Communication apparatus, control method, and storage medium

Abstract

To provide a mechanism for achieving efficient roaming in a Multi-linkdevice.SOLUTION: The communication device is a communication device conforming to the IEEE802. 11 series standard, establishes a plurality of links including at least a first link and a second link with a first other communication device, executes a process of acquiring information of other surrounding communication devices based on disconnection of any one link among the plurality of links established with the first other communication device, and performs control to perform roaming to a second other communication device based on the acquired information.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a wireless communication device, method, and program for improving the communication efficiency of a wireless LAN device that can simultaneously use multiple links in a wireless LAN that complies with IEEE802.11. [Background technology]

[0002] With the recent increase in the amount of data being transmitted, development of communication technologies such as wireless local area networks (WLANs) is progressing. The IEEE (Institute of Electrical and Electronics Engineers) 802.11 series of standards is known as the main communication standard for WLANs. The IEEE 802.11 series of standards includes IEEE 802.11a / b / g / n / ac / ax. For example, the latest standard, IEEE 802.11ax, uses Orthogonal Frequency Division Multiple Access (OFDMA) to achieve a high peak throughput of up to 9.6 gigabits per second (Gbps) and also to improve communication speeds under congested conditions. OFDMA stands for Orthogonal Frequency Division Multiple Access.

[0003] In order to develop a successor standard that aims to further improve throughput, frequency utilization efficiency, and communication latency, a new Task Group was established within the IEEE802.11 Working Group to develop the IEEE802.11be standard. This Task Group is considering multi-link communication as one of the new functions to be specified in the IEEE802.11be standard. In multi-link communication, a communication device called a multi-link device (MLD) uses multiple links in parallel by coordinating and coordinating multiple communication interfaces.

[0004] Furthermore, a conventional STA (station, terminal) that operates only on a single link can search for and connect to another AP (access point, base station) when the received signal strength (RSSI) from the currently connected AP drops below a certain threshold. This technology for moving between multiple APs is called roaming. In this way, a conventional STA that operates only on a single link would initiate roaming based on a drop in the received signal strength from the currently connected AP.

[0005] Furthermore, for example, Patent Document 1 describes a roaming technology executed by a communication device that is an STA capable of establishing multiple links. This technology discloses seamless roaming that simultaneously maintains a link with a roaming source AP and a roaming destination AP. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2023-107741 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in MLD, which allows multi-link communication, roaming based on conventional standards may result in a decrease in communication efficiency due to a decrease in throughput and an increase in the amount of calculation required to calculate comparison values ​​related to roaming standards. Therefore, an object of the present invention is to provide a mechanism for realizing efficient roaming in MLD. [Means for solving the problem]

[0008] In order to solve the above problem, a communication device according to one embodiment of the present invention is a communication device that complies with the IEEE 802.11 series standard, and has an establishment means for establishing multiple links with a first other communication device, including at least a first link and a second link, an acquisition means for executing a process for acquiring information about other communication devices in the vicinity based on the disconnection of any one of the multiple links established with the first other communication device, and a control means for controlling roaming to a second other communication device based on the information acquired by the acquisition means. [Effects of the Invention]

[0009] According to the present invention, an efficient roaming mechanism in MLD is provided. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a wireless communication system. [Figure 2] FIG. 10 is a diagram illustrating an example of a sequence between an AP and a STA when establishing a multi-link. [Figure 3] FIG. 10 is a diagram illustrating an example of the configuration of a Reduced Neighbor Report element. [Figure 4] FIG. 2 illustrates an example of a hardware configuration of a communication device. [Figure 5] FIG. 2 illustrates an example of a functional configuration of a communication device. [Figure 6] 10 is a diagram illustrating an example of an operation flow when a STA roams to another AP when any link among multiple links is disconnected. [Figure 7] FIG. 10 is a diagram illustrating an example of an operational flow when a STA determines to perform roaming based on communication quality information when any link among multiple links is disconnected. [Figure 8] FIG. 10 is a diagram illustrating an example of an operational flow when a STA determines to perform roaming based on its own settings when any link among multiple links is disconnected. [Figure 9] FIG. 10 is a diagram showing an example of an operational flow when a STA determines to perform roaming based on the number of connectable links and communication quality information. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] (System Configuration) FIG. 1 shows an example of the configuration of a wireless communication system according to this embodiment. This wireless communication system includes, for example, two access points (APs) 101 and 105 and one station (STA) 102. Each communication device (APs 101, 105, STA 102) is a wireless communication device capable of performing wireless communication in accordance with the IEEE 802.11 series of standards, including the IEEE 802.11be standard. IEEE stands for Institute of Electrical and Electronics Engineers. The IEEE 802.11be standard may also be referred to as the EHT standard. EHT may also stand for Extremely High Throughput. The IEEE 802.11 series of standards may include the IEEE 802.11a / b / g / n / ac / ax standards. These standards may be referred to as legacy standards. That is, each communication device may support one or more legacy standards in addition to the IEEE 802.11be standard. A network 100 formed by AP 101 indicates a range in which AP 101 and STA 102 can communicate with each other. That is, within the range of network 100, STA 102 can receive signals transmitted by AP 101, and signals transmitted by STA 102 can be received by AP 101. Similarly, a network 106 formed by AP 105 indicates a range in which AP 105 and STA 102 can communicate with each other. Note that each communication device may support other communication standards such as Bluetooth (registered trademark), NFC, UWB, ZigBee, and MBOA in addition to the IEEE 802.11 series standards. Note that UWB stands for Ultra Wide Band, and MBOA stands for Multi Band OFDM Alliance. NFC stands for Near Field Communication. UWB includes wireless USB, wireless 1394, WiNET, etc. Each communication device may also support a wired communication standard such as a wired LAN.

