Patent Description:
The Institute of Electrical and Electronics Engineers (IEEE) <NUM> series is known as wireless local area network (WLAN) communication standards formulated by the IEEE. The IEEE <NUM> series standards include standards such as the IEEE <NUM> a/b/g/n/ac/ax standards.

Patent Literature <NUM> (PTL1) discusses performance of wireless communication in which, in a case of communication compliant with the IEEE <NUM>. 11ax standard, orthogonal frequency division multiplex access (OFDMA) is used. In the wireless communication compliant with The IEEE <NUM>. 11ax standard, using OFDMA allows to achieve high peak throughput.

The IEEE is considering the formulation of the IEEE <NUM>. 11be standard as a new IEEE <NUM> series standard for even higher throughput and improved frequency use efficiency. As for the IEEE <NUM>. 11be standard, a technique for establishing a plurality of links between an access point (AP) and a station (STA) via a plurality of different frequency channels to perform communication is being considered.

<CIT> discusses an access point (AP), station (STA) and method of communication. The AP may be included in a plurality of APs affiliated with a multi-link AP logical entity. As part of a multi-link AP logical entity, the plurality of APs may share a common medium access control (MAC) data service interface to an upper layer. The AP may exchange signaling with an STA as part of a multi-link setup process between the multi-link TP logical entity and a multi-link non-AP logical entity. The STA may be included in a plurality of STAs affiliated with the multi-link non-AP logical entity. The multi-link setup process may establish a link between each AP of the plurality of APs and a corresponding STA of the plurality of STAs. Document <CIT> discloses methods for multi-link setup between a multi-link AP logical entity and multi-link non-AP logical entity.

As described above, in the IEEE <NUM>. 11be standard, multi-link communication in which an AP and an STA establish a plurality of links on different frequency channels and communicate in parallel is being considered. To perform multi-link communication, multi-link communication-related information, such as multi-link communication capability information about the AP, needs to be communicated between the AP and the STA. A media access control (MAC) frame which is a frame for appropriately communicating the multi-link communication-related information is a newly developed format.

In view of the foregoing, the present invention is directed to enabling use of an appropriate MAC frame to communicate information about communication via a plurality of links compliant with an IEEE <NUM> series standard to be established with a partner apparatus on a plurality of different frequency channels.

With the above-described objective, a communication apparatus includes a communication means for communicating a media access control, MAC, frame compliant with an Institute of Electrical and Electronics Engineers (IEEE) <NUM> series standard with another communication apparatus, and establishment means for establishing a plurality of links on a plurality of different frequency channels where multi-link communication can be performed with a partner apparatus, wherein the MAC frame communicated by the communication means includes a multi-link element as information related to communications via the plurality of links, and wherein the multi-link element includes a common info field and a link info field, and the common info field includes a field capable of indicating a distance between frequency channels recommended for a communication apparatus which transmits the MAC frame including the multi-link element, in the communications via the plurality of links, to perform the communications via the plurality of links asynchronously.

According to the present invention, information about communication via a plurality of links compliant with the IEEE <NUM> series standard to be established with the partner apparatus on a plurality of different frequency channels can be communicated using an appropriate MAC frame.

An exemplary embodiment of the present invention will be described in detail below with reference to the attached drawings. The configuration described in the following exemplary embodiment is just an example, and the present invention is not limited to the illustrated configuration.

<FIG> illustrates a configuration of a network in which a communication apparatus <NUM> according to the present exemplary embodiment participates. The communication apparatus <NUM> is an access point (AP) intended to construct a network <NUM>. The network <NUM> is a wireless network. In the present exemplary embodiment, in a case where the communication apparatus <NUM> constructs a plurality of networks, all the networks have the same basic service set identifier (BSSID). A BSSID is an identifier for identifying a network. Service set identifiers (SSIDs) that are presented by the communication apparatus <NUM> in any of the networks are also the same. An SSID is an identifier for identifying an AP. In the present exemplary embodiment, the communication apparatus <NUM> uses one SSID even if a plurality of connections is established.

A communication apparatus <NUM> is a station (STA) intended to join the network <NUM>. Each communication apparatus supports the Institute of Electrical and Electronics Engineers (IEEE) <NUM>. 11be (Extremely High Throughput or Extreme High Throughput [EHT]) standard, and can perform wireless communication compliant with the IEEE <NUM>. 11be standard via the network <NUM>. Each communication apparatus can communicate in <NUM>-GHz, <NUM>-GHz, and <NUM>-GHz frequency bands. The frequency bands for the communication apparatuses are not limited thereto. Other frequency bands such as a <NUM>-GHz band may be used. Each communication apparatus can communicate in bandwidths of <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>.

The communication apparatuses <NUM> and <NUM> can implement multi-user (MU) communication where signals from a plurality of users are multiplexed by performing orthogonal frequency division multiple access (OFDMA) communication compliant with the IEEE <NUM>. 11be standard. In OFDMA communication, grouped portions (Resource Units [RU]) of a frequency band are assigned to STAs in a non-overlapping manner, and carriers assigned to the respective STAs are orthogonal to each other. The AP can thus communicate with a plurality of STAs in parallel.

The communication apparatuses <NUM> and <NUM> perform multi-link communication by establishing links via a plurality of frequency channels. As employed herein, a frequency channel refers to a channel which is defined in an IEEE <NUM> series standard, and also in which wireless communication compliant with the IEEE <NUM> series standard can be performed. The IEEE <NUM> series standard defines a plurality of frequency channels in each of the <NUM>-GHz, <NUM>-GHz, and <NUM>-GHz frequency bands. In the IEEE <NUM> series standard, each frequency channel is defined to have a bandwidth of <NUM>. Further, a bandwidth of <NUM> or more can also be used as a single frequency channel by adjoining frequency bands. For example, the communication apparatus <NUM> can establish a first link <NUM> via a first frequency channel in the <NUM>-GHz band and a second link <NUM> via a second frequency channel in the <NUM>-GHz band with the communication apparatus <NUM>, and communicate via both the links. In such a case, the communication apparatus <NUM> maintains the second link <NUM> via the second frequency channel in parallel with the first link <NUM> via the first frequency channel. The communication apparatus <NUM> can improve the throughput of the communication with the communication apparatus <NUM> by thus establishing links via a plurality of frequency channels with the communication apparatus <NUM>. The communication apparatuses <NUM> and <NUM> may establish a plurality of links at different frequency bands in multi-link communication. For example, the communication apparatuses <NUM> and <NUM> may establish a third link in the <NUM>-GHz band in addition to the first link <NUM> in the <NUM>-GHz band and the second link <NUM> in the <NUM>-GHz band. Alternatively, the communication apparatuses <NUM> and <NUM> may establish links via a plurality of different channels included in the same frequency band. For example, the communication apparatuses <NUM> and <NUM> may establish the first link <NUM> via 1ch of the <NUM>-GHz band and the second link <NUM> via 5ch of the <NUM>-GHz band. Links in the same frequency band and links in different frequency bands can be established at the same time. For example, the communication apparatuses <NUM> and <NUM> may establish a third link via 36ch of the <NUM>-GHz band in addition to the first link <NUM> via 1ch of the <NUM>-GHz band and the second link <NUM> via 5ch of the <NUM>-GHz. By establishing a plurality of connections in different frequency bands with the communication apparatus <NUM>, the communication apparatus <NUM> can communicate with the communication apparatus <NUM> in one band even in a case where another band is congested. This can prevent a drop in the throughput of the communication with the communication apparatus <NUM>.

In multi-link communication, a plurality of links established between the communication apparatuses <NUM> and <NUM> is at least links each on a different frequency channel. In multi-link communication, the channel distance between the frequency channels of the plurality of links established between the communication apparatuses <NUM> and <NUM> is at least greater than <NUM>. While, in the present exemplary embodiment, the communication apparatuses <NUM> and <NUM> establish the first link <NUM> and the second link <NUM>, the communication apparatuses <NUM> and <NUM> may establish three or more links.

In the multi-link communication, the communication apparatuses <NUM> and <NUM> can communicate in three modes. One is an asynchronous mode (async mode). In this mode, communications via the plurality of links in the multi-link communication are performed asynchronously from each other. Specifically, the communication via the first link and the communication via the second link are performed at respective independent timings. The first link and the second link each can thus perform communication at a timing irrespective of the communication timing of the other. In such a case, if the channel distance between the frequency channels (channels) of the respective links is narrow, the communication on one link can affect the communication on the other. Specifically, if the frequency channels of the links are close, the communication performed on one link can be detected by the other in carrier sensing, which disables the communication on the other link while the one link is communicating. Thus, in the async mode, the channel distance between links is set wide. Another mode is a synchronous mode (sync mode). In this mode, the communications via the plurality of links is asynchronously performed. Specifically, the first link and the second link start respective communications at the same timing. Since the communications via the respective links are started at the same time, the communication on one link will not be detected by the other link in carrier sensing. The channel distance between the channels of the respective links can thus be set narrow. The other mode is a semi-asynchronous mode (semi-async mode). In this mode, in a case where data is to be communicated via one link and the frequency channel of the other link is idle, communication via both the links is synchronously performed. For example, in a case where a back-off counter of the first link becomes <NUM> and the frequency channel of the second link is idle, communication via the first link and the second link is started at the same timing. Here, the back-off counter of the second link does not need to be <NUM>. In a case where the back-off counter of the first link becomes <NUM> and the frequency channel of the second link is not idle, only the communication via the first link is started without starting the communication via the second link. In this mode, in a case where communications via a plurality of links are performed in parallel, the communications via the respective links is started at the same time. Thus, the distance between the channels of the respective links may be set narrow. The communication apparatuses <NUM> and <NUM> may select the mode to be used in the multi-link communication, based on the channel distance between the plurality of links established.

