Note that in this embodiment, the printer 101 transmits an Association Request frame when connecting to an AP without including information on the channel used in the AP mode as a Non-preferred channel. In one example, the printer 101 transmits such an Association Request frame when the pre-interference avoidance setting during roaming as described in S401 above is disabled. However, this is just one example, and an Association Request frame that does not include information on the channel used in the AP mode as a non-preferred channel for other reasons may be transmitted. Note that the connection process of F603 is similar to the process described with reference to F306 to F308 in the first embodiment, except that information on the channel used in the AP mode is not included in the Association Request frame. When the printer 101 establishes a connection with the AP 102, it performs data communication with the AP 102 (F604).

[0055] Thereafter, the AP 102 detects that the network 112 formed by the AP 102 itself is congested and decides to transfer the connected STA to another network. The congestion detection can be performed by the method described in the first embodiment. Here, the AP 102 determines to transfer the printer 101 to another network in response to detecting the congestion of the network 112. Here, as described above, the network 113 formed by the AP 103 and the network 114 formed by the AP 104 exist as candidates for roaming destinations from the network 112. Of these networks, the AP 102 selects the network 113 formed by the AP 103 as a candidate for roaming destination. This selection can be performed, for example, based on information on the congestion levels of the networks 113 and 114. For example, when the network 114 is congested, the AP 102 can remove the network 114 from the candidates for roaming destinations and select the network 113 as a candidate for roaming destination. In accordance with this selection, the AP 102 transmits a BTM Request frame including information about the network 113 to the printer 101 (F605). Note that the BTM Request frame may be used to notify only information capable of identifying the network, such as the BSSID of the network 113, or may also be used to notify information about the channels used in the network. If the AP 102 notifies only the BSSIDs of the roaming candidate networks, the printer 101 must separately identify the channels used in each network. The printer 101 can identify the channels used in the roaming candidate networks by, for example, receiving Beacon frames in each of the available frequency channels. The printer 101 may also separately receive information indicating the channels used in the roaming candidate networks from the AP 102 or the like.

[0056] When the printer 101 receives the BTM Request frame, it executes a roaming instruction reception determination process based on the information contained in the frame (F606). Here, the only candidate for a roaming destination is the network 113, which uses the same channel (6ch) as the channel used in the AP mode of the printer 101. Therefore, the printer 101 may decide to change the channel used in the AP mode in order to roam to the network 113. Details of the roaming instruction reception determination process will be described later.

[0057] The printer 101 transmits a BTM Response frame including information indicating that roaming is to be performed and information on the roaming destination network 113 to the AP 102 (F607). Then, the printer 101 executes processing for changing the channel to be used in the AP mode. In this processing, the printer 101 executes processing for changing the channel to be used and restarting the AP mode. That is, the printer 101 executes processing for restarting the AP mode so as to use a channel different from the channel used in the roaming destination network in the AP mode. Also, if the STA 105 connected to the network 111 complies with the Wi-Fi Agile Multiband standard, the printer 101 roams the STA 105 to the network to be formed in the AP mode after the restart. For this processing, first, the printer 101 transmits a BTM Request message to the STA 105 (F608). The BTM Request message can include information on the AP mode after the restart and information on the time until roaming is started. This information on the time until roaming is started is specified based on, for example, the time required to restart the AP mode in the printer 101. When the STA 105 receives the BTM Request message from the printer 101, it determines whether or not roaming can be performed, and transmits a BTM Response message to the printer 101 (F609). It is assumed here that the STA 105 determines that roaming can be performed, and transmits a BTM Response message including information indicating that roaming will be performed to the printer 101. The printer 101 and the STA 105 then perform a process of disconnecting the STA 105 from the network 111 (F610). Thereafter, the printer 101 executes a process of restarting the AP mode so as to change the channel to be used in the AP mode from the currently used channel (F611). It is assumed here that the printer 101 has changed the channel to be used from 6ch to 8ch.

[0058] After restarting the AP mode, the printer 101 disconnects the connection with the AP 102 in the STA mode (F612). Next, the printer 101 executes processing for re-establishing a connection in the AP mode based on information of the BTM Request frame and the BTM Response frame previously transmitted and received between the printer 101 and the STA 105 (F613). Then, in the AP mode, the printer 101 performs data communication with the STA 105 after completing this connection processing (F614). Also, in the STA mode, the printer 101 performs connection processing with the AP 103, which is the roaming destination, based on information of the BTM Request frame from the AP 102 (F615). This connection processing is the same as the processing of F603 described above. Then, in the STA mode, the printer 101 performs data communication with the AP 103 (F616).

