Transmission of Buffer Status Report Frame in a Multi-Link Communication Environment

Abstract

A non-access point (non-AP) multi-link device (MLD) transmits a frame of a traffic identifier (TID) on a first link to an access point (AP) MLD, where the TID is mapped by a TID-to-link mapping. The non-AP MLD receives a trigger frame on a second link from the AP MLD, where the TID is not mapped by the TID-to-link mapping. In response to the trigger frame, the non-AP MLD transmits a quality of service (QoS) null frame including the TID on the second link to the AP MLD.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 304,031, filed on January 28, 2022, which is hereby incorporated by reference in its entirety.

Summary of the Invention

Means for Solving the Problems

[0002] In this disclosure, various embodiments are presented as examples of how the disclosed technology can be implemented and / or how the disclosed technology can be practiced in environments and scenarios. It will be apparent to those skilled in the relevant technical fields that various changes in form and detail can be made without departing from the scope. After reading the specification, methods for implementing alternative embodiments will be apparent to those skilled in the relevant technical fields. The present embodiments should not be limited by any of the exemplary embodiments. The embodiments of this disclosure are described with reference to the accompanying drawings. Limitations, features, and / or elements from the disclosed exemplary embodiments can be combined to create further embodiments within the scope of this disclosure. Figures highlighting functions and advantages are shown for illustrative purposes only. The disclosed architecture is sufficiently flexible and configurable to be utilized in ways other than those shown. For example, any action listed in any flowchart can be rearranged or optionally used only in some embodiments.

[0003] Embodiments can be configured to operate as needed. The disclosed mechanisms can be implemented, for example, in a station, an access point, a wireless environment, a network, combinations of the above, etc., when certain criteria are met. Exemplary criteria can be based at least in part on, for example, wireless device or network node configuration, traffic load, initial system setup, packet size, traffic characteristics, combinations of the above, etc. When one or more criteria are met, various exemplary embodiments can be applied. Thus, it may be possible to implement exemplary embodiments that selectively implement the disclosed protocol. The present invention provides, for example, the following items. (Item 1) A method comprising: Receiving, by a non-access point (non-AP) multi-link device (MLD) from an access point (AP) MLD, an association frame including a traffic identifier (TID)-to-link mapping that maps a TID to a set of links among a plurality of links between the non-AP MLD and the AP MLD; Transmitting, by the non-AP MLD, to the AP MLD, a frame including a media access control (MAC) service data unit (MSDU) or an aggregated MSDU (A-MSDU) corresponding to the TID on a first link of the set of links; Receiving, by the non-AP MLD, from the AP MLD, a buffer status report polling (BSRP) trigger frame on a second link among the plurality of links that does not belong to the set of links to which the TID is mapped; Transmitting, by the non-AP MLD, to the AP MLD, a quality of service (QoS) null frame including a buffer status report (BSR) for the TID on the second link in response to the BSRP trigger frame. (Item 2) A method comprising: Transmitting, by a non-access point (non-AP) multi-link device (MLD), to an access point (AP) MLD, a frame of a traffic identifier (TID) on a first link to which the TID is mapped; Receiving, by the non-AP MLD, from the AP MLD, a trigger frame on a second link to which the TID is not mapped; Transmitting, by the non-AP MLD, to the AP MLD, a quality of service (QoS) null frame including the TID on the second link in response to the trigger frame. (Item 3) The method according to item 2, further comprising receiving, by the non-AP MLD from the AP MLD, an association frame including a TID-to-link mapping that maps the TID to the first link. (Item 4) The method according to any one of items 2 to 3, wherein the trigger frame includes a buffer status report polling (BSRP) trigger frame or a basic trigger frame. (Item 5) The method according to any one of items 2 to 4, wherein the frame of the TID includes a media access control (MAC) service data unit (MSDU) or an aggregated MSDU (A-MSDU) for the TID. (Item 6) The method according to any one of items 3 to 5, wherein the second link is an activated link to which at least one TID is mapped according to the TID-to-link mapping. (Item 7) The method according to any one of items 3 to 5, wherein the second link is a deactivated link to which a TID is not mapped according to the TID-to-link mapping. (Item 8) The method according to any one of items 2 to 7, wherein the QoS null frame includes a buffer status report (BSR) for the TID. (Item 9) The method according to item 8, wherein the QoS null frame includes a BSR for another TID mapped to the second link. (Item 10) The method according to any one of items 8 to 9, wherein the QoS null frame includes a QoS control field including the BSR for the TID. (Item 11) The QoS control field is a TID subfield that identifies a traffic class (TC) or a traffic stream (TS) for which a transmission opportunity (TXOP) is requested, and a queue size subfield indicating the total size in octets of a MAC service data unit (MSDU) and an aggregated MSDU (A-MSDU), having a TID equal to the value of the TID subfield and buffered in the non-AP MLD, the method according to item 10, including at least one of the queue size subfields. (Item 12) The method according to any one of items 8 to 9, wherein the QoS null frame includes a BSR control subfield including the BSR for the TID. (Item 13) Receiving, by the non-AP MLD, in response to the QoS null frame, a trigger frame from the AP MLD on the first link, the trigger frame allocating uplink resources on the first link to the non-AP MLD for the TID. The non-AP MLD transmits, in response to the trigger frame, a frame including a QoS data frame for the TID to the AP MLD. The method according to any one of items 2 to 12 includes this step. (Item 14) A non-access point (non-AP) multi-link device (MLD), including one or more processors, and a memory storing instructions that, when executed by the one or more processors, cause the non-AP MLD to perform the method according to any one of items 1 to 13. A non-access point (non-AP) multi-link device (MLD). (Item 15) A non-transitory computer-readable medium including instructions that, when executed by one or more processors, cause the one or more processors to perform the method according to any one of items 1 to 13. (Item 16) A method, wherein an access point (AP) multi-link device (MLD) transmits an association frame including a traffic identifier (TID)-to-link mapping that maps a TID to a set of links among a plurality of links between the non-AP MLD and the AP MLD to the non-AP MLD; the AP MLD receives, from the non-AP MLD, a frame including a media access control (MAC) service data unit (MSDU) or an aggregated MSDU (A-MSDU) corresponding to the TID on a first link of the set of links; the AP MLD transmits, to the non-AP MLD, a buffer status report polling (BSRP) trigger frame on a second link among the plurality of links that does not belong to the set of links to which the TID is mapped; and the AP MLD receives, in response to the BSRP trigger frame, a quality of service (QoS) null frame including a buffer status report (BSR) for the TID on the second link from the non-AP MLD. The method includes these steps. (Item 17) A method, wherein an access point (AP) multi-link device (MLD) receives, from a non-access point (non-AP) MLD, a frame of a traffic identifier (TID) on a first link to which the TID is mapped. The AP MLD transmits a trigger frame on a second link to the non-AP MLD, on which the TID is not mapped. The method includes: the AP MLD receiving, in response to the trigger frame, a Quality of Service (QoS) null frame including the TID on the second link from the non-AP MLD. (Item 18) The method according to item 17, further including: the AP MLD transmitting an association frame including a TID-to-link mapping that maps the TID to the first link to the non-AP MLD. (Item 19) The method according to any one of items 17 to 18, wherein the trigger frame includes a Buffer Status Report Polling (BSRP) trigger frame or a basic trigger frame. (Item 20) The method according to any one of items 17 to 19, wherein the frame of the TID includes a Medium Access Control (MAC) Service Data Unit (MSDU) or an Aggregated MSDU (A-MSDU) for the TID. (Item 21) The method according to any one of items 18 to 20, wherein the second link is an activated link on which at least one TID is mapped according to the TID-to-link mapping. (Item 22) The method according to any one of items 18 to 20, wherein the second link is a deactivated link on which the TID is not mapped according to the TID-to-link mapping. (Item 23) The method according to any one of items 17 to 22, wherein the QoS null frame includes a Buffer Status Report (BSR) for the TID. (Item 24) The method according to item 23, wherein the QoS null frame includes a BSR for another TID mapped to the second link. (Item 25) The method according to any one of items 23 to 24, wherein the QoS null frame includes a QoS control field including the BSR for the TID. (Item 26) The QoS control field includes: a TID subfield that identifies a Traffic Class (TC) or a Traffic Stream (TS) for which a Transmission Opportunity (TXOP) is requested. A queue size subfield indicating the total size in octets of a MAC service data unit (MSDU) and an aggregated MSDU (A-MSDU), having a TID equal to the value of the TID subfield and buffered at the non-AP MLD, and at least one of the queue size subfield, as described in item 25. (Item 27) The method according to any one of items 23 to 24, wherein the QoS null frame includes a BSR control subfield including the BSR for the TID. (Item 28) By the AP MLD, in response to the QoS null frame, to the non-AP MLD, Transmitting a trigger frame on the first link, the trigger frame allocating uplink resources on the first link to the non-AP MLD for the TID, and transmitting; The method according to any one of items 17 to 27, further comprising receiving, by the AP MLD, in response to the trigger frame, a frame including a QoS data frame for the TID from the non-AP MLD. (Item 29) An access point (AP) multi-link device (MLD), One or more processors; A memory storing instructions that, when executed by the one or more processors, cause the AP MLD to perform the method according to any one of items 16 to 28, an access point (AP) multi-link device (MLD). (Item 30) A non-transitory computer-readable medium including instructions that, when executed by one or more processors, cause the one or more processors to perform the method according to any one of items 16 to 28. (Item 31) A method, Receiving, by a non-access point (non-AP) multi-link device (MLD), from an access point (AP) MLD, a trigger frame on a first link among a plurality of links between the non-AP MLD and the AP MLD; In response to the trigger frame by the non-AP MLD, regardless of whether the TID is mapped to the second link in the TID-to-link mapping, the AP MLD transmits a quality of service (QoS) null frame including a traffic identifier (TID) on the second link of the plurality of links to the AP MLD. The method includes this. (Item 32) The method according to item 31, wherein the TID is not mapped to the second link in the TID-to-link mapping. (Item 33) The method according to item 31, wherein the TID is mapped to the second link in the TID-to-link mapping. (Item 34) The method according to any one of items 31 to 33, wherein the TID is mapped to the first link in the TID-to-link mapping. (Item 35) The method according to any one of items 31 to 33, wherein the TID is not mapped to the first link in the TID-to-link mapping. (Item 36) A method, An access point (AP) multi-link device (MLD) transmits a trigger frame on the first link of a plurality of links between the AP MLD and the non-access point (non-AP) MLD to the non-AP MLD. In response to the trigger frame by the AP MLD, regardless of whether the TID is mapped to the second link in the TID-to-link mapping, the AP MLD receives a quality of service (QoS) null frame including a traffic identifier (TID) on the second link of the plurality of links from the non-AP MLD. The method includes this. (Item 37) The method according to item 36, wherein the TID is not mapped to the second link in the TID-to-link mapping. (Item 38) The method according to item 36, wherein the TID is mapped to the second link in the TID-to-link mapping. (Item 39) The method according to any one of items 36 to 38, wherein the TID is mapped to the first link in the TID-to-link mapping. (Item 40) The method according to any one of items 36 to 38, wherein the TID is not mapped to the first link in the TID-to-link mapping.

Brief Description of the Drawings

[0004] Examples of some of the various embodiments of the present disclosure are described herein with reference to the drawings.

[0005]

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[0006] As used herein, the terms "a" and "an", and similar phrases are to be interpreted as "at least one" and "one or more". Similarly, any term ending with the suffix "(s)" should be interpreted as "at least one" and "one or more". As used herein, the term "may" should be interpreted as "for example, may be". In other words, the term "may" indicates that the phrase following the term "may" is a plurality of suitable possible embodiments, and may or may not be used by one or more of the various embodiments. As used herein, the terms "comprises" and "consists of" enumerate one or more components of the recited element. The term "comprises" is interchangeable with "includes" and does not exclude unenumerated components included in the recited element. In contrast, "consists of" provides a complete enumeration of one or more components of the recited element. As used herein, the term "based on" may be interpreted as "at least partially based on", rather than, for example, "based only on". As used herein, the term "and / or" represents any possible combination of the recited elements. For example, "A, B, and / or C" may represent A, B, C, A and B, A and C, B and C, or A, B, and C.

[0007] If A and B are a set and all elements of A are also elements of B, then A is called a subset of B. In this specification, only non-empty sets and subsets are considered. For example, the possible subsets of B = {STA1, STA2} are {STA1}, {STA2}, and {STA1, STA2}. The phrase "based on" (or equivalently "at least based on") indicates that there are a number of preferred possible embodiments where the phrase following "based on" may or may not be used in one or more of the various embodiments. The phrase "in response to" (or equivalently "at least in response to") indicates that there are a number of preferred possible embodiments where the phrase following "in response to" may or may not be used in one or more of the various embodiments. The phrase "responsive to" (or equivalently "at least responsive to") indicates that there are a number of preferred possible embodiments where the phrase following "responsive to" may or may not be used in one or more of the various embodiments. The phrase "employed / used" (or equivalently "at least employed / used") indicates that there is one of a number of preferred possible embodiments where the phrase following "employed / used" may or may not be used in one or more of the various embodiments.