In performing multi-link communication, at least either one of the communication apparatuses <NUM> and <NUM> is an apparatus that can transmit data via a link and receive data via another link at the same time. Alternatively, at least either one of the communication apparatuses <NUM> and <NUM> may be an apparatus that, when transmitting data via one link, can only transmit data via another link at the same time. Alternatively, at least either one of the communication apparatuses <NUM> and <NUM> may be an apparatus that, when receiving data via one link, can only receive data via another link at the same time. Alternatively, at least either one of the communication apparatuses <NUM> and <NUM> may be an apparatus that can maintain a plurality of links at the same time but, when communicating data via one link, is unable to communicate data via another link at the same time. Such a communication apparatus is regarded as not supporting the sync mode or the semi-async mode.

In performing multi-link communication, the communication apparatuses <NUM> and <NUM> each divide a piece of data and transmit the divided pieces of data to the partner apparatus via the plurality of links. Alternatively, the communication apparatuses <NUM> and <NUM> may transmit the same data via the plurality of links so that the communication via one link serves as a backup to the communication via the other. Specifically, the communication apparatus <NUM> transmits the same data to the communication apparatus <NUM> via the first link using the first frequency channel and the second link using the second frequency channel. In such a case, if an error occurs in the communication via the first link, for example, the communication apparatus <NUM> can receive the data transmitted from the communication apparatus <NUM> since the same data is also transmitted via the second link. Alternatively, the communication apparatuses <NUM> and <NUM> may selectively use the links in accordance with the type of frame or data to be communicated. For example, the communication apparatus <NUM> may transmit a management frame via the first link and transmit data frame including data via the second link. Specific examples of the management frame include a Beacon frame, Probe Request/Response frames, and Association Request/Response frames. In addition to such frames, a Disassociation frame, an Authentication frame, a Deauthentication frame, and an Action frame are also referred to as management frames. The Beacon frame is a frame for notifying network information. The Probe Request frame is a frame for requesting network information. The Probe Response frame is a response to the Request frame and is a frame for providing network information. The Association Request frame is a frame for requesting connection. The Association Response frame is a response to the Association Request frame and is a frame indicating a connection permission, an error, etc. The Disassociation frame is a frame for disconnecting the connection. The Authentication frame is a frame for authenticating the partner apparatus. The Deauthentication frame is a frame for aborting the authentication of the partner apparatus and disconnecting the connection. The Action frame is a frame for performing an additional function other than the foregoing functions. The communication apparatuses <NUM> and <NUM> transmit and receive management frames compliant with the IEEE <NUM> series standard. Alternatively, in transmitting data related to a captured image, for example, the communication apparatus <NUM> may transmit meta information, such as the date, imaging parameters (aperture value and shutter speed), and position information via the first link, and transmit pixel information via the second link.

The communication apparatuses <NUM> and <NUM> may be capable of multiple-input and multiple-output (MIMO) communication. In such a case, the communication apparatuses <NUM> and <NUM> include a plurality of antennas. Either one of the communication apparatuses <NUM> and <NUM> transmits different signals from the respective antennas using the same frequency channel. The receiver apparatus receives all the signals arriving from the plurality of streams using the plurality of antennas at the same time, and divides and decodes the signals of the respective streams. By performing such MIMO communication, the communication apparatuses <NUM> and <NUM> can communicate a greater amount of data, in the same amount of time, than the amount of data of when the MIMO communication is not performed. The communication apparatuses <NUM> and <NUM> may perform MIMO communication using some of the links in performing multi-link communication.

While, in the above description, the communication apparatuses <NUM> and <NUM> support the IEEE <NUM>. 11be standard, the supporting standard can be at least any one of legacy standards preceding the IEEE <NUM>. 11be standard. The legacy standards refer to the IEEE <NUM>. 11a/b/g/n/ac/ax standards. In the present exemplary embodiment, at least one of the IEEE <NUM>. 11a/b/g/n/ac/ax/be standards will be referred to as an IEEE <NUM> series standard. In addition to the IEEE <NUM> series standard, the communication apparatuses <NUM> and <NUM> may support other communication standards, such as Bluetooth®, near field communication (NFC), ultra wide band (UWB), Zigbee, and Multiband orthogonal frequency division multiplexing (OFDM) Alliance (MBOA). UWB includes wireless Universal Serial Bus (USB), wireless <NUM>, and Winet. Wired communication standards, such as a wired local area network (LAN), may also be supported.

Specific examples of the communication apparatus <NUM> include, but not limited to, a wireless LAN router and a personal computer (PC). The communication apparatus <NUM> may be any communication apparatus that can perform multi-link communication with another communication apparatus. The communication apparatus <NUM> may be an information processing apparatus, such as a wireless chip, that can perform wireless communication compliant with the IEEE <NUM>. 11be standard. Specific examples of the communication apparatus <NUM> include, but not limited to, a camera, a tablet, a smartphone, a PC, a mobile phone, and a video camera. The communication apparatus <NUM> may be any communication apparatus that can perform multi-link communication with another communication apparatus. The communication apparatus <NUM> may be an information processing apparatus, such as a wireless chip, that can perform wireless communication compliant with the IEEE <NUM>. 11be standard. While the network illustrated in <FIG> is a network including one AP and one STA, the numbers of APs and STAs are not limited thereto. The information processing apparatus, such as a wireless chip, includes an antenna for transmitting generated signals.

<FIG> illustrates a hardware configuration of the communication apparatus <NUM> according to the present exemplary embodiment. The communication apparatus <NUM> includes a storage unit <NUM>, a control unit <NUM>, a functional unit <NUM>, an input unit <NUM>, an output unit <NUM>, a communication unit <NUM>, and an antenna <NUM>.

The storage unit <NUM> includes one or more memories, such as a read-only memory (ROM) and a random access memory (RAM), and stores a computer program for performing various operations to be described below and various types of information, such as communication parameters for wireless communication. Aside from memories such as a ROM and a RAM, storage media, such as a flexible disk, a hard disk, an optical disc, a magneto-optic disc, a compact disc read-only memory (CD-ROM), a compact disc recordable (CD-R), a magnetic tape, a nonvolatile memory card, and a digital versatile disc (DVD) may be used as the storage unit <NUM>. The storage unit <NUM> may include a plurality of memories.

The control unit <NUM> includes one or more processors, such as a central processing unit (CPU) and a micro processing unit (MPU), and controls entire operation of the communication apparatus <NUM> by executing the computer program stored in the storage unit <NUM>. The control unit <NUM> may be configured to control the entire operation of the communication apparatus <NUM> through cooperation of the computer program stored in the storage unit <NUM> and an operating system (OS). Moreover, the control unit <NUM> generates data and signals (wireless frames) to be transmitted during communication with other communication apparatuses. The control unit <NUM> may include a plurality of processors like a multi-core processor, and control entire operation of the communication apparatus <NUM> using the plurality of processors.

The control unit <NUM> controls the functional unit <NUM> to perform wireless communication and predetermined processing, such as imaging, printing, and projection. The functional unit <NUM> is a piece of hardware for the communication apparatus <NUM> to perform the predetermined processing.

The input unit <NUM> accepts various operations from the user. The output unit <NUM> performs various outputs to the user via a monitor screen and a speaker. The outputs made by the output unit <NUM> may include display on the monitor screen, an audio output from the speaker, and a vibration output. Both the input unit <NUM> and the output unit <NUM> may be implemented by one module, such as a touch panel. The input unit <NUM> and the output unit <NUM> each may be integrated with the communication apparatus <NUM> or separate from the communication apparatus <NUM>.

The communication unit <NUM> controls wireless communication compliant with the IEEE <NUM>. 11be standard. The communication unit <NUM> may also control wireless communication compliant with other IEEE <NUM> series standards in addition to the IEEE <NUM>. 11be standard, or control wired communication, such as wired LAN communication. The communication unit <NUM> controls the antenna <NUM> to transmit and receive signals, for wireless communication, generated by the control unit <NUM>. In a case where the communication apparatus <NUM> supports the NFC standard or the Bluetooth® standard in addition to the IEEE <NUM>. 11be standard, the communication unit <NUM> may control wireless communication compliant with such communication standards. In a case where the communication apparatus <NUM> can perform wireless communication compliant with a plurality of communication standards, the communication apparatus <NUM> may include communication units and antennas supporting the respective communication standards separately. The communication apparatus <NUM> communicates data, such as image data, document data, and video data, with the communication apparatus <NUM> via the communication unit <NUM>. The antenna <NUM> may be configured as a separate member from the communication unit <NUM>. The antenna <NUM> may be combined with the communication unit <NUM> as a single module.

The antenna <NUM> is an antenna capable of communication in the <NUM>-GHz, <NUM>-GHz, and <NUM>-GHz bands. In the present exemplary embodiment, the communication apparatus <NUM> has one antenna. However, the communication apparatus <NUM> may include antennas each corresponding to different one of the frequency bands. In a case where the communication apparatus <NUM> includes a plurality of antennas, the communication apparatus <NUM> may also include communication units <NUM> each corresponding to different one of the plurality of antennas.