[0013] 1 shows a state in which there are two APs, APs 101 and 105, and one STA 102, but the number of APs and STAs is not limited to these. AP 101 and AP 105 may be, but are not limited to, a wireless LAN router or a personal computer (PC). STA 102 may be, but is not limited to, any electronic device, such as a smartphone, tablet, mobile phone, PC, video camera, headset, printer, or display. Each communication device may be an information processing device, such as a wireless chip, capable of performing wireless communication in accordance with the IEEE 802.11be standard.

[0014] Multi-link communication is one of the new features defined in the IEEE 802.11be standard. In the previous IEEE 802.11 series standards, the STA 102 establishes a single link with the AP 101 to perform data communication. With multi-link communication, the STA 102 can achieve improved throughput by performing data communication with the AP 101 using two or more links in parallel. The IEEE 802.11be standard also considers support for the 6 GHz band to expand the frequency bands available to communication devices. Specifically, the IEEE 802.11 series standards specify the use of the 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz frequency bands for multi-link communication. Each frequency band defines multiple frequency channels. For example, a channel with a bandwidth of 20 MHz is defined as a frequency channel used for a single wireless link. The IEEE 802.11 series standards also define a bandwidth of 40 MHz or more for a single frequency channel by combining (bonding) adjacent frequency channels. As an example, AP 101 may establish a first link with STA 102 using a first frequency channel in the 5 GHz band and communicate therewith. STA 102 may establish a second link with AP 101 using a second frequency channel in the 6 GHz band and communicate therewith. In this case, AP 101 and STA 102 may perform multi-link communication using the second link in parallel while maintaining the first link. In this way, in this embodiment, AP 101 and STA 102 are configured to be able to perform multi-link communication using multiple links in network 100.

[0015] FIG. 1 shows an example in which two wireless links (links 103 and 104) are established between AP 101 and STA 102. As described above, the respective wireless links may have different frequency bands. For example, AP 101 and STA 102 may concurrently establish link 103 using the 5 GHz band and link 104 using the 6 GHz band. Furthermore, multiple wireless links may be configured using multiple different frequency channels belonging to the same frequency band. For example, a multi-link may be configured using two links: a link using channel 15 in the 6 GHz band and a link using channel 207 in the 6 GHz band. In this embodiment, ch (wireless channel) is identification information used to identify a specific frequency channel.

[0016] Furthermore, the AP 101 and the STA 102 may be configured to establish three or more wireless links in parallel. For example, when three or more wireless links are established in parallel, multiple links belonging to the same frequency band may be mixed with links belonging to different frequency bands. A multi-link may be configured with a link on channel 36 in the 5 GHz band, a link on channel 149 in the 5 GHz band, and a link on channel 15 in the 6 GHz band. By establishing multiple links using different frequency channels between the AP 101 and the STA 102, even if one of the frequency channels is congested, communication can be performed using links using other frequency channels. This makes it possible to avoid a decrease in throughput and an increase in delay.

