Patent Description:
A wireless local area network (WLAN) has been improved in various ways. For example, the IEEE <NUM>. 11ax standard proposed an improved communication environment using orthogonal frequency division multiple access (OFDMA) and downlink multi-user multiple input multiple output (DL MU MIMO) techniques.

The present specification proposes a technical feature that can be utilized in a new communication standard. For example, the new communication standard may be an extreme high throughput (EHT) standard which is currently being discussed. The EHT standard may use an increased bandwidth, an enhanced PHY layer protocol data unit (PPDU) structure, an enhanced sequence, a hybrid automatic repeat request (HARQ) scheme, or the like, which is newly proposed. The EHT standard may be called the IEEE <NUM>. 11be standard.

In a new WLAN standard, an increased number of spatial streams may be used. In this case, in order to properly use the increased number of spatial streams, a signaling technique in the WLAN system may need to be improved.

Prior art is found in <NPL>, and <NPL>, which teach that a Multi-link Element includes information of other link(s) and also an indication across the links regarding ML setup and operation, wherein the link specific information includes the information per link, such as beacon interval. <NPL> defines a Multi-Link (ML) element structure to include information that a STA of an MLD provides as MLD information being common to all the STAs of the MLD and per-link information with Capabilities and Operational parameter of other STAs of the MLD other than the advertising STA.

<CIT> (prior art falling under Article <NUM>(<NUM>) EPC) discloses that a MLD element includes a common control field and one or more optional subelements, wherein one subelement describes information about one AP in the multi-AP multi-link device and each subelement includes a link identifier of the AP and further includes fields related to the AP, such as a beacon interval field.

The present specification seeks an improved way of receiving relevant information on a beacon interval of another AP in a transmitting MLD in a wireless LAN system.

An example of this specification proposes a method for receiving information on a beacon interval of another AP in a transmitting MLD.

The present embodiment may be performed in a network environment in which a next generation WLAN system (IEEE <NUM>. 11be or EHT WLAN system) is supported. The next generation wireless LAN system is a WLAN system that is enhanced from an <NUM>. 11ax system and may, therefore, satisfy backward compatibility with the <NUM>. 11ax system.

This embodiment proposes a method and apparatus in which a non-AP STA receives information on a beacon interval of an AP other than a peer AP through an ML element in MLD communication and sets its own listen interval. Here, the transmitting MLD may correspond to the AP MLD, and the receiving MLD may correspond to the non-AP MLD. If the non-AP STA is a first receiving STA, a first transmitting STA connected to the first receiving STA through a first link may be referred to as a peer AP, and the second and third transmitting STAs connected through different links may be referred to as different APs.

A receiving multi-link device (MLD) receives a multi-link (ML) element from a transmitting MLD through a first link.

The receiving MLD decodes the ML element.

The transmitting MLD includes a first transmitting station (STA) operating on the first link and a second transmitting STA operating on a second link. The transmitting MLD may further include a third transmitting STA operating in a third link.

The ML element includes common information and link information. The link information includes information on a beacon interval of the second transmitting STA.

The receiving MLD may include a first receiving STA operating on the first link, a second receiving STA operating on the second link, and a third receiving STA operating on the third link.

The link information may further include information on a beacon interval of the third transmitting STA.

That is, this embodiment proposes a method in which the transmitting MLD informs the receiving MLD of beacon intervals of other APs (the second and third transmitting STAs) within the transmitting MLD through the ML element.

According to the embodiment proposed in this specification, the first receiving STA belonging to the receiving MLD can receive beacon intervals of other APs without separate signaling. There is an effect of being able to set one's own listen interval in the ML configuration step (or after the ML configuration step) by using the beacon intervals of other APs.

In the present specification, "A or B" may mean "only A", "only B" or "both A and B". In other words, in the present specification, "A or B" may be interpreted as "A and/or B". For example, in the present specification, "A, B, or C" may mean "only A", "only B", "only C", or "any combination of A, B, C".

A slash (/) or comma used in the present specification may mean "and/or". For example, "A, B, C" may mean "A, B, or C".

In the present specification, "at least one of A and B" may mean "only A", "only B", or "both A and B". In addition, in the present specification, the expression "at least one of A or B" or "at least one of A and/or B" may be interpreted as "at least one of A and B".

In addition, in the present specification, "at least one of A, B, and C" may mean "only A", "only B", "only C", or "any combination of A, B, and C". In addition, "at least one of A, B, or C" or "at least one of A, B, and/or C" may mean "at least one of A, B, and C".

In addition, a parenthesis used in the present specification may mean "for example". Specifically, when indicated as "control information (EHT-signal)", it may denote that "EHT-signal" is proposed as an example of the "control information". In other words, the "control information" of the present specification is not limited to "EHT-signal", and "EHT-signal" may be proposed as an example of the "control information". In addition, when indicated as "control information (i.e., EHT-signal)", it may also mean that "EHT-signal" is proposed as an example of the "control information".

Technical features described individually in one figure in the present specification may be individually implemented, or may be simultaneously implemented.

The following example of the present specification may be applied to various wireless communication systems. For example, the following example of the present specification may be applied to a wireless local area network (WLAN) system. For example, the present specification may be applied to the IEEE <NUM>. 11a/g/n/ac standard or the IEEE <NUM>. 11ax standard. In addition, the present specification may also be applied to the newly proposed EHT standard or IEEE <NUM>. 11be standard. In addition, the example of the present specification may also be applied to a new WLAN standard enhanced from the EHT standard or the IEEE <NUM>. 11be standard. In addition, the example of the present specification may be applied to a mobile communication system. For example, it may be applied to a mobile communication system based on long term evolution (LTE) depending on a <NUM>rd generation partnership project (3GPP) standard and based on evolution of the LTE. In addition, the example of the present specification may be applied to a communication system of a <NUM> NR standard based on the 3GPP standard.

Hereinafter, in order to describe a technical feature of the present specification, a technical feature applicable to the present specification will be described.

<FIG> shows an example of a transmitting apparatus and/or receiving apparatus of the present specification.

In the example of <FIG>, various technical features described below may be performed. <FIG> relates to at least one station (STA). For example, STAs <NUM> and <NUM> of the present specification may also be called in various terms such as a mobile terminal, a wireless device, a wireless transmit/receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile subscriber unit, or simply a user. The STAs <NUM> and <NUM> of the present specification may also be called in various terms such as a network, a base station, a node-B, an access point (AP), a repeater, a router, a relay, or the like. The STAs <NUM> and <NUM> of the present specification may also be referred to as various names such as a receiving apparatus, a transmitting apparatus, a receiving STA, a transmitting STA, a receiving device, a transmitting device, or the like.

For example, the STAs <NUM> and <NUM> may serve as an AP or a non-AP. That is, the STAs <NUM> and <NUM> of the present specification may serve as the AP and/or the non-AP.

The STAs <NUM> and <NUM> of the present specification may support various communication standards together in addition to the IEEE <NUM> standard. For example, a communication standard (e.g., LTE, LTE-A, <NUM> NR standard) or the like based on the 3GPP standard may be supported. In addition, the STA of the present specification may be implemented as various devices such as a mobile phone, a vehicle, a personal computer, or the like. In addition, the STA of the present specification may support communication for various communication services such as voice calls, video calls, data communication, and self-driving (autonomous-driving), or the like.

The STAs <NUM> and <NUM> of the present specification may include a medium access control (MAC) conforming to the IEEE <NUM> standard and a physical layer interface for a radio medium.

The STAs <NUM> and <NUM> will be described below with reference to a sub-figure (a) of <FIG>.

The first STA <NUM> may include a processor <NUM>, a memory <NUM>, and a transceiver <NUM>. The illustrated process, memory, and transceiver may be implemented individually as separate chips, or at least two blocks/functions may be implemented through a single chip.

The transceiver <NUM> of the first STA performs a signal transmission/reception operation. Specifically, an IEEE <NUM> packet (e.g., IEEE <NUM>. 11a/b/g/n/ac/ax/be, etc.) may be transmitted/received.

For example, the first STA <NUM> may perform an operation intended by an AP. For example, the processor <NUM> of the AP may receive a signal through the transceiver <NUM>, process a reception (RX) signal, generate a transmission (TX) signal, and provide control for signal transmission. The memory <NUM> of the AP may store a signal (e.g., RX signal) received through the transceiver <NUM>, and may store a signal (e.g., TX signal) to be transmitted through the transceiver.

For example, the second STA <NUM> may perform an operation intended by a non-AP STA. For example, a transceiver <NUM> of a non-AP performs a signal transmission/reception operation. Specifically, an IEEE <NUM> packet (e.g., IEEE <NUM>. 11a/b/g/n/ac/ax/be packet, etc.) may be transmitted/received.

For example, a processor <NUM> of the non-AP STA may receive a signal through the transceiver <NUM>, process an RX signal, generate a TX signal, and provide control for signal transmission. A memory <NUM> of the non-AP STA may store a signal (e.g., RX signal) received through the transceiver <NUM>, and may store a signal (e.g., TX signal) to be transmitted through the transceiver.