The communication apparatus <NUM> has a similar hardware configuration to that of the communication apparatus <NUM>.

<FIG> illustrates a functional configuration of the communication apparatus <NUM> according to the present exemplary embodiment. The communication apparatus <NUM> includes a capability information generation unit <NUM> for multi-link communication, an operation information determination unit <NUM> for multi-link communication, and a connection processing unit <NUM>. The communication apparatus <NUM> further includes a media access control (MAC) frame generation unit <NUM> and a data transmission and reception unit <NUM>.

The capability information generation unit <NUM> is a block for generating multi-link communication-related capability information about the communication apparatus <NUM>. The communication apparatus <NUM> generates the capability information for notifying another communication apparatus of the multi-link communication-related capabilities of the own apparatus. The multi-link communication-related capability information will be described below with reference to <FIG>. As for the capability information, the communication apparatus <NUM> may notify another communication apparatus of the capability information about the own apparatus, or only receive capability information about another communication apparatus as the partner apparatus.

The operation information determination unit <NUM> is a block for determining operation information about multi-link communication with the partner apparatus, based on the multi-link communication-related capability information about the own apparatus and the partner apparatus. The operation information about the multi-link communication refers to frequency channels and bandwidths to be used in the multi-link communication between the communication apparatuses <NUM> and <NUM>. Details of the multi-link communication-related operation information will be described below with reference to <FIG>. The communication apparatus <NUM> may or may not notify the partner apparatus of the determined operation information.

The connection processing unit <NUM> is a block for performing processing for enabling the communication apparatus <NUM>, serving as a STA, to join the network <NUM> constructed by the communication apparatus <NUM>. Specifically, the connection processing unit <NUM> causes the communication apparatus <NUM> to transmit an Association Response frame as a response to an Association Request that is a connection request received from the communication apparatus <NUM>. The communication apparatus <NUM> includes connection processing units <NUM> each corresponding to different one of a plurality of links which are established by the own apparatus.

The MAC frame generation unit <NUM> is a block for generating a MAC frame including the multi-link communication-related capability information generated by the capability information generation unit <NUM> and the multi-link communication-related operation information determined by the operation information determination unit <NUM>. The MAC frame generated by the MAC frame generation unit <NUM> is included in at least any one of Beacon, Probe Response, and Association Response wireless frames, and transmitted. In addition to or instead of this, the generated MAC frame is included in a Reassociation Response, and transmitted. The capability information and the operation information included in the MAC frame generated by the MAC frame generation unit <NUM> are expressed by an element illustrated in <FIG> to be described below.

The data transmission and reception unit <NUM> is a block for transmitting and receiving data frames in multi-link communication, based on the multi-link communication-related operation information determined by the operation information determination unit <NUM>. The data transmission and reception unit <NUM> may transmit a wireless frame including the MAC frame generated by the MAC frame generation unit <NUM>, and receive a wireless frame from the partner apparatus.

The communication apparatus <NUM> has a similar functional configuration to that of the communication apparatus <NUM> except for the following points.

The communication apparatus <NUM> includes, instead of the operation information determination unit <NUM>, a request information determination unit (not illustrated). The request information determination unit is a block for determining request information about the multi-link communication with the partner apparatus, based on the multi-link communication-related capability information about the own apparatus and the partner apparatus. The request information about the multi-link communication refers to frequency channels and bandwidths that are requested to be used in the multi-link communication between the communication apparatuses <NUM> and <NUM>. Details of the multi-link communication-related request information will be described below with reference to <FIG>. The communication apparatus <NUM> may or may not notify the partner apparatus of the determined request information.

The connection processing unit <NUM> is a block for performing processing for enabling the communication apparatus <NUM> to join the network <NUM> constructed by the communication apparatus <NUM> serving as the AP. Specifically, the connection processing unit <NUM> causes the communication apparatus <NUM> to transmit an Association Request that is a connection request to the communication apparatus <NUM>, and receives an Association Response from the communication apparatus <NUM> as a response.

The MAC frame generation unit <NUM> is a block for generating a MAC frame including the multi-link communication-related capability information generated by the capability information generation unit <NUM> and the multi-link communication-related request information determined by the request information determination unit. The MAC frame generated by the MAC frame generation unit <NUM> is included in at least any one of Probe Request, Association Request, and Reassociation Request wireless frames, and transmitted. The capability information and the request information included in the MAC frame generated by the MAC frame generation unit <NUM> are expressed by the element illustrated in <FIG> to be described below.

<FIG> is a sequence diagram illustrating an example of processing executed in a case where the communication apparatuses <NUM> and <NUM> perform multi-link communication.

The communication apparatuses <NUM> and <NUM> each include connection processing units <NUM> corresponding to a plurality of respective links. The connection processing unit <NUM> of the communication apparatus <NUM> corresponding to the first link is referred to as an AP1. The connection processing unit <NUM> of the communication apparatus <NUM> corresponding to the second link is referred to as an AP2. The connection processing unit <NUM> of the communication apparatus <NUM> corresponding to the first link is referred to as an STA1. The connection processing unit <NUM> of the communication apparatus <NUM> corresponding to the second link <NUM> is referred to as an STA2. The STA1 and the AP1 perform communication processing via the first frequency channel (for example, 1ch of the <NUM>-GHz band). The STA2 and the AP2 perform communication processing via the second frequency channel (for example, 36ch of the <NUM>-GHz band).

The processing of this sequence is started in response to power-on of each of the communication apparatuses <NUM> and <NUM>. Alternatively, at least either one of the communication apparatuses <NUM> and <NUM> may start the processing in response to receipt of an instruction to start multi-link communication from the user or an application. Alternatively, at least either one of the communication apparatuses <NUM> and <NUM> may start the processing in response to the amount of data to be communicated with the partner apparatus being reached or exceeded a predetermined threshold.

In step S401, the communication apparatus <NUM> initially notifies nearby STAs of network information about the own apparatus by transmitting a Beacon including the network information on the first frequency channel. Specific examples of the network information include a transmission interval at which the communication apparatus <NUM> transmits a Beacon, and the SSID of the communication apparatus <NUM>. In addition, the communication apparatus <NUM> may notify the nearby STAs of the multi-link communication-related capability information about the communication apparatus <NUM> by including the multi-link capability element illustrated in <FIG> to be described below into the Beacon as the network information.

In step S402, in response to receipt of the Beacon transmitted from the communication apparatus <NUM> on the first frequency channel, the communication apparatus <NUM> transmits a Probe Request on the first frequency channel to inquire of the network information about the communication apparatus <NUM>. The Probe Request includes the SSID of the communication apparatus <NUM>. In addition, the communication apparatus <NUM> may notify the communication apparatus <NUM> of the multi-link communication-related capability information about the communication apparatus <NUM> by including the multi-link capability element illustrated in <FIG> to be described below into the Probe Request.

In step S403, in response to receipt of the Probe Request, the communication apparatus <NUM> transmits a Probe Response to the communication apparatus <NUM> on the first frequency channel as a response. In a case where the multi-link capability element illustrated in <FIG> is not included in the Beacon, the communication apparatus <NUM> includes the element in the Probe Response and transmits the Probe Response. Alternatively, the communication apparatus <NUM> may include only a part of the information included in the multi-link capability element illustrated in <FIG> to be described below into the Beacon, and include the remaining information or all the information into the Probe Response.

By performing the processing of steps S401 to S403, the communication apparatuses <NUM> and <NUM> can exchange their multi-link communication-related capability information with each other.

Next, the communication apparatus <NUM> transmits an Association Request that is a connection request to the communication apparatus <NUM> on the first frequency channel. Here, the communication apparatus <NUM> may notify the communication apparatus <NUM> of the multi-link communication-related capability information about the communication apparatus <NUM> by including the multi-link capability element illustrated in <FIG> into the Association Request. The communication apparatus <NUM> may determine the capability information to be transmitted in step S404, based on the multi-link communication-related capability information about the communication apparatus <NUM> obtained at least in either one of steps S401 and S403. For example, in a case where the communication apparatus <NUM> can support a combination of links in the <NUM>-GHz band and the <NUM>-GHz in multi-link communication while the communication apparatus <NUM> only supports a plurality of links in the <NUM>-GHz band, the communication apparatus <NUM> may transmit only capability information related to the establishment of a plurality of links in the <NUM>-GHz band as the capability information to be transmitted in this step. In the above-described present exemplary embodiment, the communication apparatus <NUM> transmits the multi-link communication-related capability information about the own apparatus in step S402. However, this is not restrictive. The communication apparatus <NUM> may transmit the capability information not in step S402 but only in this step. Alternatively, the communication apparatus <NUM> may transmit not capability information but request information to be requested in performing multi-link communication by including the multi-link capability element illustrated in <FIG> into the Association Request. The request information to be requested by the communication apparatus <NUM> may be expressed by the multi-link capability element illustrated in <FIG>, or by another element. Details of the request information will be described below with reference to <FIG>.

In step S405, in response to receipt of the Association Request, the communication apparatus <NUM> transmits an Association Response to the communication apparatus <NUM> on the first frequency channel as a response. The Association Response transmitted here includes the multi-link capability element expressing the operation information for use in performing multi-link communication with the communication apparatus <NUM>, determined by the communication apparatus <NUM>. The operation information may be expressed by an element other than the multi-link capability element. In a case where the Association Request transmitted in step S404 includes the operation information requested by the communication apparatus <NUM> serving as the STA, the communication apparatus <NUM> may transmit an Association Response including only information about whether the request is accepted.