[0008] The term "configured" may relate to the capacity of a device regardless of whether the device is in an operating state or a non-operating state. "Configured" may refer to a specific setting of a device that affects the operating characteristics of the device regardless of whether the device is in an operating state or a non-operating state. In other words, hardware, software, firmware, registers, memory values, etc. may be "configured" within a device regardless of whether the device is in an operating state or a non-operating state in order for the device to provide certain characteristics. Terms such as "control messages generated in a device" may mean that control messages may be used to configure certain characteristics in a device or may have parameters used to implement certain actions in a device regardless of whether the device is in an operating state or a non-operating state.

[0009] In the present disclosure, a parameter (or equivalently a field, or an information element: IE for short) may include one or more information objects, and an information object may include one or more other objects. For example, if parameter (IE) N includes parameter (IE) M, parameter (IE) M includes parameter (IE) K, and parameter (IE) K includes parameter (information element) J, then N includes K and N includes J. In an exemplary embodiment, when one or more messages / frames include a plurality of parameters, it means that the parameters among the plurality of parameters are included in at least one of the one or more messages / frames, but do not necessarily have to be included in each of the one or more messages / frames.

[0010] Many of the features presented are described as being optional, either through the use of "may" or the use of parentheses. For the sake of brevity and readability, the present disclosure does not explicitly describe every possible combination that could be obtained by selecting from a set of optional features. The present disclosure should be construed as disclosing all such variations explicitly. For example, a system described as having three optional features could be implemented in seven ways, namely, by only one of the three possible features, by any two of the three features, or by all three of the three features.

[0011] Many of the elements described in the disclosed embodiments can be implemented as modules. Here, a module is defined as an element that performs a defined function and has a defined interface to other elements. The modules described in this disclosure can be implemented in hardware, software combined with hardware, firmware, wetware (e.g., hardware having biological elements), or combinations thereof, which can be behaviorally equivalent. For example, a module can be implemented as a software routine described in a computer language configured to be executed on a hardware machine (such as C, C++, Fortran, Java®, Basic, Matlab®) or in Simulink, Stateflow, GNU Octave, or LabVIEW MathScript. It is also possible to implement a module using physical hardware incorporating discrete or programmable analog, digital, and / or quantum hardware. Examples of programmable hardware include computers, microcontrollers, microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), and complex programmable logic devices (CPLDs). Computers, microcontrollers, and microprocessors are programmed using languages such as assembly, C, and C++. FPGAs, ASICs, and CPLDs are often programmed using hardware description languages (HDLs) such as VHSIC Hardware Description Language (VHDL) or Verilog, which configure connections between internal hardware modules with fewer programmable device functions. To achieve the results of functional modules, the above techniques are often used in combination.

[0012] FIG. 1 shows an exemplary wireless communication network in which embodiments of the present disclosure can be implemented.

[0013] As shown in FIG. 1, an exemplary wireless communication network may include an Institute of Electrical and Electronics Engineers (IEEE) 802.11 (WLAN) infrastructure network 102. The WLAN infrastructure network 102 may include one or more basic service sets (BSSs) 110 and 120, as well as a distribution system (DS) 130.

[0014] BSSs 110-1 and 110-2 each include a set of an access point (AP or AP STA) and at least one station (STA or non-AP STA). For example, BSS 110-1 includes AP 104-1 and STA 106-1, and BSS 110-2 includes AP 104-2 and STAs 106-2 and 106-3. The AP and at least one STA within a BSS perform an association procedure for communicating with each other.

[0015] DS 130 may be configured to connect BSSs 110-1 and 110-2. In this way, DS 130 may enable an extended service set (ESS) 150. Within ESS 150, APs 104-1 and 104-2 may be connected via DS 130 and may have the same service set identifier (SSID).

[0016] The WLAN infrastructure network 102 may be coupled to one or more external networks. For example, as shown in FIG. 1, the WLAN infrastructure network 102 may be connected to another network 108 (e.g., 802.X) via a portal 140. The portal 140 may function as a bridge that connects the DS 130 of the WLAN infrastructure network 102 to the other network 108.

[0017] The exemplary wireless communication network shown in FIG. 1 may further include one or more ad hoc networks or independent basic service sets (IBSSs). An ad hoc network or IBSS is a network that includes a plurality of STAs within each other's communication range. The plurality of STAs are configured to communicate with each other using direct peer-to-peer communication (i.e., not via an AP).

[0018] For example, in FIG. 1, STAs 106-4, 106-5, and 106-6 may be configured to form a first IBSS 112-1. Similarly, STAs 106-7 and 106-8 may be configured to form a second IBSS 112-2. Since an IBSS does not include an AP, it does not include a centralized management entity. Rather, the STAs within an IBSS are managed in a decentralized manner. The STAs forming an IBSS may be fixed or mobile.

[0019] An STA as a given functional medium may include a media access control (MAC) layer compliant with the IEEE 802.11 standard. A physical layer interface for the wireless medium may be used between an AP and a non-AP station (STA). An STA may also be referred to using various other terms, including 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 a user. For example, the term "user" may be used to indicate an STA involved in uplink multi-user multiple-input, multiple-output (MU MIMO), and / or uplink orthogonal frequency division multiple access (OFDMA) transmission.

[0020] A Physical Layer (PHY) Protocol Data Unit (PPDU) can be a composite structure that includes a PHY preamble and a payload in the form of a PLCP Service Data Unit (PSDU). For example, the PSDU can include a PHY Convergence Protocol (PLCP) preamble and header and / or one or more MAC Protocol Data Units (MPDUs). The information provided in the PHY preamble can be used by a receiving device to decode subsequent data within the PSDU. When the PPDU is transmitted over a bonded channel (a channel formed via channel bonding), the preamble field can be replicated and transmitted in each of the plurality of component channels. The PHY preamble can include both a legacy portion (or "legacy preamble") and a non-legacy portion (or "non-legacy preamble"). The legacy preamble can be used, among other things, for packet detection, automatic gain control, and channel estimation. The legacy preamble can also generally be used to maintain compatibility with legacy devices. The format, coding, and information provided in the non-legacy portion of the preamble are based on the specific IEEE 802.11 protocol used to transmit the payload.

[0021] A frequency band can include one or more sub-bands or frequency channels. For example, a PPDU compliant with the amendments to the IEEE 802.11n, 802.11ac, 802.11ax, and / or 802.11be standards may be transmitted across the 2.4 GHz band, 5 GHz band, and / or 6 GHz band, each of which may be divided into a plurality of 20 MHz channels. A PPDU can be transmitted over a physical channel having a minimum bandwidth of 20 MHz. Larger channels can be formed through channel bonding. For example, a PPDU can be transmitted over a physical channel having a bandwidth of 40 MHz, 80 MHz, 160 MHz, or 520 MHz by combining a plurality of 20 MHz channels together.

[0022] FIG. 2 is a block diagram showing an exemplary implementation of STA 210 and AP 260. As shown in FIG. 2, STA 210 may include at least one processor 220, a memory 230, and at least one transceiver 240. AP 260 may include at least one processor 270, a memory 280, and at least one transceiver 290. Processor 220 / 270 may be operably connected to transceiver 240 / 290.

[0023] Transceiver 240 / 290 may be configured to transmit / receive wireless signals. In one embodiment, transceiver 240 / 290 may implement the PHY layer of the corresponding device (STA 210 or AP 260).

[0024] In one embodiment, STA 210 and / or AP 260 may be a multi-link device (MLD), i.e., a device that can operate on multiple links as defined by the IEEE 802.11be standard amendment. Thus, STA 210 and / or AP 260 may each have multiple PHY layers. The multiple PHY layers may be implemented using one or more of transceivers 240 / 290.

[0025] Processor 220 / 270 may implement the functions of the PHY layer, MAC layer, and / or logical link control (LLC) layer of the corresponding device (STA 210 or AP 260).

[0026] Processor 220 / 270 and / or transceiver 240 / 290 may include application-specific integrated circuits (ASICs), other chip sets, logic circuits, and / or data processors. Memory 230 / 280 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage units.

[0027] When the embodiments are implemented by software, the techniques (or methods) described herein may be executed by modules (e.g., processes, functions, etc.) that implement the functions described herein. The modules may be stored in the memories 230 / 280 and can be executed by the processors 220 / 270. The memories 230 / 280 may be implemented (or located) within or external to the processors 220 / 270. The memories 230 / 280 may be operably connected to the processors 220 / 270 via various means known in the art.

[0028] FIG. 3 shows an exemplary format of a MAC frame. During operation, a STA may construct a subset of the MAC frame for transmission and may decode a subset of the received MAC frame during verification. The specific subset of frames that a STA can construct and / or decode may be determined by the functions supported by the STA. The STA may verify the received MAC frame using the frame check sequence (FCS) included in the frame and may interpret specific fields from the MAC headers of all frames.

[0029] As shown in FIG. 3, a MAC frame includes a MAC header, a variable-length frame body, and a frame check sequence (FCS).

[0030] The MAC header includes a frame control field, an optional duration / ID field, an address field, an optional sequence control field, an optional QoS control field, and an optional HT control field.

[0031] The frame control field includes sub-fields for protocol version, type, subtype, To DS, From DS, more fragment, retry, power management, more data, protected frame, and +HTC.

[0032] The subfield for protocol version is of a constant size and placement across all revisions of the IEEE 802.11 standard. The value of the protocol version subfield is 0 in the case of a MAC frame.

[0033] The subfields for type and subtype identify the function of the MAC frame. There are three types of frames: control, data, and management. Each frame type has several defined subtypes. The bits within the subtype subfield are used to indicate specific modifications to the basic data frame (subtype 0). For example, in a data frame, the most significant bit (MSB) of the subtype subfield, bit 7 (B7) of the frame control field, is defined as the QoS subfield. When the QoS subfield is set to 1, it indicates a QoS subtype data frame, which is a data frame that includes a QoS control field within its MAC header. The second MSB of the subtype field, bit 6 (B6) of the frame control field, indicates a data frame that does not include a frame body field when set to 1 for data subtypes.

[0034] The To DS subfield indicates whether the data frame is headed towards the distribution system (DS). The From DS subfield indicates whether the data frame originated from the DS.

[0035] In all data or management frames that have another fragment following the MAC service data unit (MSDU) or MAC management protocol data unit (MMPDU) carried by the MAC frame, the more fragments subfield is set to 1. This is set to 0 in all other frames where the more fragments subfield exists.

[0036] The retry subfield is set to 1 in any data or management frame that is a retransmission of a previous frame. This is set to 0 in all other frames in which the retry subfield exists. When receiving a frame, this indicator is used to assist in the process of removing duplicate frames. These rules do not apply to frames transmitted by the STA based on a block contract.

[0037] The power management subfield is used to indicate the power management mode of the STA.

[0038] The additional data subfield indicates to the STA in power save (PS) mode that a buffered unit (Bus) is buffered at the AP for that STA. The additional data subfield is valid in individually addressed data or management frames transmitted by the AP to the STA in PS mode. The additional data subfield is set to 1 to indicate that there is at least one additional buffered BU for the STA.

[0039] The protected frame subfield is set to 1 if the frame body field contains information that has been processed by an encryption encapsulation algorithm.

[0040] The +HTC subfield indicates that the MAC frame contains an HT control field.

[0041] The Duration / ID field of the MAC header indicates various contents depending on the frame type and subtype, as well as the QoS capabilities of the transmitting STA. For example, in the control frame of the Power Save Poll (PS-Poll) subtype, the Duration / ID field carries the Association Identifier (AID) of the STA that transmitted the frame in its 14 least significant bits (LSBs), and both of its 2 most significant bits (MSBs) are set to 1. In other frames transmitted by the STA, the Duration / ID field contains the duration value (in microseconds) used by the receiver to update the Network Allocation Vector (NAV). The NAV is a counter that indicates to the STA the length of time it must defer access to the shared medium.

[0042] The MAC frame format can have up to four address fields. These fields are used to indicate the Basic Service Set Identifier (BSSID), Source Address (SA), Destination Address (DA), Transmitter Address (TA), and Receiver Address (RA). Some specific frames may not include some of the address fields. The use of a specific address field can be specified by the relative position of the address fields (1 to 4) in the MAC header, regardless of the type of address present in that field. Specifically, the Address 1 field always identifies the intended receiver of the frame, and if present, the Address 2 field always identifies the transmitter of the frame.