For example, an operation of a device indicated as an AP in the specification described below may be performed in the first STA <NUM> or the second STA <NUM>. For example, if the first STA <NUM> is the AP, the operation of the device indicated as the AP may be controlled by the processor <NUM> of the first STA <NUM>, and a related signal may be transmitted or received through the transceiver <NUM> controlled by the processor <NUM> of the first STA <NUM>. In addition, control information related to the operation of the AP or a TX/RX signal of the AP may be stored in the memory <NUM> of the first STA <NUM>. In addition, if the second STA <NUM> is the AP, the operation of the device indicated as the AP may be controlled by the processor <NUM> of the second STA <NUM>, and a related signal may be transmitted or received through the transceiver <NUM> controlled by the processor <NUM> of the second STA <NUM>. In addition, control information related to the operation of the AP or a TX/RX signal of the AP may be stored in the memory <NUM> of the second STA <NUM>.

For example, in the specification described below, an operation of a device indicated as a non-AP (or user-STA) may be performed in the first STA <NUM> or the second STA <NUM>. For example, if the second STA <NUM> is the non-AP, the operation of the device indicated as the non-AP may be controlled by the processor <NUM> of the second STA <NUM>, and a related signal may be transmitted or received through the transceiver <NUM> controlled by the processor <NUM> of the second STA <NUM>. In addition, control information related to the operation of the non-AP or a TX/RX signal of the non-AP may be stored in the memory <NUM> of the second STA <NUM>. For example, if the first STA <NUM> is the non-AP, the operation of the device indicated as the non-AP may be controlled by the processor <NUM> of the first STA <NUM>, and a related signal may be transmitted or received through the transceiver <NUM> controlled by the processor <NUM> of the first STA <NUM>. In addition, control information related to the operation of the non-AP or a TX/RX signal of the non-AP may be stored in the memory <NUM> of the first STA <NUM>.

In the specification described below, a device called a (transmitting/receiving) STA, a first STA, a second STA, a STA1, a STA2, an AP, a first AP, a second AP, an AP1, an AP2, a (transmitting/receiving) terminal, a (transmitting/receiving) device, a (transmitting/receiving) apparatus, a network, or the like may imply the STAs <NUM> and <NUM> of <FIG>. For example, a device indicated as, without a specific reference numeral, the (transmitting/receiving) STA, the first STA, the second STA, the STA1, the STA2, the AP, the first AP, the second AP, the AP1, the AP2, the (transmitting/receiving) terminal, the (transmitting/receiving) device, the (transmitting/receiving) apparatus, the network, or the like may imply the STAs <NUM> and <NUM> of <FIG>. For example, in the following example, an operation in which various STAs transmit/receive a signal (e.g., a PPDU) may be performed in the transceivers <NUM> and <NUM> of <FIG>. In addition, in the following example, an operation in which various STAs generate a TX/RX signal or perform data processing and computation in advance for the TX/RX signal may be performed in the processors <NUM> and <NUM> of <FIG>. For example, an example of an operation for generating the TX/RX signal or performing the data processing and computation in advance may include: <NUM>) an operation of determining/obtaining/configuring/computing/decoding/encoding bit information of a sub-field (SIG, STF, LTF, Data) included in a PPDU; <NUM>) an operation of determining/configuring/obtaining a time resource or frequency resource (e.g., a subcarrier resource) or the like used for the sub-field (SIG, STF, LTF, Data) included the PPDU; <NUM>) an operation of determining/configuring/obtaining a specific sequence (e.g., a pilot sequence, an STF/LTF sequence, an extra sequence applied to SIG) or the like used for the sub-field (SIG, STF, LTF, Data) field included in the PPDU; <NUM>) a power control operation and/or power saving operation applied for the STA; and <NUM>) an operation related to determining/obtaining/configuring/decoding/encoding or the like of an ACK signal. In addition, in the following example, a variety of information used by various STAs for determining/obtaining/configuring/computing/decoding/decoding a TX/RX signal (e.g., information related to a field/subfield/control field/parameter/power or the like) may be stored in the memories <NUM> and <NUM> of <FIG>.

The aforementioned device/STA of the sub-figure (a) of <FIG> may be modified as shown in the sub-figure (b) of <FIG>. Hereinafter, the STAs <NUM> and <NUM> of the present specification will be described based on the sub-figure (b) of <FIG>.

For example, the transceivers <NUM> and <NUM> illustrated in the sub-figure (b) of <FIG> may perform the same function as the aforementioned transceiver illustrated in the sub-figure (a) of <FIG>. For example, processing chips <NUM> and <NUM> illustrated in the sub-figure (b) of <FIG> may include the processors <NUM> and <NUM> and the memories <NUM> and <NUM>. The processors <NUM> and <NUM> and memories <NUM> and <NUM> illustrated in the sub-figure (b) of <FIG> may perform the same function as the aforementioned processors <NUM> and <NUM> and memories <NUM> and <NUM> illustrated in the sub-figure (a) of <FIG>.

A mobile terminal, a wireless device, a wireless transmit/receive unit (WTRU), a user equipment (UE), a mobile station (MS), a mobile subscriber unit, a user, a user STA, a network, a base station, a Node-B, an access point (AP), a repeater, a router, a relay, a receiving unit, a transmitting unit, a receiving STA, a transmitting STA, a receiving device, a transmitting device, a receiving apparatus, and/or a transmitting apparatus, which are described below, may imply the STAs <NUM> and <NUM> illustrated in the sub-figure (a)/(b) of <FIG>, or may imply the processing chips <NUM> and <NUM> illustrated in the sub-figure (b) of <FIG>. That is, a technical feature of the present specification may be performed in the STAs <NUM> and <NUM> illustrated in the sub-figure (a)/(b) of <FIG>, or may be performed only in the processing chips <NUM> and <NUM> illustrated in the sub-figure (b) of <FIG>. For example, a technical feature in which the transmitting STA transmits a control signal may be understood as a technical feature in which a control signal generated in the processors <NUM> and <NUM> illustrated in the sub-figure (a)/(b) of <FIG> is transmitted through the transceivers <NUM> and <NUM> illustrated in the sub-figure (a)/(b) of <FIG>. Alternatively, the technical feature in which the transmitting STA transmits the control signal may be understood as a technical feature in which the control signal to be transferred to the transceivers <NUM> and <NUM> is generated in the processing chips <NUM> and <NUM> illustrated in the sub-figure (b) of <FIG>.

For example, a technical feature in which the receiving STA receives the control signal may be understood as a technical feature in which the control signal is received by means of the transceivers <NUM> and <NUM> illustrated in the sub-figure (a) of <FIG>. Alternatively, the technical feature in which the receiving STA receives the control signal may be understood as the technical feature in which the control signal received in the transceivers <NUM> and <NUM> illustrated in the sub-figure (a) of <FIG> is obtained by the processors <NUM> and <NUM> illustrated in the sub-figure (a) of <FIG>. Alternatively, the technical feature in which the receiving STA receives the control signal may be understood as the technical feature in which the control signal received in the transceivers <NUM> and <NUM> illustrated in the sub-figure (b) of <FIG> is obtained by the processing chips <NUM> and <NUM> illustrated in the sub-figure (b) of <FIG>.

Referring to the sub-figure (b) of <FIG>, software codes <NUM> and <NUM> may be included in the memories <NUM> and <NUM>. The software codes <NUM> and <NUM> may include instructions for controlling an operation of the processors <NUM> and <NUM>. The software codes <NUM> and <NUM> may be included as various programming languages.

The processors <NUM> and <NUM> or processing chips <NUM> and <NUM> of <FIG> may include an application-specific integrated circuit (ASIC), other chipsets, a logic circuit and/or a data processing device. The processor may be an application processor (AP). For example, the processors <NUM> and <NUM> or processing chips <NUM> and <NUM> of <FIG> may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), and a modulator and demodulator (modem). For example, the processors <NUM> and <NUM> or processing chips <NUM> and <NUM> of <FIG> may be SNAPDRAGONTM series of processors made by Qualcomm®, EXYNOSTM series of processors made by Samsung®, A series of processors made by Apple®, HELIOTM series of processors made by MediaTek®, ATOMTM series of processors made by Intel® or processors enhanced from these processors.

In the present specification, an uplink may imply a link for communication from a non-AP STA to an SP STA, and an uplink PPDU/packet/signal or the like may be transmitted through the uplink. In addition, in the present specification, a downlink may imply a link for communication from the AP STA to the non-AP STA, and a downlink PPDU/packet/signal or the like may be transmitted through the downlink.

<FIG> is a conceptual view illustrating the structure of a wireless local area network (WLAN).

An upper part of <FIG> illustrates the structure of an infrastructure basic service set (BSS) of institute of electrical and electronic engineers (IEEE) <NUM>.

Referring the upper part of <FIG>, the wireless LAN system may include one or more infrastructure BSSs <NUM> and <NUM> (hereinafter, referred to as BSS). The BSSs <NUM> and <NUM> as a set of an AP and a STA such as an access point (AP) <NUM> and a station (STA1) <NUM>-<NUM> which are successfully synchronized to communicate with each other are not concepts indicating a specific region. The BSS <NUM> may include one or more STAs <NUM>-<NUM> and <NUM>-<NUM> which may be joined to one AP <NUM>.

The BSS may include at least one STA, APs providing a distribution service, and a distribution system (DS) <NUM> connecting multiple APs.

The distribution system <NUM> may implement an extended service set (ESS) <NUM> extended by connecting the multiple BSSs <NUM> and <NUM>. The ESS <NUM> may be used as a term indicating one network configured by connecting one or more APs <NUM> or <NUM> through the distribution system <NUM>. The AP included in one ESS <NUM> may have the same service set identification (SSID).