[0017] A communication device capable of multi-link communication is called a multi-link device (MLD). A communication device that operates as an AP or STA conforming to the IEEE 802.11be standard and has the functionality to operate as an MLD is called an AP MLD or STA MLD, respectively. A STA MLD may also be called a non-AP MLD. In an AP MLD or STA MLD, the communication interfaces (I / Fs) constituting each link may be called Affiliated APs (A-APs) or Affiliated STAs (A-STAs), respectively. Affiliated STAs may also be called Affiliated non-AP STAs. An A-AP is associated with an AP MLD and operates on a different frequency channel. An A-STA is associated with a STA MLD and operates on a different frequency channel. A state in which an A-AP and an A-STA are associated with an AP MLD and a STA MLD, respectively, may be referred to as belonging to an MLD. Note that the following embodiment describes a case in which multi-link communication is performed using the IEEE 802.11be standard, but is not limited to this. For example, the following discussion can also be applied to multi-link communication conforming to other wireless communication standards or multi-link communication using multiple wired links.

[0018] 2 shows an example of a sequence for establishing a multi-link between the AP 101 and the STA 102. The AP 101, which is the AP MLD, has Affiliated APs (A-AP)-A201 to A-AP-C203 as wireless I / Fs that operate on frequency channels corresponding to the respective links. The STA 102, which is the STA MLD, has Affiliated STAs (A-STA)-A204 to A-STA-C206 as wireless I / Fs that operate on frequency channels corresponding to the respective links. Information necessary for establishing multi-link communication between the AP 101 and the STA 102 can be mutually notified by a Basic Multi-Link element. For example, the AP MLD transmits a Beacon and a Probe Response including a Basic Multi-Link element via each of the A-APs A201 to A-AP-C203 (F211 to F219). The Probe Response can be transmitted in response to a Probe Request transmitted from the STA 102 (F214 to F219). On the other hand, the STA MLD notifies the AP of the Basic Multi-Link element using an Association Request transmitted via an A-STA (described later). The STA 102 receives a Beacon or a Probe Response via each of A-STA-A 204 to A-STA-C 206. The STA 102 can detect that the AP 101 is the AP MLD by checking whether the received Beacon or Probe Response includes a Basic Multi-Link element. When the STA 102 detects that the AP 101 is the AP MLD, it obtains information about each A-AP belonging to the AP MLD from the RNR element included in the received Beacon or Probe Response. RNR is an abbreviation for Reduced Neighbor Report. Note that the RNR element may include information about the APs surrounding the A-AP transmitting this RNR element, in addition to information about each A-AP belonging to the same AP MLD.For example, the RNR element may include information such as frequency bands and channels used by each A-AP belonging to the same AP MLD and surrounding APs. The fact that the APs reported by the RNR element belong to the same AP MLD may be indicated by a value of 0 for the MLD ID associated with the AP. The STA 102 may establish a multi-link with the AP 101 using one of the A-STAs. For example, the STA 102 may execute a procedure for establishing a multi-link with the A-AP-A 201 via the A-STA-A 204. The procedure for establishing a multi-link may involve exchanging an authentication frame, an association request, and an association response with the AP 101 (F220 to F222). For example, the STA 102 may request the AP 101 to establish a multi-link by transmitting an association request including a basic multi-link element (F221). As an example, the STA MLD determines the frequency channel on which each A-STA will operate based on the information about each A-AP acquired by the RNR element. The STA MLD then notifies the AP MLD of information such as the frequency channel on which each A-STA operates, using a Basic Multi-Link element. The AP MLD acquires information such as the frequency channel on which each A-STA operates from the received Basic Multi-Link element. When the AP MLD returns an Association Response, a multi-link can be established between the AP 101 and the STA 102 (F222). The STA MLD switches the frequency channel on which each A-STA operates to the determined frequency channel. This makes it possible to establish multiple links between each A-AP and each A-STA at once, without having to perform a link establishment procedure for each link individually. After establishing the multi-link, the AP 101 and the STA 102 can exchange security information and the like using a 4-way handshake procedure (F223). If the AP 101 is not the AP MLD, the STA 102 can establish a connection using a single frequency channel.The technique using the Basic Multi-Link element and the RNR element is one example of a technique for exchanging information about multi-links between the AP 101 and the STA, and other techniques may also be used.