[0043] The sequence control field includes two sub-fields: a sequence number sub-field and a fragment number sub-field. The sequence number sub-field within a data frame indicates the sequence number of an MSDU (if not an aggregated MSDU (A-MSDU)) or an A-MSDU. The sequence number sub-field within a management frame indicates the sequence number of the frame. The fragment number sub-field indicates the number of each fragment of an MSDU or MMPDU. The fragment number is set to 0 only in the first fragment or fragment of an MSDU or MMPDU, and is incremented by 1 for each successive fragment of that MSDU or MMPDU. The fragment number is set to 0 in a MAC protocol data unit (MPDU) containing an A-MSDU, or an MPDU containing an MSDU or MMPDU that is not fragmented. The fragment number remains unchanged in all retransmissions of a fragment.

[0044] The QoS control field identifies the traffic category (TC) or traffic stream (TS) to which a MAC frame belongs. The QoS control field may also indicate various other QoS-related, A-MSDU-related, and mesh-related information regarding the frame. This information can vary depending on the frame type, frame sub-type, and type of transmitting STA. The QoS control field is present in all data frames where the QoS sub-field of the sub-type sub-field is equal to 1.

[0045] The HT control field is present in QoS data, QoS null, and management frames determined by the +HTC sub-field of the frame control field.

[0046] The frame body field is a variable-length field that contains information specific to individual frame types and sub-types. This may include one or more MSDUs or MMPDUs. The minimum length of the frame body is 0 octets.

[0047] The FCS field contains a 32-bit Cyclic Redundancy Check (CRC) code. The FCS field value is calculated across all fields of the MAC header and the frame body fields.

[0048] Figure 4 shows an example of a QoS null frame indicating buffer status information. The QoS null frame refers to a QoS data frame with an empty frame body. The QoS null frame includes a QoS control field and an optional HT control field that may include a buffer status report (BSR) control subfield. The QoS null frame indicating buffer status information can be transmitted from the STA to the AP.

[0049] The QoS control field may include a Traffic Identifier (TID) subfield, an Ack Policy Indicator subfield, and a queue size subfield (or a Transmit Opportunity (TXOP) duration request subfield).

[0050] The TID subfield identifies the TC or TS of the traffic for which a TXOP is requested, through the setting of the requested TXOP duration or queue size subfield. The encoding of the TID subfield depends on the access policy (e.g., allowed values 0 - 7 for the Extended Distributed Channel Access (EDCA) access policy to identify user priority for either TC or TS).

[0051] The Ack Policy Indicator subfield identifies the positive response policy to follow upon delivery of the MPDU, among other information (e.g., normal Ack, implicit block Ack request, no Ack, block Ack, etc.).

[0052] The Queue Size subfield is an 8-bit field that indicates the amount of buffered traffic for a given TC or TS at a STA for transmission to an AP identified by the receiving address of the frame containing the subfield. The Queue Size subfield is present in the QoS Null frame transmitted by the STA when bit 4 of the QoS Control field is set to 1. The AP may use the information contained in the Queue Size subfield to determine the t TXOP duration assigned to the STA or to determine the uplink (UL) resources assigned to the STA.

[0053] For frames transmitted by or to a non-high efficiency (non-HE) STA, the following rules may apply to the queue size value. - The queue size value is the rounded-up, approximate total size, in 256-octet units, of all MSDUs and A-MSDUs buffered at the STA in the delivery queue used for MSDUs and A-MSDUs having a TID value equal to the value indicated in the TID subfield of the QoS Control field (excluding the MSDU or A-MSDU included in the current QoS data frame), to the nearest multiple of 256 octets. - The queue size value 0 is used only to indicate that there is no traffic buffered in the queue used for the specified TID. - The queue size value 254 is used for all sizes exceeding 64,768 octets. - The queue size value 255 is used to indicate an unspecified or unknown size.

[0054] For frames transmitted by an HE STA to an HE AP, the following rules may apply to the queue size value.

[0055] The queue size value (QS) is approximately the total size in octets of all MSDUs and A-MSDUs buffered in the delivery queue of the STA (including the MSDU or A-MSDU contained in the same PSDU as the frame containing the queue size subfield) that have a TID value equal to the value indicated in the TID subfield of the QoS control field and are used for MSDUs and A-MSDUs.

[0056] The queue size subfield includes a scaling factor subfield in bits B14 - B15 of the QoS control field and an unscaled value (UV) in bits B8 - B13 of the QoS control field. The scaling factor subfield provides a scaling factor (SF).

[0057] The STA obtains the queue size (QS) from the received QoS control field that includes the scaling factor (SF) and the unscaled value (UV) as follows. QS = 16 × UV (when SF is equal to 0), 1024 + 256 × UV (when SF is equal to 1), 17408 + 2048 × UV (when SF is equal to 2), 148480 + 32768 × UV (when SF is equal to 3 and UV is less than 62), > 2147328 (when SF is equal to 3 and UV is equal to 62), unspecified or unknown (when SF is equal to 3 and UV is equal to 63).

[0058] The TXOP duration request subfield, which may be included instead of the queue size subfield, indicates the duration in 32 microseconds (us) for which the transmitting STA determines the need for its next TXOP for the specified TID. The TXOP duration request subfield is set to 0 to indicate that no TXOP is requested for the specified TID in the current service period (SP). The TXOP duration request subfield is set to a non-zero value to indicate the requested TXOP duration in the range of 32 us to 8160 us in 32 us increments.

[0059] The HT control field may include a BSR control subfield that may contain buffer status information used for UL MU operation. The BSR control subfield may be formed from an access category index (ACI) bitmap subfield, a delta TID subfield, an ACI high subfield, a scaling factor subfield, a queue size high subfield, and the queue size full subfield of the HT control field.

[0060] The ACI bitmap subfield indicates the access category for which the buffer status is reported (e.g., B0: Best Effort (AC_BE), B1: Background (AC_BK), B2: Video (AC_VI), B3: Voice (AC_VO), etc.). Each bit of the ACI bitmap subfield is set to 1 to indicate that the buffer status of the corresponding AC is included in the queue size full subfield, and is set to 0 except when the ACI bitmap subfield is 0 and the delta TID subfield is 3, in which case the buffer status for all 8 TIDs is included.

[0061] The delta TID subfield, together with the value of the ACI bitmap subfield, indicates the number of TIDs for which the STA is reporting buffer status.

[0062] The ACI high subfield indicates the ACI of the AC that the BSR indicates with the queue size high subfield. The mapping from ACI to AC is defined as the ACI value 0 mapping to AC_BE, the ACI value 1 mapping to AC_BK, the ACI value 2 mapping to AC_VI, and the ACI value 3 mapping to AC_VO.

[0063] The scaling factor subfield indicates the unit SF of the queue size high subfield and the queue size full subfield in octets.

[0064] The queue size high subfield indicates the amount of buffered traffic in SF octet units for the AC identified by the ACI high subfield, which targets the STA identified by the receiving address of the frame including the BSR control subfield.

[0065] The queue size full subfield indicates the amount of buffered traffic in SF octet units for all Acs identified by the ACI bitmap subfield, which targets the STA identified by the receiving address of the frame including the BSR control subfield.

[0066] The queue size values in the queue size high subfield and the queue size full subfield are the total size of all MSDUs and A-MSDUs buffered in the STAs (including MSDUs or A-MSDUs included in the same PSDU as the frame including the BSR control subfield) in the delivery queue associated with the AC specified by the ACI high subfield and the ACI bitmap subfield respectively, rounded up to the nearest multiple of the SF octet.

[0067] The queue size high and the queue size value 254 of the queue size all subfields indicate that the amount of buffered traffic is greater than 254 × SF octets. The queue size high and the queue size value 255 of the queue size all subfields indicate that the amount of buffered traffic is of an unspecified or unknown size. The queue size value of a QoS data frame containing fragments can remain invariant even when the amount of traffic added to the queue changes when consecutive fragments are transmitted.

[0068] The MAC service provides the ability to exchange MSDUs with peer entities. To support this service, the local MAC uses the underlying PHY-level service to transmit the MSDU to the peer MAC entity. Such asynchronous MSDU transmissions are connectionless.

[0069] Figure 5 shows an exemplary format of the PPDU. As shown, the PPDU can include a PHY preamble, a PHY header, a PSDU, and tail bits and padding bits.

[0070] The PSDU can include one or more MPDUs such as QoS data frames, MMPDUs, MAC control frames, or QoS null frames. In the case of an MPDU carrying a QoS data frame, the frame body of the MPDU can include an MSDU or an A-MSDU.

[0071] By default, MSDU transmission is best-effort. That is, there is no guarantee that the transmitted MSDU will be successfully delivered. However, QoS facilities use traffic identifiers (TIDs) to specify differentiated services for each MSDU.

[0072] The STA can distinguish MSDU delivery according to the specified traffic category (TC) or traffic stream (TS) of each MSDU. The MAC sublayer entity determines the user priority (UP) for an MSDU based on the TID value provided for the MSDU. The QoS facility supports eight UP values. The UP values range from 0 to 7, form a priority order, with 1 being the lowest value, 7 being the highest value, and 0 corresponding to 2 - 3.

[0073] An MSDU with a specific UP is considered to belong to the traffic category with that UP. The UP can be directly provided for each MSDU at the media access control service access point (MAC SAP) with the UP parameter. An A - MPDU can contain MPDUs with different TID values.

[0074] The STA can deliver a buffer status report (BSR) to assist the AP in allocating UL MU resources. The STA can implicitly deliver the BSR within the QoS control field or the BSR control subfield of any frame sent to the AP (non - solicited BSR), or explicitly deliver the BSR within the frame sent to the AP in response to a BSRP trigger frame (solicited BSR).

[0075] The buffer status reported in the QoS control field includes the queue size value for a given TID. The buffer status reported in the BSR control field includes an ACI bitmap, delta TID, high - priority AC, and two queue sizes.

[0076] The STA can report the buffer status of the transmitted QoS null frames, QoS data frames, and management frames to the AP in the QoS control field for the transmitted QoS null frames and QoS data frames, and in the BSR control subfield (if present), as defined below.

[0077] The STA can report the queue size for a given TID in the queue size subfield of the QoS control field of the transmitted QoS data frame or QoS null frame, and the STA can set the queue size subfield to 255 to indicate an unknown / unspecified queue size for that TID. The STA can aggregate multiple QoS data frames or QoS null frames within an A-MPDU and report the queue sizes for different TIDs.

[0078] When the STA indicates its support for the AP to receive the BSR control subfield, the STA can report the buffer status in the BSR control subfield of the transmitted frame.

[0079] A High Efficiency (HE) STA can report the queue size of the preferred AC indicated by the ACI high subfield in the queue size high subfield of the BSR control subfield. The STA can set the queue size high subfield to 255 to indicate an unknown / unspecified queue size for that AC.

[0080] The HE STA can report the queue sizes of the ACs indicated by the ACI bitmap subfield in the queue size all subfield of the BSR control subfield. The STA can set the queue size all subfield to 255 to indicate an unknown / unspecified BSR for those ACs.

[0081] FIG. 6 shows an example including buffer status reporting by the STA, scheduling by the AP for uplink multi-user (MU) transmission, and transmission of scheduled uplink transmission by the STA.

[0082] As shown, the AP may solicit one or more associated STAs (STA 1 and STA 2) for buffer status by transmitting a Buffer Status Report Polling (BSRP) trigger frame. When receiving the BSRP trigger frame, STA 1 and / or STA 2 may each generate a trigger-based (TB) PPDU if the BSRP trigger frame contains the 12 LSBs of the STA's AID in the user information field.

[0083] STA 1 and / or STA 2 may each include one or more QoS null frames within the TB PPDU. The one or more QoS null frames may include one or more QoS control fields or one or more BSR control subfields.

[0084] As described above, the QoS control field may include a queue size subfield for a TID having a queue size for reporting by the STA to the AP. For example, as shown in FIG. 6, STA 1 may respond to a BSRP trigger frame from the AP by transmitting an A-MPDU that includes a plurality of QoS null frames. Each QoS null frame indicates the queue size of its respective TID, e.g., TID 0 and TID 2, in its respective QoS control field. Similarly, STA 2 may respond to the BSRP trigger frame by transmitting an MPDU that includes a QoS null frame indicating the queue size of TID 2 within its QoS control field.

[0085] The BSR control subfield can include a queue size all subfield indicating the queue size of the AC indicated by the ACI bit map subfield, so that the STA has a queue size for reporting to the AP when the AP indicates support for receiving the BSR control subfield. The STA sets the delta TID, scaling factor, ACI high, and queue size high subfields of the BSR control subfield.

[0086] When the AP receives BSRs from STA 1 and STA 2, it may send a basic trigger frame to allocate UL MU resources to STA 1 and STA 2. In response, STA 1 may send a TB PPDU containing QoS data frames with TID 0 and TID 2, and STA 2 may send a TB PPDU containing one or more QoS data frames with a TID. The AP may acknowledge the TB PPDUs transmitted from STA 1 and STA 2 by sending a multi-STA block Ack frame.

[0087] Figure 7 shows an exemplary reference model of a multi-link device (MLD).