A portal <NUM> may serve as a bridge which connects the wireless LAN network (IEEE <NUM>) and another network (e.g., <NUM>.

In the BSS illustrated in the upper part of <FIG>, a network between the APs <NUM> and <NUM> and a network between the APs <NUM> and <NUM> and the STAs <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> may be implemented. However, the network is configured even between the STAs without the APs <NUM> and <NUM> to perform communication. A network in which the communication is performed by configuring the network even between the STAs without the APs <NUM> and <NUM> is defined as an Ad-Hoc network or an independent basic service set (IBSS).

A lower part of <FIG> illustrates a conceptual view illustrating the IBSS.

Referring to the lower part of <FIG>, the IBSS is a BSS that operates in an Ad-Hoc mode. Since the IBSS does not include the access point (AP), a centralized management entity that performs a management function at the center does not exist. That is, in the IBSS, STAs <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> are managed by a distributed manner. In the IBSS, all STAs <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, and <NUM>-<NUM> may be constituted by movable STAs and are not permitted to access the DS to constitute a self-contained network.

<FIG> illustrates a general link setup process.

In S310, a STA may perform a network discovery operation. The network discovery operation may include a scanning operation of the STA. That is, to access a network, the STA needs to discover a participating network. The STA needs to identify a compatible network before participating in a wireless network, and a process of identifying a network present in a particular area is referred to as scanning. Scanning methods include active scanning and passive scanning.

<FIG> illustrates a network discovery operation including an active scanning process. In active scanning, a STA performing scanning transmits a probe request frame and waits for a response to the probe request frame in order to identify which AP is present around while moving to channels. A responder transmits a probe response frame as a response to the probe request frame to the STA having transmitted the probe request frame. Here, the responder may be a STA that transmits the last beacon frame in a BSS of a channel being scanned. In the BSS, since an AP transmits a beacon frame, the AP is the responder. In an IBSS, since STAs in the IBSS transmit a beacon frame in turns, the responder is not fixed. For example, when the STA transmits a probe request frame via channel <NUM> and receives a probe response frame via channel <NUM>, the STA may store BSS-related information included in the received probe response frame, may move to the next channel (e.g., channel <NUM>), and may perform scanning (e.g., transmits a probe request and receives a probe response via channel <NUM>) by the same method.

Although not shown in <FIG>, scanning may be performed by a passive scanning method. In passive scanning, a STA performing scanning may wait for a beacon frame while moving to channels. A beacon frame is one of management frames in IEEE <NUM> and is periodically transmitted to indicate the presence of a wireless network and to enable the STA performing scanning to find the wireless network and to participate in the wireless network. In a BSS, an AP serves to periodically transmit a beacon frame. In an IBSS, STAs in the IBSS transmit a beacon frame in turns. Upon receiving the beacon frame, the STA performing scanning stores information related to a BSS included in the beacon frame and records beacon frame information in each channel while moving to another channel. The STA having received the beacon frame may store BSS-related information included in the received beacon frame, may move to the next channel, and may perform scanning in the next channel by the same method.

After discovering the network, the STA may perform an authentication process in S320. The authentication process may be referred to as a first authentication process to be clearly distinguished from the following security setup operation in S340. The authentication process in S320 may include a process in which the STA transmits an authentication request frame to the AP and the AP transmits an authentication response frame to the STA in response. The authentication frames used for an authentication request/response are management frames.

The authentication frames may include information related to an authentication algorithm number, an authentication transaction sequence number, a status code, a challenge text, a robust security network (RSN), and a finite cyclic group.

The STA may transmit the authentication request frame to the AP. The AP may determine whether to allow the authentication of the STA based on the information included in the received authentication request frame. The AP may provide the authentication processing result to the STA via the authentication response frame.

When the STA is successfully authenticated, the STA may perform an association process in S330. The association process includes a process in which the STA transmits an association request frame to the AP and the AP transmits an association response frame to the STA in response. The association request frame may include, for example, information related to various capabilities, a beacon listen interval, a service set identifier (SSID), a supported rate, a supported channel, RSN, a mobility domain, a supported operating class, a traffic indication map (TIM) broadcast request, and an interworking service capability. The association response frame may include, for example, information related to various capabilities, a status code, an association ID (AID), a supported rate, an enhanced distributed channel access (EDCA) parameter set, a received channel power indicator (RCPI), a received signal-to-noise indicator (RSNI), a mobility domain, a timeout interval (association comeback time), an overlapping BSS scanning parameter, a TIM broadcast response, and a QoS map.

In S340, the STA may perform a security setup process. The security setup process in S340 may include a process of setting up a private key through four-way handshaking, for example, through an extensible authentication protocol over LAN (EAPOL) frame.

<FIG> illustrates an example of a PPDU used in an IEEE standard.

As illustrated, various types of PHY protocol data units (PPDUs) are used in IEEE a/g/n/ac standards. Specifically, an LTF and a STF include a training signal, a SIG-A and a SIG-B include control information for a receiving STA, and a data field includes user data corresponding to a PSDU (MAC PDU/aggregated MAC PDU).

<FIG> also includes an example of an HE PPDU according to IEEE <NUM>. The HE PPDU according to <FIG> is an illustrative PPDU for multiple users. An HE-SIG-B may be included only in a PPDU for multiple users, and an HE-SIG-B may be omitted in a PPDU for a single user.

As illustrated in <FIG>, the HE-PPDU for multiple users (MUs) may include a legacy-short training field (L-STF), a legacy-long training field (L-LTF), a legacy-signal (L-SIG), a high efficiency-signal A (HE-SIG A), a high efficiency-signal-B (HE-SIG B), a high efficiency-short training field (HE-STF), a high efficiency-long training field (HE-LTF), a data field (alternatively, an MAC payload), and a packet extension (PE) field. The respective fields may be transmitted for illustrated time periods (i.e., <NUM> or <NUM>).

Hereinafter, a resource unit (RU) used for a PPDU is described. An RU may include a plurality of subcarriers (or tones). An RU may be used to transmit a signal to a plurality of STAs according to OFDMA. Further, an RU may also be defined to transmit a signal to one STA. An RU may be used for an STF, an LTF, a data field, or the like.

The RU described in the present specification may be used in uplink (UL) communication and downlink (DL) communication. For example, when UL-MU communication which is solicited by a trigger frame is performed, a transmitting STA (e.g., an AP) may allocate a first RU (e.g., <NUM>/<NUM>/<NUM>/<NUM>-RU, etc.) to a first STA through the trigger frame, and may allocate a second RU (e.g., <NUM>/<NUM>/<NUM>/<NUM>-RU, etc.) to a second STA. Thereafter, the first STA may transmit a first trigger-based PPDU based on the first RU, and the second STA may transmit a second trigger-based PPDU based on the second RU. The first/second trigger-based PPDU is transmitted to the AP at the same (or overlapped) time period.

For example, when a DL MU PPDU is configured, the transmitting STA (e.g., AP) may allocate the first RU (e.g., <NUM>/<NUM>/<NUM>/<NUM>-RU. etc.) to the first STA, and may allocate the second RU (e.g., <NUM>/<NUM>/<NUM>/<NUM>-RU, etc.) to the second STA. That is, the transmitting STA (e.g., AP) may transmit HE-STF, HE-LTF, and Data fields for the first STA through the first RU in one MU PPDU, and may transmit HE-STF, HE-LTF, and Data fields for the second STA through the second RU.

<FIG> illustrates an operation based on UL-MU. As illustrated, a transmitting STA (e.g., an AP) may perform channel access through contending (e.g., a backoff operation), and may transmit a trigger frame <NUM>. That is, the transmitting STA may transmit a PPDU including the trigger frame <NUM>. Upon receiving the PPDU including the trigger frame, a trigger-based (TB) PPDU is transmitted after a delay corresponding to SIFS.

TB PPDUs <NUM> and <NUM> may be transmitted at the same time period, and may be transmitted from a plurality of STAs (e.g., user STAs) having AIDs indicated in the trigger frame <NUM>. An ACK frame <NUM> for the TB PPDU may be implemented in various forms.

A specific feature of the trigger frame is described with reference to <FIG>. Even if UL-MU communication is used, an orthogonal frequency division multiple access (OFDMA) scheme or a MU MIMO scheme may be used, and the OFDMA and MU-MIMO schemes may be simultaneously used.

<FIG> illustrates an example of a trigger frame. The trigger frame of <FIG> allocates a resource for uplink multiple-user (MU) transmission, and may be transmitted, for example, from an AP. The trigger frame may be configured of a MAC frame, and may be included in a PPDU.

Each field shown in <FIG> may be partially omitted, and another field may be added. In addition, a length of each field may be changed to be different from that shown in the figure.

A frame control field <NUM> of <FIG> may include information related to a MAC protocol version and extra additional control information. A duration field <NUM> may include time information for NAV configuration or information related to an identifier (e.g., AID) of a STA.

In addition, an RA field <NUM> may include address information of a receiving STA of a corresponding trigger frame, and may be optionally omitted. A TA field <NUM> may include address information of a STA (e.g., an AP) which transmits the corresponding trigger frame. A common information field <NUM> includes common control information applied to the receiving STA which receives the corresponding trigger frame. For example, a field indicating a length of an L-SIG field of an uplink PPDU transmitted in response to the corresponding trigger frame or information for controlling content of a SIG-A field (i.e., HE-SIG-A field) of the uplink PPDU transmitted in response to the corresponding trigger frame may be included. In addition, as common control information, information related to a length of a CP of the uplink PPDU transmitted in response to the corresponding trigger frame or information related to a length of an LTF field may be included.