[0059] In the above example, the BSS candidate list in the BTM Request frame from the AP 102 in F605 includes only the BSS (network 113) formed by the AP 103. Here, the network 113 uses 6ch, which is the same channel used by the printer 101 in the AP mode. Therefore, the printer 101 performs a process to change the channel used in the AP mode in order to roam to the network 113 in the STA mode. On the other hand, the BTM Request frame from the AP 102 may include both the BSSs (networks 113 and 114) formed by the AP 103 and the AP 104, respectively. The channel used in the network 114 is different from the channel used by the printer 101 in the AP mode. Therefore, the printer 101 does not need to change the channel used in the AP mode by deciding to roam to the network 114 in the STA mode. An example of such a process is shown in FIG. 7. Note that in FIG. 7, the same reference numerals are used for the processes similar to those in FIG. 6, and the description thereof is omitted.

[0060] In the example of FIG. 7, it is assumed that the AP 102 selects both the network 113 formed by the AP 103 and the network 114 formed by the AP 104 as candidates for roaming destinations. In this case, the AP 102 transmits a BTM Request frame including information on both the network 113 and the network 114 to the printer 101 in accordance with this selection (F701). When the printer 101 receives the BTM Request frame, it executes a reception determination process for a roaming instruction based on the information included in the frame (F702). In this case, the candidates for roaming destinations include the network 114 using a channel different from the channel (6ch) used in the AP mode of the printer 101. Therefore, the printer 101 decides to roam to the network 114. Then, the printer 101 transmits a BTM Response frame including information indicating that roaming to the network 114 will be executed to the AP 102 (F703). Then, the printer 101 disconnects from the AP 102 (F704). Thereafter, the printer 101 executes a process for connecting to the AP 104 that provides the roaming destination network 114 (F705). Then, the printer 101 connects to the AP 104, and when roaming is completed, performs data communication with the AP 104 (F706). Note that the process of F703 to F706 is the same as the process of F311 to F314 in FIG. 3.

[0061] Next, an example of the flow of the roaming instruction reception determination process executed in the printer 101 in the above-mentioned F606 and F702 will be described with reference to Fig. 8. The printer 101 can execute the process in Fig. 8 by, for example, reading and executing a computer program stored in the storage unit 209 by the control unit 210. Note that this is just one example, and dedicated hardware for executing at least a part of the process in Fig. 8 may be provided.

[0062] When the printer 101 receives a roaming instruction from the connected AP (YES in S801), it determines whether or not the AP mode is active (S802). Note that a BTM Request frame may be used as a roaming instruction from the AP, but other frames may also be used. If the AP mode is active (YES in S802), the printer 101 proceeds to S803, and if the AP mode is not active (NO in S802), the printer 101 proceeds to S809. In S809, the printer 101 transmits a BTM Response frame including information indicating that roaming will be performed to the AP.

[0063] In S803, the printer 101 checks the list of candidates for the BSS of the roaming destination included in the BTM Request frame, and determines whether the candidates include a BSS that uses a channel different from the channel being used in the AP mode. The list of candidates for the BSS of the roaming destination is notified using, for example, a BSS Transition Candidate List included in the BTM Request frame. If the candidates include a BSS that uses a channel different from the channel being used in the AP mode (YES in S803), the printer 101 advances the process to S804. On the other hand, if the candidates do not include a BSS that uses a channel different from the channel being used in the AP mode (NO in S803), the printer 101 advances the process to S805. If the candidates include only BSSs that use channels that are expected to strongly interfere with communication in the AP mode, such as channels adjacent to the channel being used in the AP mode, the printer 101 may advance the process to S805.

[0064] In S804, the printer 101 selects a BSS using a channel different from the channel being used in AP mode as a roaming destination. Then, in S809, the printer 101 transmits a BTM Response frame including information indicating that roaming will be performed to the AP. Then, the printer 101 performs roaming in accordance with the roaming instruction from the AP in the BTM Request frame (S810).