[0019] FIG. 3 shows an example of an RNR element. The RNR element may include Element ID 301, Length 302, and Neighbor AP Information 303. Element ID 301 indicates the type of this element. For example, in the case of an RNR element, 201 may be stored in Element ID 301. Length 302 indicates the length of this element. The same number of pieces of Neighbor AP Information 303 may be allocated as the number of APs to be reported. Each piece of Neighbor AP Information 303 may include TBTT Information Header 304, Operation Class 305, and Channel Number 306. Each piece of Neighbor AP Information 303 may also include TBTT Information Set 307. TBTT Information Header 304 is header information indicating the length of each piece of TBTT Information included in TBTT Information Set 307. Operation Class 305, together with Channel Number 306, indicates the start frequency of the primary channel used by the AP associated with the Neighbor AP Information 303 (the AP to be reported). The TBTT Information Set 307 may include a Neighbor AP TBTT Offset 308, a BSSID 309, a Short SSID 310, BSS Parameters 311, and a 20MHz PSD 312. The TBTT Information Set 307 may also include MLD Parameters 313. The Neighbor AP TBTT Offset 308 indicates information regarding the timing of a Beacon transmitted by the AP that is the subject of the report. The BSSID 309 indicates an identifier of a network that the AP that is the subject of the report constitutes. The Short SSID 310 indicates a value obtained by applying an SSID (Service Set Identifier) ​​to a predetermined calculation formula. The BSS Parameters 311 indicate parameters of a network that the AP that is the subject of the report constitutes.MLD Parameters 313 may be configured to include MLD ID 314, Link ID 315, BSS Parameters Change Count 316, All Updates Included 317, and Reserved 318. MLD ID 314 indicates the identifier of the AP MLD to which the reporting AP belongs. If the reporting AP belongs to the same AP MLD as the AP transmitting the RNR element, the value of MLD ID 314 may be set to 0. Link ID 315 indicates the link identifier of the reporting AP. BSS Parameters Change Count 316 indicates the period until a network parameter change is executed in the reporting AP. All Updates Included 317 is set to 1 if all updated elements are included in the latest parameter update. Reserved 318 is a reserved field.

[0020] (Configuration of communication device) 4 shows an example of the hardware configuration of each communication device in this embodiment. Each communication device has a storage unit 401, a control unit 402, a function unit 403, an input unit 404, an output unit 405, a communication unit 406, and an antenna 407. Note that there may be multiple antennas.

[0021] The storage unit 401 is configured with one or more memories such as ROM and 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. The storage unit 401 may be a storage medium such as a flexible disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, magnetic tape, non-volatile memory card, or DVD, in addition to memories such as ROM and RAM. The storage unit 401 may also be equipped with multiple memories.

[0022] The control unit 402 is configured with one or more processors, such as a CPU or MPU, and controls the entire AP 101 by executing a computer program stored in the storage unit 401. The control unit 402 may control the entire AP 101 in cooperation with the computer program stored in the storage unit 401 and an OS (Operating System). The control unit 402 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 402 may also include multiple processors, such as multi-core processors, and the entire STA 102 may be controlled by the multiple processors. The control unit 402 also controls the function unit 403 to perform predetermined processes, such as wireless communication, imaging, printing, and projection. The function unit 403 is hardware that enables each communication device to perform predetermined processes.

[0023] The input unit 404 receives various operations from the user. The output unit 405 outputs various types of information to the user via a monitor screen or a speaker. Here, the output from the output unit 405 may be a display on a monitor screen, an audio output from a speaker, a vibration output, or the like. Note that both the input unit 404 and the output unit 405 may be implemented in a single module, such as a touch panel. Furthermore, the input unit 404 and the output unit 405 may be integrated with the STA 102 or may be separate units.

[0024] The communication unit 406 controls wireless communications compliant with the IEEE 802.11be standard. The communication unit 406 may also control wireless communications compliant with other IEEE 802.11 series standards in addition to the IEEE 802.11be standard, or wired communications such as a wired LAN. The communication unit 406 controls the antenna 407 to transmit and receive signals for wireless communications generated by the control unit 402. If each communication device supports standards such as the NFC standard or Bluetooth in addition to the IEEE 802.11be standard, the communication unit 406 may control wireless communications compliant with these communication standards. If each communication device can perform wireless communications compliant with multiple communication standards, the communication unit 406 may have a separate communication unit and antenna compatible with each communication standard. Each communication device communicates data such as image data, document data, and video data via the communication unit 406. The antenna 407 may be configured separately from the communication unit 406, or may be configured together with the communication unit 406 as a single module.

[0025] Antenna 407 is an antenna capable of communication in the 2.4 GHz band, 5 GHz band, and 6 GHz band. In this embodiment, each communication device has two antennas, but it may have three antennas. Alternatively, it may have a different antenna for each frequency band. Furthermore, if each communication device has multiple antennas, it may have a communication unit 406 corresponding to each antenna.

[0026] 5 is a block diagram showing the functional configuration of each communication device in this embodiment. Each communication device can include a multi-link establishment unit 501, a wireless I / F setting unit 502, a frame processing unit 503, a frame transmission / reception unit 504, and a communication quality measurement unit 505.

[0027] The multi-link establishment unit 501 controls a communication start process for establishing one or more links used by a communication device for wireless communication with a partner communication device, a control process for functions related to multi-link, a process for adding and deleting links after communication has started, and a communication end process for deleting all links. For example, the connection process can be composed of an authentication process, an association process, and a 4-Way Hand Shake (4WHS) process.