[0088] An MLD is an entity that can manage communications over multiple links. An MLD can be a logical entity and can also have multiple associated stations (STAs). An MLD can be an access point MLD (AP MLD), and the STAs associated with the MLD are AP STAs (or APs). An MLD can be a non-access point MLD (non-AP MLD) where the STAs associated with the MLD are non-AP STAs (or STAs).

[0089] Communications over different frequency bands / channels can occur simultaneously or not simultaneously, depending on the capabilities of both the communicating AP MLD and non-AP MLD.

[0090] As shown in Figure 7, an MLD can have a single MAC service access point (MAC-SAP) to the LLC layer, including a MAC data service. An MLD can support multiple MAC sublayers that are coordinated by a sublayer management entity (SME). Each AP STA (or non-AP STA) associated with an AP MLD (or non-AP MLD) has a different MAC address within the MLD.

[0091] The SME is responsible for coordinating the MAC sublayer management entity (MLME) of the relevant STAs of the MLD to maintain a single robust security network association (RSNA) key management entity and a single IEEE 802.1X authenticator or supplicant for multi-link operation (MLO).

[0092] The multi-link operation (MLO) procedure enables a pair of MLDs to detect, synchronize, authenticate (de-authenticate), (re-)associate, disassociate, and manage resources with each other on any common band or channel supported by both MLDs. The authenticator and MAC-SAP of the AP MLD can be identified by the same AP MLD MAC address. The supplicant and MAC-SAP of the non-AP MLD can be identified by the same non-AP MLD MAC address.

[0093] Figure 8 shows an example of an AP MLD and a related non-AP MLD.

[0094] As shown, the AP MLD has two related APs (AP1 and AP2), and the non-AP MLD has two related STAs (STA 1 and STA 2). The AP MLD and the non-AP MLD can be communicatively coupled by two links (Link 1 and Link 2). Link 1 is established between AP1 and STA1, and Link 2 is established between AP2 and STA2.

[0095] Generally, the MAC addresses of the MLD and its related STAs are different from each other. For example, as shown in Figure 8, the AP MLD may have a MAC address M, AP 1 may have a MAC address w, and AP2 may have a MAC address x. Similarly, the non-AP MLD may have a MAC address P, STA 1 may have a MAC address y, and STA2 may have a MAC address z.

[0096] As shown in FIG. 8, in each MLD, the MAC sublayer can be further divided into an upper MLD MAC sublayer and a lower MLD MAC sublayer. The upper MLD MAC sublayer (MLD) performs functions common to all links. The lower MLD MAC sublayer performs functions local to each link. Some functions require joint processing of both the upper MLD and the lower MLD MAC sublayers.

[0097] The upper MLD MAC sublayer functions include - Authentication, association, and re-association (between AP MLD and non-AP MLD), - Security association (e.g., pairwise master key security association (PMKSA), pairwise transient key security association (PTKSA)), and distribution of group temporal key (GTK) / integrity GTK (IGTK) / beacon IGTK (BIGTK), - Assignment of sequence number (SN) / packet number (PN) of frames encrypted by pairwise transient key (PTK) for unicast frames, - Encryption / decryption using PTK for unicast frames, - Selection of the lower MLD MAC sublayer for transmission (TID-to-link mapping), - Reordering of packets to ensure in-order delivery for each block access session, - Block Ack scoring of individually addressed frames (in cooperation with the lower MLD MAC sublayer), optionally, the upper MLD MAC sublayer distributes the block Ack record on one link to the lower MLD MAC sublayer of other links, - May include MLD-level management information exchange / display via the lower MLD MAC sublayer.

[0098] The lower MLD MAC sublayer functions include - Maintenance of link-specific GTK / IGTK / BIGTK (between the AP related to the AP MLD and the STA related to the non-AP MLD), - Link-specific encryption / decryption / integrity protection and PN assignment using GTK / IGTK / BIGTK (between an AP associated with AP MLD and an STA associated with non-AP MLD), - Link-specific management information exchange / display (e.g., beacon), - Link-specific control information exchange / display (e.g., RTS / CTS, positive acknowledgment, etc.), - Power-saving states and modes, - MAC address filtering for frame reception, and - Block Ack scoring for individually addressed frames (in cooperation with the MLD upper MAC sublayer), optionally, the MLD lower MAC sublayer may include receiving block Ack records on other links from the MLD upper MAC sublayer.

[0099] Multi-link (re)setup between non-AP MLD and AP MLD may include the exchange of (re)association request / response frames. The (re)association request / response frame exchange for multi-link setup may include both frames carrying basic multi-link elements.

[0100] In the (re)association request frame, the non-AP MLD indicates the links required for (re)setup, and the capabilities and operating parameters of the requested links. The non-AP MLD may request to (re)setup links using a subset of the APs associated with the AP MLD. The links requested for (re)setup, and the capabilities and operating parameters of the requested links are independent of the existing setup links having the associated AP MLD, as well as the capabilities and operating parameters of the setup links.

[0101] In the (re)association response frame, the AP MLD may indicate the requested links to be approved, the requested links to be rejected for (re)setup, as well as the capabilities and operating parameters of the requested links. The AP MLD may approve a subset of the links requested for (re)setup. The (re)association response frame is sent to the non-AP STA associated with the non-AP MLD that sent the (re)association request frame.

[0102] The MLD that requests or approves multi-link (re)setup for any two links ensures that each link is located on a different non-overlapping channel. After the multi-link (re)setup between the non-AP MLD and the AP MLD is successful, the non-AP MLD and the AP MLD setup links for multi-link operation, and the non-AP MLD is (re)associated with the AP MLD. For each setup link, the corresponding non-AP STA associated with the non-AP MLD is in the same association state as the non-AP MLD and is associated with the corresponding AP associated with the AP MLD. For each setup link, the function between the non-AP STA and its associated AP is enabled unless the function is extended to the MLD level or otherwise specified.

[0103] Figure 9 shows an example of multi-link setup between an AP MLD and a non-AP MLD. As shown, the AP MLD has three associated APs: AP 1 operating in the 2.4 GHz band, AP 2 operating in the 5 GHz band, and AP 3 operating in the 6 GHz band. The non-AP MLD has three associated STAs: non-AP STA 1 operating in the 2.4 GHz band, non-AP STA 2 operating in the 5 GHz band, and non-AP STA 3 operating in the 6 GHz band.

[0104] The non-AP MLD may initiate a multi-link setup by the non-AP STA 1 sending an association request frame to the AP 1 associated with the AP MLD. In the association request frame, the transmitter address (TA) field is set to the MAC address of the non-AP STA 1, and the receiver address (RA) field is set to the MAC address of the AP 1. The association request frame includes the MLD MAC address of the non-AP MLD and a basic multi-link element indicating the complete information of the non-AP STA 1, non-AP STA 2, and non-AP STA 3. The association request frame may request the setup of a set of three links (the link between AP 1 and non-AP STA 1, the link between AP 2 and non-AP STA 2, and the link between AP 3 and non-AP STA 3) between the non-AP MLD and the AP MLD.

[0105] The AP MLD may respond to the requested multi-link setup by the AP sending an association response frame to the non-AP STA 1 associated with the non-AP MLD. In the association response frame, the TA field is set to the MAC address of the AP 1, and the RA field is set to the MAC address of the non-AP STA 1. The association response frame includes the MLD MAC address of the AP MLD and a basic multi-link element indicating the complete information of the AP 1, AP 2, and AP 3. The multi-link setup is successful by the setup of three links (link 1 between AP 1 and non-AP STA 1, link 2 between AP 2 and non-AP STA 2, and link 3 between AP 3 and non-AP STA 3) between the non-AP MLD and the AP MLD.

[0106] By default, all TIDs of non-AP MLDs are mapped to all setup uplinks for both uplink and downlink. The TID-to-link mapping mechanism enables multi-link setup for AP MLDs and non-AP MLDs that have already executed or are in the process of executing multi-link setup to specify how UL and DL QoS traffic corresponding to different TIDs (e.g., 0 to 7) can be assigned to setup uplinks. In the negotiated TID-to-link mapping, a TID can be mapped to a link set that is a subset of the setup uplinks spanning from a single setup uplink to all setup uplinks.

[0107] A setup uplink is defined as valid for a non-AP MLD if at least one TID is mapped to that link either in DL or UL, and is defined as invalid if there is no TID mapped to that link in both DL and UL. At any given time, a TID is always mapped to at least one configured link for both DL and UL, which means that a TID-to-link mapping change can be valid and successful only if it does not result in a mapped link set consisting of zero setup uplinks.

[0108] By default, all setup uplinks are enabled. If a link is enabled for a non-AP MLD, it can be used for the exchange of individually addressed frames, subject to the power state of the non-AP STA operating on that link. Only MSDUs or A-MSDUs with a TID mapped to a link can be transmitted on that link in the direction (DL / UL) corresponding to the TID-to-link mapping. Individually addressed management frames and control frames can be transmitted on any enabled link between the associated STA of the non-AP MLD and the corresponding AP of the AP MLD for both DL and UL.

[0109] If a link is disabled for a non-AP MLD, the link may not be used for the exchange of individually addressed frames between the associated STA of the non-AP MLD and the corresponding AP of the AP MLD.

[0110] If a TID is mapped UL to a set of links enabled for a non-AP MLD, the non-AP MLD may use any link within this set of enabled links to transmit an individually addressed MSDU or A-MSDU corresponding to that TID.

[0111] If a TID is mapped DL to a set of links enabled for a non-AP MLD, the non-AP MLD may obtain an individually addressed BU buffered at the AP MLD that is an MSDU or A-MSDU corresponding to the TID on any link of the set of enabled links. Conversely, the AP MLD may use any link within the set of enabled links to transmit an individually addressed MSDU or A-MSDU corresponding to the TID, conditional on the power state of the non-AP STA on each link being used.

[0112] When using the default mode, the non-AP MLD may obtain a BU buffered by the AP MLD on any setup uplink, but the AP MLD may recommend a link.

[0113] The non-AP MLD may obtain a buffered BU that is an MMPDU buffered at the AP MLD on any enabled link. The AP MLD may use any enabled link to transmit an individually addressed bufferable management frame that is not a measurement MMPDU, conditional on the power state of the non-AP STA on the link being used.

[0114] When a STA associated with a non-AP MLD is in active mode on a link with a set of TIDs mapped for DL transmission, the associated AP associated with the AP MLD may send to the STA an MSDU / A-MSDU for the set of TIDs mapped to the non-AP MLD and a MMPDU that is not a measurement MMPDU for the non-AP MLD or its associated STA, unless the frame is transmitted in active mode to another STA associated with the same non-AP MLD.

[0115] As described above, in the default mapping mode, all TIDs are mapped to all setup links for DL and UL, and all setup links are enabled. Non-AP MLDs and AP MLDs that perform multi-link setup will operate in this mode if no negotiation of TID-to-link mapping for different mappings occurs, fails, or is removed.

[0116] In a multi-link (re)setup procedure, if the AP MLD indicates support for negotiation of TID-to-link mapping, the non-AP MLD may initiate negotiation of TID-to-link mapping by including a TID-to-link mapping element in the (re)association request frame.

[0117] After receiving a (re)association request frame that includes a TID-to-link mapping element, the AP MLD may respond to the (re)association request frame according to the following rules. The AP MLD can approve the requested TID-to-link mapping indicated in the TID-to-link mapping element within the received (re)association request frame only if it approves a multi-link (re)setup for all links to which at least one TID is required to be mapped. In this case, the non-AP MLD includes a TID-to-link mapping element in the (re)association response frame. Otherwise, the non-AP MLD indicates the rejection of the proposed TID-to-link mapping by including in the (re)association response frame a TID-to-link mapping element that suggests a preferred TID-to-link mapping.

[0118] After the successful multi-link (re)setup, to negotiate a new TID-to-link mapping, the initiating MLD may send an individually addressed TID-to-link mapping request frame to the responding MLD that indicated support for the negotiation of the TID-to-link mapping.

[0119] When receiving an individually addressed TID-to-link mapping request frame, the responding MLD transmits an individually addressed TID-to-link mapping response frame to the initiating MLD according to the following rules. By transmitting the TID-to-link mapping response frame, the responding MLD may approve the requested TID-to-link mapping indicated in the TID-to-link mapping element within the received TID-to-link mapping request frame. Otherwise, the responding MLD may indicate the rejection of the proposed TID-to-link mapping in the TID-to-link mapping response frame. By including a TID-to-link mapping element in the TID-to-link mapping response frame, the responding MLD may propose a preferred TID-to-link mapping in the TID-to-link mapping response frame.

[0120] The MLD may propose a preferred TID-to-link mapping to the peer MLD by transmitting an unsolicited TID-to-link mapping response frame containing a TID-to-link mapping element.

[0121] If the peer MLD indicates a preferred TID-to-link mapping, the MLD may take the preferred TID-to-link mapping into account when starting a new TID-to-link mapping. Additionally, the AP MLD may take into account the traffic flows related to the non-AP MLD and the capabilities and constraints (if any) of the non-AP MLD.