In addition, per user information fields <NUM>#<NUM> to <NUM>#N corresponding to the number of receiving STAs which receive the trigger frame of <FIG> are preferably included. The per user information field may also be called an "allocation field".

In addition, the trigger frame of <FIG> may include a padding field <NUM> and a frame check sequence field <NUM>.

Each of the per user information fields <NUM>#<NUM> to <NUM>#N shown in <FIG> may include a plurality of subfields.

<FIG> illustrates an example of a common information field of a trigger frame. A subfield of <FIG> may be partially omitted, and an extra subfield may be added. In addition, a length of each subfield illustrated may be changed.

A length field <NUM> illustrated has the same value as a length field of an L-SIG field of an uplink PPDU transmitted in response to a corresponding trigger frame, and a length field of the L-SIG field of the uplink PPDU indicates a length of the uplink PPDU. As a result, the length field <NUM> of the trigger frame may be used to indicate the length of the corresponding uplink PPDU.

In addition, a cascade identifier field <NUM> indicates whether a cascade operation is performed. The cascade operation implies that downlink MU transmission and uplink MU transmission are performed together in the same TXOP. That is, it implies that downlink MU transmission is performed and thereafter uplink MU transmission is performed after a pre-set time (e.g., SIFS). During the cascade operation, only one transmitting device (e.g., AP) may perform downlink communication, and a plurality of transmitting devices (e.g., non-APs) may perform uplink communication.

A CS request field <NUM> indicates whether a wireless medium state or a NAV or the like is necessarily considered in a situation where a receiving device which has received a corresponding trigger frame transmits a corresponding uplink PPDU.

An HE-SIG-A information field <NUM> may include information for controlling content of a SIG-A field (i.e., HE-SIG-A field) of the uplink PPDU in response to the corresponding trigger frame.

A CP and LTF type field <NUM> may include information related to a CP length and LTF length of the uplink PPDU transmitted in response to the corresponding trigger frame. A trigger type field <NUM> may indicate a purpose of using the corresponding trigger frame, for example, typical triggering, triggering for beamforming, a request for block ACK/NACK, or the like.

It may be assumed that the trigger type field <NUM> of the trigger frame in the present specification indicates a trigger frame of a basic type for typical triggering. For example, the trigger frame of the basic type may be referred to as a basic trigger frame.

<FIG> illustrates an example of a subfield included in a per user information field. A user information field <NUM> of <FIG> may be understood as any one of the per user information fields <NUM>#<NUM> to <NUM>#N mentioned above with reference to <FIG>. A subfield included in the user information field <NUM> of <FIG> may be partially omitted, and an extra subfield may be added. In addition, a length of each subfield illustrated may be changed.

A user identifier field <NUM> of <FIG> indicates an identifier of a STA (i.e., receiving STA) corresponding to per user information. An example of the identifier may be the entirety or part of an association identifier (AID) value of the receiving STA.

In addition, an RU allocation field <NUM> may be included. That is, when the receiving STA identified through the user identifier field <NUM> transmits a TB PPDU in response to the trigger frame, the TB PPDU is transmitted through an RU indicated by the RU allocation field <NUM>.

The subfield of <FIG> may include a coding type field <NUM>. The coding type field <NUM> may indicate a coding type of the TB PPDU. For example, when BCC coding is applied to the TB PPDU, the coding type field <NUM> may be set to '<NUM>', and when LDPC coding is applied, the coding type field <NUM> may be set to '<NUM>'.

In addition, the subfield of <FIG> may include an MCS field <NUM>. The MCS field <NUM> may indicate an MCS scheme applied to the TB PPDU. For example, when BCC coding is applied to the TB PPDU, the coding type field <NUM> may be set to '<NUM>', and when LDPC coding is applied, the coding type field <NUM> may be set to '<NUM>'.

Hereinafter, a UL OFDMA-based random access (UORA) scheme will be described.

<FIG> describes a technical feature of the UORA scheme.

A transmitting STA (e.g., an AP) may allocate six RU resources through a trigger frame as shown in <FIG>. Specifically, the AP may allocate a 1st RU resource (AID <NUM>, RU <NUM>), a 2nd RU resource (AID <NUM>, RU <NUM>), a 3rd RU resource (AID <NUM>, RU <NUM>), a 4th RU resource (AID <NUM>, RU <NUM>), a 5th RU resource (AID <NUM>, RU <NUM>), and a 6th RU resource (AID <NUM>, RU <NUM>). Information related to the AID <NUM>, AID <NUM>, or AID <NUM> may be included, for example, in the user identifier field <NUM> of <FIG>. Information related to the RU <NUM> to RU <NUM> may be included, for example, in the RU allocation field <NUM> of <FIG>. AID=<NUM> may imply a UORA resource for an associated STA, and AID=<NUM> may imply a UORA resource for an un-associated STA. Accordingly, the 1st to 3rd RU resources of <FIG> may be used as a UORA resource for the associated STA, the 4th and 5th RU resources of <FIG> may be used as a UORA resource for the un-associated STA, and the 6th RU resource of <FIG> may be used as a typical resource for UL MU.

In the example of <FIG>, an OFDMA random access backoff (OBO) of a STA1 is decreased to <NUM>, and the STA1 randomly selects the 2nd RU resource (AID <NUM>, RU <NUM>). In addition, since an OBO counter of a STA2/<NUM> is greater than <NUM>, an uplink resource is not allocated to the STA2/<NUM>. In addition, regarding a STA4 in <FIG>, since an AID (e.g., AID=<NUM>) of the STA4 is included in a trigger frame, a resource of the RU <NUM> is allocated without backoff.

Specifically, since the STA1 of <FIG> is an associated STA, the total number of eligible RA RUs for the STA1 is <NUM> (RU <NUM>, RU <NUM>, and RU <NUM>), and thus the STA1 decreases an OBO counter by <NUM> so that the OBO counter becomes <NUM>. In addition, since the STA2 of <FIG> is an associated STA, the total number of eligible RA RUs for the STA2 is <NUM> (RU <NUM>, RU <NUM>, and RU <NUM>), and thus the STA2 decreases the OBO counter by <NUM> but the OBO counter is greater than <NUM>. In addition, since the STA3 of <FIG> is an un-associated STA, the total number of eligible RA RUs for the STA3 is <NUM> (RU <NUM>, RU <NUM>), and thus the STA3 decreases the OBO counter by <NUM> but the OBO counter is greater than <NUM>.

Hereinafter, a PPDU transmitted/received in a STA of the present specification will be described.

<FIG> illustrates an example of a PPDU used in the present specification.

The PPDU of <FIG> may be called in various terms such as an EHT PPDU, a TX PPDU, an RX PPDU, a first type or N-th type PPDU, or the like. For example, in the present specification, the PPDU or the EHT PPDU may be called in various terms such as a TX PPDU, a RX PPDU, a first type or N-th type PPDU, or the like. In addition, the EHT PPDU may be used in an EHT system and/or a new WLAN system enhanced from the EHT system.

The PPDU of <FIG> may indicate the entirety or part of a PPDU type used in the EHT system. For example, the example of <FIG> may be used for both of a single-user (SU) mode and a multi-user (MU) mode. In other words, the PPDU of <FIG> may be a PPDU for one receiving STA or a plurality of receiving STAs. When the PPDU of <FIG> is used for a trigger-based (TB) mode, the EHT-SIG of <FIG> may be omitted. In other words, an STA which has received a trigger frame for uplink-MU (UL-MU) may transmit the PPDU in which the EHT-SIG is omitted in the example of <FIG>.

In <FIG>, an L-STF to an EHT-LTF may be called a preamble or a physical preamble, and may be generated/transmitted/received/obtained/decoded in a physical layer.

A subcarrier spacing of the L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, and EHT-SIG fields of <FIG> may be determined as <NUM>, and a subcarrier spacing of the EHT-STF, EHT-LTF, and Data fields may be determined as <NUM>. That is, a tone index (or subcarrier index) of the L-STF, L-LTF, L-SIG, RL-SIG, U-SIG, and EHT-SIG fields may be expressed in unit of <NUM>, and a tone index (or subcarrier index) of the EHT-STF, EHT-LTF, and Data fields may be expressed in unit of <NUM>.

In the PPDU of <FIG>, the L-LTE and the L-STF may be the same as those in the conventional fields.

The L-SIG field of <FIG> may include, for example, bit information of <NUM> bits. For example, the <NUM>-bit information may include a rate field of <NUM> bits, a reserved bit of <NUM> bit, a length field of <NUM> bits, a parity bit of <NUM> bit, and a tail bit of <NUM> bits. For example, the length field of <NUM> bits may include information related to a length or time duration of a PPDU. For example, the length field of <NUM> bits may be determined based on a type of the PPDU. For example, when the PPDU is a non-HT, HT, VHT PPDU or an EHT PPDU, a value of the length field may be determined as a multiple of <NUM>. For example, when the PPDU is an HE PPDU, the value of the length field may be determined as "a multiple of <NUM>"+<NUM> or "a multiple of <NUM>"+<NUM>. In other words, for the non-HT, HT, VHT PPDI or the EHT PPDU, the value of the length field may be determined as a multiple of <NUM>, and for the HE PPDU, the value of the length field may be determined as "a multiple of <NUM>"+ <NUM> or "a multiple of <NUM>"+<NUM>.