[0028] The wireless I / F setting unit 502 performs communication settings for each link. For example, the wireless I / F setting unit 502 of the STA 102 selects and determines the A-AP to which each A-STA will connect, sets the frequency channel to be used by each A-STA, etc. The wireless I / F setting unit 502 of the AP 101 sets information about each A-AP and the A-STA to connect to. The wireless I / F setting unit 502 of the AP 101 also notifies the frame processing unit 503 and the frame transmitting / receiving unit 504 of information about the A-AP and A-STA to establish a link.

[0029] The frame processing unit 503 generates frames to be transmitted in accordance with the settings of the wireless I / F setting unit 502. For example, the frame processing unit 503 of the AP 101 generates a beacon, probe response, etc., including a basic multi-link element and an RNR element. The frame processing unit 503 of the AP 101 also generates an authentication, association response, EML operating mode notification frame, etc. The frame processing unit 503 of the STA 102 generates a probe request, association request, etc., including a basic multi-link element and an RNR element. The frame processing unit 503 of the STA 102 also generates an EML operating mode notification frame. The frame processing unit 503 also processes frames received from the other communication device and acquires information. For example, the frame processing unit 503 of the STA 102 acquires information indicating that the AP 101 can perform multi-link communication or EMLSR from the basic multi-link element and RNR element included in the received beacon, etc. Furthermore, the frame processing unit 503 of the STA 102 acquires the number of devices in the frequency channel used in the multi-link communication.

[0030] The frame transmitting / receiving unit 504, in accordance with instructions from the wireless I / F setting unit 502, transmits wireless frames including Beacon and Probe Response frames and data frames generated by the frame processing unit 503, and receives wireless frames from the other device.

[0031] The communication quality measurement unit 505 measures and calculates the communication quality of the Beacon / Probe Response frame received from the frame transmission / reception unit 504. Note that communication quality information includes, but is not limited to, MCS, RSSI, SNR, etc. Note that MCS is an abbreviation for Modulation and Coding Scheme, and is information indicating a combination of a wireless modulation scheme, coding rate, etc., as an index. Also, RSSI is an abbreviation for Receive Signal Strength Indicator, and is information indicating the reception strength of a signal. Also, SNR is an abbreviation for Signal-to-Noise Ratio, and is information indicating the ratio between the reception strength of a signal in communication and the reception strength of a signal that is noise different from the signal. Also, for example, the value of MCS changes depending on the communication environment, and for example, an MCS of MCS0 is the method with the lowest throughput.

[0032] (Processing flow) Next, the flow of the processing executed by the STA 102 as described above, the sequence in the wireless communication system, etc. will be described using several examples.

[0033] Example 1 6 shows an example of a process for starting roaming to another AP MLD based on the determination that any of the multiple links established between the STA 102 and the AP 101 has been disconnected. This process can be started, for example, when the STA 102 attempts to connect to the AP 101.

[0034] First, the STA102 receives a Beacon or Probe Response via one of the A-STAs (S601). At this time, the STA102 confirms that the AP 101 is the AP MLD by confirming that the received Beacon or Probe Response includes a Basic Multi-Link element. Then, the STA102 acquires information such as the frequency band and frequency channel of each A-AP belonging to the AP 101 that is the AP MLD based on the Basic Multi-Link element and the RNR element (S602). For example, when the STA102 receives a Beacon transmitted by A-AP-A201 via A-STA-A204, the STA102 can acquire information about A-AP-B202 and A-AP-C203 from the Basic Multi-Link element, etc. The STA102 can measure the communication quality with A-AP-B202 and A-AP-C203 using the RSSI, etc., of the received Beacon, etc. Then, the STA 102 establishes a multi-link with the AP 101 (S603).

[0035] After establishing a multi-link with the AP 101, the STA 102 determines whether any of the multi-links has been disconnected (S604). The STA 102 determines that the link has been disconnected, for example, when it receives a Link Reconfiguration Notify frame from the AP 101 in which the value of the Reconfiguration Operation type in the STA Control of the Per-STA Profile subelement of the Link Info of the Reconfiguration Multi-Link element is 3, or when it is no longer possible to acquire a Beacon frame transmitted by the A-AP of any of the links.

[0036] When the STA 102 determines that the link has been disconnected (S604, Yes), it acquires information about the MLD of APs that can be connected to around the STA 102 (S605). For example, the STA 102 acquires the information about the MLD of surrounding APs by receiving a Beacon, a Probe Response, or a frame including the RNR element described above on an operable frequency channel.