[0065] In S805, the printer 101 determines whether roaming is possible. For example, the printer 101 is in a state where only BSSs using the same channel as the channel used in the AP mode can be selected as candidates for roaming destinations. For this reason, the printer 101 determines that roaming is not possible when, for example, the printer 101 is in a state where it is not possible to restart the AP mode (NO in S805). For example, the printer 101 may determine that roaming is not possible when, for example, an interruption in data communication due to restarting the AP mode during printing processing, etc., is not acceptable between the STA connected using the AP mode and the printer 101 and the printer 101 is not able to restart the AP mode and the printer 101 may determine that roaming is not possible. In addition, the printer 101 may receive, for example, a user setting via a user interface as to whether or not to allow the use of the same channel in the AP mode and the STA mode. Then, the printer 101 may determine that roaming is not possible when only BSSs using the same channel as the channel used in the AP mode are included in the candidates and the printer 101 does not allow the use of the same channel in the AP mode and the STA mode. If the printer 101 determines that roaming cannot be performed (NO in S805), the process proceeds to S806. On the other hand, if the printer 101 determines that roaming can be performed (YES in S805), the process proceeds to S807.

[0066] In S806, the printer 101 transmits a BTM Response frame including information indicating that roaming will not be performed to the AP. In S807, the printer 101 transmits a BTM Response frame including information indicating that roaming will be performed to the AP, and then performs processing to change the channel used in AP mode (S808). The processing to change the channel used in AP mode will be described later. Then, after changing the channel used in AP mode, the printer 101 performs roaming in accordance with the roaming instruction (S810).

[0067] In the above-mentioned FIG. 6, an example was described in which only the BSS (network 113) formed by AP 103 is included in the BSS candidate list in the BTM Request frame from AP 102. Here, in the network 113, 6ch is used, which is the same channel used by the printer 101 in AP mode. Therefore, in this case, the printer 101 determines that the candidates do not include a BSS using a channel different from the channel being used in AP mode (NO in S803). Then, when the printer 101 determines to perform roaming (YES in S805), it changes the channel used in AP mode (S808) and performs roaming in STA mode (S810). On the other hand, in FIG. 7, both of the BSSs (networks 113 and 114) formed by AP 103 and AP 104 are included in the BTM Request frame from AP 102. Then, in the network 114, 11ch is used, which is different from the channel used by the printer 101 in AP mode. Therefore, in this case, the printer 101 determines that the candidates include a BSS that uses a channel different from the channel being used in the AP mode (YES in S803). In this case, the printer 101 selects that network 114 as a roaming destination (S804) and executes roaming (S810).

[0068] In the above example, a method for determining 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 method for selecting a roaming destination network is not limited to this. For example, priority information may be included in the BTM Request frame, and a roaming destination network may be selected based on this priority information and the communication status. For example, the printer 101 may determine whether the same channel as that in the AP mode is used in the BSS candidate list, starting with the BSS with the highest priority, and determine whether to select the BSS as a roaming destination. Note that the priority may be used to change the criteria for determining whether roaming is possible depending on the communication status in the AP mode and the STA mode. In one example, when the priority is a first value, it may be determined that roaming is possible if the channel used in the AP mode can be changed. On the other hand, when the priority is a second value lower than the first value, it may be determined that roaming is not possible when it is necessary to change the channel used in the AP mode. In addition, when the priority is a first value, it may be determined that roaming is possible even if the channel used in AP mode cannot be changed immediately, and when the priority is a second value, it may be determined that roaming is possible on the condition that the channel used in AP mode is changed immediately.

[0069] Next, an example of the flow of the process of changing the channel used in the AP mode executed in S808 will be described with reference to FIG. 9. First, the printer 101 determines whether or not there is an STA connected to the network 111 formed in the AP mode (S901). If there is an STA connected to the network 111 (YES in S901), the printer 101 proceeds to the process of S902. On the other hand, if there is no STA connected to the network 111 (NO in S901), the printer 101 proceeds to the process of S907. In S902, the printer 101 determines whether or not the connected STA supports the Wi-Fi Agile Multiband standard. The printer 101 can make this determination based on, for example, information included in an Association Request frame or a Probe Request frame received during the process of connecting with the STA. For example, the printer 101 can determine that the STA supports the Wi-Fi Agile Multiband standard when information indicating that the STA supports the Wi-Fi Agile Multiband standard is included in any of these frames. If the printer 101 determines that the connected STA does not support the Wi-Fi Agile Multiband standard (NO in S902), the process proceeds to S903. On the other hand, if the printer 101 determines that the connected STA supports the Wi-Fi Agile Multiband standard (YES in S902), the process proceeds to S905.