In step S406, in a case where the communication apparatus <NUM> is capable of the multi-link communication specified by the operation information included in the Association Response, the communication apparatuses <NUM> and <NUM> establish a link via the first frequency channel, and start data communication. Here, in a case where the operation information transmitted from the communication apparatus <NUM> includes operation information about a link via the second frequency channel, then in step S407, the communication apparatuses <NUM> and <NUM> also establish another link via the second frequency channel and start data communication.

In a case where, in step S405, the communication apparatus <NUM> accepts the request information requested by the communication apparatus <NUM> in step S404, the processing of step S406 is similarly performed. In a case where the request information transmitted by the communication apparatus <NUM> in step S404 also includes request information about the link via the second frequency channel, the processing of step S407 is performed.

In the present exemplary embodiment, two links are established by the transmission and reception of frames on one frequency channel. However, this is not restrictive, and three or more links may be established.

In the above-described present exemplary embodiment, the multi-link communication is started from a state where no link is established between the communication apparatuses <NUM> and <NUM> yet. However, this is not restrictive. The communication apparatuses <NUM> and <NUM> may start multi-link communication by establishing a new link in addition to already established one. In such a case, the communication apparatus <NUM> serving as the STA may start processing at step S404 in a case where the multi-link communication-related capability information about the communication apparatus <NUM> serving as the AP has already been obtained. Alternatively, the communication apparatus <NUM> may enable the communication apparatus <NUM> to start processing at step S404 by transmitting a signal for causing the communication apparatus <NUM> to transmit an Association Request in a case where the multi-link communication-related capability information about the communication apparatus <NUM> has already been obtained. Alternatively, the communication apparatuses <NUM> and <NUM> may establish a new link in addition to a plurality of already established links. Here, the sequence of <FIG> can also be started at step S404.

In the above-described present exemplary embodiment, links via a plurality of frequency channels are established by the transmission and reception of frames on one frequency channel. However, this is not restrictive. The communication apparatuses <NUM> and <NUM>, in a case of performing multi-link communication, may disconnect already established links via a plurality of frequency channels by transmitting and receiving frames via one frequency channel. For example, in a case where the communication apparatuses <NUM> and <NUM> have established the first link via the first frequency channel and the second link via the second frequency channel, and are performing multi-link communication, and when either one of the communication apparatuses <NUM> and <NUM> transmits a Disassociation that is a link disconnection request to the partner apparatus via the first link, the communication apparatuses <NUM> and <NUM> disconnect not only the first link but the second link as well if the transmitted Disassociation includes information about the second link. In such a manner, by transmitting and receiving a Disassociation, the communication apparatuses <NUM> and <NUM> may disconnect not only the link via which the Disassociation is transmitted and received but also the other link indicated by information included in the Disassociation. Moreover, the communication apparatuses <NUM> and <NUM> may disconnect three or more links at the same time. In a case where the Disassociation includes information about a link other than the one via which the Disassociation is transmitted and received, the communication apparatuses <NUM> and <NUM> may disconnect only the other link. In such a case, the communication apparatuses <NUM> and <NUM> do not disconnect the link via which the Disassociation is transmitted and received.

As illustrated in <FIG>, the communication apparatuses <NUM> and <NUM> can control establishment and disconnection of a link on another frequency channel by transmitting and receiving frames via one frequency channel (or link). The communication apparatuses <NUM> and <NUM> can also control establishment and disconnection of links on a plurality of frequency channels by transmitting and receiving frames via one frequency channel (or link).

<FIG> is a diagram illustrating an example of the frame format of the multi-link capability element. In the present exemplary embodiment, the element illustrated in <FIG> is named multi-link capability element. However, this is not restrictive, and other names, such as multi-link element, may be used.

The communication apparatuses <NUM> and <NUM> each can notify the partner apparatus of the capability information indicating the capabilities of the own apparatus in multi-link communication by using the multi-link capability element illustrated in <FIG>. Moreover, the communication apparatus <NUM> can notify the partner apparatus of the operation information in performing multi-link communication in addition to or instead of the capability information, by using the multi-link capability element illustrated in <FIG>. The communication apparatus <NUM> can notify the partner apparatus of request information in performing multi-link communication in addition to or instead of the capability information, by using the multi-link capability element illustrated in <FIG>.

The multi-link capability element illustrated in <FIG> includes an Element identifier (ID) <NUM>, a Length <NUM>, and a Multi-Link (ML) Capabilities <NUM>. The Element ID <NUM> is a field containing an ID for identifying the element. In the present exemplary embodiment, the Element ID <NUM> contains an ID representing the multi-link capability element. The Length <NUM> is a field indicating the data length of the element. In the present exemplary embodiment, the Length <NUM> contains information indicating the data length of the ML Capabilities <NUM>. The ML Capabilities <NUM> contains information specific to the multi-link capability element, i.e., multi-link communication-related information. Details of the information contained in the ML Capabilities <NUM> will be described below.

The communication apparatuses <NUM> and <NUM> each generate the multi-link capability element illustrated in <FIG> in order from the Element ID <NUM>, and transmit the generated multi-link capability element to the partner apparatus. In such a case, the communication apparatuses <NUM> and <NUM> generates all the fields in the frame before transmission. Specifically, the communication apparatuses <NUM> and <NUM> each generate all of the Element ID <NUM>, the Length <NUM>, and the ML Capabilities <NUM> before transmission to the other apparatus. Alternatively, the communication apparatuses <NUM> and <NUM> may generate and transmit the fields in parallel. Specifically, the communication apparatuses <NUM> and <NUM> may transmit the generated Element ID <NUM> concurrently with the generation of the Length <NUM>.

The communication apparatus <NUM> serving as the AP adds a MAC frame including the multi-link capability element to a wireless frame, such as a Beacon and a Probe Response, and transmits the resulting wireless frame. Aside from these wireless frames, the communication apparatus <NUM> can also add the MAC frame including the element to a wireless frame, such as an Association Response and a Reassociation Response. The communication apparatus <NUM> serving as the STA adds a MAC frame including the multi-link capability element to a wireless frame, such as a Probe Request and an Association Request, and transmits the resulting wireless frame. Aside from these wireless frames, the communication apparatus <NUM> can also add the MAC frame including the element to a Reassociation Request.

The ML Capabilities <NUM> includes a Common Info <NUM>, Per Band Infos <NUM>, and Per Link Infos <NUM>. The Common Info <NUM> is a field indicating information common to all frequency bands and links. The Per Band Infos <NUM> are fields indicating information common to all links included in respective specific frequency bands. The information is indicated frequency band by frequency band. The Per Link Infos <NUM> are fields indicating information about the respective links.

The Common Info <NUM> includes a Primary Channel (Ch) <NUM>, a Sync Mode Support <NUM>, an Async Mode Support <NUM>, and a Semi-Async Mode Support <NUM>. The Common Info <NUM> further includes a Total Max Link Number <NUM>, a Band Combination Info <NUM>, and a Per Band Info Number <NUM>. The Common Info <NUM> further includes a Per Link Info Number <NUM>, and a Device Type <NUM>.

The Primary CH <NUM> is a field containing information indicating the frequency channel on which management frames related to multi-link communication are transmitted and received. A primary CH refers to the frequency channel for use in transmitting and receiving management frames when links in multi-link communication are connected and disconnected. Specifically, the Primary CH <NUM> contains information indicating the frequency channel to transmit and receive a Beacon including the multi-link capability element. The communication apparatus <NUM> serving as the AP adds, to the Primary CH <NUM>, information indicating the frequency channel for use in transmitting a Beacon frame including the multi-link capability element. The communication apparatus <NUM> serving as the STA adds, to the Primary CH <NUM>, information indicating the frequency channel on which the Beacon including the multi-link capability element is received (in other words, on which a Probe Request including the element is to be transmitted). In the present exemplary embodiment, the information indicating the first frequency channel on which the Beacon and the Probe Request/Response are transmitted and received in <FIG> is included into the Primary CH <NUM>. In a case where the frequency channel on which management frames are transmitted and received is changed after the start of multi-link communication by the communication apparatuses <NUM> and <NUM>, the Primary CH <NUM> contains information about the changed frequency channel. The Primary CH <NUM> contains the information indicating the frequency channel on which management frames are transmitted and received, regardless of information, among capability information, operation information, and request information, expressed by the element expresses.

The Sync Mode Support <NUM> is a field containing capability information indicating whether the apparatus, which is the communication apparatus <NUM> or <NUM>, transmitted the element supports the sync mode of multi-link communication. For example, in a case where this field contains <NUM>, it indicates not supporting the sync mode by the apparatus transmitted the element. In a case where this field contains <NUM>, it indicates supporting the sync mode by the apparatus transmitted the element.

In a case where the multi-link capability element expresses operation information, the Sync Mode Support <NUM> may indicate whether the sync mode of multi-link communication is to be used. For example, in a case where the communication apparatus <NUM> transmits an Association Response including the element, this field indicates whether the sync mode is to be used in communication via the links established by exchanging the Association Response. For example, in a case where this field contains <NUM>, it indicates performing the multi-link communication not in the sync mode. In a case where this field contains <NUM>, it indicates performing the multi-link communication in the sync mode.