[0037] After acquiring the information about the surrounding AP MLDs, the STA 102 determines whether there is a surrounding AP MLD with a greater number of links that can be established with the AP 101 than the total number of links currently established with the AP 101 (S606). If the determination shows that there is a surrounding AP MLD with a greater number of links that can be established with the AP 101 than the total number of links that are currently established with the AP 101 (S606, Yes), the STA 102 roams to the AP MLD (S607). If the determination shows that there is no surrounding AP MLD with a greater number of links that can be established with the AP 101 than the total number of links that can be established with the AP 101 (S606, No), the STA 102 maintains the current connection with the AP 101 (S608). Note that if there are multiple surrounding AP MLDs with a greater number of links that can be established with the AP 101 than the total number of links that can be established with the AP 101, the STA 102 may roam to the AP MLD with the greatest number of links that can be established.

[0038] In this way, when the STA 102 has established multiple links with the AP 101, the disconnection of any of the multiple links can be used as a trigger for roaming, thereby reducing the amount of calculation required to determine whether or not to roam. Furthermore, by roaming to a suitable AP in the surrounding environment, it is possible to improve throughput and communication efficiency.

[0039] Example 2 In this embodiment, when any link among the multilinks between the STA 102 and the AP 101 is disconnected, the STA 102 acquires communication quality information of each A-AP of the AP 101 and each A-AP of the surrounding AP MLD, and then determines whether to perform roaming based on the acquired communication quality information.

[0040] Fig. 7 shows an example of a process in which the STA 102 in this embodiment determines whether to perform roaming based on the communication quality information of each A-AP. Note that the processes of S701, S702, and S703 in Fig. 7 are similar to the processes of S601, S602, and S603 in Fig. 6, and therefore description thereof will be omitted.

[0041] After the STA 102 establishes a multi-link with the AP 101, if the STA 102 determines that any link in the multi-link has been disconnected (S704, Yes), the STA 102 acquires communication quality information of the AP 101 and each A-AP in the surrounding AP MLD (S705). For example, the STA 102 acquires communication quality information of each A-AP based on a frame including a Beacon, a Probe Response, or the above-mentioned RNR element received on an operable frequency channel.

[0042] Based on the acquired communication quality information, STA102 determines whether each A-AP in the surrounding AP MLD satisfies a predetermined condition (S706). For example, STA102 may determine that each A-AP in the surrounding AP MLD satisfies a predetermined condition if the communication quality information of each A-AP in the surrounding AP MLD is a better value than the communication quality information of each A-AP in AP101. Also, for example, STA102 may determine that each A-AP in the surrounding AP MLD satisfies a predetermined condition if the MCS of each A-AP in the surrounding AP MLD is a better scheme than MCS0.

[0043] If the STA 102 determines that each A-AP in the surrounding AP MLD satisfies a predetermined condition (S706, Yes), it roams to that AP MLD (S707). On the other hand, if the STA 102 determines that each A-AP in the surrounding AP MLD does not satisfy a predetermined condition (S706, Yes), it maintains the current connection with AP 101 (S708).

[0044] In this embodiment, the STA 102 acquires communication quality information of surrounding A-APs to determine whether to perform roaming when a link is disconnected. Then, if the communication quality information satisfies a predetermined condition, the STA 102 performs roaming. In this embodiment, by determining whether to perform roaming based on the communication quality information of surrounding A-APs, it is possible to prevent a decrease in communication efficiency due to roaming to an unintended AP. Furthermore, in this embodiment, the communication quality information of multiple A-APs is compared, but this is not limiting. For example, it is also possible to compare only the A-APs with the best communication quality.

[0045] Example 3 Next, in this embodiment, when any link among the multiple links between the STA 102 and the AP 101 is disconnected, the STA 102 determines whether to perform roaming based on its own settings.

[0046] Fig. 8 shows an example of the process when STA 102 determines whether to perform roaming based on its own settings when any link is disconnected. Also, S801, S802, and S803 in Fig. 8 are the same as the processes of S601, S602, and S603 in Fig. 6, so their explanation will be omitted.

[0047] After establishing a multi-link with the AP 101, if the STA 102 determines that any link in the multi-link has been disconnected (S804, Yes), the STA 102 acquires configuration information for the STA 102 (S805). Based on the acquired configuration information, the STA 102 determines whether to perform roaming (S806). For example, if the STA 102 determines that the STA 102 is running a power-saving mode based on the acquired configuration information, the STA 102 determines not to perform roaming. For example, if the STA 102 determines that the STA 102 is running on battery power based on the acquired configuration information, the STA 102 determines not to perform roaming. For example, if the STA 102 determines that the STA 102 is running EMLMR or EMLSR based on the acquired configuration information, the STA 102 determines not to perform roaming. In this way, the configuration information is, for example, information indicating that the STA 102 is running a power-saving mode. For example, the configuration information is information indicating that the STA 102 is running on battery power. For example, the configuration information is information indicating that the STA 102 is running EMLMR or EMLSR.

