Communication device, control method, and program

Abstract

To improve communication efficiency by selecting an appropriate link when establishing a link.SOLUTION: A communication device receives a predetermined frame including a predetermined multilink element from another communication device. When the communication device receives the predetermined frame, the communication device selects a link to be established with the other communication device based on communication quality of a link that can be established with the other communication device. The communication device establishes the selected link with the other communication device. When a multilink is established, the communication device performs multilink communication via the multilink.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a communication device that performs wireless communication, a control method for the communication device, and a program. [Background technology]

[0002] The Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard series is known as the main communication standard for wireless LANs. The IEEE 802.11 standard series includes standards such as IEEE 802.11a / b / g / n / ac / ax.

[0003] In addition, the IEEE802.11be standard, which is the successor to the IEEE802.11ax standard, is being developed. As a new function of the IEEE802.11be standard, a function such as multi-link communication in which an AP and a STA establish multiple links with different frequency channels and communicate in parallel is being considered. For example, Patent Document 1 describes a mechanism for establishing multiple links for multi-link communication.

[0004] Moreover, APs and STAs that support multi-link communication are called AP MLD (Multi-Link Device) and non-AP-MLD (or STA MLD). Moreover, an AP that is associated with an AP MLD and operates on a different channel is called an affiliated AP, and a STA that is associated with a STA MLD and operates on a different channel is called an affiliated non-AP STA (or affiliated STA). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-103805 Summary of the Invention [Problem to be solved by the invention]

[0006] As mentioned above, the IEEE802.11be standard and its successor standards consider multi-link communication, in which multiple links are established in parallel between a pair of terminals and communication is performed via the multiple links. In multi-link communication, the STA MLD and AP MLD perform data communication simultaneously via two or more links, thereby improving throughput.

[0007] However, even if multiple links with poor communication quality are established when the multiple links are established, errors in sending and receiving frames may occur, which may result in a decrease in communication throughput. Also, even if a link with good communication quality and a link with poor communication quality are established, extra frames are exchanged to exchange information about the link with poor communication quality, which may result in an increase in communication overhead compared to communication via a single link.

[0008] The present invention has been made in consideration of at least one of the above problems. One aspect of the present invention has an object to provide a mechanism for improving communication efficiency by selecting an appropriate link when establishing links. Another aspect of the present invention has an object to improve communication efficiency by establishing an appropriate number of links when establishing links. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, a communication device according to one embodiment of the present invention has a receiving means for receiving a predetermined frame including a predetermined multilink element from another communication device, a selection means for selecting a link to be established with the other communication device based on the communication quality of a link that can be established with the other communication device when the receiving means receives the predetermined frame, an establishment means for establishing the link selected by the selection means with the other communication device, and a communication means for performing multilink communication via the multilink when the establishment means establishes a multilink. Effect of the Invention

[0010] According to one aspect of the present invention, it is possible to improve communication efficiency by selecting an appropriate link when establishing links, and according to another aspect of the present invention, it is possible to improve communication efficiency by establishing an appropriate number of links when establishing links. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 illustrates an example of a network configuration. [Diagram 2] FIG. 2 is a diagram illustrating an example of the hardware configuration of AP MLD / STA MLD. [Diagram 3] FIG. 11 is a diagram illustrating an example of the functional configuration of AP MLD / STA MLD. [Figure 4] FIG. 11 is a diagram illustrating an example of a Multi-Link connection sequence. [Diagram 5] FIG. 4 is a diagram showing an example of a flowchart regarding link establishment in the first embodiment. [Figure 6] FIG. 11 is a diagram showing an example of a flowchart regarding link establishment in the second embodiment. [Figure 7] FIG. 11 is a diagram showing an example of a flowchart regarding link establishment in the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Embodiment 1> Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Note that the configurations shown in the following embodiments are merely examples, and the present invention is not limited to the configurations shown in the drawings.

[0013] FIG. 1 shows an example of a network configuration according to the present embodiment. FIG. 1 shows an example of a network configuration in which a STA MLD 102 operating as a terminal station participates in a network 100 constructed by an AP MLD 101 operating as a base station. AP MLD stands for Access Point Multi-Link Device, and STA MLD stands for Station Multi-Link Device. STA MLD is also called non-AP MLD. AP MLD 101 and STA MLD 102 are communication devices and can transmit and receive signals to each other. Each communication device (AP MLD 101, STA MLD 102) can perform wireless communication in accordance with the IEEE802.11be (EHT) standard. IEEE stands for Institute of Electrical and Electronics Engineers. EHT stands for Extremely High Throughput. EHT may be interpreted as an abbreviation for Extreme High Throughput. Each communication device can communicate at frequencies in the 2.4 GHz band, the 5 GHz band, and the 6 GHz band. The frequency bands used by each communication device are not limited to these, and may use different frequency bands, such as the 60 GHz band. Also, each communication device can communicate using channels with frequency widths of 20 MHz, 40 MHz, 80 MHz, 160 MHz, and 320 MHz. The frequency width of the channel used by each communication device is not limited to these, and may use different frequency widths, such as 240 MHz and 4 MHz.

