Communication apparatus, method of controlling the same, and storage medium

Abstract

To enable communication connection with an appropriate external device in a communication device capable of communicating with the external device by a plurality of links using a plurality of frequency bands.SOLUTION: A communication device capable of performing multi-link communication using a plurality of links having different frequency bands receives one or more frames transmitted from each of a plurality of external devices via one or more links, and determines an external device that is a transmission source of the one or more frames based on a parameter included in each of the one or more frames. When two or more frames are received from one external device via two or more different links, the communication device determines that transmission sources of the two or more frames are the one external device, and determines a priority order of communication connections of the plurality of external devices based on communication states of the frames whose transmission sources are determined to be the same external device.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a communication device, a control method thereof, and a program. [Background technology]

[0002] With the recent increase in the amount of data being communicated, development of communication technologies such as wireless local area networks (LANs) is progressing. The IEEE (Institute of Electrical and Electronics Engineers) 802.11 standard series is known as a major communication standard for wireless LANs. The IEEE 802.11 standard series includes standards such as IEEE 802.11a / b / g / n / ac / ax. For example, the latest standard, IEEE 802.11ax, uses orthogonal frequency division multiple access (OFDMA) to standardize technology that not only achieves a high peak throughput of up to 9.6 gigabits per second (Gbps) but also improves communication speeds under congested conditions (see Patent Document 1). OFDMA stands for Orthogonal Frequency Division Multiple Access.

[0003] A task group called IEEE802.11be was established as a successor standard aiming to further improve throughput, frequency utilization efficiency, and communication latency. IEEE802.11be considers multi-link communication. In multi-link communication, one access point (AP) establishes multiple links with one station (STA) using frequency bands such as 2.4GHz, 5GHz, and 6GHz, and communicates simultaneously. A communication device that operates in multi-link mode is called a multi-link device (MLD). One MLD has a configuration equivalent to multiple STAs or multiple APs, each associated with a different link. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-050133 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, the range of radio waves varies depending on the frequency. The lower the frequency, the greater the diffraction, resulting in a longer reach. The higher the frequency, the less diffraction, resulting in a shorter reach. Even if there is an obstacle along the way, low-frequency radio waves can navigate around the obstacle, while high-frequency radio waves, due to their high directivity, have difficulty navigating and may not reach their destination. On the other hand, the 2.4 GHz frequency is also widely used by other devices; for example, microwave ovens are known to emit radio waves in the same frequency band. Thus, even when radio waves are emitted by the same communication device, differences in the signal strength and signal-to-noise (SN) ratio can occur depending on the location and environment. Therefore, even if a STA can connect to an AP capable of communicating over multiple frequency bands in multi-link communication, the signal strength and SN ratio in certain frequency bands may be degraded, potentially preventing communication using multiple links.

[0006] The present invention provides a technique that enables a communication device capable of communicating with external devices via a plurality of links using a plurality of frequency bands to select an appropriate external device as a target for communication connection. [Means for solving the problem]

[0007] A communication device according to one aspect of the present invention comprises the following arrangement: A communication device capable of performing multi-link communication using a plurality of links with different frequency bands, receiving means for receiving one or more frames transmitted from each of a plurality of external devices via one or more links; a determination means for determining an external device that is a sender of the one or more frames based on a parameter included in each of the one or more frames, the determination means determining that the sender of the two or more frames is the one external device when two or more frames are received from a single external device via two or more different links; and a determining means for determining the priority of communication connections of the plurality of external devices based on the communication status of frames determined by the determining means to be sent from the same external device. [Effects of the Invention]

[0008] According to the present invention, in a communication device capable of communicating with external devices via a plurality of links using a plurality of frequency bands, it is possible to select an appropriate external device as a target for communication connection. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of a network configuration according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of the hardware configuration of a communication device according to the first embodiment. [Figure 3] FIG. 2 is a block diagram showing an example of the functional configuration of a communication device according to the first embodiment. [Figure 4] 5 is a flowchart showing a process of determining a priority order according to the first embodiment. [Figure 5] FIG. 10 is a diagram showing an example of elements assigned in accordance with a multi-link operation. [Figure 6] 10 is a flowchart showing a process of determining a priority order in a multi-link priority mode. [Figure 7] 10 is a flowchart showing a process of determining a priority order in the RSSI priority mode. [Figure 8] FIG. 10 is a diagram showing an example of a graphic user interface display. [Figure 9] 10 is a flowchart showing a reconnection process according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0011] [First embodiment] (Configuration of wireless communication system) 1 shows an example of the configuration of a network to which a communication device 101 (hereinafter, STA101) according to this embodiment is connected. Communication devices 102 to 104 (hereinafter, AP102 to 104) are access points (APs) that serve to construct a wireless network. Each of the APs 102 to 104 can communicate with the STA 101. The STA 101 can connect to the network by connecting and communicating with any of the APs 102 to 104.

[0012] Each of the APs 102 to 104 and the STA 101 can perform wireless communication in accordance with the IEEE 802.11be (EHT) standard. IEEE stands for Institute of Electrical and Electronics Engineers. The APs 102 to 103 and the STA 101 are multilink devices (MLDs) capable of communication in the 2.4 Hz, 5 GHz, and 6 GHz frequency bands. In this embodiment, the AP 104 does not support multilink communication. The frequency bands used by each communication device are not limited to the above example, and the number of frequency bands is not limited to three. Other frequency bands, such as the 60 GHz band, may also be available. The APs 102 to 104 and the STA 101 can communicate using bandwidths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 320 MHz. However, the bandwidths used by each communication device are not limited to these, and different bandwidths, such as 240 MHz or 4 MHz, may also be used.

[0013] The APs 102 to 104 and the STA 101 perform OFDMA communication compliant with the IEEE 802.11be standard, thereby realizing multi-user (MU) communication by multiplexing signals from multiple users. OFDMA stands for Orthogonal Frequency Division Multiple Access. In OFDMA communication, portions of the divided frequency band (RU, Resource Unit) are assigned to each STA without overlapping, and the carrier waves of each STA are orthogonal. This allows the AP to communicate with multiple STAs in parallel within a specified bandwidth.