For example, the transmitting STA may apply BCC encoding based on a <NUM>/<NUM> coding rate to the <NUM>-bit information of the L-SIG field. Thereafter, the transmitting STA may obtain a BCC coding bit of <NUM> bits. BPSK modulation may be applied to the <NUM>-bit coding bit, thereby generating <NUM> BPSK symbols. The transmitting STA may map the <NUM> BPSK symbols to positions except for a pilot subcarrier{subcarrier index -<NUM>, - <NUM>, +<NUM>, +<NUM>} and a DC subcarrier{subcarrier index <NUM>}. As a result, the <NUM> BPSK symbols may be mapped to subcarrier indices -<NUM> to -<NUM>, -<NUM> to -<NUM>, -<NUM> to -<NUM>, +<NUM> to +<NUM>, +<NUM> to +<NUM>, and +<NUM> to +<NUM>. The transmitting STA may additionally map a signal of {-<NUM>, -<NUM>, -<NUM>, <NUM>} to a subcarrier index{-<NUM>, -<NUM>, +<NUM>, +<NUM>}. The aforementioned signal may be used for channel estimation on a frequency domain corresponding to {-<NUM>, -<NUM>, +<NUM>, +<NUM>}.

The transmitting STA may generate an RL-SIG generated in the same manner as the L-SIG. BPSK modulation may be applied to the RL-SIG. The receiving STA may know that the RX PPDU is the HE PPDU or the EHT PPDU, based on the presence of the RL-SIG.

A universal SIG (U-SIG) may be inserted after the RL-SIG of <FIG>. The U-SIB may be called in various terms such as a first SIG field, a first SIG, a first type SIG, a control signal, a control signal field, a first (type) control signal, or the like.

The U-SIG may include information of N bits, and may include information for identifying a type of the EHT PPDU. For example, the U-SIG may be configured based on two symbols (e.g., two contiguous OFDM symbols). Each symbol (e.g., OFDM symbol) for the U-SIG may have a duration of <NUM>. Each symbol of the U-SIG may be used to transmit the <NUM>-bit information. For example, each symbol of the U-SIG may be transmitted/received based on <NUM> data tomes and <NUM> pilot tones.

Through the U-SIG (or U-SIG field), for example, A-bit information (e.g., <NUM> un-coded bits) may be transmitted. A first symbol of the U-SIG may transmit first X-bit information (e.g., <NUM> un-coded bits) of the A-bit information, and a second symbol of the U-SIB may transmit the remaining Y-bit information (e.g. <NUM> un-coded bits) of the A-bit information. For example, the transmitting STA may obtain <NUM> un-coded bits included in each U-SIG symbol. The transmitting STA may perform convolutional encoding (i.e., BCC encoding) based on a rate of R=<NUM>/<NUM> to generate <NUM>-coded bits, and may perform interleaving on the <NUM>-coded bits. The transmitting STA may perform BPSK modulation on the interleaved <NUM>-coded bits to generate <NUM> BPSK symbols to be allocated to each U-SIG symbol. One U-SIG symbol may be transmitted based on <NUM> tones (subcarriers) from a subcarrier index -<NUM> to a subcarrier index +<NUM>, except for a DC index <NUM>. The <NUM> BPSK symbols generated by the transmitting STA may be transmitted based on the remaining tones (subcarriers) except for pilot tones, i.e., tones -<NUM>, -<NUM>, +<NUM>, +<NUM>.

For example, the A-bit information (e.g., <NUM> un-coded bits) generated by the U-SIG may include a CRC field (e.g., a field having a length of <NUM> bits) and a tail field (e.g., a field having a length of <NUM> bits). The CRC field and the tail field may be transmitted through the second symbol of the U-SIG. The CRC field may be generated based on <NUM> bits allocated to the first symbol of the U-SIG and the remaining <NUM> bits except for the CRC/tail fields in the second symbol, and may be generated based on the conventional CRC calculation algorithm. In addition, the tail field may be used to terminate trellis of a convolutional decoder, and may be set to, for example, "<NUM>".

The A-bit information (e.g., <NUM> un-coded bits) transmitted by the U-SIG (or U-SIG field) may be divided into version-independent bits and version-dependent bits. For example, the version-independent bits may have a fixed or variable size. For example, the version-independent bits may be allocated only to the first symbol of the U-SIG, or the version-independent bits may be allocated to both of the first and second symbols of the U-SIG. For example, the version-independent bits and the version-dependent bits may be called in various terms such as a first control bit, a second control bit, or the like.

For example, the version-independent bits of the U-SIG may include a PHY version identifier of <NUM> bits. For example, the PHY version identifier of <NUM> bits may include information related to a PHY version of a TX/RX PPDU. For example, a first value of the PHY version identifier of <NUM> bits may indicate that the TX/RX PPDU is an EHT PPDU. In other words, when the transmitting STA transmits the EHT PPDU, the PHY version identifier of <NUM> bits may be set to a first value. In other words, the receiving STA may determine that the RX PPDU is the EHT PPDU, based on the PHY version identifier having the first value.

For example, the version-independent bits of the U-SIG may include a UL/DL flag field of <NUM> bit. A first value of the UL/DL flag field of <NUM> bit relates to UL communication, and a second value of the UL/DL flag field relates to DL communication.

For example, the version-independent bits of the U-SIG may include information related to a TXOP length and information related to a BSS color ID.

For example, when the EHT PPDU is divided into various types (e.g., various types such as an EHT PPDU related to an SU mode, an EHT PPDU related to a MU mode, an EHT PPDU related to a TB mode, an EHT PPDU related to extended range transmission, or the like), information related to the type of the EHT PPDU may be included in the version-dependent bits of the U-SIG.

For example, the U-SIG may include: <NUM>) a bandwidth field including information related to a bandwidth; <NUM>) a field including information related to an MCS scheme applied to EHT-SIG; <NUM>) an indication field including information regarding whether a dual subcarrier modulation (DCM) scheme is applied to EHT-SIG; <NUM>) a field including information related to the number of symbol used for EHT-SIG; <NUM>) a field including information regarding whether the EHT-SIG is generated across a full band; <NUM>) a field including information related to a type of EHT-LTF/STF; and <NUM>) information related to a field indicating an EHT-LTF length and a CP length.

In the following example, a signal represented as a (TX/RX/UL/DL) signal, a (TX/RX/UL/DL) frame, a (TX/RX/UL/DL) packet, a (TX/RX/UL/DL) data unit, (TX/RX/UL/DL) data, or the like may be a signal transmitted/received based on the PPDU of <FIG>. The PPDU of <FIG> may be used to transmit/receive frames of various types. For example, the PPDU of <FIG> may be used for a control frame. An example of the control frame may include a request to send (RTS), a clear to send (CTS), a power save-poll (PS-poll), BlockACKReq, BlockAck, a null data packet (NDP) announcement, and a trigger frame. For example, the PPDU of <FIG> may be used for a management frame. An example of the management frame may include a beacon frame, a (re-)association request frame, a (re-)association response frame, a probe request frame, and a probe response frame. For example, the PPDU of <FIG> may be used for a data frame. For example, the PPDU of <FIG> may be used to simultaneously transmit at least two or more of the control frames, the management frame, and the data frame.

<FIG> illustrates an example of a modified transmission device and/or receiving device of the present specification.

Each device/STA of the sub-figure (a)/(b) of <FIG> may be modified as shown in <FIG>. A transceiver <NUM> of <FIG> may be identical to the transceivers <NUM> and <NUM> of <FIG>. The transceiver <NUM> of <FIG> may include a receiver and a transmitter.

A processor <NUM> of <FIG> may be identical to the processors <NUM> and <NUM> of <FIG>. Alternatively, the processor <NUM> of <FIG> may be identical to the processing chips <NUM> and <NUM> of <FIG>.

A memory <NUM> of <FIG> may be identical to the memories <NUM> and <NUM> of <FIG>. Alternatively, the memory <NUM> of <FIG> may be a separate external memory different from the memories <NUM> and <NUM> of <FIG>.

Referring to <FIG>, a power management module <NUM> manages power for the processor <NUM> and/or the transceiver <NUM>. A battery <NUM> supplies power to the power management module <NUM>. A display <NUM> outputs a result processed by the processor <NUM>. A keypad <NUM> receives inputs to be used by the processor <NUM>. The keypad <NUM> may be displayed on the display <NUM>. A SIM card <NUM> may be an integrated circuit which is used to securely store an international mobile subscriber identity (IMSI) and its related key, which are used to identify and authenticate subscribers on mobile telephony devices such as mobile phones and computers.

Referring to <FIG>, a speaker <NUM> may output a result related to a sound processed by the processor <NUM>. A microphone <NUM> may receive an input related to a sound to be used by the processor <NUM>.

Hereinafter, technical features of multi-link (ML) supported by the STA of the present specification will be described.

STAs (AP and/or non-AP STA) of the present specification may support multi-link (ML) communication. ML communication may mean communication supporting a plurality of links. Links related to ML communication may include channels (e.g., <NUM>/<NUM>/<NUM>/<NUM>/<NUM>/<NUM> channels) of the <NUM> band, the <NUM> band, and the <NUM> band.