[0014] Although each communication device is described as being compatible with the IEEE802.11be standard, it may also be compatible with a legacy standard that is a standard that precedes the IEEE802.11be standard. Specifically, each communication device may be compatible with at least one of the IEEE802.11a / b / g / n / ac / ax standards. Also, each communication device may be compatible with any one of the successor standards including the IEEE802.11bn standard, which is a successor standard to the IEEE802.11be standard. The IEEE802.11bn standard is a successor standard to the IEEE802.11be standard that aims to improve reliability and achieve low latency, and may also be called IEEE802.11UHR (Ultra High Reliability). Also, a wireless frame that communicates according to the 11bn standard is also called UHR PPDU. PPDU is an abbreviation for PLCP Protocol Data Unit, and PLCP is an abbreviation for Physical Layer Convergence Protocol. The IEEE802.11 standard including the above-mentioned legacy standard and successor standard is called the IEEE802.11 series standard. In addition to the IEEE802.11 series standard, other communication standards such as Bluetooth (registered trademark), NFC, UWB, ZigBee, MBOA, etc. may be supported. 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. Also, it may be compatible with a communication standard for wired communication such as wired LAN. Specific examples of the AP MLD 101 include a wireless LAN router and a personal computer (PC), but are not limited to these, and any communication device capable of operating as an access point may be used. The AP MLD 101 may also be an information processing device such as a wireless chip capable of performing wireless communication conforming to the IEEE802.11be standard.Specific examples of the STA MLD 102 include, but are not limited to, a camera, a tablet, a smartphone, a PC, a mobile phone, a video camera, a headset, a network camera, a printer, a projector, etc. The STA MLD 102 may be an information processing device such as a wireless chip capable of performing wireless communication conforming to the IEEE802.11be standard.

[0015] The AP MLD 101 and the STA MLD 102 are Multi-Link Devices (MLDs) that can establish multiple links (multi-links) of different frequency channels and perform multi-link communication via the multiple links. The AP MLD includes multiple affiliated APs (hereinafter, APs) for establishing multiple links. The STA MLD includes multiple affiliated STAs (hereinafter, STAs) for establishing multiple links.

[0016] In the IEEE802.11 series standard, the bandwidth of each frequency channel is defined as 20 MHz. Here, the frequency channel is a frequency channel defined in the IEEE802.11 series standard, and in the IEEE802.11 series standard, multiple frequency channels are defined in each of the frequency bands of 2.4 GHz, 5 GHz, 6 GHz, and 60 GHz. Note that a bandwidth of 40 MHz or more may be used in one frequency channel by bonding with adjacent frequency channels. For example, the AP MLD 101 can establish and communicate with the STA MLD 102 a link 103 via a first frequency channel in the 5 GHz band. In parallel with this, the STA MLD 102 can establish and communicate with the AP MLD 102 a link 104 via a second frequency channel in the 6 GHz band. In this case, the STA MLD 102 executes multi-link communication that maintains the second link 104 via the second frequency channel in parallel with the link 103 via the first frequency channel.

[0017] 2 shows an example of the hardware configuration of the STA MLD 102 in this embodiment. The STA MLD 102 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. Note that there may be multiple antennas.

[0018] The storage unit 201 is composed of one or more memories such as a ROM and a 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. As the storage unit 201, in addition to memories such as ROM and RAM, 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 may be used. Furthermore, the storage unit 201 may include multiple memories.

[0019] The control unit 202 is configured with one or more processors such as a CPU or MPU, and controls the entire STA MLD 102 by executing a computer program stored in the storage unit 201. The control unit 202 may control the entire STA MLD 102 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 (radio frames) to be transmitted in communication with other communication devices. The CPU is an abbreviation for Central Processing Unit, and the MPU is an abbreviation for Micro Processing Unit. The control unit 202 may also be equipped with multiple processors such as multi-core processors, and the entire STA MLD 102 may be controlled by the multiple processors.

[0020] Furthermore, the control unit 202 controls the function unit 203 to execute predetermined processes such as wireless communication, imaging, printing, projection, etc. The function unit 203 is hardware that enables the STA MLD 102 to execute predetermined processes.