In a case where the multi-link capability element expresses request information, the Sync Mode Support <NUM> may indicate whether using of the sync mode of multi-link communication is to be requested. For example, in a case where the communication apparatus <NUM> serving as the STA transmits an Association Request including the element, this field indicates whether the communication apparatus <NUM> requests using of the sync mode in multi-link communication. For example, in a case where this field contains <NUM>, the communication apparatus <NUM> requests performing of multi-link communication not in the sync mode. In a case where this field contains <NUM>, the communication apparatus <NUM> requests performing of multi-link communication in the sync mode.

The Async Mode Support <NUM> is a field containing capability information indicating whether the apparatus, which is the communication apparatus <NUM> or <NUM>, transmitted the element supports the async mode of multi-link communication. For example, in a case where this field contains <NUM>, it indicates not supporting the async mode by the apparatus transmitted the element. In a case where this field contains <NUM>, it indicates supporting the async mode by the apparatus transmitted the element.

In a case where the multi-link capability element expresses operation information, the Async Mode Support <NUM> may indicate whether the async mode of multi-link communication is to be used. For example, in a case where the communication apparatus <NUM> transmits an Association Response including the element, this field indicates whether the async mode is to be used on the links established by exchanging the Association Response. In such a case, in a case where this field contains <NUM>, the multi-link communication is performed not in the async mode. In a case where this field contains <NUM>, the multi-link communication is performed in the async mode. Note that in a case where the element expresses operation information and the foregoing Sync Mode Support <NUM> indicates using the sync mode, this field indicates not using the async mode. Similarly, in a case where the Sync Mode Support <NUM> indicates not using the sync mode, the Async Mode Support <NUM> indicates using the async mode.

In a case where the multi-link capability element expresses request information, the Async Mode Support <NUM> may indicate whether using of the async mode of multi-link communication is to be requested. For example, in a case where the communication apparatus <NUM> serving as the STA transmits an Association Request including the element, this field indicates whether the communication apparatus <NUM> requests using of the async mode in multi-link communication. For example, in a case where this field contains <NUM>, the communication apparatus <NUM> requests performing of the multi-link communication not in the async mode. In a case where this field contains <NUM>, the communication apparatus <NUM> requests performing of the multi-link communication in the async mode.

The Semi-Async Mode Support <NUM> is a field containing capability information indicating whether the apparatus, which is the communication apparatus <NUM> or <NUM>, transmitted the element supports the semi-async mode of multi-link communication. For example, in a case where this field contains <NUM>, it indicates not supporting the semi-async mode by the apparatus transmitted the element. In a case where this field contains <NUM>, it indicates supporting the semi-async mode by the apparatus transmitted the element.

In a case where the multi-link capability element expresses operation information, this field may indicate whether the semi-async mode of multi-link communication is to be used. For example, in a case where the communication apparatus <NUM> transmits an Association Response including the element, this field indicates whether the semi-async mode is used in communication via the links established by exchanging the Association Response. For example, in a case where this field contains <NUM>, it indicates performing of the multi-link communication not in the semi-async mode. In a case where this field contains <NUM>, it indicates performing of the multi-link communication in the semi-async mode.

In a case where the multi-link capability element expresses request information, this field may indicate whether using of the semi-async mode of multi-link communication is to be requested. For example, in a case where the communication apparatus <NUM> serving as the STA transmits an Association Request including the element, this field indicates whether the communication apparatus <NUM> requests using of the semi-async mode in multi-link communication. For example, in a case where this field contains <NUM>, the communication apparatus <NUM> requests performing of the multi-link communication not in the semi-async mode. For example, in a case where this field contains <NUM>, the communication apparatus <NUM> requests performing of the multi-link communication in the semi-async mode.

In a case where a mode to be used by the communication apparatuses <NUM> and <NUM> in multi-link communication is set in advance from among the sync mode, the async mode, or the semi-async mode, the above described fields may be omitted. Specifically, the Sync Mode Support <NUM>, the Async Mode Support <NUM>, and the Semi-Async Mode Support <NUM> may be omitted.

The Total Max Link Number <NUM> is a field containing capability information indicating the maximum number of links that are supported in multi-link communication by the apparatus, which is the communication apparatus <NUM> or <NUM>, transmitted the element. The maximum number of links refers to the maximum number of links that the apparatus transmitted the element can establish with one partner apparatus. For example, in a case where this field contains a value of <NUM>, the apparatus transmitted the element can establish up to three links per partner apparatus. In such a case, the apparatus transmitted the element may maintain three links with one partner apparatus and concurrently maintain a plurality of links with another partner apparatus as well. Alternatively, the maximum number of links may refer to the maximum number of links that the apparatus transmitted the element can establish in multi-link communication, regardless of the partner apparatuses. In such a case, in a case where, for example, this field contains a value of <NUM> and the apparatus transmitted the element has already established three links with a partner apparatus or apparatuses, the apparatus transmitted the element is unable to establish another link regardless of the partner apparatuses. In this field, the communication apparatus <NUM> serving as the AP and the communication apparatus <NUM> serving as the STA each include information indicating the maximum number of links that the own apparatus can simultaneously maintain in multi-link communication.

In a case where the multi-link capability element expresses operation information, this field may contain the number of links to be actually established in multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the AP transmits an Association Response including the element, this field indicates the number of links to be established by exchanging the Association Response. Alternatively, this field may contain the maximum number of links that can be established in multi-link communication with the communication apparatus <NUM>. In such a case, the Total Max Link Number <NUM> contains a value less than or equal to the smaller value among the maximum number of links that the own apparatus can established in multi-link communication and the maximum number of links that the partner apparatus can establish.

In a case where the multi-link capability element expresses request information, this field may contain the number of links requested to be established in multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the STA transmits an Association Request including the element, this field indicates the number of links to be requested from the communication apparatus <NUM> to the communication apparatus <NUM> to establish. Alternatively, this field may contain the maximum number of links that can be established in multi-link communication with the communication apparatus <NUM>. Note that this field may be omitted in a case where the multi-link capability element expresses operation information or request information.

The Band Combination Info <NUM> is a field containing capability information indicating the frequency band or bands that is supported by the apparatus, which is the communication apparatus <NUM> or <NUM>, transmitted the element in multi-link communication. Table <NUM> illustrates an example of information indicated by each bit of this field. In Table <NUM>, which frequency band or what combination of frequency bands is supported is listed bit by bit. In the present exemplary embodiment, in a case where a bit contains <NUM>, it indicates not supporting multi-link communication corresponding to the description of the bit. In a case where a bit contains <NUM>, it indicates supporting multi-link communication corresponding to the description of the bit. For example, in a case where the Band Combination Info <NUM> transmitted by the communication apparatus <NUM> contains <NUM> in the zeroth bit, it indicates supporting multi-link communication on different channels in the <NUM>-GHz band by the communication apparatus <NUM>. For example, in a case where the Band Combination Info <NUM> contains a value of <NUM>, it indicates supporting multi-link communication using a plurality of links in different frequency bands by the communication apparatus <NUM>. It also indicates not supporting multi-link communication using a plurality of links in the same frequency bands by the communication apparatus <NUM>. Not supporting multi-link communication by the apparatus transmitted the element may be indicated by setting all the bits of the Band Combination Info <NUM> to <NUM>. Alternatively, <NUM> of each bit may indicate current unavailability of multi-link communication by the apparatus transmitted the element. Note that the communication apparatuses <NUM> and <NUM> each may support frequency bands different between communication using only one link and multi-link communication. For example, the communication apparatuses <NUM> and <NUM> may support all of the <NUM>-GHz, <NUM>-GHz, and <NUM>-GHz bands in communication using only one link, and support only the <NUM>-GHz and <NUM>-GHz bands in multi-link communication. The correspondence between the bits of the Band Combination Info <NUM> and the descriptions thereof is not limited to that illustrated in Table <NUM>. The number of bits of the Band Combination Info <NUM> may be increased to indicate whether a plurality of links can be established at more combinations of frequency bands or at other frequency bands.

In a case where the multi-link capability element expresses operation information, this field may indicate the frequency band(s) to be actually used in multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the AP transmits an Association Response including the element, this field contains information indicating the frequency band(s) of the links to be established by exchanging the Association Response. For example, in a case where the communication apparatuses <NUM> and <NUM> establish a <NUM>-GHz link and a <NUM>-GHz link, the Band Combination Info <NUM> has a value of <NUM>.

In a case where the multi-link capability element expresses request information, this field may indicate the frequency band(s) requested to be used in multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the STA transmits an Association Request including the element, this field indicates the frequency band(s) to be requested from the communication apparatus <NUM> to the communication apparatus <NUM> to perform multi-link communication. Even in a case where the element expresses operation information or request information, this field may contain capability information indicating the frequency band(s) supported by the apparatus transmitted the element in multi-link communication.

The Per Band Info Number <NUM> is a field containing information indicating the number of Per Band Infos included in the Per Band Infos <NUM> to be described below. The Per Band Infos <NUM> include a set of Per Band Infos corresponding to respective frequency bands supported by the apparatus, which is the communication apparatus <NUM> or <NUM>, transmitted the multi-link capability element in multi-link communication. Specifically, the Per Band Info Number <NUM> contains information indicating the same number as the number of frequency bands indicated by the Band Combination Info <NUM>. However, this does not apply in a case where information about more than one frequency band is indicated by the same Per Band Info among the Per Band Infos <NUM> to be described below. In a case where the Per Band Infos <NUM> to be described below are omitted, this field is also omitted.