[0048] In this embodiment, the STA 102 controls not to perform roaming when the STA 102 is not configured to increase the number of links, thereby preventing roaming from being performed at a timing when the STA 102 does not intend to perform roaming, such as when the STA 102 wants to save power.

[0049] Example 4 Although several embodiments have been described above, the present invention is not limited to these. For example, the present invention may be configured by combining several of the above-described embodiments. In this embodiment, an example in which the above-described first and second embodiments are combined will be described.

[0050] Fig. 10 shows an example of processing in the STA 102 when combining the first embodiment and the second embodiment. Fig. 10 shows an example of processing when the STA 102 roams from the AP 101 to another AP MLD by combining the determination based on the number of connectable links in the first embodiment and the determination using communication quality information in the second embodiment.

[0051] After establishing a multi-link with AP 101, STA 102 determines whether any link in the multi-link has been disconnected (S604). If STA 102 determines that a link has been disconnected (S604, Yes), it acquires information about AP MLDs that can be connected to around STA 102 (S605). After acquiring the information about the surrounding AP MLDs, STA 102 determines whether there is a surrounding AP MLD that has a greater number of establishable links than the total number of links currently established with AP 101 (S606).

[0052] Next, based on the information acquired in S605, the STA 102 determines whether each A-AP in the surrounding AP MLD satisfies a predetermined condition (S706). If the STA 102 determines that each A-AP in the surrounding AP MLD satisfies the predetermined condition (S706, Yes), the STA 102 roams to another AP MLD (S607).

[0053] In this way, the number of connectable links in each AP MLD is compared, and the communication quality of each A-AP is also compared before deciding whether to perform roaming. This makes it possible to roam to another AP MLD after recognizing that it is possible to improve throughput and communication performance.

[0054] A recording medium on which program code for software that realizes the above-described functions is recorded may be supplied to a system or device, and the computer (CPU, MPU) of the system or device may read and execute the program code stored on the recording medium. In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiments, and the recording medium on which the program code is stored constitutes the above-described device.

[0055] Examples of storage media that can be used to supply the program code include flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, ROMs, and DVDs.

[0056] In addition, the above-mentioned functions may be realized not only by the computer executing the read program code, but also by the operating system (OS) running on the computer performing some or all of the actual processing based on the instructions of the program code. OS is an abbreviation for Operating System.

[0057] Furthermore, the program code read from the storage medium may be written to a memory provided on a function expansion board inserted into a computer or a function expansion unit connected to the computer, and a CPU provided on the function expansion board or function expansion unit may then perform some or all of the actual processing based on the instructions of the program code to realize the above-mentioned functions.

[0058] 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. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0059] (Summary of the embodiment) At least some of the above-described embodiments can be summarized as follows.

[0060] (Item 1) A communication device that complies with the IEEE 802.11 series standard, establishing means for establishing a plurality of links including at least a first link and a second link with a first other communication device; an acquisition means for executing a process of acquiring information about other surrounding communication devices when any one of the plurality of links established with the first other communication device is disconnected; a control means for controlling roaming to a second other communication device based on the information acquired by the acquisition means; A communication device comprising:

[0061] (Item 2) The communication device further includes a determination unit that determines whether to roam to the second other communication device based on the information acquired by the acquisition unit and a predetermined condition, The control means controls roaming to the second other communication device based on the determination by the determination means to perform roaming to the second other communication device. 2. The communication device according to item 1,

[0062] (Item 3) the predetermined condition is that a number of links that is greater than the number of links that are established with the first other communication device can be established with the second other communication device, The determining means determines to roam to the second other communication device having a larger number of connectable links than the first other communication device. 3. The communication device according to item 2.

[0063] (Item 4) The information is information about the number of links that can be established with other communication devices in the vicinity. 4. The communication device according to any one of items 1 to 3, wherein:

[0064] (Item 5) If there is no other communication device that can establish a greater number of links than the first other communication device, the control means controls not to disconnect the connection with the first other communication device. 5. The communication device according to claim 1, wherein:

[0065] (Item 6) The predetermined condition is that the communication quality of the link that can be established with the second other communication device is better than that of each link established with the first other communication device. 3. The communication device according to item 2.