[0070] In S903, since the connected STA does not support the Wi-Fi Agile Multiband standard, the printer 101 needs to change the channel to be used in the AP mode by another method. In this embodiment, the printer 101 transmits a Channel Switch Announcement frame including information on the changed channel to the STA, and notifies the STA of the change in the channel to be used (S903). However, this is only an example, and the channel to be used in the AP mode may be changed by another method. Note that when the Channel Switch Announcement frame is used, it is not necessary to restart the AP mode. Then, the printer 101 changes the setting so that a channel different from the channel used in the roaming destination network in the STA mode is used in the AP mode (S904). Note that the printer 101 may select a channel different from the channel used in the connected network and the roaming destination network in the STA mode as the channel to be used in the AP mode at this time. The printer 101 may also select a channel different from the channel used in the BSS included in the candidate list of the BSS included in the BTM Request frame received from the connected AP in the STA mode. This allows the printer 101 to reduce the possibility that the channel used in the AP mode will be the same as the channel to which the printer 101 may roam in the STA mode.

[0071] In S905, the printer 101 transmits a BTM Request frame to the STA that supports the Wi-Fi Agile Multiband standard, instructing the STA to roam to a network formed in the AP mode after the restart. The BTM Request transmitted here includes information about the network configured in the AP mode after the restart. The information includes information about the channel used in the network. In this case, the printer 101 may change the BSSID to a second BSSID different from the current first BSSID and restart the AP mode, and the BTM Request frame may include the second BSSID after the restart. In addition, the BTM Request frame may include time information until the connection process can be started by roaming, taking into account the time required to restart the AP mode. When the STA receives the BTM Request frame, it performs roaming based on the time information included in the frame until the connection process by roaming can be started. For this reason, by starting the connection process by roaming of the STA according to the time required to restart the AP mode in the printer 101, the period during which the printer 101 is disconnected from the STA in the AP mode can be shortened.

[0072] After transmitting the BTM Request frame, the printer 101 waits for a BTM Response frame to arrive from the STA that is the destination of the frame (S906). When the printer 101 receives the BTM Response frame (YES in S906), the printer 101 advances the process to S907. If the printer 101 receives a BTM Response frame including information indicating that the STA cannot perform roaming, the printer 101 may determine, for example, in S805 that roaming is not possible. In this case, the printer 101 may execute the process of S807 after executing the process of S808. Furthermore, the printer 101 may forcibly restart the AP mode even if it receives a BTM Response frame including information indicating that the STA cannot perform roaming.

[0073] In S907, the printer 101 restarts the AP mode on a channel different from the channel used in the network to which the printer 101 roamed in the STA mode. Note that the printer 101 may determine the channel to be used in the AP mode after the restart using criteria similar to those described in relation to S904.

[0074] In this manner, when a network using a channel different from the channel used in the AP mode exists as a candidate for a roaming destination in the STA mode, the printer 101 determines the network as a roaming destination. In addition, when the channel of 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 channels used in the AP mode and the STA mode from being the same after roaming in the STA mode is performed. Therefore, it is possible to prevent the communication in the AP mode and the communication in the STA mode from interfering with each other due to roaming. In the above example, an example of a process in which the channel used in the AP mode is changed when the channel of the roaming destination in the STA mode and the channel used in the AP mode match is described, but this is not limited to this. For example, even if the channel of the roaming destination in the STA mode and the channel used in the AP mode do not match, when these channels have a relationship of mutual interference, the channel used in the AP mode may be changed. For example, when the channel of the roaming destination in the STA mode is a peripheral channel such as an adjacent channel of the channel used in the AP mode, the channel used in the AP mode may be changed. Similarly, the printer 101 can select, as a candidate for a roaming destination in the STA mode, a network that uses a channel that does not interfere with the channel used in the AP mode.

[0075] In this specification and claims, the term "mutually interfering relationship" refers to a relationship in which the interference level exceeds a predetermined value when signals of a predetermined power are communicated. For example, when the power value of a component of a signal of a first channel among a plurality of channels leaking to a second channel is attenuated by a predetermined amount or more compared to the peak power in the first channel, these channels can be identified as having a relationship in which they do not interfere with each other. That is, when a signal transmitted in the first channel is sufficiently attenuated in the frequency range of the second channel so that the influence is sufficiently small, these channels can be identified as having a relationship in which they do not interfere with each other. Conversely, when the attenuation of the power of the signal component leaking to the second channel from the peak power in the first channel falls below a predetermined amount and a large power leaks to the second channel, these channels can be identified as having a relationship in which they interfere with each other. This relationship can be specified in advance, for example, by desk calculation.