A plurality of links used for ML communication may be set in various ways. For example, a plurality of links supported by one STA for ML communication may be a plurality of channels in the <NUM> band, a plurality of channels in the <NUM> band, and a plurality of channels in the <NUM> band. Alternatively, a plurality of links may be a combination of at least one channel within the <NUM> band (or <NUM>/<NUM> band) and at least one channel within the <NUM> band (or <NUM>/<NUM> band). Meanwhile, at least one of a plurality of links supported by one STA for ML communication may be a channel to which preamble puncturing is applied.

The STA may perform ML setup to perform ML communication. ML setup may be performed based on management frames or control frames such as Beacon, Probe Request/Response, and Association Request/Response. For example, information on ML setup may be included in element fields included in Beacon, Probe Request/Response, and Association Request/Response.

When ML setup is completed, an enabled link for ML communication may be determined. The STA may perform frame exchange through at least one of a plurality of links determined as an enabled link. For example, an enabled link may be used for at least one of a management frame, a control frame, and a data frame.

When one STA supports a plurality of Links, a transmitting/receiving device supporting each Link may operate like one logical STA. For example, one STA supporting two links may be expressed as one ML device (Multi Link Device; MLD) including a first STA for a first link and a second STA for a second link. For example, one AP supporting two links may be expressed as one AP MLD including a first AP for a first link and a second AP for a second link. In addition, one non-AP supporting two links may be expressed as one non-AP MLD including a first STA for the first link and a second STA for the second link.

More specific features of the ML setup are described below.

An MLD (AP MLD and/or non-AP MLD) may transmit information about a link that the corresponding MLD can support through ML setup. Link-related information may be configured in various ways. For example, link-related information includes at least one of <NUM>) information on whether the MLD (or STA) supports simultaneous RX/TX operation, <NUM>) information on the number/upper limit of uplink/downlink links supported by the MLD (or STA), <NUM>) information on the location/band/resource of uplink/downlink link supported by MLD (or STA), <NUM>) type of frame available or preferred in at least one uplink/downlink link (management, control, data etc.), <NUM>) available or preferred ACK policy information on at least one uplink/downlink link, and <NUM>) information on available or preferred TID (traffic identifier) on at least one uplink/downlink link. The TID is related to the priority of traffic data and is represented by <NUM> types of values according to the conventional wireless LAN standard. That is, <NUM> TID values corresponding to <NUM> access categories (AC) (AC_BK (background), AC_BE (best effort), AC_VI (video), AC_VO (voice)) according to the conventional wireless LAN standard may be defined.

For example, it may be set in advance that all TIDs are mapped for uplink/downlink links. Specifically, if negotiation is not done through ML setup, all TIDs may be used for ML communication, and if mapping between uplink/downlink links and TIDs is negotiated through additional ML setup, the negotiated TIDs may be used for ML communication.

A plurality of links that can be used by the transmitting MLD and the receiving MLD related to ML communication can be set through ML setup, and this can be called an enabled link. The enabled link can be called differently in a variety of ways. For example, it may be called various expressions such as a first link, a second link, a transmitting link, and a receiving link.

After the ML setup is complete, the MLD may update the ML setup. For example, the MLD may transmit information about a new link when updating information about a link is required. Information about the new link may be transmitted based on at least one of a management frame, a control frame, and a data frame.

The device described below may be the apparatus of <FIG> and/or <NUM>, and the PPDU may be the PPDU of <FIG>. A device may be an AP or a non-AP STA. A device described below may be an AP multi-link device (MLD) or a non-AP STA MLD supporting multi-link.

In EHT (extremely high throughput), a standard being discussed after <NUM>. 11ax, a multi-link environment in which one or more bands are simultaneously used is considered. When a device supports multi-link, the device can simultaneously or alternately use one or more bands (e.g., <NUM>, <NUM>, <NUM>, <NUM>, etc.).

In the following specification, MLD means a multi-link device. The MLD has one or more connected STAs and has one MAC service access point (SAP) that communicates with the upper link layer (Logical Link Control, LLC). MLD may mean a physical device or a logical device. Hereinafter, a device may mean an MLD.

In the following specification, a transmitting device and a receiving device may mean MLD. The first link of the receiving/transmitting device may be a terminal (e.g., STA or AP) included in the receiving/transmitting device and performing signal transmission/reception through the first link. The second link of the receiving/transmitting device may be a terminal (e.g., STA or AP) that transmits/receives a signal through the second link included in the receiving/transmitting device.

In IEEE802.11be, two types of multi-link operations can be supported. For example, simultaneous transmit and receive (STR) and non-STR operations may be considered. For example, STR may be referred to as asynchronous multi-link operation, and non-STR may be referred to as synchronous multi-link operation. Multi-links may include multi-bands. That is, multi-links may mean links included in several frequency bands or may mean multiple links included in one frequency band.

EHT (11be) considers multi-link technology, where multi-link may include multi-band. That is, multi-link can represent links of several bands and multiple multi-links within one band at the same time. Two major multi-link operations are being considered. Asynchronous operation, which enables TX/RX simultaneously on several links, and synchronous operation, which is not possible, are being considered. Hereinafter, a capability that enables simultaneous reception and transmission on multiple links is referred to as STR (simultaneous transmit and receive), an STA having STR capability is referred to as STR MLD (multi-link device), and an STA that does not have STR capability is referred to as a non-STR MLD.

In the following specification, for convenience of explanation, it is described that the MLD (or the processor of the MLD) controls at least one STA, but is not limited thereto. As described above, the at least one STA may transmit and receive signals independently regardless of MLD.

According to an embodiment, an AP MLD or a non-AP MLD may have a structure having a plurality of links. In other words, a non-AP MLD can support multiple links. A non-AP MLD may include a plurality of STAs. A plurality of STAs may have Link for each STA.

In the EHT standard (<NUM>. 11be standard), the MLD (Multi-Link Device) structure in which one AP/non-AP MLD supports multiple links is considered as a major technology. STAs included in the non-AP MLD may transmit information about other STAs in the non-AP MLD together through one link. Accordingly, there is an effect of reducing the overhead of frame exchange. In addition, there is an effect of increasing the link use efficiency of the STA and reducing power consumption.

<FIG> shows an example of a structure of a non-AP MLD.

Referring to <FIG>, a non-AP MLD may be configured with a plurality of links. In other words, a non-AP MLD can support multiple links. A non-AP MLD may include a plurality of STAs. A plurality of STAs may have Link for each STA. Although <FIG> shows an example of a non-AP MLD structure, the structure of the AP MLD may also be configured identically to the example of the structure of the non-AP MLD shown in <FIG>.

For example, the non-AP MLD may include STA <NUM>, STA <NUM>, and STA <NUM>. STA <NUM> can operate on link <NUM>. link <NUM> may be included in the <NUM> band. STA <NUM> can operate on link <NUM>. link <NUM> may be included in the <NUM> band. STA <NUM> can operate on link <NUM>. link <NUM> may be included in the <NUM> band. Bands included in link <NUM>/<NUM>/<NUM> are exemplary and may be included in <NUM>, <NUM>, and <NUM>.

<FIG> shows an example in which one non-AP MLD (STA MLD) has three links, and each link has a primary channel (PCH). Basically, the AP corresponding to each link indicates and transmits the Beacon interval (BI) in the Beacon frame and Probe Response frame.

As such, in the case of an AP/non-AP MLD supporting multi-link, each AP of the AP MLD and each STA of the non-AP MLD may be connected to each link through a link setup process. And at this time, the connected link can be changed or reconnected to another link by AP MLD or non-AP MLD depending on the situation.

In addition, in the EHT standard, a link may be classified as an anchored link or a non-anchored link in order to reduce power consumption. An anchored link or non-anchored link can be called variously. For example, an anchored link may be referred to as a primary link. A non-Anchored Link can be called a Secondary link.

According to an embodiment, an AP MLD supporting multi-link can be managed by designating each link as an anchored link or a non-anchored link. The AP MLD may support one or more links among a plurality of links as an anchored link. A non-AP MLD can use it by selecting one or more of its own anchored links from the Anchored Link List (list of anchored links supported by the AP MLD).

For example, Anchored Link can be used for non-data frame exchange (i.e. Beacon and Management frame) as well as frame exchange for synchronization. Also, non-anchored links can only be used for data frame exchange.

The non-AP MLD can monitor only the anchored link for receiving beacons and management frames during the idle period. Therefore, in the case of non-AP MLD, at least one anchored link must be connected to receive beacon and management frame. The one or more Anchored Links must always maintain an enable state. In contrast, non-anchored links are used only for data frame exchange. Accordingly, an STA corresponding to a non-anchored link (or an STA connected to a non-anchored link) may enter doze during an idle period not using a channel/link. This has the effect of reducing power consumption.

Therefore, in the following specification, a protocol for recommending or requesting link reconnection by an AP MLD or a non-AP MLD dynamically according to circumstances may be proposed for efficient link connection. In addition, in the following specification, an anchored link reconnection protocol considering characteristics of an anchored link used for the purpose of power reduction as well as a general link may be additionally proposed.

According to an embodiment, each link between an AP MLD and a non-AP MLD may be determined in an Association or (re)Association process. At this time, the AP MLD and the non-AP MLD can perform frame exchange through the connected Link. A specific embodiment in which an AP MLD and a non-AP MLD are connected through a link setup process can be described with reference to <FIG>.

<FIG> illustrates an example in which an AP MLD and a non-AP MLD are connected through a link setup process.