[0122] When two MLDs negotiate a TID-to-link mapping, either MLD may remove the negotiated TID-to-link mapping by transmitting an individually addressed TID-to-link mapping removal frame. After removal, the MLD operates in the default mapping mode.

[0123] When the MLD successfully negotiates the TID-to-link mapping with the peer MLD, both the MLD and the peer MLD update the uplink and / or downlink TID-to-link mapping information according to the negotiated TID-to-link mapping.

[0124] If the MLD successfully negotiates with the peer MLD an uplink and / or downlink TID-to-link mapping in which the bit position i of the link mapping field n in the TID-to-link mapping element is set to 0, then TID n shall not be mapped to the link associated with link ID i in the uplink and / or downlink. If the MLD successfully negotiates with the peer MLD an uplink and / or downlink TID-to-link mapping in which the bit position i of the link mapping field n in the TID-to-link mapping element is set to 1, then TID n shall be mapped to the link associated with link ID i in the uplink and / or downlink.

[0125] Figure 10 shows an example of TID-to-link mapping in a multi-link communication environment. As shown, the multi-link communication environment includes an AP MLD having three associated APs and a non-AP MLD having three associated STAs.

[0126] During or after multi-link setup, the non-AP MLD and the AP MLD may negotiate the TID-to-link mapping. The TID-to-link mapping maps the TIDs in the UL and DL non-AP MLDs to set up the links between the AP MLD and the non-AP MLD. For example, as shown in FIG. 10, the TID-to-link mapping may map TIDs 0 to 6 in both the UL and DL to Link 1, and map TID 7 in both the UL and DL to Link 2. Therefore, Links 1 and 2 are activated and Link 3 is deactivated. The negotiation of the TID-to-link mapping may be performed by exchanging an association request / response frame or a TID-to-link mapping request / response frame between the non-AP MLD and the AP MLD.

[0127] FIG. 11 shows an existing buffer status report in the presence of TID-to-link mapping in an exemplary multi-link communication environment 1100. As shown in FIG. 11, the exemplary environment 1100 may include a non-AP MLD 1110 and an AP MLD 1111. The non-AP MLD 1110 and the AP MLD 1111 may be communicatively coupled by a plurality of (setup) links (e.g., Link 1, Link 2, and Link 3). The non-AP MLD 1110 may include a plurality of associated STAs (e.g., STA1, STA2, and STA3). The AP MLD 1111 may include a plurality of associated APs (e.g., AP1, AP2, and AP3). Each of the plurality of associated STAs of the non-AP MLD 1110 may be configured to communicate with one of the plurality of associated APs of the AP MLD 1111 on one of the plurality of links that communicatively couple the non-AP MLD 1110 and the AP MLD 1111.

[0128] In non-AP MLD 1110, there may be multiple UL and / or DL traffic streams. Each traffic may be associated with a TID (e.g., TID 0, TID 1, ..., TID 7). The various traffic streams can be added to the queues specified in non-AP MLD 1110. The queues can be used to add traffic of one or more TIDs to the queue.

[0129] In one embodiment, non-AP MLD 1110 and AP MLD 1111 can negotiate a TID-to-link mapping. The negotiation of the TID-to-link can include the exchange of the TID-to-link mapping element in the association request frame and the association response frame communicated between non-AP MLD 1110 and AP MLD 1111. The TID-to-link mapping maps the TID in non-AP ML 1110 to link the setup between non-AP MLD 1110 and AP MLD 1111 in the uplink and / or downlink. In one embodiment, as shown in FIG. 11, after the negotiation of the TID-to-link mapping is successful, TID 0 to TID 6 may be mapped to both link 1 and link 2, and TID 7 may be mapped to link 3.

[0130] The non-AP MLD 1110 may have buffered traffic associated with the TID that is sent to the AP MLD 1111. As described above with reference to FIG. 6, in a claim-based buffer status report, the AP MLD 1111 may request the non-AP MLD 1110 to report the buffer status by sending a buffer status report polling trigger frame (BSRP) to the AP MLD 1110. The non-AP MLD 1110 may respond by sending a QoS null frame that includes one or more buffer status reports (BSRs). In a single-link environment where all TIDs of the non-AP STA are mapped to only one link, the non-AP STA follows a clear rule that any BSR for any TID is sent on the single link between the non-AP STA and the AP. However, this does not apply in a multi-link environment where the non-AP MLD may be communicatively coupled via multiple links to the AP MLD, particularly in a multi-link environment where the non-AP MLD and the AP MLD have negotiated a TID-to-link mapping that assigns each TID in the non-AP MLD to one or more links between the non-AP MLD and the AP MLD.

[0131] In fact, the existing IEEE 802.11 standard specifications (e.g., Draft P802.11be_D1.3) are silent on which of the multiple links the QoS null frame report buffer status for a given TID can be sent to when the TID-to-link mapping is negotiated between the non-AP MLD and the AP MLD. For example, the existing standard specifications provide that only "MSDUs or A-MSDUs with TIDs mapped to the enabled links" can be transmitted on that link. Strictly speaking, while the QoS null frame does not contain an MSDU or an A-MSDU, it will have a QoS null frame that is transmitted only on the link to which the TID is mapped by following the same rules for the QoS null frame containing the TID. The existing standard specifications further provide that "management frames and control frames can be transmitted on any enabled link". However, the QoS null frame may not consider either the MAC management frame or the MAC control frame.

[0132] Returning to the exemplary environment 1100, the operation according to the existing standard specification may have an AP MLD 1111 that sends a first buffer status report polling (BSRP) trigger frame on link 1 to the non-AP MLD 1110. In response to the first BSRP trigger frame, the non-AP MLD 1110 may send a QoS null frame. According to the negotiated TID-to-link mapping that maps only TIDs 0 to 6 to link 1, and following the same rules as those existing for MSDU / A-MSDU, since the BSRP trigger frame was sent to link 1 where only TIDs 0 to 6 are mapped, the QoS null frame BSR sent by the non-AP MLD 1110 may include only for TIDs 0 to 6. Therefore, in order to obtain the buffer status for TID 7, the AP MLD 1111 may need to send a second BSRP trigger frame on link 3 to solicit the transmission of the BSR for TID 7 by the non-AP MLD 1110. Thus, the overhead and latency for the AP MLD may be increased to obtain the complete buffer status (for all TIDs) of the non-AP MLD.

[0133] Figures 12 to 15 show an exemplary method of buffer status reporting in the presence of TID-to-link mapping according to embodiments of the present disclosure. For illustrative purposes only, the exemplary method is described below in the context of an exemplary multi-link communication environment including a single non-AP MLD and a single AP MLD. As will be understood by those skilled in the art based on the teachings herein, the embodiments are not limited by these examples and can be readily extended to multi-link environments including multiple non-AP MLDs and multiple AP MLDs. Further, the exemplary method is described with reference to exemplary communication between the non-AP MLD and the AP MLD. These exemplary communications, such as a specific sequence of frame transmissions between the non-AP MLD and the AP MLD, are also provided for illustrative purposes only and are not to be used to limit the embodiments of the present disclosure.

[0134] FIG. 12 shows an exemplary method of a buffer status report according to one embodiment with respect to an exemplary environment 1200. As shown in FIG. 12, the exemplary environment 1200 may include a non-AP MLD 1210 and an AP MLD 1211. The non-AP MLD 1210 and the AP MLD 1211 may be communicatively coupled by a plurality of (setup) links (e.g., Link 1, Link 2, and Link 3). The non-AP MLD 1210 may include a plurality of associated STAs (e.g., STA1, STA2, and STA3). The AP MLD 1211 may include a plurality of associated APs (e.g., AP1, AP2, and AP3). Each of the plurality of associated STAs of the non-AP MLD 1210 may be configured to communicate with one of the plurality of associated APs of the AP MLD 1211 on each of one of the plurality of links (e.g., Link 1, Link 2, and Link 3) that communicatively couple the non-AP MLD 1210 and the AP MLD 1211.

[0135] In an exemplary embodiment, the non-AP MLD 1210 and the AP MLD 1211 may establish a multi-link setup during an association procedure. The multi-link setup may constitute a plurality of links, such as Links 1-3, as a "setup" link between the non-AP MLD 1210 and the AP MLD 1211. Each link may communicatively couple an associated STA of the non-AP MLD 1210 with a respective associated AP of the AP MLD 1210. In one embodiment, each link may correspond to a particular band among a plurality of supported frequency bands (e.g., 2.4 GHz, 5 GHz, and 6 GHz) between the non-AP MLD 1210 and the AP MLD 1211.

[0136] In an exemplary embodiment, the non-AP MLD 1210 and the AP MLD 1211 may negotiate a TID-to-link mapping. The negotiation of the TID-to-link may include exchanging TID-to-link mapping elements during an association procedure between the non-AP MLD 1110 and the AP MLD 1111. In one example, as shown in FIG. 12, TIDs 0 to 6 may be mapped uplink to Link 1 that communicatively couples STA1 associated with the non-AP MLD 1210 and AP1 associated with the AP MLD 1211, and TID 7 may be mapped uplink to Link 2 that communicatively couples STA2 associated with the non-AP MLD 1210 and AP2 associated with the AP MLD 1211. According to this exemplary TID-to-link mapping, Links 1 and 2 may be considered "active" because at least one TID is mapped to each of Links 1 and 2. On the other hand, Link 3 may be considered "inactive" because no TID is mapped to Link 3.

[0137] Based on the TID-to-link mapping, the non-AP MLD 1210 may transmit a frame (not shown in FIG. 12) carrying an MSDU or an A-MSDU with any of TIDs 0 to 6 on Link 1, and may transmit a frame (not shown in FIG. 12) carrying an MSDU or an A-MSDU with TID 7 on Link 2.

[0138] The non-AP MLD 1210 may be configured to transmit a frame carrying a buffer status report (BSR) to the AP MLD 1211. The BSR frame may be carried by a trigger-based (TB) physical layer protocol data unit (PPDU) or a non-TB PDDU. Here, various embodiments for transmitting the BSR frame in the presence of a negotiated TID-to-link mapping will be described.

[0139] In one embodiment, the non-AP MLD 1210 can be configured to transmit a BSR frame for any TID on any enabled link, independently of / irrespective of the negotiated TID-to-link mapping.

[0140] In an exemplary embodiment, the non-AP MLD 1210 can be configured to transmit a BSR frame for any TID (e.g., TID 0 to TID 7) on any enabled link in response to a trigger frame transmitted from the AP MLD 1211, independently of / irrespective of the negotiated TID-to-link mapping. For example, as shown in FIG. 12, when the non-AP MLD 1210 receives a first trigger frame 1220 on link 1 from the AP MLD 1211, it may have traffic buffered in the uplink associated with TID 7. The first trigger frame 1220 can be a buffer status report polling (BSRP) trigger frame or a basic trigger frame. Irrespective of a TID-to-link mapping that maps TID 7 only to link 2, the non-AP MLD 1210 can transmit a BSR frame 1221 including the buffer status of TID 7 on link 1 in response to the first trigger frame 1220. The BSR frame 1221 can include a QoS null frame indicating TID 7 and the queue size information of TID 7. The BSR frame 1221 can be included in a TB-PPDU.

[0141] In another exemplary embodiment, the non-AP MLD 1210 may be configured to send an unsolicited BSR frame for any TID on any enabled link, independent of / irrespective of the negotiated TID-to-link mapping, to the AP MLD 1211. The unsolicited BSR is sent without receiving a trigger frame from the AP MLD 1211 and may be sent after accessing the wireless medium (WM) using Enhanced Distributed Channel Access (EDCA). For example, as shown in FIG. 12, when obtaining a transmission opportunity (TXOP) on Link 2, the non-AP MLD 1210 may have traffic buffered for the uplink for TID 7 and at least one other TID (e.g., any one of TIDs 0 to 6). Independent of / Irrespective of the TID-to-link mapping that maps only TID 7 to Link 2, the non-AP MLD 1210 may send a non-TB PPDU carrying an unsolicited BSR frame 1223 for at least one other TID (other than TID 7). The unsolicited BSR frame 1223 may include one or more QoS null frames indicating buffer status associated with at least one other TID and the queue size information of at least one other TID, at the non-AP MLD 1210. The non-TB PPDU may also carry an MSDU or A-MSDU for TID 7.

[0142] In another exemplary embodiment, the non-AP MLD 1210 may be configured to send a BSR frame for any TID to the AP MLD 1211 on the disabled link, independent of / irrespective of the negotiated TID-to-link mapping, in response to a trigger frame sent from the AP MLD 1211. For example, as shown in FIG. 12, the non-AP MLD 1210 may receive a second trigger frame 1224 from the AP MLD 1211 indicating one or more resource units (RUs) for uplink OFDMA random access (UORA) on the disabled link 3. The second trigger frame 1224 may be a BSRP trigger frame or a basic trigger frame. In response to the second trigger frame 1224, any STA can transmit on the indicated uplink RUs, so the non-AP MLD 1210 can send a BSR frame 1225 on link 3 even though the TID is not mapped to link 3 in the TID-to-link mapping. The BSR frame 1225 may include a QoS null frame indicating any TID (e.g., TID 0 to TID 7) and the queue size information for that TID. The BSR frame 1225 may be included in the TB-PPDU.