The Per Link Info Number <NUM> is a field containing information indicating the number of Per Link Infos included in the Per Link Infos <NUM> to be described below. The Per Link Infos <NUM> include a set of Per Link Infos corresponding to respective links supported by the apparatus, which is the communication apparatus <NUM> or <NUM>, transmitted the multi-link capability element in multi-link communication. In a case where the Per Link Infos <NUM> to be described below are omitted, this field is also omitted.

The Device Type <NUM> is a field containing capability information indicating a type of the apparatus, which is the communication apparatus <NUM> or <NUM>, transmitted the element is in multi-link communication. Specifically, the Device Type <NUM> contains information indicating a type of the apparatus transmitted the element from among the following four types. A first type of apparatus refers to an apparatus that can simultaneously transmit data via a link and receive data via another link in multi-link communication. A second type of apparatus refers to an apparatus that, when transmitting data via a link, can only transmit data via another link at the same time. A third type of apparatus refers to an apparatus that, when receiving data via a link, can only receive data via another link at the same time. A fourth type of apparatus refers to an apparatus that can simultaneously maintain a plurality of links but, when communicating data via a link, is unable to simultaneously communicate data via another link.

In a case where the multi-link capability element expresses operation information, the Device Type <NUM> may indicate an apparatus operation type of each of the apparatuses in multi-link communication from among the above-described type. For example, in a case where the communication apparatus <NUM> transmits an Association Response including the element, this field indicates an apparatus operation type of the communication apparatus <NUM> in communication via the links established by exchanging the Association Response. For example, in a case where information indicating the second type is transmitted as the operation information, the communication apparatus <NUM> operates as an apparatus operating in the second type in communication via the links established by exchanging the Association Response, even in a case where the communication apparatus <NUM> can operate as an apparatus operating in the first type.

In a case where the multi-link capability element expresses request information, the Device Type <NUM> may indicate a request for an apparatus operation type in multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the STA transmits an Association Request including the element, this field indicates an apparatus operation type of the communication apparatus <NUM> in multi-link communication. For example, in a case where this field contains information indicating the second type, the communication apparatus <NUM> requests operating as an apparatus in the second type in multi-link communication with the communication apparatus <NUM>.

Each Per Band Info <NUM> is a field including a Band ID <NUM>, a Supported Bandwidth <NUM>, a Supported CH <NUM>, and an Async Mode CH Distance <NUM>. In addition to such fields, the Per Band Info <NUM> also includes a Max link Number <NUM> and a Supported number of spatial streams (Nss) <NUM>. The multi-link capability element includes a set of Per band Infos <NUM> corresponding to the respective frequencies indicated by the Band ID <NUM> to be described below.

The Band ID <NUM> is a field containing information for identifying a frequency band. Table <NUM> illustrates an example of a correspondence between values of the Band ID <NUM> and descriptions indicated by the values. For example, in a case where the Band ID <NUM> contains a value of <NUM>, the Per Band Info <NUM> including this Band ID <NUM> is information indicating information common to the links of multi-link communication in the <NUM>-GHz band. The correspondence between the values of the Band ID <NUM> and the indicated descriptions is not limited thereto. The number of bits of the Band ID <NUM> may be increased so that a greater number of frequency bands can be indicated.

The Supported Bandwidth <NUM> is a field containing capability information indicating the bandwidth supported by the apparatus, which is the communication apparatus <NUM> or <NUM>, transmitted the element in the frequency band indicated by the Band ID <NUM>. The bandwidth indicated here is information indicating the bandwidth to be supported per link in a case where the apparatus transmitted the element performs multi-link communication in the frequency band indicated by the Band ID <NUM>. Table <NUM> illustrates an example of a correspondence between values of the Supported Bandwidth <NUM> and descriptions indicated by the values. For example, in a case where the Supported Bandwidth <NUM> contains a value of <NUM>, the bandwidth supported by the apparatus transmitted the element in the frequency band indicated by the Band ID <NUM> is <NUM>. In a case where the value of the Supported Bandwidth <NUM> is <NUM> or greater, the apparatus transmitted the element can support any bandwidth narrower than or equal to that value in establishing a link in multi-link communication. For example, in a case where the Supported Bandwidth <NUM> has a value of <NUM>, the apparatus transmitted the element supports all of <NUM>, <NUM>, and <NUM> as link bandwidths. The communication apparatuses <NUM> and <NUM> each may support some bandwidths different between communication using only one link and multi-link communication. For example, the communication apparatuses <NUM> and <NUM> may support a bandwidth of <NUM> at the <NUM>-GHz band in communication using only one link, and support a bandwidth of <NUM> in multi-link communication. The correspondence between the values of the Supported Bandwidth <NUM> and the indicated descriptions is not limited thereto. The number of bits of the Supported Bandwidth <NUM> may be increased so that a greater number of band widths can be indicated.

In a case where the multi-link capability element expresses operation information, this field may indicate the bandwidth to be actually used in multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the AP transmits an Association Response including the element, this field contains information indicating the bandwidth of the link(s) established by exchanging the Association Response. For example, in a case where the communication apparatuses <NUM> and <NUM> establish a link having a bandwidth of <NUM> at the <NUM>-GHz band, the value of the Supported Bandwidth <NUM> is <NUM>.

In a case where the multi-link capability element expresses request information, this field may indicate the bandwidth requested to be used in multi-link communication. In a case where the communication apparatus <NUM> serving as the STA transmits an Association Request including the element, this field indicates the bandwidth to be requested from the communication apparatus <NUM> to the communication apparatus <NUM>. Even in a case where the element expresses operation information or request information, this field may contain capability information indicating the bandwidth supported by the apparatus transmitted the element in multi-link communication.

The Supported CH <NUM> is a field containing capability information indicating the channel supported by the apparatus, which is the communication apparatus <NUM> or <NUM>, transmitted the element in the frequency band indicated by the Band ID <NUM>. The channel indicated here is information indicating the channel where the apparatus transmitted the element supports multi-link communication in the frequency band indicated by the Band ID <NUM>. Table <NUM> illustrating an example of a correspondence between the bits of the Supported CH <NUM> and the channels indicated by the bits. For example, in a case where a bit has a value of <NUM>, it indicates not supporting the channel indicated by the bit by the apparatus transmitted the element. In a case where a bit has a value of <NUM>, it indicates supporting the channel indicated by the bit by the apparatus transmitted the element. For example, in a case where the Supported CH <NUM> contains a value of <NUM>, it indicates supporting multi-link communication on 3ch, 5ch, and 8ch by the apparatus transmitted the element. Note that the communication apparatuses <NUM> and <NUM> each may support channels different between communication using only one link and multi-link communication. For example, the communication apparatuses <NUM> and <NUM> may support all of 1ch to 13ch in communication using only one link, and support only some of the channels, such as 1ch and 5ch, in multi-link communication. The correspondence between the bits of the Supported CH <NUM> and the descriptions is not limited to that illustrated in Table <NUM>. The number of bits of the Supported CH <NUM> may be increased so that a greater number of channels can be indicated. For example, while Table <NUM> illustrates only the channels at the <NUM>-GHz as an example, the number of bits may be increased so that channels at the <NUM>-GHz and <NUM>-GHz bands can be indicated by the thirteenth and subsequent bits. Alternatively, in a case where the Band ID <NUM> contains information indicating the <NUM>-GHz band, the channels at the <NUM>-GHz band may be listed in order from the zeroth bit. Similarly, in a case where the Band ID <NUM> contains information indicating the <NUM>-GHz, the channels at the <NUM>-GHz may be listed in order from the zeroth bit.

In a case where the multi-link capability element expresses operation information, this field may indicate the channel(s) to be actually used in multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the AP transmits an Association Response including the element, this field contains information indicating the channel(s) of the link(s) established by exchanging the Association Response. For example, in a case where the communication apparatuses <NUM> and <NUM> establish links on 1ch and 4ch at the <NUM>-GHz band, the Supported CH <NUM> has a value of <NUM>.

In a case where the multi-link capability element expresses request information, this field may indicate the channel(s) requested to be used in multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the STA transmits an Association Request including the element, this field indicates the channel(s) on which the communication apparatus <NUM> requests to the communication apparatus <NUM> to establish a link or links. Even in a case where the element expresses operation information or request information, this field may contain capability information indicating the channel(s) supported by the apparatus transmitted the element in multi-link communication.

The Async Mode CH Distance <NUM> is a field containing capability information indicating a channel distance which is required by the apparatus transmitted the element for the async mode in the frequency band indicated by the Band ID <NUM>. In the async mode, since communications in the respective links is asynchronously performed, communications can interfere with each other if the channels of the links are close to each other. The required distance between the channels of the links to appropriately decode the signals of the respective links varies from one communication apparatus to another. The capability information is thus notified using this field. In a case where the Async Mode CH Distance <NUM> contains a value of <NUM>, for example, the apparatus transmitted the element requires a channel distance of at least four channels or more in the async mode. In a case where the foregoing Async Mode Support <NUM> contains information indicating not supporting the async mode, this field may contain a value of <NUM> or this field may be omitted. In the present exemplary embodiment, the channel distance required in the async mode is indicated for each of the frequency bands indicated by the Band IDs <NUM>. However, this is not restrictive. The channel distance may be information common to all the frequency bands. Specifically, this field is included in the Common Info <NUM>.