Referring to <FIG>, the AP MLD may include AP <NUM>, AP <NUM>, and AP <NUM>. The non-AP MLD may include STA <NUM> and STA <NUM>. AP <NUM> and STA <NUM> may be connected through link <NUM>. AP <NUM> and STA <NUM> may be connected through link <NUM>.

For example, AP <NUM> and STA <NUM> may be connected through link <NUM> through a first link setup process. AP <NUM> and STA <NUM> may be connected through link <NUM> through a second link setup process. For another example, AP MLD and non-AP MLD may be connected through a one-time link setup process. In other words, the AP MLD and the non-AP MLD may be connected through link <NUM> and link <NUM> based on a link setup process once.

As described above, each AP and STA may perform frame exchange through the connected Link. In addition, information of other APs on a different link or other STAs on a different link may be transmitted and received through one link.

However, after this link setup process, the AP MLD or non-AP MLD may request link change or reconnection for more efficient frame exchange (e.g., load balancing or interference avoiding, etc.) depending on the situation/environment.

Meanwhile, the non-AP MLD may set the Listen interval to the MLD level. That is, one non-AP STA included in the non-AP MLD may configure a Listen interval in consideration of Beacon intervals of APs included in the AP MLD and include it in the Association Request frame.

For reference, the value of the Listen interval field transmitted by the non-AP MLD is the unit of the maximum value of the Beacon interval corresponding to the link that the non-AP MLD intends to establish.

Therefore, a non-AP STA transmitting an Association Request frame needs to know Beacon Intervals of other APs included in the AP MLD other than the AP to which it is connected before transmitting the Association Request frame. In this specification, a signaling method is proposed to allow a non-AP STA to know the Beacon Intervals of other APs.

The designation (name) used in this specification may be changed, and the STA may include an AP STA or a non-AP STA.

Basically, as shown in <FIG>, the non-AP MLD is connected to the AP MLD through <NUM>) existing multi-link discovery (Discovery), <NUM>) MLD probing, and <NUM>) multi-link setup.

<FIG> shows an example of a Multi-link Setup process.

Referring to <FIG>, the AP MLD may include APs <NUM> to <NUM>, and the non-AP MLD may include STA A and STA B. AP <NUM> and STA A may be connected through link <NUM>. The AP MLD may designate Link <NUM> of a plurality of links as an anchored link or an association link.

In the multi-link discovery step, the AP MLD may transmit a Beacon including Link/Capability information to the non-AP MLD through link <NUM>. Alternatively, the AP MLD may exchange Link/Capability information with the non-AP MLD by exchanging a probe request frame/probe response frame through link <NUM>. Through the multi-link discovery step, the non-AP MLD can know partial or complete information of all links/APs.

In the MLD probing step, the AP MLD can exchange Link/Capability information with the non-AP MLD by exchanging ML Probe request frame/ML Probe response frame through link <NUM>. Through the Multi-link Discovery step, the non-AP MLD can know additional partial or complete information that the non-AP MLD wants to know.

In the Association step, the AP MLD and the non-AP MLD can exchange Link/Capability information by exchanging Association request frame/Association response frame through link <NUM>. Specifically, multi-link between an AP MLD and a non-AP MLD may be established by requesting link establishment through an association request frame and accepting the requested link establishment through an association response frame.

<FIG> shows an example of a TBTT information field format of an RNR element.

Referring to <FIG>, the TBTT (Target Beacon Transmission Time) information field of the RNR element may include a Neighbor AP TBTT offset subfield, a BSS parameters subfield, and a <NUM> PSD subfield. Optionally, a BSSID subfield and a Short-SSID subfield may be included in the TBTT information field of the RNR element.

In addition, as shown in <FIG>, the MAC address of the MLD, which is common information of the AP MLD, may be informed by including the ML Multi-link Information Element (IE). Basically, ML IE can indicate specific information of each AP using common information such as MLD MAC Address and Per-STA Profile.

Referring to <FIG>, the ML IE may include Element ID, Length, Element ID Extension, Multi-link Control, MLD MAC address, and Optional Subelements subfields. Optional subelement ID for the ML IE included in the Optional Subelements can be defined as follows.

<FIG> is an example showing the ML IE in more detail.

Referring to <FIG>, the ML IE may inform common information of the AP MLD through the Element ID field outside the Basic variant Multi-Link field. Through the Per-STA profile field in the Basic variant Multi-Link, information on a specific AP (according to <FIG>, information on a link in which STA x and STA y operate) can be informed.

Therefore, the non-AP MLD can know common information of not only AP <NUM> but also APs <NUM>, <NUM>, and <NUM>, and AP MLD. However, if the Beacon Interval is not included in the Per-STA Profile of the RNR or ML IE, STA A cannot know Beacon Interval information for APs other than AP <NUM>.

<NUM>) MLD Probing: This is a process in which the non-AP MLD requests the AP MLD to obtain insufficient information through the process of <NUM>) above. <NUM> shows a Per-STA Control field included in the Per-STA Profile of the ML IE mentioned above. If the value of the Complete Profile field is <NUM>, Complete information can be requested, and if <NUM>, Partial information can be requested. For example, if STA A wants to know Complete information about AP <NUM>, it can set Link ID to an ID for a link corresponding to AP <NUM> and set the value of the Complete Profile field to <NUM>. In addition, if STA A wants to know additional partial information that it did not know about AP <NUM> through the process of <NUM>), it can set the value of the Complete Profile field to <NUM> and make an additional request using an existing Request Element.

<FIG> shows the format of the Per-STA Control field included in the Per-STA Profile.

If the non-AP MLD did not know the Beacon Interval of other APs through the process of <NUM>), it can be known in this process. For example, when STA A requests Complete information on APs <NUM>, <NUM>, and <NUM> through the ML IE, the Beacon Intervals of these APs will be known. Meanwhile, since Beacon Interval is a field, it cannot be requested through Request Element. However, there is a problem that if the non-AP MLD cannot be known through the process of <NUM>), the process of <NUM>) must always be performed. That is, since MLD probing can be an optional process, if it is always forced, channel congestion and overhead may occur.

<NUM>) Multi-link Setup: If information about the AP MLD and APs belonging to it is known in the process of <NUM>) and <NUM>), the non-AP MLD requests an association and the AP MLD responds to it. In this process, STA A acquires Beacon Interval information of other APs, sets a Listen Interval, and transmits it by including it in the Association request frame.

A method for solving the problem mentioned in the above process and acquiring the Beacon Interval of other APs is as follows, but is not limited thereto.

Create a new field containing Beacon Intervals for other APs and include it in the Beacon frame and Probe Response frame. The basic format of the New field is as shown in <FIG>, and is referred to as MLD Beacon Interval. Basically, as before, each Beacon Interval can have a size of <NUM> octets, but the size can be reduced to reduce overhead. (e.g. <NUM> octet).

<FIG> shows an example of an MLD Beacon Interval field.

The format of <FIG> can be indicated when the order of APs, that is, the order in ascending order can be known using the Link ID value. For example, the link ID for each AP of the AP MLD can be known through the RNR element included in the Beacon or Probe Response. If the order of APs is known, overhead can be reduced without the need to instruct specific APs, and can be instructed as shown in <FIG>. For example, assuming that AP #<NUM> is an AP currently transmitting a beacon and there are N APs in the AP MLD, the Beacon Interval can be indicated from APs #<NUM> to #N when APs have the lowest link IDs from APs <NUM>.

<FIG> shows another example of an MLD Beacon Interval field.

The format of <FIG> is a method of indicating a Beacon Interval through each link ID indication when the order of APs is unknown.

Referring to <FIG>, since confusion may occur in decoding because the number of bits of each field is different, Number of links may be included at the beginning of the MLD Beacon Interval field.

Meanwhile, if the beacon interval was previously defined as a field, the beacon interval for other APs may be defined as an element. That is, for example, an AP other than MLD may not include this element. The contents of this element (MLD Beacon Interval in <FIG>) may include all of the aforementioned MLD Beacon Interval fields in <FIG>.

<FIG> shows an example of an MLD Beacon Interval element format.

<FIG> shows an MLD Beacon Interval element including the MLD Beacon Interval fields of <FIG>, respectively.

This embodiment may propose an alternative to reduce overhead.

In the MLD Beacon Interval field (or Beacon Interval of the MLD Beacon Interval field) of <FIG> presented above, a relative value can be used to reduce the overhead of the Beacon Interval value of each AP. That is, the difference between the Beacon Interval of the AP transmitting the MLD Beacon Interval field/element and the Beacon Interval of each of the APs other than the AP may be informed. For example, assuming that the Beacon Interval of a specific AP is indicated with <NUM> octets, the Offset of Beacon Interval representing the difference between the Beacon Intervals may also be indicated with <NUM> octet. However, it is not always limited in this way.

<FIG> shows an example of an MLD Beacon Interval element format using an offset.

If AP #<NUM> is a reporting AP, the MLD Beacon Interval element of <FIG> indicates information (Offset of Beacon Interval) by representing a relative Beacon Interval difference between each AP and AP #<NUM> as an offset.

In addition, as another alternative, a TU (Transmission Unit), which is a unit of the current Beacon Interval, may be changed. For example, the total number of field bits of the Beacon Interval may be reduced by increasing units such as <NUM>*TU or <NUM>*TU.

<NUM>) Instruction method through RNR element or multi-link element (ML IE).

This embodiment proposes a method of always including a Beacon Interval field or element in the RNR or ML IE.

<FIG> shows another example of the format of the TBTT information field of the RNR element.