[0014] Although the APs 102 to 104 and the STA 101 are described as being compatible with the IEEE 802.11be standard, they may also be compatible with legacy standards that predate the IEEE 802.11be standard. Specifically, the APs 102 to 104 and the STA 101 may be compatible with at least one of the IEEE 802.11a / b / g / n / ac / ax standards. Furthermore, in addition to the IEEE 802.11 series standards, they may also be compatible with other communication standards such as Bluetooth (registered trademark), ZigBee, NFC, UWB, and MBOA. Note that NFC stands for Near Field Communication. UWB stands for Ultra Wide Band. MBOA stands for Multi-Band OFDM Alliance. UWB includes Wireless USB, Wireless 1394, WiNET, and the like. Furthermore, the APs 102 to 104 and the STA 101 may also be compatible with wired communication standards such as wired LAN. Specific examples of the APs 102 to 104 include, but are not limited to, wireless LAN routers and personal computers (PCs). The APs 102 to 104 may also be information processing devices such as wireless chips capable of performing wireless communication in accordance with the IEEE 802.11be standard. Specific examples of the STA 101 include, but are not limited to, cameras, tablets, smartphones, PCs, mobile phones, video cameras, and headsets. The STA 101 may also be information processing devices such as wireless chips capable of performing wireless communication in accordance with the IEEE 802.11be standard.

[0015] The APs 102, 103 and the STA 101 also perform multi-link communication, establishing multiple links via multiple frequency channels for communication. The IEEE 802.11 series of standards defines the bandwidth of each frequency channel as 20 MHz. Here, a frequency channel refers to a frequency channel defined in the IEEE 802.11 series of standards, which defines multiple frequency channels for each of the 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz frequency bands. Note that a single frequency channel may utilize a bandwidth of 40 MHz or more by bonding adjacent frequency channels.

[0016] For example, the AP 102 and the STA 101 are capable of establishing and communicating via a link over a first frequency channel in the 2.4 GHz band. The AP 102 and the STA 101 are also capable of establishing and communicating via a link over a second frequency channel in the 6 GHz band in parallel. In this case, the STA 101 and the AP 102 perform multi-link communication, maintaining a first link over the first frequency channel and a second link over the second frequency channel in parallel. By establishing multiple links over multiple frequency channels in this manner, the STA 101 and the AP 102 can improve communication throughput. In this embodiment, the first link provided by the AP 102 operates at 20 MHz, channel 6 in the 2.4 GHz band, and is assigned a link number of 1. The second link provided by the AP 102 operates at 320 MHz, channel 113 in the 6 GHz band, and is assigned a link number of 2.

[0017] Similarly, AP 103 operates using link number 3, which operates at 20 MHz and channel 6 in the 2.4 GHz band, link number 4, which operates at 80 MHz and channel 36 in the 5 GHz band, and link number 5, which operates at 320 MHz and channel 252 in the 6 GHz band. AP 104 operates at 80 MHz and channel 44 in the 5 GHz band, and does not operate in multi-link mode. AP 102 operates with the SSID "Bacardi," AP 103 with the SSID "pudding," and AP 104 with the SSID "PommedEve2." It is also assumed that there are other APs around STA 101. The SSIDs of APs 102 to 104 may be the same.

[0018] In this embodiment, the STA 101 can have a maximum of two links. However, more than two links using different frequency bands may be established for multi-link communication. For example, the STA 101 may be able to establish links in each of the 2.4 GHz band, the 5 GHz band, and the 6 GHz band, or may be able to establish links via multiple different channels within the same frequency band. For example, a link on channel 6 in the 2.4 GHz band may be established as a first link, and a link on channel 1 in the 2.4 GHz band may be established as a second link. Multiple links using the same frequency band and links using different frequency bands may be mixed. For example, the STA 101 may be able to establish a link on channel 6 in the 2.4 GHz band, a link on channel 1 in the 2.4 GHz band, and a link on channel 149 in the 5 GHz band. By establishing multiple connections using different frequency bands, the STA 101 and the APs 102 to 103 can establish communication with the STA 101 using another frequency band even when one band is congested. This prevents a decrease in throughput and communication delays in communication with the STA 101.

[0019] Although the wireless network illustrated in Figure 1 uses three APs and one STA, the number and arrangement of APs and STAs are not limited to this. For example, the wireless network illustrated in Figure 1 may include one more STA. Furthermore, there are no restrictions on the frequency band of each established link, the number of links, bandwidth, etc.

[0020] In multi-link communication, for example, the AP 102 and the STA 101 divide a single piece of data and transmit it to a partner device via multiple links. At this time, the AP 102 and the STA 101 may be capable of MIMO (Multiple-Input and Multiple-Output) communication. In this case, the AP 102 and the STA 101 have multiple antennas, and the transmitting side sends different signals from each antenna using the same frequency channel. The receiving side simultaneously receives all signals arriving from multiple streams using multiple antennas, and separates and decodes the signals of each stream. By performing MIMO communication in this way, the AP 102 and the STA 101 can communicate more data in the same amount of time than if they did not perform MIMO communication. Furthermore, when performing multi-link communication, the AP 102 and the STA 101 may perform MIMO communication on some of the multiple links.

[0021] (AP and STA configuration) 2 shows an example of the hardware configuration of the STA 101 in this embodiment. The STA 101 has a storage unit 201, a control unit 202, a function unit 203, an input unit 204, an output unit 205, a communication unit 206, and an antenna 207. There may be multiple antennas 207. The APs 102 to 104 also have the same hardware configuration as the STA 101.

[0022] The storage unit 201 is configured with one or more memories such as ROM and / or RAM, and stores various information such as computer programs for performing various operations described below and communication parameters for wireless communication. ROM stands for Read Only Memory, and RAM stands for Random Access Memory. In addition to memories such as ROM and RAM, the storage unit 201 may also use storage media such as flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, and DVDs.

[0023] The control unit 202 is configured with one or more processors, such as a CPU or MPU, and controls the entire STA 101 by executing a computer program stored in the storage unit 201. The control unit 202 may control the entire STA 101 in cooperation with the computer program stored in the storage unit 201 and an OS (Operating System). The control unit 202 also generates data and signals (wireless frames) to be transmitted in communication with other communication devices. The CPU stands for Central Processing Unit, and the MPU stands for Micro Processing Unit. The control unit 202 may also include multiple processors, such as a multi-core processor, and may control the entire STA 101 using the multiple processors. The control unit 202 also controls the function unit 203 to perform predetermined processes, such as wireless communication, imaging, printing, and projection. The function unit 203 is hardware that enables the STA 101 to perform predetermined processes.

[0024] The input unit 204 receives various operations from the user. The output unit 205 outputs various types of data to the user via a monitor screen or a speaker. Here, the output from the output unit 205 may be a display on a monitor screen, an audio output from a speaker, a vibration output, or the like. Both the input unit 204 and the output unit 205 may be implemented as a single module such as a touch panel. Furthermore, the input unit 204 and the output unit 205 may be integrated with the STA 101 or may be separate units.