[0143] In another exemplary embodiment, the non-AP MLD 1210 may be configured to transmit an unsolicited BSR frame for a TID to the AP MLD 1211 according to the TID-to-link mapping. The unsolicited BSR may be transmitted without receiving a trigger frame from the AP MLD 1211 and may be transmitted after accessing the wireless medium (WM) using EDCA. For example, as shown in FIG. 12, the non-AP MLD 1210 may acquire a transmission opportunity (TXOP) on Link 1. According to the TID-to-link mapping, the non-AP MLD 1210 may transmit a non-TB PPDU carrying an unsolicited BSR frame 1222 for any of TIDs 0 to 6 on Link 1. The unsolicited BSR frame 1222 may include one or more QoS null frames indicating any of TIDs 0 to 6 and queue size information for the indicated TID. The non-TB PPDU may also be able to carry an MSDU or A-MSDU of TID 0 to TID 6.

[0144] FIG. 13 shows a further exemplary method of a buffer status report according to an embodiment with respect to an exemplary environment 1300. As shown in FIG. 13, the exemplary environment 1300 may include a non-AP MLD 1310 and an AP MLD 1311. The non-AP MLD 1310 and the AP MLD 1311 may be communicatively coupled by a plurality of (setup) links (e.g., Link 1, Link 2, and Link 3). The non-AP MLD 1310 may include a plurality of associated STAs (e.g., STA1, STA2, and STA3). The AP MLD 1311 may include a plurality of associated APs (e.g., AP1, AP2, and AP3). Each of the plurality of associated STAs of the non-AP MLD 1310 may be configured to communicate with one of the plurality of associated APs of the AP MLD 1311 on each of one of the plurality of links communicatively coupling the non-AP MLD 1310 and the AP MLD 1311.

[0145] As described above with reference to FIG. 12, in an exemplary embodiment, the non-AP MLD 1310 and the AP MLD 1311 can establish a multi-link setup and negotiate a TID-to-link mapping during an association procedure. In one example, as shown in FIG. 13, TIDs 0 to 6 may be mapped uplink to Link 1 that communicatively couples STA1 and AP1, and TID 7 may be mapped uplink to Link 2 that communicatively couples STA2 and AP2. According to this exemplary TID-to-link mapping, Links 1 and 2 may be considered “active” because at least one TID is mapped to each of Links 1 and 2. On the other hand, Link 3 may be considered “inactive” because no TID is mapped to Link 3.

[0146] Based on the TID-to-link mapping, the non-AP MLD 1310 may transmit a frame (not shown in FIG. 13) carrying an MSDU or A-MSDU with any of TIDs 0 to 6 on Link 1, and may transmit a frame (not shown in FIG. 13) carrying an MSDU or A-MSDU with TID 7 on Link 2.

[0147] In one example, the AP MLD 1311 may transmit a first trigger frame 1320 (e.g., a BSRP trigger frame, a basic trigger frame, etc.) to the non-AP MLD 1310 on an activated link (e.g., Link 1). The non-AP MLD 1310 that receives the first trigger frame 1320 may respond with a BSR frame 1321 in a first TB PPDU on the activated link (e.g., Link 1), indicating buffer status for any TID, regardless of the TID-to-link mapping. For example, the BSR frame 1321 may include one or more QoS null frames indicating a TID of any of TIDs 0 to 7 and queue size information for the indicated TID.

[0148] When the AP MLD 1311 receives a BSR frame 1321 indicating one or more TIDs between TID 0 and TID 6, the AP MLD 1311 may transmit a second trigger frame 1322 (e.g., a basic trigger frame, a MU-RTS TXS trigger frame) on Link 1 to allocate uplink resources to the non-AP MLD 1310 for the one or more TIDs indicated in the BSR frame 1321. In response to the second trigger frame 1322, the non-AP MLD 1310 may transmit a second TB-PPDU including one or more QoS data frames 1323 for the one or more indicated TIDs on Link 1. The QoS data frame 1323 may include an MSDU or an A-MSDU for the one or more indicated TIDs. The AP MLD 1311 receiving the second TB PPDU may transmit a first acknowledgment frame 1324 on Link 1 in response to the QoS data frame 1323 included in the second TB PPDU.

[0149] If the BSR frame 1321 indicates TID 7, the AP MLD 1311 may transmit a third trigger frame 1325 (e.g., a basic trigger frame, a MU-RTS TXS trigger frame) on Link 2 to allocate uplink resources to the non-AP MLD 1310 for the transmission of TID 7. In response to the third trigger frame 1325, the non-AP MLD 1310 may transmit a third TB-PPDU including one or more QoS data frames 1326 for TID 7 on Link 2. The QoS data frame 1326 may include an MSDU or an A-MSDU for TID 7. The AP MLD 1311 receiving the third TB PPDU may transmit a second acknowledgment frame 1327 in response to the QoS data frame 1326 included in the third TB PPDU.

[0150] In another example, the AP MLD 1311 may transmit a fourth trigger frame 1330 (e.g., a BSRP trigger frame, a basic trigger frame, etc.) on an invalidated link (e.g., link 3) to the non-AP MLD 1310. The non-AP MLD 1310 that receives the fourth trigger frame 1330 on the invalidated link may respond on the invalidated link using a BSR frame 1331 within a fourth TB PPDU that indicates buffer status for any TID, independent of the TID-to-link mapping. For example, the BSR frame 1331 may include one or more QoS null frames indicating a TID of any of TID 0 to TID 7 and queue size information for the indicated TID. The AP MLD 1311 that receives the fourth TB PPDU may transmit subsequent trigger frames on link 1 and / or link 2 to allocate UL resources to the non-AP MLD 1310 based on the indicated TIDs and their queue size information indicated in the BSR frame 1331.

[0151] FIG. 14 shows a further exemplary method of a buffer status report according to an embodiment with respect to an exemplary environment 1400. As shown in FIG. 14, the exemplary environment 1400 may include a non-AP MLD 1410 and an AP MLD 1411. The non-AP MLD 1410 and the AP MLD 1411 may be communicatively coupled by a plurality of (setup) links (e.g., link 1, link 2, and link 3). The non-AP MLD 1410 may include a plurality of associated STAs (e.g., STA1, STA2, and STA3). The AP MLD 1411 may include a plurality of associated APs (e.g., AP1, AP2, and AP3). Each of the plurality of associated STAs of the non-AP MLD 1410 may be configured to communicate with one of the plurality of associated APs of the AP MLD 1411 on each of one of the plurality of links communicatively coupling the non-AP MLD 1410 and the AP MLD 1411.

[0152] As described above with reference to FIG. 12, in an exemplary embodiment, the non-AP MLD 1410 and the AP MLD 1411 may establish a multi-link setup and negotiate a TID-to-link mapping during an association procedure. In one example, as shown in FIG. 14, TIDs 0 to 6 may be mapped uplink to Link 1 that communicatively couples STA1 and AP1, and TID 7 may be mapped uplink to Link 2 that communicatively couples STA2 and AP2. According to this exemplary TID-to-link mapping, Links 1 and 2 may be considered “active” because at least one TID is mapped to each of Links 1 and 2. On the other hand, Link 3 may be considered “inactive” because no TID is mapped to Link 3.

[0153] Based on the TID-to-link mapping, the non-AP MLD 1410 may transmit a frame (not shown in FIG. 14) carrying an MSDU or A-MSDU with any of TIDs 0 to 6 on Link 1, and may transmit a frame (not shown in FIG. 14) carrying an MSDU or A-MSDU with TID 7 on Link 2.

[0154] In one example, the non-AP MLD 1410 may use EDCA to transmit a BSR frame 1420 within a first non-TB PPDU indicating a buffer status for any TID on an activated link (e.g., Link 1), independent of / regardless of the TID-to-link mapping. For example, the BSR frame 1420 may include one or more QoS null frames indicating a TID of any of TIDs 0 to 7 and queue size information for the indicated TID.

[0155] When the AP MLD 1411 receives a BSR frame 1420 indicating one or more TIDs between TID 0 and TID 6, the AP MLD 1411 can send a first trigger frame 1422 (e.g., a basic trigger frame, a MU-RTS TXS trigger frame) on Link 1 to allocate uplink resources to the non-AP MLD 1410 for one or more TIDs indicated in the BSR frame 1420. In response to the first trigger frame 1422, the non-AP MLD 1410 may send a first TB PPDU including one or more QoS data frames 1423 for one or more indicated TIDs on Link 1. The QoS data frame 1423 may include an MSDU or an A-MSDU for one or more indicated TIDs. The AP MLD 1411 receiving the first TB PPDU may send a first positive acknowledgment frame 1424 in response to the QoS data frame 1423 included in the first TB PPDU.

[0156] If the BSR frame 1420 indicates TID 7, the AP MLD 1411 can send a second trigger frame 1425 (e.g., a basic trigger frame, a MU-RTS TXS trigger frame) on Link 2 to allocate uplink resources to the non-AP MLD 1410 for the transmission of TID 7. In response to the second trigger frame 1425, the non-AP MLD 1410 may send a second TB PPDU including one or more QoS data frames 1426 on Link 2. The one or more QoS data frames may include an MSDU or an A-MSDU for TID 7. The AP MLD 1411 receiving the second TB PPDU may send a second positive acknowledgment frame 1427 in response to the QoS data frame 1426 included in the second TB PPDU.

[0157] In another example, the non-AP MLD 1410 may be configured to transmit a BSR frame indicating the buffer status of TIDs on an enabled link other than the link to which the shown TID is mapped. For example, as shown in FIG. 14, the non-AP MLD 1410 may transmit a BSR frame 1421 in a second non-TB PPDU indicating the buffer status of one or more of TIDs 0 to 6 on the enabled link 2. The BSR frame 1421 may include one or more QoS null frames indicating one or more of TIDs 0 to TID 6 and the queue size information of the shown TID. The AP MLD 1411 that receives the second non-TB PPDU may transmit a trigger frame (not shown) on link 1 based on the TIDs and their queue size information indicated in the BSR frame 1421. In response to the trigger frame, the non-AP MLD 1410 may transmit a TB PPDU (not shown) on link 1 including one or more QoS data frames for the shown TID. The one or more QoS frames may include MSDUs or A-MSDUs for the shown TID. The AP MLD 1411 that receives the TB PPDU may transmit an acknowledgment frame (not shown) in response to the QoS data frame included in the TB PPDU.

[0158] FIG. 15 shows a further exemplary method of a buffer status report, according to one embodiment, with respect to an exemplary environment 1500. As shown in FIG. 15, the exemplary environment 1500 may include a non-AP MLD 1510 and an AP MLD 1511. The non-AP MLD 1510 and the AP MLD 1511 may be communicatively coupled by a plurality of (setup) links (e.g., Link 1, Link 2, and Link 3). The non-AP MLD 1510 may include a plurality of associated STAs (e.g., STA1, STA2, and STA3). The AP MLD 1511 may include a plurality of associated APs (e.g., AP1, AP2, and AP3). Each of the plurality of associated STAs of the non-AP MLD 1510 may be configured to communicate with one of the plurality of associated APs of the AP MLD 1511 over one of each of the plurality of links communicatively coupling the non-AP MLD 1510 and the AP MLD 1511.

[0159] As described above with reference to FIG. 12, in an exemplary embodiment, the non-AP MLD 1510 and the AP MLD 1511 may establish a multi-link setup and negotiate a TID-to-link mapping during an association procedure. In one example, as shown in FIG. 15, TIDs 0 to 6 may be mapped uplink to Link 1 communicatively coupling STA1 and AP1, and TID 7 may be mapped uplink to Link 2 communicatively coupling STA2 and AP2. According to this exemplary TID-to-link mapping, Links 1 and 2 may be considered “active” because at least one TID is mapped to each of Links 1 and 2. On the other hand, Link 3 may be considered “inactive” because no TID is mapped to Link 3.

[0160] Based on the TID-to-link mapping, the non-AP MLD 1510 may transmit a frame (not shown in FIG. 15) carrying an MSDU or A-MSDU with any of TIDs 0 to 6 on Link 1, and may transmit a frame (not shown in FIG. 15) carrying an MSDU or A-MSDU with TID 7 on Link 2.

[0161] In one example, the non-AP MLD 1510 may be configured to transmit an unrequested BSR frame indicating the buffer status of a TID according to the TID-to-link mapping using EDCA on an enabled link. For example, as shown in FIG. 15, the non-AP MLD 510 may transmit a first non-TB PPDU including an unrequested BSR 1520 indicating the buffer status of any TID (i.e., TIDs 0 to 6) mapped to Link 1 on Link 1. The BSR frame 1520 may include one or more QoS null frames indicating any one of TIDs 0 to 6 and the queue size information of the indicated TID.