[0021] The input unit 204 receives various operations from the user. The output unit 205 outputs various types of information to the user via a monitor screen or a speaker. Here, the output by the output unit 205 may be a display on a monitor screen, a voice output by a speaker, a vibration output, or the like. Note that both the input unit 204 and the output unit 205 may be realized by a single module, such as a touch panel. Also, the input unit 204 and the output unit 205 may be integrated with the STA MLD 102, or may be separate.

[0022] The communication unit 206 controls wireless communication conforming to the IEEE802.11be standard. The communication unit 206 may also control wireless communication conforming to other IEEE802.11 series standards in addition to the IEEE802.11be standard, and control wired communication such as a wired LAN. The communication unit 206 controls the antenna 207 to transmit and receive signals generated by the control unit 202 for wireless communication.

[0023] If the STA MLD 102 supports the NFC standard, Bluetooth standard, etc. in addition to the IEEE802.11be standard, it may control wireless communication in accordance with these communication standards. If the STA MLD 102 can perform wireless communication in accordance with a plurality of communication standards, it may be configured to have a communication unit and an antenna that support each communication standard. The STA MLD 102 communicates data such as image data, document data, and video data with the AP MLD 101 via the communication unit 206. The antenna 207 may be configured as a separate unit from the communication unit 206, or may be configured together with the communication unit 206 as a single module.

[0024] Antenna 207 is an antenna capable of communication in the 2.4 GHz band, the 5 GHz band, and the 6 GHz band. STA MLD 102 may have one or more antennas. Also, a different antenna may be provided for each frequency band. Also, when STA MLD 102 has multiple antennas, it may have a communication unit 206 corresponding to each antenna.

[0025] The AP MLD 101 has the same hardware configuration as the STA MLD 102. The STA MLD 102 may have each component in the number equal to the number of STAs included in the STA MLD, or may have a configuration shared by each STA.

[0026] FIG. 3 shows a block diagram showing an example of the functional configuration of the STA MLD 102 in this embodiment. In this embodiment, each functional block is stored as a program in the storage unit 201, and the function is implemented by executing the program by the control unit 202. The control unit 202 executes the program to control each hardware and perform calculations and processing of information to realize each function. Note that some or all of the functional blocks may be implemented as hardware. In this case, some or all of the functional blocks are configured by, for example, an ACIC (Application Specific Integrated Circuit). Note that, in this embodiment, the AP MLD 101 also has a similar configuration, but for the AP MLD 101, the affiliated STA setting unit 302 in this configuration is an affiliated AP setting unit.

[0027] In this embodiment, the STA MLD 102 includes a multi-link control unit 301 , an affiliated STA setting unit 302 , a frame generation unit 303 , a frame transmission / reception unit 304 , a communication quality measurement unit 305 , and a UI control unit 306 .

[0028] The multi-link control unit 301 controls processes related to link establishment, such as link establishment process and communication start process for establishing one or more links used by the STA MLD 102 for wireless communication with the AP MLD 101, link addition and deletion process after link establishment, and communication end process for deleting all links. The link establishment process mainly consists of authentication process, association process, and 4-Way Hand Shake (4WHS) process.

[0029] The affiliated STA setting unit 302 selects and determines the affiliated STAs for various processes. For example, it controls the selection and determination of the affiliated STAs of the STA MLD 102 used in the link establishment process, and the selection and determination of the affiliated STAs of the STA MLD 102 used in the frame transmission and reception process.

[0030] The frame processing unit 303 performs processing to generate a wireless control frame to be transmitted by the frame transmitting / receiving unit 304 and processing to analyze a frame received via the frame transmitting / receiving unit 304. The frame processing unit 303 refers to operation settings such as parameters for communication stored in the storage unit 201 and performs processing to interpret and generate frames. The operation settings can also be configured to be changed based on a user operation accepted via the UI control unit 306. Information on the frame generated by the processing unit 303 is transmitted to the communication partner via the frame transmitting / receiving unit 304. Information on the frame received by the frame transmitting / receiving unit 304 is passed to the frame processing unit 302 and analyzed.

[0031] The frame transmitting / receiving unit 304 includes an antenna and a circuit for transmitting and receiving wireless signals to and from other wireless LAN devices, and a program for controlling them. The frame transmitting / receiving unit 304 executes wireless LAN communication control based on the frames generated by the frame processing unit 303 in accordance with the IEEE802.11 standard series.

[0032] The communication quality measurement unit 305 measures the communication quality of the communication environment based on the Beacon / Probe Response frame received by the frame transmission / reception unit 304. The communication quality may be, but is not limited to, RSSI, SNR, MCS, etc. RSSI is an abbreviation for Received Signal Strength Indicator, which is a value indicating the strength of radio waves. SNR is an abbreviation for Signal-to-Noise Ratio (or Signal Noise Rate), which is a value indicating the ratio of the strength of the radio waves of the target terminal to the strength of the radio waves of other terminals. MCS is an abbreviation for Modulation and Coding Scheme, which is information obtained by indexing a combination of a wireless modulation scheme, coding rate, etc.