[0025] The communication unit 206 controls wireless communication in accordance with the IEEE 802.11be standard. The communication unit 206 may also control wireless communication in accordance with other IEEE 802.11 series standards in addition to the IEEE 802.11be standard, or control wired communication such as a wired LAN. The communication unit 206 controls the antenna 207 to transmit signals for wireless communication generated by the control unit 202 and receive signals transmitted from the device. The antenna 207 is an antenna capable of communication in the 2.4 GHz, 5 GHz, and 6 GHz bands. While the present embodiment describes the STA 101 having one antenna, the STA 101 may have multiple antennas. Alternatively, the STA 101 may have a different antenna for each frequency band. If the STA 101 has multiple antennas, a communication unit 206 corresponding to each antenna may be provided.

[0026] If the STA 101 supports the NFC standard, Bluetooth standard, or the like in addition to the IEEE 802.11be standard, the communication unit 206 may control wireless communication in accordance with these communication standards. If the STA 101 can perform wireless communication in accordance with multiple communication standards, the STA 101 may have separate communication units 206 and antennas 207 that support each of the communication standards. The STA 101 communicates data such as image data, document data, and video data with an external communication device via the communication unit 206. The antenna 207 may be configured separately from the communication unit 206, or may be configured together with the communication unit 206 as a single module.

[0027] 3 is a block diagram showing an example of the functional configuration of the STA 101 according to this embodiment. As shown in FIG. 3, the STA 101 includes a wireless LAN control unit 301, a frame generation unit 302, a device discrimination unit 303, a priority determination unit 304, a UI control unit 305, a memory control unit 306, and a wireless antenna 307.

[0028] The wireless LAN control unit 301 includes an antenna and circuitry for transmitting and receiving wireless signals to and from other communication devices that communicate over the wireless LAN, as well as a program for controlling these. The wireless LAN control unit 301 controls wireless LAN communications based on frames generated by the frame generation unit 302 in accordance with the IEEE 802.11 standard series. The number of wireless LAN control units 301 is not limited to one, and multiple units may be provided. The frame generation unit 302 generates frames for wireless control to be transmitted by the wireless LAN control unit 301. The content of the frames generated by the frame generation unit 302 may be restricted by settings stored in the storage unit 201, or may be changed by user settings from the UI control unit 305. The generated frames are supplied to the wireless LAN control unit 301 and transmitted to the communication partner via the wireless antenna 307.

[0029] The device identification unit 303 identifies the sender (external communication device) of each of the multiple frames received by the wireless LAN control unit 301 based on parameters included in each of the multiple frames. When two or more frames are received from a single external device via two or more different links, the device identification unit 303 determines that the sender of these two or more frames is a single external device. The priority order determination unit 304 determines the priority order for communication with the external device based on the result of the identification by the device identification unit 303 and the communication status (meta information such as radio wave strength and SNR) of the frames received by the wireless LAN control unit 301. The UI control unit 305 displays a list of connection candidate communication devices on the output unit 205 based on the determined priority order.

[0030] The UI control unit 305 includes hardware related to a user interface, such as a touch panel or buttons, for accepting operations by the user of the STA 101, and a program for controlling these. The UI control unit 305 also has a function for presenting information to the user, such as displaying images or outputting audio. The memory control unit 306 controls writing and reading of various types of information to and from the memory unit 201.

[0031] (Processing flow) Next, a process flow for determining the priority order of connection candidate communication devices (APs) executed by the STA 101 having the above-described configuration in the wireless communication system of this embodiment will be described. FIG. 4 is a flowchart showing the process flow from when the STA 101 searches for APs, determines the priority order of connection candidate APs, and establishes a communication connection with the AP with the highest priority order. The wireless LAN control unit 301 is capable of multi-link communication, as well as communication solely in the 2.4 GHz band, the 5 GHz band, and the 6 GHz band. Note that the effect of this embodiment is not impaired even if communication is not possible in some of these frequency bands. The wireless LAN control unit 301 may also be capable of communication in frequency bands other than the above-described frequency bands.

[0032] AP102, AP103, and AP104 may operate with the same SSID and password, or may operate with different SSIDs and passwords. When multiple APs operate with the same SSID and password, the process shown in FIG. 4 can be used to determine the priority of connection candidate APs in a roaming process to reconnect a disconnected AP. In a system in which multiple APs form a single network, STA101 performs a process to determine the priority of connection candidate APs and connects to the AP with the highest priority. On the other hand, when multiple APs operate with different SSIDs and passwords, STA101 performs the process shown in FIG. 4 when displaying the results of a scan process to the user. In this case, after determining the priority of the APs, STA101 displays a list of connectable APs in the order of priority determined by the process in FIG. 4, as shown in FIG. 8 (described later). For example, when a user selects an AP from the list, STA101 establishes a communication connection with the selected AP.

[0033] The process shown in the flowchart of Fig. 4 starts when STA 101 searches for a network. However, the start of the process shown in Fig. 4 is not limited to this. For example, the process shown in Fig. 4 may start when an AP operating inside STA 101 starts up or when Peer-to-Peer (P2P) starts up. Alternatively, the process shown in Fig. 4 may start when the radio wave strength or SNR value from the connected AP deteriorates or when the quality of communication data deteriorates. For example, the process shown in Fig. 4 may start when the frequency of occurrence of error bits exceeds a threshold.

[0034] The wireless LAN control unit 301 of the STA 101 starts a scan process in response to a user instruction to connect to an AP, an instruction to activate the Wi-Fi function, an instruction to scan, or automatic periodic execution (S401). There are two types of scan processes: passive scan and active scan. If the scan process is passive scan (YES in S402), the wireless LAN control unit 301 receives a beacon transmitted by a surrounding AP (S403). On the other hand, if the scan type is active scan (NO in S402), the wireless LAN control unit 301 transmits a probe request in each frequency band (S404) and receives a probe response from the AP (S405). Beacons and probe responses are generally called management frames, but hereinafter, these frames received in the scan process will be referred to as scan frames. The STA 101 can obtain information about surrounding APs based on the information attached to the scan frame (i.e., beacon or probe response) received in this manner. The scanning process (the processes S402 to S405 enclosed by the dashed line) is executed for a predetermined period of time, and by receiving scanning frames during this period, information about APs around the STA 101 is collected.