[0162] When the AP MLD 1511 receives the BSR frame 1520, the AP MLD 1511 may transmit a first trigger frame 1521 (e.g., a basic trigger frame, a MU-RTS TXS trigger frame) on Link 1 to allocate uplink resources to the non-AP MLD 1510 for one or more TIDs indicated in the BSR frame 1520. In response to the first trigger frame 1521, the non-AP MLD 1510 may transmit a first TB PPDU including one or more QoS data frames 1522 for one or more indicated TIDs on Link 1. The QoS data frame may include an MSDU or A-MSDU for one or more indicated TIDs. The AP MLD 1511 receiving the first TB PPDU may transmit a first positive acknowledgment frame 1523 in response to the QoS data frame 1522 included in the first TB PPDU.

[0163] In another example, the AP MLD 1411 may send a second trigger frame 1524 (e.g., BSRP trigger frame) on link 2 to solicit the non-AP MLD 1510 about the buffer status at the non-AP MLD 1510. In response to the second trigger frame 1524, the non-AP MLD 1510 may send a second TB PPDU including a BSR frame 1525 indicating the buffer status of TID 7 (e.g., a QoS null frame indicating TID 7 and queue size information of TID 7) on link 2 according to the TID-to-link mapping. The AP MLD 1511 that receives the BSR frame 1525 may send a third trigger frame 1526 (e.g., basic trigger frame, MU-RTS TXS trigger frame) on link 2 to allocate uplink resources to the non-AP MLD 1510 for TID 7. In response to the third trigger frame 1526, the non-AP MLD 1510 may send a third TB PPDU including one or more QoS data frames 1527 for TID 7 on link 2. The one or more QoS data frames 1527 may include MSDUs or A-MSDUs for TID 7. The AP MLD 1511 that receives the third TB PPDU may send a second acknowledgment frame 1528 in response to the QoS data frame 1527 included in the third TB PPDU.

[0164] FIG. 16 shows an exemplary process 1600 for transmitting buffer status according to an embodiment of the present disclosure. The exemplary process 1600 may be implemented in an exemplary environment including an AP MLD and a non-AP MLD. The non-AP MLD and the AP MLD may be communicatively coupled by a plurality of links and may be associated with a TID-to-link mapping. The TID-to-link mapping may include a first mapping of a first TID in an uplink to a first set of links among the plurality of links, and a second mapping of a second TID in an uplink to a second set of links among the plurality of links. In one embodiment, the TID-to-link mapping is based on TID-to-link mapping elements exchanged in an association request frame and an association response frame between the non-AP MLD and the AP MLD, or a default mapping mode in which the TID is mapped to all of the plurality of links for both downlink and uplink.

[0165] The exemplary process 1600 may be implemented by the non-AP MLD.

[0166] As shown in FIG. 16, the process 1600 may include, at step 1610, transmitting a frame of a first TID according to the TID-to-link mapping on a first link of a first set of links.

[0167] In one embodiment, the frame of the first TID includes a frame carrying one or more MSDUs or A-MSDUs for the first TID.

[0168] At step 1620, the process 1600 may include determining the buffer status of the first TID.

[0169] At step 1630, the process 1600 may include transmitting a BSR frame indicating the buffer status for the first TID on any of the plurality of links, independent of / irrespective of the TID-to-link mapping.

[0170] In one embodiment, the link on which the BSR frame is transmitted is an enabled link, i.e., a link having at least one TID mapped thereto according to the TID-to-link mapping.

[0171] In one embodiment, the link on which the BSR frame is transmitted belongs to the first set of links among a plurality of links.

[0172] In one embodiment, the link on which the BSR frame is transmitted belongs to the second set of links among a plurality of links.

[0173] In one embodiment, the link on which the BSR frame is transmitted is a link to which the first TID is not mapped in the TID-to-link mapping.

[0174] In one embodiment, the link on which the BSR frame is transmitted is a disabled link, i.e., a link having no TID mapped thereto according to the TID-to-link mapping.

[0175] In one embodiment, the BSR frame includes a QoS null frame indicating the first TID and the queue size information of the first TID.

[0176] In one embodiment, the BSR frame includes a QoS null frame including a QoS control field, or a QoS null frame including a QoS control field and a BSR control subfield.

[0177] In one embodiment, the QoS control field is a TID subfield, where the TID subfield identifies a traffic class (TC) or traffic stream (TS) for which a transmission opportunity (TXOP) is requested, and a queue size subfield, where the queue size subfield has a TID equal to the value of the TID subfield and indicates the total size in octets of MSDUs or A-MSDUs buffered at the non-AP MLD, and includes at least one of them.

[0178] In one embodiment, the BSR control subfield includes at least one of an access category index (ACI) bitmap subfield, a delta TID subfield, an ACI high subfield, a scaling factor subfield, a queue size high subfield, and a queue size full subfield. The ACI bitmap subfield indicates at least one access category (AC) for which the buffer status is reported within the BSR frame. The delta TID subfield indicates the number of TIDs for which the buffer status is reported within the BSR frame. The ACI high subfield indicates the ACI of at least one AC for which the buffer status is indicated by the queue size high subfield. The scaling factor indicates the size in octets of the unit (SF) of the queue size high subfield and the queue size full subfield. The queue size high subfield indicates the amount of traffic buffered in SF units for the AC identified by the ACI high subfield. The queue size full subfield indicates the amount of traffic buffered in SF units for at least one AC identified by the ACI bitmap subfield.

[0179] In one embodiment, transmitting the BSR frame in step 1630 includes transmitting the BSR frame in a TB PPDU or a non-TB PPDU.

[0180] In one embodiment, transmitting the BSR frame in step 1630 is in response to a trigger frame received from the AP MLD. The trigger frame may include a BSRP trigger frame or a basic trigger frame. The BSR frame may be transmitted in a TB PPDU.

[0181] In one embodiment, transmitting the BSR frame in step 1630 includes performing EDCA-based transmission. EDCA-based transmission may include transmitting a non-TB PPDU.

[0182] In one embodiment, process 1600 may optionally include steps 1640 and 1650.

[0183] In step 1640, process 1600 may include a non-AP MLD that receives a trigger frame from the AP MLD in response to the BSR frame. The trigger frame may be received on a link where the first TID is mapped in the TID-to-link mapping. The trigger frame may be a basic trigger frame or a MU-RTS TXS trigger frame.

[0184] In step 1650, the non-AP MLD that receives the trigger frame in step 1640 may transmit a frame carrying an MSDU or an A-MSDU for the first TID on the link where the trigger frame is received.

[0185] FIG. 17 shows an exemplary process 1700 for receiving buffer status according to an embodiment of the present disclosure. The exemplary process 1700 may be implemented in an exemplary environment including an AP MLD and a non-AP MLD. The non-AP MLD and the AP MLD may be communicatively coupled by a plurality of links and may be associated with a TID-to-link mapping. The TID-to-link mapping may include a first mapping of a first TID in an uplink to a first set of links among the plurality of links, and a second mapping of a second TID in an uplink to a second set of links among the plurality of links. In one embodiment, the TID-to-link mapping is based on TID-to-link mapping elements exchanged in an association request frame and an association response frame between the non-AP MLD and the AP MLD, or a default mapping mode in which the TID is mapped to all of the plurality of links for both downlink and uplink.

[0186] The exemplary process 1700 may be performed by the AP MLD.

[0187] As shown in FIG. 17, process 1700 may include, at step 1710, receiving, on a first link of a first set of links, a frame of a first TID from the non-AP MLD according to the TID-to-link mapping. The first frame may carry a MAC service data unit (MSDU) or an aggregated MSDU (A-MSDU) for the first TID.

[0188] At step 1720, process 1700 may include receiving a buffer status report (BSR) frame for the first TID on any link of the plurality of links, independently of / irrespective of the TID-to-link mapping.

[0189] In one embodiment, the link on which the BSR frame is received is an enabled link, i.e., a link having at least one TID mapped thereto according to the TID-to-link mapping.

[0190] In one embodiment, the link on which the BSR frame is received belongs to a first set of links among the plurality of links.

[0191] In one embodiment, the link on which the BSR frame is received belongs to a second set of links among the plurality of links.

[0192] In one embodiment, the link on which the BSR frame is received is a link to which the first TID is not mapped in the TID-to-link mapping.

[0193] In one embodiment, the link on which the BSR frame is received is a disabled link, i.e., a link that does not have a TID mapped to it according to the TID-to-link mapping.

[0194] In one embodiment, the BSR frame includes a QoS null frame indicating the first TID and the queue size information of the first TID.

[0195] In one embodiment, the BSR frame includes a QoS null frame including a QoS control field, or a QoS null frame including a QoS control field and a BSR control subfield.

[0196] In one embodiment, the QoS control field is a TID subfield, and the TID subfield is a TID subfield that identifies a traffic class (TC) or a traffic stream (TS) for which a transmission opportunity (TXOP) is requested, and a queue size subfield, and the queue size subfield has a TID equal to the value of the TID subfield and indicates the total size in octets of an MSDU or A-MSDU buffered at a non-AP MLD. The QoS control field includes at least one of the queue size subfields.

[0197] In one embodiment, the BSR control subfield includes at least one of an access category index (ACI) bitmap subfield, a delta TID subfield, an ACI high subfield, a scaling factor subfield, a queue size high subfield, and a queue size all subfield. The ACI bitmap subfield indicates at least one access category (AC) for which buffer status is reported within the BSR frame. The delta TID subfield indicates the number of TIDs for which buffer status is reported within the BSR frame. The ACI high subfield indicates the ACI of at least one AC indicated by the queue size high subfield for which buffer status is reported. The scaling factor indicates the size in octets of the unit (SF) of the queue size high subfield and the queue size all subfield. The queue size high subfield indicates the amount of buffered traffic in SF units for the AC identified by the ACI high subfield. The queue size all subfield indicates the amount of buffered traffic in SF units for at least one AC identified by the ACI bitmap subfield.

[0198] In one embodiment, receiving the BSR frame in step 1720 includes receiving the BSR frame in a TB PPDU or a non-TB PPDU.

[0199] In one embodiment, receiving the BSR frame is in response to a trigger frame transmitted by the AP MLD. The trigger frame may include a BSRP trigger frame or a basic trigger frame.

[0200] In one embodiment, process 1700 may optionally include steps 1730 and 1740.

[0201] In step 1730, process 1700 may include transmitting a trigger frame in response to a BSR on a link to which the first TID is mapped in the TID-to-link mapping. The link can be any link of the first set of links. The trigger frame allocates uplink resources to the AP MLD for the first TID. The trigger frame may include a basic trigger frame or a MU-RTS TXS trigger frame.

[0202] In step 1740, process 1700 may include receiving one or more MSDUs or A-MSDUs for the first TID on the link on which the trigger frame is transmitted.

[0203] In an exemplary embodiment, the non-AP MLD may send a frame to the AP MLD based on the TID-to-link mapping, which indicates the mapping of the first set of links for the first TID and the mapping of the second set of links for the second TID. The non-AP MLD may send a buffer status report (BSR) frame to the AP MLD indicating the buffer status for the first TID on any link, regardless of the TID-to-link mapping.

[0204] In an exemplary embodiment, the non-AP MLD and the AP MLD may set up a plurality of links for multi-link operation, may negotiate a TID-to-link mapping during an association procedure between the non-AP MLD and the AP MLD, and the TID-to-link mapping may include a first mapping of a first TID for an uplink to a first set of links among the plurality of links, and a second mapping of a second TID for an uplink to a second set of links among the plurality of links. The non-AP MLD may send a frame carrying an MSDU or an A-MSDU for the first TID on the first link of the first set of links to the AP MLD. The non-AP MLD may determine a buffer status of the first TID. The non-AP MLD may send a BSR frame indicating a buffer status of the first TID (e.g., a QoS null frame indicating the first TID and including queue size information of the first TID) on any link among the plurality of links, regardless of the TID-to-link mapping.

[0205] In an exemplary embodiment, regardless of the negotiated TID-to-link mapping, the transmission of a BSR frame on any link among the plurality of links may reduce the latency of the AP MLD and obtain the buffer status of the non-AP MLD. Further, the signaling overhead may be reduced by the AP MLD not sending a trigger frame to the polling buffer status report of each enabled link. The AP MLD may obtain the accurate buffer status of the non-AP MLD in a timely manner by receiving a PPDU including a buffer status report frame.