[0033] The UI control unit 306 is composed of hardware related to a user interface such as a touch panel or buttons for accepting operations from a user, and a program for controlling them. For example, the multilink control unit 301 selects a remote device to which the STA MLD 102 will connect by accepting an operation from a user via the UI control unit 306. Also, the affiliated STA setting unit 302 performs processing for selecting and determining an affiliated STA of the STA MLD 102 to be used when the STA MLD 102 establishes a link by accepting an operation from a user via the UI control unit 306. The UI control unit 306 may further have a function for showing information such as audio output to the user.

[0034] Next, an overview of the establishment process of Multi-Link communication will be described. Fig. 4 shows a sequence diagram showing an example of the multi-link establishment process in this embodiment. Note that in this embodiment, an overview of the search process in which the STA MLD and AP MLD search and detect surrounding MLDs using a Beacon frame and a Probe Request / Response frame will be described. Then, a link establishment process in which the STA MLD and AP MLD establish a link with the MLD detected in the search process using an Authentication Request / Response frame and an Association Request / Response frame will be described.

[0035] 4, AP MLD 101 includes affiliated AP1 (AP1), affiliated AP2 (AP2), and affiliated AP3 (AP3). AP1 operates in the 2.4 GHz band, AP2 in the 5 GHz band, and AP3 in the 6 GHz band. STA MLD 102 includes affiliated STA1 (STA1), affiliated STA2 (STA2), and affiliated STA3 (STA3). STA1 operates in the 2.4 GHz band, STA2 in the 5 GHz band, and STA3 in the 6 GHz band.

[0036] First, each AP included in the AP MLD 101 transmits a Beacon frame in a frequency band in which the AP operates, thereby transmitting information about the network established by the AP MLD 101 to surrounding communication devices. Note that, in this embodiment, each AP (AP1, AP2, AP3) transmits a Beacon frame, but this is not limiting, and only a selected AP (for example, only AP1) may transmit a Beacon frame.

[0037] Next, each STA included in the STA MLD102 searches for and acquires information about the STA MLD102 by transmitting a Probe Request frame in the frequency band in which the STA operates. In this embodiment, each STA (STA1, STA2, STA3) transmits a Probe Request frame, but this is not limited to the above, and only selected STAs (for example, only STA1) may transmit an ML Probe Request frame. The ML Probe Request frame is a search request including a Multi-Link element described later, and is a frame transmitted to search for surrounding AP MLDs. Each STA acquires information about the AP MLD101 by receiving a Probe Response frame (or an ML Probe Response frame) transmitted by the AP of the AP MLD101 as a response to the transmitted Probe Request frame. In response, the AP MLD101 acquires information about the STA MLD102 by receiving a Probe Request frame (or an ML Probe Request frame) transmitted by the STA MLD102.

[0038] In this embodiment, the AP MLD 101 transmits a Beacon frame, and then the STA MLD 102 transmits a Probe Request frame. However, this is not limited to the above. The STA MLD 102 may transmit a Probe Request frame first, and the AP MLD 101 may not transmit a Beacon.

[0039] In this way, in the search process of this embodiment, each communication device includes a Multi-Link element in each frame it transmits. The Multi-Link element is, for example, a Basic Multi-Link element or a Probe Request Multi-Link element. Then, based on the fact that a Multi-Link element is included in any frame received in this search process, each communication device judges that a multi-link can be established in connection with the communication device that transmitted the frame including the Multi-Link element. That is, based on the fact that a Probe Request frame received from the STA MLD 102 includes a Multi-Link element, the AP MLD 101 judges that the STA MLD 102 is an MLD and that a multi-link can be established. Also, based on the fact that a Beacon frame or a Probe Response frame received from the AP MLD 101 includes a Multi-Link element, the STA MLD 102 judges that the AP MLD 101 is an MLD and that a multi-link can be established.

[0040] Furthermore, the STA MLD 102 acquires information on each AP of the opposing AP MLD 101 in this search process as information for establishing a link in the link establishment process described below. The STA MLD 102 acquires frequency band and channel information of each AP belonging to the AP 101 from an RNR (Reduced Neighbor Report) element included in a Beacon frame or a Probe Response frame transmitted by the AP MLD 101. The STA MLD 102 then performs the link establishment process described below based on the information on each AP acquired from the RNR element.