[0066] (Item 7) The information is information about the communication quality of links that can be established with other surrounding communication devices. 7. The communication device according to any one of items 1 to 6, wherein:

[0067] (Item 8) When there is no other communication device having a link with communication quality that is superior to that of the first other communication device, the control means controls the first other communication device so as not to disconnect the connection with the first other communication device. 8. The communication device according to any one of items 1 to 7, wherein:

[0068] (Item 9) The communication device further includes a determining means for determining that a link with an affiliated AP belonging to the first other communication device has been disconnected based on a predetermined Link Reconfiguration Notify frame received from the affiliated AP. 9. The communication device according to any one of items 1 to 8, wherein:

[0069] (Item 10) The communication device further includes a determination means for determining that a link with an affiliated AP belonging to the first other communication device has been disconnected based on the inability to receive a Beacon frame transmitted from the affiliated AP. 10. The communication device according to any one of items 1 to 9,

[0070] (Item 11) When any one of the plurality of links established with the first other communication device is disconnected, the control means controls the communication device not to roam to the second other communication device if the communication device is in a predetermined state. 11. The communication device according to any one of items 1 to 10,

[0071] (Item 12) The predetermined state is a state in which EMLSR or EMLMR is being performed in the multiple links established with the other communication device. Item 12. The device according to item 11, characterized in that

[0072] (Item 13) The predetermined state is a state in which the communication device is operating in a power saving mode. Item 12. The device according to item 11, characterized in that [Explanation of symbols]

[0073] 101 AP 102 Station 105 AP 401 Storage section 402 Control Unit 403 Functional Department 404 Input section 405 Output Section 406 Communications Department

Claims

1. A communication device conforming to the IEEE 802.11 series standard, establishing means for establishing a plurality of links, including at least a first link and a second link, with a first other communication device; an acquisition means for executing a process of acquiring information about other surrounding communication devices when any one of the plurality of links established with the first other communication device is disconnected; a control means for controlling roaming to a second other communication device based on the information acquired by the acquisition means; A communication device comprising:

2. The communication device further includes a determination unit that determines whether to roam to the second other communication device based on the information acquired by the acquisition unit and a predetermined condition, The control means controls roaming to the second other communication device based on the determination by the determination means to perform roaming to the second other communication device.

2. The communication device according to claim 1.

3. the predetermined condition is that a number of links that is greater than the number of links that are established with the first other communication device can be established with the second other communication device, The determining means determines to roam to the second other communication device having a larger number of connectable links than the first other communication device.

3. The communication device according to claim 2.

4. The information is information about the number of links that can be established with other communication devices in the vicinity.

2. The communication device according to claim 1.

5. If there is no other communication device that can establish a greater number of links than the first other communication device, the control means controls not to disconnect the connection with the first other communication device.

2. The communication device according to claim 1.

6. The predetermined condition is that the communication quality of the link that can be established with the second other communication device is better than that of each link established with the first other communication device.

3. The communication device according to claim 2.

7. The information is information about the communication quality of links that can be established with other surrounding communication devices.

2. The communication device according to claim 1.

8. When there is no other communication device having a link with communication quality that is superior to that of the first other communication device, the control means controls the first other communication device so as not to disconnect the connection with the first other communication device.

2. The communication device according to claim 1.

9. The communication device further comprises a determining means for determining that a link between the communication device and an Affiliated AP belonging to the first other communication device has been disconnected based on a predetermined Link Reconfiguration Notify frame received from the Affiliated AP.

2. The communication device according to claim 1.

10. The communication device further comprises a determining means for determining that a link with an Affiliated AP belonging to the first other communication device has been disconnected based on the inability to receive a beacon frame transmitted from the Affiliated AP.

2. The communication device according to claim 1.

11. When any one of the plurality of links established with the first other communication device is disconnected, the control means controls the communication device not to roam to the second other communication device if the communication device is in a predetermined state.

2. The communication device according to claim 1.

12. The predetermined state is a state in which EMLSR or EMLMR is being implemented in the plurality of links established with the other communication device.

12. The device of claim 11 .

13. The predetermined state is a state in which the communication device is operating in a power saving mode.

12. The device of claim 11 .

14. A method for controlling a communication device conforming to the IEEE 802.11 series standard, comprising: establishing a plurality of links including at least a first link and a second link with a first other communication device; an acquisition step of executing a process of acquiring information about other surrounding communication devices based on the fact that any one of the plurality of links established with the first other communication device has been disconnected; a control step of controlling roaming to a second other communication device based on the information acquired by the acquisition means; A method for controlling a communication device, comprising:

15. A program for causing a computer to execute the communication device control method according to claim 14.

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