[0076] In the above two embodiments, the printer 101 operates as both an STA and an AP. The AP here may be read as Group Owner (GO) of Wi-Fi Direct (registered trademark). The above process may also be applied when the printer 101 operates in a second STA mode instead of the AP mode, that is, when the printer 101 participates in multiple networks as an STA. The second STA mode here may be, for example, a mode in which the printer operates as a P2P Client of Wi-Fi Direct. More generally, the above process may be executed when a communication device connectable to multiple networks needs to roam from a first network to a second network among the multiple networks.

[0077] That is, in the first embodiment, the communication device can be said to notify information on a frequency channel used in a third network among a plurality of networks to another communication device having a function of instructing roaming from a first network to a second network. In addition, when there are a plurality of third networks, the communication device can notify the other communication device of information on a frequency channel used in each of the plurality of third networks. Furthermore, a priority may be assigned to each of the plurality of third networks, and the communication device can notify the other communication device of information on a frequency channel used in each of a predetermined number of networks in descending order of priority among the plurality of third networks. In other words, the communication device may notify the other communication device of all of the frequency channels used in each of the plurality of third networks, or may notify the other communication device of only a part of them. When the communication device receives an instruction for roaming based on the notification from the other communication device, it can execute roaming based on the instruction. In addition, the other communication device can generally be a base station (AP) of the first network, but may also be a control device other than a base station. For example, a control device may be provided that adjusts the load across the network, and the control device may instruct the communication device to roam from one network connection to another network connection via any network to which the communication device is connected.

[0078] In the second embodiment, when a communication device receives an instruction to roam from a first network to a second network from another communication device, the communication device determines whether the second network and a third network among the multiple networks use the same frequency channel. Then, when a first frequency channel used in the second network and a second frequency channel used in the third network match, the communication device changes the frequency channel used in the third network to a third frequency channel. Note that, when the first frequency channel and the second frequency channel are in a mutually interfering relationship as described above, the communication device may change the second frequency channel to a third frequency channel. Note that, the communication device may receive one or more second networks as candidates for a roaming destination. Then, when there is a candidate network for a roaming destination that uses a frequency channel that is not in a mutually interfering relationship with the second frequency channel, the communication device may roam to the candidate network. Note that, the communication device may receive information on the frequency channel used in the second network in the roaming instruction, or may obtain the information separately from the roaming instruction.

[0079] As described above, the procedures described in the above two embodiments are applicable to any communication device that can connect to multiple networks. That is, even if the communication device is not necessarily compliant with the IEEE802.11 series standard, the above procedures can be used to suppress interference with other networks caused by roaming of one network.