[0041] Next, the link establishment process of each communication device in the multi-link establishment process will be described. In the link establishment process of this embodiment, the AP MLD 101 and the STA MLD 102 establish a link by transmitting and receiving various frames such as an authentication frame, an association frame, and a frame related to a 4-way handshake.

[0042] First, the STA MLD 102 transmits an Authentication Request frame using one of the links it wishes to establish with the AP MLD 101. It is assumed that communication of various frames in this establishment process is performed using the link through which the Authentication Request frame was transmitted. In response to this, the AP MLD 101 transmits an Authentication Response frame. It is assumed in this embodiment that the STA MLD 102 and the AP MLD 101 establish a multi-link by transmitting and receiving various frames using STA1 and AP1, respectively.

[0043] Next, the STA MLD 102 transmits an Assciation Request frame including information about links to be established with the AP MLD 101. For example, the STA MLD 102 indicates that it wishes to establish multiple links with the AP MLD 101 by including information about multiple links in which AP1, AP2, and AP3 are operating in the frame. In response, the AP MLD 101 transmits an Assciation Response frame including information permitting (or denying) the establishment of a link with the STA MLD 102. As the establishment of multiple links is permitted in the Assciation Response frame, multiple links are established between the STA MLD 102 and the AP MLD 101.

[0044] The above is the establishment process of each communication device in the multi-link establishment process. In the above description, the establishment process of this embodiment is described as establishing three links, that is, links in the 2.4 GHz band, the 5 GHz band, and the 6 GHz band, but is not limited to this. For example, only one link (single link) may be established in the link establishment process.

[0045] In addition, in multi-link communication, links between communication devices may be established via multiple different channels included in the same frequency band. For example, 36ch in the 5GHz band may be established as a first link, and 48ch in the 5GHz band may be established as a second link. Links of the same frequency band and links of different frequency bands may be mixed. For example, in addition to link 103 of 36ch in the 5GHz band, AP MLD 101 and STA MLD 102 may establish a link of 149ch in the 5GHz band and a link of 15ch in the 6GHz band. By establishing multiple connections of different frequency bands with STA MLD 102, AP MLD 101 can establish communication with STA MLD 102 in another band even when one band is congested, so that a decrease in throughput and communication delays in communication with STA MLD 102 can be prevented.

[0046] However, if the multiple links are established through the establishment process described in FIG. 4 by simply establishing all communication links that can be established based on the device's capabilities, multiple links may be established, including links with poor communication quality.

[0047] Here, even if multiple links with poor communication quality are established, errors may occur in sending and receiving frames, and communication throughput may not be improved. In addition, even if a link with good communication quality and a link with poor communication quality are established, an extra frame is exchanged to exchange information about the link with poor communication quality, so that communication overhead may increase more than when communicating with a single link. In view of this, in this embodiment, when performing a process of establishing multiple links, a mechanism is provided for establishing a more suitable link by measuring the communication quality and controlling the selection of the link to be established based on the communication quality. A specific description will be given below using a flowchart. FIG. 5 is a flowchart showing an example of a process in which the STA MLD 102 determines which link to use to establish a link (multi-link or single link) after recognizing that the opposing AP MLD 101 is a communication device (MLD) capable of establishing a multi-link. In this embodiment, the STA MLD 102 determines which link to use to establish a link based on the communication quality of each link. In this embodiment, it is assumed that each process shown in the flowchart of Fig. 5 is realized by the processor of the control unit 202 of the STA MLD 102 executing a program for implementing each control module. Note that data transmission and reception processes are realized in cooperation with hardware such as a communication unit. Note that in cases where it is desired to clarify the subject of processing, each functional unit realized by the control unit 202 executing a program will be described as the subject. Note that, as described above, it is also possible to realize some or all of the processing by hardware such as ASIC, ASSP, SoC, etc. ASSP is an abbreviation for Application Specific Standard Product, and SoC is an abbreviation for System on a Chip.

[0048] This process may be started based on the control of the multi-link control unit 301, for example, when the power of the STA MLD 102 is turned on.

[0049] First, the frame transmission / reception unit 304 of the STA MLD 102 receives a Beacon frame or a Probe Response frame transmitted by the opposing AP (S501). In this embodiment, it is assumed that the Beacon / Probe Response frame transmitted by the AP1 of the AP MLD 101 is received by the STA1 of the STA MLD 102.