In a case where the multi-link capability element expresses operation information, this field may contain information indicating the channel distance to be actually used in the async mode of multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the AP transmits an Association Response including the element, this field contains information indicating the channel distance between the plurality of links established by exchanging the Association Response.

In a case where the multi-link capability element expresses request information, this field may contain information indicating the channel distance requested to be used in the async mode of multi-link communication. Information indicating the minimum channel distance supported in the async mode in multi-link communication with the partner apparatus may be included. In a case where the element expresses operation information, this field contains a value greater than or equal to the greater value among the channel distance presented by the communication apparatus <NUM> as its capability information and the channel distance presented by the communication apparatus <NUM> as its capability information. In a case where the Async Mode Support <NUM> contains information indicating not using the async mode, or in a case where the Async Mode Support <NUM> is omitted, this field may contain a value of <NUM>. Alternatively, this field may be omitted. In a case where the communication apparatus <NUM> serving as the STA transmits an Association Request including the element, this field indicates the channel distance to be requested from the communication apparatus <NUM> in the async mode with the communication apparatus <NUM>. In a case where the communication apparatus <NUM> does not request using of the async mode, this field may contain a value of <NUM> or be omitted. In a case where the multi-link capability element expresses operation information or request information, this field may be omitted.

The Max link Number <NUM> is a field containing capability information indicating the maximum number of links supported by the apparatus transmitted the element in multi-link communication in the frequency band indicated by the Band ID <NUM>. In a case where the foregoing Band Combination Info <NUM> does not contain information indicating supporting multi-link communication using links in the same frequency band, this field may contain a value of <NUM>. Alternatively, this field may be omitted. In the exemplary embodiment, the maximum number of links can be indicated frequency band by frequency band. However, this is not restrictive. The maximum number of links may be indicated as information common to all the frequency bands. Specifically, this field may be included in the Common Info <NUM>.

In a case where the multi-link capability element expresses operation information, this field may indicate the total number of links to be actually used in the frequency band indicated by the Band ID <NUM> in multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the AP transmits an Association Response including the element, this field contains information indicating the number of links to be established by exchanging the Association Response, which is one or more. For example, in a case where the communication apparatuses <NUM> and <NUM> establish two links at the <NUM>-GHz band, this field contains a value of <NUM>.

In a case where the multi-link capability element expresses request information, this field may indicate the total number of links requested to be used in the frequency band indicated by the Band ID <NUM> in multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the STA transmits an Association Request including the element, this field indicates the number of links to be requested from the communication apparatus <NUM> to the communication apparatus <NUM> to establish. Even in a case where the element expresses operation information or request information, this field may contain capability information indicating the maximum number of links capable of being established by the apparatus transmitted the element in multi-link communication.

The Supported Nss <NUM> is a field containing capability information indicating the maximum number of (spatial) streams supported by the apparatus transmitted the element in multi-link communication in the frequency band indicated by the Band ID <NUM>. The number of streams indicated by this field is the number of streams in MIMO communication. In a case where the multi-link communication in the frequency band indicated by the Band ID <NUM> does not support MIMO communication, this field contains a value of <NUM> or <NUM>, or this field is omitted. In the present exemplary embodiment, the maximum number of streams can be indicated frequency band by frequency band. However, this is not restrictive. The maximum number of streams may be indicated as information common to all the frequency bands. Specifically, this field may be included in the Common Info <NUM>.

In a case where the multi-link capability element expresses operation information, this field may indicate the number of streams to be actually used in the frequency band indicated by the Band ID <NUM> in multi-link communication. For example, in a case where the communication apparatus <NUM> serving as the AP transmits an Association Response including the element, this field contains information indicating the number of streams of MIMO communication to be actually performed by exchanging the Association Response. For example, in a case where the communication apparatuses <NUM> and <NUM> perform MIMO communication with three streams in a link where multi-link communication is performed at the <NUM>-GHz band, this field contains a value of <NUM>. In a case where MIMO communication is not performed, this field may contain a value of <NUM> or <NUM>, or this field may be omitted.

In a case where the multi-link capability element expresses request information, this field may indicate the number of streams requested to be used in the frequency band indicated by the Band ID 531in multi-link communication. In a case where the communication apparatus <NUM> serving as the STA transmits an Association Request including the element, this field indicates the number of streams to be requested from the communication apparatus <NUM> in MIMO communication in multi-link communication. In a case where the communication apparatus <NUM> does not request MIMO communication, this field may contain a value of <NUM> or <NUM>, or this field may be omitted. Even in a case where the element expresses operation information or request information, this field may contain capability information indicating the maximum number of streams supported by the apparatus transmitted the element for MIMO communication in multi-link communication.

Each Per Link Info <NUM> is a field including fields such as a link ID <NUM>, a Band ID <NUM>, a Bandwidth <NUM>, a CH <NUM>, and an Nss <NUM>. In a case where the multi-link capability element expresses capability information, the Per Link Info <NUM> indicates information about a channel on which the apparatus transmitted the element supports multi-link communication. In such a case, the set of Per Link Infos <NUM> includes as many Per Link Infos <NUM> as the number of channels (links) the apparatus transmitted the element supports multi-link communication. In a case where the element expresses capability information and multi-link communication links have already been established, the Per Link Infos <NUM> indicate information about the already established links. In such a case, the set of Per Link Infos <NUM> includes as many Per Link Infos <NUM> as the number of already established links. Moreover, in such a case, links about which information is presented by the communication apparatus <NUM> using the Per Link Infos <NUM> are ones already established with at least either the communication apparatus <NUM> or another communication apparatus. Moreover, in such a case, links about which information is presented by the communication apparatus <NUM> using the Per Link Infos <NUM> are ones already established with at least either the communication apparatus <NUM> or another communication apparatus. Alternatively, in a case where the element expresses capability information, the element does not need to include any Per Link Info <NUM>. This is not restrictive in a case where the multi-link capability element expresses operation information and the communication apparatus <NUM> serving as the AP transmits an Association Response including the element. In such a case, the Per link Infos <NUM> indicate information about the links to be established by exchanging the Association Response. In such a case, as many Per link Infos <NUM> as the number of links to be established by exchanging the Association Response are included. In a case where the communication apparatus <NUM> presents request information by transmitting an Association Request including the element, the Per link Infos <NUM> indicate information about the links that the communication apparatus <NUM> requests to establish. In such a case, as many Per link Infos <NUM> as the number of links that the communication apparatus <NUM> requests to establish are included.

The link ID <NUM> is a field containing an identifier for identifying a link.

The Band ID <NUM> is a field containing information indicating the frequency band to which the link indicated by the link ID <NUM> belongs. This field is expressed in a similar manner to the Band ID <NUM>.

The Bandwidth <NUM> is a field containing information indicating the bandwidth of the link indicated by the link ID <NUM>. This field is expressed in a similar manner to the Supported Bandwidth <NUM>. In a case where the multi-link capability element expresses capability information, this field indicates the bandwidth supported by the link indicated by the link ID <NUM>. In a case where the communication apparatus <NUM> serving as the AP presents operation information by transmitting an Association Response including the element, this field indicates the bandwidth to be used in the link indicated by the link ID <NUM>. In a case where the communication apparatus <NUM> serving as the STA presents request information by transmitting an Association Request including the element, this field indicates the bandwidth to be requested by the communication apparatus <NUM> in the link indicated by the link ID <NUM>.

The CH <NUM> is a field containing information indicating the frequency channel of the link indicated by the link ID <NUM>. This field may contain the number itself that represents the channel. Alternatively, the channel may be represented as in Table <NUM>. In a case where the multi-link capability element expresses capability information, this field indicates the channel supported in the link indicated by the link ID <NUM>. In a case where the communication apparatus <NUM> serving as the AP presents operation information by transmitting an Association Response including the element, this field indicates the channel to be used in the link indicated by the link ID <NUM>. In a case where the communication apparatus <NUM> serving as the STA presents request information by transmitting an Association Request including the element, this field indicates the channel to be requested by the communication apparatus <NUM> in the link indicated by the link ID <NUM>.

The Nss <NUM> is a field containing information indicating the number of MIMO communication streams in the link indicated by the link ID <NUM>. In a case where MIMO communication is not performed, this field may contain a value of <NUM> or <NUM>, or this field may be omitted. In a case where the multi-link capability element expresses capability information, this field indicates the maximum number of streams supported in the link indicated by the link ID <NUM>. In a case where the communication apparatus <NUM> serving as the AP presents operation information by transmitting an Association Response including the element, this field indicates the number of streams to be used in the link indicated by the link ID <NUM>. In a case where the communication apparatus <NUM> presents request information by transmission an Association Request including the element, this field indicates the number of streams to be requested by the communication apparatus <NUM> in the link indicated by the link ID <NUM>.

By transmitting and receiving MAC frames including the foregoing multi-link capability element, the communication apparatuses <NUM> and <NUM> exchange multi-link communication capability information, operation information, and request information. In the present exemplary embodiment, multi-link communication capability information, operation information, and request information are expressed by the same multi-link capability element. However, this is not restrictive. Capability information and operation information, or capability information and request information, may be expressed by information elements different from each other. In such a case, capability information may be expressed by an element including the Common Info <NUM> and the Per Band Infos <NUM>, for example. Operation information and request information may be expressed by an element including the Common Info <NUM> and the Per Link Infos <NUM>. In a case where the multi-link capability element expresses capability information, some of the fields may express operation information or request information. Alternatively, in a case where the multi-link capability element expresses operation information or request information, some of the fields may express capability information.