[0035] Upon completion of the scanning process, the device identification unit 303 extracts detected scan frames from the received scan frames (S406). Note that in S406, only APs with a matching SSID used for the search and a security method that meets the conditions may be selected. The device identification unit 303 searches for scan frames with a matching source address (MAC address) among the extracted scan frames. If there are multiple scan frames with a matching source address, the device identification unit 303 keeps one of them and discards the others (S407). Note that any method can be used to determine which scan frame to keep from the multiple scan frames with a matching source address. For example, the first scan frame received may be kept, or the scan frame with the largest amount of information may be kept. Alternatively, the scan frame to which a multi-link-related element is attached may be kept. Note that in this embodiment, multiple scan frames transmitted from a single AP over multiple links in different frequency bands each have a different source address. However, this is not limiting, and multiple scanning frames transmitted from one AP via multiple links with different frequency bands may use the same source address (MAC address). In this case, in S407, the device identification unit 303 does not reject scanning frames received via links with different frequency bands, even if they have the same source address.

[0036] Once the received scanning frames have been organized in this manner, the process of determining the priority order of APs (S408 to S410) begins.

[0037] First, the priority determination unit 304 determines whether to use a method of prioritizing multi-link-compatible APs (hereinafter, referred to as multi-link priority mode) as a method of determining the priority of APs when selecting an AP to connect to (S408). The multi-link priority mode is used, for example, when low-latency communication is required. Possible applications for such applications include remote control, AR, VR, and action games, which require low latency. Alternatively, the multi-link priority mode may be selected when a large amount of communication capacity is required in a short period of time, such as AR and VR. In addition, when providing a wireless LAN to stores in a shopping center or using a wireless LAN at home, it is also preferable to select an AP using the multi-link priority mode when communication stability is required. If the multi-link priority mode is not selected, a method of prioritizing APs by prioritizing communication conditions is used. In this embodiment, a method of prioritizing APs with strong RSSI (Received Signal Strength Indicator) (hereinafter, referred to as RSSI priority mode) is used. The RSSI priority mode may be selected when optimization of the connection destination AP is required, such as when using a wireless LAN in facilities such as an airport or a university. In RSSI priority mode, connecting to an AP with stronger radio waves means connecting to an AP that is physically closer, which can prevent interference and congestion with other STAs and APs. Note that the selection between multi-link priority mode and RSSI priority mode is performed by, for example, a user operation.

[0038] If the multi-link priority mode is selected (YES in S408), the priority determination unit 304 performs a priority determination process to determine the priority so as to give priority to the multi-link AP (S410). A specific flow of the priority determination process in the multi-link priority mode in S410 will be described later with reference to the flowchart in FIG. 6. On the other hand, if the RSSI priority mode is selected (NO in S408), the priority determination unit 304 performs a priority determination process in the RSSI priority mode (S409). A specific flow of the priority determination process in the RSSI priority mode in S409 will be described later with reference to the flowchart in FIG. 7. When the priority for connecting to the APs is set in S409 or S410, the wireless LAN control unit 301 attempts a wireless communication connection to the AP with the highest priority (S411).

[0039] Next, the priority order determination process in the multi-link priority mode will be specifically described with reference to the flowchart in Fig. 6. The process shown in Fig. 6 is a subroutine executed in S410 in Fig. 4. The priority order determination unit 304 sequentially selects the scanning frames extracted in S407 and determines the priority order.

[0040] The device identification unit 303 selects one of the scan frames remaining after the process of S407 (S600) and checks whether the communication device that transmitted the selected scan frame is an AP that supports multilink communication (S601). Hereinafter, support for multilink communication is also referred to as "multilink-capable." A specific method for checking whether the transmission AP is multilink-capable is to determine whether an ML element is attached to the received frame. Because the ML element contains information about multilink, there is no need to prepare a separate field indicating multilink capability. Alternatively, for example, a bit indicating multilink capability may be provided in the Extended Capability element attached to the scan frame, and whether the AP is multilink-capable may be determined based on whether the bit is set. In this case, since it is not necessary to attach an ML element to the scan frame, it is possible to indicate whether the AP is multilink-capable while keeping the scan frame size small.

[0041] If it is determined that the source of the selected scanning frame is not multi-link compatible (NO in S601), the device identification unit 303 adds the AP of the source of the selected scanning frame to the candidate list as a new AP candidate (S607). On the other hand, if it is determined that the AP of the source of the selected scanning frame is multi-link compatible (YES in S601), the processing proceeds to S602 and subsequent steps. The device identification unit 303 checks whether the same AP MLD as the AP of the source of the currently selected scanning frame is included in the candidate APs already recorded in the candidate list (S602). Note that the AP MLD is a multi-link compatible AP.

[0042] If the AP transmitting the currently selected scan frame has already been recorded in the candidate list through confirmation of a scan frame received on another link, the device determination unit 303 determines that the AP MLD identical to that of the selected scan frame exists in the candidate list. For example, if the source address of the currently selected scan frame matches one of multiple MAC addresses corresponding to multiple links of the candidate AP listed in the candidate list, the source AP is determined to have been confirmed. If the AP transmitting the scan frame supports multiple links in multiple frequency bands, the scan frame includes MAC address information for the other links. In step S606 (described later), when a new AP is added to the candidate list, the MAC addresses of the other links are also recorded in addition to the MAC address of the scan frame's source. The device determination unit 303 references the MAC addresses of the candidate APs recorded in the candidate list and determines whether there is a candidate AP with a MAC address matching the source address of the scan frame. This makes it possible to determine whether the same AP as the AP transmitting the scan frame exists in the candidate list.

[0043] Alternatively, an ML element may be assigned, and the presence or absence of the same AP in the candidate list may be confirmed by checking whether the MLD MAC address included therein is included in the MLD MAC address of a candidate AP listed in the candidate list. In this case, if an MLD MAC address is present, confirmation may be performed by comparing the MLD MAC addresses. If not, confirmation may be performed by comparing the MAC addresses as described above. In S602, the MLD SSID (see FIG. 5) included in the ML element may be used instead of or in addition to the MLD MAC address. As described with respect to S407, when a single AP uses multiple links with different frequency bands, a configuration may be used that allows the same MAC address to be used across these multiple links. In such a case, the device identification unit 303 may determine whether the same AP as the AP that transmitted the scanning frame is present in the candidate list by checking whether an AP with a MAC address matching the source address of the currently selected scanning frame is present in the candidate list. It is sufficient to be able to determine that an AP is MLD based on any of multiple links. Therefore, even if it cannot be determined that the current scan frame is an AP MLD, if it is later determined that the same MLD is associated with a scan frame from another link, the record in the candidate list may be updated at that point.If it is determined in this way that the candidate list contains the same AP MLD as the AP that sent the scan frame (YES in S602), the process proceeds to S608.