[0050] Next, the frame processing unit 303 of the STA MLD 102 analyzes the Beacon / Probe Response frame received by the frame transmission / reception unit 304 in S501. Then, based on the result of the analysis, it is determined whether the opposing AP is an MLD that supports multi-link (S502). In S502, it is determined whether the opposing AP is an MLD based on whether the Beacon / Probe Response frame transmitted by the opposing AP includes a Multi-Link element. If the frame includes a Multi-Link element, it is determined that the opposing AP that transmitted the frame is an MLD and is an AP that can establish a multi-link. On the other hand, if the Beacon / Probe Response frame received in S601 does not include a Multi-Link element, a single link is established between the opposing AP that transmitted the frame and the link that received the frame (S503). Note that in this embodiment, it is assumed that the opposing AP is the AP MLD 101, and the Beacon / Probe Response frame transmitted by AP1 of the AP MLD 101 includes a Multi-Link element.

[0051] If it is determined in S502 that the opposing AP is an AP MLD that supports multi-link, the RNR element included in the Beacon / Probe Response frame transmitted by the AP MLD is analyzed. Then, based on the result of the analysis, information on an AP other than the AP that transmitted the frame provided in the opposing AP MLD is acquired (S504). Note that in this embodiment, the STA MLD 102 acquires information on AP2 and AP3 of the AP MLD 101 from the Beacon / Probe Response frame transmitted by AP1 of the AP MLD 101. Also, here, for example, information that can identify the frequency band of the link on which each AP operates and information that can identify the channel are acquired from the RNR Element included in the Beacon / Probe ResponseBeacon / Probe Response frame.

[0052] Next, based on the information acquired in S504, the beacon / probe response frames transmitted by AP2 and AP3 are received, and detailed information about AP2 and AP3 is acquired (S505).

[0053] Next, based on the frame received by the frame transmission / reception unit 304 of the STA MLD 102, the communication quality measurement unit 305 measures the communication quality of each link on which each AP belonging to the AP MLD 101 operates (S506). For example, the STA MLD 102 transmits a Probe Request frame to each AP on the link on which each AP belonging to the AP MLD 101 operates via the frame transmission / reception unit 304, and receives a Probe Response frame from each AP. Then, the communication quality determination unit 305 measures communication quality information based on the received frame.

[0054] Then, it is determined whether the communication quality of each link acquired in S506 exceeds a predetermined threshold (S507). Here, the predetermined threshold may be, for example, RSSI=-30 dBm or RSSI=-50 dBm. By setting such a threshold, it becomes possible to select only links with high communication quality as links to be established. The predetermined threshold may also be RSSI=-90 dBm or RSSI=-100 dBm. By setting such a threshold, it becomes possible to select links that ensure a minimum communication quality as links to be established.

[0055] The predetermined threshold may be, for example, SNR=40, SNR=25, or SNR=20. By setting such a threshold, it becomes possible to select only links with high communication quality as links to be established. The predetermined threshold may be SNR=10. By setting such a threshold, it becomes possible to select links that ensure a minimum communication quality as links to be established.

[0056] The predetermined threshold may be, for example, the communication quality required to use MCS0. MCS is an index of a combination of a wireless modulation method, a coding rate, etc., and the MCS to be used varies depending on the communication environment. MCS0 is the method with the lowest throughput and is used when the communication environment is very bad. If the RSSI is below the threshold for using MCS0, it may be determined that the communication environment is bad for the link. In this embodiment, the communication quality required to use MCS0 is set as the predetermined threshold, but this is not limited thereto. For example, the communication quality required to use an MCS used in a better communication environment than MCS0, such as MCS4, may be set as the predetermined threshold. The above-mentioned predetermined threshold is an example, and the predetermined threshold may be set by the user via the UI control unit 306.

[0057] If it is determined in S507 that there are a plurality of links whose communication quality exceeds a predetermined threshold, a multi-link is established between the AP MLD 101 and the plurality of links (S509).

[0058] On the other hand, if the result of the determination in S507 is that there are not multiple links whose communication quality exceeds the predetermined threshold, a single link is established with the AP MLD 101 (S508). Note that if there is not even one link whose communication quality exceeds the predetermined threshold, a single link may be established with the link with the best communication quality.

[0059] The above describes an embodiment in which the STA MLD 102 establishes a multi-link based on the presence of multiple links whose communication quality exceeds a predetermined threshold when establishing a link with the AP MLD 101. In this way, by appropriately determining whether or not the STA MLD 102 establishes a multi-link with the AP MLD 101, the STA 102 can prevent the overhead from increasing after establishing a multi-link with the AP 101, compared to establishing a single link.

[0060] <Embodiment 2> In the first embodiment, the case where communication quality is used as a criterion for selecting a link is exemplified. In the second embodiment, a mechanism for selecting a link with fewer restrictions on transmission and reception as a criterion for selecting a link will be described.