The multi-link capability element illustrated in <FIG> includes fields, such as the Primary CH <NUM>, the Supported CH <NUM>, and CH <NUM>, as information indicating frequency channels. However, this is not restrictive, and the multi-link capability element may include at least any one of the Primary CH <NUM>, the Supported CH <NUM>, and the CH <NUM> as information indicating a frequency channel.

The names of the fields, the number of fields, and the order of the fields are not limited to those illustrated in <FIG>. Any field may be included before or after a given one of the fields illustrated in <FIG>. The fields included in the Common Info <NUM> may be included in the Per Band Infos <NUM> or the Per Link Infos <NUM>. Similarly, the fields included in the Per Band Infos <NUM> or the Per Link Infos <NUM> may be included in the other or in the Common Info <NUM>. Any of the fields illustrated <FIG> may be omitted.

<FIG> is a flowchart illustrating processing performed by the control unit <NUM> reading the computer program stored in the storage unit <NUM> and executing the computer program when the communication apparatus <NUM> performs multi-link communication.

This flowchart is started in response to the power-on of the communication apparatus <NUM>. Alternatively, the communication apparatus <NUM> may start this flowchart in response to an instruction issued from the user or an application to start multi-link communication. Alternatively, the communication apparatus <NUM> may start this flowchart when the data amount of data to be transmitted to the communication apparatus <NUM> reaches or exceeds a predetermined threshold.

In step S601, the communication apparatus <NUM> initially obtains multi-link communication capability information about the partner apparatus. Specifically, the communication apparatus <NUM> obtains the capability information about the communication apparatus <NUM> by receiving a Beacon including the multi-link capability element, transmitted from the communication apparatus <NUM>. Alternatively, the communication apparatus <NUM> may perform the processing of this step by receiving a Probe Response including the multi-link capability element, transmitted from the communication apparatus <NUM>. In such a case, this step and step S602 described below are reversed in order.

In step S602, the communication apparatus <NUM> notifies the multi-link communication capability information about the own apparatus. Specifically, the communication apparatus <NUM> notifies the multi-link capability information about the own apparatus by transmitting a Probe Request including the multi-link capability element. In a case where the capability information about the partner apparatus is obtained before this step, the communication apparatus <NUM> may determine the capability information for the own apparatus to be notified, based on the capability information about the partner apparatus. Specifically, the communication apparatus <NUM> may determine the capability information to be notified in this step within the extent not exceeding the capabilities of the communication apparatus <NUM>. For example, in a case where the communication apparatus <NUM> supports multi-link communication at the <NUM>-GHz, <NUM>-GHz, and <NUM>-GHz bands, and the communication apparatus <NUM> supports multi-link communication only at the <NUM>-GHz and <NUM>-GHz bands, the communication apparatus <NUM> notifies in this step that multi-link communication at the <NUM>-GHz and <NUM>-GHz bands is supported, as the capability information. Note that in a case where the communication apparatus <NUM> transmits an Association Request including request information indicating a multi-link communication-related request to the communication apparatus <NUM> in step S603 to be described below, the processing of this step may be omitted.

In step S603, the communication apparatus <NUM> transmits an Association Request including multi-link communication request information. The request information transmitted in this step indicates information about the multi-link communication that the communication apparatus <NUM> requests to perform. In this step, the communication apparatus <NUM> may transmit an Association Request not including request information.

In step S604, the communication apparatus <NUM> determines whether an Association Response is received from the communication apparatus <NUM> serving as the AP. If Association Response is not received (NO in step S604), the communication apparatus <NUM> performs the processing of this step again. In a case where a predetermined time has elapsed since the transmission of the Association Request in step S603 and a YES determination is not performed in this step, the communication apparatus <NUM> notifies the user of an error. The processing of this procedure ends. On the other hand, in a case where an Association Response is received (YES in step S604), the communication apparatus <NUM> performs the processing of step S605.

In step S605, the communication apparatus <NUM> starts multi-link communication with the communication apparatus <NUM>. In a case where the Association Response received in step S604 includes multi-link communication operation information, the communication apparatus <NUM> starts multi-link communication based on the operation information. In a case where the request information is transmitted in step S603 and an Association Response including only information indicating permission is received in step S604, the communication apparatus <NUM> starts multi-link communication based on the request information transmitted in step S603. After the processing of step S605 is performed, the processing of this procedure ends.

This flowchart is started in response to the power-on of the communication apparatus <NUM>. Alternatively, the communication apparatus <NUM> may start this flowchart in response to an instruction issued from the user or an application to start multi-link communication. Alternatively, the communication apparatus <NUM> may start this flowchart in response to the data amount of data to be transmitted to the communication apparatus <NUM> reaching or exceeding a predetermined threshold.

In step S701, the communication apparatus <NUM> initially notifies the multi-link communication capability information about the own apparatus. Specifically, the communication apparatus <NUM> notifies the multi-link communication capability information about the own apparatus by transmitting a Beacon including the multi-link capability element. Alternatively, the communication apparatus <NUM> may perform the processing of this step by transmitting a Probe Response including the multi-link capability element in response to a Probe Response received from the communication apparatus <NUM>. In such a case, this step and step S702 described below are reversed in order.

In step S702, the communication apparatus <NUM> obtains multi-link communication capability information about the partner apparatus. Specifically, the communication apparatus <NUM> obtains the multi-link communication capability information about the partner apparatus by receiving a Probe Request including the multi-link capability element. In a case where Probe Request including the multi-link capability element is not received from the partner apparatus, the processing of this step may be omitted.

In response to the Probe Request received from the communication apparatus <NUM>, the communication apparatus <NUM> returns a Probe Response as a response. Here, in a case where a Beacon including the multi-link capability element has been transmitted, the Probe Response does not need to include the multi-link capability element.

In step S703, the communication apparatus <NUM> determines whether an Association Request is received from the communication apparatus <NUM>. In a case where Association Request is not received (NO in step S703), the communication apparatus <NUM> performs the processing of this step again. In a case where a predetermined time has elapsed since the transmission of the Probe Response in step S702 and a YES determination is not performed in step S703, the communication apparatus <NUM> notifies the user of an error, and the processing of this procedure ends. On the other hand, in a case where an Association Request is received (YES in step S703), the communication apparatus <NUM> performs the processing of step S704.

In step S704, the communication apparatus <NUM> transmits an Association Response as a response to the Association Request. In a case where request information is not received from the communication apparatus <NUM> in step S703, the communication apparatus <NUM> transmits an Association Response including operation information about the multi-link communication with the communication apparatus <NUM>. Here, the communication apparatus <NUM> determines what operation information to be included in the Association Response, based on the multi-link communication capability information about the communication apparatus <NUM>. The operation information to be included in the Association Response from the communication apparatus <NUM> indicates information about the multi-link communication to be actually performed between the communication apparatuses <NUM> and <NUM>. Note that the communication apparatus <NUM> may transmit an Association Response including operation information even in a case where the Association Request received in step S703 includes request information from the communication apparatus <NUM>. In such a case, the communication apparatus <NUM> determines what operation information to be included in the Association Response, based on the request information contained in the Association Request received from the communication apparatus <NUM>. Alternatively, in a case where request information is received from the communication apparatus <NUM> in step S703, the communication apparatus <NUM> may transmit an Association Response including only information indicating whether to permit multi-link communication.

In step S705, the communication apparatus <NUM> starts multi-link communication with the communication apparatus <NUM>. In a case where the Association Response transmitted in step S704 includes multi-link communication operation information, the communication apparatus <NUM> starts multi-link communication based on the operation information. In a case where request information is received in step S703 and an Association Response including only information indicating permission is transmitted in step S704, the communication apparatus <NUM> starts multi-link communication based on the request information received in step S703. After the processing of step S705 is performed, the processing of this procedure ends.

As described above, the communication apparatuses <NUM> and <NUM> add the element indicating multi-link communication capability information to the MAC frames, whereby multi-link communication factoring in each other's capabilities can be performed.

At least a part or all of the flowcharts of the communication apparatuses <NUM> and <NUM> illustrated in <FIG> and <FIG> may be implemented by hardware. For example, by using a predetermined complier, a dedicated circuit may be generated on a field programmable gate array (FPGA) from the computer programs for implementing the steps, and the dedicated circuit is used for hardware implementation. Like an FPGA, a gate array circuit may be formed for hardware implementation. An application specific integrated circuit (ASIC) may be used for implementation.

Claim 1:
A communication apparatus (<NUM>) comprising:
communication means (<NUM>, <NUM>) for communicating a media access control, MAC, frame compliant with an Institute of Electrical and Electronics Engineers (IEEE) <NUM> series standard with another communication apparatus (<NUM>), and
establishment means (<NUM>) for establishing a plurality of links on a plurality of different frequency channels where multi-link communication can be performed with a partner apparatus,
wherein the MAC frame communicated by the communication means (<NUM>, <NUM>) includes a multi-link element as information related to communications via the plurality of links, and
wherein the multi-link element includes a common info field (<NUM>) and a link info field (<NUM>), and the common info field includes a field (<NUM>) capable of indicating a distance between frequency channels recommended for a communication apparatus which transmits the MAC frame including the multi-link element, in the communications via the plurality of links, to perform the communications via the plurality of links asynchronously.