[0080] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0081] (Summary of the embodiment) At least some of the above-described embodiments can be summarized as follows. (Item 1) 1. A communication device, comprising: A communication means for wirelessly communicating; a notification means for notifying another communication device having a function of instructing roaming from a first network to a second network when the communication device is connected to the first network of information on a frequency channel used in a third network in which the communication device can communicate in parallel with the first network as information on a frequency channel in which the communication device cannot roam; an execution means for executing roaming based on the instruction when the instruction for roaming based on the notification is received from the other communication device after connecting to the first network; A communication device comprising: (Item 2) The communication device described in item 1 is a wireless LAN communication device that complies with the IEEE 802.11 series standard, and information on a frequency channel used in the third network is notified to the other communication device as a Non-preferred Channel in a frame communicated via the wireless LAN. (Item 3) 3. The communication device according to item 2, wherein the communication means participates in the first network as a station and forms the third network as an access point. (Item 4) 3. The communication device according to item 2, wherein the communication means communicates using the third network as a Group Owner in Wi-Fi Direct (registered trademark). (Item 5) 5. The communication device according to item 3 or 4, wherein the other communication device is an access point forming the first network. (Item 6) 6. The communication device according to item 5, wherein the notification means performs the notification by transmitting an Association Request frame including the Non-preferred Channel to the other communication device. (Item 7) 7. The communication device according to item 5 or 6, wherein the notification means performs the notification by transmitting a WNM-Notification Request frame including the Non-preferred Channel to the other communication device. (Item 8) The communication device according to any one of items 1 to 7, characterized in that the notification means notifies the other communication device of information on a frequency channel that is expected to be used when connecting to the third network when the third network is not being used, as information on a frequency channel that cannot be roamed. (Item 9) The communication device according to any one of items 1 to 8, characterized in that, when notifying information of a frequency channel used in the third network, the notification means further notifies information of a frequency channel adjacent to the frequency channel. (Item 10) The communication device according to any one of items 1 to 8, characterized in that the notification means notifies information about a frequency band including the frequency channel used in the third network as information about the frequency channel. (Item 11) The communication device according to any one of items 1 to 10, characterized in that the notification means notifies the other communication device of information on a frequency channel used in the third network based on the presence of a device connected to the communication device in the third network. (Item 12) The communication device according to any one of items 1 to 11, characterized in that the notification means determines whether or not to notify the other communication device of information about a frequency channel used in the third network based on a congestion status of the frequency channel used in the third network. (Item 13) 3. The communication device according to item 2, wherein the communication means participates in the first network as a station and also participates in the third network as a station. (Item 14) A control method executed by a communication device that communicates wirelessly, comprising: notifying another communication device having a function of instructing roaming from the first network to a second network when the communication device is connected to the first network of information on a frequency channel used in a third network in which the communication device can communicate in parallel with the first network as information on a frequency channel in which the communication device cannot roam; after connecting to the first network, when an instruction for roaming based on the notification is received from the other communication device, performing roaming based on the instruction; A control method comprising: (Item 15) A program for causing a computer to function as each of the means possessed by the communication device according to any one of items 1 to 13.

[0082] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0083] 101: printer, 102 to 104: access points, 105: station, 207: STA function unit, 208: AP function unit

Claims

1. 1. A communication device, comprising: A communication means for wirelessly communicating; a notification means for notifying another communication device having a function of instructing roaming from the first network to a second network when the communication device is connected to the first network of information on a frequency channel used in a third network in which the communication device can communicate in parallel with the first network as information on a frequency channel in which the communication device cannot roam; an execution means for executing roaming based on the instruction when the instruction for roaming based on the notification is received from the other communication device after connecting to the first network; A communication device comprising:

2. The communication device according to claim 1, characterized in that the communication device is a wireless LAN communication device conforming to the IEEE 802.11 series standard, and information on a frequency channel used in the third network is notified to the other communication device as a Non-preferred Channel in a frame communicated by the wireless LAN.

3. 3. The communication device according to claim 2, wherein said communication means participates in said first network as a station and forms said third network as an access point.

4. 3. The communication device according to claim 2, wherein the communication means communicates using the third network as a Group Owner in Wi-Fi Direct (registered trademark).

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

6. 6. The communication device according to claim 5, wherein the notification means performs the notification by transmitting an Association Request frame including the Non-preferred Channel to the other communication device.

7. 6. The communication device according to claim 5, wherein said notification means performs said notification by transmitting a WNM-Notification Request frame including said Non-preferred Channel to said other communication device.

8. The communication device according to claim 1, characterized in that the notification means notifies the other communication device of information on a frequency channel that is expected to be used when connecting to the third network when the third network is not being used, as information on a frequency channel that cannot be roamed.

9. 2. The communication device according to claim 1, wherein the notification means, when notifying information of a frequency channel used in the third network, further notifies information of a frequency channel adjacent to the frequency channel.

10. 2. The communication device according to claim 1, wherein the notification means notifies information on a frequency band including the frequency channel used in the third network as the information on the frequency channel.

11. The communication device according to claim 1, characterized in that the notification means notifies the other communication device of information about a frequency channel used in the third network based on the existence of a device connected to the communication device in the third network.

12. The communication device according to claim 1, characterized in that the notification means determines whether or not to notify the other communication device of information about a frequency channel used in the third network based on a congestion status of the frequency channel used in the third network.

13. 3. The communication device according to claim 2, wherein said communication means participates in said first network as a station and also participates in said third network as a station.

14. A control method executed by a communication device that communicates wirelessly, comprising: notifying another communication device having a function of instructing roaming from the first network to a second network when the communication device is connected to the first network of information on a frequency channel used in a third network in which the communication device can communicate in parallel with the first network as information on a frequency channel in which the communication device cannot roam; after connecting to the first network, when an instruction for roaming based on the notification is received from the other communication device, performing roaming based on the instruction; A control method comprising:

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

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