[0044] On the other hand, if it is determined that the AP MLD that is the same as the AP that transmitted the frame is not included in the candidate list (NO in S602), the process proceeds to S603. If the AP that transmitted the selected scanning frame is an AP MLD (multi-link compatible) (YES in S601) and is not included in the candidate list (NO in S602), steps S603 to S606 are executed.

[0045] Here, the ML element will be described. The ML element is attached to a scanning frame transmitted by the AP 102 or AP 103 or to an ML Probe Response, which will be described later. FIG. 5 is a diagram showing an example of the data structure of an ML (Multi-Link) element, which is a type of element defined in IEEE 802.11. The fields that make up an ML element include, from the beginning, an Element ID field 501, a Length field 502, an Element ID Extension field 503, a Multi-Link Control field 504, a common info field 505, and a link information field 506. The combination of the Element ID field 501 and the Element ID Extension field 503 indicates that the element is an ML element. In this example, for an ML element, the values ​​of the Element ID field 501 and the Element ID Extension field 503 are 255 and 94, respectively. However, these values ​​may be different.

[0046] The Multi-Link Control field 504 includes a Type subfield 507, an MLD Address Present subfield 508, and an MLD SSID Present subfield 509. The Type subfield 507 determines the format of the following common info field 505 and link information field 506. The MLD Address Present subfield 508 indicates whether the following common info field 505 contains an MLD MAC Address. The MLD SSID Present subfield 509 indicates whether the following common info field 505 contains an MLD SSID.

[0047] The common info field 505 contains different subfields depending on the value of the Multi-Link Control field 504. Here, the common info field 505 contains an MLD Address subfield 510 and an MLD SSID subfield 511. The MLD Address subfield 510 indicates a 6-octet address (MLD MAC Address) assigned to each source MLD. A communication device receiving a frame via multilink can determine, based on this address, which frames were sent from the same MLD.

[0048] Returning to FIG. 6, if the determination in S602 above is NO, the device identification unit 303 determines whether the selected scanning frame includes an MLD MAC Address (S603). If it is determined that the MLD MAC Address is not included (NO in S603), the process proceeds to S604. The device identification unit 303 transmits an ML Probe Request to the AP that transmitted the scanning frame (S604) and receives an ML Probe Response from the AP (S605). Thereafter, the device identification unit 303 adds the AP that transmitted the selected scanning frame to the candidate list as a new AP MLD (S606). At this time, the device identification unit 303 records the MAC Address, MLD MAC Address, and MAC addresses of links in other frequency bands as information about the transmitting AP in the candidate list. Note that the transmission and reception of the ML Probe Request and ML Probe Response in S603 to S604 in FIG. 6 may be omitted. In this case, an AP that transmitted a scanning frame that does not include an MLD MAC Address is treated as an AP with multiple independently operating links, even if it is multi-link compatible. Alternatively, if the MLD MAC Address of the target AP is included in the link information field 506 (FIG. 5) of another frame, the frame may be treated as a scanning frame transmitted from one of the AP MLD links. Also, when the MLD MAC Address is used in the determination of S602, the processes of S603 to S605 may be executed before S602 so that the MLD MAC Address can be obtained as quickly as possible.

[0049] After checking the AP that sent the selected scanning frame in this way, the priority determination unit 304 checks the RSSI or SN ratio of the received scanning frame (S608). The RSSI and SN ratio are measured when the scanning frame is received and are managed in association with each scanning frame.

[0050] If the same AP MLD is included in the candidate list, the priority determination unit 304 checks whether the link of the confirmed scanning frame and the link of the selected scanning frame are STR (S609). Note that STR stands for simultaneous transmit and receive. Multiple links being STR indicates that the multiple links can simultaneously transmit and receive frames. Conversely, NSTR (Non STR) indicates that frame transmission and reception on one link restricts frame transmission and reception on other links. For example, if multiple links operate on the same channel, frames cannot be transmitted and received on one link while frames are being transmitted and received on the other link. Furthermore, if the frequencies of the two links are close, it is possible that while one link is transmitting frames, the other link can transmit frames but cannot receive frames.

[0051] If it is determined that the RSSI value is stronger than the threshold and that the conditions that links can be connected by STR are met (YES in S609), the priority determination unit 304 increments the number of links that the source AP can support by one (S610). If it is determined that the above conditions are not met (NO in S609), the number of links that the source AP can support is not increased. Note that the conditions of "RSSI is greater than or equal to the threshold," "SN ratio is greater than or equal to the threshold," and "STR or not" may be any one of them, or may include multiple of them. Alternatively, the STR condition (e.g., the threshold for the frequency closeness of links to determine whether STR is possible) may be changed depending on the RSSI or SN ratio value. Alternatively, the threshold for RSSI or SN ratio may be changed depending on whether STR is possible. In this way, the priority determination unit 304 controls the count of the number of links that the AP can support based on the communication state of the scanning frame (based on the RSSI or SN ratio in this embodiment). Note that being an STR can mean either "STA (itself) becomes the STR" or "AP (the other party) becomes the STR" when two links are established, or both.

[0052] In addition, the number of supported links may be held for each AP recorded in the candidate list. For example, the number of supported links, the number of links through which the AP can communicate smoothly, and the number of links through which the AP can STR may be recorded for each AP in the candidate list. Furthermore, the values ​​for each of these items may be used as reference values ​​when determining the priority in the processes of S613 to S615 described below. Furthermore, the threshold used in S609 may be, for example, a level of received radio wave strength that the STA 101 can receive. Alternatively, a level of received radio wave strength that allows smooth communication after connection may be used as the threshold.

[0053] The priority order determination unit 304 checks whether the above process has been performed on all of the scanning frames remaining after the process of S407 (S611). The priority order determination unit 304 repeats the processes of S601 to S611 until the above process has been performed on all of the scanning frames (while the determination in S611 is NO).

[0054] After checking all received scanning frames (YES in S611), the number of supported links for each candidate AP in the candidate list is determined. Next, the priority determination unit 304 determines the priority for communication connection of the candidate APs recorded in the candidate list (S612 to S615). First, the priority determination unit 304 checks whether the candidate list contains a candidate AP with a number of supported links equal to or greater than the number of supported links for the STA 101 (S612). If one or more such candidate APs exist (YES in S612), the priority determination unit 304 determines the priority of the candidate APs so that they are arranged in descending order of RSSI (or descending order of SNR) (S613). Then, the process from S614 onward is performed on candidate APs in the candidate list whose priority has not yet been determined (APs whose number of supported links is less than the number of links for the STA 101). On the other hand, if the candidate list does not contain a candidate AP with a number of supported links equal to or greater than the number of supported links for the STA 101 (NO in S612), the prioritization from S614 onward is performed on all candidate APs in the candidate list.