Referring to <FIG>, the TBTT information field of the RNR element may include a Neighbor AP TBTT offset subfield, a BSS parameters subfield, a <NUM> PSD subfield, and an MLD Parameters subfield. Optionally, a BSSID subfield and a Short-SSID subfield may be included in the TBTT information field of the RNR element.

<FIG> shows an example of the MLD Parameters subfield format.

Referring to <FIG>, the MLD Parameters subfield included in the TBTT information field includes MLD ID, Link ID, Change Sequence, Beacon Interval, and Reserved fields.

For example, as shown in <FIG>, the Beacon interval field for the corresponding Link ID is included in the MLD Parameters subfield of the TBTT Information field of the RNR element. As mentioned above, the Beacon Interval field included in the RNR element can be replaced with the Offset of Beacon Interval field. The Offset of Beacon Interval means a relative difference from the Beacon Interval of the AP transmitting the RNR element. However, this method has a requirement that the non-AP STA always decode the RNR, and it may not be necessary to know the Beacon Interval of APs belonging to other AP MLDs other than the MLD to which it belongs. To this end, a new subfield may be created and included in the TBTT Information field in addition to the MLD Parameters subfield for the Beacon Interval field.

As mentioned above, each Beacon Interval field mentioned in relation to the RNR element can be replaced with an Offset of Beacon Interval field (refer to Alternative to reduce overhead), each Offset of Beacon Interval field associated with the corresponding AP means a relative difference from the Beacon Interval of the AP transmitting the ML element. Also, as another alternative, the TU, which is the unit of the current Beacon Interval, may be changed. For example, the total number of field bits of the Beacon Interval may be reduced by increasing units such as <NUM>*TU or <NUM>*TU.

The Beacon Interval field or element for the corresponding Link ID may always be included in the Per-STA Profile of the ML IE mentioned in <FIG>. However, this method also always includes the ML IE in the Beacon frame and the Probe Response frame, and if the ML IE is included, the Per-STA Profile must always be included.

In order to relieve the above overhead to some extent, the MLD Beacon Interval field may be included in Common information rather than Per-STA Profile of ML IE.

<FIG> shows an example in which the MLD Beacon Interval is included in the common information of the ML IE.

Referring to <FIG>, like the MLD MAC address, the MLD Beacon Interval may also be included in common information, and may be always included or indicated (or presence/absence) through a multi-link control field.

<FIG> shows an example of requesting an MLD Beacon Interval when using the ML IE included in the Probe Request frame.

In addition, when it can be indicated as shown in <FIG>, the non-AP MLD may request the MLD Beacon Interval element using a Request element belonging to Common information of the ML IE included in the Probe Request Frame (see <FIG>).

<FIG> shows an example in which the Beacon Interval field is always included in the Per-STA Profile of the ML IE.

Referring to <FIG>, the Beacon Interval field (or Beacon Interval element form) may always be included in the Per-STA Profile of the ML IE.

As mentioned above, each Beacon Interval field mentioned in relation to ML IE can be replaced with an Offset of Beacon Interval field (refer to Alternative to reduce overhead), each Offset of Beacon Interval field associated with the corresponding AP means a relative difference from the Beacon Interval of the AP transmitting the ML element. Also, as another alternative, the TU, which is the unit of the current Beacon Interval, may be changed. For example, the total number of field bits of the Beacon Interval may be reduced by increasing units such as <NUM>*TU or <NUM>*TU.

The ML IE can be used in all MLD connection procedures (<NUM>), <NUM>), and <NUM>) except when a beacon is used. However, the RNR element cannot be used in the Association step (<NUM>) procedure).

Hereinafter, the above-described embodiment will be described with reference to <FIG>.

<FIG> is a flowchart illustrating a procedure in which a transmitting MLD provides information on a beacon interval of another AP to a receiving MLD according to the present embodiment.

The example of <FIG> may be performed in a network environment in which a next generation WLAN system (IEEE <NUM>. 11be or EHT WLAN system) is supported. The next generation wireless LAN system is a WLAN system that is enhanced from an <NUM>. 11ax system and may, therefore, satisfy backward compatibility with the <NUM>. 11ax system.

In step S2910, a transmitting multi-link device (MLD) generates a multi-link (ML) element.

In step S2920, the transmitting MLD transmits the ML element to the receiving MLD through a first link.

That is, this embodiment proposes a method in which the transmitting MLD informs the receiving MLD of beacon intervals of other APs (the second and third transmitting STAs) within the transmitting MLD through the ML element. Thus, the first receiving STA belonging to the receiving MLD can receive beacon intervals of other APs without separate signaling. There is an effect of being able to set one's own listen interval in the ML configuration step (or after the ML configuration step) by using the beacon intervals of other APs.

The link information may include a profile field of the second transmitting STA and a profile field of the third transmitting STA. The profile field of the second transmitting STA may include information on a beacon interval of the second transmitting STA. The profile field of the third transmitting STA may include information on a beacon interval of the third transmitting STA.

As another example, the information on the beacon interval of the second transmitting STA may include the beacon interval of the second transmitting STA, or first offset information for a relative difference between the beacon interval of the first transmitting STA and the beacon interval of the second transmitting STA. The information on the beacon interval of the third transmitting STA may include the beacon interval of the second third STA, or second offset information for a relative difference between the beacon interval of the first transmitting STA and the beacon interval of the third transmitting STA. When offset information other than the beacon interval values of the second and third transmitting STAs is used, the overall overhead can be reduced by reducing the size of information about the beacon intervals of the second and third transmitting STAs. For example, the beacon interval values of the second and third transmitting STAs are <NUM> octets, offset information (the first and second offset information) for the beacon interval of the second and third transmitting STAs is <NUM> octet, and thus the size of the information can be reduced.

The transmitting MLD may transmit a reduced neighbor report (RNR) element to the receiving MLD through the first link. The RNR element may include a neighbor access point target beacon transmission time offset (Neighbor Access TBTT offset), a basic service set identifier (BSSID), a short service set identifier (SSID), a BSS parameter, a <NUM> power spectral density (PSD), and an MLD parameter.

The transmitting MLD may transmit a beacon frame to the receiving MLD through the first link. The transmitting MLD may receive an ML probe request frame from the receiving MLD through the first link. The transmitting MLD may transmit an ML probe response frame to the receiving MLD through the first link. The transmitting MLD may receive an Association request frame from the receiving MLD through the first link. The transmitting MLD may transmit an Association response frame to the receiving MLD through the first link.

The ML element may be included in the ML probe response frame or the Association response frame. The RNR element may be included in the ML probe response frame. The beacon frame may include the information on the beacon intervals of the second and third transmitting STAs.

The receiving MLD may set a listen interval of the first receiving STA based on the information on the beacon intervals of the second and third transmitting STAs. Information on the listen interval of the first receiving STA may be included in the Association request frame.

The ML element further may include an element identifier field, a length field, an element identifier extension field, and a Multi-Link (ML) control field. The common information may include an MLD MAC address.

<FIG> is a flowchart illustrating a procedure in which a receiving MLD receives information on a beacon interval of another AP from a transmitting MLD according to the present embodiment.

In step S3010, a receiving multi-link device (MLD) receives a multi-link (ML) element from a transmitting MLD through a first link.

In step S3020, the receiving MLD decodes the ML element.

The receiving MLD may receive a Reduced Neighbor Report (RNR) element from the transmitting MLD through the first link. The RNR element may include a neighbor access point target beacon transmission time offset (Neighbor Access TBTT offset), a basic service set identifier (BSSID), a short service set identifier (SSID), a BSS parameter, a <NUM> power spectral density (PSD), and an MLD parameter.

The receiving MLD may receive a beacon frame from the transmitting MLD through the first link. The receiving MLD may transmit an ML probe request frame to the transmitting MLD through the first link. The receiving MLD may receive an ML probe response frame from the transmitting MLD through the first link. The receiving MLD may transmit an Association request frame to the transmitting MLD through the first link. The receiving MLD may receive an Association response frame from the transmitting MLD through the first link.

The technical features of the present disclosure may be applied to various devices and methods. For example, the technical features of the present disclosure may be performed/supported through the device(s) of <FIG> and/or <FIG>. For example, the technical features of the present disclosure may be applied to only part of <FIG> and/or <FIG>. For example, the technical features of the present disclosure may be implemented based on the processing chip(s) <NUM> and <NUM> of <FIG>, or implemented based on the processor(s) <NUM> and <NUM> and the memory(s) <NUM> and <NUM>, or implemented based on the processor <NUM> and the memory <NUM> of <FIG>. For example, the device according to the present disclosure receives a multi-link (ML) element from a transmitting multi-link device (MLD) through a first link; and decodes the ML element.

The technical features of the present disclosure may be implemented based on a computer readable medium (CRM). For example, a CRM according to the present disclosure is at least one computer readable medium including instructions designed to be executed by at least one processor.

Claim 1:
A method performed by a second multi-link device, MLD, in a wireless local area network, WLAN, system, the method comprising:
receiving a multi-link, ML, element from a first MLD through a first link (S3010); and
decoding the ML element (S3020),
wherein the first MLD includes a first access point (AP) operating on the first link and a second AP operating on a second link,
wherein the ML element includes common information and link information,
wherein the common information includes an MLD Beacon Interval Present subfield, and
wherein a beacon interval of the second AP is included in the link information based on the MLD Beacon Interval Present subfield.