[0061] There are two types of multilinks: one capable of STR operation, and one capable of only NSTR operation (not capable of STR operation). A multilink capable of STR operation is a multilink consisting of a pair of links in which, when a multilink including at least a first link and a second link is established with another communication device, a transmission operation is possible with the second link while a reception operation is being performed with the first link. In contrast, a multilink capable of only NSTR operation is a multilink consisting of a pair of links with the constraint that the second link must perform the same transmission and reception operation in synchronization with the transmission and reception operation of the first link. Therefore, a multilink capable of STR operation is considered to have improved communication throughput compared to a multilink that is restricted by the NSTR operation.

[0062] Therefore, in this embodiment, in order to establish a multi-link that is not subject to the above-mentioned NSTR constraints (STR operation possible), when the STA MLD 102 establishes a link with the AP MLD 101, it is determined whether or not to establish a multi-link based on whether STR operation is possible when the AP MLD 101 establishes a multi-link.

[0063] Note that STR is an abbreviation for Simultaneous Transmit and Receive, and NSTR is an abbreviation for Nonsimultaneous Transmit and Receive.

[0064] The flow of this embodiment will be described below with reference to FIG.

[0065] The processing from S601 to S604 in this embodiment is the same as the processing from S501 to S504 in the first embodiment, and therefore a description thereof will be omitted.

[0066] In this embodiment, when a multi-link is established with the opposing AP MLD, it is determined whether or not to perform a multi-link connection based on whether STR operation is possible (S605).

[0067] For example, the MLD determines whether the opposing AP can perform STR based on the information included in the Multi-Link element of the Beacon / Probe Response frame sent by the opposing AP MLD. In more detail, the MLD determines whether the opposing AP MLD can perform STR by looking at bit 7 of the MLD Capabilities and Operations subfield of the Multi-Link element. If the bit is 1, the opposing AP MLD is determined to be capable of STR, and if the bit is 0, the opposing AP MLD is determined to be incapable of STR.

[0068] As a result of this determination, it is determined that the opposing AP MLD can operate in STR and that establishing a multi-link is expected to improve communication throughput, and so a multi-link is established (S607).On the other hand, if it is determined in S607 that the opposing AP MLD cannot operate in STR, a single link is established with the AP with the best communication quality based on the communication quality information of each link calculated in S606 (S606).

[0069] <Embodiment 3> In the first embodiment, a case where communication quality is used as a criterion for selecting a link is exemplified. In the second embodiment, a case where a link with fewer restrictions on transmission and reception is selected as a criterion for selecting a link is exemplified. In the third embodiment, a flow for determining whether or not to establish a multi-link based on the remaining battery level of the STA MLD 102 when the STA MLD 102 establishes a link with the AP MLD 101 will be described.

[0070] The processing from S701 to S704 in this embodiment is the same as the processing from S501 to S504 in the first embodiment, and therefore a description thereof will be omitted.

[0071] In this embodiment, after the calculation of the communication quality information of each AP is completed, it is confirmed whether the remaining battery charge of the STA MLD 102 is equal to or greater than a given threshold (S705). If the remaining battery charge of the STA MLD 102 is equal to or greater than the given threshold, a multi-link is established with the AP MLD 101 (S707). On the other hand, if the remaining battery charge of the STA MLD 102 is less than the given threshold, a single link is established with the AP MLD 101 (S706).

[0072] In addition, the predetermined threshold in this embodiment may be, for example, a battery remaining capacity of 20% or a battery remaining capacity of 10%. By providing such a threshold, when it is desired to reduce power consumption, it is possible to further reduce power consumption by not establishing a multi-link.

[0073] <Other embodiments> Each communication device described in each of the above embodiments may be a printer having a printing means. When operating as a printer, for example, it is possible to print image data acquired by data exchange with a partner device on a sheet such as paper. The printing method of the printer may be an electrophotographic method that realizes printing by transferring and fixing toner on a sheet such as paper, or an inkjet method that realizes printing by ejecting color material on a sheet such as paper.

[0074] Furthermore, each communication device described in the present embodiment may be a digital still camera having an image capturing means. When operating as a camera, it is possible to communicate captured image data by data exchange with a partner device, for example.

[0075] In the third embodiment, whether or not to establish a multi-link with the opposing AP MLD is selected based on the remaining battery power of the STA MLD, but this is not limiting. For example, whether or not to establish a multi-link may be determined based on whether the STA MLD is operating in a power-saving mode that consumes less power than during normal operation. In this case, when the STA MLD is operating in normal operation, a multi-link is established with the AP MLD. On the other hand, when the STA MLD is operating in a power-saving mode, a single link is established with the AP MLD.

[0076] In addition, the above-mentioned embodiments can be appropriately combined. For example, the STA MLD 102 may be configured to establish a multi-link only when the STR operation is possible when there are a plurality of links with communication quality exceeding a predetermined threshold among the links that can be established with the AP MLD 101, and when a multi-link is established with the plurality of links exceeding the predetermined threshold.