[0055] The priority determination unit 304 determines the priority of candidate APs in the candidate list whose priority has not yet been determined in descending order of the number of corresponding links (S614). If there are multiple candidate APs with the same number of corresponding links, the priority determination unit 304 determines the priority of the candidate APs so that they are arranged in descending order of RSSI (or SNR) (S615). The RSSI or SNR used in S613 and S615 is the RSSI or SNR of a specific frequency band. In this example, the specific frequency band is the 5 GHz band, but this is not limited to this and may be, for example, 6 GHz or 2.4 GHz. The RSSI (SNR) to be compared is not limited to a specific frequency band and may be, for example, the average or median of the RSSI (SNR) obtained for multiple frequency bands. In this case, scan frames of links showing RSSI or SNRs greater than a threshold may be considered, or all scan frames received in relation to AP MLD may be considered. Thus, the priorities of all candidate APs are determined. However, if the purpose of this process is to reconnect, the process may proceed to connect to the AP as soon as the AP with the highest priority has been determined, without waiting until the priorities of all APs have been determined.

[0056] As described above, in Figure 6, the reception status (received signal strength, S / N ratio) of all scanning frames associated with multiple links of one candidate AP is checked, and the priority of the connection candidate APs is set. Furthermore, in the above processing example, the reception status at the time of receiving the scanning frame is referenced, but it is also possible to consider the number of links that can maintain a reception status above a predetermined level (received signal strength or S / N ratio above a threshold) even after connection. By doing so, high throughput and low latency can be achieved even after connection to the AP selected based on priority.

[0057] Next, a specific flow of the RSSI priority mode process (S409 in FIG. 4), which determines the priority of APs by prioritizing received radio wave strength, will be described with reference to FIG. 7. In the process in FIG. 7, the priority is determined roughly as in the following (1) to (3). Note that, although received radio wave strength (RSSI) is used as the communication status of the scanning frame below, the SN ratio may also be used, or both the RSSI and the SN ratio may also be taken into consideration. (1) APs are sorted in descending order of the received signal strength (RSSI) of the scanning frame. When determining this order, if an AP is transmitting multiple scanning frames, the RSSI of the scanning frame with the strongest RSSI is used. In other words, APs are sorted so that the scanning frames with the strongest RSSI among those transmitted from the same AP are sorted in descending order of RSSI. (2) If the difference in RSSI between the scanning frames transmitted by two adjacent APs in the AP arrangement in (1) is less than a threshold, the AP that supports multi-link among those two APs is assigned a higher priority than the other AP. (3) In (2), if both APs are multi-link capable, the priority is determined by referring to the RSSI of the scan frame received on the other link.

[0058] In RSSI priority mode, all APs that are the senders of scanning frames extracted in the process up to S407 are subject to processing. In the process shown in FIG. 7, there are unconfirmed APs, APs of interest, next candidate APs, and APs that are already listed in the priority list. An unconfirmed AP refers to an AP that is the sender of an extracted scanning frame and whose priority has not been determined. Initially, all APs are unconfirmed APs. The priority determination unit 304 extracts an AP of interest and a next candidate AP from the unconfirmed APs in descending order of RSSI, determines their priority, and lists them in the priority list. APs listed in the priority list become listed APs.

[0059] First, the priority determination unit 304 sorts the received scanning frames in order of RSSI (S701). Next, the priority determination unit 304 selects the AP that transmitted the scanning frame with the strongest RSSI as the noted AP (S702). The priority determination unit 304 confirms that the noted AP is multi-link compatible, that an ML element has been assigned, and that the ML element contains information about other links and an MLD MAC address (S703). The method for confirming whether the noted AP is multi-link compatible is as described above. If the noted AP is multi-link compatible and does not contain an MLD MAC address, the priority determination unit 304 sends an ML Probe Request to the noted AP (S704). The priority determination unit 304 receives an ML Probe Response from the noted AP (S705) and obtains the above information, such as the MLD MAC address. Note that the sending and receiving processes of the ML Probe Request and ML Probe Response (S704, S705) are not essential. If S704 and S705 are omitted, an AP that has sent a scanning frame that does not include an MLD MAC Address will be treated as an AP in which each of multiple links operates independently, even if the AP is multi-link compatible. Note that when another scanning frame is received, if the ML MAC Address of the target AP is included in the link information field 506 in Figure 5, the frame may be treated as having been sent from one of the links of that AP MLD.

[0060] Once the information on the noted AP has been collected, the priority determination unit 304 checks whether any unconfirmed APs other than the noted AP remain (S706). If there are no unconfirmed APs other than the noted AP (NO in S706), the process proceeds to S717. If there are unconfirmed APs other than the noted AP (YES in S706), the priority determination unit 304 selects the AP that transmitted the scanning frame received with the strongest RSSI among the unconfirmed APs other than the noted AP as the next candidate AP (S707). The priority determination unit 304 checks whether the next candidate AP is multi-link compatible, has an ML element assigned to it, and includes information on other links and an MLD MAC address in the ML element (S708). If the next candidate AP is multi-link compatible but does not include information on other links or an MLD MAC address (NO in S708), the priority determination unit 304 sends an ML Probe Request to the next candidate AP (S709). The priority determination unit 304 receives an ML Probe Response from the next candidate AP (S710) and obtains the above information. Note that the processes of S709 to S710 are not essential. If the processes of S709 to S710 are omitted, the next candidate AP that is the source of a scanning frame that does not include an MLD MAC Address will be treated as a standalone AP even if it supports multi-link. Alternatively, when another frame is received, if the MAC address of the target AP is included in the link information field 506 in FIG. 5, the frame may be treated as having been sent from one of the links of that AP MLD.

[0061] Next, the priority determination unit 304 compares the RSSI of the scanning frame received from the attention AP with the RSSI of the scanning frame received from the next candidate AP (S711). If the difference between the two RSSIs is equal to or less than the threshold (YES in S711), the priority determination unit 304 checks whether the attention AP and the next candidate AP are multi-link compatible (S712). If only one of the attention AP and the next candidate AP is multi-link compatible (YES in S712), the priority determination unit 304 sets the multi-link compatible AP as the attention AP (S713) and repeats the processing from S706 onwards. If the attention AP is multi-link compatible, there is no change; however, if the next candidate AP is multi-link compatible, the next candidate AP is re-set as the attention AP. In this case, the AP that was the attention AP is temporarily removed from the list of unconfirmed APs, and processing is suspended.