[0206] In an exemplary embodiment, when the TID-to-link mapping is negotiated, the BSR frame can be transmitted based on different rules depending on which PPDU carries the BSR frame. In an exemplary embodiment, a trigger-based (TB) PPDU including a BSR frame (e.g., a QoS null frame) indicating the buffer status of a TID can be transmitted on any of a plurality of links regardless of the TID-to-link mapping, and the TB PPDU is transmitted by a non-AP MLD in response to a trigger frame (e.g., a buffer status report polling (BSRP) trigger frame, a basic trigger frame, etc.) transmitted by an AP MLD. In another exemplary embodiment, a non-TB PPDU including a BSR frame (e.g., a QoS null frame) indicating the buffer status of a TID can be transmitted on the link to which the TID is mapped according to the TID-to-link mapping.

[0207] In an exemplary embodiment, the transmission of the BSR frame in a non-TB PPDU may follow the TID-to-link mapping rule, and the non-AP MLD may have the same implementation for the transmission of frames having the TID using EDCA channel access when the TID-to-link mapping is negotiated. In an exemplary embodiment, the transmission of the BSR frame in a TB PPDU for any TID on any of a plurality of links can provide low latency and more accurate BSR to the AP MLD by the AP MLD transmitting a trigger frame to the non-AP MLD when the AP MLD needs to obtain BSR information from the non-AP MLD, regardless of the TID-to-link mapping.

[0208] FIG. 18 shows an exemplary process 1800 according to one embodiment. The exemplary process 1800 may be implemented in an exemplary environment that includes AP MLD and non-AP MLD. The non-AP MLD and AP MLD may be communicatively coupled by a plurality of links and may be associated with a TID-to-link mapping. The TID-to-link mapping may include a mapping of TIDs in an uplink and / or downlink to a first set of links among the plurality of links. The exemplary process 1800 may be implemented by the non-AP MLD.

[0209] As shown in FIG. 18, process 1800 can begin with an optional step 1802, which includes transmitting, to the AP MLD, a frame for a TID on a first link of a first set of links, for which the TID is mapped in the TID-to-link mapping. In one embodiment, the frame of the TID includes an MSDU or A-MSDU of the TID.

[0210] In step 1804, process 1800 includes receiving, from the AP MLD, a trigger frame on a second link for which the TID is not mapped in the TID-to-link mapping. In one embodiment, the trigger frame includes a BSRP trigger frame or a basic trigger frame.

[0211] In step 1806, process 1800 includes transmitting, in response to the trigger frame, a QoS null frame including the TID on the second link to the AP MLD. In one embodiment, the second link is an enabled link for which at least one TID is mapped according to the TID-to-link mapping. In another embodiment, the second link is a disabled link for which the TID is not mapped according to the TID-to-link mapping. In one embodiment, the QoS null frame includes a BSR for the TID. In another embodiment, the QoS null frame further includes a BSR for another TID mapped to the second link.

[0212] In one embodiment, the QoS null frame includes a QoS control field that includes a BSR for a TID. In one embodiment, the QoS control field includes at least one of a TID subfield that identifies a traffic class (TC) or a traffic stream (TS) for which a transmission opportunity (TXOP) is requested, and a queue size subfield that has a TID equal to the value of the TID subfield and indicates the total size in octets of MSDUs and A-MSDUs buffered at the non-AP MLD. In another embodiment, the QoS null frame includes a BSR control subfield that includes a BSR for a TID.

[0213] In one embodiment, process 1800 may further include receiving, from the AP MLD, an association frame that includes a TID-to-link mapping that maps a TID to a first set of links, prior to step 1802.

[0214] In one embodiment, process 1800 includes receiving, from the AP MLD, in response to the QoS null frame, a trigger frame on the first link, where the trigger frame allocates uplink resources on the first link to the non-AP MLD for the TID, and transmitting, in response to the trigger frame, to the AP MLD, a frame that includes a QoS data frame for the TID.

[0215] FIG. 19 shows an exemplary process 1900 according to one embodiment. The exemplary process 1900 may be implemented in an exemplary environment that includes an AP MLD and a non-AP MLD. The non-AP MLD and the AP MLD may be communicatively coupled by a plurality of links and may be associated with a TID-to-link mapping. The TID-to-link mapping may include a mapping of a TID in an uplink and / or a downlink to a first set of links of the plurality of links. The exemplary process 1900 may be implemented by the AP MLD.

[0216] As shown in FIG. 19, process 1900 can begin with optional step 1902, which includes receiving, from a non-AP MLD, a frame for a TID on a first link of a set of links for which the TID is mapped in a TID-to-link mapping. In one embodiment, the frame for the TID includes an MSDU or A-MSDU of the TID.

[0217] In step 1904, process 1900 includes transmitting, to the non-AP MLD, a trigger frame on a second link for which the TID is not mapped in the TID-to-link mapping. In one embodiment, the trigger frame includes a BSRP trigger frame or a basic trigger frame.

[0218] In step 1906, process 1900 includes receiving, from the non-AP MLD, a QoS null frame including the TID on the second link in response to the trigger frame. In one embodiment, the second link is an enabled link on which at least one TID is mapped according to the TID-to-link mapping. In another embodiment, the second link is a disabled link on which the TID is not mapped according to the TID-to-link mapping. In one embodiment, the QoS null frame includes a BSR for the TID. In another embodiment, the QoS null frame further includes a BSR for another TID mapped to the second link.

[0219] In one embodiment, the QoS null frame includes a QoS control field including a BSR for the TID. In one embodiment, the QoS control field includes at least one of a TID subfield identifying a TC or TS for which a TXOP is requested, a queue size subfield indicating a total size in octets of the MSDU, and an A-MSDU having a TID buffered at the non-AP MLD and equal to a value of the TID subfield. In another embodiment, the QoS null frame includes a BSR control subfield including a BSR for the TID.

[0220] In one embodiment, process 1800 may further include, before step 1902, sending to the non-AP MLD an association frame including a TID-to-link mapping that maps the TID to the first set of links.

[0221] In one embodiment, process 1900 may further include, in response to the QoS null frame, sending to the non-AP MLD a trigger frame on the first link, where the trigger frame allocates uplink resources on the first link to the non-AP MLD of the TID, and receiving, in response to the trigger frame, from the non-AP MLD a frame including the QoS data frame of the TID.

[0222] In an exemplary embodiment, the non-AP MLD may receive from the AP MLD a trigger frame on the first link among a plurality of links between the non-AP MLD and the AP MLD. The non-AP MLD may, in response to the trigger frame, send to the AP MLD a QoS null frame including the TID on the second link among the plurality of links, regardless of whether the TID is mapped to the second link in the TID-to-link mapping. In one embodiment, the TID is not mapped to the second link in the TID-to-link mapping. The TID may or may not be mapped to the first link in the TID-to-link mapping. In another embodiment, the TID is mapped to the second link in the TID-to-link mapping. The TID may or may not be mapped to the first link in the TID-to-link mapping.

[0223] In another exemplary embodiment, the AP MLD may transmit a trigger frame on a first link among a plurality of links between the AP MLD and the non-AP MLD to the non-AP MLD. In response to the trigger frame, the AP MLD may receive, from the non-AP MLD, a QoS null frame including a TID on a second link among the plurality of links, regardless of whether the TID is mapped to the second link in the TID-to-link mapping. In one embodiment, the TID is not mapped to the second link in the TID-to-link mapping. The TID may or may not be mapped to the first link in the TID-to-link mapping. In another embodiment, the TID is mapped to the second link in the TID-to-link mapping. The TID may or may not be mapped to the first link in the TID-to-link mapping.

Claims

1. A non-access point (non-AP) multi-link device (MLD), comprising: one or more processors; and when executed by the one or more processors, cause the non-AP MLD to receive, from an access point (AP) MLD, an association frame including a traffic identifier (TID)-to-link (TID-to-link) mapping that maps a TID to a first link; send, to the AP MLD, a first frame for the TID on the first link; receive, from the AP MLD, a first trigger frame on a second link to which the TID is not mapped, the first trigger frame including a buffer status report polling (BSRP) trigger frame or a basic trigger frame; and in response to the first trigger frame, send, to the AP MLD, a quality of service (QoS) null frame including the TID on the second link, the QoS null frame including a first buffer status report (BSR) for the TID, a memory storing instructions to cause the non-access point (non-AP) multi-link device (MLD).

2. The non-AP MLD according to claim 1, wherein the second link is an activated link to which at least one TID is mapped according to the TID-to-link mapping.

3. The non-AP MLD according to claim 1, wherein the first frame of the TID includes a media access control (MAC) service data unit (MSDU) or an aggregated MSDU (A-MSDU) of the TID.

4. The non-AP MLD according to claim 1, wherein the QoS null frame includes a second BSR for another TID mapped to the second link.

5. The non-AP MLD according to claim 1, wherein the QoS null frame includes a QoS control field or a BSR control subfield including the first BSR for the TID.

6. When the instructions are executed by the one or more processors, further cause the non-AP MLD to Receiving, by the AP MLD, a second trigger frame on the first link in response to the QoS null frame, wherein the second trigger frame allocates uplink resources on the first link to the non-AP MLD for the TID Causing the AP MLD to transmit, in response to the second trigger frame, a second frame including a QoS data frame for the TID, the non-AP MLD according to claim 1 **Claim 7** An access point (AP) multi-link device (MLD), comprising One or more processors; and When executed by the one or more processors, causing the AP MLD to Transmit, to a non-access point (non-AP) MLD, an association frame including a traffic identifier (TID)-to-link (TID-to-link) mapping that maps the TID to a first link Receive, from the non-AP MLD, a first frame for the TID on the first link Transmit, to the non-AP MLD, a first trigger frame on a second link to which the TID is not mapped, the first trigger frame including a buffer status report polling (BSRP) trigger frame or a basic trigger frame A memory storing instructions that, when executed by the one or more processors, cause the AP MLD to receive, from the non-AP MLD, a quality of service (QoS) null frame including the TID on the second link in response to the first trigger frame, the QoS null frame including a first buffer status report (BSR) for the TID, an access point (AP) multi-link device (MLD). **Claim 8** The AP MLD according to claim 7, wherein the second link is an activated link to which at least one TID is mapped according to the TID-to-link mapping **Claim 9** The AP MLD according to claim 7, wherein the first frame of the TID includes a media access control (MAC) service data unit (MSDU) or an aggregated MSDU (A-MSDU) of the TID **Claim 10** The AP MLD according to claim 7, wherein the QoS null frame includes a second BSR for another TID mapped to the second link.

11. The AP MLD according to claim 7, wherein the QoS null frame includes a QoS control field or a BSR control subfield including the first BSR for the TID.

12. When the instruction is executed by the one or more processors, the AP MLD is further caused to in response to the QoS null frame, transmit, to the non-AP MLD, a second trigger frame on the first link, wherein the second trigger frame allocates uplink resources on the first link to the non-AP MLD for the TID; in response to the second trigger frame, receive, from the non-AP MLD, a second frame including a QoS data frame for the TID. The AP MLD according to claim 7.

13. A non-transitory computer-readable medium that, when executed by one or more processors of a non-access point (non-AP) multi-link device (MLD), causes the non-AP MLD to receive, from an access point (AP) MLD, an association frame including a traffic identifier (TID)-to-link (TID-to-link) mapping that maps a TID to a first link; transmit, to the AP MLD, a first frame for the TID on the first link; receive, from the AP MLD, a first trigger frame on a second link to which the TID is not mapped; in response to the first trigger frame, transmit, to the AP MLD, a quality of service (QoS) null frame including the TID on the second link, wherein the QoS null frame includes a first buffer status report (BSR) for the TID. A non-transitory computer-readable medium that causes the execution of the instruction.

14. The non-transitory computer-readable medium according to claim 13, wherein the second link is an enabled link to which at least one TID is mapped according to the TID-to-link mapping.

15. The non-transitory computer-readable medium according to claim 13, wherein the first frame of the TID includes the media access control (MAC) service data unit (MSDU) or the aggregated MSDU (A-MSDU) of the TID.

16. The non-transitory computer-readable medium according to claim 13, wherein the QoS null frame includes a second BSR for another TID mapped to the second link.

17. The non-transitory computer-readable medium according to claim 13, wherein the QoS null frame includes a QoS control field or a BSR control subfield including the first BSR for the TID.

18. When the instruction is executed by the one or more processors, further, to the non-AP MLD, receiving, in response to the QoS null frame, from the AP MLD, a second trigger frame on the first link, wherein the second trigger frame allocates uplink resources on the first link to the non-AP MLD for the TID; causing, in response to the second trigger frame, the AP MLD to transmit a second frame including a QoS data frame for the TID, the non-transitory computer-readable medium according to claim 13.

19. The non-AP MLD according to claim 5, wherein the QoS null frame includes the QoS control field, and the QoS control field includes a TID subfield that identifies a traffic class (TC) or a traffic stream (TS) for which a transmission opportunity (TXOP) is requested by the non-AP MLD.

20. The AP MLD according to claim 11, wherein the QoS null frame includes the QoS control field, and the QoS control field includes a TID subfield that identifies a traffic class (TC) or a traffic stream (TS) for which a transmission opportunity (TXOP) is requested by the non-AP MLD.

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