[0077] Also, a recording medium on which the program code of the software that realizes the above-mentioned functions is recorded may be supplied to the system or device, and the computer (CPU, MPU) of the system or device may read and execute the program code stored in the recording medium. In this case, the program code itself read from the storage medium realizes the functions of the above-mentioned embodiments, and the storage medium on which the program code is stored constitutes the above-mentioned device.

[0078] Examples of storage media for supplying 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.

[0079] In addition, the above-mentioned functions may be realized not only by the computer executing the read program code, but also by the OS running on the computer performing all or part of the actual processing based on the instructions of the program code. OS is an abbreviation for Operating System.

[0080] Furthermore, the program code read from the storage medium may be written to a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, and a CPU provided in the function expansion board or function expansion unit may perform part or all of the actual processing based on instructions in the program code to realize the above-mentioned functions.

[0081] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0082] The disclosure of each of the above-described embodiments includes the following configurations.

[0083] (Configuration 1) 1. A communication device, comprising: receiving means for receiving a predetermined frame including a predetermined multilink element from another communication device; a selection means for selecting a link to be established with the other communication device based on a communication quality of a link that can be established with the other communication device when the receiving means receives the predetermined frame; an establishing means for establishing the link selected by the selecting means with the other communication device; a communication means for performing multilink communication via the multilink when the establishing means establishes the multilink; A communication device comprising:

[0084] (Configuration 2) When the selection means selects only one link as the link to be established, the establishment means establishes a single link with the other communication device. 2. The communication device according to configuration 1.

[0085] (Configuration 3) When the selection means selects a plurality of links as links to be established with the other communication device, the establishment means establishes the multi-link consisting of the plurality of links. 3. The communication device according to configuration 1 or 2.

[0086] (Configuration 4) When the receiving means receives the predetermined frame, the selecting means selects a link whose communication quality is higher than a predetermined threshold. 4. The communication device according to claim 1, wherein the first and second communication devices are connected to each other.

[0087] (Configuration 5) The predetermined frame is a management frame. 5. The communication device according to claim 1, wherein the first and second communication devices are connected to each other.

[0088] (Configuration 6) The communication quality mentioned above is the Received Signal Strength Indicator (RSSI). 6. The communication device according to any one of configurations 1 to 5,

[0089] (Configuration 7) The communication quality mentioned above refers to the Signal-to-Noise Ratio (SNR). 6. The communication device according to any one of configurations 1 to 5,

[0090] (Configuration 8) If there is no link with a communication quality higher than a predetermined threshold, the selection means selects the link with the highest communication quality among the links that can be established. 8. The communication device according to claim 3, wherein: [Explanation of symbols]

[0091] 201 Storage section 202 Control section 203 Functional Department 204 Input section 205 Output section 206 Communications Department

Claims

1. A communication device, Receiving means for receiving a predetermined frame containing a predetermined multilink element from another communication device, When the receiving means receives the predetermined frame, the selection means selects a link to establish with the other communication device based on the communication quality of the link that can be established with the other communication device, The selection means establishes a link selected by the selection means with the other communication device, When the establishment means establishes a multilink, the communication means performs multilink communication via the multilink. A communication device characterized by having the following features.

2. If the selection means selects only one link as the link to be established, the establishment means establishes a single link with the other communication device. The communication device according to feature 1.

3. If the selection means selects multiple links as links to be established with the other communication device, the establishment means establishes the multilink composed of the multiple links. The communication device according to feature 1.

4. When the receiving means receives the predetermined frame, the selection means selects a link with a communication quality higher than a predetermined threshold. The communication device according to feature 3.

5. The aforementioned predetermined frame refers to a management frame. The communication device according to feature 1.

6. The aforementioned communication quality refers to the Received Signal Strength Indicator (RSSI). The communication device according to feature 4.

7. The aforementioned communication quality refers to the Signal-to-Noise Ratio (SNR). The communication device according to feature 4.

8. If there are no links with communication quality higher than a predetermined threshold, the selection means selects the link with the highest communication quality among the available links. The communication device according to feature 4.

9. A method for controlling a communication device, A receiving step of receiving a predetermined frame containing a predetermined multilink element from another communication device, If the predetermined frame is received by the receiving step, a selection step is made to select a link to be established with the other communication device based on the communication quality of the link that can be established with the other communication device. An establishment step is to establish the link selected in the selection step with the other communication device, If a multilink is established in the establishment step, a communication step is performed to perform multilink communication via the multilink. A method for controlling a communication device, characterized by having the following features.

10. A program for causing a computer to function as a control method for the communication device described in any one of claims 9.

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