[0062] If the determination in S711 is NO, either both the focused AP and the next candidate AP support multi-link or neither support multi-link. The priority determination unit 304 checks whether both the focused AP and the next candidate AP support multi-link (S714). If neither support multi-link (NO in S714), the priority determination unit 304 compares the RSSIs of the received scanning frames and sets the AP that sent the scanning frame with the strongest RSSI as the focused AP (S715). In this case, the focused AP does not change, so S715 may be omitted. If both support multi-link (YES in S714), the priority determination unit 304 compares the RSSIs of the scanning frames with the second strongest RSSI sent from the focused AP and the next candidate AP. Based on the comparison of the second strongest RSSI, the priority determination unit 304 sets the source of the scanning frame with the strongest RSSI as the focused AP (S716) and repeats the processing from S706 onwards. If the difference between the second strongest RSSIs is also smaller than the threshold, the scanning frame with the third strongest RSSI may be compared. Alternatively, the RSSIs of the scanning frames may be acquired up to the number of links that the STA 101 can support, and the AP of interest may be selected using their average value. Alternatively, instead of comparing the RSSIs, the AP of interest or the next candidate AP that has the greater number of supported links may be set as the AP of interest. As in S713, when the AP of interest is changed, the AP that was the AP of interest is temporarily removed from the list of unconfirmed APs, and processing is suspended.

[0063] On the other hand, if the RSSI difference is greater than the threshold in S711 (NO in S711), or if there are no APs other than the AP of interest among the unconfirmed APs in S706 (NO in S706), the process proceeds to S717. In this case, the priority determination unit 304 determines the AP of interest to be the AP with the highest priority among the unconfirmed APs and lists it in the priority list (S717). As a result, the AP of interest becomes a recorded AP and is no longer an unconfirmed AP.

[0064] Next, the priority determination unit 304 checks whether all APs that are the senders of the received scanning frames are listed in the priority list (S718). At this time, if there is an AP whose handling was suspended as a result of changing the target AP in S713 or S716, the priority determination unit 304 returns the AP to an unconfirmed AP, and then determines whether there is an unconfirmed AP that is not listed in the priority list. If an unconfirmed AP is present (NO in S718), the priority determination unit 304 selects the AP that is the sender of the scanning frame with the strongest RSSI from the unconfirmed AP as the target AP and repeats the process from S703. In this way, all APs that are the senders of all received scanning frames are listed in the priority list in order of priority. However, if the purpose of the process is to reconnect, the process may proceed to connect to the AP when the AP with the highest priority is first set in the priority list, without waiting for the AP priority list to be completed.

[0065] Note that the processing in the RSSI priority mode may not be the processing shown in FIG. 7, but may be processing that simply assigns priorities according to the RSSI of the received link. In this case, in S411, a connection is attempted to the AP that sent the scanning frame with the strongest RSSI among all the links. Also, the priority determination processing described in FIGS. 6 and 7 may be performed when a scan instruction is issued that does not involve a connection. In this case, a list of APs arranged in order of priority is displayed in response to the scan instruction. For example, APs with higher priority are displayed at the top, and APs with lower priority are displayed at the bottom.

[0066] FIG. 8 shows an example of how APs prioritized by the process of FIG. 4 are displayed to the user. For example, suppose the RSSI for each link of AP 102 is −35 dBm for link 1 and −37 dBm for link 2. The RSSI for each link of AP 103 is −29 dBm, −48 dBm, and −78 dBm for link 3, link 4, and link 5, respectively. The RSSI for AP 104 is −36 dBm. If the threshold used in S609 of FIG. 6 is −45 dBm and priorities are assigned using the priority order assignment process (multi-link priority mode) shown in FIG. 6, a list of APs arranged in this order is obtained: AP 102, AP 103, and AP 104. On the other hand, if priorities are assigned using the priority order assignment process (RSSI priority mode) of FIG. 7, a list of APs arranged in this order is obtained: AP 103, AP 102, and AP 104. In the AP list, the APs are displayed on the UI screen in this order of priority. However, the SSID of the AP that has been connected to once may be displayed at the top, and other APs may be displayed second or subsequent according to the priority set by the processing in Figure 6 or Figure 7. Also, STA 101 may display connection candidates in the GUI in order of priority according to the set priority, as shown in Figure 8. Also, connection may be attempted in order from the AP with the highest priority.

[0067] [Second embodiment] In the first embodiment, the RSSI and SN ratio of the AP to be connected to are checked before connecting to the AP, and then the connection or AP list is displayed. In the second embodiment, an example of processing from connection to reconnection will be described.

[0068] FIG. 9 is a flowchart showing the flow of a process (hereinafter, "reconnection process") in which the STA 101, after establishing a communication connection to the AP 103 using multiple links, reconnects to another AP because one of the multiple links has a low SNR. After connecting to the AP 103, the wireless LAN control unit 301 checks whether any of the multiple links used for communication (multi-link communication) has an SNR below a threshold (S901). This allows the wireless LAN control unit 301 to determine whether a reconnection process is necessary. The determination of whether a reconnection process is necessary is not limited to determining the SNR, but may also be based on, for example, the RSSI of a scanning frame received from the AP 103. Alternatively, the determination of whether a reconnection process is necessary may be based on detecting a link with a throughput lower than a threshold, a link with a delay greater than a threshold, or a link with a transmission data error greater than a threshold. The number of links that the STA 101 and the AP 103 can establish and the number of links that have actually been established may also be used as criteria for determining whether a reconnection process is necessary. For example, the STA 101 may be configured to determine that reconnection processing is necessary when it can establish three links but has actually established only one link with the AP 103. Alternatively, when the STA 101 has established three links with the AP 103, the STA 101 may be configured to determine that reconnection processing is necessary when the SNR or throughput decreases in two or more links.

[0069] If it is determined that reconnection processing is necessary (YES in S901), the wireless LAN control unit 301 checks whether there are any other connection candidate APs. If there are no other connection candidate APs, the connection to the currently connected AP 103 continues. If there are other connection candidate APs (YES in S902), the priority determination unit 304 performs a priority determination process for the connection candidate APs excluding the currently connected AP (S904). Here, it is assumed that AP 102 is selected as the AP with the highest priority. The priority determination process may be the process shown in the first embodiment (FIGS. 6 and 7), or may simply select an AP with the strongest received radio wave strength from a single link. Once the highest priority AP is determined in the priority determination process, the wireless LAN control unit 301 disconnects communication with the currently connected AP (S905). In this embodiment, the connection to AP 103 is disconnected. Next, the wireless LAN control unit 301 connects to the AP determined to have the highest priority in S904 (S906). As mentioned above, a connection is now established with AP 102.

[0070] Although the currently connected AP is excluded from the reconnection candidates in S903, the priority determination process may be performed including the currently connected AP. If, as a result of performing the priority determination process including the currently connected AP, for example, the currently connected AP 103 is determined to be the AP with the highest priority (determined to be the AP to be reconnected), S905 and S906 may be omitted.

[0071] As described above, the second embodiment is effective when, after STA 101 connects to a certain AP, STA 101 moves and the radio wave environment changes. Furthermore, because the reconnection process is automatically performed in response to detection of a deterioration in the radio wave environment in some of the multiple links used for communication, the time during which STA 101 is unable to communicate can be reduced. The process of this embodiment can also be used when a multi-link-compatible AP transmits scanning frames only through one link. That is, after STA 101 connects to an AP based on the radio wave strength of one link and starts communication through multi-link, it can temporarily disconnect from that AP and reconnect to another AP depending on the radio wave conditions of other links. This is expected to provide a high-quality communication environment.

[0072] As described above, according to each of the above embodiments, even when communication conditions differ for each frequency band, it is possible to select an appropriate AP for communication.

[0073] In the above embodiments, the STA 101 is connected to only one AP at a time, but multiple APs may be connected. For example, link 1 may be connected to AP 102, and link 2 may be connected to AP 103. This may be implemented when the AP from which the STA 101 can receive the strongest radio waves differs depending on the frequency band supported by the STA 101.

[0074] (Other embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the 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 realizes one or more functions.

[0075] The invention is not limited to the above-described embodiments, and various changes and modifications can be made 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]

[0076] 101: communication device (STA), 102 to 104: communication devices (AP), 301: wireless LAN control unit, 302: frame generation unit, 303: device discrimination unit, 304: priority determination unit, 305: UI control unit, 306: storage control unit

Claims

1. A communication device capable of performing multi-link communication using a plurality of links with different frequency bands, receiving means for receiving one or more frames transmitted from each of a plurality of external devices via one or more links; a determination means for determining an external device that is a sender of the one or more frames based on a parameter included in each of the one or more frames, the determination means determining that the sender of the two or more frames is the one external device when two or more frames are received from a single external device via two or more different links; a determination means for determining the priority of communication connections of the plurality of external devices based on the communication status of frames determined by the determination means to be sent from the same external device.

2. The communication device according to claim 1, characterized in that the determination means determines the priority based on the number of frames whose received radio wave strength or signal-to-noise ratio is above a threshold among frames determined to have been sent from the same external device.

3. The communication device according to claim 1 or 2, characterized in that the determination means determines the priority based on the number of frames received via a link that can transmit and receive simultaneously, among frames that are determined to have originated from the same external device.

4. The communication device according to claim 2 or 3, characterized in that the determination means determines the priority so that external devices whose number of frames is equal to or greater than the number of links used by the communication device for multi-link communication are arranged in order of received radio wave strength in a specified frequency band.

5. The communication device according to any one of claims 2 to 4, characterized in that the determination means determines the priority so that external devices having a number of frames less than the number of links used by the communication device for multi-link communication are arranged in order of the number of frames.

6. The communication device described in claim 5, characterized in that the determination means determines the priority so that, among external devices having a number of frames less than the number of links used by the communication device for multi-link communication, external devices having the same number of frames are arranged in order of strongest received radio wave strength in a specified frequency band.

7. a determination unit that determines whether each of the plurality of external devices supports multi-link communication based on the result of the determination of the source by the determination unit, The determining means determining a priority order for the plurality of external devices such that frames having the same external device as a transmission source are arranged in order of strength in the frames with the strongest received radio wave intensity; The communication device described in claim 1, characterized in that when the difference in received radio wave intensity of frames received from two external devices with adjacent priorities is below a threshold, the priority of the two external devices is determined based on whether or not they support multi-link communication.

8. The communication device according to claim 7, characterized in that, when the difference is equal to or less than the threshold value, the determination means determines that the external device that supports multi-link communication has a higher priority than the other external device.

9. The communication device described in claim 7 or 8, characterized in that the determination means determines the priority of the two external devices based on a comparison of the second strongest received radio wave strength among frames sent from each of the two external devices when the difference is less than or equal to the threshold and both of the two external devices are compatible with multi-link communication.

10. 10. The communication device according to claim 1, further comprising a connection unit that attempts to establish a communication connection with an external device in descending order of priority determined by the determination unit.

11. a determination means for determining whether or not a reconnection process is necessary based on the communication status of each of a plurality of links established with other communication devices; The communication device according to any one of claims 1 to 9, further comprising a reconnection means for disconnecting communication with the other communication device when it is determined that the reconnection process is necessary, and for executing a connection process with one of the plurality of external devices based on the priority determined by the determination means.

12. The communication device described in claim 11, characterized in that the judgment means determines whether or not the reconnection process is necessary based on at least one of the following: the presence of a frame with an S / N ratio lower than a threshold, the presence of a frame with an RSSI lower than a threshold, and the presence of a frame with a communication throughput lower than a threshold among the multiple frames received from the other communication device via multiple links.

13. 13. The communication device according to claim 11, wherein the reconnection unit attempts to establish a communication connection with the external device in descending order of priority determined by the determination unit.

14. 14. The communication device according to claim 1, further comprising a display unit that displays a list of the plurality of external devices in the order of priority determined by the determination unit.

15. 15. The communication device according to claim 1, wherein the multi-link communication complies with IEEE 802.

11.

16. 16. The communication device according to claim 1, wherein the frame is a beacon or a probe response conforming to IEEE802.

11.

17. A control method for a communication device capable of performing multi-link communication using a plurality of links with different frequency bands, comprising: receiving one or more frames transmitted over one or more links from each of a plurality of external devices; a determination step of determining an external device that is a sender of the one or more frames based on parameters included in each of the one or more frames; and in the determination step, when two or more frames are received from one external device via two or more different links, determining that the sender of the two or more frames is the one external device; A control method for a communication device, comprising: a determination step of determining the priority of communication connections of the plurality of external devices based on the communication status of frames determined to be sent from the same external device by the determination step.

18. A program for causing a computer to function as each of the means of the communication device according to any one of claims 1 to 16.

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